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Sample records for catalysis sensing drug

  1. Mesoporous Silica Nanomaterials for Applications in Catalysis, Sensing, Drug Delivery and Gene Transfection

    Energy Technology Data Exchange (ETDEWEB)

    Radu, Daniela Rodica [Iowa State Univ., Ames, IA (United States)

    2004-01-01

    The central theme of this dissertation is represented by the versatility of mesoporous silica nanomaterials in various applications such as catalysis and bio-applications, with main focus on biological applications of Mesoporous Silica Nanospheres (MSN). The metamorphosis that we impose to these materials from catalysis to sensing and to drug and gene delivery is detailed in this dissertation. First, we developed a synthetic method that can fine tune the amount of chemically accessible organic functional groups on the pores surface of MSN by exploiting electrostatic and size matching between the cationic alkylammonium head group of the cetyltrimethylammonium bromide (CTAB) surfactant and various anionic organoalkoxysilane precursors at the micelle-water interface in a base-catalyzed condensation reaction of silicate. Aiming nature imitation, we demonstrated the catalytic abilities of the MSNs, We utilized an ethylenediamine functional group for chelating Cu2+ as a catalytic functional group anchored inside the mesopores. Thus, a polyalkynylene-based conducting polymer (molecular wire) was synthesized within the Cu-functionalized MSNs silica catalyst. For sensing applications, we have synthesized a poly(lactic acid) coated mesoporous silica nanosphere (PLA-MSN) material that serves as a fluorescence sensor system for detection of amino-containing neurotransmitters in neutral aqueous buffer. We exploited the mesoporosity of MSNs for encapsulating pharmaceutical drugs. We examined bio-friendly capping molecules such as polyamidoamine dendrimers of generations G2 to G4, to prevent the drug leaching. Next, the drug delivery system employed MSNs loaded with Doxorubicin, an anticancer drug. The results demonstrated that these nano-Trojan horses have ability to deliver Doxorubicin to cancer cells and induce their death. Finally, to demonstrate the potential of MSN as an universal cellular transmembrane nanovehicle, we anchored positively charged dendrimers on

  2. Mesoporous Silica Nanomaterials for Applications in Catalysis, Sensing, Drug Delivery and Gene Transfection

    Energy Technology Data Exchange (ETDEWEB)

    Daniela Rodica Radu

    2005-12-19

    The central theme of this dissertation is represented by the versatility of mesoporous silica nanomaterials in various applications such as catalysis and bio-applications, with main focus on biological applications of Mesoporous Silica Nanospheres (MSN). The metamorphosis that we impose to these materials from catalysis to sensing and to drug and gene delivery is detailed in this dissertation. First, we developed a synthetic method that can fine tune the amount of chemically accessible organic functional groups on the pores surface of MSN by exploiting electrostatic and size matching between the cationic alkylammonium head group of the cetyltrimethylammonium bromide (CTAB) surfactant and various anionic organoalkoxysilane precursors at the micelle-water interface in a base-catalyzed condensation reaction of silicate. Aiming nature imitation, we demonstrated the catalytic abilities of the MSNs, We utilized an ethylenediamine functional group for chelating Cu{sup 2+} as a catalytic functional group anchored inside the mesopores. Thus, a polyalkynylene-based conducting polymer (molecular wire) was synthesized within the Cu-functionalized MSNs silica catalyst. For sensing applications, we have synthesized a poly(lactic acid) coated mesoporous silica nanosphere (PLA-MSN) material that serves as a fluorescence sensor system for detection of amino-containing neurotransmitters in neutral aqueous buffer. We exploited the mesoporosity of MSNs for encapsulating pharmaceutical drugs. We examined bio-friendly capping molecules such as polyamidoamine dendrimers of generations G2 to G4, to prevent the drug leaching. Next, the drug delivery system employed MSNs loaded with Doxorubicin, an anticancer drug. The results demonstrated that these nano-Trojan horses have ability to deliver Doxorubicin to cancer cells and induce their death. Finally, to demonstrate the potential of MSN as an universal cellular transmembrane nanovehicle, we anchored positively charged dendrimers on the

  3. Catalysis and Sulfa Drug Resistance in Dihydropteroate Synthase

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Mi-Kyung; Wu, Yinan; Li, Zhenmei; Zhao, Ying; Waddell, M. Brett; Ferreira, Antonio M.; Lee, Richard E.; Bashford, Donald; White, Stephen W. (SJCH)

    2013-04-08

    The sulfonamide antibiotics inhibit dihydropteroate synthase (DHPS), a key enzyme in the folate pathway of bacteria and primitive eukaryotes. However, resistance mutations have severely compromised the usefulness of these drugs. We report structural, computational, and mutagenesis studies on the catalytic and resistance mechanisms of DHPS. By performing the enzyme-catalyzed reaction in crystalline DHPS, we have structurally characterized key intermediates along the reaction pathway. Results support an S{sub N}1 reaction mechanism via formation of a novel cationic pterin intermediate. We also show that two conserved loops generate a substructure during catalysis that creates a specific binding pocket for p-aminobenzoic acid, one of the two DHPS substrates. This substructure, together with the pterin-binding pocket, explains the roles of the conserved active-site residues and reveals how sulfonamide resistance arises.

  4. Functional lipid membranes: Bio-inspired nanomaterials for sensing and catalysis

    OpenAIRE

    Gruber, Benjamin

    2013-01-01

    This work describes the functionalization of biomimetic vesicle membranes by the incorporation of various synthetic amphiphiles. The presented approach enables rapid and simple development of bio-inspired nanomaterials for applications in biomolecule sensing and catalysis. Chapter 1 introduces the general concept of functional synthetic vesicle membranes and provides a brief overview about significant developments in this area. Chapter 2 describes synthesis and membrane-embedding of amp...

  5. Applications of nanodiamonds in drug delivery and catalysis

    KAUST Repository

    Moosa, Basem

    2014-01-01

    The interest of researchers in utilizing nanomaterials as carriers for a wide spectrum of molecules has exploded in the last two decades. Nanodiamonds are one class of carbon-based nanomaterials that have emerged as promising drug delivery vehicles and imaging probes. Their ease of functionalization also led to the generation of stimuli-responsive nanodiamonds that deliver drugs on demand in a controlled manner. The ample surface area of NDs allowed for a higher loading of not only small molecules but also macromolecules like genes and proteins. Recently, the unique surface of NDs has attracted more attention as catalyst support in a huge range of organic modification and C-C bond formation reactions. Herein, recent advances in the utilization of nanodiamonds as a drug delivery vehicle and catalytical support are highlighted and summarized to illustrate the potential and versatility of this cheap and commercially available nanomaterial. Copyright © 2014 American Scientific Publishers All rights reserved.

  6. Metallocenyl dendrimers and their applications in molecular electronics, sensing, and catalysis.

    Science.gov (United States)

    Astruc, Didier; Ornelas, Cátia; Ruiz, Jaime

    2008-07-01

    We have investigated the movement of electrons around the peripheries of dendrimers and between their redox termini and electrodes through studies of the electrochemistry of dendrimers presenting metallocenes (and other transition metal sandwich complexes) as terminal groups. Because these compounds can be stabilized in both their oxidized and their reduced forms, their electrochemical and chemical redox processes proceed without decomposition (chemical reversibility). Most interestingly, electrochemical studies reveal that electron transfer within the dendrimers and between the dendrimers and electrodes are both very fast processes when the branches are flexible (electrochemical reversibility). When the dendrimer branches are sufficiently long, the redox events at the many termini of the metallodendrimer are independent, appearing as a single wave in the cyclic voltammogram, because of very weak electrostatic effects. As a result, these metallodendrimers have applications in the molecular recognition, sensing, and titration of anions (e.g., ATP(2-)) and cations (e.g., transition metal complexes). When the recognition properties are coupled with catalysis, the metallodendrimers function in an enzyme-like manner. For example, Pd(II) can be recognized and titrated using the dendrimer's terminal redox centers and internal coordinate ligands. Redox control over the number of Pd(II) species located within a dendrimer allows us to predetermine the number of metal atoms that end up in the form of a dendrimer-encapsulated Pd nanoparticle (PdNP). For hydrogenation of olefins, the efficiency (turnover frequency, TOF) and stability (turnover number, TON) depend on the size of the dendrimer-encapsulated PdNP catalysts, similar to the behavior of polymer-supported PdNP catalysts, suggesting a classic mechanism in which all of the steps proceed on the PdNP surface. On the other hand, Miyaura-Suzuki carbon-carbon bond-forming reactions catalyzed by dendrimer-encapsulated Pd

  7. Supramolecular catalysis: Refocusing catalysis

    NARCIS (Netherlands)

    P.W.N.M. van Leeuwen; Z. Freixa

    2008-01-01

    This chapter contains sections titled: * Introduction: A Brief Personal History * Secondary Phosphines or Phosphites as Supramolecular Ligands * Host-Guest Catalysis * Ionic Interactions as a Means to Form Heterobidentate Assembly Ligands * Ditopic Ligands for the Construction of Bidentate Phosphine

  8. "Click" chemistry mildly stabilizes bifunctional gold nanoparticles for sensing and catalysis.

    Science.gov (United States)

    Li, Na; Zhao, Pengxiang; Liu, Na; Echeverria, María; Moya, Sergio; Salmon, Lionel; Ruiz, Jaime; Astruc, Didier

    2014-07-01

    A large family of bifunctional 1,2,3-triazole derivatives that contain both a polyethylene glycol (PEG) chain and another functional fragment (e.g., a polymer, dendron, alcohol, carboxylic acid, allyl, fluorescence dye, redox-robust metal complex, or a β-cyclodextrin unit) has been synthesized by facile "click" chemistry and mildly coordinated to nanogold particles, thus providing stable water-soluble gold nanoparticles (AuNPs) in the size range 3.0-11.2 nm with various properties and applications. In particular, the sensing properties of these AuNPs are illustrated through the detection of an analogue of a warfare agent (i.e., sulfur mustard) by means of a fluorescence "turn-on" assay, and the catalytic activity of the smallest triazole-AuNPs (core of 3.0 nm) is excellent for the reduction of 4-nitrophenol in water.

  9. Heterogeneous Catalysis.

    Science.gov (United States)

    Vannice, M. A.

    1979-01-01

    Described is a graduate course in catalysis offered at Penn State University. A detailed course outline with 30 lecture topics is presented. A list of 42 references on catalysis used in place of a textbook is provided. (BT)

  10. Sense and sensitivity: physical limits to multicellular sensing and drug response

    CERN Document Server

    Varennes, Julien

    2015-01-01

    Metastasis is a process of cell migration that can be collective and guided by chemical cues. Viewing metastasis in this way, as a physical phenomenon, allows one to draw upon insights from other studies of collective sensing and migration in cell biology. Here we review recent progress in the study of cell sensing and migration as collective phenomena, including in the context of metastatic cells. We describe simple physical models of sensing and migration, and we survey the experimental evidence that cells operate near the purely physical limits to their behavior. We conclude by contrasting cells' sensory abilities with their sensitivity to drugs, and suggesting potential alternatives to cell-death-based cancer therapies.

  11. Drug-sensing hydrogels for the inducible release of biopharmaceuticals

    Science.gov (United States)

    Ehrbar, Martin; Schoenmakers, Ronald; Christen, Erik H.; Fussenegger, Martin; Weber, Wilfried

    2008-10-01

    Drug-dependent dissociation or association of cellular receptors represents a potent pharmacologic mode of action for regulating cell fate and function. Transferring the knowledge of pharmacologically triggered protein-protein interactions to materials science will enable novel design concepts for stimuli-sensing smart hydrogels. Here, we show the design and validation of an antibiotic-sensing hydrogel for the trigger-inducible release of human vascular endothelial growth factor. Genetically engineered bacterial gyrase subunit B (GyrB) (ref. 4) coupled to polyacrylamide was dimerized by the addition of the aminocoumarin antibiotic coumermycin, resulting in hydrogel formation. Addition of increasing concentrations of clinically validated novobiocin (Albamycin) dissociated the GyrB subunits, thereby resulting in dissociation of the hydrogel and dose- and time-dependent liberation of the entrapped protein pharmaceutical VEGF121 for triggering proliferation of human umbilical vein endothelial cells. Pharmacologically controlled hydrogels have the potential to fulfil the promises of stimuli-sensing materials as smart devices for spatiotemporally controlled delivery of drugs within the patient.

  12. Nanomaterial-based electrochemical sensing of neurological drugs and neurotransmitters

    International Nuclear Information System (INIS)

    Nanomaterial-modified detection systems represent a chief driver towards the adoption of electrochemical methods, since nanomaterials enable functional tunability, ability to self-assemble, and novel electrical, optical and catalytic properties that emerge at this scale. This results in tremendous gains in terms of sensitivity, selectivity and versatility. We review the electrochemical methods and mechanisms that may be applied to the detection of neurological drugs. We focus on understanding how specific nano-sized modifiers may be applied to influence the electron transfer event to result in gains in sensitivity, selectivity and versatility of the detection system. This critical review is structured on the basis of the Anatomical Therapeutic Chemical (ATC) Classification System, specifically ATC Code N (neurotransmitters). Specific sections are dedicated to the widely used electrodes based on the carbon materials, supporting electrolytes, and on electrochemical detection paradigms for neurological drugs and neurotransmitters within the groups referred to as ATC codes N01 to N07. We finally discuss emerging trends and future challenges such as the development of strategies for simultaneous detection of multiple targets with high spatial and temporal resolutions, the integration of microfluidic strategies for selective and localized analyte pre-concentration, the real-time monitoring of neurotransmitter secretions from active cell cultures under electro- and chemotactic cues, aptamer-based biosensors, and the miniaturization of the sensing system for detection in small sample volumes and for enabling cost savings due to manufacturing scale-up. The Electronic Supporting Material (ESM) includes review articles dealing with the review topic in last 40 years, as well as key properties of the analytes, viz., pKa values, half-life of drugs and their electrochemical mechanisms. The ESM also defines analytical figures of merit of the drugs and neurotransmitters. The

  13. Computer-aided identification of recognized drugs as Pseudomonas aeruginosa quorum-sensing inhibitors

    DEFF Research Database (Denmark)

    Yang, Liang; Rybtke, Morten Theil; Jakobsen, Tim Holm;

    2009-01-01

    R, and a quorum-sensing receptor agonist. Six top-ranking compounds, all recognized drugs, were identified and tested for quorum-sensing-inhibitory activity. Three compounds, salicylic acid, nifuroxazide, and chlorzoxazone, showed significant inhibition of quorum-sensing-regulated gene expression and related...

  14. Heterogeneous Catalysis.

    Science.gov (United States)

    Miranda, R.

    1989-01-01

    Described is a heterogeneous catalysis course which has elements of materials processing embedded in the classical format of catalytic mechanisms and surface chemistry. A course outline and list of examples of recent review papers written by students are provided. (MVL)

  15. Synthesis and microwave modification of CuO nanoparticles: crystallinity and morphological variations, catalysis, and gas sensing.

    Science.gov (United States)

    Yang, Chao; Xiao, Feng; Wang, Jide; Su, Xintai

    2014-12-01

    CuO nanoparticles with different morphologies were synthesized by chemical precipitation and subsequently modified by microwave hydrothermal processing. The nanoparticles were precipitated by the introduction of a strong base to an aqueous solution of copper cations in the presence/absence of the polyethylene glycol and urea additives. The modification of the nanoparticles was subsequently carried out by a microwave hydrothermal treatment of suspensions of the precipitates, precipitated with and without the additives. X-ray powder diffraction analysis indicated that the crystallinity and crystallite size of the CuO nanoparticles increased after the microwave hydrothermal modification. Microscopy observations revealed the morphology changes induced by microwave hydrothermal processing. The thermal decomposition of ammonium perchlorate and the detection of volatile gases were performed to evaluate the catalytic and gas sensing properties of the synthesized CuO nanoparticles.

  16. Computer-Aided Identification of Recognized Drugs as Pseudomonas aeruginosa Quorum-Sensing Inhibitors▿ †

    OpenAIRE

    Yang, Liang; Rybtke, Morten Theil; Jakobsen, Tim Holm; Hentzer, Morten; Bjarnsholt, Thomas; Givskov, Michael; Tolker-Nielsen, Tim

    2009-01-01

    Attenuation of Pseudomonas aeruginosa virulence by the use of small-molecule quorum-sensing inhibitors (referred to as the antipathogenic drug principle) is likely to play a role in future treatment strategies for chronic infections. In this study, structure-based virtual screening was used in a search for putative quorum-sensing inhibitors from a database comprising approved drugs and natural compounds. The database was built from compounds which showed structural similarities to previously ...

  17. Computer-Aided Identification of Recognized Drugs as Pseudomonas aeruginosa Quorum-Sensing Inhibitors▿ †

    Science.gov (United States)

    Yang, Liang; Rybtke, Morten Theil; Jakobsen, Tim Holm; Hentzer, Morten; Bjarnsholt, Thomas; Givskov, Michael; Tolker-Nielsen, Tim

    2009-01-01

    Attenuation of Pseudomonas aeruginosa virulence by the use of small-molecule quorum-sensing inhibitors (referred to as the antipathogenic drug principle) is likely to play a role in future treatment strategies for chronic infections. In this study, structure-based virtual screening was used in a search for putative quorum-sensing inhibitors from a database comprising approved drugs and natural compounds. The database was built from compounds which showed structural similarities to previously reported quorum-sensing inhibitors, the ligand of the P. aeruginosa quorum-sensing receptor LasR, and a quorum-sensing receptor agonist. Six top-ranking compounds, all recognized drugs, were identified and tested for quorum-sensing-inhibitory activity. Three compounds, salicylic acid, nifuroxazide, and chlorzoxazone, showed significant inhibition of quorum-sensing-regulated gene expression and related phenotypes in a dose-dependent manner. These results suggest that the identified compounds have the potential to be used as antipathogenic drugs. Furthermore, the results indicate that structure-based virtual screening is an efficient tool in the search for novel compounds to combat bacterial infections. PMID:19364871

  18. Computer-aided identification of recognized drugs as Pseudomonas aeruginosa quorum-sensing inhibitors.

    Science.gov (United States)

    Yang, Liang; Rybtke, Morten Theil; Jakobsen, Tim Holm; Hentzer, Morten; Bjarnsholt, Thomas; Givskov, Michael; Tolker-Nielsen, Tim

    2009-06-01

    Attenuation of Pseudomonas aeruginosa virulence by the use of small-molecule quorum-sensing inhibitors (referred to as the antipathogenic drug principle) is likely to play a role in future treatment strategies for chronic infections. In this study, structure-based virtual screening was used in a search for putative quorum-sensing inhibitors from a database comprising approved drugs and natural compounds. The database was built from compounds which showed structural similarities to previously reported quorum-sensing inhibitors, the ligand of the P. aeruginosa quorum-sensing receptor LasR, and a quorum-sensing receptor agonist. Six top-ranking compounds, all recognized drugs, were identified and tested for quorum-sensing-inhibitory activity. Three compounds, salicylic acid, nifuroxazide, and chlorzoxazone, showed significant inhibition of quorum-sensing-regulated gene expression and related phenotypes in a dose-dependent manner. These results suggest that the identified compounds have the potential to be used as antipathogenic drugs. Furthermore, the results indicate that structure-based virtual screening is an efficient tool in the search for novel compounds to combat bacterial infections. PMID:19364871

  19. UV resonance Raman sensing of pharmaceutical drugs in hollow fibers

    Science.gov (United States)

    Yan, D.; Popp, J.; Frosch, T.

    2014-05-01

    We report about the experimental combination of UV resonance Raman sensing (UV-RRS) and fiber enhanced Raman sensing (FERS) on pharmaceuticals. The results show that the chemical sensitivity is highly improved and at the same time the sample volume is reduced compared to conventional measurements. A hundreds-fold improvement of the limit of detection (LOD) has been achieved with the combination of resonance Raman enhancement and fiber enhancement. The enhanced Raman signal has a reliable linear relationship with the concentration of the analyte, and therefore shows great potential for quantitative analysis of pharmaceuticals.

  20. EFFECTS OF PSYCHOTROPIC DRUGS AS BACTERIAL EFFLUX PUMP INHIBITORS ON QUORUM SENSING REGULATED BEHAVIORS

    OpenAIRE

    Aynur Aybey; Alev Usta; Elif Demirkan

    2014-01-01

    Psychotropic drugs are known to have antimicrobial activity against several groups of microorganisms. The antidepressant agents such as duloxetine, paroxetine, hydroxyzine and venlafaxine are shown to act as efflux pump inhibitors in bacterial cells. In order to the investigation of the effects of psychotropic drugs were determined for clinically significant pathogens by using standart broth microdillusion method. The anti-quorum sensing (anti-QS) activity of psychotropic drugs was tested aga...

  1. Photoredox Catalysis in Organic Chemistry

    Science.gov (United States)

    2016-01-01

    In recent years, photoredox catalysis has come to the forefront in organic chemistry as a powerful strategy for the activation of small molecules. In a general sense, these approaches rely on the ability of metal complexes and organic dyes to convert visible light into chemical energy by engaging in single-electron transfer with organic substrates, thereby generating reactive intermediates. In this Perspective, we highlight the unique ability of photoredox catalysis to expedite the development of completely new reaction mechanisms, with particular emphasis placed on multicatalytic strategies that enable the construction of challenging carbon–carbon and carbon–heteroatom bonds. PMID:27477076

  2. Photoredox Catalysis in Organic Chemistry.

    Science.gov (United States)

    Shaw, Megan H; Twilton, Jack; MacMillan, David W C

    2016-08-19

    In recent years, photoredox catalysis has come to the forefront in organic chemistry as a powerful strategy for the activation of small molecules. In a general sense, these approaches rely on the ability of metal complexes and organic dyes to convert visible light into chemical energy by engaging in single-electron transfer with organic substrates, thereby generating reactive intermediates. In this Perspective, we highlight the unique ability of photoredox catalysis to expedite the development of completely new reaction mechanisms, with particular emphasis placed on multicatalytic strategies that enable the construction of challenging carbon-carbon and carbon-heteroatom bonds. PMID:27477076

  3. Photoredox Catalysis in Organic Chemistry.

    Science.gov (United States)

    Shaw, Megan H; Twilton, Jack; MacMillan, David W C

    2016-08-19

    In recent years, photoredox catalysis has come to the forefront in organic chemistry as a powerful strategy for the activation of small molecules. In a general sense, these approaches rely on the ability of metal complexes and organic dyes to convert visible light into chemical energy by engaging in single-electron transfer with organic substrates, thereby generating reactive intermediates. In this Perspective, we highlight the unique ability of photoredox catalysis to expedite the development of completely new reaction mechanisms, with particular emphasis placed on multicatalytic strategies that enable the construction of challenging carbon-carbon and carbon-heteroatom bonds.

  4. Quorum sensing Inhibitors as anti-pathogenic drugs

    DEFF Research Database (Denmark)

    Rasmussen, Thomas Bovbjerg; Givskov, Michael Christian

    2006-01-01

    as well as elevated tolerance to the activity of the innate immune system. Gram-negative bacteria commonly use N-acyl homoserine lactones (AHL) as QS signal molecules. The use of signal molecule based drugs to attenuate bacterial pathogenecity rather than bacterial growth is attractive for several reasons......, particularly considering the emergence of increasingly antibiotic-resistant bacteria. Compounds capable of this type of interference have been termed anti-pathogenic drugs. A large variety of synthetic AHL analogues and natural products libraries have been screened and a number of QS inhibitors (QSI) have been...

  5. Remedies for Common Cold Symptoms: Making sense of myriad drugs

    OpenAIRE

    Miller, Penny F.

    1991-01-01

    Individuals suffering from intolerable symptoms of the common cold can now be advised of safe and effective products for symptomatic relief. This article describes and discusses four categories of drugs used to treat the common cold. To simplify the product selection process for family physicians, suggestions are included for possible ingredients for treatments of specific cold symptoms.

  6. Structure-Processing-Property Relationship of Poly(Glycolic Acid for Drug Delivery Systems 1: Synthesis and Catalysis

    Directory of Open Access Journals (Sweden)

    Vineet Singh

    2010-01-01

    Full Text Available Till date, market is augmented with a huge number of improved drug delivery systems. The success in this area is basically due to biodegradable polymers. Although conventional systems of drug delivery utilizing the natural and semisynthetic polymers so long but synthetic polymer gains success in the controlled drug delivery area due to better degradation profile and controlled network and functionality. The polyesters are the most studied class group due the susceptible ester linkage in their backbone. The Poly(glycolic Acid (PGA, Poly(lactic acid (PLA, and Polylactide-co-glycolide (PLGA are the best profiled polyesters and are most widely used in marketed products. These polymers, however, still are having drawbacks which failed them to be used in platform technologies like matrix systems, microspheres, and nanospheres in some cases. The common problems arose with these polymers are entrapment inefficiency, inability to degrade and release drugs with required profile, and drug instability in the microenvironment of the polymers. These problems are forcing us to develop new polymers with improved physicochemical properties. The present review gave us an insight in the various structural elements of Poly(glycolic acid, polyester, with in depth study. The first part of the review focuses on the result of studies related to synthetic methodologies and catalysts being utilized to synthesize the polyesters. However the author will also focus on the effect of processing methodologies but due some constraints those are not included in the preview of this part of review.

  7. EFFECTS OF PSYCHOTROPIC DRUGS AS BACTERIAL EFFLUX PUMP INHIBITORS ON QUORUM SENSING REGULATED BEHAVIORS

    Directory of Open Access Journals (Sweden)

    Aynur Aybey

    2014-10-01

    Full Text Available Psychotropic drugs are known to have antimicrobial activity against several groups of microorganisms. The antidepressant agents such as duloxetine, paroxetine, hydroxyzine and venlafaxine are shown to act as efflux pump inhibitors in bacterial cells. In order to the investigation of the effects of psychotropic drugs were determined for clinically significant pathogens by using standart broth microdillusion method. The anti-quorum sensing (anti-QS activity of psychotropic drugs was tested against four test pathogens using the agar well diffusion method. All drugs showed strong inhibitory effect on the growth of S. typhimurium. Additionally, quorum sensing-regulated behaviors of Pseudomonas aeruginosa, including swarming, swimming and twitching motility and alkaline protease production were investigated. Most effective drugs on swarming, swimming and twitching motility and alkaline protease production, respectively, were paroxetine and duloxetine; duloxetine; hydroxyzine and venlafaxine; paroxetine and venlafaxine; venlafaxine. Accordingly, psychotropic drugs were shown strongly anti-QS activity by acting as bacterial efflux pump inhibitors and effection on motility and alkaline protease production of P. aeruginosa.

  8. Catalysis of Photochemical Reactions.

    Science.gov (United States)

    Albini, A.

    1986-01-01

    Offers a classification system of catalytic effects in photochemical reactions, contrasting characteristic properties of photochemical and thermal reactions. Discusses catalysis and sensitization, examples of catalyzed reactions of excepted states, complexing ground state substrates, and catalysis of primary photoproducts. (JM)

  9. Design and synthesis of multifunctional poly(ethylene glycol)s using enzymatic catalysis for multivalent cancer drug delivery

    Science.gov (United States)

    Seo, Kwang Su

    The objective of this research was to design and synthesize multifunctional poly(ethylene glycol)s (PEG)s using enzyme-catalyzed reactions for multivalent targeted drug delivery. Based on computer simulation for optimum folate binding, a four-arm PEG star topology with Mn = 1000 g/mol was proposed. First, a four-functional core based on tetraethylene glycol (TEG) was designed and synthesized using transesterification and Michael addition reactions in the presence of Candida antarctica lipase B (CALB) as a biocatalyst. The four-functional core (HO)2-TEG-(OH)2 core was successfully prepared by the CALB-catalyzed transesterification of vinyl acrylate (VA) with TEG and then Michael addition of diethanolamine to the resulting TEG diacrylate with/without the use of solvent. The functional PEG arms with fluorescein isothiocyanate (FITC) and folic acid (FA) were prepared using both traditional organic chemistry and enzyme-catalyzed reactions. FITC was reacted with the amine group of H2N-PEG-OH in the presence of triethylamine via nucleophilic addition onto the isothiocyanate group. Then, divinyl adipate (DVA) was transesterified with the FITC-PEG-OH product in the presence of CALB to produce the FITC-PEG vinyl ester that will be attached to the four-functional core via CALC-catalyzed transesterification. For the synthesis of FA-PEG vinyl ester arm, DVA was first reacted with PEG-monobenzyl ether (BzPEG-OH) in bulk in the presence of CALB. The BzPEG vinyl ester was then transesterified with 12-bromo-1-dodecanol in the presence of CALB. Finally, BzPEG-Br was attached to FA exclusively in the gamma position using a new method. The thesis also discusses fundamental studies that were carried out in order to get better understanding of enzyme catalyzed transesterification and Michael addition reactions. First, in an effort to investigate the effects of reagent and enzyme concentrations in transesterification, vinyl methacrylate (VMA) was reacted with 2-(hydroxyethyl) acrylate (2

  10. Advances in catalysis

    CERN Document Server

    Jentoft, Friederike C

    2014-01-01

    Advances in Catalysis fills the gap between the journal papers and the textbooks across the diverse areas of catalysis research. For more than 60 years Advances in Catalysis has been dedicated to recording progress in the field of catalysis and providing the scientific community with comprehensive and authoritative reviews. This series is invaluable to chemical engineers and chemists working in the field of catalysis in academia or industry. Authoritative reviews written by experts in the field. Topics selected to reflect progress of the field. Insightful and critical articles, fully edite

  11. Advances in catalysis

    CERN Document Server

    Gates, Bruce C

    2012-01-01

    Advances in Catalysis fills the gap between the journal papers and the textbooks across the diverse areas of catalysis research. For more than 60 years Advances in Catalysis has been dedicated to recording progress in the field of catalysis and providing the scientific community with comprehensive and authoritative reviews. This series in invaluable to chemical engineers, physical chemists, biochemists, researchers and industrial chemists working in the fields of catalysis and materials chemistry. * In-depth, critical, state-of-the-art reviews * Comprehensive, covers of all as

  12. Cooperative photoredox catalysis.

    Science.gov (United States)

    Lang, Xianjun; Zhao, Jincai; Chen, Xiaodong

    2016-05-31

    Visible-light photoredox catalysis has been experiencing a renaissance in response to topical interest in renewable energy and green chemistry. The latest progress in this area indicates that cooperation between photoredox catalysis and other domains of catalysis could provide effective results. Thus, we advance the concept of cooperative photoredox catalysis for organic transformations. It is important to note that this concept can bridge the gap between visible-light photoredox catalysis and other types of redox catalysis such as transition-metal catalysis, biocatalysis or electrocatalysis. In doing so, one can take advantage of the best of both worlds in establishing organic synthesis with visible-light-induced redox reaction as a crucial step. PMID:27094803

  13. Silicon nanowire based biosensing platform for electrochemical sensing of Mebendazole drug activity on breast cancer cells.

    Science.gov (United States)

    Shashaani, Hani; Faramarzpour, Mahsa; Hassanpour, Morteza; Namdar, Nasser; Alikhani, Alireza; Abdolahad, Mohammad

    2016-11-15

    Electrochemical approaches have played crucial roles in bio sensing because of their Potential in achieving sensitive, specific and low-cost detection of biomolecules and other bio evidences. Engineering the electrochemical sensing interface with nanomaterials tends to new generations of label-free biosensors with improved performances in terms of sensitive area and response signals. Here we applied Silicon Nanowire (SiNW) array electrodes (in an integrated architecture of working, counter and reference electrodes) grown by low pressure chemical vapor deposition (LPCVD) system with VLS procedure to electrochemically diagnose the presence of breast cancer cells as well as their response to anticancer drugs. Mebendazole (MBZ), has been used as antitubulin drug. It perturbs the anodic/cathodic response of the cell covered biosensor by releasing Cytochrome C in cytoplasm. Reduction of cytochrome C would change the ionic state of the cells monitored by SiNW biosensor. By applying well direct bioelectrical contacts with cancer cells, SiNWs can detect minor signal transduction and bio recognition events, resulting in precise biosensing. Our device detected the trace of MBZ drugs (with the concentration of 2nM) on electrochemical activity MCF-7 cells. Also, experimented biological analysis such as confocal and Flowcytometry assays confirmed the electrochemical results. PMID:27196254

  14. Multicatalyst system in asymmetric catalysis

    CERN Document Server

    Zhou, Jian

    2014-01-01

    This book introduces multi-catalyst systems by describing their mechanism and advantages in asymmetric catalysis.  Helps organic chemists perform more efficient catalysis with step-by-step methods  Overviews new concepts and progress for greener and economic catalytic reactions  Covers topics of interest in asymmetric catalysis including bifunctional catalysis, cooperative catalysis, multimetallic catalysis, and novel tandem reactions   Has applications for pharmaceuticals, agrochemicals, materials, and flavour and fragrance

  15. Engineering cell-compatible paper chips for cell culturing, drug screening, and mass spectrometric sensing.

    Science.gov (United States)

    Chen, Qiushui; He, Ziyi; Liu, Wu; Lin, Xuexia; Wu, Jing; Li, Haifang; Lin, Jin-Ming

    2015-10-28

    Paper-supported cell culture is an unprecedented development for advanced bioassays. This study reports a strategy for in vitro engineering of cell-compatible paper chips that allow for adherent cell culture, quantitative assessment of drug efficiency, and label-free sensing of intracellular molecules via paper spray mass spectrometry. The polycarbonate paper is employed as an excellent alternative bioscaffold for cell distribution, adhesion, and growth, as well as allowing for fluorescence imaging without light scattering. The cell-cultured paper chips are thus amenable to fabricate 3D tissue construction and cocultures by flexible deformation, stacks and assembly by layers of cells. As a result, the successful development of cell-compatible paper chips subsequently offers a uniquely flexible approach for in situ sensing of live cell components by paper spray mass spectrometry, allowing profiling the cellular lipids and quantitative measurement of drug metabolism with minimum sample pretreatment. Consequently, the developed paper chips for adherent cell culture are inexpensive for one-time use, compatible with high throughputs, and amenable to label-free and rapid analysis.

  16. Kinetics and Catalysis Demonstrations.

    Science.gov (United States)

    Falconer, John L.; Britten, Jerald A.

    1984-01-01

    Eleven videotaped kinetics and catalysis demonstrations are described. Demonstrations include the clock reaction, oscillating reaction, hydrogen oxidation in air, hydrogen-oxygen explosion, acid-base properties of solids, high- and low-temperature zeolite reactivity, copper catalysis of ammonia oxidation and sodium peroxide decomposition, ammonia…

  17. Molecular water oxidation catalysis

    CERN Document Server

    Llobet, Antoni

    2014-01-01

    Photocatalytic water splitting is a promising strategy for capturing energy from the sun by coupling light harvesting and the oxidation of water, in order to create clean hydrogen fuel. Thus a deep knowledge of the water oxidation catalysis field is essential to be able to come up with useful energy conversion devices based on sunlight and water splitting. Molecular Water Oxidation Catalysis: A Key Topic for New Sustainable Energy Conversion Schemes presents a comprehensive and state-of-the-art overview of water oxidation catalysis in homogeneous phase, describing in detail the most importan

  18. Surface and nanomolecular catalysis

    CERN Document Server

    Richards, Ryan

    2006-01-01

    Using new instrumentation and experimental techniques that allow scientists to observe chemical reactions and molecular properties at the nanoscale, the authors of Surface and Nanomolecular Catalysis reveal new insights into the surface chemistry of catalysts and the reaction mechanisms that actually occur at a molecular level during catalysis. While each chapter contains the necessary background and explanations to stand alone, the diverse collection of chapters shows how developments from various fields each contributed to our current understanding of nanomolecular catalysis as a whole. The

  19. Progress towards bioorthogonal catalysis with organometallic compounds.

    Science.gov (United States)

    Völker, Timo; Dempwolff, Felix; Graumann, Peter L; Meggers, Eric

    2014-09-22

    The catalysis of bioorthogonal transformations inside living organisms is a formidable challenge--yet bears great potential for future applications in chemical biology and medicinal chemistry. We herein disclose highly active organometallic ruthenium complexes for bioorthogonal catalysis under biologically relevant conditions and inside living cells. The catalysts uncage allyl carbamate protected amines with unprecedented high turnover numbers of up to 270 cycles in the presence of water, air, and millimolar concentrations of thiols. By live-cell imaging of HeLa cells and with the aid of a caged fluorescent probe we could reveal a rapid development of intense fluorescence within the cellular cytoplasm and therefore support the proposed bioorthogonality of the catalysts. In addition, to illustrate the manifold applications of bioorthogonal catalysis, we developed a method for catalytic in-cell activation of a caged anticancer drug, which efficiently induced apoptosis in HeLa cells.

  20. Research on Catalysis.

    Science.gov (United States)

    Bartholomew, Calvin H.; Hecker, William C.

    1984-01-01

    The objectives and philosophy of the Catalysis Laboratory at Brigham Young University are discussed. Also discusses recent and current research activities at the laboratory as well as educational opportunities, research facilities, and sources of research support. (JN)

  1. Xenobiotic-sensing nuclear receptors CAR and PXR as drug targets in cholestatic liver disease.

    Science.gov (United States)

    Kakizaki, Satoru; Takizawa, Daichi; Tojima, Hiroki; Yamazaki, Yuichi; Mori, Masatomo

    2009-11-01

    Cholestasis results in the intrahepatic retention of cytotoxic bile acid and it can thus lead to liver injury and/or liver fibrosis. Cholestatic liver damage is counteracted by a variety of intrinsic hepatoprotective mechanisms including a complex network of drug metabolizing enzymes and transporters. During the last decade, much progress has been made in dissecting the mechanisms which regulate the hepatic xeno- and endobiotic metabolism by nuclear receptors. The xenobiotic receptors CAR and PXR are two important members of the NR1I nuclear receptor family. They function as sensors of toxic byproducts derived from the endogenous metabolism and of exogenous chemicals, in order to enhance their elimination. Ligands for both receptors, including phenobarbital, have already been used to treat cholestatic liver diseases before the mechanisms of these receptors were revealed. Furthermore, Yin Zhi Huang, a traditional Chinese herbal medicine, which has been used to prevent and treat neonatal jaundice, was identified to be a CAR ligand which also accelerates bilirubin clearance. Therefore, CAR and PXR have a protective effect on cholestasis by activating both detoxification enzymes and transporters. As a result, novel compounds targeting CAR and PXR with specific effects and fewer side effects will therefore be useful for the treatment of cholestatic liver diseases. This article will review the current knowledge on xenobiotic-sensing nuclear receptors CAR and PXR, while also discussing their potential role in the treatment of cholestatic liver diseases. PMID:19925451

  2. Homogeneous, Heterogeneous, and Enzymatic Catalysis.

    Science.gov (United States)

    Oyama, S. Ted; Somorjai, Gabor A.

    1988-01-01

    Discusses three areas of catalysis: homegeneous, heterogeneous, and enzymatic. Explains fundamentals and economic impact of catalysis. Lists and discusses common industrial catalysts. Provides a list of 107 references. (MVL)

  3. Catalysis for alternative energy generation

    CERN Document Server

    2012-01-01

    Summarizes recent problems in using catalysts in alternative energy generation and proposes novel solutions  Reconsiders the role of catalysis in alternative energy generation  Contributors include catalysis and alternative energy experts from across the globe

  4. Asymmetric catalysis with helical polymers

    NARCIS (Netherlands)

    Megens, Rik P.; Roelfes, Gerard

    2011-01-01

    Inspired by nature, the use of helical biopolymer catalysts has emerged over the last years as a new approach to asymmetric catalysis. In this Concept article the various approaches and designs and their application in asymmetric catalysis will be discussed.

  5. [Research progress of new antibacterial drugs that target bacterial quorum sensing systems].

    Science.gov (United States)

    Yin, Shou-Liang; Chang, Ya-Jing; Deng, Su-Ping; Wang, Qing-Chi; Yu, Wen-Gong; Gong, Qian-Hong

    2011-06-01

    In recent years, antibiotic resistance of bacteria has become a global health crisis. Especially, the new class of "superbug" was found in South Asia, which is resistant to almost known antibiotics and causes worldwide alarm. Through the underlying mechanisms of bacterial pathogenecity, the expression of many pathogen virulence factors is regulated by the process of quorum sensing. Screening efficient quorum sensing inhibitors is an especially compelling approach to the future treatment of bacterial infections and antibiotic resistance. This article focuses on bacterial quorum sensing system, quorum sensing screening model for in vitro and evaluation of animal models in vivo, recent research of quorum sensing inhibitors and so on. PMID:21882519

  6. Isotopes in heterogeneous catalysis

    CERN Document Server

    Hargreaves, Justin SJ

    2006-01-01

    The purpose of this book is to review the current, state-of-the-art application of isotopic methods to the field of heterogeneous catalysis. Isotopic studies are arguably the ultimate technique in in situ methods for heterogeneous catalysis. In this review volume, chapters have been contributed by experts in the field and the coverage includes both the application of specific isotopes - Deuterium, Tritium, Carbon-14, Sulfur-35 and Oxygen-18 - as well as isotopic techniques - determination of surface mobility, steady state transient isotope kinetic analysis, and positron emission profiling.

  7. Characterization of a new degradation product of nifedipine formed on catalysis by atenolol: A typical case of alteration of degradation pathway of one drug by another.

    Science.gov (United States)

    Handa, Tarun; Singh, Saranjit; Singh, Inder Pal

    2014-02-01

    An increasing interest is being shown throughout the world on the use of fixed-dose combinations of drugs in the therapy of select diseases, like cardiovascular diseases, due to their multiple advantages. Though the main criterion for combining drugs in a single dosage form is the rationale, but consideration like stability of formulation is equally important, due to an added aspect of drug-drug interaction. The objective of this study was to evaluate interaction among the drugs in an antihypertensive combination of nifedipine and atenolol. Nifedipine is a known light sensitive drug, which degrades via intra-molecular mechanisms to nitro- and nitroso-pyridine analogs, along with a few minor secondary products that are formed through inter-molecular interactions amongst primary degradation products and their intermediates. Atenolol is reasonably stable weakly basic drug that is mainly hydrolyzed at acetamide terminal amide moiety to its corresponding carboxylic acid. To the best of our knowledge, there is no known information on chemical compatibility among the two drugs. The present study involved subjecting of nifedipine, atenolol and their combination to a variety of accelerated and stress conditions. HPLC studies revealed formation of a new product in the mixture of two drugs (∼2%), which was also generated from nifedipine alone, but at trace levels (<0.1%). The product was isolated by preparative chromatography and subjected to indepth studies for its characterization. Ultra-violet, FT-IR, mass spectrometric and nuclear magnetic resonance spectroscopic studies highlighted that the principal photo-degradation pathway of nifedipine was modified and diverted in the presence of atenolol. To verify the same, a study was conducted employing two other β-blockers with similar structures to atenolol, and the same product was formed in relatively higher quantity therein also. The new product is postulated to be produced as a result of rearrangement of hydroxylamine

  8. Au/TiO2 nanobelt heterostructures for the detection of cancer cells and anticancer drug activity by potential sensing

    Science.gov (United States)

    Cui, Jingjie; Chen, Jing; Chen, Shaowei; Gao, Li; Xu, Ping; Li, Hong

    2016-03-01

    Cancer is a cell dysfunction disease. The detection of cancer cells is extremely important for early diagnosis and clinical treatments. At present, the pretreatment for the detection of cancer cells is costly, complicated and time-consuming. As different species of the analytes may give rise to specific voltammetric signals at distinctly different potentials, simple potential sensing has the specificity to detect different cellular species. By taking advantage of the different electrochemical characteristics of normal cells, cancer cells and biointeractions between anticancer drugs and cancer cells, we develop a specific, sensitive, direct, cost-effective and rapid method for the detection of cancer cells by electrochemical potential sensing based on Au/TiO2 nanobelt heterostructure electrodes that will be of significance in early cancer diagnosis, in vitro screening of anticancer drugs and molecular biology research.

  9. Template-assisted synthesis of III-nitride and metal-oxide nano-heterostructures using low-temperature atomic layer deposition for energy, sensing, and catalysis applications (Presentation Recording)

    Science.gov (United States)

    Biyikli, Necmi; Ozgit-Akgun, Cagla; Eren, Hamit; Haider, Ali; Uyar, Tamer; Kayaci, Fatma; Guler, Mustafa Ozgur; Garifullin, Ruslan; Okyay, Ali K.; Ulusoy, Gamze M.; Goldenberg, Eda

    2015-08-01

    Recent experimental research efforts on developing functional nanostructured III-nitride and metal-oxide materials via low-temperature atomic layer deposition (ALD) will be reviewed. Ultimate conformality, a unique propoerty of ALD process, is utilized to fabricate core-shell and hollow tubular nanostructures on various nano-templates including electrospun nanofibrous polymers, self-assembled peptide nanofibers, metallic nanowires, and multi-wall carbon nanotubes (MWCNTs). III-nitride and metal-oxide coatings were deposited on these nano-templates via thermal and plasma-enhanced ALD processes with thickness values ranging from a few mono-layers to 40 nm. Metal-oxide materials studied include ZnO, TiO2, HfO2, ZrO2, and Al2O3. Standard ALD growth recipes were modified so that precursor molecules have enough time to diffuse and penetrate within the layers/pores of the nano-template material. As a result, uniform and conformal coatings on high-surface area nano-templates were demonstrated. Substrate temperatures were kept below 200C and within the self-limiting ALD window, so that temperature-sensitive template materials preserved their integrity III-nitride coatings were applied to similar nano-templates via plasma-enhanced ALD (PEALD) technique. AlN, GaN, and InN thin-film coating recipes were optimized to achieve self-limiting growth with deposition temperatures as low as 100C. BN growth took place only for >350C, in which precursor decomposition occured and therefore growth proceeded in CVD regime. III-nitride core-shell and hollow tubular single and multi-layered nanostructures were fabricated. The resulting metal-oxide and III-nitride core-shell and hollow nano-tubular structures were used for photocatalysis, dye sensitized solar cell (DSSC), energy storage and chemical sensing applications. Significantly enhanced catalysis, solar efficiency, charge capacity and sensitivity performance are reported. Moreover, core-shell metal-oxide and III-nitride materials

  10. Pollution Control by Catalysis

    DEFF Research Database (Denmark)

    Eriksen, Kim Michael; Fehrmann, Rasmus

    1998-01-01

    The report summarises the results of two years of collaboration supported by INTAS between Department of Chemistry,DTU,DK , IUSTI,Universite de Provence,FR, ICE/HT University 6of Patras,GR, and Boreskov Institute of Catalysis,RU.The project has been concerned with mechanistic studies of de...

  11. Preface: Catalysis Today

    DEFF Research Database (Denmark)

    Li, Yongdan

    2016-01-01

    This special issue of Catalysis Today with the theme “Sustain-able Energy” results from a great success of the session “Catalytic Technologies Accelerating the Establishment of Sustainable and Clean Energy”, one of the two sessions of the 1st International Symposium on Catalytic Science and Techn...

  12. Anion-π catalysis.

    Science.gov (United States)

    Zhao, Yingjie; Beuchat, César; Domoto, Yuya; Gajewy, Jadwiga; Wilson, Adam; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2014-02-01

    The introduction of new noncovalent interactions to build functional systems is of fundamental importance. We here report experimental and theoretical evidence that anion-π interactions can contribute to catalysis. The Kemp elimination is used as a classical tool to discover conceptually innovative catalysts for reactions with anionic transition states. For anion-π catalysis, a carboxylate base and a solubilizer are covalently attached to the π-acidic surface of naphthalenediimides. On these π-acidic surfaces, transition-state stabilizations up to ΔΔGTS = 31.8 ± 0.4 kJ mol(-1) are found. This value corresponds to a transition-state recognition of KTS = 2.7 ± 0.5 μM and a catalytic proficiency of 3.8 × 10(5) M(-1). Significantly increasing transition-state stabilization with increasing π-acidity of the catalyst, observed for two separate series, demonstrates the existence of "anion-π catalysis." In sharp contrast, increasing π-acidity of the best naphthalenediimide catalysts does not influence the more than 12 000-times weaker substrate recognition (KM = 34.5 ± 1.6 μM). Together with the disappearance of Michaelis-Menten kinetics on the expanded π-surfaces of perylenediimides, this finding supports that contributions from π-π interactions are not very important for anion-π catalysis. The linker between the π-acidic surface and the carboxylate base strongly influences activity. Insufficient length and flexibility cause incompatibility with saturation kinetics. Moreover, preorganizing linkers do not improve catalysis much, suggesting that the ideal positioning of the carboxylate base on the π-acidic surface is achieved by intramolecular anion-π interactions rather than by an optimized structure of the linker. Computational simulations are in excellent agreement with experimental results. They confirm, inter alia, that the stabilization of the anionic transition states (but not the neutral ground states) increases with the π-acidity of the

  13. Catalysis of Supramolecular Hydrogelation.

    Science.gov (United States)

    Trausel, Fanny; Versluis, Frank; Maity, Chandan; Poolman, Jos M; Lovrak, Matija; van Esch, Jan H; Eelkema, Rienk

    2016-07-19

    One often thinks of catalysts as chemical tools to accelerate a reaction or to have a reaction run under more benign conditions. As such, catalysis has a role to play in the chemical industry and in lab scale synthesis that is not to be underestimated. Still, the role of catalysis in living systems (cells, organisms) is much more extensive, ranging from the formation and breakdown of small molecules and biopolymers to controlling signal transduction cascades and feedback processes, motility, and mechanical action. Such phenomena are only recently starting to receive attention in synthetic materials and chemical systems. "Smart" soft materials could find many important applications ranging from personalized therapeutics to soft robotics to name but a few. Until recently, approaches to control the properties of such materials were largely dominated by thermodynamics, for instance, looking at phase behavior and interaction strength. However, kinetics plays a large role in determining the behavior of such soft materials, for instance, in the formation of kinetically trapped (metastable) states or the dynamics of component exchange. As catalysts can change the rate of a chemical reaction, catalysis could be used to control the formation, dynamics, and fate of supramolecular structures when the molecules making up these structures contain chemical bonds whose formation or exchange are susceptible to catalysis. In this Account, we describe our efforts to use synthetic catalysts to control the properties of supramolecular hydrogels. Building on the concept of synthesizing the assembling molecule in the self-assembly medium from nonassembling precursors, we will introduce the use of catalysis to change the kinetics of assembler formation and thereby the properties of the resulting material. In particular, we will focus on the synthesis of supramolecular hydrogels where the use of a catalyst provides access to gel materials with vastly different appearance and mechanical

  14. Anion-π catalysis.

    Science.gov (United States)

    Zhao, Yingjie; Beuchat, César; Domoto, Yuya; Gajewy, Jadwiga; Wilson, Adam; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2014-02-01

    The introduction of new noncovalent interactions to build functional systems is of fundamental importance. We here report experimental and theoretical evidence that anion-π interactions can contribute to catalysis. The Kemp elimination is used as a classical tool to discover conceptually innovative catalysts for reactions with anionic transition states. For anion-π catalysis, a carboxylate base and a solubilizer are covalently attached to the π-acidic surface of naphthalenediimides. On these π-acidic surfaces, transition-state stabilizations up to ΔΔGTS = 31.8 ± 0.4 kJ mol(-1) are found. This value corresponds to a transition-state recognition of KTS = 2.7 ± 0.5 μM and a catalytic proficiency of 3.8 × 10(5) M(-1). Significantly increasing transition-state stabilization with increasing π-acidity of the catalyst, observed for two separate series, demonstrates the existence of "anion-π catalysis." In sharp contrast, increasing π-acidity of the best naphthalenediimide catalysts does not influence the more than 12 000-times weaker substrate recognition (KM = 34.5 ± 1.6 μM). Together with the disappearance of Michaelis-Menten kinetics on the expanded π-surfaces of perylenediimides, this finding supports that contributions from π-π interactions are not very important for anion-π catalysis. The linker between the π-acidic surface and the carboxylate base strongly influences activity. Insufficient length and flexibility cause incompatibility with saturation kinetics. Moreover, preorganizing linkers do not improve catalysis much, suggesting that the ideal positioning of the carboxylate base on the π-acidic surface is achieved by intramolecular anion-π interactions rather than by an optimized structure of the linker. Computational simulations are in excellent agreement with experimental results. They confirm, inter alia, that the stabilization of the anionic transition states (but not the neutral ground states) increases with the π-acidity of the

  15. Plausible Drug Targets in the Streptococcus mutans Quorum Sensing Pathways to Combat Dental Biofilms and Associated Risks.

    Science.gov (United States)

    Kaur, Gurmeet; Rajesh, Shrinidhi; Princy, S Adline

    2015-12-01

    Streptococcus mutans, a Gram positive facultative anaerobe, is one among the approximately seven hundred bacterial species to exist in human buccal cavity and cause dental caries. Quorum sensing (QS) is a cell-density dependent communication process that respond to the inter/intra-species signals and elicit responses to show behavioral changes in the bacteria to an aggressive forms. In accordance to this phenomenon, the S. mutans also harbors a Competing Stimulating Peptide (CSP)-mediated quorum sensing, ComCDE (Two-component regulatory system) to regulate several virulence-associated traits that includes the formation of the oral biofilm (dental plaque), genetic competence and acidogenicity. The QS-mediated response of S. mutans adherence on tooth surface (dental plaque) imparts antibiotic resistance to the bacterium and further progresses to lead a chronic state, known as periodontitis. In recent years, the oral streptococci, S. mutans are not only recognized for its cariogenic potential but also well known to worsen the infective endocarditis due to its inherent ability to colonize and form biofilm on heart valves. The review significantly appreciate the increasing complexity of the CSP-mediated quorum-sensing pathway with a special emphasis to identify the plausible drug targets within the system for the development of anti-quorum drugs to control biofilm formation and associated risks.

  16. Applied heterogeneous catalysis

    International Nuclear Information System (INIS)

    This reference book explains the scientific principles of heterogeneous catalysis while also providing details on the methods used to develop commercially viable catalyst products. A section of the book presents reactor design engineering theory and practices for the profitable application of these catalysts in large-scale industrial processes. A description of the mechanisms and commercial applications of catalysis is followed by a review of catalytic reaction kinetics. There are five chapters on selecting catalyst agents, developing and preparing industrial catalysts, measuring catalyst properties, and analyzing the physico-chemical characteristics of solid catalyst particles. The final chapter reviews the elements of catalytic reactor design, with emphasis on flow regimes vs. reactor types, heat and mass transfer in reactor beds, single- and multi-phase flows, and the effects of thermodynamics and other catalyst properties on the process flow scheme

  17. Magnetic Catalysis in Graphene

    CERN Document Server

    Winterowd, Christopher; Zafeiropoulos, Savvas

    2015-01-01

    One of the most important developments in condensed matter physics in recent years has been the discovery and characterization of graphene. A two-dimensional layer of Carbon arranged in a hexagonal lattice, graphene exhibits many interesting electronic properties, most notably that the low energy excitations behave as massless Dirac fermions. These excitations interact strongly via the Coulomb interaction and thus non-perturbative methods are necessary. Using methods borrowed from lattice QCD, we study the graphene effective theory in the presence of an external magnetic field. Graphene, along with other $(2+1)$-dimensional field theories, has been predicted to undergo spontaneous breaking of flavor symmetry including the formation of a gap as a result of the external magnetic field. This phenomenon is known as magnetic catalysis. Our study investigates magnetic catalysis using a fully non-perturbative approach.

