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Sample records for reusable transition metal-free

  1. Transition metal-free olefin polymerization catalyst

    DOEpatents

    Sen, Ayusman; Wojcinski, II, Louis M.; Liu, Shengsheng

    2001-01-01

    Ethylene and/or propylene are polymerized to form high molecular weight, linear polymers by contacting ethylene and/or propylene monomer, in the presence of an inert reaction medium, with a catalyst system which consists essentially of (1) an aluminum alkyl component, such as trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-octylaluminum and diethylaluminum hydride and (2) a Lewis acid or Lewis acid derivative component, such as B (C.sub.6 F.sub.5).sub.3, [(CH.sub.3).sub.2 N (H) (C.sub.6 H.sub.5)].sup.+ [B (C.sub.6 F.sub.5)4].sup.-, [(C.sub.2 H.sub.5).sub.3 NH].sup.+ [B C.sub.6 F.sub.5).sub.4 ],.sup.-, [C(C.sub.6 F.sub.5).sub.3 ].sup.+ [B(C.sub.6 F.sub.5).sub.4 ].sup.-, (C.sub.2 H.sub.5).sub.2 Al(OCH.sub.3), (C.sub.2 H.sub.5).sub.2 Al(2,6-di-t-butyl-4-methylphenoxide), (C.sub.2 H.sub.5)Al(2,6 -di-t-butylphenoxide).sub.2, (C.sub.2 H.sub.5).sub.2 Al(2,6-di-t-butylphonoxide) , 2,6 -di-t-butylphenol.multidot.methylaluminoxane or an alkylaluminoxane, and which may be completely free any transition metal component(s).

  2. Transition-Metal-Free Biomolecule-Based Flexible Asymmetric Supercapacitors.

    PubMed

    Yang, Yun; Wang, Hua; Hao, Rui; Guo, Lin

    2016-09-01

    A transition-metal-free asymmetric supercapacitor (ASC) is successfully fabricated based on an earth-abundant biomass derived redox-active biomolecule, named lawsone. Such an ASC exhibits comparable or even higher energy densities than most of the recently reported transition-metal-based ASCs, and this green ASC generation from renewable resources is promising for addressing current issues of electronic hazard processing, high cost, and unsustainability. PMID:26890876

  3. Transition Metal-Free Tryptophan-Selective Bioconjugation of Proteins.

    PubMed

    Seki, Yohei; Ishiyama, Takashi; Sasaki, Daisuke; Abe, Junpei; Sohma, Youhei; Oisaki, Kounosuke; Kanai, Motomu

    2016-08-31

    Chemical modifications of native proteins can facilitate production of supernatural protein functions that are not easily accessible by complementary methods relying on genetic manipulations. However, accomplishing precise control over selectivity while maintaining structural integrity and homogeneity still represents a formidable challenge. Herein, we report a transition metal-free method for tryptophan-selective bioconjugation of proteins that is based on an organoradical and operates under ambient conditions. This method exhibits low levels of cross-reactivity and leaves higher-order structures of the protein and various functional groups therein unaffected. The strategy to target less abundant amino acids contributes to the formation of structurally homogeneous conjugates, which may even be suitable for protein crystallography. The absence of toxic metals and biochemically incompatible conditions allows a rapid functional modulation of native proteins such as antibodies and pathogenic aggregative proteins, and this method may thus easily find therapeutic applications. PMID:27534812

  4. Transition-metal-free atropo-selective synthesis of biaryl compounds based on arynes.

    PubMed

    Leroux, Frédéric R; Berthelot, Anaïs; Bonnafoux, Laurence; Panossian, Armen; Colobert, Françoise

    2012-11-01

    A modular way towards biaryls: Highly enantioenriched biphenyls can be prepared based on a transition-metal-free aryl-aryl coupling followed by efficient desymmetrization or deracemization and chemoselective functionalization (see scheme).

  5. Transition-Metal-Free Coupling Annulation of Arynes with Ketones and Alkynoates: Assembly of Functionalized Naphthalenes.

    PubMed

    Shu, Wen-Ming; Zheng, Kai-Lu; Ma, Jun-Rui; Wu, An-Xin

    2016-08-01

    A transition-metal-free coupling annulation reaction of arynes, ketones, and alkynoates has been demonstrated. Using this formal [2 + 2 + 2] cycloaddition reaction, a wide variety of naphthalene derivatives were conveniently constructed in one pot with high efficiency. In addition, this novel and valid annulation has been successfully applied to the synthesis of 1-phenanthrenol derivatives. PMID:27463418

  6. Transition metal-free one-pot synthesis of nitrogen-containing heterocycles.

    PubMed

    Kumari, Simpal; Kishore, Dharma; Paliwal, Sarvesh; Chauhan, Rajani; Dwivedi, Jaya; Mishra, Aakanksha

    2016-02-01

    One-pot heterocyclic synthesis is an exciting research area as it can open routes for the development of otherwise complex transformations in organic synthesis. Heterocyclic compounds show wide spectrum of applications in medicinal chemistry, chemical biology, and materials science. These heterocycles can be generated very efficiently through highly economical and viable routes using one-pot synthesis. In particular, the metal-free one-pot synthetic protocols are highly fascinating due to several advantages for the industrial production of heterocyclic frameworks. This comprehensive review is devoted to the transition metal-free one-pot synthesis of nitrogen-containing heterocycles from the period 2010-2013.

  7. Transition-metal-free direct alkylation of aryl tetrazoles via intermolecular oxidative C-N formation.

    PubMed

    Wang, Liang; Zhu, Kaiqiang; Chen, Qun; He, Mingyang

    2014-12-01

    A transition-metal-free synthetic approach for constructing alkylated aryl tetrazoles has been developed using n-Bu4NI as the catalyst and t-BuOOH as the oxidant. It involves the direct C-N bond formation through sp(3) C-H activation. A wide range of benzylic C-H substrates (or alkyl ethers) and aryl tetrazoles undergo this reaction smoothly to deliver the corresponding products in good yields.

  8. Regioselective, Transition Metal-Free C-O Coupling Reactions Involving Aryne Intermediates.

    PubMed

    Dong, Yuyang; Lipschutz, Michael I; Tilley, T Don

    2016-04-01

    A new transition-metal-free synthetic method for C-O coupling between various aryl halides and alkoxides is described. This type of transformation is typically accomplished using palladium catalysts containing a specialized phosphine ligand. The reactions reported here can be performed under mild, ambient conditions using certain potassium alkoxides and a range of aryl halides, with iodide and bromide derivatives giving the best results. A likely mechanistic pathway involves the in situ generation of an aryne intermediate, and directing groups on the aryl ring inductively control regioselectivity.

  9. Transition-Metal-Free ipso-Functionalization of Arylboronic Acids and Derivatives

    PubMed Central

    Zhu, Chen; Falck, John R.

    2014-01-01

    Arylboronic acids and their derivatives have been widely exploited as important synthetic precursors in organic synthesis, materials science, and pharmaceutical development. In addition to numerous applications in transition-metal-mediated cross-coupling reactions, transition-metal-free transformations involving arylboronic acids and derivatives have recently received a surge of attention for converting the C-B bond to C-C, C-N, C-O, and many other C-X bonds. Consequently, a wide range of useful compounds, e.g., phenols, anilines, nitroarenes, and haloarenes, have been readily synthesized. Amongst these efforts, many versatile reagents have been developed and a lot of practical approaches demonstrated. The research in this promising field is summarized in the current review and organized on the basis of the type of bonds being formed. PMID:25414624

  10. Direct Oxidation of Aliphatic C-H Bonds in Amino-Containing Molecules under Transition-Metal-Free Conditions.

    PubMed

    Li, Xin; Che, Xing; Chen, Gui-Hua; Zhang, Jun; Yan, Jia-Lei; Zhang, Yun-Fei; Zhang, Li-Sheng; Hsu, Chao-Ping; Gao, Yi Qin; Shi, Zhang-Jie

    2016-03-18

    By employing a simple, inexpensive, and transition-metal-free oxidation system, secondary C-H bonds in a series of phthaloyl protected primary amines and amino acid derivatives were oxidized to carbonyls with good regioselectivities. This method could also be applied to oxidize tertiary C-H bonds and modify synthetic dipeptides.

  11. Transition metal-free intramolecular regioselective couplings of aliphatic and aromatic C-H bonds.

    PubMed

    Tian, Hua; Yang, Haijun; Zhu, Changjin; Fu, Hua

    2016-01-29

    Cross-dehydrogenative couplings of two different C-H bonds have emerged as an attractive goal in organic synthesis. However, achieving regioselective C-H activation is a great challenge because C-H bonds are ubiquitous in organic compounds. Actually, the regioselective couplings promoted by enzymes are a common occurrence in nature. Herein, we have developed simple, efficient and general transition metal-free intramolecular couplings of alphatic and aromatic C-H bonds. The protocol uses readily available aryl triazene as the radical initiator, cheap K2S2O8 as the oxidant, and the couplings were performed well with excellent tolerance of functional groups. Interestingly, α-carbon configuration of some amino acid residues in the substrates was kept after the reactions, and the couplings for substrates with substituted phenylalanine residues exhibited complete β-carbon diastereoselectivity for induction of the chiral α-carbon. Therefore, the present study should provide a novel strategy for regioselective cross-dehydrogenative couplings of two different C-H bonds.

  12. Transition metal-free intramolecular regioselective couplings of aliphatic and aromatic C-H bonds

    PubMed Central

    Tian, Hua; Yang, Haijun; Zhu, Changjin; Fu, Hua

    2016-01-01

    Cross-dehydrogenative couplings of two different C-H bonds have emerged as an attractive goal in organic synthesis. However, achieving regioselective C-H activation is a great challenge because C-H bonds are ubiquitous in organic compounds. Actually, the regioselective couplings promoted by enzymes are a common occurrence in nature. Herein, we have developed simple, efficient and general transition metal-free intramolecular couplings of alphatic and aromatic C-H bonds. The protocol uses readily available aryl triazene as the radical initiator, cheap K2S2O8 as the oxidant, and the couplings were performed well with excellent tolerance of functional groups. Interestingly, α-carbon configuration of some amino acid residues in the substrates was kept after the reactions, and the couplings for substrates with substituted phenylalanine residues exhibited complete β-carbon diastereoselectivity for induction of the chiral α-carbon. Therefore, the present study should provide a novel strategy for regioselective cross-dehydrogenative couplings of two different C-H bonds. PMID:26822836

  13. Transition-metal-free C-S bond formation: a facile access to aryl sulfones from sodium sulfinates via arynes.

    PubMed

    Pandya, Virat G; Mhaske, Santosh B

    2014-07-18

    Sulfones have been attractive targets for synthetic organic chemists owing to their immense applications in medicinal, material, and synthetic chemistry. In this context, an efficient transition-metal-free process has been demonstrated, wherein a broad range of alkyl/aryl/heteroaryl sodium sulfinates react with varyingly substituted aryne precursors (o-silyl aryl triflates) under mild reaction conditions to afford structurally diverse sulfones in good to excellent yields.

  14. Ammonia and hydrazine. Transition-metal-catalyzed hydroamination and metal-free catalyzed functionalization

    SciTech Connect

    Bertrand, Guy

    2012-06-29

    high temperatures and long reaction times. To address this issue, we have developed several new families of carbon- and boron-based ligands, which are even better donors. The corresponding metal complexes (particularly gold, rhodium, iridium, and ruthenium) of all these species will be tested in the Markovnikov and anti-Markovnikov hydroamination of alkynes, allenes, and also alkenes with ammonia and hydrazine. We will also develop metal-free catalytic processes for the functionalization of ammonia and hydrazine. By possessing both a lone pair of electrons and an accessible vacant orbital, singlet carbenes resemble and can mimic the chemical behavior of transition metals. Our preliminary results demonstrate that specially designed carbenes can split the N–H bond of ammonia by an initial nucleophilic activation that prevents the formation of Lewis acid-base adducts, which is the major hurdle for the transition metal catalyzed functionalization of NH3. The use of purely organic compounds as catalysts will eliminate the major drawbacks of transition-metal-catalysis technology, which are the excessive cost of metal complexes (metal + ligands) and in many cases the toxicity of the metal.

  15. Understanding the Kinetics and Spectroscopy of Photoredox Catalysis and Transition-Metal-Free Alternatives.

    PubMed

    Pitre, Spencer P; McTiernan, Christopher D; Scaiano, Juan C

    2016-06-21

    Over the past decade, the field of photoredox catalysis has gained increasing attention in synthetic organic chemistry because of its wide applicability in sustainable free-radical-mediated processes. Numerous examples have shown that under carefully optimized conditions, efficient and highly selective processes can be developed through excitation of a photosensitizer using inexpensive, readily available light sources. However, despite all of these recent advancements, some generalizations and/or misconceptions have become part of the photoredox culture, and often many of these discoveries lack in-depth investigations into the excited-state kinetics and underlying mechanisms. In this Account, we begin with a tutorial for understanding both the redox properties of excited states and how to measure the kinetics of excited-state processes. We discuss the generalization of direct excitation of closed-shell species to generate more potent reductive or oxidative excited states, using the helium atom as a quantitative example. We also outline how to apply redox potentials to calculate whether the proposed electron transfer events are thermodynamically feasible. In the second half of our tutorial, we discuss how to measure the kinetics of excited-state processes using techniques such as steady-state and time-resolved fluorescence and transient spectroscopy and how to apply the data using Stern-Volmer and kinetic analysis. Then we shift gears to discuss our recent contributions to the field of photoredox catalysis. Our lab focuses on developing transition-metal-free alternatives to ruthenium and iridium bipyridyl complexes for these transformations, with the goal of developing systems in which the reaction kinetics is more favorable. We have found that methylene blue, a member of the thiazine dye family, can be employed in photoredox processes such as oxidative hydroxylations of arylboronic acids to phenols. Interestingly, we were able to demonstrate that methylene blue is

  16. Visible-Light-Mediated Synthesis of Amidyl Radicals: Transition-Metal-Free Hydroamination and N-Arylation Reactions.

    PubMed

    Davies, Jacob; Svejstrup, Thomas D; Fernandez Reina, Daniel; Sheikh, Nadeem S; Leonori, Daniele

    2016-07-01

    The development of photoredox reactions of aryloxy-amides for the generation of amidyl radicals and their use in hydroamination-cyclization and N-arylation reactions is reported. Owing to the ease of single-electron-transfer reduction of the aryloxy-amides, the organic dye eosin Y was used as the photoredox catalyst, which results in fully transition-metal-free processes. These transformations exhibit a broad scope, are tolerant to several important functionalities, and have been used in the late-stage modification of complex and high-value N-containing molecules.

  17. A transition metal-free tandem process to pyridazinopyrido[3,2-f][1,4]thiazepine-diones via Smiles rearrangement.

    PubMed

    Niu, Xiaoyi; Yang, Bingchuan; Li, Yanqiu; Fang, Shuai; Huang, Zixiao; Xie, Caixia; Ma, Chen

    2013-06-28

    A transition metal-free methodology for the synthesis of pyridazinopyrido[3,2-f][1,4]thiazepine-diones was studied. The construction of this tricyclic system went through a one-pot coupling/Smiles rearrangement/cyclization process. The high yields of pure products were obtained through simple recrystallization.

  18. Transition-metal-free visible-light photoredox catalysis at room-temperature for decarboxylative fluorination of aliphatic carboxylic acids by organic dyes.

    PubMed

    Wu, Xinxin; Meng, Chunna; Yuan, Xiaoqian; Jia, Xiaotong; Qian, Xuhong; Ye, Jinxing

    2015-07-28

    We report herein an efficient, general and green method for decarboxylative fluorination of aliphatic carboxylic acids. By using a transition-metal-free, organocatalytic photoredox system, the reaction of various aliphatic carboxylic acids with the Selectfluor reagent afforded the corresponding alkyl fluorides in satisfactory yields under visible light irradiation at room temperature.

  19. Employing Arynes in Diels-Alder Reactions and Transition-Metal-Free Multicomponent Coupling and Arylation Reactions.

    PubMed

    Bhojgude, Sachin Suresh; Bhunia, Anup; Biju, Akkattu T

    2016-09-20

    Arynes are highly reactive intermediates having several applications in organic synthesis for the construction of various ortho-disubstituted arenes. Traditionally, arynes are generated in solution from haloarenes under strongly basic conditions. However, the scopes of many of the aryne reactions are limited because of the harsh conditions used for their generation. The renaissance of interest in aryne chemistry is mainly due to the mild conditions for their generation by the fluoride-induced 1,2-elimination of 2-(trimethylsilyl)aryl triflates. This Account is focused on the Diels-Alder reaction of arynes and their transition-metal-free application in multicomponent couplings as well as arylation reactions. The Diels-Alder reaction of arynes is a powerful tool for constructing benzo-fused carbocycles and heterocycles. In 2012, we developed an efficient, broad-scope, and scalable Diels-Alder reaction of pentafulvenes with arynes affording benzonorbornadiene derivatives. Subsequently, we accomplished the Diels-Alder reaction of arynes with dienes such as 1,2-benzoquinones and tropones. Moreover, we uncovered a transition-metal-free protocol for the synthesis of 9,10-dihydrophenanthrenes by the reaction of arynes with styrenes that proceeds via a Diels-Alder/ene-reaction cascade. In addition, we demonstrated the reaction of arynes with indene/benzofurans, which proceeds via a tandem [4 + 2]/[2 + 2] sequence. Multicomponent coupling (MCC) involving arynes mainly comprises the initial addition of a nucleophile to the aryne followed by interception of the aryl anion intermediate with an electrophile (provided the nucleophilic and electrophilic moieties do not belong to the same molecule). We have disclosed aryne MCCs initiated by N-heterocycles such as (iso)quinoline, pyridine, and aziridines. When (iso)quinoline is used as the nucleophilic trigger and N-substituted isatin as the third component, the reaction affords spirooxazino(iso)quinolines via 1,4-dipolar

  20. Employing Arynes in Diels-Alder Reactions and Transition-Metal-Free Multicomponent Coupling and Arylation Reactions.

    PubMed

    Bhojgude, Sachin Suresh; Bhunia, Anup; Biju, Akkattu T

    2016-09-20

    Arynes are highly reactive intermediates having several applications in organic synthesis for the construction of various ortho-disubstituted arenes. Traditionally, arynes are generated in solution from haloarenes under strongly basic conditions. However, the scopes of many of the aryne reactions are limited because of the harsh conditions used for their generation. The renaissance of interest in aryne chemistry is mainly due to the mild conditions for their generation by the fluoride-induced 1,2-elimination of 2-(trimethylsilyl)aryl triflates. This Account is focused on the Diels-Alder reaction of arynes and their transition-metal-free application in multicomponent couplings as well as arylation reactions. The Diels-Alder reaction of arynes is a powerful tool for constructing benzo-fused carbocycles and heterocycles. In 2012, we developed an efficient, broad-scope, and scalable Diels-Alder reaction of pentafulvenes with arynes affording benzonorbornadiene derivatives. Subsequently, we accomplished the Diels-Alder reaction of arynes with dienes such as 1,2-benzoquinones and tropones. Moreover, we uncovered a transition-metal-free protocol for the synthesis of 9,10-dihydrophenanthrenes by the reaction of arynes with styrenes that proceeds via a Diels-Alder/ene-reaction cascade. In addition, we demonstrated the reaction of arynes with indene/benzofurans, which proceeds via a tandem [4 + 2]/[2 + 2] sequence. Multicomponent coupling (MCC) involving arynes mainly comprises the initial addition of a nucleophile to the aryne followed by interception of the aryl anion intermediate with an electrophile (provided the nucleophilic and electrophilic moieties do not belong to the same molecule). We have disclosed aryne MCCs initiated by N-heterocycles such as (iso)quinoline, pyridine, and aziridines. When (iso)quinoline is used as the nucleophilic trigger and N-substituted isatin as the third component, the reaction affords spirooxazino(iso)quinolines via 1,4-dipolar

  1. NOx Reduction on a Transition Metal-free γ-Al2O3 Catalyst Using Dimethylether (DME)

    SciTech Connect

    Ozensoy, Emrah; Herling, Darrell R.; Szanyi, Janos

    2008-07-15

    NO2 and dimethylether (DME) adsorption as well as DME and NO2 coadsorption on a transition metal-free γ-alumina catalyst were investigated via in-situ transmission Fourier transform infrared spectroscopy (in-situ FTIR), residual gas analysis (RGA) and temperature programmed desorption (TPD) techniques. NO2 adsorption at room temperature leads to the formation of surface nitrates and nitrites. DME adsorption on the alumina surface at 300 K leads to molecularly adsorbed DME, molecularly adsorbed methanol and surface methoxides. Upon heating the DME-exposed alumina to 500-600 K the surface is dominated by methoxide groups. At higher temperatures methoxide groups are converted into formates. At T > 510 K formate decomposition takes place to form H2O(g) and CO(g). DME and NO2 coadsorption at 423 K do not indicate a significant reaction between DME and NO2. However, in similar experiments at 573 K, fast reaction occurs and the methoxides present at 573 K before the NO2 adsorption are converted into formates, simultaneously with the formation of isocyanates. Under these conditions, NCO can further be hydrolyzed into isocyanic acid or ammonia with the help of water which is generated during the formate formation, decomposition and/or NCO formation steps.

  2. Transition-Metal-Free Cyclopropanation of 2-Aminoacrylates with N-Tosylhydrazones: A General Route to Cyclopropane α-Amino Acid with Contiguous Quaternary Carbon Centers.

    PubMed

    Zhu, Chuanle; Li, Jiawei; Chen, Pengquan; Wu, Wanqing; Ren, Yanwei; Jiang, Huanfeng

    2016-03-18

    Cyclopropanation of 2-aminoacrylates with N-tosylhydrazones could proceed smoothly under transition-metal-free conditions via a [3 + 2] cycloaddition process. This robust protocol exhibits excellent generality, delivering a wide spectrum of cyclopropane α-amino acid esters bearing contiguous quaternary carbon centers in high yields and diastereoselectivities. With these readily available products, the steric convergence of cyclopropane α-amino acids could be readily obtained.

  3. NIS-catalyzed oxidative cyclization of alcohols with amidines: a simple and efficient transition-metal free method for the synthesis of 1,3,5-triazines.

    PubMed

    Tiwari, Abhishek R; T, Akash; Bhanage, Bhalchandra M

    2015-12-01

    An efficient method for the synthesis of 1,3,5-triazines by NIS-catalyzed oxidative cyclization of alcohols with amidines has been developed. The reaction works smoothly under transition-metal free and phosphine-free conditions to afford a wide range of 1,3,5-triazine derivatives in moderate to good yields. The synthetic methodology was achieved via in situ oxidation of alcohols to aldehydes. PMID:26477749

  4. Syntheses of [1,2,4]triazolo[1,5-a]benzazoles enabled by the transition-metal-free oxidative N-N bond formation.

    PubMed

    Shang, Erchang; Zhang, Junzhi; Bai, Jinyi; Wang, Zhan; Li, Xiang; Zhu, Bing; Lei, Xiaoguang

    2016-05-19

    A transition-metal-free oxidative N-N bond formation strategy was developed to generate various structurally interesting [1,2,4]triazolo[1,5-a]benzazoles efficiently. The mechanism of the key oxidative N-N bond formation was investigated by using an intramolecular competition reaction. Notably, the first single crystal structure was also obtained to confirm the structure of 2-aryl[1,2,4]triazolo[1,5-a]benzimidazole. PMID:27161847

  5. Transition-Metal-Free Coupling of Alkynes with α-Bromo Carbonyl Compounds: An Efficient Approach towards β,γ-Alkynoates and Allenoates.

    PubMed

    Liu, Wenbo; Chen, Zhengwang; Li, Lu; Wang, Haining; Li, Chao-Jun

    2016-04-18

    A direct transition-metal-free coupling between alkynes and α-bromo carbonyl compounds has been developed with ultraviolet (UV) light in aqueous media. This method represents a facile approach to synthetically useful β,γ-alkynyl esters and amides stereoselectively from two readily available starting materials. As an example of the synthetic application of the products, the alkynyl esters were readily converted into allenoates. PMID:26910833

  6. Base-promoted synthesis of coumarins from salicylaldehydes and aryl-substituted 1,1-dibromo-1-alkenes under transition-metal-free conditions.

    PubMed

    Liu, Jianming; Zhang, Xin; Shi, Lijun; Liu, Muwen; Yue, Yuanyuan; Li, Fuwei; Zhuo, Kelei

    2014-09-01

    Facile synthesis of coumarin via the tandem reaction of salicylaldehyde with aryl-substituted 1,1-dibromo-1-alkene was developed. This new protocol proceeds smoothly under mild and transition-metal-free conditions, it allows rapid access to coumarins containing various heteroatoms that are more difficult to prepare by traditional methods. Based on the isolated intermediate of 4-(diethylamino)-3-phenylchroman-2-one and detailed mechanistic studies, a credible tandem pathway was proposed. PMID:25027244

  7. Transition-metal free reactions of boronic acids: cascade addition - ring-opening of furans towards functionalized γ-ketoaldehydes.

    PubMed

    Roscales, S; Csákÿ, A G

    2016-02-18

    We describe the first ring-opening of furfuryl alcohols with boronic acids to afford functionalized γ-ketoaldehydes. The transformation builds a new C-C bond at the original C-4 of the starting furan, and tolerates ring-substitution at C-3 and C-4 positions. The reaction takes place under metal-free conditions by promotion with tartaric acid.

  8. Transition-metal-free carbofluorination of TBS-protected nitrogen-containing cyclic enynols: synthesis of fluorinated azabicycles.

    PubMed

    Yeh, Ming-Chang P; Liang, Chia-Jung; Huang, Tzu-Lin; Hsu, Hsiao-Ju; Tsau, Yu-Shuo

    2013-06-01

    The synthesis of fluorinated azabicycles from tert-butyldimethylsilyl-protected N-containing cyclic enynols using inexpensive BF3·OEt2 is described. In this reaction, BF3 reacts as both the Lewis acid and the fluoride source for cyclization/fluorination of the TBS-protected cyclic N-containing enynols. The method provides an easy access to fluorinated azabicycles where a new C(sp(2))-F bond and a new bicyclic skeleton are generated at ambient temperature within 1-13 min under metal-free reaction conditions.

  9. Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp(2) C-H and sp(3) C-H bonds.

    PubMed

    Kumar, Nivesh; Ghosh, Santanu; Bhunia, Subhajit; Bisai, Alakesh

    2016-01-01

    The synthesis of a variety of 2-oxindoles bearing an all-carbon quaternary center at the pseudo benzylic position has been achieved via a 'transition-metal-free' intramolecular dehydrogenative coupling (IDC). The construction of 2-oxindole moieties was carried out through formation of carbon-carbon bonds using KOt-Bu-catalyzed one pot C-alkylation of β-N-arylamido esters with alkyl halides followed by a dehydrogenative coupling. Experimental evidences indicated toward a radical-mediated path for this reaction. PMID:27559367

  10. Transition-Metal-Free Cross-Coupling of Indium Organometallics with Chromene and Isochroman Acetals Mediated by BF3·OEt2.

    PubMed

    Gil-Negrete, José M; Pérez Sestelo, José; Sarandeses, Luis A

    2016-09-01

    A transition-metal-free coupling of triorganoindium reagents with benzopyranyl acetals mediated by a Lewis acid has been developed. The reaction of R3In with chromene and isochroman acetals in the presence of BF3·OEt2 afforded 2-substituted chromenes and 1-substituted isochromans, respectively, in good yields. The reactions proceed with a variety of triorganoindium reagents (aryl, heteroaryl, alkynyl, alkenyl, alkyl) using only 50 mol % of the organometallic, thus demonstrating the efficiency of these species. Preliminary mechanistic studies indicate the formation of an oxocarbenium ion intermediate in the presence of the Lewis acid. PMID:27530143

  11. Beyond Metal-Hydrides: Non-Transition-Metal and Metal-Free Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation.

    PubMed

    Haddad, Andrew Z; Garabato, Brady D; Kozlowski, Pawel M; Buchanan, Robert M; Grapperhaus, Craig A

    2016-06-29

    A new pathway for homogeneous electrocatalytic H2 evolution and H2 oxidation has been developed using a redox active thiosemicarbazone and its zinc complex as seminal metal-free and transition-metal-free examples. Diacetyl-bis(N-4-methyl-3-thiosemicarbazone) and zinc diacetyl-bis(N-4-methyl-3-thiosemicarbazide) display the highest reported TOFs of any homogeneous ligand-centered H2 evolution catalyst, 1320 and 1170 s(-1), respectively, while the zinc complex also displays one of the highest reported TOF values for H2 oxidation, 72 s(-1), of any homogeneous catalyst. Catalysis proceeds via ligand-centered proton-transfer and electron-transfer events while avoiding traditional metal-hydride intermediates. The unique mechanism is consistent with electrochemical results and is further supported by density functional theory. The results identify a new direction for the design of electrocatalysts for H2 evolution and H2 oxidation that are not reliant on metal-hydride intermediates. PMID:27326672

  12. KO(t)Bu-Mediated Coupling of Indoles and [60]Fullerene: Transition-Metal-Free and General Synthesis of 1,2-(3-Indole)(hydro)[60]fullerenes.

    PubMed

    Li, Fei; Haj Elhussin, Imad Elddin; Li, Shengli; Zhou, Hongping; Wu, Jieying; Tian, Yupeng

    2015-11-01

    Direct coupling of indoles with C60 has been achieved for the first time. Transition-metal-free KO(t)Bu-mediated reaction of indoles to [60]fullerene has been developed as a practical and efficient method for the synthesis of various 1,2-(3-indole)(hydro)[60]fullerenes that are otherwise difficult to direct synthesize in an efficient and selective manner. This methodology tolerates sensitive functionalities such as chloro, ester, and nitro on indole and builds molecular complexity rapidly, with most reactions reaching completion in <1 h. A plausible reaction mechanism is proposed to explain the high regioselectivity at the 3-position of the indoles and the formation of 1,2-(3-indole)(hydro)[60]fullerenes.

  13. Transition-metal-free C-H oxidative activation: persulfate-promoted selective benzylic mono- and difluorination.

    PubMed

    Ma, Jing-jing; Yi, Wen-bin; Lu, Guo-ping; Cai, Chun

    2015-03-14

    An operationally simple and selective method for the direct conversion of benzylic C-H to C-F to obtain mono- and difluoromethylated arenes using Selectfluor™ as a fluorine source is developed. Persulfate can be used to selectively activate benzylic hydrogen atoms toward C-F bond formation without the aid of transition metal catalysts.

  14. Transition Metal-Free Selective Double sp(3) C-H Oxidation of Cyclic Amines to 3-Alkoxyamine Lactams.

    PubMed

    Osorio-Nieto, Urbano; Chamorro-Arenas, Delfino; Quintero, Leticia; Höpfl, Herbert; Sartillo-Piscil, Fernando

    2016-09-16

    The first chemical method for selective dual sp(3) C-H functionalization at the alpha-and beta positions of cyclic amines to their corresponding 3-alkoxyamine lactams is reported. Unlike traditional Cα-H oxidation of amines to amides mediated by transition metals, the present protocol, which involves the use of NaClO2/TEMPO/NaClO in either aqueous or organic solvent, not only allows the Cα-H oxidation but also the subsequent functionalization of the unreactive β-methylene group in an unprecedented tandem fashion and using environmentally friendly reactants.

  15. Transition Metal-Free Selective Double sp(3) C-H Oxidation of Cyclic Amines to 3-Alkoxyamine Lactams.

    PubMed

    Osorio-Nieto, Urbano; Chamorro-Arenas, Delfino; Quintero, Leticia; Höpfl, Herbert; Sartillo-Piscil, Fernando

    2016-09-16

    The first chemical method for selective dual sp(3) C-H functionalization at the alpha-and beta positions of cyclic amines to their corresponding 3-alkoxyamine lactams is reported. Unlike traditional Cα-H oxidation of amines to amides mediated by transition metals, the present protocol, which involves the use of NaClO2/TEMPO/NaClO in either aqueous or organic solvent, not only allows the Cα-H oxidation but also the subsequent functionalization of the unreactive β-methylene group in an unprecedented tandem fashion and using environmentally friendly reactants. PMID:27564379

  16. Transition-Metal-Free Cascade Synthesis of 4-Quinolones: Umpolung of Michael Acceptors via Ene Reaction with Arynes.

    PubMed

    Santhosh Reddy, R; Lagishetti, Chandraiah; Kiran, I N Chaithanya; You, Hengyao; He, Yun

    2016-08-01

    A novel "one-pot" aryne transformation is described that affords various 4-quinolone derivatives without recourse to transition-metal catalysis. Arynes react with aza-Morita-Baylis-Hillman (AMBH) adducts through a cascade sequence involving an insertion/cyclization/ene reaction process to afford 4-quinolones in high yields with a broad substrate scope under mild reaction conditions. Essentially, an umpolung of reactivity at the β carbon of α,β-unsaturated ketone has been achieved by an inverse electron demand aryne-ene reaction to provide a C-arylated product. PMID:27434217

  17. Synthesis of Dibenzosultams by "Transition-Metal-Free" Photoinduced Intramolecular Arylation of N-Aryl-2-halobenzenesulfonamides.

    PubMed

    Guerra, Walter D; Rossi, Roberto A; Pierini, Adriana B; Barolo, Silvia M

    2016-06-17

    A new and general synthetic route to prepare dibenzosultams is here reported. This approach involves the synthesis of N-aryl-2-halobenzenesulfonamides (3), followed by intramolecular C-C photoinduced arylation under soft conditions without the use of "Transition Metal". The photostimulated reactions exhibit very good tolerance to different substituent groups with good to excellent isolated yields (42-98%) of products. Moreover, it is shown that LED (λ = 395 nm) is an efficient light energy source to initiate efficiently the reactions. Theoretical inspection of the mechanism was made to probe the involvement of the radical-anion SRN1 process. PMID:27166973

  18. Metal-free and transition-metal tetraferrocenylporphyrins part 1: synthesis, characterization, electronic structure, and conformational flexibility of neutral compounds.

    PubMed

    Nemykin, Victor N; Galloni, Pierluca; Floris, Barbara; Barrett, Christopher D; Hadt, Ryan G; Subbotin, Roman I; Marrani, Andrea G; Zanoni, Robertino; Loim, Nikolay M

    2008-08-28

    H(2)TFcP [TFcP = 5,10,15,20-tetraferrocenyl porphyrin(2-)] was prepared by a direct tetramerization reaction between pyrrole and ferrocene carbaldehyde in the presence of a BF(3) catalyst, while the series of MTFcP (M = Zn, Ni, Co and Cu) were prepared by a metallation reaction between H(2)TFcP and respective metal acetates. All compounds were characterized by UV-vis and MCD spectroscopy, APCI MS and MS/MS methods, high-resolution ESI MS and XPS spectroscopy. Diamagnetic compounds were additionally characterized using (1)H and (13)C NMR methods, while the presence of low-spin iron(ii) centers in the neutral compounds was confirmed by Mössbauer spectroscopy and by analysis of the XPS Fe 2p peaks, revealing equivalent Fe sites. XPS additionally showed the influence on Fe 2p binding energies exerted by the distinct central metal ions. The conformational flexibility of ferrocene substituents in H(2)TFcP and MTFcP, was confirmed using variable-temperature NMR and computational methods. Density functional theory predicts that alpha,beta,alpha,beta atropisomers with ruffled porphyrin cores represent minima on the potential energy surfaces of both H(2)TFcP and MTFcP. The degree of non-planarity is central-metal dependent and follows the trend: ZnTFcP < H(2)TFcP approximately CuTFcP < CoTFcP < NiTFcP. In all cases, a set of occupied, predominantly ferrocene-based molecular orbitals were found between the highest occupied and the lowest unoccupied, predominantly porphyrin-based molecular orbitals. The vertical excitation energies of H(2)TFcP were calculated at the TDDFT level and confirm the presence of numerous predominantly metal-to-ligand charge-transfer bands coupled via configurational interaction with expected intra-ligand pi-pi* transitions.

  19. Facile Access to Fluoroaromatic Molecules by Transition-Metal-Free C-F Bond Cleavage of Polyfluoroarenes: An Efficient, Green, and Sustainable Protocol.

    PubMed

    Liu, Cuibo; Zhang, Bin

    2016-04-01

    The creation of new bonds via C-F bond cleavage of polyfluoroarenes has proven to be an important and powerful tool in synthetic chemistry. Using such a strategy, a myriad of valuable partially fluoroaromatic molecules and building blocks can be obtained. The transition-metal-free nucleophilic aromatic substitution (SN Ar) strategy has aroused the continuing interest of researchers due to its simple, mild, economical, and environmentally benign characteristics, which have been successfully applied to C-F bond functionalizations. In this account, we present a summary of the recent investigations of polyfluoroarenes involving SN Ar reactions and discuss some of our recent endeavors in the construction of partially fluoroaromatic molecules. Through this strategy, many new bonds including C-C, C-N, C-O, C-S, and C-H bonds can be created. Additionally, brief discussions on the transformation mechanisms are also provided. Finally, we discuss the existing limitations of the SN Ar reactions of polyfluoroarenes as well as our perspective on the future development of this chemistry.

  20. Direct synthesis of 2-aryl-4-quinolones via transition-metal-free intramolecular oxidative C(sp(3))-H/C(sp(3))-H coupling.

    PubMed

    Hu, Wei; Lin, Jian-Ping; Song, Li-Rui; Long, Ya-Qiu

    2015-03-01

    A novel, metal-free oxidative intramolecular Mannich reaction was developed between secondary amines and unmodified ketones, affording a simple and direct access to a broad range of 2-arylquinolin-4(1H)-ones through C(sp(3))-H activation/C(sp(3))-C(sp(3)) bond formation from readily available N-arylmethyl-2-aminophenylketones, using TEMPO as the oxidant and KO(t)Bu as the base.

  1. Reusable fast opening switch

    DOEpatents

    Van Devender, John P.; Emin, David

    1986-01-01

    A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and insulating states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

  2. Reusable fast opening switch

    DOEpatents

    Van Devender, J.P.; Emin, D.

    1983-12-21

    A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and metallic states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

  3. Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp2 C–H and sp3 C–H bonds

    PubMed Central

    Bhunia, Subhajit

    2016-01-01

    Summary The synthesis of a variety of 2-oxindoles bearing an all-carbon quaternary center at the pseudo benzylic position has been achieved via a ‘transition-metal-free’ intramolecular dehydrogenative coupling (IDC). The construction of 2-oxindole moieties was carried out through formation of carbon–carbon bonds using KOt-Bu-catalyzed one pot C-alkylation of β-N-arylamido esters with alkyl halides followed by a dehydrogenative coupling. Experimental evidences indicated toward a radical-mediated path for this reaction. PMID:27559367

  4. Investigation of the Qx -Qy Equilibrium in a Metal-Free Phthalocyanine.

    PubMed

    Baeten, Yannick; Fron, Eduard; Ruzié, Christian; Geerts, Yves Henri; Van Der Auweraer, Mark

    2015-12-21

    Phthalocyanines (Pcs) have attracted a lot of interest as small molecules for organic electronics. However, some excited-state properties of metal-free phthalocyanines, as for example, the dynamics of the transition between the nondegenerate Qx and Qy states in a metal-free phthalocyanine, have not been fully established. This effect results in a blue-shifted shoulder with low intensity in the Pc fluorescence spectrum. This shoulder was suggested to be related to emission from the more energetic Qy state. By using ultrafast femtosecond transient absorption, we have found a clear equilibrium between the Qx and Qy state of metal-free phthalocyanines in solution.

  5. Investigation of the Qx -Qy Equilibrium in a Metal-Free Phthalocyanine.

    PubMed

    Baeten, Yannick; Fron, Eduard; Ruzié, Christian; Geerts, Yves Henri; Van Der Auweraer, Mark

    2015-12-21

    Phthalocyanines (Pcs) have attracted a lot of interest as small molecules for organic electronics. However, some excited-state properties of metal-free phthalocyanines, as for example, the dynamics of the transition between the nondegenerate Qx and Qy states in a metal-free phthalocyanine, have not been fully established. This effect results in a blue-shifted shoulder with low intensity in the Pc fluorescence spectrum. This shoulder was suggested to be related to emission from the more energetic Qy state. By using ultrafast femtosecond transient absorption, we have found a clear equilibrium between the Qx and Qy state of metal-free phthalocyanines in solution. PMID:26346288

  6. Reusable Autonomy

    NASA Technical Reports Server (NTRS)

    Truszkowski, Walt; Obenschain, Arthur F. (Technical Monitor)

    2002-01-01

    highlights some of the major issues that need to be addressed when considering the situation where Group A is composed of software-based agents (not their human counterparts) and they migrate from one mission support system to another. This paper will address: - definition of an agent architecture appropriate to support reuse; - identification of non-mission-specific agent capabilities required; - appropriate knowledge representation schemes for mission-specific knowledge; - agent interface with mission-specific knowledge (a type of Learning); development of a fully-operational group of cooperative software agents for ground system support; architecture and operation of a repository of reusable agents that could be the source of intelligent components for realizing an autonomous (or nearly autonomous) agent-based ground system, and an agent-based approach to repository management and operation (an intelligent interface for human use of the repository in a ground-system development activity).

  7. Metal-free direct intramolecular carbotrifluoromethylation of alkenes to functionalized trifluoromethyl azaheterocycles.

    PubMed

    Li, Lei; Deng, Min; Zheng, Sheng-Cai; Xiong, Ya-Ping; Tan, Bin; Liu, Xin-Yuan

    2014-01-17

    The first example of a metal-free direct carbotrifluoromethylation of alkenes using inexpensive TMSCF3 as the CF3 source is described. The methodology not only exhibits high chemoselectivity for this transformation but also expands the substrate scope that is difficult to access by known transition-metal-catalyzed methods. PMID:24351111

  8. Metal-free transfer hydrogenation of olefins via dehydrocoupling catalysis

    PubMed Central

    Pérez, Manuel; Caputo, Christopher B.; Dobrovetsky, Roman; Stephan, Douglas W.

    2014-01-01

    A major advance in main-group chemistry in recent years has been the emergence of the reactivity of main-group species that mimics that of transition metal complexes. In this report, the Lewis acidic phosphonium salt [(C6F5)3PF][B(C6F5)4] 1 is shown to catalyze the dehydrocoupling of silanes with amines, thiols, phenols, and carboxylic acids to form the Si-E bond (E = N, S, O) with the liberation of H2 (21 examples). This catalysis, when performed in the presence of a series of olefins, yields the concurrent formation of the products of dehydrocoupling and transfer hydrogenation of the olefin (30 examples). This reactivity provides a strategy for metal-free catalysis of olefin hydrogenations. The mechanisms for both catalytic reactions are proposed and supported by experiment and density functional theory calculations. PMID:25002489

  9. Knowledge-based reusable software synthesis system

    NASA Technical Reports Server (NTRS)

    Donaldson, Cammie

    1989-01-01

    The Eli system, a knowledge-based reusable software synthesis system, is being developed for NASA Langley under a Phase 2 SBIR contract. Named after Eli Whitney, the inventor of interchangeable parts, Eli assists engineers of large-scale software systems in reusing components while they are composing their software specifications or designs. Eli will identify reuse potential, search for components, select component variants, and synthesize components into the developer's specifications. The Eli project began as a Phase 1 SBIR to define a reusable software synthesis methodology that integrates reusabilityinto the top-down development process and to develop an approach for an expert system to promote and accomplish reuse. The objectives of the Eli Phase 2 work are to integrate advanced technologies to automate the development of reusable components within the context of large system developments, to integrate with user development methodologies without significant changes in method or learning of special languages, and to make reuse the easiest operation to perform. Eli will try to address a number of reuse problems including developing software with reusable components, managing reusable components, identifying reusable components, and transitioning reuse technology. Eli is both a library facility for classifying, storing, and retrieving reusable components and a design environment that emphasizes, encourages, and supports reuse.

  10. Reusable Software Technology

    NASA Technical Reports Server (NTRS)

    Morgan, Timothy E.

    1995-01-01

    The objective of the Reusable Software System (RSS) is to provide NASA Langley Research Center and its contractor personnel with a reusable software technology through the Internet. The RSS is easily accessible, provides information that is extractable, and the capability to submit information or data for the purpose of scientific research at NASA Langley Research Center within the Atmospheric Science Division.

  11. Reactivity of Metal-Free and Metal-Associated Amyloid-β with Glycosylated Polyphenols and Their Esterified Derivatives

    PubMed Central

    Korshavn, Kyle J.; Jang, Milim; Kwak, Yeon Ju; Kochi, Akiko; Vertuani, Silvia; Bhunia, Anirban; Manfredini, Stefano; Ramamoorthy, Ayyalusamy; Lim, Mi Hee

    2015-01-01

    Both amyloid-β (Aβ) and transition metal ions are shown to be involved in the pathogenesis of Alzheimer’s disease (AD), though the importance of their interactions remains unclear. Multifunctional molecules, which can target metal-free and metal-bound Aβ and modulate their reactivity (e.g., Aβ aggregation), have been developed as chemical tools to investigate their function in AD pathology; however, these compounds generally lack specificity or have undesirable chemical and biological properties, reducing their functionality. We have evaluated whether multiple polyphenolic glycosides and their esterified derivatives can serve as specific, multifunctional probes to better understand AD. The ability of these compounds to interact with metal ions and metal-free/-associated Aβ, and further control both metal-free and metal-induced Aβ aggregation was investigated through gel electrophoresis with Western blotting, transmission electron microscopy, UV-Vis spectroscopy, fluorescence spectroscopy, and NMR spectroscopy. We also examined the cytotoxicity of the compounds and their ability to mitigate the toxicity induced by both metal-free and metal-bound Aβ. Of the polyphenols investigated, the natural product (Verbascoside) and its esterified derivative (VPP) regulate the aggregation and cytotoxicity of metal-free and/or metal-associated Aβ to different extents. Our studies indicate Verbascoside represents a promising structure for further multifunctional tool development against both metal-free Aβ and metal-Aβ. PMID:26657338

  12. Reactivity of Metal-Free and Metal-Associated Amyloid-β with Glycosylated Polyphenols and Their Esterified Derivatives.

    PubMed

    Korshavn, Kyle J; Jang, Milim; Kwak, Yeon Ju; Kochi, Akiko; Vertuani, Silvia; Bhunia, Anirban; Manfredini, Stefano; Ramamoorthy, Ayyalusamy; Lim, Mi Hee

    2015-12-10

    Both amyloid-β (Aβ) and transition metal ions are shown to be involved in the pathogenesis of Alzheimer's disease (AD), though the importance of their interactions remains unclear. Multifunctional molecules, which can target metal-free and metal-bound Aβ and modulate their reactivity (e.g., Aβ aggregation), have been developed as chemical tools to investigate their function in AD pathology; however, these compounds generally lack specificity or have undesirable chemical and biological properties, reducing their functionality. We have evaluated whether multiple polyphenolic glycosides and their esterified derivatives can serve as specific, multifunctional probes to better understand AD. The ability of these compounds to interact with metal ions and metal-free/-associated Aβ, and further control both metal-free and metal-induced Aβ aggregation was investigated through gel electrophoresis with Western blotting, transmission electron microscopy, UV-Vis spectroscopy, fluorescence spectroscopy, and NMR spectroscopy. We also examined the cytotoxicity of the compounds and their ability to mitigate the toxicity induced by both metal-free and metal-bound Aβ. Of the polyphenols investigated, the natural product (Verbascoside) and its esterified derivative (VPP) regulate the aggregation and cytotoxicity of metal-free and/or metal-associated Aβ to different extents. Our studies indicate Verbascoside represents a promising structure for further multifunctional tool development against both metal-free Aβ and metal-Aβ.

  13. Reactivity of Metal-Free and Metal-Associated Amyloid-β with Glycosylated Polyphenols and Their Esterified Derivatives

    NASA Astrophysics Data System (ADS)

    Korshavn, Kyle J.; Jang, Milim; Kwak, Yeon Ju; Kochi, Akiko; Vertuani, Silvia; Bhunia, Anirban; Manfredini, Stefano; Ramamoorthy, Ayyalusamy; Lim, Mi Hee

    2015-12-01

    Both amyloid-β (Aβ) and transition metal ions are shown to be involved in the pathogenesis of Alzheimer’s disease (AD), though the importance of their interactions remains unclear. Multifunctional molecules, which can target metal-free and metal-bound Aβ and modulate their reactivity (e.g., Aβ aggregation), have been developed as chemical tools to investigate their function in AD pathology; however, these compounds generally lack specificity or have undesirable chemical and biological properties, reducing their functionality. We have evaluated whether multiple polyphenolic glycosides and their esterified derivatives can serve as specific, multifunctional probes to better understand AD. The ability of these compounds to interact with metal ions and metal-free/-associated Aβ, and further control both metal-free and metal-induced Aβ aggregation was investigated through gel electrophoresis with Western blotting, transmission electron microscopy, UV-Vis spectroscopy, fluorescence spectroscopy, and NMR spectroscopy. We also examined the cytotoxicity of the compounds and their ability to mitigate the toxicity induced by both metal-free and metal-bound Aβ. Of the polyphenols investigated, the natural product (Verbascoside) and its esterified derivative (VPP) regulate the aggregation and cytotoxicity of metal-free and/or metal-associated Aβ to different extents. Our studies indicate Verbascoside represents a promising structure for further multifunctional tool development against both metal-free Aβ and metal-Aβ.

  14. Recent Advances in Metal-Free Quinoline Synthesis.

    PubMed

    Ramann, Ginelle A; Cowen, Bryan J

    2016-01-01

    The quinoline ring system is one of the most ubiquitous heterocycles in the fields of medicinal and industrial chemistry, forming the scaffold for compounds of great significance. These include anti-inflammatory and antitumor agents, the antimalarial drugs quinine and chloroquine, and organic light-emitting diodes. Quinolines were first synthesized in 1879, and since then a multitude of synthetic routes have been developed. Many of these methods, such as the Skraup, Doebner-Von Miller, and Friedlander quinoline syntheses, are well-known but suffer from inefficiency, harsh reaction conditions, and toxic reagents. This review focuses on recent transition metal-free processes toward these important heterocycles, including both novel routes and modifications to established methods. For example, variations on the Skraup method include microwave irradiation, ionic liquid media, and novel annulation partners, all of which have shown increased reaction efficiency and improved yield of the heteroring-unsubstituted quinoline products. Similarly, modifications to other synthetic routes have been implemented, with the quinoline products displaying a wide variety of substitution patterns. PMID:27483222

  15. Using reusable learning objects.

    PubMed

    Billings, Diane M

    2010-02-01

    Reusable learning objects (RLOs) are predeveloped digital learning activities that can be integrated into lessons, modules, and courses. Several repositories have nursing-specific RLOs waiting to be used by nurse educators.

  16. Silica reusable surface insulation

    NASA Technical Reports Server (NTRS)

    Goldstein, H. E.; Smith, M.; Leiser, D. B. (Inventor)

    1976-01-01

    A reusable silica surface insulation material is provided by bonding amorphous silica fibers with colloidal silica at an elevated temperature. The surface insulation is ordinarily manufactured in the form of blocks (i.e., tiles).

  17. Suppressing molecular motions for enhanced room-temperature phosphorescence of metal-free organic materials

    PubMed Central

    Kwon, Min Sang; Yu, Youngchang; Coburn, Caleb; Phillips, Andrew W.; Chung, Kyeongwoon; Shanker, Apoorv; Jung, Jaehun; Kim, Gunho; Pipe, Kevin; Forrest, Stephen R.; Youk, Ji Ho; Gierschner, Johannes; Kim, Jinsang

    2015-01-01

    Metal-free organic phosphorescent materials are attractive alternatives to the predominantly used organometallic phosphors but are generally dimmer and are relatively rare, as, without heavy-metal atoms, spin–orbit coupling is less efficient and phosphorescence usually cannot compete with radiationless relaxation processes. Here we present a general design rule and a method to effectively reduce radiationless transitions and hence greatly enhance phosphorescence efficiency of metal-free organic materials in a variety of amorphous polymer matrices, based on the restriction of molecular motions in the proximity of embedded phosphors. Covalent cross-linking between phosphors and polymer matrices via Diels–Alder click chemistry is devised as a method. A sharp increase in phosphorescence quantum efficiency is observed in a variety of polymer matrices with this method, which is ca. two to five times higher than that of phosphor-doped polymer systems having no such covalent linkage. PMID:26626796

  18. Suppressing molecular motions for enhanced room-temperature phosphorescence of metal-free organic materials.

    PubMed

    Kwon, Min Sang; Yu, Youngchang; Coburn, Caleb; Phillips, Andrew W; Chung, Kyeongwoon; Shanker, Apoorv; Jung, Jaehun; Kim, Gunho; Pipe, Kevin; Forrest, Stephen R; Youk, Ji Ho; Gierschner, Johannes; Kim, Jinsang

    2015-01-01

    Metal-free organic phosphorescent materials are attractive alternatives to the predominantly used organometallic phosphors but are generally dimmer and are relatively rare, as, without heavy-metal atoms, spin-orbit coupling is less efficient and phosphorescence usually cannot compete with radiationless relaxation processes. Here we present a general design rule and a method to effectively reduce radiationless transitions and hence greatly enhance phosphorescence efficiency of metal-free organic materials in a variety of amorphous polymer matrices, based on the restriction of molecular motions in the proximity of embedded phosphors. Covalent cross-linking between phosphors and polymer matrices via Diels-Alder click chemistry is devised as a method. A sharp increase in phosphorescence quantum efficiency is observed in a variety of polymer matrices with this method, which is ca. two to five times higher than that of phosphor-doped polymer systems having no such covalent linkage. PMID:26626796

  19. Synthesis of C60-Fused Tetrahydrocarbazole/Dibenzothiophene/Benzothiophene and Dibenzofuran Derivatives via Metal-Free Oxidative Dehydrogenative Carboannulation.

    PubMed

    Liu, Tong-Xin; Ma, Jinliang; Chao, Di; Zhang, Pengling; Ma, Nana; Liu, Qingfeng; Shi, Lei; Zhang, Zhiguo; Zhang, Guisheng

    2016-08-19

    A transition-metal-free oxidative dehydrogenative coupling reaction has been developed for the direct construction of novel C60-fused tetrahydrocarbazoles, dibenzothiophenes, benzothiophenes, and dibenzofurans. This new carboannulation reaction features high atom economy, operational simplicity, broad substrate scope, and excellent functional-group tolerance and provides a convenient access to a scarce class of fullerene derivatives. PMID:27487008

  20. Peroxide promoted tunable decarboxylative alkylation of cinnamic acids to form alkenes or ketones under metal-free conditions.

    PubMed

    Ji, Jing; Liu, Ping; Sun, Peipei

    2015-05-01

    A tunable decarboxylative alkylation of cinnamic acids with alkanes was developed to form alkenes or ketones under transition metal-free conditions. In the presence of DTBP or DTBP/TBHP, the reaction gave alkenes and ketones respectively via a radical mechanism in moderate to good yields.

  1. Stealth polymeric vesicles via metal-free click coupling.

    PubMed

    Isaacman, Michael J; Corigliano, Eleonora M; Theogarajan, Luke S

    2013-09-01

    The strain-promoted azide-alkyne cycloaddition represents an optimal metal-free method for the modular coupling of amphiphilic polymer blocks. Hydrophilic poly(oxazoline) (PMOXA) or poly(ethylene glycol) (PEG) A-blocks were coupled with a hydrophobic poly(siloxane) B-block to provide triblock copolymers capable of self-assembling into vesicular nanostructures. Stealth properties investigated via a complement activation assay revealed the superior in vitro stealth attributes of polymeric vesicles synthesized via a metal-free approach to those coupled via the widely used copper-catalyzed click method. Furthermore, the ability to change a single parameter, such as the hydrophilic block, allowed the direct comparison of the biocompatibility properties of triblock copolymers containing PMOXA or PEG. Our studies convincingly demonstrate the need for a metal-free approach, both in preventing cytotoxicity while imparting optimal stealth properties for potential biomedical applications.

  2. Metal-free carbonylations by photoredox catalysis.

    PubMed

    Majek, Michal; Jacobi von Wangelin, Axel

    2015-02-01

    The synthesis of benzoates from aryl electrophiles and carbon monoxide is a prime example of a transition-metal-catalyzed carbonylation reaction which is widely applied in research and industrial processes. Such reactions proceed in the presence of Pd or Ni catalysts, suitable ligands, and stoichiometric bases. We have developed an alternative procedure that is free of any metal, ligand, and base. The method involves a redox reaction driven by visible light and catalyzed by eosin Y which affords alkyl benzoates from arene diazonium salts, carbon monoxide, and alcohols under mild conditions. Tertiary esters can also be prepared in high yields. DFT calculations and radical trapping experiments support a catalytic photoredox pathway without the requirement for sacrificial redox partners.

  3. REUSABLE REACTION VESSEL

    DOEpatents

    Soine, T.S.

    1963-02-26

    This patent shows a reusable reaction vessel for such high temperature reactions as the reduction of actinide metal chlorides by calcium metal. The vessel consists of an outer metal shell, an inner container of refractory material such as sintered magnesia, and between these, a bed of loose refractory material impregnated with thermally conductive inorganic salts. (AEC)

  4. Reusable Release Mechanism

    NASA Technical Reports Server (NTRS)

    Bunker, J. W.; Ritchie, R. S.

    1984-01-01

    Slider release mechanism reusable. Bears heavy loads while latched, yet gives smooth release motion. Release effected by explosively driving perpendicular slider out of engagement with load-bearing shank. Device has potential industrial applications such as emergency release of lifting cables from helicopters, cranes and hoists.

  5. Reusable thermal cycling clamp

    NASA Technical Reports Server (NTRS)

    Debnam, W. J., Jr.; Fripp, A. L.; Crouch, R. K. (Inventor)

    1985-01-01

    A reusable metal clamp for retaining a fused quartz ampoule during temperature cycling in the range of 20 deg C to 1000 deg C is described. A compressible graphite foil having a high radial coefficient of thermal expansion is interposed between the fused quartz ampoule and metal clamp to maintain a snug fit between these components at all temperature levels in the cycle.

  6. Metal-Free Chemoselective Oxidative Dehomologation or Direct Oxidation of Alcohols: Implication for Biomass Conversion.

    PubMed

    Kim, Sun Min; Shin, Hun Yi; Kim, Dong Wan; Yang, Jung Woon

    2016-02-01

    A transition metal-free, chemoselective reaction was performed using the sodium tert-butoxide-oxygen (NaO(t) Bu-O2 ) system, resulting in either oxidative dehomologation or direct oxidation of alcohols. In particular, the newly developed protocol may be used to predict the major product formed, which depends on alkyl chain length of the alcohols and reaction conditions. The rational mechanism of this transformation was also demonstrated by performing an (18) O isotopic labelling experiment. This protocol presents a straightforward method for biomass conversion of a lignin model compound to phenol and benzoic acid.

  7. Noble-metal-free plasmonic photocatalyst: hydrogen doped semiconductors

    PubMed Central

    Ma, Xiangchao; Dai, Ying; Yu, Lin; Huang, Baibiao

    2014-01-01

    The unique capacity of localized surface plasmon resonance (LSPR) offers a new opportunity to overcome the limited efficiency of semiconductor photocatalyst. Here we unravel that LSPR, which usually occurs in noble metal nanoparticles, can be realized by hydrogen doping in noble-metal-free semiconductor using TiO2 as a model photocatalyst. Moreover, its LSPR is located in infrared region, which supplements that of noble metal whose LSPR is generally in the visible region, making it possible to extend the light response of photocatalyst to infrared region. The near field enhancement is shown to be comparable with that of noble-metal nanoparticles, indicating that highly enhanced light absorption rate can be expected. The present work can provide a key guideline for the creation of highly efficient noble-metal-free plasmonic photocatalysts and have a much wider impact in infrared bioimaging and spectroscopy where infrared LSPR is essential. PMID:24496400

  8. Room Temperature, Metal-Free Arylation of Aliphatic Alcohols

    PubMed Central

    Ghosh, Raju; Lindstedt, Erik; Jalalian, Nazli; Olofsson, Berit

    2014-01-01

    Diaryliodonium salts are demonstrated as efficient arylating agents of aliphatic alcohols under metal-free conditions. The reaction proceeds at room temperature within 90 min to give alkyl aryl ethers in good to excellent yields. Aryl groups with electron-withdrawing substituents are transferred most efficiently, and unsymmetric iodonium salts give chemoselective arylations. The methodology has been applied to the formal synthesis of butoxycaine. PMID:24808991

  9. Topological Defects in Metal-Free Nanocarbon for Oxygen Electrocatalysis.

    PubMed

    Tang, Cheng; Wang, Hao-Fan; Chen, Xiang; Li, Bo-Quan; Hou, Ting-Zheng; Zhang, Bingsen; Zhang, Qiang; Titirici, Maria-Magdalena; Wei, Fei

    2016-08-01

    A bifunctional graphene catalyst with abundant topological defects is achieved via the carbonization of natural gelatinized sticky rice to probe the underlying oxygen electrocatalytic mechanism. A nitrogen-free configuration with adjacent pentagon and heptagon carbon rings is revealed to exhibit the lowest overpotential for both oxygen reduction and evolution catalysis. The versatile synthetic strategy and novel insights on the activity origin facilitate the development of advanced metal-free carbocatalysts for a wide range of electrocatalytic applications. PMID:27167616

  10. Advantages of reusable accessories.

    PubMed

    Wolfsen, H C

    2000-04-01

    Despite scant evidence supporting the use of disposable accessories, these devices have been widely disseminated. Manufacturers and governmental regulators, the most devout proponents of one-time use accessories, have framed the issue in economic terms-parsimonious practitioners reusing disposable accessories at the risk of cross-contamination, mechanical failure and product liability. This simplistic view represents revisionist history and ignores the long tradition of reusing these devices. This article reviews the numerous studies that support the safe and cost effective reuse of disposable and reusable accessories.

