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Sample records for hydroliquefaction solvent-induced scission

  1. Viral Membrane Scission

    PubMed Central

    Rossman, Jeremy S.; Lamb, Robert A.

    2014-01-01

    Virus budding is a complex, multistep process in which viral proteins make specific alterations in membrane curvature. Many different viral proteins can deform the membrane and form a budding virion, but very few can mediate membrane scission to complete the budding process. As a result, enveloped viruses have developed numerous ways of facilitating membrane scission, including hijacking host cellular scission machinery and expressing their own scission proteins. These proteins mediate scission in very different ways, though the biophysical mechanics underlying their actions may be similar. In this review, we explore the mechanisms of membrane scission and the ways in which enveloped viruses use these systems to mediate the release of budding virions. PMID:24099087

  2. Microscopic Description of Scission Configurations

    SciTech Connect

    Dubray, N.; Goutte, H.; Berger, J. F.

    2007-02-26

    Properties of 226Th, 256Fm, 258Fm and 260Fm nuclei in the scission region are described using a full-microscopic Hartree-Fock-Bogoliubov approach with the effective Gogny nucleon-nucleon interaction. In a first step, the Potential Energy Surfaces are computed in the (q 20, q30) plane, the scission lines are found, fulfilling a given criterion on the density in the nuclear neck. Finally a few properties of the fragments along this line are presented.

  3. Investigation of the heating up period of hydroliquefaction

    SciTech Connect

    Konig, M.; Fehl, C. ); Engelke, F. ); Mittelmeijer-Hazeleger, M. )

    1990-01-01

    Earthy soft brown coals from deposits of GDR (Leipzig area) were found to be a highly reactive feedstock for slurry phase hydroliquefaction (1). The question arose as to whether short-contact-time hydrogenation may be an efficient process for hydroconversion of reactive coals (2). Rapid heating up of the slurry to the final reaction temperature may have a beneficial effect on product yields. Moreover, a more detailed study of the heating up period in hydrogenation is of importance for the explanation of the phenomenon of coke formation in the preheater sections of hydrogenation units.

  4. Evaluation of humic fractions potential to produce bio-oil through catalytic hydroliquefaction.

    PubMed

    Lemée, L; Pinard, L; Beauchet, R; Kpogbemabou, D

    2013-12-01

    Humic substances were extracted from biodegraded lignocellulosic biomass (LCBb) and submitted to catalytic hydroliquefaction. The resulting bio-oils were compared with those of the initial biomass. Compared to fulvic and humic acids, humin presented a high conversion rate (74 wt.%) and the highest amount of liquid fraction (66 wt.%). Moreover it represented 78% of LCBb. Humin produced 43 wt.% of crude oil and 33 wt.% of hexane soluble fraction containing hydrocarbons which is a higher yield than those from other humic substances as well as from the initial biomass. Hydrocarbons were mainly aromatics, but humin produces the highest amount of aliphatics. Considering the quantity, the quality and the molecular composition of the humic fractions, a classification of the potential of the latter to produce fuel using hydroliquefaction process can be assess: Hu>AF>AH. The higher heating value (HHV) and oxygen content of HSF from humin were fully compatible with biofuel characteristics. PMID:24140851

  5. Alternative fuel production by catalytic hydroliquefaction of solid municipal wastes, primary sludges and microalgae.

    PubMed

    Lemoine, F; Maupin, I; Lemée, L; Lavoie, J-M; Lemberton, J-L; Pouilloux, Y; Pinard, L

    2013-08-01

    An alternative fuel production was investigated through catalytic hydroliquefaction of three different carbonaceous sources: solid municipal wastes (MW), primary sludges (PS), and microalgae (MA). The reaction was carried out under hydrogen pressure, at different temperatures (330, 380 and 450°C), with a Raney nickel catalyst and two different hydrogen donor solvents: a "fossil solvent" (tetralin) and a "green solvent" (2-methyl-hydro-furan). The feeds analyses (TDA-TGA, ICP-AES, lipids quantification) showed that MW and PS had similar characteristics and physico-chemical properties, but different from those of MA. The hydroliquefaction of these feeds allowed to obtain high oil yields, with a significant energetic value, similar to that of a bio-petroleum. 2-methyl-hydro-furan was more efficient than tetralin for the treatment of the strongly bio-degraded biomasses MW and PS, while better results were obtained with tetralin in the case of MA.

  6. The scission point configuration of fissioning nuclei

    NASA Astrophysics Data System (ADS)

    Ivanyuk, Fedir

    2016-06-01

    We define the optimal shape which fissioning nuclei attain just before the scission and calculate the deformation energy as function of the mass asymmetry at the scission point. The calculated deformation energy is used in quasi-static approximation for the estimation of mass distribution, total kinetic and excitation energy of fission fragments, and the total number of prompt neutrons. The calculated results reproduce rather well the experimental data on the position of the peaks in the mass distribution of fission fragments, the total kinetic and excitation energy of fission fragments. The calculated value of neutron multiplicity is somewhat larger than experimental results. The saw-tooth structure of neutron multiplicity is qualitatively reproduced.

  7. Low energy fission: dynamics and scission configurations

    NASA Astrophysics Data System (ADS)

    Goutte, H.; Berger, J.-F.; Gogny, D.; Younes, W.

    2005-11-01

    In the first part of this paper we recall a recent study concerning low energy fission dynamics. Propagation is made by use of the Time Dependent Generator Coordinate Method, where the basis states are taken from self-consistent Hartree-Fock-Bogoliubov calculations with the Gogny force. Theoretical fragment mass distributions are presented and compared with the evaluation made by Wahl. In the second part of this paper, new results concerning scission configurations are shown. Deviations of the fission fragment proton numbers from the Unchanged Charge Distribution prescription and fission fragment deformations are discussed.

  8. Scissionable bile acid nanostructures for lithography

    NASA Astrophysics Data System (ADS)

    Meagley, Robert P.; Sharma, Geeta; Guptab, Ankur

    2007-03-01

    Pixelated photoresists, i.e. resists that compartmentalize photochemistry into discrete imaging elements are an emerging design for improved resolution. A pixelated design seeks to overcome chaotic organization in complex resist formulations through application of small regular or symmetric imaging species, and/or through the application of preorganization of resist components. [1] Another approach, backbone scission, has also emerged as a powerful method to improve resist performance. [2] In this approach, the parts of the resist structure that have undergone radiation driven chemistry are disconnected from the unaffected material. This enhances contrast and also confers an additional mechanism: structural disruption. Bile acids have been used recently as building blocks to enable host-guest chemistry [3] and have been incorporated as additives in photoresists [4] and structural elements [5]. They as a class are fairly large (mw ~400) highly functionalized molecules possessing a hydrophobic face, alcohol groups and a carboxylic acid group. We describe here a scissionable pixelated resist architecture based on bile acids bound by acid-sensitive tertiary ester linkages into dendrimeric arrays. This design seeks to employ structural disintegration and catalyst pre-organization in addition to solubility switching as contrast mechanisms. Preliminary EUV and ebeam studies have shown G0 and G1 materials capable of sub-micron imaging.

  9. Bio-oil from thermo-chemical hydro-liquefaction of wet sewage sludge.

    PubMed

    Malins, Kristaps; Kampars, Valdis; Brinks, Janis; Neibolte, Ilze; Murnieks, Raimonds; Kampare, Ruta

    2015-01-01

    The present work demonstrates the influence of experimental conditions such as weight ratio of sewage sludge to water (1/0-1/15), reaction temperature (200-350°C), initial H2 pressure (2.0-11.0MPa), residence time (10-100min) and type of catalysts (Na2CO3, Raney nickel, FeSO4, MoS2) on hydro-liquefaction process of sewage sludge. High amount of water improves the hydro-liquefaction process of sewage sludge by increasing the yield of bio-oil and the total conversion. The highest yield of bio-oil (47.79 wt.%) from sewage sludge was obtained with initial H2 pressure 5.0MPa, reaction temperature 300°C, and residence time 40min. Under these experimental conditions, using weight ratio of sewage sludge to water 1/5, catalyst (FeSO4) - 5 wt.% of dry SS, mixing speed 350rpm the obtained bio-oil had the highest energy recovery (69.84%), total conversion (70.64%) and its calorific value was 35.22MJ/kg.

  10. Bio-oil from hydro-liquefaction of Dunaliella salina over Ni/REHY catalyst.

    PubMed

    Yang, Chao; Jia, Lishan; Chen, Changping; Liu, Guangfa; Fang, Weiping

    2011-03-01

    The hydro-liquefaction of Dunaliella salina over solid acid catalyst was examined under moderate conditions (200°C, 2.0 MPa, 60 min). The significant increment of bio-oil yield was obtained over Ni/REHY catalyst, increasing about 20% compared without modified REHY. H(2)-temperature-programmed desorption (H(2)-TPD) and X-ray powder diffraction (XRD) demonstrated that Ni/REHY as bifunctional catalyst played roles in hydrogenation and cracking, and further achieved the deoxygenation and desulfurization of D. salina under hydrogen gas. The oxygen and sulfur contents of bio-oils decreased relative to D. salina, and the higher heating value (HHV) significantly increased to 30.11 MJ/kg. From gas chromatography/mass spectrometry (GC/MS), the dominant compounds of the bio-oils were found to be esters, glycerins. The qualities of bio-oils were greatly improved. Hydro-liquefaction was beneficial to the exploration of bio-oils from microalgae.

  11. Hydro-liquefaction of microcrystalline cellulose, xylan and industrial lignin in different supercritical solvents.

    PubMed

    Li, Qingyin; Liu, Dong; Hou, Xulian; Wu, Pingping; Song, Linhua; Yan, Zifeng

    2016-11-01

    The influences of solvent on hydro-liquefaction of cellulose, xylan, and lignin were investigated using micro-autoclave. The maximum conversion and bio-oil yield obtained from cellulose and xylan liquefaction were achieved in methanol, whereas similar liquefaction characteristics of lignin were observed in methanol and ethanol. The molecular simulation of interactions between solvents and subcomponents indicated that methanol and ethanol were highly miscible with raw materials. GC-MS and FT-ICR MS characterization revealed that the chemical compositions of liquid products highly depended on the utilized feedstocks. Esters, ketones, and aldehydes were mainly produced from cellulose and xylan conversion, whereas aromatic compounds were primarily derived from lignin conversion. EA results showed that methanol favored the hydrogenation and deoxygenation, resulting in the heating value increased. It could be concluded that the oil quality was highly improved in supercritical methanol. PMID:27497089

  12. Hydro-liquefaction of microcrystalline cellulose, xylan and industrial lignin in different supercritical solvents.

    PubMed

    Li, Qingyin; Liu, Dong; Hou, Xulian; Wu, Pingping; Song, Linhua; Yan, Zifeng

    2016-11-01

    The influences of solvent on hydro-liquefaction of cellulose, xylan, and lignin were investigated using micro-autoclave. The maximum conversion and bio-oil yield obtained from cellulose and xylan liquefaction were achieved in methanol, whereas similar liquefaction characteristics of lignin were observed in methanol and ethanol. The molecular simulation of interactions between solvents and subcomponents indicated that methanol and ethanol were highly miscible with raw materials. GC-MS and FT-ICR MS characterization revealed that the chemical compositions of liquid products highly depended on the utilized feedstocks. Esters, ketones, and aldehydes were mainly produced from cellulose and xylan conversion, whereas aromatic compounds were primarily derived from lignin conversion. EA results showed that methanol favored the hydrogenation and deoxygenation, resulting in the heating value increased. It could be concluded that the oil quality was highly improved in supercritical methanol.

  13. Solvent-induced desorption of alkanethiol ligands from Au nanoparticles.

    PubMed

    Huang, Yuanyuan; Liu, Wei; Cheng, Hao; Yao, Tao; Yang, Lina; Bao, Jie; Huang, Ting; Sun, Zhihu; Jiang, Yong; Wei, Shiqiang

    2016-06-21

    Removing surfactants from a colloidal metal nanoparticle surface is necessary for their realistic applications, and how they could be stripped is a subject of active investigation. Here, we report a solvent-induced desorption of dodecanethiol ligands from the gold nanoparticle surface, and traced this desorption process using a combination of in situ X-ray absorption fine structure (XAFS) and Raman spectroscopic techniques. In situ analysis results reveal that the solvent exchange of ethanol with tetrahydrofuran (THF) can effectively remove dodecanethiol ligands while keeping the particle morphology unchanged. Upon increasing the THF/ethanol ratio from 0 : 1 to 5 : 1, the surface coverage of thiol on the Au surface is reduced from 0.47 to 0.07, suggesting the depletion of ligands first from the nanoparticle facet sites, then from the edge sites, while the ligands at the corner sites are intact. This work enriches our knowledge on surfactant removal and may pave the way towards preparing surface-clean nanoparticles for practical applications. PMID:27241025

  14. Silk fibroin gelation via non-solvent induced phase separation.

    PubMed

    Kasoju, Naresh; Hawkins, Nicholas; Pop-Georgievski, Ognen; Kubies, Dana; Vollrath, Fritz

    2016-03-01

    Tissue engineering benefits from novel materials with precisely tunable physical, chemical and mechanical properties over a broad range. Here we report a practical approach to prepare Bombyx mori silk fibroin hydrogels using the principle of non-solvent induced phase separation (NIPS). A combination of reconstituted silk fibroin (RSF) and methanol (non-solvent), with a final concentration of 2.5% w/v and 12.5% v/v respectively, maintained at 22 °C temperature turned into a hydrogel within 10 hours. Freeze-drying of this gel gave a foam with a porosity of 88%, a water uptake capacity of 89% and a swelling index of 8.6. The gelation kinetics and the loss tangent of the gels were investigated by rheometry. The changes in the morphology of the porous foams were visualized by SEM. The changes in RSF chemical composition and the relative fraction of its secondary structural elements were analyzed by ATR-FTIR along with Fourier self-deconvolution. And, the changes in the glass transition temperature, specific heat capacity and the relative fraction of crystallinity of RSF were determined by TM-DSC. Data suggested that RSF-water-methanol behaved as a polymer-solvent-non-solvent ternary phase system, wherein the demixing of the water-methanol phases altered the thermodynamic equilibrium of RSF-water phases and resulted in the desolvation and eventual separation of the RSF phase. Systematic analysis revealed that both gelation time and the properties of hydrogels and porous foams could be controlled by the ratios of RSF and non-solvent concentration as well as by the type of non-solvent and incubation temperature. Due to the unique properties we envisage that the herein prepared NIPS induced RSF hydrogels and porous foams can possibly be used for the encapsulation of cells and/or for the controlled release of both hydrophilic and hydrophobic drugs. PMID:26730413

  15. Characterization of a Middle Distillate Oil from a Coal hydroliquefaction Plant

    SciTech Connect

    Lin, H.; Zhang, D.; Yang, L.; Pan, T.; Gao, J.

    2009-07-01

    In this article, a middle distillate oil obtained from a coal hydroliquefaction pilot plant was characterized by modern analytical instruments. First, using {sup 1}H and {sup 13}C nuclear magnetic resonance, the distribution of hydrogen and carbon atoms were obtained, and the presence of configurations such as long aliphatic carbon chains, alkyl-substituted aromatic ring, and partially hydrogenated aromatics in the middle distillate oil was found. Then the oil was separated into three fractions: saturates, aromatics, and polars by neutral silica gel liquid chromatography, and the detailed compositions of saturates and aromatics were respectively analyzed by gas chromatography-mass spectrometry. The results show that the aromatics fraction is the most abundant one in this oil, but they are not normal aromatics and mainly consist of dicyclic-, tricyclic-, and tetracyclic-partially hydrogenated aromatics with carbon atom numbers from C10-C21, such as tetralin, alkyl-substituted tetralin, hydrophenanthrene, hydroanthracene, hydropyrene, and so on. Saturates mainly comprise n-C12-C27 alkanes. These results are of significance for the further processing and marketing of this oil.

  16. Evaluation of the Rockwell International flash-hydroliquefaction process. Final summary report

    SciTech Connect

    Sirohi, V.P.

    1980-09-01

    At the request of the Department of Energy, UOP/SDC has evaluated the Rockwell Hydroliquefaction Process to determine the adequacy of the existing PDU data base and to assess the practicability and operability of the process. UOP/SDC conducted nine studies. Their findings follow: (1) A complete designed set of experiments must be run on the present PDU to make possible satisfactory analysis of the effects of variables especially the effect of diluents in the H/sub 2/ feed and the possibility of carbon deposition problems. (2) Basic improvements in the equipment and operation of the PDU should first be made (Ten specific recommendations are made). (3) A reactor design concept must be developed that looks feasible for design, fabrication, and operation. (4) A conceptual commercial design and economics should be prepared based on a realistic set of design bases and criteria. (5) If the above are accomplished successfully with attractive results, then and only then: (a) A study should be made of the refining requirements of the product, which are expected to be expensive based on the H/C ratio. (b) The PDU should be modified for continuous runs of up to one month to: Confirm the data correlations, estimate the reliability of the reactor and process, adhere to the requirements stated above, test cryogenic gas separation, study fouling and erosion, study lockhopper feeding, establish initial reliability of the coal injector and precombustion assembly head, collect scale-up and design data, and conduct a materials study and confirm materials choices. (c) Determine particle size of the char and of the solids in the oil product, the degree to which they may be separated, and how the ash should be removed from the product oil.

  17. Combination of pyrolysis and hydroliquefaction of CCB-treated wood for energy recovery: optimization and products characterization.

    PubMed

    Kinata, Silao Espérance; Loubar, Khaled; Paraschiv, Maria; Belloncle, Christophe; Tazerout, Mohand

    2012-08-01

    In this paper, pyrolysis and hydroliquefaction processes were successively used to convert CCB-treated wood into bio-oil with respect to environment. Pyrolysis temperature has been optimized to produce maximum yield of charcoal with a high metal content (Cu, Cr, and B). The results obtained indicate that the pyrolysis at 300 °C and 30 min are the optimal conditions giving high yield of charcoal about 45% which contains up to 94% of Cu, 100% of Cr and 88% of B. After pyrolysis process, the charcoal has been converted into bio-oil using hydroliquefaction process. The optimization approach for the yield of bio-oil using a complete factorial design with three parameters: charcoal/solvent, temperature and hydrogen pressure was discussed. It is observed that the temperature is the most significant parameter and the optimum yield of bio-oil is around 82%. The metal analysis shows that the metals present in the bio-oil is very negligible.

  18. Combination of pyrolysis and hydroliquefaction of CCB-treated wood for energy recovery: optimization and products characterization.

    PubMed

    Kinata, Silao Espérance; Loubar, Khaled; Paraschiv, Maria; Belloncle, Christophe; Tazerout, Mohand

    2012-08-01

    In this paper, pyrolysis and hydroliquefaction processes were successively used to convert CCB-treated wood into bio-oil with respect to environment. Pyrolysis temperature has been optimized to produce maximum yield of charcoal with a high metal content (Cu, Cr, and B). The results obtained indicate that the pyrolysis at 300 °C and 30 min are the optimal conditions giving high yield of charcoal about 45% which contains up to 94% of Cu, 100% of Cr and 88% of B. After pyrolysis process, the charcoal has been converted into bio-oil using hydroliquefaction process. The optimization approach for the yield of bio-oil using a complete factorial design with three parameters: charcoal/solvent, temperature and hydrogen pressure was discussed. It is observed that the temperature is the most significant parameter and the optimum yield of bio-oil is around 82%. The metal analysis shows that the metals present in the bio-oil is very negligible. PMID:22705538

  19. Endocytic vesicle scission by lipid phase boundary forces

    PubMed Central

    Liu, Jian; Kaksonen, Marko; Drubin, David G.; Oster, George

    2006-01-01

    Endocytosis in budding yeast is thought to occur in several phases. First, the membrane invaginates and then elongates into a tube. A vesicle forms at the end of the tube, eventually pinching off to form a “free” vesicle. Experiments show that actin polymerization is an active participant in the endocytic process, along with a number of membrane-associated proteins. Here we investigate the possible roles of these components in driving vesiculation by constructing a quantitative model of the process beginning at the stage where the membrane invagination has elongated into a tube encased in a sheath of membrane-associated protein. This protein sheath brings about the scission step where the vesicle separates from the tube. When the protein sheath is dynamin, it is commonly assumed that scission is brought about by the constriction of the sheath. Here, we show that an alternative scenario can work as well: The protein sheath acts as a “filter” to effect a phase separation of lipid species. The resulting line tension tends to minimize the interface between the tube region and the vesicle region. Interestingly, large vesicle size can further facilitate the reduction of the interfacial diameter down to a few nanometers, small enough so that thermal fluctuations can fuse the membrane and pinch off the vesicle. To deform the membrane into the tubular vesicle shape, the membrane elastic resistance forces must be balanced by some additional forces that we show can be generated by actin polymerization and/or myosin I. These active forces are shown to be important in successful scission processes as well. PMID:16801551

  20. Constitutive models for rubber networks undergoing simultaneous crosslinking and scission.

    SciTech Connect

    Thompson, Aidan Patrick; Curro, John G.; Rottach, Dana R.; Grest, Gary Stephen; Budzien, Joanne L.; Lo, David Chi S.

    2006-01-01

    Constitutive models for chemically reacting networks are formulated based on a generalization of the independent network hypothesis. These models account for the coupling between chemical reaction and strain histories, and have been tested by comparison with microscopic molecular dynamics simulations. An essential feature of these models is the introduction of stress transfer functions that describe the interdependence between crosslinks formed and broken at various strains. Efforts are underway to implement these constitutive models into the finite element code Adagio. Preliminary results are shown that illustrate the effects of changing crosslinking and scission rates and history.

  1. Basic results of investigations of scission neutrons in nuclear fission at low excitation energies

    SciTech Connect

    Petrov, G. A. Gagarski, A. M.; Guseva, I. S.; Sokolov, V. E.; Val'ski, G. V.; Vorobiev, A. S.; Krinitcin, D. O.; Shcherbakov, O. A.; Nikolaev, D. V.; Pleva, Yu. S.; Petrova, V. I.; Zavarukhina, T. A.

    2008-07-15

    To estimate the main characteristics of neutrons emitted shortly before the scission of a fissioning nucleus, various experiments sensitive to the presence of these scission neutrons in thermal-neutron-induced fission of {sup 235}U and spontaneous fission of {sup 252}Cf were performed. The results of the experiments were analyzed within theoretical calculations allowing for various possible neutron-emission mechanisms, including the possibility of the emergence of neutrons from the scission of a nucleus.