  18. Solid Base Catalysis

    CERN Document Server

    Ono, Yoshio

    2011-01-01

    The importance of solid base catalysts has come to be recognized for their environmentally benign qualities, and much significant progress has been made over the past two decades in catalytic materials and solid base-catalyzed reactions. The book is focused on the solid base. Because of the advantages over liquid bases, the use of solid base catalysts in organic synthesis is expanding. Solid bases are easier to dispose than liquid bases, separation and recovery of products, catalysts and solvents are less difficult, and they are non-corrosive. Furthermore, base-catalyzed reactions can be performed without using solvents and even in the gas phase, opening up more possibilities for discovering novel reaction systems. Using numerous examples, the present volume describes the remarkable role solid base catalysis can play, given the ever increasing worldwide importance of "green" chemistry. The reader will obtain an overall view of solid base catalysis and gain insight into the versatility of the reactions to whic...

  19. Catalysis of carboxypeptidase A

    DEFF Research Database (Denmark)

    Wu, Shanshan; Zhang, Chunchun; Xu, Dingguo;

    2010-01-01

    The catalytic mechanism of carboxypeptidase A (CPA) for the hydrolysis of ester substrates is investigated using hybrid quantum mechanical/molecular mechanical (QM/MM) methods and high-level density functional theory. The prevailing mechanism was found to utilize an active-site water molecule ass...... here and in our earlier publication, a unified model is proposed to account for nearly all experimental observations concerning the catalysis of CPA....

  20. Heterogeneous radiation catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Cabicar, J.; Kudlacek, R.; Motl, A.; Mucka, V.; Pospisil, M. (Ceske Vysoke Uceni Technicke, Prague (Czechoslovakia). Fakulta Jaderna a Fysikalne Inzenyrska)

    1982-01-01

    Results of the investigation of some radiation catalysis problems are reviewed. Main attention is paid to the radiation effect on the catalytic activity of various catalysts in the decomposition of hydrogen peroxide and in the hydrogenation of maleic acid. The results presented are obtained in the study of the kinetics of reduction of several pre-irradiated metal oxides and of the radiation effect on catalysts used in some catalytic reactions important for industry.

  1. The quorum-sensing molecule farnesol is a modulator of drug efflux mediated by ABC multidrug transporters and synergizes with drugs in Candida albicans.

    Science.gov (United States)

    Sharma, Monika; Prasad, Rajendra

    2011-10-01

    Overexpression of the CaCDR1-encoded multidrug efflux pump protein CaCdr1p (Candida drug resistance protein 1), belonging to the ATP binding cassette (ABC) superfamily of transporters, is one of the most prominent contributors of multidrug resistance (MDR) in Candida albicans. Thus, blocking or modulating the function of the drug efflux pumps represents an attractive approach in combating MDR. In the present study, we provide first evidence that the quorum-sensing molecule farnesol (FAR) is a specific modulator of efflux mediated by ABC multidrug transporters, such as CaCdr1p and CaCdr2p of C. albicans and ScPdr5p of Saccharomyces cerevisiae. Interestingly, FAR did not modulate the efflux mediated by the multidrug extrusion pump protein CaMdr1p, belonging to the major facilitator superfamily (MFS). Kinetic data revealed that FAR competitively inhibited rhodamine 6G efflux in CaCdr1p-overexpressing cells, with a simultaneous increase in an apparent K(m) without affecting the V(max) values and the ATPase activity. We also observed that when used in combination, FAR at a nontoxic concentration synergized with the drugs at their respective nonlethal concentrations, as was evident from their resistant clinical isolates of C. albicans. Our biochemical experiments revealed that the synergistic interaction of FAR with the drugs led to reactive oxygen species accumulation, which triggered early apoptosis, and that both could be partly reversed by the addition of an antioxidant. Collectively, FAR modulates drug extrusion mediated exclusively by ABC proteins and is synergistic to fluconazole (FLC), ketoconazole (KTC), miconazole (MCZ), and amphotericin (AMB). PMID:21768514

  2. Inorganic Reaction Mechanisms Part II: Homogeneous Catalysis

    Science.gov (United States)

    Cooke, D. O.

    1976-01-01

    Suggests several mechanisms for catalysis by metal ion complexes. Discusses the principal factors of importance in these catalysis reactions and suggests reactions suitable for laboratory study. (MLH)

  3. Hybrid Amyloid Membranes for Continuous Flow Catalysis.

    Science.gov (United States)

    Bolisetty, Sreenath; Arcari, Mario; Adamcik, Jozef; Mezzenga, Raffaele

    2015-12-29

    Amyloid fibrils are promising nanomaterials for technological applications such as biosensors, tissue engineering, drug delivery, and optoelectronics. Here we show that amyloid-metal nanoparticle hybrids can be used both as efficient active materials for wet catalysis and as membranes for continuous flow catalysis applications. Initially, amyloid fibrils generated in vitro from the nontoxic β-lactoglobulin protein act as templates for the synthesis of gold and palladium metal nanoparticles from salt precursors. The resulting hybrids possess catalytic features as demonstrated by evaluating their activity in a model catalytic reaction in water, e.g., the reduction of 4-nitrophenol into 4-aminophenol, with the rate constant of the reduction increasing with the concentration of amyloid-nanoparticle hybrids. Importantly, the same nanoparticles adsorbed onto fibrils surface show improved catalytic efficiency compared to the same unattached particles, pointing at the important role played by the amyloid fibril templates. Then, filter membranes are prepared from the metal nanoparticle-decorated amyloid fibrils by vacuum filtration. The resulting membranes serve as efficient flow catalysis active materials, with a complete catalytic conversion achieved within a single flow passage of a feeding solution through the membrane.

  4. DNA-based hybrid catalysis

    NARCIS (Netherlands)

    Rioz-Martínez, Ana; Roelfes, Gerard

    2015-01-01

    In the past decade, DNA-based hybrid catalysis has merged as a promising novel approach to homogeneous (asymmetric) catalysis. A DNA hybrid catalysts comprises a transition metal complex that is covalently or supramolecularly bound to DNA. The chiral microenvironment and the second coordination sphe

  5. Catalysis and prebiotic RNA synthesis

    Science.gov (United States)

    Ferris, James P.

    1993-01-01

    The essential role of catalysis for the origins of life is discussed. The status of the prebiotic synthesis of 2',5'- and 3'5'-linked oligomers of RNA is reviewed. Examples of the role of metal ion and mineral catalysis in RNA oligomer formation are discussed.

  6. Convertible MRI contrast: Sensing the delivery and release of anti-glioma nano-drugs

    OpenAIRE

    Zhang, Liang; Zhang, Zhongwei; Mason, Ralph P.; Sarkaria, Jann N.; Zhao, Dawen

    2015-01-01

    There is considerable interest in developing nanohybrids of imaging contrast agents and drugs for image-guided drug delivery. We have developed a strategy of utilizing manganese (Mn) to enhance the nano-encapsulation of arsenic trioxide (ATO). Formation of arsenite (As3+)-Mn precipitates in liposomes generates magnetic susceptibility effects, reflected as dark contrast on T2-weighted MRI. Intriguingly, following cell uptake, the As-Mn complex decomposes in response to low pH in endosome-lysos...

  7. RELATIONSHIP BETWEEN RESILIENCE AND SENSE OF COHERENCE FOR REHABILITATING DRUG ABUSERS%戒毒者心理韧性与心理一致感的关系

    Institute of Scientific and Technical Information of China (English)

    高云鹏

    2013-01-01

    To explore the relationship between resilience and sense of coherence for rehabilitating drug abusers. Methods-. Using the Chinese revision of Connor -Davidson Resilience Scale and Sense of Coherence - 13 scale to survey 365 rehabilitating drug abusers. Results-. ( 1 ) The sense of coherence of higher resilient rehabilitating drug abusers (55.03 ±s 8. 12) are better than that of the lower ones ( 46. 26 ± s 7. 51 ) , P ( 0. 001; ( 2) Sense of coherence in rehabilitating drug abusers are positively related to resilience ( r = 0. 40) ; ( 3) The comprehensibility and meaningfulness of sense of coherence positively predicted the resilience in rehabilitating drug abusers. Conclusion-. There is a significant correlation between resilience and sense of coherence in rehabilitating drug abusers.%目的:探讨戒毒者心理韧性与心理一致感的关系.方法:采用中国版Connor-Davidson Resilience Scale量表和Sense of Coherence-13量表对365名戒毒者进行凋查.结果:(1)高心理韧性戒毒者的心理一致感(55.03±s 8.12)显著高于低心理韧性戒毒者(46.26±s 7.51),P<0.001;(2)心理韧性与心理一致感存在显著正相关(r=0.40);(3)可理解感和有意义感对心理韧性具有显著的正向预测作用.结论:戒毒者心理韧性与心理一致感之间存在密切联系.

  8. Quorum sensing inhibitory drugs as next generation antimicrobials: worth the effort?

    DEFF Research Database (Denmark)

    Bjarnsholt, Thomas; Givskov, Michael Christian

    2008-01-01

    as biofilms are more tolerant to antibiotics than their planktonic counterparts. Therefore, research should identify new antimicrobial agents and their corresponding targets to decrease the biofilm-forming capability or persistence of the infectious bacteria. Here, we review one such drug target: bacterial...

  9. Spin-modified catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Choudhary, R. [Department of Physics and Astronomy and NCMN, University of Nebraska, Lincoln, Nebraska 68588 (United States); School of Basic Sciences, Indian Institute of Technology Mandi, Mandi 175001, Himachal Pradesh (India); Manchanda, P.; Enders, A.; Balamurugan, B.; Sellmyer, D. J.; Skomski, R., E-mail: rskomski@unl.edu [Department of Physics and Astronomy and NCMN, University of Nebraska, Lincoln, Nebraska 68588 (United States); Kashyap, A. [School of Basic Sciences, Indian Institute of Technology Mandi, Mandi 175001, Himachal Pradesh (India); Sykes, E. C. H. [Department of Chemistry, Pearson Chemistry Laboratory, Tufts University, Medford, Massachusetts 02155 (United States)

    2015-05-07

    First-principle calculations are used to explore the use of magnetic degrees of freedom in catalysis. We use the Vienna Ab-Initio Simulation Package to investigate both L1{sub 0}-ordered FePt and CoPt bulk materials and perform supercell calculations for FePt nanoclusters containing 43 atoms. As the catalytic activity of transition-metal elements and alloys involves individual d levels, magnetic alloying strongly affects the catalytic performance, because it leads to shifts in the local densities of states and to additional peaks due to magnetic-moment formation. The peak shift persists in nanoparticles but is surface-site specific and therefore depends on cluster size. Our research indicates that small modifications in stoichiometry and cluster size are a useful tool in the search for new catalysts.

  10. Spin-modified catalysis

    International Nuclear Information System (INIS)

    First-principle calculations are used to explore the use of magnetic degrees of freedom in catalysis. We use the Vienna Ab-Initio Simulation Package to investigate both L10-ordered FePt and CoPt bulk materials and perform supercell calculations for FePt nanoclusters containing 43 atoms. As the catalytic activity of transition-metal elements and alloys involves individual d levels, magnetic alloying strongly affects the catalytic performance, because it leads to shifts in the local densities of states and to additional peaks due to magnetic-moment formation. The peak shift persists in nanoparticles but is surface-site specific and therefore depends on cluster size. Our research indicates that small modifications in stoichiometry and cluster size are a useful tool in the search for new catalysts

  11. Asymmetric trienamine catalysis: new opportunities in amine catalysis.

    Science.gov (United States)

    Kumar, Indresh; Ramaraju, Panduga; Mir, Nisar A

    2013-02-01

    Amine catalysis, through HOMO-activating enamine and LUMO-activating iminium-ion formation, is receiving increasing attention among other organocatalytic strategies, for the activation of unmodified carbonyl compounds. Particularly, the HOMO-raising activation concept has been applied to the greatest number of asymmetric transformations through enamine, dienamine, and SOMO-activation strategies. Recently, trienamine catalysis, an extension of amine catalysis, has emerged as a powerful tool for synthetic chemists with a novel activation strategy for polyenals/polyenones. In this review article, we discuss the initial developments of trienamine catalysis for highly asymmetric Diels-Alder reactions with different dienophiles and emerging opportunities for other types of cycloadditions and cascade reactions.

  12. DNA-based hybrid catalysis.

    Science.gov (United States)

    Rioz-Martínez, Ana; Roelfes, Gerard

    2015-04-01

    In the past decade, DNA-based hybrid catalysis has merged as a promising novel approach to homogeneous (asymmetric) catalysis. A DNA hybrid catalysts comprises a transition metal complex that is covalently or supramolecularly bound to DNA. The chiral microenvironment and the second coordination sphere interactions provided by the DNA are key to achieve high enantioselectivities and, often, additional rate accelerations in catalysis. Nowadays, current efforts are focused on improved designs, understanding the origin of the enantioselectivity and DNA-induced rate accelerations, expanding the catalytic scope of the concept and further increasing the practicality of the method for applications in synthesis. Herein, the recent developments will be reviewed and the perspectives for the emerging field of DNA-based hybrid catalysis will be discussed.

  13. A Survey Course in Catalysis.

    Science.gov (United States)

    Skaates, J. M.

    1982-01-01

    Describes a 10-week survey course in catalysis for chemical engineering and chemistry students designed to show how modern chemistry and chemical engineering interact in the ongoing development of industrial catalysts. Includes course outline and instructional strategies. (Author/JN)

  14. Editorial: Nanoscience makes catalysis greener

    KAUST Repository

    Polshettiwar, Vivek

    2012-01-09

    Green chemistry by nanocatalysis: Catalysis is a strategic field of science because it involves new ways of meeting energy and sustainability challenges. The concept of green chemistry, which makes the science of catalysis even more creative, has become an integral part of sustainability. This special issue is at the interface of green chemistry and nanocatalysis, and features excellent background articles as well as the latest research results. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Novel strategies in drug discovery of the calcium-sensing receptor based on biased signaling

    DEFF Research Database (Denmark)

    Thomsen, Alex Rojas Bie; Smajilovic, Sanela; Bräuner-Osborne, Hans

    2012-01-01

    A hallmark of chronic kidney disease is hyperphosphatemia due to renal phosphate retention. Prolonged parathyroid gland exposure to hyperphosphatemia leads to secondary hyperparathyroidism characterized by hyperplasia of the glands and excessive secretion of parathyroid hormone (PTH), which cause...... of hypocalcemia by virtue of it not affecting calcitonin secretion. The present review will focus on recent advancements in understanding signaling and biased signaling of the CaSR, and how that may be utilized to discover new and smarter drugs targeting the CaSR....

  16. Convertible MRI contrast: Sensing the delivery and release of anti-glioma nano-drugs

    Science.gov (United States)

    Zhang, Liang; Zhang, Zhongwei; Mason, Ralph P.; Sarkaria, Jann N.; Zhao, Dawen

    2015-05-01

    There is considerable interest in developing nanohybrids of imaging contrast agents and drugs for image-guided drug delivery. We have developed a strategy of utilizing manganese (Mn) to enhance the nano-encapsulation of arsenic trioxide (ATO). Formation of arsenite (As3+)-Mn precipitates in liposomes generates magnetic susceptibility effects, reflected as dark contrast on T2-weighted MRI. Intriguingly, following cell uptake, the As-Mn complex decomposes in response to low pH in endosome-lysosome releasing ionic As3+, the active form of ATO, and Mn2+, the T1 contrast agent that gives a bright signal. Glioblastoma (GBM) is well known for its high resistance to chemotherapy, e.g., temozolomide (TMZ). Building upon the previously established phosphatidylserine (PS)-targeted nanoplatform that has excellent GBM-targeting specificity, we now demonstrate the effectiveness of the targeted nanoformulated ATO for treating TMZ-resistant GBM cells and the ability of the convertible Mn contrast as a surrogate revealing the delivery and release of ATO.

  17. Asymmetric fluorination of α-branched cyclohexanones enabled by a combination of chiral anion phase-transfer catalysis and enamine catalysis using protected amino acids.

    Science.gov (United States)

    Yang, Xiaoyu; Phipps, Robert J; Toste, F Dean

    2014-04-01

    We report a study involving the successful merger of two separate chiral catalytic cycles: a chiral anion phase-transfer catalysis cycle to activate Selectfluor and an enamine activation cycle, using a protected amino acid as organocatalyst. We have demonstrated the viability of this approach with the direct asymmetric fluorination of α-substituted cyclohexanones to generate quaternary fluorine-containing stereocenters. With these two chiral catalytic cycles operating together in a matched sense, high enantioselectivites can be achieved, and we envisage that this dual catalysis method has the potential to be more broadly applicable, given the breadth of enamine catalysis. It also represents a rare example of chiral enamine catalysis operating successfully on α-branched ketones, substrates commonly inert to this activation mode.

  18. Making sense of the transition from the Detroit streets to drug treatment.

    Science.gov (United States)

    Draus, Paul; Roddy, Juliette; Asabigi, Kanzoni

    2015-02-01

    In this article we consider the process of adjustment from active street sex work to life in structured substance abuse treatment among Detroit-area women who participated in a semicoercive program administered through a drug court. We examine this transition in terms of changes in daily routines and social networks, drawing on extensive qualitative data to illuminate the ways in which women defined their own situations. Using concepts from Bourdieu and Latour as analytical aids, we analyze the role of daily routines, environments, and networks in producing the shifts in identity that those who embraced the goals of recovery demonstrated. We conclude with a discussion of how the restrictive environments and redundant situations experienced by women in treatment could be paradoxically embraced as a means to achieve expanded opportunity and enhanced individual responsibility because women effectively reassembled their social networks and identities to align with the goals of recovery. PMID:25246332

  19. Enhanced Micellar Catalysis LDRD.

    Energy Technology Data Exchange (ETDEWEB)

    Betty, Rita G.; Tucker, Mark D; Taggart, Gretchen; Kinnan, Mark K.; Glen, Crystal Chanea; Rivera, Danielle; Sanchez, Andres; Alam, Todd Michael

    2012-12-01

    The primary goals of the Enhanced Micellar Catalysis project were to gain an understanding of the micellar environment of DF-200, or similar liquid CBW surfactant-based decontaminants, as well as characterize the aerosolized DF-200 droplet distribution and droplet chemistry under baseline ITW rotary atomization conditions. Micellar characterization of limited surfactant solutions was performed externally through the collection and measurement of Small Angle X-Ray Scattering (SAXS) images and Cryo-Transmission Electron Microscopy (cryo-TEM) images. Micellar characterization was performed externally at the University of Minnesotas Characterization Facility Center, and at the Argonne National Laboratory Advanced Photon Source facility. A micellar diffusion study was conducted internally at Sandia to measure diffusion constants of surfactants over a concentration range, to estimate the effective micelle diameter, to determine the impact of individual components to the micellar environment in solution, and the impact of combined components to surfactant phase behavior. Aerosolized DF-200 sprays were characterized for particle size and distribution and limited chemical composition. Evaporation rates of aerosolized DF-200 sprays were estimated under a set of baseline ITW nozzle test system parameters.

  20. Solid-state probe based electrochemical aptasensor for cocaine: a potentially convenient, sensitive, repeatable, and integrated sensing platform for drugs.

    Science.gov (United States)

    Du, Yan; Chen, Chaogui; Yin, Jianyuan; Li, Bingling; Zhou, Ming; Dong, Shaojun; Wang, Erkang

    2010-02-15

    Aptamers, which are artificial oligonucleotides selected in vitro, have been employed to design novel biosensors (i.e., aptasensors). In this work, we first constructed a label-free electrochemical aptasensor introducing a probe immobilization technique by the use of a layer-by-layer (LBL) self-assembled multilayer with ferrocene-appended poly(ethyleneimine) (Fc-PEI) on an indium tin oxide (ITO) array electrode for detection of cocaine. The Fc-PEI and gold nanoparticles (AuNPs) were LBL assembled on the electrode surface via electrostatic interaction. Then, cocaine aptamer fragments, SH-C2, were covalently labeled onto the outermost AuNP layer. When the target cocaine and cocaine aptamer C1 were present simultaneously, the SH-C2 layer hybridized partly with C1 to bind the cocaine, which led to a decreased differential pulse voltammetry (DPV) signal of Fc-PEI. This DPV signal change could be used to sensitively detect cocaine with the lowest detectable concentration down to 0.1 microM and the detection range up to 38.8 microM, which falls in the the expected range for medical use of detecting drug abuse involving cocaine. Meanwhile, the sensor was specific to cocaine in complex biologic fluids such as human plasma, human saliva, etc. The sensing strategy had general applicability, and the detection of thrombin could also be realized, displayed a low detection limit, and exhibited worthiness to other analytes. The aptasensor based on the array electrode held promising potential for integration of the sensing ability in multianalysis for simultaneous detection.

  1. Environmental catalysis: the Canadian situation

    Energy Technology Data Exchange (ETDEWEB)

    Aye, T.; Christensen, D.; Gostick, J.; Mogharei, A.; Oskin, G. O.; Won, W.; Aida, T. [Waterloo Univ. ON (Canada)

    2000-10-01

    The Canadian situation with respect to research in environmental catalysis was investigated by analyzing catalysis papers appearing in the 1999 and 2000 issues of major journals devoted to research in catalysis (Journal of Catalysis; Catalysis Today; Applied Catalysis A: General and B: Environmental). A total of 2150 papers were surveyed; of these 34 were by Canadian authors, with Canada ranking twentieth in the world in terms of research in this field. About 40 per cent of the catalysis papers were related to the environment, with nitrogen and sulphur emissions being the most important topics and energy conversion second. Hydrodesulphurization of petroleum oil, use of low sulphur coal and flue gas desulphurization are the principal processes for controlling sulfur emissions into the air, while nitrogen oxides emissions in automobiles are ccontrolled bt three-way catalysts. In power generation, selective catalytic reduction is the preferred method, although not in Canada, where installing low-NOx burners or using low nitrogen fuels such as natural gas are favored. The control of volatile organic compounds is also a serious problem. The two most promising processes for the Canadian situation are adsorption by activated carbon and catalysis using low-temperature catalysts. Water treatment of textile mill effluents, a favorite topics by Canadian authors, includes photocatalytic oxidation with titanium oxide photocatalyst, ozonation with activated carbons and a combination of photocatalysis and biological treatment. Carbon dioxide conversion was also a favoured topic by Canadian researchers; not surprising in view if the fact that Canada is the highest per capita producer of carbon dioxide emissions. Nearly two-thirds of the carbon dioxide emissions is due to the transportation and energy production sectors, therefore, any carbon dioxide mitigation strategies should be applied initially in these areas. Catalytic conversion of carbon dioxide into methanol, which then

  2. Catalysis and sustainable (green) chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Centi, Gabriele; Perathoner, Siglinda [Dipartimento di Chimica Industriale ed Ingegneria dei Materiali, University of Messina, Salita Sperone 31, 98166 Messina (Italy)

    2003-01-15

    Catalysis is a key technology to achieve the objectives of sustainable (green) chemistry. After introducing the concepts of sustainable (green) chemistry and a brief assessment of new sustainable chemical technologies, the relationship between catalysis and sustainable (green) chemistry is discussed and illustrated via an analysis of some selected and relevant examples. Emphasis is also given to the concept of catalytic technologies for scaling-down chemical processes, in order to develop sustainable production processes which reduce the impact on the environment to an acceptable level that allows self-depuration processes of the living environment.

  3. CAS Researcher Wins International Catalysis Award

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    @@ Prof. Li Can, a CAS member and director of the State Key Laboratory of Catalysis at the CAS Dalian Institute of Chemical Physics, received the International Catalysis Award at the 13th International Catalysis Congress (ICC)held from July 11 to 16 in Paris.

  4. EMSL and Institute for Integrated Catalysis (IIC) Catalysis Workshop

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, Charles T.; Datye, Abhaya K.; Henkelman, Graeme A.; Lobo, Raul F.; Schneider, William F.; Spicer, Leonard D.; Tysoe, Wilfred T.; Vohs, John M.; Baer, Donald R.; Hoyt, David W.; Thevuthasan, Suntharampillai; Mueller, Karl T.; Wang, Chong M.; Washton, Nancy M.; Lyubinetsky, Igor; Teller, Raymond G.; Andersen, Amity; Govind, Niranjan; Kowalski, Karol; Kabius, Bernd C.; Wang, Hongfei; Campbell, Allison A.; Shelton, William A.; Bylaska, Eric J.; Peden, Charles HF; Wang, Yong; King, David L.; Henderson, Michael A.; Rousseau, Roger J.; Szanyi, Janos; Dohnalek, Zdenek; Mei, Donghai; Garrett, Bruce C.; Ray, Douglas; Futrell, Jean H.; Laskin, Julia; DuBois, Daniel L.; Kuprat, Laura R.; Plata, Charity

    2011-05-24

    Within the context of significantly accelerating scientific progress in research areas that address important societal problems, a workshop was held in November 2010 at EMSL to identify specific and topically important areas of research and capability needs in catalysis-related science.

  5. Cyclopalladated complexes in enantioselective catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Dunina, Valeria V; Gorunova, Olga N; Zykov, P A; Kochetkov, Konstantin A

    2011-01-31

    The results of the use of optically active palladacycles in enantioselective catalysis of [3,3]-sigmatropic rearrangements, aldol condensation, the Michael reaction and cross-coupling are analyzed. Reactions with allylic substrates or reagents and some other transformations are considered.

  6. Cyclopalladated complexes in enantioselective catalysis

    Science.gov (United States)

    Dunina, Valeria V.; Gorunova, Olga N.; Zykov, P. A.; Kochetkov, Konstantin A.

    2011-01-01

    The results of the use of optically active palladacycles in enantioselective catalysis of [3,3]-sigmatropic rearrangements, aldol condensation, the Michael reaction and cross-coupling are analyzed. Reactions with allylic substrates or reagents and some other transformations are considered.

  7. Catalysis in Molten Ionic Media

    DEFF Research Database (Denmark)

    Boghosian, Soghomon; Fehrmann, Rasmus

    2013-01-01

    This chapter deals with catalysis in molten salts and ionic liquids, which are introduced and reviewed briefly, while an in-depth review of the oxidation catalyst used for the manufacturing of sulfuric acid and cleaning of flue gas from electrical power plants is the main topic of the chapter...

  8. Binding Energy and Enzymatic Catalysis.

    Science.gov (United States)

    Hansen, David E.; Raines, Ronald T.

    1990-01-01

    Discussed is the fundamental role that the favorable free energy of binding of the rate-determining transition state plays in catalysis. The principle that all of the catalytic factors discussed are realized by the use of this binding energy is reviewed. (CW)

  9. Nanoconfinement Effects in Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Kung, Harold [Northwestern Univ., Evanston, IL (United States)

    2016-09-19

    The objective of this study is to improve our understanding of the effect of active site environment in heterogeneous catalysis by synthesizing and probing the properties of nanostructures that would define the environment around an active site and could be modified according to design. In this investigation, the unique properties that stem from the constrained environment and enforced proximity of functional groups at the active site were demonstrated for a number of systems. The first system is a nanocage structure with silicon-based, atom-thick shells and molecular-size cavities. The shell imparts the expected size exclusion for access to the interior cavity, and the confined space together with the hydrophobic shell strongly influences the stability of charged groups. One consequence is that the interior amine groups in a siloxane nanocage exhibit a shift in their protonation ability that is equivalent to about 4 pH units. In another nanocage structure designed to possess a core-shell structure in which the core periphery is decorated with carboxylic acid groups and the shell interior is populated with silanol groups, the restricted motion of the core results in limiting the stoichiometry of reaction between carboxylic acid and a Co2CO8 complex, which leads to formation and stabilization of Co(I) ions in the nanocage. The second designed catalytic structure is a supported, isolated, Lewis acid Sn-oxide unit derived from a (POSS)-Sn-(POSS) molecular complex (POSS = incompletely condensed silsesquioxane). The Sn center in the (POSS)-Sn-(POSS) complex is present in a tetrahedral coordination, as confirmed by single crystal x-ray crystallography and Sn NMR, and its Lewis acid character is demonstrated with its binding to amines. The retention of the tetrahedral coordination of Sn after heterogenization and mild oxidative treatment is confirmed by characterization using EXAFS, NMR, UV-vis, and DRIFT, and its Lewis acid character is confirmed by stoichiometric

  10. Beyond relationships between homogeneous and heterogeneous catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, David A. [Univ. of Alabama, Tuscaloosa, AL (United States); Katz, Alexander [Univ. of California, Berkeley, CA (United States); Arslan, Ilke [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Gates, Bruce C. [Univ. of California, Davis, CA (United States)

    2014-08-13

    Scientists who regard catalysis as a coherent field have been striving for decades to articulate the fundamental unifying principles. But because these principles seem to be broader than chemistry, chemical engineering, and materials science combined, catalytic scientists commonly interact within the sub-domains of homogeneous, heterogeneous, and bio-catalysis, and increasingly within even narrower domains such as organocatalysis, phase-transfer catalysis, acid-base catalysis, zeolite catalysis, etc. Attempts to unify catalysis have motivated researchers to find relationships between homogeneous and heterogeneous catalysis and to mimic enzymes. These themes have inspired vibrant international meetings and workshops, and we have benefited from the idea exchanges and have some thoughts about a path forward.

  11. Elucidating the signal responses of multi-parametric surface plasmon resonance living cell sensing: a comparison between optical modeling and drug-MDCKII cell interaction measurements.

    Directory of Open Access Journals (Sweden)

    Tapani Viitala

    Full Text Available In vitro cell-based assays are widely used during the drug discovery and development process to test the biological activity of new drugs. Most of the commonly used cell-based assays, however, lack the ability to measure in real-time or under dynamic conditions (e.g. constant flow. In this study a multi-parameter surface plasmon resonance approach in combination with living cell sensing has been utilized for monitoring drug-cell interactions in real-time, under constant flow and without labels. The multi-parameter surface plasmon resonance approach, i.e. surface plasmon resonance angle versus intensity plots, provided fully specific signal patterns for various cell behaviors when stimulating cells with drugs that use para- and transcellular absorption routes. Simulated full surface plasmon resonance angular spectra of cell monolayers were compared with actual surface plasmon resonance measurements performed with MDCKII cell monolayers in order to better understand the origin of the surface plasmon resonance signal responses during drug stimulation of cells. The comparison of the simulated and measured surface plasmon resonance responses allowed to better understand and provide plausible explanations for the type of cellular changes, e.g. morphological or mass redistribution in cells, that were induced in the MDCKII cell monolayers during drug stimulation, and consequently to differentiate between the type and modes of drug actions. The multi-parameter surface plasmon resonance approach presented in this study lays the foundation for developing new types of cell-based tools for life science research, which should contribute to an improved mechanistic understanding of the type and contribution of different drug transport routes on drug absorption.

  12. Methane Activation by Heterogeneous Catalysis

    OpenAIRE

    Horn, R.; Schlögl, R.

    2015-01-01

    Methane activation by heterogeneous catalysis will play a key role to secure the supply of energy, chemicals and fuels in the future. Methane is the main constituent of natural gas and biogas and it is also found in crystalline hydrates at the continental slopes of many oceans and in permafrost areas. In view of this vast reserves and resources, the use of methane as chemical feedstock has to be intensified. The present review presents recent results and developments in heterogeneous catalyti...

  13. Magnetic catalysis in nuclear matter

    OpenAIRE

    Haber, Alexander; Preis, Florian; Schmitt, Andreas

    2014-01-01

    A strong magnetic field enhances the chiral condensate at low temperatures. This so-called magnetic catalysis thus seeks to increase the vacuum mass of nucleons. We employ two relativistic field-theoretical models for nuclear matter, the Walecka model and an extended linear sigma model, to discuss the resulting effect on the transition between vacuum and nuclear matter at zero temperature. In both models we find that the creation of nuclear matter in a sufficiently strong magnetic field becom...

  14. Reaction Selectivity in Heterogeneous Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai, Gabor A.; Kliewer, Christopher J.

    2009-02-02

    The understanding of selectivity in heterogeneous catalysis is of paramount importance to our society today. In this review we outline the current state of the art in research on selectivity in heterogeneous catalysis. Current in-situ surface science techniques have revealed several important features of catalytic selectivity. Sum frequency generation vibrational spectroscopy has shown us the importance of understanding the reaction intermediates and mechanism of a heterogeneous reaction, and can readily yield information as to the effect of temperature, pressure, catalyst geometry, surface promoters, and catalyst composition on the reaction mechanism. DFT calculations are quickly approaching the ability to assist in the interpretation of observed surface spectra, thereby making surface spectroscopy an even more powerful tool. HP-STM has revealed three vitally important parameters in heterogeneous selectivity: adsorbate mobility, catalyst mobility, and selective site-blocking. The development of size controlled nanoparticles from 0.8 to 10 nm, of controlled shape, and of controlled bimetallic composition has revealed several important variables for catalytic selectivity. Lastly, DFT calculations may be paving the way to guiding the composition choice for multi-metallic heterogeneous catalysis for the intelligent design of catalysts incorporating the many factors of selectivity we have learned.

  15. Nanometallic chemistry: deciphering nanoparticle catalysis from the perspective of organometallic chemistry and homogeneous catalysis.

    Science.gov (United States)

    Yan, Ning; Yuan, Yuan; Dyson, Paul J

    2013-10-01

    Nanoparticle (NP) catalysis is traditionally viewed as a sub-section of heterogeneous catalysis. However, certain properties of NP catalysts, especially NPs dispersed in solvents, indicate that there could be benefits from viewing them from the perspective of homogeneous catalysis. By applying the fundamental approaches and concepts routinely used in homogeneous catalysis to NP catalysts it should be possible to rationally design new nanocatalysts with superior properties to those currently in use.

  16. Cosmic strings and baryon decay catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Gregory, R.; Perkins, W.B.; Davis, A.C.; Brandenberger, R.H. (Fermi National Accelerator Lab., Batavia, IL (USA); Cambridge Univ. (UK); Brown Univ., Providence, RI (USA). Dept. of Physics)

    1989-09-01

    Cosmic strings, like monopoles, can catalyze proton decay. For integer charged fermions, the cross section for catalysis is not amplified, unlike in the case of monopoles. We review the catalysis processes both in the free quark and skyrmion pictures and discuss the implications for baryogenesis. We present a computation of the cross section for monopole catalyzed skyrmion decay using classical physics. We also discuss some effects which can screen catalysis processes. 32 refs., 1 fig.

  17. Cooperative catalysis designing efficient catalysts for synthesis

    CERN Document Server

    Peters, René

    2015-01-01

    Written by experts in the field, this is a much-needed overview of the rapidly emerging field of cooperative catalysis. The authors focus on the design and development of novel high-performance catalysts for applications in organic synthesis (particularly asymmetric synthesis), covering a broad range of topics, from the latest progress in Lewis acid / Br?nsted base catalysis to e.g. metal-assisted organocatalysis, cooperative metal/enzyme catalysis, and cooperative catalysis in polymerization reactions and on solid surfaces. The chapters are classified according to the type of cooperating acti

  18. Solid acid catalysis from fundamentals to applications

    CERN Document Server

    Hattori, Hideshi

    2014-01-01

    IntroductionTypes of solid acid catalystsAdvantages of solid acid catalysts Historical overviews of solid acid catalystsFuture outlookSolid Acids CatalysisDefinition of acid and base -Brnsted acid and Lewis acid-Acid sites on surfacesAcid strengthRole of acid sites in catalysisBifunctional catalysisPore size effect on catalysis -shape selectivity-Characterization of Solid Acid Catalysts Indicator methodTemperature programmed desorption (TPD) of ammoniaCalorimetry of adsorption of basic moleculesInfrare

  19. Hydrogen Production by Homogeneous Catalysis: Alcohol Acceptorless Dehydrogenation

    DEFF Research Database (Denmark)

    Nielsen, Martin

    2015-01-01

    in hydrogen production from biomass using homogeneous catalysis. Homogeneous catalysis has the advance of generally performing transformations at much milder conditions than traditional heterogeneous catalysis, and hence it constitutes a promising tool for future applications for a sustainable energy sector...

  20. Fundamental concepts in heterogeneous catalysis

    CERN Document Server

    Norskov, Jens K; Abild-Pedersen, Frank; Bligaard, Thomas

    2014-01-01

    This book is based on a graduate course and suitable as a primer for any newcomer to the field, this book is a detailed introduction to the experimental and computational methods that are used to study how solid surfaces act as catalysts.   Features include:First comprehensive description of modern theory of heterogeneous catalysisBasis for understanding and designing experiments in the field   Allows reader to understand catalyst design principlesIntroduction to important elements of energy transformation technologyTest driven at Stanford University over several semesters

  1. Heterogeneous catalysis fundamentals and applications

    CERN Document Server

    Ross, Julian RH

    2011-01-01

    Heterogeneous catalysis plays a part in the production of more than 80% of all chemical products. It is therefore essential that all chemists and chemical engineers have an understanding of the fundamental principles as well as the applications of heterogeneous catalysts. This book introduces the subject, starting at a basic level, and includes sections on adsorption and surface science, catalytic kinetics, experimental methods for preparing and studying heterogeneous catalysts, as well as some aspects of the design of industrial catalytic reactors. It ends with a chapter that covers a range

  2. DOE Laboratory Catalysis Research Symposium - Abstracts

    Energy Technology Data Exchange (ETDEWEB)

    Dunham, T.

    1999-02-01

    The conference consisted of two sessions with the following subtopics: (1) Heterogeneous Session: Novel Catalytic Materials; Photocatalysis; Novel Processing Conditions; Metals and Sulfides; Nuclear Magnetic Resonance; Metal Oxides and Partial Oxidation; Electrocatalysis; and Automotive Catalysis. (2) Homogeneous Catalysis: H-Transfer and Alkane Functionalization; Biocatalysis; Oxidation and Photocatalysis; and Novel Medical, Methods, and Catalyzed Reactions.

  3. "Nanocrystal bilayer for tandem catalysis"

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Yusuke; Tsung, Chia Kuang; Huang, Wenyu; Huo, Ziyang; E.Habas, Susan E; Soejima, Tetsuro; Aliaga, Cesar E; Samorjai, Gabor A; Yang, Peidong

    2011-01-24

    Supported catalysts are widely used in industry and can be optimized by tuning the composition and interface of the metal nanoparticles and oxide supports. Rational design of metal-metal oxide interfaces in nanostructured catalysts is critical to achieve better reaction activities and selectivities. We introduce here a new class of nanocrystal tandem catalysts that have multiple metal-metal oxide interfaces for the catalysis of sequential reactions. We utilized a nanocrystal bilayer structure formed by assembling platinum and cerium oxide nanocube monolayers of less than 10 nm on a silica substrate. The two distinct metal-metal oxide interfaces, CeO2-Pt and Pt-SiO2, can be used to catalyse two distinct sequential reactions. The CeO2-Pt interface catalysed methanol decomposition to produce CO and H2, which were subsequently used for ethylene hydroformylation catalysed by the nearby Pt-SiO2 interface. Consequently, propanal was produced selectively from methanol and ethylene on the nanocrystal bilayer tandem catalyst. This new concept of nanocrystal tandem catalysis represents a powerful approach towards designing high-performance, multifunctional nanostructured catalysts

  4. Synthesis of a Small Library of Imidazolidin-2-ones using Gold Catalysis on Solid Phase.

    Science.gov (United States)

    La-Venia, Agustina; Medran, Noelia S; Krchňák, Viktor; Testero, Sebastián A

    2016-08-01

    An efficient and high-yielding solid phase synthesis of a small library of imidazolidin-2-ones and imidazol-2-ones was carried out employing a high chemo- and regioselective gold-catalyzed cycloisomerization as a key step. Polymer-supported amino acids derivatized with several alkyne functionalities combined with tosyl- and phenylureas have been subjected to gold-catalysis exhibiting exclusively C-N bond formation. The present work proves the potential of solid phase synthesis and homogeneous gold catalysis as an efficient and powerful synthetic tool for the generation of drug-like heterocycles. PMID:27337593

  5. Surface science and heterogeneous catalysis

    International Nuclear Information System (INIS)

    The catalytic reactions studied include hydrocarbon conversion over platinum, the transition metal-catalyzed hydrogenation of carbon monoxide, and the photocatalyzed dissociation of water over oxide surfaces. The method of combined surface science and catalytic studies is similar to those used in synthetic organic chemistry. The single-crystal models for the working catalyst are compared with real catalysts by comparing the rates of cyclopropane ring opening on platinum and the hydrogenation of carbon monoxide on rhodium single crystal surface with those on practical commercial catalyst systems. Excellent agreement was obtained for these reactions. This document reviews what was learned about heterogeneous catalysis from these surface science approaches over the past 15 years and present models of the active catalyst surface

  6. Magnetic Catalysis vs Magnetic Inhibition

    CERN Document Server

    Fukushima, Kenji

    2012-01-01

    We discuss the fate of chiral symmetry in an extremely strong magnetic field B. We investigate not only quark fluctuations but also neutral meson effects. The former would enhance the chiral-symmetry breaking at finite B according to the Magnetic Catalysis, while the latter would suppress the chiral condensate once B exceeds the scale of the hadron structure. Using a chiral model we demonstrate how neutral mesons are subject to the dimensional reduction and the low dimensionality favors the chiral-symmetric phase. We point out that this effect, the Magnetic Inhibition, can be a feasible explanation for recent lattice-QCD data indicating the decreasing behavior of the chiral-restoration temperature with increasing B.

  7. Nanocrystal assembly for tandem catalysis

    Science.gov (United States)

    Yang, Peidong; Somorjai, Gabor; Yamada, Yusuke; Tsung, Chia-Kuang; Huang, Wenyu

    2014-10-14

    The present invention provides a nanocrystal tandem catalyst comprising at least two metal-metal oxide interfaces for the catalysis of sequential reactions. One embodiment utilizes a nanocrystal bilayer structure formed by assembling sub-10 nm platinum and cerium oxide nanocube monolayers on a silica substrate. The two distinct metal-metal oxide interfaces, CeO.sub.2--Pt and Pt--SiO.sub.2, can be used to catalyze two distinct sequential reactions. The CeO.sub.2--Pt interface catalyzed methanol decomposition to produce CO and H.sub.2, which were then subsequently used for ethylene hydroformylation catalyzed by the nearby Pt--SiO.sub.2 interface. Consequently, propanal was selectively produced on this nanocrystal bilayer tandem catalyst.

  8. Inverse Magnetic/Shear Catalysis

    CERN Document Server

    McInnes, Brett

    2015-01-01

    It is well known that very large magnetic fields are generated when the Quark-Gluon Plasma is formed during peripheral heavy-ion collisions. Lattice, holographic, and other studies strongly suggest that these fields may, for observationally relevant field values, induce ``inverse magnetic catalysis'', signalled by a lowering of the critical temperature for the chiral/deconfinement transition. The theoretical basis of this effect has recently attracted much attention; yet so far these investigations have not included another, equally dramatic consequence of the peripheral collision geometry: the QGP acquires a large angular momentum vector, parallel to the magnetic field. Here we use holographic techniques to argue that the angular momentum can also, independently, have an effect on transition temperatures, and we obtain a rough estimate of the relative effects of the presence of both a magnetic field and an angular momentum density. We find that the shearing angular momentum reinforces the effect of the magne...

  9. Palladium catalysis for energy applications

    Energy Technology Data Exchange (ETDEWEB)

    Pfefferle, L. D.; Datye, Abhaya

    2001-03-01

    Palladium (Pd) is an attractive catalyst for a range of new combustion applications comprising primary new technologies for future industrial energy needs, including gas turbine catalytic combustion, auto exhaust catalysts, heating and fuel cells. Pd poses particular challenges because it changes both chemical state and morphology as a function of temperature and reactant environment and those changes result in positive and negative changes in activity. Interactions with the support, additives, water, and contaminants as well as carbon formation have also been observed to affect Pd catalyst performance. This report describes the results of a 3.5 year project that resolves some of the conflicting reports in the literature about the performance of Pd-based catalysis.

  10. Supported Ionic Liquid Phase (SILP) catalysis

    DEFF Research Database (Denmark)

    Riisager, Anders; Fehrmann, Rasmus; Haumann, Marco;

    2006-01-01

    Applications of ionic liquids to replace conventional solvents in homogeneous transition-metal catalysis have increased significantly during the last decade. Biphasic ionic liquid/organic liquid systems offer advantages with regard to product separation, catalyst stability, and recycling...... but utilise in the case of fast chemical reactions only a small amount of expensive ionic liquid and catalyst. The novel Supported Ionic Liquid Phase (SILP) catalysis concept overcomes these drawbacks and allows the use of fixed-bed reactors for continuous reactions. In this Microreview the SILP catalysis...

  11. Asymmetric catalysis with short-chain peptides.

    Science.gov (United States)

    Lewandowski, Bartosz; Wennemers, Helma

    2014-10-01

    Within this review article we describe recent developments in asymmetric catalysis with peptides. Numerous peptides have been established in the past two decades that catalyze a wide variety of transformations with high stereoselectivities and yields, as well as broad substrate scope. We highlight here catalytically active peptides, which have addressed challenges that had thus far remained elusive in asymmetric catalysis: enantioselective synthesis of atropoisomers and quaternary stereogenic centers, regioselective transformations of polyfunctional substrates, chemoselective transformations, catalysis in-flow and reactions in aqueous environments.

  12. Biomimetic catalysis: Taking on the turnover challenge

    Science.gov (United States)

    Hooley, Richard J.

    2016-03-01

    Emulating the efficiency with which enzymes catalyse reactions has often been used as inspiration to develop self-assembled cages. Now two studies present approaches to achieving catalyst turnover -- one of the biggest challenges in achieving truly biomimetic catalysis.

  13. Bioorthogonal catalysis: Rise of the nanobots

    Science.gov (United States)

    Unciti-Broceta, Asier

    2015-07-01

    Bioorthogonal catalysis provides new ways of mediating artificial transformations in living environs. Now, researchers have developed a nanodevice whose catalytic activity can be regulated by host-guest chemistry.

  14. A Course in Kinetics and Catalysis.

    Science.gov (United States)

    Bartholomew, C. H.

    1981-01-01

    Describes a one-semester, three-credit hour course integrating the fundamentals of kinetics and the scientific/engineering principles of heterogeneous catalysis. Includes course outline, list of texts, background readings, and topical journal articles. (SK)

  15. Micelle Catalysis of an Aromatic Substitution Reaction

    Science.gov (United States)

    Corsaro, Gerald; Smith J. K.

    1976-01-01

    Describes an experiment in which the iodonation of aniline reaction is shown to undergo catalysis in solution of sodium lauryl sulfate which forms micelles with negatively charged pseudo surfaces. (MLH)

  16. Theory of laser catalysis with pulses

    CERN Document Server

    Vardi, A

    2001-01-01

    The possibility of accelerating molecular reactions by lasers has attracted considerable theoretical and experimental interest. A particular example of laser-modified reaction dynamics is laser catalysis, a process in which the tunneling through a potential barrier is enhanced by transient excitation to a bound electronic state. We have performed detailed calculations of pulsed laser catalysis on one- and two-dimensional potentials, as a function of the reactants' collision energy and the laser's central frequency. In agreement with previous CW results, the reactive lineshapes are Fano-type curves, resulting from interference between nonradiative tunneling and the optically assisted pathway. In contrast to the CW process, the power requirements of pulsed laser catalysis are well within the reach of commonly used pulsed laser sources, making an experimental realization possible. The laser catalysis scenario is shown to be equivalent in the ``dressed'' state picture, to resonant tunneling through a double-barri...

  17. Making Sense of Commercial Speech: A Theoretical Framework and A Case Study in Food and Drug Law

    OpenAIRE

    Sukhatme, Neel

    2005-01-01

    This Note creates a theoretical framework for understanding commercial speech as a form of hybrid expression. It describes how commercial speech shares some features with expressive conduct and other characteristics with fully regulable “speech†such as exterior product designs. It also discusses how courts have been increasingly treating commercial speech like core First Amendment expression, and how many food and drug regulations have been invalidated in recen...

  18. Amperometric sensing of anti-HIV drug zidovudine on Ag nanofilm-multiwalled carbon nanotubes modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Rafati, Amir Abbas, E-mail: aa_rafati@basu.ac.ir; Afraz, Ahmadreza

    2014-06-01

    The zidovudine (ZDV) is the first drug approved for the treatment of HIV virus infection. The detection and determination of this drug are very importance in human serum because of its undesirable effects. A new ZDV sensor was fabricated on the basis of nanocomposite of silver nanofilm (Ag-NF) and multiwalled carbon nanotubes (MWCNTs) immobilized on glassy carbon electrode (GCE). The modified electrodes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), cyclic voltammetry (CV), and linear sweep voltammetry (LSV) techniques. Results showed that the electrodeposited silver has a nanofilm structure and further electrochemical studies showed that the prepared nanocomposite has high electrocatalytic activity and is appropriate for using in sensors. The amperometric technique under optimal conditions is used for the determination of ZDV ranging from 0.1 to 400 ppm (0.37 μM–1.5 mM) with a low detection limit of 0.04 ppm (0.15 μM) (S/N = 3) and good sensitivity. The prepared sensor possessed accurate and rapid response to ZDV and shows an average recovery of 98.6% in real samples. - Highlights: • New anti-HIV drug sensor was fabricated on the basis of nanomaterials composite. • The GCE modified by prepared hydrophilic MWCNT silver nanoparticles. • Silver nanofilm electrodeposited on MWCNT/GCE and characterized by SEM, EDX, CV and LSV • Response of electrode to ZDV was thoroughly investigated by electrochemical techniques.

  19. Applications of Chiral Anions in Asymmetric Catalysis

    OpenAIRE

    Hamilton, Gregory Lawrence

    2011-01-01

    The synthesis of molecules with control over their three-dimensional configuration, known as absolute stereochemistry, is one of the highest goals of synthetic organic chemists. As is so often the case, we strive to reach the facility and efficiency with which Nature achieves this goal. Fortunately, the chemist's imagination allows us to envision nearly unlimited possibilities for new modes of catalysis. In this dissertation, I discuss one branch of asymmetric catalysis that has in a short ti...

  20. Sucrose Inversion An Experiment on Heterogeneous Catalysis

    OpenAIRE

    Adélio Mendes; Magalhães, Fernão D.; Luis M. Madeira

    2003-01-01

    llustration of heterogeneous catalysis concepts in laboratory courses is not usually simple or economical. For our undergraduate senior lab course we have developed an environmentally friendly experiment dealing with several aspects of heterogeneous catalysis, having in mind the use of readily available and relatively inexpensive equipment, and chemicals on a compact setup, which students can safely operate. The experiment deals with the acid-catalyzed sucrose inversion, performed in packed b...

  1. Recent advances in homogeneous nickel catalysis.

    Science.gov (United States)

    Tasker, Sarah Z; Standley, Eric A; Jamison, Timothy F

    2014-05-15

    Tremendous advances have been made in nickel catalysis over the past decade. Several key properties of nickel, such as facile oxidative addition and ready access to multiple oxidation states, have allowed the development of a broad range of innovative reactions. In recent years, these properties have been increasingly understood and used to perform transformations long considered exceptionally challenging. Here we discuss some of the most recent and significant developments in homogeneous nickel catalysis, with an emphasis on both synthetic outcome and mechanism.

  2. Loop residues and catalysis in OMP synthase

    DEFF Research Database (Denmark)

    Wang, Gary P.; Hansen, Michael Riis; Grubmeyer, Charles

    2012-01-01

    (preceding paper in this issue, DOI 10.1021/bi300083p)]. The full expression of KIEs by H105A and E107A may result from a less secure closure of the catalytic loop. The lower level of expression of the KIE by K103A suggests that in these mutant proteins the major barrier to catalysis is successful closure...... of the catalytic loop, which when closed, produces rapid and reversible catalysis....

  3. ISOTOPE METHODS IN HOMOGENEOUS CATALYSIS.

    Energy Technology Data Exchange (ETDEWEB)

    BULLOCK,R.M.; BENDER,B.R.

    2000-12-01

    The use of isotope labels has had a fundamentally important role in the determination of mechanisms of homogeneously catalyzed reactions. Mechanistic data is valuable since it can assist in the design and rational improvement of homogeneous catalysts. There are several ways to use isotopes in mechanistic chemistry. Isotopes can be introduced into controlled experiments and followed where they go or don't go; in this way, Libby, Calvin, Taube and others used isotopes to elucidate mechanistic pathways for very different, yet important chemistries. Another important isotope method is the study of kinetic isotope effects (KIEs) and equilibrium isotope effect (EIEs). Here the mere observation of where a label winds up is no longer enough - what matters is how much slower (or faster) a labeled molecule reacts than the unlabeled material. The most careti studies essentially involve the measurement of isotope fractionation between a reference ground state and the transition state. Thus kinetic isotope effects provide unique data unavailable from other methods, since information about the transition state of a reaction is obtained. Because getting an experimental glimpse of transition states is really tantamount to understanding catalysis, kinetic isotope effects are very powerful.

  4. Inverse magnetic/shear catalysis

    Science.gov (United States)

    McInnes, Brett

    2016-05-01

    It is well known that very large magnetic fields are generated when the Quark-Gluon Plasma is formed during peripheral heavy-ion collisions. Lattice, holographic, and other studies strongly suggest that these fields may, for observationally relevant field values, induce "inverse magnetic catalysis", signalled by a lowering of the critical temperature for the chiral/deconfinement transition. The theoretical basis of this effect has recently attracted much attention; yet so far these investigations have not included another, equally dramatic consequence of the peripheral collision geometry: the QGP acquires a large angular momentum vector, parallel to the magnetic field. Here we use holographic techniques to argue that the angular momentum can also, independently, have an effect on transition temperatures, and we obtain a rough estimate of the relative effects of the presence of both a magnetic field and an angular momentum density. We find that the shearing angular momentum reinforces the effect of the magnetic field at low values of the baryonic chemical potential, but that it can actually decrease that effect at high chemical potentials.