  11. Saenger - European reusability

    NASA Astrophysics Data System (ADS)

    Hoegenauer, E.

    1988-06-01

    An account is given of the design features and performance capabilities of the Saenger two-stage-to-orbit reusable launch vehicle. Saenger, in addition to employing a novel, airbreathing lower-stage propulsion system, is unique in its alternative employment of either a manned, reentry-capable upper stage or an expendable, unmanned cargo-carrying one. This configuration is also noted to offer the use of the lower stage as a hypersonic-cruise passenger aircraft. It is in the choice of a propulsion system configuration that Saenger's designers face the most critical challenge.

  12. Reusable Surface Insulation

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Advanced Flexible Reusable Surface Insulation, developed by Ames Research Center, protects the Space Shuttle from the searing heat that engulfs it on reentry into the Earth's atmosphere. Initially integrated into the Space Shuttle by Rockwell International, production was transferred to Hi-Temp Insulation Inc. in 1974. Over the years, Hi-Temp has created many new technologies to meet the requirements of the Space Shuttle program. This expertise is also used commercially, including insulation blankets to cover aircrafts parts, fire barrier material to protect aircraft engine cowlings and aircraft rescue fire fighter suits. A Fire Protection Division has also been established, offering the first suit designed exclusively by and for aircraft rescue fire fighters. Hi-Temp is a supplier to the Los Angeles City Fire Department as well as other major U.S. civil and military fire departments.

  13. Application of a stream-aquifer model to Monument Creek for development of a method to estimate transit losses for reusable water, El Paso County, Colorado

    USGS Publications Warehouse

    Kuhn, Gerhard; Arnold, L. Rick

    2006-01-01

    The U.S. Geological Survey, in cooperation with Colorado Springs Utilities, the Colorado Water Conservation Board, and the El Paso County Water Authority, began a study in 2004 to (1) apply a stream-aquifer model to Monument Creek, (2) use the results of the modeling to develop a transit-loss accounting program for Monument Creek, (3) revise the existing transit-loss accounting program for Fountain Creek to incorporate new water-management strategies and allow for incorporation of future changes in water-management strategies, and (4) integrate the two accounting programs into a single program with a Web-based user interface. The purpose of this report is to present the results of applying a stream-aquifer model to the Monument Creek study reach. More...

  14. Metal-free carbonaceous electrocatalysts and photocatalysts for water splitting.

    PubMed

    Xu, You; Kraft, Markus; Xu, Rong

    2016-05-31

    Water splitting driven by sunlight or renewable resource-derived electricity has attracted great attention for sustainable production of hydrogen from water. Current research interest in this field is focused on the development of earth-abundant photo- or electrocatalytic materials with high activity and long-term stability for hydrogen and/or oxygen evolution reactions. Due to their unique properties and characteristics, carbon and related carbon-based materials show great potential to replace some of the existing precious metal catalysts in water splitting technology. This tutorial review summarizes the recent significant progress in the fabrication and application of metal-free carbonaceous materials as photo- or electrocatalysts for water splitting. Synthetic strategies and applications of various carbonaceous materials, including graphitic carbon nitride (g-C3N4), graphene, carbon nanotubes (CNTs) as well as other forms of carbon-containing materials, for electrochemical or photochemical water splitting are presented, accompanied by a discussion of the key scientific issues and prospects for the future development of metal-free photo- and electrocatalysts. PMID:27094875

  15. Noble metal-free hydrogen evolution catalysts for water splitting.

    PubMed

    Zou, Xiaoxin; Zhang, Yu

    2015-08-01

    Sustainable hydrogen production is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochemical and photoelectrochemical water splitting are promising pathways for sustainable hydrogen production. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, especially at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/composition-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochemical and photoelectrochemical water splitting systems, when combined with suitable semiconductor photocatalysts.

  16. Metal-free carbonaceous electrocatalysts and photocatalysts for water splitting.

    PubMed

    Xu, You; Kraft, Markus; Xu, Rong

    2016-05-31

    Water splitting driven by sunlight or renewable resource-derived electricity has attracted great attention for sustainable production of hydrogen from water. Current research interest in this field is focused on the development of earth-abundant photo- or electrocatalytic materials with high activity and long-term stability for hydrogen and/or oxygen evolution reactions. Due to their unique properties and characteristics, carbon and related carbon-based materials show great potential to replace some of the existing precious metal catalysts in water splitting technology. This tutorial review summarizes the recent significant progress in the fabrication and application of metal-free carbonaceous materials as photo- or electrocatalysts for water splitting. Synthetic strategies and applications of various carbonaceous materials, including graphitic carbon nitride (g-C3N4), graphene, carbon nanotubes (CNTs) as well as other forms of carbon-containing materials, for electrochemical or photochemical water splitting are presented, accompanied by a discussion of the key scientific issues and prospects for the future development of metal-free photo- and electrocatalysts.

  17. N-tosylhydrazones: versatile reagents for metal-catalyzed and metal-free cross-coupling reactions.

    PubMed

    Shao, Zhihui; Zhang, Hongbin

    2012-01-21

    Transition metal-catalyzed cross-coupling reactions have been established as one of the most powerful tools for the construction of C-C and C-X bonds. In this context, the development of novel metal-catalyzed cross-coupling processes that do not require stoichiometric organometallic reagents is particularly attractive. Recently, N-tosylhydrazones have emerged as a new type of versatile coupling partners for transition metal-catalyzed cross-coupling reactions as well as metal-free cross-coupling reactions, and have attracted increasing attention. This tutorial review summarizes recent important developments in this area with N-tosylhydrazones as versatile coupling partners.

  18. Reusable launch vehicle technology program

    NASA Astrophysics Data System (ADS)

    Freeman, Delma C.; Talay, Theodore A.; Austin, R. Eugene

    Industry/NASA reusable launch vehicle (RLV) technology program efforts are underway to design, test, and develop technologies and concepts for viable commercial launch systems that also satisfy national needs at acceptable recurring costs. Significant progress has been made in understanding the technical challenges of fully reusable launch systems and the accompanying management and operational approaches for achieving a low-cost program. This paper reviews the current status of the RLV technology program including the DC-XA, X-33 and X-34 flight systems and associated technology programs. It addresses the specific technologies being tested that address the technical and operability challenges of reusable launch systems including reusable cryogenic propellant tanks, composite structures, thermal protection systems, improved propulsion, and subsystem operability enhancements. The recently concluded DC-XA test program demonstrated some of these technologies in ground and flight tests. Contracts were awarded recently for both the X-33 and X-34 flight demonstrator systems. The Orbital Sciences Corporation X-34 flight test vehicle will demonstrate an air-launched reusable vehicle capable of flight to speeds of Mach 8. The Lockheed-Martin X-33 flight test vehicle will expand the test envelope for critical technologies to flight speeds of Mach 15. A propulsion program to test the X-33 linear aerospike rocket engine using a NASA SR-71 high speed aircraft as a test bed is also discussed. The paper also describes the management and operational approaches that address the challenge of new cost-effective, reusable launch vehicle systems.

  19. Nonlinear Optothermal Properties of Metal-Free Phthalocyanine

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossin A.; Frazier, Donald O.; Penn, Benjamin G.; Smith, David D.; Banks, Curtis E.

    1998-01-01

    The nonlinear optical properties of metal-free phthalocyanine (MFPC) thin films were examined using the second harmonic at 532 nm from a pulsed Nd:YAG laser, and the cw He-Ne , and Ar+ lasers. The He-Ne laser transmission at fixed input intensity was found to increase temporally within a time scale of twelve hours. The origin of this temporal change of transmission is discussed. The third order nonlinear susceptibilities (chi (exp(3))) by four-wave mixing were measured for films of different thickness. The saturation intensity of MFPC, and its absorption cross section, at 633 nm from a He-Ne laser, are reported. An optical bistability was recorded using a He-Ne laser. An AND logic gate was also demonstrated in the system. These phenomena in the system are attributed to refractive index modulation by thermal excitations.

  20. Hydrogen evolution by a metal-free electrocatalyst

    NASA Astrophysics Data System (ADS)

    Zheng, Yao; Jiao, Yan; Zhu, Yihan; Li, Lu Hua; Han, Yu; Chen, Ying; Du, Aijun; Jaroniec, Mietek; Qiao, Shi Zhang

    2014-04-01

    Electrocatalytic reduction of water to molecular hydrogen via the hydrogen evolution reaction may provide a sustainable energy supply for the future, but its commercial application is hampered by the use of precious platinum catalysts. All alternatives to platinum thus far are based on nonprecious metals, and, to our knowledge, there is no report about a catalyst for electrocatalytic hydrogen evolution beyond metals. Here we couple graphitic-carbon nitride with nitrogen-doped graphene to produce a metal-free hybrid catalyst, which shows an unexpected hydrogen evolution reaction activity with comparable overpotential and Tafel slope to some of well-developed metallic catalysts. Experimental observations in combination with density functional theory calculations reveal that its unusual electrocatalytic properties originate from an intrinsic chemical and electronic coupling that synergistically promotes the proton adsorption and reduction kinetics.

  1. Frustrated Lewis pairs: metal-free hydrogen activation and more.

    PubMed

    Stephan, Douglas W; Erker, Gerhard

    2010-01-01

    Sterically encumbered Lewis acid and Lewis base combinations do not undergo the ubiquitous neutralization reaction to form "classical" Lewis acid/Lewis base adducts. Rather, both the unquenched Lewis acidity and basicity of such sterically "frustrated Lewis pairs (FLPs)" is available to carry out unusual reactions. Typical examples of frustrated Lewis pairs are inter- or intramolecular combinations of bulky phosphines or amines with strongly electrophilic RB(C(6)F(5))(2) components. Many examples of such frustrated Lewis pairs are able to cleave dihydrogen heterolytically. The resulting H(+)/H(-) pairs (stabilized for example, in the form of the respective phosphonium cation/hydridoborate anion salts) serve as active metal-free catalysts for the hydrogenation of, for example, bulky imines, enamines, or enol ethers. Frustrated Lewis pairs also react with alkenes, aldehydes, and a variety of other small molecules, including carbon dioxide, in cooperative three-component reactions, offering new strategies for synthetic chemistry. PMID:20025001

  2. Technology demonstration for reusable launchers

    NASA Astrophysics Data System (ADS)

    Baiocco, P.; Bonnal, Ch.

    2016-03-01

    Reusable launchers have been studied under CNES contracts for more than 30 years, with early concepts such as STS-2000 or Oriflamme, more recently with very significant efforts devoted to Liquid Fly Back Boosters as with the Bargouzin project led with Tsniimash, TSTO with the Everest concept studied by Airbus-DS as prime contractor or the RFS Reusable First Stage concept of a large first stage associated to a cryotechnic second stage. These investigations, summarized in the first part of the paper, enabled CNES to identify clearly the technology requirements associated to reusability, as well as cost efficiency through detailed non-recurring costs and mission costs analysis. In parallel, CNES set in place development logic for sub-systems and equipment based on demonstrators, hardware test benches enabling maturation of technologies up to a TRL such that an actual development can be decided with limited risk. This philosophy has been applied so far to a large number of cases, such as TPTech and TPX for Hydrogen turbo pump, GGPX as demonstrator of innovative gas generator, HX demonstrator of modern cryotechnic upper stage with a dozen of different objectives (Thermal Protection, 20K Helium storage, measurements …). This virtuous approach, "learn as you test", is currently applied in the phased approach towards scaled down reusable booster stage, whose possibility to be used as first stage of a microlaunch vehicle is under investigation. The selected technologies allow paving the way towards reusable booster stages for Ariane 6 evolutions or main reusable stage for a further generation of heavy launchers. The paper describes the logic behind this project, together with the demonstration objectives set for the various sub-systems as well as operations.

  3. Metal-Free Sensitizers for Dye-Sensitized Solar Cells.

    PubMed

    Chaurasia, Sumit; Lin, Jiann T

    2016-06-01

    This review focuses on our work on metal-free sensitizers for dye-sensitized solar cells (DSSCs). Sensitizers based on D-A'-π-A architecture (D is a donor, A is an acceptor, A' is an electron-deficient entity) exhibit better light harvesting than D-π-A-type sensitizers. However, appropriate molecular design is needed to avoid excessive aggregation of negative charge at the electron-deficient entity upon photoexcitation. Rigidified aromatics, including aromatic segments comprising fused electron-excessive and -deficient units in the spacer, allow effective electronic communication, and good photoinduced charge transfer leads to excellent cell performance. Sensitizers with two anchors/acceptors, D(-π-A)2 , can more efficiently harvest light, inject electrons, and suppress dark current compared with congeners with a single anchor. Appropriate incorporation of heteroaromatic units in the spacer is beneficial to DSSC performance. High-performance, aqueous-based DSSCs can be achieved with a dual redox couple comprising imidazolium iodide and 2,2,6,6-tetramethylpiperidin-N-oxyl, and/or using dyes of improved wettability through the incorporation of a triethylene oxide methyl ether chain. PMID:27114164

  4. A precious-metal free micro fuel cell accumulator

    NASA Astrophysics Data System (ADS)

    Bretthauer, C.; Müller, C.; Reinecke, H.

    2011-05-01

    In recent years, integrated fuel cell (FC) type primary and secondary batteries attracted a great deal of attention as integrated on-chip power sources due to their high theoretical power densities. Unfortunately, the costs of these devices have been rather high. This is partially due to the involved clean-room processes, but also due to the fact that these devices generally rely on expensive precious-metals such as Pd and Pt. Therefore we developed a novel integrated FC type accumulator that is based on non-precious-metals only. The key component of the presented accumulator is its alkaline polymer electrolyte membrane that allows not only the usage of a low-cost AB5 type hydrogen storage electrode, but also the usage of La0.6Ca0.4CoO3 as a precious-metal free bifunctional catalyst for the air-breathing electrode. Additionally the presented design requires only comparatively few cleanroom processes which further reduces the overall production costs. Although abdicating precious-metals, the presented accumulator shows an open circuit voltage of 0.81 V and a maximum power density of 0.66 mW cm-2 which is comparable or even superior to former precious-metal based cells.

  5. System For Retrieving Reusable Software

    NASA Technical Reports Server (NTRS)

    Van Warren, Lloyd; Beckman, Brian C.

    1993-01-01

    Encyclopedia of Software Components (ESC) is information-retrieval system of computer hardware and software providing access to generic reusable software tools and parts. Core of ESC is central tool base, which is repository of reusable software. It receives queries and submissions from user through local browser subsystem and receives authorized updates from maintenance subsystem. Sends retrievals to local browser subsystem and user's submissions to maintenance subsystem. Future versions will provide for advanced media, including voice and video, and will link system to database-management system. Programmers will not only retrieve software, but also modify, execute, and cross-link with other software.

  6. Metal-Free and Noble Metal-Free Heteroatom-Doped Nanostructured Carbons as Prospective Sustainable Electrocatalysts.

    PubMed

    Asefa, Tewodros

    2016-09-20

    The large-scale deployment of many types of fuel cells and electrolyzers is currently constrained by the lack of sustainable and efficient catalysts that can replace the less earth-abundant, noble metal-based catalysts, which are commonly used in these renewable energy systems. This burgeoning issue has led to explosive research efforts worldwide to find alternative, metal-free and noble metal-free catalysts that are composed of inexpensive and earth-abundant elements. Hence, the recent discoveries that doping carbon nanomaterials with heteroatoms (such as N, S, B, etc.) can give sustainable materials with good electrocatalytic activity for reactions carried out in fuel cells and electrolyzers have been not only quite exciting but also very promising to address these challenging issues. Interestingly, even though they contain no metals or involve only the inexpensive, more earth-abundant ones, the catalytic activity of some of these materials fares well with those of the commercially used noble metal-based electrocatalysts, such as Pt/C. However, research efforts to improve the catalytic activity, selectivity, and stability of some of these materials for various reactions are still necessary and thus continuing. While some of these efforts have focused on finding synthetic methods that can tune the structures and compositions of already known materials and thereby improve their catalytic properties (activity, selectivity, stability, etc.), others have focused on developing entirely new materials that can exhibit better or superior catalytic properties. In these efforts, additional considerations are also being paid to find facile synthetic routes or renewable and inexpensive precursors that can lead to such types of catalysts in order to make the entire process highly sustainable and widely applicable. In this Account, notable heteroatom-doped carbon catalysts that have been developed for reactions in fuel cells and water electrolyzers, the various synthetic

  7. Metal-Free and Noble Metal-Free Heteroatom-Doped Nanostructured Carbons as Prospective Sustainable Electrocatalysts.

    PubMed

    Asefa, Tewodros

    2016-09-20

    The large-scale deployment of many types of fuel cells and electrolyzers is currently constrained by the lack of sustainable and efficient catalysts that can replace the less earth-abundant, noble metal-based catalysts, which are commonly used in these renewable energy systems. This burgeoning issue has led to explosive research efforts worldwide to find alternative, metal-free and noble metal-free catalysts that are composed of inexpensive and earth-abundant elements. Hence, the recent discoveries that doping carbon nanomaterials with heteroatoms (such as N, S, B, etc.) can give sustainable materials with good electrocatalytic activity for reactions carried out in fuel cells and electrolyzers have been not only quite exciting but also very promising to address these challenging issues. Interestingly, even though they contain no metals or involve only the inexpensive, more earth-abundant ones, the catalytic activity of some of these materials fares well with those of the commercially used noble metal-based electrocatalysts, such as Pt/C. However, research efforts to improve the catalytic activity, selectivity, and stability of some of these materials for various reactions are still necessary and thus continuing. While some of these efforts have focused on finding synthetic methods that can tune the structures and compositions of already known materials and thereby improve their catalytic properties (activity, selectivity, stability, etc.), others have focused on developing entirely new materials that can exhibit better or superior catalytic properties. In these efforts, additional considerations are also being paid to find facile synthetic routes or renewable and inexpensive precursors that can lead to such types of catalysts in order to make the entire process highly sustainable and widely applicable. In this Account, notable heteroatom-doped carbon catalysts that have been developed for reactions in fuel cells and water electrolyzers, the various synthetic

  8. OSU-6: A Highly Efficient, Metal-Free, Heterogeneous Catalyst for the Click Synthesis of 5-Benzyl and 5-Aryl-1H-tetrazoles.

    PubMed

    Nammalwar, Baskar; Muddala, Nagendra Prasad; Pitchimani, Rajasekar; Bunce, Richard A

    2015-12-19

    OSU-6, an MCM-41 type hexagonal mesoporous silica with mild Brönsted acid properties, has been used as an efficient, metal-free, heterogeneous catalyst for the click synthesis of 5-benzyl and 5-aryl-1H-tetrazoles from nitriles in DMF at 90 °C. This catalyst offers advantages including ease of operation, milder conditions, high yields, and reusability. Studies are presented that demonstrate the robust nature of the catalyst under the optimized reaction conditions. OSU-6 promotes the 1,3-dipolar addition of azides to nitriles without significant degradation or clogging of the nanoporous structure. The catalyst can be reused up to five times without a significant reduction in yield, and it does not require treatment with acid between reactions.

  9. Carbon-Based Metal-Free Catalysts for Electrocatalysis beyond the ORR.

    PubMed

    Hu, Chuangang; Dai, Liming

    2016-09-19

    Besides their use in fuel cells for energy conversion through the oxygen reduction reaction (ORR), carbon-based metal-free catalysts have also been demonstrated to be promising alternatives to noble-metal/metal oxide catalysts for the oxygen evolution reaction (OER) in metal-air batteries for energy storage and for the splitting of water to produce hydrogen fuels through the hydrogen evolution reaction (HER). This Review focuses on recent progress in the development of carbon-based metal-free catalysts for the OER and HER, along with challenges and perspectives in the emerging field of metal-free electrocatalysis. PMID:27460826

  10. Carbon-Based Metal-Free Catalysts for Electrocatalysis beyond the ORR.

    PubMed

    Hu, Chuangang; Dai, Liming

    2016-09-19

    Besides their use in fuel cells for energy conversion through the oxygen reduction reaction (ORR), carbon-based metal-free catalysts have also been demonstrated to be promising alternatives to noble-metal/metal oxide catalysts for the oxygen evolution reaction (OER) in metal-air batteries for energy storage and for the splitting of water to produce hydrogen fuels through the hydrogen evolution reaction (HER). This Review focuses on recent progress in the development of carbon-based metal-free catalysts for the OER and HER, along with challenges and perspectives in the emerging field of metal-free electrocatalysis.

  11. A metal-free organic-inorganic aqueous flow battery.

    PubMed

    Huskinson, Brian; Marshak, Michael P; Suh, Changwon; Er, Süleyman; Gerhardt, Michael R; Galvin, Cooper J; Chen, Xudong; Aspuru-Guzik, Alán; Gordon, Roy G; Aziz, Michael J

    2014-01-01

    As the fraction of electricity generation from intermittent renewable sources--such as solar or wind--grows, the ability to store large amounts of electrical energy is of increasing importance. Solid-electrode batteries maintain discharge at peak power for far too short a time to fully regulate wind or solar power output. In contrast, flow batteries can independently scale the power (electrode area) and energy (arbitrarily large storage volume) components of the system by maintaining all of the electro-active species in fluid form. Wide-scale utilization of flow batteries is, however, limited by the abundance and cost of these materials, particularly those using redox-active metals and precious-metal electrocatalysts. Here we describe a class of energy storage materials that exploits the favourable chemical and electrochemical properties of a family of molecules known as quinones. The example we demonstrate is a metal-free flow battery based on the redox chemistry of 9,10-anthraquinone-2,7-disulphonic acid (AQDS). AQDS undergoes extremely rapid and reversible two-electron two-proton reduction on a glassy carbon electrode in sulphuric acid. An aqueous flow battery with inexpensive carbon electrodes, combining the quinone/hydroquinone couple with the Br2/Br(-) redox couple, yields a peak galvanic power density exceeding 0.6 W cm(-2) at 1.3 A cm(-2). Cycling of this quinone-bromide flow battery showed >99 per cent storage capacity retention per cycle. The organic anthraquinone species can be synthesized from inexpensive commodity chemicals. This organic approach permits tuning of important properties such as the reduction potential and solubility by adding functional groups: for example, we demonstrate that the addition of two hydroxy groups to AQDS increases the open circuit potential of the cell by 11% and we describe a pathway for further increases in cell voltage. The use of π-aromatic redox-active organic molecules instead of redox-active metals

  12. A metal-free organic-inorganic aqueous flow battery.

    PubMed

    Huskinson, Brian; Marshak, Michael P; Suh, Changwon; Er, Süleyman; Gerhardt, Michael R; Galvin, Cooper J; Chen, Xudong; Aspuru-Guzik, Alán; Gordon, Roy G; Aziz, Michael J

    2014-01-01

    As the fraction of electricity generation from intermittent renewable sources--such as solar or wind--grows, the ability to store large amounts of electrical energy is of increasing importance. Solid-electrode batteries maintain discharge at peak power for far too short a time to fully regulate wind or solar power output. In contrast, flow batteries can independently scale the power (electrode area) and energy (arbitrarily large storage volume) components of the system by maintaining all of the electro-active species in fluid form. Wide-scale utilization of flow batteries is, however, limited by the abundance and cost of these materials, particularly those using redox-active metals and precious-metal electrocatalysts. Here we describe a class of energy storage materials that exploits the favourable chemical and electrochemical properties of a family of molecules known as quinones. The example we demonstrate is a metal-free flow battery based on the redox chemistry of 9,10-anthraquinone-2,7-disulphonic acid (AQDS). AQDS undergoes extremely rapid and reversible two-electron two-proton reduction on a glassy carbon electrode in sulphuric acid. An aqueous flow battery with inexpensive carbon electrodes, combining the quinone/hydroquinone couple with the Br2/Br(-) redox couple, yields a peak galvanic power density exceeding 0.6 W cm(-2) at 1.3 A cm(-2). Cycling of this quinone-bromide flow battery showed >99 per cent storage capacity retention per cycle. The organic anthraquinone species can be synthesized from inexpensive commodity chemicals. This organic approach permits tuning of important properties such as the reduction potential and solubility by adding functional groups: for example, we demonstrate that the addition of two hydroxy groups to AQDS increases the open circuit potential of the cell by 11% and we describe a pathway for further increases in cell voltage. The use of π-aromatic redox-active organic molecules instead of redox-active metals

  13. A metal-free organic-inorganic aqueous flow battery

    NASA Astrophysics Data System (ADS)

    Huskinson, Brian; Marshak, Michael P.; Suh, Changwon; Er, Süleyman; Gerhardt, Michael R.; Galvin, Cooper J.; Chen, Xudong; Aspuru-Guzik, Alán; Gordon, Roy G.; Aziz, Michael J.

    2014-01-01

    As the fraction of electricity generation from intermittent renewable sources--such as solar or wind--grows, the ability to store large amounts of electrical energy is of increasing importance. Solid-electrode batteries maintain discharge at peak power for far too short a time to fully regulate wind or solar power output. In contrast, flow batteries can independently scale the power (electrode area) and energy (arbitrarily large storage volume) components of the system by maintaining all of the electro-active species in fluid form. Wide-scale utilization of flow batteries is, however, limited by the abundance and cost of these materials, particularly those using redox-active metals and precious-metal electrocatalysts. Here we describe a class of energy storage materials that exploits the favourable chemical and electrochemical properties of a family of molecules known as quinones. The example we demonstrate is a metal-free flow battery based on the redox chemistry of 9,10-anthraquinone-2,7-disulphonic acid (AQDS). AQDS undergoes extremely rapid and reversible two-electron two-proton reduction on a glassy carbon electrode in sulphuric acid. An aqueous flow battery with inexpensive carbon electrodes, combining the quinone/hydroquinone couple with the Br2/Br- redox couple, yields a peak galvanic power density exceeding 0.6Wcm-2 at 1.3Acm-2. Cycling of this quinone-bromide flow battery showed >99 per cent storage capacity retention per cycle. The organic anthraquinone species can be synthesized from inexpensive commodity chemicals. This organic approach permits tuning of important properties such as the reduction potential and solubility by adding functional groups: for example, we demonstrate that the addition of two hydroxy groups to AQDS increases the open circuit potential of the cell by 11% and we describe a pathway for further increases in cell voltage. The use of π-aromatic redox-active organic molecules instead of redox-active metals represents a new and

  14. Metal Free Azide-Alkyne Click Reaction: Role of Substituents and Heavy Atom Tunneling.

    PubMed

    Karmakar, Sharmistha; Datta, Ayan

    2015-09-01

    Metal free click reactions provide an excellent noninvasive tool to modify and understand the processes in biological systems. Release of ring strain in cyclooctynes on reaction with azides on the formation of triazoles results in small activation energies for various intermolecular Huisgen reactions (1-9). Substitution of difluoro groups at the α, α' position of the cyclooctyne ring enhances the rates of cycloadditions by 10 and 20 times for methyl azide and benzyl azide respectively at room temperature. The computed rate enhancement on difluoro substitution using direct dynamical calculations using the canonical variational transition state theory (CVT/CAG) with small curvature tunneling (SCT) corrections are in excellent agreement with the experimental results. For the intramolecular click reaction (10) notwithstanding its much higher activation energy, quantum mechanical tunneling (QMT) enhances the rate of cycloaddition significantly and increases the N(14)/N(15) primary kinetic isotope effect at 298 K. QMT is shown to be rather efficient in 10 due to a thin barrier of ∼2.4 Å. The present study shows that tunneling effects can be significant for intramolecular click reactions.

  15. Metal Free Azide-Alkyne Click Reaction: Role of Substituents and Heavy Atom Tunneling.

    PubMed

    Karmakar, Sharmistha; Datta, Ayan

    2015-09-01

    Metal free click reactions provide an excellent noninvasive tool to modify and understand the processes in biological systems. Release of ring strain in cyclooctynes on reaction with azides on the formation of triazoles results in small activation energies for various intermolecular Huisgen reactions (1-9). Substitution of difluoro groups at the α, α' position of the cyclooctyne ring enhances the rates of cycloadditions by 10 and 20 times for methyl azide and benzyl azide respectively at room temperature. The computed rate enhancement on difluoro substitution using direct dynamical calculations using the canonical variational transition state theory (CVT/CAG) with small curvature tunneling (SCT) corrections are in excellent agreement with the experimental results. For the intramolecular click reaction (10) notwithstanding its much higher activation energy, quantum mechanical tunneling (QMT) enhances the rate of cycloaddition significantly and increases the N(14)/N(15) primary kinetic isotope effect at 298 K. QMT is shown to be rather efficient in 10 due to a thin barrier of ∼2.4 Å. The present study shows that tunneling effects can be significant for intramolecular click reactions. PMID:26264958

  16. Reusable sounding-rocket design

    NASA Astrophysics Data System (ADS)

    Woo, Dick L. Y.; Martin, James A.

    1995-03-01

    As a result of the reduction of budgets for flights, the ideas of reusability and cost-effectiveness in launch vehicles are becoming more and more important. One class of rockets, in particular the sounding rockets operating in a less demanding environment, has many potentials for many more flights. By augmenting the basic rocket configuration with wings, landing gear, flight controls and guidance systems, the vehicle can be made to glide and land back at the launch site or at a specific recovery site. In this paper, the design of such a reusable rocket is presented. This design can be extended and adapted to larger vehicles, thus attaining higher altitudes required in some of the applications of sounding rockets.

  17. Metal-free oxidative decarbonylative coupling of aromatic aldehydes with arenes: direct access to biaryls.

    PubMed

    Tang, Ren-Jin; He, Qing; Yang, Luo

    2015-04-01

    A metal-free oxidative decarbonylative coupling of aromatic aldehydes with electron-rich or electron-deficient arenes to produce biaryl compounds was developed. This novel coupling was proposed to proceed via a non-chain radical homolytic aromatic substitution (HAS) type mechanism, based on the substrate scope, ortho-regioselectivity, radical trapping experiments and DFT calculation studies. With the ready availability of aromatic aldehydes and arenes, metal-free conditions should make this coupling attractive for the biaryl synthesis.

  18. Reusable launch vehicle development research

    NASA Technical Reports Server (NTRS)

    1995-01-01

    NASA has generated a program approach for a SSTO reusable launch vehicle technology (RLV) development which includes a follow-on to the Ballistic Missile Defense Organization's (BMDO) successful DC-X program, the DC-XA (Advanced). Also, a separate sub-scale flight demonstrator, designated the X-33, will be built and flight tested along with numerous ground based technologies programs. For this to be a successful effort, a balance between technical, schedule, and budgetary risks must be attained. The adoption of BMDO's 'fast track' management practices will be a key element in the eventual success of NASA's effort.

  19. Simulating Metal-Poor and Metal-Free Star Formation in the Earliest Galaxies

    NASA Astrophysics Data System (ADS)

    Safranek-Shrader, Chalence

    2014-01-01

    The end of the cosmic dark ages was brought about by the formation of the first stars and galaxies. Since this epoch is currently outside of observational reach, numerical studies are key in understanding this uncharted cosmic epoch. In this dissertation talk, I will describe my work using high-resolution, zoom-in simulations to understand the formation of these earliest stellar associations in a cosmological setting. The overarching focus will be on the fragmentation of collapsing gas and how this process is moderated by the gas chemistry, radiation fields, and realistic cosmological initial conditions. A key aspect of this work has been the development of sophisticated physics modules for the hydrodynamics code FLASH, including non-equilibrium chemistry, radiative transfer schemes, and sink particles. I will begin by describing how more moderate mass Population III stars ended their lives with a relatively quick heavy-element enrichment of their host dark matter halos, resulting in prompt Population II star formation. The introduction of metals from the first supernovae is believed to induce a star formation mode transition from high to low characteristic mass. I will show how the fragmentation of such metal enriched gas depends strongly on the metallicity, with fragmentation setting in when gas hits the CMB temperature floor. If present, an H2 photo-dissociating Lyman-Werner radiation background can delay the formation of the first stars and potentially result in clustered metal-free star formation in more massive, self-shielding halos at lower redshift. I will present results from recent simulations that follow the collapse and fragmentation of the first dust enriched gas to high densities (n ~ 10^14 cm^-3), analyzing the interplay of dust cooling with a CMB temperature floor and gauging the effect that dust heating from protostellar feedback has on the outcome of star formation. Finally, I will discuss this work’s implications for next

  20. Operational considerations for reusable launch vehicles

    SciTech Connect

    Adelgren, R.G.; Ray, D.; Lashinski, P.

    1997-01-01

    The reusable launch vehicle single stage to orbit concept is a long term goal of the space program. With the reusable concept, government and industry hope to reduce the cost of spacelift and provide fast reliable access to space. For a viable reusable concept, certain operational areas should be well thought out and considered. For instance, {open_quotes}aircraft like{close_quotes} operations should be a goal of the reusable launch vehicle concept. This paper outlines some initial operational considerations for a reusable launch vehicle. The operational areas considered are viewed from the standpoint of operationally testing the system in the areas of effectiveness and suitability. This paper represents thoughts and ideas of the authors and does not represent official Air Force or Air Force Operational Test and Evaluation Center policies, positions, or direction. {copyright} {ital 1997 American Institute of Physics.}

  1. Reusable ultralight personnel carrier (RUPC)

    NASA Astrophysics Data System (ADS)

    Clark, B. C., III; McCandless, B., II

    1992-08-01

    Attention is given to a personnel-carrying space vehicle concept developed to minimize the cost of access to LEO. The RUPC could provide alternate access to Space Station Freedom (SSF) for six passengers per flight. It can also bring and return small amounts of cargo, up to and including one SSF double rack. These capabilities are ideal for utilization flights during man-tended operations at SSF and for crew rotation during permanently manned periods. The RUPC is a reusable conical reentry vehicle and disposable adapter with propulsion and power subsystems. Avionics subsystem benefit from advanced low-power high-performance microelectronics developed for both the civilian and military space sectors. The RUPC core cabin concept has growth potential for other applications, including assured crew return, ground-launched crew rescue, delivery and retrieval of SSF cargo, and crew cabin for flights to the moon.

  2. The Reusable Astronomy Portal (TRAP)

    NASA Astrophysics Data System (ADS)

    Donaldson, T.; Rogers, A.; Wallace, G.

    2012-09-01

    The Reusable Astronomy Portal (TRAP) aims to provide a common platform for rapidly deploying Astronomy Archives to the web. TRAP is currently under development for both the VAO Data Discovery Portal and the MAST Multi-Mission Portal (Figure 1). TRAP consists of 2 major software packages: the TRAP Client and the TRAP Server. The TRAP framework allows developers to deploy the Server, connect to data resources, then focus on building custom tools for the Client. TRAP is built upon proven industry technologies including the Ext/JS JavaScript Component Library, Mono.NET Web Services, and JSON message based APIs. The multi-layered architecture of TRAP decouples each layer: Client, Service and Data Access, enabling each to evolve independently over time. Although currently deployed to provide astronomy science data access, the TRAP architecture is flexible enough to thrive in any distributed data environment.

  3. A metal-free general procedure for oxidation of secondary amines to nitrones.

    PubMed

    Gella, Carolina; Ferrer, Eric; Alibés, Ramon; Busqué, Félíx; de March, Pedro; Figueredo, Marta; Font, Josep

    2009-08-21

    An efficient and metal-free protocol for direct oxidation of secondary amines to nitrones has been developed, using Oxone in a biphasic basic medium as the sole oxidant. The method is general and tolerant with other functional groups or existing stereogenic centers, providing rapid access to enantiomerically pure compounds in good yields.

  4. A highly reducing metal-free photoredox catalyst: design and application in radical dehalogenations.

    PubMed

    Discekici, Emre H; Treat, Nicolas J; Poelma, Saemi O; Mattson, Kaila M; Hudson, Zachary M; Luo, Yingdong; Hawker, Craig J; Read de Alaniz, Javier

    2015-07-25

    Here we report the use of 10-phenylphenothiazine (PTH) as an inexpensive, highly reducing metal-free photocatalyst for the reduction of carbon-halogen bonds via the trapping of carbon-centered radical intermediates with a mild hydrogen atom donor. Dehalogenations were carried out on various substrates with excellent yields at room temperature in the presence of air. PMID:26104847

  5. Metal-Free Oxidative Radical Alkynylation/Ring Expansion Rearrangement of Alkenyl Cyclobutanols with Ethynylbenziodoxolones.

    PubMed

    Zhang, Ruo-Yi; Xi, Long-Yi; Shi, Lei; Zhang, Xiao-Zhuan; Chen, Shan-Yong; Yu, Xiao-Qi

    2016-08-19

    The first metal-free alkynylation/ring expansion cascade process of alkenyl cyclobutanols with ethynylbenziodoxolones has been developed. A variety of synthetically valuable β-alkynylated cyclopentanones were prepared in moderate to good yields. Alkynyl cyclobutanols could also undergo this transformation, providing a new approach to substituted ene-yne-carbonyl compounds. PMID:27500598

  6. Transition metal-free addition of ketones or nitriles to 1,3-dienes.

    PubMed

    Gaudin, Jean-Marc; Millet, Pascal

    2008-02-01

    The simpler the better (or going green): The first examples of the catalytic addition of 1,3-dienes to simple ketones or nitriles are described. These reactions can be effected on a kilogram scale, representing the shortest access featuring a perfect atom economy to molecules of interest in the perfume industry.

  7. Chemo- and Stereoselective Transition-Metal-Free Amination of Amides with Azides

    PubMed Central

    2016-01-01

    The synthesis of α-amino carbonyl/carboxyl compounds is a contemporary challenge in organic synthesis. Herein, we present a stereoselective α-amination of amides employing simple azides that proceeds under mild conditions with release of nitrogen gas. The amide is used as the limiting reagent, and through simple variation of the azide pattern, various differently substituted aminated products can be obtained. The reaction is fully chemoselective for amides even in the presence of esters or ketones and lends itself to preparation of optically enriched products. PMID:27350334

  8. Chemo- and Stereoselective Transition-Metal-Free Amination of Amides with Azides.

    PubMed

    Tona, Veronica; de la Torre, Aurélien; Padmanaban, Mohan; Ruider, Stefan; González, Leticia; Maulide, Nuno

    2016-07-13

    The synthesis of α-amino carbonyl/carboxyl compounds is a contemporary challenge in organic synthesis. Herein, we present a stereoselective α-amination of amides employing simple azides that proceeds under mild conditions with release of nitrogen gas. The amide is used as the limiting reagent, and through simple variation of the azide pattern, various differently substituted aminated products can be obtained. The reaction is fully chemoselective for amides even in the presence of esters or ketones and lends itself to preparation of optically enriched products. PMID:27350334

  9. Reusable Surface Insulation (RSI) Material Samples

    NASA Technical Reports Server (NTRS)

    Banas, R. P.

    1977-01-01

    Test specimen data sheets are presented for 48 high temperature and 40 low temperature reusable surface insulation tiles. Tabular data show dimensions, density, coating weight, and final tile weight. Codes indicate basic material, surface coating, and hydrophobic treatment.

  10. Reusable, tamper-indicating seal

    DOEpatents

    Ryan, Michael J.

    1978-01-01

    A reusable, tamper-indicating seal comprises a drum confined within a fixed body and rotatable in one direction therewithin, the top of the drum constituting a tray carrying a large number of small balls of several different colors. The fixed body contains parallel holes for looping a seal wire therethrough. The base of the drums carries cams adapted to coact with cam followers to lock the wire within the seal at one angular position of the drum. A channel in the fixed body -- visible from outside the seal -- adjacent the tray constitutes a segregated location for a small plurality of the colored balls. A spring in the tray forces colored balls into the segregated location at one angular position of the drum, further rotation securing the balls in position and the wires in the seal. A wedge-shaped plough removes the balls from the segregated location, at a different angular position of the drum, the wire being unlocked at the same position. A new pattern of colored balls will appear in the segregated location when the seal is relocked.

  11. Reusable experiment controllers, case studies

    NASA Astrophysics Data System (ADS)

    Buckley, Brian A.; Gaasbeck, Jim Van

    1996-03-01

    Congress has given NASA and the science community a reality check. The tight and ever shrinking budgets are trimming the fat from many space science programs. No longer can a Principal Investigator (PI) afford to waste development dollars on re-inventing spacecraft controllers, experiment/payload controllers, ground control systems, or test sets. Inheritance of the Ground Support Equipment (GSE) from one program to another is not a significant re-use of technology to develop a science mission in these times. Reduction of operational staff and highly autonomous experiments are needed to reduce the sustaining cost of a mission. The re-use of an infrastructure from one program to another is needed to truly attain the cost and time savings required. Interface and Control Systems, Inc. (ICS) has a long history of re-usable software. Navy, Air Force, and NASA programs have benefited from the re-use of a common control system from program to program. Several standardization efforts in the AIAA have adopted the Spacecraft Command Language (SCL) architecture as a point solution to satisfy requirements for re-use and autonomy. The Environmental Research Institute of Michigan (ERIM) has been a long-standing customer of ICS and are working on their 4th generation system using SCL. Much of the hardware and software infrastructure has been re-used from mission to mission with little cost for re-hosting a new experiment. The same software infrastructure has successfully been used on Clementine, and an end-to-end system is being deployed for the Far Ultraviolet Spectroscopic Explorer (FUSE) for Johns Hopkins University. A case study of the ERIM programs, Clementine and FUSE will be detailed in this paper.

  12. Metal-free carbon nanotubes: synthesis, and enhanced intrinsic microwave absorption properties

    PubMed Central

    Qi, Xiaosi; Xu, Jianle; Hu, Qi; Deng, Yu; Xie, Ren; Jiang, Yang; Zhong, Wei; Du, Youwei

    2016-01-01

    In order to clearly understand the intrinsic microwave absorption properties of carbon nanomaterials, we proposed an efficient strategy to synthesize high purity metal-free carbon nanotubes (CNTs) over water-soluble K2CO3 particles through chemical vapor decomposition and water-washing process. The comparison results indicated the leftover catalyst caused negative effects in intrinsic microwave absorption properties of CNTs, while an enhanced microwave absorption performance could be observed over the metal-free CNT sample. Moreover, the results indicated that the microwave absorption properties could be tuned by the CNT content. Therefore, we provided a simple route to investigate the intrinsic properties of CNTs and a possible enhanced microwave absorbing mechanism. PMID:27324290

  13. Sulfoxide-Directed Metal-Free ortho-Propargylation of Aromatics and Heteroaromatics.

    PubMed

    Eberhart, Andrew J; Shrives, Harry J; Álvarez, Estela; Carrër, Amandine; Zhang, Yuntong; Procter, David J

    2015-05-11

    A sulfoxide-directed, metal-free ortho-propargylation of aromatics and heteroaromatics exploits intermolecular delivery of a propargyl nucleophile to sulfur followed by an intramolecular relay to carbon. The operationally simple cross-coupling procedure is general, regiospecific with regard to the propargyl nucleophile, and shows complete selectivity for products of ortho-propargylation over allenylation. The use of secondary propargyl silanes allows metal-free ortho-coupling to form carbon-carbon bonds between aromatic and heteroaromatic rings and secondary propargylic centres. The 'safety-catch' nature of the sulfoxide directing group is illustrated in a selective, iterative double cross-coupling process. The products of propargylation are versatile intermediates and they have been readily converted into substituted benzothiophenes.

  14. Renewable and metal-free carbon nanofibre catalysts for carbon dioxide reduction

    NASA Astrophysics Data System (ADS)

    Kumar, Bijandra; Asadi, Mohammad; Pisasale, Davide; Sinha-Ray, Suman; Rosen, Brian A.; Haasch, Richard; Abiade, Jeremiah; Yarin, Alexander L.; Salehi-Khojin, Amin

    2013-12-01

    The development of an efficient catalyst system for the electrochemical reduction of carbon dioxide into energy-rich products is a major research topic. Here we report the catalytic ability of polyacrylonitrile-based heteroatomic carbon nanofibres for carbon dioxide reduction into carbon monoxide, via a metal-free, renewable and cost-effective route. The carbon nanofibre catalyst exhibits negligible overpotential (0.17 V) for carbon dioxide reduction and more than an order of magnitude higher current density compared with the silver catalyst under similar experimental conditions. The carbon dioxide reduction ability of carbon nanofibres is attributed to the reduced carbons rather than to electronegative nitrogen atoms. The superior performance is credited to the nanofibrillar structure and high binding energy of key intermediates to the carbon nanofibre surfaces. The finding may lead to a new generation of metal-free and non-precious catalysts with much greater efficiency than the existing noble metal catalysts.

  15. Metal-free carbon nanotubes: synthesis, and enhanced intrinsic microwave absorption properties.

    PubMed

    Qi, Xiaosi; Xu, Jianle; Hu, Qi; Deng, Yu; Xie, Ren; Jiang, Yang; Zhong, Wei; Du, Youwei

    2016-01-01

    In order to clearly understand the intrinsic microwave absorption properties of carbon nanomaterials, we proposed an efficient strategy to synthesize high purity metal-free carbon nanotubes (CNTs) over water-soluble K2CO3 particles through chemical vapor decomposition and water-washing process. The comparison results indicated the leftover catalyst caused negative effects in intrinsic microwave absorption properties of CNTs, while an enhanced microwave absorption performance could be observed over the metal-free CNT sample. Moreover, the results indicated that the microwave absorption properties could be tuned by the CNT content. Therefore, we provided a simple route to investigate the intrinsic properties of CNTs and a possible enhanced microwave absorbing mechanism.

  16. Metal-free carbon nanotubes: synthesis, and enhanced intrinsic microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Qi, Xiaosi; Xu, Jianle; Hu, Qi; Deng, Yu; Xie, Ren; Jiang, Yang; Zhong, Wei; Du, Youwei

    2016-06-01

    In order to clearly understand the intrinsic microwave absorption properties of carbon nanomaterials, we proposed an efficient strategy to synthesize high purity metal-free carbon nanotubes (CNTs) over water-soluble K2CO3 particles through chemical vapor decomposition and water-washing process. The comparison results indicated the leftover catalyst caused negative effects in intrinsic microwave absorption properties of CNTs, while an enhanced microwave absorption performance could be observed over the metal-free CNT sample. Moreover, the results indicated that the microwave absorption properties could be tuned by the CNT content. Therefore, we provided a simple route to investigate the intrinsic properties of CNTs and a possible enhanced microwave absorbing mechanism.

  17. Metal-Free C–H Alkyliminylation and Acylation of Alkenes with Secondary Amides

    PubMed Central

    Huang, Pei-Qiang; Huang, Ying-Hong; Geng, Hui; Ye, Jian-Liang

    2016-01-01

    Carbon–carbon bond formation by metal-free cross-coupling of two reactants with low reactivity represents a challenge in organic synthesis. Secondary amides and alkenes are two classes of bench-stable compounds. The low electrophilicity of the former and low nucleophilicity of the latter make the direct coupling of these two partners challenging yet highly desirable. We report herein an unprecedented intermolecular reaction of secondary amides with alkenes to afford α,β-unsaturated ketimines or enones, which are versatile intermediates for organic synthesis and are prevalent in bioactive compounds and functional materials. Our strategy relies on the chemoselective activation of the secondary amide with trifluoromethanesulfonic anhydride (Tf2O)/2-fluoropyridine to generate a highly reactive nitrilium intermediate, which reacts efficiently with alkenes. This metal-free synthesis is characterized by its mild reaction conditions, excellent functional group tolerance and chemoselectivity, allowing the preparation of multi-functionalized compounds without using protecting groups. PMID:27356173

  18. Metal-Free C-H Alkyliminylation and Acylation of Alkenes with Secondary Amides.

    PubMed

    Huang, Pei-Qiang; Huang, Ying-Hong; Geng, Hui; Ye, Jian-Liang

    2016-01-01

    Carbon-carbon bond formation by metal-free cross-coupling of two reactants with low reactivity represents a challenge in organic synthesis. Secondary amides and alkenes are two classes of bench-stable compounds. The low electrophilicity of the former and low nucleophilicity of the latter make the direct coupling of these two partners challenging yet highly desirable. We report herein an unprecedented intermolecular reaction of secondary amides with alkenes to afford α,β-unsaturated ketimines or enones, which are versatile intermediates for organic synthesis and are prevalent in bioactive compounds and functional materials. Our strategy relies on the chemoselective activation of the secondary amide with trifluoromethanesulfonic anhydride (Tf2O)/2-fluoropyridine to generate a highly reactive nitrilium intermediate, which reacts efficiently with alkenes. This metal-free synthesis is characterized by its mild reaction conditions, excellent functional group tolerance and chemoselectivity, allowing the preparation of multi-functionalized compounds without using protecting groups. PMID:27356173

  19. Sulfoxide-Directed Metal-Free ortho-Propargylation of Aromatics and Heteroaromatics

    PubMed Central

    Eberhart, Andrew J; Shrives, Harry J; Álvarez, Estela; Carrër, Amandine; Zhang, Yuntong; Procter, David J

    2015-01-01

    A sulfoxide-directed, metal-free ortho-propargylation of aromatics and heteroaromatics exploits intermolecular delivery of a propargyl nucleophile to sulfur followed by an intramolecular relay to carbon. The operationally simple cross-coupling procedure is general, regiospecific with regard to the propargyl nucleophile, and shows complete selectivity for products of ortho-propargylation over allenylation. The use of secondary propargyl silanes allows metal-free ortho-coupling to form carbon–carbon bonds between aromatic and heteroaromatic rings and secondary propargylic centres. The ‘safety-catch’ nature of the sulfoxide directing group is illustrated in a selective, iterative double cross-coupling process. The products of propargylation are versatile intermediates and they have been readily converted into substituted benzothiophenes. PMID:25752800

  20. Metal free carboamination of internal alkynes--an easy access to polysubstituted quinolines.

    PubMed

    Stopka, T; Niggemann, M

    2016-04-28

    A metal free carboamination of unactivated alkynes towards highly substituted quinolines was realized in the presence of a synergistic Brønsted acid catalyst system. Supported by mechanistic probes, the reaction proceeds via a highly reactive vinyl cation in a C-C bond formation--Schmidt reaction sequence. The irreversible extrusion of N2, as a powerful driving force, allows for a general conversion of poorly nucleophilic aliphatic alkynes. PMID:27049140

  1. Metal-Free Asymmetric Synthesis of Indanes through Chiral Hypervalent Iodine(III)-Mediated Ring Contraction.

    PubMed

    Ahmad, Anees; Silva, Luiz F

    2016-03-01

    The iodine(III)-mediated asymmetric oxidative rearrangement of 1,2-dihydronaphthalenes was investigated to prepare optically active 1-substituted indanes. The chiral hypervalent iodine species is generated in situ from a chiral aryl iodide, prepared in 94% yield in one step. This metal-free protocol was applied to different cyclic alkenes, substituted with oxygen, with nitrogen, or at position 1 with aryl or methyl. Indanes can be isolated as an acetal or alcohol in up to 78% ee. PMID:26866897

  2. Metal-free intermolecular formal cycloadditions enable an orthogonal access to nitrogen heterocycles

    PubMed Central

    Xie, Lan-Gui; Niyomchon, Supaporn; Mota, Antonio J.; González, Leticia; Maulide, Nuno

    2016-01-01

    Nitrogen-containing heteroaromatic cores are ubiquitous building blocks in organic chemistry. Herein, we present a family of metal-free intermolecular formal cycloaddition reactions that enable highly selective and orthogonal access to isoquinolines and pyrimidines at will. Applications of the products are complemented by a density functional theory mechanistic analysis that pinpoints the crucial factors responsible for the selectivity observed, including stoichiometry and the nature of the heteroalkyne. PMID:26975182

  3. Graphene from Alginate Pyrolysis as a Metal-Free Catalyst for Hydrogenation of Nitro Compounds.

    PubMed

    Trandafir, Mihaela-Mirela; Florea, Mihaela; Neaţu, Florentina; Primo, Ana; Parvulescu, Vasile I; García, Hermenegildo

    2016-07-01

    Graphene obtained by pyrolysis of alginate at 900 °C under inert atmosphere and exfoliation is used as a metal-free catalyst for reduction of nitro to amino groups with hydrogen as a reagent. The process is general for aromatic and aliphatic, conjugated and isolated nitro groups, and occurs with low selectivity over hydrogenation of carbon-carbon double bonds. PMID:27246529

  4. Photocatalytic water reduction with copper-based photosensitizers: a noble-metal-free system.

    PubMed

    Luo, Shu-Ping; Mejía, Esteban; Friedrich, Aleksej; Pazidis, Alexandra; Junge, Henrik; Surkus, Annette-Enrica; Jackstell, Ralf; Denurra, Stefania; Gladiali, Serafino; Lochbrunner, Stefan; Beller, Matthias

    2013-01-01

    Of noble descent: a fully noble-metal-free system for the photocatalytic reduction of water at room temperature has been developed. This system consists of Cu(I) complexes as photosensitizers and [Fe(3)(CO)(12)] as the water-reduction catalyst. The novel Cu-based photosensitizers are relatively inexpensive, readily available from commercial sources, and stable to ambient conditions, thus making them an attractive alternative to the widely used noble-metal based systems. PMID:23047871

  5. A Highly Efficient Metal-Free Oxygen Reduction Electrocatalyst Assembled from Carbon Nanotubes and Graphene.

    PubMed

    Yang, Jia; Sun, Haiyan; Liang, Haiyi; Ji, Hengxing; Song, Li; Gao, Chao; Xu, Hangxun

    2016-06-01

    A novel carbon-nanotube-graphene hybrid nanostructure is developed using an aerosol-assisted assembly approach. After doping with nitrogen and phosphorus, the prepared hybrid nanomaterials exhibit excellent electrocatalytic performance for oxygen reduction in both alkaline and acidic media. This research presents a continuous and low-cost route to prepare high-performance metal-free electrocatalysts while replacing Pt-based materials. PMID:27062506

  6. Eco-Friendly ELID Grinding Using Metal-Free Electro-Conductive Resinoid Bonded Wheel

    NASA Astrophysics Data System (ADS)

    Itoh, Nobuhide; Nemoto, Akihiko; Katoh, Teruko; Ohmori, Hitoshi

    In this study, a metal-free electro-conductive resinoid bonded wheel made of carbon as the conductive material was experimentally built to reduce metal ions in the grinding fluid and metal contamination of the workpiece in the aim to develop environmentally-friendly ELID (Electrolytic In-Process Dressing) grinding techniques. At the same time, characteristics of initial electrolytic-dressing and grinding were also investigated. The results showed that the prototyped metal-free electro-conductive resinoid bonded wheel consisted of a layer of oxides with high oxygen level formed on the wheel surface by electrolytic dressing. The layer generated by electrolytic dressing was found to wear more easily than the matrix composition and in addition have a high frictional coefficient. This wheel was also found to have good surface roughness compared to the cast iron bonded wheel generally used for ELID grinding. The obtained surface roughness was about 30nmPV using a #8000 metal-free electro-conductive resinoid bonded diamond wheel.

  7. Noble-Metal-Free Materials for Surface-Enhanced Raman Spectroscopy Detection.

    PubMed

    Tan, Xianjun; Melkersson, Jenny; Wu, Shiqun; Wang, Lingzhi; Zhang, Jinlong

    2016-09-01

    Surface-enhanced Raman spectroscopy (SERS) is an attractive tool for the sensing of molecules in the fields of chemical and biochemical analysis as it enables the sensitive detection of molecular fingerprint information even at the single-molecule level. In addition to traditional coinage metals in SERS analysis, recent research on noble-metal-free materials has also yielded highly sensitive SERS activity. This Minireview presents the recent development of noble-metal-free materials as SERS substrates and their potential applications, especially semiconductors and emerging graphene-based nanostructures. Rather than providing an exhaustive review of this field, possible contributions from semiconductor substrates, characteristics of graphene enhanced Raman scattering, as well as effect factors such as surface plasmon resonance, structure and defects of the nanostructures that are considered essential for SERS activity are emphasized. The intention is to illustrate, through these examples, that the promise of noble-metal-free materials for enhancing detection sensitivity can further fuel the development of SERS-related applications. PMID:27191682

  8. B4CN3 and B3CN4 monolayers as the promising candidates for metal-free spintronic materials

    NASA Astrophysics Data System (ADS)

    Pan, Hongzhe; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-09-01

    The search for candidates of spintronic materials, especially among the two-dimensional (2D) materials, has attracted tremendous attentions over the past decades. By using a particle swarm optimization structure searching method combined with density functional calculations, two kinds of boron carbonitride monolayer structures (B4CN3 and B3CN4) are proposed and confirmed to be dynamically and kinetically stable. Intriguingly, we demonstrate that the magnetic ground states of the two B x C y N z systems are ferromagnetic ordering with a high Curie temperature of respectively 337 K for B4CN3 and 309 K for B3CN4. Furthermore, based on their respective band structures, the B4CN3 is found to be a bipolar magnetic semiconductor (BMS), while the B3CN4 is identified to be a type of spin gapless semiconductor (SGS), both of which are potential spintronic materials. In particular, carrier doping in the B4CN3 can induce a transition from BMS to half-metal, and its spin polarization direction is switchable depending on the doped carrier type. The BMS property of B4CN3 is very robust under an external strain or even a strong electric field. By contrast, as a SGS, the electronic structure of B3CN4 is relatively sensitive to external influences. Our findings successfully disclose two promising materials toward 2D metal-free spintronic applications.

  9. Reusable Agena study. Volume 2: Technical

    NASA Technical Reports Server (NTRS)

    Carter, W. K.; Piper, J. E.; Douglass, D. A.; Waller, E. W.; Hopkins, C. V.; Fitzgerald, E. T.; Sagawa, S. S.; Carter, S. A.; Jensen, H. L.

    1974-01-01

    The application of the existing Agena vehicle as a reusable upper stage for the space shuttle is discussed. The primary objective of the study is to define those changes to the Agena required for it to function in the reusable mode in the 100 percent capture of the NASA-DOD mission model. This 100 percent capture is achieved without use of kick motors or stages by simply increasing the Agena propellant load by using optional strap-on-tanks. The required shuttle support equipment, launch and flight operations techniques, development program, and cost package are also defined.

  10. Reusable thermal protection system development: A prospective

    NASA Technical Reports Server (NTRS)

    Goldstein, Howard

    1992-01-01

    The state of the art in passive reusable thermal protection system materials is described. Development of the Space Shuttle Orbiter, which was the first reusable vehicle, is discussed. The thermal protection materials and given concepts and some of the shuttle development and manufacturing problems are described. Evolution of a family of grid and flexible ceramic external insulation materials from the initial shuttle concept in the early 1970's to the present time is described. The important properties and their evolution are documented. Application of these materials to vehicles currently being developed and plans for research to meet the space programs future needs are summarized.

  11. A reusable rocket engine intelligent control

    NASA Technical Reports Server (NTRS)

    Merrill, Walter C.; Lorenzo, Carl F.

    1988-01-01

    An intelligent control system for reusable space propulsion systems for future launch vehicles is described. The system description includes a framework for the design. The framework consists of an execution level with high-speed control and diagnostics, and a coordination level which marries expert system concepts with traditional control. A comparison is made between air breathing and rocket engine control concepts to assess the relative levels of development and to determine the applicability of air breathing control concepts ot future reusable rocket engine systems.

  12. Noble-metal-free BODIPY-cobaloxime photocatalysts for visible-light-driven hydrogen production.

    PubMed

    Luo, Geng-Geng; Fang, Kai; Wu, Ji-Huai; Dai, Jing-Cao; Zhao, Qing-Hua

    2014-11-21

    In this study a series of supramolecular BODIPY-cobaloxime systems Co-Bn (n = 1-4): [{Co(dmgH)2Cl}{4,4-difluoro-8-(4-pyridyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene}] (Co-B1), [{Co(dmgH)2Cl}{4,4-difluoro-8-(4-pyridyl)-1,3,5,7-tetramethyl-2,6-diiodo-4-bora-3a,4a-diaza-s-indacene}] (Co-B2), [{Co(dmgH)2Cl}{4,4-difluoro-8-(3-pyridyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene}] (Co-B3), and [{Co(dmgH)2Cl}{4,4-difluoro-8-(3-pyridyl)-1,3,5,7-tetramethyl-2,6-diiodo-4-bora-3a,4a-diaza-s-indacene}] (Co-B4) (BODIPY = boron dipyrromethene, dmgH = dimethylglyoxime) have been synthesized by replacing one axial chlorine of cobaloxime moieties with the pyridine residues of BODIPYs, and structurally characterized. Absorption spectra show that the optical properties of the BODIPY-cobaloximes are essentially the sum of their constituent components, indicating weak interactions between the cobaloxime units and BODIPY chromophores in the ground state. If any, electronic communications may take place through the intramolecular electron transfer across their orthogonal structures. The possibility of intramolecular electron transfer is further supported by the results of the density functional theory (DFT) calculations at UB3LYP/LANL2DZ levels on Co-B2˙(-) and Co-B4˙(-), which show that the highest occupied molecular orbitals (HOMOs) possess predominantly BODIPY character, while the lowest unoccupied molecular orbitals (LUMOs) are located on the cobalt centers. The HOMO → LUMO transition is an electron-transfer process (BODIPY˙(-) radical anions → cobaloxime fragments). In view of the possible occurrence of electron transfer, these noble-metal-free BODIPY-cobaloximes are studied as single-component homogeneous photocatalysts for H2 generation in aqueous media. Under optimized conditions, the 2,6-diiodo BODIPY-sensitized cobaloxime Co-B4 that contains a meta-pyridyl at the 8-position of BODIPY presents excellent H2 photoproduction catalytic activity with a

  13. A metal-free N-annulated thienocyclopentaperylene dye: power conversion efficiency of 12% for dye-sensitized solar cells.