  2. [Solvent-induced lesions in Tröndelag. How were they treated?].

    PubMed

    Leira, H L; Bratt, U; Gustafsson, O; Saksvik, P O

    1990-11-20

    The article presents the most important results of a follow-up study of 60 patients with solvent induced encephalopathy, carried out 3-5 years after diagnosis. Factors concerning health, work and social life were registered. These encephalopathies seem to remain stable after cessation of exposure to solvents. The majority of the patients did not fully understand the diagnosis. Only a minority of the patients followed recommendations concerning further work and exposure to solvents. The disease has major consequences for the social well-being of the patients, and they do not seem to receive adequate support from the social welfare authorities. PMID:2260062

  3. Solvent-induced current-voltage hysteresis and negative differential resistance in molecular junctions

    NASA Astrophysics Data System (ADS)

    Dzhioev, Alan A.; Kosov, D. S.

    2012-01-01

    We consider a single molecule circuit embedded into solvent. The Born dielectric solvation model is combined with Keldysh nonequilibrium Green's functions to describe the electron-transport properties of the system. Depending on the dielectric constant, the solvent induces multiple nonequilibrium steady states with corresponding hysteresis in molecular current-voltage characteristics as well as negative differential resistance. We identify the physical range of solvent and molecular parameters where the effects are present. The position of the negative differential resistance peak can be controlled by the dielectric constant of the solvent.

  4. The solvent-induced interaction of spherical solutes in associated and non-associated liquids.

    PubMed

    Djikaev, Yuri S; Ruckenstein, Eli

    2014-07-21

    We propose an efficient method for studying the solvent-induced interaction of two solvophobic particles immersed in a liquid solvent. The method is based on the combination of the probabilistic hydrogen bond model with the density functional theory. An analytic expression for the number of hydrogen bonds per water molecule near two spherical hydrophobes is derived as a function of the molecule distance to both hydrophobes, distance between hydrophobes, and their radii. Using this expression, one can construct an approximation for the distribution of fluid (liquid water) molecules in the system which provides a reasonably good (much faster and accurate enough) alternative to a standard iteration procedure. Such an approximate density distribution constitutes an efficient foundation for studying the length-scale and temperature dependence of hydrophobic interactions. The model is applied to the interaction of solvophobic solutes in both associated and non-associated liquids. Of these two cases, the model predictions for the solvent-induced potential of mean force between two solutes in associated liquids are closer to the results of molecular dynamics simulation of hydrophobic interactions in the SPC/E model water. Our results suggest that the hydrogen bonding ability of water molecules may play a major role in hydrophobic phenomena.

  5. Nitroxides block DNA scission and protect cells from oxidative damage

    SciTech Connect

    Samuni, A.; Godinger, D.; Aronovitch, J. ); Russo, A.; Mitchell, J. )

    1991-01-01

    The protective effect of cyclic stable nitroxide free radicals, having SOD-like activity, against oxidative damage was studied by using Escherichia coli xthA DNA repair-deficient mutant hypersensitive to H{sub 2}O{sub 2}. Oxidative damage induced by H{sub 2}O{sub 2} was assayed by monitoring cell survival. The metal chelator 1,10-phenanthroline (OP), which readily intercalates into DNA, potentiated with H{sub 2}O{sub 2}-induced damage. The extent of in vivo DNA scission and degradation was studied and compared with the loss of cell viability. The extent of DNA breakage correlated with cell killing, supporting previous suggestions that DNA is the crucial cellular target of H{sub 2}O{sub 2} cytotoxicity. The xthA cells were protected by catalase but not by superoxide dismutase (SOD). Both five- and six-membered ring nitroxides, having SOD-like activity, protected growing and resting cells from H{sub 2}O{sub 2} toxicity, without lowering H{sub 2}O{sub 2} concentration. To check whether nitroxides protect against O{sub 2}{sup {center dot}{minus}}-independent injury also, experiments were repeated under hypoxia. These nitroxides also protected hypoxic cells against H{sub 2}O{sub 2}, suggesting alternative modes of protection. Since nitroxides were found to reoxidize DNA-bound iron(II), the present results suggest that nitroxides protect by oxidizing reduced transition metals, thus interfering with the Fenton reaction.

  6. Endophilin-A2 functions in membrane scission in clathrin-independent endocytosis.

    PubMed

    Renard, Henri-François; Simunovic, Mijo; Lemière, Joël; Boucrot, Emmanuel; Garcia-Castillo, Maria Daniela; Arumugam, Senthil; Chambon, Valérie; Lamaze, Christophe; Wunder, Christian; Kenworthy, Anne K; Schmidt, Anne A; McMahon, Harvey T; Sykes, Cécile; Bassereau, Patricia; Johannes, Ludger

    2015-01-22

    During endocytosis, energy is invested to narrow the necks of cargo-containing plasma membrane invaginations to radii at which the opposing segments spontaneously coalesce, thereby leading to the detachment by scission of endocytic uptake carriers. In the clathrin pathway, dynamin uses mechanical energy from GTP hydrolysis to this effect, assisted by the BIN/amphiphysin/Rvs (BAR) domain-containing protein endophilin. Clathrin-independent endocytic events are often less reliant on dynamin, and whether in these cases BAR domain proteins such as endophilin contribute to scission has remained unexplored. Here we show, in human and other mammalian cell lines, that endophilin-A2 (endoA2) specifically and functionally associates with very early uptake structures that are induced by the bacterial Shiga and cholera toxins, which are both clathrin-independent endocytic cargoes. In controlled in vitro systems, endoA2 reshapes membranes before scission. Furthermore, we demonstrate that endoA2, dynamin and actin contribute in parallel to the scission of Shiga-toxin-induced tubules. Our results establish a novel function of endoA2 in clathrin-independent endocytosis. They document that distinct scission factors operate in an additive manner, and predict that specificity within a given uptake process arises from defined combinations of universal modules. Our findings highlight a previously unnoticed link between membrane scaffolding by endoA2 and pulling-force-driven dynamic scission.

  7. ENDOPHILIN-A2 FUNCTIONS IN MEMBRANE SCISSION IN CLATHRIN-INDEPENDENT ENDOCYTOSIS

    PubMed Central

    Renard, Henri-François; Simunovic, Mijo; Lemière, Joël; Boucrot, Emmanuel; Garcia-Castillo, Maria-Daniela; Arumugam, Senthil; Chambon, Valérie; Lamaze, Christophe; Wunder, Christian; Kenworthy, Anne K.; Schmidt, Anne A.; McMahon, Harvey T.; Sykes, Cécile; Bassereau, Patricia; Johannes, Ludger

    2015-01-01

    During endocytosis, energy is invested to narrow the necks of cargo-containing plasma membrane invaginations to radii at which the opposing segments spontaneously coalesce, thereby leading to the detachment by scission of endocytic uptake carriers1. In the clathrin pathway, dynamin uses mechanical energy from GTP hydrolysis to this effect2–4, assisted by the BIN/amphiphysin/Rvs (BAR) domain-containing protein endophilin5,6. Clathrin-independent endocytic events are often less reliant on dynamin7, and whether in these cases BAR domain proteins such as endophilin contribute to scission has remained unexplored. Here we found that endophilin-A2 (endoA2) specifically and functionally associates with very early uptake structures that are induced by the bacterial Shiga and cholera toxins, which both are clathrin-independent endocytic cargoes8. In controlled in vitro systems, endoA2 reshapes membranes prior to scission. Furthermore, we demonstrate that endoA2, dynamin, and actin contribute in parallel to the scission of Shiga toxin-induced tubules. Our results establish a novel function of endoA2 in clathrin-independent endocytosis. They document that distinct scission factors operate in an additive manner, and predict that specificity within a given uptake process arises from defined combinations of universal modules. Our findings finally highlight a previously unnoticed link between membrane scaffolding by endoA2 and pulling force-driven dynamic scission. PMID:25517096

  8. Can solvent induced surface modifications applied to screen-printed platforms enhance their electroanalytical performance?

    PubMed

    Blanco, Elias; Foster, Christopher W; Cumba, Loanda R; do Carmo, Devaney R; Banks, Craig E

    2016-04-25

    In this paper the effect of solvent induced chemical surface enhancements upon graphitic screen-printed electrodes (SPEs) is explored. Previous literature has indicated that treating the working electrode of a SPE with the solvent N,N-dimethylformamide (DMF) offers improvements within the electroanalytical response, resulting in a 57-fold increment in the electrode surface area compared to their unmodified counterparts. The protocol involves two steps: (i) the SPE is placed into DMF for a selected time, and (ii) it is cured in an oven at a selected time and temperature. Beneficial electroanalytical outputs are reported to be due to the increased surface area attributed to the binder within the bulk surface of the SPEs dissolving out during the immersion step (step i). We revisit this exciting concept and explore these solvent induced chemical surface enhancements using edge- and basal-plane like SPEs and a new bespoke SPE, utilising the solvent DMF and explore, in detail, the parameters utilised in steps (i) and (ii). The electrochemical performance following steps (i) and (ii) is evaluated using the outer-sphere redox probe hexaammineruthenium(iii) chloride/0.1 M KCl, where it is found that the largest improvement is obtained using DMF with an immersion time of 10 minutes and a curing time of 30 minutes at 100 °C. Solvent induced chemical surface enhancement upon the electrochemical performance of SPEs is also benchmarked in terms of their electroanalytical sensing of NADH (dihydronicotinamide adenine dinucleotide reduced form) and capsaicin both of which are compared to their unmodified SPE counterparts. In both cases, it is apparent that a marginal improvement in the electroanalytical sensitivity (i.e. gradient of calibration plots) of 1.08-fold and 1.38-fold are found respectively. Returning to the original exciting concept, interestingly it was found that when a poor experimental technique was employed, only then significant increases within the working

  9. Can solvent induced surface modifications applied to screen-printed platforms enhance their electroanalytical performance?

    PubMed

    Blanco, Elias; Foster, Christopher W; Cumba, Loanda R; do Carmo, Devaney R; Banks, Craig E

    2016-04-25

    In this paper the effect of solvent induced chemical surface enhancements upon graphitic screen-printed electrodes (SPEs) is explored. Previous literature has indicated that treating the working electrode of a SPE with the solvent N,N-dimethylformamide (DMF) offers improvements within the electroanalytical response, resulting in a 57-fold increment in the electrode surface area compared to their unmodified counterparts. The protocol involves two steps: (i) the SPE is placed into DMF for a selected time, and (ii) it is cured in an oven at a selected time and temperature. Beneficial electroanalytical outputs are reported to be due to the increased surface area attributed to the binder within the bulk surface of the SPEs dissolving out during the immersion step (step i). We revisit this exciting concept and explore these solvent induced chemical surface enhancements using edge- and basal-plane like SPEs and a new bespoke SPE, utilising the solvent DMF and explore, in detail, the parameters utilised in steps (i) and (ii). The electrochemical performance following steps (i) and (ii) is evaluated using the outer-sphere redox probe hexaammineruthenium(iii) chloride/0.1 M KCl, where it is found that the largest improvement is obtained using DMF with an immersion time of 10 minutes and a curing time of 30 minutes at 100 °C. Solvent induced chemical surface enhancement upon the electrochemical performance of SPEs is also benchmarked in terms of their electroanalytical sensing of NADH (dihydronicotinamide adenine dinucleotide reduced form) and capsaicin both of which are compared to their unmodified SPE counterparts. In both cases, it is apparent that a marginal improvement in the electroanalytical sensitivity (i.e. gradient of calibration plots) of 1.08-fold and 1.38-fold are found respectively. Returning to the original exciting concept, interestingly it was found that when a poor experimental technique was employed, only then significant increases within the working

  10. Desalination membranes from functional block copolymer via non-solvent induced phase inversion

    NASA Astrophysics Data System (ADS)

    Sung, Hyemin; Poelma, Justin; Leibfarth, Frank; Hawker, Craig; Bang, Joona

    2012-02-01

    Commercially available reverse osmosis (RO) and forward osmosis (FO) membranes are most commonly derived from materials such as polysulfone, polyimide, and cellulose acetate. While these membranes have improved the efficiency of the desalination process, they suffer from mechanical and chemical stability, fouling issues, and low fluxes. In this study, we combine a well-established membrane formation method, non-solvent-induced phase separation, with the self-assembly of a functional amphiphilic block copolymersAn amine and acid functional polystyrene-block-poly(ethylene oxide-co-allyl glycidyl ether) were chosen for the membranes. Membranes were formed by casting a concentrated polymer solution (12 to 25 wt% polymer) on PET fabric followed by immersion in a non-solvent bath. Scanning electron microscopy revealed an asymmetric porous structure consisting of a dense skin layer on top of a highly porous layer. Membrane performance was investigating using an FO test cell under the seawater condition.

  11. Solvent induced modifications to fiber nanostructure and morphology for 12HSA molecular gels

    NASA Astrophysics Data System (ADS)

    Gao, Jie

    Molecular organogels are thermo reversible quasi-solid materials, which are formed by low molecular weight organogelators (LMOGs) undergoing supramolecular aggregation via non-covalent interactions, forming a three-dimensional fibrillar network. Numerous applications of molecular organogels are been investigated as edible oils, drug release matrices and personal care products. The chemistry of the organic phase (i.e., solvent) influences every level of structure in organogels. Different solvents induce LMOG to assemble into "crystal like" fibers, which have more than one crystal form, lamellar arrangement and domain size. Differences in these solid states are known to affect the macroscopic properties of the gel, including critical gelator concentration (CGC), melting point, melting enthalpy and opacity.12-hydroxystearic acid (12HSA) was examined in several classes of organic solvents with different function groups. These gels, sols or precipitates were analyzed using a series of techniques including: powder x-ray diffraction (XRD), differential scanning calorimetry (DSC), fourier-transform infrared spectroscopy (FT-IR), pulsed nuclear magnetic resonance spectroscopy (pNMR) and microscopy. Specifically, certain solvents caused 12HSA to self-assemble into a triclinic parallel polymorphic form with subcell spacing of ~4.6, 3.9, and 3.8 A and an interdigitated unit cell with a lamellar arrangement (38~44 A). This polymorphic form corresponded to a less effective sphereultic supramolecular crystalline network, which immobilizes solvents at CGC greater than 1.5 wt %. The other group of solvents induce a hexagonal subcell spacing (i.e., unit sub cell spacing ~4.1 A) and are arranged in a multi lamellar fashion with a unit cell greater than the bimolecular length of 12HSA (~54 A).This polymorphic form corresponds to fibrillar aggregates with a CGC less than 1 wt %.

  12. Solvent-Induced Single Crystal-Single Crystal Transformation of an Interpenetrated Three-Dimensional Copper Triazole Catalytic Framework.

    PubMed

    Wang, Ying; Meng, Shan-Shan; Lin, Peng-Xiang; Xiao, Yi-Wei; Ma, Qing-Qing; Xie, Qiong; Chen, Yuan-Yuan; Zhao, Xiao-Jun; Chen, Jun

    2016-05-01

    The 2-fold interpenetrated 3D framework 1 can be solvent-induced to noninterpenetrated framework 1' in a reversible single crystal-single crystal transformation fashion. In addition, 1' represents the first catalyst based on triazole to catalyze the aerobic homocoupling of various substituted arylboronic acids.

  13. Kinetic analysis of mechanochemical chain scission of linear poly(phthalaldehyde).

    PubMed

    Peterson, Gregory I; Boydston, Andrew J

    2014-09-01

    The kinetics of mechanochemical chain scission of poly(phthalaldehyde) (PPA) are investigated. Ultrasound-induced cavitation is capable of causing chain scission in the PPA backbone that ultimately leads to rapid depolymerization of each resulting polymer fragment when above the polymer's ceiling temperature (Tc ). An interesting feature of the mechanochemical breakdown of PPA is that "half-chain" daughter fragments are not observed, since the depolymerization is rapid following chain scission. These features facilitate the determination of rate constants of activation for multiple molecular weights from a single sonication experiment. Additionally, the degradation kinetics are modified with chain-end trapping agents through variation of the nature and amount of small molecule nucleophile or electrophile.

  14. New statistical scission-point model to predict fission fragment observables

    NASA Astrophysics Data System (ADS)

    Lemaître, Jean-François; Panebianco, Stefano; Sida, Jean-Luc; Hilaire, Stéphane; Heinrich, Sophie

    2015-09-01

    The development of high performance computing facilities makes possible a massive production of nuclear data in a full microscopic framework. Taking advantage of the individual potential calculations of more than 7000 nuclei, a new statistical scission-point model, called SPY, has been developed. It gives access to the absolute available energy at the scission point, which allows the use of a parameter-free microcanonical statistical description to calculate the distributions and the mean values of all fission observables. SPY uses the richness of microscopy in a rather simple theoretical framework, without any parameter except the scission-point definition, to draw clear answers based on perfect knowledge of the ingredients involved in the model, with very limited computing cost.

  15. SPY: A new scission point model based on microscopic ingredients to predict fission fragments properties

    NASA Astrophysics Data System (ADS)

    Lemaître, J.-F.; Dubray, N.; Hilaire, S.; Panebianco, S.; Sida, J.-L.

    2013-12-01

    Our purpose is to determine fission fragments characteristics in a framework of a scission point model named SPY for Scission Point Yields. This approach can be considered as a theoretical laboratory to study fission mechanism since it gives access to the correlation between the fragments properties and their nuclear structure, such as shell correction, pairing, collective degrees of freedom, odd-even effects. Which ones are dominant in final state? What is the impact of compound nucleus structure? The SPY model consists in a statistical description of the fission process at the scission point where fragments are completely formed and well separated with fixed properties. The most important property of the model relies on the nuclear structure of the fragments which is derived from full quantum microscopic calculations. This approach allows computing the fission final state of extremely exotic nuclei which are inaccessible by most of the fission model available on the market.

  16. Solvent induced conformational fluctuation of alanine dipeptide studied by using vibrational probes.

    PubMed

    Cai, Kaicong; Du, Fenfen; Liu, Jia; Su, Tingting

    2015-02-25

    The solvation effect on the three dimensional structure and the vibrational feature of alanine dipeptide (ALAD) was evaluated by applying the implicit solvents from polarizable continuum solvent model (PCM) through ab initio calculations, by using molecular dynamic (MD) simulations with explicit solvents, and by combining these two approaches. The implicit solvent induced potential energy fluctuations of ALAD in CHCl3, DMSO and H2O are revealed by means of ab initio calculations, and a global view of conformational and solvation environmental dependence of amide I frequencies is achieved. The results from MD simulations with explicit solvents show that ALAD trends to form PPII, αL, αR, and C5 in water, PPII and C5 in DMSO, and C5 in CHCl3, ordered by population, and the demonstration of the solvated structure, the solute-solvent interaction and hydrogen bonding is therefore enhanced. Representative ALAD-solvent clusters were sampled from MD trajectories and undergone ab initio calculations. The explicit solvents reveal the hydrogen bonding between ALAD and solvents, and the correlation between amide I frequencies and the CO bond length is built. The implicit solvents applied to the ALAD-solvent clusters further compensate the solvation effect from the bulk, and thus enlarge the degree of structural distortion and the amide I frequency red shift. The combination of explicit solvent in the first hydration shell and implicit solvent in the bulk is helpful for our understanding about the conformational fluctuation of solvated polypeptides through vibrational probes.

  17. Control of charge transport in a semiconducting copolymer by solvent-induced long-range order

    NASA Astrophysics Data System (ADS)

    Luzio, Alessandro; Criante, Luigino; D'Innocenzo, Valerio; Caironi, Mario

    2013-12-01

    Recent reports on high-mobility organic field-effect transistors (FETs) based on donor-acceptor semiconducting co-polymers have indicated an apparently strong deviation from the paradigm, valid for a series of semi-crystalline polymers, which has been strictly correlating charges mobility to crystalline order. This poses a severe limit on the control of mobility and a fundamental question on the critical length scale which is dominating charge transport. Here we focus on a well-known model material for electron transport, a naphthalene-diimide based copolymer, and we demonstrate that mobility can be controlled over two orders of magnitude, with maximum saturation mobility exceeding 1 cm2/Vs at high gate voltages, by controlling the extent of orientational domains through a deposition process as simple as spin-coating. High mobility values can be achieved by adopting solvents inducing a higher amount of pre-aggregates in the solution, which through the interaction with the substrate, provide the polymer with liquid-crystalline like ordering properties.

  18. Solvent-Induced Crystallization in Poly(Ethylene Terephthalate) during Mass Transport

    NASA Astrophysics Data System (ADS)

    Ouyang, Hao

    2001-03-01

    The solvent transport in poly(ethylene terephthalate) (PET) and related phase transformation were investigated. The data of mass sorption were analyzed according to Harmon¡¦s model for Case I (Fickian), Case II (swelling) and anomalous transport. This transport process in PET is accompanied by the induced crystallization of the original amorphous state. The transformation was studied by wide angle x-ray scattering (WAXS), small angle x-ray scattering (SAXS), Differential Scanning Calorimeter (DSC), density gradient column, and Fourier Transform Infra-Red (FTIR). During this process, the matrix is under a compressive strain that causes different kinetic path of crystallization as compared to that by thermal annealing. This state of strain will assist the development of the solvent-induced crystallization. It also can be explained in terms of the principle of Le Chatelier if the local equilibrium is assumed. The model regarding the crystallization was proposed in terms of the study of long period L, the crystal thickness lc and the thickness of amorphous layer la, obtained from the linear correlation function and interface distribution function.