  5. Advanced Resources for Catalysis Science; Recommendations for a National Catalysis Research Institute

    Energy Technology Data Exchange (ETDEWEB)

    Peden, Charles HF.; Ray, Douglas

    2005-10-05

    Catalysis is one of the most valuable contributors to our economy and historically an area where the United States has enjoyed, but is now losing, international leadership. While other countries are stepping up their work in this area, support for advanced catalysis research and development in the U.S. has diminished. Yet, more than ever, innovative and improved catalyst technologies are imperative for new energy production processes to ease our dependence on imported resources, for new energy-efficient and environmentally benign chemical production processes, and for new emission reduction technologies to minimize the environmental impact of an active and growing economy. Addressing growing concerns about the future direction of U.S. catalysis science, experts from the catalysis community met at a workshop to determine and recommend advanced resources needed to address the grand challenges for catalysis research and development. The workshop's primary conclusion: To recapture our position as the leader in catalysis innovation and practice, and promote crucial breakthroughs, the U.S. must establish one or more well-funded and well-equipped National Catalysis Research Institutes competitively selected, centered in the national laboratories and, by charter, networked to other national laboratories, universities, and industry. The Institute(s) will be the center of a national collaboratory that gives catalysis researchers access to the most advanced techniques available in the scientific enterprise. The importance of catalysis to our energy, economic, and environmental security cannot be overemphasized. Catalysis is a vital part of our core industrial infrastructure, as it is integral to chemical processing and petroleum refining, and is critical to proposed advances needed to secure a sustainable energy future. Advances in catalysis could reduce our need for foreign oil by making better use of domestic carbon resources, for example, allowing cost-effective and

  6. Electric-field enhanced performance in catalysis and solid-state devices involving gases

    Science.gov (United States)

    Blackburn, Bryan M.; Wachsman, Eric D.; Van Assche, IV, Frederick Martin

    2015-05-19

    Electrode configurations for electric-field enhanced performance in catalysis and solid-state devices involving gases are provided. According to an embodiment, electric-field electrodes can be incorporated in devices such as gas sensors and fuel cells to shape an electric field provided with respect to sensing electrodes for the gas sensors and surfaces of the fuel cells. The shaped electric fields can alter surface dynamics, system thermodynamics, reaction kinetics, and adsorption/desorption processes. In one embodiment, ring-shaped electric-field electrodes can be provided around sensing electrodes of a planar gas sensor.

  7. Impairment of Pseudomonas aeruginosa Biofilm Resistance to Antibiotics by Combining the Drugs with a New Quorum-Sensing Inhibitor

    Science.gov (United States)

    Lajoie, Barbora; El Hage, Salome; Baziard, Genevieve; Roques, Christine

    2015-01-01

    Pseudomonas aeruginosa plays an important role in chronic lung infections among patients with cystic fibrosis (CF) through its ability to form antibiotic-resistant biofilms. In P. aeruginosa, biofilm development and the production of several virulence factors are mainly regulated by the rhl and las quorum-sensing (QS) systems, which are controlled by two N-acyl-homoserine lactone signal molecules. In a previous study, we discovered an original QS inhibitor, N-(2-pyrimidyl)butanamide, called C11, based on the structure of C4-homoserine lactone, and found that it is able to significantly inhibit P. aeruginosa biofilm formation. However, recent data indicate that P. aeruginosa grows under anaerobic conditions and forms biofilms in the lungs of CF patients that are denser and more robust than those formed under aerobic conditions. Our confocal microscopy observations of P. aeruginosa biofilms developed under aerobic and anaerobic conditions confirmed that the biofilms formed under these two conditions have radically different architectures. C11 showed significant dose-dependent antibiofilm activity on biofilms grown under both aerobic and anaerobic conditions, with a greater inhibitory effect being seen under conditions of anaerobiosis. Gene expression analyses performed by quantitative reverse transcriptase PCR showed that C11 led to the significant downregulation of rhl QS regulatory genes but also to the downregulation of both las QS regulatory genes and QS system-regulated virulence genes, rhlA and lasB. Furthermore, the activity of C11 in combination with antibiotics against P. aeruginosa biofilms was tested, and synergistic antibiofilm activity between C11 and ciprofloxacin, tobramycin, and colistin was obtained under both aerobic and anaerobic conditions. This study demonstrates that C11 may increase the efficacy of treatments for P. aeruginosa infections by increasing the susceptibility of biofilms to antibiotics and by attenuating the pathogenicity of the

  8. Impairment of Pseudomonas aeruginosa Biofilm Resistance to Antibiotics by Combining the Drugs with a New Quorum-Sensing Inhibitor.

    Science.gov (United States)

    Furiga, Aurelie; Lajoie, Barbora; El Hage, Salome; Baziard, Genevieve; Roques, Christine

    2016-03-01

    Pseudomonas aeruginosa plays an important role in chronic lung infections among patients with cystic fibrosis (CF) through its ability to form antibiotic-resistant biofilms. In P. aeruginosa, biofilm development and the production of several virulence factors are mainly regulated by the rhl and las quorum-sensing (QS) systems, which are controlled by two N-acyl-homoserine lactone signal molecules. In a previous study, we discovered an original QS inhibitor, N-(2-pyrimidyl)butanamide, called C11, based on the structure of C4-homoserine lactone, and found that it is able to significantly inhibit P. aeruginosa biofilm formation. However, recent data indicate that P. aeruginosa grows under anaerobic conditions and forms biofilms in the lungs of CF patients that are denser and more robust than those formed under aerobic conditions. Our confocal microscopy observations of P. aeruginosa biofilms developed under aerobic and anaerobic conditions confirmed that the biofilms formed under these two conditions have radically different architectures. C11 showed significant dose-dependent antibiofilm activity on biofilms grown under both aerobic and anaerobic conditions, with a greater inhibitory effect being seen under conditions of anaerobiosis. Gene expression analyses performed by quantitative reverse transcriptase PCR showed that C11 led to the significant downregulation of rhl QS regulatory genes but also to the downregulation of both las QS regulatory genes and QS system-regulated virulence genes, rhlA and lasB. Furthermore, the activity of C11 in combination with antibiotics against P. aeruginosa biofilms was tested, and synergistic antibiofilm activity between C11 and ciprofloxacin, tobramycin, and colistin was obtained under both aerobic and anaerobic conditions. This study demonstrates that C11 may increase the efficacy of treatments for P. aeruginosa infections by increasing the susceptibility of biofilms to antibiotics and by attenuating the pathogenicity of the

  9. Shape-Persistent Multimetallic Cartwheel Complexes: Design, Catalysis and Recycling

    NARCIS (Netherlands)

    Dijkstra, H.P.

    2002-01-01

    An important new research area in the field of homogeneous catalysis is the development of catalytic processes which combine the advantages of homogeneous (high activity/selectivity, mild conditions, reproducibility, good catalyst description) and heterogeneous catalysis (easy catalyst recycling, lo

  10. Geometrically induced magnetic catalysis and critical dimensions

    CERN Document Server

    Flachi, Antonino; Vitagliano, Vincenzo

    2015-01-01

    We discuss the combined effect of magnetic fields and geometry in interacting fermionic systems. At leading order in the heat-kernel expansion, the infrared singularity (that in flat space leads to the magnetic catalysis) is regulated by the chiral gap effect and the catalysis is deactivated by effect of the curvature. We discover that an infrared singularity may reappear from higher-order terms in the heat kernel expansion leading to a novel form of geometrically induced magnetic catalysis (absent in flat space). The dynamical mass squared is then modified not only due to the chiral gap effect by an amount proportional to the curvature, but also by a magnetic shift $\\propto (4-D)eB$ where $D$ represents the number of space-time dimensions. We argue that $D=4$ is a critical dimension across which the behaviour of the magnetic shift changes qualitatively.

  11. Green chemistry by nano-catalysis

    KAUST Repository

    Polshettiwar, Vivek

    2010-01-01

    Nano-materials are important in many diverse areas, from basic research to various applications in electronics, biochemical sensors, catalysis and energy. They have emerged as sustainable alternatives to conventional materials, as robust high surface area heterogeneous catalysts and catalyst supports. The nano-sized particles increase the exposed surface area of the active component of the catalyst, thereby enhancing the contact between reactants and catalyst dramatically and mimicking the homogeneous catalysts. This review focuses on the use of nano-catalysis for green chemistry development including the strategy of using microwave heating with nano-catalysis in benign aqueous reaction media which offers an extraordinary synergistic effect with greater potential than these three components in isolation. To illustrate the proof-of-concept of this "green and sustainable" approach, representative examples are discussed in this article. © 2010 The Royal Society of Chemistry.

  12. Next-Generation Catalysis for Renewables: Combining Enzymatic with Inorganic Heterogeneous Catalysis for Bulk Chemical Production

    DEFF Research Database (Denmark)

    Vennestrøm, Peter Nicolai Ravnborg; Christensen, C.H.; Pedersen, S.;

    2010-01-01

    chemical platform under different conditions than those conventionally employed. Indeed, new process and catalyst concepts need to be established. Both enzymatic catalysis (biocatalysis) and heterogeneous inorganic catalysis are likely to play a major role and, potentially, be combined. One type...... of combination involves one-pot cascade catalysis with active sites from bio- and inorganic catalysts. In this article the emphasis is placed specifically on oxidase systems involving the coproduction of hydrogen peroxide, which can be used to create new in situ collaborative oxidation reactions for bulk...

  13. RNA catalysis and the origins of life

    Science.gov (United States)

    Orgel, Leslie E.

    1986-01-01

    The role of RNA catalysis in the origins of life is considered in connection with the discovery of riboszymes, which are RNA molecules that catalyze sequence-specific hydrolysis and transesterification reactions of RNA substrates. Due to this discovery, theories positing protein-free replication as preceding the appearance of the genetic code are more plausible. The scope of RNA catalysis in biology and chemistry is discussed, and it is noted that the development of methods to select (or predict) RNA sequences with preassigned catalytic functions would be a major contribution to the study of life's origins.

  14. Bioinspired catalysis metal-sulfur complexes

    CERN Document Server

    Weigand, Wolfgang

    2014-01-01

    The growing interest in green chemistry calls for new, efficient and cheap catalysts. Living organisms contain a wide range of remarkably powerful enzymes, which can be imitated by chemists in the search for new catalysts. In bioinspired catalysis, chemists use the basic principles of biological enzymes when creating new catalyst analogues. In this book, an international group of experts cover the topic from theoretical aspects to applications by including a wide variety of examples of different systems. This valuable overview of bioinspired metal-sulfur catalysis is a must-have for all sci

  15. Catalysis by nonmetals rules for catalyst selection

    CERN Document Server

    Krylov, Oleg V

    1970-01-01

    Catalysis by Non-metals: Rules of Catalyst Selection presents the development of scientific principles for the collection of catalysts. It discusses the investigation of the mechanism of chemosorption and catalysis. It addresses a series of properties of solid with catalytic activity. Some of the topics covered in the book are the properties of a solid and catalytic activity in oxidation-reduction reactions; the difference of electronegativities and the effective charges of atoms; the role of d-electrons in the catalytic properties of a solid; the color of solids; and proton-acid and proton-ba

  16. Heterogeneous catalysis at nanoscale for energy applications

    CERN Document Server

    Tao, Franklin (Feng); Kamat, Prashant V

    2015-01-01

    This book presents both the fundamentals concepts and latest achievements of a field that is growing in importance since it represents a possible solution for global energy problems.  It focuses on an atomic-level understanding of heterogeneous catalysis involved in important energy conversion processes. It presents a concise picture for the entire area of heterogeneous catalysis with vision at the atomic- and nano- scales, from synthesis, ex-situ and in-situ characterization, catalytic activity and selectivity, to mechanistic understanding based on experimental exploration and theoretical si

  17. Keynotes in energy-related catalysis

    CERN Document Server

    Kaliaguine, S

    2011-01-01

    Catalysis by solid acids, which includes (modified) zeolites, is of special relevance to energy applications. Acid catalysis is highly important in modern petroleum refining operations - large-scale processes such as fluid catalytic cracking, catalytic reforming, alkylation and olefin oligomerization rely on the transformation of hydrocarbons by acid catalysts. (Modified) zeolites are therefore essential for the improvement of existing processes and for technical innovations in the conversion of crude. There can be little doubt that zeolite-based catalysts will play a major role in the futu

  18. Evaluation of the taste of crude drug and Kampo formula by a taste-sensing system (4): taste of Processed Aconite Root.

    Science.gov (United States)

    Anjiki, Naoko; Hosoe, Junko; Fuchino, Hiroyuki; Kiuchi, Fumiyuki; Sekita, Setsuko; Ikezaki, Hidekazu; Mikage, Masayuki; Kawahara, Nobuo; Goda, Yukihiro

    2011-04-01

    It is difficult to describe the taste of Processed Aconite Root (PAR) because it contains toxic compounds, and tasting poses some risk to the examiner. Therefore, there is no description of the taste of PAR in the latest Japanese Pharmacopoeia, although the taste of crude drugs has been regulated as a criterion for judgment. In this study, we revealed the objective taste of PAR by using a taste-sensing system. The PAR samples examined were classified into four types by how the samples were processed: PAR1 processed by autoclaving; PAR2-a processed by autoclaving after rinsing in salt (sodium chloride) solution; PAR2-h processed by heating after rinsing in calcium chloride solution; PAR3 processed by treating with hydrated lime after rinsing in salt solution. The most characteristic taste factor of PAR is an aftertaste of cationic bitterness, which was detected in all PAR sample solutions, even at the concentration of 0.1 mg/ml. In addition, anionic bitterness and saltiness were detected in all sample solutions at 1 mg/ml. Furthermore, umami was detected in the PAR1, PAR2-a, and PAR3 sample solutions at 1 mg/ml. Detailing the analyses of the four taste factors on the four sample types, we found each type has its own characteristic taste pattern. On the basis of these results, we proposed a method for discriminating one PAR type from another by using the system. PMID:21153604

  19. Pharmaceutical Industry Oriented Homogeneous Catalysis

    Institute of Scientific and Technical Information of China (English)

    Zhang Xumu

    2004-01-01

    Chiral therapeutics already makes up over one-third of pharmaceutical drugs currently sold worldwide. This is a growing industry with global chiral drug sales for 2002 increasing by 12%to $160 billion (Technology Catalysts International) of a total drug market of $410bn. The increasing demand to produce enantiomerically pure pharmaceuticals, agrochemicals, flavors, and other fine chemicals has advanced the field of asymmetric catalytic technologies.We aim to become a high value technology provider and partner in the chiral therapeutics industry by offering proprietary catalysts, novel building blocks, and collaborative synthetic solutions. In decade, we have developed a set of novel chiral homogeneous phosphorus ligands such as Binaphane, Me-KetalPhos, TangPhos, f-Binaphane, Me-f-KetalPhos, C4TunePhos and Binapine,which we called Chiral Ligand ToolKit. Complementing the ToolKit, (R, S, S, R)-DIOP*, T-Phos,o-BIPHEP, o-BINAPO and FAP were added recently[1].These ligands can be applied to a broad variety of drug structural features by asymmetric hydrogenation of dehydroamino acid derivatives, enamides, unsatisfied acids and esters, ketones,beta ketoesters, imines and cyclic imines. And ligand FAP had been apllied succefully in allylic alkylation and [3+2] cycloaddition.

  20. Asymmetric Hydroarylation of Vinylarenes Using a Synergistic Combination of CuH and Pd Catalysis.

    Science.gov (United States)

    Friis, Stig D; Pirnot, Michael T; Buchwald, Stephen L

    2016-07-13

    Detailed in this Communication is the enantioselective synthesis of 1,1-diarylalkanes, a structure found in a range of pharmaceutical drug agents and natural products, through the employment of copper(I) hydride and palladium catalysis. Judicious choice of ligand for both Cu and Pd enabled this hydroarylation protocol to work for an extensive array of aryl bromides and styrenes, including β-substituted vinylarenes and six-membered heterocycles, under relatively mild conditions.

  1. Domino [Pd]-Catalysis: One-Pot Synthesis of Isobenzofuran-1(3H)-ones.

    Science.gov (United States)

    Mahendar, Lodi; Satyanarayana, Gedu

    2016-09-01

    An efficient domino [Pd]-catalysis for the synthesis of isobenzofuran-1(3H)-ones is presented. The strategy shows broad substrate scope and is amenable to o-bromobenzyl tertiary/secondary/primary alcohols. Significantly, the method was applied to the synthesis of antiplatelet drug n-butyl phthalide and cytotoxic agonist 3a-[4'-methoxylbenzyl]-5,7-dimethoxyphthalide. PMID:27509096

  2. Asymmetric Hydroarylation of Vinylarenes Using a Synergistic Combination of CuH and Pd Catalysis.

    Science.gov (United States)

    Friis, Stig D; Pirnot, Michael T; Buchwald, Stephen L

    2016-07-13

    Detailed in this Communication is the enantioselective synthesis of 1,1-diarylalkanes, a structure found in a range of pharmaceutical drug agents and natural products, through the employment of copper(I) hydride and palladium catalysis. Judicious choice of ligand for both Cu and Pd enabled this hydroarylation protocol to work for an extensive array of aryl bromides and styrenes, including β-substituted vinylarenes and six-membered heterocycles, under relatively mild conditions. PMID:27346525

  3. Direct sp(3)C-H acroleination of N-aryl-tetrahydroisoquinolines by merging photoredox catalysis with nucleophilic catalysis.

    Science.gov (United States)

    Feng, Zhu-Jia; Xuan, Jun; Xia, Xu-Dong; Ding, Wei; Guo, Wei; Chen, Jia-Rong; Zou, You-Quan; Lu, Liang-Qiu; Xiao, Wen-Jing

    2014-04-01

    Sequence catalysis merging photoredox catalysis (PC) and nucleophilic catalysis (NC) has been realized for the direct sp(3) C-H acroleination of N-aryl-tetrahydroisoquinoline (THIQ). The reaction was performed under very mild conditions and afforded products in 50-91% yields. A catalytic asymmetric variant was proved to be successful with moderate enantioselectivities (up to 83 : 17 er).

  4. Microwave catalysis for the production of fine chemicals and pharmaceuticals

    International Nuclear Information System (INIS)

    conventional heating, even when reaction temperatures were constant in both sets of experiments. The origin of these rate enhancements is still a matter of some debate. Microwave catalysis is also making an impact on fine chemicals production. Due to the reduced scale of manufacture it is more likely that microwave stimulation of catalytic reactions is more likely to make an impact in the short term in this area. Therefore as there is insufficient time to provide a thorough overview of the whole of microwave catalysis, as the title conveys, this presentation will concentrated on the stimulation of catalytic reactions for the production of fine chemicals and pharmaceuticals. Microwave catalysis can be broken down into two distinctly differing approaches. The first of these are referred to as being 'Dry reactions' in which the reactants are adsorbed on to the surface of an inorganic support prior to irradiation. The products are then extracted and the support may be reused. One may argue that these reactions are not truly catalytic in the true sense of the word, as the catalyst (support) are not used in catalytic quantities, but as the supports can be recycled this does give them catalytic qualities. The supports used are often based on alumina or clays that may or may not have been treated with additional reagents. There are countless reports of this approach being used in synthetic chemistry and Varma has reviewed this area. Attention is being given to the scale-up of these types of reaction and a pilot scale facility has been described by Esveld et al. The alternative approach is to use catalysts in a more conventional manner, where the concentration of the catalyst is vastly exceeded by the concentration of the reactants. Using this approach examples of reactions using zeolites, oxides and precious metal catalysts will be presented in the following areas: Acylation is an area that has long been problematic for the chemicals industries, the use of stiochiometric amounts of

  5. µ-reactors for Heterogeneous Catalysis

    DEFF Research Database (Denmark)

    Jensen, Robert

    is described in detail. Since heating and temperature measurement is an extremely important point in heterogeneous catalysis an entire chapter is dedicated to this subject. Three different types of heaters have been implemented and tested both for repeatability and homogeneity of the heating as well...

  6. Homogeneous Catalysis by Transition Metal Compounds.

    Science.gov (United States)

    Mawby, Roger

    1988-01-01

    Examines four processes involving homogeneous catalysis which highlight the contrast between the simplicity of the overall reaction and the complexity of the catalytic cycle. Describes how catalysts provide circuitous routes in which all energy barriers are relatively low rather than lowering the activation energy for a single step reaction.…

  7. Supported ionic liquid-phase (SILP) catalysis

    DEFF Research Database (Denmark)

    Riisager, Anders; Fehrmann, Rasmus; Wasserscheid, P.;

    2005-01-01

    The concept of supported ionic liquid-phase (SILP) catalysis has been demonstrated for gas- and liquid-phase continuous fixed-bed reactions using rhodium phosphine catalyzed hydroformylation of propene and 1-octene as examples. The nature of the support had important influence on both the catalytic...

  8. Heterogeneous catalysis in highly sensitive microreactors

    DEFF Research Database (Denmark)

    Olsen, Jakob Lind

    This thesis present a highly sensitive silicon microreactor and examples of its use in studying catalysis. The experimental setup built for gas handling and temperature control for the microreactor is described. The implementation of LabVIEW interfacing for all the experimental parts makes...

  9. Diffusion and Surface Reaction in Heterogeneous Catalysis

    Science.gov (United States)

    Baiker, A.; Richarz, W.

    1978-01-01

    Ethylene hydrogenation on a platinum catalyst, electrolytically applied to a tube wall, is a good system for the study of the interactions between diffusion and surface reaction in heterogeneous catalysis. Theoretical background, apparatus, procedure, and student performance of this experiment are discussed. (BB)

  10. A molecular view of heterogeneous catalysis

    DEFF Research Database (Denmark)

    Christensen, Claus H.; Nørskov, Jens Kehlet

    2008-01-01

    by enabling a rational design of new catalysts. We illustrate this important development in heterogeneous catalysis by highlighting recent examples of catalyst systems for which it has been possible to achieve such a detailed understanding. In particular, we emphasize examples where this progress has made...

  11. Hydroxide catalysis bonding of silicon carbide

    NARCIS (Netherlands)

    Veggel, A.A. van; Ende, D.A. van den; Bogenstahl, J.; Rowan, S.; Cunningham, W.; Gubbels, G.H.M.; Nijmeijer, H.

    2008-01-01

    For bonding silicon carbide optics, which require extreme stability, hydroxide catalysis bonding is considered [Rowan, S., Hough, J. and Elliffe, E., Silicon carbide bonding. UK Patent 040 7953.9, 2004. Please contact Mr. D. Whiteford for further information: D.Whiteford@admin.gla.ac.uk]. This techn

  12. Graphitic carbon nitride "reloaded": emerging applications beyond (photo)catalysis.

    Science.gov (United States)

    Liu, Jian; Wang, Hongqiang; Antonietti, Markus

    2016-04-21

    Despite being one of the oldest materials described in the chemical literature, graphitic carbon nitride (g-C3N4) has just recently experienced a renaissance as a highly active photocatalyst, and the metal-free polymer was shown to be able to generate hydrogen under visible light. The semiconductor nature of g-C3N4 has triggered tremendous endeavors on its structural manipulation for enhanced photo(electro)chemical performance, aiming at an affordable clean energy future. While pursuing the stem of g-C3N4 related catalysis (photocatalysis, electrocatalysis and photoelectrocatalysis), a number of emerging intrinsic properties of g-C3N4 are certainly interesting, but less well covered, and we believe that these novel applications outside of conventional catalysis can be favorably exploited as well. Thanks to the general efforts devoted to the exploration and enrichment of g-C3N4 based chemistry, the boundaries of this area have been possibly pushed far beyond what people could imagine in the beginning. This review strives to cover the achievements of g-C3N4 related materials in these unconventional application fields for depicting the broader future of these metal-free and fully stable semiconductors. This review starts with the general protocols to engineer g-C3N4 micro/nanostructures for practical use, and then discusses the newly disclosed applications in sensing, bioimaging, novel solar energy exploitation including photocatalytic coenzyme regeneration, templating, and carbon nitride based devices. Finally, we attempt an outlook on possible further developments in g-C3N4 based research.

  13. Engineering new supramolecular gels: From catalysis to drug delivery

    OpenAIRE

    Bachl, Jürgen

    2015-01-01

    The present dissertation evaluates the design, characterization and potential applications of functional supramolecular gel-materials. Gels have attracted tremendous scientific interest as they can be obtained from natural sources or derive from readily available building blocks by facile preparation methods. They have conquered our daily life appearing as constituents of commercial products in the fields of biomedicine, agriculture, cosmetics, food thickeners and many more. Gel-materials exh...

  14. Bimetallic redox synergy in oxidative palladium catalysis.

    Science.gov (United States)

    Powers, David C; Ritter, Tobias

    2012-06-19

    Polynuclear transition metal complexes, which are embedded in the active sites of many metalloenzymes, are responsible for effecting a diverse array of oxidation reactions in nature. The range of chemical transformations remains unparalleled in the laboratory. With few noteworthy exceptions, chemists have primarily focused on mononuclear transition metal complexes in developing homogeneous catalysis. Our group is interested in the development of carbon-heteroatom bond-forming reactions, with a particular focus on identifying reactions that can be applied to the synthesis of complex molecules. In this context, we have hypothesized that bimetallic redox chemistry, in which two metals participate synergistically, may lower the activation barriers to redox transformations relevant to catalysis. In this Account, we discuss redox chemistry of binuclear Pd complexes and examine the role of binuclear intermediates in Pd-catalyzed oxidation reactions. Stoichiometric organometallic studies of the oxidation of binuclear Pd(II) complexes to binuclear Pd(III) complexes and subsequent C-X reductive elimination from the resulting binuclear Pd(III) complexes have confirmed the viability of C-X bond-forming reactions mediated by binuclear Pd(III) complexes. Metal-metal bond formation, which proceeds concurrently with oxidation of binuclear Pd(II) complexes, can lower the activation barrier for oxidation. We also discuss experimental and theoretical work that suggests that C-X reductive elimination is also facilitated by redox cooperation of both metals during reductive elimination. The effect of ligand modification on the structure and reactivity of binuclear Pd(III) complexes will be presented in light of the impact that ligand structure can exert on the structure and reactivity of binuclear Pd(III) complexes. Historically, oxidation reactions similar to those discussed here have been proposed to proceed via mononuclear Pd(IV) intermediates, and the hypothesis of mononuclear Pd

  15. Late-stage functionalization of biologically active heterocycles through photoredox catalysis.

    Science.gov (United States)

    Dirocco, Daniel A; Dykstra, Kevin; Krska, Shane; Vachal, Petr; Conway, Donald V; Tudge, Matthew

    2014-05-01

    The direct CH functionalization of heterocycles has become an increasingly valuable tool in modern drug discovery. However, the introduction of small alkyl groups, such as methyl, by this method has not been realized in the context of complex molecule synthesis since existing methods rely on the use of strong oxidants and elevated temperatures to generate the requisite radical species. Herein, we report the use of stable organic peroxides activated by visible-light photoredox catalysis to achieve the direct methyl-, ethyl-, and cyclopropylation of a variety of biologically active heterocycles. The simple protocol, mild reaction conditions, and unique tolerability of this method make it an important tool for drug discovery.

  16. Micromotors Powered by Enzyme Catalysis.

    Science.gov (United States)

    Dey, Krishna K; Zhao, Xi; Tansi, Benjamin M; Méndez-Ortiz, Wilfredo J; Córdova-Figueroa, Ubaldo M; Golestanian, Ramin; Sen, Ayusman

    2015-12-01

    Active biocompatible systems are of great current interest for their possible applications in drug or antidote delivery at specific locations. Herein, we report the synthesis and study of self-propelled microparticles powered by enzymatic reactions and their directed movement in substrate concentration gradient. Polystyrene microparticles were functionalized with the enzymes urease and catalase using a biotin-streptavidin linkage procedure. The motion of the enzyme-coated particles was studied in the presence of the respective substrates, using optical microscopy and dynamic light scattering analysis. The diffusion of the particles was found to increase in a substrate concentration dependent manner. The directed chemotactic movement of these enzyme-powered motors up the substrate gradient was studied using three-inlet microfluidic channel architecture. PMID:26587897

  17. Tandem Catalysis Utilizing Olefin Metathesis Reactions.

    Science.gov (United States)

    Zieliński, Grzegorz K; Grela, Karol

    2016-07-01

    Since olefin metathesis transformation has become a favored synthetic tool in organic synthesis, more and more distinct non-metathetical reactions of alkylidene ruthenium complexes have been developed. Depending on the conditions applied, the same olefin metathesis catalysts can efficiently promote isomerization reactions, hydrogenation of C=C double bonds, oxidation reactions, and many others. Importantly, these transformations can be carried out in tandem with olefin metathesis reactions. Through addition of one portion of a catalyst, a tandem process provides structurally advanced products from relatively simple substrates without the need for isolation of the intermediates. These aspects not only make tandem catalysis very attractive from a practical point of view, but also open new avenues in (retro)synthetic planning. However, in the literature, the term "tandem process" is sometimes used improperly to describe other types of multi-reaction sequences. In this Concept, a number of examples of tandem catalysis involving olefin metathesis are discussed with an emphasis on their synthetic value.

  18. Inverse magnetic catalysis in dense holographic matter

    CERN Document Server

    Preis, Florian; Schmitt, Andreas

    2010-01-01

    We study the chiral phase transition in a magnetic field at finite temperature and chemical potential within the Sakai-Sugimoto model, a holographic top-down approach to (large-N_c) QCD. We consider the limit of a small separation of the flavor D8-branes, which corresponds to a dual field theory comparable to a Nambu-Jona Lasinio (NJL) model. Mapping out the surface of the chiral phase transition in the parameter space of magnetic field strength, quark chemical potential, and temperature, we find that for small temperatures the addition of a magnetic field decreases the critical chemical potential for chiral symmetry restoration - in contrast to the case of vanishing chemical potential where, in accordance with the familiar phenomenon of magnetic catalysis, the magnetic field favors the chirally broken phase. This "inverse magnetic catalysis" (IMC) appears to be associated with a previously found magnetic phase transition within the chirally symmetric phase that shows an intriguing similarity to a transition ...

  19. ELECTROCHEMICAL PROMOTED CATALYSIS: TOWARDS PRACTICAL UTILIZATION

    Directory of Open Access Journals (Sweden)

    DIMITRIOS TSIPLAKIDES

    2008-07-01

    Full Text Available Electrochemical promotion (EP of catalysis has already been recognized as “a valuable development in catalytic research” (J. Pritchard, 1990 and as “one of the most remarkable advances in electrochemistry since 1950” (J. O’M. Bockris, 1996. Laboratory studies have clearly elucidated the phenomenology of electrochemical promotion and have proven that EP is a general phenomenon at the interface of catalysis and electrochemistry. The major progress toward practical utilization of EP is surveyed in this paper. The focus is given on the electropromotion of industrial ammonia synthesis catalyst, the bipolar EP and the development of a novel monolithic electropromoted reactor (MEPR in conjunction with the electropromotion of thin sputtered metal films. Future perspectives of electrochemical promotion applications in the field of hydrogen technologies are discussed.

  20. Transition metal catalysis in confined spaces.

    Science.gov (United States)

    Leenders, Stefan H A M; Gramage-Doria, Rafael; de Bruin, Bas; Reek, Joost N H

    2015-01-21

    Transition metal catalysis plays an important role in both industry and in academia where selectivity, activity and stability are crucial parameters to control. Next to changing the structure of the ligand, introducing a confined space as a second coordination sphere around a metal catalyst has recently been shown to be a viable method to induce new selectivity and activity in transition metal catalysis. In this review we focus on supramolecular strategies to encapsulate transition metal complexes with the aim of controlling the selectivity via the second coordination sphere. As we will discuss, catalyst confinement can result in selective processes that are impossible or difficult to achieve by traditional methods. We will describe the template-ligand approach as well as the host-guest approach to arrive at such supramolecular systems and discuss how the performance of the catalyst is enhanced by confining it in a molecular container.

  1. Heterogeneous Catalysis on a Disordered Surface

    OpenAIRE

    Frachebourg, L.; Krapivsky, P. L.; Redner, S.

    1995-01-01

    We introduce a simple model of heterogeneous catalysis on a disordered surface which consists of two types of randomly distributed sites with different adsorption rates. Disorder can create a reactive steady state in situations where the same model on a homogeneous surface exhibits trivial kinetics with no steady state. A rich variety of kinetic behaviors occur for the adsorbate concentrations and catalytic reaction rate as a function of model parameters.

  2. Kinetics of Catalysis with Surface Disorder

    OpenAIRE

    Head, DA; Rodgers, GJ

    1996-01-01

    We study the effects of generalised surface disorder on the monomer-monomer model of heterogeneous catalysis, where disorder is implemented by allowing different adsorption rates for each lattice site. By mapping the system in the reaction-controlled limit onto a kinetic Ising model, we derive the rate equations for the one and two-spin correlation functions. There is good agreement between these equations and numerical simulations. We then study the inclusion of desorption of monomers from t...

  3. Application of scanning electron microscopy in catalysis

    OpenAIRE

    Lomić Gizela A.; Kiš Erne E.; Bošković Goran C.; Marinković-Nedučin Radmila P.

    2004-01-01

    A short survey of various information obtained by scanning electron microscopy (SEM) in the investigation of heterogeneous catalysts and nano-structured materials have been presented. The capabilities of SEM analysis and its application in testing catalysts in different fields of heterogeneous catalysis are illustrated. The results encompass the proper way of catalyst preparation, the mechanism of catalyst active sites formation catalysts changes and catalyst degradation during their applicat...

  4. Selective Homogeneous Catalysis in Asymmetric Synthesis

    DEFF Research Database (Denmark)

    Fristrup, Peter

    The subject of this thesis is selectivity in homogeneous asymmetric transition metalcatalyzed reactions. Four different reactions within organic chemistry have been studied by kinetic measurements, computational chemistry (modelling) or both of them in parallel. A Hammett study was performed....... A thorough computational study succeeded in explaining the observed results, although other significant results were also obtained during this study. Finally, an intramolecular reaction was studied computationally, and the rate increase observed under phase transfer catalysis conditions could be related...

  5. USD Catalysis Group for Alternative Energy

    Energy Technology Data Exchange (ETDEWEB)

    Hoefelmeyer, James D.; Koodali, Ranjit; Sereda, Grigoriy; Engebretson, Dan; Fong, Hao; Puszynski, Jan; Shende, Rajesh; Ahrenkiel, Phil

    2012-03-13

    The South Dakota Catalysis Group (SDCG) is a collaborative project with mission to develop advanced catalysts for energy conversion with two primary goals: (1) develop photocatalytic systems in which polyfunctionalized TiO2 are the basis for hydrogen/oxygen synthesis from water and sunlight (solar fuels group), (2) develop new materials for hydrogen utilization in fuel cells (fuel cell group). In tandem, these technologies complete a closed chemical cycle with zero emissions.

  6. Bimetallic Redox Synergy in Oxidative Palladium Catalysis

    OpenAIRE

    Powers, David Charles; Ritter, Tobias

    2012-01-01

    Polynuclear transition metal complexes, which are embedded in the active sites of many metalloenzymes, are responsible for effecting a diverse array of oxidation reactions in nature. The range of chemical transformations remains unparalleled in the laboratory. With few noteworthy exceptions, chemists have primarily focused on mononuclear transition metal complexes in developing homogeneous catalysis. Our group is interested in the development of carbon–heteroatom bond-forming reactions, wi...

  7. Spatially Assisted Schwinger Mechanism and Magnetic Catalysis

    CERN Document Server

    Copinger, Patrick

    2016-01-01

    Using the worldline formalism we compute an effective action for fermions under a temporally modulated electric field and a spatially modulated magnetic field. It is known that the former leads to an enhanced Schwinger Mechanism, while we find that the latter can also result in enhanced particle production and even cause a reorganization of the vacuum to acquire a larger dynamical mass in equilibrium which spatially assists the Magnetic Catalysis.

  8. Nanoscale Advances in Catalysis and Energy Applications

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yimin; Somorjai, Gabor A.

    2010-05-12

    In this perspective, we present an overview of nanoscience applications in catalysis, energy conversion, and energy conservation technologies. We discuss how novel physical and chemical properties of nanomaterials can be applied and engineered to meet the advanced material requirements in the new generation of chemical and energy conversion devices. We highlight some of the latest advances in these nanotechnologies and provide an outlook at the major challenges for further developments.

  9. Catalysis in micellar and macromoleular systems

    CERN Document Server

    Fendler, Janos

    1975-01-01

    Catalysis in Micellar and Macromolecular Systems provides a comprehensive monograph on the catalyses elicited by aqueous and nonaqueous micelles, synthetic and naturally occurring polymers, and phase-transfer catalysts. It delineates the principles involved in designing appropriate catalytic systems throughout. Additionally, an attempt has been made to tabulate the available data exhaustively. The book discusses the preparation and purification of surfactants; the physical and chemical properties of surfactants and micelles; solubilization in aqueous micellar systems; and the principles of

  10. Computational approaches to homogeneous gold catalysis.

    Science.gov (United States)

    Faza, Olalla Nieto; López, Carlos Silva

    2015-01-01

    Homogenous gold catalysis has been exploding for the last decade at an outstanding pace. The best described reactivity of Au(I) and Au(III) species is based on gold's properties as a soft Lewis acid, but new reactivity patterns have recently emerged which further expand the range of transformations achievable using gold catalysis, with examples of dual gold activation, hydrogenation reactions, or Au(I)/Au(III) catalytic cycles.In this scenario, to develop fully all these new possibilities, the use of computational tools to understand at an atomistic level of detail the complete role of gold as a catalyst is unavoidable. In this work we aim to provide a comprehensive review of the available benchmark works on methodological options to study homogenous gold catalysis in the hope that this effort can help guide the choice of method in future mechanistic studies involving gold complexes. This is relevant because a representative number of current mechanistic studies still use methods which have been reported as inappropriate and dangerously inaccurate for this chemistry.Together with this, we describe a number of recent mechanistic studies where computational chemistry has provided relevant insights into non-conventional reaction paths, unexpected selectivities or novel reactivity, which illustrate the complexity behind gold-mediated organic chemistry.

  11. Shape-controlled nanostructures in heterogeneous catalysis.

    Science.gov (United States)

    Zaera, Francisco

    2013-10-01

    Nanotechnologies have provided new methods for the preparation of nanomaterials with well-defined sizes and shapes, and many of those procedures have been recently implemented for applications in heterogeneous catalysis. The control of nanoparticle shape in particular offers the promise of a better definition of catalytic activity and selectivity through the optimization of the structure of the catalytic active site. This extension of new nanoparticle synthetic procedures to catalysis is in its early stages, but has shown some promising leads already. Here, we survey the major issues associated with this nanotechnology-catalysis synergy. First, we discuss new possibilities associated with distinguishing between the effects originating from nanoparticle size versus those originating from nanoparticle shape. Next, we survey the information available to date on the use of well-shaped metal and non-metal nanoparticles as active phases to control the surface atom ensembles that define the catalytic site in different catalytic applications. We follow with a brief review of the use of well-defined porous materials for the control of the shape of the space around that catalytic site. A specific example is provided to illustrate how new selective catalysts based on shape-defined nanoparticles can be designed from first principles by using fundamental mechanistic information on the reaction of interest obtained from surface-science experiments and quantum-mechanics calculations. Finally, we conclude with some thoughts on the state of the field in terms of the advances already made, the future potentials, and the possible limitations to be overcome.

  12. Plasma Catalysis: Synergistic Effects at the Nanoscale.

    Science.gov (United States)

    Neyts, Erik C; Ostrikov, Kostya Ken; Sunkara, Mahendra K; Bogaerts, Annemie

    2015-12-23

    Thermal-catalytic gas processing is integral to many current industrial processes. Ever-increasing demands on conversion and energy efficiencies are a strong driving force for the development of alternative approaches. Similarly, synthesis of several functional materials (such as nanowires and nanotubes) demands special processing conditions. Plasma catalysis provides such an alternative, where the catalytic process is complemented by the use of plasmas that activate the source gas. This combination is often observed to result in a synergy between plasma and catalyst. This Review introduces the current state-of-the-art in plasma catalysis, including numerous examples where plasma catalysis has demonstrated its benefits or shows future potential, including CO2 conversion, hydrocarbon reforming, synthesis of nanomaterials, ammonia production, and abatement of toxic waste gases. The underlying mechanisms governing these applications, as resulting from the interaction between the plasma and the catalyst, render the process highly complex, and little is known about the factors leading to the often-observed synergy. This Review critically examines the catalytic mechanisms relevant to each specific application. PMID:26619209

  13. Quantum dots derived from two-dimensional materials and their applications for catalysis and energy.

    Science.gov (United States)

    Wang, Xuewan; Sun, Gengzhi; Li, Nan; Chen, Peng

    2016-04-21

    Quantum dots (QDs) derived from the atomically-thin two-dimensional (2D) sheets (graphene, transition metal dichalcogenide, graphitic carbon nitride, hexagonal boron nitride, and phosphorene) are emerging extraordinary zero-dimensional materials. Covering a broad spectrum of interesting optical, catalytic, electronic, chemical and electrochemical properties, these 2D-QDs promise a wide range of novel applications including imaging, sensing, cancer therapy, optoelectronics, display, catalysis, and energy. In this article, we discuss the synthesis methods and the properties of these 2D-QDs and emphasize their applications in electrocatalysis, photocatalysis, supercapacitors, batteries, and photovoltaics. PMID:26848039

  14. Neutrons for Catalysis: A Workshop on Neutron Scattering Techniques for Studies in Catalysis

    International Nuclear Information System (INIS)

    This report summarizes the Workshop on Neutron Scattering Techniques for Studies in Catalysis, held at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on September 16 and 17, 2010. The goal of the Workshop was to bring experts in heterogeneous catalysis and biocatalysis together with neutron scattering experimenters to identify ways to attack new problems, especially Grand Challenge problems in catalysis, using neutron scattering. The Workshop locale was motivated by the neutron capabilities at ORNL, including the High Flux Isotope Reactor (HFIR) and the new and developing instrumentation at the SNS. Approximately 90 researchers met for 1 1/2 days with oral presentations and breakout sessions. Oral presentations were divided into five topical sessions aimed at a discussion of Grand Challenge problems in catalysis, dynamics studies, structure characterization, biocatalysis, and computational methods. Eleven internationally known invited experts spoke in these sessions. The Workshop was intended both to educate catalyst experts about the methods and possibilities of neutron methods and to educate the neutron community about the methods and scientific challenges in catalysis. Above all, it was intended to inspire new research ideas among the attendees. All attendees were asked to participate in one or more of three breakout sessions to share ideas and propose new experiments that could be performed using the ORNL neutron facilities. The Workshop was expected to lead to proposals for beam time at either the HFIR or the SNS; therefore, it was expected that each breakout session would identify a few experiments or proof-of-principle experiments and a leader who would pursue a proposal after the Workshop. Also, a refereed review article will be submitted to a prominent journal to present research and ideas illustrating the benefits and possibilities of neutron methods for catalysis research.

  15. Neutrons for Catalysis: A Workshop on Neutron Scattering Techniques for Studies in Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Overbury, Steven {Steve} H [ORNL; Coates, Leighton [ORNL; Herwig, Kenneth W [ORNL; Kidder, Michelle [ORNL

    2011-10-01

    This report summarizes the Workshop on Neutron Scattering Techniques for Studies in Catalysis, held at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on September 16 and 17, 2010. The goal of the Workshop was to bring experts in heterogeneous catalysis and biocatalysis together with neutron scattering experimenters to identify ways to attack new problems, especially Grand Challenge problems in catalysis, using neutron scattering. The Workshop locale was motivated by the neutron capabilities at ORNL, including the High Flux Isotope Reactor (HFIR) and the new and developing instrumentation at the SNS. Approximately 90 researchers met for 1 1/2 days with oral presentations and breakout sessions. Oral presentations were divided into five topical sessions aimed at a discussion of Grand Challenge problems in catalysis, dynamics studies, structure characterization, biocatalysis, and computational methods. Eleven internationally known invited experts spoke in these sessions. The Workshop was intended both to educate catalyst experts about the methods and possibilities of neutron methods and to educate the neutron community about the methods and scientific challenges in catalysis. Above all, it was intended to inspire new research ideas among the attendees. All attendees were asked to participate in one or more of three breakout sessions to share ideas and propose new experiments that could be performed using the ORNL neutron facilities. The Workshop was expected to lead to proposals for beam time at either the HFIR or the SNS; therefore, it was expected that each breakout session would identify a few experiments or proof-of-principle experiments and a leader who would pursue a proposal after the Workshop. Also, a refereed review article will be submitted to a prominent journal to present research and ideas illustrating the benefits and possibilities of neutron methods for catalysis research.

  16. Special Issue: Coinage Metal (Copper, Silver, and Gold Catalysis

    Directory of Open Access Journals (Sweden)

    Sónia Alexandra Correia Carabineiro

    2016-06-01

    Full Text Available The subject of catalysis by coinage metals (copper, silver, and gold comes up increasingly day-by-day. This Special Issue aims to cover the numerous aspects of the use of these metals as catalysts for several reactions. It deals with synthesis and characterization of copper, silver and gold based catalysis, their characterization and use, both for heterogeneous and homogeneous catalysis, and some of their potential applications.

  17. A new era of catalysis: efficiency, value, and sustainability.

    Science.gov (United States)

    Cheng, Soofin; Lin, Shawn D

    2014-06-01

    Value proposition: Global warming and climate change urge the chemical industry to develop new processes, in which sustainability is a necessity and requirement. Catalysis is recognized to be one of the key technologies in enabling sustainability. This special issue, assembled by guest editors Soofing Chen and Shawn D. Lin, highlights some of the best work presented at "The 6th Asia-Pacific Congress on Catalysis (APCAT-6)", with as major theme "New Era of Catalysis: Efficiency, Value, and Sustainability".

  18. Magnetic catalysis and inverse magnetic catalysis in nonlocal chiral quark models

    CERN Document Server

    Pagura, V P; Noguera, S; Scoccola, N N

    2016-01-01

    We study the behavior of strongly interacting matter under an external constant magnetic field in the context of nonlocal chiral quark models within the mean field approximation. We find that at zero temperature the behavior of the quark condensates shows the expected magnetic catalysis effect, our predictions being in good quantitative agreement with lattice QCD results. On the other hand, in contrast to what happens in the standard local Nambu-Jona-Lasinio model, when the analysis is extended to the case of finite temperature our results show that nonlocal models naturally lead to the Inverse Magnetic Catalysis effect.

  19. Controllable Catalysis with Nanoparticles: Bimetallic Alloy Systems and Surface Adsorbates

    KAUST Repository

    Chen, Tianyou

    2016-05-16

    Transition metal nanoparticles are privileged materials in catalysis due to their high specific surface areas and abundance of active catalytic sites. While many of these catalysts are quite useful, we are only beginning to understand the underlying catalytic mechanisms. Opening the “black box” of nanoparticle catalysis is essential to achieve the ultimate goal of catalysis by design. In this Perspective we highlight recent work addressing the topic of controlled catalysis with bimetallic alloy and “designer” adsorbate-stabilized metal nanoparticles.

  20. Catalysis Science Initiative: Catalyst Design by Discovery Informatics

    Energy Technology Data Exchange (ETDEWEB)

    Delgass, William Nicholas [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Abu-Omar, Mahdi [Purdue Univ., West Lafayette, IN (United States) Department of Chemistry; Caruthers, James [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Ribeiro, Fabio [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Thomson, Kendall [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Schneider, William [Univ. of Notre Dame, IN (United States)

    2016-07-08

    Catalysts selectively enhance the rates of chemical reactions toward desired products. Such reactions provide great benefit to society in major commercial sectors such as energy production, protecting the environment, and polymer products and thereby contribute heavily to the country’s gross national product. Our premise is that the level of fundamental understanding of catalytic events at the atomic and molecular scale has reached the point that more predictive methods can be developed to shorten the cycle time to new processes. The field of catalysis can be divided into two regimes: heterogeneous and homogeneous. For the heterogeneous catalysis regime, we have used the water-gas shift (WGS) reaction (CO + H2O + CO2 + H2O) over supported metals as a test bed. Detailed analysis and strong coupling of theory with experiment have led to the following conclusions: • The sequence of elementary steps goes through a COOH intermediate • The CO binding energy is a strong function of coverage of CO adsorbed on the surface in many systems • In the case of Au catalysts, the CO adsorption is generally too weak on surface with close atomic packing, but the enhanced binding at corner atoms (which are missing bonding partners) of cubo-octahedral nanoparticles increases the energy to a near optimal value and produces very active catalysts. • Reaction on the metal alone cannot account for the experimental results. The reaction is dual functional with water activation occurring at the metal-support interface. It is clear from our work that the theory component is essential, not only for prediction of new systems, but also for reconciling data and testing hypotheses regarding potential descriptors. Particularly important is the finding that the interface between nano-sized metal particles and the oxides that are used to support them represent a new state of matter in the sense that the interfacial bonding perturbs the chemical state of both metals atoms and the support

  1. New strategies in chemical synthesis and catalysis

    CERN Document Server

    Pignataro, Bruno

    2012-01-01

    Providing a comprehensive overview of the essential topics, this book covers the core areas of organic, inorganic, organometallic, biochemical synthesis and catalysis.The authors are among the rising stars in European chemistry, a selection of participants in the 2010 European Young Chemists Award competition, and their contributions deal with most of the frontier issues in chemical synthesis. They give an account of the latest research results in chemistry in Europe, as well as the state of the art in their field of research and the outlook for the future.

  2. Concepts of Modern Catalysis and Kinetics

    CERN Document Server

    Chorkendorff, I

    2003-01-01

    Until now, the literature has offered a rather limited approach to the use of fundamental kinetics and their application to catalytic reactions. Subsequently, this book spans the full range from fundamentals of kinetics and heterogeneous catalysis via modern experimental and theoretical results of model studies to their equivalent large-scale industrial production processes. The result is key knowledge for students at technical universities and professionals already working in industry. "...such an enterprise will be of great value to the community, to professionals as well as graduate an

  3. Relativistic effects in homogeneous gold catalysis.

    Science.gov (United States)

    Gorin, David J; Toste, F Dean

    2007-03-22

    Transition-metal catalysts containing gold present new opportunities for chemical synthesis, and it is therefore not surprising that these complexes are beginning to capture the attention of the chemical community. Cationic phosphine-gold(i) complexes are especially versatile and selective catalysts for a growing number of synthetic transformations. The reactivity of these species can be understood in the context of theoretical studies on gold; relativistic effects are especially helpful in rationalizing the reaction manifolds available to gold catalysts. This Review draws on experimental and computational data to present our current understanding of homogeneous gold catalysis, focusing on previously unexplored reactivity and its application to the development of new methodology.

  4. Surface Science Foundations of Catalysis and Nanoscience

    CERN Document Server

    Kolasinski, Kurt K

    2012-01-01

    Surface science has evolved from being a sub-field of chemistry or physics, and has now established itself as an interdisciplinary topic. Knowledge has developed sufficiently that we can now understand catalysis from a surface science perspective. No-where is the underpinning nature of surface science better illustrated than with nanoscience. Now in its third edition, this successful textbook aims to provide students with an understanding of chemical transformations and the formation of structures at surfaces. The chapters build from simple to more advanced principles with each featuring exerc

  5. LI Can elected president of int'l catalysis association

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ Prof.LI Can,vice directorgeneral of the CAS Dalian Institute of Chemical Physics,was elected new president of the Executive Committee of the International Association for Catalysis Societies (IACS) at the 14th International Congress on Catalysis held from 13 to 18 July in Seoul,ROK.It is the first time for a Chinese scientist to serve the post.

  6. Factors Affecting the Relative Efficiency of General Acid Catalysis

    Science.gov (United States)

    Kwan, Eugene E.

    2005-01-01

    A simple framework for evaluating experimental kinetic data to provide support for Specific Acid Catalysis (SAC) and General Acid Catalysis (GAC) is described based on the factors affecting their relative efficiency. Observations reveal that increasing the SAC-to-GAC rate constant ratio reduces the effective pH range for GAC.

  7. The nature of the active site in heterogeneous metal catalysis

    DEFF Research Database (Denmark)

    Nørskov, Jens Kehlet; Bligaard, Thomas; Larsen, Britt Hvolbæk;

    2008-01-01

    This tutorial review, of relevance for the surface science and heterogeneous catalysis communities, provides a molecular-level discussion of the nature of the active sites in metal catalysis. Fundamental concepts such as "Bronsted-Evans-Polanyi relations'' and "volcano curves'' are introduced...

  8. Tandem Catalysis Utilizing Olefin Metathesis Reactions.

    Science.gov (United States)

    Zieliński, Grzegorz K; Grela, Karol

    2016-07-01

    Since olefin metathesis transformation has become a favored synthetic tool in organic synthesis, more and more distinct non-metathetical reactions of alkylidene ruthenium complexes have been developed. Depending on the conditions applied, the same olefin metathesis catalysts can efficiently promote isomerization reactions, hydrogenation of C=C double bonds, oxidation reactions, and many others. Importantly, these transformations can be carried out in tandem with olefin metathesis reactions. Through addition of one portion of a catalyst, a tandem process provides structurally advanced products from relatively simple substrates without the need for isolation of the intermediates. These aspects not only make tandem catalysis very attractive from a practical point of view, but also open new avenues in (retro)synthetic planning. However, in the literature, the term "tandem process" is sometimes used improperly to describe other types of multi-reaction sequences. In this Concept, a number of examples of tandem catalysis involving olefin metathesis are discussed with an emphasis on their synthetic value. PMID:27203528

  9. Mechanical catalysis on the centimetre scale.

    Science.gov (United States)

    Miyashita, Shuhei; Audretsch, Christof; Nagy, Zoltán; Füchslin, Rudolf M; Pfeifer, Rolf

    2015-03-01

    Enzymes play important roles in catalysing biochemical transaction paths, acting as logical machines through the morphology of the processes. A key challenge in elucidating the nature of these systems, and for engineering manufacturing methods inspired by biochemical reactions, is to attain a comprehensive understanding of the stereochemical ground rules of enzymatic reactions. Here, we present a model of catalysis that can be performed magnetically by centimetre-sized passive floating units. The designed system, which is equipped with permanent magnets only, passively obeys the local causalities imposed by magnetic interactions, albeit it shows a spatial behaviour and an energy profile analogous to those of biochemical enzymes. In this process, the enzyme units trigger physical conformation changes of the target by levelling out the magnetic potential barrier (activation potential) to a funnel type and, thus, induce cascading conformation changes of the targeted substrate units reacting in parallel. The inhibitor units, conversely, suppress such changes by increasing the potential. Because the model is purely mechanical and established on a physics basis in the absence of turbulence, each performance can be explained by the morphology of the unit, extending the definition of catalysis to systems of alternative scales.