    PubMed

    Yao, Zhaoyang; Zhang, Min; Li, Renzhi; Yang, Lin; Qiao, Yongna; Wang, Peng

    2015-05-11

    Reported are two highly efficient metal-free perylene dyes featuring N-annulated thienobenzoperylene (NTBP) and N-annulated thienocyclopentaperylene (NTCP), which are coplanar polycyclic aromatic hydrocarbons. Without the use of any coadsorbate, the metal-free organic dye derived from the NTCP segment was used for a dye-sensitized solar cell which attained a power conversion efficiency of 12% under an irradiance of 100 mW cm(-2), simulated air mass global (AM1.5G) sunlight.

  14. Metal-free (Boc)2O-mediated C4-selective direct indolation of pyridines using TEMPO.

    PubMed

    Qin, Wen-Bing; Zhu, Jia-Yi; Kong, Yu-Bo; Bao, Yun-Hong; Chen, Zheng-Wang; Liu, Liang-Xian

    2014-06-28

    Direct metal-free C-4-selective indolation of pyridines is achieved for the first time using TEMPO and (Boc)2O. A variety of substituents on both indoles and pyridines are tolerated to give 3-(pyridin-4-yl)-1H-indole derivatives in moderate to excellent yields. This finding provides a novel approach for developing metal-free C-H functionalization of pyridines.

  15. Nitrimines as reagents for metal-free formal C(sp(2) )-C(sp(2) ) cross-coupling reactions.

    PubMed

    Angeles-Dunham, Veronica V; Nickerson, David M; Ray, Devin M; Mattson, Anita E

    2014-12-22

    Nitrimines are employed as powerful reagents for metal-free formal C(sp(2) )-C(sp(2) ) cross-coupling reactions. The new chemical process is tolerant of a wide array of nitrimine and heterocyclic coupling partners giving rise to the corresponding di- or trisubstituted alkenes, typically in high yield and with high stereoselectivity. This method is ideal for the metal-free construction of heterocycle-containing drug targets, such as phenprocoumon. PMID:25365926

  16. FEEDBACK SCORING SYSTEMS FOR REUSABLE KINDERGARTEN WORKBOOKS.

    ERIC Educational Resources Information Center

    GACH, PENELOPE J.; AND OTHERS

    THE DEVELOPMENT OF ECONOMICAL FEEDBACK SCORING SYSTEMS FOR REUSABLE KINDERGARTEN WORKBOOKS IS DESCRIBED. THREE PROTOTYPE SYSTEMS WERE DEVELOPED--(1) A METAL FOIL ACTIVATING AN ELECTRICAL PROBE, (2) A METAL FOIL REACTING WITH A MAGNETIC PROBE, AND (3) INVISIBLE FLUORESCENT INK REVEALED BY THE APPLICATION OF LONGWAVE ULTRAVIOLET LIGHT. (MS)

  17. Development Status of Reusable Rocket Engine

    NASA Astrophysics Data System (ADS)

    Yoshida, Makoto; Takada, Satoshi; Naruo, Yoshihiro; Niu, Kenichi

    A 30-kN rocket engine, a pilot engine, is being developed in Japan. Development of this pilot engine has been initiated in relation to a reusable sounding rocket, which is also being developed in Japan. This rocket takes off vertically, reaches an altitude of 100 km, lands vertically at the launch site, and is launched again within several days. Due to advantage of reusability, successful development of this rocket will mean that observation missions can be carried out more frequently and economically. In order to realize this rocket concept, the engines installed on the rocket should be characterized by reusability, long life, deep throttling and health monitoring, features which have not yet been established in Japanese rocket engines. To solve the engineering factors entitled by those features, a new design methodology, advanced engine simulations and engineering testing are being focused on in the pilot engine development stage. Especially in engineering testing, limit condition data is acquired to facilitate development of new diagnostic techniques, which can be applied by utilizing the mobility of small-size hardware. In this paper, the development status of the pilot engine is described, including fundamental design and engineering tests of the turbopump bearing and seal, turbine rig, injector and combustion chamber, and operation and maintenance concepts for one hundred flights by a reusable rocket are examined.

  18. Reusable Reentry Satellite (RRS): Launch tradeoff study

    NASA Technical Reports Server (NTRS)

    1990-01-01

    A goal of the Phase B study is to define the launch system interfaces for the reusable reentry satellite (RRS) program. The focus of the launch tradeoff study, documented in this report, is to determine which expendable launch vehicles (ELV's) are best suited for the RRS application by understanding the impact of all viable launch systems on RRS design and operation.

  19. System specification for the reusable reentry satellite

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The RRS design shall provide a relatively inexpensive method of access to micro and fractional gravity space environments for an extended period of time, with eventual intact recovery on the surface of the Earth. This specification establishes the performance, design, development, and test requirements for the Reusable Reentry Satellite (RRS) system.

  20. The Venture Star Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    1996-01-01

    In this artist's concept, the X-33 Venture Star, a Reusable Launch Vehicle (RLV), manufactured by Lockheed Martin Skunk Works, is shown in orbit with a deployed payload. The Venture Star was one of the earliest versions of the RLV's developed to replace the aging shuttle fleet. The X-33 program was cancelled in 2001.

  1. X-33 Venture Star - Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    1996-01-01

    In this artist's concept, the X-33 Venture Star, a Reusable Launch Vehicle (RLV), manufactured by Lockheed Martin Skunk Works, is shown in orbit with a deployed payload. The Venture Star was one of the earliest versions of the RLV's developed to replace the aging shuttle fleet. The X-33 program was cancelled in 2001.

  2. A Three-Cent Reusable Craig Tube

    NASA Astrophysics Data System (ADS)

    Russo, Thomas J.

    1998-07-01

    A rugged three-cent reusable Craig tube is easily made from a cotton swab and disposable pipet tip. The tube costs three cents or less and can be reused. Craig tubes made of glass cost as much as $15 and are very fragile.

  3. 14 CFR 437.67 - Tracking a reusable suborbital rocket.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Tracking a reusable suborbital rocket. 437... a reusable suborbital rocket. A permittee must— (a) During permitted flight, measure in real time the position and velocity of its reusable suborbital rocket; and (b) Provide position and...

  4. 14 CFR 437.67 - Tracking a reusable suborbital rocket.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 4 2014-01-01 2014-01-01 false Tracking a reusable suborbital rocket. 437... a reusable suborbital rocket. A permittee must— (a) During permitted flight, measure in real time the position and velocity of its reusable suborbital rocket; and (b) Provide position and...

  5. 14 CFR 437.67 - Tracking a reusable suborbital rocket.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 false Tracking a reusable suborbital rocket. 437... a reusable suborbital rocket. A permittee must— (a) During permitted flight, measure in real time the position and velocity of its reusable suborbital rocket; and (b) Provide position and...

  6. 14 CFR 437.67 - Tracking a reusable suborbital rocket.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Tracking a reusable suborbital rocket. 437... a reusable suborbital rocket. A permittee must— (a) During permitted flight, measure in real time the position and velocity of its reusable suborbital rocket; and (b) Provide position and...

  7. Formation of Amides from Imines via Cyanide-Mediated Metal-Free Aerobic Oxidation.

    PubMed

    Seo, Hong-Ahn; Cho, Yeon-Ho; Lee, Ye-Sol; Cheon, Cheol-Hong

    2015-12-18

    A new protocol for the direct formation of amides from imines derived from aromatic aldehydes via metal-free aerobic oxidation in the presence of cyanide is described. This protocol was applicable to various aldimines, and the desired amides were obtained in moderate to good yields. Mechanistic studies suggested that this aerobic oxidative amidation might proceed via the addition of cyanide to imines followed by proton transfer from carbon to nitrogen in the original imines, leading to carbanions of α-amino nitriles, which undergo subsequent oxidation with molecular oxygen in air to provide the desired amide compounds.

  8. Transitions.

    ERIC Educational Resources Information Center

    Field, David; And Others

    1992-01-01

    Includes four articles: "Career Aspirations" (Field); "Making the Transition to a New Curriculum" (Baker, Householder); "How about a 'Work to School' Transition?" (Glasberg); and "Technological Improvisation: Bringing CNC to Woodworking" (Charles, McDuffie). (SK)

  9. Metal-free photochemical silylations and transfer hydrogenations of benzenoid hydrocarbons and graphene

    NASA Astrophysics Data System (ADS)

    Papadakis, Raffaello; Li, Hu; Bergman, Joakim; Lundstedt, Anna; Jorner, Kjell; Ayub, Rabia; Haldar, Soumyajyoti; Jahn, Burkhard O.; Denisova, Aleksandra; Zietz, Burkhard; Lindh, Roland; Sanyal, Biplab; Grennberg, Helena; Leifer, Klaus; Ottosson, Henrik

    2016-10-01

    The first hydrogenation step of benzene, which is endergonic in the electronic ground state (S0), becomes exergonic in the first triplet state (T1). This is in line with Baird's rule, which tells that benzene is antiaromatic and destabilized in its T1 state and also in its first singlet excited state (S1), opposite to S0, where it is aromatic and remarkably unreactive. Here we utilized this feature to show that benzene and several polycyclic aromatic hydrocarbons (PAHs) to various extents undergo metal-free photochemical (hydro)silylations and transfer-hydrogenations at mild conditions, with the highest yield for naphthalene (photosilylation: 21%). Quantum chemical computations reveal that T1-state benzene is excellent at H-atom abstraction, while cyclooctatetraene, aromatic in the T1 and S1 states according to Baird's rule, is unreactive. Remarkably, also CVD-graphene on SiO2 is efficiently transfer-photohydrogenated using formic acid/water mixtures together with white light or solar irradiation under metal-free conditions.

  10. Effects of Computer-Aided Manufacturing Technology on Precision of Clinical Metal-Free Restorations

    PubMed Central

    Lee, Ki-Hong; Yeo, In-Sung; Wu, Benjamin M.; Yang, Jae-Ho; Han, Jung-Suk; Kim, Sung-Hun; Yi, Yang-Jin; Kwon, Taek-Ka

    2015-01-01

    Purpose. The purpose of this study was to investigate the marginal fit of metal-free crowns made by three different computer-aided design/computer-aided manufacturing (CAD/CAM) systems. Materials and Methods. The maxillary left first premolar of a dentiform was prepared for all-ceramic crown restoration. Thirty all-ceramic premolar crowns were made, ten each manufactured by the Lava system, Cercon, and Cerec. Ten metal ceramic gold (MCG) crowns served as control. The marginal gap of each sample was measured under a stereoscopic microscope at 75x magnification after cementation. One-way ANOVA and the Duncan's post hoc test were used for data analysis at the significance level of 0.05. Results. The mean (standard deviation) marginal gaps were 70.5 (34.4) μm for the MCG crowns, 87.2 (22.8) μm for Lava, 58.5 (17.6) μm for Cercon, and 72.3 (30.8) μm for Cerec. There were no significant differences in the marginal fit among the groups except that the Cercon crowns had significantly smaller marginal gaps than the Lava crowns (P < 0.001).  Conclusions. Within the limitation of this study, all the metal-free restorations made by the digital CAD/CAM systems had clinically acceptable marginal accuracy. PMID:26557681

  11. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    NASA Astrophysics Data System (ADS)

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-07-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.

  12. Mechanism of Photoinduced Metal-Free Atom Transfer Radical Polymerization: Experimental and Computational Studies.

    PubMed

    Pan, Xiangcheng; Fang, Cheng; Fantin, Marco; Malhotra, Nikhil; So, Woong Young; Peteanu, Linda A; Isse, Abdirisak A; Gennaro, Armando; Liu, Peng; Matyjaszewski, Krzysztof

    2016-02-24

    Photoinduced metal-free atom transfer radical polymerization (ATRP) of methyl methacrylate was investigated using several phenothiazine derivatives and other related compounds as photoredox catalysts. The experiments show that all selected catalysts can be involved in the activation step, but not all of them participated efficiently in the deactivation step. The redox properties and the stability of radical cations derived from the catalysts were evaluated by cyclic voltammetry. Laser flash photolysis (LFP) was used to determine the lifetime and activity of photoexcited catalysts. Kinetic analysis of the activation reaction according to dissociative electron-transfer (DET) theory suggests that the activation occurs only with an excited state of catalyst. Density functional theory (DFT) calculations revealed the structures and stabilities of the radical cation intermediates as well as the reaction energy profiles of deactivation pathways with different photoredox catalysts. Both experiments and calculations suggest that the activation process undergoes a DET mechanism, while an associative electron transfer involving a termolecular encounter (the exact reverse of DET pathway) is favored in the deactivation process. This detailed study provides a deeper understanding of the chemical processes of metal-free ATRP that can aid the design of better catalytic systems. Additionally, this work elucidates several important common pathways involved in synthetically useful organic reactions catalyzed by photoredox catalysts. PMID:26820243

  13. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts.

    PubMed

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S; Kumta, Prashant N

    2016-01-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations. PMID:27380719

  14. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    PubMed Central

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-01-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations. PMID:27380719

  15. The electrochemical and spectroelectrochemical properties of metal free and metallophthalocyanines containing triazole/piperazine units

    NASA Astrophysics Data System (ADS)

    Demirbaş, Ümit; Akyüz, Duygu; Mermer, Arif; Akçay, Hakkı Türker; Demirbaş, Neslihan; Koca, Atıf; Kantekin, Halit

    2016-01-01

    The synthesis and characterization of novel peripherally tetra [1,2,4]-triazole substituted metal-free phthalocyanine and its metal complexes (Zn(II), Ni(II), Pb(II), Cu(II) and Fe(II)) and the investigation of electrochemical and spectroelectrochemical properties of metal-free, Zn(II), Pb(II), Fe(II) phthalocyanines were performed for the first time in this study. Electrochemical characterizations of the complexes were performed with voltammetric and in situ spectroelectrochemical measurements. Voltammetric responses of the complexes supported the proposed structures, since complexes bearing redox inactive Pc ring metal centers just gave Pc based electron transfer reactions, while iron phthalocyanine went to metal based electron transfer reaction in addition to the Pc based ones. Electron withdrawing nature of [1,2,4]-triazole substituents shifted the redox processes toward the positive potentials. All complexes were electropolymerized during the oxidation reactions in dichloromethane (DCM) solvent. Types of the metal center of the complexes altered the electropolymerization reactions of the complexes. Spectra and colors of the electrogenerated redox species of the complexes were also determined with in situ spectroelectrochemical and in situ electrocolorimetric measurements.

  16. Metal-free photochemical silylations and transfer hydrogenations of benzenoid hydrocarbons and graphene

    PubMed Central

    Papadakis, Raffaello; Li, Hu; Bergman, Joakim; Lundstedt, Anna; Jorner, Kjell; Ayub, Rabia; Haldar, Soumyajyoti; Jahn, Burkhard O.; Denisova, Aleksandra; Zietz, Burkhard; Lindh, Roland; Sanyal, Biplab; Grennberg, Helena; Leifer, Klaus; Ottosson, Henrik

    2016-01-01

    The first hydrogenation step of benzene, which is endergonic in the electronic ground state (S0), becomes exergonic in the first triplet state (T1). This is in line with Baird's rule, which tells that benzene is antiaromatic and destabilized in its T1 state and also in its first singlet excited state (S1), opposite to S0, where it is aromatic and remarkably unreactive. Here we utilized this feature to show that benzene and several polycyclic aromatic hydrocarbons (PAHs) to various extents undergo metal-free photochemical (hydro)silylations and transfer-hydrogenations at mild conditions, with the highest yield for naphthalene (photosilylation: 21%). Quantum chemical computations reveal that T1-state benzene is excellent at H-atom abstraction, while cyclooctatetraene, aromatic in the T1 and S1 states according to Baird's rule, is unreactive. Remarkably, also CVD-graphene on SiO2 is efficiently transfer-photohydrogenated using formic acid/water mixtures together with white light or solar irradiation under metal-free conditions. PMID:27708336

  17. Growth of metal-free carbon nanotubes on glass substrate with an amorphous carbon catalyst layer.

    PubMed

    Seo, Jae Keun; Choi, Won Seok; Kim, Hee Dong; Lee, Jae-Hyeoung; Choi, Eun Chang; Kim, Hyung Jin; Hong, Byungyou

    2011-12-01

    We have investigated the direct growth of metal-free carbon nanotubes (CNTs) on glass substrates with microwave-plasma enhanced chemical vapor deposition (MPECVD). Amorphous carbon (a-C) films were used as a catalyst layer to grow metal-free CNTs. The a-C films were deposited on Corning glass substrates using RF magnetron sputtering with the use of a carbon target (99.99%) at room temperature. They were pretreated with hydrogen plasma using a microwave PECVD at 600 degrees C. Then, CNTs were prepared using microwave PECVD with a mixture of methane (CH4) and hydrogen (H2) gases. The CNTs were grown at different substrate temperatures (400 degrees C, 500 degrees C, and 600 degrees C) for 30 minutes. Other conditions were fixed. The growth trends of CNTs against substrate temperature were observed by field emission scanning electron microscopy (FE-SEM). The structure of a-C catalyst layer and grown CNTs were measured by Raman spectroscopy. High-resolution transmission electron microscopy (HR-TEM) images showed that the CNTs had bamboo-like multi-walled structures. Energy dispersive spectroscopy (EDS) measurements confirmed that the CNTs consisted of only carbon. PMID:22409050

  18. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts.

    PubMed

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S; Kumta, Prashant N

    2016-07-06

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.

  19. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    DOE PAGES

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-07-06

    We report that identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Furthermore, we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM basedmore » systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.« less

  20. Wear of metal-free resin composite crowns after three years in service.

    PubMed

    Zenthöfer, Andreas; Rammelsberg, Peter; Schmitt, Clemens; Ohlmann, Brigitte

    2013-01-01

    To compare differences between the wear behavior of two types of metal-free resin composite crown with a control after three years in clinical service. Sixty-six participants needing one to three posterior single crowns were fitted with 120 crowns. Abutment teeth were randomly assigned to three groups: 40 resin composite crowns with fiber-reinforced framework, 40 resin composite crowns without fiber-reinforced framework, and 40 metal-ceramic crowns. To assess wear, gypsum replicas of the crowns were fabricated and scanned with a 3D laser scanner at baseline and after three years. Differences between the groups were analyzed by use of mixed-effects regression models. Wear of resin composite crowns with fiber-reinforced framework (p=0.0043) and resin composite crowns without framework (p=0.0246) was significantly greater than in the metal-ceramic group. Wear of metal-free resin composite crowns after three years was significantly greater than that of metal-ceramic crowns, but the wear was still clinically acceptable.

  1. Reusable space systems (Eugen Saenger Lecture, 1987)

    NASA Technical Reports Server (NTRS)

    Fletcher, J. C.

    1988-01-01

    The history and current status of reusable launch vehicle (RLV) development are surveyed, with emphases on the contributions of Eugen Saenger and ongoing NASA projects. Topics addressed include the capabilities and achievements of the Space Shuttle, the need to maintain a fleet with both ELVs and RLVs to meet different mission requirements, the X-30 testbed aircraft for the National Aerospace Plane program, current design concepts for Shuttle II (a 1000-ton fully reusable two-stage rocket-powered spacecraft capable of carrying 11,000 kg to Space Station orbit), proposals for dual-fuel-propulsion SSTO RLVs, and the Space Station Orbital Maneuvering Vehicle and Orbital Transfer Vehicle. The importance of RLVs and of international cooperation in establishing the LEO infrastructure needed for planetary exploration missions is stressed.

  2. Cytocompatible in situ forming chitosan/hyaluronan hydrogels via a metal-free click chemistry for soft tissue engineering.

    PubMed

    Fan, Ming; Ma, Ye; Mao, Jiahui; Zhang, Ziwei; Tan, Huaping

    2015-07-01

    Injectable hydrogels are important cell scaffolding materials for tissue engineering and regenerative medicine. Here, we report a new class of biocompatible and biodegradable polysaccharide hydrogels derived from chitosan and hyaluronan via a metal-free click chemistry, without the addition of copper catalyst. For the metal-free click reaction, chitosan and hyaluronan were modified with oxanorbornadiene (OB) and 11-azido-3,6,9-trioxaundecan-1-amine (AA), respectively. The gelation is attributed to the triazole ring formation between OB and azido groups of polysaccharide derivatives. The molecular structures were verified by FT-IR spectroscopy and elemental analysis, giving substitution degrees of 58% and 47% for chitosan-OB and hyaluronan-AA, respectively. The in vitro gelation, morphologies, equilibrium swelling, compressive modulus and degradation of the composite hydrogels were examined. The potential of the metal-free hydrogel as a cell scaffold was demonstrated by encapsulation of human adipose-derived stem cells (ASCs) within the gel matrix in vitro. Cell culture showed that this metal-free hydrogel could support survival and proliferation of ASCs. A preliminary in vivo study demonstrated the usefulness of the hydrogel as an injectable scaffold for adipose tissue engineering. These characteristics provide a potential opportunity to use the metal-free click chemistry in preparation of biocompatible hydrogels for soft tissue engineering applications.

  3. The reusable launch vehicle technology program

    NASA Technical Reports Server (NTRS)

    Cook, S.

    1995-01-01

    Today's launch systems have major shortcomings that will increase in significance in the future, and thus are principal drivers for seeking major improvements in space transportation. They are too costly; insufficiently reliable, safe, and operable; and increasingly losing market share to international competition. For the United States to continue its leadership in the human exploration and wide ranging utilization of space, the first order of business must be to achieve low cost, reliable transportatin to Earth orbit. NASA's Access to Space Study, in 1993, recommended the development of a fully reusable single-stage-to-orbit (SSTO) rocket vehicle as an Agency goal. The goal of the Reusable Launch Vehicle (RLV) technology program is to mature the technologies essential for a next-generation reusable launch system capable of reliably serving National space transportation needs at substantially reduced costs. The primary objectives of the RLV technology program are to (1) mature the technologies required for the next-generation system, (2) demonstrate the capability to achieve low development and operational cost, and rapid launch turnaround times and (3) reduce business and technical risks to encourage significant private investment in the commercial development and operation of the next-generation system. Developing and demonstrating the technologies required for a Single Stage to Orbit (SSTO) rocket is a focus of the program becuase past studies indicate that it has the best potential for achieving the lowest space access cost while acting as an RLV technology driver (since it also encompasses the technology requirements of reusable rocket vehicles in general).

  4. Self-unloading, reusable, lunar lander project

    NASA Technical Reports Server (NTRS)

    Arseculeratne, Ruwan; Cavazos, Melissa; Euker, John; Ghavidel, Fred; Hinkel, Todd J.; Hitzfelder, John; Leitner, Jesse; Nevik, James; Paynter, Scott; Zolondek, Allen

    1990-01-01

    In the early 21st century, NASA will return to the Moon and establish a permanent base. To achieve this goal safely and economically, B&T Engineering has designed an unmanned, reusable, self-unloading lunar lander. The lander is designed to deliver 15,000 kg payloads from an orbit transfer vehicle (OTV) in a low lunar polar orbit and an altitude of 200 km to any location on the lunar surface.

  5. Improvement of reusable surface insulation material

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The results are presented of a program to improve the reusable surface insulation (RSI) system through the improvement of the LI-1500 material properties and the simplification of the RSI system. The improvements made include: 2500 F-capability RSI systems, water-impervious surface coatings, establishment of a high-emittance coating constituent, development of a secondary water-reduction system, and achievement of a lower density (9 pcf) RSI material.

  6. The Venture Star Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This artist's concept is of the X-33 Advanced Technology Demonstrator, a subscale prototype Reusable Launch Vehicle (RLV), in its 1997 configuration. Named the Venture Star, this vehicle manufactured by Lockheed Martin Skunk Works, is shown in orbit with a deployed payload. The Venture Star was one of the earliest versions of the RLV's developed in attempt to replace the aging shuttle fleet. The X-33 program has been discontinued.

  7. Australia and the new reusable launch vehicles

    NASA Astrophysics Data System (ADS)

    Stalker, R. J.

    The new generation of reusable launch vehicles represented by ESA's Hermes and HOTOL, NASA's National Aerospace Plane, and the DFVLR's Saenger, promises to radically alter the economic basis of space flight by allowing such operations as the on-orbit servicing of satellites. Attention is presently drawn to the opportunities that arise for Australia's aerospace industry from the availability in Australia of two wind tunnel facilities capable of furnishing the requisite hypersonic aerothermodynamics testing capabilities for these vehicles' development.

  8. 24 Inch Reusable Solid Rocket Motor Test

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A scaled-down 24-inch version of the Space Shuttle's Reusable Solid Rocket Motor was successfully fired for 21 seconds at a Marshall Space Flight Center (MSFC) Test Stand. The motor was tested to ensure a replacement material called Lycocel would meet the criteria set by the Shuttle's Solid Motor Project Office. The current material is a heat-resistant, rayon-based, carbon-cloth phenolic used as an insulating material for the motor's nozzle. Lycocel, a brand name for Tencel, is a cousin to rayon and is an exceptionally strong fiber made of wood pulp produced by a special 'solvent-spirning' process using a nontoxic solvent. It will also be impregnated with a phenolic resin. This new material is expected to perform better under the high temperatures experienced during launch. The next step will be to test the material on a 48-inch solid rocket motor. The test, which replicates launch conditions, is part of Shuttle's ongoing verification of components, materials, and manufacturing processes required by MSFC, which oversees the Reusable Solid Rocket Motor project. Manufactured by the ATK Thiokol Propulsion Division in Promontory, California, the Reusable Solid Rocket Motor measures 126 feet (38.4 meters) long and 12 feet (3.6 meters) in diameter. It is the largest solid rocket motor ever flown and the first designed for reuse. During its two-minute burn at liftoff, each motor generates an average thrust of 2.6 million pounds (1.2 million kilograms).

  9. In-plane graphene/boron-nitride heterostructures as an efficient metal-free electrocatalyst for the oxygen reduction reaction.

    PubMed

    Sun, Qiao; Sun, Caixia; Du, Aijun; Dou, Shixue; Li, Zhen

    2016-08-01

    Exploiting metal-free catalysts for the oxygen reduction reaction (ORR) and understanding their catalytic mechanisms are vital for the development of fuel cells (FCs). Our study has demonstrated that in-plane heterostructures of graphene and boron nitride (G/BN) can serve as an efficient metal-free catalyst for the ORR, in which the C-N interfaces of G/BN heterostructures act as reactive sites. The formation of water at the heterointerface is both energetically and kinetically favorable via a four-electron pathway. Moreover, the water formed can be easily released from the heterointerface, and the catalytically active sites can be regenerated for the next cycle. Since G/BN heterostructures with controlled domain sizes have been successfully synthesized in recent reports (e.g. Nat. Nanotechnol., 2013, 8, 119), our results highlight the great potential of such heterostructures as a promising metal-free catalyst for the ORR in FCs. PMID:27396486

  10. The catalytic pathways of hydrohalogenation over metal-free nitrogen-doped carbon nanotubes.

    PubMed

    Zhou, Kai; Li, Bo; Zhang, Qiang; Huang, Jia-Qi; Tian, Gui-Li; Jia, Jin-Chao; Zhao, Meng-Qiang; Luo, Guo-Hua; Su, Dang Sheng; Wei, Fei

    2014-03-01

    Nitrogen-doped carbon nanotubes (N-CNTs) are found to be active as one novel heterogeneous catalyst for acetylene hydrochlorination reaction, possessing good activity (TOF=2.3×10(-3)  s(-1) ) and high selectivity (>98 %). Compared to toxic and energy-consuming conventional catalysts, such as HgCl2 , N-CNTs are more favorable in terms of sustainability, because of their thermo-stability, metal-free make up, and the wide availability of bulk CNT. Coupling X-ray photoelectron spectroscopy and density functional theory computations (DFT), the main active source and reaction pathway are shown. Good linearity between the quaternary nitrogen content and conversion is revealed. DFT study shows that the nitrogen doping enhanced the formation of the covalent bond between C2 H2 and NCNT compared with the undoped CNT, and therefore promoted the addition reaction of the C2 H2 and HCl into C2 H3 Cl.

  11. A metal-free strategy to release chemisorbed H2 from hydrogenated boron nitride nanotubes.

    PubMed

    Roy, Lisa; Bhunya, Sourav; Paul, Ankan

    2014-11-10

    Chemisorbed hydrogen on boron nitride nanotubes (BNNT) can only be released thermally at very high temperatures above 350 °C. However, no catalyst has been identified that could liberate H2 from hydrogenated BN nanotubes under moderate conditions. Using different density functional methods we predict that the desorption of chemisorbed hydrogen from hydrogenated BN nanotubes can be facilitated catalytically by triflic acid at low free-energy activation barriers and appreciable rates under metal free conditions and mildly elevated temperatures (40-50 °C). Our proposed mechanism shows that the acid is regenerated in the process and can further facilitate similar catalytic release of H2 , thus suggesting all the chemisorbed hydrogen on the surface of the hydrogenated nanotube can be released in the form of H2 . These findings essentially raise hope for the development of a sustainable chemical hydrogen storage strategy in BN nanomaterials. PMID:25132421

  12. Metal-Free Flat Lens Using Negative Refraction by Nonlinear Four-Wave Mixing

    NASA Astrophysics Data System (ADS)

    Cao, Jianjun; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Wan, Wenjie

    2014-11-01

    A perfect lens with unlimited resolution has always posed a challenge to both theoretical and experimental physicists. Recent developments in optical metamaterials promise an attractive approach towards perfect lenses using negative refraction to overcome the diffraction limit, improving resolution. However, those artificially engineered metamaterials are usually accompanied by high losses from metals and are extremely difficult to fabricate. An alternative proposal using negative refraction by four-wave mixing has attracted much interest recently, though most existing experiments still require metals and none of them have been implemented for an optical lens. Here, we experimentally demonstrate a metal-free flat lens for the first time using negative refraction by degenerate four-wave mixing with a thin glass slide. We realize an optical lensing effect utilizing a nonlinear refraction law, which may have potential applications in microscopy.

  13. Metal-Free on-Surface Photochemical Homocoupling of Terminal Alkynes.

    PubMed

    Colazzo, Luciano; Sedona, Francesco; Moretto, Alessandro; Casarin, Maurizio; Sambi, Mauro

    2016-08-17

    On-surface synthesis involving the homocoupling of aryl-alkynes affords the buildup of bisacetylene derivatives directly at surfaces, which in turn may be further used as ingredients for the production of novel functional materials. Generally, homocoupling of terminal alkynes takes place by thermal activation of molecular precursors on metal surfaces. However, the interaction of alkynes with surface metal atoms often induces unwanted reaction pathways when thermal energy is provided to the system. In this contribution we report about light-induced metal-free homocoupling of terminal alkynes on highly oriented pyrolitic graphite (HOPG). The reaction occurred with high efficiency and selectivity within a self-assembled monolayer (SAM) of aryl-alkynes and led to the generation of large domains of ordered butadiynyl derivatives. Such a photochemical uncatalyzed pathway represents an original approach in the field of topological C-C coupling at the solid/liquid interface. PMID:27437555

  14. Photoelectric properties of unsymmetrical metal-free phthalocyanine and C60 complex thin films

    NASA Astrophysics Data System (ADS)

    Yang, Zhigang; Shen, Yue; Zhang, Jiancheng

    2004-12-01

    In this paper, novel one amino-group substituted unsymmetrical metal-free phthalocyanine (AUMPc) was synthesized, then the complex of AUMPc with C60 (The Complex) was obtained in the mixed solvents. Ultraviolet-visible (Uv-vis) spectrophotometer, fluorescence spectrophotometer and home-made photoconductivity meter were used to study the photoelectric properties of AUMPc and the complex. It was found that the absorbance of The Complex was larger than that of the total of AUMPc and C60 in the B belt (333nm), the absorbance of The Complex in the Q belt (693nm) where C60 had no absorbance was also increased. C60 took the role as annihilation in AUMPc, the photoconductivity of the Complex thin film was clearly increased when the film was exposed in the light.

  15. Hydrogen Sulfide Induced Carbon Dioxide Activation by Metal-Free Dual Catalysis.

    PubMed

    Kumar, Manoj; Francisco, Joseph S

    2016-03-18

    The role of metal free dual catalysis in the hydrogen sulfide (H2S)-induced activation of carbon dioxide (CO2) and subsequent decomposition of resulting monothiolcarbonic acid in the gas phase has been explored. The results suggest that substituted amines and monocarboxylic type organic or inorganic acids via dual activation mechanisms promote both activation and decomposition reactions, implying that the judicious selection of a dual catalyst is crucial to the efficient C-S bond formation via CO2 activation. Considering that our results also suggest a new mechanism for the formation of carbonyl sulfide from CO2 and H2S, these new insights may help in better understanding the coupling between the carbon and sulfur cycles in the atmospheres of Earth and Venus.

  16. Metal-free flat lens using negative refraction by nonlinear four-wave mixing.

    PubMed

    Cao, Jianjun; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Wan, Wenjie

    2014-11-21

    A perfect lens with unlimited resolution has always posed a challenge to both theoretical and experimental physicists. Recent developments in optical metamaterials promise an attractive approach towards perfect lenses using negative refraction to overcome the diffraction limit, improving resolution. However, those artificially engineered metamaterials are usually accompanied by high losses from metals and are extremely difficult to fabricate. An alternative proposal using negative refraction by four-wave mixing has attracted much interest recently, though most existing experiments still require metals and none of them have been implemented for an optical lens. Here, we experimentally demonstrate a metal-free flat lens for the first time using negative refraction by degenerate four-wave mixing with a thin glass slide. We realize an optical lensing effect utilizing a nonlinear refraction law, which may have potential applications in microscopy.

  17. Metal-Free Ammonia-Borane Dehydrogenation Catalyzed by a Bis(borane) Lewis Acid.

    PubMed

    Lu, Zhenpin; Schweighauser, Luca; Hausmann, Heike; Wegner, Hermann A

    2015-12-14

    The storage of energy in a safe and environmentally benign way is one of the main challenges of today's society. Ammonia-borane (AB=NH3 BH3 ) has been proposed as a possible candidate for the chemical storage of hydrogen. However, the efficient release of hydrogen is still an active field of research. Herein, we present a metal-free bis(borane) Lewis acid catalyst that promotes the evolution of up to 2.5 equivalents of H2 per AB molecule. The catalyst can be reused multiple times without loss of activity. The moderate temperature of 60 °C allows for controlling the supply of H2 on demand simply by heating and cooling. Mechanistic studies give preliminary insights into the kinetics and mechanism of the catalytic reaction. PMID:26537288

  18. Metal-free flat lens using negative refraction by nonlinear four-wave mixing.

    PubMed

    Cao, Jianjun; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Wan, Wenjie

    2014-11-21

    A perfect lens with unlimited resolution has always posed a challenge to both theoretical and experimental physicists. Recent developments in optical metamaterials promise an attractive approach towards perfect lenses using negative refraction to overcome the diffraction limit, improving resolution. However, those artificially engineered metamaterials are usually accompanied by high losses from metals and are extremely difficult to fabricate. An alternative proposal using negative refraction by four-wave mixing has attracted much interest recently, though most existing experiments still require metals and none of them have been implemented for an optical lens. Here, we experimentally demonstrate a metal-free flat lens for the first time using negative refraction by degenerate four-wave mixing with a thin glass slide. We realize an optical lensing effect utilizing a nonlinear refraction law, which may have potential applications in microscopy. PMID:25479522

  19. Pioneering Metal-Free Oxidative Coupling Strategy of Aromatic Compounds Using Hypervalent Iodine Reagents.

    PubMed

    Kita, Yasuyuki; Dohi, Toshifumi

    2015-10-01

    We started our hypervalent iodine research about 30 years ago in the mid-1980s. We soon successfully developed the single-electron-transfer oxidation ability of a hypervalent iodine reagent, specifically, phenyliodine(III) bis(trifluoroacetate) (PIFA), toward aromatic rings of phenyl ethers for forming aromatic cation radicals. This was one of the exciting and unexpected events in our research studies so far, and the discovery was reported in 1991. It also led to the next challenge, developing the metal-free oxidative couplings for C-H functionalizations and direct couplings between the C-H bonds of valuable aromatic compounds in organic synthesis. In order to realize the effective oxidative coupling, pioneering new aromatic ring activations was essential and several useful methodologies have been found for oxidizable arenes. The achievements regarding this objective obtained in our continuous research are herein summarized with classification of the aromatic ring activation strategies.

  20. A Precious Metal-Free Electroless Technique for the Deposition of Copper on Carbon Fibers

    NASA Astrophysics Data System (ADS)

    Che, Dehui; Yao, Guangchun; Cao, Zhuokun

    2012-11-01

    This article introduces a new technique of electroless copper deposition on carbon fibers in the absence of precious metal as the catalyst. Copper layers were electrolessly deposited on the surface of carbon fiber without using the conventional palladium or silver catalyst to initiate redox reactions leading to metallization. This new technique shows that nickel seeds can serve as excellent catalysts to expedite the redox reactions. By performing experiments, parameters such as activation temperature, nickel ion concentration, and pH value were optimized, and an orbicular copper plating layer of carbon fiber was obtained in the copper sulfate salt-based conventional electroless solution. The surface morphology of copper coating was characterized by scanning electron microscopy and X-ray diffraction. The results indicate that uniform and smooth copper coating could be obtained by the new precious-metal free activation process. The resulting copper coating thickness is about 1 μm.

  1. Indium tin oxide-free and metal-free semitransparent organic solar cells

    SciTech Connect

    Zhou, Yinhua; Cheun, Hyeunseok; Choi, Seungkeun; Potscavage, William J.; Fuentes-Hernandez, Canek; Kippelen, Bernard

    2010-01-01

    We report on indium tin oxide (ITO)-free and metal-free semitransparent organic solar cells with a high-conductivity poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) (PH1000) as both the bottom and the top electrodes. The PH1000 film showed a conductivity of 680±50 S/cm . A ZnO layer was used as an interlayer to produce an electron-selective electrode. The semitransparent devices with a structure of glass/PH1000/ZnO/poly(3-hexylthiophene):phenyl-C61 -butyric acid methyl ester/PEDOT:PSS (CPP 105 D)/PH1000 exhibited an average power conversion efficiency of 1.8% estimated for 100 mW/cm2 air mass 1.5 global illumination. This geometry alleviates the need of vacuum deposition of a top electrode.

  2. Metal-free organic sensitizers for use in water-splitting dye-sensitized photoelectrochemical cells

    PubMed Central

    Swierk, John R.; Méndez-Hernández, Dalvin D.; McCool, Nicholas S.; Liddell, Paul; Terazono, Yuichi; Pahk, Ian; Tomlin, John J.; Oster, Nolan V.; Moore, Thomas A.; Moore, Ana L.; Gust, Devens; Mallouk, Thomas E.

    2015-01-01

    Solar fuel generation requires the efficient capture and conversion of visible light. In both natural and artificial systems, molecular sensitizers can be tuned to capture, convert, and transfer visible light energy. We demonstrate that a series of metal-free porphyrins can drive photoelectrochemical water splitting under broadband and red light (λ > 590 nm) illumination in a dye-sensitized TiO2 solar cell. We report the synthesis, spectral, and electrochemical properties of the sensitizers. Despite slow recombination of photoinjected electrons with oxidized porphyrins, photocurrents are low because of low injection yields and slow electron self-exchange between oxidized porphyrins. The free-base porphyrins are stable under conditions of water photoelectrolysis and in some cases photovoltages in excess of 1 V are observed. PMID:25583488

  3. In-plane graphene/boron-nitride heterostructures as an efficient metal-free electrocatalyst for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Sun, Qiao; Sun, Caixia; Du, Aijun; Dou, Shixue; Li, Zhen

    2016-07-01

    Exploiting metal-free catalysts for the oxygen reduction reaction (ORR) and understanding their catalytic mechanisms are vital for the development of fuel cells (FCs). Our study has demonstrated that in-plane heterostructures of graphene and boron nitride (G/BN) can serve as an efficient metal-free catalyst for the ORR, in which the C-N interfaces of G/BN heterostructures act as reactive sites. The formation of water at the heterointerface is both energetically and kinetically favorable via a four-electron pathway. Moreover, the water formed can be easily released from the heterointerface, and the catalytically active sites can be regenerated for the next cycle. Since G/BN heterostructures with controlled domain sizes have been successfully synthesized in recent reports (e.g. Nat. Nanotechnol., 2013, 8, 119), our results highlight the great potential of such heterostructures as a promising metal-free catalyst for the ORR in FCs.Exploiting metal-free catalysts for the oxygen reduction reaction (ORR) and understanding their catalytic mechanisms are vital for the development of fuel cells (FCs). Our study has demonstrated that in-plane heterostructures of graphene and boron nitride (G/BN) can serve as an efficient metal-free catalyst for the ORR, in which the C-N interfaces of G/BN heterostructures act as reactive sites. The formation of water at the heterointerface is both energetically and kinetically favorable via a four-electron pathway. Moreover, the water formed can be easily released from the heterointerface, and the catalytically active sites can be regenerated for the next cycle. Since G/BN heterostructures with controlled domain sizes have been successfully synthesized in recent reports (e.g. Nat. Nanotechnol., 2013, 8, 119), our results highlight the great potential of such heterostructures as a promising metal-free catalyst for the ORR in FCs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr03288e

  4. Transits

    NASA Astrophysics Data System (ADS)

    Gilliland, Ronald L.

    Transits of the planets Mercury and especially Venus have been exciting events in the development of astronomy over the past few hundred years. Just two years ago the first transiting extra-solar planet, HD 209458b, was discovered, and subsequent studies during transit have contributed fundamental new knowledge. From the photometric light curve during transit one obtains a basic confirmation that the radial velocity detected object is indeed a planet by allowing precise determination of its mass and radius relative to these stellar quantities. From study of spectroscopic changes during transit it has been possible to probe for individual components of the transiting planets atmosphere. Planet transits are likely to become a primary tool for detection of new planets, especially other Earth-like planets with the Kepler Discovery Mission. Looking ahead, the additional aperture of the James Webb Space Space Telescope promises to allow the first possibility of studying the atmosphere of extra-solar Earth-analogue planets, perhaps even providing the first evidence of direct relevance to the search for signs of life on other planets.

  5. High reactivity of metal-free nitrogen-doped carbon nanotube for the C-H activation

    NASA Astrophysics Data System (ADS)

    Hu, Xingbang; Zhou, Zheng; Lin, Qiuxing; Wu, Youting; Zhang, Zhibing

    2011-02-01

    Generally speaking, metal is necessary to serve as the active center in C-H activation. Herein, we found that the N-C part of the metal-free nitrogen-doped carbon nanotube (NCNT) can be used as the active center in methane C-H activation. The NCNT can activate O 2 and further activate methane by the adsorbed oxygen atoms. The catalytic ability of this metal-free NCNT is comparable to these reported noble metal catalysts and enzymes. Another character being different from many previous catalysts is that both two O atoms of O 2 can be effectively used as oxidant in the catalytic cycle of NCNT.

  6. Highly reusable space transportation system study

    SciTech Connect

    Haney, J.W.

    1997-01-01

    To significantly increase demand for launch services by stimulating existing and planned markets as well as enabling new markets, the cost to orbit needs to be reduced a factor of ten below projected Reusable Launch Vehicle (RLV) goals. This will place the recurring operations cost around {dollar_sign}200 per payload pound to low earth orbit (LEO). Methods for reducing the cost include: increasing relative vehicle performance, increasing vehicle reusability, and decreasing recurring operations. A study was conducted for NASA in support of its Highly Reusable Space Transportation (HRST) initiative to identify for further assessment and development, those launch strategies that hold the greatest potential with respect to meeting this goal. During this study a number of candidate strategies were evaluated associated with access to space. Both technical and cost trades were performed, and concluded that there are two airbreathing propulsion concepts utilizing launch assist that appear promising in achieving the HRST-cost goals. These concepts employ both turbine based combine cycle (TBCC) and rocket based combine cycle (RBCC) propulsion systems. The launch assist selected uses electromagnetic propulsion and a guideway to provide both delta velocity and altitude. A first order investigation of system level requirements associated with HRST launch assist for a magnetically launched vehicle including guideway concept and requirements as well as magnetic levitation and propulsion concepts and requirements were also conducted. This study concluded that the HRST goals of total recurring operations cost of {dollar_sign}200 per payload pound to Low Earth Orbit based on a ten year operational period were feasible if the required technology was matured. The most promising concept to achieve these goals is based on a RBCC powered vehicle with electromagnetic launch assist. {copyright} {ital 1997 American Institute of Physics.}

  7. Highly reusable space transportation system study

    NASA Astrophysics Data System (ADS)

    Haney, J. W.

    1997-01-01

    To significantly increase demand for launch services by stimulating existing and planned markets as well as enabling new markets, the cost to orbit needs to be reduced a factor of ten below projected Reusable Launch Vehicle (RLV) goals. This will place the recurring operations cost around 200 per payload pound to low earth orbit (LEO). Methods for reducing the cost include: increasing relative vehicle performance, increasing vehicle reusability, and decreasing recurring operations. A study was conducted for NASA in support of its Highly Reusable Space Transportation (HRST) initiative to identify for further assessment and development, those launch strategies that hold the greatest potential with respect to meeting this goal. During this study a number of candidate strategies were evaluated associated with access to space. Both technical and cost trades were performed, and concluded that there are two airbreathing propulsion concepts utilizing launch assist that appear promising in achieving the HRST-cost goals. These concepts employ both turbine based combine cycle (TBCC) and rocket based combine cycle (RBCC) propulsion systems. The launch assist selected uses electromagnetic propulsion and a guideway to provide both delta velocity and altitude. A first order investigation of system level requirements associated with HRST launch assist for a magnetically launched vehicle including guideway concept and requirements as well as magnetic levitation and propulsion concepts and requirements were also conducted. This study concluded that the HRST goals of total recurring operations cost of 200 per payload pound to Low Earth Orbit based on a ten year operational period were feasible if the required technology was matured. The most promising concept to achieve these goals is based on a RBCC powered vehicle with electromagnetic launch assist.

  8. Reusable crucible for containing corrosive liquids

    DOEpatents

    Pruneda, J.A.H. de.

    1995-01-24

    A reusable, non-wetting, corrosion-resistant material suitable for containment of corrosive liquids is formed of a tantalum or tantalum alloy substrate that is permeated with carbon atoms. The substrate is carburized to form surface layers of TaC and Ta[sub 2]C, and then is heated at high temperature under vacuum until the carbon atoms in the carbide layers diffuse throughout the substrate to form a solid solution of carbon atoms randomly interspersed in the tantalum or tantalum alloy lattice. 10 figures.

  9. Reusable launch vehicle facts and fantasies

    NASA Astrophysics Data System (ADS)

    Kaplan, Marshall H.

    2002-01-01

    Many people refuse to address many of the realities of reusable launch vehicle systems, technologies, operations and economics. Basic principles of physics, space flight operations, and business limitations are applied to the creation of a practical vision of future expectations. While reusable launcher concepts have been proposed for several decades, serious review of potential designs began in the mid-1990s, when NASA decided that a Space Shuttle replacement had to be pursued. A great deal of excitement and interest was quickly generated by the prospect of ``orders-of-magnitude'' reduction in launch costs. The potential for a vastly expanded space program motivated the entire space community. By the late-1990s, and after over one billion dollars were spent on the technology development and privately-funded concepts, it had become clear that there would be no new, near-term operational reusable vehicle. Many factors contributed to a very expensive and disappointing effort to create a new generation of launch vehicles. It began with overly optimistic projections of technology advancements and the belief that a greatly increased demand for satellite launches would be realized early in the 21st century. Contractors contributed to the perception of quickly reachable technology and business goals, thus, accelerating the enthusiasm and helping to create a ``gold rush'' euphoria. Cost, schedule and performance margins were all highly optimistic. Several entrepreneurs launched start up companies to take advantage of the excitement and the availability of investor capital. Millions were raised from private investors and venture capitalists, based on little more than flashy presentations and animations. Well over $500 million were raised by little-known start up groups to create reusable systems, which might complete for the coming market in launch services. By 1999, it was clear that market projections, made just two years earlier, were not going to be realized. Investors

  10. Reusable crucible for containing corrosive liquids

    DOEpatents

    de Pruneda, Jean A. H.

    1995-01-01

    A reusable, non-wetting, corrosion-resistant material suitable for containment of corrosive liquids is formed of a tantalum or tantalum alloy substrate that is permeated with carbon atoms. The substrate is carburized to form surface layers of TaC and Ta.sub.2 C, and then is heated at high temperature under vacuum until the carbon atoms in the carbide layers diffuse throughout the substrate to form a solid solution of carbon atoms randomly interspersed in the tantalum or tantalum alloy lattice.

  11. Military applications of reusable launch vehicles (RLVs)

    NASA Astrophysics Data System (ADS)

    Sponable, Jess M.

    1996-03-01

    With the development and operational fielding of fully reusable launch vehicles (RLVs) becoming imminent, coupled with the ``end of the Cold War'' and fractionalization of the former ``bi-polar'' world into a ``multi-polar'' one, the need and potential for military versions of RLVs are being recognized by the military strategic planner. Recognizing the instability of the world order, especially with the potential for terrorism from all quarters, planning for the development of systems capable of defending our critical space based assests is becoming more essential. This paper presents some of the potential military applications of RLVs to support the Nation's defense and security interests world-wide.

  12. Metal-free transannulation reaction of indoles with nitrostyrenes: a simple practical synthesis of 3-substituted 2-quinolones†

    PubMed Central

    Aksenov, Alexander V.; Smirnov, Alexander N.; Aksenov, Nicolai A.; Aksenova, Inna V.; Frolova, Liliya V.; Kornienko, Alexander; Magedov, Igor V.; Rubin, Michael

    2016-01-01

    3-Substituted 2-quinolones are obtained via a novel, metal-free transannulation reaction of 2-substituted indoles with 2-nitroalkenes in polyphosphoric acid. The reaction can be used in conjunction with the Fisher indole synthesis offering a practical three-component heteroannulation methodology to produce 2-quinolones from arylhydrazines, 2-nitroalkenes and acetophenone. PMID:23999797

  13. Metal-free one-pot synthesis of 2-substituted and 2,3-disubstituted morpholines from aziridines.

    PubMed

    Sun, Hongnan; Huang, Binbin; Lin, Run; Yang, Chao; Xia, Wujiong

    2015-01-01

    The metal-free synthesis of 2-substituted and 2,3-disubstituted morpholines through a one-pot strategy is described. A simple and inexpensive ammonium persulfate salt enables the reaction of aziridines with halogenated alcohols to proceed via an SN2-type ring opening followed by cyclization of the resulting haloalkoxy amine. PMID:25977727

  14. Metal-Free [2 + 2 + 2] Cycloaddition of Ynamides with Nitriles to Construct 2,4-Diaminopyridines.

    PubMed

    Zhang, Jingyi; Zhang, Qingshuang; Xia, Biao; Wu, Jie; Wang, Xiao-Na; Chang, Junbiao

    2016-07-15

    We present a metal-free [2 + 2 + 2] cycloaddition of ynamides with nitriles that enables highly efficient access to 2,4-diaminopyridines. This catalytic protocol is more environmentally friendly and allows for a concomitant construction of C-C and C-N bonds between ynamides and nitriles, exhibiting excellent chemoselectivity, regioselectivity, and wide functional groups tolerance. PMID:27366955

  15. Porous graphene-based material as an efficient metal free catalyst for the oxidative dehydrogenation of ethylbenzene to styrene.

    PubMed

    Diao, Jiangyong; Liu, Hongyang; Wang, Jia; Feng, Zhenbao; Chen, Tong; Miao, Changxi; Yang, Weimin; Su, Dang Sheng

    2015-02-25

    Reduced porous graphene oxide as a metal free catalyst was selected for the oxidative dehydrogenation of ethylbenzene to styrene. It showed the best catalytic performance compared with other carbon materials (routinely reduced graphene oxide, graphite powder and oxidized carbon nanotubes) and commercial iron oxide. PMID:25625943

  16. Visible-light initiated oxidative cyclization of phenyl propiolates with sulfinic acids to coumarin derivatives under metal-free conditions.

    PubMed

    Yang, Wenchao; Yang, Shuai; Li, Pinhua; Wang, Lei

    2015-05-01

    A visible-light initiated oxidative cyclization of phenyl propiolates with sulfinic acids has been developed. The arylsulfonylation of alkynes was performed at room temperature under metal-free conditions to generate coumarin derivatives with wide functional group tolerance, good yields and high regioselectivity.

  17. A Flexible Reusable Space Transportation System

    NASA Astrophysics Data System (ADS)

    Pietrobon, S. S.

    A crewless reusable vertical take-off horizontal landing space transportation system is investigated. The single stage launch vehicle goes into a very low orbit around the Earth. At burnout, the payload is deployed. At apogee, the upper stage fires to put the payload into its desired orbit. The launch vehicle continues in a single orbit of the Earth, re-entering the atmosphere and returning to the launch site. We call this near single stage to orbit (NSTO). For satellite payloads, the satellite and upper stage are carried in a reusable pod attached to the top of the vehicle. For crewed vehicles, the pod is replaced by a small winged vehicle which can be used for crew transfer and rescue from the International Space Station. This allows the launch vehicle to use a common bulkhead between the fuel and oxidiser tanks, further reducing launch vehicle mass. A number of propellant combinations are investigated. Computer simulations indicate that liquid oxygen with quadricyclene promises to give the largest payload mass for similar size vehicles. The launch vehicle can also be modified to be a fly- back booster for a heavy lift launch vehicle (HLLV). In this case the upper stage and payload are replaced with jet engines and kerosene fuel tanks. A pod is used to recover the second stage engines for reuse.

  18. Architecture and systems design of a reusable Martian twin rotor tailsitter

    NASA Astrophysics Data System (ADS)

    Forshaw, Jason L.; Lappas, Vaios J.

    2012-11-01

    A rapidly developing field is that of tailsitters, aircraft capable of transitioning between horizontal and vertical flight, a premise that supports a diverse range of applications. Tailsitters can effortlessly land and hover at will, yet can also move at high speed between destinations making them ideal in undertaking 'multiple missions to land at multiple destinations far apart'. This paper considers how the concept of twin helicopter rotor tailsitters, such as QinetiQ's Eye-OnTM, can be adapted for use in a Martian environment. The mission architecture and system requirements for both reusable and single-use tailsitters are considered and 12 disparate subsystems or fields (including propulsion, power and aerodynamics) are designed using a high-level systems approach. The resulting tailsitter is capable of covering 100km and 450km in reusable and single-use architectures respectively. A docking station is also designed utilising a four stage process for deployment of the tailsitter.

  19. Graphitic silicon nitride: a metal-free ferromagnet with charge and spin current rectification.

    PubMed

    Sen, Sabyasachi; Chakrabarti, Swapan

    2014-09-15

    As a first example, herein we show that g-Si(4)N(3) is expected to act as a metal-free ferromagnet featuring both charge and spin current rectification simultaneously. Such rectification is crucial for envisioning devices that contain both logic and memory functionality on a single chip. The spin coherent quantum-transport calculations on g-Si(4)N(3) reveal that the chosen system is a unique molecular spin filter, the current-voltage characteristics of which is asymmetric in nature, which can create a perfect background for synchronous charge and spin current rectification. To shed light on this highly unusual in-silico observation, we have meticulously inspected the bias-dependent modulation of the spin-polarized eigenstates. The results indicate that, whereas only the localized 2p orbitals of the outer-ring (OR) Si atoms participate in the transmission process in the positive bias, both OR Si and N atoms contribute in the reverse bias. Furthermore, we have evaluated the spin-polarized electron-transfer rate in the tunneling regime, and the results demonstrate that the transfer rates are unequal in the positive and negative bias range, leading to the possible realization of a simultaneous logic-memory device.

  20. Circularly Polarized Persistent Room-Temperature Phosphorescence from Metal-Free Chiral Aromatics in Air.

    PubMed

    Hirata, Shuzo; Vacha, Martin

    2016-04-21

    Circularly polarized room-temperature phosphorescence (RTP) with persistent emission characteristics was observed from metal-free chiral binaphthyl structures. Enantiomers of the binaphthyl compounds doped into an amorphous hydroxylated steroid matrix produced blue fluorescence and yellow persistent RTP in air. The lifetime and quantum yield of the yellow persistent RTP were 0.67 s and 2.3%, respectively. The dissymmetry factors of circular dichroism (CD) in the first absorption band, circularly polarized fluorescence (CPF), and circularly polarized persistent RTP were |1.1 × 10(-3)|, |4.5 × 10(-4)|, and |2.3 × 10(-3)|, respectively. A comparison between the experimental data and calculations by time-dependent density functional theory for transient CD spectra confirmed that the binaphthyl conformations in the lowest singlet excited state (S1) and the lowest triplet state (T1) were different. The large difference in the dissymmetry factors for the CPF and the circularly polarized persistent RTP was likely caused by this conformational change between S1 and T1. PMID:27058743

  1. Nitrogen-doped carbon nanotube as a potential metal-free catalyst for CO oxidation.

    PubMed

    Lin, I-Hsiang; Lu, Yu-Huan; Chen, Hsin-Tsung

    2016-04-28

    We elucidate the possibility of nitrogen-doped carbon nanotube as a robust catalyst for CO oxidation. We have performed first-principles calculations considering the spin-polarization effect to demonstrate the reaction of CO oxidation catalyzed by the nitrogen-doped carbon nanotube. The calculations show that O2 species can be partially reduced with charge transfer from the nitrogen-doped carbon nanotube and directly chemisorbed on the C-N sites of the nitrogen-doped carbon nanotube. The partially reduced O2 species at the C-N sites can further directly react with a CO molecule via the Eley-Rideal mechanism with the barriers of 0.45-0.58 eV for the different diameter of nanotube. Ab initio molecular dynamics (AIMD) simulations were performed and showed that the oxidation of CO occurs by the Eley-Rideal mechanism. The relationship between the curvature and reactivity of the nitrogen doped carbon nanotube was also unraveled. It appears that the barrier height of the rate-limiting step depends on the curvature of the nitrogen-doped carbon nanotube in the trend of (3,3)-NCNT < (4,4)-NCNT < (5,5)-NCNT (decreases with increased curvature). Using this relationship, we can predict the barriers for other N-doped carbon nanotubes with different tube diameters. Our results reveal that the nitrogen doped carbon nanomaterials can be a good, low-cost, and metal-free catalyst for CO oxidation.

  2. Circularly Polarized Persistent Room-Temperature Phosphorescence from Metal-Free Chiral Aromatics in Air.

    PubMed

    Hirata, Shuzo; Vacha, Martin

    2016-04-21

    Circularly polarized room-temperature phosphorescence (RTP) with persistent emission characteristics was observed from metal-free chiral binaphthyl structures. Enantiomers of the binaphthyl compounds doped into an amorphous hydroxylated steroid matrix produced blue fluorescence and yellow persistent RTP in air. The lifetime and quantum yield of the yellow persistent RTP were 0.67 s and 2.3%, respectively. The dissymmetry factors of circular dichroism (CD) in the first absorption band, circularly polarized fluorescence (CPF), and circularly polarized persistent RTP were |1.1 × 10(-3)|, |4.5 × 10(-4)|, and |2.3 × 10(-3)|, respectively. A comparison between the experimental data and calculations by time-dependent density functional theory for transient CD spectra confirmed that the binaphthyl conformations in the lowest singlet excited state (S1) and the lowest triplet state (T1) were different. The large difference in the dissymmetry factors for the CPF and the circularly polarized persistent RTP was likely caused by this conformational change between S1 and T1.

  3. Highly stable precious metal-free cathode catalyst for fuel cell application

    NASA Astrophysics Data System (ADS)

    Serov, Alexey; Workman, Michael J.; Artyushkova, Kateryna; Atanassov, Plamen; McCool, Geoffrey; McKinney, Sam; Romero, Henry; Halevi, Barr; Stephenson, Thomas

    2016-09-01

    A platinum group metal-free (PGM-free) oxygen reduction reaction (ORR) catalyst engineered for stability has been synthesized using the sacrificial support method (SSM). This catalyst was comprehensively characterized by physiochemical analyses and tested for performance and durability in fuel cell membrane electrode assemblies (MEAs). This catalyst, belonging to the family of Fe-N-C materials, is easily scalable and can be manufactured in batches up to 200 g. The fuel cell durability tests were performed in a single cell configuration at realistic operating conditions of 0.65 V, 1.25 atmgauge air, and 90% RH for 100 h. In-depth characterization of surface chemistry and morphology of the catalyst layer before and after durability tests were performed. The failure modes of the PGM-free electrodes were derived from structure-to-property correlations. It is suggested that under constant voltage operation, the performance loss results from degradation of the electrode pore structure, while under carbon corrosion accelerated test protocols the failure mode is catalyst corrosion.

  4. Nitrogen-doped carbon nanotubes as a highly active metal-free catalyst for selective oxidation.

    PubMed

    Chizari, Kambiz; Deneuve, Adrien; Ersen, Ovidiu; Florea, Ileana; Liu, Yu; Edouard, David; Janowska, Izabela; Begin, Dominique; Pham-Huu, Cuong

    2012-01-01

    Catalytic reactions are generally carried out on supported metals or oxides, which act as an active phase and require impregnation and thermal treatment steps. During tests, the metal or oxide nanoparticles could be further sintered, which would induces deactivation. Direct incorporation of the active phase into the matrix of a support could be an elegant alternative to prevent catalyst deactivation. Here, we report that nitrogen-doped carbon nanotubes (N-CNTs) can be efficiently employed as a metal-free catalyst for oxidative reactions that allow the selective transformation of the harmful, gaseous H(2)S into solid sulfur. The catalyst exhibits a high stability during the test at high space velocity. The macroscopic shaping of the catalyst on the silicon carbide foam also increases its catalytic activity by improving the contact between the reactants and the catalyst. Such macroscopic shaping allows the avoidance of problems linked with transport and handling of nanoscopic materials and also reduces the pressure drop across the catalyst bed to a large extent.