  19. Enhanced hydrophobicity of polyurethane via non-solvent induced surface aggregation of silica nanoparticles.

    PubMed

    Seyfi, Javad; Hejazi, Iman; Jafari, Seyed Hassan; Khonakdar, Hossein Ali; Simon, Frank

    2016-09-15

    Fabrication of superhydrophobic surfaces from hydrophilic polymers has always been regarded as a challenge. In this study, to achieve superhydrophobic polyurethane (PU) surfaces, silica nanoparticles and ethanol as non-solvent were simultaneously utilized during a solution casting-based process. Such modified version of phase separation process was found to be highly efficient, and also it required much lower concentration of nanoparticles to achieve superhydrophobicity as compared to the previously reported methods in the literature. According to the proposed mechanism, non-solvent induces a more profound aggregation of silica nanoparticles at the surface's top layer causing the surface energy to be highly diminished, and thus, the water repellency is improved. Morphology and topography results showed that a unique "triple-sized" structure was formed on the surface of superhydrophobic samples. X-ray photoelectron spectroscopy results proved that both PU macromolecules and silica nanoparticles were concurrently present at the surface layer of the superhydrophobic sample. It was concluded that surface composition and roughness could be regarded as competing factors in achieving superhydrophobicity. Based on the obtained results, the proposed method exhibits a promising potential in large-scale fabrication of surface layers with superhydrophobic property. Moreover, a mechanism was also presented to further explicate the physics behind the suggested method. PMID:27288577

  20. Control of charge transport in a semiconducting copolymer by solvent-induced long-range order

    PubMed Central

    Luzio, Alessandro; Criante, Luigino; D'Innocenzo, Valerio; Caironi, Mario

    2013-01-01

    Recent reports on high-mobility organic field-effect transistors (FETs) based on donor-acceptor semiconducting co-polymers have indicated an apparently strong deviation from the paradigm, valid for a series of semi-crystalline polymers, which has been strictly correlating charges mobility to crystalline order. This poses a severe limit on the control of mobility and a fundamental question on the critical length scale which is dominating charge transport. Here we focus on a well-known model material for electron transport, a naphthalene-diimide based copolymer, and we demonstrate that mobility can be controlled over two orders of magnitude, with maximum saturation mobility exceeding 1 cm2/Vs at high gate voltages, by controlling the extent of orientational domains through a deposition process as simple as spin-coating. High mobility values can be achieved by adopting solvents inducing a higher amount of pre-aggregates in the solution, which through the interaction with the substrate, provide the polymer with liquid-crystalline like ordering properties. PMID:24305756

  1. A dynamin-actin interaction is required for vesicle scission during endocytosis in yeast.

    PubMed

    Palmer, Sarah E; Smaczynska-de Rooij, Iwona I; Marklew, Christopher J; Allwood, Ellen G; Mishra, Ritu; Johnson, Simeon; Goldberg, Martin W; Ayscough, Kathryn R

    2015-03-30

    Actin is critical for endocytosis in yeast cells, and also in mammalian cells under tension. However, questions remain as to how force generated through actin polymerization is transmitted to the plasma membrane to drive invagination and scission. Here, we reveal that the yeast dynamin Vps1 binds and bundles filamentous actin. Mutational analysis of Vps1 in a helix of the stalk domain identifies a mutant RR457-458EE that binds actin more weakly. In vivo analysis of Vps1 function demonstrates that the mutation disrupts endocytosis but not other functions of Vps1 such as vacuolar trafficking or peroxisome fission. The mutant Vps1 is stably expressed in cells and co-localizes with the endocytic reporters Abp1 and the amphiphysin Rvs167. Detailed analysis of individual endocytic patch behavior indicates that the mutation causes aberrant movements in later stages of endocytosis, consistent with a scission defect. Ultrastructural analysis of yeast cells using electron microscopy reveals a significant increase in invagination depth, further supporting a role for the Vps1-actin interaction during scission. In vitro analysis of the mutant protein demonstrates that--like wild-type Vps1--it is able to form oligomeric rings, but, critically, it has lost its ability to bundle actin filaments into higher-order structures. A model is proposed in which actin filaments bind Vps1 during invagination, and this interaction is important to transduce the force of actin polymerization to the membrane to drive successful scission.

  2. Influence of dynamical parameters on pre-scission particles and fission probability in heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Pahlavani, M. R.; Naderi, D.

    2011-02-01

    A stochastic approach to fission dynamics based on one- and three-dimensional Langevin equations was applied to calculate the fission probability and the pre-scission particle multiplicity. Evaporation of pre-scission light particles along Langevin fission trajectories from the ground state of the compound nucleus to its scission and fission probability have been calculated using a Monte Carlo simulation technique. To examine this approach we used F19+Ta181 and O16+Au197 systems. Our results show that the fission probability and pre-scission particle multiplicity in three dimensions is different from the one-dimensional Langevin approach. The theoretical results of pre-scission neutron, proton, and α-particle multiplicities and the fission probability for given systems based on this model are compared with available experimental data. The obtained results using three-dimensional calculations are in better agreement with experimental data.

  3. Controlling Palladium Nanocrystals by Solvent-Induced Strategy for Efficient Multiple Liquid Fuels Electrooxidation.

    PubMed

    Zhang, Ying; Zhu, Xing; Guo, Jun; Huang, Xiaoqing

    2016-08-17

    Pd has been considered as the possible economical substitute of rare Pt for catalyzing the liquid fuels electrooxidation reaction. However, the biggest problem of Pd nanocatalysts for alcohol oxidations is that they show the limited stability and activity, greatly impacting the development of liquid fuels-based fuel cell technology. We report herein a new solvent-induced procedure for making distinct Pd NCs with geometry tuning from Pd nanosheets, Pd tetrapods, to Pd concave tetrahedra by switching the solvent from 1-methyl-2-pyrrolidone, formamide, to acetylacetonate. The key features for the preparation of dimension-controlled Pd NCs herein are that the use of molybdenum carbonyl (Mo(CO)6) determines the exposed {111} facet in the final Pd NCs, while different solvents control the reduction kinetics to induce the growth of Pd NCs with distinct morphologies. The as-prepared distinct Pd NCs show the interesting shape-dependent electrocatalytic activities toward multiple liquid fuels electrooxidation reactions including ethylene glycol oxidation reaction, glycerol oxidation reaction, ethanol oxidation reaction, and also methanol oxidation reaction with Pd nanosheets exhibiting higher activity than all the other Pd catalysts and higher activity than the commercial Pd/C and also Pd black due to the thin character of Pd nanosheets. Most importantly, the Pd nanosheets exhibit much higher stability for multiple liquid fuels electrooxidation than all the other Pd catalysts tested. The present work gives the first example in exploring the effect of solvent in tuning the dimensions of Pd NCs, and thus optimizing the electrocatalytic performance for liquid fuels electrooxidation. PMID:27442912

  4. Prediction of enhanced solvent-induced enantioselectivity for a ring opening with a bifurcating reaction path

    DOE PAGESBeta

    Carpenter, Barry K.; Harvey, Jeremy N.; Glowacki, David R.

    2014-12-11

    Classical molecular dynamics simulations are reported for the deazetisation and ring opening of meso-2,3-difluoro-2,3-dimethyldiazocyclopropane in three solvents: CHCl3, CHFClBr and CH3CH(OH)CF3 (TFIPA). In this study, the achiral reactant leads to enantiomeric allene products, and the question addressed in the study is whether either of the chiral, enantiomerically pure solvents can induce significant enantiomeric excess in the products. The direct dynamics calculations use an empirical valence bond potential for the solute, with empirical parameters optimised against M06-2X/cc-pVTZ density functional results. The results reveal that the exothermic N2 loss and ring opening promote transient strong solvent–solute interactions within the first ~100 fsmore » of the reaction. Because of the bifurcating reaction path, these interactions occur at time when the “decision” about which enantiomer of the product to form has yet to be made (at least for many of the trajectories). Hence, it is possible in principle that the solvent could exert a larger-than-normal influence on the course of the reaction. In fact, the results reveal no such effect for CHFClBr but do predict that TFIPA should induce 15.2 ± 2.1% enantiomeric excess. This is roughly an order of magnitude larger than solvent-induced enantiomeric excesses found experimentally in reactions where the conversion of reactant(s) to enantiomeric products occur over separate transition states.« less

  5. Solvent induced phase inversion-based in situ forming controlled release drug delivery implants.

    PubMed

    Thakur, Raghu Raj Singh; McMillan, Hannah L; Jones, David S

    2014-02-28

    In situ forming (ISF) drug delivery implants have gained tremendous levels of interest over the last few decades. This is due to their wide range of biomedical applications such as in tissue engineering, cell encapsulation, microfluidics, bioengineering and drug delivery. Drug delivery implants forming upon injection has shown a range of advantages which include localized drug delivery, easy and less invasive application, sustained drug action, ability to tailor drug delivery, reduction in side effects associated with systemic delivery and also improved patient compliance and comfort. Different factors such as temperature, pH, ions, and exchange of solvents are involved in in situ implant formation. This review especially focuses on ISF implants that are formed through solvent induced phase inversion (SPI) technique. The article critically reviews and compares a wide range of polymers, solvents, and co-solvents that have been used in SPI implant preparation for control release of a range of drug molecules. Major drawback of SPI systems has been their high burst release. In this regard, the article exhaustively discusses factors that affect the burst release and different modification strategies that has been utilised to reduce the burst effect from these implants. Performance and controversial issues associated with the use of different biocompatible solvents in SPI systems is also discussed. Biodegradation, formulation stability, methods of characterisation and sterilisation techniques of SPI systems is comprehensively reviewed. Furthermore, the review also examines current SPI-based marketed products, their therapeutic application and associated clinical data. It also exemplifies the interest of multi-billion dollar pharma companies worldwide for further developments of SPI systems to a range of therapeutic applications. The authors believe that this will be the first review article that extensively investigate and discusses studies done to date on SPI systems

  6. Prediction of enhanced solvent-induced enantioselectivity for a ring opening with a bifurcating reaction path

    SciTech Connect

    Carpenter, Barry K.; Harvey, Jeremy N.; Glowacki, David R.

    2014-12-11

    Classical molecular dynamics simulations are reported for the deazetisation and ring opening of meso-2,3-difluoro-2,3-dimethyldiazocyclopropane in three solvents: CHCl3, CHFClBr and CH3CH(OH)CF3 (TFIPA). In this study, the achiral reactant leads to enantiomeric allene products, and the question addressed in the study is whether either of the chiral, enantiomerically pure solvents can induce significant enantiomeric excess in the products. The direct dynamics calculations use an empirical valence bond potential for the solute, with empirical parameters optimised against M06-2X/cc-pVTZ density functional results. The results reveal that the exothermic N2 loss and ring opening promote transient strong solvent–solute interactions within the first ~100 fs of the reaction. Because of the bifurcating reaction path, these interactions occur at time when the “decision” about which enantiomer of the product to form has yet to be made (at least for many of the trajectories). Hence, it is possible in principle that the solvent could exert a larger-than-normal influence on the course of the reaction. In fact, the results reveal no such effect for CHFClBr but do predict that TFIPA should induce 15.2 ± 2.1% enantiomeric excess. This is roughly an order of magnitude larger than solvent-induced enantiomeric excesses found experimentally in reactions where the conversion of reactant(s) to enantiomeric products occur over separate transition states.

  7. Solvent-induced helical assembly and reversible chiroptical switching of chiral cyclic-dipeptide-functionalized naphthalenediimides.

    PubMed

    Manchineella, Shivaprasad; Prathyusha, V; Priyakumar, U Deva; Govindaraju, T

    2013-12-01

    Understanding the roles of various parameters in orchestrating the preferential chiral molecular organization in supramolecular self-assembly processes is of great significance in designing novel molecular functional systems. Cyclic dipeptide (CDP) chiral auxiliary-functionalized naphthalenediimides (NCDPs 1-6) have been prepared and their chiral self-assembly properties have been investigated. Detailed photophysical and circular dichroism (CD) studies have unveiled the crucial role of the solvent in the chiral aggregation of these NCDPs. NCDPs 1-3 form supramolecular helical assemblies and exhibit remarkable chiroptical switching behaviour (M- to P-type) depending on the solvent composition of HFIP and DMSO. The strong influence of solvent composition on the supramolecular chirality of NCDPs has been further corroborated by concentration and solid-state thin-film CD studies. The chiroptical switching between supramolecular aggregates of opposite helicity (M and P) has been found to be reversible, and can be achieved through cycles of solvent removal and redissolution in solvent mixtures of specific composition. The control molecular systems (NCDPs 4-6), with an achiral or D-isomer second amino acid in the CDP auxiliary, did not show chiral aggregation properties. The substantial roles of hydrogen bonding and π-π interactions in the assembly of the NCDPs have been validated through nuclear magnetic resonance (NMR), photophysical, and computational studies. Quantum chemical calculations at the ab initio, semiempirical, and density functional theory levels have been performed on model systems to understand the stabilities of the right (P-) and left (M-) handed helical supramolecular assemblies and the nature of the intermolecular interactions. This study emphasizes the role of CDP chiral auxiliaries on the solvent-induced helical assembly and reversible chiroptical switching of naphthalenediimides. PMID:24281809

  8. Hydroliquefaction of coal

    DOEpatents

    Sze, Morgan C.; Schindler, Harvey D.

    1982-01-01

    Coal is catalytically hydroliquefied by passing coal dispersed in a liquefaction solvent and hydrogen upwardly through a plurality of parallel expanded catalyst beds, in a single reactor, in separate streams, each having a cross-sectional flow area of no greater than 255 inches square, with each of the streams through each of the catalyst beds having a length and a liquid and gas superficial velocity to maintain an expanded catalyst bed and provide a Peclet Number of at least 3. If recycle is employed, the ratio of recycle to total feed (coal and liquefaction solvent) is no greater than 2:1, based on volume. Such conditions provide for improved selectivity to liquid product to thereby reduce hydrogen consumption. The plurality of beds are formed by partitions in the reactor.

  9. The comparison of binary- and ternary-fission configurations close to the instant of scission

    NASA Astrophysics Data System (ADS)

    Guseva, I. S.; Gagarski, A. M.; Gusev, Yu. I.; Petrov, G. A.; Valski, G. V.

    2013-07-01

    A new way to bring into comparison the binary- and ternary-fission configurations is proposed. The method is founded on recently discovered ROT effect. The angle of fission axis deflection from its initial orientation at the moment of scission comes into existence as a result of dividing system rotation and carries information about fissioning nucleus deformation. The comparison of proper angles for binary and ternary fission can be used to estimate the difference in the rupture configurations.

  10. Dynamical interpretation of average fission-fragment kinetic energy systematics and nuclear scission

    SciTech Connect

    Nadtochy, P.N.; Adeev, G.D.

    2005-11-01

    A dynamical interpretation of the well-known systematics for average total kinetic energy of fission fragments over a wide range of the Coulomb parameter (600scission criteria traditionally employed in fission theory--at zero neck radius and at finite neck radius--have been applied in dynamical calculations. Both have resulted in a fairly good description of the dependence of on the Coulomb parameter. The results of dynamical calculations of within three-dimensional Langevin dynamics show that the mean distance between the centers of mass of nascent fragments at the scission configuration increases linearly with the parameter Z{sup 2}/A{sup 1/3}. This distance changes approximately from 2.35R{sub 0} for {sup 119}Xe to 2.6R{sub 0} for {sup 256}Fm. In spite of this increase in mean distance between future fragments at scission, the linear dependence of on the parameter Z{sup 2}/A{sup 1/3} remains approximately valid over a wide range of the Coulomb parameter Z{sup 2}/A{sup 1/3}.

  11. High-energy radiation forming chain scission and branching in polypropylene

    NASA Astrophysics Data System (ADS)

    Otaguro, H.; de Lima, L. F. C. P.; Parra, D. F.; Lugão, A. B.; Chinelatto, M. A.; Canevarolo, S. V.

    2010-03-01

    The degradation of high molecular weight isotactic polypropylene (iPP) subjected to gamma rays irradiation up to 100 kGy in inert atmosphere was analyzed. The investigation relied upon complex viscosity, elastic modulus, gel fraction, morphology of the insoluble fraction and deconvoluted molecular weight distribution (MWD) curves. At low irradiation doses, already at 5 kGy, the MWD curve is strongly shifted to the low molecular weight side showing chain scission, which is confirmed using the calculated chain scission distribution function (CSDF). At high dose levels, the appearance of a shoulder in the high molecular weight side of the MWD curve indicates the formation of chain branching. The presence of a considerable insoluble fraction at these high dose levels indicates also the formation of cross-linking, which has different morphology then the insoluble fraction present in the original iPP. The rheological results show changes in the molecular structure of irradiated samples in agreement with the gel content data. The chromatographic and rheological data has shown that gamma irradiation of iPP produces chain scission, branching and cross-linking.

  12. SPY: a new scission-point model based on microscopic inputs to predict fission fragment properties

    NASA Astrophysics Data System (ADS)

    Panebianco, Stefano; Dubray, Nöel; Goriely, Stéphane; Hilaire, Stéphane; Lemaître, Jean-François; Sida, Jean-Luc

    2014-04-01

    Despite the difficulty in describing the whole fission dynamics, the main fragment characteristics can be determined in a static approach based on a so-called scission-point model. Within this framework, a new Scission-Point model for the calculations of fission fragment Yields (SPY) has been developed. This model, initially based on the approach developed by Wilkins in the late seventies, consists in performing a static energy balance at scission, where the two fragments are supposed to be completely separated so that their macroscopic properties (mass and charge) can be considered as fixed. Given the knowledge of the system state density, averaged quantities such as mass and charge yields, mean kinetic and excitation energy can then be extracted in the framework of a microcanonical statistical description. The main advantage of the SPY model is the introduction of one of the most up-to-date microscopic descriptions of the nucleus for the individual energy of each fragment and, in the future, for their state density. These quantities are obtained in the framework of HFB calculations using the Gogny nucleon-nucleon interaction, ensuring an overall coherence of the model. Starting from a description of the SPY model and its main features, a comparison between the SPY predictions and experimental data will be discussed for some specific cases, from light nuclei around mercury to major actinides. Moreover, extensive predictions over the whole chart of nuclides will be discussed, with particular attention to their implication in stellar nucleosynthesis. Finally, future developments, mainly concerning the introduction of microscopic state densities, will be briefly discussed.

  13. Nonadiabatic effects in C-Br bond scission in the photodissociation of bromoacetyl chloride

    NASA Astrophysics Data System (ADS)

    Valero, Rosendo; Truhlar, Donald G.

    2006-11-01

    Bromoacetyl chloride photodissociation has been interpreted as a paradigmatic example of a process in which nonadiabatic effects play a major role. In molecular beam experiments by Butler and co-workers [J. Chem. Phys. 95, 3848 (1991); J. Chem. Phys. 97, 355 (1992)], BrCH2C(O )Cl was prepared in its ground electronic state (S0) and excited with a laser at 248nm to its first excited singlet state (S1). The two main ensuing photoreactions are the ruptures of the C-Cl bond and of the C-Br bond. A nonadiabatic model was proposed in which the C-Br scission is strongly suppressed due to nonadiabatic recrossing at the barrier formed by the avoided crossing between the S1 and S2 states. Recent reduced-dimensional dynamical studies lend support to this model. However, another interpretation that has been given for the experimental results is that the reduced probability of C-Br scission is a consequence of incomplete intramolecular energy redistribution. To provide further insight into this problem, we have studied the energetically lowest six singlet electronic states of bromoacetyl chloride by using an ab initio multiconfigurational perturbative electronic structure method. Stationary points (minima and saddle points) and minimum energy paths have been characterized on the S0 and S1 potential energy surfaces. The fourfold way diabatization method has been applied to transform five adiabatic excited electronic states to a diabatic representation. The diabatic potential energy matrix of the first five excited singlet states has been constructed along several cuts of the potential energy hypersurfaces. The thermochemistry of the photodissociation reactions and a comparison with experimental translational energy distributions strongly suggest that nonadiabatic effects dominate the C-Br scission, but that the reaction proceeds along the energetically allowed diabatic pathway to excited-state products instead of being nonadiabatically suppressed. This conclusion is also

  14. Analysis of pre- and post-scission neutrons emitted in the reaction sup 169 Tm( sup 36 Ar, f ) at E sub lab =205 MeV

    SciTech Connect

    Rossner, H.; Hilscher, D.; Hinde, D.J.; Gebauer, B.; Lehmann, M.; Wilpert, M. ); Mordhorst, E. )

    1989-12-01

    Pre- and post-scission neutron multiplicities for the reaction {sup 169}Tm({sup 36}Ar,{ital f}) at {ital E}{sub lab}=205 MeV were measured in coincidence with fission fragments of different masses and total kinetic energies. The mass and total kinetic energy dependence of the total neutron multiplicity as well as the width of the out-of-plane fission fragment correlation angle are well described by evaporation calculations. An average time before scission of several 10{sup {minus}20} s is deduced from the average pre-scission neutron multiplicity. The mass dependence of the post-scission neutron multiplicity is consistent with an energy division at scission proportional to the mass of the fragments. For the first time clear evidence for an increase in pre-scission neutrons with increasing total kinetic energy values has been observed. Possible interpretations of this unexpected behavior are discussed.

  15. Comparing different energy partitions at scission used in prompt emission model codes GEF and Point-by-Point

    NASA Astrophysics Data System (ADS)

    Tudora, A.; Hambsch, F.-J.; Visan, I.; Giubega, G.

    2015-08-01

    Different methods to partition the total excitation energy (TXE) of fully accelerated fragments, presently used in prompt emission calculations include different assumptions about what is happening at scission. In fact the energy partition takes place at scission or even before scission, depending on the physical assumptions supporting the models used in different methods of TXE partition. The paper discusses two TXE partition methods in which the amount of energy to be shared (at scission and before scission, respectively) is very different. These methods (based on different principles and physical considerations) are: A. The method used in the Point-by-Point (PbP) treatment of prompt emission in which the available excitation energy at scission is shared between complementary nascent fragments. The amount of energy to be shared is sufficiently high to consider the nascent fragments in the Fermi-gas regime of the level density. B. The method used in the GEF code, in which the intrinsic energy before scission is shared between pre-nascent fragments according to the "energy sorting mechanism". This sorting mechanism is based on the assumption of level densities in the constant temperature regime, only. This is supported by the low amount of the shared intrinsic energy in the case of thermal and low energy neutron induced fission. Taking into account that the principles and physical considerations of any TXE partition method are independent on the way to treat the prompt emission (i.e. deterministically as in the PbP model or probabilistically by Monte-Carlo as in the code GEF) the methods A and B are applied to the same fission fragment range (built as in the PbP treatment). Extreme hypotheses are made for the fragment level densities on which the partitions are based (only in the Fermi-gas regime or only in the constant temperature regime). The results are compared with the energy partition obtained with fragment level densities described by the composite Gilbert

  16. ESCRT-III and Vps4: a dynamic multipurpose tool for membrane budding and scission.

    PubMed

    Alonso Y Adell, Manuel; Migliano, Simona M; Teis, David

    2016-09-01

    Complex molecular machineries bud, scission and repair cellular membranes. Components of the multi-subunit endosomal sorting complex required for transport (ESCRT) machinery are enlisted when multivesicular bodies are generated, extracellular vesicles are formed, the plasma membrane needs to be repaired, enveloped viruses bud out of host cells, defective nuclear pores have to be cleared, the nuclear envelope must be resealed after mitosis and for final midbody abscission during cytokinesis. While some ESCRT components are only required for specific processes, the assembly of ESCRT-III polymers on target membranes and the action of the AAA-ATPase Vps4 are mandatory for every process. In this review, we summarize the current knowledge of structural and functional features of ESCRT-III/Vps4 assemblies in the growing pantheon of ESCRT-dependent pathways. We describe specific recruitment processes for ESCRT-III to different membranes, which could be useful to selectively inhibit ESCRT function during specific processes, while not affecting other ESCRT-dependent processes. Finally, we speculate how ESCRT-III and Vps4 might function together and highlight how the characterization of their precise spatiotemporal organization will improve our understanding of ESCRT-mediated membrane budding and scission in vivo. PMID:26910595

  17. Pre- and post- scission particle emission in 3D Langevin calculations with various macroscopic potentials

    NASA Astrophysics Data System (ADS)

    Mazurek, K.; Nadtochy, P. N.; Schmitt, C.; Wasiak, P.; Kmiecik, M.; Maj, A.; Bonnet, E.; Chbihi, A.; Frankland, J.; Gruyer, D.; Wieleczko, J.-P.