  10. Asymmetric catalysis in Brazil: development and potential for advancement of Brazilian chemical industry

    International Nuclear Information System (INIS)

    The preparation of enantiomerically pure or enriched substances is of fundamental importance to pharmaceutical, food, agrochemical, and cosmetics industries and involves a growing market of hundreds of billions of dollars. However, most chemical processes used for their production are not environmentally friendly because in most cases, stoichiometric amounts of chiral inductors are used and substantial waste is produced. In this context, asymmetric catalysis has emerged as an efficient tool for the synthesis of enantiomerically enriched compounds using chiral catalysts. More specifically, considering the current scenario in the Brazilian chemical industry, especially that of pharmaceuticals, the immediate prospect for the use of synthetic routes developed in Brazil in an enantioselective fashion or even the discovery of new drugs is practically null. Currently, the industrial production of drugs in Brazil is primarily focused on the production of generic drugs and is basically supported by imports of intermediates from China and India. In order to change this panorama and move forward toward the gradual incorporation of genuinely Brazilian synthetic routes, strong incentive policies, especially those related to continuous funding, will be needed. These incentives could be a breakthrough once we establish several research groups working in the area of organic synthesis and on the development and application of chiral organocatalysts and ligands in asymmetric catalysis, thus contributing to boost the development of the Brazilian chemical industry. Considering these circumstances, Brazil can benefit from this opportunity because we have a wide biodiversity and a large pool of natural resources that can be used as starting materials for the production of new chiral catalysts and are creating competence in asymmetric catalysis and related areas. This may decisively contribute to the growth of chemistry in our country. (author)

  11. Magnetic catalysis (and inverse catalysis) at finite temperature in two-color lattice QCD

    CERN Document Server

    Ilgenfritz, E -M; Petersson, B; Schreiber, A

    2013-01-01

    Two-color lattice QCD with N_f=4 staggered fermion degrees of freedom (no rooting trick is applied) with equal electric charge q is studied in a homogeneous magnetic background field B and at non-zero temperature T. In order to circumvent renormalization as a function of the bare coupling we apply a fixed-scale approach. We study the influence of the magnetic field on the critical temperature. At rather small pseudo-scalar meson mass (m_pi \\approx 175 MeV \\approx T_c(B=0)) we confirm magnetic catalysis for sufficiently strong magnetic field strength, while at T=195 MeV and weak magnetic field (qB {\\lesssim} 0.8 GeV^2) we find a rise of the Polyakov loop with qB and thus, indications for an inverse magnetic catalysis.

  12. Organic photoredox catalysis for the oxidation of silicates: applications in radical synthesis and dual catalysis.

    Science.gov (United States)

    Lévêque, Christophe; Chenneberg, Ludwig; Corcé, Vincent; Ollivier, Cyril; Fensterbank, Louis

    2016-08-01

    Metal free photooxidation of alkyl bis(catecholato)silicates with the organic dye 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyano-benzene (4CzIPN) allows the smooth formation of alkyl radicals. The latter can be efficiently engaged either with radical acceptors to provide homolytic addition products or in photoredox/nickel dual catalysis reactions to obtain cross-coupling products.

  13. Magnetic Catalysis in Graphene Effective Field Theory

    CERN Document Server

    DeTar, Carleton; Zafeiropoulos, Savvas

    2016-01-01

    We report on the first observation of magnetic catalysis at zero temperature in a fully nonperturbative simulation of the graphene effective field theory. Using lattice gauge theory, a nonperturbative analysis of the theory of strongly-interacting, massless, (2+1)-dimensional Dirac fermions in the presence of an external magnetic field is performed. We show that in the zero-temperature limit, a nonzero value for the chiral condensate is obtained which signals the spontaneous breaking of chiral symmetry. This result implies a nonzero value for the dynamical mass of the Dirac quasiparticle. This in turn has been posited to account for the quantum-Hall plateaus that are observed at large magnetic fields.

  14. Novel Catalysis by Gold: A Modern Alchemy

    Science.gov (United States)

    Haruta, Masatake

    Gold has long been neglected as a catalyst because of its chemical inertness. However, when gold is deposited as nanoparticles on carbon and polymer materials as well as on base metal oxides and hydroxides, it exhibits unique catalytic properties for many reactions such as CO oxidation at a temperature as low as 200 K, gas phase direct epoxidation of propylene, and aerobic oxidation of glucose to gluconic acid. The structure-catalytic activity correlations are discussed with emphasis on the contact structure, support selection, and the size control of gold particles. Gold clusters with diameters smaller than 2 nm are expected to exhibit novel properties in catalysis, optics, and electronics depending on the size (number of atoms), shape, and the electronic and chemical interaction with the support materials. The above achievements and attempts can be regarded as a modern alchemy that creates valuables by means of the noblest element with little practical use.

  15. Microbial electro-catalysis in fuel cell

    International Nuclear Information System (INIS)

    Microbial fuel cells (MFC) are devices that ensure the direct conversion of organic matter into electricity using bacterial bio-films as the catalysts of the electrochemical reactions. This study aims at improving the comprehension of the mechanisms involved in electron transfer pathways between the adhered bacteria and the electrodes. This optimization of the MFC power output could be done, for example, in exploring and characterizing various electrode materials. The electrolysis experiments carried out on Geobacter sulfurreducens deal with the microbial catalysis of the acetate oxidation, on the one hand, and the catalysis of the fumarate reduction on the other hand. On the anodic side, differences in current densities appeared on graphite, DSAR and stainless steel (8 A/m2, 5 A/m2 and 0.7 A/m2 respectively). These variations were explained more by materials roughness differences rather than their nature. Impedance spectroscopy study shows that the electro-active bio-film developed on stainless steel does not seem to modify the evolution of the stainless steel oxide layer, only the imposed potential remains determining. On the cathodic side, stainless steel sustained current densities more than twenty times higher than those obtained with graphite electrodes. The adhesion study of G. sulfurreducens on various materials in a flow cell, suggests that the bio-films resist to the hydrodynamic constraints and are not detached under a shear stress threshold value. The installation of two MFC prototypes, one in a sea station and the other directly in Genoa harbour (Italy) confirms some results obtained in laboratory and were promising for a MFC scale-up. (author)

  16. Prebiotic RNA Synthesis by Montmorillonite Catalysis

    Directory of Open Access Journals (Sweden)

    Sohan Jheeta

    2014-08-01

    Full Text Available This review summarizes our recent findings on the role of mineral salts in prebiotic RNA synthesis, which is catalyzed by montmorillonite clay minerals. The clay minerals not only catalyze the synthesis of RNA but also facilitate homochiral selection. Preliminary data of these findings have been presented at the “Horizontal Gene Transfer and the Last Universal Common Ancestor (LUCA” conference at the Open University, Milton Keynes, UK, 5–6 September 2013. The objective of this meeting was to recognize the significance of RNA in LUCA. We believe that the prebiotic RNA synthesis from its monomers must have been a simple process. As a first step, it may have required activation of the 5'-end of the mononucleotide with a leaving group, e.g., imidazole in our model reaction (Figure 1. Wide ranges of activating groups are produced from HCN under plausible prebiotic Earth conditions. The final step is clay mineral catalysis in the presence of mineral salts to facilitate selective production of functional RNA. Both the clay minerals and mineral salts would have been abundant on early Earth. We have demonstrated that while montmorillonite (pH 7 produced only dimers from its monomers in water, addition of sodium chloride (1 M enhanced the chain length multifold, as detected by HPLC. The effect of monovalent cations on RNA synthesis was of the following order: Li+ > Na+ > K+. A similar effect was observed with the anions, enhancing catalysis in the following order: Cl− > Br− > I−. The montmorillonite-catalyzed RNA synthesis was not affected by hydrophobic or hydrophilic interactions. We thus show that prebiotic synthesis of RNA from its monomers was a simple process requiring only clay minerals and a small amount of salt.

  17. Prebiotic RNA Synthesis by Montmorillonite Catalysis

    Science.gov (United States)

    Jheeta, Sohan; Joshi, Prakash C.

    2014-08-01

    This review summarizes our recent findings on the role of mineral salts in prebiotic RNA synthesis, which is catalyzed by montmorillonite clay minerals. The clay minerals not only catalyze the synthesis of RNA but also facilitate homochiral selection. Preliminary data of these findings have been presented at the "Horizontal Gene Transfer and the Last Universal Common Ancestor (LUCA)" conference at the Open University, Milton Keynes, UK, 5-6 September 2013. The objective of this meeting was to recognize the significance of RNA in LUCA. We believe that the prebiotic RNA synthesis from its monomers must have been a simple process. As a first step, it may have required activation of the 5'-end of the mononucleotide with a leaving group, e.g., imidazole in our model reaction (Figure 1). Wide ranges of activating groups are produced from HCN under plausible prebiotic Earth conditions. The final step is clay mineral catalysis in the presence of mineral salts to facilitate selective production of functional RNA. Both the clay minerals and mineral salts would have been abundant on early Earth. We have demonstrated that while montmorillonite (pH 7) produced only dimers from its monomers in water, addition of sodium chloride (1 M) enhanced the chain length multifold, as detected by HPLC. The effect of monovalent cations on RNA synthesis was of the following order: Li+ > Na+ > K+. A similar effect was observed with the anions, enhancing catalysis in the following order: Cl- > Br- > I-. The montmorillonite-catalyzed RNA synthesis was not affected by hydrophobic or hydrophilic interactions. We thus show that prebiotic synthesis of RNA from its monomers was a simple process requiring only clay minerals and a small amount of salt.

  18. Remote Sensing

    CERN Document Server

    Khorram, Siamak; Koch, Frank H; van der Wiele, Cynthia F

    2012-01-01

    Remote Sensing provides information on how remote sensing relates to the natural resources inventory, management, and monitoring, as well as environmental concerns. It explains the role of this new technology in current global challenges. "Remote Sensing" will discuss remotely sensed data application payloads and platforms, along with the methodologies involving image processing techniques as applied to remotely sensed data. This title provides information on image classification techniques and image registration, data integration, and data fusion techniques. How this technology applies to natural resources and environmental concerns will also be discussed.

  19. Inverse opal ceria–zirconia: architectural engineering for heterogeneous catalysis

    OpenAIRE

    Umeda, G. A.; Chueh, William C.; Noailles, Liam; Haile, Sossina M.; Dunn, B. S.

    2008-01-01

    The application of inverse opal structured materials is extended to the ceria–zirconia (Ce_(0.5)Zr_(0.5)O_2) system and the significance of material architecture on heterogeneous catalysis, specifically, chemical oxidation, is examined.

  20. Nanostructured Membranes for Enzyme Catalysis and Green Synthesis of Nanoparticles

    Science.gov (United States)

    Macroporous membranes functionalized with ionizable macromolecules provide promising applications in toxic metal capture at high capacity, nanoparticle synthesis, and catalysis. Our low-pressure membrane approach is marked by reaction and separation selectivity and their tunabil...

  1. Catalysis of Radical Reactions: A Radical Chemistry Perspective.

    Science.gov (United States)

    Studer, Armido; Curran, Dennis P

    2016-01-01

    The area of catalysis of radical reactions has recently flourished. Various reaction conditions have been discovered and explained in terms of catalytic cycles. These cycles rarely stand alone as unique paths from substrates to products. Instead, most radical reactions have innate chains which form products without any catalyst. How do we know if a species added in "catalytic amounts" is a catalyst, an initiator, or something else? Herein we critically address both catalyst-free and catalytic radical reactions through the lens of radical chemistry. Basic principles of kinetics and thermodynamics are used to address problems of initiation, propagation, and inhibition of radical chains. The catalysis of radical reactions differs from other areas of catalysis. Whereas efficient innate chain reactions are difficult to catalyze because individual steps are fast, both inefficient chain processes and non-chain processes afford diverse opportunities for catalysis, as illustrated with selected examples.

  2. Selective Oxidation and Ammoxidation of Olefins by Heterogeneous Catalysis.

    Science.gov (United States)

    Grasselli, Robert K.

    1986-01-01

    Shows how the ammoxidation of olefins can be understood in terms of free radicals and surface bound organometallic intermediates. Also illustrates the close intellectual relationships between heterogeneous catalysis and organometallic chemistry. (JN)

  3. Density functional theory studies of transition metal nanoparticles in catalysis

    DEFF Research Database (Denmark)

    Greeley, Jeffrey Philip; Rankin, Rees; Zeng, Zhenhua;

    2013-01-01

    Periodic Density Functional Theory calculations are capable of providing powerful insights into the structural, energetics, and electronic phenomena that underlie heterogeneous catalysis on transition metal nanoparticles. Such calculations are now routinely applied to single crystal metal surfaces...... and to subnanometer metal clusters. Descriptions of catalysis on truly nanosized structures, however, are generally not as well developed. In this talk, I will illustrate different approaches to analyzing nanocatalytic phenomena with DFT calculations. I will describe case studies from heterogeneous catalysis...... and electrocatalysis, in which single crystal models are combined with Wulff construction-based ideas to produce descriptions of average nanocatalyst behavior. Then, I will proceed to describe explicitly DFT-based descriptions of catalysis on truly nanosized particles (

  4. Applications of metal-organic frameworks in heterogeneous supramolecular catalysis.

    Science.gov (United States)

    Liu, Jiewei; Chen, Lianfen; Cui, Hao; Zhang, Jianyong; Zhang, Li; Su, Cheng-Yong

    2014-08-21

    This review summarizes the use of metal-organic frameworks (MOFs) as a versatile supramolecular platform to develop heterogeneous catalysts for a variety of organic reactions, especially for liquid-phase reactions. Following a background introduction about catalytic relevance to various metal-organic materials, crystal engineering of MOFs, characterization and evaluation methods of MOF catalysis, we categorize catalytic MOFs based on the types of active sites, including coordinatively unsaturated metal sites (CUMs), metalloligands, functional organic sites (FOS), as well as metal nanoparticles (MNPs) embedded in the cavities. Throughout the review, we emphasize the incidental or deliberate formation of active sites, the stability, heterogeneity and shape/size selectivity for MOF catalysis. Finally, we briefly introduce their relevance into photo- and biomimetic catalysis, and compare MOFs with other typical porous solids such as zeolites and mesoporous silica with regard to their different attributes, and provide our view on future trends and developments in MOF-based catalysis.

  5. Intermetallic compounds in heterogeneous catalysis - a quickly developing field

    OpenAIRE

    Armbrüster, M.; Schlögl, R.; Grin, Y.

    2014-01-01

    The application of intermetallic compounds for understanding in heterogeneous catalysis developed in an excellent way during the last decade. This review provides an overview of concepts and developments revealing the potential of intermetallic compounds in fundamental as well as applied catalysis research. Intermetallic compounds may be considered as platform materials to address current and future catalytic challenges, e.g. in respect to the energy transition.

  6. 3. International conference on catalysis in membrane reactors

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-09-01

    The 3. International Conference on Catalysis in Membrane Reactors, Copenhagen, Denmark, is a continuation of the previous conferences held in Villeurbanne 1994 and Moscow 1996 and will deal with the rapid developments taking place within membranes with emphasis on membrane catalysis. The approx. 80 contributions in form of plenary lectures and posters discuss hydrogen production, methane reforming into syngas, selectivity and specificity of various membranes etc. The conference is organised by the Danish Catalytic Society under the Danish Society for Chemical Engineering. (EG)

  7. Glucose Sensing

    CERN Document Server

    Geddes, Chris D

    2006-01-01

    Topics in Fluorescence Spectroscopy, Glucose Sensing is the eleventh volume in the popular series Topics in Fluorescence Spectroscopy, edited by Drs. Chris D. Geddes and Joseph R. Lakowicz. This volume incorporates authoritative analytical fluorescence-based glucose sensing reviews specialized enough to be attractive to professional researchers, yet also appealing to the wider audience of scientists in related disciplines of fluorescence. Glucose Sensing is an essential reference for any lab working in the analytical fluorescence glucose sensing field. All academics, bench scientists, and industry professionals wishing to take advantage of the latest and greatest in the continuously emerging field of glucose sensing, and diabetes care & management, will find this volume an invaluable resource. Topics in Fluorescence Spectroscopy Volume 11, Glucose Sensing Chapters include: Implantable Sensors for Interstitial Fluid Smart Tattoo Glucose Sensors Optical Enzyme-based Glucose Biosensors Plasmonic Glucose Sens...

  8. Dedicated Beamline Facilities for Catalytic Research. Synchrotron Catalysis Consortium (SCC)

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jingguang [Columbia Univ., New York, NY; Frenkel, Anatoly [Yeshiva Univ., New York, NY (United States); Rodriguez, Jose [Brookhaven National Lab. (BNL), Upton, NY (United States); Adzic, Radoslav [Brookhaven National Lab. (BNL), Upton, NY (United States); Bare, Simon R. [UOP LLC, Des Plaines, IL (United States); Hulbert, Steve L. [Brookhaven National Lab. (BNL), Upton, NY (United States); Karim, Ayman [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Mullins, David R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Overbury, Steve [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-03-04

    Synchrotron spectroscopies offer unique advantages over conventional techniques, including higher detection sensitivity and molecular specificity, faster detection rate, and more in-depth information regarding the structural, electronic and catalytic properties under in-situ reaction conditions. Despite these advantages, synchrotron techniques are often underutilized or unexplored by the catalysis community due to various perceived and real barriers, which will be addressed in the current proposal. Since its establishment in 2005, the Synchrotron Catalysis Consortium (SCC) has coordinated significant efforts to promote the utilization of cutting-edge catalytic research under in-situ conditions. The purpose of the current renewal proposal is aimed to provide assistance, and to develop new sciences/techniques, for the catalysis community through the following concerted efforts: Coordinating the implementation of a suite of beamlines for catalysis studies at the new NSLS-II synchrotron source; Providing assistance and coordination for catalysis users at an SSRL catalysis beamline during the initial period of NSLS to NSLS II transition; Designing in-situ reactors for a variety of catalytic and electrocatalytic studies; Assisting experimental set-up and data analysis by a dedicated research scientist; Offering training courses and help sessions by the PIs and co-PIs.

  9. Force sensing

    OpenAIRE

    Sanders, David

    2007-01-01

    A young child can explore and learn and compensate for unknown dynamics by prodding, pushing, touching, grasping and feeling. Force sensing and software research could soon allow artificial mechanisms to do the same. Force sensing has its roots in strain gauges, piezoelectrics, Wheatstone bridges, automation, robotics, grippers and virtual reality. That force sensing research has now become commonplace and has expanded from those roots to include so much more: video games, athletic equipment,...

  10. Some General Themes in Catalysis at LANL

    Energy Technology Data Exchange (ETDEWEB)

    Gordon, John C. [Los Alamos National Laboratory

    2012-07-19

    Some general themes in catalysis at LANL are: (1) Storage and release of energy within chemical bonds (e.g. H{sub 2} storage in and release from covalent bonds, N{sub 2} functionalization, CO{sub 2} functionalization, H{sub 2} oxidation/evolution, O{sub 2} reduction/evolution); (2) Can we control the chemistry of reactive substrates to effect energy relevant transformations in non-traditional media (e.g. can we promote C-C couplings, dehydrations, or hydrogenations in water under relatively mild conditions)? (3) Can we supplant precious metal or rare earth catalysts to effect these transformations, by using earth abundant metals/elements instead? Can we use organocatalysis and circumvent the use of metals completely? (4) Can we improve upon existing rare earth catalyst systems (e.g. in rare earth oxides pertinent to fluid cracking or polymerization) and reduce amounts required for catalytic efficacy? Carbohydrates can be accessed from non-food based biomass sources such as woody residues and switchgrass. After extracted from the plant source, our goal is to upgrade these classes of molecules into useful fuels.

  11. Ferroelectric based catalysis: Switchable surface chemistry

    Science.gov (United States)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab

    2015-03-01

    We describe a new class of catalysts that uses an epitaxial monolayer of a transition metal oxide on a ferroelectric substrate. The ferroelectric polarization switches the surface chemistry between strongly adsorptive and strongly desorptive regimes, circumventing difficulties encountered on non-switchable catalytic surfaces where the Sabatier principle dictates a moderate surface-molecule interaction strength. This method is general and can, in principle, be applied to many reactions, and for each case the choice of the transition oxide monolayer can be optimized. Here, as a specific example, we show how simultaneous NOx direct decomposition (into N2 and O2) and CO oxidation can be achieved efficiently on CrO2 terminated PbTiO3, while circumventing oxygen (and sulfur) poisoning issues. One should note that NOx direct decomposition has been an open challenge in automotive emission control industry. Our method can expand the range of catalytically active elements to those which are not conventionally considered for catalysis and which are more economical, e.g., Cr (for NOx direct decomposition and CO oxidation) instead of canonical precious metal catalysts. Primary support from Toyota Motor Engineering and Manufacturing, North America, Inc.

  12. Catalysis of Forster Resonances in Rubidium

    Science.gov (United States)

    Win, A. L.; Williams, W. D.; Sukenik, C. I.

    2016-05-01

    When two ultracold Rydberg atoms collide they may change their quantum state if the total electronic energy of the two atoms before and after the collision is about the same. This process can be made resonant by tuning the energy levels of the atoms with an electric field, via the Stark shift, so that the energy difference between incoming and outgoing channels vanishes. This condition is known as a ``Forster resonance.'' We have studied a particular Forster resonance in rubidium: 34p + 34p --> 34s + 35s, by investigating the time dependence of the state change in an ultracold environment. Furthermore, we have added 34d state atoms to the mix and observed an enhancement of 34s atom production. We attribute this enhancement to a catalysis effect whereby the 34d atoms alter the spatial distribution of 34p atoms that participate in the energy transfer interaction. We will present results from the experiment and compare them to model calculations. Present address: Department of Physics, Smith College, Northampton, MA.

  13. Remote Sensing.

    Science.gov (United States)

    Williams, Richard S., Jr.; Southworth, C. Scott

    1983-01-01

    The Landsat Program became the major event of 1982 in geological remote sensing with the successful launch of Landsat 4. Other 1982 remote sensing accomplishments, research, publications, (including a set of Landsat worldwide reference system index maps), and conferences are highlighted. (JN)

  14. Catalysis of peptide bond formation by histidyl-histidine in a fluctuating clay environment

    Science.gov (United States)

    White, D. H.; Erickson, J. C.

    1980-01-01

    The condensation of glycine to form oligoglycines during wet-dry fluctuations on clay surfaces was enhanced up to threefold or greater by small amounts of histidyl-histidine. In addition, higher relative yields of the longer oligomers were produced. Other specific dipeptides tested gave no enhancement, and imidazole, histidine, and N-acetylhistidine gave only slight enhancements. Histidyl-histidine apparently acts as a true catalyst (in the sense of repeatedly catalyzing the reaction), since up to 52 nmol of additional glycine were incorporated into oligoglycine for each nmol of catalyst added. This is the first known instance of a peptide or similar molecule demonstrating a catalytic turnover number greater than unity in a prebiotic oligomer synthesis reaction, and suggests that histidyl-histidine is a model for a primitive prebiotic proto-enzyme. Catalysis of peptide bond synthesis by a molecule which is itself a peptide implies that related systems may be capable of exhibiting autocatalytic growth.

  15. Exhaust aftertreatment using plasma-assisted catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Penetrante, B

    2000-01-20

    In the field of catalysis, one application that has been classified as a breakthrough technology is the catalytic reduction of NO{sub x} in oxygen-rich environments using hydrocarbons. This breakthrough will require dramatic improvements in both catalyst and engine technology, but the benefits will be substantial for energy efficiency and a cleaner environment. Engine and automobile companies are placing greater emphasis on the diesel engine because of its potential for saving fuel resources and reducing CO{sub 2} emissions. The modern direct-injection diesel engine offers demonstrated fuel economy advantages unmatched by any other commercially-viable engine. The main drawback of diesel engines is exhaust emissions. A modification of existing oxidation catalyst/engine technology is being used to address the CO, hydrocarbon and particulates. However, no satisfactory solution currently exists for NO{sub x}. Diesel engines operate under net oxidizing conditions, thus rendering conventional three-way catalytic converters ineffective for the controlling the NO{sub x} emission. NO{sub x} reduction catalysts, using ammonia as a reductant, do exist for oxygen-rich exhausts; however, for transportation applications, the use of on-board hydrocarbon fuels is a more feasible, cost-effective, and environmentally-sound approach. Selective catalytic reduction (SCR) by hydrocarbons is one of the leading catalytic aftertreatment technologies for the reduction of NO{sub x} in lean-burn engine exhaust (often referred to as lean-NO{sub x}). The objective is to chemically reduce the pollutant molecules of NO{sub x} to benign molecules such as N{sub 2}. Aftertreatment schemes have focused a great deal on the reduction of NO because the NO{sub x} in engine exhaust is composed primarily of NO. Recent studies, however, have shown that the oxidation of NO to NO{sub 2} serves an important role in enhancing the efficiency for reduction of NO{sub x} to N{sub 2}. It has become apparent that

  16. Center for Catalysis at Iowa State University

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, George A.

    2006-10-17

    The overall objective of this proposal is to enable Iowa State University to establish a Center that enjoys world-class stature and eventually enhances the economy through the transfer of innovation from the laboratory to the marketplace. The funds have been used to support experimental proposals from interdisciplinary research teams in areas related to catalysis and green chemistry. Specific focus areas included: • Catalytic conversion of renewable natural resources to industrial materials • Development of new catalysts for the oxidation or reduction of commodity chemicals • Use of enzymes and microorganisms in biocatalysis • Development of new, environmentally friendly reactions of industrial importance These focus areas intersect with barriers from the MYTP draft document. Specifically, section 2.4.3.1 Processing and Conversion has a list of bulleted items under Improved Chemical Conversions that includes new hydrogenation catalysts, milder oxidation catalysts, new catalysts for dehydration and selective bond cleavage catalysts. Specifically, the four sections are: 1. Catalyst development (7.4.12.A) 2. Conversion of glycerol (7.4.12.B) 3. Conversion of biodiesel (7.4.12.C) 4. Glucose from starch (7.4.12.D) All funded projects are part of a soybean or corn biorefinery. Two funded projects that have made significant progress toward goals of the MYTP draft document are: Catalysts to convert feedstocks with high fatty acid content to biodiesel (Kraus, Lin, Verkade) and Conversion of Glycerol into 1,3-Propanediol (Lin, Kraus). Currently, biodiesel is prepared using homogeneous base catalysis. However, as producers look for feedstocks other than soybean oil, such as waste restaurant oils and rendered animal fats, they have observed a large amount of free fatty acids contained in the feedstocks. Free fatty acids cannot be converted into biodiesel using homogeneous base-mediated processes. The CCAT catalyst system offers an integrated and cooperative catalytic

  17. Kinetic evolutionary behavior of catalysis-select migration

    Science.gov (United States)

    Wu, Yuan-Gang; Lin, Zhen-Quan; Ke, Jian-Hong

    2012-06-01

    We propose a catalysis-select migration driven evolution model of two-species (A- and B-species) aggregates, where one unit of species A migrates to species B under the catalysts of species C, while under the catalysts of species D the reaction will become one unit of species B migrating to species A. Meanwhile the catalyst aggregates of species C perform self-coagulation, as do the species D aggregates. We study this catalysis-select migration driven kinetic aggregation phenomena using the generalized Smoluchowski rate equation approach with C species catalysis-select migration rate kernel K(k;i,j) = Kkij and D species catalysis-select migration rate kernel J(k;i,j)= Jkij. The kinetic evolution behaviour is found to be dominated by the competition between the catalysis-select immigration and emigration, in which the competition is between JD0 and KC0 (D0 and C0 are the initial numbers of the monomers of species D and C, respectively). When JD0 -KC0 > 0, the aggregate size distribution of species A satisfies the conventional scaling form and that of species B satisfies a modified scaling form. And in the case of JD0-KC0 0 case.

  18. Kinetic evolutionary behavior of catalysis-select migration

    Institute of Scientific and Technical Information of China (English)

    Wu Yuan-Gang; Lin Zhen-Quan; Ke Jian-Hong

    2012-01-01

    We propose a catalysis-select migration driven evolution model of two-species (A- and B-species) aggregates,where one unit of species A migrates to species B under the catalysts of species C,while under the catalysts of species D the reaction will become one unit of species B migrating to species A.Meanwhile the catalyst aggregates of species C perform self-coagulation,as do the species D aggregates.We study this catalysis-select migration driven kinetic aggregation phenomena using the generalized Smoluchowski rate equation approach with C species catalysis-select migration rate kernel K(k;i,j) =Kkij and D species catalysis-select migration rate kernel J(k;i,j) =Jkij.The kinetic evolution behaviour is found to be dominated by the competition between the catalysis-select immigration and emigration,in which the competition is between JD0 and KC0 (D0 and C0 are the initial numbers of the monomers of species D and C,respectively).When JD0 - KC0 > 0,the aggregate size distribution of species A satisfies the conventional scaling form and that of species B satisfies a modified scaling form.And in the case of JDo - KCo < 0,species A and B exchange their aggregate size distributions as in the above JD0 - KC0 > 0 case.

  19. Kinetic evolutionary behavior of catalysis-select migration

    International Nuclear Information System (INIS)

    We propose a catalysis-select migration driven evolution model of two-species (A- and B-species) aggregates, where one unit of species A migrates to species B under the catalysts of species C, while under the catalysts of species D the reaction will become one unit of species B migrating to species A. Meanwhile the catalyst aggregates of species C perform self-coagulation, as do the species D aggregates. We study this catalysis-select migration driven kinetic aggregation phenomena using the generalized Smoluchowski rate equation approach with C species catalysis-select migration rate kernel K(k;i,j) = Kkij and D species catalysis-select migration rate kernel J(k;i,j)= Jkij. The kinetic evolution behaviour is found to be dominated by the competition between the catalysis-select immigration and emigration, in which the competition is between JD0 and KC0 (D0 and C0 are the initial numbers of the monomers of species D and C, respectively). When JD0 −KC0 > 0, the aggregate size distribution of species A satisfies the conventional scaling form and that of species B satisfies a modified scaling form. And in the case of JD0−KC0 0−KC0 > 0 case. (interdisciplinary physics and related areas of science and technology)

  20. Inverse Magnetic Catalysis in Bottom-Up Holographic QCD

    CERN Document Server

    Evans, Nick; Scott, Marc

    2016-01-01

    We explore the effect of magnetic field on chiral condensation in QCD via a simple bottom up holographic model which inputs QCD dynamics through the running of the anomalous dimension of the quark bilinear. Bottom up holography is a form of effective field theory and we use it to explore the dependence on the coefficients of the two lowest order terms linking the magnetic field and the quark condensate. In the massless theory, we identify a region of parameter space where magnetic catalysis occurs at zero temperature but inverse magnetic catalysis at temperatures of order the thermal phase transition. The model shows similar non-monotonic behaviour in the condensate with B at intermediate T as the lattice data. This behaviour is due to the separation of the meson melting and chiral transitions in the holographic framework. The introduction of quark mass raises the scale of B where inverse catalysis takes over from catalysis until the inverse catalysis lies outside the regime of validity of the effective descr...

  1. Catalysis-by-design impacts assessment

    Energy Technology Data Exchange (ETDEWEB)

    Fassbender, L L; Young, J K [Pacific Northwest Lab., Richland, WA (USA); Sen, R K [Sen (R.K.) and Associates, Washington, DC (USA)

    1991-05-01

    Catalyst researchers have always recognized the need to develop a detailed understanding of the mechanisms of catalytic processes, and have hoped that it would lead to developing a theoretical predictive base to guide the search for new catalysts. This understanding allows one to develop a set of hierarchical models, from fundamental atomic-level ab-initio models to detailed engineering simulations of reactor systems, to direct the search for optimized, efficient catalyst systems. During the last two decades, the explosions of advanced surface analysis techniques have helped considerably to develop the building blocks for understanding various catalytic reactions. An effort to couple these theoretical and experimental advances to develop a set of hierarchical models to predict the nature of catalytic materials is a program entitled Catalysis-by-Design (CRD).'' In assessing the potential impacts of CBD on US industry, the key point to remember is that the value of the program lies in developing a novel methodology to search for new catalyst systems. Industrial researchers can then use this methodology to develop proprietary catalysts. Most companies involved in catalyst R D have two types of ongoing projects. The first type, what we call market-driven R D,'' are projects that support and improve upon a company's existing product lines. Project of the second type, technology-driven R D,'' are longer term, involve the development of totally new catalysts, and are initiated through scientists' research ideas. The CBD approach will impact both types of projects. However, this analysis indicates that the near-term impacts will be on market-driven'' projects. The conclusions and recommendations presented in this report were obtained by the authors through personal interviews with individuals involved in a variety of industrial catalyst development programs and through the three CBD workshops held in the summer of 1989. 34 refs., 7 figs., 7 tabs.

  2. High-Spin Cobalt Hydrides for Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Holland, Patrick L. [Yale University

    2013-08-29

    Organometallic chemists have traditionally used catalysts with strong-field ligands that give low-spin complexes. However, complexes with a weak ligand field have weaker bonds and lower barriers to geometric changes, suggesting that they may lead to more rapid catalytic reactions. Developing our understanding of high-spin complexes requires the use of a broader range of spectroscopic techniques, but has the promise of changing the mechanism and/or selectivity of known catalytic reactions. These changes may enable the more efficient utilization of chemical resources. A special advantage of cobalt and iron catalysts is that the metals are more abundant and cheaper than those currently used for major industrial processes that convert unsaturated organic molecules and biofeedstocks into useful chemicals. This project specifically evaluated the potential of high-spin cobalt complexes for small-molecule reactions for bond rearrangement and cleavage reactions relevant to hydrocarbon transformations. We have learned that many of these reactions proceed through crossing to different spin states: for example, high-spin complexes can flip one electron spin to access a lower-energy reaction pathway for beta-hydride elimination. This reaction enables new, selective olefin isomerization catalysis. The high-spin cobalt complexes also cleave the C-O bond of CO2 and the C-F bonds of fluoroarenes. In each case, the detailed mechanism of the reaction has been determined. Importantly, we have discovered that the cobalt catalysts described here give distinctive selectivities that are better than known catalysts. These selectivities come from a synergy between supporting ligand design and electronic control of the spin-state crossing in the reactions.

  3. Biodiesel forming reactions using heterogeneous catalysis

    Science.gov (United States)

    Liu, Yijun

    Biodiesel synthesis from biomass provides a means for utilizing effectively renewable resources, a way to convert waste vegetable oils and animal fats to a useful product, a way to recycle carbon dioxide for a combustion fuel, and production of a fuel that is biodegradable, non-toxic, and has a lower emission profile than petroleum-diesel. Free fatty acid (FFA) esterification and triglyceride (TG) transesterification with low molecular weight alcohols constitute the synthetic routes to prepare biodiesel from lipid feedstocks. This project was aimed at developing a better understanding of important fundamental issues involved in heterogeneous catalyzed biodiesel forming reactions using mainly model compounds, representing part of on-going efforts to build up a rational base for assay, design, and performance optimization of solid acids/bases in biodiesel synthesis. As FFA esterification proceeds, water is continuously formed as a byproduct and affects reaction rates in a negative manner. Using sulfuric acid (as a catalyst) and acetic acid (as a model compound for FFA), the impact of increasing concentrations of water on acid catalysis was investigated. The order of the water effect on reaction rate was determined to be -0.83. Sulfuric acid lost up to 90% activity as the amount of water present increased. The nature of the negative effect of water on esterification was found to go beyond the scope of reverse hydrolysis and was associated with the diminished acid strength of sulfuric acid as a result of the preferential solvation by water molecules of its catalytic protons. The results indicate that as esterification progresses and byproduct water is produced, deactivation of a Bronsted acid catalyst like H2SO4 occurs. Using a solid composite acid (SAC-13) as an example of heterogeneous catalysts and sulfuric acid as a homogeneous reference, similar reaction inhibition by water was demonstrated for homogeneous and heterogeneous catalysis. This similarity together with

  4. Recyclable enzyme mimic of cubic Fe3O4 nanoparticles loaded on graphene oxide-dispersed carbon nanotubes with enhanced peroxidase-like catalysis and electrocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hua; Li, Shuai; Si, Yanmei; Sun, Zhongzhao; Li, Shuying; Lin, Yuehe

    2014-01-01

    Fe3O4 nanoparticles as nanocatalysts may present peroxidase-like catalysis activities and high electrocatalysis if loaded on conductive carbon nanotube (CNT) supports; however, their catalysis performances in an aqueous system might still be challenged by the poor aqueous dispersion of hydrophobic carbon supports and/or low stability of loaded iron catalysts. In this work, amphiphilic graphene oxide nanosheets were employed as “surfactant” to disperse CNTs to create stable graphene oxide-dispersed CNT (GCNT) supports in water for covalently loading cubic Fe3O4 nanoparticles with improved distribution and binding efficiency. Compared with original Fe3O4 nanos and CNT-loaded Fe3O4 nanocomplex, the prepared GCNT–Fe3O4 nanocomposite could achieve higher aqueous stability and, especially, much stronger peroxidase-like catalysis and electrocatalysis to H2O2, presumably resulting from the synergetic effects of two conductive carbon supports and cubic Fe3O4 nanocatalysts effectively loaded. Colorimetric and direct electrochemical detections of H2O2 and glucose using the GCNT–Fe3O4 nanocomposite were conducted with high detection sensitivities, demonstrating the feasibility of practical sensing applications. Such a magnetically recyclable “enzyme mimic” may circumvent some disadvantages of natural protein enzymes and common inorganic catalysts, featuring the multi-functions of high peroxidase-like catalysis, strong electrocatalysis, magnetic separation/recyclability, environmental stability, and direct H2O2 electrochemistry.

  5. Catalysis Science Initiative: Catalyst Design by Discovery Informatics

    Energy Technology Data Exchange (ETDEWEB)

    Delgass, William Nicholas [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Abu-Omar, Mahdi [Purdue Univ., West Lafayette, IN (United States) Department of Chemistry; Caruthers, James [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Ribeiro, Fabio [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Thomson, Kendall [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Schneider, William [Univ. of Notre Dame, IN (United States)

    2016-07-08

    Catalysts selectively enhance the rates of chemical reactions toward desired products. Such reactions provide great benefit to society in major commercial sectors such as energy production, protecting the environment, and polymer products and thereby contribute heavily to the country’s gross national product. Our premise is that the level of fundamental understanding of catalytic events at the atomic and molecular scale has reached the point that more predictive methods can be developed to shorten the cycle time to new processes. The field of catalysis can be divided into two regimes: heterogeneous and homogeneous. For the heterogeneous catalysis regime, we have used the water-gas shift (WGS) reaction (CO + H2O + CO2 + H2O) over supported metals as a test bed. Detailed analysis and strong coupling of theory with experiment have led to the following conclusions: • The sequence of elementary steps goes through a COOH intermediate • The CO binding energy is a strong function of coverage of CO adsorbed on the surface in many systems • In the case of Au catalysts, the CO adsorption is generally too weak on surface with close atomic packing, but the enhanced binding at corner atoms (which are missing bonding partners) of cubo-octahedral nanoparticles increases the energy to a near optimal value and produces very active catalysts. • Reaction on the metal alone cannot account for the experimental results. The reaction is dual functional with water activation occurring at the metal-support interface. It is clear from our work that the theory component is essential, not only for prediction of new systems, but also for reconciling data and testing hypotheses regarding potential descriptors. Particularly important is the finding that the interface between nano-sized metal particles and the oxides that are used to support them represent a new state of matter in the sense that the interfacial bonding perturbs the chemical state of both metals atoms and the support

  6. Gold Nanoparticle-Biological Molecule Interactions and Catalysis

    Directory of Open Access Journals (Sweden)

    Jonathan G. Heddle

    2013-09-01

    Full Text Available This review gives a brief summary of the field of gold nanoparticle interactions with biological molecules, particularly those with possible catalytic relevance. Gold nanoparticles are well known as catalysts in organic chemistry but much is unknown regarding their potential as catalysts of reactions involving biological molecules such as protein and nucleic acids. Biological molecules may be the substrate for catalysis or, if they are the ligand coating the gold particle, may be the catalyst itself. In other cases biological molecules may form a template upon which gold nanoparticles can be precisely arrayed. As relatively little is currently known about the catalytic capabilities of gold nanoparticles in this area, this review will consider templating in general (including, but not restricted to, those which result in structures having potential as catalysts before going on to consider firstly catalysis by the gold nanoparticle itself followed by catalysis by ligands attached to gold nanoparticles, all considered with a focus on biological molecules.

  7. Catalysis induced by radiations; Catalisis inducida por radiaciones

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez B, J.; Gonzalez J, J. C., E-mail: jaime.jimenez@inin.gob.m [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2010-07-01

    In Mexico is generated a great quantity of residuals considered as dangerous, for its capacity of corrosion, reactivity, toxicity to the environment, inflammability and biological-infectious potential. It is important to mention that the toxic compounds cannot be discharged to the sewerage systems and much less to the receiving bodies of water. The usual treatment that receives the dangerous residuals is the incineration and the bordering. The incineration is an efficient form of treating the residuals, but it can be dioxins source and benzofurans, being the phenol and chloro phenol the precursors of these compounds. At the present time the radiolytic degradation of organic compounds has been broadly studied, especially the 4-chloro phenol and of same form the photo catalysis of organic compounds. However the combination of both processes, called radio catalysis is barely reported. In this work the results of the experiments realized for to degrade the 4-chloro phenol by means of radio catalysis are reported. (Author)

  8. Ceramics in Environmental Catalysis:Applications and Possibilities%Ceramics in Environmental Catalysis: Applications and Possibilities

    Institute of Scientific and Technical Information of China (English)

    Nitin LABHSETWAR; P.DOGGALI; S.RAYALU; R.YADAV; T.MISTUHASHI; H.HANEDA

    2012-01-01

    Environmental catalysis has been steadily growing because of the advances in its scientific and engineering aspects,as well as due to the new environmental challenges in the industrial era.The development of new catalysts and materials is essential for new technologies for various environmental applications.Ceramics play important roles in various environmental applications including the identification,monitoring,and quantification of pollutants and their control.Ceramics have important applications as sensors and photocatalysts,and they are extensively used as catalyst carriers and supports.Many ceramics are being explored as catalysts for pollution control applications.Their low cost,thermal and chemical stability,and capability of being tailored make them especially attractive for pollution control applications.Although a wide variety of materials have been developed as catalyst supports,this area is still of interest with new or modified catalyst supports being frequently reported.It is of equal importance to develop new or modified processes for the loading of catalysts on specific supports.Applications like chemical looping combustion (CLC) and other catalytic combustion processes are raising the demands to a new scale.We have been working on the development of both new and modified support materials,including mesoporous materials without structural order for possible applications in CLC and other catalytic reactions.Successful attempts have been made in the modification of conventional γ-Al2O3 and improved synthesis processes for supporting perovskite type catalysts.Our research on environmental catalysis applications of ceramic materials and processes are also briefly discussed.

  9. Role of catalysis in sustainable production of synthetic elastomers

    Indian Academy of Sciences (India)

    Vivek K Srivastava; Madhuchhanda Maiti; Ganesh C Basak; Raksh V Jasra

    2014-03-01

    Elastomer business plays a significant role in the transportation industry. In fact, elastomers make the world move. Due to limited availability of natural rubber, synthetic elastomers bridge the gap between demand and supply in today’s growing tyre and automobile industry.With more than ∼10000 KTA total world productions, the impact of synthetic elastomer business cannot be overlooked. The need of synthetic elastomers for tyre and automobile industries is stringently specific. Catalysis plays an inevitable role in achieving the growing demand of specific synthetic elastomers. The present study will describe how catalysis plays a significant role in the sustainable development of elastomers with special reference to polybutadiene rubber.

  10. New and future developments in catalysis activation of carbon dioxide

    CERN Document Server

    Suib, Steven L

    2013-01-01

    New and Future Developments in Catalysis is a package of books that compile the latest ideas concerning alternate and renewable energy sources and the role that catalysis plays in converting new renewable feedstock into biofuels and biochemicals. Both homogeneous and heterogeneous catalysts and catalytic processes will be discussed in a unified and comprehensive approach. There will be extensive cross-referencing within all volumes. This volume presents a complete picture of all carbon dioxide (CO2) sources, outlines the environmental concerns regarding CO2, and critica

  11. A Possible Macroscopic-Photo-Catalysis Mechanism in Solar Furnace

    Institute of Scientific and Technical Information of China (English)

    HO Tsohsiu; QING Cheng-Rui; CHEN Ying-Tian

    2011-01-01

    Based on the experimental results of Chen et al.to use the solar furnace and medium frequency induction furnace to extract boron impurity from metallurgical silicon, we propose a strong radiation catalysis mechanism to explain the difference of reaction rates in these two furnaces.The postulate assuming the photons striking on the material not only increase the thermal energy of the molecules of reactants but also lower down the energy barrier of the reaction to speed up the chemical reaction.It is believed the photon catalysis mechanism is universall in most of high temperature chemical reactions and looking forward to more evidences for the postulate proposed in this article.

  12. KCC1: First Nanoparticle developed by KAUST Catalysis Center

    KAUST Repository

    Basset, Jean-Marie

    2010-08-01

    KCC1 is the first Nanoparticle developed by KAUST Catalysis Center. Director of KAUST Catalysis Center, Dr. Jean-Marie Basset, Senior Research Scientist at KCC, Dr. Vivek Polshettiwar, and Dr. Dongkyu Cha of the Advanced Nanofabrication Imaging & Characterization Core Laboratory discuss the details of this recent discovery. This video was produced by KAUST Visualization Laboratory and KAUST Technology Transfer and Innovation - Terence McElwee, Director, Technology Transfer and Innovation - IP@kaust.edu.sa This technology is part of KAUST\\'s technology commercialization program that seeks to stimulate development and commercial use of KAUST-developed technologies. For more information email us at ip@kaust.edu.sa.

  13. Switching on Elusive Organometallic Mechanisms with Photoredox Catalysis

    OpenAIRE

    Terrett, Jack A.; Cuthbertson, James D.; Shurtleff, Valerie W.; MacMillan, David W. C.

    2015-01-01

    Transition metal-catalyzed cross-coupling reactions have become one of the most utilized carbon–carbon and carbon–heteroatom bond-forming reactions in chemical synthesis. More recently, nickel catalysis has been shown to participate in a wide variety of C–C bond forming reactions, most notably Negishi, Suzuki–Miyaura, Stille, Kumada, and Hiyama couplings 1,2 . Despite the tremendous advances in C–C fragment couplings, the ability to forge C–O bonds in a general fashion via nickel catalysis ha...

  14. Seventh BES [Basic Energy Sciences] catalysis and surface chemistry research conference

    International Nuclear Information System (INIS)

    Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases

  15. Seventh BES (Basic Energy Sciences) catalysis and surface chemistry research conference

    Energy Technology Data Exchange (ETDEWEB)

    1990-03-01

    Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases. (CBS)

  16. Enantioselective conjugate additions of α-amino radicals via cooperative photoredox and Lewis acid catalysis.

    Science.gov (United States)

    Ruiz Espelt, Laura; McPherson, Iain S; Wiensch, Eric M; Yoon, Tehshik P

    2015-02-25

    We report the highly enantioselective addition of photogenerated α-amino radicals to Michael acceptors. This method features a dual-catalyst protocol that combines transition metal photoredox catalysis with chiral Lewis acid catalysis. The combination of these two powerful modes of catalysis provides an effective, general strategy to generate and control the reactivity of photogenerated reactive intermediates.

  17. A conceptual translation of homogeneous catalysis into heterogeneous catalysis: homogeneous-like heterogeneous gold nanoparticle catalyst induced by ceria supporter.

    Science.gov (United States)

    Li, Zhen-Xing; Xue, Wei; Guan, Bing-Tao; Shi, Fu-Bo; Shi, Zhang-Jie; Jiang, Hong; Yan, Chun-Hua

    2013-02-01

    Translation of homogeneous catalysis into heterogeneous catalysis is a promising solution to green and sustainable development in chemical industry. For this purpose, noble metal nanoparticles represent a new frontier in catalytic transformations. Many challenges remain for researchers to transform noble metal nanoparticles of heterogeneous catalytic active sites into ionic species of homogeneous catalytic active sites. We report here a successful design on translating homogeneous gold catalysis into a heterogeneous system with a clear understanding of the catalytic pathway. This study initiates a novel concept to immobilize a homogeneous catalyst based on electron transfer between supporting base and supported nanoparticles. Meanwhile, on the basis of theoretical calculation, it has deepened the understanding of the interactions between noble metal nanoparticles and the catalyst support.

  18. Dynamic control of chirality in phosphine ligands for enantioselective catalysis

    NARCIS (Netherlands)

    Zhao, Depeng; Neubauer, Thomas M; Feringa, Ben L

    2015-01-01

    Chirality plays a fundamental role in biology and chemistry and the precise control of chirality in a catalytic conversion is a key to modern synthesis most prominently seen in the production of pharmaceuticals. In enantioselective metal-based catalysis, access to each product enantiomer is commonly

  19. A Course in Heterogeneous Catalysis Involving Video-Based Seminars.

    Science.gov (United States)

    White, Mark G.

    1984-01-01

    A video-based format was used during a graduate seminar course designed to educate students on the nature of catalysis, to help transfer information among students working on similar problems, and to improve communication skills. The mechanics of and student reaction to this seminar course are discussed. (JN)

  20. Surface Chemistry in Heterogeneous Catalysis: An Emerging Discipline.

    Science.gov (United States)

    White, J. M.; Campbell, Charles T.

    1980-01-01

    Provides background data on surface chemistry as an emerging discipline. Highlights the important role which surfaces play in catalysis by focusing on the catalyzed oxidation of carbon monoxide. Provides a demonstration of how surfaces exert their influences in heterogeneous phenomena and illustrates how experimental problems in this field are…

  1. Applying homogeneous catalysis for the synthesis of pharmaceuticals.

    Science.gov (United States)

    Beller, M

    2006-01-01

    This article describes recent achievements of my research group in the Leibniz-Institut für Katalyse e.V. in the area of applied homogeneous catalysis for the synthesis of biologically active compounds. Special focus is given on the development of novel and practical palladium and copper catalysts for the functionalization of haloarenes and haloheteroarenes.

  2. Synergy between experimental and computational approaches to homogeneous photoredox catalysis.

    Science.gov (United States)

    Demissie, Taye B; Hansen, Jørn H

    2016-07-01

    In this Frontiers article, we highlight how state-of-the-art density functional theory calculations can contribute to the field of homogeneous photoredox catalysis. We discuss challenges in the fields and potential solutions to be found at the interface between theory and experiment. The exciting opportunities and insights that can arise through such an interdisciplinary approach are highlighted.

  3. Multiphoton catalysis with coherent state input: nonclassicality and decoherence

    Science.gov (United States)

    Hu, Li-Yun; Wu, Jia-Ni; Liao, Zeyang; Zubairy, M. Suhail

    2016-09-01

    We propose a scheme to generate a new kind of non-Gaussian state—the Laguerre polynomial excited coherent state (LPECS)—by using multiphoton catalysis with coherent state input. The nonclassical properties of the LPECS are studied in terms of nonclassical depth, Mandel’s parameter, second-order correlation, quadrature squeezing, and the negativity of the Wigner function (WF). It is found that the LPECS is highly nonclassical and its nonclassicality depends on the amplitude of the coherent state, the catalysis photon number, and the parameters of the unbalanced beam splitter (BS). In particular, the maximum degree of squeezing can be enhanced by increasing the catalysis photon number. In addition, we examine the effect of decoherence using the WF, which shows that the negative region, the characteristic time of decoherence, and the structure of the WF are affected by catalysis photon number and the parameters of the unbalanced BS. Our work provides general analysis on how to prepare polynomial quantum states, which may be useful in the fields of quantum information and quantum computation.

  4. Cooperative catalysis with first-row late transition metals

    NARCIS (Netherlands)

    J.I. van der Vlugt

    2012-01-01

    Cooperative catalysis with first-row transition metals holds much promise for future developments regarding sustainable, selective transformations, including e.g. alkenes, dienes and a variety of small molecules such as CO2, N2 and water. This non-exhaustive analysis of the current state-of-the-art

  5. Self-catalysis growth of zinc oxide nanopillar array

    Institute of Scientific and Technical Information of China (English)

    YUAN Zhihao; DUAN Yueqin; WU Yang; BIE Lijian; FAN Shoushan

    2005-01-01

    Zn nanodot array was prepared by using a nano-masking with porous alumina membrane as mask. Based on such a nanodot array, a self-catalysis method was developed for fabricating ZnO nanopillars on Si substrate. The resultant nanopillars show a two-dimensional, and regular array with uniform size and orientation.

  6. Support and promoter effects in automotive exhaust catalysis

    NARCIS (Netherlands)

    Lepage, M.

    2009-01-01

    Automotive catalysis being a mature technology, it can only be improved by the introduction of new breakthroughs. The ideas generating these technical advances in material science can be found thanks to the synthesis and study of model systems with controlled geometries, compositions, interactions a

  7. Heterogeneous Catalysis: On Bathroom Mirrors and Boiling Stones

    Science.gov (United States)

    Philipse, Albert P.

    2011-01-01

    Though heterogeneous nucleation of liquid droplets on a smooth surface (such as a bathroom mirror) is a classical topic in nucleation theory, it is not well-known that this topic is actually a pedagogical example of heterogeneous catalysis: the one and only effect of the surface is to lower the activation Gibbs energy of droplet formation. In…

  8. Robustness of the rotary catalysis mechanism of F1-ATPase.

    Science.gov (United States)

    Watanabe, Rikiya; Matsukage, Yuki; Yukawa, Ayako; Tabata, Kazuhito V; Noji, Hiroyuki

    2014-07-11

    F1-ATPase (F1) is the rotary motor protein fueled by ATP hydrolysis. Previous studies have suggested that three charged residues are indispensable for catalysis of F1 as follows: the P-loop lysine in the phosphate-binding loop, GXXXXGK(T/S); a glutamic acid that activates water molecules for nucleophilic attack on the γ-phosphate of ATP (general base); and an arginine directly contacting the γ-phosphate (arginine finger). These residues are well conserved among P-loop NTPases. In this study, we investigated the role of these charged residues in catalysis and torque generation by analyzing alanine-substituted mutants in the single-molecule rotation assay. Surprisingly, all mutants continuously drove rotary motion, even though the rotational velocity was at least 100,000 times slower than that of wild type. Thus, although these charged residues contribute to highly efficient catalysis, they are not indispensable to chemo-mechanical energy coupling, and the rotary catalysis mechanism of F1 is far more robust than previously thought.