  5. Simple and versatile molecular donors for organic photovoltaics prepared by metal-free synthesis.

    PubMed

    Diac, Andreea; Demeter, Dora; Allain, Magali; Grosu, Ion; Roncali, Jean

    2015-01-19

    Donor-acceptor molecules (D-π-A) built by connecting a diphenylhydrazone block to a dicyanovinyl acceptor group via various thiophene-based π-conjugating spacers (1-5) were synthesized from mono- or dialdehydes by a simple metal-free procedure. Cyclic voltammetry and UV/Vis absorption spectroscopy show that the extension and/or increase of the donor strength of the spacer produces a decrease of the HOMO and LUMO energy level, a red shift of the absorption spectrum and an increase of the molecular absorption coefficient. Compared to solutions, the optical spectra of spin-cast thin films of compounds 1-3 show a broadening and red shift of the absorption bands, consistent with the formation of J-aggregates. In contrast the blue shift observed for the EDOT-containing compounds 4 and 5 suggests the presence of H-aggregates. Solution-cast and vacuum-deposited films of donors 1-5 were evaluated in solar cells with fullerene C60 as acceptor. A power-conversion efficiency among the highest reported for bilayer devices of basic configuration was obtained with compound 2. On the other hand, the results obtained with 4 and 5 suggest that the presence of EDOT in the structure can have deleterious effects on the organization and performances of the donor material.

  6. Bicarbonate-induced activation of H₂O₂ for metal-free oxidative desulfurization.

    PubMed

    Bokare, Alok D; Choi, Wonyong

    2016-03-01

    Efficient oxidative desulfurization (ODS) of model oil containing dibenzothiophene (DBT) and aromatic thiophenic derivatives has been achieved at room temperature using hydrogen peroxide activation by inorganic bicarbonate (HCO3(-)). Using in-situ formation of peroxymonocarbonate as oxidant, the transformation of main model substrate DBT to corresponding DBT-sulfone was easily accomplished in biphasic reaction conditions. In the presence of water-acetonitrile polar phase, increasing the water content upto 50% decreased the extraction capacity more than 3 times, but ∼ 90% DBT oxidation was still achieved. The oxidizing capacity of bicarbonate catalyst was maintained during repeated ODS cycles, but DBT removal efficiency was critically dependent on the extraction capacity of the polar phase. Under heterogeneous reaction conditions, bicarbonate-modified ion-exchange resin achieved similar ODS activity compared to the homogeneous catalytic system. Additionally, the efficient formation of peroxymonocarbonate using gaseous CO2 precursor in alkaline conditions was also utilized for DBT oxidation. The present study proposes the NaHCO3/H2O2 catalytic system as an efficient and cheap metal-free alternative for the oxidative removal of aromatic sulfur compounds from fuel oil. PMID:26561755

  7. Synthesis of Stacked-Cup Carbon Nanotubes in a Metal Free Low Temperature System

    NASA Technical Reports Server (NTRS)

    Kimura, Yuki; Nuth, Joseph A.; Johnson, Natasha M.; Farmer, Kevin D.; Roberts, Kenneth P.; Hussaini, Syed R.

    2011-01-01

    Stacked-cup carbon nanotubes were formed by either Fischer-Tropsch type or Haber Bosch type reactions in a metal free system. Graphite particles were used as the catalyst. The samples were heated at 600 C in a gas mixture of CO 75 Torr, N2 75 Torr and H2 550 Torr for three days. Trans mission electron microscope analysis of the catalyst surface at the completion of the experiment recognized the growth of nanotubes. They were 10-50 nm in diameter and approximately 1 micrometer in length. They had a hollow channel of 5-20 nm in the center. The nanotubes may have grown on graphite surfaces by the CO disproportionation reaction and the surface tension of the carbon nucleus may have determined the diameter. Although, generally, the diameter of a carbon nanotube depends on the size of the cataly1ic particles, the diameter of the nanotubes on graphite particles was independent of the particle size and significantly confined within a narrow range compared with that produced using catalytic amorphous iron-silicate nanoparticles. Therefore, they must have an unknown formation process that is different than the generally accepted mechanism.

  8. Sulfur-doped graphene as an efficient metal-free cathode catalyst for oxygen reduction.

    PubMed

    Yang, Zhi; Yao, Zhen; Li, Guifa; Fang, Guoyong; Nie, Huagui; Liu, Zheng; Zhou, Xuemei; Chen, Xi'an; Huang, Shaoming

    2012-01-24

    Tailoring the electronic arrangement of graphene by doping is a practical strategy for producing significantly improved materials for the oxygen-reduction reaction (ORR) in fuel cells (FCs). Recent studies have proven that the carbon materials doped with the elements, which have the larger (N) or smaller (P, B) electronegative atoms than carbon such as N-doped carbon nanotubes (CNTs), P-doped graphite layers and B-doped CNTs, have also shown pronounced catalytic activity. Herein, we find that the graphenes doped with the elements, which have the similar electronegativity with carbon such as sulfur and selenium, can also exhibit better catalytic activity than the commercial Pt/C in alkaline media, indicating that these doped graphenes hold great potential for a substitute for Pt-based catalysts in FCs. The experimental results are believed to be significant because they not only give further insight into the ORR mechanism of these metal-free doped carbon materials, but also open a way to fabricate other new low-cost NPMCs with high electrocatalytic activity by a simple, economical, and scalable approach for real FC applications. PMID:22201338

  9. A noble-metal-free system for photocatalytic hydrogen production from water.

    PubMed

    Mejía, Esteban; Luo, Shu-Ping; Karnahl, Michael; Friedrich, Aleksej; Tschierlei, Stefanie; Surkus, Annette-Enrica; Junge, Henrik; Gladiali, Serafino; Lochbrunner, Stefan; Beller, Matthias

    2013-11-18

    A series of heteroleptic copper(I) complexes with bidentate PP and NN chelate ligands was prepared and successfully applied as photosensitizers in the light-driven production of hydrogen, by using [Fe3(CO)12] as a water-reduction catalyst (WRC). These systems efficiently reduces protons from water/THF/triethylamine mixtures, in which the amine serves as a sacrificial electron donor (SR). Turnover numbers (for H) up to 1330 were obtained with these fully noble-metal-free systems. The new complexes were electrochemically and photophysically characterized. They exhibited a correlation between the lifetimes of the MLCT excited state and their efficiency as photosensitizers in proton-reduction systems. Within these experiments, considerably long excited-state lifetimes of up to 54 μs were observed. Quenching studies with the SR, in the presence and absence of the WRC, showed that intramolecular deactivation was more efficient in the former case, thus suggesting the predominance of an oxidative quenching pathway. PMID:24123302

  10. A Class of High Performance Metal-Free Oxygen Reduction Electrocatalysts based on Cheap Carbon Blacks

    NASA Astrophysics Data System (ADS)

    Sun, Xiujuan; Song, Ping; Zhang, Yuwei; Liu, Changpeng; Xu, Weilin; Xing, Wei

    2013-08-01

    For the goal of practical industrial development of fuel cells, cheap, sustainable and high performance electrocatalysts for oxygen reduction reactions (ORR) which rival those based on platinum (Pt) and other rare materials are highly desirable. In this work, we report a class of cheap and high-performance metal-free oxygen reduction electrocatalysts obtained by co-doping carbon blacks with nitrogen and fluorine (CB-NF).The CB-NF electrocatalysts are highly active and exhibit long-term operation stability and tolerance to poisons during oxygen reduction process in alkaline medium. The alkaline direct methanol fuel cell with the best CB-NF as cathode (3 mg/cm2) outperforms the one with commercial platinum-based cathode (3 mg Pt/cm2). To the best of our knowledge, these are among the most efficient non-Pt based electrocatalysts. Since carbon blacks are 10,000 times cheaper than Pt, these CB-NF electrocatalysts possess the best price/performance ratio for ORR, and are the most promising alternatives to Pt-based ones to date.

  11. B-Methylated Amine-Boranes: Substituent Redistribution, Catalytic Dehydrogenation, and Facile Metal-Free Hydrogen Transfer Reactions.

    PubMed

    Stubbs, Naomi E; Schäfer, André; Robertson, Alasdair P M; Leitao, Erin M; Jurca, Titel; Sparkes, Hazel A; Woodall, Christopher H; Haddow, Mairi F; Manners, Ian

    2015-11-16

    Although the dehydrogenation chemistry of amine-boranes substituted at nitrogen has attracted considerable attention, much less is known about the reactivity of their B-substituted analogues. When the B-methylated amine-borane adducts, RR'NH·BH2Me (1a: R = R' = H; 1b: R = Me, R' = H; 1c: R = R' = Me; 1d: R = R' = iPr), were heated to 70 °C in solution (THF or toluene), redistribution reactions were observed involving the apparent scrambling of the methyl and hydrogen substituents on boron to afford a mixture of the species RR'NH·BH3-xMex (x = 0-3). These reactions were postulated to arise via amine-borane dissociation followed by the reversible formation of diborane intermediates and adduct reformation. Dehydrocoupling of 1a-1d with Rh(I), Ir(III), and Ni(0) precatalysts in THF at 20 °C resulted in an array of products, including aminoborane RR'N═BHMe, cyclic diborazane [RR'N-BHMe]2, and borazine [RN-BMe]3 based on analysis by in situ (11)B NMR spectroscopy, with peak assignments further supported by density functional theory (DFT) calculations. Significantly, very rapid, metal-free hydrogen transfer between 1a and the monomeric aminoborane, iPr2N═BH2, to yield iPr2NH·BH3 (together with dehydrogenation products derived from 1a) was complete within only 10 min at 20 °C in THF, substantially faster than for the N-substituted analogue MeNH2·BH3. DFT calculations revealed that the hydrogen transfer proceeded via a concerted mechanism through a cyclic six-membered transition state analogous to that previously reported for the reaction of the N-dimethyl species Me2NH·BH3 and iPr2N═BH2. However, as a result of the presence of an electron donating methyl substituent on boron rather than on nitrogen, the process was more thermodynamically favorable and the activation energy barrier was reduced. PMID:26535961

  12. 14 CFR 437.67 - Tracking a reusable suborbital rocket.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Tracking a reusable suborbital rocket. 437.67 Section 437.67 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION... a reusable suborbital rocket. A permittee must— (a) During permitted flight, measure in real...

  13. Methodology for Evaluating Quality and Reusability of Learning Objects

    ERIC Educational Resources Information Center

    Kurilovas, Eugenijus; Bireniene, Virginija; Serikoviene, Silvija

    2011-01-01

    The aim of the paper is to present the scientific model and several methods for the expert evaluation of quality of learning objects (LOs) paying especial attention to LOs reusability level. The activities of eQNet Quality Network for a European Learning Resource Exchange (LRE) aimed to improve reusability of LOs of European Schoolnet's LRE…

  14. Structural Integrity and Durability of Reusable Space Propulsion Systems

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The space shuttle main engine (SSME), a reusable space propulsion system, is discussed. The advances in high pressure oxygen hydrogen rocket technology are reported to establish the basic technology and to develop new analytical tools for the evaluation in reusable rocket systems.

  15. Reusable Rocket Engine Turbopump Health Management System

    NASA Technical Reports Server (NTRS)

    Surko, Pamela

    1994-01-01

    A health monitoring expert system software architecture has been developed to support condition-based health monitoring of rocket engines. Its first application is in the diagnosis decisions relating to the health of the high pressure oxidizer turbopump (HPOTP) of Space Shuttle Main Engine (SSME). The post test diagnostic system runs off-line, using as input the data recorded from hundreds of sensors, each running typically at rates of 25, 50, or .1 Hz. The system is invoked after a test has been completed, and produces an analysis and an organized graphical presentation of the data with important effects highlighted. The overall expert system architecture has been developed and documented so that expert modules analyzing other line replaceable units may easily be added. The architecture emphasizes modularity, reusability, and open system interfaces so that it may be used to analyze other engines as well.

  16. Reusable Rocket Engine Operability Modeling and Analysis

    NASA Technical Reports Server (NTRS)

    Christenson, R. L.; Komar, D. R.

    1998-01-01

    This paper describes the methodology, model, input data, and analysis results of a reusable launch vehicle engine operability study conducted with the goal of supporting design from an operations perspective. Paralleling performance analyses in schedule and method, this requires the use of metrics in a validated operations model useful for design, sensitivity, and trade studies. Operations analysis in this view is one of several design functions. An operations concept was developed given an engine concept and the predicted operations and maintenance processes incorporated into simulation models. Historical operations data at a level of detail suitable to model objectives were collected, analyzed, and formatted for use with the models, the simulations were run, and results collected and presented. The input data used included scheduled and unscheduled timeline and resource information collected into a Space Transportation System (STS) Space Shuttle Main Engine (SSME) historical launch operations database. Results reflect upon the importance not only of reliable hardware but upon operations and corrective maintenance process improvements.

  17. Reusable Metallic Thermal Protection Systems Development

    NASA Technical Reports Server (NTRS)

    Blosser, Max L.; Martin, Carl J.; Daryabeigi, Kamran; Poteet, Carl C.

    1998-01-01

    Metallic thermal protection systems (TPS) are being developed to help meet the ambitious goals of future reusable launch vehicles. Recent metallic TPS development efforts at NASA Langley Research Center are described. Foil-gage metallic honeycomb coupons, representative of the outer surface of metallic TPS were subjected to low speed impact, hypervelocity impact, rain erosion, and subsequent arcjet exposure. TPS panels were subjected to thermal vacuum, acoustic, and hot gas flow testing. Results of the coupon and panel tests are presented. Experimental and analytical tools are being developed to characterize and improve internal insulations. Masses of metallic TPS and advanced ceramic tile and blanket TPS concepts are compared for a wide range of parameters.

  18. Enhancement of the electrical characteristics of metal-free phthalocyanine films using cold isostatic pressing

    SciTech Connect

    Matsushima, Toshinori E-mail: adachi@cstf.kyushu-u.ac.jp; Adachi, Chihaya E-mail: adachi@cstf.kyushu-u.ac.jp; Esaki, Yu

    2014-12-15

    Spatial gaps between grains and other grains, substrates, or electrodes in organic electronic devices are one of the causes of the reduction in the electrical characteristics. In this study, we demonstrate that cold isostatic pressing (CIP) is an effective method to crush the gaps and enhance the electrical characteristics. CIP of metal-free phthalocyanine (H{sub 2}PC) films induced a decrease in the film thickness by 34%–40% because of the gap crush. The connection of smaller grains into a larger grain and planarization of the film surface were also observed in the CIP film. The crystal axes of the H{sub 2}PC crystallites were rearranged from the a-axis to the c-axis of the α-phase crystal structure in a direction perpendicular to the substrate by CIP, indicating favorable hole injection and transport in this direction because of a better overlap of π orbitals. Thermally stimulated current measurements showed that deep hole traps disappeared and the total hole-trap density decreased after CIP. These CIP-induced changes of the film thicknesses, crystal axes and the hole traps lead to a marked increase in the hole mobility of the H{sub 2}PC films from 2.0 × 10{sup −7} to 4.0 × 10{sup −4} cm{sup 2}/V s by 2000 times in the perpendicular direction. We believe that these findings are important for unveiling the underlying carrier injection and transport mechanisms of organic films and for enhancing the performance of future organic electronic devices.

  19. Graphdiyne as a metal-free catalyst for low-temperature CO oxidation.

    PubMed

    Wu, Ping; Du, Pan; Zhang, Hui; Cai, Chenxin

    2014-03-28

    The oxidation of CO has attracted great interest in recent years because of its important role in enhancing the catalyst durability in fuel cells and in solving the growing environmental problems caused by CO emission. The usually used noble metal nanocatalysts are costly and require high reaction temperature for efficient operation. We report here a density functional theory (DFT) study of low-temperature CO oxidation catalyzed by graphdiyne, which is a new two-dimensional periodic carbon allotrope with a one-atom-thick sheet of carbon building of sp- and sp(2)-hybridized carbon atoms and has been shown in our recent work to have high catalytic activity for oxygen reduction reactions (ORRs). We studied the adsorption properties of CO and O2 on graphdiyne, simulated the reaction mechanism of CO oxidation involving graphdiyne, and analyzed electronic structures at each step of reaction progress. The simulation results indicate that the adsorption of O2 prevails over CO adsorption on the graphdiyne sheet; the reaction of CO oxidation by adsorbed O2 on graphdiyne proceeds via the Eley-Rideal (ER) mechanism with a decrease in the energy of the system and the energy barrier as low as 0.18 eV in the rate-limiting step. The oxidation reaction includes the breakage of the O-O bond in the adsorbed O2, formation of the metastable carbonate-like intermediate state, and the creation of CO2 molecules. The results presented here demonstrate that graphdiyne is a good, low-cost, and metal-free catalyst for low-temperature CO oxidation, can be used to solve problems caused by environmental CO emission and has a high ability of CO tolerance by its removal through oxidation in fuel cells.

  20. Aeroheating Design Issues for Reusable Launch Vehicles: A Perspective

    NASA Technical Reports Server (NTRS)

    Zoby, E. Vincent; Thompson, Richard A.; Wurster, Kathryn E.

    2004-01-01

    An overview of basic aeroheating design issues for Reusable Launch Vehicles (RLV), which addresses the application of hypersonic ground-based testing, and computational fluid dynamic (CFD) and engineering codes, is presented. Challenges inherent to the prediction of aeroheating environments required for the successful design of the RLV Thermal Protection System (TPS) are discussed in conjunction with the importance of employing appropriate experimental/computational tools. The impact of the information garnered by using these tools in the resulting analyses, ultimately enhancing the RLV TPS design is illustrated. A wide range of topics is presented in this overview; e.g. the impact of flow physics issues such as boundary-layer transition, including effects of distributed and discrete roughness, shock-shock interactions, and flow separation/reattachment. Also, the benefit of integrating experimental and computational studies to gain an improved understanding of flow phenomena is illustrated. From computational studies, the effect of low-density conditions and of uncertainties in material surface properties on the computed heating rates a r e highlighted as well as the significant role of CFD in improving the Outer Mold Line (OML) definition to reduce aeroheating while maintaining aerodynamic performance. Appropriate selection of the TPS design trajectories and trajectory shaping to mitigate aeroheating levels and loads are discussed. Lastly, an illustration of an aeroheating design process is presented whereby data from hypersonic wind-tunnel tests are integrated with predictions from CFD codes and engineering methods to provide heating environments along an entry trajectory as required for TPS design.

  1. Aeroheating Design Issues for Reusable Launch Vehicles: A Perspective

    NASA Technical Reports Server (NTRS)

    Zoby, E. Vincent; Thompson, Richard A.; Wurster, Kathryn E.

    2004-01-01

    An overview of basic aeroheating design issues for Reusable Launch Vehicles (RLV), which addresses the application of hypersonic ground-based testing, and computational fluid dynamic (CFD) and engineering codes, is presented. Challenges inherent to the prediction of aeroheating environments required for the successful design of the RLV Thermal Protection System (TPS) are discussed in conjunction with the importance of employing appropriate experimental/computational tools. The impact of the information garnered by using these tools in the resulting analyses, ultimately enhancing the RLV TPS design is illustrated. A wide range of topics is presented in this overview; e.g. the impact of flow physics issues such as boundary-layer transition, including effects of distributed and discrete roughness, shockshock interactions, and flow separation/reattachment. Also, the benefit of integrating experimental and computational studies to gain an improved understanding of flow phenomena is illustrated. From computational studies, the effect of low-density conditions and of uncertainties in material surface properties on the computed heating rates are highlighted as well as the significant role of CFD in improving the Outer Mold Line (OML) definition to reduce aeroheating while maintaining aerodynamic performance. Appropriate selection of the TPS design trajectories and trajectory shaping to mitigate aeroheating levels and loads are discussed. Lastly, an illustration of an aeroheating design process is presented whereby data from hypersonic wind-tunnel tests are integrated with predictions from CFD codes and engineering methods to provide heating environments along an entry trajectory as required for TPS design.

  2. Facile and Gram-scale Synthesis of Metal-free Catalysts: Toward Realistic Applications for Fuel Cells

    PubMed Central

    Kim, Ok-Hee; Cho, Yong-Hun; Chung, Dong Young; Kim, Min Jeong; Yoo, Ji Mun; Park, Ji Eun; Choe, Heeman; Sung, Yung-Eun

    2015-01-01

    Although numerous reports on nonprecious metal catalysts for replacing expensive Pt-based catalysts have been published, few of these studies have demonstrated their practical application in fuel cells. In this work, we report graphitic carbon nitride and carbon nanofiber hybrid materials synthesized by a facile and gram-scale method via liquid-based reactions, without the use of toxic materials or a high pressure-high temperature reactor, for use as fuel cell cathodes. The resulting materials exhibited remarkable methanol tolerance, selectivity, and stability even without a metal dopant. Furthermore, these completely metal-free catalysts exhibited outstanding performance as cathode materials in an actual fuel cell device: a membrane electrode assembly with both acidic and alkaline polymer electrolytes. The fabrication method and remarkable performance of the single cell produced in this study represent progressive steps toward the realistic application of metal-free cathode electrocatalysts in fuel cells. PMID:25728910

  3. Facile and Gram-scale Synthesis of Metal-free Catalysts: Toward Realistic Applications for Fuel Cells

    NASA Astrophysics Data System (ADS)

    Kim, Ok-Hee; Cho, Yong-Hun; Chung, Dong Young; Kim, Min Jeong; Yoo, Ji Mun; Park, Ji Eun; Choe, Heeman; Sung, Yung-Eun

    2015-03-01

    Although numerous reports on nonprecious metal catalysts for replacing expensive Pt-based catalysts have been published, few of these studies have demonstrated their practical application in fuel cells. In this work, we report graphitic carbon nitride and carbon nanofiber hybrid materials synthesized by a facile and gram-scale method via liquid-based reactions, without the use of toxic materials or a high pressure-high temperature reactor, for use as fuel cell cathodes. The resulting materials exhibited remarkable methanol tolerance, selectivity, and stability even without a metal dopant. Furthermore, these completely metal-free catalysts exhibited outstanding performance as cathode materials in an actual fuel cell device: a membrane electrode assembly with both acidic and alkaline polymer electrolytes. The fabrication method and remarkable performance of the single cell produced in this study represent progressive steps toward the realistic application of metal-free cathode electrocatalysts in fuel cells.

  4. Structural Design Principle of Small-Molecule Organic Semiconductors for Metal-Free, Visible-Light-Promoted Photocatalysis.

    PubMed

    Wang, Lei; Huang, Wei; Li, Run; Gehrig, Dominik; Blom, Paul W M; Landfester, Katharina; Zhang, Kai A I

    2016-08-01

    Herein, we report on the structural design principle of small-molecule organic semiconductors as metal-free, pure organic and visible light-active photocatalysts. Two series of electron-donor and acceptor-type organic semiconductor molecules were synthesized to meet crucial requirements, such as 1) absorption range in the visible region, 2) sufficient photoredox potential, and 3) long lifetime of photogenerated excitons. The photocatalytic activity was demonstrated in the intermolecular C-H functionalization of electron-rich heteroaromates with malonate derivatives. A mechanistic study of the light-induced electron transport between the organic photocatalyst, substrate, and the sacrificial agent are described. With their tunable absorption range and defined energy-band structure, the small-molecule organic semiconductors could offer a new class of metal-free and visible light-active photocatalysts for chemical reactions.

  5. Facile and gram-scale synthesis of metal-free catalysts: toward realistic applications for fuel cells.

    PubMed

    Kim, Ok-Hee; Cho, Yong-Hun; Chung, Dong Young; Kim, Min Jeong; Yoo, Ji Mun; Park, Ji Eun; Choe, Heeman; Sung, Yung-Eun

    2015-03-02

    Although numerous reports on nonprecious metal catalysts for replacing expensive Pt-based catalysts have been published, few of these studies have demonstrated their practical application in fuel cells. In this work, we report graphitic carbon nitride and carbon nanofiber hybrid materials synthesized by a facile and gram-scale method via liquid-based reactions, without the use of toxic materials or a high pressure-high temperature reactor, for use as fuel cell cathodes. The resulting materials exhibited remarkable methanol tolerance, selectivity, and stability even without a metal dopant. Furthermore, these completely metal-free catalysts exhibited outstanding performance as cathode materials in an actual fuel cell device: a membrane electrode assembly with both acidic and alkaline polymer electrolytes. The fabrication method and remarkable performance of the single cell produced in this study represent progressive steps toward the realistic application of metal-free cathode electrocatalysts in fuel cells.

  6. Sustaining Human Presence on Mars Using ISRU and a Reusable Lander

    NASA Technical Reports Server (NTRS)

    Arney, Dale C.; Jones, Christopher A.; Klovstad, Jordan J.; Komar, D.R.; Earle, Kevin; Moses, Robert; Shyface, Hilary R.

    2015-01-01

    This paper presents an analysis of the impact of ISRU (In-Site Resource Utilization), reusability, and automation on sustaining a human presence on Mars, requiring a transition from Earth dependence to Earth independence. The study analyzes the surface and transportation architectures and compared campaigns that revealed the importance of ISRU and reusability. A reusable Mars lander, Hercules, eliminates the need to deliver a new descent and ascent stage with each cargo and crew delivery to Mars, reducing the mass delivered from Earth. As part of an evolvable transportation architecture, this investment is key to enabling continuous human presence on Mars. The extensive use of ISRU reduces the logistics supply chain from Earth in order to support population growth at Mars. Reliable and autonomous systems, in conjunction with robotics, are required to enable ISRU architectures as systems must operate and maintain themselves while the crew is not present. A comparison of Mars campaigns is presented to show the impact of adding these investments and their ability to contribute to sustaining a human presence on Mars.

  7. Metal-free synthesis of 2-oxindoles via PhI(OAc)2-mediated oxidative C–C bond formation.

    PubMed

    Lv, Jinglei; Zhang-Negrerie, Daisy; Deng, Jun; Du, Yunfei; Zhao, Kang

    2014-02-01

    The series of 3-monofunctionalized 2-oxindoles 2 were conveniently synthesized from reactions between anilide 1 and phenyliodine(III) diacetate (PIDA) through hypervalent iodine mediated C(sp2)–C(sp2) bond formation followed by a subsequent deacylation reaction. This metal-free method, shown to provide direct access to an important oxindole intermediate, could be applied to the total synthesis of naturally occurring horsfiline.

  8. Metal-Free Oxidative Spirocyclization of Alkynes with Sulfonylhydrazides Leading to 3-Sulfonated Azaspiro[4,5]trienones.

    PubMed

    Wen, Jiangwei; Wei, Wei; Xue, Shengnan; Yang, Daoshan; Lou, Yu; Gao, Chaoyang; Wang, Hua

    2015-05-15

    A novel and direct oxidative spirocyclization of arylpropiolamides with sulfonylhydrazides leading to 3-sulfonated azaspiro[4,5]trienones has been developed under metal-free conditions. The reaction is performed in a tandem manner constituted by the sequential sulfonylation of alkynes, ipso-carbocyclization, dearomatization, hydration, and oxidation processes, providing a convenient and efficient approach to various sulfonated azaspiro[4,5] trienones of biological importance.

  9. Metal-free synthesis of N-fused heterocyclic iodides via C-H functionalization mediated by tert-butylhydroperoxide.

    PubMed

    Sharma, Krishna K; Patel, Dhananjay I; Jain, Rahul

    2015-10-21

    Direct, regioselective and metal-free synthesis of fused N-heterocyclic iodides is reported. This regioselective C-H functionalization is mediated by tert-butylhydroperoxide (TBHP), via dual activation of molecular iodine and a heterocyclic substrate, resulting in the in situ generation of electrophilic iodine species (I(+)), and free radical(s) (t)BuO˙ or (t)BuOO˙, driving the iodination reaction.

  10. Metal-free direct trifluoromethylation of activated alkenes with Langlois' reagent leading to CF3-containing oxindoles.

    PubMed

    Wei, Wei; Wen, Jiangwei; Yang, Daoshan; Liu, Xiaoxia; Guo, Mengyuan; Dong, Ruimei; Wang, Hua

    2014-05-01

    A metal-free and cost-effective synthesis protocol has been initially proposed for the construction of CF3-containing oxindoles via the direct oxidative trifluoromethylation of activated alkenes with Langlois' reagent (CF3SO2Na). The present methodology, which utilizes very cheap CF3 reagent and a simple oxidant, provides a convenient and practical approach to CF3-containing oxindoles with a wide variety of functional groups. PMID:24689970

  11. Production of Metal-Free Composites Composed of Graphite Oxide and Oxidized Carbon Nitride Nanodots and Their Enhanced Photocatalytic Performances.

    PubMed

    Kim, Seung Yeon; Oh, Junghoon; Park, Sunghee; Shim, Yeonjun; Park, Sungjin

    2016-04-01

    A novel metal-free composite (GN) composed of two types of carbon-based nanomaterials, graphite oxide (GO) and 2D oxidized carbon nitride (OCN) nanodots was produced. Chemical and morphological characterizations reveal that GN contains a main component of GO with well-dispersed 2D OCN nanodots. GN shows enhanced photocatalytic performance for degrading an organic pollutant, Rhodamine B, under visible light.

  12. Synthesis of 2-Alkenylquinoline by Reductive Olefination of Quinoline N-Oxide under Metal-Free Conditions.

    PubMed

    Xia, Hong; Liu, Yuanhong; Zhao, Peng; Gou, Shaohua; Wang, Jun

    2016-04-15

    Synthesis of 2-alkenylquinoline by reductive olefination of quinoline N-oxide under metal-free conditions is disclosed. Practically, the reaction could be performed with quinoline as starting material via a one-pot, two-step process. A possible mechanism is proposed that involves a sequential 1,3-dipolar cycloaddition and acid-assisted ring opening followed by a dehydration process. PMID:26987040

  13. Structural and biophysical properties of metal-free pathogenic SOD1 mutants A4V and G93A

    SciTech Connect

    Galaleldeen, Ahmad; Strange, Richard W.; Whitson, Lisa J.; Antonyuk, Svetlana V.; Narayana, Narendra; Taylor, Alexander B.; Schuermann, Jonathan P.; Holloway, Stephen P.; Hasnain, S.Samar; Hart, P. John

    2010-07-19

    Amyotrophic lateral sclerosis (ALS) is a fatal, progressive neurodegenerative disease characterized by the destruction of motor neurons in the spinal cord and brain. A subset of ALS cases are linked to dominant mutations in copper-zinc superoxide dismutase (SOD1). The pathogenic SOD1 variants A4V and G93A have been the foci of multiple studies aimed at understanding the molecular basis for SOD1-linked ALS. The A4V variant is responsible for the majority of familial ALS cases in North America, causing rapidly progressing paralysis once symptoms begin and the G93A SOD1 variant is overexpressed in often studied murine models of the disease. Here we report the three-dimensional structures of metal-free A4V and of metal-bound and metal-free G93A SOD1. In the metal-free structures, the metal-binding loop elements are observed to be severely disordered, suggesting that these variants may share mechanisms of aggregation proposed previously for other pathogenic SOD1 proteins.

  14. Electrocatalytic oxidation of nitrite using metal-free nitrogen-doped reduced graphene oxide nanosheets for sensitive detection.

    PubMed

    Chen, Dong; Jiang, Jingjing; Du, Xuezhong

    2016-08-01

    Nitrite can become poisonous to animals and human beings as it can lead to generation of carcinogenic N-nitrosamines. Metal-free nitrogen-doped reduced graphene oxide (NrGO) exhibited a good electrocatalytic activity toward oxidation of nitrite with the relatively low oxidation potential of 0.68V (v.s. saturated calomel electrode), thus, a facile electrochemical sensor based on metal-free NrGO was fabricated for sensitive detection of nitrite for the first time. The novel sensor showed a wide linear concentration range from 0.5 to 5000μM and a low detection limit of 0.2μM at the signal-to-noise ratio of 3 with good selectivity, stability, and reproducibility. This fabricated sensor was used for the determination of nitrite in pickled garlic and river water. These results demonstrate that the facile metal-free NrGO-modified electrochemical sensor has promising applications for the determination of nitrite in food and environment. PMID:27216690

  15. Reusable high-temperature heat pipes and heat pipe panels

    NASA Technical Reports Server (NTRS)

    Camarda, Charles J. (Inventor); Ransone, Philip O. (Inventor)

    1989-01-01

    A reusable, durable heat pipe which is capable of operating at temperatures up to about 3000 F in an oxidizing environment and at temperatures above 3000 F in an inert or vacuum environment is produced by embedding a refractory metal pipe within a carbon-carbon composite structure. A reusable, durable heat pipe panel is made from an array of refractory-metal pipes spaced from each other. The reusable, durable, heat-pipe is employed to fabricate a hypersonic vehicle leading edge and nose cap.

  16. Transition-Metal-Free Regioselective Alkylation of Pyridine N-Oxides Using 1,1-Diborylalkanes as Alkylating Reagents.

    PubMed

    Jo, Woohyun; Kim, Junghoon; Choi, Seoyoung; Cho, Seung Hwan

    2016-08-01

    Reported herein is an unprecedented base-promoted deborylative alkylation of pyridine N-oxides using 1,1-diborylalkanes as alkyl sources. The reaction proceeds efficiently for a wide range of pyridine N-oxides and 1,1-diborylalkanes with excellent regioselectivity. The utility of the developed method is demonstrated by the sequential C-H arylation and methylation of pyridine N-oxides. The reaction also can be applied for the direct introduction of a methyl group to 9-O-methylquinine N-oxide, thus it can serve as a powerful method for late-stage functionalization. PMID:27351367

  17. Formation of meta-Substituted Phenols by Transition Metal-Free Aromatization: Use of 2-Bromocyclohex-2-en-1-ones.

    PubMed

    Yu, Guojun; Clive, Derrick L J

    2016-09-16

    Addition of Grignard or other organometallic reagents to 2-halocyclohex-2-en-1-ones bearing an alkyl or aryl group at C-5, followed by mild acid treatment and exposure to 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) at room temperature, generates meta-substituted phenols in which the newly introduced meta substituent originates from the Grignard reagent. The range of effective organometallic reagents includes alkyl, allyl, alkynyl, aryl, and heteroaryl compounds including those with fluorine substituents. The initial halocyclohexenone can be deprotonated at C-6 and reacted with carbon, fluorine, or sulfur electrophiles before the Grignard addition so as to generate highly substituted phenols. PMID:27563935

  18. Transition-metal-free access to primary anilines from boronic acids and a common (+)NH2 equivalent.

    PubMed

    Voth, Samantha; Hollett, Joshua W; McCubbin, J Adam

    2015-03-01

    Diversely substituted anilines are prepared by treatment of functionalized arylboronic acids with a common, inexpensive source of electrophilic nitrogen (H2N-OSO3H, HSA) under basic aqueous conditions. Electron-rich substrates are found to be the most reactive by this method. However, even moderately electron-poor substrates are well tolerated under the room temperature conditions. Sterically hindered substrates appear to be equally effective compared to unhindered ones. Highly electron-deficient substrates afford product in very low yields at room temperature, but moderate to good yields are obtained at refluxing temperatures. Our method is also amenable to electrophilic amination of several common boronic acid derivatives (e.g., pinacol esters). We demonstrate that it can be combined with metal-halogen exchange reactions or a variety of directed ortho metalation protocols in a "one-pot" sequence for the synthesis of aromatic amines with unique substitution patterns. DFT studies, in combination with experimental results, suggest that the reaction occurs via base-mediated activation of HSA, followed by 1,2 aryl B-N migration. This mode of activation appears to be critical for the success of the reaction and allows, for the first time, a general, electrophilic amination of boronic acids at ambient temperature.

  19. Conceptual Design of an APT Reusable Spaceplane

    NASA Astrophysics Data System (ADS)

    Corpino, S.; Viola, N.

    This paper concerns the conceptual design of an Aerial Propellant Transfer reusable spaceplane carried out during our PhD course under the supervision of prof. Chiesa. The new conceptual design methodology employed in order to develop the APT concept and the main characteristics of the spaceplane itself will be presented and discussed. The methodology for conceptual design has been worked out during the last three years. It was originally thought for atmospheric vehicle design but, thanks to its modular structure which makes it very flexible, it has been possible to convert it to space transportation systems design by adding and/or modifying a few modules. One of the major improvements has been for example the conception and development of the mission simulation and trajectory optimisation module. The methodology includes as main characteristics and innovations the latest techniques of geometric modelling and logistic, operational and cost aspects since the first stages of the project. Computer aided design techniques are used to obtain a better definition of the product at the end of the conceptual design phase and virtual reality concepts are employed to visualise three-dimensional installation and operational aspects, at least in part replacing full-scale mock- ups. The introduction of parametric three-dimensional CAD software integrated into the conceptual design methodology represents a great improvement because it allows to carry out different layouts and to assess them immediately. It is also possible to link the CAD system to a digital prototyping software which combines 3D visualisation and assembly analysis, useful to define the so-called Digital Mock-Up at Conceptual Level (DMUCL) which studies the integration between the on board systems, sized with simulation algorithms, and the airframe. DMUCL represents a very good means to integrate the conceptual design with a methodology turned towards dealing with Reliability, Availability, Maintainability and

  20. 14 CFR 431.79 - Reusable launch vehicle mission reporting requirements.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 false Reusable launch vehicle mission reporting... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) Post-Licensing Requirements-Reusable Launch Vehicle Mission License Terms and Conditions § 431.79 Reusable...

  1. 14 CFR 431.79 - Reusable launch vehicle mission reporting requirements.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Reusable launch vehicle mission reporting... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) Post-Licensing Requirements-Reusable Launch Vehicle Mission License Terms and Conditions § 431.79 Reusable...

  2. 14 CFR 431.79 - Reusable launch vehicle mission reporting requirements.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Reusable launch vehicle mission reporting... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) Post-Licensing Requirements-Reusable Launch Vehicle Mission License Terms and Conditions § 431.79 Reusable...

  3. 14 CFR 431.79 - Reusable launch vehicle mission reporting requirements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Reusable launch vehicle mission reporting... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) Post-Licensing Requirements-Reusable Launch Vehicle Mission License Terms and Conditions § 431.79 Reusable...

  4. Reusable Component Model Development Approach for Parallel and Distributed Simulation

    PubMed Central

    Zhu, Feng; Yao, Yiping; Chen, Huilong; Yao, Feng

    2014-01-01

    Model reuse is a key issue to be resolved in parallel and distributed simulation at present. However, component models built by different domain experts usually have diversiform interfaces, couple tightly, and bind with simulation platforms closely. As a result, they are difficult to be reused across different simulation platforms and applications. To address the problem, this paper first proposed a reusable component model framework. Based on this framework, then our reusable model development approach is elaborated, which contains two phases: (1) domain experts create simulation computational modules observing three principles to achieve their independence; (2) model developer encapsulates these simulation computational modules with six standard service interfaces to improve their reusability. The case study of a radar model indicates that the model developed using our approach has good reusability and it is easy to be used in different simulation platforms and applications. PMID:24729751

  5. Coatings and Surface Treatments for Reusable Entry Systems

    NASA Technical Reports Server (NTRS)

    Johnson, Sylvia M.

    2016-01-01

    This talk outlines work in coatings for TPS done at NASA Ames. coatings and surface treatments on reusable TPS are critical for controlling the behavior of the materials. coatings discussed include RCG, TUFI and HETC. TUFROc is also discussed.

  6. Reusable Reentry Satellite (RRS): Configuration trade study

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The overall Reusable Reentry Satellite (RRS) Phase B Study objective is to design a relatively inexpensive satellite to access space for extended periods of time, with eventual recovery of experiments on Earth. The expected principal use for such a system is research on the effects of variable gravity (0-1.5 g) and radiation on small animals, plants, lower life forms, tissue samples, and materials processes. The RRS will be capable of: (1) being launched by a variety of expendable launch vehicles; (2) operating in low earth orbit as a free flying unmanned laboratory; and (3) executing independent atmospheric reentry and soft landing. The RRS will be designed to be refurbished and reused up to three times a year for a period of 10 years. The information provided in this report describes the process involved in the evolution of the RRS overall configuration. This process considered reentry aerodynamics, aerothermodynamics, internal equipment layout, and vehicle mass properties. This report delineates the baseline design decisions that were used to initiate the RRS design effort. As a result, there will be deviations between this report and the RRS Final Report. In those instances, the RRS Final Report shall be considered to be the definitive reference.

  7. A reusable knowledge acquisition shell: KASH

    NASA Technical Reports Server (NTRS)

    Westphal, Christopher; Williams, Stephen; Keech, Virginia

    1991-01-01

    KASH (Knowledge Acquisition SHell) is proposed to assist a knowledge engineer by providing a set of utilities for constructing knowledge acquisition sessions based on interviewing techniques. The information elicited from domain experts during the sessions is guided by a question dependency graph (QDG). The QDG defined by the knowledge engineer, consists of a series of control questions about the domain that are used to organize the knowledge of an expert. The content information supplies by the expert, in response to the questions, is represented in the form of a concept map. These maps can be constructed in a top-down or bottom-up manner by the QDG and used by KASH to generate the rules for a large class of expert system domains. Additionally, the concept maps can support the representation of temporal knowledge. The high degree of reusability encountered in the QDG and concept maps can vastly reduce the development times and costs associated with producing intelligent decision aids, training programs, and process control functions.

  8. Improvement of Reusable Surface Insulation (RSI) materials

    NASA Technical Reports Server (NTRS)

    Blome, J. C.

    1972-01-01

    The mullite fiber based hardened compacted fibers (HCF) type of reusable surface insulation was further developed for use in the Space Shuttle Program. Two hundred fifty formulations of fiber mixtures, fillers, binders, and organic processing aids were made using mullite fibers as the basic ingredient. Most of the work was accomplished on 15-lb/cu ft material. It was established that higher density materials are stronger with strength values as high as 250 lb/sq in. in tension. New measurement techniques and equipment were developed for accurate determination of strength and strain to failure. Room temperature to 2300 F stress-strain relationships were made. The room temperature tensile modulus of elasticity is 61,700 lb/sq in. and the strain at failure is 0.165 percent, typically, when measured longitudinally parallel to the long axes of the fibers. Thermal insulating effectiveness was increased 20 percent by reducing the diameter of some of the fibers in the material. Improvements were made in density uniformity and strength uniformity in a block of HCF by mixing improvements and by the use of organic additives. Specifications were established on the materials and processes used in making the insulation.

  9. Lightweight Reusable Solar Array For Balloons

    NASA Astrophysics Data System (ADS)

    Aaron, K.; Tensor, P.; Nock, K.; Wyszkowski, C.

    We will discuss a new lightweight reusable solar array system, dubbed HighPower, which is being developed for the Ultra-Long Duration Balloon (ULDB) program using NASA/SBIR funding, but which is also applicable to other balloon systems. The system uses a vertically deployed stack of panels suspended from their corners by cables. The stack act likes a two-dimensional Venetian blind. By raising and lowering opposite corners, the array of parallel panels can be pointed over most of the upper hemisphere. This allows the panels to remain normal to the sun despite the slow rotation of the gondola and without requiring rotation of the system (no slip rings) or heavy cantilevered rotation joints. The system is sized to generate 2000 W using six 2m x 2m panels. The modularity of the system allows panels to be added or removed to tailored the power to the needs of the mission. Prior to cut -down of the balloon, the panels can be retracted and stowed compactly in the lower part of the gondola. This will protect the array during landing, allowing the array to be reused on subsequent flights.

  10. Synthetic and mechanistic studies of metal-free transfer hydrogenations applying polarized olefins as hydrogen acceptors and amine borane adducts as hydrogen donors.

    PubMed

    Yang, Xianghua; Fox, Thomas; Berke, Heinz

    2012-01-28

    Metal-free transfer hydrogenation of polarized olefins (RR'C=CEE': R, R' = H or organyl, E, E' = CN or CO(2)Me) using amine borane adducts RR'NH-BH(3) (R = R' = H, AB; R = Me, R' = H, MAB; R = (t)Bu, R' = H, tBAB; R = R' = Me, DMAB) as hydrogen donors, were studied by means of in situ NMR spectroscopy. Deuterium kinetic isotope effects and the traced hydroboration intermediate revealed that the double H transfer process occurred regio-specifically in two steps with hydride before proton transfer characteristics. Studies on substituent effects and Hammett correlation indicated that the rate determining step of the H(N) transfer is in agreement with a concerted transition state. The very reactive intermediate [NH(2)=BH(2)] generated from AB was trapped by addition of cyclohexene into the reaction mixture forming Cy(2)BNH(2). The final product borazine (BHNH)(3) is assumed to be formed by dehydrocoupling of [NH(2)=BH(2)] or its solvent stabilized derivative [NH(2)=BH(2)]-(solvent), rather than by dehydrogenation of cyclotriborazane (BH(2)NH(2))(3) which is the trimerization product of [NH(2)=BH(2)]. PMID:22124505

  11. Viability of a Reusable In-Space Transportation System

    NASA Technical Reports Server (NTRS)

    Jefferies, Sharon A.; McCleskey, Carey M.; Nufer, Brian M.; Lepsch, Roger A.; Merrill, Raymond G.; North, David D.; Martin, John G.; Komar, David R.

    2015-01-01

    The National Aeronautics and Space Administration (NASA) is currently developing options for an Evolvable Mars Campaign (EMC) that expands human presence from Low Earth Orbit (LEO) into the solar system and to the surface of Mars. The Hybrid in-space transportation architecture is one option being investigated within the EMC. The architecture enables return of the entire in-space propulsion stage and habitat to cis-lunar space after a round trip to Mars. This concept of operations opens the door for a fully reusable Mars transportation system from cis-lunar space to a Mars parking orbit and back. This paper explores the reuse of in-space transportation systems, with a focus on the propulsion systems. It begins by examining why reusability should be pursued and defines reusability in space-flight context. A range of functions and enablers associated with preparing a system for reuse are identified and a vision for reusability is proposed that can be advanced and implemented as new capabilities are developed. Following this, past reusable spacecraft and servicing capabilities, as well as those currently in development are discussed. Using the Hybrid transportation architecture as an example, an assessment of the degree of reusability that can be incorporated into the architecture with current capabilities is provided and areas for development are identified that will enable greater levels of reuse in the future. Implications and implementation challenges specific to the architecture are also presented.

  12. Highly efficient metal-free growth of nitrogen-doped single-walled carbon nanotubes on plasma-etched substrates for oxygen reduction.

    PubMed

    Yu, Dingshan; Zhang, Qiang; Dai, Liming

    2010-11-01

    We have for the first time developed a simple plasma-etching technology to effectively generate metal-free particle catalysts for efficient metal-free growth of undoped and/or nitrogen-doped single-walled carbon nanotubes (CNTs). Compared with undoped CNTs, the newly produced metal-free nitrogen-containing CNTs were demonstrated to show relatively good electrocatalytic activity and long-term stability toward oxygen reduction reaction (ORR) in an acidic medium. Owing to the highly generic nature of the plasma etching technique, the methodology developed in this study can be applied to many other substrates for efficient growth of metal-free CNTs for various applications, ranging from energy related to electronic and to biomedical systems.

  13. Dynamic reusable workflows for ocean science

    USGS Publications Warehouse

    Signell, Richard; Fernandez, Filipe; Wilcox, Kyle

    2016-01-01

    Digital catalogs of ocean data have been available for decades, but advances in standardized services and software for catalog search and data access make it now possible to create catalog-driven workflows that automate — end-to-end — data search, analysis and visualization of data from multiple distributed sources. Further, these workflows may be shared, reused and adapted with ease. Here we describe a workflow developed within the US Integrated Ocean Observing System (IOOS) which automates the skill-assessment of water temperature forecasts from multiple ocean forecast models, allowing improved forecast products to be delivered for an open water swim event. A series of Jupyter Notebooks are used to capture and document the end-to-end workflow using a collection of Python tools that facilitate working with standardized catalog and data services. The workflow first searches a catalog of metadata using the Open Geospatial Consortium (OGC) Catalog Service for the Web (CSW), then accesses data service endpoints found in the metadata records using the OGC Sensor Observation Service (SOS) for in situ sensor data and OPeNDAP services for remotely-sensed and model data. Skill metrics are computed and time series comparisons of forecast model and observed data are displayed interactively, leveraging the capabilities of modern web browsers. The resulting workflow not only solves a challenging specific problem, but highlights the benefits of dynamic, reusable workflows in general. These workflows adapt as new data enters the data system, facilitate reproducible science, provide templates from which new scientific workflows can be developed, and encourage data providers to use standardized services. As applied to the ocean swim event, the workflow exposed problems with two of the ocean forecast products which led to improved regional forecasts once errors were corrected. While the example is specific, the approach is general, and we hope to see increased use of dynamic

  14. Dynamic Reusable Workflows for Ocean Science

    USGS Publications Warehouse

    Signell, Richard; Fernandez, Filipe; Wilcox, Kyle

    2016-01-01

    Digital catalogs of ocean data have been available for decades, but advances in standardized services and software for catalog search and data access make it now possible to create catalog-driven workflows that automate — end-to-end — data search, analysis and visualization of data from multiple distributed sources. Further, these workflows may be shared, reused and adapted with ease. Here we describe a workflow developed within the US Integrated Ocean Observing System (IOOS) which automates the skill-assessment of water temperature forecasts from multiple ocean forecast models, allowing improved forecast products to be delivered for an open water swim event. A series of Jupyter Notebooks are used to capture and document the end-to-end workflow using a collection of Python tools that facilitate working with standardized catalog and data services. The workflow first searches a catalog of metadata using the Open Geospatial Consortium (OGC) Catalog Service for the Web (CSW), then accesses data service endpoints found in the metadata records using the OGC Sensor Observation Service (SOS) for in situ sensor data and OPeNDAP services for remotely-sensed and model data. Skill metrics are computed and time series comparisons of forecast model and observed data are displayed interactively, leveraging the capabilities of modern web browsers. The resulting workflow not only solves a challenging specific problem, but highlights the benefits of dynamic, reusable workflows in general. These workflows adapt as new data enters the data system, facilitate reproducible science, provide templates from which new scientific workflows can be developed, and encourage data providers to use standardized services. As applied to the ocean swim event, the workflow exposed problems with two of the ocean forecast products which led to improved regional forecasts once errors were corrected. While the example is specific, the approach is general, and we hope to see increased use of dynamic

  15. Reusable Reentry Satellite (RRS) system design study

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The Reusable Reentry Satellite (RRS) is intended to provide investigators in several biological disciplines with a relatively inexpensive method to access space for up to 60 days with eventual recovery on Earth. The RRS will permit totally intact, relatively soft, recovery of the vehicle, system refurbishment, and reflight with new and varied payloads. The RRS is to be capable of three reflights per year over a 10-year program lifetime. The RRS vehicle will have a large and readily accessible volume near the vehicle center of gravity for the Payload Module (PM) containing the experiment hardware. The vehicle is configured to permit the experimenter late access to the PM prior to launch and rapid access following recovery. The RRS will operate in one of two modes: (1) as a free-flying spacecraft in orbit, and will be allowed to drift in attitude to provide an acceleration environment of less than 10(exp -5) g. the acceleration environment during orbital trim maneuvers will be less than 10(exp -3) g; and (2) as an artificial gravity system which spins at controlled rates to provide an artificial gravity of up to 1.5 Earth g. The RRS system will be designed to be rugged, easily maintained, and economically refurbishable for the next flight. Some systems may be designed to be replaced rather than refurbished, if cost effective and capable of meeting the specified turnaround time. The minimum time between recovery and reflight will be approximately 60 days. The PMs will be designed to be relatively autonomous, with experiments that require few commands and limited telemetry. Mass data storage will be accommodated in the PM. The hardware development and implementation phase is currently expected to start in 1991 with a first launch in late 1993.

  16. Entry Guidance for the Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    Lu, Ping

    1999-01-01

    The X-33 Advanced Technology Demonstrator is a half-scale prototype developed to test the key technologies needed for a full-scale single-stage reusable launch vehicle (RLV). The X-33 is a suborbital vehicle that will be launched vertically, and land horizontally. The goals of this research were to develop an alternate entry guidance scheme for the X-33 in parallel to the actual X-33 entry guidance algorithms, provide comparative and complementary study, and identify potential new ways to improve entry guidance performance. Toward these goals, the nominal entry trajectory is defined by a piecewise linear drag-acceleration-versus-energy profile, which is in turn obtained by the solution of a semi-analytical parameter optimization problem. The closed-loop guidance is accomplished by tracking the nominal drag profile with primarily bank-angle modulation on-board. The bank-angle is commanded by a single full-envelope nonlinear trajectory control law. Near the end of the entry flight, the guidance logic is switched to heading control in order to meet strict conditions at the terminal area energy management interface. Two methods, one on ground-track control and the other on heading control, were proposed and examined for this phase of entry guidance where lateral control is emphasized. Trajectory dispersion studies were performed to evaluate the effectiveness of the entry guidance algorithms against a number of uncertainties including those in propulsion system, atmospheric properties, winds, aerodynamics, and propellant loading. Finally, a new trajectory-regulation method is introduced at the end as a promising precision entry guidance method. The guidance principle is very different and preliminary application in X-33 entry guidance simulation showed high precision that is difficult to achieve by existing methods.

  17. Mars Conjunction Crewed Missions With a Reusable Hybrid Architecture

    NASA Technical Reports Server (NTRS)

    Merrill, Raymond G.; Strange, Nathan J.; Qu, Min; Hatten, Noble

    2015-01-01

    A new crew Mars architecture has been developed that provides many potential benefits for NASA-led human Mars moons and surface missions beginning in the 2030s or 2040s. By using both chemical and electric propulsion systems where they are most beneficial and maintaining as much orbital energy as possible, the Hybrid spaceship that carries crew round trip to Mars is pre-integrated before launch and can be delivered to orbit by a single launch. After check-out on the way to cis-lunar space, it is refueled and can travel round trip to Mars in less than 1100 days, with a minimum of 300 days in Mars vicinity (opportunity dependent). The entire spaceship is recaptured into cis-lunar space and can be reused. The spaceship consists of a habitat for 4 crew attached to the Hybrid propulsion stage which uses long duration electric and chemical in-space propulsion technologies that are in use today. The hybrid architecture's con-ops has no in-space assembly of the crew transfer vehicle and requires only rendezvous of crew in a highly elliptical Earth orbit for arrival at and departure from the spaceship. The crew transfer vehicle does not travel to Mars so it only needs be able to last in space for weeks and re-enter at lunar velocities. The spaceship can be refueled and resupplied for multiple trips to Mars (every other opportunity). The hybrid propulsion stage for crewed transits can also be utilized for cargo delivery to Mars every other opportunity in a reusable manner to pre-deploy infrastructure required for Mars vicinity operations. Finally, the Hybrid architecture provides evolution options for mitigating key long-duration space exploration risks, including crew microgravity and radiation exposure.

  18. I2/Aqueous TBHP-Catalyzed Coupling of Amides with Methylarenes/Aldehydes/Alcohols: Metal-Free Synthesis of Imides.

    PubMed

    Aruri, Hariprasad; Singh, Umed; Kumar, Sanjay; Kushwaha, Manoj; Gupta, Ajai Prakash; Vishwakarma, Ram A; Singh, Parvinder Pal

    2016-08-01

    We present a metal-free method for the synthesis of imides by the direct coupling of NH-amides with methylarenes under iodine/aqueous TBHP conditions. The optimized conditions worked very well with benzaldehydes and benzyl alcohol and furnished the corresponding imides in good to excellent yields. A series of control and radical scavenger experiments were also performed, which suggested the involvement of radical pathways. The labeling experiment in the presence of (18)O-labeled H2O suggested water as a source of oxygen in the imides.

  19. Automated metal-free multiple-column nanoLC for improved phosphopeptide analysis sensitivity and throughput

    SciTech Connect

    Zhao, Rui; Ding, Shi-Jian; Shen, Yufeng; Camp, David G.; Livesay, Eric A.; Udseth, Harold R.; Smith, Richard D.

    2009-03-15

    We report on the development and characterization of an automated metal-free nanoscale multiple-capillary system for reversed-phase liquid chromatography-mass spectrometry analysis of phosphopeptides. The system incorporates a capillary column (50 um i.d. × 30 cm, packed with 5 um C18 particles) coupled on-line to a solid phase extraction column (150 um i.d. × 4 cm, packed with 5 um C18 particles). Electrospray ionization tips are constructed on the packed capillary column to couple the reversed-phase liquid chromatographic separation to a linear ion trap tandem mass spectrometer.

  20. Metal-free α-Amination of Secondary Amines: Computational and Experimental Evidence for Azaquinone Methide and Azomethine Ylide Intermediates

    PubMed Central

    Dieckmann, Arne; Richers, Matthew T.; Platonova, Alena Yu.; Zhang, Chen; Seidel, Daniel; Houk, K. N.

    2013-01-01

    We have performed a combined computational and experimental study to elucidate the mechanism of a metal-free α-amination of secondary amines. Calculations predicted azaquinone methides and azomethine ylides as the reactive intermediates and showed that iminium ions are unlikely to participate in these transformations. These results were confirmed by experimental deuterium labeling studies and the successful trapping of the postulated azomethine ylide and azaquinone methide intermediates. In addition, computed barrier heights for the rate-limiting step correlate qualitatively with experimental findings. PMID:23517448

  1. Metal-free metathesis reaction of C-chiral allylic sulfilimines with aryl isocyanates: construction of chiral nonracemic allylic isocyanates.

    PubMed

    Grange, Rebecca L; Evans, P Andrew

    2014-08-27

    We report the facile and efficient metal-free metathesis reaction of C-chiral allylic sulfilimines with aryl isocyanates. This process facilitates the room temperature construction of an array of chiral nonracemic allylic isocyanates, which are versatile intermediates for the construction of unsymmetrical ureas, carbamates, thiocarbamates and amides. Furthermore, the sulfilimine/isocyanate metathesis reaction with 4,4'-methylene diphenyl diisocyanate (4,4'-MDI) circumvents harsh reaction conditions and/or hazardous reagents employed with more classical methods for the preparation of this important functional group.

  2. Nitrogen-doped graphdiyne as a metal-free catalyst for high-performance oxygen reduction reactions.

    PubMed

    Liu, Rongji; Liu, Huibiao; Li, Yuliang; Yi, Yuanping; Shang, Xinke; Zhang, Shuangshuang; Yu, Xuelian; Zhang, Suojiang; Cao, Hongbin; Zhang, Guangjin

    2014-10-01

    Fuel cells and metal-air batteries will only become widely available in everyday life when the expensive platinum-based electrocatalysts used for the oxygen reduction reactions are replaced by other efficient, low-cost and stable catalysts. We report here the use of nitrogen-doped graphdiyne as a metal-free electrode with a comparable electrocatalytic activity to commercial Pt/C catalysts for the oxygen reduction reaction in alkaline fuel cells. Nitrogen-doped graphdiyne has a better stability and increased tolerance to the cross-over effect than conventional Pt/C catalysts. PMID:25141067

  3. Metal free earth abundant elemental red phosphorus: a new class of visible light photocatalyst and photoelectrode materials.

    PubMed

    Ansari, Sajid Ali; Ansari, Mohammad Shahnawaze; Cho, Moo Hwan

    2016-02-01

    Developing a high-performance photocatalyst and a photoelectrode with enhanced visible light harvesting properties is essential for practical visible light photocatalytic applications. Noble metal-free, highly visible light-active, elemental red phosphorus (RP) was prepared by a facile mechanical ball milling method, which is a reproducible, low cost and controllable synthesis process. The synthesis used inexpensive and abundant raw materials because most RP hybrids are based on expensive noble-metals. The novel milled RP showed significantly enhanced photocatalytic and photoelectrochemical performances with a lower charge transfer resistance compared to commercial RP under wide visible photoirradiation, making it a feasible alternative for photocatalytic applications. PMID:26765211

  4. I2/Aqueous TBHP-Catalyzed Coupling of Amides with Methylarenes/Aldehydes/Alcohols: Metal-Free Synthesis of Imides.

    PubMed

    Aruri, Hariprasad; Singh, Umed; Kumar, Sanjay; Kushwaha, Manoj; Gupta, Ajai Prakash; Vishwakarma, Ram A; Singh, Parvinder Pal

    2016-08-01

    We present a metal-free method for the synthesis of imides by the direct coupling of NH-amides with methylarenes under iodine/aqueous TBHP conditions. The optimized conditions worked very well with benzaldehydes and benzyl alcohol and furnished the corresponding imides in good to excellent yields. A series of control and radical scavenger experiments were also performed, which suggested the involvement of radical pathways. The labeling experiment in the presence of (18)O-labeled H2O suggested water as a source of oxygen in the imides. PMID:27434140

  5. Three-unit bridge construction in anterior single-pontic areas using a metal-free restorative.

    PubMed

    Narcisi, E M

    1999-02-01

    A new glass-ceramic material, IPS Empress 2, is revolutionizing esthetic restorative dentistry by allowing metal-free, three-unit bridge construction in anterior and premolar single-pontic areas. The case discussed in this article illustrates the material's application in the dual-arch restoration of a young woman with congenitally missing teeth. The material was used as an alternative to single-tooth implant restorations to place two maxillary three-unit bridges, one mandibular three-unit bridge, and two mandibular porcelain veneers. IPS Empress 2 provides an esthetic alternative to porcelain-fused-to-metal restorations by facilitating attractive, functional tooth restoration.

  6. The Road from the NASA Access to Space Study to a Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    Powell, Richard W.; Cook, Stephen A.; Lockwood, Mary Kae

    1998-01-01

    NASA is cooperating with the aerospace industry to develop a space transportation system that provides reliable access-to-space at a much lower cost than is possible with today's launch vehicles. While this quest has been on-going for many years it received a major impetus when the U.S. Congress mandated as part of the 1993 NASA appropriations bill that: "In view of budget difficulties, present and future..., the National Aeronautics and Space Administration shall ... recommend improvements in space transportation." NASA, working with other organizations, including the Department of Transportation, and the Department of Defense identified three major transportation architecture options that were to be evaluated in the areas of reliability, operability and cost. These architectural options were: (1) retain and upgrade the Space Shuttle and the current expendable launch vehicles; (2) develop new expendable launch vehicles using conventional technologies and transition to these new vehicles beginning in 2005; and (3) develop new reusable vehicles using advanced technology, and transition to these vehicles beginning in 2008. The launch needs mission model was based on 1993 projections of civil, defense, and commercial payload requirements. This "Access to Space" study concluded that the option that provided the greatest potential for meeting the cost, operability, and reliability goals was a rocket-powered single-stage-to-orbit fully reusable launch vehicle (RLV) fleet designed with advanced technologies.