    2013-12-01

    The fission dynamics described by solving differential equations of the Langevin type in three dimensional space of the deformation parameters is very sensitive on the choice of the macroscopic components such as potential energy models. The mass or charge distribution or total kinetic energy has been already shown to be different when one uses the Finite Range Liquid Drop Model or Lublin - Strasbourg Drop model. Also the shape-dependent congruence or shape-dependent Wigner energy and A0 terms are important especially for the fission of medium mass nuclei. We would like to make step forward and answer the question about the varying of the post-scission multiplicity by including different PES. Up to now there are only few experimental data for the medium mass nuclei where the pre- and post- scission emission has been estimated and isotopic distributions have been shown. The isotopic distributions of the fission products for light compound nucleus such as 111 In with two beam energies (Ebeam = 10.6 AMeV and 5.9 AMeV) and two heavy systems: 229Np with Ebeam = 7.4 AMeV and 260 No (Ebeam = 6 AMeV and 7.5 AMeV) have been studied theoretically. The agreement with the experimental data is discussed.

  18. Scission neutrons for U, Pu, Cm, and Cf isotopes: Relative multiplicities calculated in the sudden limit

    NASA Astrophysics Data System (ADS)

    Capote, R.; Carjan, N.; Chiba, S.

    2016-02-01

    The multiplicities of scission neutrons νs c are calculated for series of U, Pu, Cm, and Cf isotopes assuming a sudden transition between two different nuclear configurations (αi→αf ): one just before the neck rupture and one immediately after the disappearance of the neck. This calculation requires only the knowledge of the corresponding two sets of neutron eigenstates. The nuclear shapes around the scission point are described in terms of Cassinian ovals with only two parameters: α (that positions the shape with respect to the zero-neck shape) and α1 (that defines the mass asymmetry). Based on these shapes, a neutron mean field of the Woods-Saxon type is constructed using two prescriptions to calculate the distance to the nuclear surface. The accent in the present work is put on the dependence of νs c on the neutron number Nf of the fissioning nucleus and on the mass asymmetry AL/AH of the primary fission fragments. The relative dependence of these multiplicities, averaged over the mass yields, <νs c> , are finally compared with existing experimental data on prompt fission neutrons <νp> .

  19. Crosslink density, oxidation and chain scission in retrieved, highly cross-linked UHMWPE tibial bearings.

    PubMed

    Reinitz, Steven D; Currier, Barbara H; Levine, Rayna A; Van Citters, Douglas W

    2014-05-01

    Irradiated, thermally stabilized, highly cross-linked UHMWPE bearings have demonstrated superior wear performance and improved in vitro oxidation resistance compared with terminally gamma-sterilized bearings, yet retrieval analysis reveals unanticipated in vivo oxidation in these materials despite fewer or no measurable free radicals. There has been little evidence to date that the oxidation mechanism in thermally stabilized materials is the same as that in conventional materials, and so it is unknown whether oxidation in these materials is leading to chain scission and a degradation of mechanical properties, molecular weight, and crosslink density. The aim of this study was to determine whether measured in vivo oxidation in retrieved, highly cross-linked tibial bearings corresponds with a decreasing crosslink density. Analysis of three tibial bearing materials revealed that crosslink density decreased following in vivo duration, and that the change in crosslink density was strongly correlated with oxidation. The results suggest that oxidation in highly cross-linked materials is causing chain scissions that may, in time, impact the material properties. If in vivo oxidation continues over longer durations, there is potential for a clinically significant degradation of mechanical properties.

  20. Durable, superoleophobic polymer–nanoparticle composite surfaces with re-entrant geometry via solvent-induced phase transformation

    NASA Astrophysics Data System (ADS)

    Brown, Philip S.; Bhushan, Bharat

    2016-02-01

    Superoleophobic plastic surfaces are useful in a wide variety of applications including anti-fouling, self-cleaning, anti-smudge, and low-drag. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating re-entrant geometries desirable for superoleophobicity via entrapment of nanoparticles in polycarbonate surfaces. Nanoparticle incorporation occurs during solvent-induced swelling and subsequent crystallization of the polymer surface. The resulting surface was found to comprise of re-entrant structures, a result of the nanoparticle agglomerates acting as nucleation points for polymer crystallization. Examples of such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. This method of impregnating nanoparticles into polymer surfaces could prove useful in improving the anti-bacterial, mechanical, and liquid-repellent properties of plastic devices.

  1. A QSPR study on the solvent-induced frequency shifts of acetone and dimethyl sulfoxide in organic solvents

    NASA Astrophysics Data System (ADS)

    Ou, Yu Heng; Chang, Chia Ming; Chen, Ying Shao

    2016-06-01

    In this study, solvent-induced frequency shifts (SIFS) in the infrared spectrum of acetone and dimethyl sulfoxide in organic solvents were investigated by using four types of quantum-chemical reactivity descriptors. The results showed that the SIFS of acetone is mainly affected by the electron-acceptance chemical potential and the maximum nucleophilic condensed local softness of organic solvents, which represent the electron flow and the polarization between acetone and solvent molecules. On the other hand, the SIFS of dimethyl sulfoxide changes with the maximum positive charge of hydrogen atom and the inverse of apolar surface area of solvent molecules, showing that the electrostatic and hydrophilic interactions are main mechanisms between dimethyl sulfoxide and solvent molecules. The introduction of the four-element theory model-based quantitative structure-property relationship approach improved the assessing quality and provided a basis for interpreting the solute-solvent interactions.

  2. Solvent-induced variable conformation of bis(terpyridine) derivatives during supramolecular self-assembly at liquid/HOPG interfaces.

    PubMed

    Wang, Shuai; Zhao, Fengying; Luo, Shiwen; Geng, Yanfang; Zeng, Qingdao; Wang, Chen

    2015-05-14

    Variable supramolecular structures constructed by bis-(2,2':6',2''-terpyridine)-4'-oxyhexadecane (BT-O-C16) on a highly oriented pyrolytic graphite (HOPG) surface were investigated by scanning tunneling microscopy (STM). Seven different solvents (1-phenyloctane, n-tetradecane, n-dodecane, n-decane, n-octane, 1-heptanoic acid, and 1-octanoic acid) were utilized to affect the self-assembling structures of BT-O-C16 at liquid/HOPG interfaces. High-resolution STM analyses revealed that various nanostructures were formed by the change of molecular conformation, which are actually driven by the cooperative interaction effect under different environments. Therefore, the solvent-induced cooperative influence on the molecular self-assembly is important for constructing supramolecular nanostructures.

  3. A QSPR study on the solvent-induced frequency shifts of acetone and dimethyl sulfoxide in organic solvents.

    PubMed

    Ou, Yu Heng; Chang, Chia Ming; Chen, Ying Shao

    2016-06-01

    In this study, solvent-induced frequency shifts (SIFS) in the infrared spectrum of acetone and dimethyl sulfoxide in organic solvents were investigated by using four types of quantum-chemical reactivity descriptors. The results showed that the SIFS of acetone is mainly affected by the electron-acceptance chemical potential and the maximum nucleophilic condensed local softness of organic solvents, which represent the electron flow and the polarization between acetone and solvent molecules. On the other hand, the SIFS of dimethyl sulfoxide changes with the maximum positive charge of hydrogen atom and the inverse of apolar surface area of solvent molecules, showing that the electrostatic and hydrophilic interactions are main mechanisms between dimethyl sulfoxide and solvent molecules. The introduction of the four-element theory model-based quantitative structure-property relationship approach improved the assessing quality and provided a basis for interpreting the solute-solvent interactions. PMID:26994584

  4. Solvent-induced variable conformation of bis(terpyridine) derivatives during supramolecular self-assembly at liquid/HOPG interfaces.

    PubMed

    Wang, Shuai; Zhao, Fengying; Luo, Shiwen; Geng, Yanfang; Zeng, Qingdao; Wang, Chen

    2015-05-14

    Variable supramolecular structures constructed by bis-(2,2':6',2''-terpyridine)-4'-oxyhexadecane (BT-O-C16) on a highly oriented pyrolytic graphite (HOPG) surface were investigated by scanning tunneling microscopy (STM). Seven different solvents (1-phenyloctane, n-tetradecane, n-dodecane, n-decane, n-octane, 1-heptanoic acid, and 1-octanoic acid) were utilized to affect the self-assembling structures of BT-O-C16 at liquid/HOPG interfaces. High-resolution STM analyses revealed that various nanostructures were formed by the change of molecular conformation, which are actually driven by the cooperative interaction effect under different environments. Therefore, the solvent-induced cooperative influence on the molecular self-assembly is important for constructing supramolecular nanostructures. PMID:25897523

  5. Durable, superoleophobic polymer-nanoparticle composite surfaces with re-entrant geometry via solvent-induced phase transformation

    NASA Astrophysics Data System (ADS)

    Brown, Philip S.; Bhushan, Bharat

    2016-02-01

    Superoleophobic plastic surfaces are useful in a wide variety of applications including anti-fouling, self-cleaning, anti-smudge, and low-drag. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating re-entrant geometries desirable for superoleophobicity via entrapment of nanoparticles in polycarbonate surfaces. Nanoparticle incorporation occurs during solvent-induced swelling and subsequent crystallization of the polymer surface. The resulting surface was found to comprise of re-entrant structures, a result of the nanoparticle agglomerates acting as nucleation points for polymer crystallization. Examples of such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. This method of impregnating nanoparticles into polymer surfaces could prove useful in improving the anti-bacterial, mechanical, and liquid-repellent properties of plastic devices.

  6. Durable, superoleophobic polymer–nanoparticle composite surfaces with re-entrant geometry via solvent-induced phase transformation

    PubMed Central

    Brown, Philip S.; Bhushan, Bharat

    2016-01-01

    Superoleophobic plastic surfaces are useful in a wide variety of applications including anti-fouling, self-cleaning, anti-smudge, and low-drag. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating re-entrant geometries desirable for superoleophobicity via entrapment of nanoparticles in polycarbonate surfaces. Nanoparticle incorporation occurs during solvent-induced swelling and subsequent crystallization of the polymer surface. The resulting surface was found to comprise of re-entrant structures, a result of the nanoparticle agglomerates acting as nucleation points for polymer crystallization. Examples of such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. This method of impregnating nanoparticles into polymer surfaces could prove useful in improving the anti-bacterial, mechanical, and liquid-repellent properties of plastic devices. PMID:26876479

  7. Clathrin modulates vesicle scission, but not invagination shape, in yeast endocytosis

    PubMed Central

    Kukulski, Wanda; Picco, Andrea; Specht, Tanja

    2016-01-01

    In a previous paper (Picco et al., 2015), the dynamic architecture of the protein machinery during clathrin-mediated endocytosis was visualized using a new live imaging and particle tracking method. Here, by combining this approach with correlative light and electron microscopy, we address the role of clathrin in this process. During endocytosis, clathrin forms a cage-like coat around the membrane and associated protein components. There is growing evidence that clathrin does not determine the membrane morphology of the invagination but rather modulates the progression of endocytosis. We investigate how the deletion of clathrin heavy chain impairs the dynamics and the morphology of the endocytic membrane in budding yeast. Our results show that clathrin is not required for elongating or shaping the endocytic membrane invagination. Instead, we find that clathrin contributes to the regularity of vesicle scission and thereby to controlling vesicle size. DOI: http://dx.doi.org/10.7554/eLife.16036.001 PMID:27341079

  8. Compound nucleus decay: Comparison between saddle point and scission point barriers

    SciTech Connect

    Santos, T. J.; Carlson, B. V.

    2014-11-11

    One of the principal characteristics of nuclear multifragmentation is the emission of complex fragments of intermediate mass. An extension of the statistical multifragmentation model has been developed, in which the process can be interpreted as the near simultaneous limit of a series of sequential binary decays. In this extension, intermediate mass fragment emissions are described by expressions almost identical to those of light particle emission. At lower temperatures, similar expressions have been shown to furnish a good description of very light intermediate mass fragment emission but not of the emission of heavier fragments, which seems to be determined by the transition density at the saddle-point rather than at the scission point. Here, we wish to compare these different formulations of intermediate fragmment emission and analyze the extent to which they remain distinguishable at high excitation energy.

  9. Robust self-replication of combinatorial information via crystal growth and scission

    PubMed Central

    Schulman, Rebecca; Yurke, Bernard; Winfree, Erik

    2012-01-01

    Understanding how a simple chemical system can accurately replicate combinatorial information, such as a sequence, is an important question for both the study of life in the universe and for the development of evolutionary molecular design techniques. During biological sequence replication, a nucleic acid polymer serves as a template for the enzyme-catalyzed assembly of a complementary sequence. Enzymes then separate the template and complement before the next round of replication. Attempts to understand how replication could occur more simply, such as without enzymes, have largely focused on developing minimal versions of this replication process. Here we describe how a different mechanism, crystal growth and scission, can accurately replicate chemical sequences without enzymes. Crystal growth propagates a sequence of bits while mechanically-induced scission creates new growth fronts. Together, these processes exponentially increase the number of crystal sequences. In the system we describe, sequences are arrangements of DNA tile monomers within ribbon-shaped crystals. 99.98% of bits are copied correctly and 78% of 4-bit sequences are correct after two generations; roughly 40 sequence copies are made per growth front per generation. In principle, this process is accurate enough for 1,000-fold replication of 4-bit sequences with 50% yield, replication of longer sequences, and Darwinian evolution. We thus demonstrate that neither enzymes nor covalent bond formation are required for robust chemical sequence replication. The form of the replicated information is also compatible with the replication and evolution of a wide class of materials with precise nanoscale geometry such as plasmonic nanostructures or heterogeneous protein assemblies. PMID:22493232

  10. Cerebrospinal fluid proteins and free amino acids in patients with solvent induced chronic toxic encephalopathy and healthy controls.

    PubMed Central

    Moen, B E; Kyvik, K R; Engelsen, B A; Riise, T

    1990-01-01

    The concentrations of protein, albumin, IgG, and free amino acids in the cerebrospinal fluid of 16 patients with chronic toxic encephalopathy due to organic solvents were measured. The patient group consisted of all patients with this diagnosis in a neurological department in 1985. The diagnosis was based on neuraesthenic symptoms, pathological psychometric performance, and verified exposure to neurotoxic organic solvents. A control group of 16 patients with myalgias or backache, or both, and no signs of disease was used for comparison. The purpose was to study possible changes in the cerebrospinal fluid that might contribute to understanding the aetiology of solvent induced chronic toxic encephalopathy. A rise in protein, albumin, and IgG was found in the patient group compared with the control group, as well as reduced concentrations of phosphoethanolamine, taurine, homocarnosine, ethanolamine, alpha-aminobutyric acid, and leucine. Using a stepwise multiple regression analysis, taurine was negatively correlated to exposure to solvents. These findings may indicate membrane alterations in the central nervous system related to exposure to organic solvents. PMID:2337535

  11. Amide Link Scission in the Polyamide Active Layers of Thin-Film Composite Membranes upon Exposure to Free Chlorine: Kinetics and Mechanisms.

    PubMed

    Powell, Joshua; Luh, Jeanne; Coronell, Orlando

    2015-10-20

    The volume-averaged amide link scission in the aromatic polyamide active layer of a reverse osmosis membrane upon exposure to free chlorine was quantified at a variety of free chlorine exposure times, concentrations, and pH and rinsing conditions. The results showed that (i) hydroxyl ions are needed for scission to occur, (ii) hydroxide-induced amide link scission is a strong function of exposure to hypochlorous acid, (iii) the ratio between amide links broken and chlorine atoms taken up increased with the chlorination pH and reached a maximum of ∼25%, (iv) polyamide disintegration occurs when high free chlorine concentrations, alkaline conditions, and high exposure times are combined, (v) amide link scission promotes further chlorine uptake, and (vi) scission at the membrane surface is unrepresentative of volume-averaged scission in the active layer. Our observations are consistent with previously proposed mechanisms describing amide link scission as a result of the hydrolysis of the N-chlorinated amidic N-C bond due to nucleophilic attack by hydroxyl ions. This study increases the understanding of the physicochemical changes that could occur for membranes in treatment plants using chlorine as an upstream disinfectant and the extent and rate at which those changes would occur. PMID:26394532

  12. Amide Link Scission in the Polyamide Active Layers of Thin-Film Composite Membranes upon Exposure to Free Chlorine: Kinetics and Mechanisms.

    PubMed

    Powell, Joshua; Luh, Jeanne; Coronell, Orlando

    2015-10-20

    The volume-averaged amide link scission in the aromatic polyamide active layer of a reverse osmosis membrane upon exposure to free chlorine was quantified at a variety of free chlorine exposure times, concentrations, and pH and rinsing conditions. The results showed that (i) hydroxyl ions are needed for scission to occur, (ii) hydroxide-induced amide link scission is a strong function of exposure to hypochlorous acid, (iii) the ratio between amide links broken and chlorine atoms taken up increased with the chlorination pH and reached a maximum of ∼25%, (iv) polyamide disintegration occurs when high free chlorine concentrations, alkaline conditions, and high exposure times are combined, (v) amide link scission promotes further chlorine uptake, and (vi) scission at the membrane surface is unrepresentative of volume-averaged scission in the active layer. Our observations are consistent with previously proposed mechanisms describing amide link scission as a result of the hydrolysis of the N-chlorinated amidic N-C bond due to nucleophilic attack by hydroxyl ions. This study increases the understanding of the physicochemical changes that could occur for membranes in treatment plants using chlorine as an upstream disinfectant and the extent and rate at which those changes would occur.

  13. Cell Division by Longitudinal Scission in the Insect Endosymbiont Spiroplasma poulsonii

    PubMed Central

    Maclachlan, Catherine; Clerc-Rosset, Stéphanie; Knott, Graham W.

    2016-01-01

    ABSTRACT Spiroplasma bacteria are highly motile bacteria with no cell wall and a helical morphology. This clade includes many vertically transmitted insect endosymbionts, including Spiroplasma poulsonii, a natural endosymbiont of Drosophila melanogaster. S. poulsonii bacteria are mainly found in the hemolymph of infected female flies and exhibit efficient vertical transmission from mother to offspring. As is the case for many facultative endosymbionts, S. poulsonii can manipulate the reproduction of its host; in particular, S. poulsonii induces male killing in Drosophila melanogaster. Here, we analyze the morphology of S. poulsonii obtained from the hemolymph of infected Drosophila. This endosymbiont was not only found as long helical filaments, as previously described, but was also found in a Y-shaped form. The use of electron microscopy, immunogold staining of the FtsZ protein, and antibiotic treatment unambiguously linked the Y shape of S. poulsonii to cell division. Observation of the Y shape in another Spiroplasma, S. citri, and anecdotic observations from the literature suggest that cell division by longitudinal scission might be prevalent in the Spiroplasma clade. Our study is the first to report the Y-shape mode of cell division in an endosymbiotic bacterium and adds Spiroplasma to the so far limited group of bacteria known to utilize this cell division mode. PMID:27460796

  14. Chain scission and anti fungal effect of electron beam on cellulose membrane

    NASA Astrophysics Data System (ADS)

    Wanichapichart, Pikul; Taweepreeda, Wirach; Nawae, Safitree; Choomgan, Pastraporn; Yasenchak, Dan

    2012-08-01

    Two types of bacterial cellulose (BC) membranes were produced under a modified H&S medium using sucrose as a carbon source, with (CCB) and without (SHB) coconut juice supplement. Both membranes showed similar crystallinity of 69.24 and 71.55%. After being irradiated with E-beams under oxygen limited and ambient condition, the results from water contact angle showed that only the irradiated membrane CCB was increased from 30 to 40 degrees, and irradiation under oxygen ambient condition provided the greatest value. Comparing with the control membranes, smaller water flux was the cases after electron beam irradiation which indicated a reduction of membrane pore area. However, the results from molecular weight cut off (MWCO) revealed that chain scission was greater for membrane SHB and its cut off was increased from 28,000 Da to more than 35,000 Da. FTIR analysis revealed some changes in membrane functional groups, corresponding with the above results. These changes initiated new property of cellulose membranes, an anti-fungal food wrap.