  9. Functionalized pyrazines as ligands for minor actinide extraction and catalysis

    NARCIS (Netherlands)

    Nikishkin, N.

    2013-01-01

    The research presented in this thesis concerns the design of ligands for a wide range of applications, from nuclear waste treatment to catalysis. The strategies employed to design actinide-selective extractants, for instance, comprise the fine tuning of the ligand electronic properties as well as us

  10. Early Main Group Metal Catalysis : How Important is the Metal?

    NARCIS (Netherlands)

    Penafiel, Johanne; Maron, Laurent; Harder, Sjoerd

    2015-01-01

    Organocalcium compounds have been reported as efficient catalysts for various alkene transformations. In contrast to transition metal catalysis, the alkenes are not activated by metal-alkene orbital interactions. Instead it is proposed that alkene activation proceeds through an electrostatic interac

  11. Research progress in synthesis and catalysis of polyoxometalates

    Institute of Scientific and Technical Information of China (English)

    GONG Yun; HU Changwen; LIANG Hong

    2005-01-01

    Recent progress in the synthetic chemistry and catalysis of polyoxometalates (POMs) is reviewed. The novel POMs and their derivatives emerging in nearly three years (2002-2004) are introduced, including POMs with novel structure, POMs-organic hybrid compounds and host-guest complexes. Our review is focused on the elaboration of POMs' supramolecular chemistry.

  12. Physical applications of muon catalysis: Muon capture in hydrogen

    Science.gov (United States)

    Filchenkov, V. V.

    2016-07-01

    Results of theoretical and experimental research on capture of negative muons in hydrogen are reported with an emphasis on the accompanying phenomenon of muon catalysis in hydrogen and subtleties of the experimental method. A conclusion is drawn that precise determination of the capture rate is important for refining the standard model.

  13. Chemometric Optimization Studies in Catalysis Employing High-Throughput Experimentation

    NARCIS (Netherlands)

    Pereira, S.R.M.

    2008-01-01

    The main topic of this thesis is the investigation of the synergies between High-Throughput Experimentation (HTE) and Chemometric Optimization methodologies in Catalysis research and of the use of such methodologies to maximize the advantages of using HTE methods. Several case studies were analysed

  14. Nitrogen doped carbon nanotubes : synthesis, characterization and catalysis

    NARCIS (Netherlands)

    van Dommele, S.

    2008-01-01

    Nitrogen containing Carbon Nanotubes (NCNT) have altered physical- and chemical properties with respect to polarity, conductivity and reactivity as compared to conventional carbon nanotubes (CNT) and have potential for use in electronic applications or catalysis. In this thesis the incorporation of

  15. Non Sense

    DEFF Research Database (Denmark)

    Hjort, Katrin

    2010-01-01

    ’t make sense but appeared extremely complicated and contradictionary. This article studies the school reform through the filter of discourse analysis. The reform represents an advances version of liberal management and is construed as an alliance between 4 conflicting regimes of practice. Consequently...

  16. Excess mutual catalysis is required for effective evolvability.

    Science.gov (United States)

    Markovitch, Omer; Lancet, Doron

    2012-01-01

    It is widely accepted that autocatalysis constitutes a crucial facet of effective replication and evolution (e.g., in Eigen's hypercycle model). Other models for early evolution (e.g., by Dyson, Gánti, Varela, and Kauffman) invoke catalytic networks, where cross-catalysis is more apparent. A key question is how the balance between auto- (self-) and cross- (mutual) catalysis shapes the behavior of model evolving systems. This is investigated using the graded autocatalysis replication domain (GARD) model, previously shown to capture essential features of reproduction, mutation, and evolution in compositional molecular assemblies. We have performed numerical simulations of an ensemble of GARD networks, each with a different set of lognormally distributed catalytic values. We asked what is the influence of the catalytic content of such networks on beneficial evolution. Importantly, a clear trend was observed, wherein only networks with high mutual catalysis propensity (p(mc)) allowed for an augmented diversity of composomes, quasi-stationary compositions that exhibit high replication fidelity. We have reexamined a recent analysis that showed meager selection in a single GARD instance and for a few nonstationary target compositions. In contrast, when we focused here on compotypes (clusters of composomes) as targets for selection in populations of compositional assemblies, appreciable selection response was observed for a large portion of the networks simulated. Further, stronger selection response was seen for high p(mc) values. Our simulations thus demonstrate that GARD can help analyze important facets of evolving systems, and indicate that excess mutual catalysis over self-catalysis is likely to be important for the emergence of molecular systems capable of evolutionlike behavior.

  17. Drug Facts

    Medline Plus

    Full Text Available ... People Drug Abuse Hurts Families Drug Abuse Hurts Kids Drug Abuse Hurts Unborn Children Drug Abuse Hurts ... Children and Teens Stay Drug-Free Talking to Kids About Drugs: What To Say if You Were ...

  18. Young drug addicts and the drug scene.

    Science.gov (United States)

    Lucchini, R

    1985-01-01

    The drug scene generally comprises the following four distinct categories of young people: neophytes, addicts who enjoy a high status vis-à-vis other addicts, multiple drug addicts, and non-addicted drug dealers. It has its own evolution, hierarchy, structure and criteria of success and failure. The members are required to conform to the established criteria. The integration of the young addict into the drug scene is not voluntary in the real sense of the word, for he is caught between the culture that he rejects and the pseudo-culture of the drug scene. To be accepted into the drug scene, the neophyte must furnish proof of his reliability, which often includes certain forms of criminal activities. The addict who has achieved a position of importance in the drug world serves as a role model for behaviour to the neophyte. In a more advanced phase of addiction, the personality of the addict and the social functions of the drug scene are overwhelmed by the psychoactive effects of the drug, and this process results in the social withdrawal of the addict. The life-style of addicts and the subculture they develop are largely influenced by the type of drug consumed. For example, it is possible to speak of a heroin subculture and a cocaine subculture. In time, every drug scene deteriorates so that it becomes fragmented into small groups, which is often caused by legal interventions or a massive influx of new addicts. The fragmentation of the drug scene is followed by an increase in multiple drug abuse, which often aggravates the medical and social problems of drug addicts. PMID:4075000

  19. HORIZON SENSING

    Energy Technology Data Exchange (ETDEWEB)

    Larry G. Stolarczyk, Sc.D.

    2002-07-31

    Real-time horizon sensing (HS) on continuous mining (CM) machines is becoming an industry tool. Installation and testing of production-grade HS systems has been ongoing this quarter at Oxbow Mining Company, Monterey Coal Company (EXXON), FMC Trona, Twentymile Coal Company (RAG America), and SASOL Coal. Detailed monitoring of system function, user experience, and mining benefits is ongoing. All horizon sensor components have finished MSHA (United States) and IEC (International) certification.

  20. Molecular-Level Design of Heterogeneous Chiral Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Francisco Zaera

    2012-03-21

    The following is a proposal to continue our multi-institutional research on heterogeneous chiral catalysis. Our team combines the use of surface-sensitive analytical techniques for the characterization of model systems with quantum and statistical mechanical calculations to interpret experimental data and guide the design of future research. Our investigation focuses on the interrelation among the three main mechanisms by which enantioselectivity can be bestowed to heterogeneous catalysts, namely: (1) by templating chirality via the adsorption of chiral supramolecular assemblies, (2) by using chiral modifiers capable of forming chiral complexes with the reactant and force enantioselective surface reactions, and (3) by forming naturally chiral surfaces using imprinting chiral agents. Individually, the members of our team are leaders in these various aspects of chiral catalysis, but the present program provides the vehicle to generate and exploit the synergies necessary to address the problem in a comprehensive manner. Our initial work has advanced the methodology needed for these studies, including an enantioselective titration procedure to identify surface chiral sites, infrared spectroscopy in situ at the interface between gases or liquids and solids to mimic realistic catalytic conditions, and DFT and Monte Carlo algorithms to simulate and understand chirality on surfaces. The next step, to be funded by the monies requested in this proposal, is to apply those methods to specific problems in chiral catalysis, including the identification of the requirements for the formation of supramolecular surface structures with enantioselective behavior, the search for better molecules to probe the chiral nature of the modified surfaces, the exploration of the transition from supramolecular to one-to-one chiral modification, the correlation of the adsorption characteristics of one-to-one chiral modifiers with their physical properties, in particular with their configuration

  1. Highly Potent, Chemically Stable Quorum Sensing Agonists for Vibrio Cholerae

    OpenAIRE

    Perez, Lark J; Karagounis, Theodora K.; Hurley, Amanda; Bassler, Bonnie L.; Semmelhack, Martin F.

    2013-01-01

    In the Vibrio cholerae pathogen, initiation of bacterial quorum sensing pathways serves to suppress virulence. We describe herein a potent and chemically stable small molecule agonist of V. cholerae quorum sensing, which was identified through rational drug design based on the native quorum sensing signal. This novel agonist may serve as a useful lead compound for the control of virulence in V. cholerae.

  2. Heterogeneous Catalysis of Polyoxometalate Based Organic–Inorganic Hybrids

    Directory of Open Access Journals (Sweden)

    Yuanhang Ren

    2015-03-01

    Full Text Available Organic–inorganic hybrid polyoxometalate (POM compounds are a subset of materials with unique structures and physical/chemical properties. The combination of metal-organic coordination complexes with classical POMs not only provides a powerful way to gain multifarious new compounds but also affords a new method to modify and functionalize POMs. In parallel with the many reports on the synthesis and structure of new hybrid POM compounds, the application of these compounds for heterogeneous catalysis has also attracted considerable attention. The hybrid POM compounds show noteworthy catalytic performance in acid, oxidation, and even in asymmetric catalytic reactions. This review summarizes the design and synthesis of organic–inorganic hybrid POM compounds and particularly highlights their recent progress in heterogeneous catalysis.

  3. Homogeneous Catalysis with Metal Complexes Fundamentals and Applications

    CERN Document Server

    Duca, Gheorghe

    2012-01-01

    The book about homogeneous catalysis with metal complexes deals with the description of the reductive-oxidative, metal complexes  in a liquid phase (in polar solvents, mainly in water, and less in nonpolar solvents). The exceptional importance of the redox processes in chemical systems, in the reactions occuring in living organisms, the environmental processes, atmosphere, water, soil, and in industrial technologies (especially in food-processing industries) is discussed. The detailed practical aspects of the established regularities are explained for solving the specific practical tasks in various fields of industrial chemistry, biochemistry, medicine, analytical chemistry and ecological chemistry. The main scope of the book is the survey and systematization of the latest advances in homogeneous catalysis with metal complexes. It gives an overview of the research results and practical experience accumulated by the author during the last decade.

  4. Advantages of Catalysis in Self-Assembled Molecular Capsules.

    Science.gov (United States)

    Catti, Lorenzo; Zhang, Qi; Tiefenbacher, Konrad

    2016-06-27

    Control over the local chemical environment of a molecule can be achieved by encapsulation in supramolecular host systems. In supramolecular catalysis, this control is used to gain advantages over classical homogeneous catalysis in bulk solution. Two of the main advantages concern influencing reactions in terms of substrate and product selectivity. Due to size and/or shape recognition, substrate selective conversion can be realized. Additionally, noncovalent interactions with the host environment facilitate alternative reaction pathways and can yield unusual products. This Concept article discusses and highlights literature examples utilizing self-assembled molecular capsules to achieve catalytic transformations displaying a high degree of substrate and/or product selectivity. Furthermore, the advantage of supramolecular hosts in multicatalyst tandem reactions is covered. PMID:27150251

  5. Flexibility, diversity, and cooperativity: pillars of enzyme catalysis.

    Science.gov (United States)

    Hammes, Gordon G; Benkovic, Stephen J; Hammes-Schiffer, Sharon

    2011-12-01

    This brief review discusses our current understanding of the molecular basis of enzyme catalysis. A historical development is presented, beginning with steady state kinetics and progressing through modern fast reaction methods, nuclear magnetic resonance, and single-molecule fluorescence techniques. Experimental results are summarized for ribonuclease, aspartate aminotransferase, and especially dihydrofolate reductase (DHFR). Multiple intermediates, multiple conformations, and cooperative conformational changes are shown to be an essential part of virtually all enzyme mechanisms. In the case of DHFR, theoretical investigations have provided detailed information about the movement of atoms within the enzyme-substrate complex as the reaction proceeds along the collective reaction coordinate for hydride transfer. A general mechanism is presented for enzyme catalysis that includes multiple intermediates and a complex, multidimensional standard free energy surface. Protein flexibility, diverse protein conformations, and cooperative conformational changes are important features of this model. PMID:22029278

  6. Carbon mediated catalysis:A review on oxidative dehydrogenation

    Institute of Scientific and Technical Information of China (English)

    De Chen; Anders Holmen; Zhijun Sui; Xinggui Zhou

    2014-01-01

    Carbon mediated catalysis has gained an increasing attention in both areas of nanocatalysis and nanomaterials. The progress in carbon nanomaterials provides many new opportunities to manip-ulate the types and properties of active sites of catalysts through manipulating structures, function-alities and properties of carbon surfaces. The present review focuses on progresses in carbon medi-ated oxidative dehydrogenation reactions of ethylbenzene, propane, and butane. The state-of-the-art of the developments of carbon mediated catalysis is discussed in terms of fundamental studies on adsorption of oxygen and hydrocarbons, reaction mechanism as well as effects of carbon nano-material structures and surface functional groups on the catalytic performance. We highlight the importance and challenges in tuning of the electron density of carbon and oxygen on carbon surfac-es for improving selectivity in oxidative dehydrogenation reactions.

  7. Global Solutions for a Class of Heterogeneous Catalysis Models

    OpenAIRE

    Bothe, Dieter; Köhne, Matthias; Maier, Siegfried; Saal, Jürgen

    2015-01-01

    We consider a mathematical model for heterogeneous catalysis in a finite three-dimensional pore of cylinder-like geometry, with the lateral walls acting as a catalytic surface. The system under consideration consists of a diffusion-advection system inside the bulk phase and a reaction-diffusion-sorption system modeling the processes on the catalytic wall and the exchange between bulk and surface. We assume Fickian diffusion with constant coefficients, sorption kinetics with linear growth boun...

  8. Quasi-Stationary Distributions for Models of Heterogeneous Catalysis

    OpenAIRE

    de Oliveira, Marcelo M.; Dickman, Ronald

    2004-01-01

    We construct the quasi-stationary (QS) distribution for two models of heterogeneous catalysis having two absorbing states: the ZGB model for the oxidation of CO, and a version with noninstantaneous reactions. Using a mean-field-like approximation, we study the quasi-stationary surface coverages, moment ratios and the lifetime of the QS state. We also derive an improved, consistent one-site mean-field theory for the ZGB model.

  9. Protruding interfacial OH groups and 'on-water' heterogeneous catalysis

    International Nuclear Information System (INIS)

    The key aspect of the remarkable organic catalysis that is observed to occur at the organic/water phase boundary, the so-called 'on-water' catalysis (Narayan et al 2005 Angew. Chem. 44 3275), was recently proposed to be the protruding OH groups of water molecules at the interface that interact with the transition state (TS) via hydrogen bonding and lower activation barriers (Jung and Marcus 2007 J. Am. Chem. Soc. 129 5492). In particular, the cycloaddition reaction of quadricyclane (Q) with dimethyl azodicarboxylate (DMAD) on-water was calculated to be more than 100 000 times more efficient in terms of rate constant than the neat reaction. In this paper, we review and consider a related reaction of Q with dimethyl acetylenedicarboxylate, where nitrogen, a good H-bond acceptor, in DMAD is replaced by carbon, a poor H-bond acceptor. A very low rate acceleration of acetylenedicarboxylate on-water relative to the neat reaction is obtained theoretically, as compared to DMAD on-water, due to the relatively low H-bonding ability of acetylenedicarboxylate with water at the TS relative to the reactants. We suggest that there may also be an 'intrinsic steric effect' or orientational advantage in the on-water catalysis in general, and both electronic and steric effects may be in operation for the smaller on-water catalysis for the cycloaddition reaction of quadricyclane and acetylenedicarboxylate. A preliminary quantum mechanical/molecular mechanical (QM/MM) simulation including 1264 water molecules for the on-water reaction of DMAD + Q also suggests that there are indeed approximately two-four more H-bonds between the TS and the dangling OH groups than between the reactants and the surface.

  10. Observations of exoelectron emission associated with heterogeneous catalysis

    Science.gov (United States)

    Hoenig, S. A.; Utter, M. G.

    1977-01-01

    It is suggested that the exoelectron emission from the catalyst may be used to monitor the rate of oxidation of CO and CH4 over palladium catalysts. Indirect heating of the catalyst and atmospheric pressure have no effect upon this monitoring system. Although the mechanism relating catalysis to exoelectron emission is not clear, it is considered possible that electron emission is triggered by the adsorption-desorption cycle.

  11. Conversion of lignocellulose into renewable chemicals by heterogeneous catalysis

    OpenAIRE

    Kobayashi, Hirokazu; Ohta, Hidetoshi; Fukuoka, Atsushi

    2012-01-01

    Conversion of lignocellulose into renewable chemicals and fuels has received great attention for building up the sustainable societies. However, the utilisation of lignocellulose in the chemical industry has almost been limited for paper manufacturing because of the complicated chemical structure and persistent property of lignocellulose. Heterogeneous catalysis has the potential to selectively convert lignocellulosic biomasses into various useful chemicals, and this methodology has rapidly p...

  12. Catalysis in the alkylation reaction of 1-naphthol with epichlorohydrin

    Directory of Open Access Journals (Sweden)

    SLOBODANKA JOVANOVIC

    2006-09-01

    Full Text Available Two new and improved procedures were developed for the synthesis of 1-(1-naphthyloxy-2,3-epoxypropane as an important intermediate in the production of the beta-blocker and antioxidant, 1-[(1-methylethylamino]-3-(1-naphthyloxy-2-propanol (propranolol. Both base homogeneous and heterogeneous PTC catalysis were employed. High yields and remarkable selectivity were achieved. The improved purity is particularly important, in view of the quality requirements for propranolol hydrochloride as an active pharmaceutical ingredient.

  13. Collective synthesis of natural products by means of organocascade catalysis

    OpenAIRE

    Jones, Spencer B.; Simmons, Bryon; Mastracchio, Anthony; MacMillan, David W. C.

    2011-01-01

    Organic chemists are now able to synthesize small quantities of almost any known natural product, given sufficient time, resources and effort. However, translation of the academic successes in total synthesis to the large-scale construction of complex natural products and the development of large collections of biologically relevant molecules present significant challenges to synthetic chemists. Here we show that the application of two nature-inspired techniques, namely organocascade catalysi...

  14. Selective catalysis utilizing bifunctionalized MCM-41 mesoporous materials

    Energy Technology Data Exchange (ETDEWEB)

    Strosahl, Kasey Jean

    2005-05-01

    Selective catalysis is a field that has been under intense investigation for the last 100 years. The most widely used method involves catalysts with stereochemical selectivity. In this type of catalysis, the catalyst controls which reactants will be transformed into the desired product. The secret to employing this type of catalysis, though, is to design the proper catalyst, which can be difficult. One may spend as much time developing the catalyst as spent separating the various products achieved. Another method of selective catalysis is now being explored. The method involves utilizing a multifunctional mesoporous silica catalyst with a gate-keeping capability. Properly functionalized mesoporous materials with well-defined pore morphology and surface properties can provide an ideal three-dimensional environment for anchoring various homogeneous catalysts. These materials can circumvent the multi-sited two-dimensional nature most heterogeneous systems have without adversely impacting the reactant diffusivity. These single-site nanostructured catalysts with ordered geometrical structure are advantageous in achieving high selectivity and reactivity. Mesoporous materials can be prepared to include pores lined homogeneously with tethered catalysts via co-condensation. Additionally, these materials can be reacted with another (RO){sub 3}Si{approx}Z group by using the traditional grafting method; this group is anchored predominantly at the entrances to the pores rather than inside the pores. Thus, if these {approx}Z groups are chosen properly, they can select certain molecules to enter the pores and be converted to products (Scheme 1). In such multifunctional catalysts, the selectivity depends on the discrimination of the gatekeeper. Gate-keeping MCM-41 materials are at the forefront of catalytic substances.

  15. Membrane catalysis in the dehydrogenation and hydrogen production processes

    International Nuclear Information System (INIS)

    Data on the applications of membrane catalysis in the dehydrogenation of organic compounds and hydrogen production are analyzed and generalized. It is shown that the integration of membrane reactors into existing plants is necessary for production of hydrogen of high purity. The steam reforming and oxidative reforming of methane and steam reforming of light alcohols seem to be the most promising processes for hydrogen production in membrane reactors. The bibliography includes 165 references.

  16. Exploring the scope of organic syntheses with semiconductor photoredox catalysis

    OpenAIRE

    Manley, David

    2014-01-01

    Under dry, anaerobic conditions TiO₂ photoredox catalysis has been directed away from oxidative/degradative chemistry. Instead, carboxylic acid photoredox reactions resulted in carbon-carbon bond forming processes. High yields of radical homodimers were obtained from TiO₂ treatment of carboxylic acids alone. “Benzyl-type” radicals in particular performed very well in this system. Attempts at carrying out hetero-dimerisations were unsuccessful as it is thought that the differing rates of forma...

  17. Bionic catalysis of porphyrin for electrochemical detection of nucleic acids

    International Nuclear Information System (INIS)

    Highlights: ► This is the first application of bionic catalysis of porphyrin as detection probe in bioanalysis. ► Porphyrin–DNA–gold nanoparticle probe is synthesized. ► Binding model between FeTMPyP and DNA is verified. ► The detection probe shows excellent electrocatalytic behaviors toward the reduction of O2. ► The biosensor exhibited good performance with wide linear range and high specificity. - Abstract: A novel electrochemical strategy was designed for the detection of DNA based on the bionic catalysis of porphyrin. The detection probe was prepared via the assembly of thiolated double strand DNA (dsDNA) with gold nanoparticles (AuNPs), and then interacted with cationic iron (III) meso-tetrakis (N-methylphyridinum-4-yl) porphyrin (FeTMPyP) via groove binding along the dsDNA surface. The resulting nanocomplex was characterized with transmission electron microscopy, UV–vis absorption and circular dichroism spectroscopy. The FeTMPyP–DNA–AuNPs probe on gold electrode demonstrated the excellent electrocatalytic behaviors toward the reduction of O2 due to the largely loading of FeTMPyP and good conductivity. Based on bionic catalysis of porphyrin for the reduction of O2, the resulting biosensor exhibited a good performance for the detection of DNA with a wide linear range from 1 × 10−12 to 1 × 10−8 mol L−1 and detection limit of 2.5 × 10−13 mol L−1 at the signal/noise of 3. More importantly, the biosensor presented excellent ability to discriminate the perfectly complementary target and the mismatched stand. This strategy could be conveniently extended for detection of other biomolecules. To the best of our knowledge, this is the first application of bionic catalysis of porphyrin as detection probe and opens new opportunities for sensitive detection of biorecognition events.

  18. From Inverse to Delayed Magnetic Catalysis in Strong Magnetic Field

    CERN Document Server

    Mao, Shijun

    2016-01-01

    We study magnetic field effect on chiral phase transition in a Nambu--Jona-Lasinio model. In comparison with mean field approximation containing quarks only, including mesons as quantum fluctuations in the model leads to a transition from inverse to delayed magnetic catalysis at finite temperature and delays the transition at finite baryon chemical potential. The location of the critical end point depends on the the magnetic field non-monotonously.

  19. A nature-inspired approach to reactor and catalysis engineering

    OpenAIRE

    Coppens, M-O

    2012-01-01

    Mechanisms used by biology to solve fundamental problems, such as those related to scalability, efficiency and robustness could guide the design of innovative solutions to similar challenges in chemical engineering. Complementing progress in bioinspired chemistry and materials science, we identify three methodologies as the backbone of nature-inspired reactor and catalysis engineering. First, biology often uses hierarchical networks to bridge scales and facilitate transport, leading to broadl...

  20. Catalysis at the Homogeneous-Heterogeneous Chemistry Interface

    Institute of Scientific and Technical Information of China (English)

    Howard; Alper

    2007-01-01

    1 Results Significant progress has been made in recent years in developing efficient, atom economical catalytic reactions of potential applicability to the pharmaceutical, petrochemical, and commodity chemical business sectors. In some cases, homogeneous catalytic processes offer advantages, but in others the use of heterogenized homogeneous catalysis provides a competitive advantage concerning recyclability and catalyst recovery. This presentation will consider new approaches to cyclization reactions a...

  1. HORIZON SENSING

    Energy Technology Data Exchange (ETDEWEB)

    Larry G. Stolarczyk

    2003-03-18

    With the aid of a DOE grant (No. DE-FC26-01NT41050), Stolar Research Corporation (Stolar) developed the Horizon Sensor (HS) to distinguish between the different layers of a coal seam. Mounted on mining machine cutter drums, HS units can detect or sense the horizon between the coal seam and the roof and floor rock, providing the opportunity to accurately mine the section of the seam most desired. HS also enables accurate cutting of minimum height if that is the operator's objective. Often when cutting is done out-of-seam, the head-positioning function facilitates a fixed mining height to minimize dilution. With this technology, miners can still be at a remote location, yet cut only the clean coal, resulting in a much more efficient overall process. The objectives of this project were to demonstrate the feasibility of horizon sensing on mining machines and demonstrate that Horizon Sensing can allow coal to be cut cleaner and more efficiently. Stolar's primary goal was to develop the Horizon Sensor (HS) into an enabling technology for full or partial automation or ''agile mining''. This technical innovation (R&D 100 Award Winner) is quickly demonstrating improvements in productivity and miner safety at several prominent coal mines in the United States. In addition, the HS system can enable the cutting of cleaner coal. Stolar has driven the HS program on the philosophy that cutting cleaner coal means burning cleaner coal. The sensor, located inches from the cutting bits, is based upon the physics principles of a Resonant Microstrip Patch Antenna (RMPA). When it is in proximity of the rock-coal interface, the RMPA impedance varies depending on the thickness of uncut coal. The impedance is measured by the computer-controlled electronics and then sent by radio waves to the mining machine. The worker at the machine can read the data via a Graphical User Interface, displaying a color-coded image of the coal being cut, and direct the machine

  2. Crown ethers and phase transfer catalysis in polymer science

    CERN Document Server

    Carraher, Charles

    1984-01-01

    Phase transfer catalysis or interfacial catalysis is a syn­ thetic technique involving transport of an organic or inorganic salt from a solid or aqueous phase into an organic liquid where reaction with an organic-soluble substrate takes place. Over the past 15 years there has been an enormous amount of effort invested in the development of this technique in organic synthe­ sis. Several books and numerous review articles have appeared summarizing applications in which low molecular weight catalysts are employed. These generally include either crown ethers or onium salts of various kinds. While the term phase transfer catalysis is relatively new, the concept of using a phasetrans­ fer agent (PTA) is much older~ Both Schnell and Morgan employed such catalysts in synthesis of polymeric species in the early 1950's. Present developments are really extensions of these early applications. It has only been within the last several years that the use of phase transfer processes have been employed in polymer synthesis...

  3. Compartmentalized Droplets for Continuous Flow Liquid-Liquid Interface Catalysis.

    Science.gov (United States)

    Zhang, Ming; Wei, Lijuan; Chen, Huan; Du, Zhiping; Binks, Bernard P; Yang, Hengquan

    2016-08-17

    To address the limitations of batch organic-aqueous biphasic catalysis, we develop a conceptually novel method termed Flow Pickering Emulsion, or FPE, to process biphasic reactions in a continuous flow fashion. This method involves the compartmentalization of bulk water into micron-sized droplets based on a water-in-oil Pickering emulsion, which are packed into a column reactor. The compartmentalized water droplets can confine water-soluble catalysts, thus "immobilizing" the catalyst in the column reactor, while the interstices between the droplets allow the organic (oil) phase to flow. Key fundamental principles underpinning this method such as the oil phase flow behavior, the stability of compartmentalized droplets and the confinement capability of these droplets toward water-soluble catalysts are experimentally and theoretically investigated. As a proof of this concept, case studies including a sulfuric acid-catalyzed addition reaction, a heteropolyacid-catalyzed ring opening reaction and an enzyme-catalyzed chiral reaction demonstrate the generality and versatility of the FPE method. Impressively, in addition to the excellent durability, the developed FPE reactions exhibit up to 10-fold reaction efficiency enhancement in comparison to the existing batch reactions, indicating a unique flow interface catalysis effect. This study opens up a new avenue to allow conventional biphasic catalysis reactions to access more sustainable and efficient flow chemistry using an innovative liquid-liquid interface protocol. PMID:27429173

  4. Switching on elusive organometallic mechanisms with photoredox catalysis.

    Science.gov (United States)

    Terrett, Jack A; Cuthbertson, James D; Shurtleff, Valerie W; MacMillan, David W C

    2015-08-20

    Transition-metal-catalysed cross-coupling reactions have become one of the most used carbon-carbon and carbon-heteroatom bond-forming reactions in chemical synthesis. Recently, nickel catalysis has been shown to participate in a wide variety of C-C bond-forming reactions, most notably Negishi, Suzuki-Miyaura, Stille, Kumada and Hiyama couplings. Despite the tremendous advances in C-C fragment couplings, the ability to forge C-O bonds in a general fashion via nickel catalysis has been largely unsuccessful. The challenge for nickel-mediated alcohol couplings has been the mechanistic requirement for the critical C-O bond-forming step (formally known as the reductive elimination step) to occur via a Ni(III) alkoxide intermediate. Here we demonstrate that visible-light-excited photoredox catalysts can modulate the preferred oxidation states of nickel alkoxides in an operative catalytic cycle, thereby providing transient access to Ni(III) species that readily participate in reductive elimination. Using this synergistic merger of photoredox and nickel catalysis, we have developed a highly efficient and general carbon-oxygen coupling reaction using abundant alcohols and aryl bromides. More notably, we have developed a general strategy to 'switch on' important yet elusive organometallic mechanisms via oxidation state modulations using only weak light and single-electron-transfer catalysts.

  5. Pacific Northwest National Laboratory Catalysis Highlights for FY2007

    Energy Technology Data Exchange (ETDEWEB)

    Garrett, Bruce C.

    2007-11-15

    To reduce the nation’s dependence on imported oil, the U.S. Department of Energy (DOE) and other federal and private agencies are investing in understanding catalysis. This report focuses on catalysis research conducted by Pacific Northwest National Laboratory (PNNL) and its collaborators. Using sophisticated instruments in DOE’s Environmental Molecular Sciences Laboratory, a national scientific user facility, research was conducted to answer key questions related to the nation’s use of automotive fuels. Research teams investigated how hydrogen can be safely stored and efficiently released, critical questions to use this alternative fuel. Further, they are answering key questions to design molecular catalysts to control the transfer of hydrogen atoms, hydrides, and protons important to hydrogen production. In dealing with today’s fuels, researchers examined adsorption of noxious nitrous oxides in automotive exhaust. Beyond automotive fuel, researchers worked on catalysts to harness solar power. These catalysts include the rutile and anatase forms of titanium dioxide. Basic research was conducted on designing catalysts for these and other applications. Our scientists examined how to build catalysts with the desired properties atom by atom and molecule by molecule. In addition, this report contains brief descriptions of the outstanding accomplishments of catalysis experts at PNNL.

  6. Plasmonic sensing

    DEFF Research Database (Denmark)

    Mogensen, Klaus Bo

    2015-01-01

    that cannot be obtained by traditional refractive index sensing, without the use of bioprobes. A simple modified Drude model is used to account for shifts in the plasmon band position due to electrical charging. Here, a screening parameter is introduced in the expression for the free electron density...... particle ensemble, thereby overcoming typical variations due to differences between samples. For small particle sizes, charge displacement/transfer processes at the particle surface can change the material properties and morphology of the NPs dramatically, resulting in, e.g., a decrease of and a blue shift...

  7. Drug Facts

    Medline Plus

    Full Text Available ... Addiction? Addiction Risk Factors Does Addiction Run in Families? Why Is It So Hard to Quit Drugs? ... Drug Abuse Hurts Other People Drug Abuse Hurts Families Drug Abuse Hurts Kids Drug Abuse Hurts Unborn ...

  8. Drug Facts

    Medline Plus

    Full Text Available ... Abuse Hurts Unborn Children Drug Abuse Hurts Your Health Drug Abuse Hurts Bodies Drug Abuse Hurts Brains Drug Abuse and Mental Health Problems Often Happen Together The Link Between Drug ...

  9. Hybrid Organic-Inorganic Materials Based on Polyoxometalates and Ionic Liquids and Their Application in Catalysis

    OpenAIRE

    Svetlana Ivanova

    2014-01-01

    An overview of the recent advances in the field of polyoxometalate, ionic liquid hybrids, is proposed with a special attention paid to their application in catalysis, more precisely biphasic and heterogeneous catalysis. Both components of the hybrids are separately outlined pointing to their useful properties and potential for catalysis, followed by the description of the hybrids preparation and synergy between components in a large range of organic transformations. And finally a vision on th...

  10. Catalysis in electrochemistry from fundamental aspects to strategies for fuel cell development

    CERN Document Server

    Santos, Elizabeth

    2011-01-01

    Catalysis in Electrochemistry: From Fundamental Aspects to Strategies for Fuel Cell Development is a modern, comprehensive reference work on catalysis in electrochemistry, including principles, methods, strategies, and applications. It points out differences between catalysis at gas/surfaces and electrochemical interfaces, along with the future possibilities and impact of electrochemical science on energy problems. This book contributes both to fundamental science; experience in the design, preparation, and characterization of electrocatalytic materials; and the industrial application o

  11. Combining Zn Ion Catalysis with Homogeneous Gold Catalysis: An Efficient Annulation Approach to N-Protected Indoles.

    Science.gov (United States)

    Wang, Yanzhao; Liu, Lianzhu; Zhang, Liming

    2013-02-01

    The Fischer indole synthesis is perhaps the most powerful method for indole preparation, but it often suffers from low regioselectivities with unsymmetric aliphatic ketone substrates and strong acidic conditions and is not suitable for α,β-unsaturated ketones. In this article, we disclose an efficient synthesis of N-protected indoles from N-arylhydroxamic acids/N-aryl-N-hydroxycarbamates and a variety of alkynes via a cooperative gold and zinc catalysis. The zinc catalysis is similar to the related zinc ion catalysis in metalloenzymes such as human carbonic anhydrase II and substantially enhances the O-nucleophilicity of N-acylated hydroxamines by forming the corresponding Zn chelates. The Zn chelates can attack gold-activated alkynes to form O-alkenyl-N-arylhydroxamates, which can undergo facile 3,3-sigmatropic rearrangements and subsequent cyclodehydrations to yield N-protected indole products. This new chemistry offers several important improvements over the Fischer indole synthesis: a) the reaction conditions are mildly acidic and can tolerate sensitive groups such as Boc; b) broader substrate scopes including substrates with pendant carbonyl groups (reactive in the Fischer chemistry) and alkyl chlorides (e.g., 3f); c) better regioselectivities for the formation of 2-substituted indoles under much milder conditions; d) 2-alkenylindoles can be prepared readily in good to excellent yields, but the Fischer chemistry could not; e) with internal alkynes both steric and electronic controls are available for achieving good regioselectivities, while the Fischer chemistry is in general problematic.

  12. Nucleoside Sensing

    OpenAIRE

    Thomas Schrader; Frank-Gerrit Klärner; Michael Fokkens

    2006-01-01

    A rigid molecular clip comprising bisphosphonate binding sites and aromatic sidewalls forming an electron-rich cavity is able to distinguish between nucleosides and nucleotides in aqueous solution. Neutral nucleosides as well as antibiotics derived thereof are drawn into the unpolar interior of the cleft and lead to substantial upfield-shifts in the 1H NMR spectrum. Nucleoside drugs can therefore be detected with high selectivity in the presence of their phosphorylated pendants or nucleic acids.

  13. Opportunities for Catalysis in The 21st Century. A report from the Basic Energy Sciences Advisory Committee

    Energy Technology Data Exchange (ETDEWEB)

    White, J. M.; Bercaw, J.

    2002-05-16

    Chemical catalysis affects our lives in myriad ways. Catalysis provides a means of changing the rates at which chemical bonds are formed and broken and of controlling the yields of chemical reactions to increase the amounts of desirable products from these reactions and reduce the amounts of undesirable ones. Thus, it lies at the heart of our quality of life: The reduced emissions of modern cars, the abundance of fresh food at our stores, and the new pharmaceuticals that improve our health are made possible by chemical reactions controlled by catalysts. Catalysis is also essential to a healthy economy: The petroleum, chemical, and pharmaceutical industries, contributors of $500 billion to the gross national product of the United States, rely on catalysts to produce everything from fuels to ''wonder drugs'' to paints to cosmetics. Today, our Nation faces a variety of challenges in creating alternative fuels, reducing harmful by-products in manufacturing, cleaning up the environment and preventing future pollution, dealing with the causes of global warming, protecting citizens from the release of toxic substances and infectious agents, and creating safe pharmaceuticals. Catalysts are needed to meet these challenges, but their complexity and diversity demand a revolution in the way catalysts are designed and used. This revolution can become reality through the application of new methods for synthesizing and characterizing molecular and material systems. Opportunities to understand and predict how catalysts work at the atomic scale and the nanoscale are now appearing, made possible by breakthroughs in the last decade in computation, measurement techniques, and imaging and by new developments in catalyst design, synthesis, and evaluation.

  14. Infrastructure sensing.

    Science.gov (United States)

    Soga, Kenichi; Schooling, Jennifer

    2016-08-01

    Design, construction, maintenance and upgrading of civil engineering infrastructure requires fresh thinking to minimize use of materials, energy and labour. This can only be achieved by understanding the performance of the infrastructure, both during its construction and throughout its design life, through innovative monitoring. Advances in sensor systems offer intriguing possibilities to radically alter methods of condition assessment and monitoring of infrastructure. In this paper, it is hypothesized that the future of infrastructure relies on smarter information; the rich information obtained from embedded sensors within infrastructure will act as a catalyst for new design, construction, operation and maintenance processes for integrated infrastructure systems linked directly with user behaviour patterns. Some examples of emerging sensor technologies for infrastructure sensing are given. They include distributed fibre-optics sensors, computer vision, wireless sensor networks, low-power micro-electromechanical systems, energy harvesting and citizens as sensors.

  15. Infrastructure sensing.

    Science.gov (United States)

    Soga, Kenichi; Schooling, Jennifer

    2016-08-01

    Design, construction, maintenance and upgrading of civil engineering infrastructure requires fresh thinking to minimize use of materials, energy and labour. This can only be achieved by understanding the performance of the infrastructure, both during its construction and throughout its design life, through innovative monitoring. Advances in sensor systems offer intriguing possibilities to radically alter methods of condition assessment and monitoring of infrastructure. In this paper, it is hypothesized that the future of infrastructure relies on smarter information; the rich information obtained from embedded sensors within infrastructure will act as a catalyst for new design, construction, operation and maintenance processes for integrated infrastructure systems linked directly with user behaviour patterns. Some examples of emerging sensor technologies for infrastructure sensing are given. They include distributed fibre-optics sensors, computer vision, wireless sensor networks, low-power micro-electromechanical systems, energy harvesting and citizens as sensors. PMID:27499845

  16. Sensing temperature.

    Science.gov (United States)

    Sengupta, Piali; Garrity, Paul

    2013-04-22

    Temperature is an omnipresent physical variable reflecting the rotational, vibrational and translational motion of matter, what Richard Feynman called the "jiggling" of atoms. Temperature varies across space and time, and this variation has dramatic effects on the physiology of living cells. It changes the rate and nature of chemical reactions, and it alters the configuration of the atoms that make up nucleic acids, proteins, lipids and other biomolecules, significantly affecting their activity. While life may have started in a "warm little pond", as Charles Darwin mused, the organisms that surround us today have only made it this far by devising sophisticated systems for sensing and responding to variations in temperature, and by using these systems in ways that allow them to persist and thrive in the face of thermal fluctuation.

  17. Drug Facts

    Medline Plus

    Full Text Available ... Health Drug Abuse Hurts Bodies Drug Abuse Hurts Brains Drug Abuse and Mental Health Problems Often Happen Together The Link Between Drug Abuse and HIV/AIDS Recovery & Treatment Drug Treatment Facts Does Drug Treatment Work? Types of Drug Treatment What Is a Relapse? ...

  18. Parents who use drugs

    DEFF Research Database (Denmark)

    Rhodes, Tim; Bernays, Sarah; Houmøller, Kathrin

    2010-01-01

    Parents who use drugs parent in a context of heightened concern regarding the damaging effects of parental drug use on child welfare and family life. Yet there is little research exploring how parents who use drugs account for such damage and its limitation. We draw here upon analyses of audio......-recorded depth qualitative interviews, conducted in south-east England between 2008 and 2009, with 29 parents who use drugs. Our approach to thematic analysis treated accounts as co-produced and socially situated. An over-arching theme of accounts was 'damage limitation'. Most damage limitation work centred...... on efforts to create a sense of normalcy of family life, involving keeping drug use secret from children, and investing heavily in strategies to maintain ambiguity regarding children's awareness. Our analysis highlights that damage limitation strategies double-up in accounts as resources of child protection...

  19. Drug allergies

    Science.gov (United States)

    Allergic reaction - drug (medication); Drug hypersensitivity; Medication hypersensitivity ... A drug allergy involves an immune response in the body that produces an allergic reaction to a medicine. The ...

  20. Catalysis as a foundational pillar of green chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Anastas, Paul T. [White House Office of Science and Technology Policy, Department of Chemistry, University of Nottingham Nottingham, (United Kingdom); Kirchhoff, Mary M. [U.S. Environmental Protection Agency and Trinity College, Washington, DC (United States); Williamson, Tracy C. [U.S. Environmental Protection Agency, Washington, DC (United States)

    2001-11-30

    Catalysis is one of the fundamental pillars of green chemistry, the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. The design and application of new catalysts and catalytic systems are simultaneously achieving the dual goals of environmental protection and economic benefit. Green chemistry, the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances, is an overarching approach that is applicable to all aspects of chemistry. From feedstocks to solvents, to synthesis and processing, green chemistry actively seeks ways to produce materials in a way that is more benign to human health and the environment. The current emphasis on green chemistry reflects a shift away from the historic 'command-and-control' approach to environmental problems that mandated waste treatment and control and clean up through regulation, and toward preventing pollution at its source. Rather than accepting waste generation and disposal as unavoidable, green chemistry seeks new technologies that are cleaner and economically competitive. Utilizing green chemistry for pollution prevention demonstrates the power and beauty of chemistry: through careful design, society can enjoy the products on which we depend while benefiting the environment. The economic benefits of green chemistry are central drivers in its advancement. Industry is adopting green chemistry methodologies because they improve the corporate bottom line. A wide array of operating costs are decreased through the use of green chemistry. When less waste is generated, environmental compliance costs go down. Treatment and disposal become unnecessary when waste is eliminated. Decreased solvent usage and fewer processing steps lessen the material and energy costs of manufacturing and increase material efficiency. The environmental, human health, and the economic advantages realized through green chemistry

  1. Radio catalysis application in degradation of complex organic samples

    International Nuclear Information System (INIS)

    The generation of wastewater is a consequence of human activities, industries to be the generators of a large part of these discharges. These contaminated waters can be processed for their remediation; however the recalcitrant organic compounds are hardly removed through conventional treatments applied, so that new technologies have been developed for disposal such as the advanced oxidation technologies or processes. With the aim of the study is to apply ionizing radiation as a method of remediation in wastewater, in this work were carried out experiments of radiolysis and radio catalysis, which are techniques considered advanced oxidation technologies, that consist in irradiate with 60Co gamma radiation solutions of 4- chloro phenol and methylene blue, applied at different concentrations and using as process control measurements of the compound not degraded by UV-vis spectrophotometry at 507 and 664 nm for 4-chloro phenol and methylene blue respectively. At doses greater than 2.5 kGy were near-zero degradation. Degradation experiments were also conducted by photo catalysis by irradiation with a UV lamp of 354 nm wavelength. For 4-chloro phenol results showed that degradation is efficient (39%). With those previous results, these techniques were applied to degrade complex mixtures of organic compounds from samples of wastewater from a sewage treatment plant, where was considered as process control measurement of the dissolved organic carbon obtained by a spectrophotometric analysis at 254 nm, and a maximum of 26% degradation was obtained by applying 80 kGy. On the other hand, a series of experiments fractionating the irradiations at intervals of 20 kGy to obtain a cumulative dose of 80 kGy, which was 2.8 times greater with respect to degradation by radio catalysis with continuous irradiation. (Author)

  2. Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

    Directory of Open Access Journals (Sweden)

    Pierre Vogel

    2016-08-01

    Full Text Available Catalysis fulfills the promise that high-yielding chemical transformations will require little energy and produce no toxic waste. This message is carried by the study of the evolution of molecular catalysis of some of the most important reactions in organic chemistry. After reviewing the conceptual underpinnings of catalysis, we discuss the applications of different catalysts according to the mechanism of the reactions that they catalyze, including acyl group transfers, nucleophilic additions and substitutions, and C–C bond forming reactions that employ umpolung by nucleophilic additions to C=O and C=C double bonds. We highlight the utility of a broad range of organocatalysts other than compounds based on proline, the cinchona alkaloids and binaphthyls, which have been abundantly reviewed elsewhere. The focus is on organocatalysts, although a few examples employing metal complexes and enzymes are also included due to their significance. Classical Brønsted acids have evolved into electrophilic hands, the fingers of which are hydrogen donors (like enzymes or other electrophilic moieties. Classical Lewis base catalysts have evolved into tridimensional, chiral nucleophiles that are N- (e.g., tertiary amines, P- (e.g., tertiary phosphines and C-nucleophiles (e.g., N-heterocyclic carbenes. Many efficient organocatalysts bear electrophilic and nucleophilic moieties that interact simultaneously or not with both the electrophilic and nucleophilic reactants. A detailed understanding of the reaction mechanisms permits the design of better catalysts. Their construction represents a molecular science in itself, suggesting that sooner or later chemists will not only imitate Nature but be able to catalyze a much wider range of reactions with high chemo-, regio-, stereo- and enantioselectivity. Man-made organocatalysts are much smaller, cheaper and more stable than enzymes.

  3. The structural basis for specificity in lipoxygenase catalysis.

    Science.gov (United States)

    Newcomer, Marcia E; Brash, Alan R

    2015-03-01

    Many intriguing facets of lipoxygenase (LOX) catalysis are open to a detailed structural analysis. Polyunsaturated fatty acids with two to six double bonds are oxygenated precisely on a particular carbon, typically forming a single chiral fatty acid hydroperoxide product. Molecular oxygen is not bound or liganded during catalysis, yet it is directed precisely to one position and one stereo configuration on the reacting fatty acid. The transformations proceed upon exposure of substrate to enzyme in the presence of O2 (RH + O2 → ROOH), so it has proved challenging to capture the precise mode of substrate binding in the LOX active site. Beginning with crystal structures with bound inhibitors or surrogate substrates, and most recently arachidonic acid bound under anaerobic conditions, a picture is consolidating of catalysis in a U-shaped fatty acid binding channel in which individual LOX enzymes use distinct amino acids to control the head-to-tail orientation of the fatty acid and register of the selected pentadiene opposite the non-heme iron, suitably positioned for the initial stereoselective hydrogen abstraction and subsequent reaction with O2 . Drawing on the crystal structures available currently, this review features the roles of the N-terminal β-barrel (C2-like, or PLAT domain) in substrate acquisition and sensitivity to cellular calcium, and the α-helical catalytic domain in fatty acid binding and reactions with O2 that produce hydroperoxide products with regio and stereospecificity. LOX structures combine to explain how similar enzymes with conserved catalytic machinery differ in product, but not substrate, specificities.

  4. Catalysis of protein disulfide bond isomerization in a homogeneous substrate.

    Science.gov (United States)

    Kersteen, Elizabeth A; Barrows, Seth R; Raines, Ronald T

    2005-09-13

    Protein disulfide isomerase (PDI) catalyzes the rearrangement of nonnative disulfide bonds in the endoplasmic reticulum of eukaryotic cells, a process that often limits the rate at which polypeptide chains fold into a native protein conformation. The mechanism of the reaction catalyzed by PDI is unclear. In assays involving protein substrates, the reaction appears to involve the complete reduction of some or all of its nonnative disulfide bonds followed by oxidation of the resulting dithiols. The substrates in these assays are, however, heterogeneous, which complicates mechanistic analyses. Here, we report the first analysis of disulfide bond isomerization in a homogeneous substrate. Our substrate is based on tachyplesin I, a 17-mer peptide that folds into a beta hairpin stabilized by two disulfide bonds. We describe the chemical synthesis of a variant of tachyplesin I in which its two disulfide bonds are in a nonnative state and side chains near its N and C terminus contain a fluorescence donor (tryptophan) and acceptor (N(epsilon)-dansyllysine). Fluorescence resonance energy transfer from 280 to 465 nm increases by 28-fold upon isomerization of the disulfide bonds into their native state (which has a lower E(o') = -0.313 V than does PDI). We use this continuous assay to analyze catalysis by wild-type human PDI and a variant in which the C-terminal cysteine residue within each Cys-Gly-His-Cys active site is replaced with alanine. We find that wild-type PDI catalyzes the isomerization of the substrate with kcat/K(M) = 1.7 x 10(5) M(-1) s(-1), which is the largest value yet reported for catalysis of disulfide bond isomerization. The variant, which is a poor catalyst of disulfide bond reduction and dithiol oxidation, retains virtually all of the activity of wild-type PDI in catalysis of disulfide bond isomerization. Thus, the C-terminal cysteine residues play an insignificant role in the isomerization of the disulfide bonds in nonnative tachyplesin I. We conclude

  5. Electrified magnetic catalysis in three-dimensional topological insulators

    Science.gov (United States)

    Gorbar, E. V.; Miransky, V. A.; Shovkovy, I. A.; Sukhachov, P. O.

    2016-09-01

    The gap equations for the surface quasiparticle propagators in a slab of three-dimensional topological insulator in external electric and magnetic fields perpendicular to the slab surfaces are analyzed and solved. A different type of magnetic catalysis is revealed with the dynamical generation of both Haldane and Dirac gaps. Its characteristic feature manifests itself in the crucial role that the electric field plays in dynamical symmetry breaking and the generation of a Dirac gap in the slab. It is argued that, for a sufficiently large external electric field, the ground state of the system is a phase with a homogeneous surface charge density.

  6. Plasma Chemistry and Catalysis in Gases and Liquids

    CERN Document Server

    Parvulescu, Vasile I; Lukes, Petr

    2012-01-01

    Filling the gap for a book that not only covers gases but also plasma methods in liquids, this is all set to become the standard reference on the topic. It considers the central aspects in plasma chemistry and plasma catalysis by focusing on the green and environmental applications, while also taking into account their practical and economic viability. With the topics addressed by an international group of major experts, this is a must-have for researchers, PhD students and postdocs specializing in the field.

  7. Development of catalysts and ligands for enantioselective gold catalysis.

    Science.gov (United States)

    Wang, Yi-Ming; Lackner, Aaron D; Toste, F Dean

    2014-03-18

    During the past decade, the use of Au(I) complexes for the catalytic activation of C-C π-bonds has been investigated intensely. Over this time period, the development of homogeneous gold catalysis has been extraordinarily rapid and has yielded a host of mild and selective methods for the formation of carbon-carbon and carbon-heteroatom bonds. The facile formation of new bonds facilitated by gold naturally led to efforts toward rendering these transformations enantioselective. In this Account, we survey the development of catalysts and ligands for enantioselective gold catalysis by our research group as well as related work by others. We also discuss some of our strategies to address the challenges of enantioselective gold(I) catalysis. Early on, our work with enantioselective gold-catalyzed transformations focused on bis(phosphinegold) complexes derived from axially chiral scaffolds. Although these complexes were highly successful in some reactions like cyclopropanation, the careful choice of the weakly coordinating ligand (or counterion) was necessary to obtain high levels of enantioselectivity for the case of allene hydroamination. These counterion effects led us to use the anion itself as a source of chirality, which was successful in the case of allene hydroalkoxylation. In general, these tactics enhance the steric influence around the reactive gold center beyond the two-coordinate ligand environment. The use of binuclear complexes allowed us to use the second gold center and its associated ligand (or counterion) to exert a further steric influence. In a similar vein, we employed a chiral anion (in place of or in addition to a chiral ligand) to move the chiral information closer to the reactive center. In order to expand the scope of reactions amenable to enantioselective gold catalysis to cycloadditions and other carbocyclization processes, we also developed a new class of mononuclear phosphite and phosphoramidite ligands to supplement the previously widely

  8. Electrified magnetic catalysis in 3D topological insulators

    CERN Document Server

    Gorbar, E V; Shovkovy, I A; Sukhachov, P O

    2016-01-01

    The gap equations for the surface quasiparticle propagators in a slab of three-dimensional topological insulator in external electric and magnetic fields perpendicular to the slab surfaces are analyzed and solved. A new type of magnetic catalysis is revealed with the dynamical generation of both Haldane and Dirac gaps. Its characteristic feature manifests itself in the crucial role that the electric field plays in dynamical symmetry breaking and the generation of a Dirac gap in the slab. It is argued that, for a sufficiently large external electric field, the ground state of the system is a phase with a homogeneous surface charge density.