  7. Future Launch Vehicle Structures - Expendable and Reusable Elements

    NASA Astrophysics Data System (ADS)

    Obersteiner, M. H.; Borriello, G.

    2002-01-01

    Further evolution of existing expendable launch vehicles will be an obvious element influencing the future of space transportation. Besides this reusability might be the change with highest potential for essential improvement. The expected cost reduction and finally contributing to this, the improvement of reliability including safe mission abort capability are driving this idea. Although there are ideas of semi-reusable launch vehicles, typically two stages vehicles - reusable first stage or booster(s) and expendable second or upper stage - it should be kept in mind that the benefit of reusability will only overwhelm if there is a big enough share influencing the cost calculation. Today there is the understanding that additional technology preparation and verification will be necessary to master reusability and get enough benefits compared with existing launch vehicles. This understanding is based on several technology and system concepts preparation and verification programmes mainly done in the US but partially also in Europe and Japan. The major areas of necessary further activities are: - System concepts including business plan considerations - Sub-system or component technologies refinement - System design and operation know-how and capabilities - Verification and demonstration oriented towards future mission mastering: One of the most important aspects for the creation of those coming programmes and activities will be the iterative process of requirements definition derived from concepts analyses including economical considerations and the results achieved and verified within technology and verification programmes. It is the intention of this paper to provide major trends for those requirements focused on future launch vehicles structures. This will include the aspects of requirements only valid for reusable launch vehicles and those common for expendable, semi-reusable and reusable launch vehicles. Structures and materials is and will be one of the

  8. Ordered mesoporous boron-doped carbons as metal-free electrocatalysts for the oxygen reduction reaction in alkaline solution.

    PubMed

    Bo, Xiangjie; Guo, Liping

    2013-02-21

    Ordered mesoporous boron-doped carbons (BOMCs) were prepared by co-impregnation and carbonization of sucrose and 4-hydroxyphenylboronic acid into SBA-15 silica template. Nitrogen sorption, small angle X-ray diffraction (XRD), and transmission electron microscopy (TEM) reveals that BOMCs possess highly ordered mesoporous structure, uniform pore size distribution, and high surface area. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that B atoms can be successfully doped into the framework of OMCs. Due to the desirable characteristics of BOMCs, BOMCs are highly active, cheap, and selective metal-free electrocatalysts for the oxygen reduction reaction (ORR) in alkaline solution. Although B content is a key factor in determining ORR activity, the ORR activity of BOMCs is also dependent on the surface area. The high surface area of BOMCs facilitates the exposure of the active sites for ORR. BOMCs may be further exploited as potentially efficient and inexpensive metal-free ORR catalysts with good long-term stability in alkaline solution. PMID:23318553

  9. P-Doped Porous Carbon as Metal Free Catalysts for Selective Aerobic Oxidation with an Unexpected Mechanism.

    PubMed

    Patel, Mehulkumar A; Luo, Feixiang; Khoshi, M Reza; Rabie, Emann; Zhang, Qing; Flach, Carol R; Mendelsohn, Richard; Garfunkel, Eric; Szostak, Michal; He, Huixin

    2016-02-23

    An extremely simple and rapid (seconds) approach is reported to directly synthesize gram quantities of P-doped graphitic porous carbon materials with controlled P bond configuration. For the first time, it is demonstrated that the P-doped carbon materials can be used as a selective metal free catalyst for aerobic oxidation reactions. The work function of P-doped carbon materials, its connectivity to the P bond configuration, and the correlation with its catalytic efficiency are studied and established. In direct contrast to N-doped graphene, the P-doped carbon materials with higher work function show high activity in catalytic aerobic oxidation. The selectivity trend for the electron donating and withdrawing properties of the functional groups attached to the aromatic ring of benzyl alcohols is also different from other metal free carbon based catalysts. A unique catalytic mechanism is demonstrated, which differs from both GO and N-doped graphene obtained by high temperature nitrification. The unique and unexpected catalytic pathway endows the P-doped materials with not only good catalytic efficiency but also recyclability. This, combined with a rapid, energy saving approach that permits fabrication on a large scale, suggests that the P-doped porous materials are promising materials for "green catalysis" due to their higher theoretical surface area, sustainability, environmental friendliness, and low cost.

  10. Surface-nitrogen-rich ordered mesoporous carbon as an efficient metal-free electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Xiao, Chunhui; Chen, Xu; Fan, Zhaoyang; Liang, Jin; Zhang, Bo; Ding, Shujiang

    2016-11-01

    Exploring efficient metal-free electrocatalysts for oxygen reduction reactions (ORR) will have a great impact on the field of fuel cells and metal-air batteries. In this paper, we report a simple and efficient routine to coat ordered mesoporous carbon (CMK-3) with nitrogen-doped carbon via pyrolysis of the surface-self-polymerized polydopamine. The optimized CMK-3 catalyst with a coating of nitrogen-doped carbon demonstrates excellent electrocatalytic activity towards ORR in alkaline media. The coating procedure under optimized conditions lowers the ORR half-wave-potential by 80 mV, giving a genuine metal-free catalyst with an onset ORR potential of 0.96 V (vs reversible hydrogen electrode (RHE)) and half-wave potential of 0.83 V (vs RHE) in 0.1 M KOH, which is much better than other carbon material-based catalysts (such as carbon nanotubes and their composites). The performance of this surface-nitrogen-rich CMK-3 catalyst is also superior to that of N-doped ordered mesoporous carbon synthesized by means of the ‘nanocasting’ technique. Furthermore, the as-prepared catalyst performs comparably in terms of activity, superior durability, and higher tolerance to methanol compared with commercially available Pt/C.

  11. Functionalized Graphitic Carbon Nitride for Metal-free, Flexible and Rewritable Nonvolatile Memory Device via Direct Laser-Writing

    PubMed Central

    Zhao, Fei; Cheng, Huhu; Hu, Yue; Song, Long; Zhang, Zhipan; Jiang, Lan; Qu, Liangti

    2014-01-01

    Graphitic carbon nitride nanosheet (g-C3N4-NS) has layered structure similar with graphene nanosheet and presents unusual physicochemical properties due to the s-triazine fragments. But their electronic and electrochemical applications are limited by the relatively poor conductivity. The current work provides the first example that atomically thick g-C3N4-NSs are the ideal candidate as the active insulator layer with tunable conductivity for achieving the high performance memory devices with electrical bistability. Unlike in conventional memory diodes, the g-C3N4-NSs based devices combined with graphene layer electrodes are flexible, metal-free and low cost. The functionalized g-C3N4-NSs exhibit desirable dispersibility and dielectricity which support the all-solution fabrication and high performance of the memory diodes. Moreover, the flexible memory diodes are conveniently fabricated through the fast laser writing process on graphene oxide/g-C3N4-NSs/graphene oxide thin film. The obtained devices not only have the nonvolatile electrical bistability with great retention and endurance, but also show the rewritable memory effect with a reliable ON/OFF ratio of up to 105, which is the highest among all the metal-free flexible memory diodes reported so far, and even higher than those of metal-containing devices. PMID:25073687

  12. Nitrogen-doped graphdiyne as a metal-free catalyst for high-performance oxygen reduction reactions

    NASA Astrophysics Data System (ADS)

    Liu, Rongji; Liu, Huibiao; Li, Yuliang; Yi, Yuanping; Shang, Xinke; Zhang, Shuangshuang; Yu, Xuelian; Zhang, Suojiang; Cao, Hongbin; Zhang, Guangjin

    2014-09-01

    Fuel cells and metal-air batteries will only become widely available in everyday life when the expensive platinum-based electrocatalysts used for the oxygen reduction reactions are replaced by other efficient, low-cost and stable catalysts. We report here the use of nitrogen-doped graphdiyne as a metal-free electrode with a comparable electrocatalytic activity to commercial Pt/C catalysts for the oxygen reduction reaction in alkaline fuel cells. Nitrogen-doped graphdiyne has a better stability and increased tolerance to the cross-over effect than conventional Pt/C catalysts.Fuel cells and metal-air batteries will only become widely available in everyday life when the expensive platinum-based electrocatalysts used for the oxygen reduction reactions are replaced by other efficient, low-cost and stable catalysts. We report here the use of nitrogen-doped graphdiyne as a metal-free electrode with a comparable electrocatalytic activity to commercial Pt/C catalysts for the oxygen reduction reaction in alkaline fuel cells. Nitrogen-doped graphdiyne has a better stability and increased tolerance to the cross-over effect than conventional Pt/C catalysts. Electronic supplementary information (ESI) available: Detailed RDE and RRDE experiments, additional tables and figures. See DOI: 10.1039/c4nr03185g

  13. Theoretical investigations on SiC2 siligraphene as promising metal-free catalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Dong, Huilong; Lin, Bin; Gilmore, Keith; Hou, Tingjun; Lee, Shuit-Tong; Li, Youyong

    2015-12-01

    The design and discovery of high-performance metal-free catalytic materials for oxygen reduction reaction (ORR) electrocatalysis is vital for the development of fuel cells. By performing density functional theory (DFT) calculations, we investigate the potential applications of SiC2 siligraphene (g-SiC2) as metal-free ORR catalyst. The g-SiC2 exhibits higher adsorption affinity for the O2 molecule and other ORR intermediates than the traditional Pt (111), and shows good tolerance against CO poisoning. The detailed LH and ER mechanisms in catalyzing ORR by g-SiC2 are simulated and discussed, both in acidic and alkaline environment. We find that, in alkaline environment, the g-SiC2 presents a very low activation barrier (0.16 eV) for the rate determining step (RDS) and shows no overpotential at the equilibrium potential. Our theoretical simulations validate that the siligraphene with alternatively arranged Si and C atoms holds great potential as ORR catalyst in alkaline environment.

  14. Functionalized graphitic carbon nitride for metal-free, flexible and rewritable nonvolatile memory device via direct laser-writing.

    PubMed

    Zhao, Fei; Cheng, Huhu; Hu, Yue; Song, Long; Zhang, Zhipan; Jiang, Lan; Qu, Liangti

    2014-07-30

    Graphitic carbon nitride nanosheet (g-C3N4-NS) has layered structure similar with graphene nanosheet and presents unusual physicochemical properties due to the s-triazine fragments. But their electronic and electrochemical applications are limited by the relatively poor conductivity. The current work provides the first example that atomically thick g-C3N4-NSs are the ideal candidate as the active insulator layer with tunable conductivity for achieving the high performance memory devices with electrical bistability. Unlike in conventional memory diodes, the g-C3N4-NSs based devices combined with graphene layer electrodes are flexible, metal-free and low cost. The functionalized g-C3N4-NSs exhibit desirable dispersibility and dielectricity which support the all-solution fabrication and high performance of the memory diodes. Moreover, the flexible memory diodes are conveniently fabricated through the fast laser writing process on graphene oxide/g-C3N4-NSs/graphene oxide thin film. The obtained devices not only have the nonvolatile electrical bistability with great retention and endurance, but also show the rewritable memory effect with a reliable ON/OFF ratio of up to 10(5), which is the highest among all the metal-free flexible memory diodes reported so far, and even higher than those of metal-containing devices.

  15. Surface-nitrogen-rich ordered mesoporous carbon as an efficient metal-free electrocatalyst for oxygen reduction reaction.

    PubMed

    Xiao, Chunhui; Chen, Xu; Fan, Zhaoyang; Liang, Jin; Zhang, Bo; Ding, Shujiang

    2016-11-01

    Exploring efficient metal-free electrocatalysts for oxygen reduction reactions (ORR) will have a great impact on the field of fuel cells and metal-air batteries. In this paper, we report a simple and efficient routine to coat ordered mesoporous carbon (CMK-3) with nitrogen-doped carbon via pyrolysis of the surface-self-polymerized polydopamine. The optimized CMK-3 catalyst with a coating of nitrogen-doped carbon demonstrates excellent electrocatalytic activity towards ORR in alkaline media. The coating procedure under optimized conditions lowers the ORR half-wave-potential by 80 mV, giving a genuine metal-free catalyst with an onset ORR potential of 0.96 V (vs reversible hydrogen electrode (RHE)) and half-wave potential of 0.83 V (vs RHE) in 0.1 M KOH, which is much better than other carbon material-based catalysts (such as carbon nanotubes and their composites). The performance of this surface-nitrogen-rich CMK-3 catalyst is also superior to that of N-doped ordered mesoporous carbon synthesized by means of the 'nanocasting' technique. Furthermore, the as-prepared catalyst performs comparably in terms of activity, superior durability, and higher tolerance to methanol compared with commercially available Pt/C.

  16. Surface-nitrogen-rich ordered mesoporous carbon as an efficient metal-free electrocatalyst for oxygen reduction reaction.

    PubMed

    Xiao, Chunhui; Chen, Xu; Fan, Zhaoyang; Liang, Jin; Zhang, Bo; Ding, Shujiang

    2016-11-01

    Exploring efficient metal-free electrocatalysts for oxygen reduction reactions (ORR) will have a great impact on the field of fuel cells and metal-air batteries. In this paper, we report a simple and efficient routine to coat ordered mesoporous carbon (CMK-3) with nitrogen-doped carbon via pyrolysis of the surface-self-polymerized polydopamine. The optimized CMK-3 catalyst with a coating of nitrogen-doped carbon demonstrates excellent electrocatalytic activity towards ORR in alkaline media. The coating procedure under optimized conditions lowers the ORR half-wave-potential by 80 mV, giving a genuine metal-free catalyst with an onset ORR potential of 0.96 V (vs reversible hydrogen electrode (RHE)) and half-wave potential of 0.83 V (vs RHE) in 0.1 M KOH, which is much better than other carbon material-based catalysts (such as carbon nanotubes and their composites). The performance of this surface-nitrogen-rich CMK-3 catalyst is also superior to that of N-doped ordered mesoporous carbon synthesized by means of the 'nanocasting' technique. Furthermore, the as-prepared catalyst performs comparably in terms of activity, superior durability, and higher tolerance to methanol compared with commercially available Pt/C. PMID:27668508

  17. Silicon and phosphorus dual doped graphene as the promising metal-free catalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Lu, Zhansheng; Li, Shuo; Yang, Zongxian; Wu, Ruqian

    The pathways of oxygen reduction reaction (ORR) on the metal-free silicon and phosphorus dual doped graphene (Si-P-G) catalyst are systematically investigated based on the dispersion-corrected density functional theory (DFT-D) method. It is found that the Si-P-G can be stable at high temperature from the first-principles molecular dynamics simulation and the local region of dopants displays an important role in the adsorption and reduction of oxygen. Both of the four-electron O2 direct dissociation and the two-electron OOH dissociation pathways are probable for ORR on the Si-P-G, while the latter pathway is mainly followed by the pathway of the OH hydrogenation into H2O. For the OOH dissociation pathway, the hydrogenation of O2 to OOH is the rate-limiting step with a rather small barrier energy of 0.66 eV. The current results indicate that the Si-P-G is a novel metal-free catalyst for ORR, and which is comparable to that of the Pt catalyst. Work was supported by the National Science Foundation Center for Chemical Innovation on Chemistry at the Space-Time Limit (CaSTL) under Grant No. CHE-1414466, and the National Natural Science Foundation of China (Grant Nos. 51401078, and 11474086).

  18. Theoretical study on the Si-doped graphene as an efficient metal-free catalyst for CO oxidation

    NASA Astrophysics Data System (ADS)

    Tang, Yanan; Liu, Zhiyong; Dai, Xianqi; Yang, Zongxian; Chen, Weiguang; Ma, Dongwei; Lu, Zhansheng

    2014-07-01

    The reduction of noble metal used in carbon monoxide (CO) oxidation remains a challenge. Based on the first-principle methods, the geometry, electronic structure and catalytic properties of Si-doped graphene (Si-graphene) are investigated. The Si adatom has smaller adsorption energy on pristine graphene as compared with that of the Si dopant in graphene. The large atomic radii of Si dopant in graphene can induce the local surface curvature and modulate the electronic structure through inducing the charge redistribution. Besides, the metal-free Si-graphene can weaken the CO adsorption and facilitates the O2 adsorption, thus enhancing the catalytic activity for CO oxidation. It is found that the preadsorbed O2 molecule on the Si-atom can greatly enhance the interaction with CO molecule. Moreover, the complete CO oxidation reactions on the Si-graphene include a two-step process of the Eley-Rideal (ER) reactions, in which the first step has a low energy barrier of 0.43 eV and the second step exhibits an even negligible energy barrier of 0.07 eV. The results validate the reactivity of catalysts on the atomic-scale and initiate a clue for fabricating metal-free catalysts with low cost and high activity.

  19. Metal Free Bi(hetero)aryl Synthesis: A Benzyne Truce-Smiles Rearrangement.

    PubMed

    Holden, Catherine M; Sohel, Shariar M A; Greaney, Michael F

    2016-02-12

    A new benzyne transformation is described that affords versatile biaryl structures without recourse to transition-metal catalysis or stoichiometric amounts of organometallic building blocks. Aryl sulfonamides add to benzyne upon fluoride activation, and then undergo an aryl Truce-Smiles rearrangement to afford biaryls with sulfur dioxide extrusion. The reaction proceeds under simple reaction conditions and has excellent scope for the synthesis of sterically hindered atropisomeric biaryl amines.

  20. 2nd Generation Reusable Launch Vehicle Potential Commercial Development Scenarios

    NASA Technical Reports Server (NTRS)

    Creech, Stephen D.; Rogacki, John R. (Technical Monitor)

    2001-01-01

    The presentation will discuss potential commercial development scenarios for a Second Generation Reusable Launch Vehicle. The analysis of potential scenarios will include commercial rates of return, government return on investment, and market considerations. The presentation will include policy considerations in addition to analysis of Second Generation Reusable Launch Vehicle economics. The data discussed is being developed as a part of NASA's Second Generation Reusable Launch Vehicle Program, for consideration as potential scenarios for enabling a next generation system. Material will include potential scenarios not previously considered by NASA or presented at other conferences. Candidate paper has not been presented at a previous meeting, and conference attendance of the author has been approved by NASA.

  1. Benefits of Government Incentives for Reusable Launch Vehicle Development

    NASA Technical Reports Server (NTRS)

    Shaw, Eric J.; Hamaker, Joseph W.; Prince, Frank A.

    1998-01-01

    Many exciting new opportunities in space, both government missions and business ventures, could be realized by a reduction in launch prices. Reusable launch vehicle (RLV) designs have the potential to lower launch costs dramatically from those of today's expendable and partially-expendable vehicles. Unfortunately, governments must budget to support existing launch capability, and so lack the resources necessary to completely fund development of new reusable systems. In addition, the new commercial space markets are too immature and uncertain to motivate the launch industry to undertake a project of this magnitude and risk. Low-cost launch vehicles will not be developed without a mature market to service; however, launch prices must be reduced in order for a commercial launch market to mature. This paper estimates and discusses the various benefits that may be reaped from government incentives for a commercial reusable launch vehicle program.

  2. Orbital Debris Impact Damage to Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Robinson, Jennifer H.

    1998-01-01

    In an effort by the National Aeronautics and Space Administration (NASA), hypervelocity impact tests were performed on thermal protection systems (TPS) applied on the external surfaces of reusable launch vehicles (RLV) to determine the potential damage from orbital debris impacts. Three TPS types were tested, bonded to composite structures representing RLV fuel tank walls. The three heat shield materials tested were Alumina-Enhanced Thermal Barrier-12 (AETB-12), Flexible Reusable Surface Insulation (FRSI), and Advanced Flexible Reusable Surface Insulation (AFRSI). Using this test data, predictor equations were developed for the entry hole diameters in the three TPS materials, with correlation coefficients ranging from 0.69 to 0.86. Possible methods are proposed for approximating damage occurring at expected orbital impact velocities higher than tested, with references to other published work.

  3. Legislative and regulatory issues related to reusable launch systems

    NASA Astrophysics Data System (ADS)

    Peinemann, Manfred K. A.

    1996-03-01

    The development of reusable launch systems with private investment funds for primarily commercial launch services raises a number of novel legal and regulatory issues. The issues discussed include requirements for a whole new spectrum of safety and environmental issues; new certification rules, procedures and oversight organizations; liability and jurisdiction definitions, taxation treatments; government commitments and/or participation in commercial enterprises; and international legal and business issues. The satisfactory solution to all of these issues is a necessary condition for the development and operation of reusable launch vehicles to be a viable commercial enterprise.

  4. Reusable rocket engine intelligent control system framework design, phase 2

    NASA Technical Reports Server (NTRS)

    Nemeth, ED; Anderson, Ron; Ols, Joe; Olsasky, Mark

    1991-01-01

    Elements of an advanced functional framework for reusable rocket engine propulsion system control are presented for the Space Shuttle Main Engine (SSME) demonstration case. Functional elements of the baseline functional framework are defined in detail. The SSME failure modes are evaluated and specific failure modes identified for inclusion in the advanced functional framework diagnostic system. Active control of the SSME start transient is investigated, leading to the identification of a promising approach to mitigating start transient excursions. Key elements of the functional framework are simulated and demonstration cases are provided. Finally, the advanced function framework for control of reusable rocket engines is presented.

  5. Reusable Hot-Wire Cable Cutter

    NASA Technical Reports Server (NTRS)

    Pauken, Michael T.; Steinkraus, Joel M.

    2010-01-01

    During the early development stage of balloon deployment systems for missions, nichrome wire cable cutters were often used in place of pyro-actuated cutters. Typically, a nichrome wire is wrapped around a bundle of polymer cables with a low melting point and connected to a relay-actuated electric circuit. The heat from the nichrome reduces the strength of the cable bundle, which quickly breaks under a mechanical load and can thus be used as a release mechanism for a deployment system. However, the use of hand-made heated nichrome wire for cutters is not very reliable. Often, the wrapped nichrome wire does not cut through the cable because it either pulls away from its power source or does not stay in contact with the cable being cut. Because nichrome is not readily soldered to copper wire, unreliable mechanical crimps are often made to connect the nichrome to an electric circuit. A self-contained device that is reusable and reliable was developed to sever cables for device release or deployment. The nichrome wire in this new device is housed within an enclosure to prevent it from being damaged by handling. The electric power leads are internally connected within the unit to the nichrome wire using a screw terminal connection. A bayonet plug, a quick and secure method of connecting the cutter to the power source, is used to connect the cutter to the power leads similar to those used in pyro-cutter devices. A small ceramic tube [0.25-in. wide 0.5-in. long (.6.4-mm wide 13-mm long)] houses a spiraled nichrome wire that is heated when a cable release action is required. The wire is formed into a spiral coil by wrapping it around a mandrel. It is then laid inside the ceramic tube so that it fits closely to the inner surface of the tube. The ceramic tube provides some thermal and electrical insulation so that most of the heat generated by the wire is directed toward the cable bundle in the center of the spiral. The ceramic tube is cemented into an aluminum block, which

  6. Metal-Free Markovnikov-Type Alkyne Hydration under Mild Conditions.

    PubMed

    Liu, Wenbo; Wang, Haining; Li, Chao-Jun

    2016-05-01

    A Markovnikov-type alkyne hydration protocol is presented using 20% CF3SO3H (TfOH) as the catalyst under unprecedented mild conditions applicable to various alkynes, including terminal arylalkynes, terminal nonfunctionalized aliphatic alkynes, and internal alkynes with excellent regioselectivity in good to excellent yields (average yields >85%). The reaction procedure operates under mild conditions (25-70 °C), with broad functional group compatibility, and uses only slightly more than a stoichiometric amount of water in the absence of any transition metal. The success of this protocol hinges upon the utilization of trifluoroethanol as the solvent. PMID:27082159

  7. A highly efficient noble metal free photocatalytic hydrogen evolution system containing MoP and CdS quantum dots

    NASA Astrophysics Data System (ADS)

    Yin, Shengming; Han, Jianyu; Zou, Yinjun; Zhou, Tianhua; Xu, Rong

    2016-07-01

    We report the construction of a highly efficient noble metal free photocatalytic hydrogen (H2) evolution system using CdS quantum dots as the light absorber and metallic MoP as the cocatalyst. MoP can be prepared by a facile temperature programmed reduction method and small clusters of MoP nanoparticles sized 10-30 nm were obtained by probe ultrasonication. The effect of synthesis conditions on the electrocatalytic and photocatalytic H2 evolution activity of MoP was investigated. The highest H2 evolution rate of 1100 μmol h-1 can be achieved by the optimized system under visible light (λ >= 420 nm), which is comparable to that when Pt was used as the cocatalyst. A high quantum efficiency of 45% is obtained at 460 nm irradiation.We report the construction of a highly efficient noble metal free photocatalytic hydrogen (H2) evolution system using CdS quantum dots as the light absorber and metallic MoP as the cocatalyst. MoP can be prepared by a facile temperature programmed reduction method and small clusters of MoP nanoparticles sized 10-30 nm were obtained by probe ultrasonication. The effect of synthesis conditions on the electrocatalytic and photocatalytic H2 evolution activity of MoP was investigated. The highest H2 evolution rate of 1100 μmol h-1 can be achieved by the optimized system under visible light (λ >= 420 nm), which is comparable to that when Pt was used as the cocatalyst. A high quantum efficiency of 45% is obtained at 460 nm irradiation. Electronic supplementary information (ESI) available: SEM image with EDS, XPS survey spectrum, XRD and TEM images of MoP samples prepared under different conditions; XRD, TEM, UV-vis and photoluminescence spectra of CdS QDs; H2 evolution activity comparison for different MoP/CdS samples; the effect of pH value on H2 evolution activity of a MoP/CdS system; the XPS spectrum of MoP/CdS after photoreaction; table of literature studies on H2 evolution activity by different noble metal free photocatalytic systems

  8. Micelle-Template Synthesis of Nitrogen-Doped Mesoporous Graphene as an Efficient Metal-Free Electrocatalyst for Hydrogen Production

    PubMed Central

    Huang, Xiaodan; Zhao, Yufei; Ao, Zhimin; Wang, Guoxiu

    2014-01-01

    Synthesis of mesoporous graphene materials by soft-template methods remains a great challenge, owing to the poor self-assembly capability of precursors and the severe agglomeration of graphene nanosheets. Herein, a micelle-template strategy to prepare porous graphene materials with controllable mesopores, high specific surface areas and large pore volumes is reported. By fine-tuning the synthesis parameters, the pore sizes of mesoporous graphene can be rationally controlled. Nitrogen heteroatom doping is found to remarkably render electrocatalytic properties towards hydrogen evolution reactions as a highly efficient metal-free catalyst. The synthesis strategy and the demonstration of highly efficient catalytic effect provide benchmarks for preparing well-defined mesoporous graphene materials for energy production applications. PMID:25523276

  9. N,P-Codoped Carbon Networks as Efficient Metal-free Bifunctional Catalysts for Oxygen Reduction and Hydrogen Evolution Reactions.

    PubMed

    Zhang, Jintao; Qu, Liangti; Shi, Gaoquan; Liu, Jiangyong; Chen, Jianfeng; Dai, Liming

    2016-02-01

    The high cost and scarcity of noble metal catalysts, such as Pt, have hindered the hydrogen production from electrochemical water splitting, the oxygen reduction in fuel cells and batteries. Herein, we developed a simple template-free approach to three-dimensional porous carbon networks codoped with nitrogen and phosphorus by pyrolysis of a supermolecular aggregate of self-assembled melamine, phytic acid, and graphene oxide (MPSA/GO). The pyrolyzed MPSA/GO acted as the first metal-free bifunctional catalyst with high activities for both oxygen reduction and hydrogen evolution. Zn-air batteries with the pyrolyzed MPSA/GO air electrode showed a high peak power density (310 W g(-1) ) and an excellent durability. Thus, the pyrolyzed MPSA/GO is a promising bifunctional catalyst for renewable energy technologies, particularly regenerative fuel cells. PMID:26709954

  10. Metal-free Ketjenblack incorporated nitrogen-doped carbon sheets derived from gelatin as oxygen reduction catalysts.

    PubMed

    Nam, Gyutae; Park, Joohyuk; Kim, Sun Tai; Shin, Dong-bin; Park, Noejung; Kim, Youngsik; Lee, Jang-Soo; Cho, Jaephil

    2014-01-01

    Electrocatalysts facilitating oxygen reduction reaction (ORR) are vital components in advanced fuel cells and metal-air batteries. Here we report Ketjenblack incorporated nitrogen-doped carbon sheets derived from gelatin and apply these easily scalable materials as metal-free electrocatalysts for ORR. These carbon nanosheets demonstrate highly comparable catalytic activity for ORR as well as better durability than commercial Vulcan carbon supported Pt catalysts in alkaline media. Physico-chemical characterization and theoretical calculations suggest that proper combination of graphitic and pyridinic nitrogen species with more exposed edge sites effectively facilitates a formation of superoxide, [O2(ad)](-), via one-electron transfer, thus increasing catalytic activities for ORR. Our results demonstrate a novel strategy to expose more nitrogen doped edge sites by irregular stacked small sheets in developing better electrocatalysts for Zn-air batteries. These desirable architectures are embodied by an amphiphlilic gelatin mediated compatible synthetic strategy between hydrophobic carbon and aqueous water.

  11. N,P-Codoped Carbon Networks as Efficient Metal-free Bifunctional Catalysts for Oxygen Reduction and Hydrogen Evolution Reactions.

    PubMed

    Zhang, Jintao; Qu, Liangti; Shi, Gaoquan; Liu, Jiangyong; Chen, Jianfeng; Dai, Liming

    2016-02-01

    The high cost and scarcity of noble metal catalysts, such as Pt, have hindered the hydrogen production from electrochemical water splitting, the oxygen reduction in fuel cells and batteries. Herein, we developed a simple template-free approach to three-dimensional porous carbon networks codoped with nitrogen and phosphorus by pyrolysis of a supermolecular aggregate of self-assembled melamine, phytic acid, and graphene oxide (MPSA/GO). The pyrolyzed MPSA/GO acted as the first metal-free bifunctional catalyst with high activities for both oxygen reduction and hydrogen evolution. Zn-air batteries with the pyrolyzed MPSA/GO air electrode showed a high peak power density (310 W g(-1) ) and an excellent durability. Thus, the pyrolyzed MPSA/GO is a promising bifunctional catalyst for renewable energy technologies, particularly regenerative fuel cells.

  12. Ceramic fragments and metal-free full crowns: a conservative esthetic option for closing diastemas and rehabilitating smiles.

    PubMed

    Miranda, M E; Olivieri, K A; Rigolin, F J; Basting, R T

    2013-01-01

    Dental ceramics make it possible to restore anterior teeth that have been esthetically compromised, presenting a high resistance to wear, biocompatibility, color stability, and low thermal conductivity. The development of different types of ceramic and techniques for adhesive cementation have made it possible to produce more conservative restorations without involving the healthy dental structure and with minimally invasive preparation, such as the bonding of ceramic fragments. The purpose of this article is to describe a clinical case in which diastemas were closed by using nanofluorapatite ceramic (e.max Ceram, Ivoclar-Vivadent) fragments on teeth 7 and 10 with minimal tooth preparation and metal-free ceramic crowns (e-max Ceram) reinforced with zirconia copings through a computer-aided design/computer-aided manufacturing system (Lava, 3M-ESPE) on teeth 8 and 9.

  13. Undeniable Confirmation of the syn-Addition Mechanism for Metal-Free Diboration by Using the Crystalline Sponge Method.

    PubMed

    Cuenca, Ana B; Zigon, Nicolas; Duplan, Vincent; Hoshino, Manabu; Fujita, Makoto; Fernández, Elena

    2016-03-24

    The stereochemical outcome of the recently developed metal-free 1,2-diboration of aliphatic alkenes has, until now, only been elucidated by indirect means (e.g. derivatization). This is because classical conformational analysis of the resulting 1,2-diboranes is not viable; in the (1)H NMR spectrum the relevant (1)H resonances are broadened by (11)B, and the occurrence of the products as oily compounds precludes X-ray crystallographic analysis. Herein, the crystalline sponge method is used to display the crystal structures of the diboronic esters formed from internal E and Z olefins, evidencing the stereospecific syn addition mechanism of the reaction, which is fully consistent with the prediction from DFT calculations.

  14. New concept for organic light-emitting devices under high excitations using emission from a metal-free area

    NASA Astrophysics Data System (ADS)

    Slowik, Irma; Fischer, Axel; Gutsche, Stefan; Brückner, Robert; Fröb, Hartmut; Lenk, Simone; Reineke, Sebastian; Leo, Karl

    2016-04-01

    In this work, a new organic light-emitting device (OLED) structure is proposed that allows light-emission from a metal-free device region, thus reducing the hurdles towards an electrically pumped organic solid state laser (OSL). Our design concept employs a stepwise change from a highly conductive but opaque metal part to a highly transparent but less conductive intrinsic emission layer. Here, the high current densities are localized to an area of a few micrometer in square, which is in the range of the mode volume of the transverse mode of an organic vertical-cavity surface-emitting laser (VCSEL). Besides these experimental results, we present findings from simulations which further support the feasibility of our design concept. Using an equivalent circuit approach, representing the current flow in the device, we calculate the time-dependent length of the emission zone and give estimations for appropriate material parameters.

  15. Copper-zinc alloy nanopowder: a robust precious-metal-free catalyst for the conversion of 5-hydroxymethylfurfural.

    PubMed

    Bottari, Giovanni; Kumalaputri, Angela J; Krawczyk, Krzysztof K; Feringa, Ben L; Heeres, Hero J; Barta, Katalin

    2015-04-24

    Noble-metal-free copper-zinc nanoalloy (<150 nm) is found to be uniquely suited for the highly selective catalytic conversion of 5-hydroxymethylfurfural (HMF) to potential biofuels or chemical building blocks. Clean mixtures of 2,5-dimethylfuran (DMF) and 2,5-dimethyltetrahydrofuran (DMTHF) with combined product yields up to 97 % were obtained at 200-220 °C using 20-30 bar H2 . It is also possible to convert 10 wt % HMF solutions in CPME, with an excellent DMF yield of 90 %. Milder temperatures favor selective (95 %) formation of 2,5-furandimethanol (FDM). The one-pot conversion of fructose to valuable furan-ethers was also explored. Recycling experiments for DMF production show remarkable catalyst stability. Transmission electron microscopy (TEM) characterization provides more insight into morphological changes of this intriguing class of materials during catalysis. PMID:25833148

  16. Si-embedded boron-nitride nanotubes as an efficient and metal-free catalyst for NO oxidation

    NASA Astrophysics Data System (ADS)

    Esrafili, Mehdi D.; Saeidi, Nasibeh

    2015-05-01

    We study the catalytic capability of Si-embedded boron nitride nanotubes (Si-BNNTs) as a metal-free catalyst for NO oxidation by using density functional theory. Our results reveal that a vacancy defect in BNNT strongly stabilizes the Si adatom and makes it more positively charged. These results confirm the fact that Si-BNNTs are stable enough to be utilized in catalytic NO oxidation reactions. The complete NO oxidation reactions involve the direct oxidization of NO to NO2 by O2 adsorbed on the surface of Si-BNNTs, as in NO + O2 → NO2 + O. The remaining O atom can further oxidize NO to NO2. The calculated energy barriers range from 0.2 to 2.4 kcal/mol, which suggests that the NO oxidation catalyzed by the Si-BNNTs is likely to occur at the room temperature. These values are much less than those processes using noble metal catalysts.

  17. Metal-free Ketjenblack incorporated nitrogen-doped carbon sheets derived from gelatin as oxygen reduction catalysts.

    PubMed

    Nam, Gyutae; Park, Joohyuk; Kim, Sun Tai; Shin, Dong-bin; Park, Noejung; Kim, Youngsik; Lee, Jang-Soo; Cho, Jaephil

    2014-01-01

    Electrocatalysts facilitating oxygen reduction reaction (ORR) are vital components in advanced fuel cells and metal-air batteries. Here we report Ketjenblack incorporated nitrogen-doped carbon sheets derived from gelatin and apply these easily scalable materials as metal-free electrocatalysts for ORR. These carbon nanosheets demonstrate highly comparable catalytic activity for ORR as well as better durability than commercial Vulcan carbon supported Pt catalysts in alkaline media. Physico-chemical characterization and theoretical calculations suggest that proper combination of graphitic and pyridinic nitrogen species with more exposed edge sites effectively facilitates a formation of superoxide, [O2(ad)](-), via one-electron transfer, thus increasing catalytic activities for ORR. Our results demonstrate a novel strategy to expose more nitrogen doped edge sites by irregular stacked small sheets in developing better electrocatalysts for Zn-air batteries. These desirable architectures are embodied by an amphiphlilic gelatin mediated compatible synthetic strategy between hydrophobic carbon and aqueous water. PMID:24635744

  18. A highly efficient noble metal free photocatalytic hydrogen evolution system containing MoP and CdS quantum dots.

    PubMed

    Yin, Shengming; Han, Jianyu; Zou, Yinjun; Zhou, Tianhua; Xu, Rong

    2016-08-14

    We report the construction of a highly efficient noble metal free photocatalytic hydrogen (H2) evolution system using CdS quantum dots as the light absorber and metallic MoP as the cocatalyst. MoP can be prepared by a facile temperature programmed reduction method and small clusters of MoP nanoparticles sized 10-30 nm were obtained by probe ultrasonication. The effect of synthesis conditions on the electrocatalytic and photocatalytic H2 evolution activity of MoP was investigated. The highest H2 evolution rate of 1100 μmol h(-1) can be achieved by the optimized system under visible light (λ≥ 420 nm), which is comparable to that when Pt was used as the cocatalyst. A high quantum efficiency of 45% is obtained at 460 nm irradiation. PMID:27406067

  19. Synthesis of l- and d-Ubiquitin by One-Pot Ligation and Metal-Free Desulfurization.

    PubMed

    Huang, Yi-Chao; Chen, Chen-Chen; Gao, Shuai; Wang, Ye-Hai; Xiao, Hua; Wang, Feng; Tian, Chang-Lin; Li, Yi-Ming

    2016-05-23

    Native chemical ligation combined with desulfurization has become a powerful strategy for the chemical synthesis of proteins. Here we describe the use of a new thiol additive, methyl thioglycolate, to accomplish one-pot native chemical ligation and metal-free desulfurization for chemical protein synthesis. This one-pot strategy was used to prepare ubiquitin from two or three peptide segments. Circular dichroism spectroscopy and racemic protein X-ray crystallography confirmed the correct folding of ubiquitin. Our results demonstrate that proteins synthesized chemically by streamlined 9-fluorenylmethoxycarbonyl (Fmoc) solid-phase peptide synthesis coupled with a one-pot ligation-desulfurization strategy can supply useful molecules with sufficient purity for crystallographic studies.

  20. Soda-lime glass as a binder in reusable experimental investment for dental castings.

    PubMed

    Yagi, Satoshi; Zhang, Zutai; Aida, Yoshiteru; Hotta, Yasuhiro; Tamaki, Yukimichi; Miyazaki, Takashi

    2011-01-01

    In this study, different glasses were investigated to improve reusable investments. Borosilicate glass (BSG) powder and soda-lime glass (SLG) powder were prepared by milling broken beakers and microscope slides, respectively, and used in experimental investments (I-BSG, I-SLG) by blending glass powder (10 wt%) with cristobalite (90 wt%). Some properties and casting fits were evaluated with commercial gypsum-bonded investment as the control. Both BSG and SLG were mainly composed of Si, but SLG had a large Ca content. The glass transition temperatures were approximately 800°C (BSG) and 700°C (SLG). Experimental investments with heating showed the significantly (p<0.05) higher expansion than that of the control. The compressive strength of I-SLG was higher than that of I-BSG, and increased with temperature. The MOD inlay obtained from I-SLG had a significantly smaller gap than that from I-BSG, and was comparable to the control. These results suggest SLG could be applied clinically as a reusable dental investment.

  1. Reusability Studies for Ares I and Ares V Propulsion

    NASA Technical Reports Server (NTRS)

    Williams, Thomas J.; Priskos, Alex S.; Schorr, Andrew A.; Barrett, Gregory

    2008-01-01

    looks at one of the most important trade studies to date, the "Ares I First Stage Expendability Trade Study." The purpose of this study was to determine the utility of flying the first stage as an expendable booster rather than making it reusable. To lower the study complexity, four operational scenarios (or cases) were defined. This assessment then included an evaluation of the development, reliability, performance, and transition impacts associated with an expendable solution. The paper looks at these scenarios from the perspectives of cost, reliability, and performance. The presentation provides an overview of the paper.

  2. Reusability Studies for Ares I and Ares V Propulsion

    NASA Technical Reports Server (NTRS)

    Williams, Thomas J.; Priskos, Alex S.; Schorr, Andrew A.; Barrett, Greg

    2008-01-01

    looks at one of the most important trade studies to date, the "Ares I First Stage Expendability Trade Study." The purpose of this study was to determine the utility of flying the first stage as an expendable booster rather than making it reusable. To lower the study complexity, four operational scenarios (or cases) were defined. This assessment then included an evaluation of the development, reliability, performance, and transition impacts associated with an expendable solution. This paper looks at these scenarios from the perspectives of cost, reliability, and performance.

  3. 2nd Generation Reusable Launch Vehicle NASA Led Propulsion Tasks

    NASA Technical Reports Server (NTRS)

    Richards, Steve

    2000-01-01

    Design, development and test of a 2nd generation Reusable Launch Vehicle (RLV) is presented. This current paper discusses the following: 2nd Generation RLV Propulsion Project, Overview of NASA Led Tasks in Propulsion, Gen2 Turbo Machinery Technology Demonstrator, and Combustion Devices Test Bed, GRCop-84 Sheet For Combustion Chambers, Nozzles and Large Actively Cooled Structures

  4. Reusable Launch Vehicle (RLV) Mission/Market Model

    NASA Technical Reports Server (NTRS)

    Prince, Frank A.

    1999-01-01

    The goal of this model was to assess the Reusable Launch Vehicle's (RLV) capability to support the International Space Station (ISS) servicing, determine the potential to leverage the commercial marketplace to reduce NASA's cost, and to evaluate the RLV's ability to expand the space economy. The presentation is in view-graph format.

  5. Mobile Authoring of Open Educational Resources as Reusable Learning Objects

    ERIC Educational Resources Information Center

    Kinshuk; Jesse, Ryan

    2013-01-01

    E-learning technologies have allowed authoring and playback of standardized reusable learning objects (RLO) for several years. Effective mobile learning requires similar functionality at both design time and runtime. Mobile devices can play RLO using applications like SMILE, mobile access to a learning management system (LMS), or other systems…

  6. A Re-Usable Algorithm for Teaching Procedural Skills.

    ERIC Educational Resources Information Center

    Jones, Mark K.; And Others

    The design of a re-usable instructional algorithm for computer based instruction (CBI) is described. The prototype is implemented on IBM PC compatibles running the Windows(TM) graphical environment, using the prototyping tool ToolBook(TM). The algorithm is designed to reduce development and life cycle costs for CBI by providing an authoring…

  7. Design optimization for a space based, reusable orbit transfer vehicle

    NASA Technical Reports Server (NTRS)

    Redd, L.

    1985-01-01

    Future NASA and DOD missions will benefit from high performance, reusable orbit transfer vehicles. With the advent of a space station, advanced engine technology, and various new vehicle concepts, reusable orbit transfer vehicles that provide significant economic benefits and mission capability improvements will be realized. Engine and vehicle design criteria previously have lacked definition with regard to issues such as space basing and servicing, man-rating and reliability, performance, mission flexibility, and life cycle cost for a reusable vehicle. The design study described here has resulted in the definition of a reusable orbit transfer vehicle concept and subsequent recommendations for the design criteria of an advanced LO2/LH2 engine. These design criteria include number of engines per vehicle, nozzle design, etc. The major characteristics of the vehicle preliminary design include low lift to drag aerocapture capability, a main propulsion system failure criteria of fail operational/fail safe, and either two main engines with a high performance attitude control system for back-up or three main engines with which to meet this failure criteria. In addition, a maintenance approach has been established for the advanced vehicle concept.

  8. 76 FR 24495 - Reprocessing of Reusable Medical Devices; Public Workshop

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-02

    ... Conference Center, Bldg. 31, Rm. 1503, 10903 New Hampshire Ave., Silver Spring, MD 20993. Contact Person: Carol Krueger, Food and Drug Administration, 10903 New Hampshire Ave., Bldg. 66, Rm. 5437, Silver Spring... in the retention of blood, tissue, and other biological debris (soil) in reusable medical...

  9. Reusable Reentry Satellite (RRS): Thermal control trade study

    NASA Technical Reports Server (NTRS)

    Wallace, Clark

    1990-01-01

    The design and assessment work performed in defining the on-orbit Thermal Control Subsystem (TCS) requirements for the Reusable Reentry Satellite (RRS) is discussed. Specifically, it describes the hardware and design measures necessary for maintaining the Payload Module (PM) Environmental Control Life Support System (ECLSS) heat exchanger, the hydrazine propellant, and PM water supply within their required temperature limits.

  10. Structural Integrity and Durability of Reusable Space Propulsion Systems

    NASA Technical Reports Server (NTRS)

    1987-01-01

    A two-day conference on the structural integrity and durability of reusable space propulsion systems was held on May 12 and 13, 1987, at the NASA Lewis research Center. Aerothermodynamic loads; instrumentation; fatigue, fracture, and constitutive modeling; and structural dynamics were discussed.

  11. Reusable chelating resins concentrate metal ions from highly dilute solutions

    NASA Technical Reports Server (NTRS)

    Bauman, A. J.; Weetal, H. H.; Weliky, N.

    1966-01-01

    Column chromatographic method uses new metal chelating resins for recovering heavy-metal ions from highly dilute solutions. The absorbed heavy-metal cations may be removed from the chelating resins by acid or base washes. The resins are reusable after the washes are completed.

  12. 14 CFR 431.3 - Types of reusable launch vehicle mission licenses.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 false Types of reusable launch vehicle mission licenses. 431.3 Section 431.3 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.3 Types of reusable...

  13. 14 CFR 431.3 - Types of reusable launch vehicle mission licenses.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Types of reusable launch vehicle mission licenses. 431.3 Section 431.3 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.3 Types of reusable...

  14. 14 CFR 431.3 - Types of reusable launch vehicle mission licenses.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Types of reusable launch vehicle mission licenses. 431.3 Section 431.3 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.3 Types of reusable...

  15. 14 CFR 431.3 - Types of reusable launch vehicle mission licenses.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Types of reusable launch vehicle mission licenses. 431.3 Section 431.3 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.3 Types of reusable...

  16. Silylations of Arenes with Hydrosilanes: From Transition-Metal-Catalyzed C¢X Bond Cleavage to Environmentally Benign Transition-Metal-Free C¢H Bond Activation.

    PubMed

    Xu, Zheng; Xu, Li-Wen

    2015-07-01

    The construction of carbon-silicon bonds is highlighted as an exciting achievement in the field of organosilicon chemistry and green chemistry. Recent developments in this area will enable the sustainable chemical conversion of silicon resources into synthetically useful compounds. Especially, the catalytic silylation through C¢H bond activation without directing groups and hydrogen acceptors is one of the most challenging topics in organic chemistry and green chemistry. These remarkable findings on catalytic silylation can pave the way to a more environmentally benign utilization of earth-abundant silicon-based resources in synthetic chemistry. PMID:26073645

  17. Metal-free oxidation of aromatic carbon-hydrogen bonds through a reverse-rebound mechanism.

    PubMed

    Yuan, Changxia; Liang, Yong; Hernandez, Taylor; Berriochoa, Adrian; Houk, Kendall N; Siegel, Dionicio

    2013-07-11

    Methods for carbon-hydrogen (C-H) bond oxidation have a fundamental role in synthetic organic chemistry, providing functionality that is required in the final target molecule or facilitating subsequent chemical transformations. Several approaches to oxidizing aliphatic C-H bonds have been described, drastically simplifying the synthesis of complex molecules. However, the selective oxidation of aromatic C-H bonds under mild conditions, especially in the context of substituted arenes with diverse functional groups, remains a challenge. The direct hydroxylation of arenes was initially achieved through the use of strong Brønsted or Lewis acids to mediate electrophilic aromatic substitution reactions with super-stoichiometric equivalents of oxidants, significantly limiting the scope of the reaction. Because the products of these reactions are more reactive than the starting materials, over-oxidation is frequently a competitive process. Transition-metal-catalysed C-H oxidation of arenes with or without directing groups has been developed, improving on the acid-mediated process; however, precious metals are required. Here we demonstrate that phthaloyl peroxide functions as a selective oxidant for the transformation of arenes to phenols under mild conditions. Although the reaction proceeds through a radical mechanism, aromatic C-H bonds are selectively oxidized in preference to activated Csp3-H bonds. Notably, a wide array of functional groups are compatible with this reaction, and this method is therefore well suited for late-stage transformations of advanced synthetic intermediates. Quantum mechanical calculations indicate that this transformation proceeds through a novel addition-abstraction mechanism, a kind of 'reverse-rebound' mechanism as distinct from the common oxygen-rebound mechanism observed for metal-oxo oxidants. These calculations also identify the origins of the experimentally observed aryl selectivity.

  18. Transient structural distortion of metal-free Cu/Zn superoxide dismutase triggers aberrant oligomerization.

    PubMed

    Teilum, Kaare; Smith, Melanie H; Schulz, Eike; Christensen, Lea C; Solomentsev, Gleb; Oliveberg, Mikael; Akke, Mikael

    2009-10-27

    Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease linked to the misfolding of Cu/Zn superoxide dismutase (SOD1). ALS-related defects in SOD1 result in a gain of toxic function that coincides with aberrant oligomerization. The structural events triggering oligomerization have remained enigmatic, however, as is the case in other protein-misfolding diseases. Here, we target the critical conformational change that defines the earliest step toward aggregation. Using nuclear spin relaxation dispersion experiments, we identified a short-lived (0.4 ms) and weakly populated (0.7%) conformation of metal-depleted SOD1 that triggers aberrant oligomerization. This excited state emanates from the folded ground state and is suppressed by metal binding, but is present in both the disulfide-oxidized and disulfide-reduced forms of the protein. Our results pinpoint a perturbed region of the excited-state structure that forms intermolecular contacts in the earliest nonnative dimer/oligomer. The conformational transition that triggers oligomerization is a common feature of WT SOD1 and ALS-associated mutants that have widely different physicochemical properties. But compared with WT SOD1, the mutants have enhanced structural distortions in their excited states, and in some cases slightly higher excited-state populations and lower kinetic barriers, implying increased susceptibility to oligomerization. Our results provide a unified picture that highlights both (i) a common denominator among different SOD1 variants that may explain why diverse mutations cause the same disease, and (ii) a structural basis that may aid in understanding how different mutations affect disease propensity and progression.

  19. Assessment of the Feasibility of Innovative Reusable Launchers

    NASA Astrophysics Data System (ADS)

    Chiesa, S.; Corpino, S.; Viola, N.

    The demand for getting access to space, in particular to Low Earth Orbit, is increasing and fully reusable launch vehicles (RLVs) are likely to play a key role in the development of future space activities. Up until now this kind of space systems has not been successfully carried out: in fact today only the Space Shuttle, which belongs to the old generation of launchers, is operative and furthermore it is not a fully reusable system. In the nineties many studies regarding advanced transatmospheric planes were started, but no one was accomplished because of the technological problems encountered and the high financial resources required with the corresponding industrial risk. One of the most promising project was the Lockheed Venture Star, which seemed to have serious chances to be carried out. Anyway, if this ever happens, it will take quite a long time thus the operative life of Space Shuttle will have to be extended for the International Space Station support. The purpose of the present work is to assess the feasibility of different kinds of advanced reusable launch vehicles to gain access to space and to meet the requirements of today space flight needs, which are mainly safety and affordability. Single stage to orbit (SSTO), two stage to orbit (TSTO) and the so called "one and a half" stage to orbit vehicles are here taken into account to highlight their advantages and disadvantages. The "one and a half" stage to orbit vehicle takes off and climbs to meet a tanker aircraft to be aerially refuelled and then, after disconnecting from the tanker, it flies to reach the orbit. In this case, apart from the space vehicle, also the tanker aircraft needs a dedicated study to examine the problems related to the refuelling at high subsonic speeds and at a height near the tropopause. Only winged vehicles which take off and land horizontally are considered but different architectural layouts and propulsive configurations are hypothesised. Unlike the Venture Star, which

  20. Forming heterojunction: an effective strategy to enhance the photocatalytic efficiency of a new metal-free organic photocatalyst for water splitting.

    PubMed

    Li, Hengshuai; Hu, Haiquan; Bao, Chunjiang; Guo, Feng; Zhang, Xiaoming; Liu, Xiaobiao; Hua, Juan; Tan, Jie; Wang, Aizhu; Zhou, Hongcai; Yang, Bo; Qu, Yuanyuan; Liu, Xiangdong

    2016-07-29

    Photocatalytic water splitting is a new technology for the conversion and utilization of solar energy and has a potential prospect. One important aspect of enhancing the photocatalytic efficiency is how to improve the electron-hole separation. Up to now, there is still no ideal strategy to improve the electron-hole separation. In this article, for metal-free organic photocatalysts, we propose a good strategy- forming heterojunction, which can effectively improve the electron-hole separation. We provide a metal-free organic photocatalyst g-C12N7H3 for water splitting. The stability of g-C12N7H3 has been investigated, the X-ray diffraction spectra has been simulated. Using first-principles calculations, we have systematically studied the electronic structure, band edge alignment, and optical properties for the g-C12N7H3. The results demonstrated that g-C12N7H3 is a new organocatalyst material for water splitting. In order to enhance the photocatalytic efficiency, we provided four strategies, i.e., multilayer stacking, raising N atoms, forming g-C9N10/g-C12N7H3 heterojunction, and forming graphene/g-C12N7H3 heterojunction. Our research is expected to stimulate experimentalists to further study novel 2D metal-free organic materials as visible light photocatalysts. Our strategies, especially forming heterojunction, will substantially help to enhance the photocatalytic efficiency of metal-free organic photocatalyst.

  1. Forming heterojunction: an effective strategy to enhance the photocatalytic efficiency of a new metal-free organic photocatalyst for water splitting

    NASA Astrophysics Data System (ADS)

    Li, Hengshuai; Hu, Haiquan; Bao, Chunjiang; Guo, Feng; Zhang, Xiaoming; Liu, Xiaobiao; Hua, Juan; Tan, Jie; Wang, Aizhu; Zhou, Hongcai; Yang, Bo; Qu, Yuanyuan; Liu, Xiangdong

    2016-07-01

    Photocatalytic water splitting is a new technology for the conversion and utilization of solar energy and has a potential prospect. One important aspect of enhancing the photocatalytic efficiency is how to improve the electron-hole separation. Up to now, there is still no ideal strategy to improve the electron-hole separation. In this article, for metal-free organic photocatalysts, we propose a good strategy- forming heterojunction, which can effectively improve the electron-hole separation. We provide a metal-free organic photocatalyst g-C12N7H3 for water splitting. The stability of g-C12N7H3 has been investigated, the X-ray diffraction spectra has been simulated. Using first-principles calculations, we have systematically studied the electronic structure, band edge alignment, and optical properties for the g-C12N7H3. The results demonstrated that g-C12N7H3 is a new organocatalyst material for water splitting. In order to enhance the photocatalytic efficiency, we provided four strategies, i.e., multilayer stacking, raising N atoms, forming g-C9N10/g-C12N7H3 heterojunction, and forming graphene/g-C12N7H3 heterojunction. Our research is expected to stimulate experimentalists to further study novel 2D metal-free organic materials as visible light photocatalysts. Our strategies, especially forming heterojunction, will substantially help to enhance the photocatalytic efficiency of metal-free organic photocatalyst.

  2. The Ability of Dental Specialists to Distinguish Lateral Incisor Metal-Free From Porcelain-Fused-to-Metal Implant Supported Crowns.

    PubMed

    De Melo, Eduardo V; Kauling, Ana Elisa C; Freitas, Sérgio Fernando T; Cardoso, Antônio C; Ferreira, Cimara Fortes

    2014-12-01

    The objective of this study was to evaluate the ability of dental specialists to distinguish lateral incisor metal-free from porcelain-fused-to-metal implant supported crowns in the anterior region. Five single-tooth implants in the maxillary lateral incisor region were restored with two types of implant-supported crowns (porcelain-fused-to-metal and metal-free). Photographs were presented to 20 evaluators. The evaluators had to answer whether the crown was: metal-free, porcelain-fused-to-metal or they could not tell the difference. The results showed that groups 1 (all participants), 3 (Restorative & Prosthodontic specialists), 4 (graduated 10 years) and 5 (graduated > 10 years) failed to respond correctly (P > 0.05) to which type of crown was presented to them. Group 2 (Periodontology & Implantology specialists) showed an accuracy rate of 35.6% (P = 0.009), in relation to metal-free crowns, 5.6 which is below the random index. The authors concluded that the evaluators from the 5 groups studied were unable to significantly distinguish which type of crown was used in the 10 presented situations.

  3. One-pot synthesis of nitrogen and sulfur co-doped graphene as efficient metal-free electrocatalysts for the oxygen reduction reaction.

    PubMed

    Wang, Xin; Wang, Jie; Wang, Deli; Dou, Shuo; Ma, Zhaoling; Wu, Jianghong; Tao, Li; Shen, Anli; Ouyang, Canbin; Liu, Qiuhong; Wang, Shuangyin

    2014-05-14

    Novel N, S co-doped graphene (NSG) was prepared by annealing graphene oxide with thiourea as the single N and S precursor. The NSG electrodes, as efficient metal-free electrocatalysts, show a direct four-electron reaction pathway, high onset potential, high current density and high stability for the oxygen reduction reaction.

  4. Metal-free nitro-carbocyclization of activated alkenes: a direct approach to synthesize oxindoles by cascade C-N and C-C bond formation.

    PubMed

    Shen, Tao; Yuan, Yizhi; Jiao, Ning

    2014-01-18

    A novel and direct metal-free nitro-carbocyclization of activated alkenes leading to valuable nitro-containing oxindoles via cascade C-N and C-C bond formation has been developed. The mechanistic study indicates that the initial NO and NO2 radical addition and the following C-H functionalization processes are involved in this transformation.

  5. Direct oxidative coupling of amidine hydrochlorides and methylarenes: TBHP-mediated synthesis of substituted 1,3,5-triazines under metal-free conditions.

    PubMed

    Guo, Wei

    2015-11-01

    Various 2,4,6-trisubstituted 1,3,5-triazines were smoothly formed via TBHP-mediated direct oxidative coupling of amidine and methylarenes. This tandem oxidation-imination-cyclization transformation exhibits a straightforward protocol to prepare 1,3,5-triazines from easily available starting materials and green oxidants under metal-free conditions.

  6. IBX mediated reaction of β-enamino esters with allylic alcohols: a one pot metal free domino approach to functionalized pyridines.

    PubMed

    Gade, Narendar Reddy; Devendram, V; Pal, Manojit; Iqbal, Javed

    2013-09-18

    IBX facilitated the reaction of β-enamino esters with allylic alcohols affording a direct, one-pot and metal free synthesis of functionalized pyridines including 2-substituted nicotinic acids, densely substituted pyridines and precursors of azafluorenones. The methodology also afforded the racemic pyridine core of cyclothiazomycin.

  7. Metal-free oxidative radical addition of carbonyl compounds to α,α-diaryl allylic alcohols: synthesis of highly functionalized ketones.

    PubMed

    Chu, Xue-Qiang; Meng, Hua; Zi, You; Xu, Xiao-Ping; Ji, Shun-Jun

    2014-12-15

    A metal-free direct alkylation of simple carbonyl compounds (ketones, esters, and amides) with α,α-diaryl allylic alcohols is described. The protocol provides facile access to highly functionalized dicarbonyl ketones by a radical addition/1,2-aryl migration cascade. The regioselectivity of the reaction was precisely controlled by the nature of the carbonyl compound.

  8. The Ability of Dental Specialists to Distinguish Lateral Incisor Metal-Free From Porcelain-Fused-to-Metal Implant Supported Crowns.

    PubMed

    De Melo, Eduardo V; Kauling, Ana Elisa C; Freitas, Sérgio Fernando T; Cardoso, Antônio C; Ferreira, Cimara Fortes

    2014-12-01

    The objective of this study was to evaluate the ability of dental specialists to distinguish lateral incisor metal-free from porcelain-fused-to-metal implant supported crowns in the anterior region. Five single-tooth implants in the maxillary lateral incisor region were restored with two types of implant-supported crowns (porcelain-fused-to-metal and metal-free). Photographs were presented to 20 evaluators. The evaluators had to answer whether the crown was: metal-free, porcelain-fused-to-metal or they could not tell the difference. The results showed that groups 1 (all participants), 3 (Restorative & Prosthodontic specialists), 4 (graduated 10 years) and 5 (graduated > 10 years) failed to respond correctly (P > 0.05) to which type of crown was presented to them. Group 2 (Periodontology & Implantology specialists) showed an accuracy rate of 35.6% (P = 0.009), in relation to metal-free crowns, 5.6 which is below the random index. The authors concluded that the evaluators from the 5 groups studied were unable to significantly distinguish which type of crown was used in the 10 presented situations. PMID:26466439

  9. Metal-Free Arylation of Ethyl Acetoacetate with Hypervalent Diaryliodonium Salts: an Immediate Access to Diverse 3-Aryl-4(1H)-Quinolones

    PubMed Central

    Manetsch, Roman

    2015-01-01

    A clean arylation protocol of ethyl acetoacetate was developed using hypervalent diaryliodonium salts under mild and metal-free conditions. The scope of the reaction, using symmetric and unsymmetric iodonium salts with varying sterics and electronics was examined. Further, this method has been applied for the synthesis of antimalarial compound ELQ-300, which is currently in preclinical development. PMID:25558982

  10. Efficient generation of perfluoroalkyl radicals from sodium perfluoroalkanesulfinates and a hypervalent iodine(iii) reagent: mild, metal-free synthesis of perfluoroalkylated organic molecules.