  15. Catalytic strategy for carbon-carbon bond scission by the cytochrome P450 OleT.

    PubMed

    Grant, Job L; Mitchell, Megan E; Makris, Thomas Michael

    2016-09-01

    OleT is a cytochrome P450 that catalyzes the hydrogen peroxide-dependent metabolism of Cn chain-length fatty acids to synthesize Cn-1 1-alkenes. The decarboxylation reaction provides a route for the production of drop-in hydrocarbon fuels from a renewable and abundant natural resource. This transformation is highly unusual for a P450, which typically uses an Fe(4+)-oxo intermediate known as compound I for the insertion of oxygen into organic substrates. OleT, previously shown to form compound I, catalyzes a different reaction. A large substrate kinetic isotope effect (≥8) for OleT compound I decay confirms that, like monooxygenation, alkene formation is initiated by substrate C-H bond abstraction. Rather than finalizing the reaction through rapid oxygen rebound, alkene synthesis proceeds through the formation of a reaction cycle intermediate with kinetics, optical properties, and reactivity indicative of an Fe(4+)-OH species, compound II. The direct observation of this intermediate, normally fleeting in hydroxylases, provides a rationale for the carbon-carbon scission reaction catalyzed by OleT. PMID:27555591

  16. Dynamin recruitment and membrane scission at the neck of a clathrin-coated pit

    PubMed Central

    Cocucci, Emanuele; Gaudin, Raphaël; Kirchhausen, Tom

    2014-01-01

    Dynamin, the GTPase required for clathrin-mediated endocytosis, is recruited to clathrin-coated pits in two sequential phases. The first is associated with coated pit maturation; the second, with fission of the membrane neck of a coated pit. Using gene-edited cells that express dynamin2-EGFP instead of dynamin2 and live-cell TIRF imaging with single-molecule EGFP sensitivity and high temporal resolution, we detected the arrival of dynamin at coated pits and defined dynamin dimers as the preferred assembly unit. We also used live-cell spinning-disk confocal microscopy calibrated by single-molecule EGFP detection to determine the number of dynamins recruited to the coated pits. A large fraction of budding coated pits recruit between 26 and 40 dynamins (between 1 and 1.5 helical turns of a dynamin collar) during the recruitment phase associated with neck fission; 26 are enough for coated vesicle release in cells partially depleted of dynamin by RNA interference. We discuss how these results restrict models for the mechanism of dynamin-mediated membrane scission. PMID:25232009

  17. DNA- and protein-scission activities of ascorbate in the presence of copper ion and a copper-peptide complex.

    PubMed

    Chiou, S H

    1983-10-01

    L-Ascorbic acid, when combined with either copper(II) ion or a copper(II)-tripeptide complex, extensively cleaved several viral DNAs and proteins under in vitro conditions. Neither ascorbate nor copper tripeptide (Cu2+-diglycyl-L-histidine) alone caused any apparent changes on these molecules. Various transition metal ions and reducing agents were examined under comparable conditions to determine the basic requirements for both DNA degradation and protein scission activities. Copper and iron are the two most effective transition metal ions examined that exhibit these activities in the presence of ascorbate. The addition of catalase, but not superoxide dismutase, can partially inhibit the scission of DNA in vitro, suggesting that H2O2 may be involved in these activities. Among the various reducing agents tested, ascorbate was most effective in causing DNA scission and protein cleavage, corroborating the possible role of H2O2 in the cleavage reactions. One of the products of the reactions of copper/ascorbate is probably the hydroxyl radical generated from H2O2, which can be formed from the oxidation of ascorbate. PMID:6654857

  18. Vibrational spectra from atomic fluctuations in dynamics simulations. II. Solvent-induced frequency fluctuations at femtosecond time resolution

    NASA Astrophysics Data System (ADS)

    Schmitz, Matthias; Tavan, Paul

    2004-12-01

    The midinfrared (MIR) spectra of molecules in polar solvents exhibit inhomogeneously broadened bands whose spectral positions are shifted as compared to the gas phase. The shifts are caused by interactions with structured solvation shells and the broadenings by fluctuations of these interactions. The MIR spectra can be calculated from hybrid molecular dynamics (MD) simulations, which treat the solute molecule by density functional theory and the solvent by molecular mechanics by the so-called instantaneous normal mode analysis (INMA) or by Fourier transforming the time correlation function (FTTCF) of the molecular dipole moment. In Paper I of this work [M. Schmitz and P. Tavan, J. Chem. Phys. 121, 12233 (2004)] we explored an alternative method based on generalized virial (GV) frequencies noting, however, that GV systematically underestimates frequencies. As shown by us these artifacts are caused by solvent-induced fluctuations of the (i) equilibrium geometry, (ii) force constants, and (iii) normal mode directions as well as by (iv) diagonal and (v) off-diagonal anharmonicities. Here we now show, by analyzing the time scales of fluctuations and sample MD trajectories of formaldehyde in the gas phase and in water, that all these sources of computational artifacts can be made visible by a Fourier analysis of the normal coordinates. Correspondingly, the error sources (i) and (iii)-(v) can be removed by bandpass filtering, as long as the spectral signatures of the respective effects are well separated from the fundamental band. Furthermore, the artifacts arising from effect (ii) can be strongly diminished by a time-resolved version of the GV approach (TF-GV). The TF-GV method then yields for each mode j a trajectory of the vibrational frequency ωj(t|τ) at a time resolution τ>τj, which is only limited by the corresponding oscillation time τj=2π/ωj and, thus, is in the femtosecond range. A correlation analysis of these trajectories clearly separates the

  19. Decomposition Pathways of Glycerol via C–H, O–H, and C–C Bond Scission on Pt(111): A Density Functional Theory Study

    SciTech Connect

    Liu, Bin; Greeley, Jeffrey P.

    2011-10-13

    Glycerol decomposition on Pt(111) via dehydrogenation or C–C bond scission is examined with periodic density functional theory (DFT) calculations. The thermochemistry of dehydrogenation intermediates is first estimated using an empirical correlation scheme with parameters fit to selected DFT calculations; the resulting estimates for the more stable intermediates are refined with full DFT calculations. Brønsted–Evans–Polanyi (BEP) relationships for dehydrogenation and C–C bond scission reactions are developed and used to estimate the kinetics of elementary dehydrogenation and C–C bond scission steps in the reaction network. The combined thermochemical and kinetic analysis implies that glycerol dehydrogenation products at intermediate levels of dehydrogenation are the most thermochemically stable. Additionally, although C–C bond scission transition state energies are high for glycerol and for intermediates at early stages of dehydrogenation, these energies decrease as the intermediates are successively dehydrogenated, reaching a minimum after the removal of several hydrogen atoms from glycerol. At these levels of dehydrogenation, the C–C scission transition state energies become comparable to those of O–H or C–H scission. These results suggest that C–C bonds are only broken after glycerol has been significantly dehydrogenated and demonstrate that DFT-based analyses, combined with simple correlation schemes, can be effective for elucidating general features of complex biomassic reaction networks.

  20. Decomposition Pathways of Glycerol via C–H, O–H, and C–C Bond Scission on Pt(111): A Density Functional Theory Study

    SciTech Connect

    Liu, Bin; Greeley, Jeffrey

    2011-09-01

    Glycerol decomposition on Pt(111) via dehydrogenation or C–C bond scission is examined with periodic density functional theory (DFT) calculations. The thermochemistry of dehydrogenation intermediates is first estimated using an empirical correlation scheme with parameters fit to selected DFT calculations; the resulting estimates for the more stable intermediates are refined with full DFT calculations. Brønsted–Evans–Polanyi (BEP) relationships for dehydrogenation and C–C bond scission reactions are developed and used to estimate the kinetics of elementary dehydrogenation and C–C bond scission steps in the reaction network. The combined thermochemical and kinetic analysis implies that glycerol dehydrogenation products at intermediate levels of dehydrogenation are the most thermochemically stable. Additionally, although C–C bond scission transition state energies are high for glycerol and for intermediates at early stages of dehydrogenation, these energies decrease as the intermediates are successively dehydrogenated, reaching a minimum after the removal of several hydrogen atoms from glycerol. At these levels of dehydrogenation, the C–C scission transition state energies become comparable to those of O–H or C–H scission. These results suggest that C–C bonds are only broken after glycerol has been significantly dehydrogenated and demonstrate that DFT-based analyses, combined with simple correlation schemes, can be effective for elucidating general features of complex biomassic reaction networks.

  1. Density Functional Theory Study of Selectivity Considerations for C–C Versus C–O Bond Scission in Glycerol Decomposition on Pt(111)

    SciTech Connect

    Liu, Bin; Greeley, Jeffrey

    2012-05-01

    Glycerol decomposition via a combination of dehydrogenation, C–C bond scission, and C–O bond scission reactions is examined on Pt(111) with periodic Density Functional Theory (DFT) calculations. Building upon a previous study focused on C–C bond scission in glycerol, the current work presents a first analysis of the competition between C–O and C–C bond cleavage in this reaction network. The thermochemistry of various species produced from C–O bond breaking in glycerol dehydrogenation intermediates is estimated using an extension of a previously introduced empirical correlation scheme, with parameters fit to DFT calculations. Brønsted–Evans–Polanyi (BEP) relationships are then used to estimate the kinetics of C–O bond breaking. When combined with the previous results, the thermochemical and kinetic analyses imply that, while C–O bond scission may be competitive with C–C bond scission during the early stages of glycerol dehydrogenation, the overall rates are likely to be very low. Later in the dehydrogenation process, where rates will be much higher, transition states for C–C bond scission involving decarbonylation are much lower in energy than are the corresponding transition states for C–O bond breaking, implying that the selectivity for C–C scission will be high for glycerol decomposition on smooth platinum surfaces. Finally, it is anticipated that the correlation schemes described in this work will provide an efficient strategy for estimating thermochemical and kinetic energetics for a variety of elementary bond breaking processes on Pt(111) and may ultimately facilitate computational catalyst design for these and related catalytic processes.

  2. An atomic finite element model for biodegradable polymers. Part 2. A model for change in Young's modulus due to polymer chain scission.

    PubMed

    Gleadall, Andrew; Pan, Jingzhe; Kruft, Marc-Anton

    2015-11-01

    Atomic simulations were undertaken to analyse the effect of polymer chain scission on amorphous poly(lactide) during degradation. Many experimental studies have analysed mechanical properties degradation but relatively few computation studies have been conducted. Such studies are valuable for supporting the design of bioresorbable medical devices. Hence in this paper, an Effective Cavity Theory for the degradation of Young's modulus was developed. Atomic simulations indicated that a volume of reduced-stiffness polymer may exist around chain scissions. In the Effective Cavity Theory, each chain scission is considered to instantiate an effective cavity. Finite Element Analysis simulations were conducted to model the effect of the cavities on Young's modulus. Since polymer crystallinity affects mechanical properties, the effect of increases in crystallinity during degradation on Young's modulus is also considered. To demonstrate the ability of the Effective Cavity Theory, it was fitted to several sets of experimental data for Young's modulus in the literature.

  3. A 3D MOF showing unprecedented solvent-induced single-crystal-to-single-crystal transformation and excellent CO2 adsorption selectivity at room temperature.

    PubMed

    Qin, Tao; Gong, Jun; Ma, Junhan; Wang, Xin; Wang, Yonghua; Xu, Yan; Shen, Xuan; Zhu, Dunru

    2014-12-28

    A water stable porous 3D metal-organic framework, [Cu3L2(μ3-OH)2(μ2-H2O)]·2DMA (1, mother crystal, H2L = 2,2'-dinitrobiphenyl-4,4'-dicarboxylic acid, DMA = N,N-dimethylacetamide), shows unprecedented irreversible solvent-induced substitutions of bridging aqua ligands and guest-exchanges in single-crystal-to-single-crystal (SCSC) transformations at room temperature (RT), producing quantitatively three daughter crystals, [Cu3L2(μ3-OH)2]·2S (2: 2A, S = acetone; 2B, S = 2-propanol; 2C, S = 2-butanol), which exhibit reversible interconversion by guest-exchanges at RT in SCSC transformations. MOF 1 shows excellent separation selectivity (128) of CO2/N2 at RT and is a better sorbent of micro-solid-phase extraction (μ-SPE) than currently known benchmark ZIF-8.

  4. Elementary steps in Fischer-Tropsch synthesis: CO bond scission, CO oxidation and surface carbiding on Co(0001)

    NASA Astrophysics Data System (ADS)

    Weststrate, C. J.; van Helden, P.; van de Loosdrecht, J.; Niemantsverdriet, J. W.

    2016-06-01

    Dissociation of CO on a Co(0001) surface is explored in the context of Fischer-Tropsch synthesis on cobalt catalysts. Experiments show that CO dissociation can occur on defect sites around 330 K, with an estimated barrier between 90 and 104 kJ mol- 1. Despite the ease of CO dissociation on defect sites, extensive carbon deposition onto the cobalt surface up to 0.33 ML requires a combination of high surface temperature and a relatively high CO pressure. Experimental data on the CO oxidation reaction indicate a high reaction barrier for the CO + O reaction, and it is argued that, due to the rather strong Co-O bond, (i) oxygen removal is the rate-limiting step during surface carbidization and (ii) in the context of Fischer-Tropsch synthesis, removal of surface oxygen rather than CO bond scission might be limiting the overall reaction rate.

  5. Anisotropic pyrochemical microetching of poly(tetrafluoroethylene) initiated by synchrotron radiation-induced scission of molecule bonds

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Akinobu; Kido, Hideki; Ukita, Yoshiaki; Kishihara, Mitsuyoshi; Utsumi, Yuichi

    2016-02-01

    We developed a process for micromachining polytetrafluoroethylene (PTFE): anisotropic pyrochemical microetching induced by synchrotron X-ray irradiation. X-ray irradiation was performed at room temperature. Upon heating, the irradiated PTFE substrates exhibited high-precision features. Both the X-ray diffraction peak and Raman signal from the irradiated areas of the substrate decreased with increasing irradiation dose. The etching mechanism is speculated as follows: X-ray irradiation caused chain scission, which decreased the number-average degree of polymerization. The melting temperature of irradiated PTFE decreased as the polymer chain length decreased, enabling the treated regions to melt at a lower temperature. The anisotropic pyrochemical etching process enabled the fabrication of PTFE microstructures with higher precision than simultaneously heating and irradiating the sample.

  6. Elongational flow studies on DNA in aqueous solution and stress-induced scission of the double helix.

    PubMed

    Atkins, E D; Taylor, M A

    1992-08-01

    Elongational flow techniques are used to investigate the birefringent response and flow-induced molecular scission of monodisperse phage-DNA samples in aqueous solution. A 4-roll mill apparatus was used to characterize the solutions at low stain rates, epsilon less than or equal to 300 s-1, and the opposed jets apparatus used to study fracture of the DNA molecules at strain rates up to 15 x 10(3) s-1. The molecular weight values were measured before and after fracture in elongational flow using the high-resolution technique of pulsed field gel electrophoresis (PFGE). The birefringent response incorporates both rigid and flexible components. The birefringence is nonlocalized and rises gradually to a plateau value, similar to rigid-rod behavior. In addition a certain minimum value in the strain rate is necessary, an onset value epsilon 0, before the signal appears, indicating a flexible component. This behavior is consistent with a hinged-rod model and is similar to that observed for the protein collagen molecule at elevated temperature. We propose that this type of behavior is likely for multistrand rope-like macromolecules where localized separation or partial untwisting of the intertwined chains occurs, creating temporary hinges, in accordance with biochemical evidence for sequence-specific sites of flexibility. Results are presented on the entanglement effects at high concentrations. We have calculated rotational diffusion rates as a function of concentration and molecular weight. Using PFGE to measure the molecular weight profiles, our fracture studies at high strain rates demonstrate chain halving and quartering in accordance with the predictions of the thermally activated barrier to scission theory for single-chain polymers.

  7. The amphipathic helix of influenza A virus M2 protein is required for filamentous bud formation and scission of filamentous and spherical particles.

    PubMed

    Roberts, Kari L; Leser, George P; Ma, Chunlong; Lamb, Robert A

    2013-09-01

    Influenza virus assembles and buds at the infected-cell plasma membrane. This involves extrusion of the plasma membrane followed by scission of the bud, resulting in severing the nascent virion from its former host. The influenza virus M2 ion channel protein contains in its cytoplasmic tail a membrane-proximal amphipathic helix that facilitates the scission process and is also required for filamentous particle formation. Mutation of five conserved hydrophobic residues to alanines within the amphipathic helix (M2 five-point mutant, or 5PM) reduced scission and also filament formation, whereas single mutations had no apparent phenotype. Here, we show that any two of these five residues mutated together to alanines result in virus debilitated for growth and filament formation in a manner similar to 5PM. Growth kinetics of the M2 mutants are approximately 2 logs lower than the wild-type level, and plaque diameter was significantly reduced. When the 5PM and a representative double mutant (I51A-Y52A) were introduced into A/WSN/33 M2, a strain that produces spherical particles, similar debilitation in viral growth occurred. Electron microscopy showed that with the 5PM and the I51A-Y52A A/Udorn/72 and WSN viruses, scission failed, and emerging virus particles exhibited a "beads-on-a-string" morphology. The major spike glycoprotein hemagglutinin is localized within lipid rafts in virus-infected cells, whereas M2 is associated at the periphery of rafts. Mutant M2s were more widely dispersed, and their abundance at the raft periphery was reduced, suggesting that the M2 amphipathic helix is required for proper localization in the host membrane and that this has implications for budding and scission.

  8. Reactions of the alkoxy radicals formed following OH-addition to alpha-pinene and beta-pinene. C-C bond scission reactions.

    PubMed

    Dibble, T S

    2001-05-01

    The atmospheric degradation pathways of the atmospherically important terpenes alpha-pinene and beta-pinene are studied using density functional theory. We employ the correlation functional of Lee, Yang, and Parr and the three-parameter HF exchange functional of Becke (B3LYP) together with the 6-31G(d) basis set. The C-C bond scission reactions of the beta-hydroxyalkoxy radicals that are formed after OH addition to alpha-pinene and beta-pinene are investigated. Both of the alkoxy radicals formed from the alpha-pinene-OH adduct possess a single favored C-C scission pathway with an extremely low barrier (approximately 3 kcal/mol) leading to the formation of pinonaldehyde. Neither of these pathways produces formaldehyde, and preliminary computational results offer some support for suggestions that 1,5 or 1,6 H-shift (isomerization) reactions of alkoxy radicals contribute to formaldehyde production. In the case of the alkoxy radical formed following OH addition to the methylene group of beta-pinene, there exists two C-C scission reactions with nearly identical barrier heights (approximately 7.5 kcal/mol); one leads to known products (nopinone and formaldehyde) but the ultimate products of the competing reaction are unknown. The single C-C scission pathway of the other alkoxy radical from beta-pinene possesses a very low (approximately 4 kcal/mol) barrier. The kinetically favored C-C scission reactions of all four alkoxy radicals appear to be far faster than expected rates of reaction with O2. The rearrangement of the alpha-pinene-OH adduct, a key step in the proposed mechanism of formation of acetone from alpha-pinene, is determined to possess a barrier of 11.6 kcal/mol. This value is consistent with another computational result and is broadly consistent with the modest acetone yields observed in product yield studies.

  9. A solvent induced crystallisation method to imbue bioactive ingredients of neem oil into the compact structure of poly (ethylene terephthalate) polyester.

    PubMed

    Ali, Wazed; Sultana, Parveen; Joshi, Mangala; Rajendran, Subbiyan

    2016-07-01

    Neem oil, a natural antibacterial agent from neem tree (Azadarichtaindica) has been used to impart antibacterial activity to polyester fabrics. Solvent induced polymer modification method was used and that facilitated the easy entry of neem molecules into the compact structure of polyethylene terephthalate (PET) polyester. The polyester fabric was treated with trichloroacetic acid-methylene chloride (TCAMC) solvent system at room temperature prior to treatment with neem oil. The concentration of TCAMC and the treatment time were optimised. XRD and SEM results showed that the TCAMC treatment causes polymer modification and morphological changes in the PET polyester. Antibacterial activity of TCAMC pre-treated and neem-oil-treated polyester fabric was tested using AATCC qualitative and quantitative methods. Both Gram-positive and Gram-negative organisms were used to determine the antimicrobial activity. It was observed that the treated fabric registers substantial antimicrobial activity against both the Staphylococcus aureus (Gram-positive) and the Escherichia coli (Gram-negative) and the effect increases with the increase in concentration of TCAMC treatment. The antibacterial effect remains substantial even after 25 launderings. A kinetic growth study involving the effect of antibacterial activity at various incubation times was carried out.

  10. Solvent-induced chirality inversion involving supramolecular helix transformation and color-tunable fluorescence of a C(6)-symmetric hexakis(phenylethynyl)benzene derivative.

    PubMed

    Sakajiri, Koichi; Sugisaki, Takeshi; Moriya, Keiichi; Kutsumizu, Shoichi

    2009-09-21

    A C(6)-symmetric disk-like molecule, a hexakis(phenylethynyl)benzene derivative bearing chiral alanine parts, L-1, exhibited a solvent-induced supramolecular helix-sense inversion involving conformational changes followed by destruction of the supramolecular helical column. This phenomenon has been found by investigating the supramolecular assembly state of L-1 in mixed solvents of various chloroform (CHCl(3))/n-hexane (Hx) ratios. L-1 forms a stable helical columnar assembly via multiple noncovalent bonding interactions in nonpolar Hx, while the molecules in relatively polar CHCl(3) are in a molecularly dispersed state. Although one would expect disruption of the helical column with the addition of nonhelicogenic CHCl(3), an opposite-handed helical columnar structure was formed at 8-15 vol% of CHCl(3), and subsequently the inverted helical column was disassembled by a further increase of CHCl(3). In addition, this morphological transformation was accompanied by a significant change in fluorescent color, which varies over a wide visible range from orange in an original helical columnar state to light blue in a molecularly dispersed state through yellow in an inverted helical columnar state. These unprecedented behaviors are shown by the spectroscopic results, and the molecular conformations of L-1 and the driving force for the helical sense inversion are discussed.

  11. A solvent induced crystallisation method to imbue bioactive ingredients of neem oil into the compact structure of poly (ethylene terephthalate) polyester.

    PubMed

    Ali, Wazed; Sultana, Parveen; Joshi, Mangala; Rajendran, Subbiyan

    2016-07-01

    Neem oil, a natural antibacterial agent from neem tree (Azadarichtaindica) has been used to impart antibacterial activity to polyester fabrics. Solvent induced polymer modification method was used and that facilitated the easy entry of neem molecules into the compact structure of polyethylene terephthalate (PET) polyester. The polyester fabric was treated with trichloroacetic acid-methylene chloride (TCAMC) solvent system at room temperature prior to treatment with neem oil. The concentration of TCAMC and the treatment time were optimised. XRD and SEM results showed that the TCAMC treatment causes polymer modification and morphological changes in the PET polyester. Antibacterial activity of TCAMC pre-treated and neem-oil-treated polyester fabric was tested using AATCC qualitative and quantitative methods. Both Gram-positive and Gram-negative organisms were used to determine the antimicrobial activity. It was observed that the treated fabric registers substantial antimicrobial activity against both the Staphylococcus aureus (Gram-positive) and the Escherichia coli (Gram-negative) and the effect increases with the increase in concentration of TCAMC treatment. The antibacterial effect remains substantial even after 25 launderings. A kinetic growth study involving the effect of antibacterial activity at various incubation times was carried out. PMID:27127070

  12. Transformation of epiandrosterone into 3-oxa-, 3-thia-, 3-selena-, and 3-aza-17-oxaandrostanes of the 5 alpha series based on beta-scission of alkoxyl radicals.