  9. USD Catalysis Group for Alternative Energy - Final report

    Energy Technology Data Exchange (ETDEWEB)

    Hoefelmeyer, James

    2014-10-03

    I. Project Summary Catalytic processes are a major technological underpinning of modern society, and are essential to the energy sector in the processing of chemical fuels from natural resources, fine chemicals synthesis, and energy conversion. Advances in catalyst technology are enormously valuable since these lead to reduced chemical waste, reduced energy loss, and reduced costs. New energy technologies, which are critical to future economic growth, are also heavily reliant on catalysts, including fuel cells and photo-electrochemical cells. Currently, the state of South Dakota is underdeveloped in terms of research infrastructure related to catalysis. If South Dakota intends to participate in significant economic growth opportunities that result from advances in catalyst technology, then this area of research needs to be made a high priority for investment. To this end, a focused research effort is proposed in which investigators from The University of South Dakota (USD) and The South Dakota School of Mines and Technology (SDSMT) will contribute to form the South Dakota Catalysis Group (SDCG). The multidisciplinary team of the (SDCG) include: (USD) Dan Engebretson, James Hoefelmeyer, Ranjit Koodali, and Grigoriy Sereda; (SDSMT) Phil Scott Ahrenkiel, Hao Fong, Jan Puszynski, Rajesh Shende, and Jacek Swiatkiewicz. The group is well suited to engage in a collaborative project due to the resources available within the existing programs. Activities within the SDCG will be monitored through an external committee consisting of three distinguished professors in chemistry. The committee will provide expert advice and recommendations to the SDCG. Advisory meetings in which committee members interact with South Dakota investigators will be accompanied by individual oral and poster presentations in a materials and catalysis symposium. The symposium will attract prominent scientists, and will enhance the visibility of research in the state of South Dakota. The SDCG requests

  10. Lewis Acid Catalysis in the Oxidative Cycloaddition of Thiophenes

    OpenAIRE

    Li, Yuanqiang; Thiemann, Thies; Sawada, Tsuyoshi; Mataka, Shuntaro; Tashiro, Masashi

    1997-01-01

    Thiophenes 1 were treated with m-chloroperbenzoic acid (m-CPBA) under BF3·Et2O catalysis to afford thiophene S-monoxides. These could be reacted in situ as intermediary species with a number of dienophiles to provide arenes (with alkynes as dienophiles) or 7-thiabicyclo[2.2.1]hept-2-ene 7-oxides (with alkenes as dienophiles). It was also possible to isolate thiophene S-monoxides in solution and to cycloadd them in a second step. In either way it could be shown that the use of BF3·Et2O enhance...

  11. Charge Transfer and Catalysis at the Metal Support Interface

    Energy Technology Data Exchange (ETDEWEB)

    Baker, Lawrence Robert [Univ. of California, Berkeley, CA (United States)

    2012-07-31

    Kinetic, electronic, and spectroscopic characterization of model Pt–support systems are used to demonstrate the relationship between charge transfer and catalytic activity and selectivity. The results show that charge flow controls the activity and selectivity of supported metal catalysts. This dissertation builds on extensive existing knowledge of metal–support interactions in heterogeneous catalysis. The results show the prominent role of charge transfer at catalytic interfaces to determine catalytic activity and selectivity. Further, this research demonstrates the possibility of selectively driving catalytic chemistry by controlling charge flow and presents solid-state devices and doped supports as novel methods for obtaining electronic control over catalytic reaction kinetics.

  12. Proton–hydride tautomerism in hydrogen evolution catalysis

    OpenAIRE

    Aguirre Quintana, Luis M.; Johnson, Samantha I.; Corona, Sydney L.; Villatoro, Walther; Goddard, William A.; Takase, Michael K.; VanderVelde, David G.; Winkler, Jay R.; Gray, Harry B.; Blakemore, James D.

    2016-01-01

    Efficient generation of hydrogen from renewable resources requires development of catalysts that avoid deep wells and high barriers. Information about the energy landscape for H_2 production can be obtained by chemical characterization of catalytic intermediates, but few have been observed to date. We have isolated and characterized a key intermediate in 2e^– + 2H^+ → H_2 catalysis. This intermediate, obtained by treatment of Cp*Rh(bpy) (Cp*, η^5-pentamethylcyclopentadienyl; bpy, κ^2-2,2′-bip...

  13. Application of gold in the field of heterogeneous catalysis

    CERN Document Server

    Luo, Siwei

    2014-01-01

    Gold has been long thought as an inert metal which finds most of its use in jewelry and monetary exchange. However, catalysis by gold has rapidly become a hot topic in chemistry ever since Haruta and Hutchings found gold to be an extraordinary good heterogeneous catalyst in certain reactions. Here in this paper, several model reactions which made gold historically famous as a catalyst and a currently hot topic will be demonstrated, such as oxidation of CO, selective oxidation, and hydrodechlorination. Conclusions on the chemical nature of gold will be made as well as future perspectives of designing gold as a better catalyst.

  14. Synthetic and mechanistic prospects of homogeneous gold catalysis

    OpenAIRE

    Pankajakshan, Sreekumar

    2009-01-01

    a) The first chapter of this thesis manifests the exploration of homogeneous gold-catalyzed conversions of furan containing aryl-ynamides and ynol ethers. Enynes boast to be the most explored substrate structures in the realm of homogeneous gold catalysis, whereas the reactivity of ene-ynamides and ene-ynol ethers are much less explored till date.34, 45 Hashmi and co-workers recently reported the homogeneous gold-catalyzed synthesis of phenols from furan containing ynamides/ynol ethers.45e Th...

  15. Inorganic Chemistry in Hydrogen Storage and Biomass Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Thorn, David [Los Alamos National Laboratory

    2012-06-13

    Making or breaking C-H, B-H, C-C bonds has been at the core of catalysis for many years. Making or breaking these bonds to store or recover energy presents us with fresh challenges, including how to catalyze these transformations in molecular systems that are 'tuned' to minimize energy loss and in molecular and material systems present in biomass. This talk will discuss some challenging transformations in chemical hydrogen storage, and some aspects of the inorganic chemistry we are studying in the development of catalysts for biomass utilization.

  16. Selenium nanomaterials: applications in electronics, catalysis and sensors.

    Science.gov (United States)

    Chaudhary, Savita; Mehta, S K

    2014-02-01

    This review provides insights into the synthesis, functionalization, and applications of selenium nanoparticles in electronics, optics, catalysis and sensors. The variation of physicochemical properties such as particle size, surface area, and shape of the selenium nanoparticles and the effect of experimental conditions has also been discussed. An overview has also been provided on the fundamental electrical and optical properties of selenium nanomaterials as well as their utilization in different research fields. The work presents an insight on selenium nanoparticles with interesting properties and their future applications.

  17. Club Drugs

    Science.gov (United States)

    ... uses. Other uses of these drugs are abuse. Club drugs are also sometimes used as "date rape" drugs, to make someone unable to say no to or fight back against sexual assault. Abusing these drugs can ...

  18. Generic Drugs

    Science.gov (United States)

    ... name drug. A brand- name drug has a patent. When the patent runs out— usually after 10 to 14 years— ... if you do not have drug coverage. Condition Diabetes Heart failure High cholesterol Migraine Brand-name drug ...

  19. Drug Facts

    Science.gov (United States)

    ... text to you. This web site talks about drug abuse, addiction and treatment. Watch Videos Information About Drugs Alcohol ... of the drug. "Max" was addicted to prescription drugs. The addiction slowly took over his life. I need different ...

  20. Homogeneous vs heterogeneous polymerization catalysis revealed by single-particle fluorescence microscopy.

    Science.gov (United States)

    Esfandiari, N Melody; Blum, Suzanne A

    2011-11-16

    A high-sensitivity and high-resolution single-particle fluorescence microscopy technique differentiated between homogeneous and heterogeneous metathesis polymerization catalysis by imaging the location of the early stages of polymerization. By imaging single polymers and single crystals of Grubbs II, polymerization catalysis was revealed to be solely homogeneous rather than heterogeneous or both.

  1. Inverse Magnetic Catalysis in hot quark matter within (P)NJL models

    CERN Document Server

    Ferreira, M; Providência, C; Lourenço, O; Frederico, T

    2015-01-01

    Apart from Magnetic Catalysis at low temperatures, recent LQCD studies have shown the opposite effect at temperatures near the transition region: instead of enhancing, the magnetic field suppresses the quark condensates (Inverse Magnetic Catalysis). In this paper, two approaches are discussed within NJL-type models with Polyakov Loop that reproduce both effects.

  2. Drug Facts

    Medline Plus

    Full Text Available ... Drug Abuse Hurts Other People Drug Abuse Hurts Families Drug Abuse Hurts Kids Drug Abuse Hurts Unborn Children ... a Relapse? Find Treatment/Rehab Resources Friends and Family Can Help Prevent Drug Abuse Help Children and Teens Stay Drug-Free ...

  3. Aggregation processes with catalysis-driven monomer birth/death

    Institute of Scientific and Technical Information of China (English)

    Chen Yu; Han An-Jia; Ke Jian-Hong; Lin Zhen-Quan

    2006-01-01

    We propose two solvable cluster growth models, in which an irreversible aggregation spontaneously occurs between any two clusters of the same species; meanwhile, monomer birth or death of species A occurs with the help of species B. The system with the size-dependent monomer birth/death rate kernel K(i,j) = Jijv is then investigated by means of the mean-field rate equation. The results show that the kinetic scaling behaviour of species A depends crucially on the value of the index v. For the model with catalysis-driven monomer birth, the cluster-mass distribution of species A obeys the conventional scaling law in the v ≤ 0 case, while it satisfies a generalized scaling form in the v>0 case; moreover, the total mass of species A is a nonzero value in the v< 0 case while it grows continuously with time in the v>0 case. For the model with catalysis-driven monomer death, the cluster-mass distribution also approaches the conventional scaling form in the v < 0 case, while the conventional scaling description of the system breaks down in the v ≥ 0 case. Additionally, the total mass of species A retains a nonzero quantity in the v <0 case, but it decreases to zero with time in the v ≥ 0 case.

  4. Asymmetric catalysis in Brazil: development and potential for advancement of Brazilian chemical industry; Catalise assimetrica no Brasil: desenvolvimento e potencialidades para o avanco da industria quimica brasileira

    Energy Technology Data Exchange (ETDEWEB)

    Braga, Antonio Luiz, E-mail: braga.antonio@ufsc.br [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Departamento de Quimica; Luedtke, Diogo Seibert; Schneider, Paulo Henrique [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Instituto de Quimica; Andrade, Leandro Helgueira [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Quimica; Paixao, Marcio Weber [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Departamento de Quimica

    2013-07-01

    The preparation of enantiomerically pure or enriched substances is of fundamental importance to pharmaceutical, food, agrochemical, and cosmetics industries and involves a growing market of hundreds of billions of dollars. However, most chemical processes used for their production are not environmentally friendly because in most cases, stoichiometric amounts of chiral inductors are used and substantial waste is produced. In this context, asymmetric catalysis has emerged as an efficient tool for the synthesis of enantiomerically enriched compounds using chiral catalysts. More specifically, considering the current scenario in the Brazilian chemical industry, especially that of pharmaceuticals, the immediate prospect for the use of synthetic routes developed in Brazil in an enantioselective fashion or even the discovery of new drugs is practically null. Currently, the industrial production of drugs in Brazil is primarily focused on the production of generic drugs and is basically supported by imports of intermediates from China and India. In order to change this panorama and move forward toward the gradual incorporation of genuinely Brazilian synthetic routes, strong incentive policies, especially those related to continuous funding, will be needed. These incentives could be a breakthrough once we establish several research groups working in the area of organic synthesis and on the development and application of chiral organocatalysts and ligands in asymmetric catalysis, thus contributing to boost the development of the Brazilian chemical industry. Considering these circumstances, Brazil can benefit from this opportunity because we have a wide biodiversity and a large pool of natural resources that can be used as starting materials for the production of new chiral catalysts and are creating competence in asymmetric catalysis and related areas. This may decisively contribute to the growth of chemistry in our country. (author)

  5. Organically functionalized mesoporous silica as a support for synthesis and catalysis

    Science.gov (United States)

    McEleney, Kevin Andrew

    Mesoporous silicates are excellent materials for supported catalysis due to their ease of functionalization, tunable pore size and high surface areas. Mesoporous silicates have been utilized in a variety of applications such as drug delivery scaffolds and catalyst supports. Functionalization of the surface can be achieved by either grafting of alkoxy silanes or co-condensation of the organosilane with the inorganic silica source. My research in this area can be divided into two components. In the first, we address the significant issue of metal contamination after reactions that are catalyzed by transition metals. In the second, we examine the design of new catalysts based on organic/inorganic composites. Ruthenium catalyzed processes such as olefin metathesis or asymmetric hydrogenation, are often underutilized due to the difficulty of removing the ruthenium by-products. Attempts to remove ruthenium involve treating the solution with a scavenging reagent followed by silica chromatography. Often these scavenging agents are expensive phosphines or toxic agents like lead tetra-acetate. SBA-15 functionalized with aminopropyl triethoxysilane displays a high affinity for ruthenium. Furthermore, it can be utilized to remove ruthenium by-products from olefin metathesis or hydrogenation reactions without the need for silica chromatography. We have also prepared sulfur-functionalized mesoporous silicates that have a high affinity for palladium. The materials after loading prove to be active catalysts for a variety of palladium catalyzed processes such as Suzuki-Miyaura and Sonogashira couplings. The catalysts are recyclable with moderate loss of activity and structure, depending on the method of incorporation of the thiol. We have characterized the as-synthesized and used catalysts by nitrogen sorption, TEM, X-ray photoelectron spectroscopy (XPS) and a variety of homogeneity tests were performed on the catalysts. Periodic mesoporous organosilicates (PMOs) are a well known

  6. Prescription Drugs

    Science.gov (United States)

    ... Us Search Search close Teens Teachers Parents Drugs & Health Blog NDAFW Enter Search Term(s): Teens / Drug Facts / Prescription Drugs Prescription Drugs Print What Is Prescription Drug Abuse? Also known as: Opioids: Hillbilly heroin, oxy, OC, oxycotton, percs, happy pills, vikes Depressants: ...

  7. Cobalt catalysis involving π components in organic synthesis.

    Science.gov (United States)

    Gandeepan, Parthasarathy; Cheng, Chien-Hong

    2015-04-21

    Over the last three decades, transition-metal-catalyzed organic transformations have been shown to be extremely important in organic synthesis. However, most of the successful reactions are associated with noble metals, which are generally toxic, expensive, and less abundant. Therefore, we have focused on catalysis using the abundant first-row transition metals, specifically cobalt. In this Account, we demonstrate the potential of cobalt catalysis in organic synthesis as revealed by our research. We have developed many useful catalytic systems using cobalt complexes. Overall, they can be classified into several broad types of reactions, specifically [2 + 2 + 2] and [2 + 2] cycloadditions; enyne reductive coupling; reductive [3 + 2] cycloaddition of alkynes/allenes with enones; reductive coupling of alkyl iodides with alkenes; addition of organoboronic acids to alkynes, alkenes, or aldehydes; carbocyclization of o-iodoaryl ketones/aldehydes with alkynes/electron-deficient alkenes; coupling of thiols with aryl and alkyl halides; enyne coupling; and C-H bond activation. Reactions relying on π components, specifically cycloaddition, reductive coupling, and enyne coupling, mostly afford products with excellent stereo- and regioselectivity and superior atom economy. We believe that these cobalt-catalyzed π-component coupling reactions proceed through five-membered cobaltacyclic intermediates formed by the oxidative cyclometalation of two coordinated π bonds of the substrates to the low-valent cobalt species. The high regio- and stereoselectivity of these reactions are achieved as a result of the electronic and steric effects of the π components. Mostly, electron-withdrawing groups and bulkier groups attached to the π bonds prefer to be placed near the cobalt center of the cobaltacycle. Most of these transformations proceed through low-valent cobalt complexes, which are conveniently generated in situ from air-stable Co(II) salts by Zn- or Mn-mediated reduction

  8. Bayesian Word Sense Induction

    OpenAIRE

    Brody, Samuel; Lapata, Mirella

    2009-01-01

    Sense induction seeks to automatically identify word senses directly from a corpus. A key assumption underlying previous work is that the context surrounding an ambiguous word is indicative of its meaning. Sense induction is thus typically viewed as an unsupervised clustering problem where the aim is to partition a word’s contexts into different classes, each representing a word sense. Our work places sense induction in a Bayesian context by modeling the contexts of the ambiguous word as samp...

  9. 以病原菌群体感应系统为靶标的新型抗菌药物的研究进展%Research progress of new antibacterial drugs that target bacterial quorum sensing systems

    Institute of Scientific and Technical Information of China (English)

    尹守亮; 常亚婧; 邓苏萍; 王清池; 于文功; 宫倩红

    2011-01-01

    In recent years, antibiotic resistance of bacteria has become a global health crisis. Especially, the new class of "superbug" was found in South Asia, which is resistant to almost known antibiotics and causes worldwide alarm. Through the underlying mechanisms of bacterial pathogenecity, the expression of many pathogen virulence factors is regulated by the process of quonun sensing. Screening efficient quorum sensing inhibitors is an especially compelling approach to the future treatment of bacterial infections and antibiotic resistance. This article focuses on bacterial quorum sensing system, quorum sensing screening model for in vitro and evaluation of animal models in vivo. recent research of quorum sensing inhibitors and so on.%近年来,日益严重的细菌耐药性成为全球关注的焦点,尤其是南亚发现的新型"超级细菌"几乎对绝大多数抗生素都具有抗性,在世界范围内引起了恐慌.对病原菌致病机制的研究发现,许多病原菌的致病机制都依赖细菌群体感应系统的调节和控制.筛选高效的群体感应抑制剂有望成为解决细菌感染以及耐药性问题的一个有效途径.本文主要阐述了细菌群体感应信号调控系统、群体感应抑制因子体外筛选模型及体内动物模型评价,群体感应抑制因子的研究近况等内容.

  10. Drug Resistance

    Science.gov (United States)

    HIV Treatment Drug Resistance (Last updated 3/1/2016; last reviewed 3/1/2016) Key Points As HIV multiplies in the ... the risk of drug resistance. What is HIV drug resistance? Once a person becomes infected with HIV, ...

  11. Club Drugs

    Science.gov (United States)

    ... Science Adolescent Brain Comorbidity College-Age & Young Adults Criminal Justice Drugged Driving Drug Testing Drugs and the ... Learn more Statistics and Trends Swipe left or right to scroll. Monitoring the Future Study: Trends in ...

  12. Drug Facts

    Medline Plus

    Full Text Available ... Weed, Pot) Facts Meth (Crank, Ice) Facts Pain Medicine (Oxy, Vike) Facts Other Drugs of Abuse What ... About Drugs Alcohol Cocaine Heroin Marijuana Meth Pain Medicines Tobacco Other Drugs You can call 1-800- ...

  13. Drug Reactions

    Science.gov (United States)

    ... problem is interactions, which may occur between Two drugs, such as aspirin and blood thinners Drugs and food, such as statins and grapefruit Drugs and supplements, such as ginkgo and blood thinners ...

  14. π Activation of Alkynes in Homogeneous and Heterogeneous Gold Catalysis.

    Science.gov (United States)

    Bistoni, Giovanni; Belanzoni, Paola; Belpassi, Leonardo; Tarantelli, Francesco

    2016-07-14

    The activation of alkynes toward nucleophilic attack upon coordination to gold-based catalysts (neutral and positively charged gold clusters and gold complexes commonly used in homogeneous catalysis) is investigated to elucidate the role of the σ donation and π back-donation components of the Au-C bond (where we consider ethyne as prototype substrate). Charge displacement (CD) analysis is used to obtain a well-defined measure of σ donation and π back-donation and to find out how the corresponding charge flows affect the electron density at the electrophilic carbon undergoing the nucleophilic attack. This information is used to rationalize the activity of a series of catalysts in the nucleophilic attack step of a model hydroamination reaction. For the first time, the components of the Dewar-Chatt-Duncanson model, donation and back-donation, are put in quantitative correlation with the kinetic parameters of a chemical reaction. PMID:27119994

  15. Degradation of Residual Formaldehyde in Fabric by Photo-catalysis

    Institute of Scientific and Technical Information of China (English)

    YAO Yadong; GUO Xiangli; KANG Yunqing; LI Xieji; CHEN Aizheng; YANG Weizhong; YIN Guangfu

    2008-01-01

    The residual formaldehyde (HCHO) in fabric was degraded using photo-catalysis assisted by the compound catalyst of nano-TiO2 and nano-ZnO. The effects of several factors on the degradation,such as the composing of catalyst, irradiation time, pH value and the H2CHO concentration of the immersed solution were investigated. Results showed that H2CHO of the immersed solution had degraded 93% after 5 h irradiation, and the degradation ratio of formaldehyde could be improved and the aging of the fabric can be avoided with the addition of ZnO nanoparticles and pH value of the immersed-fibric solution. The fabric with residual formaldehyde about 1 800 μg/g can be efficiently treated to satisfy the China National Standard(GB/2912.1-1998) with the photo-catalytic degradation.

  16. Immobilization of Homogeneous Catalysis on Phosphinated MCM-41

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ Homogeneous catalysis Rh(PPh3)3Cl immobilized on MCM-41 modified with (OEt)3Si(CH2)3PPh2 results in a stable hydrogenation catalyst with turn over frequency (TOF) three times higher than that of Rh(PPh3)3C1 in the hydrogenation of cyclohexene. Leaching of the catalyst is only a minor factor with leaching rate 0.04 % for each cycle. However, immobilization of Rh(PPh3)2(CO)C1 on similar support can only have catalytic hydroformylation properties for the first few cycles. Decay of the catalyst is due to largh leaching rate with totally 22.4 % of Rh leached for the first three cycles.

  17. Immobilization of Homogeneous Catalysis on Phosphinated MCM-41

    Institute of Scientific and Technical Information of China (English)

    SHYU; Shin-Guang

    2001-01-01

    Homogeneous catalysis Rh(PPh3)3Cl immobilized on MCM-41 modified with (OEt)3Si(CH2)3PPh2 results in a stable hydrogenation catalyst with turn over frequency (TOF) three times higher than that of Rh(PPh3)3C1 in the hydrogenation of cyclohexene. Leaching of the catalyst is only a minor factor with leaching rate 0.04 % for each cycle. However, immobilization of Rh(PPh3)2(CO)C1 on similar support can only have catalytic hydroformylation properties for the first few cycles. Decay of the catalyst is due to largh leaching rate with totally 22.4 % of Rh leached for the first three cycles.  ……

  18. π Activation of Alkynes in Homogeneous and Heterogeneous Gold Catalysis.

    Science.gov (United States)

    Bistoni, Giovanni; Belanzoni, Paola; Belpassi, Leonardo; Tarantelli, Francesco

    2016-07-14

    The activation of alkynes toward nucleophilic attack upon coordination to gold-based catalysts (neutral and positively charged gold clusters and gold complexes commonly used in homogeneous catalysis) is investigated to elucidate the role of the σ donation and π back-donation components of the Au-C bond (where we consider ethyne as prototype substrate). Charge displacement (CD) analysis is used to obtain a well-defined measure of σ donation and π back-donation and to find out how the corresponding charge flows affect the electron density at the electrophilic carbon undergoing the nucleophilic attack. This information is used to rationalize the activity of a series of catalysts in the nucleophilic attack step of a model hydroamination reaction. For the first time, the components of the Dewar-Chatt-Duncanson model, donation and back-donation, are put in quantitative correlation with the kinetic parameters of a chemical reaction.

  19. UV LASER INITIATED STEREOSELECTIVE HOMOGENEOUS CATALYSIS POLYMERIZATION OF PHENYLACETYLENE

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jie; SHE Yongbo; FU Kejian; ZHOU Yihua

    1993-01-01

    In this paper, the stereoselective homogeneous catalysis polymerization of phenylacetylene by using two kinds of catalysts W(CO)5CH3I and W(CO)4I2 produced from UV laser photolysis of W (CO)6 in CH3I, I2 -C6H6 and CHI3 -C6H6 respectively was studied . The effects of laser energy,laser irradiation time and lifetime of catalyst on the polymerization of phenylacetylene were discussed . The photoproducts of W (CO)6 in CH3I, I2 - C6H6 and CHI3 - C6H6 were determined by IR spectra. The structures of polyphenylacetylene obtained by W (CO)5CH3I and W (CO)4I2 catalysts were characterized by IR spectra and 1H NMR spectra.

  20. In Silico Design in Homogeneous Catalysis Using Descriptor Modelling

    Directory of Open Access Journals (Sweden)

    Gadi Rothenberg

    2006-09-01

    Full Text Available This review summarises the state-of-the-art methodologies used for designinghomogeneous catalysts and optimising reaction conditions (e.g. choosing the right solvent.We focus on computational techniques that can complement the current advances in high-throughput experimentation, covering the literature in the period 1996-2006. The reviewassesses the use of molecular modelling tools, from descriptor models based onsemiempirical and molecular mechanics calculations, to 2D topological descriptors andgraph theory methods. Different techniques are compared based on their computational andtime cost, output level, problem relevance and viability. We also review the application ofvarious data mining tools, including artificial neural networks, linear regression, andclassification trees. The future of homogeneous catalysis discovery and optimisation isdiscussed in the light of these developments.

  1. Quantum chemical study on asymmetric catalysis reduction of imine

    Institute of Scientific and Technical Information of China (English)

    李明; 田安民

    2003-01-01

    The quantum chemical method is employed to study the enantioselective reduction of imine with borane catalyzed by chiral oxazaborolidine. All the structures are optimized completely at the B3LYP/6-31G(d) level. The catalysis property of oxazaborolidine is notable. The reduction goes mainly through the formations of the catalyst-borane adduct, the catalyst-borane-imine adduct, and the catalyst-amidoborane adduct and the dissociation of the catalyst-amidoborane adduct with the regeneration of the catalyst. The controlling step for the reduction is the dissociation of the catalyst-amidoborane adduct. The main reduced product predicted theoretically is (R )-sec- ondary amine, which is in agreement with the experiment.

  2. Cooperative catalysis with block copolymer micelles: A combinatorial approach

    KAUST Repository

    Bukhryakov, Konstantin V.

    2015-02-09

    A rapid approach to identifying complementary catalytic groups using combinations of functional polymers is presented. Amphiphilic polymers with "clickable" hydrophobic blocks were used to create a library of functional polymers, each bearing a single functionality. The polymers were combined in water, yielding mixed micelles. As the functional groups were colocalized in the hydrophobic microphase, they could act cooperatively, giving rise to new modes of catalysis. The multipolymer "clumps" were screened for catalytic activity, both in the presence and absence of metal ions. A number of catalyst candidates were identified across a wide range of model reaction types. One of the catalytic systems discovered was used to perform a number of preparative-scale syntheses. Our approach provides easy access to a range of enzyme-inspired cooperative catalysts.

  3. Synthesis of Hydroxypropyl Guar Gum by Phase Transfer Catalysis

    Institute of Scientific and Technical Information of China (English)

    Rong Chun XIONG; Ming Zhu CHANG; Jian Ming CHEN; Nan ZHOU; Gang WEI

    2005-01-01

    HGG (Hydroxypropyl guar gum) was synthesized by phase transfer catalysis for the first time. The effects of alkalinity, phase transfer catalyst, etherification, pH value, temperature,reaction time and stirring speed were investigated. An optimal synthetic reaction technology was established, namely, dose of guar gum is 100 g, propylene oxide 40-50 g, HTAC (hexadecyl trimethyl ammonium chloride ) 1.3-1.7 g, pH value 10-10.5, temperature 45-50℃, and reaction time 3-4 hours. The result shows that the improved HGG has high viscosity. Its dissolution speed, content of insoluble residue, colloid light transparency and stability are apparently superior to guar flour.

  4. Mineral catalysis of a potentially prebiotic aldol condensation

    Science.gov (United States)

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

    1998-01-01

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

  5. Nanoscale magnetic stirring bars for heterogeneous catalysis in microscopic systems.

    Science.gov (United States)

    Yang, Shuliang; Cao, Changyan; Sun, Yongbin; Huang, Peipei; Wei, Fangfang; Song, Weiguo

    2015-02-23

    Nanometer-sized magnetic stirring bars containing Pd nanoparticles (denoted as Fe3 O4 -NC-PZS-Pd) for heterogeneous catalysis in microscopic system were prepared through a facile two-step process. In the hydrogenation of styrene, Fe3 O4 -NC-PZS-Pd showed an activity similar to that of the commercial Pd/C catalyst, but much better stability. In microscopic catalytic systems, Fe3 O4 -NC-PZS-Pd can effectively stir the reaction solution within microdrops to accelerate mass transfer, and displays far better catalytic activity than the commercial Pd/C for the hydrogenation of methylene blue in an array of microdroplets. These results suggested that the Fe3 O4 -NC-PZS-Pd could be used as nanoscale stirring bars in nanoreactors.

  6. Contrast and Synergy between Electrocatalysis and Heterogeneous Catalysis

    Directory of Open Access Journals (Sweden)

    Andrzej Wieckowski

    2011-01-01

    Full Text Available The advances in spectroscopy and theory that have occurred over the past two decades begin to provide detailed in situ resolution of the molecular transformations that occur at both gas/metal as well as aqueous/metal interfaces. These advances begin to allow for a more direct comparison of heterogeneous catalysis and electrocatalysis. Such comparisons become important, as many of the current energy conversion strategies involve catalytic and electrocatalytic processes that occur at fluid/solid interfaces and display very similar characteristics. Herein, we compare and contrast a few different catalytic and electrocatalytic systems to elucidate the principles that cross-cut both areas and establish characteristic differences between the two with the hope of advancing both areas.

  7. Development of chiral sulfoxide ligands for asymmetric catalysis.

    Science.gov (United States)

    Trost, Barry M; Rao, Meera

    2015-04-20

    Nitrogen-, phosphorus-, and oxygen-based ligands with chiral backbones have been the historic workhorses of asymmetric transition-metal-catalyzed reactions. On the contrary, sulfoxides containing chirality at the sulfur atom have mainly been used as chiral auxiliaries for diastereoselective reactions. Despite several distinct advantages over traditional ligand scaffolds, such as the proximity of the chiral information to the metal center and the ability to switch between S and O coordination, these compounds have only recently emerged as a versatile class of chiral ligands. In this Review, we detail the history of the development of chiral sulfoxide ligands for asymmetric catalysis. We also provide brief descriptions of metal-sulfoxide bonding and strategies for the synthesis of enantiopure sulfoxides. Finally, insights into the future development of this underutilized ligand class are discussed.

  8. Cooperative catalysis with block copolymer micelles: a combinatorial approach.

    Science.gov (United States)

    Bukhryakov, Konstantin V; Desyatkin, Victor G; O'Shea, John-Paul; Almahdali, Sarah R; Solovyeva, Vera; Rodionov, Valentin O

    2015-02-01

    A rapid approach to identifying complementary catalytic groups using combinations of functional polymers is presented. Amphiphilic polymers with "clickable" hydrophobic blocks were used to create a library of functional polymers, each bearing a single functionality. The polymers were combined in water, yielding mixed micelles. As the functional groups were colocalized in the hydrophobic microphase, they could act cooperatively, giving rise to new modes of catalysis. The multipolymer "clumps" were screened for catalytic activity, both in the presence and absence of metal ions. A number of catalyst candidates were identified across a wide range of model reaction types. One of the catalytic systems discovered was used to perform a number of preparative-scale syntheses. Our approach provides easy access to a range of enzyme-inspired cooperative catalysts.

  9. Acetylation of barnyardgrass starch with acetic anhydride under iodine catalysis.

    Science.gov (United States)

    Bartz, Josiane; Goebel, Jorge Tiago; Giovanaz, Marcos Antônio; Zavareze, Elessandra da Rosa; Schirmer, Manoel Artigas; Dias, Alvaro Renato Guerra

    2015-07-01

    Barnyardgrass (Echinochloa crus-galli) is an invasive plant that is difficult to control and is found in abundance as part of the waste of the paddy industry. In this study, barnyardgrass starch was extracted and studied to obtain a novel starch with potential food and non-food applications. We report some of the physicochemical, functional and morphological properties as well as the effect of modifying this starch with acetic anhydride by catalysis with 1, 5 or 10mM of iodine. The extent of the introduction of acetyl groups increased with increasing iodine levels as catalyst. The shape of the granules remained unaltered, but there were low levels of surface corrosion and the overall relative crystallinity decreased. The pasting temperature, enthalpy and other gelatinisation temperatures were reduced by the modification. There was an increase in the viscosity of the pastes, except for the peak viscosity, which was strongly reduced in 10mM iodine.

  10. Lattice Field Theory Study of Magnetic Catalysis in Graphene

    CERN Document Server

    DeTar, Carleton; Zafeiropoulos, Savvas

    2016-01-01

    We discuss the simulation of the low-energy effective field theory (EFT) for graphene in the presence of an external magnetic field. Our fully nonperturbative calculation uses methods of lattice gauge theory to study the theory using a hybrid Monte Carlo approach. We investigate the phenomenon of magnetic catalysis in the context of graphene by studying the chiral condensate which is the order parameter characterizing the spontaneous breaking of chiral symmetry. In the EFT, the symmetry breaking pattern is given by $U(4) \\to U(2) \\times U(2)$. We also comment on the difficulty, in this lattice formalism, of studying the time-reversal-odd condensate characterizing the ground state in the presence of a magnetic field. Finally, we study the mass spectrum of the theory, in particular the Nambu-Goldstone (NG) mode as well as the Dirac quasiparticle, which is predicted to obtain a dynamical mass.

  11. Structural Models for Cytochrome P450�Mediated Catalysis

    Directory of Open Access Journals (Sweden)

    David F.V. Lewis

    2003-01-01

    Full Text Available This review focuses on the structural models for cytochrome P450 that are improving our knowledge and understanding of the P450 catalytic cycle, and the way in which substrates bind to the enzyme leading to catalytic conversion and subsequent formation of mono-oxygenated metabolites. Various stages in the P450 reaction cycle have now been investigated using X-ray crystallography and electronic structure calculations, whereas homology modelling of mammalian P450s is currently revealing important aspects of pharmaceutical and other xenobiotic metabolism mediated by P450 involvement. These features are explored in the current review on P450-based catalysis, which emphasises the importance of structural modelling to our understanding of this enzyme's function. In addition, the results of various QSAR analyses on series of chemicals, which are metabolised via P450 enzymes, are presented such that the importance of electronic and other structural factors in explaining variations in rates of metabolism can be appreciated.

  12. Catalysis of Electroweak Baryogenesis via Fermionic Higgs Portal Dark Matter

    CERN Document Server

    Chao, Wei

    2015-01-01

    We investigate catalysis of electroweak baryogenesis by fermionic Higgs portal dark matter using a two Higgs doublet model augmented by vector-like fermions. The lightest neutral fermion mass eigenstate provides a viable dark matter candidate in the presence of a stabilizing symmetry Z_2 or gauged U(1)_D symmetry. Allowing for a non-vanishing CP-violating phase in the lowest-dimension Higgs portal dark matter interactions allows generation of the observed dark matter relic density while evading direct detection bounds. The same phase provides a source for electroweak baryogenesis. We show that it is possible to obtain the observed abundances of visible and dark matter while satisfying present bounds from electric dipole moment (EDM) searches and direct detection experiments. Improving the present electron (neutron) EDM sensitivity by one (two) orders of magnitude would provide a conclusive test of this scenario.

  13. Catalysis. Innovative applications in petrochemistry and refining. Preprints

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, S.; Balfanz, U.; Jess, A.; Lercher, J.A.; Lichtscheidl, J.; Marchionna, M.; Nees, F.; Santacesaria, E. (eds.)

    2011-07-01

    Within the DGMK conference at 4th to 6th October, 2011 in Dresden (Federal Republic of Germany) the following lectures were held: (1) Developing linear-alpha-olefins technology - From laboratory to a commercial plant (A. Meiswinkel); (2) New developments in oxidation catalysis (F. Rosowski); (3) Study of the performance of vanadium based catalysts prepared by grafting in the oxidative dehydrogenation of propane (E. Santacesaria); (4) Hydrocracking for oriented conversion of heavy oils: recent trends for catalyst development (F. Bertoncini); (5) Acidic ionic liquids for n-alkane isomerization in a liquid-liquid or slurry-phase reaction mode (C. Meyer); (6) Dual catalyst system for the hydrocracking of heavy oils and residues (G. Bellussi); (7) Understanding hydrodenitrogenation on novel unsupported sulphide Mo-W-Ni catalysts (J. Hein); (8) Hydrocracking of ethyllaurate on bifunctional micro-/mesoporous composite materials (M. Adam); (9) Catalytic dehydration of ethanol to ethylene (Ying Zhu); (10) The Evonik-Uhde HPPO process for propylene oxide production (B. Jaeger); (11) A green two-step process for adipic acid production from cyclohexene: A study on parameters affecting selectivity (F. Cavani); (12) DISY: The direct synthesis of hydrogen peroxide, a bridge for innovative applications (R, Buzzoni); (13) Solid catalyst with ionic liquid layer (SCILL) - A concept to improve the selectivity of selective hydrogenations (A. Jess); (14) Co-Zn-Al based hydrotalcites as catalysts for Fischer-Tropsch process (C.L. Bianchi); (15) Honeycomb supports with high thermal conductivity for the Fischer-Tropsch synthesis (C.G. Visconti); (16) How to make Fischer-Tropsch catalyst scale-up fully reliable (L. Fischer); (17) New developments in FCC catalysis (C.P. Kelkar); (18) The potential of medium-pore zeolites for improved propene yields from catalytic cracking (F. Bager).

  14. Mobile Sensing Systems

    Science.gov (United States)

    Macias, Elsa; Suarez, Alvaro; Lloret, Jaime

    2013-01-01

    Rich-sensor smart phones have made possible the recent birth of the mobile sensing research area as part of ubiquitous sensing which integrates other areas such as wireless sensor networks and web sensing. There are several types of mobile sensing: individual, participatory, opportunistic, crowd, social, etc. The object of sensing can be people-centered or environment-centered. The sensing domain can be home, urban, vehicular… Currently there are barriers that limit the social acceptance of mobile sensing systems. Examples of social barriers are privacy concerns, restrictive laws in some countries and the absence of economic incentives that might encourage people to participate in a sensing campaign. Several technical barriers are phone energy savings and the variety of sensors and software for their management. Some existing surveys partially tackle the topic of mobile sensing systems. Published papers theoretically or partially solve the above barriers. We complete the above surveys with new works, review the barriers of mobile sensing systems and propose some ideas for efficiently implementing sensing, fusion, learning, security, privacy and energy saving for any type of mobile sensing system, and propose several realistic research challenges. The main objective is to reduce the learning curve in mobile sensing systems where the complexity is very high. PMID:24351637

  15. Mobile Sensing Systems

    Directory of Open Access Journals (Sweden)

    Elsa Macias

    2013-12-01

    Full Text Available Rich-sensor smart phones have made possible the recent birth of the mobile sensing research area as part of ubiquitous sensing which integrates other areas such as wireless sensor networks and web sensing. There are several types of mobile sensing: individual, participatory, opportunistic, crowd, social, etc. The object of sensing can be people-centered or environment-centered. The sensing domain can be home, urban, vehicular… Currently there are barriers that limit the social acceptance of mobile sensing systems. Examples of social barriers are privacy concerns, restrictive laws in some countries and the absence of economic incentives that might encourage people to participate in a sensing campaign. Several technical barriers are phone energy savings and the variety of sensors and software for their management. Some existing surveys partially tackle the topic of mobile sensing systems. Published papers theoretically or partially solve the above barriers. We complete the above surveys with new works, review the barriers of mobile sensing systems and propose some ideas for efficiently implementing sensing, fusion, learning, security, privacy and energy saving for any type of mobile sensing system, and propose several realistic research challenges. The main objective is to reduce the learning curve in mobile sensing systems where the complexity is very high.

  16. Mobile sensing systems.

    Science.gov (United States)

    Macias, Elsa; Suarez, Alvaro; Lloret, Jaime

    2013-01-01

    Rich-sensor smart phones have made possible the recent birth of the mobile sensing research area as part of ubiquitous sensing which integrates other areas such as wireless sensor networks and web sensing. There are several types of mobile sensing: individual, participatory, opportunistic, crowd, social, etc. The object of sensing can be people-centered or environment-centered. The sensing domain can be home, urban, vehicular… Currently there are barriers that limit the social acceptance of mobile sensing systems. Examples of social barriers are privacy concerns, restrictive laws in some countries and the absence of economic incentives that might encourage people to participate in a sensing campaign. Several technical barriers are phone energy savings and the variety of sensors and software for their management. Some existing surveys partially tackle the topic of mobile sensing systems. Published papers theoretically or partially solve the above barriers. We complete the above surveys with new works, review the barriers of mobile sensing systems and propose some ideas for efficiently implementing sensing, fusion, learning, security, privacy and energy saving for any type of mobile sensing system, and propose several realistic research challenges. The main objective is to reduce the learning curve in mobile sensing systems where the complexity is very high. PMID:24351637

  17. Biodiesel production through in situ transesterification of sunflower seeds by homogeneous and heterogeneous catalysis

    International Nuclear Information System (INIS)

    The objective of this work is to show the results of the in situ transesterification of sunflower seed oil with methanol on basic homogeneous and heterogeneous catalysis for the production of biodiesel. In homogeneous catalysis, the activity of KOH and K2CO3 were evaluated using the same oil:methanol ratio of 1:90. KOH showed to be more active than K2CO3, leading to total conversion in biodiesel after 1h reaction time. In the heterogeneous catalysis the activity of K2CO3/Al2O3 was comparable to the activity of K2CO3 bulk: 53.0 and 66.6% resp. The properties of samples of biodiesel produced by homogeneous and heterogeneous catalysis were evaluated and are in accordance with the recommended fuel properties. (author)

  18. A Course in Heterogeneous Catalysis: Principles, Practice, and Modern Experimental Techniques.

    Science.gov (United States)

    Wolf, Eduardo E.

    1981-01-01

    Outlines a multidisciplinary course which comprises fundamental, practical, and experimental aspects of heterogeneous catalysis. The course structure is a combination of lectures and demonstrations dealing with the use of spectroscopic techniques for surface analysis. (SK)

  19. Core–shell nanoparticles: synthesis and applications in catalysis and electrocatalysis

    Science.gov (United States)

    Core–shell nanoparticles (CSNs) are a class of nanostructured materials that have recently received increased attention owing to their interesting properties and broad range of applications in catalysis, biology, materials chemistry and sensors. By rationally tuning the cores as ...

  20. Drug Abuse

    Science.gov (United States)

    ... as drugged driving, violence, stress, and child abuse. Drug abuse can lead to homelessness, crime, and missed work or problems with keeping a job. It harms unborn babies and destroys families. There are different types of treatment for drug abuse. But the best is to prevent drug ...

  1. Drug Facts

    Medline Plus

    Full Text Available ... text to you. This web site talks about drug abuse, addiction and treatment. Watch Videos Information About Drugs Alcohol ... of the drug. "Max" was addicted to prescription drugs. The addiction slowly took over his life. I need different ...

  2. Mechanistic insights into enzymatic and homogeneous transition metal catalysis from quantum-chemical calculations

    OpenAIRE

    Crawford, Luke

    2015-01-01

    Catalysis is a key area of chemistry. Through catalysis it is possible to achieve better synthetic routes, exploit molecules normally considered to be inactive and also attain novel chemical transformations. The development of new catalysts is crucial to furthering chemistry as a field. Computational chemistry, arising from applying the equations of quantum and classical mechanics to solving chemical problems, offers an essential route to investigating the underlying atomistic detail of ca...

  3. Inverse magnetic catalysis in Nambu-Jona-Lasinio model beyond mean field

    Science.gov (United States)

    Mao, Shijun

    2016-07-01

    We study inverse magnetic catalysis in the Nambu-Jona-Lasinio model beyond mean field approximation. The feed-down from mesons to quarks is embedded in an effective coupling constant at finite temperature and magnetic field. While the magnetic catalysis is still the dominant effect at low temperature, the meson dressed quark mass drops down with increasing magnetic field at high temperature due to the dimension reduction of the Goldstone mode in the Pauli-Villars regularization scheme.

  4. Interrelation of chemistry and process design in biodiesel manufacturing by heterogeneous catalysis

    OpenAIRE

    Dimian, A.C.; Srokol, Z.W.; Mittelmeijer-Hazeleger, M.C.; Rothenberg, G.

    2010-01-01

    The pros and cons of using heterogeneous catalysis for biodiesel manufacturing are introduced, and explained from a chemistry and engineering viewpoint. Transesterification reactions of various feed types are then compared in batch and continuous process operation modes. The results show that the reaction chemistry and process kinetics characterising a particular feedstock are determinant factors for obtaining high-grade biodiesel. When using heterogeneous catalysis, the biodiesel quality of ...

  5. Challenges and perspectives for catalysis in production of diesel from biomass

    DEFF Research Database (Denmark)

    Madsen, Anders Theilgaard; Søndergaard, Helle; Fehrmann, Rasmus;

    2011-01-01

    oils or waste fats with methanol is the most prominent and has been applied industrially for a decade. Homogeneous acid and base catalysis is normally used, but solid acids, solid bases, ionic liquids and lipases are being developed as replacements. Hydrodeoxygenation of vegetable oils has likewise...... gas of CO and H2 and liquefaction to alkanes via Fischer-Tropsch synthesis. Here, the current challenges and perspectives regarding catalysis and raw materials for diesel production from biomass are surveyed. © Future Science Ltd....

  6. Liquid phase oxidation via heterogeneous catalysis organic synthesis and industrial applications

    CERN Document Server

    Clerici, Mario G

    2013-01-01

    Sets the stage for environmentally friendly industrial organic syntheses From basic principles to new and emerging industrial applications, this book offers comprehensive coverage of heterogeneous liquid-phase selective oxidation catalysis. It fully examines the synthesis, characterization, and application of catalytic materials for environmentally friendly organic syntheses. Readers will find coverage of all the important classes of catalysts, with an emphasis on their stability and reusability. Liquid Phase Oxidation via Heterogeneous Catalysis features contributions from an internation

  7. Inverse Magnetic Catalysis in Nambu--Jona-Lasinio Model beyond Mean Field

    CERN Document Server

    Mao, Shijun

    2016-01-01

    We study inverse magnetic catalysis in the Nambu--Jona-Lasinio model beyond mean field approximation. The feed-down from mesons to quarks is embedded in an effective coupling constant at finite temperature and magnetic field. While the magnetic catalysis is still the dominant effect at low temperature, the meson dressed quark mass drops down with increasing magnetic field at high temperature due to the dimension reduction of the Goldstone mode in the Pauli-Villars regularization scheme.

  8. Combination of sunlight irradiated oxidative processes for landfill leachate: heterogeneous catalysis (TiO2 versus homogeneous catalysis (H2O2

    Directory of Open Access Journals (Sweden)

    Oswaldo Luiz Cobra Guimarães

    2013-04-01

    Full Text Available The objective of this work was to study the treatment of landfill leachate liquid in nature, after the use of a combination of advanced oxidation processes. More specifically, it compared heterogeneous catalysis with TiO2 to homogeneous catalysis with H2O2, both under photo-irradiated sunlight. The liquid used for the study was the leachate from the landfill of the city of Cachoeira Paulista, São Paulo State, Brazil. The experiments were conducted in a semi-batch reactor open to the absorption of solar UV radiation, with 120 min reaction time. The factors and their respective levels (-1, 0 and 1 were distributed in a experimental design 24-1 with duplicate and triplicate in the central point, resulting in an array with 19 treatment trials. The studied factors in comparing the two catalytic processes were: liquid leachate dilution, TiO2 concentration on the reactor plate, the H2O2 amount and pH level. The leachate had low photo-catalytic degradability, with NOPC reductions ranging from 1% to a maximum of 24.9%. When considering each factor alone, neither homogeneous catalysis with H2O2, nor heterogeneous catalysis with TiO2, could degrade the percolated liquid without significant reductions (5% level in total NOPC. On the other hand, the combined use of homogenous catalysis with H2O2 and heterogeneous catalysis H2O2 resulted in the greatest reductions in NOPC. The optimum condition for the NOPC reduction was obtained at pH 7, dilution of percolated:water at 1:1 (v v-1 rate; excess of 12.5% H2O2 and coating plate reactor with 0.025 g cm-2 TiO2.

  9. Analgesic drugs

    OpenAIRE

    Kerec Kos, Mojca

    2015-01-01

    In the management of pain analgesic drugs are chosen regarding the intensity and type of pain. The selection of analgesic drug depends on pharmacokinetic properties of the drug and available pharmaceutical dosage forms. Beside non-opioid analgesics (non-steroidal antiinflammatory drugs, acetaminophen), opioid analgesic drugs have an important role in the treatment of pain. Pri zdravljenju bolečine izberemo analgetik glede na jakost in vrsto bolečine. Na izbiro ustreznega analgetika vplivaj...

  10. Introduction to remote sensing

    CERN Document Server

    Cracknell, Arthur P

    2007-01-01

    Addressing the need for updated information in remote sensing, Introduction to Remote Sensing, Second Edition provides a full and authoritative introduction for scientists who need to know the scope, potential, and limitations in the field. The authors discuss the physical principles of common remote sensing systems and examine the processing, interpretation, and applications of data. This new edition features updated and expanded material, including greater coverage of applications from across earth, environmental, atmospheric, and oceanographic sciences. Illustrated with remotely sensed colo

  11. Effect of Water Vapor on Toluene Removal in Catalysis-DBD Plasma Reactors

    Science.gov (United States)

    Wang, Jingting; Cao, Xu; Zhang, Renxi; Gong, Ting; Hou, Huiqi; Chen, Shanping; Zhang, Ruina

    2016-04-01

    The experiment was carried out in a cylindrical dielectric barrier discharge (DBD) reactor assisted with a catalyst to decompose toluene under different humidity. In order to explore the synergistic effect on removing toluene in the catalysis-DBD reactor, this paper investigated the decomposition efficiency and the energy consumption in the catalysis-DBD and the non-catalyst DBD reactors under different humidity. The results showed that the catalysis-DBD reactor had a better performance than the non-catalysis one at the humidity ratio of 0.4%, and the removal efficiency of toluene could reach 88.6% in the catalysis-DBD reactor, while it was only 59.9% in the non-catalytic reactor. However, there was no significant difference in the removal efficiency of toluene between the two reactors when the humidities were 1.2% and 2.4%. Additionally, the degradation products were also analyzed in order to gain a better understanding of the mechanism of decomposing toluene in a catalysis-DBD reactor. supported by the Key Project which is sponsored by the Science and Technology Commission of Shanghai Municipality (No. 13231201903), the Key Programs for Science and Technology Development sponsored by the Science and Technology Commission of Shanghai Municipality (Nos. 13231201901 and 14DZ1208401), and the Key Project sponsored by the State-owned Assets Supervision and Administration Commission of Shanghai, China (No. 2013019)

  12. Supported Organometallic Complexes: Surface Chemistry, Spectroscopy, Catalysis, and Homogeneous Models

    Energy Technology Data Exchange (ETDEWEB)

    Marks, Tobin J. [Northwestern Univ., Evanston, IL (United States); Stalzer, Madelyn M. [Northwestern Univ., Evanston, IL (United States); Delferro, Massimiliano [Northwestern Univ., Evanston, IL (United States)

    2016-09-09

    The goal of this project is to model, understand at a fundamental level, expand, and exploit pathways by which organometallic molecules of varying nuclearity undergo chemisorptive activation and catalytic activity enhancement on solid surfaces. Such processes connect to real-world, large-scale industrial hydrocarbon processes and to manufacturing cleaner, greener, more environmentally acceptable products, including those from renewable resources. This research program combines catalyst synthesis, surface chemistry and spectroscopy, homogeneous analogue catalysis, structural analysis, and computation, and involves collaboration with national laboratory and industrial researchers. The objectives are to: 1) Investigate mononuclear and binuclear organometallic chemisorption on “super Brønsted acid” and related oxide surfaces, 2) Synthesize and characterize mononuclear and polynuclear catalyst precursors for understanding-based surface and solution phase catalysis, 3) Use this information to produce new types of efficient energy storage materials, 4) Computationally model both solution phase and chemisorbed catalysts, and investigate their reactivity modes. Of relevance to national energy issues is the potential to transform/metathesize inert saturated hydrocarbons,to drive “uphill” processes by coupling to exoergic transformations, to better utilize biofeedstocks (e.g., Dow’s world-scale Brazilian non-petroleum polyethylene process), and to address challenges articulated in recent BES Catalysis BRN and Grand Research Challenges reports. The long-range objective is therefore to understand and exploit (catalyst)∙∙∙(catalyst) and (catalyst )∙∙∙(surface/cocatalyst) interactions for new, instructive reactivity patterns, and to connect activating surface environments with mechanistically less complex solution environments. The information obtained is then fed back into further catalyst discovery efforts. We have pursued correlated synthesis

  13. Math Sense: Placement Test.

    Science.gov (United States)

    2003

    Math Sense consists of five books that develop from basic to more advanced math skills. This document contains a placement test used with Math Sense to help students and their teachers decide into which Math Sense book to begin working. The placement test is divided into six parts, each consisting of 10 to 22 problems, and is based on exit skill…

  14. Drug: D08991 [KEGG MEDICUS

    Lifescience Database Archive (English)

    Full Text Available oporosis calcium sensing receptor antagonist [HSA:846] [KO:K04612] Target-based cla...D08991 Drug Ronacaleret hydrochloride (USAN) C25H31F2NO4. HCl 483.1988 483.9757 D08991.gif Treatment of oste

  15. Substance use - prescription drugs

    Science.gov (United States)

    Substance use disorder - prescription drugs; Substance abuse - prescription drugs; Drug abuse - prescription drugs; Drug use - prescription drugs; Narcotics - substance use; Opioid - substance use; Sedative - substance use; Hypnotic - substance ...

  16. Attenuation of Pseudomonas aeruginosa virulence by quorum sensing inhibitors

    DEFF Research Database (Denmark)

    Hentzer, Morten; Wu, H.; Andersen, Jens Bo;

    2003-01-01

    Traditional treatment of infectious diseases is based on compounds that kill or inhibit growth of bacteria. A major concern with this approach is the frequent development of resistance to antibiotics. The discovery of communication systems (quorum sensing systems) regulating bacterial virulence has...... of natural furanone compounds can act as a potent antagonist of bacterial quorum sensing. We employed GeneChip((R)) microarray technology to identify furanone target genes and to map the quorum sensing regulon. The transcriptome analysis showed that the furanone drug specifically targeted quorum sensing...

  17. Ferroelectrics: A pathway to switchable surface chemistry and catalysis

    Science.gov (United States)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab; Altman, Eric I.

    2016-08-01

    It has been known for more than six decades that ferroelectricity can affect a material's surface physics and chemistry thereby potentially enhancing its catalytic properties. Ferroelectrics are a class of materials with a switchable electrical polarization that can affect surface stoichiometry and electronic structure and thus adsorption energies and modes; e.g., molecular versus dissociative. Therefore, ferroelectrics may be utilized to achieve switchable surface chemistry whereby surface properties are not fixed but can be dynamically controlled by, for example, applying an external electric field or modulating the temperature. Several important examples of applications of ferroelectric and polar materials in photocatalysis and heterogeneous catalysis are discussed. In photocatalysis, the polarization direction can control band bending at water/ferroelectric and ferroelectric/semiconductor interfaces, thereby facilitating charge separation and transfer to the electrolyte and enhancing photocatalytic activity. For gas-surface interactions, available results suggest that using ferroelectrics to support catalytically active transition metals and oxides is another way to enhance catalytic activity. Finally, the possibility of incorporating ferroelectric switching into the catalytic cycle itself is described. In this scenario, a dynamic collaboration of two polarization states can be used to drive reactions that have been historically challenging to achieve on surfaces with fixed chemical properties (e.g., direct NOx decomposition and the selective partial oxidation of methane). These predictions show that dynamic modulation of the polarization can help overcome some of the fundamental limitations on catalytic activity imposed by the Sabatier principle.