    PubMed

    Sakamoto, Ryu; Kashiwagi, Hirotaka; Selvakumar, Sermadurai; Moteki, Shin A; Maruoka, Keiji

    2016-07-01

    This article describes an efficient method for the introduction of perfluoroalkyl groups into N-acrylamides, 2-isocyanides, olefins, and other heterocycles using perfluoroalkyl radicals that were generated from the reaction between sodium perfluoroalkanesulfinates and a hypervalent iodine(iii) reagent. This approach represents a simple, scalable perfluoroalkylation method under mild and metal-free conditions.

  11. Synthesis, structures, and properties of crystalline salts with radical anions of metal-containing and metal-free phthalocyanines.

    PubMed

    Konarev, Dmitri V; Kuzmin, Alexey V; Faraonov, Maxim A; Ishikawa, Manabu; Khasanov, Salavat S; Nakano, Yoshiaki; Otsuka, Akihiro; Yamochi, Hideki; Saito, Gunzi; Lyubovskaya, Rimma N

    2015-01-12

    Radical anion salts of metal-containing and metal-free phthalocyanines [MPc(3-)](·-), where M = Cu(II), Ni(II), H2, Sn(II), Pb(II), Ti(IV)O, and V(IV)O (1-10) with tetraalkylammonium cations have been obtained as single crystals by phthalocyanine reduction with sodium fluorenone ketyl. Their formation is accompanied by the Pc ligand reduction and affects the molecular structure of metal phthalocyanine radical anions as well as their optical and magnetic properties. Radical anions are characterized by the alternation of short and long C-Nimine bonds in the Pc ligand owing to the disruption of its aromaticity. Salts 1-10 show new bands at 833-1041 nm in the NIR range, whereas the Q- and Soret bands are blue-shifted by 0.13-0.25 eV (38-92 nm) and 0.04-0.07 eV (4-13 nm), respectively. Radical anions with Ni(II), Sn(II), Pb(II), and Ti(IV)O have S = 1/2 spin state, whereas [Cu(II)Pc(3-)](·-) and [V(IV)OPc(3-)](·-) containing paramagnetic Cu(II) and V(IV)O have two S = 1/2 spins per radical anion. Central metal atoms strongly affect EPR spectra of phthalocyanine radical anions. Instead of narrow EPR signals characteristic of metal-free phthalocyanine radical anions [H2Pc(3-)](·-) (linewidth of 0.08-0.24 mT), broad EPR signals are manifested (linewidth of 2-70 mT) with g-factors and linewidths that are strongly temperature-dependent. Salt 11 containing the [Na(I)Pc(2-)](-) anions as well as previously studied [Fe(I)Pc(2-)](-) and [Co(I)Pc(2-)](-) anions that are formed without reduction of the Pc ligand do not show changes in molecular structure or optical and magnetic properties characteristic of [MPc(3-)](·-) in 1-10.

  12. Synthesis, structures, and properties of crystalline salts with radical anions of metal-containing and metal-free phthalocyanines.

    PubMed

    Konarev, Dmitri V; Kuzmin, Alexey V; Faraonov, Maxim A; Ishikawa, Manabu; Khasanov, Salavat S; Nakano, Yoshiaki; Otsuka, Akihiro; Yamochi, Hideki; Saito, Gunzi; Lyubovskaya, Rimma N

    2015-01-12

    Radical anion salts of metal-containing and metal-free phthalocyanines [MPc(3-)](·-), where M = Cu(II), Ni(II), H2, Sn(II), Pb(II), Ti(IV)O, and V(IV)O (1-10) with tetraalkylammonium cations have been obtained as single crystals by phthalocyanine reduction with sodium fluorenone ketyl. Their formation is accompanied by the Pc ligand reduction and affects the molecular structure of metal phthalocyanine radical anions as well as their optical and magnetic properties. Radical anions are characterized by the alternation of short and long C-Nimine bonds in the Pc ligand owing to the disruption of its aromaticity. Salts 1-10 show new bands at 833-1041 nm in the NIR range, whereas the Q- and Soret bands are blue-shifted by 0.13-0.25 eV (38-92 nm) and 0.04-0.07 eV (4-13 nm), respectively. Radical anions with Ni(II), Sn(II), Pb(II), and Ti(IV)O have S = 1/2 spin state, whereas [Cu(II)Pc(3-)](·-) and [V(IV)OPc(3-)](·-) containing paramagnetic Cu(II) and V(IV)O have two S = 1/2 spins per radical anion. Central metal atoms strongly affect EPR spectra of phthalocyanine radical anions. Instead of narrow EPR signals characteristic of metal-free phthalocyanine radical anions [H2Pc(3-)](·-) (linewidth of 0.08-0.24 mT), broad EPR signals are manifested (linewidth of 2-70 mT) with g-factors and linewidths that are strongly temperature-dependent. Salt 11 containing the [Na(I)Pc(2-)](-) anions as well as previously studied [Fe(I)Pc(2-)](-) and [Co(I)Pc(2-)](-) anions that are formed without reduction of the Pc ligand do not show changes in molecular structure or optical and magnetic properties characteristic of [MPc(3-)](·-) in 1-10. PMID:25388432

  13. Structures and materials technology issues for reusable launch vehicles

    NASA Technical Reports Server (NTRS)

    Dixon, S. C.; Tenney, D. R.; Rummler, D. R.; Wieting, A. R.; Bader, R. M.

    1985-01-01

    Projected space missions for both civil and defense needs require significant improvements in structures and materials technology for reusable launch vehicles: reductions in structural weight compared to the Space Shuttle Orbiter of up to 25% or more, a possible factor of 5 or more increase in mission life, increases in maximum use temperature of the external surface, reusable containment of cryogenic hydrogen and oxygen, significant reductions in operational costs, and possibly less lead time between technology readiness and initial operational capability. In addition, there is increasing interest in hypersonic airbreathing propulsion for launch and transmospheric vehicles, and such systems require regeneratively cooled structure. The technology issues are addressed, giving brief assessments of the state-of-the-art and proposed activities to meet the technology requirements in a timely manner.

  14. Towards automated support for extraction of reusable components

    NASA Technical Reports Server (NTRS)

    Abd-El-hafiz, S. K.; Basili, Victor R.; Caldiera, Gianluigi

    1992-01-01

    A cost effective introduction of software reuse techniques requires the reuse of existing software developed in many cases without aiming at reusability. This paper discusses the problems related to the analysis and reengineering of existing software in order to reuse it. We introduce a process model for component extraction and focus on the problem of analyzing and qualifying software components which are candidates for reuse. A prototype tool for supporting the extraction of reusable components is presented. One of the components of this tool aids in understanding programs and is based on the functional model of correctness. It can assist software engineers in the process of finding correct formal specifications for programs. A detailed description of this component and an example to demonstrate a possible operational scenario are given.

  15. Towards automated support for extraction of reusable components

    NASA Technical Reports Server (NTRS)

    Abd-El-hafiz, S. K.; Basili, V. R.; Caldier, G.

    1991-01-01

    A cost effective introduction of software reuse techniques requires the reuse of existing software developed in many cases without aiming at reusability. This paper discusses the problems related to the analysis and reengineering of existing software in order to reuse it. We introduce a process model for component extraction and focus on the problem of analyzing and qualifying software components which are candidates for reuse. A prototype tool for supporting the extraction of reusable components is presented. One of the components of this tool aids in understanding programs and is based on the functional model of correctness. It can assist software engineers in the process of finding correct formal specifications for programs. A detailed description of this component and an example to demonstrate a possible operational scenario are given.

  16. Reusable solid rocket motor case - Optimum probabilistic fracture control

    NASA Technical Reports Server (NTRS)

    Hanagud, S.; Uppaluri, B.

    1979-01-01

    A methodology for the reliability analysis of a reusable solid rocket motor case is discussed in this paper. The analysis is based on probabilistic fracture mechanics and probability distribution for initial flaw sizes. The developed reliability analysis can be used to select the structural design variables of the solid rocket motor case on the basis of minimum expected cost and specified reliability bounds during the projected design life of the case. Effects on failure prevention plans such as nondestructive inspection and the material erosion between missions can also be considered in the developed procedure for selection of design variables. The reliability-based procedure that has been discussed in this paper can easily be modified to consider other similar structures of reusable space vehicle systems with different fracture control plans.

  17. NASA's Reusable Launch Vehicle Technologies: A Composite Materials Overview

    NASA Technical Reports Server (NTRS)

    Clinton, R. G., Jr.; Cook, Steve; Effinger, Mike; Smith, Dennis; Swint, Shayne

    1999-01-01

    A materials overview of the NASA's Earth-to-Orbit Space Transportation Program is presented. The topics discussed are: Earth-to-Orbit Goals and Challenges; Space Transportation Program Structure; Generations of Reusable Launch Vehicles; Space Transportation Derived Requirements; X 34 Demonstrator; Fastrac Engine System; Airframe Systems; Propulsion Systems; Cryotank Structures; Advanced Materials, Fabrication, Manufacturing, & Assembly; Hot and Cooled Airframe Structures; Ceramic Matrix Composites; Ultra-High Temp Polymer Matrix Composites; Metal Matrix Composites; and PMC Lines Ducts and Valves.

  18. A reusable, low-profile, cryogenic wire seal

    NASA Astrophysics Data System (ADS)

    Stewart, M. D., Jr.; Koutroulakis, G.; Kalechofsky, N.; Mitrović, V. F.

    2010-01-01

    We describe the design of a reusable indium wire seal which has a small profile and is leak tight to better than 1×10-10 std. cc/s from room temperature down to ≈ 50mK. The pressure necessary to deform the indium wire o-ring is provided by a screw-cap mating to threads on the outside of the cylindrical volume to be sealed.

  19. Analyses of Noise from Reusable Solid Rocket Motor (RSRM) Firings

    NASA Technical Reports Server (NTRS)

    Gee, Kent L.; Kenny, R. Jeremy; Jerome, Trevor W.; Neilsen, Tracianne B.; Hobbs, Christopher M.; James, Michael M.

    2012-01-01

    NASA s Space Launch Vehicle (SLS) program has chosen the Reusable Solid Rocket Motor V (RSRMV) as the booster system for initial flights. Lift off acoustics continue to be a consideration in overall vehicle vibroacoustic evaluations and launch pad modifications. Work started with the Ares program to understand solid rocket noise mechanisms is continuing through SLS program in conjunction with BYU/Blue Ridge Research Consulting.

  20. Self-unloading, unmanned, reusable lunar lander project

    NASA Technical Reports Server (NTRS)

    Cowan, Kevin; Lewis, Ron; Mislinski, Philip; Rivers, Donna; Smith, Solar; Vasicek, Clifford; Verona, Matt

    1991-01-01

    A payload delivery system will be required to support the buildup and operation of a manned lunar base. In response, a self-unloading, unmanned, reusable lunar lander was conceptually designed. The lander will deliver a 7000 kg payload, with the same dimensions as a space station logistics module, from low lunar orbit to any location on the surface of the moon. The technical aspects of the design is introduced as well as the management structure and project cost.

  1. Future reusable space launcher systems - A European view

    NASA Astrophysics Data System (ADS)

    Reichert, Rudi G.

    Plans for future, reusable space launcher systems in Europe, beyond Ariane V/Hermes, are discussed. A family of launch vehicles, known as the European Advanced Rocket Launchers (EARLs), is presented. Technical and performance data for the EARL concept are given and the cost of development and operating the launchers is estimated. Also, the EARL concept is compared with other planned and existing concepts, including the Saenger launcher.

  2. X-33 Reusable Launch Vehicle Demonstrator, Spaceport and Range

    NASA Technical Reports Server (NTRS)

    Letchworth, Gary F.

    2011-01-01

    The X-33 was a suborbital reusable spaceplane demonstrator, in development from 1996 to early 2001. The intent of the demonstrator was to lower the risk of building and operating a full-scale reusable vehicle fleet. Reusable spaceplanes offered the potential to lower the cost of access to space by an order of magnitude, compared with conventional expendable launch vehicles. Although a cryogenic tank failure during testing ultimately led to the end of the effort, the X-33 team celebrated many successes during the development. This paper summarizes some of the accomplishments and milestones of this X-vehicle program, from the perspective of an engineer who was a member of the team throughout the development. X-33 Program accomplishments include rapid, flight hardware design, subsystem testing and fabrication, aerospike engine development and testing, Flight Operations Center and Operations Control Center ground systems design and construction, rapid Environmental Impact Statement NEPA process approval, Range development and flight plan approval for test flights, and full-scale system concept design and refinement. Lessons from the X-33 Program may have potential application to new RLV and other aerospace systems being developed a decade later.

  3. Operations Analysis of the 2nd Generation Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    Noneman, Steven R.; Smith, C. A. (Technical Monitor)

    2002-01-01

    The Space Launch Initiative (SLI) program is developing a second-generation reusable launch vehicle. The program goals include lowering the risk of loss of crew to 1 in 10,000 and reducing annual operations cost to one third of the cost of the Space Shuttle. The SLI missions include NASA, military and commercial satellite launches and crew and cargo launches to the space station. The SLI operations analyses provide an assessment of the operational support and infrastructure needed to operate candidate system architectures. Measures of the operability are estimated (i.e. system dependability, responsiveness, and efficiency). Operations analysis is used to determine the impact of specific technologies on operations. A conceptual path to reducing annual operations costs by two thirds is based on key design characteristics, such as reusability, and improved processes lowering labor costs. New operations risks can be expected to emerge. They can be mitigated with effective risk management with careful identification, assignment, tracking, and closure. SLI design characteristics such as nearly full reusability, high reliability, advanced automation, and lowered maintenance and servicing coupled with improved processes are contributors to operability and large operating cost reductions.

  4. Metal-free aqueous redox capacitor via proton rocking-chair system in an organic-based couple

    PubMed Central

    Tomai, Takaaki; Mitani, Satoshi; Komatsu, Daiki; Kawaguchi, Yuji; Honma, Itaru

    2014-01-01

    Safe and inexpensive energy storage devices with long cycle lifetimes and high power and energy densities are mandatory for the development of electrical power grids that connect with renewable energy sources. In this study, we demonstrated metal-free aqueous redox capacitors using couples comprising low-molecular-weight organic compounds. In addition to the electric double layer formation, proton insertion/extraction reactions between a couple consisting of inexpensive quinones/hydroquinones contributed to the energy storage. This energy storage mechanism, in which protons are shuttled back and forth between two electrodes upon charge and discharge, can be regarded as a proton rocking-chair system. The fabricated capacitor showed a large capacity (>20 Wh/kg), even in the applied potential range between 0–1 V, and high power capability (>5 A/g). The support of the organic compounds in nanoporous carbon facilitated the efficient use of the organic compounds with a lifetime of thousands of cycles. PMID:24395117

  5. A Bio-Inspired, Heavy-Metal-Free, Dual-Electrolyte Liquid Battery towards Sustainable Energy Storage.

    PubMed

    Ding, Yu; Yu, Guihua

    2016-04-01

    Wide-scale exploitation of renewable energy requires low-cost efficient energy storage devices. The use of metal-free, inexpensive redox-active organic materials represents a promising direction for environmental-friendly, cost-effective sustainable energy storage. To this end, a liquid battery is designed using hydroquinone (H2BQ) aqueous solution as catholyte and graphite in aprotic electrolyte as anode. The working potential can reach 3.4 V, with specific capacity of 395 mA h g(-1) and stable capacity retention about 99.7% per cycle. Such high potential and capacity is achieved using only C, H and O atoms as building blocks for redox species, and the replacement of Li metal with graphite anode can circumvent potential safety issues. As H2BQ can be extracted from biomass directly and its redox reaction mimics the bio-electrochemical process of quinones in nature, using such a bio-inspired organic compound in batteries enables access to greener and more sustainable energy-storage technology.

  6. Modeling the interactions of phthalocyanines in water: from the Cu(II)-tetrasulphonate to the metal-free phthalocyanine.

    PubMed

    Martín, Elisa I; Martínez, Jose M; Sánchez Marcos, Enrique

    2011-01-14

    A quantum and statistical study on the effects of the ions Cu(2+) and SO(3)(-) in the solvent structure around the metal-free phthalocyanine (H(2)Pc) is presented. We developed an ab initio interaction potential for the system CuPc-H(2)O based on quantum chemical calculations and studied its transferability to the H(2)Pc-H(2)O and [CuPc(SO(3))(4)](4-)-H(2)O interactions. The use of the molecular dynamics technique allows the determination of energetic and structural properties of CuPc, H(2)Pc, and [CuPc(SO(3))(4)](4-) in water and the understanding of the keys for the different behaviors of the three phthalocyanine (Pc) derivatives in water. The inclusion of the Cu(2+) cation in the Pc structure reinforces the appearance of two axial water molecules and second-shell water molecules in the solvent structure, whereas the presence of SO(3)(-) anions implies a well defined hydration shell of about eight water molecules around them making the macrocycle soluble in water. Debye-Waller factors for axial water molecules have been obtained in order to examine the potential sensitivity of the extended x-ray absorption fine structure technique to detect the axial water molecules.

  7. Metal-free organic dyes for TiO2 and ZnO dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Selopal, Gurpreet Singh; Wu, Hui-Ping; Lu, Jianfeng; Chang, Yu-Cheng; Wang, Mingkui; Vomiero, Alberto; Concina, Isabella; Diau, Eric Wei-Guang

    2016-01-01

    We report the synthesis and characterization of new metal-free organic dyes (namely B18, BTD-R, and CPTD-R) which designed with D-π-A concept to extending the light absorption region by strong conjugation group of π-linker part and applied as light harvester in dye sensitized solar cells (DSSCs). We compared the photovoltaic performance of these dyes in two different photoanodes: a standard TiO2 mesoporous photoanode and a ZnO photoanode composed of hierarchically assembled nanostructures. The results demonstrated that B18 dye has better photovoltaic properties compared to other two dyes (BTD-R and CPTD-R) and each dye has higher current density (Jsc) when applied to hierarchical ZnO nanocrystallites than the standard TiO2 mesoporous film. Transient photocurrent and photovoltage decay measurements (TCD/TVD) were applied to systematically study the charge transport and recombination kinetics in these devices, showing the electron life time (τR) of B18 dye in ZnO and TiO2 based DSSCs is higher than CPTD-R and BTD-R based DSSCs, which is consistent with the photovoltaic performances. The conversion efficiency in ZnO based DSSCs can be further boosted by 35%, when a compact ZnO blocking layer (BL) is applied to inhibit electron back reaction.

  8. Modeling the interactions of phthalocyanines in water: From the Cu(II)-tetrasulphonate to the metal-free phthalocyanine

    NASA Astrophysics Data System (ADS)

    Martín, Elisa I.; Martínez, Jose M.; Marcos, Enrique Sánchez

    2011-01-01

    A quantum and statistical study on the effects of the ions Cu^{2+} and SO3- in the solvent structure around the metal-free phthalocyanine (H2Pc) is presented. We developed an ab initio interaction potential for the system CuPc-H2O based on quantum chemical calculations and studied its transferability to the H2Pc-H2O and [CuPc(SO3)4]^{4-}-H2O interactions. The use of the molecular dynamics technique allows the determination of energetic and structural properties of CuPc, H2Pc, and [CuPc(SO3)4]^{4-} in water and the understanding of the keys for the different behaviors of the three phthalocyanine (Pc) derivatives in water. The inclusion of the Cu^{2+} cation in the Pc structure reinforces the appearance of two axial water molecules and second-shell water molecules in the solvent structure, whereas the presence of SO3{}^- anions implies a well defined hydration shell of about eight water molecules around them making the macrocycle soluble in water. Debye-Waller factors for axial water molecules have been obtained in order to examine the potential sensitivity of the extended x-ray absorption fine structure technique to detect the axial water molecules.

  9. Metal-free phthalocyanine aggregation and binding with amines: Specific and general solvent effects on absorption and fluorescence properties

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Zhang, Xian-Fu; Lu, Xulin

    2015-03-01

    The fluorescence and absorption properties of a metal-free phthalocyanine (Pc) H2PcR4 and its zinc-centered complex ZnPcR4 (R is the isopropyloxy at the β-position of a Pc ring) were measured and compared in protic and aprotic solvents. H2PcR4 shows strong bonding interaction with amines and aggregation in alcohols in addition to the general solvent effect in aprotic solvents due to polarity change. The specific solvent effect leads to substantial changes in its spectra, fluorescence quantum yield (Φf) and fluorescence lifetime (τf) values. In contrast, ZnPcR4 does not show the specific effects due to the presence of a central element in a Pc cavity. For H2PcR4 the change of solvents caused a large variation of Φf (0.050-0.48) and τf (3.45-6.88 ns), in contrast to the slight changes for ZnPcR4. On the other hand, the general solvent effect of H2PcR4 due to polarity is also more significant than that of ZnPcR4. The increase of solvent polarity decreases both Φf and τf, but increases the Stoke's shift.

  10. Facile synthesis of nitrogen and sulfur codoped carbon from ionic liquid as metal-free catalyst for oxygen reduction reaction.

    PubMed

    She, Yiyi; Lu, Zhouguang; Ni, Meng; Li, Li; Leung, Michael K H

    2015-04-01

    Developing metal-free catalysts for oxygen reduction reaction (ORR) is a great challenge in the development of fuel cells. Nitrogen and sulfur codoped carbon with remarkably high nitrogen content up to 13.00 at % was successfully fabricated by pyrolysis of homogeneous mixture of exfoliated graphitic flakes and ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bimi][Tf2N]). The exfoliated graphite flakes served as a structure-directing substance as well as additional carbon source in the fabrication. It was demonstrated that the use of graphite flakes increased the nitrogen doping level, optimized the composition of active nitrogen configurations, and enlarged the specific surface area of the catalysts. Electrochemical characterizations revealed that the N and S codoped carbon fabricated by this method exhibited superior catalytic activities toward ORR under both acidic and alkaline conditions. Particularly in alkaline solution, the current catalyst compared favorably to the conventional 20 wt % Pt/C catalyst via four-electron transfer pathway with better ORR selectivity. The excellent catalytic activity was mainly ascribed to high nitrogen doping content, appropriate constitution of active nitrogen configurations, large specific surface area, and synergistic effect of N and S codoping. PMID:25781628

  11. Metal-free organic dyes for TiO2 and ZnO dye-sensitized solar cells

    PubMed Central

    Selopal, Gurpreet Singh; Wu, Hui-Ping; Lu, Jianfeng; Chang, Yu-Cheng; Wang, Mingkui; Vomiero, Alberto; Concina, Isabella; Diau, Eric Wei-Guang

    2016-01-01

    We report the synthesis and characterization of new metal-free organic dyes (namely B18, BTD-R, and CPTD-R) which designed with D-π-A concept to extending the light absorption region by strong conjugation group of π-linker part and applied as light harvester in dye sensitized solar cells (DSSCs). We compared the photovoltaic performance of these dyes in two different photoanodes: a standard TiO2 mesoporous photoanode and a ZnO photoanode composed of hierarchically assembled nanostructures. The results demonstrated that B18 dye has better photovoltaic properties compared to other two dyes (BTD-R and CPTD-R) and each dye has higher current density (Jsc) when applied to hierarchical ZnO nanocrystallites than the standard TiO2 mesoporous film. Transient photocurrent and photovoltage decay measurements (TCD/TVD) were applied to systematically study the charge transport and recombination kinetics in these devices, showing the electron life time (τR) of B18 dye in ZnO and TiO2 based DSSCs is higher than CPTD-R and BTD-R based DSSCs, which is consistent with the photovoltaic performances. The conversion efficiency in ZnO based DSSCs can be further boosted by 35%, when a compact ZnO blocking layer (BL) is applied to inhibit electron back reaction. PMID:26738698

  12. Magnesiothermic synthesis of sulfur-doped graphene as an efficient metal-free electrocatalyst for oxygen reduction

    PubMed Central

    Wang, Jiacheng; Ma, Ruguang; Zhou, Zhenzhen; Liu, Guanghui; Liu, Qian

    2015-01-01

    Efficient metal-free electrocatalysts for oxygen reduction reaction (ORR) are highly expected in future low-cost energy systems. We have successfully prepared crumpled, sheet-like, sulfur-doped graphene by magnesiothermic reduction of easily available, low-cost, nontoxic CO2 (in the form of Na2CO3) and Na2SO4 as the carbon and sulfur sources, respectively. At high temperature, Mg can reduce not only carbon in the oxidation state of +4 in CO32− to form graphene, but also sulfur in SO42− from its highest (+6) to lowest valence which was hybridized into the carbon sp2 framework. Various characterization results show that sulfur-doped graphene with only few layers has an appropriate sulfur content, hierarchically robust porous structure, large surface area/pore volume, and highly graphitized textures. The S-doped graphene samples exhibit not only a high activity for ORR with a four-electron pathway, but also superior durability and tolerance to MeOH crossover to 40% Pt/C. This is mainly ascribed to the combination of sulfur-related active sites and hierarchical porous textures, facilitating fast diffusion of oxygen molecules and electrolyte to catalytic sites and release of products from the sites. PMID:25790856

  13. Magnesiothermic synthesis of sulfur-doped graphene as an efficient metal-free electrocatalyst for oxygen reduction

    NASA Astrophysics Data System (ADS)

    Wang, Jiacheng; Ma, Ruguang; Zhou, Zhenzhen; Liu, Guanghui; Liu, Qian

    2015-03-01

    Efficient metal-free electrocatalysts for oxygen reduction reaction (ORR) are highly expected in future low-cost energy systems. We have successfully prepared crumpled, sheet-like, sulfur-doped graphene by magnesiothermic reduction of easily available, low-cost, nontoxic CO2 (in the form of Na2CO3) and Na2SO4 as the carbon and sulfur sources, respectively. At high temperature, Mg can reduce not only carbon in the oxidation state of +4 in CO32- to form graphene, but also sulfur in SO42- from its highest (+6) to lowest valence which was hybridized into the carbon sp2 framework. Various characterization results show that sulfur-doped graphene with only few layers has an appropriate sulfur content, hierarchically robust porous structure, large surface area/pore volume, and highly graphitized textures. The S-doped graphene samples exhibit not only a high activity for ORR with a four-electron pathway, but also superior durability and tolerance to MeOH crossover to 40% Pt/C. This is mainly ascribed to the combination of sulfur-related active sites and hierarchical porous textures, facilitating fast diffusion of oxygen molecules and electrolyte to catalytic sites and release of products from the sites.

  14. Facile preparation of nitrogen-doped graphene as a metal-free catalyst for oxygen reduction reaction.

    PubMed

    Lin, Ziyin; Song, Min-kyu; Ding, Yong; Liu, Yan; Liu, Meilin; Wong, Ching-ping

    2012-03-14

    Nitrogen-doped graphene (nG) is a promising metal-free catalyst for oxygen reduction reaction (ORR) on the cathode of fuel cells. Here we report a facile preparation of nG via pyrolysis of graphene oxide with melamine. The morphology of the nG is revealed using scanning electron microscopy and transmission electron microscopy while the successful N doping is confirmed by electron energy loss spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The resulting nG shows high electrocatalytic activity toward ORR in an alkaline solution with an onset potential of -0.10 V vs. Ag/AgCl reference electrode. The nG catalyzed oxygen reduction exhibits a favorable formation of water via a four-electron pathway. Good stability and anti-crossover property are also observed, which are advantageous over the Pt/C catalyst. Furthermore, the effect of pyrolysis temperature on the structure and activity of nG is systematically studied to gain some insights into the chemical reactions during pyrolysis. PMID:22307527

  15. Self-Supported Cu-Based Nanowire Arrays as Noble-Metal-Free Electrocatalysts for Oxygen Evolution.

    PubMed

    Hou, Chun-Chao; Fu, Wen-Fu; Chen, Yong

    2016-08-23

    Crystalline Cu-based nanowire arrays (NWAs) including Cu(OH)2 , CuO, Cu2 O, and CuOx are facilely grown on Cu foil and are found to act as highly efficient, low-cost, and robust electrocatalysts for the oxygen evolution reaction (OER). Impressively, this noble-metal-free 3 D Cu(OH)2 -NWAs/Cu foil electrode shows the highest catalytic activity with a Tafel slope of 86 mV dec(-1) , an overpotential (η) of about 530 mV at ∼10 mA cm(-2) (controlled-potential electrolysis method without iR correction) and almost 100 % Faradic efficiency, paralleling the performance of the state-of-the-art RuO2 OER catalyst in 0.1 m NaOH solution (pH 12.8). To the best of our knowledge, this work represents one of the best results ever reported on Cu-based OER systems. PMID:27440473

  16. Metal-Free sp(2)-C-H Borylation as a Common Reactivity Pattern of Frustrated 2-Aminophenylboranes.

    PubMed

    Chernichenko, Konstantin; Lindqvist, Markus; Kótai, Bianka; Nieger, Martin; Sorochkina, Kristina; Pápai, Imre; Repo, Timo

    2016-04-13

    C-H borylation is a powerful and atom-efficient method for converting affordable and abundant chemicals into versatile organic reagents used in the production of fine chemicals and functional materials. Herein we report a facile C-H borylation of aromatic and olefinic C-H bonds with 2-aminophenylboranes. Computational and experimental studies reveal that the metal-free C-H insertion proceeds via a frustrated Lewis pair mechanism involving heterolytic splitting of the C-H bond by cooperative action of the amine and boryl groups. The adapted geometry of the reactive B and N centers results in an unprecedentently low kinetic barrier for both insertion into the sp(2)-C-H bond and intramolecular protonation of the sp(2)-C-B bond in 2-ammoniophenyl(aryl)- or -(alkenyl)borates. This common reactivity pattern serves as a platform for various catalytic reactions such as C-H borylation and hydrogenation of alkynes. In particular, we demonstrate that simple 2-aminopyridinium salts efficiently catalyze the C-H borylation of hetarenes with catecholborane. This reaction is presumably mediated by a borenium species isoelectronic to 2-aminophenylboranes.

  17. Biomass-derived nitrogen self-doped porous carbon as effective metal-free catalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Liu, Xiaojun; Zhou, Yucheng; Zhou, Weijia; Li, Ligui; Huang, Shaobin; Chen, Shaowei

    2015-03-01

    Biomass-derived nitrogen self-doped porous carbon was synthesized by a facile procedure based on simple pyrolysis of water hyacinth (eichhornia crassipes) at controlled temperatures (600-800 °C) with ZnCl2 as an activation reagent. The obtained porous carbon exhibited a BET surface area up to 950.6 m2 g-1, and various forms of nitrogen (pyridinic, pyrrolic and graphitic) were found to be incorporated into the carbon molecular skeleton. Electrochemical measurements showed that the nitrogen self-doped carbons possessed a high electrocatalytic activity for ORR in alkaline media that was highly comparable to that of commercial 20% Pt/C catalysts. Experimentally, the best performance was identified with the sample prepared at 700 °C, with the onset potential at ca. +0.98 V vs. RHE, that possessed the highest concentrations of pyridinic and graphitic nitrogens among the series. Moreover, the porous carbon catalysts showed excellent long-term stability and much enhanced methanol tolerance, as compared to commercial Pt/C. The performance was also markedly better than or at least comparable to the leading results in the literature based on biomass-derived carbon catalysts for ORR. The results suggested a promising route based on economical and sustainable biomass towards the development and engineering of value-added carbon materials as effective metal-free cathode catalysts for alkaline fuel cells.Biomass-derived nitrogen self-doped porous carbon was synthesized by a facile procedure based on simple pyrolysis of water hyacinth (eichhornia crassipes) at controlled temperatures (600-800 °C) with ZnCl2 as an activation reagent. The obtained porous carbon exhibited a BET surface area up to 950.6 m2 g-1, and various forms of nitrogen (pyridinic, pyrrolic and graphitic) were found to be incorporated into the carbon molecular skeleton. Electrochemical measurements showed that the nitrogen self-doped carbons possessed a high electrocatalytic activity for ORR in alkaline media

  18. Metal-free, polyether-mediated H2-release from ammonia borane: roles of hydrogen bonding interactions in promoting dehydrogenation.

    PubMed

    Kim, Yongmin; Baek, Hyunjae; Lee, Jin Hee; Yeo, Shinyoung; Kim, Kibum; Hwang, Son-Jong; Eun, Bit; Nam, Suk Woo; Lim, Tae-Hoon; Yoon, Chang Won

    2013-12-01

    Polyetheral additives were found to be efficient promoters to enhance the rate of H2-release from ammonia borane (AB) at various temperatures. In particular, tetraethylene glycol dimethyl ether (T4EGDE, 29 wt% relative to AB + T4EGDE) exhibited significantly improved activities for AB dehydrogenation, with the material-based hydrogen storage capacity of 10.3 wt% at 125 °C within 40 min. In situ FT-IR spectroscopy indicated the formation of B-(cyclodiborazanyl)amino-borohydride (BCDB), borazine, and μ-aminodiborane as gaseous byproducts. In addition, (11)B nuclear magnetic resonance (NMR) spectroscopy further revealed that diammoniate of diborane (DADB) was initially formed to give polyaminoborane as liquid and/or solid spent-fuel, consistent with previous reports. Density Functional Theory (DFT) calculations suggested that hydrogen bonding interactions between AB and a polyetheral promoter initially played an important role in increasing the reactivity of B-H bonds of AB by transferring electron density from oxygen atoms of the promoter into B-H bonds of AB. These partially activated, hydridic B-H bonds were proposed to help promote the formation of diammoniate of diborane (DADB), which is considered as a reactive intermediate, eventually enhancing the rate of H2-release from AB. In addition, our in situ solid state (11)B magic angle spinning (MAS) NMR measurements further confirmed that the rate of DADB formation from AB with a small quantity of T4EGDE was found to be much faster than that of pristine AB even at 50 °C. This metal-free method for H2-release from AB with an added, small quantity of polyethers would be helpful to develop feasible hydrogen storage systems for long-term fuel cell applications. PMID:24068365

  19. Catalytic amplification based on hole-transporting materials as efficient metal-free electrocatalysts for non-enzymatic glucose sensing.

    PubMed

    Gu, Yue; Yuan, Rongrong; Yan, Xiaoyi; Li, Cong; Liu, Weilu; Chen, Ruixue; Tang, Liu; Zheng, Bo; Li, Yaru; Zhang, Zhiquan; Yang, Ming

    2015-08-19

    Hole-transporting materials with tunable structures and properties are mainly applied in organic light-emitting diodes as transport layer. But their catalytic properties as signal amplifiers in biological assays are seldom reported. In this paper, a starburst molecule, 4,4,4″-tri(N-carbazolyl)-triphenylamine (TCT), containing a triphenylamine as the central core and three carbazoles as the peripheral functional groups was designed and synthesized. Subsequently, the hole-transporting material based on the TCT polymer, poly(TCT) (PTCT), was achieved via a low-cost electrochemical method and exploited as an efficient metal-free electrocatalyst for non-enzymatic glucose detection. Here, this hole-transporting material served three purposes: electrochemical recognition (owing to hydrogen bonding interaction and the biomimetic microenvironment created by the polymer), electrocatalysis (owing to the hole-transporting capability of triphenylamine and the catalytic property of carbazole), and signal amplification (owing to energy migration along the conductive polymer backbone). The electrocatalytic and sensing performances of the sensor based on PTCT were evaluated in detail. Results revealed that the PTCT film could efficiently catalyze the oxidation of glucose at a less-positive potential (+0.20 V) in the absence of any enzymes. The response to glucose was linear in the concentration range of 1.0-6000 μM, and the detection limit was 0.20 μM. With good stability and selectivity, the proposed sensor could be feasibly applied to detect glucose in practical samples. The encouraging sensing performances suggest that the hole-transporting material is one of the promising biomimetic catalysts for electrocatalysis and relevant fields. PMID:26343433

  20. Al- or Si-decorated graphene oxide: A favorable metal-free catalyst for the N2O reduction

    NASA Astrophysics Data System (ADS)

    Esrafili, Mehdi D.; Sharifi, Fahimeh; Nematollahi, Parisa

    2016-11-01

    The structural and catalytic properties of Al- or Si-decorated graphene oxide (Al-/Si-GO) are studied by means of density functional theory calculations. The relatively large adsorption energy together with the small Alsbnd O or Sisbnd O binding distances indicate that the epoxy groups over the GO surface can strongly stabilize the single Al or Si atom. Hence, Al-GO and Si-GO are stable enough to be utilized in catalytic reduction of N2O by CO molecule. It is found that the adsorption and decomposition of N2O molecule over Si-GO is more favorable than over Al-GO, due to its larger adsorption energy (Eads) and charge transfer (qCT) values. On the other hand, the CO molecule is physically adsorbed over both surfaces, with relatively small Eads and qCT values. Therefore, at the presence of N2O and CO molecules as the reaction gas, the Al or Si atom of the surface should be dominantly covered by N2O molecule. Our results indicate that the N2O decomposition process can take place with a negligible activation energy over Al-/Si-GO surface, where the N2 molecule can be easily released from the surface. Then, the activated oxygen atom (Oads) which remains over the surface reacts with the CO molecule to form the CO2 molecule via the reaction Oads + CO → CO2. Based on the calculated activation energies, it is suggested that both Al-GO and Si-GO can be used as an efficient metal-free catalyst for the reduction of N2O molecule at ambient conditions.

  1. Sulfur-doped graphene derived from cycled lithium-sulfur batteries as a metal-free electrocatalyst for the oxygen reduction reaction.

    PubMed

    Ma, Zhaoling; Dou, Shuo; Shen, Anli; Tao, Li; Dai, Liming; Wang, Shuangyin

    2015-02-01

    Heteroatom-doped carbon materials have been extensively investigated as metal-free electrocatalysts to replace commercial Pt/C catalysts in oxygen reduction reactions in fuel cells and Li-air batteries. However, the synthesis of such materials usually involves high temperature or complicated equipment. Graphene-based sulfur composites have been recently developed to prolong the cycling life of Li-S batteries, one of the most attractive energy-storage devices. Given the high cost of graphene, there is significant demand to recycle and reuse graphene from Li-S batteries. Herein, we report a green and cost-effective method to prepare sulfur-doped graphene, achieved by the continuous charge/discharge cycling of graphene-sulfur composites in Li-S batteries. This material was used as a metal-free electrocatalyst for the oxygen reduction reaction and shows better electrocatalytic activity than pristine graphene and better methanol tolerance durability than Pt/C.

  2. A Discussion on the Activity Origin in Metal-Free Nitrogen-Doped Carbons For Oxygen Reduction Reaction and their Mechanisms.

    PubMed

    Wu, Kuang-Hsu; Wang, Da-Wei; Su, Dang-Sheng; Gentle, Ian R

    2015-09-01

    The origin of oxygen reduction reaction activity in metal-free N-doped carbons has been a stimulating, yet unsolved issue for the rational design of cost-effective electrocatalysts for fuel cells and metal-air batteries. At present, there are several inconsistent opinions on the materials chemistry and the mechanism of the oxygen reduction reaction (ORR) performed on this type of materials. This article provides a brief review of the current understanding of ORR processes and the history of electrocatalyst development. With special attention, the focus of the discussion is on the major contentions of the current opinions towards metal-free N-doped carbon chemistry and the arguments for the probable ORR mechanisms. By clarifying the fundamental aspects of each opinion, a converging consensus on N-doped carbon electrocatalysts can be established and thus facilitate the substantial development of large-capacity energy devices.

  3. Synthesis, characterization and electrical properties of peripherally tetra-aldazine substituted novel metal free phthalocyanine and its zinc(II) and nickel(II) complexes.

    PubMed

    Bayrak, Rıza; Dumludağ, Fatih; Akçay, Hakkı Türker; Değirmencioğlu, İsmail

    2013-03-15

    The novel phthalonitrile containing azine segment and its corresponding tetra aldazine substituted metal free- and metallo-phthalocyanines (Zn(II) and Ni(II)) were synthesized and characterized by IR, (1)H NMR, Mass, UV-Vis spectroscopy and elemental analysis and addition to these techniques for substituted phthalonitrile (13)C NMR have been used. In addition, dc and ac electrical properties of the films of these novel phthalocyanines were investigated as a function of temperature (295-523 K) and frequency (40-10(5)Hz). Activation energy values of the films of the phthalocyanines were calculated from straight portions of the Arrhenius plot (lnσ(dc)-1/T curves) as 0.70 eV, 0.93 eV and 0.91 eV for the films of metal free, nickel- and zinc-phthalocyanines, respectively. From impedance spectroscopy measurements, it is observed that bulk resistance decreases with increasing temperature indicating semiconductor property.

  4. Rapid hybridization of chitosan-gold-antibodies via metal-free click in water-based systems: a model approach for naked-eye detectable antigen sensors.

    PubMed

    Jirawutthiwongchai, Jatesuda; Draeger, Gerald; Chirachanchai, Suwabun

    2014-07-01

    A surface plasmon resonance (SPR) expression after hybridization of chitosan-gold nanoparticle-antibody (CS-AuNPs-Ab) based on: i) metal-free click chemistry, and, ii) in water system as an approach for a rapid antigen sensing, is proposed. The chitosan-hydroxybenzyl triazole complex enables us to carry out the conjugation of mPEG and trifluoromethylated oxanorbornadiene (OND) in water. CS-mPEG-OND further allows metal-free click to hybridize chitosan (CS) with azido-modified gold nanoparticles (azido-AuNPs) in aqueous solution at room temperature. The CS-mPEG-OND conjugated with LipL32 antibody (Ab) not only effectively binds with LipL32 antigen (Ag) but also performs the cycloaddition with azido-AuNPs to display a change in color within 2 min. The phenomenon leads to a simple and efficient naked-eye antigen detection technique.

  5. Nitrogen and sulfur co-doped carbon with three-dimensional ordered macroporosity: An efficient metal-free oxygen reduction catalyst derived from ionic liquid

    NASA Astrophysics Data System (ADS)

    Wu, Hui; Shi, Liang; Lei, Jiaheng; Liu, Dan; Qu, Deyu; Xie, Zhizhong; Du, Xiaodi; Yang, Peng; Hu, Xiaosong; Li, Junsheng; Tang, Haolin

    2016-08-01

    The development of efficient and durable catalyst for oxygen reduction reaction (ORR) is critical for the practical application of proton exchange membrane fuel cell (PEMFC). A novel imidazole based ionic liquid is synthesized in this study and used subsequently for the preparation of a N and S co-doped metal-free catalyst with three dimensional ordered microstructure. The catalyst prepared at 1100 °C showed improved ORR catalytic performance and stability compared to commercial Pt/C catalyst. We demonstrate that the high graphitic N content and high degree of graphitization of the synthesized catalyst is responsible for its superb ORR activity. Our results suggest that the N and S co-doped metal-free catalyst reported here is a promising alternative to traditional ORR catalyst based on noble metal. Furthermore, the current study also demonstrate that importance of morphology engineering in the development of high performance ORR catalyst.

  6. Acid-Catalyzed Multicomponent Tandem Double Cyclization: A One-pot, Metal-free Route to Synthesize Polyfunctional 4,9-Dihydropyrrolo[2,1-b]quinazolines.

    PubMed

    Cai, Qun; Li, Deng-Kui; Zhou, Rong-Rong; Zhuang, Shi-Yi; Ma, Jin-Tian; Wu, Yan-Dong; Wu, An-Xin

    2016-09-01

    An acid-catalyzed multicomponent tandem double cyclization protocol has been developed for the synthesis of polyfunctional 4,9-dihydropyrrolo[2,1-b]quinazolines from simple and readily available arylglyoxal monohydrates, 2-aminobenzylamine, and trans-β-nitrostyrenes. This practical and metal-free reaction proceeds through an imine formation/cyclization/Michael addition/Henry cyclization protocol, resulting in the construction of four new bonds and two ring moieties directly in one pot.

  7. Metal-Free Cross-Coupling of Arylboronic Acids and Derivatives with DAST-Type Reagents for Direct Access to Diverse Aromatic Sulfinamides and Sulfonamides.

    PubMed

    Wang, Qiang; Tang, Xiang-Ying; Shi, Min

    2016-08-26

    We have developed a simple and convenient method for the cross-coupling of arylboronic acids and their derivatives with DAST-type reagents under mild and metal-free conditions to directly afford sulfinamides in moderate to good yields. Moreover, sulfonamides were obtained after a simple oxidation reaction. The reaction mechanism was investigated by (18) O-labeling experiments, and the synthetic utility was demonstrated by the sulfoxidation of natural products.

  8. Metal-Free Decarboxylative Cyclization/Ring Expansion: Construction of Five-, Six-, and Seven-Membered Heterocycles from 2-Alkynyl Benzaldehydes and Cyclic Amino Acids.

    PubMed

    Samala, Srinivas; Singh, Gajendra; Kumar, Ravi; Ampapathi, Ravi Sankar; Kundu, Bijoy

    2015-08-10

    A one pot synthesis of 1H-benzo[g]indoles, tetrahydrobenzo[h]quinolines, and naphtho[1,2-b]azepines from 2-alkynyl benzaldehydes and cyclic amino acids is reported. The salient feature of the strategy involves formation of three new bonds (one C-N and two C-C bonds) by a metal-free decarboxylation/cyclization/one-carbon ring expansion sequence in one pot. PMID:26148838

  9. Forming heterojunction: an effective strategy to enhance the photocatalytic efficiency of a new metal-free organic photocatalyst for water splitting.

    PubMed

    Li, Hengshuai; Hu, Haiquan; Bao, Chunjiang; Guo, Feng; Zhang, Xiaoming; Liu, Xiaobiao; Hua, Juan; Tan, Jie; Wang, Aizhu; Zhou, Hongcai; Yang, Bo; Qu, Yuanyuan; Liu, Xiangdong

    2016-01-01

    Photocatalytic water splitting is a new technology for the conversion and utilization of solar energy and has a potential prospect. One important aspect of enhancing the photocatalytic efficiency is how to improve the electron-hole separation. Up to now, there is still no ideal strategy to improve the electron-hole separation. In this article, for metal-free organic photocatalysts, we propose a good strategy- forming heterojunction, which can effectively improve the electron-hole separation. We provide a metal-free organic photocatalyst g-C12N7H3 for water splitting. The stability of g-C12N7H3 has been investigated, the X-ray diffraction spectra has been simulated. Using first-principles calculations, we have systematically studied the electronic structure, band edge alignment, and optical properties for the g-C12N7H3. The results demonstrated that g-C12N7H3 is a new organocatalyst material for water splitting. In order to enhance the photocatalytic efficiency, we provided four strategies, i.e., multilayer stacking, raising N atoms, forming g-C9N10/g-C12N7H3 heterojunction, and forming graphene/g-C12N7H3 heterojunction. Our research is expected to stimulate experimentalists to further study novel 2D metal-free organic materials as visible light photocatalysts. Our strategies, especially forming heterojunction, will substantially help to enhance the photocatalytic efficiency of metal-free organic photocatalyst. PMID:27470223

  10. A hybrid of titanium nitride and nitrogen-doped amorphous carbon supported on SiC as a noble metal-free electrocatalyst for oxygen reduction reaction.

    PubMed

    Jia, Yingdan; Wang, Yanhui; Dong, Liang; Huang, Junjie; Zhang, Yan; Su, Jing; Zang, Jianbing

    2015-02-14

    A novel noble metal-free catalyst, with nitrogen-doped amorphous carbon and titanium nitride particles supported on SiC (NC-TiN/SiC), was synthesized. The NC-TiN/SiC catalyst exhibited excellent oxygen reduction reaction activities as well as superior stability and methanol tolerance. The catalytic activities were attributed to the synergistic effect of TiN and NC. PMID:25574526

  11. Forming heterojunction: an effective strategy to enhance the photocatalytic efficiency of a new metal-free organic photocatalyst for water splitting

    PubMed Central

    Li, Hengshuai; Hu, Haiquan; Bao, Chunjiang; Guo, Feng; Zhang, Xiaoming; Liu, Xiaobiao; Hua, Juan; Tan, Jie; Wang, Aizhu; Zhou, Hongcai; Yang, Bo; Qu, Yuanyuan; Liu, Xiangdong

    2016-01-01

    Photocatalytic water splitting is a new technology for the conversion and utilization of solar energy and has a potential prospect. One important aspect of enhancing the photocatalytic efficiency is how to improve the electron-hole separation. Up to now, there is still no ideal strategy to improve the electron-hole separation. In this article, for metal-free organic photocatalysts, we propose a good strategy- forming heterojunction, which can effectively improve the electron-hole separation. We provide a metal-free organic photocatalyst g-C12N7H3 for water splitting. The stability of g-C12N7H3 has been investigated, the X-ray diffraction spectra has been simulated. Using first-principles calculations, we have systematically studied the electronic structure, band edge alignment, and optical properties for the g-C12N7H3. The results demonstrated that g-C12N7H3 is a new organocatalyst material for water splitting. In order to enhance the photocatalytic efficiency, we provided four strategies, i.e., multilayer stacking, raising N atoms, forming g-C9N10/g-C12N7H3 heterojunction, and forming graphene/g-C12N7H3 heterojunction. Our research is expected to stimulate experimentalists to further study novel 2D metal-free organic materials as visible light photocatalysts. Our strategies, especially forming heterojunction, will substantially help to enhance the photocatalytic efficiency of metal-free organic photocatalyst. PMID:27470223

  12. Metal-free C(sp(3))-H functionalization: oxidative carbo-oxygenation of α-diazo carbonyls via radical dediazotization.

    PubMed

    Wang, Nan-Nan; Hao, Wen-Juan; Zhang, Tian-Shu; Li, Guigen; Wu, Ya-Nan; Tu, Shu-Jiang; Jiang, Bo

    2016-04-14

    A novel three-component carbo-oxygenation of α-diazo carbonyls for flexible synthesis of unprecedented α-aminooxy-β-amino ketones has been established through metal-free C(sp(3))-H functionalization from readily accessible N,N-dimethylanilines and N-hydroxyphthalimide. The reaction pathway involves an in situ-generated phthalimide N-oxyl radical-triggered dediazotization/radical coupling sequence, leading to C-O and C-C bond formation. PMID:26997205

  13. Structural Integrity and Durability of Reusable Space Propulsion Systems

    NASA Technical Reports Server (NTRS)

    1991-01-01

    A two-day conference on the structural integrity and durability of reusable space propulsion systems was held on 14 to 15 May 1991 at the NASA Lewis Research Center. Presentations were made by industry, university, and government researchers organized into four sessions: (1) aerothermodynamic loads; (2) instrumentation; (3) fatigue, fracture, and constitutive modeling; and (4) structural dynamics. The principle objectives were to disseminate research results and future plans in each of four areas. This publication contains extended abstracts and the visual material presented during the conference. Particular emphasis is placed on the Space Shuttle Main Engine (SSME) and the SSME turbopump.

  14. A reusable suture anchor for arthroscopy psychomotor skills training.

    PubMed

    Tillett, Edward D; Rogers, Rainie; Nyland, John

    2003-03-01

    For residents to adequately develop the early arthroscopy psychomotor skills required to better learn how to manage the improvisational situations they will encounter during actual patient cases, they need to experience sufficient practice repetitions within a contextually relevant environment. Unfortunately, the cost of suture anchors can be a practice repetition-limiting factor in learning arthroscopic knot-tying techniques. We describe a technique for creating inexpensive reusable suture anchors and provide an example of their application to repair the anterior glenoid labrum during an arthroscopy psychomotor skills laboratory training session.

  15. Reusable orbital transfer vehicle spacelift concepts study results

    SciTech Connect

    Feuchter, C.A.; Grobman, J.H.

    1997-01-01

    This paper reports on the feasibility and cost-effectiveness of expendable and reusable orbital transfer vehicle concepts utilizing innovative low thrust, high specific impulse electric and thermal propulsion technologies. Comparisons are made to launch systems using current chemical upper stages. These innovative technologies often produce significant savings over chemical upper-stages when used with the current fleet of expendable launch vehicles, and evolved expendable launch vehicles. Savings are driven by the ability of the innovative technologies to lower combined payload and upper stage mass, allowing payloads to be launched on smaller, less expensive launch vehicles. {copyright} {ital 1997 American Institute of Physics.}

  16. Space shuttle orbit maneuvering engine reusable thrust chamber program

    NASA Technical Reports Server (NTRS)

    Senneff, J. M.

    1975-01-01

    The feasibility of potential reusable thrust chamber concepts is studied. Propellant condidates were examined and analytically combined with potential cooling schemes. A data base of engine data which would assist in a configuration selection was produced. The data base verification was performed by the demonstration of a thrust chamber of a selected coolant scheme design. A full scale insulated columbium thrust chamber was used for propellant coolant configurations. Combustion stability of the injectors and a reduced size thrust chamber were experimentally verified as proof of concept demonstrations of the design and study results.

  17. Picosecond spectroscopic studies of equilibrium structural fluctuations of native and partially unfolded states of Zinc II-substituted and metal-free cytochromes C

    NASA Astrophysics Data System (ADS)

    Tripathy, Jagnyaseni

    Picosecond time-resolved fluorescence spectroscopy was employed to characterize the equilibrium and non-equilibrium protein structural fluctuations in Zn II-substituted (ZnCytc) and metal-free (fbCytc) cytochromes c using dynamic fluorescence Stokes shift (FSS) and fluorescence anisotropy (FA) measurements. The intrinsic porphyrin chromophore is used as the probe for the structural fluctuations of the surrounding protein and solvent. The FSS experiments examine how the time scales detected from the dynamic solvation of a chromoprotein report changes in the character of motion. ZnCytc and fbCytc serve as limited, single-chromophore models for photosynthetic reaction center and light-harvesting proteins. The dynamic solvation of redox and light-harvesting chromophores in photosynthesis plays an important role in the quantum efficiency of electron transfer and energy transfer performed by these systems, respectively. The FSS response function of fbCytc in water is biexponential over the 100-ps--50-ns regime and the two time constants are 1.4 ns and 9.1 ns. ZnCytc under similar solution conditions shows a biexponential FSS response but with time constants of 0.2 ns and 1.5 ns. The two correlation times from the FSS response function correspond to motions of the hydrophobic core and the solvent-contact layer, respectively. Both FSS correlation times were lengthened and the solvation reorganization energy was reduced from 43 cm-1 to 33 cm-1 in the presence of 50% (v/v) glycerol. A Brownian diffusion model with thermally activated barrier crossings on the protein-folding energy landscape is used to interpret these results. The conclusion is that the mean-squared deviations of the fluctuations exhibited by fbCytc are perhaps a factor of ten larger than those in ZnCytc, which is consistent with the suggestion that fbCytc assumes a dynamic, partially unfolded structure with some of the characteristics of a molten globule. The nature of the motion associated with the

  18. Reusable launch vehicle: Technology development and test program

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The National Aeronautics and Space Administration (NASA) requested that the National Research Council (NRC) assess the Reusable Launch Vehicle (RLV) technology development and test programs in the most critical component technologies. At a time when discretionary government spending is under close scrutiny, the RLV program is designed to reduce the cost of access to space through a combination of robust vehicles and a streamlined infrastructure. Routine access to space has obvious benefits for space science, national security, commercial technologies, and the further exploration of space. Because of technological challenges, knowledgeable people disagree about the feasibility of a single-stage-to-orbit (SSTO) vehicle. The purpose of the RLV program proposed by NASA and industry contractors is to investigate the status of existing technology and to identify and advance key technology areas required for development and validation of an SSTO vehicle. This report does not address the feasibility of an SSTO vehicle, nor does it revisit the roles and responsibilities assigned to NASA by the National Transportation Policy. Instead, the report sets forth the NRC committee's findings and recommendations regarding the RLV technology development and test program in the critical areas of propulsion, a reusable cryogenic tank system (RCTS), primary vehicle structure, and a thermal protection system (TPS).

  19. Distributed Health Monitoring System for Reusable Liquid Rocket Engines

    NASA Technical Reports Server (NTRS)

    Lin, C. F.; Figueroa, F.; Politopoulos, T.; Oonk, S.

    2009-01-01

    The ability to correctly detect and identify any possible failure in the systems, subsystems, or sensors within a reusable liquid rocket engine is a major goal at NASA John C. Stennis Space Center (SSC). A health management (HM) system is required to provide an on-ground operation crew with an integrated awareness of the condition of every element of interest by determining anomalies, examining their causes, and making predictive statements. However, the complexity associated with relevant systems, and the large amount of data typically necessary for proper interpretation and analysis, presents difficulties in implementing complete failure detection, identification, and prognostics (FDI&P). As such, this paper presents a Distributed Health Monitoring System for Reusable Liquid Rocket Engines as a solution to these problems through the use of highly intelligent algorithms for real-time FDI&P, and efficient and embedded processing at multiple levels. The end result is the ability to successfully incorporate a comprehensive HM platform despite the complexity of the systems under consideration.

  20. Russian aluminum-lithium alloys for advanced reusable spacecraft

    NASA Astrophysics Data System (ADS)

    Charette, Ray O.; Leonard, Bruce G.; Bozich, William F.; Deamer, David A.

    1998-01-01

    Cryotanks that are cost-affordable, robust, fuel-compatible, and lighter weight than current aluminum design are needed to support next-generation launch system performance and operability goals. The Boeing (McDonnell Douglas Aerospace-MDA) and NASA's Delta Clipper-Experimental Program (DC-XA) flight demonstrator test bed vehicle provided the opportunity for technology transfer of Russia's extensive experience base with weight-efficient, highly weldable aluminum-lithium (Al-Li) alloys for cryogenic tank usage. As part of NASA's overall reusable launch vehicle (RLV) program to help provide technology and operations data for use in advanced RLVs, MDA contracted with the Russian Academy of Sciences (RAS/IMASH) for design, test, and delivery of 1460 Al-Li alloy liquid oxygen (LO2) cryotanks: one for development, one for ground tests, and one for DC-XA flight tests. This paper describes the development of Al-Li 1460 alloy for reusable LO2 tanks, including alloy composition tailoring, mechanical properties database, forming, welding, chemical milling, dissimilar metal joining, corrosion protection, completed tanks proof, and qualification testing. Mechanical properties of the parent and welded materials exceeded expectations, particularly the fracture toughness, which promise excellent reuse potential. The LO2 cryotank was successfully demonstrated in DC-XA flight tests.

  1. Systems integration and demonstration of advanced reusable structure for ALS

    NASA Technical Reports Server (NTRS)

    Gibbins, Martin N.

    1991-01-01

    The objective was to investigate the potential of advanced material to achieve life cycle cost (LCC) benefits for reusable structure on the advanced launch system. Three structural elements were investigated - all components of an Advanced Launch System reusable propulsion/avionics module. Leading aeroshell configurations included sandwich structure using titanium, graphite/polyimide (Gr/PI), or high-temperature aluminum (HTA) face sheets. Thrust structure truss concepts used titanium, graphite/epoxy, or silicon carbide/aluminum struts. Leading aft bulkhead concepts employed graphite epoxy and aluminum. The technical effort focused on the aeroshell because the greatest benefits were expected there. Thermal analyses show the structural temperature profiles during operation. Finite element analyses show stresses during splash-down. Weight statements and manufacturing cost estimates were prepared for calculation of LCC for each design. The Gr/PI aeroshell showed the lowest potential LCC, but the HTA aeroshell was judged to be lower risk. A technology development plan was prepared to validate the applicable structural technology.

  2. Structures for the 3rd Generation Reusable Concept Vehicle

    NASA Technical Reports Server (NTRS)

    Hrinda, Glenn A.

    2001-01-01

    A major goal of NASA is to create an advance space transportation system that provides a safe, affordable highway through the air and into space. The long-term plans are to reduce the risk of crew loss to 1 in 1,000,000 missions and reduce the cost of Low-Earth Orbit by a factor of 100 from today's costs. A third generation reusable concept vehicle (RCV) was developed to assess technologies required to meet NASA's space access goals. The vehicle will launch from Cape Kennedy carrying a 25,000 lb. payload to the International Space Station (ISS). The system is an air breathing launch vehicle (ABLV) hypersonic lifting body with rockets and uses triple point hydrogen and liquid oxygen propellant. The focus of this paper is on the structural concepts and analysis methods used in developing the third generation reusable launch vehicle (RLV). Member sizes, concepts and material selections will be discussed as well as analysis methods used in optimizing the structure. Analysis based on the HyperSizer structural sizing software will be discussed. Design trades required to optimize structural weight will be presented.

  3. Linear quadratic servo control of a reusable rocket engine

    NASA Technical Reports Server (NTRS)

    Musgrave, Jeffrey L.

    1991-01-01

    A design method for a servo compensator is developed in the frequency domain using singular values. The method is applied to a reusable rocket engine. An intelligent control system for reusable rocket engines was proposed which includes a diagnostic system, a control system, and an intelligent coordinator which determines engine control strategies based on the identified failure modes. The method provides a means of generating various linear multivariable controllers capable of meeting performance and robustness specifications and accommodating failure modes identified by the diagnostic system. Command following with set point control is necessary for engine operation. A Kalman filter reconstructs the state while loop transfer recovery recovers the required degree of robustness while maintaining satisfactory rejection of sensor noise from the command error. The approach is applied to the design of a controller for a rocket engine satisfying performance constraints in the frequency domain. Simulation results demonstrate the performance of the linear design on a nonlinear engine model over all power levels during mainstage operation.