    PubMed

    Suginome, H; Wang, J B

    1990-08-01

    3 beta-Hydroxy-5 alpha-androstan-17-one was transformed into 17-oxa-5 alpha-androstan-3 beta-ol in five steps involving conversion of the 17-ketone via the corresponding lactol to its hypoiodite and thence a regioselective beta-scission under irradiation to give ring D seco iodoformate, from which the 17-oxasteroids were derived. Four bisheterosteroids 3,17-dioxa-5 alpha-androstane, 3-thia-17-oxa-5 alpha-androstane, 3-aza-17-oxa-5 alpha-androstane, and 3-selena-17-oxa-5 alpha-androstane) were synthesized from 17-oxa-5 alpha-androstan-3 beta-ol via 5, 8, 8, and 9 steps, respectively, involving a second regioselective beta-scission of an alkoxyl radical as the key step.

  13. Organic solvent-induced changes in membrane geometry in human SH-SY5Y neuroblastoma cells - a common narcotic effect?

    PubMed

    Meulenberg, Cécil J W; de Groot, Aart; Westerink, Remco H S; Vijverberg, Henk P M

    2016-07-01

    Exposure to organic solvents may cause narcotic effects. At the cellular level, these narcotic effects have been associated with a reduction in neuronal excitability caused by changes in membrane structure and function. In order to critically test whether changes in membrane geometry contribute to these narcotic effects, cultured human SH-SY5Y neuroblastoma cells have been exposed to selected organic solvents. The solvent-induced changes in cell membrane capacitance were investigated using the whole-cell patch clamp technique for real-time capacitance measurements. Exposure of SH-SY5Y cells to the cyclic hydrocarbons m-xylene, toluene, and cyclohexane caused a rapid and reversible increase of membrane capacitance. The aliphatic, nonpolar n-hexane did not cause a detectable change of whole-cell membrane capacitance, whereas the amphiphiles n-hexanol and n-hexylamine caused an increase of membrane capacitance and a concomitant reduction in membrane resistance. Despite a large difference in dielectric properties, the chlorinated hydrocarbons 1,1,2,2-tetrachoroethane and tetrachloroethylene caused a similar magnitude increase in membrane capacitance. The theory on membrane capacitance has been applied to deduce changes in membrane geometry caused by solvent partitioning. Although classical observations have shown that solvents increase the membrane capacitance per unit area of membrane, i.e., increase membrane thickness, the present results demonstrate that solvent partitioning predominantly leads to an increase in membrane surface area and to a lesser degree to an increase in membrane thickness. Moreover, the present results indicate that the physicochemical properties of each solvent are important determinants for its specific effects on membrane geometry. This implies that the hypothesis that solvent partitioning is associated with a common perturbation of membrane structure needs to be revisited and cannot account for the commonly observed narcotic effects of

  14. Solvent-induced synthesis of cobalt(II) coordination polymers based on a rigid ligand and flexible carboxylic acid ligands: syntheses, structures and magnetic properties.

    PubMed

    Wang, Ting; Zhang, Chuanlei; Ju, Zemin; Zheng, Hegen

    2015-04-21

    Five new cobalt(ii) coordination architectures, {[Co(L)2(H2O)2]·2H2O·2NO3}n (), {[Co(L)(ppda)]·2H2O}n (), {[Co2(L)(ppda)2]2·H2O}n (), {[Co(L)(nba)]·5H2O}n (), and {[Co(L)(oba)]2·3H2O}n (), have been constructed from the rigid ligand L [L = 2,8-di(1H-imidazol-1-yl)dibenzofuran] and different flexible carboxylic acid ligands [H2ppda = 4,4'-(perfluoropropane-2,2-diyl)dibenzoic acid, H2nba = 4,4'-azanediyldibenzoic acid, and H2oba = 4,4'-oxydibenzoic acid]. Depending on the nature of the solvent systems, these five different coordination polymers were synthesized and characterized by single-crystal X-ray diffraction, IR, PXRD and elemental analysis. Compounds , and were obtained by a one-pot method, and then we utilized the solvent-induced effect to obtain almost pure crystals of , respectively. Compound is an infinite 1D chain which is formed by L ligands and Co atoms. Compound contains a [Co2(CO2)4] secondary building unit (SBU), and can be topologically represented as a 6-connected 2-fold interpenetrating pcu net with the point symbol of {4(12)·6(3)}. Compound can be characterized as a 4-connected sql tetragonal planar network with the point symbol of {4(4)·6(2)}. In compounds and , there is a 1D chain which is formed by flexible carboxylic acid ligands and Co atoms; then the 1D chain is linked by L ligands in the tilting direction, leading to the formation of a 2D layer. Furthermore, UV-vis, TGA and magnetic properties have been investigated in detail. PMID:25778448

  15. A toxicological study of inhalable particulates in an industrial region of Lanzhou City, northwestern China: Results from plasmid scission assay

    NASA Astrophysics Data System (ADS)

    Xiao, Zhenghui; Shao, Longyi; Zhang, Ning; Wang, Jing; Chuang, Hsiao-Chi; Deng, Zhenzhen; Wang, Zhen; BéruBé, Kelly

    2014-09-01

    The city of Lanzhou in northwestern China experiences serious air pollution episodes in the form of PM10 that is characterized by having high levels of heavy metals. The Xigu District represents the industrial core area of Lanzhou City and is denoted by having the largest petrochemical bases in western China. This study investigates heavy metal compositions and oxidative potential of airborne PM10 (particulate matter with aerodynamic diameter of 10 μm or less) collected in Xigu District in the summer and winter of 2010. An in vitro plasmid scission assay (PSA) was employed to study the oxidative potential of airborne PM10 and inductively coupled plasma-mass spectrometry (ICP-MS) was used to examine heavy metal compositions. Transmission electron microscopy coupled with energy-dispersive X-ray spectrometry (TEM/EDX) was used to investigate elemental compositions and mixing states of PM10. The average mass concentrations of PM10 collected in Xigu District were generally higher than the national standard for daily PM10 (150 μg/m3). Cr, Zn, Pb and Mn were the most abundant metals in the intact whole particles of PM10. Zn, Mn and As was the most abundant metal in the water-soluble fraction, while Cr, Pb, and V existed primarily in insoluble forms. TD20 values (i.e. toxic dosage of PM10 causing 20% of plasmid DNA damage) varied considerably in both winter and summer (from 19 μg/mL to >1000 μg/mL) but were typically higher in summer, suggesting that the winter PM10 exhibited greater bioreactivity. In addition, the PM10 collected during a dust storm episode had a highest TD20 value and thus the least oxidative damage to supercoiled plasmid DNA, while the particles collected on a hazy day had a lowest TD20 value and thus the highest oxidative damage to supercoiled plasmid DNA. The particles collected on the first day after snow fall and on a day of cold air intrusion exhibited minor oxidative potential (i.e. caused limited DNA damage). The water-soluble Zn, Mn, As, and

  16. Self-assembly polymorphism of 2,7-bis-nonyloxy-9-fluorenone: solvent induced the diversity of intermolecular dipole-dipole interactions.

    PubMed

    Cui, Lihua; Miao, Xinrui; Xu, Li; Hu, Yi; Deng, Wenli

    2015-02-01

    dipole-dipole and van der Waals (vdWs) forces at l/s interface. It is believed that the results are of significance to the fields of solvent induced polymorphism assembly and surface science.

  17. Self-assembly polymorphism of 2,7-bis-nonyloxy-9-fluorenone: solvent induced the diversity of intermolecular dipole-dipole interactions.

    PubMed

    Cui, Lihua; Miao, Xinrui; Xu, Li; Hu, Yi; Deng, Wenli

    2015-02-01

    dipole-dipole and van der Waals (vdWs) forces at l/s interface. It is believed that the results are of significance to the fields of solvent induced polymorphism assembly and surface science. PMID:25554245

  18. Mass asymmetry dependence of scission times in the reactions of 18.5A MeV 136Xe+48Ti

    NASA Astrophysics Data System (ADS)

    Gui, M.; Hagel, K.; Wada, R.; Lou, Y.; Utley, D.; Xiao, B.; Li, J.; Natowitz, J. B.; Enders, G.; Kühn, W.; Metag, V.; Novotny, R.; Schwalb, O.; Charity, R. J.; Freifelder, R.; Gobbi, A.; Henning, W.; Hildenbrand, K. D.; Mayer, R.; Simon, R. S.; Wessels, J. P.; Casini, G.; Olmi, A.; Stefanini, A. A.

    1993-10-01

    The multiplicities of p and α particles detected in coincidence with fragments emitted in fully relaxed collisions in the reactions of 18.5A MeV 136Xe+48Ti have been measured for different exit channel mass asymmetries. A kinematic source analysis of the spectra and angular distributions of the light particles has been used to separate the total multiplicities into prescission and postscission contributions. From these results, the excitation energies at scission are determined using an empirical technique based upon previous measurements of light charged particle multiplicities observed in coincidence with evaporation residues. These excitation energies are found to decrease from ~400 MeV to 110 MeV as the fragment mass asymmetry, AH/AL, varies from 4.8 to 1.0. A corresponding increase of the mean lifetime of the scissioning nucleus from ~5×10-22 s to ~1×10-20 s is derived using calculated statistical model decay widths. The extent to which this variation of lifetime with mass asymmetry may be attributed to completely damped deep inelastic collisions or to dynamic delays in the decay of a compound nucleus is discussed as is the need for inclusion of dynamics in the deexcitation calculations for hot nuclei. Observed three fragment events are also discussed.

  19. Hydroliquefaction of green wastes to produce fuels.

    PubMed

    Beauchet, R; Pinard, L; Kpogbemabou, D; Laduranty, J; Lemee, L; Lemberton, J L; Bataille, F; Magnoux, P; Ambles, A; Barbier, J

    2011-05-01

    The direct liquefaction of a biomass composed of a mixture of wastes (straw, wood and grass) was studied using Nickel Raney as catalyst and tetralin as a solvent. Tetralin allows to solubilize green waste from 330°C at relatively low hydrogen pressure, and avoids the recondensation of the intermediate products. The green waste deoxygenation results mainly from a decarboxylation reaction. The addition of Raney Ni in the feed, increases the gas yield due to methane formation, without diminishing the yield in solvolysis oil. The catalyst hydrogenolyses the small molecules present in the light fraction. Moreover, it improves the quality of the oil by increasing the hydrogen transfer between the solvent and the solvolysis oil. As a consequence, the oxygen content decreases and the yield of oil soluble in hexane strongly increases. The catalyst allows to obtain straight long chain alkanes (C(13)-C(26)), which result from the hydrogenation of the extractives compounds of the green waste. PMID:21377355

  20. Tailoring the properties of thermoplastic starch by blending with cinnamyl alcohol and radiation processing: An insight into the competitive grafting and scission reactions

    NASA Astrophysics Data System (ADS)

    Khandal, Dhriti; Mikus, Pierre-Yves; Dole, Patrice; Bliard, Christophe; Soulestin, Jérémie; Lacrampe, Marie-France; Baumberger, Stéphanie; Coqueret, Xavier

    2012-08-01

    The present paper focuses on the effects of electron beam (EB) irradiation on thermoplastic materials based on destructurized starch including glycerol and water as plasticizers to assess the potentiality of cinnamyl alcohol as reactive additive capable of counterbalancing the degradation of the polysaccharide by inducing interchain covalent linkages. The tensile properties at break of test specimens of controlled composition submitted to EB irradiation at doses ranging from 50 to 200 kGy revealed the presence of competitive chain scission and bridging in samples containing cinnamyl alcohol at a relative concentration of 2.5% with regard to dry starch. The occurrence of crosslinking under particular conditions was evidenced by gel fraction measurements. The treatment under radiation was also applied to model blends including maltodextrin as a model for starch and the other ingredients to gain an insight into the radiation induced mechanisms at the molecular level. The presence of cinnamyl alcohol is found to limit degradation. Size exclusion chromatography and gel fraction allowed to monitor the effects and confirmed unambiguously the attachment of UV-absorbing chromophores onto the maltodextrin main chain. The combination of the obtained results demonstrates the possibility of altering in a favorable way the tensile properties of plasticized starch by applying high energy radiation to properly formulated blends including aromatic compounds like cinnamyl alcohol.

  1. Solvent-induced syntheses, crystal structures, magnetic properties, and single-crystal-to-single-crystal transformation of azido-Cu(II) coordination polymers with 2-naphthoic acid as co-ligand.

    PubMed

    Liu, Xiangyu; Cen, Peipei; Li, Hui; Ke, Hongshan; Zhang, Sheng; Wei, Qing; Xie, Gang; Chen, Sanping; Gao, Shengli

    2014-08-01

    Based on the solvent-induced effect, three new azido-copper coordination polymers--[Cu(2-na)(N3)] (1), [Cu(2-na)(N3)] (2), and [Cu(2-na)(N3)(C2H5OH)] (3) (where 2-na = 2-naphthoic acid)--have been successfully prepared. Structure analysis shows that the Cu(II) cations in compounds 1-3 present tetra-, penta-, and hexa-coordination geometries, respectively. Compound 1 is a well-isolated one-dimensional (1D) chain with the EO-azido group, while 2 is an isomer of 1 and exhibits a two-dimensional (2D) layer involving the EE-azido group. Thermodynamically, density functional theory (DFT) calculation reveals that 2 occupies the stable state and 1 locates in the metastable state. Compound 3 consists of a 1D chain with triple bridging mode, which is derived from 1, and undergoes a single-crystal-to-single-crystal transformation by soaking in ethanol solvent; the powdery product of 1, namely 1b, could be yielded after the dealcoholization of compound 3. Magnetic measurements indicate that compounds 1-3 perform strong intrachain ferromagnetic interactions, experiencing long-range magnetic ordering and slow magnetic relaxation. Compound 1 features the metamagnetic behavior with a transition temperature of 15 K, while 2 and 3 display spin glass behavior with the phase transition temperatures of 15 and 12 K, respectively. Magneto-structure relationships are investigated as well.

  2. Solvent-induced autolysis of cells

    SciTech Connect

    Hopkins, T.R.

    1989-01-03

    A process is described for the recovery of alcohol oxidase from whole cells of Pichia pastoris grown on methanol which comprises (a) forming an aqueous mixture of the whole cells, wherein the cells are present in an amount of from 85 to 150 grams per liter of aqueous mixture and from 0.8 to 6 volume percent of a treating agent selected from the group consisting of chloroform, 1,1,1-trichloroethane and methylene chloride or mixtures thereof, and wherein, the aqueous mixture has a pH of about 6.5 to about 8.5; (b) incubating the aqueous mixture at a temperature of about 20/sup 0/ to 35/sup 0/C for a time of about 16 to 90 hours whereby at least a portion of the alcohol oxidase is released from the cells thereby forming a alcohol oxidase-containing aqueous liquor; and (c) separating alcohol oxidase-containing liquor liquid from solid cell material.

  3. Solvent induced conformer specific photochemistry of guaiacol.

    PubMed

    Greenough, Simon E; Horbury, Michael D; Thompson, James O F; Roberts, Gareth M; Karsili, Tolga N V; Marchetti, Barbara; Townsend, Dave; Stavros, Vasilios G

    2014-08-14

    Using a combination of ultrafast solution- and gas-phase spectroscopies, together with high-level theory calculations, we demonstrate that we are able to track conformer-specific photodissociation dynamics in solution through solvent choice. We reveal this phenomenon in guaiacol (2-methoxyphenol), a key subunit of the natural biopolymer lignin. In cyclohexane, the first electronically excited (1)ππ* (S1) state in guaiacol relaxes with a time-constant of τ = 4.5 ± 0.2 ns, mediated through intersystem crossing to lower lying triplet (Tn) states and internal conversion and fluorescence back to the ground state (S0). In contrast, in methanol, a further relaxation channel is also present; the S1 state relaxes with a time-constant of τ = 2.9 ± 0.1 ns, which is now additionally mediated through coupling onto a dissociative (1)πσ* (S2) state and subsequent O-H bond fission, evidenced through the appearance of a spectral signature for the guaiacoxyl radical after ∼250 ps. With the aid of complementary calculations, we attribute this to the now absent intramolecular H-bond between OH and OMe moieties, which now favours intermolecular H-bonding to methanol, lowering the barrier to O-H dissociation and facilitating H-atom loss via tunnelling.

  4. A Green Solvent Induced DNA Package

    NASA Astrophysics Data System (ADS)

    Satpathi, Sagar; Sengupta, Abhigyan; Hridya, V. M.; Gavvala, Krishna; Koninti, Raj Kumar; Roy, Bibhisan; Hazra, Partha

    2015-03-01

    Mechanistic details of DNA compaction is essential blue print for gene regulation in living organisms. Many in vitro studies have been implemented using several compaction agents. However, these compacting agents may have some kinds of cytotoxic effects to the cells. To minimize this aspect, several research works had been performed, but people have never focused green solvent, i.e. room temperature ionic liquid as DNA compaction agent. To the best of our knowledge, this is the first ever report where we have shown that guanidinium tris(pentafluoroethyl)trifluorophosphate (Gua-IL) acts as a DNA compacting agent. The compaction ability of Gua-IL has been verified by different spectroscopic techniques, like steady state emission, circular dichroism, dynamic light scattering and UV melting. Notably, we have extensively probed this compaction by Gua-IL through field emission scanning electron microscopy (FE-SEM) and fluorescence microscopy images. We also have discussed the plausible compaction mechanism process of DNA by Gua-IL. Our results suggest that Gua-IL forms a micellar kind of self aggregation above a certain concentration (>=1 mM), which instigates this compaction process. This study divulges the specific details of DNA compaction mechanism by a new class of compaction agent, which is highly biodegradable and eco friendly in nature.

  5. Nonuniform character of the population of spin projections K for a fissile nucleus at the scission point and anisotropies in the angular distributions of fragments originating from the induced fission of nuclei

    SciTech Connect

    Kadmensky, S. G.; Bunakov, V. E.; Kadmensky, S. S.

    2012-11-15

    It is shown that the emergence of anisotropies in the angular distributions of fragments originating from the spontaneous and induced fission of oriented actinide nuclei is possible only if nonuniformities in the population of the projectionsM (K) of the fissile-nucleus spin onto the z axis of the laboratory frame (fissile-nucleus symmetry axis) appear simultaneously in the vicinity of the scission point but not in the vicinity of the outer saddle point of the deformation potential. The possibilities for creating the orientation of fissile nuclei for spontaneous and induced fission and the effect of these orientations on the anisotropies under analysis are considered. The role of Coriolis interaction as a unique source of the mixing of different-K fissile-nucleus states at all stages of the fission process is studied with allowance for the dynamical enhancement of this interaction for excited thermalized states of the nucleus involved that is characterized by a high energy density. It is shown that the absence of thermalization of excited states of the fissile nucleus that appear because of the effect of nonadiabaticity of its collective deformation motion in the vicinity of the scission point is a condition of conservation of the influence that transition fission states formed at the inner and outer fission barriers exerts on the distribution of the spin projections K for lowenergy spontaneous nuclear fission. It is confirmed that anisotropies observed in the angular distributions of fragments originating from the fission of nuclei that is induced by fast light particles (multiply charged ions) are due to the appearance of strongly excited equilibrium(nonequilibrium) states of the fissile nucleus in the vicinity of its scission point that have a Gibbs (non-Gibbs) distribution of projections K.

  6. Model compound studies of the beta-O-4 linkage in lignin: absolute rate expressions for beta-scission of phenoxyl radical from 1-phenyl-2-phenoxyethanol-1-yl radical.

    PubMed

    Kandanarachchi, Pramod H; Autrey, Tom; Franz, James A

    2002-11-15

    Arrhenius rate expressions were determined for beta-scission of phenoxyl radical from 1-phenyl-2-phenoxyethanol-1-yl, PhC*(OH)CH2OPh (V). Ketyl radical V was competitively trapped by thiophenol to yield PhCH(OH)CH2OPh in competition with beta-scission to yield phenoxyl radical and acetophenone. A basis rate expression for hydrogen atom abstraction by sec-phenethyl alcohol, PhC*(OH)CH3, from thiophenol, log(k(abs)/M(-1) s(-1)) = (8.88 +/- 0.24) - (6.07 +/- 0.34)/theta, theta = 2.303RT, was determined by competing hydrogen atom abstraction with radical self-termination. Self-termination rates for PhC*(OH)CH3 were calculated using the Smoluchowski equation employing experimental diffusion coefficients of the parent alcohol, PhCH(OH)CH3, as a model for the radical. The hydrogen abstraction basis reaction was employed to determine the activation barrier for the beta-scission of phenoxyl from 1-phenyl-2-phenoxyethanol-1-yl (V): log(k beta)/s(-1)) = (12.85 +/- 0.22) - (15.06 +/- 0.38)/theta, k beta (298 K) ca. (64.0 s(-1) in benzene), and log(k beta /s(-1)) = (12.50 +/- 0.18) - (14.46 +/- 0.30)/theta, k beta (298 K) = 78.7 s(-1) in benzene containing 0.8 M 2-propanol. B3LYP/cc-PVTZ electronic structure calculations predict that intramolecular hydrogen bonding between the alpha-OH and the -OPh leaving group of ketyl radical (V) stabilizes both ground- and transition-state structures. The computed activation barrier, 14.9 kcal/mol, is in good agreement with the experimental activation barrier.

  7. Model Compound Studies of the Beta-O-4 Linkage in Lignin: Absolute Rate Expressions for Beta-Scission of Phenoxyl Radical from 1-Phenyl-2-phenoxyethanol-1-yl Radical.