  18. Parahydrogen Induced polarization by homogeneous catalysis: theory and applications.

    Science.gov (United States)

    Buljubasich, Lisandro; Franzoni, María Belén; Münnemann, Kerstin

    2013-01-01

    The alignment of the nuclear spins in parahydrogen can be transferred to other molecules by a homogeneously catalyzed hydrogenation reaction resulting in dramatically enhanced NMR signals. In this chapter we introduce the involved theoretical concepts by two different approaches: the well known, intuitive population approach and the more complex but more complete density operator formalism. Furthermore, we present two interesting applications of PHIP employing homogeneous catalysis. The first demonstrates the feasibility of using PHIP hyperpolarized molecules as contrast agents in (1)H MRI. The contrast arises from the J-coupling induced rephasing of the NMR signal of molecules hyperpolarized via PHIP. It allows for the discrimination of a small amount of hyperpolarized molecules from a large background signal and may open up unprecedented opportunities to use the standard MRI nucleus (1)H for, e.g., metabolic imaging in the future. The second application shows the possibility of continuously producing hyperpolarization via PHIP by employing hollow fiber membranes. The continuous generation of hyperpolarization can overcome the problem of fast relaxation times inherent in all hyperpolarization techniques employed in liquid-state NMR. It allows, for instance, the recording of a reliable 2D spectrum much faster than performing the same experiment with thermally polarized protons. The membrane technique can be straightforwardly extended to produce a continuous flow of a hyperpolarized liquid for MRI enabling important applications in natural sciences and medicine.

  19. State of Supported Nanoparticle Ni during Catalysis in Aqueous Media

    Energy Technology Data Exchange (ETDEWEB)

    Chase, Zizwe; Vjunov, Aleksei; Fulton, John; Camaioni, Donald; Balasubramanian, Mahalingam; Lercher, Johannes

    2015-11-09

    The state of Ni supported on HZSM-5 zeolite, silica, and sulfonated carbon was studied during aqueous-phase catalysis of phenol hydrodeoxygenation using in situ extended X-ray absorption fine structure spectroscopy. On sulfonated carbon and HZSM-5 supports, NiO and Ni(OH)(2) were readily reduced to Ni-0 under reaction conditions (approximate to 35bar H-2 in aqueous phenol solutions containing up to 0.5wt.% phosphoric acid at 473K). In contrast, Ni supported on SiO2 was not stable in a fully reduced Ni-0 state. Water enables the formation of Ni-II phyllosilicate, which is more stable, that is, difficult to reduce, than either -Ni(OH)(2) or NiO. Leaching of Ni from the supports was not observed over a broad range of reaction conditions. Ni-0 particles on HZSM-5 were stable even in presence of 15wt.% acetic acid at 473K and 35bar H-2.

  20. Recent advances in heterogeneous selective oxidation catalysis for sustainable chemistry.

    Science.gov (United States)

    Guo, Zhen; Liu, Bin; Zhang, Qinghong; Deng, Weiping; Wang, Ye; Yang, Yanhui

    2014-05-21

    Oxidation catalysis not only plays a crucial role in the current chemical industry for the production of key intermediates such as alcohols, epoxides, aldehydes, ketones and organic acids, but also will contribute to the establishment of novel green and sustainable chemical processes. This review is devoted to dealing with selective oxidation reactions, which are important from the viewpoint of green and sustainable chemistry and still remain challenging. Actually, some well-known highly challenging chemical reactions involve selective oxidation reactions, such as the selective oxidation of methane by oxygen. On the other hand some important oxidation reactions, such as the aerobic oxidation of alcohols in the liquid phase and the preferential oxidation of carbon monoxide in hydrogen, have attracted much attention in recent years because of their high significance in green or energy chemistry. This article summarizes recent advances in the development of new catalytic materials or novel catalytic systems for these challenging oxidation reactions. A deep scientific understanding of the mechanisms, active species and active structures for these systems are also discussed. Furthermore, connections among these distinct catalytic oxidation systems are highlighted, to gain insight for the breakthrough in rational design of efficient catalytic systems for challenging oxidation reactions.

  1. Mesoporous Phosphate Heterostructures: Synthesis and Application on Adsorption and Catalysis

    Science.gov (United States)

    Moreno-Tost, Ramón; Jiménez-Jiménez, José; Infantes-Molina, Antonia; Cavalcante, Celio L.; Azevedo, Diana C. S.; Soriano, María Dolores; López Nieto, José Manuel; Jiménez-López, Antonio; Rodríguez-Castellón, Enrique

    Porous phosphate heterostructures (PPHs) are solids formed by a layered metal(IV) phosphate expanded with silica galleries obtained by combining the two main strategies for obtaining mesoporous materials [pillared layered structures (PLS') and MCM-41]. The different synthetic pathways for obtaining mesoporous phosphate structures with silica galleries with Zr- or Ti-doped silica, the study of their structural, textural and acid properties, its functionalisation with different organic substances such as propionitrile, 3-aminopropyl triethoxysilane, (3-mercaptopropyl)trimethoxysilane, vinyltrimethoxysilane, phenyltriethoxysilane and 3-(triethoxysilyl)propionitrile are discussed. The preparation of metal-supported catalysts and their application in gas separation, adsorption and catalysis are reviewed. Specifically, the use of Cu- and Fe-exchanged PPH for the adsorption of benzothiophene and the separation of propane/propene is the main application as adsorbent. The hydrotreating of aromatic hydrocarbons using ruthenium-impregnated catalysts via hydrogenation and hydrogenolysis/hydrocracking for the production of clean diesel fuels, the selective catalytic reduction of NO from stationary and mobile sources by using Cu-PPH with 1, 3 and 7 wt% of Cu and the selective oxidation of hydrogen sulphide to sulphur with vanadium-containing PPH are the three catalytic reactions of environmental interest studied.

  2. Application of solid ash based catalysts in heterogeneous catalysis.

    Science.gov (United States)

    Wang, Shaobin

    2008-10-01

    Solid wastes, fly ash, and bottom ash are generated from coal and biomass combustion. Fly ash is mainly composed of various metal oxides and possesses higher thermal stability. Utilization of fly ash for other industrial applications provides a cost-effective and environmentally friendly way of recycling this solid waste, significantly reducing its environmental effects. On the one hand, due to the higher stability of its major component, aluminosilicates, fly ash could be employed as catalyst support by impregnation of other active components for various reactions. On the other hand, other chemical compounds in fly ash such as Fe2O3 could also provide an active component making fly ash a catalyst for some reactions. In this paper, physicochemical properties of fly ash and its applications for heterogeneous catalysis as a catalyst support or catalyst in a variety of catalytic reactions were reviewed. Fly-ash-supported catalysts have shown good catalytic activities for H2 production, deSO(x), deNO(x), hydrocarbon oxidation,and hydrocracking, which are comparable to commercially used catalysts. As a catalyst itself, fly ash can also be effective for gas-phase oxidation of volatile organic compounds, aqueous-phase oxidation of organics, solid plastic pyrolysis, and solvent-free organic synthesis. PMID:18939526

  3. General base-general acid catalysis by terpenoid cyclases.

    Science.gov (United States)

    Pemberton, Travis A; Christianson, David W

    2016-07-01

    Terpenoid cyclases catalyze the most complex reactions in biology, in that more than half of the substrate carbon atoms often undergo changes in bonding during the course of a multistep cyclization cascade that proceeds through multiple carbocation intermediates. Many cyclization mechanisms require stereospecific deprotonation and reprotonation steps, and most cyclization cascades are terminated by deprotonation to yield an olefin product. The first bacterial terpenoid cyclase to yield a crystal structure was pentalenene synthase from Streptomyces exfoliatus UC5319. This cyclase generates the hydrocarbon precursor of the pentalenolactone family of antibiotics. The structures of pentalenene synthase and other terpenoid cyclases reveal predominantly nonpolar active sites typically lacking amino acid side chains capable of serving general base-general acid functions. What chemical species, then, enables the Brønsted acid-base chemistry required in the catalytic mechanisms of these enzymes? The most likely candidate for such general base-general acid chemistry is the co-product inorganic pyrophosphate. Here, we briefly review biological and nonbiological systems in which phosphate and its derivatives serve general base and general acid functions in catalysis. These examples highlight the fact that the Brønsted acid-base activities of phosphate derivatives are comparable to the Brønsted acid-base activities of amino acid side chains.

  4. Hydrogen and methane synthesis through radiation catalysis. Final report

    International Nuclear Information System (INIS)

    The goal of this research was to evaluate the potential for using reactor wastes to synthesize useful products in quasi-photochemical configuration. It was found that semiconductor oxides act as heterogenous catalysts for the formation of H2 in aqueous media under 60Co irradiation. The principle of a gamma-ray solar cell was demonstrated experimentally. Experiments with ultraviolet irradiated TiO2 and ZnO grains demonstrated that both H2 and H2O2 were formed, in contrast to the results of work by previous authors. These results were rationalized by energy band diagram representations and by applying principles of semiconductor photoelectrochemistry. The concept of gamma-ray assisted desulfurization of coal through radiological degradation and heterogenous catalysis was experimentally demonstrated. The proof-of-concept experiments in the present study provide the basis for further fundamental and applied investigations, particularly in a potentially efficient system with a fresh source and 1.5 m path length

  5. Towards Rational Design of Nanoparticle Catalysis in Ionic Liquids

    Directory of Open Access Journals (Sweden)

    Ning Yan

    2013-06-01

    Full Text Available This feature article introduces the strategies on the design of highly efficient nanoparticle (NP catalytic systems in ionic liquids (ILs. The employment of functional ILs as the media for NP preparation and catalysis could prove advantageous in terms of enhancing both NP stability and catalytic activity. Hydroxyl group functionalized ILs, in particular, exhibited a remarkable promotion effect on a variety of reactions catalyzed by NPs, such as hydrogenation over Rh NPs, hydrodehalogenation over Pt NPs and Suzuki reaction over Pd NPs. In some cases, tailor-made stabilizer is used in addition to keep the NPs sufficiently stable. For example, a carboxylic group modified polyvinylpyrrolidone endows NPs three-fold stabilization, including steric, electrostatic and ligand stabilizations, which leads to excellent stability of the NPs. The catalytic activities of these NPs, on the other hand, are not compromised, as each of these stabilizations is not too strong. Following that, the article describes our recent work on the rational design of bimetallic NPs in ILs and the development of multifunctional systems involving NPs for a tandem reaction sequence that convert lignin-derived phenolic compounds into fuels.

  6. Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

    Directory of Open Access Journals (Sweden)

    David W. Manley

    2015-09-01

    Full Text Available Heterogeneous semiconductor photoredox catalysis (SCPC, particularly with TiO2, is evolving to provide radically new synthetic applications. In this review we describe how photoactivated SCPCs can either (i interact with a precursor that donates an electron to the semiconductor thus generating a radical cation; or (ii interact with an acceptor precursor that picks up an electron with production of a radical anion. The radical cations of appropriate donors convert to neutral radicals usually by loss of a proton. The most efficient donors for synthetic purposes contain adjacent functional groups such that the neutral radicals are resonance stabilized. Thus, ET from allylic alkenes and enol ethers generated allyl type radicals that reacted with 1,2-diazine or imine co-reactants to yield functionalized hydrazones or benzylanilines. SCPC with tertiary amines enabled electron-deficient alkenes to be alkylated and furoquinolinones to be accessed. Primary amines on their own led to self-reactions involving C–N coupling and, with terminal diamines, cyclic amines were produced. Carboxylic acids were particularly fruitful affording C-centered radicals that alkylated alkenes and took part in tandem addition cyclizations producing chromenopyrroles; decarboxylative homo-dimerizations were also observed. Acceptors initially yielding radical anions included nitroaromatics and aromatic iodides. The latter led to hydrodehalogenations and cyclizations with suitable precursors. Reductive SCPC also enabled electron-deficient alkenes and aromatic aldehydes to be hydrogenated without the need for hydrogen gas.

  7. Theoretical Heterogeneous Catalysis: Scaling Relationships and Computational Catalyst Design.

    Science.gov (United States)

    Greeley, Jeffrey

    2016-06-01

    Scaling relationships are theoretical constructs that relate the binding energies of a wide variety of catalytic intermediates across a range of catalyst surfaces. Such relationships are ultimately derived from bond order conservation principles that were first introduced several decades ago. Through the growing power of computational surface science and catalysis, these concepts and their applications have recently begun to have a major impact in studies of catalytic reactivity and heterogeneous catalyst design. In this review, the detailed theory behind scaling relationships is discussed, and the existence of these relationships for catalytic materials ranging from pure metal to oxide surfaces, for numerous classes of molecules, and for a variety of catalytic surface structures is described. The use of the relationships to understand and elucidate reactivity trends across wide classes of catalytic surfaces and, in some cases, to predict optimal catalysts for certain chemical reactions, is explored. Finally, the observation that, in spite of the tremendous power of scaling relationships, their very existence places limits on the maximum rates that may be obtained for the catalyst classes in question is discussed, and promising strategies are explored to overcome these limitations to usher in a new era of theory-driven catalyst design.

  8. Polarization-driven catalysis via ferroelectric oxide surfaces.

    Science.gov (United States)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab

    2016-07-20

    The surface chemistry and physics of oxide ferroelectric surfaces with a fixed polarization state have been studied experimentally for some time. Here, we discuss the possibility of using these materials in a different mode, namely under cyclically changing polarization conditions achievable via periodic perturbations by external fields (e.g., temperature, strain or electric field). We use Density Functional Theory (DFT) and electronic structure analysis to understand the polarization-dependent surface physics and chemistry of ferroelectric oxide PbTiO3 as an example of this class of materials. This knowledge is then applied to design catalytic cycles for industrially important reactions including NOx direct decomposition and SO2 oxidation into SO3. The possibility of catalyzing direct partial oxidation of methane to methanol is also investigated. More generally, we discuss how using ferroelectrics under cyclically changing polarization conditions can help overcome some of the fundamental challenges facing the catalysis community such as the limitations imposed by the Sabatier principle and scaling relations. PMID:27381676

  9. Heterogeneous and homogeneous chiral Cu(II) catalysis in water: enantioselective boron conjugate additions to dienones and dienoesters.

    Science.gov (United States)

    Kitanosono, Taku; Xu, Pengyu; Kobayashi, Shū

    2013-09-25

    It was proved that a judicious choice of counteranion played a prominent role in Cu(II) catalysis for enantioselective boron conjugate additions in water; the use of Cu(OH)2 renders heterogeneous catalysis, whereas Cu(OAc)2 renders homogeneous catalysis; cyclic dienones underwent a remarkable switch of regioselectivity between 1,4- and 1,6-modes of the additions through these catalyses.

  10. Sequential rhodium/palladium catalysis: enantioselective formation of dihydroquinolinones in the presence of achiral and chiral ligands.

    Science.gov (United States)

    Zhang, Lei; Qureshi, Zafar; Sonaglia, Lorenzo; Lautens, Mark

    2014-12-01

    Compatible combinations of achiral and chiral ligands can be used in rhodium/palladium catalysis to achieve highly enantioselective domino reactions. The difference in rates of catalysis and minimal effects of ligand interference confer control in the domino sequence. The "all-in-one" 1,4-conjugate arylation and C-N cross-coupling through sequential Rh/Pd catalysis provides access to enantioenriched dihydroquinolinone building blocks.

  11. Drug Facts

    Medline Plus

    Full Text Available ... Cocaine (Coke, Crack) Facts Heroin (Smack, Junk) Facts Marijuana (Weed, Pot) Facts Meth (Crank, Ice) Facts Pain ... Watch Videos Information About Drugs Alcohol Cocaine Heroin Marijuana Meth Pain Medicines Tobacco Other Drugs You can ...

  12. Drug Facts

    Medline Plus

    Full Text Available ... Numbers and Websites Search Share Listen English Español Information about this page Click on the button that ... about drug abuse, addiction and treatment. Watch Videos Information About Drugs Alcohol Cocaine Heroin Marijuana Meth Pain ...

  13. Drug Facts

    Medline Plus

    Full Text Available Easy-to-Read Drug Facts Search form Search Menu Home Drugs That People Abuse Alcohol Facts Cigarette and Tobacco Facts Cocaine (Coke, Crack) Facts Heroin (Smack, Junk) Facts Marijuana ( ...

  14. Drug Facts

    Medline Plus

    Full Text Available ... People Abuse Alcohol Facts Cigarette and Tobacco Facts Cocaine (Coke, Crack) Facts Heroin (Smack, Junk) Facts Marijuana (Weed, ... and treatment. Watch Videos Information About Drugs Alcohol Cocaine Heroin Marijuana Meth Pain Medicines Tobacco Other Drugs ...

  15. Drug Facts

    Medline Plus

    Full Text Available ... People Abuse Alcohol Facts Cigarette and Tobacco Facts Cocaine (Coke, Crack) Facts Heroin (Smack, Junk) Facts Marijuana ( ... and treatment. Watch Videos Information About Drugs Alcohol Cocaine Heroin Marijuana Meth Pain Medicines Tobacco Other Drugs ...

  16. Drug Facts

    Medline Plus

    Full Text Available ... abuse, addiction and treatment. Watch Videos Information About Drugs Alcohol Cocaine Heroin Marijuana Meth Pain Medicines Tobacco ... 662-HELP (4357) at any time to find drug treatment centers near you. I want my daughter ...

  17. Drug Facts

    Medline Plus

    Full Text Available ... Bodies Drug Abuse Hurts Brains Drug Abuse and Mental Health Problems Often Happen Together The Link Between ... This Website Tools and Resources | Contact Us | Site Map | Accessibility | Privacy | FOIA (NIH) The National Institute on ...

  18. Drug Facts

    Medline Plus

    Full Text Available ... Search form Search Menu Home Drugs That People Abuse Alcohol Facts Cigarette and Tobacco Facts Cocaine (Coke, ... Pain Medicine (Oxy, Vike) Facts Other Drugs of Abuse What is Addiction? Do You or a Loved ...

  19. Drug Facts

    Medline Plus

    Full Text Available ... Cigarette and Tobacco Facts Cocaine (Coke, Crack) Facts Heroin (Smack, Junk) Facts Marijuana (Weed, Pot) Facts Meth ( ... treatment. Watch Videos Information About Drugs Alcohol Cocaine Heroin Marijuana Meth Pain Medicines Tobacco Other Drugs You ...

  20. Drug Addiction

    OpenAIRE

    Justinova, Zuzana; Panlilio, Leigh V; Goldberg, Steven R.

    2009-01-01

    Many drugs of abuse, including cannabinoids, opioids, alcohol and nicotine, can alter the levels of endocannabinoids in the brain. Recent studies show that release of endocannabinoids in the ventral tegmental area can modulate the reward-related effects of dopamine and might therefore be an important neurobiological mechanism underlying drug addiction. There is strong evidence that the endocannabinoid system is involved in drug-seeking behavior (especially behavior that is reinforced by drug-...

  1. Medicaid Drugs

    OpenAIRE

    Poisal, John A.

    2004-01-01

    The following commentary unites a collection of articles primarily concerned with prescription drug issues in Medicaid. It also features highlights from a piece outlining Australia's pharmaceutical delivery system. Specifically, in this issue, you will find comprehensive analyses of drug expenditure trends, issues regarding access to pharmaceuticals in Medicaid, and an evaluation of ongoing generic drug cost-containment programs.

  2. Drug Facts

    Medline Plus

    Full Text Available ... Watch Videos Information About Drugs Alcohol Cocaine Heroin Marijuana Meth Pain Medicines Tobacco Other Drugs You can call 1-800-662-HELP (4357) at any time to find drug treatment centers near ... different people around me. To stop using marijuana, "Cristina" is making positive changes in her life. ...

  3. Drug Addiction, Love, and the Higher Power

    Science.gov (United States)

    Sussman, Steve; Reynaud, Michel; Aubin, Henri-Jean; Leventhal, Adam M.

    2011-01-01

    This discussion piece suggests that reliance on a Higher Power in drug abuse recovery programs is entertained among some addicts for its psychobiological effects. Prayer, meditation, early romantic love, and drug abuse may have in common activation of mesolimbic dopaminergic pathways of the brain and the generation of intense emotional states. In this sense, reliance on a Higher Power may operate as a substitute addiction, which replaces the psychobiological functions formerly served by drug use. Implications of this perspective are discussed. PMID:21411471

  4. Drug Addiction, Love, and the Higher Power

    OpenAIRE

    Sussman, Steve; Reynaud, Michel; Aubin, Henri-Jean; Leventhal, Adam M.

    2011-01-01

    This discussion piece suggests that reliance on a Higher Power in drug abuse recovery programs is entertained among some addicts for its psychobiological effects. Prayer, meditation, early romantic love, and drug abuse may have in common activation of mesolimbic dopaminergic pathways of the brain and the generation of intense emotional states. In this sense, reliance on a Higher Power may operate as a substitute addiction, which replaces the psychobiological functions formerly served by drug ...

  5. Drug allergy

    Directory of Open Access Journals (Sweden)

    Warrington Richard

    2011-11-01

    Full Text Available Abstract Drug allergy encompasses a spectrum of immunologically-mediated hypersensitivity reactions with varying mechanisms and clinical presentations. This type of adverse drug reaction (ADR not only affects patient quality of life, but may also lead to delayed treatment, unnecessary investigations, and even mortality. Given the myriad of symptoms associated with the condition, diagnosis is often challenging. Therefore, referral to an allergist experienced in the identification, diagnosis and management of drug allergy is recommended if a drug-induced allergic reaction is suspected. Diagnosis relies on a careful history and physical examination. In some instances, skin testing, graded challenges and induction of drug tolerance procedures may be required. The most effective strategy for the management of drug allergy is avoidance or discontinuation of the offending drug. When available, alternative medications with unrelated chemical structures should be substituted. Cross-reactivity among drugs should be taken into consideration when choosing alternative agents. Additional therapy for drug hypersensitivity reactions is largely supportive and may include topical corticosteroids, oral antihistamines and, in severe cases, systemic corticosteroids. In the event of anaphylaxis, the treatment of choice is injectable epinephrine. If a particular drug to which the patient is allergic is indicated and there is no suitable alternative, induction of drug tolerance procedures may be considered to induce temporary tolerance to the drug. This article provides a backgrounder on drug allergy and strategies for the diagnosis and management of some of the most common drug-induced allergic reactions, such allergies to penicillin, sulfonamides, cephalosporins, radiocontrast media, local anesthetics, general anesthetics, acetylsalicylic acid (ASA and non-steroidal anti-inflammatory drugs.

  6. Optical remote sensing

    CERN Document Server

    Prasad, Saurabh; Chanussot, Jocelyn

    2011-01-01

    Optical remote sensing relies on exploiting multispectral and hyper spectral imagery possessing high spatial and spectral resolutions respectively. These modalities, although useful for most remote sensing tasks, often present challenges that must be addressed for their effective exploitation. This book presents current state-of-the-art algorithms that address the following key challenges encountered in representation and analysis of such optical remotely sensed data: challenges in pre-processing images, storing and representing high dimensional data, fusing different sensor modalities, patter

  7. Atomic-Scale Observations of Catalyst Structures under Reaction Conditions and during Catalysis.

    Science.gov (United States)

    Tao, Franklin Feng; Crozier, Peter A

    2016-03-23

    Heterogeneous catalysis is a chemical process performed at a solid-gas or solid-liquid interface. Direct participation of catalyst atoms in this chemical process determines the significance of the surface structure of a catalyst in a fundamental understanding of such a chemical process at a molecular level. High-pressure scanning tunneling microscopy (HP-STM) and environmental transmission electron microscopy (ETEM) have been used to observe catalyst structure in the last few decades. In this review, instrumentation for the two in situ/operando techniques and scientific findings on catalyst structures under reaction conditions and during catalysis are discussed with the following objectives: (1) to present the fundamental aspects of in situ/operando studies of catalysts; (2) to interpret the observed restructurings of catalyst and evolution of catalyst structures; (3) to explore how HP-STM and ETEM can be synergistically used to reveal structural details under reaction conditions and during catalysis; and (4) to discuss the future challenges and prospects of atomic-scale observation of catalysts in understanding of heterogeneous catalysis. This Review focuses on the development of HP-STM and ETEM, the in situ/operando characterizations of catalyst structures with them, and the integration of the two structural analytical techniques for fundamentally understanding catalysis.

  8. Accelerating Strain-Promoted Azide-Alkyne Cycloaddition Using Micellar Catalysis.

    Science.gov (United States)

    Anderton, Grant I; Bangerter, Alyssa S; Davis, Tyson C; Feng, Zhiyuan; Furtak, Aric J; Larsen, Jared O; Scroggin, Triniti L; Heemstra, Jennifer M

    2015-08-19

    Bioorthogonal conjugation reactions such as strain-promoted azide-alkyne cycloaddition (SPAAC) have become increasingly popular in recent years, as they enable site-specific labeling of complex biomolecules. However, despite a number of improvements to cyclooctyne design, reaction rates for SPAAC remain significantly lower than those of the related copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. Here we explore micellar catalysis as a means to increase reaction rate between a cyclooctyne and hydrophobic azide. We find that anionic and cationic surfactants provide the most efficient catalysis, with rate enhancements of up to 179-fold for reaction of benzyl azide with DIBAC cyclooctyne. Additionally, we find that the presence of surfactant can provide up to 51-fold selectivity for reaction with a hydrophobic over hydrophilic azide. A more modest, but still substantial, 11-fold rate enhancement is observed for micellar catalysis of the reaction between benzyl azide and a DIBAC-functionalized DNA sequence, demonstrating that micellar catalysis can be successfully applied to hydrophilic biomolecules. Together, these results demonstrate that micellar catalysis can provide higher conjugation yields in reduced time when using hydrophobic SPAAC reagents.

  9. Sequence-regulated copolymers via tandem catalysis of living radical polymerization and in situ transesterification.

    Science.gov (United States)

    Nakatani, Kazuhiro; Ogura, Yusuke; Koda, Yuta; Terashima, Takaya; Sawamoto, Mitsuo

    2012-03-01

    Sequence regulation of monomers is undoubtedly a challenging issue as an ultimate goal in polymer science. To efficiently produce sequence-controlled copolymers, we herein developed the versatile tandem catalysis, which concurrently and/or sequentially involved ruthenium-catalyzed living radical polymerization and in situ transesterification of methacrylates (monomers: RMA) with metal alkoxides (catalysts) and alcohols (ROH). Typically, gradient copolymers were directly obtained from the synchronization of the two reactions: the instantaneous monomer composition in feed gradually changed via the transesterification of R(1)MA into R(2)MA in the presence of R(2)OH during living polymerization to give R(1)MA/R(2)MA gradient copolymers. The gradient sequence of monomers along a chain was catalytically controlled by the reaction conditions such as temperature, concentration and/or species of catalysts, alcohols, and monomers. The sequence regulation of multimonomer units was also successfully achieved in one-pot by monomer-selective transesterification in concurrent tandem catalysis and iterative tandem catalysis, providing random-gradient copolymers and gradient-block counterparts, respectively. In contrast, sequential tandem catalysis via the variable initiation of either polymerization or in situ transesterification led to random or block copolymers. Due to the versatile adaptability of common and commercially available reagents (monomers, alcohols, catalysts), this tandem catalysis is one of the most efficient, convenient, and powerful tools to design tailor-made sequence-regulated copolymers.

  10. Solar photo-catalysis to remove paper mill wastewater pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Amat, A.M.; Arques, A. [Departamento de Ingenieria Textil y Papelera, Universidad Politecnica de Valencia, EPSA-UPV, Paseo del Viaducto 1, E-03801 Alcoy (Spain); Lopez, F. [Departamento de Ingenieria Quimica y Nuclear, Universidad Politecnica de Valencia, EPSA-UPV, Paseo del Viaducto 1, E-03801 Alcoy (Spain); Miranda, M.A. [Departamento de Quimica, Instituto de Tecnologia Quimica, Universidad Politecnica de Valencia, UPV-CSIC, 46071 Valencia (Spain)

    2005-10-01

    Solar degradation of effluents in board paper industries has been studied using different photo-catalysts: Fenton reagent and TiO{sub 2}. p-Toluenesulfonic acid was chosen as a model compound for sulfonated pollutants already present in the incoming waters. The abatement of a 0.005M solution of this pollutant after 6h was found to be 47% for photo-Fenton and 27% for TiO{sub 2} (pseudo-first-order rate constants 0.002 and 0.001min{sup -1}, respectively). Eugenol and guaiacol were chosen as models for lignin degradation products. They were efficiently degraded by both photo-catalysts, and reaction rates were higher for eugenol (0.0024min{sup -1}) than for guaiacol (0.0018min{sup -1}). A solution of sodium acetate, sodium butyrate and d-glucose was chosen to study the effect of photo-catalysis towards volatile fatty acids and saccharides arising from starch degradation. In this case a clearly worse performance was observed: only 20% degradation was observed after 7h of treatment. When the real wastewater was treated with photo-catalytic methods, the best performance was obtained in closed circuits, when the COD values were higher. This fact can be explained by taking into account that closure of the circuits results in an accumulation of reluctant phenolic pollutants, while starch derivatives are continuously degraded by microorganisms in the circuits; as phenolic compounds are more easily degraded by photo-catalytic means, these methods are suitable for closed circuits. Finally, changes in the BOD{sub st} were determined by means of active sludges respirometry. A noticeable BOD{sub st} increase (30-50%) was observed in all cases, attributable to chemical oxidation of biodegradable species. (author)

  11. Mechanistic Insights into Homogeneous and Heterogeneous Asymmetric Iron Catalysis

    Science.gov (United States)

    Sonnenberg, Jessica

    Our group has been focused on replacing toxic and expensive precious metal catalysts with iron for the synthesis of enantiopure compounds for industrial applications. During an investigation into the mechanism of asymmetric transfer hydrogenation with our first generation iron-(P-N-N-P) catalysts we found substantial evidence for zero-valent iron nanoparticles coated in chiral ligand acting as the active site. Extensive experimental and computational experiments were undertaken which included NMR, DFT, reaction profile analysis, substoichiometric poisoning, electron microscope imaging, XPS and multiphasic analysis, all of which supported the fact that NPs were the active species in catalysis. Reversibility of this asymmetric reaction on the nanoparticle surface was then probed using oxidative kinetic resolution of racemic alcohols, yielding modest enantiopurity and high turnover frequencies (TOF) for a range of aromatic alcohols. Efficient dehydrogenation of ammonia-borane for hydrogen evolution and the formation of B-N oligomers was also shown using the NP system, yielding highly active systems, with a maximum TOF of 3.66 H2/s-1 . We have also begun to focus on the development of iron catalysts for asymmetric direct hydrogenation of ketones using hydrogen gas. New chiral iron-(P-N-P) catalysts were developed and shown to be quite active and selective for a wide range of substrates. Mechanistic investigations primarily using NMR and DFT indicated that a highly active trans-dihydride species was being formed during catalyst activation. Lastly, a new library of chiral P-N-P and P-NH-P ligands were developed, as well as their corresponding iron complexes, some of which show promise for the development of future generations of active asymmetric direct hydrogenation catalysts.

  12. Catalysis of acetoin formation by brewers' yeast pyruvate decarboxylase isozymes.

    Science.gov (United States)

    Stivers, J T; Washabaugh, M W

    1993-12-14

    Catalysis of C(alpha)-proton transfer from 2-(1-hydroxyethyl)thiamin diphosphate (HETDP) by pyruvate decarboxylase isozymes (PDC; EC 4.1.1.1) from Saccharomyces carlsbergensis was investigated by determining the steady-state kinetics of the reaction of [1-L]acetaldehyde (L = H, D, or T) to form acetoin and the primary kinetic isotope effects on the reaction. The PDC isozyme mixture and alpha 4 isozyme (alpha 4-PDC) have different steady-state kinetic parameters and isotope effects for acetoin formation in the presence and absence of the nonsubstrate allosteric effector pyruvamide: pyruvamide activation occurs by stabilization of the acetaldehyde/PDC ternary complex. The magnitudes of primary L(V/K)-type (L = D or T) isotope effects on C(alpha)-proton transfer from alpha 4-PDC-bound HETDP provide no evidence for significant breakdown of the Swain-Schaad relationship that would indicate partitioning of the putative C(alpha)-carbanion/enamine intermediate between HETDP and products. The substrate concentration dependence of the deuterium primary kinetic isotope effects provides evidence for an intrinsic isotope effect of 4.1 for C(alpha)-proton transfer from alpha 4-PDC-bound HETDP. A 1.10 +/- 0.02-fold 14C isotope discrimination against [1,2-14C]acetaldehyde in acetoin formation is inconsistent with a stepwise mechanism, in which the addition step occurs after rate-limiting formation of the C(alpha)-carbanion/enamine as a discrete enzyme-bound intermediate, and provides evidence for a concerted reaction mechanism with an important component of carbon-carbon bond formation in the transition state.

  13. State of Supported Nickel Nanoparticles during Catalysis in Aqueous Media

    Energy Technology Data Exchange (ETDEWEB)

    Chase, Zizwe; Kasakov, Stanislav; Shi, Hui; Vjunov, Aleksei; Fulton, John L.; Camaioni, Donald M.; Balasubramanian, Mahalingam; Zhao, Chen; Wang, Yong; Lercher, Johannes A.

    2015-11-09

    The state of Ni supported on HZSM-5 zeolite, silica, and sulfonated carbon was determined during aqueous phase catalysis of phenol hydrodeoxygenation using in situ extended X-ray absorption fine structure spectroscopy (EXAFS). On sulfonated carbon and HZSM-5 supports, the NiO and Ni(OH)2 were readily reduced to Ni(0) under reaction conditions (~35 bar H2 in aqueous phenol solutions containing up to 0.5 wt. % phosphoric acid at 473 K). On the silica support, less than 70% of the Ni was converted to Ni(0) under reaction conditions, which is attributed to the formation of Ni phyllosilicates. Over a broad range of reaction conditions there was no leaching of Ni from the supports. In contrast, rapid leaching of the Ni(II) from HZSM-5 was observed, when 15 wt. % aqueous acetic acid was substituted for the aqueous phenol solution. Once the metallic state of Ni was established there was no leaching in 15 wt. % acetic acid at 473 K and 35 bar H2. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), Division of Chemical Sciences, Geosciences & Biosciences. The STEM was supported under the Laboratory Directed Research and Development Program: Chemical Imaging Initiative at Pacific Northwest National Laboratory (PNNL), a multi-program national laboratory operated for DOE by Battelle under Contract DE-AC05-76RL01830. STEM was performed at EMSL, a DOE Office of Science user facility sponsored by the Office of Biological and Environmental Research and located at PNNL.

  14. Anti-DNA antibody mediated catalysis is isotype dependent.

    Science.gov (United States)

    Xia, Yumin; Eryilmaz, Ertan; Zhang, Qiuting; Cowburn, David; Putterman, Chaim

    2016-01-01

    Anti-DNA antibodies are the serological hallmark of systemic lupus erythematosus, and participate in the pathogenesis of lupus nephritis by cross-reacting with multiple renal antigens. Previously, using a panel of murine anti-DNA IgGs that share identical variable regions but that differ in the constant regions, we demonstrated that the cross-reaction and renal pathogenicity of anti-DNA antibodies are isotype dependent. In this study, we investigated the catalytic potential of this anti-DNA antibody panel, and determined its isotype dependency. The three isotype switch variants (IgG1, IgG2a, IgG2b) and the parent IgG3 PL9-11 anti-DNA antibodies were compared in their catalysis of 500 base pair linear double stranded DNA and a 12-mer peptide (ALWPPNLHAWVP), by gel analysis, MALDI-TOF mass spectrometry, and nuclear magnetic resonance spectroscopy. The binding affinity of anti-DNA antibodies to double stranded DNA and peptide antigens were assessed by ELISA and surface plasmon resonance. We found that the PL9-11 antibody isotypes vary significantly in their potential to catalyze the cleavage of both linear and double stranded DNA and the proteolysis of peptides. The degree of the cleavage and proteolysis increases with the incubation temperature and time. While different PL9-11 isotypes have the same initial attack sites within the ALWPPNLHAWVP peptide, there was no correlation between binding affinity to the peptide and proteolysis rates. In conclusion, the catalytic properties of anti-DNA antibodies are isotype dependent. This finding provides further evidence that antibodies that share the same variable region, but which have different constant regions, are functionally distinct. The catalytic effects modulated by antibody constant regions need to be considered in the design of therapeutic antibodies (abzymes) and peptides designed to block pathogenic autoantibodies.

  15. Supported Molten Metal Catalysis. A New Class of Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ravindra Datta; Ajeet Singh; Manuela Serban; Istvan Halasz

    2006-06-02

    We describe a new class of heterogeneous catalysts called supported molten metal catalysis (SMMC), in which molten metal catalysts are dispersed as nanodroplets on the surface of porous supports, allowing much larger active surface area than is possible in conventional contacting techniques for catalytic metals that are molten under reaction conditions, thus greatly enhancing their activity and potential utility. Specific examples of different types of reactions are provided to demonstrate the broad applicability of the technique in designing active, selective, and stable new catalysts. It is shown that dispersing the molten metal on a support in the suggested manner can enhance the rate of a reaction by three to four orders of magnitude as a result of the concomitant increase in the active surface area. New reaction examples include {gamma}-Al{sub 2}O{sub 3} supported molten Te (melting point 450 C) and Ga (MP 30 C) catalysts for bifunctional methylcyclohexane dehydrogenation. These catalysts provide activity similar to conventional Pt-based catalysts for this with better resistance to coking. In addition, results are described for a controlled pore glass supported molten In (MP 157 C) catalyst for the selective catalytic reduction of NO with ethanol in the presence of water, demonstrating activities superior to conventional catalysts for this reaction. A discussion is also provided on the characterization of the active surface area and dispersion of these novel supported catalysts. It is clear based on the results described that the development of new active and selective supported molten metal catalysts for practical applications is entirely plausible.

  16. RNA folding and catalysis mediated by iron (II.

    Directory of Open Access Journals (Sweden)

    Shreyas S Athavale

    Full Text Available Mg²⁺ shares a distinctive relationship with RNA, playing important and specific roles in the folding and function of essentially all large RNAs. Here we use theory and experiment to evaluate Fe²⁺ in the absence of free oxygen as a replacement for Mg²⁺ in RNA folding and catalysis. We describe both quantum mechanical calculations and experiments that suggest that the roles of Mg²⁺ in RNA folding and function can indeed be served by Fe²⁺. The results of quantum mechanical calculations show that the geometry of coordination of Fe²⁺ by RNA phosphates is similar to that of Mg²⁺. Chemical footprinting experiments suggest that the conformation of the Tetrahymena thermophila Group I intron P4-P6 domain RNA is conserved between complexes with Fe²⁺ or Mg²⁺. The catalytic activities of both the L1 ribozyme ligase, obtained previously by in vitro selection in the presence of Mg²⁺, and the hammerhead ribozyme are enhanced in the presence of Fe²⁺ compared to Mg²⁺. All chemical footprinting and ribozyme assays in the presence of Fe²⁺ were performed under anaerobic conditions. The primary motivation of this work is to understand RNA in plausible early earth conditions. Life originated during the early Archean Eon, characterized by a non-oxidative atmosphere and abundant soluble Fe²⁺. The combined biochemical and paleogeological data are consistent with a role for Fe²⁺ in an RNA World. RNA and Fe²⁺ could, in principle, support an array of RNA structures and catalytic functions more diverse than RNA with Mg²⁺ alone.

  17. State of Supported Pd during Catalysis in Water

    Energy Technology Data Exchange (ETDEWEB)

    Chase, Zizwe; Fulton, John L.; Camaioni, Donald M.; Mei, Donghai; Balasubramanian, Mahalingam; Pham, Van Thai; Zhao, Chen; Weber, Robert S.; Wang, Yong; Lercher, Johannes A.

    2013-08-29

    In operando X-ray absorption was used to measure the structure and chemical state of supported Pd nanoparticles with 3 -10 nm diameter in contact with H2 saturated water at 298-473 K. The Pd-Pd distances determined were consistent with the presence of subsurface hydrogen, i.e., longer than those measured by others for bare, reduced Pd particles, and within the range of distances for Pd hydrides. During the Pd-catalyzed hydrogenation of phenol, cyclohexanone, cyclohexanol or cyclohexene in the presence of water, the Pd nanoparticles exhibited a lengthening of the Pd-Pd bond that we attribute to a change in the concentration of sorbed H related to the steady state of H at the surface of the Pd particles. This steady state is established by all reactions involving H2, i.e., the sorption/desorption into the bulk, the sorption at the surface, and the reaction with adsorbed unsaturated reactants. Thus, first insight into the chemical state of Pd and the H/Pd ratio during catalysis in water is provided. The Pd particles did not change upon their exposure to water or reactants; nor did the spectra show any effect from the interaction of the Pd particles with various supports. The experimental results are consistent with ab initio molecular dynamic simulations, which indicate that Pd-water interactions are relatively weak for Pd metal and that these interactions become even weaker, when hydrogen is incorporated into the metal particles. This work was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences (BES), Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory is a multi-program national laboratory operated for DOE by Battelle through Contract DE-AC05-76RL01830.

  18. Hyperspectral sensing of forests

    Science.gov (United States)

    Goodenough, David G.; Dyk, Andrew; Chen, Hao; Hobart, Geordie; Niemann, K. Olaf; Richardson, Ash

    2007-11-01

    Canada contains 10% of the world's forests covering an area of 418 million hectares. The sustainable management of these forest resources has become increasingly complex. Hyperspectral remote sensing can provide a wealth of new and improved information products to resource managers to make more informed decisions. Research in this area has demonstrated that hyperspectral remote sensing can be used to create more accurate products for forest inventory, forest health, foliar biochemistry, biomass, and aboveground carbon than are currently available. This paper surveys recent methods and results in hyperspectral sensing of forests and describes space initiatives for hyperspectral sensing.

  19. Optical Remote Sensing Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Optical Remote Sensing Laboratory deploys rugged, cutting-edge electro-optical instrumentation for the collection of various event signatures, with expertise in...

  20. Intelligent environmental sensing

    CERN Document Server

    Mukhopadhyay, Subhas

    2015-01-01

    Developing environmental sensing and monitoring technologies become essential especially for industries that may cause severe contamination. Intelligent environmental sensing uses novel sensor techniques, intelligent signal and data processing algorithms, and wireless sensor networks to enhance environmental sensing and monitoring. It finds applications in many environmental problems such as oil and gas, water quality, and agriculture. This book addresses issues related to three main approaches to intelligent environmental sensing and discusses their latest technological developments. Key contents of the book include:   Agricultural monitoring Classification, detection, and estimation Data fusion Geological monitoring Motor monitoring Multi-sensor systems Oil reservoirs monitoring Sensor motes Water quality monitoring Wireless sensor network protocol  

  1. Advanced Remote Sensing Research

    Science.gov (United States)

    Slonecker, Terrence; Jones, John W.; Price, Susan D.; Hogan, Dianna

    2008-01-01

    'Remote sensing' is a generic term for monitoring techniques that collect information without being in physical contact with the object of study. Overhead imagery from aircraft and satellite sensors provides the most common form of remotely sensed data and records the interaction of electromagnetic energy (usually visible light) with matter, such as the Earth's surface. Remotely sensed data are fundamental to geographic science. The Eastern Geographic Science Center (EGSC) of the U.S. Geological Survey (USGS) is currently conducting and promoting the research and development of three different aspects of remote sensing science: spectral analysis, automated orthorectification of historical imagery, and long wave infrared (LWIR) polarimetric imagery (PI).

  2. A competitive and reversible deactivation approach to catalysis-based quantitative assays.

    Science.gov (United States)

    Koide, Kazunori; Tracey, Matthew P; Bu, Xiaodong; Jo, Junyong; Williams, Michael J; Welch, Christopher J

    2016-01-01

    Catalysis-based signal amplification makes optical assays highly sensitive and widely useful in chemical and biochemical research. However, assays must be fine-tuned to avoid signal saturation, substrate depletion and nonlinear performance. Furthermore, once stopped, such assays cannot be restarted, limiting the dynamic range to two orders of magnitude with respect to analyte concentrations. In addition, abundant analytes are difficult to quantify under catalytic conditions due to rapid signal saturation. Herein, we report an approach in which a catalytic reaction competes with a concomitant inactivation of the catalyst or consumption of a reagent required for signal generation. As such, signal generation proceeds for a limited time, then autonomously and reversibly stalls. In two catalysis-based assays, we demonstrate restarting autonomously stalled reactions, enabling accurate measurement over five orders of magnitude, including analyte levels above substrate concentration. This indicates that the dynamic range of catalysis-based assays can be significantly broadened through competitive and reversible deactivation. PMID:26891765

  3. Trends in heterogeneous catalysis and their applications in process engineering (abstract)

    International Nuclear Information System (INIS)

    Interest in heterogeneous catalysis has increased dramatically in the last decade. The extent of interest in this and related field can be accessed from the newly coined terms like, semi-heterogeneous catalysis, for the processes and mechanisms that are amalgam of homogeneous and heterogeneous catalysis. Whereas the progresses made I the area of science and technology of nano materials has provided the main impetus, the innovative processing of carbon nano tubes has added to potential applications in process engineering and consumer applications. The graphene based catalysts are yet another emerging class of catalysts with huge potential. This technical review summarizes the developments made in the area of material developments, a better understanding of processes involved and role of computational chemistry in the recent achievements. The emerging applications in the areas of process engineering have also been discussed. (author)

  4. Converting Homogeneous to Heterogeneous in Electrophilic Catalysis using Monodisperse Metal Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Witham, Cole A.; Huang, Wenyu; Tsung, Chia-Kuang; Kuhn, John N.; Somorjai, Gabor A.; Toste, F. Dean

    2009-10-15

    A continuing goal in catalysis is the transformation of processes from homogeneous to heterogeneous. To this end, nanoparticles represent a new frontier in heterogeneous catalysis, where this conversion is supplemented by the ability to obtain new or divergent reactivity and selectivity. We report a novel method for applying heterogeneous catalysts to known homogeneous catalytic reactions through the design and synthesis of electrophilic platinum nanoparticles. These nanoparticles are selectively oxidized by the hypervalent iodine species PhICl{sub 2}, and catalyze a range of {pi}-bond activation reactions previously only homogeneously catalyzed. Multiple experimental methods are utilized to unambiguously verify the heterogeneity of the catalytic process. The discovery of treatments for nanoparticles that induce the desired homogeneous catalytic activity should lead to the further development of reactions previously inaccessible in heterogeneous catalysis. Furthermore, our size and capping agent study revealed that Pt PAMAM dendrimer-capped nanoparticles demonstrate superior activity and recyclability compared to larger, polymer-capped analogues.

  5. Direct asymmetric vinylogous Michael addition of cyclic enones to nitroalkenes via dienamine catalysis

    Science.gov (United States)

    Bencivenni, Giorgio; Galzerano, Patrizia; Mazzanti, Andrea; Bartoli, Giuseppe; Melchiorre, Paolo

    2010-01-01

    In spite of the many catalytic methodologies available for the asymmetric functionalization of carbonyl compounds at their α and β positions, little progress has been achieved in the enantioselective carbon–carbon bond formation γ to a carbonyl group. Here, we show that primary amine catalysis provides an efficient way to address this synthetic issue, promoting vinylogous nucleophilicity upon selective activation of unmodified cyclic α,β-unsaturated ketones. Specifically, we document the development of the unprecedented direct and vinylogous Michael addition of β-substituted cyclohexenone derivatives to nitroalkenes proceeding under dienamine catalysis. Besides enforcing high levels of diastereo- and enantioselectivity, chiral primary amine catalysts derived from natural cinchona alkaloids ensure complete γ-site selectivity: The resulting, highly functionalized vinylogous Michael adducts, having two stereocenters at the γ and δ positions, are synthesized with very high fidelity. Finally, we describe the extension of the dienamine catalysis-induced vinylogous nucleophilicity to the asymmetric γ-amination of cyclohexene carbaldehyde. PMID:20566884

  6. A new class of PN3-pincer ligands for metal–ligand cooperative catalysis

    KAUST Repository

    Li, Huaifeng

    2014-12-01

    Work on a new class of PN3-pincer ligands for metal-ligand cooperative catalysis is reviewed. While the field of the pyridine-based PN3-transition metal pincer complexes is still relatively young, many important applications of these complexes have already emerged. In several cases, the PN3-pincer complexes for metal-ligand cooperative catalysis result in significantly improved or unprecedented activities. The synthesis and coordination chemistry of PN3-pincer ligands are briefly summarized first to cover the synthetic routes for their preparation, followed by a focus review on their applications in catalysis. A specific emphasis is placed on the later section about the role of PN3-pincer ligands\\' dearomatization-rearomatization steps during the catalytic cycles. The mechanistic insights from density functional theory (DFT) calculations are also discussed.

  7. Cheese whey protein recovery by ultrafiltration through transglutaminase (TG) catalysis whey protein cross-linking.

    Science.gov (United States)

    Wen-Qiong, Wang; Lan-Wei, Zhang; Xue, Han; Yi, Lu

    2017-01-15

    In whey ultrafiltration (UF) production, two main problems are whey protein recovery and membrane fouling. In this study, membrane coupling protein transglutaminase (TG) catalysis protein cross-linking was investigated under different conditions to find out the best treatment. We found that the optimal conditions for protein recovery involved catalyzing whey protein cross-linking with TG (40U/g whey proteins) at 40°C for 60min at pH 5.0. Under these conditions, the recovery rate was increased 15-20%, lactose rejection rate was decreased by 10%, and relative permeate flux was increase 30-40% compared to the sample without enzyme treatment (control). It was noticeable that the total resistance and cake resistance were decreased after enzyme catalysis. This was mainly due to the increased particle size and decreased zeta potential. Therefore, membrane coupling enzyme catalysis protein cross-linking is a potential means for further use. PMID:27542447

  8. Asymmetric Anion-π Catalysis: Enamine Addition to Nitroolefins on π-Acidic Surfaces.

    Science.gov (United States)

    Zhao, Yingjie; Cotelle, Yoann; Avestro, Alyssa-Jennifer; Sakai, Naomi; Matile, Stefan

    2015-09-16

    Here we provide experimental evidence for anion-π catalysis of enamine chemistry and for asymmetric anion-π catalysis. A proline for enamine formation on one side and a glutamic acid for nitronate protonation on the other side are placed to make the enamine addition to nitroolefins occur on the aromatic surface of π-acidic naphthalenediimides. With increasing π acidity of the formally trifunctional catalysts, rate and enantioselectivity of the reaction increase. Mismatched and more flexible controls reveal that the importance of rigidified, precisely sculpted architectures increases with increasing π acidity as well. The absolute configuration of stereogenic sulfoxide acceptors at the edge of the π-acidic surface has a profound influence on asymmetric anion-π catalysis and, if perfectly matched, affords the highest enantio- and diastereoselectivity.

  9. 2010 CATALYSIS GORDON RESEARCH CONFERENCE, JUNE 27 - JULY 2, 2010, NEW LONDON, NEW HAMPSHIRE

    Energy Technology Data Exchange (ETDEWEB)

    Abhaya Datye

    2010-07-02

    Catalysis is a key technology for improving the quality of life while simultaneously reducing the adverse impact of human activities on the environment. The discovery of new catalytic processes and the improvement of existing ones are also critically important for securing the nation's energy supply. The GRC on Catalysis is considered one the most prestigious conference for catalysis research, bringing together leading researchers from both academia, industry and national labs to discuss the latest, most exciting research in catalysis and the future directions for the field. The 2010 GRC on Catalysis will follow time-honored traditions and feature invited talks from the world's leading experts in the fundamentals and applications of catalytic science and technology. We plan to have increased participation from industry. The extended discussions in the company of outstanding thinkers will stimulate and foster new science. The conference will include talks in the following areas: Alternative feedstocks for chemicals and fuels, Imaging and spectroscopy, Design of novel catalysts, Catalyst preparation fundamentals, Molecular insights through theory, Surface Science, Catalyst stability and dynamics. In 2010, the Catalysis conference will move to a larger conference room with a new poster session area that will allow 40 posters per session. The dorm rooms provide single and double accommodations, free WiFi and the registration fee includes all meals and the famous lobster dinner on Thursday night. Afternoons are open to enjoy the New England ambiance with opportunities for hiking, sailing, golf and tennis to create an outstanding conference that will help you network with colleagues, and make long lasting connections.

  10. Micromechanics senses biomolecules

    Directory of Open Access Journals (Sweden)

    Roberto Raiteri

    2002-01-01

    Cantilever sensors rely on relatively well known and simple transduction principles, and have attracted the interest of many researchers. This is, at least in part, because of the merging of silicon microfabrication techniques and surface functionalization biochemistry, together with the development of multi-cantilever sensing methods offering new opportunities in physical and (biochemical sensing.

  11. Hyperspectral remote sensing

    CERN Document Server

    Eismann, Michael

    2012-01-01

    Hyperspectral remote sensing is an emerging, multidisciplinary field with diverse applications that builds on the principles of material spectroscopy, radiative transfer, imaging spectrometry, and hyperspectral data processing. This book provides a holistic treatment that captures its multidisciplinary nature, emphasizing the physical principles of hyperspectral remote sensing.

  12. Sense and Sensibility

    NARCIS (Netherlands)

    Austen, Jane

    2005-01-01

    Two sisters of opposing temperament but who share the pangs of tragic love provide the subjects for Sense and Sensibility. Elinor, practical and conventional, the epitome of sense, desires a man who is promised to another woman. Marianne, emotional and sentimental, the epitome of sensibility, loses

  13. Land Remote Sensing Overview

    Science.gov (United States)

    Byrnes, Ray

    2007-01-01

    A general overview of the USGS land remote sensing program is presented. The contents include: 1) Brief overview of USGS land remote sensing program; 2) Highlights of JACIE work at USGS; 3) Update on NASA/USGS Landsat Data Continuity Mission; and 4) Notes on alternative data sources.