  4. Reusable hose fittings emerge as source of apprehension over safety

    SciTech Connect

    Not Available

    1992-05-01

    This paper reports that while the area of hose care and maintenance may not warrant the same degree of vigilance that is called for in other propane safety-related areas, it has become apparent that marketers should start paying close attention to the subject of properly installed hose-end fittings or risk the consequences of a potentially disastrous mismatch. Indeed, if there is any topic in which the seemingly ho-hum subject of propane hose generates a difference of opinion or debate, it is the subject of reusable end-fittings. Currently there are opposing schools of thought on whether this particular hardware should be used at all. The reusable ends for LPG transfer hose (commonly called the boss type) consist of two segments that grip the hose in a clamp-like fashion. A mismatched boss coupling will probably result in improper or inadequate compression of the hose. This could lead in turn to the hose separating from the hose end.

  5. Earth-to-orbit reusable launch vehicles: A comparative assessment

    NASA Technical Reports Server (NTRS)

    Chase, R. L.

    1978-01-01

    A representative set of space systems, functions, and missions for NASA and DoD from which launch vehicle requirements and characteristics was established as well as a set of air-breathing launch vehicles based on graduated technology capabilities corresponding to increasingly higher staging Mach numbers. The utility of the air-breathing launch vehicle candidates based on lift-off weight, performance, technology needs, and risk was assessed and costs were compared to alternative concepts. The results indicate that a fully reusable launch vehicle, whether two stage or one stage, could potentially reduce the cost per flight 60-80% compared to that for a partially reusable vehicle but would require advances in thermal protection system technology. A two-stage-to-orbit, parallel-lift vehicle with an air-breathing booster would cost approximately the same as a single-stage-to-orbit vehicle, but the former would have greater flexibility and a significantly reduced developmental risk. A twin-booster, subsonic-staged, parallel-lift vehicle represents the lowest system cost and developmental risk. However, if a large supersonic turbojet engine in the 350,000-N thrust class were available, supersonic staging would be preferred, and the investment in development would be returned in reduced program cost.

  6. Reusable, robust, and accurate laser-generated photonic nanosensor.

    PubMed

    Yetisen, Ali K; Montelongo, Yunuen; da Cruz Vasconcellos, Fernando; Martinez-Hurtado, J L; Neupane, Sankalpa; Butt, Haider; Qasim, Malik M; Blyth, Jeffrey; Burling, Keith; Carmody, J Bryan; Evans, Mark; Wilkinson, Timothy D; Kubota, Lauro T; Monteiro, Michael J; Lowe, Christopher R

    2014-06-11

    Developing noninvasive and accurate diagnostics that are easily manufactured, robust, and reusable will provide monitoring of high-risk individuals in any clinical or point-of-care environment. We have developed a clinically relevant optical glucose nanosensor that can be reused at least 400 times without a compromise in accuracy. The use of a single 6 ns laser (λ = 532 nm, 200 mJ) pulse rapidly produced off-axis Bragg diffraction gratings consisting of ordered silver nanoparticles embedded within a phenylboronic acid-functionalized hydrogel. This sensor exhibited reversible large wavelength shifts and diffracted the spectrum of narrow-band light over the wavelength range λpeak ≈ 510-1100 nm. The experimental sensitivity of the sensor permits diagnosis of glucosuria in the urine samples of diabetic patients with an improved performance compared to commercial high-throughput urinalysis devices. The sensor response was achieved within 5 min, reset to baseline in ∼10 s. It is anticipated that this sensing platform will have implications for the development of reusable, equipment-free colorimetric point-of-care diagnostic devices for diabetes screening. PMID:24844116

  7. Reducing the Cost of Laparoscopy: Reusable versus Disposable Laparoscopic Instruments.

    PubMed

    Manatakis, Dimitrios K; Georgopoulos, Nikolaos

    2014-01-01

    Cost-effectiveness in health care management is critical. The situation in debt-stricken Greece is further aggravated by the financial crisis and constant National Health System expense cut-downs. In an effort to minimize the cost of laparoscopy, our department introduced reusable laparoscopic instruments in December 2011. The aim of this study was to assess potential cost reduction of laparoscopic operations in the field of general surgery. Hospital records, invoice lists, and operative notes between January 2012 and December 2013, were retrospectively reviewed and data were collected on laparoscopic procedures, instrument failures, and replacement needs. Initial acquisition cost of 5 basic instrument sets was €21,422. Over the following 24 months, they were used in 623 operations, with a total maintenance cost of €11,487. Based on an average retail price of €490 per set, projected cost with disposable instruments would amount to €305,270, creating savings of €272,361 over the two-year period under study. Despite the seemingly high purchase price, each set amortized its acquisition cost after only 9 procedures and instrument cost depreciated to less than €55 per case. Disposable instruments cost 9 times more than reusable ones, and their high price would almost equal the total hospital reimbursement by social security funds for many common laparoscopic procedures. PMID:25152814

  8. Reducing the Cost of Laparoscopy: Reusable versus Disposable Laparoscopic Instruments

    PubMed Central

    Manatakis, Dimitrios K.; Georgopoulos, Nikolaos

    2014-01-01

    Cost-effectiveness in health care management is critical. The situation in debt-stricken Greece is further aggravated by the financial crisis and constant National Health System expense cut-downs. In an effort to minimize the cost of laparoscopy, our department introduced reusable laparoscopic instruments in December 2011. The aim of this study was to assess potential cost reduction of laparoscopic operations in the field of general surgery. Hospital records, invoice lists, and operative notes between January 2012 and December 2013, were retrospectively reviewed and data were collected on laparoscopic procedures, instrument failures, and replacement needs. Initial acquisition cost of 5 basic instrument sets was €21,422. Over the following 24 months, they were used in 623 operations, with a total maintenance cost of €11,487. Based on an average retail price of €490 per set, projected cost with disposable instruments would amount to €305,270, creating savings of €272,361 over the two-year period under study. Despite the seemingly high purchase price, each set amortized its acquisition cost after only 9 procedures and instrument cost depreciated to less than €55 per case. Disposable instruments cost 9 times more than reusable ones, and their high price would almost equal the total hospital reimbursement by social security funds for many common laparoscopic procedures. PMID:25152814

  9. Electron paramagnetic resonance of the excited triplet state of metal-free and metal-substituted cytochrome c.

    PubMed Central

    Angiolillo, P J; Vanderkooi, J M

    1995-01-01

    The photoactivated metastable triplate states of the porphyrin (free-base, i.e., metal-free) zinc and tin derivatives of horse cytochrome c were investigated using electron paramagnetic resonance. Zero-field splitting parameters, line shape, and Jahn-Teller distortion in the temperature range 3.8-150 K are discussed in terms of porphyrin-protein interactions. The zero-field splitting parameters D for the free-base, Zn and Sn derivatives are 465 x 10(-4), 342 x 10(-4) and 353 x 10(-4) cm-1, respectively, and are temperature invariant over the temperature ranges studied. AN E value at 4 K of 73 x 10(-4) cm-1 was obtained for Zn cytochrome c, larger than any previously found for Zn porphyrins derivatives of hemeproteins, showing that the heme site of cytochrome c imposes an asymmetric field. Though the E value for Zn cytochrome c is large, the geometry of the site appears quite constrained, as indicated by a spectral line shape showing a single species. Intersystem crossing occurred predominantly to the T2 > zero-field spin sublevel. EPR line shape changes with respect to temperature of Zn cyt c are interpreted in terms of vibronic coupling, and a maximum Jahn-Teller crystal-field splitting of approximately 180 cm-1 is obtained. Sn cytochrome c in comparison with the Zn protein exhibits a photoactivated triplet line shape that is less well resolved in the X-Y region. The magnitude of E value is approximately 60 x 10(-4) cm-1 at 4 K; its value rapidly tends toward zero with increasing temperature, from which a value for the Jahn-Teller crystal-field splitting of > or = 40 cm-1 is estimated. In contrast to those for the metal cytochromes, the magnitude of E value for the free-base derivative was essentially zero at all temperatures studied. This finding is discussed as a consequence of an excited-state tautomerization process that occurs even at 4 K. PMID:7647253

  10. Understanding Reusability as a Key Factor for Open Education: A Review

    ERIC Educational Resources Information Center

    Chiappe, Andres; Arias, Vivian

    2015-01-01

    This article describes both the process and the results of an extensive literature review on "reusability" as one of the key factors for the creation of open content in the context of open and distance learning. Qualitative analysis of texts was made from 1992 to early 2014 in order to identify meanings associated with reusability and…

  11. 14 CFR 437.95 - Inspection of additional reusable suborbital rockets.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... suborbital rockets. 437.95 Section 437.95 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL... of an Experimental Permit § 437.95 Inspection of additional reusable suborbital rockets. A permittee may launch or reenter additional reusable suborbital rockets of the same design under the permit...

  12. 14 CFR 437.95 - Inspection of additional reusable suborbital rockets.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... suborbital rockets. 437.95 Section 437.95 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL... of an Experimental Permit § 437.95 Inspection of additional reusable suborbital rockets. A permittee may launch or reenter additional reusable suborbital rockets of the same design under the permit...

  13. 14 CFR 437.95 - Inspection of additional reusable suborbital rockets.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... suborbital rockets. 437.95 Section 437.95 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL... of an Experimental Permit § 437.95 Inspection of additional reusable suborbital rockets. A permittee may launch or reenter additional reusable suborbital rockets of the same design under the permit...

  14. 14 CFR 437.95 - Inspection of additional reusable suborbital rockets.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... suborbital rockets. 437.95 Section 437.95 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL... of an Experimental Permit § 437.95 Inspection of additional reusable suborbital rockets. A permittee may launch or reenter additional reusable suborbital rockets of the same design under the permit...

  15. 14 CFR 437.95 - Inspection of additional reusable suborbital rockets.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... suborbital rockets. 437.95 Section 437.95 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL... of an Experimental Permit § 437.95 Inspection of additional reusable suborbital rockets. A permittee may launch or reenter additional reusable suborbital rockets of the same design under the permit...

  16. New Pedagogies and Re-Usable Learning Objects: Toward a Different Role for an LMS.

    ERIC Educational Resources Information Center

    Collis, Betty; Strijker, Allard

    While the idea of reusing objects in digital learning environments is not new, continual strides are being made toward improving the prospects of reusability. A major trend in company training settings is to think of reusability in terms of a LMS (learning management system), but instructor use and pedagogies are little considered. This paper…

  17. A bioinspired, reusable, paper-based system for high-performance large-scale evaporation.

    PubMed

    Liu, Yanming; Yu, Shengtao; Feng, Rui; Bernard, Antoine; Liu, Yang; Zhang, Yao; Duan, Haoze; Shang, Wen; Tao, Peng; Song, Chengyi; Deng, Tao

    2015-05-01

    A bioinspired, reusable, paper-based gold-nanoparticle film is fabricated by depositing an as-prepared gold-nanoparticle thin film on airlaid paper. This paper-based system with enhanced surface roughness and low thermal conductivity exhibits increased efficiency of evaporation, scale-up potential, and proven reusability. It is also demonstrated to be potentially useful in seawater desalination.

  18. Performance and Cost of Disposable Biopsy Forceps in Upper Gastrointestinal Endoscopy: Comparison with Reusable Biopsy Forceps

    PubMed Central

    Lim, Chul-Hyun; Kim, Won Chul; Kim, Jin Soo; Cho, Yu Kyung; Park, Jae Myung; Lee, In Seok; Kim, Sang Woo; Choi, Kyu Yong; Chung, In-Sik

    2012-01-01

    Background/Aims It is believed that disposable biopsy forceps are more costly than reusable biopsy forceps. In this study, we evaluated performance and cost of disposable forceps versus reusable forceps in esophagogastroduodenoscopic biopsy. Methods Between October 2009 and July 2010, we enrolled 200 patients undergoing esophagogastroduodenoscopic biopsy at Seoul St. Mary's Hospital. Biopsies were performed with 100 disposable or 5 reusable forceps by random assignment. Seventy-five additional patients were studied to estimate durability of reusable forceps. The assisting nurses estimated the performance of the forceps. The evaluation of costs included purchase prices and reprocessing costs. The adequacy of the sample was estimated according to the diameter of the obtained tissue. Results Performance of disposable forceps was estimated as excellent in 97.0%, good in 2.0% and adequate in 1.0%. Reusable forceps were estimated as excellent in 36.0%, good in 36.0%, adequate in 25.1% and inadequate in 2.9%. The performance of reusable forceps declined with the number of uses. The reprocessing cost of reusable forceps for one biopsy session was calculated as ₩8,021. The adequacy of the sample was excellent for both forceps. Conclusions Disposable forceps showed excellent performance. Considering the reprocessing costs of reusable forceps, usage of disposable forceps with a low price should be considered. PMID:22741133

  19. 14 CFR 431.15 - Rights not conferred by a reusable launch vehicle mission license.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Rights not conferred by a reusable launch vehicle mission license. 431.15 Section 431.15 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.15...

  20. 14 CFR 431.13 - Transfer of a reusable launch vehicle mission license.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 false Transfer of a reusable launch vehicle mission license. 431.13 Section 431.13 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.13 Transfer of...

  1. 14 CFR 431.13 - Transfer of a reusable launch vehicle mission license.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Transfer of a reusable launch vehicle mission license. 431.13 Section 431.13 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.13 Transfer of...

  2. 14 CFR 431.13 - Transfer of a reusable launch vehicle mission license.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Transfer of a reusable launch vehicle mission license. 431.13 Section 431.13 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.13 Transfer of...

  3. 14 CFR 431.15 - Rights not conferred by a reusable launch vehicle mission license.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 false Rights not conferred by a reusable launch vehicle mission license. 431.15 Section 431.15 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.15...

  4. 14 CFR 431.9 - Issuance of a reusable launch vehicle mission license.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Issuance of a reusable launch vehicle mission license. 431.9 Section 431.9 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.9 Issuance of...

  5. 14 CFR 431.15 - Rights not conferred by a reusable launch vehicle mission license.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Rights not conferred by a reusable launch vehicle mission license. 431.15 Section 431.15 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.15...

  6. 14 CFR 431.9 - Issuance of a reusable launch vehicle mission license.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Issuance of a reusable launch vehicle mission license. 431.9 Section 431.9 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.9 Issuance of...

  7. 14 CFR 431.9 - Issuance of a reusable launch vehicle mission license.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Issuance of a reusable launch vehicle mission license. 431.9 Section 431.9 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.9 Issuance of...

  8. 14 CFR 431.9 - Issuance of a reusable launch vehicle mission license.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 false Issuance of a reusable launch vehicle mission license. 431.9 Section 431.9 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.9 Issuance of...

  9. 14 CFR 431.15 - Rights not conferred by a reusable launch vehicle mission license.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Rights not conferred by a reusable launch vehicle mission license. 431.15 Section 431.15 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.15...

  10. 14 CFR 431.13 - Transfer of a reusable launch vehicle mission license.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Transfer of a reusable launch vehicle mission license. 431.13 Section 431.13 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH AND REENTRY OF A REUSABLE LAUNCH VEHICLE (RLV) General § 431.13 Transfer of...

  11. Informed maintenance for next generation reusable launch systems

    NASA Astrophysics Data System (ADS)

    Fox, Jack J.; Gormley, Thomas J.

    2001-03-01

    Perhaps the most substantial single obstacle to progress of space exploration and utilization of space for human benefit is the safety & reliability and the inherent cost of launching to, and returning from, space. The primary influence in the high costs of current launch systems (the same is true for commercial and military aircraft and most other reusable systems) is the operations, maintenance and infrastructure portion of the program's total life cycle costs. Reusable Launch Vehicle (RLV) maintenance and design have traditionally been two separate engineering disciplines with often conflicting objectives - maximizing ease of maintenance versus optimizing performance, size and cost. Testability analysis, an element of Informed Maintenance (IM), has been an ad hoc, manual effort, in which maintenance engineers attempt to identify an efficient method of troubleshooting for the given product, with little or no control over product design. Therefore, testability deficiencies in the design cannot be rectified. It is now widely recognized that IM must be engineered into the product at the design stage itself, so that an optimal compromise is achieved between system maintainability and performance. The elements of IM include testability analysis, diagnostics/prognostics, automated maintenance scheduling, automated logistics coordination, paperless documentation and data mining. IM derives its heritage from complimentary NASA science, space and aeronautic enterprises such as the on-board autonomous Remote Agent Architecture recently flown on NASA's Deep Space 1 Probe as well as commercial industries that employ quick turnaround operations. Commercial technologies and processes supporting NASA's IM initiatives include condition based maintenance technologies from Boeing's Commercial 777 Aircraft and Lockheed-Martin's F-22 Fighter, automotive computer diagnostics and autonomous controllers that enable 100,000 mile maintenance free operations, and locomotive monitoring

  12. Cryogenic Insulation Bondline Studies for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Johnson, T. F.; Weiser, E. S.; Duong, P. G.

    2003-01-01

    Cryogenic insulations bonded to metallic substrates were characterized under simulated mission conditions representative for a reusable launch vehicle. The combined thermal and mechanical test consisted of 50 to a 100 cycles. These combined thermal and mechanical cycles simulated flight missions with temperatures ranging from -423 F to 450 F and a maximum mechanical tension load ranging from 20,000 lbs. to 97,650 lbs. The combined thermal and mechanical (uniaxial tension) test apparatus (1 ft. by 2 ft. Test Apparatus) developed at the NASA Langley Research Center, was used to perform cyclic tests on cryogenic insulations bonded to tank wall substrates. No visual delamination or degradation was observed in the cryogenic insulation-to-metallic substrate bondline or butt joints between cryogenic insulation panels. In addition, after cyclic testing was performed, residual property results from tension-pull and closed-cell content tests of the cryogenic insulations indicated a decrease in the bondline strength and closed-cell content.

  13. Investigation of next generation engine for reusable launch vehicle

    NASA Astrophysics Data System (ADS)

    Konno, Akira; Kishimoto, Kenji; Atsumi, Masahiro

    1998-01-01

    A new investigation on next generation engines for fully Reusable Launch Vehicle (RLV) is under way in Japan. The RLV requires not only high specific impulse of the propulsion but also significant improvements in thrust-to weight ratio at liftoff, life cycle capability and operability. This paper will describe the conceptual outline on a new engine research program for RLV based on the main component characteristics of the LE-7A engine. This engine will be driven with tap off cycle or gas generator cycle, not staged combustion, in order to increase sea level thrust-to-weight ratio. Extendible nozzle will be also installed to enhance the vacuum specific impulse. In addition, this paper will present a new concept of Liquefied Air Cycle Engine (LACE) to boost air breathing spaceplane. The LACE engine has significantly higher specific impulse and sea level thrust-to weight ratio than rocket engine.

  14. Reusable antifouling viscoelastic adhesive with an elastic skin.

    PubMed

    Patil, Sandip; Malasi, Abhinav; Majumder, Abhijit; Ghatak, Animangsu; Sharma, Ashutosh

    2012-01-10

    Although the viscoelasticity or tackiness of a pressure-sensitive adhesive gives it strength owing to energy dissipation during peeling, it also renders it nonreusable because of structural changes such as the formation of fibrils, cohesive failure, and fouling. However, an elastic layer has good structural integrity and cohesive strength but low adhesive energy. We demonstrate an effective composite adhesive in which a soft viscoelastic bulk layer is imbedded in a largely elastic thin skin layer. The composite layer is able to meet the conflicting demands of the high peel strength comparable to the viscoelastic core and the structural integrity, reusability, and antifouling properties of the elastic skin. Our model adhesive is made of poly(dimethylsiloxane), where its core and skin are created by varying the cross-linking percentage from 2 to 10%. PMID:22201420

  15. What If Annotations Were Reusable: A Preliminary Discussion

    NASA Astrophysics Data System (ADS)

    Manouselis, Nikos; Vuorikari, Riina

    This paper discusses the rationale for the representation of user feedback in a structured and reusable format so that it can be reused by different recommender systems. We emphasize how information about the context can be included in such a representation. This work-in-progress takes place in the context of two large European initiatives that set up collections of digital educational resources in distributed repositories to serve the needs of different user communities, and to collect user feedback such as ratings, bookmarks and tags related to the resources. The overall aim is to facilitate the exchange and reuse of their data sets in order to support recommendation of appropriate resources to the end users.

  16. Advanced TSTO VTOHL reusable rocket launcher - Study status

    NASA Astrophysics Data System (ADS)

    Abriat, E.; Bombled, J. P.; Rezette, J. P.; Lacaze, H.

    1992-08-01

    Results of current investigations of an advanced TSTO, vertical-takeoff-and-horizontal landing, reusable rocket launcher are presented. Cost reduction and safety considerations, which require abort capabilities of the future manned launcher throughout the flight regime, are addressed. Recovery scenarios are investigated to determine when the stages could execute return-to-launch-site, transatlantic-abort-landing, or abort-to-orbit abort modes. It is shown that the appropriate combination of powered and gliding phases with limited relaxation on nominal constraints enables the intact stages to recover throughout the flight regime, from takeoff to orbital insertion. The results of a trade-off study performed to obtain a lightweight thermostructural concept are also presented.

  17. Reusable, flyback liquid rocket booster for the Space Shuttle

    NASA Astrophysics Data System (ADS)

    Benton, Mark G.

    1989-08-01

    This paper outlines a preliminary design for an unmanned, reusable, flyback liquid rocket booster (LRB) as an evolutionary follow-on to the Shuttle solid rocket booster (SRB). Previous Shuttle liquid-propellant booster concepts are reviewed in order to gain insight into these designs. The operating costs, environmental impacts, and abort options of the SRB are discussed. The LRB flight profile and advantages of LRB use are discussed. The preliminary design for the LRB is outlined in detail using calculations and drawings. This design maximizes the use of existing hardware and proven technology to minimize cost and development time. The LRB design is presented as a more capable, more environmentally acceptable, and safer Shuttle booster.

  18. Reusable antifouling viscoelastic adhesive with an elastic skin.

    PubMed

    Patil, Sandip; Malasi, Abhinav; Majumder, Abhijit; Ghatak, Animangsu; Sharma, Ashutosh

    2012-01-10

    Although the viscoelasticity or tackiness of a pressure-sensitive adhesive gives it strength owing to energy dissipation during peeling, it also renders it nonreusable because of structural changes such as the formation of fibrils, cohesive failure, and fouling. However, an elastic layer has good structural integrity and cohesive strength but low adhesive energy. We demonstrate an effective composite adhesive in which a soft viscoelastic bulk layer is imbedded in a largely elastic thin skin layer. The composite layer is able to meet the conflicting demands of the high peel strength comparable to the viscoelastic core and the structural integrity, reusability, and antifouling properties of the elastic skin. Our model adhesive is made of poly(dimethylsiloxane), where its core and skin are created by varying the cross-linking percentage from 2 to 10%.

  19. Large Composite Structures Processing Technologies for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Clinton, R. G., Jr.; Vickers, J. H.; McMahon, W. M.; Hulcher, A. B.; Johnston, N. J.; Cano, R. J.; Belvin, H. L.; McIver, K.; Franklin, W.; Sidwell, D.

    2001-01-01

    Significant efforts have been devoted to establishing the technology foundation to enable the progression to large scale composite structures fabrication. We are not capable today of fabricating many of the composite structures envisioned for the second generation reusable launch vehicle (RLV). Conventional 'aerospace' manufacturing and processing methodologies (fiber placement, autoclave, tooling) will require substantial investment and lead time to scale-up. Out-of-autoclave process techniques will require aggressive efforts to mature the selected technologies and to scale up. Focused composite processing technology development and demonstration programs utilizing the building block approach are required to enable envisioned second generation RLV large composite structures applications. Government/industry partnerships have demonstrated success in this area and represent best combination of skills and capabilities to achieve this goal.

  20. Optimal technology investment strategies for a reusable launch vehicle

    NASA Technical Reports Server (NTRS)

    Moore, A. A.; Braun, R. D.; Powell, R. W.

    1995-01-01

    Within the present budgetary environment, developing the technology that leads to an operationally efficient space transportation system with the required performance is a challenge. The present research focuses on a methodology to determine high payoff technology investment strategies. Research has been conducted at Langley Research Center in which design codes for the conceptual analysis of space transportation systems have been integrated in a multidisciplinary design optimization approach. The current study integrates trajectory, propulsion, weights and sizing, and cost disciplines where the effect of technology maturation on the development cost of a single stage to orbit reusable launch vehicle is examined. Results show that the technology investment prior to full-scale development has a significant economic payoff. The design optimization process is used to determine strategic allocations of limited technology funding to maximize the economic payoff.

  1. Controls for Reusable Launch Vehicles During Terminal Area Energy Management

    NASA Technical Reports Server (NTRS)

    Driessen, Brian J.

    2005-01-01

    During the terminal energy management phase of flight (last of three phases) for a reusable launch vehicle, it is common for the controller to receive guidance commands specifying desired values for (i) the roll angle roll q(sub roll), (ii) the acceleration a(sub n) in the body negative z direction, -k(sub A)-bar, and (iii) omega(sub 3), the projection of onto the body-fixed axis k(sub A)-bar, is always indicated by guidance to be zero. The objective of the controller is to regulate the actual values of these three quantities, i.e make them close to the commanded values, while maintaining system stability.

  2. Suborbital Research and Education Missions with Commercial Reusable Launch Vehicles

    NASA Astrophysics Data System (ADS)

    Rodway, K.; Nelson, A.; Voigt, J.

    2012-12-01

    Suborbital reusable launch vehicles (sRLV) will provide low-cost, flexible, and frequent access to space. In the case of XCOR's Lynx, the vehicle design and capabilities work well for hosting specially designed experiments that can be flown with a human-tended researcher or alone with the pilot on a unique mission on a customized flight trajectory. This new manned, reusable commercial platform will allow for repeated observations with a single instrument, but without the need to refurbish the vehicle between flights. In addition, the short turn-around means a researcher can do multiple observations, measurements, or targets. The vehicle is designed for multi-mission primary and secondary payload capabilities, including: in-cockpit experiments and instrumentation testing, externally mounted experiments, upper atmospheric sampling, and microsatellite launch. This vehicle takes off horizontally from a runway and will go into a powered ascent attaining Mach 2.9 maximum airspeed. After about three minutes and at approximately 58 km (190,000 ft) the engines are shutdown and the RLV then coasts upwards. The low gravity period (at or below 0.001go) begins soon after at 3.35 minutes and the microgravity period (at or below 10-6go) starts at 4.25 minutes. At approximately four and half minutes the vehicle reaches apogee of 100 km (328, 000 ft). After reentry and a Max-G force pullout of 4 g, the Lynx touches down on the takeoff runway after approximately 30 minutes.Typical Lynx Mark II flight profile

  3. Reusable Hybrid Propellant Modules for Outer-Space Transport

    NASA Technical Reports Server (NTRS)

    Mazanek, Daniel D.; Mankins, John C.

    2005-01-01

    A report summarizes the concept of reusable hybrid propellant modules (HPMs), which would be used in outer space for long-term cryogenic storage of liquefied spacecraft-propellant gases, including for example, oxygen and hydrogen for combustion-based chemical rocket engines and xenon for electric thrusters. The HPM concept would provide the fundamental building block for an efficient, reusable in-space transportation system for both crewed and uncrewed missions. Each HPM would be equipped to implement an advanced zero-boil-off method of managing cryogenic fluids, and would include a fluid-transfer interface comprising standardized fittings that would be compatible with fittings on all supply facilities and on spacecraft to be supplied. The HPM, combined with a chemical or electric orbital transfer spacecraft, would provide an integrated propulsion system. HPMs would supply chemical propellant for time-critical transfers such as crewed missions, and utilize the more efficient electric-propulsion transfer vehicles to transport filled HPMs to the destinations and to return empty HPMs back to near-Earth orbits or other intermediate locations for replenishment and reuse. The HPM prepositioned using electric propulsion would provide the chemical propellant for the crew s return trip in a much more efficient manner than a chemical-only approach. The propellants to fill the HPMs would be delivered from the Earth or other initial supply locations to the intermediate locations by use of automated, compatible spacecraft designed specifically for that purpose. Additionally, multiple HPMs could be aggregated and positioned in orbits and on planets, moons, and asteroids to supply fluids to orbiting and interplanetary spacecraft.

  4. Macroeconomic Benefits of Low-Cost Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Shaw, Eric J.; Greenberg, Joel

    1998-01-01

    The National Aeronautics and Space Administration (NASA) initiated its Reusable Launch Vehicle (RLV) Technology Program to provide information on the technical and commercial feasibility of single-stage to orbit (SSTO), fully-reusable launchers. Because RLVs would not depend on expendable hardware to achieve orbit, they could take better advantage of economies of scale than expendable launch vehicles (ELVs) that discard costly hardware on ascent. The X-33 experimental vehicle, a sub-orbital, 60%-scale prototype of Lockheed Martin's VentureStar SSTO RLV concept, is being built by Skunk Works for a 1999 first flight. If RLVs achieve prices to low-earth orbit of less than $1000 US per pound, they could hold promise for eliciting an elastic response from the launch services market. As opposed to the capture of existing market, this elastic market would represent new space-based industry businesses. These new opportunities would be created from the next tier of business concepts, such as space manufacturing and satellite servicing, that cannot earn a profit at today's launch prices but could when enabled by lower launch costs. New business creation contributes benefits to the US Government (USG) and the US economy through increases in tax revenues and employment. Assumptions about the costs and revenues of these new ventures, based on existing space-based and aeronautics sector businesses, can be used to estimate the macroeconomic benefits provided by new businesses. This paper examines these benefits and the flight prices and rates that may be required to enable these new space industries.

  5. Structures and spectroscopic properties of nonperipherally and peripherally substituted metal-free phthalocyanines: a substitution effect study based on density functional theory calculations.

    PubMed

    Zhong, Aimin; Zhang, Yuexing; Bian, Yongzhong

    2010-11-01

    The molecular structures, molecular orbitals, atomic charges, electronic absorption spectra, and infrared (IR) and Raman spectra of a series of substituted metal-free phthalocyanine compounds with four (1, 3, 5, 7) or eight (2, 4, 6, 8) methoxyl (1, 2, 5, 6) or methylthio groups (3, 4, 7, 8) on the nonperipheral (1-4) or peripheral positions (5-8) of the phthalocyanine ring are studied by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The calculated structural parameters and simulated electronic absorption and IR spectra are compared with the X-ray crystallography structures and the experimentally observed electronic absorption and IR spectra of the similar molecules, and good agreement between the calculated and experimental results is found. The substitution of the methoxyl or methylthio groups at the nonperipheral positions of the phthalocyanine ring has obvious effects on the molecular structure and spectroscopic properties of the metal-free phthalocyanine. Nonperipheral substitution has a more significant influence than peripheral substitution. The substitution effect increases with an increase in the number of substituents. The methylthio group shows more significant influence than the methoxyl group, despite the stronger electron-donating property of the methoxyl group than the methylthio group. The octa-methylthio-substituted metal-free phthalocyanine compounds have nonplanar structures whose low-lying occupied molecular orbitals and electronic absorption spectra are significantly changed by the substituents. The present systematical study will be helpful for understanding the relationship between structures and properties in phthalocyanine compounds and designing phthalocyanines with typical properties.

  6. Identification of catalytic sites for oxygen reduction and oxygen evolution in N-doped graphene materials: Development of highly efficient metal-free bifunctional electrocatalyst.

    PubMed

    Yang, Hong Bin; Miao, Jianwei; Hung, Sung-Fu; Chen, Jiazang; Tao, Hua Bing; Wang, Xizu; Zhang, Liping; Chen, Rong; Gao, Jiajian; Chen, Hao Ming; Dai, Liming; Liu, Bin

    2016-04-01

    Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are critical to renewable energy conversion and storage technologies. Heteroatom-doped carbon nanomaterials have been reported to be efficient metal-free electrocatalysts for ORR in fuel cells for energy conversion, as well as ORR and OER in metal-air batteries for energy storage. We reported that metal-free three-dimensional (3D) graphene nanoribbon networks (N-GRW) doped with nitrogen exhibited superb bifunctional electrocatalytic activities for both ORR and OER, with an excellent stability in alkaline electrolytes (for example, KOH). For the first time, it was experimentally demonstrated that the electron-donating quaternary N sites were responsible for ORR, whereas the electron-withdrawing pyridinic N moieties in N-GRW served as active sites for OER. The unique 3D nanoarchitecture provided a high density of the ORR and OER active sites and facilitated the electrolyte and electron transports. As a result, the as-prepared N-GRW holds great potential as a low-cost, highly efficient air cathode in rechargeable metal-air batteries. Rechargeable zinc-air batteries with the N-GRW air electrode in a two-electrode configuration exhibited an open-circuit voltage of 1.46 V, a specific capacity of 873 mAh g(-1), and a peak power density of 65 mW cm(-2), which could be continuously charged and discharged with an excellent cycling stability. Our work should open up new avenues for the development of various carbon-based metal-free bifunctional electrocatalysts of practical significance. PMID:27152333

  7. Identification of catalytic sites for oxygen reduction and oxygen evolution in N-doped graphene materials: Development of highly efficient metal-free bifunctional electrocatalyst

    PubMed Central

    Yang, Hong Bin; Miao, Jianwei; Hung, Sung-Fu; Chen, Jiazang; Tao, Hua Bing; Wang, Xizu; Zhang, Liping; Chen, Rong; Gao, Jiajian; Chen, Hao Ming; Dai, Liming; Liu, Bin

    2016-01-01

    Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are critical to renewable energy conversion and storage technologies. Heteroatom-doped carbon nanomaterials have been reported to be efficient metal-free electrocatalysts for ORR in fuel cells for energy conversion, as well as ORR and OER in metal-air batteries for energy storage. We reported that metal-free three-dimensional (3D) graphene nanoribbon networks (N-GRW) doped with nitrogen exhibited superb bifunctional electrocatalytic activities for both ORR and OER, with an excellent stability in alkaline electrolytes (for example, KOH). For the first time, it was experimentally demonstrated that the electron-donating quaternary N sites were responsible for ORR, whereas the electron-withdrawing pyridinic N moieties in N-GRW served as active sites for OER. The unique 3D nanoarchitecture provided a high density of the ORR and OER active sites and facilitated the electrolyte and electron transports. As a result, the as-prepared N-GRW holds great potential as a low-cost, highly efficient air cathode in rechargeable metal-air batteries. Rechargeable zinc-air batteries with the N-GRW air electrode in a two-electrode configuration exhibited an open-circuit voltage of 1.46 V, a specific capacity of 873 mAh g−1, and a peak power density of 65 mW cm−2, which could be continuously charged and discharged with an excellent cycling stability. Our work should open up new avenues for the development of various carbon-based metal-free bifunctional electrocatalysts of practical significance. PMID:27152333

  8. Metal-Free Oxidative Nitration of α-Carbon of Carbonyls Leads to One-Pot Synthesis of Thiohydroximic Acids from Acetophenones.

    PubMed

    Dighe, Shashikant U; Mukhopadhyay, Sushobhan; Priyanka, Kumari; Batra, Sanjay

    2016-09-01

    A metal-free nitration of the α-C-H to carbonyl in propiophenones was achieved with I2/NaNO2 in the presence of an oxidant in dimethyl sulfoxide (DMSO) as the medium. Conversely under similar conditions, reaction of acetophenones produced thiohydroximic acids via a radical-based cascade event which involves oxidative nitration of the α-carbon to a carbonyl followed by Michael addition of the thiomethyl group from DMSO and subsequent rearrangement. Besides DMSO, the scope of the reaction encompasses other symmetrical and unsymmetrical dialkylsulfoxides. PMID:27541178

  9. Dithiafulvenyl unit as a new donor for high-efficiency dye-sensitized solar cells: synthesis and demonstration of a family of metal-free organic sensitizers.

    PubMed

    Guo, Kunpeng; Yan, Keyou; Lu, Xiaoqing; Qiu, Yongcai; Liu, Zhike; Sun, Jianwei; Yan, Feng; Guo, Wenyue; Yang, Shihe

    2012-05-01

    This work identifies the dithiafulvenyl unit as an excellent electron donor for constructing D-π-A-type metal-free organic sensitizers of dye-sensitized solar cells (DSCs). Synthesized and tested are three sensitizers all with this donor and a cyanoacrylic acid acceptor but differing in the phenyl (DTF-C1), biphenyl (DTF-C2), and phenyl-thiopheneyl-phenyl π-bridges (DTF-C3). Devices based on these dyes exhibit a dramatically improved performance with the increasing π-bridge length, culminating with DTF-C3 in η = 8.29% under standard global AM 1.5 illumination.

  10. A surprising substituent effect provides a superior boronic acid catalyst for mild and metal-free direct Friedel-Crafts alkylations and prenylations of neutral arenes.

    PubMed

    Ricardo, Carolynne L; Mo, Xiaobin; McCubbin, J Adam; Hall, Dennis G

    2015-03-01

    The development of more general and efficient catalytic processes for Friedel-Crafts alkylations is an important objective of interest toward the production of pharmaceuticals and commodity chemicals. Herein, 2,3,4,5-tetrafluorophenylboronic acid was identified as a potent air- and moisture-tolerant metal-free catalyst that significantly improves the scope of direct Friedel-Crafts alkylations of a variety of slightly activated and neutral arenes, including polyarenes, with allylic and benzylic alcohols. This method also provides a simple alternative for the direct installation of prenyl units commonly found in naturally occurring arenes. Alkylations with benzylic alcohols occur under exceptionally mild conditions. PMID:25678266

  11. Decoration of size-tunable CuO nanodots on TiO2 nanocrystals for noble metal-free photocatalytic H2 production

    NASA Astrophysics Data System (ADS)

    Moon, Geon Dae; Joo, Ji Bong; Lee, Ilkeun; Yin, Yadong

    2014-09-01

    We report a simple yet effective approach for the decoration of the TiO2 nanocrystal surface with size-tunable CuO nanodots for high-performance noble metal-free photocatalytic H2 production. Modification with polyacrylic acid enables the surface of TiO2 nanocrystals to be selectively deposited with Cu(OH)2 nanodots, which can be subsequently converted to CuO through dehydration without changing their morphologies. UV irradiation of the nanocomposite solution in the presence of a hole scavenger produces photogenerated electrons which reduce CuO to metallic Cu nanodots, making them effective co-catalysts in a role similar to Pt for promoting photocatalytic H2 production. Due to the considerably high work function of Cu, the formation of a metal-semiconductor Schottky junction induces efficient charge separation and transfer. As a result, the TiO2 nanocrystals decorated with an optimal amount of CuO nanodots (1.7 wt%) could reach ~50% of the photocatalytic activity achievable by the Pt-TiO2 counterparts (1 wt%), clearly demonstrating the great potential of such composite catalysts for efficient noble metal-free photocatalytic H2 production.We report a simple yet effective approach for the decoration of the TiO2 nanocrystal surface with size-tunable CuO nanodots for high-performance noble metal-free photocatalytic H2 production. Modification with polyacrylic acid enables the surface of TiO2 nanocrystals to be selectively deposited with Cu(OH)2 nanodots, which can be subsequently converted to CuO through dehydration without changing their morphologies. UV irradiation of the nanocomposite solution in the presence of a hole scavenger produces photogenerated electrons which reduce CuO to metallic Cu nanodots, making them effective co-catalysts in a role similar to Pt for promoting photocatalytic H2 production. Due to the considerably high work function of Cu, the formation of a metal-semiconductor Schottky junction induces efficient charge separation and transfer. As a

  12. Transition Metal Free Intermolecular Direct Oxidative C-N Bond Formation to Polysubstituted Pyrimidines Using Molecular Oxygen as the Sole Oxidant.

    PubMed

    Guo, Wei; Li, Chunsheng; Liao, Jianhua; Ji, Fanghua; Liu, Dongqing; Wu, Wanqing; Jiang, Huanfeng

    2016-07-01

    Various polysubstituted pyrimidines are smoothly formed via a base-promoted intermolecular oxidation C-N bond formation of allylic C(sp(3))-H and vinylic C(sp(2))-H of allyllic compounds with amidines using O2 as the sole oxidant. This protocol features protecting group free nitrogen sources, good functional group tolerance, high atom economy, and environmental advantages.

  13. Transition-metal-free synthesis of aryl-substituted tert-butyl ynol ethers through addition/elimination substitution at an sp centre.

    PubMed

    Gray, Vincent J; Slater, Ben; Wilden, Jonathan D

    2012-12-01

    Nucleophilic attack of an alkoxide on an alkynyl sulfonamide leads to displacement of the sulfonamide at the sp centre and isolation of the ynol ether in good yield in a single operation. The mechanistic pathway has been probed by the use of coordinating additives, (13)C-labelling experiments and ab initio calculations, which indicated that an addition/elimination mechanism is in operation. PMID:23086681

  14. Expendable second stage reusable space shuttle booster. Volume 1: Executive summary

    NASA Technical Reports Server (NTRS)

    1971-01-01

    The development of an expendable second stage for use with a reusable space shuttle booster is discussed. The configuration of a low-cost, reusable multipurpose space transportation system for the 1980 time period is presented. A system capable of economically placing payloads in earth orbit which are larger and heavier than can be carried in the shuttle orbiter cargo bay is defined. The ESS/reusable shuttle system is complementary to the space shuttle system and provides mission flexibility to permit economical expansion of the overall space program.

  15. Arcjet Testing and Thermal Model Development for Multilayer Felt Reusable Surface Insulation

    NASA Technical Reports Server (NTRS)

    Milos, Frank S.; Scott, Carl Douglas; Papa, Steven V.

    2012-01-01

    Felt Reusable Surface Insulation was used extensively on leeward external surfaces of the Shuttle Orbiter, where the material is reusable for temperatures up to 670 K. For application on leeward surfaces of the Orion Multi-Purpose Crew Vehicle, where predicted temperatures reach 1620 K, the material functions as a pyrolyzing conformal ablator. An arcjet test series was conducted to assess the performance of multilayer Felt Reusable Surface Insulation at high temperatures, and a thermal-response, pyrolysis, and ablation model was developed. Model predictions compare favorably with the arcjet test data

  16. Launch cost analyses for reusable space transportation systems (Sänger II)

    NASA Astrophysics Data System (ADS)

    Koelle, Dietrich E.

    With the revival of studies for more economic fully reusable launch vehicles on both sides of the Atlantic, cost estimation analyses become of major importance. This is due to the fact that the essential cost reduction expected by fully reusable launch systems need to be substantiated for the justification of the development effort. The TRANSCOST model developed in the 1970-1983 period for launch vehicle cost analyses dealt mainly with expendable launch vehicles. This paper shows updated material and CERs for launch cost including fabrication and operations cost for future reusable and winged systems, such as Sänger II with the ETHV hypersonic manned winged upper stage.

  17. Nitrogen-Doped Carbon Nanoparticle-Carbon Nanofiber Composite as an Efficient Metal-Free Cathode Catalyst for Oxygen Reduction Reaction.

    PubMed

    Panomsuwan, Gasidit; Saito, Nagahiro; Ishizaki, Takahiro

    2016-03-23

    Metal-free nitrogen-doped carbon materials are currently considered at the forefront of potential alternative cathode catalysts for the oxygen reduction reaction (ORR) in fuel cell technology. Despite numerous efforts in this area over the past decade, rational design and development of a new catalyst system based on nitrogen-doped carbon materials via an innovative approach still present intriguing challenges in ORR catalysis research. Herein, a new kind of nitrogen-doped carbon nanoparticle-carbon nanofiber (NCNP-CNF) composite with highly efficient and stable ORR catalytic activity has been developed via a new approach assisted by a solution plasma process. The integration of NCNPs and CNFs by the solution plasma process can lead to a unique morphological feature and modify physicochemical properties. The NCNP-CNF composite exhibits a significantly enhanced ORR activity through a dominant four-electron pathway in an alkaline solution. The enhancement in ORR activity of NCNP-CNF composite can be attributed to the synergistic effects of good electron transport from highly graphitized CNFs as well as abundance of exposed catalytic sites and meso/macroporosity from NCNPs. More importantly, NCNP-CNF composite reveals excellent long-term durability and high tolerance to methanol crossover compared with those of a commercial 20 wt % supported on Vulcan XC-72. We expect that NCNP-CNF composite prepared by this synthetic approach can be a promising metal-free cathode catalyst candidate for ORR in fuel cells and metal-air batteries. PMID:26908214

  18. Three-dimensional nitrogen doped holey reduced graphene oxide framework as metal-free counter electrodes for high performance dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Yu, Mei; Zhang, Jindan; Li, Songmei; Meng, Yanbing; Liu, Jianhua

    2016-03-01

    Three-dimensional nitrogen doped holey reduced graphene oxide framework (NHGF) with hierarchical porosity structure was developed as high-performance metal-free counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). With plenty of exposed active sites, efficient electron and ion transport pathways as well as a high surface hydrophilicity, NHGF-CE exhibits good electrocatalytic performances for I- /I3- redox couple and a low charge transfer resistance (Rct). The Rct of NHGF-CE is 1.46 Ω cm2, which is much lower than that of Pt-CE (4.02 Ω cm2). The DSSC with NHGF-CE reaches a power conversion efficiency of 5.56% and a fill factor of 65.5%, while those of the DSSC with Pt-CE are only 5.45% and 62.3%, respectively. The achievement of the highly efficient 3D structure presents a potential way to fabricate low-cost and metal-free counter electrodes with excellent performance.

  19. Molecular Dynamics Simulations of Two Tandem Octarepeats from the Mammalian Prion Protein: Fully Cu2+-bound and Metal-Free Forms

    PubMed Central

    Pushie, M. Jake; Vogel, Hans J.

    2007-01-01

    Molecular dynamics simulations have been conducted on a model fragment (Ac-PHGGGWGQPHGGGW-NH2) of the prion protein octarepeat domain, both in the Cu2+-bound and metal-free forms. The copper-bound models are based on the consensus structure of the core Cu2+-binding site of an individual octarepeat, relevant to the fully Cu2+-occupied prion protein octarepeat region. The model peptides contain Cu2+ bound through a His imidazole ring and two deprotonated amide N-atoms in the peptide backbone supplied by the following two Gly residues. Both the copper-bound and metal-free models have been simulated with the OPLS all-atom force field with the GROMACS molecular dynamics package. These simulations, with two tandem copper-binding sites, represent the minimum model necessary to observe potential structuring between the copper-binding sites in the octarepeat region. The GWGQ residues constitute a flexible linker region that predominantly adopts a turn, serving to bring adjacent His residues into close proximity. The consequent formation of stable structures demonstrates that the copper-bound octarepeat region allows the copper-coordinating sites to come into van der Waals contact, packing into particular orientations to further stabilize the bend in the GWGQ linker region. PMID:17704169

  20. Self-Healing Nanocomposites for Reusable Composite Cryotanks

    NASA Technical Reports Server (NTRS)

    Eberly, Daniel; Ou, Runqing; Karcz, Adam; Skandan, Ganesh

    2013-01-01

    Composite cryotanks, or composite overwrapped pressure vessels (COPVs), offer advantages over currently used aluminum-lithium cryotanks, particularly with respect to weight savings. Future NASA missions are expected to use COPVs in spaceflight propellant tanks to store fuels, oxidizers, and other liquids for launch and space exploration vehicles. However, reliability, reparability, and reusability of the COPVs are still being addressed, especially in cryogenic temperature applications; this has limited the adoption of COPVs in reusable vehicle designs. The major problem with composites is the inherent brittleness of the epoxy matrix, which is prone to microcrack formation, either from exposure to cryogenic conditions or from impact from different sources. If not prevented, the microcracks increase gas permeation and leakage. Accordingly, materials innovations are needed to mitigate microcrack damage, and prevent damage in the first place, in composite cryotanks. The self-healing technology being developed is capable of healing the microcracks through the use of a novel engineered nanocomposite, where a uniquely designed nanoparticle additive is incorporated into the epoxy matrix. In particular, this results in an enhancement in the burst pressure after cryogenic cycling of the nanocomposite COPVs, relative to the control COPVs. Incorporating a novel, self-healing, epoxy-based resin into the manufacture of COPVs allows repeatable self-healing of microcracks to be performed through the simple application of a low-temperature heat source. This permits COPVs to be reparable and reusable with a high degree of reliability, as microcracks will be remediated. The unique phase-separated morphology that was imparted during COPV manufacture allows for multiple self-healing cycles. Unlike single-target approaches where one material property is often improved at the expense of another, robustness has been introduced to a COPV by a combination of a modified resin and

  1. Reusable plasmonic aptasensors: using a single nanoparticle to establish a calibration curve and to detect analytes.

    PubMed

    Guo, Longhua; Kim, Dong-Hwan

    2011-07-01

    We demonstrate plasmonic aptasensors that allow a single nanoparticle (NP) to generate a calibration curve and to detect analytes. The proposed reusable aptasensors have significant advantages over conventional single-NP based assays in terms of sensitivity and reproducibility.

  2. Segment Specification for the Payload Segment of the Reusable Reentry Satellite: Rodent Module Version

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The Reusable Reentry Satellite (RRS) System is composed of the payload segment (PS), vehicle segment (VS), and mission support (MS) segments. This specification establishes the performance, design, development, and test requirements for the RRS Rodent Module (RM).

  3. Reusable Solid Rocket Motor Nozzle Joint-4 Thermal Analysis

    NASA Technical Reports Server (NTRS)

    Clayton, J. Louie

    2001-01-01

    This study provides for development and test verification of a thermal model used for prediction of joint heating environments, structural temperatures and seal erosions in the Space Shuttle Reusable Solid Rocket Motor (RSRM) Nozzle Joint-4. The heating environments are a result of rapid pressurization of the joint free volume assuming a leak path has occurred in the filler material used for assembly gap close out. Combustion gases flow along the leak path from nozzle environment to joint O-ring gland resulting in local heating to the metal housing and erosion of seal materials. Analysis of this condition was based on usage of the NASA Joint Pressurization Routine (JPR) for environment determination and the Systems Improved Numerical Differencing Analyzer (SINDA) for structural temperature prediction. Model generated temperatures, pressures and seal erosions are compared to hot fire test data for several different leak path situations. Investigated in the hot fire test program were nozzle joint-4 O-ring erosion sensitivities to leak path width in both open and confined joint geometries. Model predictions were in generally good agreement with the test data for the confined leak path cases. Worst case flight predictions are provided using the test-calibrated model. Analysis issues are discussed based on model calibration procedures.

  4. Multiple Changes to Reusable Solid Rocket Motors, Identifying Hidden Risks

    NASA Technical Reports Server (NTRS)

    Greenhalgh, Phillip O.; McCann, Bradley Q.

    2003-01-01

    The Space Shuttle Reusable Solid Rocket Motor (RSRM) baseline is subject to various changes. Changes are necessary due to safety and quality improvements, environmental considerations, vendor changes, obsolescence issues, etc. The RSRM program has a goal to test changes on full-scale static test motors prior to flight due to the unique RSRM operating environment. Each static test motor incorporates several significant changes and numerous minor changes. Flight motors often implement multiple changes simultaneously. While each change is individually verified and assessed, the potential for changes to interact constitutes additional hidden risk. Mitigating this risk depends upon identification of potential interactions. Therefore, the ATK Thiokol Propulsion System Safety organization initiated the use of a risk interaction matrix to identify potential interactions that compound risk. Identifying risk interactions supports flight and test motor decisions. Uncovering hidden risks of a full-scale static test motor gives a broader perspective of the changes being tested. This broader perspective compels the program to focus on solutions for implementing RSRM changes with minimal/mitigated risk. This paper discusses use of a change risk interaction matrix to identify test challenges and uncover hidden risks to the RSRM program.

  5. Orbiting Depot and Reusable Lander for Lunar Transportation

    NASA Technical Reports Server (NTRS)

    Petro, Andrew

    2009-01-01

    A document describes a conceptual transportation system that would support exploratory visits by humans to locations dispersed across the surface of the Moon and provide transport of humans and cargo to sustain one or more permanent Lunar outpost. The system architecture reflects requirements to (1) minimize the amount of vehicle hardware that must be expended while maintaining high performance margins and (2) take advantage of emerging capabilities to produce propellants on the Moon while also enabling efficient operation using propellants transported from Earth. The system would include reusable single- stage lander spacecraft and a depot in a low orbit around the Moon. Each lander would have descent, landing, and ascent capabilities. A crew-taxi version of the lander would carry a pressurized crew module; a cargo version could carry a variety of cargo containers. The depot would serve as a facility for storage and for refueling with propellants delivered from Earth or propellants produced on the Moon. The depot could receive propellants and cargo sent from Earth on a variety of spacecraft. The depot could provide power and orbit maintenance for crew vehicles from Earth and could serve as a safe haven for lunar crews pending transport back to Earth.

  6. Note: Reliable and reusable ultrahigh vacuum optical viewports

    NASA Astrophysics Data System (ADS)

    Arora, P.; Gupta, A. Sen

    2012-04-01

    We report a simple technique for the realization of ultrahigh vacuum optical viewports. The technique relies on using specially designed thin copper knife-edges and using a thin layer of Vacseal® on tip of the knife-edges between the optical flat and the ConFlat® (CF) flange. The design of the windows is such that it gives uniform pressure on the flat without breaking it. The assembled window is a complete unit, which can be mounted directly onto a CF flange of the vacuum chamber. It can be removed and reused without breaking the window seal. The design is reliable as more than a dozen such windows have survived several bake out and cooling cycles and have been leak tested up to 10-11 Torr l/s level with a commercial Helium leak detector. The advantages of this technique are ease of assembly and leak proof sealing that survives multiple temperature cycling making the windows reliable and reusable.

  7. Dynamics sensor validation for reusable launch vehicle propulsion.

    SciTech Connect

    Herzog, J. P.

    1998-05-27

    Expert Microsystems teamed with Argonne National Laboratory (ANL), a DOE contractor, to develop an innovative dynamics sensor validation system under a Small Business Technology Transfer (STTR) Phase I contract with NASA. The project improves launch vehicle mission safety and system dependability by enabling rapid development and cost effective maintenance of embeddable real-time software to reliably detect process-critical sensor failures. The project focused on verifying the feasibility of two innovative software methods developed by ANL to provide high fidelity sensor data validation for nuclear power generating stations, the Sequential Probability Ratio Test (SPRT) algorithm and the Multivariate State Estimation Technique (MSET) algorithm, as core elements of a commercial Dynamics Sensor Validation System (DSVS). The research verified that ANL algorithms enable highly reliable data validation for high frequency Space Shuttle Main Engine (SSME) dynamics sensors, such as accelerometers and strain gauges. Phase I culminated in production of a prototype run-time module which validates SSME flight accelerometer data with very high reliability. The resulting sensor validation development system is widely applicable to reusable launch vehicle (RLV) and ground support control and monitoring systems.

  8. Robust adaptive backstepping control for reentry reusable launch vehicles

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Wu, Zhong; Du, Yijiang

    2016-09-01

    During the reentry process of reusable launch vehicles (RLVs), the large range of flight envelope will not only result in high nonlinearities, strong coupling and fast time-varying characteristics of the attitude dynamics, but also result in great uncertainties in the atmospheric density, aerodynamic coefficients and environmental disturbances, etc. In order to attenuate the effects of these problems on the control performance of the reentry process, a robust adaptive backstepping control (RABC) strategy is proposed for RLV in this paper. This strategy consists of two-loop controllers designed via backstepping method. Both the outer and the inner loop adopt a robust adaptive controller, which can deal with the disturbances and uncertainties by the variable-structure term with the estimation of their bounds. The outer loop can track the desired attitude by the design of virtual control-the desired angular velocity, while the inner one can track the desired angular velocity by the design of control torque. Theoretical analysis indicates that the closed-loop system under the proposed control strategy is globally asymptotically stable. Even if the boundaries of the disturbances and uncertainties are unknown, the attitude can track the desired value accurately. Simulation results of a certain RLV demonstrate the effectiveness of the control strategy.

  9. Reusable Launch Vehicle Control In Multiple Time Scale Sliding Modes

    NASA Technical Reports Server (NTRS)

    Shtessel, Yuri; Hall, Charles; Jackson, Mark

    2000-01-01

    A reusable launch vehicle control problem during ascent is addressed via multiple-time scaled continuous sliding mode control. The proposed sliding mode controller utilizes a two-loop structure and provides robust, de-coupled tracking of both orientation angle command profiles and angular rate command profiles in the presence of bounded external disturbances and plant uncertainties. Sliding mode control causes the angular rate and orientation angle tracking error dynamics to be constrained to linear, de-coupled, homogeneous, and vector valued differential equations with desired eigenvalues placement. Overall stability of a two-loop control system is addressed. An optimal control allocation algorithm is designed that allocates torque commands into end-effector deflection commands, which are executed by the actuators. The dual-time scale sliding mode controller was designed for the X-33 technology demonstration sub-orbital launch vehicle in the launch mode. Simulation results show that the designed controller provides robust, accurate, de-coupled tracking of the orientation angle command profiles in presence of external disturbances and vehicle inertia uncertainties. This is a significant advancement in performance over that achieved with linear, gain scheduled control systems currently being used for launch vehicles.

  10. Space shuttle orbit maneuvering engine reusable thrust chamber program

    NASA Technical Reports Server (NTRS)

    Senneff, J. M.

    1975-01-01

    Reusable thrust chamber and injector concepts were evaluated for the space shuttle orbit maneuvering engine (OME). Parametric engine calculations were carried out by computer program for N2O4/amine, LOX/amine and LOX/hydrocarbon propellant combinations for engines incorporating regenerative cooled and insulated columbium thrust chambers. The calculation methods are described including the fuel vortex film cooling method of combustion gas temperature control, and performance prediction. A method of acceptance of a regeneratively cooled heat rejection reduction using a silicone oil additive was also demonstrated by heated tube heat transfer testing. Regeneratively cooled thrust chamber operation was also demonstrated where the injector was characterized for the OME application with a channel wall regenerative thrust chamber. Bomb stability testing of the demonstration chambers/injectors demonstrated recovery for the nominal design of acoustic cavities. Cavity geometry changes were also evaluated to assess their damping margin. Performance and combustion stability was demonstrated of the originally developed 10 inch diameter combustion pattern operating in an 8 inch diameter thrust chamber.

  11. Predictor-Corrector Entry Guidance for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Youssef, Hussein; Chowdhry, Rajiv; Lee, Howard; Zimmerman, Curtis; Brandon, Larry (Technical Monitor)

    2001-01-01

    An online entry guidance algorithm has been developed using a predictor-corrector approach. The algorithm is designed for the Reusable Launch Vehicle (RLV) and is demonstrated by using, the X-33 model. The objective of the design is to handle widely dispersed entry conditions and deliver the vehicle at the Terminal Area Energy Management (TAEM) interface box within an acceptable tolerance and without violating any of the vehicle physical constraints. Combination of several control variables is used in testing the performance and computational requirement of the algorithm. The control variables are the bank angle, angle-of-attack and the time for roll reversal. The bank angle and angle-of-attack profiles are the nominal profiles plus the perturbations in each direction. The initial guess of the bank profile is a 45 degrees bank angle with reversal at 360 seconds from liftoff. A six-element state vector is propagated to the TAEM interface box through the integration of the equations of motion (EOM). Altitude, heading and range errors are computed between the desired and the achieved state at the TAEM interface. These errors are used to correct the initial guess of the control variables. This process is repeated until the errors meet an acceptable level at the TAEM interface. Several numerical optimization methods are used to evaluate the convergent property of the predictor-predictor methodology. Successful results are demonstrated using the X-33 model.

  12. Characterization of a reusable PRESAGE® 3D dosimeter

    NASA Astrophysics Data System (ADS)

    Juang, T.; Adamovics, J.; Oldham, M.

    2015-01-01

    This study investigates a reusable PRESAGE® 3D dosimeter (Presage-RU), which would improve cost-effectiveness and facilitate wider implementation of comprehensive, high resolution 3D dosimetry. Small (1x1x4.5 cm) and large (8 cm diameter, 4.5 cm length) sample dosimeters were irradiated multiple times to characterize dose response (i.e. radiation-induced change in optical density (ΔOD)), optical clearing rate, and dose distribution stability. Presage- RU exhibited an initial dose response sensitivity of 0.0119 ΔOD/(cm-Gy), a reduction in response with subsequent irradiations, and a small, permanent ΔOD (~1-6% of initial signal) following each irradiation. Dosimeters optically cleared at an exponential rate (average T1/2 = 24.8±3.6 h), and were effectively cleared after ~5-8 days. 3D gamma analysis (3%/3mm, 10% dose threshold) of a 4-field box plan applied to the large dosimeter showed good agreement following initial irradiation (96.6% passing), but a reduction in passing rate (89.1% passing) with subsequent irradiation. Further study is warranted to fully assess and quantify the performance of Presage-RU for repeat irradiations.

  13. Reusable fiber optic immunofluorosensor for rapid detection of pesticides

    NASA Astrophysics Data System (ADS)

    Anis, Nabil A.; Valdes, James J.; Thompson, Roy G.; Menking, Darrell E.; Wong, Rosie B.; Eldefrawi, Mohyee E.

    1993-05-01

    Quartz fibers coated with acetylcholinesterase (AChE) or antibody (Ab) are used as biosensors utilizing total reflectance fluorescence for the rapid detection of pesticides. The enzyme biosensor was constructed by immobilizing fluorescein isothiocyanate (FITC)-tagged eel electric organ AChE on quartz fibers. The fluorescent signal was generated by hydrolysis of acetylcholine (ACh) that is present in the perfusate. Organophosphate (OP) and carbamate anticholinesterase (AntiChE) insecticides inhibited AChE and reduced the fluorescent quenching resulting from AChE hydrolysis. A parathion biosensor was constructed by immobilizing casein-parathion on the quartz fibers, that bound rabbit antiparathion antibody. The optical signal was generated by perfusing the fibers with fluorescein-labeled goat antirabbit IgG. Free parathion inhibited the binding of antiparathion Abs and reduced the optical signal and provided the basis for detection of parathion. Another immunosensor developed detected the herbicide PursuitR by utilizing the reversible binding of a fluorescein-Pursuit derivative to antiPursuit Abs immobilized on the fiber. Unlabeled Pursuit competed effectively and displaced the bound fluorescent compound in a dose-dependent manner. The sensor discriminated effectively between Pursuit-like and structurally unrelated herbicides. The immunosensor offers the advantage of continuous monitoring, ease of operation, speed of detection, low cost, stability, specificity, matrix transparency, and reusability.