    SciTech Connect

    Kandanarachchi, Pramod H.; Autrey, S Thomas ); Franz, James A. )

    2002-11-15

    The lifetime of the lignin radical model compound, 1-phenyl-2-phenoxyethanol-1-yl, PhC?(OH)CH2-OPh is several orders of magnitude greater than suggested by the previous experimental studies. The ketyl radical is competitively trapped by thiophenol to yield PhCH(OH)CH2-OPh in competition with? -scission to yield phenoxyl radical and acetophenone. A basis rate expression, hydrogen atom abstraction by sec-phenethyl alcohol, PhC?(OH)CH3, from thiophenol, log(kabs/M -1 s -1 )=(8.88?0.24)? (6.07?0.34)/? ,?= 2.303RT,was determined by competing reduction and radical termination pathways. The Smoluchowski equation was used to calculate the temperature dependent rate of PhC?(OH)CH3 termination. The hydrogen abstraction pathway was used as a basis reaction to determine the activation barrier for the? -scission of phenoxyl from 1-phenyl-2-phenoxyethanol-1-yl: log(k? -sci/s -1 )= (12.85?0.22)?(15.06?0.38)/?, k? -sci(298K) ca. (64.0s -1 in benzene), log(k? -sci/s -1 )= (12.50?0.18)?(14.46?0.30)/? , k? -sc i(298K) ca. (78.7s -1 in benzene containing 0.8 M 2-propanol).B3LYP/cc-PVZT methods predict intramolecular hydrogen bonding between the? -OH on the ketyl radical and the?OPh leaving group stabilize both the ground state and transition state structures. At this level of theory the activation barrier (14.9 kcal/mol) is in fair agreement with the experimentally determined activation barrier.

  8. Dual single-scission event analysis of constitutive transferrin receptor (TfR) endocytosis and ligand-triggered β2-adrenergic receptor (β2AR) or Mu-opioid receptor (MOR) endocytosis.

    PubMed

    Lampe, Marko; Pierre, Fabienne; Al-Sabah, Suleiman; Krasel, Cornelius; Merrifield, Christien J

    2014-10-01

    The dynamic relationship between constitutive and ligand-triggered clathrin-mediated endocytosis is only poorly characterized, and it remains controversial whether clathrin-coated pits specialize to internalize particular receptor cargo. Here we analyzed the ligand-triggered endocytosis of the model G-protein-coupled receptors (GPCRs) β2-adrenergic receptor (β2AR) and Mu-opioid receptor (MOR) at the level of individual endocytic events using a total internal reflection fluorescence microscopy (TIRFM)-based assay. Similar to the constitutive endocytosis of transferrin receptor (TfR), ligand- triggered endocytosis of β2AR occurs via quantized scission events hosted by clathrin spots and plaques of variable size and persistence. To address whether clathrin-coated structures (CCSs) specialize to internalize particular GPCRs, we adapted the TIRFM imaging assay to simultaneously quantify the internalization of TfR and the ligand- triggered endocytosis of the β2AR or MOR. Agonist-triggered β2AR or MOR endocytosis extended the maturation time of CCSs, as shown previously, but did not affect the rate of constitutive TfR endocytosis or loading of TfR into individual endocytic vesicles. Both the β2AR and the MOR receptors entered cells in the same vesicles as TfR, and the overall evidence for CCS specialization was weak. These data support a simple model in which different cargoes internalize through common CCSs.

  9. Selective bond scission in forming NO/sub 2/ from NO/sub 3//sup -/ in. gamma. -irradiated crystals of urea nitrate, diglycine nitrate, and monoglycine nitrate as studied by electron spin resonance

    SciTech Connect

    Eda, B.; Iwasaki, M.

    1982-05-27

    The controlling factors of selective bond breakage in forming NO/sub 2/ from NO/sub 3//sup -/ in irradiated crystals of the title compounds have been studied by using a single-crystal ESR technique. The results indicate that the NO/sub 2/ radical with one particular orientation is formed in any of these crystals as a result of scission of a particular N-O bond of NO/sub 3//sup -/. From a comparison of the hyperfine coupling and g tensors with the crystallographic data, it was clarified that the oxygen atom participating in the strongest hydrogen bond is preferentially detached to form NO/sub 2/. Such a selective formation of NO/sub 2/ is interpreted in terms of the reaction scheme in which NO/sub 2/ is formed by protonation of the primary anion radical NO/sub 3//sup 2 -/ followed by dissociation of OH/sup -/, where the proton transfer across the strongest hydrogen-bonding path triggers the selective reaction.

  10. Dual single-scission event analysis of constitutive transferrin receptor (TfR) endocytosis and ligand-triggered β2-adrenergic receptor (β2AR) or Mu-opioid receptor (MOR) endocytosis

    PubMed Central

    Lampe, Marko; Pierre, Fabienne; Al-Sabah, Suleiman; Krasel, Cornelius; Merrifield, Christien J.

    2014-01-01

    The dynamic relationship between constitutive and ligand-triggered clathrin-mediated endocytosis is only poorly characterized, and it remains controversial whether clathrin-coated pits specialize to internalize particular receptor cargo. Here we analyzed the ligand-triggered endocytosis of the model G-protein–coupled receptors (GPCRs) β2-adrenergic receptor (β2AR) and Mu-opioid receptor (MOR) at the level of individual endocytic events using a total internal reflection fluorescence microscopy (TIRFM)–based assay. Similar to the constitutive endocytosis of transferrin receptor (TfR), ligand- triggered endocytosis of β2AR occurs via quantized scission events hosted by clathrin spots and plaques of variable size and persistence. To address whether clathrin-coated structures (CCSs) specialize to internalize particular GPCRs, we adapted the TIRFM imaging assay to simultaneously quantify the internalization of TfR and the ligand- triggered endocytosis of the β2AR or MOR. Agonist-triggered β2AR or MOR endocytosis extended the maturation time of CCSs, as shown previously, but did not affect the rate of constitutive TfR endocytosis or loading of TfR into individual endocytic vesicles. Both the β2AR and the MOR receptors entered cells in the same vesicles as TfR, and the overall evidence for CCS specialization was weak. These data support a simple model in which different cargoes internalize through common CCSs. PMID:25079691

  11. Alizarin crystals: An extreme case of solvent induced morphology change

    NASA Astrophysics Data System (ADS)

    Algra, R. E.; Graswinckel, W. S.; van Enckevort, W. J. P.; Vlieg, E.

    2005-11-01

    The organic compound alizarin (1,2-dihydroxy-9,10-anthraquinone) normally crystallizes as very long needles. However, if alcohol is used as solvent, a completely different, triangular shape is obtained. Due to disorder and twinning of the crystals single crystal X-ray diffraction could not be used to establish a possible difference in crystal structure. Differential scanning calorimetry, IR and Raman spectroscopy and powder X-ray diffraction show that the two forms of alizarin are isostructural. From this it follows that solvent influence rather than polymorphism causes the difference in crystal habit. Surface examination, using optical, scanning electron and atomic force microscopy provides information on the mechanism of habit change, which is introduced by the blocking of growth of specific crystal faces in the alcohol solutions.

  12. Mixed Organic Solvents Induce Renal Injury in Rats

    PubMed Central

    Qin, Weisong; Xu, Zhongxiu; Lu, Yizhou; Zeng, Caihong; Zheng, Chunxia; Wang, Shengyu; Liu, Zhihong

    2012-01-01

    To investigate the injury effects of organic solvents on kidney, an animal model of Sprague-Dawley (SD) rats treated with mixed organic solvents via inhalation was generated and characterized. The mixed organic solvents consisted of gasoline, dimethylbenzene and formaldehyde (GDF) in the ratio of 2∶2:1, and were used at 12,000 PPM to treat the rats twice a day, each for 3 hours. Proteinuria appeared in the rats after exposure for 5–6 weeks. The incidences of proteinuria in male and female rats after exposure for 12 weeks were 43.8% (7/16) and 25% (4/16), respectively. Urinary N-Acetyl-β-(D)-Glucosaminidase (NAG) activity was increased significantly after exposure for 4 weeks. Histological examination revealed remarkable injuries in the proximal renal tubules, including tubular epithelial cell detachment, cloud swelling and vacuole formation in the proximal tubular cells, as well as proliferation of parietal epithelium and tubular reflux in glomeruli. Ultrastructural examination found that brush border and cytoplasm of tubular epithelial cell were dropped, that tubular epithelial cells were partially disintegrated, and that the mitochondria of tubular epithelial cells were degenerated and lost. In addition to tubular lesions, glomerular damages were also observed, including segmental foot process fusion and loss of foot process covering on glomerular basement membrane (GBM). Immunofluorescence staining indicated that the expression of nephrin and podocin were both decreased after exposure of GDF. In contrast, increased expression of desmin, a marker of podocyte injury, was found in some areas of a glomerulus. TUNEL staining showed that GDF induced apoptosis in tubular cells and glomerular cells. These studies demonstrate that GDF can induce both severe proximal tubular damage and podocyte injury in rats, and the tubular lesions appear earlier than that of glomeruli. PMID:23029287

  13. Microchannel deformations due to solvent-induced PDMS swelling.

    PubMed

    Dangla, Rémi; Gallaire, François; Baroud, Charles N

    2010-11-01

    The compatibility of polydimethylsiloxane (PDMS) channels with certain solvents is a well known problem of soft lithography techniques, in particular when it leads to the swelling of the PDMS blocks. However, little is known about the modification of microchannel geometries when they are subjected to swelling solvents. Here, we experimentally measure the deformations of the roof of PDMS microchannels due to such solvents. The dynamics of impregnation of the solvents in PDMS and its relation to volume dilation are first addressed in a model experiment, allowing the precise measurement of the diffusion coefficients of oils in PDMS. When Hexadecane, a swelling solvent, fills a microchannel 1 mm in width and 50 μm in height, we measure that the channel roof bends inwards and takes a parabolic shape with a maximum deformation of 7 μm. The amplitude of the subsidence is found to increase with the channel width, reaching 28 μm for a 2 mm wide test section. On the other hand, perfluorinated oils do not swell the PDMS and the microchannel geometry is not affected by the presence of perfluorodecalin. Finally, we observe that the trajectories of droplets flowing in this microchannel are strongly affected by the deformations: drops carried by swelling oils are pushed towards the edges of the channel while those carried by non-swelling oils remain in the channel center. PMID:20848011

  14. Background Noise Contributes to Organic Solvent Induced Brain Dysfunction

    PubMed Central

    Guthrie, O'neil W.; Wong, Brian A.; McInturf, Shawn M.; Reboulet, James E.; Ortiz, Pedro A.; Mattie, David R.

    2016-01-01

    Occupational exposure to complex blends of organic solvents is believed to alter brain functions among workers. However, work environments that contain organic solvents are also polluted with background noise which raises the issue of whether or not the noise contributed to brain alterations. The purpose of the current study was to determine whether or not repeated exposure to low intensity noise with and without exposure to a complex blend of organic solvents would alter brain activity. Female Fischer344 rats served as subjects in these experiments. Asynchronous volume conductance between the midbrain and cortex was evaluated with a slow vertex recording technique. Subtoxic solvent exposure, by itself, had no statistically significant effects. However, background noise significantly suppressed brain activity and this suppression was exacerbated with solvent exposure. Furthermore, combined exposure produced significantly slow neurotransmission. These abnormal neurophysiologic findings occurred in the absence of hearing loss and detectable damage to sensory cells. The observations from the current experiment raise concern for all occupations where workers are repeatedly exposed to background noise or noise combined with organic solvents. Noise levels and solvent concentrations that are currently considered safe may not actually be safe and existing safety regulations have failed to recognize the neurotoxic potential of combined exposures. PMID:26885406

  15. Flash hydroliquefaction of coal. Quarterly technical progress report No. 3, April 4, 1981-July 3, 1981

    SciTech Connect

    Falk, A.Y.

    1982-05-24

    Rockwell has developed a reactor which allows rapid and uniform mixing of pulverized coal with heated hydrogen through the use of a rocket-engine-type injector. The hydrogen is partially heated by indirect heating and further heated by partial combustion with oxygen to supply the required process heat. The amount of hydrogen fed is being kept as low as practicable because of the recycle implication for a complete process. Successful operation of a water-cooled heat-exchange quench unit without plugging or degradation has been demonstrated. Char is separated from the vapor-phase material in a separator which is maintained at a sufficiently high temperature to allow vapor-phase removal of the liquid products. The effectiveness of the concept has been demonstrated in a series of tests. Substantial liquid yields and high overall conversions are possible. A high-pressure product recovery system contains two condensers which split the liquid product into heavy and light oil fractions. In addition, an adsorber bed BTX recovery system was installed. The new system functioned well after an initial shakedown, and they allow for better separation and recovery of the products. Evaluation showed a very high thermal efficiency and favorable economics compared with other liquefaction processes. Many potential advantages of the process were noted; however, most of these advantages remain to be demonstrated. During the first two quarters of the Phase IV effort modifications were made to the PDU to improve material balances; the PDU was activated and six successful tests were conducted; and supporting dense-phase flow, product refining and utilization, and material studies were initiated. The PDU facility modifications made to improve material balances were quite beneficial. Material and major elemental balances for the Phase IV tests are within 5% of closure, a contract target value.

  16. Direct hydro-liquefaction of sawdust in petroleum ether and comprehensive bio-oil products analysis.

    PubMed

    Liu, Dong; Song, Linhua; Wu, Pingping; Liu, Yan; Li, Qingyin; Yan, Zifeng

    2014-03-01

    The effect of temperature, time, hydrogen pressure and amount of catalyst on production distribution and the bio-oil yield obtained from the direct liquefaction of sawdust in the petroleum ether (60-90°C) are investigated. The highest sawdust conversion obtained was 72.32% with a bio-oil yield of 47.69% were obtained at 370°C, 40min and 5wt.% catalyst content with the initial H2 pressure of 3.0MPa. Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) approach was utilized to analyze the non-volatile fraction. In this study, the composition of bio-oil could be analyzed in an unprecedented detail through a combination of GC-MS and FT-ICR MS techniques. PMID:24445192

  17. Bio oil synthesis by coupling biological biomass pretreatment and catalytic hydroliquefaction process.

    PubMed

    Hamieh, S; Beauchet, R; Lemee, L; Toufaily, J; Koubaissy, B; Hamieh, T; Pouilloux, Y; Pinard, L

    2014-03-01

    The bio-oil synthesis from a mixture of wastes (7wt.% straw, 38wt.% wood, and 45wt.% grass) was carried out by direct liquefaction reaction using Raney Nickel as catalyst and tetralin as solvent. The green wastes were biologically degraded during 3 months. Longer the destructuration time; higher the yield into oil is. Biological pretreatment of green wastes promotes the liquefaction process. Among the components of degraded biomass, Humin, the major fraction (60-80wt.%) that was favored by the biological treatment, yields to a bio oil extremely energetic with a HHV close to biopetroleum (40MJ kg(-1)), contrariwise, Fulvic acids (2-12wt.%), the minor fraction is refractory to liquefaction reaction.

  18. Effects of the components of coal hydro-liquefaction residue on its rheological characteristics

    SciTech Connect

    Ren, Y.; Jin, S.; Xu, Y.; Wei, A.; Zhang, D.; Gao, J.

    2009-07-01

    Four kinds of typical coal liquefaction residue samples, coming from Shenhua coal liquefaction pilot plant, were used to investigate the effects of components of residue, separation time, and temperature on its rheological characteristics. Coal liquefaction residue is a non-Newtonian pseudoplastic fluid whose apparent viscosity decreases with increasing shear rate. Moreover, the residue has high viscosity at the initial softening temperature, and its viscosity drops greatly with increasing temperature. The oil content in residue has a great effect on the decline of the apparent viscosity of residue. The asphaltene can increase the apparent viscosity at lower temperatures but decrease it at higher temperatures. However, the solid only increases the apparent viscosity as it can be neither softened nor dissolved to become fluid. After simulating the separation condition, it is found that prolonging the separation time and enhancing the separation temperature will increase the apparent viscosity of residue, which is bad for preventing pipes from being blocked. So choosing the right separation time and separation temperature is necessary to actual industrial production.

  19. 57Fe NGR studies on three-stage hydroliquefaction of coals

    NASA Astrophysics Data System (ADS)

    Jamond, M.; Bacaud, R.; Bussiere, P.; Charcosset, H.; Nickel-Pepin-Donat, B.

    1990-06-01

    Iron Mössbauer spectroscopy has been performed on liquefaction residues of two different French coals. In a three-stage liquefaction of high volatile bituminous coal (Freyming), without an added catalyst, the coal pyrite is not entirely converted into pyrrhotites, whereas in the presence of an added catalyst, coal pyrite is totally transformed into more dispersed pyrrhotites than those from the sample without an added catalyst; furthermore, the whole added catalyst precursor is reduced into pyrrhotites. In the case of liquefaction of subbituminous coal (Gardanne), full conversion of coal pyrite into pyrrhotites (even without an added catalyst) occurs. In addition, in the presence of the added catalyst, besides pyrrhotites, FeS is evidenced. When molybdenum-iron oxide is added as a catalyst precursor, no mixed Fe-Mo phase is detected.

  20. Deuteration-induced scission of C{sub 58} oligomers

    SciTech Connect

    Loeffler, Daniel; Jester, Stefan-S.; Weis, Patrick; Boettcher, Artur; Kappes, Manfred M.

    2006-12-14

    The reaction of solid C{sub 58} films with atomic deuterium to yield deuterofullerenes, C{sub 58}D{sub x}, has been investigated by thermal desorption spectroscopy coupled with mass spectrometric detection, ultraviolet photoionization spectroscopy (21.2 eV), and atomic force microscopy (AFM). The average composition of the deuterofullerenes created depends on deuterium dose, beam flux, and surface temperature. Low deuterium exposures at room temperature yield predominantly C{sub 58}D{sub 6-8} cages. Saturation exposures at room temperature yield mass spectra peaked at C{sub 58}D{sub 26}. After saturation exposures at elevated surface temperatures ({approx}500 K), the (subsequently) desorbed material reveals a comparatively narrow mass spectral distribution centered at C{sub 58}D{sub 30}. Deuteration is associated with cleavage of covalent cage-cage bonds in the starting C{sub 58} oligomer material, as evidenced by a considerable lowering of the sublimation energies of C{sub 58}D{sub x} compared to desorption of C{sub 58} desorbed from pure oligomer films. Correspondingly, AFM images reveal a D-induced, thermally activated transition from dendritic C{sub 58} oligomer islands into smooth-rimmed islands composed of deuterated cages. Deuterated films exhibit a significantly lower work function than bare C{sub 58} films. Progressing deuteration also gradually raises the surface ionization potential.

  1. Mechanochemical Reactions Reporting and Repairing Bond Scission in Polymers.

    PubMed

    Clough, Jess M; Balan, Abidin; Sijbesma, Rint P

    2015-01-01

    The past 10 years have seen a resurgence of interest in the field of polymer mechanochemistry. Whilst the destructive effects of mechanical force on polymer chains have been known for decades, it was only recently that researchers tapped into these forces to realize more useful chemical transformations. The current review discusses the strategic incorporation of weak covalent bonds in polymers to create materials with stress-sensing and damage-repairing properties. Firstly, the development of mechanochromism and mechanoluminescence as stress reporters is considered. The second half focuses on the net formation of covalent bonds as a response to mechanical force, via mechanocatalysis and mechanically unmasked chemical reactivity, and concludes with perspectives for the field. PMID:26104999

  2. Metallogrid Single-Molecule Magnet: Solvent-Induced Nuclearity Transformation and Magnetic Hysteresis at 16 K.

    PubMed

    Huang, Wei; Shen, Fu-Xing; Wu, Shu-Qi; Liu, Li; Wu, Dayu; Zheng, Zhe; Xu, Jun; Zhang, Ming; Huang, Xing-Cai; Jiang, Jun; Pan, Feifei; Li, Yao; Zhu, Kun; Sato, Osamu

    2016-06-01

    Structural assembly and reversible transformation between a metallogrid Dy4 SMM (2) and its fragment Dy2 (1) were established in the different solvent media. The zero-field magnetization relaxation was slowed for dysprosium metallogrid (2) with relaxation barrier of Ueff = 61.3 K when compared to Dy2 (1). Both magnetic dilution and application of a moderate magnetic field suppress ground-state quantum tunneling of magnetization and result in an enhanced Ueff of 119.9 and 96.7 K for 2, respectively. Interestingly, the lanthanide metallogrid complex (2) exhibits magnetic hysteresis loop even up to 16 K at a given field sweep rate of 500 Oe/s. PMID:27164298

  3. Preparation of Low Band Gap Fibrillar Structures by Solvent Induced Crystallization

    NASA Astrophysics Data System (ADS)

    Wang, Hsin-Wei; Pentzer, Emily; Emerick, Todd; Russell, Thomas

    2014-03-01

    Solution-induced crystallization of the low band gap polymer poly[ N-9''-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) was shown to give fibril-like structures of 40-60 nm width and ~ 0.5 μm length. These structures, formed by heating and cooling PCDTBT in a marginal solvent, were characterized by AFM, TEM, GI-WAXS, and steady state absorption and emission spectroscopy. The width of the PCDTBT structures suggests that the polymer chains are oriented perpendicular to the fiber axis, while the observed undulated structures, as revealed by AFM, suggest that the nanostructures may be composed of smaller crystalline units, suggesting a crystal face-specific assembly. Surprisingly, no spectroscopic signatures in either absorption or emission were observed upon crystallization of PCDTBT, in sharp contrast to the well-known conjugated polymer poly(3-hexyl thiophene) (P3HT). The solution-based crystallization of PCDTBT offers insight into the self-assembly of conjugated polymers and a better understanding of their role in photovoltaic devices

  4. Solvent-induced changes in PEDOT:PSS films for organic electrochemical transistors

    SciTech Connect

    Zhang, Shiming; Kumar, Prajwal; Nouas, Amel Sarah; Fontaine, Laurie; Tang, Hao; Cicoira, Fabio

    2015-01-01

    Organic electrochemical transistors based on the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) are of interest for several bioelectronic applications. In this letter, we investigate the changes induced by immersion of PEDOT:PSS films, processed by spin coating from different mixtures, in water and other solvents of different polarities. We found that the film thickness decreases upon immersion in polar solvents, while the electrical conductivity remains unchanged. The decrease in film thickness is minimized via the addition of a cross-linking agent to the mixture used for the spin coating of the films.