  14. Orphan drugs

    Directory of Open Access Journals (Sweden)

    Goločorbin-Kon Svetlana

    2013-01-01

    Full Text Available Introduction. Drugs used for treatment of rare diseases are known worldwide under the term of orphan drugs because pharmaceutical companies have not been interested in ”adopting” them, that is in investing in research, developing and producing these drugs. This kind of policy has been justified by the fact that these drugs are targeted for small markets, that only a small number of patients is available for clinical trials, and that large investments are required for the development of drugs meant to treat diseases whose pathogenesis has not yet been clarified in majority of cases. The aim of this paper is to present previous and present status of orphan drugs in Serbia and other countries. The beginning of orphan drugs development. This problem was first recognized by Congress of the United States of America in January 1983, and when the ”Orphan Drug Act” was passed, it was a turning point in the development of orphan drugs. This law provides pharmaceutical companies with a series of reliefs, both financial ones that allow them to regain funds invested into the research and development and regulatory ones. Seven years of marketing exclusivity, as a type of patent monopoly, is the most important relief that enables companies to make large profits. Conclusion. There are no sufficient funds and institutions to give financial support to the patients. It is therefore necessary to make health professionals much more aware of rare diseases in order to avoid time loss in making the right diagnosis and thus to gain more time to treat rare diseases. The importance of discovery, development and production of orphan drugs lies in the number of patients whose life quality can be improved significantly by administration of these drugs as well as in the number of potential survivals resulting from the treatment with these drugs. [Projekat Ministarstva nauke Republike Srbije, br. III 41012

  15. Study Drugs

    Science.gov (United States)

    ... messages back and forth by releasing chemicals called neurotransmitters. Prescription stimulants have chemical structures that are similar to some neurotransmitters. When someone takes them, the drugs boost the ...

  16. Remote sensing; Fernerkundung

    Energy Technology Data Exchange (ETDEWEB)

    Glaessler, C.

    2001-07-01

    The potential of different multitemporal and multispectral airborne and spaceborne remote sensing methods for assessment and monitoring of the lignite open-cast mining areas are discussed in this chapter. Emphasis is placed on the successful use of different remote sensing data in variable vegetation structures for dumped sediments with different mineralogical and geochemical properties and for hydrochemical properties of the residual lakes. Multiple remote sensing data are a cost and time efficient tool for the assessment of environmental impacts, supervising of reclamation activities as well as for long term monitoring of the mining area. The airborne data are well suited for large scale detailed research and mapping in smaller sites and the satellite data for the overview scale 1:50 000. An integrated remote sensing-GIS-system including all field and lab data, DTM and other graphical data, improve the results of the remote sensing data classification for the lignite mining region in Central Germany and the Lausitz. (orig.)

  17. Sensing land pollution.

    Science.gov (United States)

    Bowden, L. W.

    1971-01-01

    Land pollution is described in numerous ways by various societies. Pollutants of land are material by-products of human activity and range from environmentally ineffective to positively toxic. The pollution of land by man is centuries old and correlates directly with economy, technology and population. In order to remotely sense land pollution, standards or thresholds must be established. Examples of the potential for sensing land pollution and quality are presented. The technological capabilities for remotely sensed land quality is far advanced over the judgment on how to use the sensed data. Until authoritative and directive decisions on land pollution policy are made, sensing of pollutants will be a random, local and academic affair.

  18. Plastids and gravitropic sensing

    Science.gov (United States)

    Sack, F. D.

    1997-01-01

    Data and theories about the identity of the mass that acts in gravitropic sensing are reviewed. Gravity sensing may have evolved several times in plants and algae in processes such as gravitropism of organs and tip-growing cells, gravimorphism, gravitaxis, and the regulation of cytoplasmic streaming in internodal cells of Chara. In the latter and in gravitaxis, the mass of the entire cell may function in sensing. But gravitropic sensing appears to rely upon the mass of amyloplasts that sediment since (i) the location of cells with sedimentation is highly regulated, (ii) such cells contain other morphological specializations favoring sedimentation, (iii) sedimentation always correlates with gravitropic competence in wild-type plants, (iv) magnetophoretic movement of rootcap amyloplasts mimics gravitropism, and (v) starchless and intermediate starch mutants show reduced gravitropic sensitivity. The simplest interpretation of these data is that gravitropic sensing is plastid-based.

  19. Combined heterogeneous metal/chiral amine: multiple relay catalysis for versatile eco-friendly synthesis.

    Science.gov (United States)

    Deiana, Luca; Jiang, Yan; Palo-Nieto, Carlos; Afewerki, Samson; Incerti-Pradillos, Celia A; Verho, Oscar; Tai, Cheuk-Wai; Johnston, Eric V; Córdova, Armando

    2014-03-24

    Herein is described a versatile and broad synergistic strategy for expansion of chemical space and the synthesis of valuable molecules (e.g. carbocycles and heterocycles), with up to three quaternary stereocenters, in a highly enantioselective fashion from simple alcohols (31 examples, 95:5 to >99.5:0.5 e.r.) using integrated heterogeneous metal/chiral amine multiple relay catalysis and air/O₂ as the terminal oxidant. A novel highly 1,4-selective heterogeneous metal/amine co-catalyzed hydrogenation of enals was also added to the relay catalysis sequences. PMID:24677482

  20. Neutral tridentate PNP ligands and their hybrid analogues: versatile non-innocent scaffolds for homogeneous catalysis.

    Science.gov (United States)

    van der Vlugt, Jarl Ivar; Reek, Joost N H

    2009-01-01

    Ligands in coordination chemistry and homogeneous catalysis are traditionally "static" spectators that do not actively participate in the catalytic cycle. However, such classic systems do not provide additional "handles" that could facilitate or trigger alternative productive reaction pathways. Recent advances in the use of novel nitrogen-centered pincer systems have unveiled interesting opportunities for cooperative catalysis. The chemistry of pyridine-derived, neutral ligands is discussed, with a specific focus on their non-innocent behavior and potential as facilitators for metal-mediated organic transformations. This overview should provide inspiration and an incentive to incorporate non-innocent ligands and their metal complexes within old and new homogeneously catalyzed reactions.

  1. Combination of organotrifluoroborates with photoredox catalysis marking a new phase in organic radical chemistry.

    Science.gov (United States)

    Koike, Takashi; Akita, Munetaka

    2016-08-01

    Combination of organotrifluoroborates and visible-light-driven photoredox catalysis, both of which have attracted the attention of synthetic chemists, marks a new phase in the field of organic radical chemistry. We have developed photoredox-catalyzed radical reactions with organotrifluoroborates, which turn out to serve not only as a source of organic radicals but also as radical acceptors. The first part of this Perspective deals with the generation of organic radicals from organotrifluoroborates, and the latter part describes addition of the CF3 radical to alkenyltrifluoroborates. The good chemistry between organoborates and photoredox catalysis and its future will be discussed.

  2. Growth mechanism of graphene on platinum: Surface catalysis and carbon segregation

    International Nuclear Information System (INIS)

    A model of the graphene growth mechanism of chemical vapor deposition on platinum is proposed and verified by experiments. Surface catalysis and carbon segregation occur, respectively, at high and low temperatures in the process, representing the so-called balance and segregation regimes. Catalysis leads to self-limiting formation of large area monolayer graphene, whereas segregation results in multilayers, which evidently “grow from below.” By controlling kinetic factors, dominantly monolayer graphene whose high quality has been confirmed by quantum Hall measurement can be deposited on platinum with hydrogen-rich environment, quench cooling, tiny but continuous methane flow and about 1000 °C growth temperature

  3. Visible-Light-Promoted Trifluoromethylthiolation of Styrenes by Dual Photoredox/Halide Catalysis.

    Science.gov (United States)

    Honeker, Roman; Garza-Sanchez, R Aleyda; Hopkinson, Matthew N; Glorius, Frank

    2016-03-18

    Herein, we report a new visible-light-promoted strategy to access radical trifluoromethylthiolation reactions by combining halide and photoredox catalysis. This approach allows for the synthesis of vinyl-SCF3 compounds of relevance in pharmaceutical chemistry directly from alkenes under mild conditions with irradiation from household light sources. Furthermore, alkyl-SCF3-containing cyclic ketone and oxindole derivatives can be accessed by radical-polar crossover semi-pinacol and cyclization processes. Inexpensive halide salts play a crucial role in activating the trifluoromethylthiolating reagent towards photoredox catalysis and aid the formation of the SCF3 radical.

  4. Dual Hypervalent Iodine(III) Reagents and Photoredox Catalysis Enable Decarboxylative Ynonylation under Mild Conditions.

    Science.gov (United States)

    Huang, Hanchu; Zhang, Guojin; Chen, Yiyun

    2015-06-26

    A combination of hypervalent iodine(III) reagents (HIR) and photoredox catalysis with visible light has enabled chemoselective decarboxylative ynonylation to construct ynones, ynamides, and ynoates. This ynonylation occurs effectively under mild reaction conditions at room temperature and on substrates with various sensitive and reactive functional groups. The reaction represents the first HIR/photoredox dual catalysis to form acyl radicals from α-ketoacids, followed by an unprecedented acyl radical addition to HIR-bound alkynes. Its efficient construction of an mGlu5 receptor inhibitor under neutral aqueous conditions suggests future visible-light-induced biological applications.

  5. Combination of organotrifluoroborates with photoredox catalysis marking a new phase in organic radical chemistry.

    Science.gov (United States)

    Koike, Takashi; Akita, Munetaka

    2016-08-01

    Combination of organotrifluoroborates and visible-light-driven photoredox catalysis, both of which have attracted the attention of synthetic chemists, marks a new phase in the field of organic radical chemistry. We have developed photoredox-catalyzed radical reactions with organotrifluoroborates, which turn out to serve not only as a source of organic radicals but also as radical acceptors. The first part of this Perspective deals with the generation of organic radicals from organotrifluoroborates, and the latter part describes addition of the CF3 radical to alkenyltrifluoroborates. The good chemistry between organoborates and photoredox catalysis and its future will be discussed. PMID:27282517

  6. Catalysis by Design Using Surface Organometallic Nitrogen-Containing Fragments

    KAUST Repository

    Hamzaoui, Bilel

    2016-06-14

    The aim of this thesis is to explore the chemistry of well-defined silica-supported group 4 and group 5 complexes that contain one or more multiply-bonded nitrogen atoms. Such species have been recognized as crucial intermediates in many catalytic reactions (e.g. hydroaminoalkylation, olefin hydrogenation, imine metathesis…). The first chapter provided a bibliographic overview of the preparation and the reactivity of group 4 and 5 complexes towards hydroaminoalkylation and imine metathesis catalysis. The second chapter deals with the isolation and the characterization of a series of well-defined group 4 ƞ2-imine complexes surfaces species. 2D solid-state NMR (1H–13C HETCOR, Multiple Quantum) experiments have revealed consistently a unique structural rearrangement, viz azametallacycle occurring on the immobilized metal-amido ligands. Hydrogenolysis of the sole Zr-C bond in such species gives selectively a silica-supported zirconium monohydride that can perform the catalytic hydrogenation of olefins. The third chapter examines the mechanistic studies of the intermolecular hydroaminoalkylation using SOMC to identify the key metallacyclic surface intermediates (silica-supported three-membred and five-membered). The catalyst was regenerated by protonolysis and afforded pure amine. Catalytic testing of a selection of amine compounds with variable electronic properties was carried out. The fourth chapter deals with the generation and the characterization of well-defined silica-supported zirconium-imido complexes. The resulting species effectively catalyzes imine/imine cross-metathesis and thus considered as the first heterogeneous catalysts active for imine metathesis reaction. The fifth chapter studies the reaction of SBA15.1100 ºC with dry aniline and derivatives leading to opening strained siloxane bridges into acid-base paired functionalities (formation of N-phenylsilanamine-silanol pairs). This approach was successfully applied to the design of a series of

  7. Catalysis applications of size-selected cluster deposition.

    Energy Technology Data Exchange (ETDEWEB)

    Vajda, Stefan; White, Michael G.

    2015-12-01

    In this Perspective, we review recent studies of size-selected cluster deposition for catalysis applications performed at the U.S. DOE National Laboratories, with emphasis on work at Argonne National Laboratory (ANL) and Brookhaven National Laboratory (BNL). The focus is on the preparation of model supported catalysts in which the number of atoms in the deposited clusters is precisely controlled using a combination of gas-phase cluster ion sources, mass spectrometry, and soft-landing techniques. This approach is particularly effective for investigations of small nanoclusters, 0.5-2 nm (<200 atoms), where the rapid evolution of the atomic and electronic structure makes it essential to have precise control over cluster size. Cluster deposition allows for independent control of cluster size, coverage, and stoichiometry (e.g., the metal-to-oxygen ratio in an oxide cluster) and can be used to deposit on any substrate without constraints of nucleation and growth. Examples are presented for metal, metal oxide, and metal sulfide cluster deposition on a variety of supports (metals, oxides, carbon/diamond) where the reactivity, cluster-support electronic interactions, and cluster stability and morphology are investigated. Both UHV and in situ/operando studies are presented that also make use of surface-sensitive X-ray characterization tools from synchrotron radiation facilities. Novel applications of cluster deposition to electrochemistry and batteries are also presented. This review also highlights the application of modern ab initio electronic structure calculations (density functional theory), which can essentially model the exact experimental system used in the laboratory (i.e., cluster and support) to provide insight on atomic and electronic structure, reaction energetics, and mechanisms. As amply demonstrated in this review, the powerful combination of atomically precise cluster deposition and theory is able to address fundamental aspects of size-effects, cluster

  8. Porous metal-organic frameworks for heterogeneous biomimetic catalysis.

    Science.gov (United States)

    Zhao, Min; Ou, Sha; Wu, Chuan-De

    2014-04-15

    Metalloporphyrins are the active sites in monooxygenases that oxidize a variety of substrates efficiently and under mild conditions. Researchers have developed artificial metalloporphyrins, but these structures have had limited catalytic applications. Homogeneous artificial metalloporphyrins can undergo catalytic deactivation via suicidal self-oxidation, which lowers their catalytic activity and sustainability relative to their counterparts in Nature. Heme molecules in protein scaffolds can maintain high efficiency over numerous catalytic cycles. Therefore, we wondered if immobilizing metalloporphyrin moieties within porous metal-organic frameworks (MOFs) could stabilize these structures and facilitate the molecular recognition of substrates and produce highly efficient biomimetic catalysis. In this Account, we describe our research to develop multifunctional porphyrinic frameworks as highly efficient heterogeneous biomimetic catalysts. Our studies indicate that porous porphyrinic frameworks provide an excellent platform for mimicking the activity of biocatalysts and developing new heterogeneous catalysts that effect new chemical transformations under mild conditions. The porous structures and framework topologies of the porphyrinic frameworks depend on the configurations, coordination donors, and porphyrin metal ions of the metalloporphyrin moieties. To improve the activity of porous porphyrinic frameworks, we have developed a two-step synthesis that introduces the functional polyoxometalates (POMs) into POM-porphyrin hybrid materials. To tune the pore structures and the catalytic properties of porphyrinic frameworks, we have designed metalloporphyrin M-H8OCPP ligands with four m-benzenedicarboxylate moieties, and introduced the secondary auxiliary ligands. The porphyrin metal ions and the secondary functional moieties that are incorporated into porous metal-organic frameworks greatly influence the catalytic properties and activities of porphyrinic frameworks in

  9. Learning Word Sense Embeddings from Word Sense Definitions

    OpenAIRE

    Li, Qi; Li, Tianshi; Chang, Baobao

    2016-01-01

    Word embeddings play a significant role in many modern NLP systems. Since learning one representation per word is problematic for polysemous words and homonymous words, researchers propose to use one embedding per word sense. Their approaches mainly train word sense embeddings on a corpus. In this paper, we propose to use word sense definitions to learn one embedding per word sense. Experimental results on word similarity tasks and word sense disambiguation task show that word sense embedding...

  10. Drug Interactions

    Science.gov (United States)

    ... WITH HIV MEDICATIONS? Protease inhibitors and non-nucleoside reverse transcriptase inhibitors are processed by the liver and cause many ... taken with any protease inhibitor or non-nucleoside reverse transcriptase inhibitor. You can also check for drug-drug and ...

  11. Drug treatment

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    2010263 Drug resistance mechanism of non-small cell lung cancer PC9/AB2 cell line with acquired drug resistance to gefitinib.JU Lixia(鞠立霞),et al. Dept Oncol,Shanghai Pulm Hosp,Tongji Univ,Shanghai 200433. Chin J Tuberc Respir Dis 2010;33(5):354-358. Objective To

  12. Taille des particules et catalyse Particle Size and Catalysis

    Directory of Open Access Journals (Sweden)

    Boitiaux J. P.

    2006-11-01

    hydrogène pouvaient tout à fait rendre compte des phénomènes observés. En plus de cela un métal déposé sur silice et un métal déposé sur alumine peuvent se comporter de façon tout à fait différente. Tout ceci montre que certaines interprétations sont trop simplistes et que faire varier la taille des particules par n'importe quel moyen et étudier les conséquences sur l'acte catalytique n'est pas suffisant. Les deux approches complémentaires, celle du cristallographe qui tente de décrire les petites particules à partir des paramètres du métal massique et celle du chimiste qui tente de déduire la structure du comportement du catalyseur observé dans la réaction étudiée, n'arrivent pas vraiment à se rejoindre pour aboutir à une description en tout point acceptable de la structure de la particule. D'un côté le physico-chimiste utilise des simplifications outrancières lorsqu'il tente de décrire ses structures grâce à l'usage de fonctions d'état qui n'ont pas toujours des solutions évidentes. D'un autre le chimiste manipule des objets réels mais arrive difficilement à isoler le paramètre qu'il veut étudier. Ses conclusions ne sont jamais à l'abri des artefacts apportés par les conditions opératoires ou les effets de support. Ce dilemme existe aussi pour le physicien qui tente de synthétiser des agrégats bien définis dans un flux gazeux mais loin de la réalité de la catalyse. De même pour le chimiste qui veut ramener les effets de structure à de simples comparaisons entre les faces exposées par les monocristaux. Néanmoins l'apport des deux est indispensable car ils donnent des idées directrices indispensables pour l'homme de catalyse qui tente de maîtriser l'ensemble des paramètres. While heterogeneous catalysis, and especially catalysis by metals, is concerned with the size of the particles and hence with the developed surface area, this is not only to prepare an effective product at minimum cost. The study of the

  13. Lean NOx Trap Catalysis for Lean Natural Gas Engine Applications

    Energy Technology Data Exchange (ETDEWEB)

    Parks, II, James E [ORNL; Storey, John Morse [ORNL; Theiss, Timothy J [ORNL; Ponnusamy, Senthil [ORNL; Ferguson, Harley Douglas [ORNL; Williams, Aaron M [ORNL; Tassitano, James B [ORNL

    2007-09-01

    efficiency and emissions of natural gas reciprocating engines are being pursued. Approaches include: stoichiometric engine operation with exhaust gas recirculation and three-way catalysis, advanced combustion modes such as homogeneous charge compression ignition, and extension of the lean combustion limit with advanced ignition concepts and/or hydrogen mixing. The research presented here addresses the technical approach of combining efficient lean spark-ignited natural gas combustion with low emissions obtained from a lean NOx trap catalyst aftertreatment system. This approach can be applied to current lean engine technology or advanced lean engines that may result from related efforts in lean limit extension. Furthermore, the lean NOx trap technology has synergy with hydrogen-assisted lean limit extension since hydrogen is produced from natural gas during the lean NOx trap catalyst system process. The approach is also applicable to other lean engines such as diesel engines, natural gas turbines, and lean gasoline engines; other research activities have focused on those applications. Some commercialization of the technology has occurred for automotive applications (both diesel and lean gasoline engine vehicles) and natural gas turbines for stationary power. The research here specifically addresses barriers to commercialization of the technology for large lean natural gas reciprocating engines for stationary power. The report presented here is a comprehensive collection of research conducted by Oak Ridge National Laboratory (ORNL) on lean NOx trap catalysis for lean natural gas reciprocating engines. The research was performed in the Department of Energy's ARES program from 2003 to 2007 and covers several aspects of the technology. All studies were conducted at ORNL on a Cummins C8.3G+ natural gas engine chosen based on industry input to simulate large lean natural gas engines. Specific technical areas addressed by the research include: NOx reduction efficiency, partial

  14. The sense of agency

    DEFF Research Database (Denmark)

    Ritterband-Rosenbaum, Anina

    investigate the sense of agency. The central aspect of the thesis work was to understand if brain lesioned children, diagnosed with hemiplegic Cerebral Palsy (CP), have an altered sense of agency, and if this different experience has an influence on the feeling of control of their movements and their actual...... of their own movements. However this perception can be optimized by intensive training. More research has to be carried out to investigate if the sense of agency should be a greater part of rehabilitation for brain lesioned patients in order to improve functionality....

  15. Compressed sensing & sparse filtering

    CERN Document Server

    Carmi, Avishy Y; Godsill, Simon J

    2013-01-01

    This book is aimed at presenting concepts, methods and algorithms ableto cope with undersampled and limited data. One such trend that recently gained popularity and to some extent revolutionised signal processing is compressed sensing. Compressed sensing builds upon the observation that many signals in nature are nearly sparse (or compressible, as they are normally referred to) in some domain, and consequently they can be reconstructed to within high accuracy from far fewer observations than traditionally held to be necessary. Apart from compressed sensing this book contains other related app

  16. Formal kinetics of heterogeneous catalysis and absorption treatment of compound solutions

    International Nuclear Information System (INIS)

    Approach creation of a tool for analyzing and estimating sorption processes for treating compound solutions of radioactively contaminated waters (RCW), based on formalization of heterogeneous catalysis kinetics mechanism for small volume level, is seen. It is the first work of series devoted to development of high-tech RCW treatment systems, and, in particular, liquid radwaste management

  17. Chemistry, spectroscopy and the role of supported vanadium oxides in heterogeneous catalysis

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Keller, D.E.

    2003-01-01

    Supported vanadium oxide catalysts are active in a wide range of applications. In this review, an overview is given of the current knowledge available about vanadium oxide-based catalysts. The review starts with the importance of vanadium in heterogeneous catalysis, a discussion of the molecular str

  18. Appreciating Formal Similarities in the Kinetics of Homogeneous, Heterogeneous, and Enzyme Catalysis

    Science.gov (United States)

    Ashby, Michael T.

    2007-01-01

    Because interest in catalysts is widespread, the kinetics of catalytic reactions have been investigated by widely diverse groups of individuals, including chemists, engineers, and biologists. This has lead to redundancy in theories, particularly with regard to the topics of homogeneous, heterogeneous, and enzyme catalysis. From a pedagogical…

  19. Nanoparticles as recyclable catalysts: the frontier between homogeneous and heterogeneous catalysis.

    Science.gov (United States)

    Astruc, Didier; Lu, Feng; Aranzaes, Jaime Ruiz

    2005-12-01

    Interest in catalysis by metal nanoparticles (NPs) is increasing dramatically, as reflected by the large number of publications in the last five years. This field, "semi-heterogeneous catalysis", is at the frontier between homogeneous and heterogeneous catalysis, and progress has been made in the efficiency and selectivity of reactions and recovery and recyclability of the catalytic materials. Usually NP catalysts are prepared from a metal salt, a reducing agent, and a stabilizer and are supported on an oxide, charcoal, or a zeolite. Besides the polymers and oxides that used to be employed as standard, innovative stabilizers, media, and supports have appeared, such as dendrimers, specific ligands, ionic liquids, surfactants, membranes, carbon nanotubes, and a variety of oxides. Ligand-free procedures have provided remarkable results with extremely low metal loading. The Review presents the recent developments and the use of NP catalysis in organic synthesis, for example, in hydrogenation and C--C coupling reactions, and the heterogeneous oxidation of CO on gold NPs.

  20. Cascade catalysis for the homogeneous hydrogenation of CO2 to methanol.

    Science.gov (United States)

    Huff, Chelsea A; Sanford, Melanie S

    2011-11-16

    This communication demonstrates the homogeneous hydrogenation of CO(2) to CH(3)OH via cascade catalysis. Three different homogeneous catalysts, (PMe(3))(4)Ru(Cl)(OAc), Sc(OTf)(3), and (PNN)Ru(CO)(H), operate in sequence to promote this transformation.

  1. Molecular recognition in homogeneous transition metal catalysis: a biomimetic strategy for high selectivity.

    Science.gov (United States)

    Das, Siddartha; Brudvig, Gary W; Crabtree, Robert H

    2008-01-28

    Traditional methods for selectivity control in homogeneous transition metal catalysis either employ steric effects in a binding pocket or chelate control. In a supramolecular strategy, encapsulation of the substrate can provide useful shape and size selectivity. A fully developed molecular recognition strategy involving hydrogen bonding or solvophobic forces has given almost completely regioselective functionalization of remote, unactivated C-H bonds.

  2. Enzyme-Like Catalysis of the Nazarov Cyclization by Supramolecular Encapsulation

    Energy Technology Data Exchange (ETDEWEB)

    Hastings, Courtney; Pluth, Michael; Bergman, Robert; Raymond, Kenneth

    2010-03-29

    A primary goal in the design and synthesis of molecular hosts has been the selective recognition and binding of a variety of guests using non-covalent interactions. Supramolecular catalysis, which is the application of such hosts towards catalysis, has much in common with many enzymatic reactions, chiefly the use of both spatially appropriate binding pockets and precisely oriented functional groups to recognize and activate specific substrate molecules. Although there are now many examples which demonstrate how selective encapsulation in a host cavity can enhance the reactivity of a bound guest, all have failed to reach the degree of increased reactivity typical of enzymes. We now report the catalysis of the Nazarov cyclization by a self-assembled coordination cage, a carbon-carbon bond-forming reaction which proceeds under mild, aqueous conditions. The acceleration in this system is over a million-fold, and represents the first example of supramolecular catalysis that achieves the level of rate enhancement comparable to that observed in several enzymes. We explain the unprecedented degree of rate increase as due to the combination of (a) preorganization of the encapsulated substrate molecule, (b) stabilization of the transition state of the cyclization by constrictive binding, and (c) increase in the basicity of the complexed alcohol functionality.

  3. Residue 182 influences the second step of protein-tyrosine phosphatase-mediated catalysis

    DEFF Research Database (Denmark)

    Pedersen, A.K.; Guo, X.; Møller, K.B.;

    2004-01-01

    Previous enzyme kinetic and structural studies have revealed a critical role for Asp(181) (PTP1B numbering) in PTP (protein-tyrosine phosphatase)-mediated catalysis. In the E-P (phosphoenzyme) formation step, Asp(181) functions as a general acid, while in the E-P hydrolysis step it acts as a gene...

  4. Development of time-resolved XAFS spectroscopy techniques : applications in homogeneous catalysis

    NARCIS (Netherlands)

    2004-01-01

    Catalysis is one of the most important methods to obtain products in a selective and sustainable manner, i.e. in an environmental responsible manner. To be able to modify and optimize these catalytic production pathways, it is important to obtain knowledge on the reaction mechanisms occurring. X-ray

  5. Redox-State Dependent Ligand Exchange in Manganese-Based Oxidation Catalysis

    NARCIS (Netherlands)

    Abdolahzadeh, Shaghayegh; de Boer, Johannes W.; Browne, Wesley R.

    2015-01-01

    Manganese-based oxidation catalysis plays a central role both in nature, in the oxidation of water in photosystem II (PSII) and the control of reactive oxygen species, as well as in chemical processes, in the oxidation of organic substrates and bleaching applications. The focus of this review is on

  6. Acyl Radicals from Aromatic Carboxylic Acids by Means of Visible-Light Photoredox Catalysis

    OpenAIRE

    Bergonzini, Giulia; Cassani, Carlo; Wallentin, Carl-Johan

    2015-01-01

    Simple and abundant carboxylic acids have been used as acyl radical precursor by means of visible-light photoredox catalysis. By the transient generation of a reactive anhydride intermediate, this redox-neutral approach offers a mild and rapid entry to high-value heterocyclic compounds without the need of UV irradiation, high temperature, high CO pressure, tin reagents, or peroxides.

  7. Hierarchical zeolites: Enhanced utilisation of microporous crystals in catalysis by advances in materials design

    DEFF Research Database (Denmark)

    Perez-Ramirez, Javier; Christensen, Claus H.; Egeblad, Kresten;

    2008-01-01

    The introduction of synthetic zeolites has led to a paradigm shift in catalysis, separations, and adsorption processes, due to their unique properties such as crystallinity, high-surface area, acidity, ion-exchange capacity, and shape-selective character. However, the sole presence of micropores ...

  8. Ligand Self-Sorting and Nonlinear Effects in Dinuclear Asymmetric Hydrogenation: Complexity in Catalysis

    NARCIS (Netherlands)

    Terrade, F.G.; Lutz, M.; Reek, J.N.H.

    2013-01-01

    Nature has been a source of inspiration for scientists as billion years of evolution have resulted in magnificent examples of how processes can be controlled efficiently. In the field of supramolecular catalysis, enzymes have been the major source of inspiration. As such, many synthetic systems have

  9. An investigation into the Ti-grafting structure on MCM-41 and epoxidation catalysis

    DEFF Research Database (Denmark)

    Yuan, Q.C.; Hagen, A.; Roessner, F.

    2006-01-01

    The structure of titanium species grafted on a purely siliceous MCM-41 and their catalysis in the epoxidation of cyclohexene with tert-butyl hydroperoxide (TBHP) were investigated. FT-IR, XANES and UV-vis were used for the examination of the Ti-grafted MCM-41. The results indicated that the titan...

  10. Silica immobilized pincer-metal complexes : catalysis, recycling, and retrospect on active species

    NARCIS (Netherlands)

    Mehendale, N.C.

    2007-01-01

    Science is continuously striving for a sustainable progress of society. This progress must be made on the economical as well as the environmental front concomitantly. Many industrial processes are being reviewed to make them environmentally more sustainable. Catalysis emerges as an important player

  11. Artificial Metalloenzymes for Asymmetric Catalysis by Creation of Novel Active Sites in Protein and DNA Scaffolds

    NARCIS (Netherlands)

    Drienovska, Ivana; Roelfes, Gerard

    2015-01-01

    Artificial metalloenzymes have emerged as a promising new approach to asymmetric catalysis. In our group, we are exploring novel artificial metalloenzyme designs involving creation of a new active site in a protein or DNA scaffold that does not have an existing binding pocket. In this review, we giv

  12. Visible-light photoredox catalysis enabled bromination of phenols and alkenes

    Directory of Open Access Journals (Sweden)

    Yating Zhao

    2014-03-01

    Full Text Available A mild and efficient methodology for the bromination of phenols and alkenes has been developed utilizing visible light-induced photoredox catalysis. The bromine was generated in situ from the oxidation of Br− by Ru(bpy33+, both of which resulted from the oxidative quenching process.

  13. Probing the Intact Cluster Catalysis Concept by Tetrahedral Clusters With Framework Chirality

    Institute of Scientific and Technical Information of China (English)

    G. Süss-Fink; L. Vieille-Petit

    2005-01-01

    @@ 1Results and Discussion In order to bring evidence for or against the hypothesis of catalytic hydrogenation by intact trinuclear arene ruthenium clusters containing an oxo cap, the substrate being hydrogenated inside the hydrophobic pocket spanned by the three arene ligands ("supramolecular cluster catalysis")[1], we synthesized cationic Ru3O clusters (See Fig. 1) with three different arene ligands (intrinsically chiral tetrahedra).

  14. Preparation of starch-sodium lignosulfonate graft copolymers via laccase catalysis and characterization of antioxidant activity

    Science.gov (United States)

    Graft copolymers of waxy maize starch and sodium lignosulfonate (SLS) were prepared by Trametes Versicolor laccase catalysis in aqueous solution. Amount of SLS grafted based on phenol analysis was 0.5% and 1.0% in the absence and presence of 1-hydroxybenzotriazole (HBT), respectively. Starch-SLS gra...

  15. [Oxidation of mercury by CuBr2 decomposition under controlled-release membrane catalysis condition].

    Science.gov (United States)

    Hu, Lin-Gang; Qu, Zan; Yan, Nai-Qiang; Guo, Yong-Fu; Xie, Jiang-Kun; Jia, Jin-Ping

    2014-02-01

    CuBr2 in the multi-porous ceramic membrane can release Br2 at high temperature, which was employed as the oxidant for Hg0 oxidation. Hg0 oxidation efficiency was studied by a membrane catalysis device. Meanwhile, a reaction and in situ monitoring device was designed to avoid the impact of Br2 on the downstream pipe. The result showed that the MnO(x)/alpha-Al2O3 catalysis membrane had a considerable "controlled-release" effect on Br2 produced by CuBr2 decomposition. The adsorption and reaction of Hg0 and Br2 on the surface of catalysis membrane obeyed the Langmuir-Hinshelwood mechanism. The removal efficiency of Hg0 increased with the rising of Br2 concentration. However, when Br2 reached a certain concentration, the removal efficiency was limited by adsorption rate and reaction rate of Hg0 and Br2 on the catalysis membrane. From 473 K to 573 K, the variation of Hg0 oxidation efficiency was relatively stable. SO2 in flue gas inhibited the oxidation of Hg0 while NO displayed no obvious effect.

  16. General Acid Catalysis: A Flexible Experiment, Adaptable to Student Ability and Various Teaching Approaches.

    Science.gov (United States)

    Bulmer, R. S.; And Others

    1981-01-01

    The acid-catalyzed hydrolysis of N-vinyl pyrrolidone provides a simple spectrophotometric kinetic experiment to introduce general acid catalysis, solvent isotope effects, and other aspects of ionic reactions in solution in advanced courses. The Bronsted equation and concept of linear free-energy changes is also covered. (SK)

  17. Chemical Ligation and Isotope Labeling to Locate Dynamic Effects during Catalysis by Dihydrofolate Reductase.

    Science.gov (United States)

    Luk, Louis Y P; Ruiz-Pernía, J Javier; Adesina, Aduragbemi S; Loveridge, E Joel; Tuñón, Iñaki; Moliner, Vincent; Allemann, Rudolf K

    2015-07-27

    Chemical ligation has been used to alter motions in specific regions of dihydrofolate reductase from E. coli and to investigate the effects of localized motional changes on enzyme catalysis. Two isotopic hybrids were prepared; one with the mobile N-terminal segment containing heavy isotopes ((2) H, (13) C, (15) N) and the remainder of the protein with natural isotopic abundance, and the other one with only the C-terminal segment isotopically labeled. Kinetic investigations indicated that isotopic substitution of the N-terminal segment affected only a physical step of catalysis, whereas the enzyme chemistry was affected by protein motions from the C-terminal segment. QM/MM studies support the idea that dynamic effects on catalysis mostly originate from the C-terminal segment. The use of isotope hybrids provides insights into the microscopic mechanism of dynamic coupling, which is difficult to obtain with other studies, and helps define the dynamic networks of intramolecular interactions central to enzyme catalysis.

  18. A Molecular Reaction Cycle with a Solvatochromic Merocyanine Dye: An Experiment in Photochemistry, Kinetics, and Catalysis.

    Science.gov (United States)

    Abdel-Kader, M. H.; Steiner, U.

    1983-01-01

    Three experiments using merocyanine M suitable as an integrated laboratory experience for undergraduates are described. Experiments demonstrate: complete molecular cycle composed of photochemical, thermal, and protolytic reaction steps; kinetics of cis-trans isomerization of the dye; and mechanism of base catalysis for thermal isomerization of the…

  19. Interaction of 1,5-Substituted Pyrrolin-2-ones with Dichlorocarbene under Phase Transfer Catalysis Conditions

    Directory of Open Access Journals (Sweden)

    Zlata Yu. Timofeyeva

    2000-10-01

    Full Text Available Treatment of 5-alkyl(aryl-3H-pyrrolin-2-ones with dichlorocarbene under phase transfer catalysis conditions at 20-30ºC results in a cycloaddition of the carbene to the C=C bond followed by skeletal rearrangement.

  20. ISHHC XIII International Symposium on the Relations betweenHomogeneous and Heterogeneous Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai (Ed.), G.A.

    2007-06-11

    The International Symposium on Relations between Homogeneous and Heterogeneous Catalysis (ISHHC) has a long and distinguished history. Since 1974, in Brussels, this event has been held in Lyon, France (1977), Groeningen, The Netherlands (1981); Asilomar, California (1983); Novosibirsk, Russia (1986); Pisa, Italy (1989); Tokyo, Japan (1992); Balatonfuered, Hungary (1995); Southampton, United Kingdom (1999); Lyon, France (2001); Evanston, Illinois (2001) and Florence, Italy (2005). The aim of this international conference in Berkeley is to bring together practitioners in the three fields of catalysis, heterogeneous, homogeneous and enzyme, which utilize mostly nanosize particles. Recent advances in instrumentation, synthesis and reaction studies permit the nanoscale characterization of the catalyst systems, often for the same reaction, under similar experimental conditions. It is hoped that this circumstance will permit the development of correlations of these three different fields of catalysis on the molecular level. To further this goal we aim to uncover and focus on common concepts that emerge from nanoscale studies of structures and dynamics of the three types of catalysts. Another area of focus that will be addressed is the impact on and correlation of nanosciences with catalysis. There is information on the electronic and atomic structures of nanoparticles and their dynamics that should have importance in catalyst design and catalytic activity and selectivity.

  1. Catalysis looks to the future. Panel on new directions in catalytic science and technology

    Energy Technology Data Exchange (ETDEWEB)

    1992-12-31

    Catalysts play a vital role in providing society with fuels, commodity and fine chemicals, pharmaceuticals, and means for protecting the environment. To be useful, a good catalyst must have a high turnover frequency (activity), produce the right kind of product (selectivity), and have a long life (durability), all at an acceptable cost. Research in the field of catalysis provides the tools and understanding required to facilitate and accelerate the development of improved catalysts and to open opportunities for the discovery of new catalytic processes. The aim of this report is to identify the research opportunities and challenges for catalysis in the coming decades and to detail the resources necessary to ensure steady progress. Chapter 2 discusses opportunities for developing new catalysts to meet the demands of the chemical and fuel industries, and the increasing role of catalysis in environmental protection. The intellectual challenges for advancing the frontiers of catalytic science are outlined in Chapter 3. The human and institutional resources available in the US for carrying out research on catalysis are summarized in Chapter 4. The findings and recommendations of the panel for industry, academe, the national laboratories, and the federal government are presented in Chapter 5.

  2. The Power of High-Throughput Experimentation in Homogeneous Catalysis Research for Fine Chemicals

    NARCIS (Netherlands)

    Vries, Johannes G. de; Vries, André H.M. de

    2003-01-01

    The use of high-throughput experimentation (HTE) in homogeneous catalysis research for the production of fine chemicals is an important breakthrough. Whereas in the past stoichiometric chemistry was often preferred because of time-to-market constraints, HTE allows catalytic solutions to be found wit

  3. Kinetic of Adsorption of Urea Nitrogen onto Chitosan Coated Dialdehyde Cellulose under Catalysis of Immobilized Urease

    Institute of Scientific and Technical Information of China (English)

    Zu Pei LIANG; Ya Qing FENG; Zhi Yan LIANG; Shu Xian MENG

    2005-01-01

    The adsorption of urea nitrogen onto chitosan coated dialdehyde cellulose (CDAC)under catalysis of immobilized urease in gelatin membrane (IE) was studied in batch system. The pseudo first-order and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model.

  4. DMPD: Nucleic acid-sensing Toll-like receptors: beyond ligand search. [Dynamic Macrophage Pathway CSML Database

    Lifescience Database Archive (English)

    Full Text Available 18321608 Nucleic acid-sensing Toll-like receptors: beyond ligand search. Miyake K. ...Adv Drug Deliv Rev. 2008 Apr 29;60(7):782-5. Epub 2008 Feb 15. (.png) (.svg) (.html) (.csml) Show Nucleic ac...id-sensing Toll-like receptors: beyond ligand search. PubmedID 18321608 Title Nucleic acid-sensing Toll-like

  5. Remote Sensing Information Classification

    Science.gov (United States)

    Rickman, Douglas L.

    2008-01-01

    This viewgraph presentation reviews the classification of Remote Sensing data in relation to epidemiology. Classification is a way to reduce the dimensionality and precision to something a human can understand. Classification changes SCALAR data into NOMINAL data.

  6. Compressed Sensing in Astronomy

    CERN Document Server

    Bobin, J; Ottensamer, R

    2008-01-01

    Recent advances in signal processing have focused on the use of sparse representations in various applications. A new field of interest based on sparsity has recently emerged: compressed sensing. This theory is a new sampling framework that provides an alternative to the well-known Shannon sampling theory. In this paper we investigate how compressed sensing (CS) can provide new insights into astronomical data compression and more generally how it paves the way for new conceptions in astronomical remote sensing. We first give a brief overview of the compressed sensing theory which provides very simple coding process with low computational cost, thus favoring its use for real-time applications often found on board space mission. We introduce a practical and effective recovery algorithm for decoding compressed data. In astronomy, physical prior information is often crucial for devising effective signal processing methods. We particularly point out that a CS-based compression scheme is flexible enough to account ...

  7. Catalysis by Using TiO2 Nanoparticles and Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Chien Shu-Hua; Kuo Ming-Chih; Liou Yuh-Cherng

    2004-01-01

    TiO2 has attracted considerable attention due to its stability, non-toxicity, low cost, and great potential for use as a photocatalyst in environmental applications. Since strong metal-support interaction (SMSI) of titania-supported noble metals was first reported in 1978, titania supported catalyst has been intensively studied in heterogeneous catalysis. However, the effective catalytic activity was restricted due to the low surface area of TiO2. Recently, TiO2-based nanotubes were extensively investigated because of their potentials in many areas such as highly efficient photocatalysis and hydrogen sensor.In the present study, formation of titanium oxide (TiO2) nanotubes was carried out by hydrothermal method, with TiO2 nanoparticle-powders immersed in concentrated NaOH solution in an autoclave at 110 ℃. Preparation of nano-size Pt on TiO2-nanoparticles or TiO2-nanotubes was performed by photochemical deposition method with UV irradiation on an aqueous solution containing TiO2 and hexachloroplatinic acid or tetrachloroauric acid. The TEM micrographs show that TiO2-nanotubes exhibit ~300 nm in length with an inner diameter of ~ 6 nm and the wall thickness of ~ 2 nm, and homogeneous nanosize Pt particles (~ 2 nm) were well-dispersed on both nanoparticle- and nanotube- titania supports. It also shows the nanotube morphology was retained up2o n Pt-immobilization. Nitrogen adsorption isotherm at 77K resulted a high surface area (~ 200m/g) of TiO2-nanotubes, which is about 40 times greater than that of "mother" TiO2 nanoparticles (~5 m/g). All the spectroscopic results exhibited that the nanotube structure was not significantly affected by the immobilized Pt particles. Ti K-edge XANES spectra of TiO2 nanotube and Pt/TiO2-nanotube represent that most titanium are in a tetrahedral coordination with few retained in the octahedral structure.In the in-situ FT-IR experiments, an IR cell was evacuated to a pressure of 10-5 torr at room temperature as soon as the

  8. Solvation and Acid Strength Effects on Catalysis by Faujasite Zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Gounder, Rajamani P.; Jones, Andrew J.; Carr, Robert T.; Iglesia, Enrique

    2012-02-01

    Kinetic, spectroscopic, and chemical titration data indicate that differences in monomolecular isobutane cracking and dehydrogenation and methanol dehydration turnover rates (per H+) among FAU zeolites treated thermally with steam (H-USY) and then chemically with ammonium hexafluorosilicate (CDHUSY) predominantly reflect differences in the size and solvating properties of their supercage voids rather than differences in acid strength. The number of protons on a given sample was measured consistently by titrations with Na+, with CH3 groups via reactions of dimethyl ether, and with 2,6-di-tert-butylpyridine during methanol dehydration catalysis; these titration values were also supported by commensurate changes in acidic OH infrared band areas upon exposure to titrant molecules. The number of protons, taken as the average of the three titration methods, was significantly smaller than the number of framework Al atoms (Alf) obtained from X-ray diffraction and 27Al magic angle spinning nuclear magnetic resonance spectroscopy on H-USY (0.35 H+/Alf) and CD-HUSY (0.69 H+/Alf). These data demonstrate that the ubiquitous use of Alf sites as structural proxies for active H+ sites in zeolites can be imprecise, apparently because distorted Al structures that are not associated with acidic protons are sometimes detected as Alf sites. Monomolecular isobutane cracking and dehydrogenation rate constants, normalized non-rigorously by the number of Alf species, decreased with increasing Na+ content on both H-USY and CD-HUSY samples and became undetectable at sub-stoichiometric exchange levels (0.32 and 0.72 Na+/Alf ratios, respectively), an unexpected finding attributed incorrectly in previous studies to the presence of minority ‘‘super-acidic’’ sites. These rate constants, when normalized rigorously by the number of residual H+ sites were independent of Na+ content on both H-USY and CD-HUSY samples, reflecting the stoichiometric replacement of protons that are uniform in

  9. Selective Catalysis in Nanoparticle Metal-Organic Framework Composites

    Science.gov (United States)

    Stephenson, Casey Justin

    The design of highly selective catalysts are becoming increasingly important, especially as chemical and pharmaceutical industries seek to improve atom economy and minimize energy intensive separations that are often required to separate side products from the desired product. Enzymes are among the most selective of all catalysts, generally operating through molecular recognition whereby an active site analogous to a lock and the substrate is analogous to a key. The assembly of a porous, crystalline material around a catalytically active metal particle could serve as an artificial enzyme. In this vein, we first synthesized the polyvinylpyrrolidone (PVP) coated nanoparticles of interest and then encapsulated them within zeolitic imidazolate framework 8 or ZIF-8. 2.8 nm Pt-PVP nanoparticles, which were encapsulated within ZIF-8 to form Pt ZIF-8 composite. Pt ZIF-8 was inactive for the hydrogenation of cyclic olefins such as cis-cyclooctene and cis-cyclohexene while the composite proved to be a highly selective catalyst for the hydrogenation of terminal olefins, hydrogenating trans-1,3-hexadiene to 3-hexene in 95% selectivity after 24 hours under 1 bar H2. We extended our encapsulation method to sub-2 nm Au nanoparticles to form Au ZIF-8. Au ZIF-8 served as a highly chemoselective catalyst for the hydrogenation of crotonaldehyde an alpha,beta-unsaturated aldehyde, to crotyl alcohol an alpha,beta-unsaturated alcohol, in 90-95% selectivity. In order to investigate nanoparticle size effects on selectivity, 6-10 nm Au nanoparticles were encapsulated within ZIF-8 to form Au6 ZIF-8. Control catalysts with nanoparticles supported on the surface of ZIF-8 were synthesized as well, Au/ZIF-8 and Au6/ZIF-8. Au6 ZIF-8 hydrogenated crotonaldehyde in 85% selectivity towards the unsaturated alcohol. Catalysts with nanoparticles supported on the exterior of ZIF-8 were far less selective towards the unsaturated alcohol. Post-catalysis transmission electron microscopy analysis of Au ZIF

  10. Dense with Sense

    Science.gov (United States)

    Aletras, Anthony H.; Ingkanisorn, W. Patricia; Mancini, Christine; Arai, Andrew E.

    2005-09-01

    Displacement encoding with stimulated echoes (DENSE) with a low encoding strength phase-cycled meta-DENSE readout and a two fold SENSE acceleration ( R = 2) is described. This combination reduces total breath-hold times for increased patient comfort during cardiac regional myocardial contractility studies. Images from phantoms, normal volunteers, and a patient are provided to demonstrate the SENSE-DENSE combination of methods. The overall breath-hold time is halved while preserving strain map quality.

  11. Online Remote Sensing Interface

    Science.gov (United States)

    Lawhead, Joel

    2007-01-01

    BasinTools Module 1 processes remotely sensed raster data, including multi- and hyper-spectral data products, via a Web site with no downloads and no plug-ins required. The interface provides standardized algorithms designed so that a user with little or no remote-sensing experience can use the site. This Web-based approach reduces the amount of software, hardware, and computing power necessary to perform the specified analyses. Access to imagery and derived products is enterprise-level and controlled. Because the user never takes possession of the imagery, the licensing of the data is greatly simplified. BasinTools takes the "just-in-time" inventory control model from commercial manufacturing and applies it to remotely-sensed data. Products are created and delivered on-the-fly with no human intervention, even for casual users. Well-defined procedures can be combined in different ways to extend verified and validated methods in order to derive new remote-sensing products, which improves efficiency in any well-defined geospatial domain. Remote-sensing products produced in BasinTools are self-documenting, allowing procedures to be independently verified or peer-reviewed. The software can be used enterprise-wide to conduct low-level remote sensing, viewing, sharing, and manipulating of image data without the need for desktop applications.

  12. Cooperatively active sensing system

    International Nuclear Information System (INIS)

    Aiming at development of a strong and flexible sensing system, a study on a sensing technology prepared with cooperativity, activity, and real time workability has been promoted. In the former period, together with preparation of plural moving robot group with real time processing capacity of a lot of sensor informations composing of platform, a parallel object direction language Eus Lisp effectively capable of describing and executing cooperative processing and action therewith was developed. And, it was also shown that capacity to adaptively act even at dynamic environment could be learnt experientially. And, on processing of individual sensor information, application of a photographing system with multiple resolution property similar to human visual sense property was attempted. In the latter period, together with intending of upgrading on adaptability of sensing function, by using moving robot group in center of a moving robot loaded with active visual sense, a cooperative active sensing prototype system was constructed to show effectiveness of this study through evaluation experiment of patrolling inspection at plant simulating environment. (G.K.)

  13. Drug Facts

    Medline Plus

    Full Text Available ... prescription drugs. The addiction slowly took over his life. I need different people around me. To stop ... marijuana, "Cristina" is making positive changes in her life. She finds support from family and friends who ...

  14. Antiretroviral drugs.

    Science.gov (United States)

    De Clercq, Erik

    2010-10-01

    In October 2010, it will be exactly 25 years ago that the first antiretroviral drug, AZT (zidovudine, 3'-azido-2',3'-dideoxythymidine), was described. It was the first of 25 antiretroviral drugs that in the past 25 years have been formally licensed for clinical use. These antiretroviral drugs fall into seven categories [nucleoside reverse transcriptase inhibitors (NRTIs), nucleotide reverse transcriptase inhibitors (NtRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), protease inhibitors (PIs), fusion inhibitors (FIs), co-receptor inhibitors (CRIs) and integrase inhibitors (INIs). The INIs (i.e. raltegravir) represent the most recent advance in the search for effective and selective anti-HIV agents. Combination of several anti-HIV drugs [often referred to as highly active antiretroviral therapy (HAART)] has drastically altered AIDS from an almost uniformly fatal disease to a chronic manageable one. PMID:20471318

  15. Drug Facts

    Medline Plus

    Full Text Available ... Websites Search Share Listen English Español Information about this page Click on the button that says "Listen" ... the computer will read the text to you. This web site talks about drug abuse, addiction and ...

  16. Drug Facts

    Medline Plus

    Full Text Available ... computer will read the text to you. This web site talks about drug abuse, addiction and treatment. ... of the U.S. Department of Health and Human Services . PDF documents require the free Adobe Reader . Microsoft ...

  17. Antiretroviral drugs.

    Science.gov (United States)

    De Clercq, Erik

    2010-10-01

    In October 2010, it will be exactly 25 years ago that the first antiretroviral drug, AZT (zidovudine, 3'-azido-2',3'-dideoxythymidine), was described. It was the first of 25 antiretroviral drugs that in the past 25 years have been formally licensed for clinical use. These antiretroviral drugs fall into seven categories [nucleoside reverse transcriptase inhibitors (NRTIs), nucleotide reverse transcriptase inhibitors (NtRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), protease inhibitors (PIs), fusion inhibitors (FIs), co-receptor inhibitors (CRIs) and integrase inhibitors (INIs). The INIs (i.e. raltegravir) represent the most recent advance in the search for effective and selective anti-HIV agents. Combination of several anti-HIV drugs [often referred to as highly active antiretroviral therapy (HAART)] has drastically altered AIDS from an almost uniformly fatal disease to a chronic manageable one.

  18. Club Drugs

    Science.gov (United States)

    ... following information: Facts and Figures – Includes the latest information and statistics. Legislation – A sample of links to online Federal and ... recognized agencies and organizations that provide services or information. CLUB DRUGS Summary Facts & ... & Technical Assistance Grants & Funding Related ...

  19. Deterministic sensing matrices in compressive sensing: a survey.

    Science.gov (United States)

    Nguyen, Thu L N; Shin, Yoan

    2013-01-01

    Compressive sensing is a sampling method which provides a new approach to efficient signal compression and recovery by exploiting the fact that a sparse signal can be suitably reconstructed from very few measurements. One of the most concerns in compressive sensing is the construction of the sensing matrices. While random sensing matrices have been widely studied, only a few deterministic sensing matrices have been considered. These matrices are highly desirable on structure which allows fast implementation with reduced storage requirements. In this paper, a survey of deterministic sensing matrices for compressive sensing is presented. We introduce a basic problem in compressive sensing and some disadvantage of the random sensing matrices. Some recent results on construction of the deterministic sensing matrices are discussed.

  20. Magnetic beads-based DNAzyme recognition and AuNPs-based enzymatic catalysis amplification for visual detection of trace uranyl ion in aqueous environment.

    Science.gov (United States)

    Zhang, Hongyan; Lin, Ling; Zeng, Xiaoxue; Ruan, Yajuan; Wu, Yongning; Lin, Minggui; He, Ye; Fu, FengFu

    2016-04-15

    We herein developed a novel biosensor for the visual detection of trace uranyl ion (UO2(2+)) in aqueous environment with high sensitivity and specificity by using DNAzyme-functionalized magnetic beads (MBs) for UO2(2+) recognition and gold nano-particles (AuNPs)-based enzymatic catalysis oxidation of TMB (3,3',5,5'-tetramethylbenzidine sulfate) for signal generation. The utilization of MBs facilitates the magnetic separation and collection of sensing system from complex sample solution, which leads to more convenient experimental operation and more strong resistibility of the biosensor to the matrix of sample, and the utilization of AuNPs-based enzymatic catalysis amplification greatly improved the sensitivity of the biosensor. Compared with the previous DNAzyme-based UO2(2+) sensors, the proposed biosensor has outstanding advantages such as relative high sensitivity and specificity, operation convenience, low cost and more strong resistibility to the matrix of sample. It can be used to detect as low as 0.02 ppb (74 pM) of UO2(2+) in aqueous environment by only naked-eye observation and 1.89 ppt (7.0 pM) of UO2(2+) by UV-visible spectrophotometer with a recovery of 93-99% and a RSD ≤ 5.0% (n=6) within 3h. Especially, the visual detection limit of 0.02 ppb (74 pM) is much lower than the maximum allowable level of UO2(2+) (130 nM) in the drinking water defined by the U.S. Environmental Protection Agency (EPA), indicating that our method meets the requirement of rapid and on-site detection of UO2(2+) in the aqueous environment by only naked-eye observation.