  14. Nonlinear Control of a Reusable Rocket Engine for Life Extension

    NASA Technical Reports Server (NTRS)

    Lorenzo, Carl F.; Holmes, Michael S.; Ray, Asok

    1998-01-01

    This paper presents the conceptual development of a life-extending control system where the objective is to achieve high performance and structural durability of the plant. A life-extending controller is designed for a reusable rocket engine via damage mitigation in both the fuel (H2) and oxidizer (O2) turbines while achieving high performance for transient responses of the combustion chamber pressure and the O2/H2 mixture ratio. The design procedure makes use of a combination of linear and nonlinear controller synthesis techniques and also allows adaptation of the life-extending controller module to augment a conventional performance controller of the rocket engine. The nonlinear aspect of the design is achieved using non-linear parameter optimization of a prescribed control structure. Fatigue damage in fuel and oxidizer turbine blades is primarily caused by stress cycling during start-up, shutdown, and transient operations of a rocket engine. Fatigue damage in the turbine blades is one of the most serious causes for engine failure.

  15. Reusability study with organic vapor air-purifying respirator cartridges

    SciTech Connect

    Wood, G.O.; Kissane, R.

    1997-11-01

    The question often arises about the reusability of organic vapor adsorption beds, such as air- purifying respirator cartridges, after periods of storage without use (airflow). The extremes of practice are: (1) use once and discard or (2) reuse multiple times assuming the protection is still afforded. The goal is to develop data and a model to provide guidance to decide when reuse is acceptable. They have studied the loss of protection of a commercial organic vapor cartridge after storage for varying periods of time. Three vapors (ethyl acetate, methylene chloride, and hexane) were individually loaded onto test cartridges using a breathing pump. Extents of loading, times of loading, and vapor concentrations were varied. After selected periods of storage the cartridges were again challenged with the same vapor concentration. The increases in concentration of a vapor in the effluent air (simulated breaths) from a cartridge immediately upon reuse depended on the storage period, the extent of loading during initial use, the volatility of the vapor, and the water vapor adsorbed, but not much on the vapor concentration.

  16. Estimating reusability of organic air-purifying respirator cartridges.

    PubMed

    Wood, Gerry O; Snyder, Jay L

    2011-10-01

    Reuse of organic vapor air-purifying respirator cartridges after a job or shift can provide economy and energy savings. However, standards and manufacturers' guidance discourage reuse, presumably due to a lack of quantitative objective exposure and use information. Storage and simulated reuse laboratory studies and modeling have been done to provide such information. Two important parameters of breakthrough curves, midpoint time (related to adsorption capacity) and midpoint slope (related to adsorption rate), have been shown to be unchanged during storage for reuse. Extrapolations to smaller breakthrough concentrations and times can be made from this reference breakthrough and time. Significant step increases in breakthrough concentration upon cartridge reuse have been observed in some cases. Values of immediate breakthrough concentrations upon reuse (IBURs) have been measured and correlated. The Dubinin/Radushkevich adsorption isotherm equation has been used to estimate maximum IBURs, which depend on many factors, including conditions and duration of first use. An empirical equation describing rate of approach to maximum IBUR as a function of storage time has been developed to provide intermediate IBUR estimates, which are also very dependent on the vapor identity and extent of first-use loading. Using these equations, IBUR estimates with appropriate safety factors can be compared with the allowable breakthrough concentration to help the Industrial Hygienist make reusability decisions. PMID:21936700

  17. First Stage of a Highly Reliable Reusable Launch System

    NASA Technical Reports Server (NTRS)

    Kloesel, Kurt J.; Pickrel, Jonathan B.; Sayles, Emily L.; Wright, Michael; Marriott, Darin; Holland, Leo; Kuznetsov, Stephen

    2009-01-01

    Electromagnetic launch assist has the potential to provide a highly reliable reusable first stage to a space access system infrastructure at a lower overall cost. This paper explores the benefits of a smaller system that adds the advantages of a high specific impulse air-breathing stage and supersonic launch speeds. The method of virtual specific impulse is introduced as a tool to emphasize the gains afforded by launch assist. Analysis shows launch assist can provide a 278-s virtual specific impulse for a first-stage solid rocket. Additional trajectory analysis demonstrates that a system composed of a launch-assisted first-stage ramjet plus a bipropellant second stage can provide a 48-percent gross lift-off weight reduction versus an all-rocket system. The combination of high-speed linear induction motors and ramjets is identified, as the enabling technologies and benchtop prototypes are investigated. The high-speed response of a standard 60 Hz linear induction motor was tested with a pulse width modulated variable frequency drive to 150 Hz using a 10-lb load, achieving 150 mph. A 300-Hz stator-compensated linear induction motor was constructed and static-tested to 1900 lbf average. A matching ramjet design was developed for use on the 300-Hz linear induction motor.

  18. A generalized reusable guidance algorithm for optimal aerobraking

    NASA Technical Reports Server (NTRS)

    Dukeman, G. A.

    1992-01-01

    A practical real-time guidance algorithm was developed for guiding aerobraking vehicles in such a way that the maximum heating rate, the maximum structural loads, and the post-aeropass delta-V requirements (for post-aeropass orbit insertion) are all minimized. The algorithm is general and reusable in the sense that a minimum of assumptions are made, thus minimizing the number of gains and mission-dependent parameters that must be laboriously determined prior to a particular mission. A particularly interesting feature is that inplane guidance performance is tuned by simply adjusting one mission-dependent parameter, the bank margin; similarly, the out-of-plane guidance performance is turned by simply adjusting a plane controller time constant. Other objectives in the algorithm development are simplicity, efficiency, and ease of use. The algorithm is developed for, but not necessarily restricted to, a single pass mission and a trimmed vehicle with a bank angle modulation as the method of trajectory control. Guidance performance is demonstrated via results obtained using this algorithm integrated into an aerobraking test-bed program. Comparisons are made with numerical results from a version of the aerobraking guidance algorithm that was to be flown onboard NASA's aeroassist flight experiment (AFE) vehicle. Promising results are obtained with a minimum of development effort.

  19. A microfabricated gecko-inspired controllable and reusable dry adhesive

    NASA Astrophysics Data System (ADS)

    Chary, Sathya; Tamelier, John; Turner, Kimberly

    2013-02-01

    Geckos utilize a robust reversible adhesive to repeatedly attach and detach from a variety of vertical and inverted surfaces, using structurally anisotropic micro- and nano-scale fibrillar structures. These fibers, when suitably articulated, are able to control the real area of contact and thereby generate high-to-low van der Waals forces. Key characteristics of the natural system include highly anisotropic adhesion and shear forces for controllable attachment, a high adhesion to initial preload force ratio (μ‧) of 8-16, lack of inter-fiber self-adhesion, and operation over more than 30 000 cycles without loss of adhesion performance. A highly reusable synthetic adhesive has been developed using tilted polydimethylsiloxane (PDMS) half-cylinder micron-scale fibers, retaining up to 77% of the initial value over 10 000 repeated test cycles against a flat glass puck. In comparison with other gecko-inspired adhesives tested over 10 000 cycles or more thus far, this paper reports the highest value of μ‧, along with a large shear force of ˜78 kPa, approaching the 88-226 kPa range of gecko toes. The anisotropic adhesion forces are close to theoretical estimates from the Kendall peel model, quantitatively showing how lateral shearing articulation in a manner similar to the gecko may be used to obtain adhesion anisotropy with synthetic fibers using a combination of tilt angle and anisotropic fiber geometry.

  20. Aspect-Oriented Design with Reusable Aspect Models

    NASA Astrophysics Data System (ADS)

    Kienzle, Jörg; Al Abed, Wisam; Fleurey, Franck; Jézéquel, Jean-Marc; Klein, Jacques

    The idea behind Aspect-Oriented Modeling (AOM) is to apply aspect-oriented techniques to (software) models with the aim of modularizing crosscutting concerns. This can be done within different modeling notations, at different levels of abstraction, and at different moments during the software development process. This paper demonstrates the applicability of AOM during the software design phase by presenting parts of an aspect-oriented design of a crisis management system. The design solution proposed in this paper is based on the Reusable Aspect Models (RAM) approach, which allows a modeler to express the structure and behavior of a complex system using class, state and sequence diagrams encapsulated in several aspect models. The paper describes how the model of the "create mission" functionality of the server backend can be decomposed into 23 inter-dependent aspect models. The presentation of the design is followed by a discussion on the lessons learned from the case study. Next, RAM is compared to 8 other AOM approaches according to 6 criteria: language, concern composition, asymmetric and symmetric composition, maturity, and tool support. To conclude the paper, a discussion section points out the features of RAM that specifically support reuse.

  1. Chemical switch based reusable dual optoelectronic sensor for nitrite.

    PubMed

    Vishnuvardhan, V; Kala, R; Prasada Rao, T

    2008-08-01

    An optical sensor was developed for sensing of nitrite based on the monotonous decrease in absorbance of Rhodamine 6G at 525 nm (the absorbance maximum of dye) with increasing concentration of nitrite. This sensor also permits naked eye detection. Various parameters like concentrations of sulphuric acid and Rhodamine 6G, response time and stability were varied and optimal conditions are reported. Under these conditions, the developed sensor enables the determination of nitrite in the concentration range 0-12.18 micromol L(-1). The nitrite response is selective as 60-2.5x10(5) fold amounts of several anions and cations have no deleterious effect. The addition of nitrite to Rhodamine 6G dye causes hypsochromic shift from 525 to 385 nm while several other anions like I(-), SCN(-), ClO(4)(-), [HgI(4)](2-) and [Zn (SCN)(4)](2-) showed a bathochromatic shift from 525 to 575 nm. The sequential addition of nitrite and sulphamic to Rhodamine 6G in 0.75 mol L(-1) sulphuric acid solution results in switching of "ON" and "OFF" absorbance. The time elapse and concentration of sulphamic acid required for chemical switching was also established. Similar "ON" and "OFF" switching behaviour was observed in fluorescence studies also. This enabled the design and development of reusable chemical switch based dual optoelectronic sensor, for monitoring of traces of nitrite in environmental and food samples. The plausible mechanism for above switching behaviour is also proposed.

  2. Lockheed Martin approach to a Reusable Launch Vehicle (RLV)

    NASA Astrophysics Data System (ADS)

    Elvin, John D.

    1996-03-01

    This paper discusses Lockheed Martin's perspective on the development of a cost effective Reusable Launch Vehicle (RLV). Critical to a successful Single Stage To Orbit (SSTO) program are; an economic development plan sensitive to fiscal constraints; a vehicle concept satisfying present and future US launch needs; and an operations concept commensurate with a market driven program. Participation in the economic plan by government, industry, and the commercial sector is a key element of integrating our development plan and funding profile. The RLV baseline concept design, development evolution and several critical trade studies illustrate the superior performance achieved by our innovative approach to the problem of SSTO. Findings from initial aerodynamic and aerothermodynamic wind tunnel tests and trajectory analyses on this concept confirm the superior characteristics of the lifting body shape combined with the Linear Aerospike rocket engine. This Aero Ballistic Rocket (ABR) concept captures the essence of The Skunk Works approach to SSTO RLV technology integration and system engineering. These programmatic and concept development topics chronicle the key elements to implementing an innovative market driven next generation RLV.

  3. Reusable, adhesiveless and arrayed in-plane microfluidic interconnects

    NASA Astrophysics Data System (ADS)

    Lo, R.; Meng, E.

    2011-05-01

    A reusable, arrayed interconnect capable of providing multiple simultaneous connections to and from a microfluidic device in an in-plane manner without the use of adhesives is presented. This method uses a 'pin-and-socket' design in which an SU-8 anchor houses multiple polydimethysiloxane septa (the socket) that each receive a syringe needle (the pin). A needle array containing multiple commercially available 33G (203 µm outer diameter) needles (up to eight) spaced either 2.54 or 1 mm (center-to-center) pierces the septa to access the microfluidic device interior. Finite element modeling and photoelastic stress experiments were used to determine the stress distribution during needle insertion; these results guided the SU-8 septa housing and septa design. The impact of needle diameter, needle tip style, insertion rate and number of needles on pre-puncture, post-puncture and removal forces was characterized. Pressurized connections to SU-8 channel systems withstood up to 62 kPa of pressurized water and maintained 25 kPa of pressurized water for over 24 h. The successful integration and functionality of the interconnect design with surface micromachined Parylene C microchannels was verified using Rhodamine B dye. Dual septa systems to access a single microchannel were demonstrated. Arrayed interconnects were compatible with integrated microfluidic systems featuring electrochemical sensors and actuators.

  4. Advanced aviation technology for reusable launch vehicle improvement

    NASA Astrophysics Data System (ADS)

    Filatyev, Alexander S.; Buzuluk, Valentin; Yanova, Olga; Ryabukha, Nikolay; Petrov, Andrey

    2014-07-01

    The new project of a spacecraft launcher (SL) with reusable winged 1st stage boosters (RWB) developed by Khrunichev Space Center is considered. Since SL is operated in the atmosphere only, it makes sense to employ technologies which may be new for the space industry but have been applied in aviation. Particular attention is given to RWB power-off reentry to a suitable airfield along the ascent lane instead of direct flying back to the launch site after staging, as well as a profound controlled RWB reconfiguration before reentry. The paper talks about results of integrated analysis of aerodynamics, through-optimized trajectories and masses of the RWB and SL, as well as an expert assessment of the maintenance costs sufficient to substantiate effectiveness of the recovery airfields solution in terms of the payload mass, launch reliability, and operational costs reduction. Four RWB layouts are considered, including ones with a delta- and unswept tilting wing, with and without subsonic air-breathing engines, and the original RWB-transformer. Objective peculiarities of the RWB recovery are highlighted for Russian and Kourou cosmodromes.

  5. Air liquefaction and enrichment system propulsion in reusable launch vehicles

    SciTech Connect

    Bond, W.H.; Yi, A.C.

    1994-07-01

    A concept is shown for a fully reusable, Earth-to-orbit launch vehicle with horizontal takeoff and landing, employing an air-turborocket for low speed and a rocket for high-speed acceleration, both using liquid hydrogen for fuel. The turborocket employs a modified liquid air cycle to supply the oxidizer. The rocket uses 90% pure liquid oxygen as its oxidizer that is collected from the atmosphere, separated, and stored during operation of the turborocket from about Mach 2 to 5 or 6. The takeoff weight and the thrust required at takeoff are markedly reduced by collecting the rocket oxidizer in-flight. This article shows an approach and the corresponding technology needs for using air liquefaction and enrichment system propulsion in a single-stage-to-orbit (SSTO) vehicle. Reducing the trajectory altitude at the end of collection reduces the wing area and increases payload. The use of state-of-the-art materials, such as graphite polyimide, in a direct substitution for aluminum or aluminum-lithium alloy, is critical to meet the structure weight objective for SSTO. Configurations that utilize `waverider` aerodynamics show great promise to reduce the vehicle weight. 5 refs.

  6. Facile in Situ Preparation of Graphitic-C₃N₄@carbon Paper As an Efficient Metal-Free Cathode for Nonaqueous Li-O₂ Battery.

    PubMed

    Yi, Jin; Liao, Kaiming; Zhang, Chaofeng; Zhang, Tao; Li, Fujun; Zhou, Haoshen

    2015-05-27

    The rechargeable Li-O2 batteries with high theoretical specific energy are considered to be a promising energy storage system for electric vehicle application. Because of the prohibitive cost, limited supply, and weak durability of precious metals, the developments of novel metal-free catalysts become significant. Herein, the graphitic-carbon nitride@carbon papers have been produced by a facile in situ method and explored as cathodes for Li-O2 batteries, which manifest considerable electrocatalytic activity toward oxygen reduction reaction and oxygen evolution reaction in nonaqueous electrolytes because of their improved electronic conductivity and high nitrogen content. The assembled Li-O2 batteries using graphitic-carbon nitride@carbon papers as cathodes deliver good rate capability and cycling stability with a capacity retention of more than 100 cycles.

  7. Sulfur and Nitrogen Codoped Carbon Tubes as Bifunctional Metal-Free Electrocatalysts for Oxygen Reduction and Hydrogen Evolution in Acidic Media.

    PubMed

    Sun, Tao; Wu, Qiang; Jiang, Yufei; Zhang, Zhiqi; Du, Lingyu; Yang, Lijun; Wang, Xizhang; Hu, Zheng

    2016-07-18

    The technological combination of fuel cells with water electrolysis is an ideal approach to address the problems of growing energy needs and environmental pollution, in which exploring cheap and stable electrocatalysts is the main challenge. Sulfur and nitrogen codoped carbon tubes (SNCTs), prepared by annealing the mixture of amorphous carbonaceous tubes and cysteine, are found to be active bifunctional metal-free electrocatalysts for both oxygen reduction and hydrogen evolution in acidic medium. The optimized SNCT catalyst exhibits a record high onset potential of 851 mV (vs. RHE) for oxygen reduction and concurrent a low overpotential of 76 mV for hydrogen evolution, with superior stability and low cost. The SNCT electrocatalyst could have great potential in proton exchange membrane fuel cells and water splitting devices. PMID:27150558

  8. A Highly Active System for the Metal-Free Aerobic Photocyanation of Tertiary Amines with Visible Light: Application to the Synthesis of Tetraponerines and Crispine A.

    PubMed

    Orejarena Pacheco, Julio Cesar; Lipp, Alexander; Nauth, Alexander M; Acke, Fabian; Dietz, Jule-Philipp; Opatz, Till

    2016-04-01

    A highly efficient metal-free catalytic system for the aerobic photocyanation of tertiary amines with visible light is reported. The use of air as terminal oxidant offers an improved safety profile compared with pure oxygen, the used compact fluorescent lamp (CFL) light sources are highly economical, and no halogenated solvents are required. This system not only proves to be effective for a wide variety of trialkylamines, pharmaceuticals, and alkaloids but remarkably also allows the lowest catalyst loading (0.00001 mol% or 0.1 ppm) ever reported for an organic dye. Bruylants reactions and C-alkylation/decyanations were performed on the obtained α-aminonitriles to demonstrate the postfunctionalization of complex molecules. The catalytic system is furthermore applied in the short and effective syntheses of the alkaloids (±)-crispine A and the tetraponerines T7 and T8.

  9. Easy conversion of protein-rich enoki mushroom biomass to a nitrogen-doped carbon nanomaterial as a promising metal-free catalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Guo, Chaozhong; Liao, Wenli; Li, Zhongbin; Sun, Lingtao; Chen, Changguo

    2015-09-01

    The search for low-cost, highly active, and stable catalysts to replace the Pt-based catalysts for oxygen reduction reaction (ORR) has recently become a topic of interest. Herein, we report a new strategy to design a nitrogen-doped carbon nanomaterial for use as a metal-free ORR catalyst based on facile pyrolysis of protein-rich enoki mushroom (Flammulina velutipes) biomass at 900 °C with carbon nanotubes as a conductive agent and inserting matrix. We found that various forms of nitrogen (nitrile, pyrrolic and graphitic) were incorporated into the carbon molecular skeleton of the product, which exhibited more excellent ORR electrocatalytic activity and better durability in alkaline medium than those in acidic medium. Remarkably, the ORR half-wave potential measured on our material was around 0.81 V in alkaline medium, slightly lower than that on the commercial 20 wt% Pt/C catalyst (0.86 V). Meanwhile, the ORR followed the desired 4-electron transfer mechanism involving the direct reduction pathway. The ORR performance was also markedly better than or at least comparable to the leading results in the literature based on biomass-derived carbon-based catalysts. Besides, we significantly proposed that the graphitic-nitrogen species that is most responsible for the ORR activity can function as the electrocatalytically active center for ORR, and the pyrrolic-nitrogen species can act as an effective promoter for ORR only. The results suggested a promising route based on economical and sustainable fungi biomass towards the large-scale production of valuable carbon nanomaterials as highly active and stable metal-free catalysts for ORR under alkaline conditions.The search for low-cost, highly active, and stable catalysts to replace the Pt-based catalysts for oxygen reduction reaction (ORR) has recently become a topic of interest. Herein, we report a new strategy to design a nitrogen-doped carbon nanomaterial for use as a metal-free ORR catalyst based on facile pyrolysis of

  10. Tuning the reactivity of an actor ligand for tandem CO2 and C-H activations: from spectator metals to metal-free.

    PubMed

    Annibale, Vincent T; Dalessandro, Daniel A; Song, Datong

    2013-10-30

    The 4,5-diazafluorenide ligand (L(-)) serves as an actor ligand in the formal insertion of CO2 into a C-H bond remote from the metal center. With the Ru(II) complex of L(-) as the starting point, Rh(III), Rh(I), and Cu(I) were used as spectator metal centers to tune the reactivity of the actor ligand toward CO2. In the case of Rh(III)-diazafluorenide a room temperature reversible activation of CO2 was observed, similar to the isoelectronic Ru(II) analogue. In the case of Rh(I)- and Cu(I)-diazafluorenide CO2 is trapped by the formation of dinuclear carboxylate complexes and diazafluorene (LH). The spectator metal center could even be replaced entirely with an organic group allowing for the first metal-free reversible tandem CO2 and C-H activation.

  11. Solar cells of metal-free phthalocyanine dispersed in polyvinyl carbazole. 1: Effects of the recrystallization of H2PC on cell characteristics

    NASA Technical Reports Server (NTRS)

    Shimura, M.; Baba, H.

    1983-01-01

    The development of an organic semiconductor solar cell and the effects of the recrystallization of metal free phthalocyanine (H2PC) on the characteristics of NESA/H2PC-PVK/Au sandwich cells were investigated. Alfa-H2PC sandwich cells showed photovoltage and photocurrent in a two direction opposite to that shown y as supplied H2PC cells, which consists mainly of beta-H2PC. Some difference was observed in the response times of the two cells. It is suggested that photocharacteristics change with the specific resistance of the H2PC, which is related to its crystal forms. In the cells with low resistance H2PC carriers are generated in H2PC by illumination, while in high resistance H2PC cells, carriers are generated in PVK which is sensitized with H2PC.

  12. Photovoltage and stability of an n-type silicon semiconductor coated with metal or metal-free phthalocyanine thin films in aqueous redox solutions

    SciTech Connect

    Nakato, Y.; Shioji, M.; Tsubomura, H.

    1981-06-11

    An n-type silicon (n-Si) semiconductor coated with an evaporated thin film of metal phthalocyanine (MPc) or metal-free phthalocyanine (H/sub 2/Pc) worked as a fairly stable photoanode in aqueous redox solutions. The photovoltage observed for a photocell, (n-Si/CuPc/Fe/sup 3 +//Fe/sup 2 +/ aqueous solution (pH 4.2) /Pt), was 0.50 V, only slightly less than that for a p-n junction Si photocell (approx. 0.6 V). The action spectrum was similar to that of a bare n-Si electrode, except for a depression caused by photoabsorption by the CuPc film in the red region. The above wet photocell has current-voltage characteristics better than those for a solid photocell, (n-Si/CuPc/Pd).

  13. Efficient metal-free oxygen reduction in alkaline medium on high-surface-area mesoporous nitrogen-doped carbons made from ionic liquids and nucleobases.

    PubMed

    Yang, Wen; Fellinger, Tim-Patrick; Antonietti, Markus

    2011-01-19

    Mesoporous nitrogen-doped carbon materials with high surface areas up to 1500 m(2) g(-1) were conveniently made by the carbonization of nucleobases dissolved in an all-organic ionic liquid (1-ethyl-3-methylimidazolium dicyanamide). Using hard templating with silica nanoparticles, this process yields high-surface-area nitrogen-doped carbon materials with nitrogen contents as high as 12 wt %, narrow mesopore size distribution of ca. 12 nm diameter, and local graphitic carbon structure. It is demonstrated that the resulting nitrogen-doped carbons show very high catalytic activity, even in the metal-free case in the oxygen reduction reaction (ORR) for fuel cells. Specifically, the as-prepared materials exhibit a low onset voltage for ORR in alkaline medium and a high methanol tolerance, compared with those of commercial 20 wt % Pt/C catalyst. We regard this as a first step toward an all-sustainable fuel cell, avoiding noble metals. PMID:21155583

  14. BF₃·OEt₂ mediated metal-free one-pot sequential multiple annulation cascade (SMAC) synthesis of complex and diverse tetrahydroisoquinoline fused hybrid molecules.

    PubMed

    Shinde, Anand H; Vidyacharan, Shinde; Sharada, Duddu S

    2016-03-28

    A highly efficient and distinct BF3·OEt2 mediated metal-free SMAC protocol for the synthesis of complex and diverse hybrid molecules viz. indazole fused tetrahydroisoquinolinoquinoxalines, and tetrahydroisoquinolinodiazepine has been developed. The transformation is based on sequential cascade processes involving 2H-indazole formation and deprotection Pictet-Spengler cyclization steps in one-pot fashion. The protocol demonstrates the utility of sequential multiple annulations in a cascade fashion. The present one-pot protocol uses the Solid State Melt Reaction (SSMR) strategy for the synthesis of the intermediate 2H-indazole. The method is operationally simple and represents a new approach for C-C, three C-N and N-N bond formation with a wide substrate scope. PMID:26935814

  15. A Highly Active System for the Metal-Free Aerobic Photocyanation of Tertiary Amines with Visible Light: Application to the Synthesis of Tetraponerines and Crispine A.

    PubMed

    Orejarena Pacheco, Julio Cesar; Lipp, Alexander; Nauth, Alexander M; Acke, Fabian; Dietz, Jule-Philipp; Opatz, Till

    2016-04-01

    A highly efficient metal-free catalytic system for the aerobic photocyanation of tertiary amines with visible light is reported. The use of air as terminal oxidant offers an improved safety profile compared with pure oxygen, the used compact fluorescent lamp (CFL) light sources are highly economical, and no halogenated solvents are required. This system not only proves to be effective for a wide variety of trialkylamines, pharmaceuticals, and alkaloids but remarkably also allows the lowest catalyst loading (0.00001 mol% or 0.1 ppm) ever reported for an organic dye. Bruylants reactions and C-alkylation/decyanations were performed on the obtained α-aminonitriles to demonstrate the postfunctionalization of complex molecules. The catalytic system is furthermore applied in the short and effective syntheses of the alkaloids (±)-crispine A and the tetraponerines T7 and T8. PMID:26929114

  16. Metal-Free Radical Haloazidation of Benzene-Tethered 1,7-Enynes Leading to Polyfunctionalized 3,4-Dihydroquinolin-2(1H)-ones.

    PubMed

    Wang, Ai-Fang; Zhu, Yi-Long; Wang, Shu-Liang; Hao, Wen-Juan; Li, Guigen; Tu, Shu-Jiang; Jiang, Bo

    2016-02-01

    A new cascade three-component haloazidation of benzene-tethered 1,7-enynes for the formation of biologically interesting azidylated 3,4-dihydroquinolin-2(1H)-ones has been achieved under mild and metal-free conditions using TMSN3 as a N3 source and NIS (or NBS or NCS) as a halogen source. The reaction pathway involves in situ-generated azidyl radical-triggered α,β-conjugated addition/6-exo-dig cyclization/radical coupling sequence, resulting in successive multiple bond-forming events, including carbon-nitrogen, carbon-carbon, and carbon-halogen bonds to rapidly construct complex heterocyclic molecules. Furthermore, the resulting products would be useful building blocks in the discovery of lead compounds and other biologically interesting N3-containing heterocycles.

  17. Aggregation-Induced Emission Active Metal-Free Chemosensing Platform for Highly Selective Turn-On Sensing and Bioimaging of Pyrophosphate Anion.

    PubMed

    Gogoi, Abhijit; Mukherjee, Sandipan; Ramesh, Aiyagari; Das, Gopal

    2015-07-01

    We report the synthesis of a metal-free chemosensor for highly selective sensing of pyrophosphate (PPi) anion in physiological medium. The novel phenylbenzimidazole functionalized imine containing chemosensor (L; [2,6-bis(((4-(1H-benzo[d]imidazol-2-yl)phenyl)imino) methyl)-4 methyl phenol]) could sense PPi anion through "turn-on" colorimetric and fluorimetric responses in a very competitive environment. The overall sensing mechanism is based on the aggregation-induced emission (AIE) phenomenon. Moreover, a real time in-field device application was demonstrated by sensing PPi in paper strips coated with L. Interestingly, detection of intracellular PPi ions in model human cells could also be possible by fluorescence microscopic studies without any toxicity to these cells. PMID:26059015

  18. Surface Functionalization of g-C3 N4 : Molecular-Level Design of Noble-Metal-Free Hydrogen Evolution Photocatalysts.

    PubMed

    Chen, Yin; Lin, Bin; Yu, Weili; Yang, Yong; Bashir, Shahid M; Wang, Hong; Takanabe, Kazuhiro; Idriss, Hicham; Basset, Jean-Marie

    2015-07-13

    A stable noble-metal-free hydrogen evolution photocatalyst based on graphite carbon nitride (g-C3 N4 ) was developed by a molecular-level design strategy. Surface functionalization was successfully conducted to introduce a single nickel active site onto the surface of the semiconducting g-C3 N4 . This catalyst family (with less than 0.1 wt % of Ni) has been found to produce hydrogen with a rate near to the value obtained by using 3 wt % platinum as co-catalyst. This new catalyst also exhibits very good stability under hydrogen evolution conditions, without any evidence of deactivation after 24 h. PMID:26073972

  19. Surface Functionalization of g-C3 N4 : Molecular-Level Design of Noble-Metal-Free Hydrogen Evolution Photocatalysts.

    PubMed

    Chen, Yin; Lin, Bin; Yu, Weili; Yang, Yong; Bashir, Shahid M; Wang, Hong; Takanabe, Kazuhiro; Idriss, Hicham; Basset, Jean-Marie

    2015-07-13

    A stable noble-metal-free hydrogen evolution photocatalyst based on graphite carbon nitride (g-C3 N4 ) was developed by a molecular-level design strategy. Surface functionalization was successfully conducted to introduce a single nickel active site onto the surface of the semiconducting g-C3 N4 . This catalyst family (with less than 0.1 wt % of Ni) has been found to produce hydrogen with a rate near to the value obtained by using 3 wt % platinum as co-catalyst. This new catalyst also exhibits very good stability under hydrogen evolution conditions, without any evidence of deactivation after 24 h.

  20. Unsymmetrical 1,1-diborated multisubstituted sp(3)-carbons formed via a metal-free concerted-asynchronous mechanism.

    PubMed

    Cuenca, Ana B; Cid, Jessica; García-López, Diego; Carbó, Jorge J; Fernández, Elena

    2015-10-01

    We have experimentally proved the unsymmetrical 1,1-diboration of diazo compounds, formed in situ from aldehydes and cyclic and non-cyclic ketones, in the absence of any transition metal complex. The heterolytic cleavage of the mixed diboron reagent, Bpin-Bdan, and the formation of two geminal C-Bpin and C-Bdan bonds has been rationalised based on DFT calculations to occur via a concerted-asynchronous mechanism. Diastereoselection is attained on substituted cyclohexanones and DFT studies provide understanding on the origin of the selectivity. The alkoxide-assisted selective deborylation of Bpin from multisubstituted sp(3)-carbon and generation of a Bdan stabilized carbanion, easily conducts a selective protodeboronation sequence.

  1. Artist concept of X-33 and Reusable Launch Vehicle (RLV)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This artist's rendering depicts the NASA/Lockheed Martin X-33 technology demonstrator alongside the Venturestar, a Single-Stage-To-Orbit (SSTO) Reusable Launch Vehicle (RLV). The X-33, a half-scale prototype for the Venturestar, is scheduled to be flight tested in 1999. NASA's Dryden Flight Research Center, Edwards, California, plays a key role in the development and flight testing of the X-33. The RLV technology program is a cooperative agreement between NASA and industry. The goal of the RLV technology program is to enable signifigant reductions in the cost of access to space, and to promote the creation and delivery of new space services and other activities that will improve U.S. economic competitiveness. NASA Headquarter's Office of Space Access and Technology is overseeing the RLV program, which is being managed by the RLV Office at NASA's Marshall Space Flight Center, located in Huntsville, Alabama. The X-33 was a wedged-shaped subscale technology demonstrator prototype of a potential future Reusable Launch Vehicle (RLV) that Lockheed Martin had dubbed VentureStar. The company had hoped to develop VentureStar early this century. Through demonstration flight and ground research, NASA's X-33 program was to provide the information needed for industry representatives such as Lockheed Martin to decide whether to proceed with the development of a full-scale, commercial RLV program. A full-scale, single-stage-to-orbit RLV was to dramatically increase reliability and lower costs of putting a pound of payload into space, from the current figure of $10,000 to $1,000. Reducing the cost associated with transporting payloads in Low Earth Orbit (LEO) by using a commercial RLV was to create new opportunities for space access and significantly improve U.S. economic competitiveness in the world-wide launch marketplace. NASA expected to be a customer, not the operator, of the commercial RLV. The X-33 design was based on a lifting body shape with two revolutionary 'linear

  2. Simple and reusable picoinjector for liquid delivery via nanofluidics approach

    NASA Astrophysics Data System (ADS)

    Li, Shunbo; Cao, Wenbin; Hui, Yu Sanna; Wen, Weijia

    2014-03-01

    Precise control of sample volume is one of the most important functions in lab-on-a-chip (LOC) systems, especially for chemical and biological reactions. The common approach used for liquid delivery involves the employment of capillaries and microstructures for generating a droplet which has a volume in the nanoliter or picoliter range. Here, we report a novel approach for constructing a picoinjector which is based on well-controlled electroosmotic (EO) flow to electrokinetically drive sample solutions. This picoinjector comprises an array of interconnected nanochannels for liquid delivery. Such technique for liquid delivery has the advantages of well-controlled sample volume and reusable nanofluidic chip, and it was reported for the first time. In the study of the pumping process for this picoinjector, the EO flow rate was determined by the intensity of the fluorescent probe. The influence of ion concentration in electrolyte solutions over the EO flow rate was also investigated and discussed. The application of this EO-driven picoinjector for chemical reactions was demonstrated by the reaction between Fluo-4 and calcium chloride with the reaction cycle controlled by the applied square waves of different duty cycles. The precision of our device can reach down to picoliter per second, which is much smaller than that of most existing technologies. This new approach, thus, opens further possibilities of adopting nanofluidics for well-controlled chemical reactions with particular applications in nanoparticle synthesis, bimolecular synthesis, drug delivery, and diagnostic testing. PACS: 85.85.+ j; 87.15.hj; 82.39.Wj

  3. Optimization of Turbine Blade Design for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Shyy, Wei

    1998-01-01

    To facilitate design optimization of turbine blade shape for reusable launching vehicles, appropriate techniques need to be developed to process and estimate the characteristics of the design variables and the response of the output with respect to the variations of the design variables. The purpose of this report is to offer insight into developing appropriate techniques for supporting such design and optimization needs. Neural network and polynomial-based techniques are applied to process aerodynamic data obtained from computational simulations for flows around a two-dimensional airfoil and a generic three- dimensional wing/blade. For the two-dimensional airfoil, a two-layered radial-basis network is designed and trained. The performances of two different design functions for radial-basis networks, one based on the accuracy requirement, whereas the other one based on the limit on the network size. While the number of neurons needed to satisfactorily reproduce the information depends on the size of the data, the neural network technique is shown to be more accurate for large data set (up to 765 simulations have been used) than the polynomial-based response surface method. For the three-dimensional wing/blade case, smaller aerodynamic data sets (between 9 to 25 simulations) are considered, and both the neural network and the polynomial-based response surface techniques improve their performance as the data size increases. It is found while the relative performance of two different network types, a radial-basis network and a back-propagation network, depends on the number of input data, the number of iterations required for radial-basis network is less than that for the back-propagation network.

  4. Project SPARC: Space-Based Aeroassisted Reusable Craft

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Future United States' space facilities include a Space Station in low Earth orbit (LEO) and a Geosynchronous Operations Support Center, or GeoShack, in geosynchronous orbit (GEO). One possible mode of transfer between the two orbits is an aerobraking vehicle. When traveling from GEO to LEO, the Earth's atmosphere can be used to aerodynamically reduce the velocity of the vehicle, which reduces the amount of propulsive change in velocity required for the mission. An aerobrake is added to the vehicle for this purpose, but the additional mass increases propellant requirements. This increase must not exceed the amount of propellant saved during the aeropass. The design and development of an aerobraking vehicle that will transfer crew and cargo between the Space Station and GeoShack is examined. The vehicle is referred to as Project SPARC, a SPace-based Aeroassisted Reusable Craft. SPARC consists of a removable 45 ft diameter aerobrake, two modified Pratt and Whitney Advanced Expander Engines with a liquid oxygen/liquid hydrogen propellant, a removable crew module with a maximum capacity of five, and standard sized payload bays providing a maximum payload capacity of 28,000 lbm. The aerobrake, a rigid, ellipsoidally blunted elliptical cone, provides lift at zero angle-of-attack due to a 73 deg rake angle, and is covered with a flexible multi-layer thermal protection system. Maximum dry mass of the vehicle without payload is 20,535 lbm, and the maximum propellant requirement is 79,753 lbm at an oxidizer to fuel ratio of 6/1. Key advantages of SPARC include its capability to meet mission changes, and its removable aerobrake and crew module.

  5. Expendable second stage reusable space shuttle booster. Volume 2: Technical summary. Book 1: Expendable second stage/reusable booster system definition

    NASA Technical Reports Server (NTRS)

    1971-01-01

    A systems analysis of the expendable second stage/reusable booster system is presented. The subjects discussed are: (1) mission/system requirements, (2) spacecraft performance, (3) trajectories, (4) aerodynamics, (5) stability and control, (6) loads, (7) heating, and (8) acoustic environment.

  6. Crystal structure of a periplasmic solute binding protein in metal-free, intermediate and metal-bound states from Candidatus Liberibacter asiaticus.

    PubMed

    Sharma, Nidhi; Selvakumar, Purushotham; Bhose, Sumit; Ghosh, Dilip Kumar; Kumar, Pravindra; Sharma, Ashwani Kumar

    2015-03-01

    The Znu system, a member of ABC transporter family, is critical for survival and pathogenesis of Candidatus Liberibacter asiaticus (CLA). Two homologues of this system have been identified in CLA. Here, we report high resolution crystal structure of a periplasmic solute binding protein from second of the two gene clusters of Znu system in CLA (CLas-ZnuA2) in metal-free, intermediate and metal-bound states. CLas-ZnuA2 showed maximum sequence identity to the Mn/Fe-specific solute binding proteins (SBPs) of cluster A-I family. The overall fold of CLas-ZnuA2 is similar to the related cluster A-I family SBPs. The sequence and structure analysis revealed the unique features of CLas-ZnuA2. The comparison of CLas-ZnuA2 structure in three states showed that metal binding and release is facilitated by a large displacement along with a change in orientation of the side chain for one of the metal binding residue (His39) flipped away from metal binding site in metal-free form. The crystal structure captured in intermediate state of metal binding revealed the changes in conformation and interaction of the loop hosting His39 during the metal binding. A rigid body movement of C-domain along with partial unfolding of linker helix at its C-terminal during metal binding, as reported for PsaA, was not observed in CLas-ZnuA2. The present results suggest that despite showing maximum sequence identity to the Mn/Fe-specific SBPs, the mechanistic resemblance of CLas-ZnuA2 seems to be closer to Zn-specific SBPs of cluster A-I family.

  7. Edge-selenated graphene nanoplatelets as durable metal-free catalysts for iodine reduction reaction in dye-sensitized solar cells

    PubMed Central

    Ju, Myung Jong; Jeon, In-Yup; Kim, Hong Mo; Choi, Ji Il; Jung, Sun-Min; Seo, Jeong-Min; Choi, In Taek; Kang, Sung Ho; Kim, Han Seul; Noh, Min Jong; Lee, Jae-Joon; Jeong, Hu Young; Kim, Hwan Kyu; Kim, Yong-Hoon; Baek, Jong-Beom

    2016-01-01

    Metal-free carbon-based electrocatalysts for dye-sensitized solar cells (DSSCs) are sufficiently active in Co(II)/Co(III) electrolytes but are not satisfactory in the most commonly used iodide/triiodide (I−/I3−) electrolytes. Thus, developing active and stable metal-free electrocatalysts in both electrolytes is one of the most important issues in DSSC research. We report the synthesis of edge-selenated graphene nanoplatelets (SeGnPs) prepared by a simple mechanochemical reaction between graphite and selenium (Se) powders, and their application to the counter electrode (CE) for DSSCs in both I−/I3− and Co(II)/Co(III) electrolytes. The edge-selective doping and the preservation of the pristine graphene basal plane in the SeGnPs were confirmed by various analytical techniques, including atomic-resolution transmission electron microscopy. Tested as the DSSC CE in both Co(bpy)32+/3+ (bpy = 2,2′-bipyridine) and I−/I3− electrolytes, the SeGnP-CEs exhibited outstanding electrocatalytic performance with ultimately high stability. The SeGnP-CE–based DSSCs displayed a higher photovoltaic performance than did the Pt-CE–based DSSCs in both SM315 sensitizer with Co(bpy)32+/3+ and N719 sensitizer with I−/I3− electrolytes. Furthermore, the I3− reduction mechanism, which has not been fully understood in carbon-based CE materials to date, was clarified by an electrochemical kinetics study combined with density functional theory and nonequilibrium Green’s function calculations. PMID:27386557

  8. Metal-free g-C{sub 3}N{sub 4} photocatalyst by sulfuric acid activation for selective aerobic oxidation of benzyl alcohol under visible light

    SciTech Connect

    Zhang, Ligang; Liu, Di; Guan, Jing; Chen, Xiufang; Guo, Xingcui; Zhao, Fuhua; Hou, Tonggang; Mu, Xindong

    2014-11-15

    Highlights: • A novel visible-light-driven acid-modified g-C{sub 3}N{sub 4} was prepared. • The texture, electronic and surface property were tuned by acid modification. • Acid-modified g-C{sub 3}N{sub 4} shows much higher activity for photocatalytic activity. • Acid sites on the surface of g-C{sub 3}N{sub 4} favor efficient charge separation. - Abstract: In this work, modification of graphitic carbon nitride photocatalyst with acid was accomplished with a facile method through reflux in different acidic substances. The g-C{sub 3}N{sub 4}-based material was found to be a metal-free photocatalyst useful for the selective oxidation of benzyl alcohol with dioxygen as the oxidant under visible light irradiation. Acid modification had a significant influence on the photocatalytic performance of g-C{sub 3}N{sub 4}. Among all acid tested, sulfuric acid-modified g-C{sub 3}N{sub 4} showed the highest catalytic activity and gave benzaldehyde in 23% yield for 4 h under visible light irradiation, which was about 2.5 times higher than that of g-C{sub 3}N{sub 4}. The acid modification effectively improved surface area, reduced structural size, enlarged band gap, enhanced surface chemical state, and facilitated photoinduced charge separation, contributing to the enhanced photocatalytic activity. It is hoped that our work can open promising prospects for the utilization of metal free g-C{sub 3}N{sub 4}-based semiconductor as visible-light photocatalyst for selective organic transformation.

  9. Edge-selenated graphene nanoplatelets as durable metal-free catalysts for iodine reduction reaction in dye-sensitized solar cells.

    PubMed

    Ju, Myung Jong; Jeon, In-Yup; Kim, Hong Mo; Choi, Ji Il; Jung, Sun-Min; Seo, Jeong-Min; Choi, In Taek; Kang, Sung Ho; Kim, Han Seul; Noh, Min Jong; Lee, Jae-Joon; Jeong, Hu Young; Kim, Hwan Kyu; Kim, Yong-Hoon; Baek, Jong-Beom

    2016-06-01

    Metal-free carbon-based electrocatalysts for dye-sensitized solar cells (DSSCs) are sufficiently active in Co(II)/Co(III) electrolytes but are not satisfactory in the most commonly used iodide/triiodide (I(-)/I3 (-)) electrolytes. Thus, developing active and stable metal-free electrocatalysts in both electrolytes is one of the most important issues in DSSC research. We report the synthesis of edge-selenated graphene nanoplatelets (SeGnPs) prepared by a simple mechanochemical reaction between graphite and selenium (Se) powders, and their application to the counter electrode (CE) for DSSCs in both I(-)/I3 (-) and Co(II)/Co(III) electrolytes. The edge-selective doping and the preservation of the pristine graphene basal plane in the SeGnPs were confirmed by various analytical techniques, including atomic-resolution transmission electron microscopy. Tested as the DSSC CE in both Co(bpy)3 (2+/3+) (bpy = 2,2'-bipyridine) and I(-)/I3 (-) electrolytes, the SeGnP-CEs exhibited outstanding electrocatalytic performance with ultimately high stability. The SeGnP-CE-based DSSCs displayed a higher photovoltaic performance than did the Pt-CE-based DSSCs in both SM315 sensitizer with Co(bpy)3 (2+/3+) and N719 sensitizer with I(-)/I3 (-) electrolytes. Furthermore, the I3 (-) reduction mechanism, which has not been fully understood in carbon-based CE materials to date, was clarified by an electrochemical kinetics study combined with density functional theory and nonequilibrium Green's function calculations. PMID:27386557

  10. Easy conversion of protein-rich enoki mushroom biomass to a nitrogen-doped carbon nanomaterial as a promising metal-free catalyst for oxygen reduction reaction.

    PubMed

    Guo, Chaozhong; Liao, Wenli; Li, Zhongbin; Sun, Lingtao; Chen, Changguo

    2015-10-14

    The search for low-cost, highly active, and stable catalysts to replace the Pt-based catalysts for oxygen reduction reaction (ORR) has recently become a topic of interest. Herein, we report a new strategy to design a nitrogen-doped carbon nanomaterial for use as a metal-free ORR catalyst based on facile pyrolysis of protein-rich enoki mushroom (Flammulina velutipes) biomass at 900 °C with carbon nanotubes as a conductive agent and inserting matrix. We found that various forms of nitrogen (nitrile, pyrrolic and graphitic) were incorporated into the carbon molecular skeleton of the product, which exhibited more excellent ORR electrocatalytic activity and better durability in alkaline medium than those in acidic medium. Remarkably, the ORR half-wave potential measured on our material was around 0.81 V in alkaline medium, slightly lower than that on the commercial 20 wt% Pt/C catalyst (0.86 V). Meanwhile, the ORR followed the desired 4-electron transfer mechanism involving the direct reduction pathway. The ORR performance was also markedly better than or at least comparable to the leading results in the literature based on biomass-derived carbon-based catalysts. Besides, we significantly proposed that the graphitic-nitrogen species that is most responsible for the ORR activity can function as the electrocatalytically active center for ORR, and the pyrrolic-nitrogen species can act as an effective promoter for ORR only. The results suggested a promising route based on economical and sustainable fungi biomass towards the large-scale production of valuable carbon nanomaterials as highly active and stable metal-free catalysts for ORR under alkaline conditions.

  11. Commercial suborbital reusable launch vehicles: ushering in a new era for turbopause exploration (Invited)

    NASA Astrophysics Data System (ADS)

    Smith, H. T.

    2013-12-01

    Multiple companies are in the process of developing commercial suborbital reusable launch vehicles (sRLV's). While these companies originally targeted space tourism as the primary customer base, it is rapidly becoming apparent that this dramatic increase in low cost access to space could provide revolutionary opportunities for scientific research, engineering/instrument development and STEM education. These burgeoning capabilities will offer unprecedented opportunities regarding access to space with frequent low-cost access to the region of space from the ground to the boundary of near-Earth space at ~100 km. In situ research of this region is difficult because it is too high for aircraft and balloons and yet too low for orbital satellites and spacecraft. However, this region is very significant because it represents the tenuous boundary of Earth's Atmosphere and Space. It contains a critical portion of the atmosphere where the regime transitions from collisional to non-collisional physics and includes complex charged and neutral particle interactions. These new launch vehicles are currently designed for manned and unmanned flights that reach altitudes up to 110 km for 5K-500K per flight with payload capacity exceeding 600 kg. Considering the much higher cost per flight for a sounding rocket with similar capabilities, high flight cadence, and guaranteed return of payload, commercial spacecraft has the potential to revolutionize access to near space. This unprecedented access to space allows participation at all levels of research, engineering, education and the public at large. For example, one can envision a model where students can conduct complete end to end projects where they design, build, fly and analyze data from individual research projects for thousands of dollars instead of hundreds of thousands. Our community is only beginning to grasp the opportunities and impactions of these new capabilities but with operational flights anticipated in 2014, it is

  12. Payload Performance Analysis for a Reusable Two-Stage-to-Orbit Vehicle

    NASA Technical Reports Server (NTRS)

    Tartabini, Paul V.; Beaty, James R.; Lepsch, Roger A.; Gilbert, Michael G.

    2015-01-01

    This paper investigates a unique approach in the development of a reusable launch vehicle where, instead of designing the vehicle to be reusable from its inception, as was done for the Space Shuttle, an expendable two stage launch vehicle is evolved over time into a reusable launch vehicle. To accomplish this objective, each stage is made reusable by adding the systems necessary to perform functions such as thermal protection and landing, without significantly altering the primary subsystems and outer mold line of the original expendable vehicle. In addition, some of the propellant normally used for ascent is used instead for additional propulsive maneuvers after staging in order to return both stages to the launch site, keep loads within acceptable limits and perform a soft landing. This paper presents a performance analysis that was performed to investigate the feasibility of this approach by quantifying the reduction in payload capability of the original expendable launch vehicle after accounting for the mass additions, trajectory changes and increased propellant requirements necessary for reusability. Results show that it is feasible to return both stages to the launch site with a positive payload capability equal to approximately 50 percent of an equivalent expendable launch vehicle. Further discussion examines the ability to return a crew/cargo capsule to the launch site and presents technical challenges that would have to be overcome.

  13. New Approaches in Reusable Booster System Life Cycle Cost Modeling

    NASA Technical Reports Server (NTRS)

    Zapata, Edgar

    2013-01-01

    This paper presents the results of a 2012 life cycle cost (LCC) study of hybrid Reusable Booster Systems (RBS) conducted by NASA Kennedy Space Center (KSC) and the Air Force Research Laboratory (AFRL). The work included the creation of a new cost estimating model and an LCC analysis, building on past work where applicable, but emphasizing the integration of new approaches in life cycle cost estimation. Specifically, the inclusion of industry processes/practices and indirect costs were a new and significant part of the analysis. The focus of LCC estimation has traditionally been from the perspective of technology, design characteristics, and related factors such as reliability. Technology has informed the cost related support to decision makers interested in risk and budget insight. This traditional emphasis on technology occurs even though it is well established that complex aerospace systems costs are mostly about indirect costs, with likely only partial influence in these indirect costs being due to the more visible technology products. Organizational considerations, processes/practices, and indirect costs are traditionally derived ("wrapped") only by relationship to tangible product characteristics. This traditional approach works well as long as it is understood that no significant changes, and by relation no significant improvements, are being pursued in the area of either the government acquisition or industry?s indirect costs. In this sense then, most launch systems cost models ignore most costs. The alternative was implemented in this LCC study, whereby the approach considered technology and process/practices in balance, with as much detail for one as the other. This RBS LCC study has avoided point-designs, for now, instead emphasizing exploring the trade-space of potential technology advances joined with potential process/practice advances. Given the range of decisions, and all their combinations, it was necessary to create a model of the original model

  14. Reusable, Extensible High-Level Data-Distribution Concept

    NASA Technical Reports Server (NTRS)

    James, Mark; Zima, Hans; Diaconescua, Roxana

    2007-01-01

    A framework for high-level specification of data distributions in data-parallel application programs has been conceived. [As used here, distributions signifies means to express locality (more specifically, locations of specified pieces of data) in a computing system composed of many processor and memory components connected by a network.] Inasmuch as distributions exert a great effect on the performances of application programs, it is important that a distribution strategy be flexible, so that distributions can be adapted to the requirements of those programs. At the same time, for the sake of productivity in programming and execution, it is desirable that users be shielded from such error-prone, tedious details as those of communication and synchronization. As desired, the present framework enables a user to refine a distribution type and adjust it to optimize the performance of an application program and conceals, from the user, the low-level details of communication and synchronization. The framework provides for a reusable, extensible, data-distribution design, denoted the design pattern, that is independent of a concrete implementation. The design pattern abstracts over coding patterns that have been found to be commonly encountered in both manually and automatically generated distributed parallel programs. The following description of the present framework is necessarily oversimplified to fit within the space available for this article. Distributions are among the elements of a conceptual data-distribution machinery, some of the other elements being denoted domains, index sets, and data collections (see figure). Associated with each domain is one index set and one distribution. A distribution class interface (where "class" is used in the object-oriented-programming sense) includes operations that enable specification of the mapping of an index to a unit of locality. Thus, "Map(Index)" specifies a unit, while "LocalLayout(Index)" specifies the local address

  15. TPS Materials and Costs for Future Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Rasky, Dan J.; Milos, Frank S.; Squire, Tom H.; Arnold, James O. (Technical Monitor)

    2000-01-01

    There is considerable interest in developing new reusable launch vehicles (RLVs) for reducing the cost of transporting payload to and from orbit. This work reviews thirteen candidate thermal protection system (TPS) options currently available for RLVs. It is useful to begin with the current Shuttle TPS layout as a reference. The nose cap and wing leading edge , which reach the highest temperatures, are made of reinforced carbon-carbon (RCC) that is protected from oxidation by an external coating (about 0.020" thick) of silicon-carbide. Most of the windward surface is 9 lb/cubic ft ceramic tiles (LI-900) with a thin (about 0.012") coating of Reaction Cured Glass (RCG). The leeward side of the vehicle is covered largely by AFRSI, a quilted ceramic blanket, and FRSI, a polyamide felt. These four materials can be considered first generation reusable TPS. Since the time of the Shuttle design, considerable progress has been made advancing TPS technologies in terms of thermal performance, robustness, and cost. For each of the major systems, a second generation ceramic TPS has been developed, tested, and characterized. Metallic-based systems have also been developed. For applications requiring RCC in the past, advanced carbon-carbon (ACC) is now available. This material has better mechanical properties, somewhat higher temperature capability to 2900F and greatly increased oxidation resistance. New carbon fiber reinforced silicon-carbide matrix composites (C/SiCs) have shown additional improvement in properties over ACC with use temperatures to 3000F and above. For rigid tiles, NASA Ames has made two significant advancements. The first is a tile substrate called Alumina Enhanced Thermal Barrier, or AETB, that incorporates alumina fibers for improved dimensional stability at high temperatures, to 2600F and above. This material can be made to densities as low as 8 lb/cubic ft. The second is a coating preparation called Toughened Uni-piece Fibrous Insulation, or TUFT, that

  16. Hypervalent iodine(III)-induced oxidative [4+2] annulation of o-phenylenediamines and electron-deficient alkynes: direct synthesis of quinoxalines from alkyne substrates under metal-free conditions.

    PubMed

    Okumura, Sota; Takeda, Youhei; Kiyokawa, Kensuke; Minakata, Satoshi

    2013-10-18

    Hypervalent iodine(III)-induced oxidative [4+2] annulation of o-phenylenediamines and electron-deficient alkynes under metal-free conditions has been developed. The reaction allows for direct access to quinoxalines bearing two electron-withdrawing groups in an efficient manner.

  17. Geometries, Electronic Structures, And Spectral Properties Of Some Metal Free Phthalonitrile Derivatives For Enhancement Of The Dye Sensitized Solar Cells

    NASA Astrophysics Data System (ADS)

    Anbarasan, P. M.

    2010-08-01

    .80628, 5.60646, 7.7979 and 1.86216 (in a.u.), respectively. The frequencies of strongest IR absorption for 3, 4-Pyridinedicarbonitrile, 3-Aminophthalonitrile, 4-Aminophthalonitrile and 4-Methylphthalonitrile are 1614 cm-1, 290 cm-1, 387 cm-1 and 846 cm-1 and the frequencies of strongest Raman activity for 3, 4-Pyridinedicarbonitrile, 3-Aminophthalonitrile, 4-Aminophthalonitrile and 4-Methylphthalonitrile are 2345 cm-1, 2338 cm-1,2329 cm-1, 2337cm-1, respectively. The electronic absorption spectral features in visible and near-UV region were assigned based on the qualitative agreement to TDDFT calculations. The absorptions are all ascribed to π→π* transition. The three excited states with the lowest excited energies of 3, 4-Pyridinedicarbonitrile, 3-Aminophthalonitrile, 4-Aminophthalonitrile and 4-Methylphthalonitrile are photoinduced electron transfer processes that contributes sensitization of photo-to-current conversion processes. The interfacial electron transfer between semiconductor TiO2 electrode and dye sensitizer 3, 4- Pyridinedicarbonitrile, 3-Aminophthalonitrile, 4-Aminophthalonitrile and 4-Methylphthalonitrile is electron injection process from excited dyes as donor to the semiconductor conduction band. Based on the comparative analysis of geometries, electronic structures, and spectrum properties between 3, 4-Pyridinedicarbonitrile, 3-Aminophthalonitrile, 4-Aminophthalonitrile and 4-Methylphthalonitrile the role of amide and methyl groups in phthalonitrile is as follows: it enlarged the distance between electron donor group and semiconductor surface, and decreased the timescale of the electron injection rate, resulted in giving lower conversion efficiency. This indicates that the choice of the appropriate conjugate bridge in dye sensitizer is very important to enhance the performance of DSSC.

  18. Geometries, Electronic Structures, And Spectral Properties Of Some Metal Free Phthalonitrile Derivatives For Enhancement Of The Dye Sensitized Solar Cells

    SciTech Connect

    Anbarasan, P. M.

    2010-08-06

    .80628, 5.60646, 7.7979 and 1.86216 (in a.u.), respectively. The frequencies of strongest IR absorption for 3, 4-Pyridinedicarbonitrile, 3-Aminophthalonitrile, 4-Aminophthalonitrile and 4-Methylphthalonitrile are 1614 cm{sup -1}, 290 cm{sup -1}, 387 cm{sup -1} and 846 cm{sup -1} and the frequencies of strongest Raman activity for 3, 4-Pyridinedicarbonitrile, 3-Aminophthalonitrile, 4-Aminophthalonitrile and 4-Methylphthalonitrile are 2345 cm{sup -1}, 2338 cm{sup -1},2329 cm{sup -1}, 2337cm{sup -1}, respectively. The electronic absorption spectral features in visible and near-UV region were assigned based on the qualitative agreement to TDDFT calculations. The absorptions are all ascribed to {pi}{yields}{pi}* transition. The three excited states with the lowest excited energies of 3, 4-Pyridinedicarbonitrile, 3-Aminophthalonitrile, 4-Aminophthalonitrile and 4-Methylphthalonitrile are photoinduced electron transfer processes that contributes sensitization of photo-to-current conversion processes. The interfacial electron transfer between semiconductor TiO{sub 2} electrode and dye sensitizer 3, 4- Pyridinedicarbonitrile, 3-Aminophthalonitrile, 4-Aminophthalonitrile and 4-Methylphthalonitrile is electron injection process from excited dyes as donor to the semiconductor conduction band. Based on the comparative analysis of geometries, electronic structures, and spectrum properties between 3, 4-Pyridinedicarbonitrile, 3-Aminophthalonitrile, 4-Aminophthalonitrile and 4-Methylphthalonitrile the role of amide and methyl groups in phthalonitrile is as follows: it enlarged the distance between electron donor group and semiconductor surface, and decreased the timescale of the electron injection rate, resulted in giving lower conversion efficiency. This indicates that the choice of the appropriate conjugate bridge in dye sensitizer is very important to enhance the performance of DSSC.

  19. Magnetically-refreshable receptor platform structures for reusable nano-biosensor chips.

    PubMed

    Yoo, Haneul; Lee, Dong Jun; Cho, Dong-guk; Park, Juhun; Nam, Ki Wan; Cho, Young Tak; Park, Jae Yeol; Chen, Xing; Hong, Seunghun

    2016-01-29

    We developed a magnetically-refreshable receptor platform structure which can be integrated with quite versatile nano-biosensor structures to build reusable nano-biosensor chips. This structure allows one to easily remove used receptor molecules from a biosensor surface and reuse the biosensor for repeated sensing operations. Using this structure, we demonstrated reusable immunofluorescence biosensors. Significantly, since our method allows one to place receptor molecules very close to a nano-biosensor surface, it can be utilized to build reusable carbon nanotube transistor-based biosensors which require receptor molecules within a Debye length from the sensor surface. Furthermore, we also show that a single sensor chip can be utilized to detect two different target molecules simply by replacing receptor molecules using our method. Since this method does not rely on any chemical reaction to refresh sensor chips, it can be utilized for versatile biosensor structures and virtually-general receptor molecular species.

  20. Magnetically-refreshable receptor platform structures for reusable nano-biosensor chips

    NASA Astrophysics Data System (ADS)

    Yoo, Haneul; Lee, Dong Jun; Cho, Dong-guk; Park, Juhun; Nam, Ki Wan; Tak Cho, Young; Park, Jae Yeol; Chen, Xing; Hong, Seunghun

    2016-01-01

    We developed a magnetically-refreshable receptor platform structure which can be integrated with quite versatile nano-biosensor structures to build reusable nano-biosensor chips. This structure allows one to easily remove used receptor molecules from a biosensor surface and reuse the biosensor for repeated sensing operations. Using this structure, we demonstrated reusable immunofluorescence biosensors. Significantly, since our method allows one to place receptor molecules very close to a nano-biosensor surface, it can be utilized to build reusable carbon nanotube transistor-based biosensors which require receptor molecules within a Debye length from the sensor surface. Furthermore, we also show that a single sensor chip can be utilized to detect two different target molecules simply by replacing receptor molecules using our method. Since this method does not rely on any chemical reaction to refresh sensor chips, it can be utilized for versatile biosensor structures and virtually-general receptor molecular species.