  5. Prediction of solvent-induced morphological changes of polyelectrolyte diblock copolymer micelles.

    PubMed

    Li, Nan K; Fuss, William H; Tang, Lei; Gu, Renpeng; Chilkoti, Ashutosh; Zauscher, Stefan; Yingling, Yaroslava G

    2015-11-14

    Self-assembly processes of polyelectrolyte block copolymers are ubiquitous in industrial and biological processes; understanding their physical properties can also provide insights into the design of polyelectrolyte materials with novel and tailored properties. Here, we report systematic analysis on how the ionic strength of the solvent and the length of the polyelectrolyte block affect the self-assembly and morphology of the polyelectrolyte block copolymer materials by constructing a salt-dependent morphological phase diagram using an implicit solvent ionic strength (ISIS) method for dissipative particle dynamics (DPD) simulations. This diagram permits the determination of the conditions for the morphological transition into a specific shape, namely vesicles or lamellar aggregates, wormlike/cylindrical micelles, and spherical micelles. The scaling behavior for the size of spherical micelles is predicted, in terms of radius of gyration (R(g,m)) and thickness of corona (Hcorona), as a function of solvent ionic strength (c(s)) and polyelectrolyte length (NA), which are R(g,m) ∼ c(s)(-0.06)N(A)(0.54) and Hcorona ∼ c(s)(-0.11)N(A)(0.75). The simulation results were corroborated through AFM and static light scattering measurements on the example of the self-assembly of monodisperse, single-stranded DNA block-copolynucleotides (polyT50-b-F-dUTP). Overall, we were able to predict the salt-responsive morphology of polyelectrolyte materials in aqueous solution and show that a spherical-cylindrical-lamellar change in morphology can be obtained through an increase in solvent ionic strength or a decrease of polyelectrolyte length. PMID:26315065

  6. Facile synthesis of porous magnetite microspheres and solvent-induced phase transition

    NASA Astrophysics Data System (ADS)

    Gan, Zibao; Zhao, Aiwu

    2013-08-01

    Uniform porous magnetite microspheres have been synthesized in a large scale by a dodecyltrimethylammonium bromide (DTAB)-assisted solvothermal route. The as-obtained products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal gravimetric analyzer, Brunauer-Emmett-Teller gas sorptometry and vibrating sample magnetometer. The factors influencing the phase and morphology of the products were investigated. It demonstrates that the ratio of water and ethylene glycol (EG) plays a crucial role for the phase structure and morphology of the products. When the ratio of water and EG does not exceed 1:3, the as-obtained products belong to magnetite phase. Nevertheless, the as-obtained products begin to convert to hematite phase with the ratio increase to 3:5. The reason could be ascribed by the increased water volume, which effectively weakens the reductive activity of EG. Followed by the change of the ratio of water and EG, the morphologies of as-obtained products undergo a series of evolution, such as from flower-like magnetite microspheres to polyhedral hematite nanoplates. On the basis of experimental investigation and analysis, a possible formation mechanism was proposed. The magnetic study demonstrated the porous magnetite microspheres with high saturation magnetization (Ms) and the decreased Ms caused by the phase transition.

  7. Solvents induced ZnO nanoparticles aggregation associated with their interfacial effect on organic solar cells.

    PubMed

    Li, Pandeng; Jiu, Tonggang; Tang, Gang; Wang, Guojie; Li, Jun; Li, Xiaofang; Fang, Junfeng

    2014-10-22

    ZnO nanofilm as a cathode buffer layer has surface defects due to the aggregations of ZnO nanoparticles, leading to poor device performance of organic solar cells. In this paper, we report the ZnO nanoparticles aggregations in solution can be controlled by adjusting the solvents ratios (chloroform vs methanol). These aggregations could influence the morphology of ZnO film. Therefore, compact and homogeneous ZnO film can be obtained to help achieve a preferable power conversion efficiency of 8.54% in inverted organic solar cells. This improvement is attributed to the decreased leakage current and the increased electron-collecting efficiency as well as the improved interface contact with the active layer. In addition, we find the enhanced maximum exciton generation rate and exciton dissociation probability lead to the improvement of device performance due to the preferable ZnO dispersion. Compared to other methods of ZnO nanofilm fabrication, it is the more convenient, moderate, and effective to get a preferable ZnO buffer layer for high-efficiency organic solar cells.

  8. Solvent-Induced Tuning of Internal Structure in a Protein Amyloid Protofibril

    PubMed Central

    Jha, Anjali; Narayan, Satya; Udgaonkar, Jayant B.; Krishnamoorthy, G.

    2012-01-01

    An important goal in studies of protein aggregation is to obtain an understanding of the structural diversity that is characteristic of amyloid fibril and protofibril structures at the molecular level. In this study, what to our knowledge are novel assays based on time-resolved fluorescence anisotropy decay and dynamic quenching measurements of a fluorophore placed at different specific locations in the primary structure of a small protein, barstar, have been used to determine the extent to which the protein sequence participates in the structural core of protofibrils. The fluorescence measurements reveal the structural basis of how modulating solvent polarity results in the tuning of the protofibril conformation from a pair of parallel β-sheets in heat-induced protofibrils to a single parallel β-sheet in trifluorethanol-induced protofibrils. In trifluorethanol-induced protofibrils, the single β-sheet is shown to be built up from in-register β-strands formed by nearly the entire protein sequence, while in heat-induced protofibrils, the pair of β-sheets motif is built up from β-strands formed by only the last two-third of the protein sequence. PMID:22947941

  9. Solvent-Induced Proton Hopping at a Water-Oxide Interface.

    PubMed

    Tocci, Gabriele; Michaelides, Angelos

    2014-02-01

    Despite widespread interest, a detailed understanding of the dynamics of proton transfer at interfaces is lacking. Here, we use ab initio molecular dynamics to unravel the connection between interfacial water structure and proton transfer for the widely studied and experimentally well-characterized water-ZnO(101̅0) interface. We find that upon going from a single layer of adsorbed water to a liquid multilayer, changes in the structure are accompanied by a dramatic increase in the proton-transfer rate at the surface. We show how hydrogen bonding and rather specific hydrogen-bond fluctuations at the interface are responsible for the change in the structure and proton-transfer dynamics. The implications of this for the chemical reactivity and for the modeling of complex wet oxide interfaces in general are also discussed.

  10. Solvent-induced conformational changes of O-phenyl-cinchonidine: a theoretical and VCD spectroscopy study.

    PubMed

    Vargas, Angelo; Bonalumi, Norberto; Ferri, Davide; Baiker, Alfons

    2006-01-26

    The conformational analysis of the synthetic chiral modifier O-phenyl-cinchonidine (PhOCD) used in enantioselective hydrogenations over noble metal catalysts has been performed at a PM3 semiempirical level in vacuum. The minimum energy conformations calculated at the DFT level with a medium-size basis set have been compared to those of the parent alkaloid cinchonidine (CD). PhOCD behaves similarly to CD and shows four main conformers, denoted as Closed(1), Closed(2), Open(3), and Open(4). Open(3) is found to be the most stable in vacuum and in CH2Cl2 and CCl4 solvents. A comprehensive normal-mode analysis has been performed for these conformers, and assignment of the infrared spectrum of PhOCD in CCl4 (epsilon = 2.2) has been performed using the calculated spectrum of Open(3), which appears to be the most populated in this solvent. A combined theoretical-experimental VCD spectroscopy approach was used to increase the spectroscopic sensitivity toward changes in the distribution of conformers upon change of solvent polarity. The VCD spectra confirm that Open(3) is by far the most stable conformation in CCl4 (epsilon = 2.2) and indicate that an excess Closed(2) conformer has to be expected in CD2Cl2 (epsilon = 8.9). The possible influence of this conformational behavior is discussed on the basis of available catalytic data and in relation to the enantioselective potential of PhOCD as a chiral modifier on supported metal catalysts.

  11. Solvent-induced size reduction of self-assembled siRNA/copolymer nanoparticles

    NASA Astrophysics Data System (ADS)

    Qu, Wei; Wu, Juan; Mao, Hai-Quan; Luijten, Erik

    2013-03-01

    Small interfering RNA (siRNA) therapeutics has a demonstrated potential for treating numerous liver diseases. However, traditional polycation vectors used for siRNA delivery typically produce siRNA-containing particles of large size (> 100 nm), along with high cytotoxicity and low colloidal stability. Inspired by earlier work on nanoparticles for plasmid DNA delivery, we graft hydrophilic and biocompatible polyethylene glycol (PEG) blocks to the polycation vector to overcome these limitations. We find that the PEG-grafted polycations result in slightly larger particle size, even though the hydrophilic PEG blocks are expected to hinder the formation of larger aggregates. To explain this observation, we investigate siRNA/copolymer self-assembly via computer simulations of coarse-grained polymer and siRNA models. Our calculations suggest that hydrogen bonding between PEG and the polycation leads to the increased particle size, and that smaller particles can be obtained by inhibiting hydrogen bonding in such system. Subsequent experiments employing solvents of lower polarity indeed lead to particles with smaller size.

  12. Organic solvents induce the formation of oil-in-ionic liquid microemulsion aggregations.

    PubMed

    Gao, Yanan; Li, Na; Zhang, Shaohua; Zheng, Liqiang; Li, Xinwei; Dong, Bin; Yu, Li

    2009-02-01

    The role of four organic solvents in the formation process of 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) based ionic liquid (IL) microemulsions is investigated. The results showed that the addition of Triton X-100 remarkably decreased the conductivity of bmimBF4. The added organic solvents provided a strong apolar environment for the hydrophobic tails of Triton X-100 and caused the surfactant molecules to aggregate into the interfacial film of oil-in-bmimBF4 (O/IL) microemulsions. As a result, the conductivities of the solutions were initially increased because the insulative Triton X-100 molecules were assembled, which corresponded to increasing the concentration of continuous bmimBF4 solutions. The hydrophobic interaction between the dispersed organic solvents and the hydrophobic tails of Triton X-100 may be the driving force for the formation of O/IL microemulsions. The droplets of O/IL microemulsions were successively swollen by organic solvents, and a bicontinuous IL-containing microemulsion was observed by freeze-fracture transmission electron microscopy for the first time. The current study can help in further understanding the ILs-containing microemulsions and thereby improve microemulsion theory. PMID:19138136

  13. Computing solvent-induced forces in the solvation approach called Semi Explicit Assembly

    NASA Astrophysics Data System (ADS)

    Brini, Emiliano; Hummel, Michelle H.; Coutsias, Evangelos A.; Fennell, Christopher J.; Dill, Ken A.

    2014-03-01

    Many biologically relevant processes (e.g. protein folding) are often too big and slow to be simulated by computer methods that model atomically detailed water. Faster physical models of water are needed. We have developed an approach called Semi Explicit Assembly (SEA) [C.J. Fennell, C.W. Kehoe, K.A. Dill, PNAS, 108, 3234 (2011)]. It is physical because it uses pre-simulations of explicit-solvent models, and it is fast because at runtime, we just combine the pre-simulated results in rapid computations. SEA has also now been proven physically accurate in two blind tests called SAMPL. Here, we describe the computation of solvation forces in SEA, so that this solvation procedure can be incorporated into standard molecular dynamics codes. We describe experimental tests.

  14. Universal Repulsive Contribution to the Solvent-Induced Interaction Between Sizable, Curved Hydrophobes.

    PubMed

    Jabes, B Shadrack; Bratko, Dusan; Luzar, Alenka

    2016-08-18

    In addition to the direct attraction, sizable hydrophobes in water experience an attractive force mediated by interfacial water. Using simple geometric arguments, we identify the conditions at which the water-induced interaction between curved hydrocarbon surfaces becomes repulsive. The repulsive contribution arises from the thermodynamic penalty due to the emergence of the liquid/vapor boundary created as water gets expelled between curved hydrophobes. By augmenting the mean field approach with atomistic simulations of pristine and alkyl-coated graphitic nanoparticles in three distinct geometries, spherical, cylindrical and planar, immersed in water, we show the macroscopic thermodynamics remarkably works down to the molecular scale. The new insights improve the prediction and control of wetting and dispersion properties for a broad class of nonpolar nanoparticles.

  15. Solvent-induced reversible solid-state colour change of an intramolecular charge-transfer complex.

    PubMed

    Li, Ping; Maier, Josef M; Hwang, Jungwun; Smith, Mark D; Krause, Jeanette A; Mullis, Brian T; Strickland, Sharon M S; Shimizu, Ken D

    2015-10-11

    A dynamic intramolecular charge-transfer (CT) complex was designed that displayed reversible colour changes in the solid-state when treated with different organic solvents. The origins of the dichromatism were shown to be due to solvent-inclusion, which induced changes in the relative orientations of the donor pyrene and acceptor naphthalenediimide units. PMID:26299357

  16. SOP-GPU: influence of solvent-induced hydrodynamic interactions on dynamic structural transitions in protein assemblies.

    PubMed

    Alekseenko, Andrey; Kononova, Olga; Kholodov, Yaroslav; Marx, Kenneth A; Barsegov, Valeri

    2016-06-30

    Hydrodynamic interactions (HI) are incorporated into Langevin dynamics of the Cα -based protein model using the Truncated Expansion approximation (TEA) to the Rotne-Prager-Yamakawa diffusion tensor. Computational performance of the obtained GPU realization demonstrates the model's capability for describing protein systems of varying complexity (10(2) -10(5) residues), including biological particles (filaments, virus shells). Comparison of numerical accuracy of the TEA versus exact description of HI reveals similar results for the kinetics and thermodynamics of protein unfolding. The HI speed up and couple biomolecular transitions through cross-communication among protein domains, which result in more collective displacements of structure elements governed by more deterministic (less variable) dynamics. The force-extension/deformation spectra from nanomanipulations in silico exhibit sharper force signals that match well the experimental profiles. Hence, biomolecular simulations without HI overestimate the role of tension/stress fluctuations. Our findings establish the importance of incorporating implicit water-mediated many-body effects into theoretical modeling of dynamic processes involving biomolecules. © 2016 Wiley Periodicals, Inc.

  17. Additives and solvents-induced phase and morphology modification of NaYF4 for improving up-conversion emission

    NASA Astrophysics Data System (ADS)

    Zhuang, Jianle; Yang, Xianfeng; Wang, Jing; Lei, Bingfu; Liu, Yingliang; Wu, Mingmei

    2016-01-01

    Both cubic and hexagonal NaYF4 were synthesized in different reaction systems via hydro/solvo-thermal route. The effects of reaction temperature, solvents, and additives on the synthesis of NaYF4 have been studied in detail. It has been shown that phase transformation from cubic NaYF4 to hexagonal NaYF4 always occurred. The sequence of the ability for inducing the phase transformation was ethanol>H2O>acetic acid. It is found that ethanol can not only facilitate the formation of hexagonal NaYF4 but also control the growth of the crystal. This is quite unusual for the growth of H-NaYF4. The up-conversion emission properties of Yb/Er co-doped NaYF4 have also been investigated and the results demonstrated some general principles for improving up-conversion emission.

  18. Solvent-induced aggregation through metal...metal/pi...pi interactions: large solvatochromism of luminescent organoplatinum(II) terpyridyl complexes.

    PubMed

    Yam, Vivian Wing-Wah; Wong, Keith Man-Chung; Zhu, Nianyong

    2002-06-12

    A dramatic color change and tremendous emission enhancement have been "switched on" upon increasing diethyl ether ratio in acetonitrile or acetone solution of [Pt(tpy)(CC-CCH)]OTf, attributed to the formation of Pt...Pt and pi-pi interactions. Two crystal forms (dark-green and red) of [Pt(tpy)(CC-CCH)]OTf, together with [Pt(tBu3-tpy)(CC-CCH)]OTf, show different crystal-packing modes as revealed by X-ray crystallography.

  19. Two-dimensional surface chirality control by solvent-induced helicity inversion of a helical polyacetylene on graphite.

    PubMed

    Sakurai, Shin-ichiro; Okoshi, Kento; Kumaki, Jiro; Yashima, Eiji

    2006-05-01

    We report the direct evidence for the macromolecular helicity inversion of a helical poly(phenylacetylene) bearing l- or d-alanine pendants with a long alkyl chain in different solvents by atomic force microscopy observations of the diastereomeric helical structures. The diastereomeric helical poly(phenylacetylene)s induced in polar and nonpolar solvents self-assembled into ordered, two-dimensional helix bundles with controlled molecular packing, helical pitch, and handedness on graphite upon exposure of each solvent. The macromolecular helicity deposited on graphite from a polar solvent further inverted to the opposite handedness by exposure to a specific nonpolar solvent, and these changes in the surface chirality based on the inversion of helicity could be visualized by atomic force microscopy with molecular resolution, and the results were quantified by X-ray diffraction of the oriented liquid crystalline, diastereomeric helical polymer films.

  20. Surface treatment by binary solvents induces the crystallization of a small molecular donor for enhanced photovoltaic performance.

    PubMed

    Zhou, Weihua; Xie, Yuanpeng; Hu, Xiaotian; Zhang, Lin; Meng, Xiangchuan; Zhang, Yong; Ma, Wei; Chen, Yiwang

    2016-01-14

    The surface treatment of the active layer with binary solvents composed of methanol (MeOH) and 1-chloronaphthalene (CN), was demonstrated to effectively improve the power conversion efficiency (PCE) from 2.4% to 6.5% for p-DTS(FBTTh2)2:PC71BM based small molecular solar cells. The optical properties and morphology of the p-DTS(FBTTh2)2:PC71BM films were carefully investigated. The results indicate that treatment with MeOH:CN binary solvents could significantly enhance the absorption of the active layer, due to the formation of more p-DTS(FBTTh2)2 nanofibrils associated with higher crystallinity as revealed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The two-dimensional grazing incidence wide-angle X-ray scattering (GIWAXS) results further demonstrate that the molecular packing of p-DTS(FBTTh2)2 molecules could be strongly enhanced after treatment with the binary solvents. In contrast, pristine methanol shows no significant influence on the crystalline structure, phase separation or the photovoltaic properties of the p-DTS(FBTTh2)2:PC71BM system, showing that the CN solvent plays the main role in inducing the crystallization of p-DTS(FBTTh2)2 molecules. PMID:26660911

  1. Single-stranded DNA detection by solvent-induced assemblies of a metallo-peptide-based complex

    NASA Astrophysics Data System (ADS)

    Das, Priyadip; Reches, Meital

    2016-05-01

    DNA detection is highly important for the sensitive sensing of different pathogenic bacteria and viruses. The major challenge is to create a sensor that can selectively detect very small concentrations of DNA without the need for amplification or complicated equipment. Different technologies such as optical, electrochemical and microgravimetric approaches can detect DNA fragments. Here we show, for the first time, the use of self-assembled nanostructures generated by a metallo-peptide as an optical sensing platform for DNA detection. The system can selectively detect single stranded DNA fragments by fluorescence measurements as it can discriminate even one base mismatch and can perform in the presence of other interfering proteins. This system may be useful in lab-on-a-chip applications.DNA detection is highly important for the sensitive sensing of different pathogenic bacteria and viruses. The major challenge is to create a sensor that can selectively detect very small concentrations of DNA without the need for amplification or complicated equipment. Different technologies such as optical, electrochemical and microgravimetric approaches can detect DNA fragments. Here we show, for the first time, the use of self-assembled nanostructures generated by a metallo-peptide as an optical sensing platform for DNA detection. The system can selectively detect single stranded DNA fragments by fluorescence measurements as it can discriminate even one base mismatch and can perform in the presence of other interfering proteins. This system may be useful in lab-on-a-chip applications. Electronic supplementary information (ESI) available: Peptide and receptor synthesis, characterization of the final and intermediate products, experimental details and additional figures including SEM, TEM, DLS, XRD, UV analysis and AFM topographic analysis. See DOI: 10.1039/c5nr07714a

  2. Gas/solvent-induced transformation and expansion of a nonporous solid to 1:1 host guest form

    SciTech Connect

    Thallapally, Praveen K.; McGrail, B. Peter; Dalgarno, Scott J.; Atwood, Jerry L.

    2008-07-01

    Herein we report the gas (CO2, N2O and propane) and solvent (CS2 and acetone) induced transformation and expansion of guest free thermodynamic form of a p-tert-butylcalix [4]arene to 1:1 host guest form.

  3. Series of solvent-induced single-crystal to single-crystal transformations with different sizes of solvent molecules.

    PubMed

    He, Yuan-Chun; Yang, Jin; Liu, Ying-Ying; Ma, Jian-Fang

    2014-07-21

    A highly stable soft porous coordination polymer (PCP), namely [Cu3(TP)4(N3)2(DMF)2]·2H2O·2DMF (1), has been synthesized via an in situ synthesis of 4-tetrazole pyridine (TP) under solvothermal conditions (DMF = N,N'-dimethylformamide). Remarkably, the solvent molecules in 1 can be respectively exchanged with cyclohexane (C6H12), cyclopentane (C5H10), decahydronaphthalene (C10H18), 1,4-dioxane (C4H8O2), and tetrahydropyrane (C5H10O) in single-crystal to single-crystal (SCSC) manners to yield [Cu3(TP)4(N3)2(DMF)2]·3C6H12 (1a), [Cu3(TP)4(N3)2(DMF)2]·2C5H10 (1b), [Cu3(TP)4(N3)2(DMF)2]·H2O·C10H18 (1c), [Cu3(TP)4(N3)2(DMF)2]·C4H8O2 (1d), [Cu3(TP)4(N3)2]·3C4H8O2 (1e), and [Cu3(TP)4(N3)2]·2H2O·C5H10O (1f). Further, the occluded cyclohexane molecules in 1a can be removed by heating to give its porous guest-free form [Cu3(TP)4(N3)2(DMF)2] (1g). Particularly, in water, 1 can lose its coordinated N3(-) anions to generate [Cu(TP)2(H2O)4]·4H2O (1h). More interestingly, the soft PCP (1) demonstrates the guest selectivity for the cycloalkane solvents, namely cyclohexane, cyclopentane, and decahydronaphthalene, in SCSC manners for the first time, attributed to the synergy effect between the size and geometry of the solvent and the shape of the framework cavity. Moreover, the desolvated samples of 1e show the highly selective gas adsorption of CO2 over N2, indicating its potential application in the separation of the CO2/N2 mixture.

  4. Hydroxylic solvent-induced ring opening of the dehydropyrrolizidine alkaloids riddelliine and seneciphylline: implications for toxicity and analytical studies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    etabolites that can also cause various cancers in animal models. Riddelliine and seneciphylline are closely-related, macrocyclic diester dehydropyrrolizidine alkaloids produced by various species in the Asteraceae. Despite the evidence of carcinogenicity in animal models, and the increasing concerns...

  5. Facile scission of isonitrile carbon–nitrogen triple bond using a diborane(4) reagent

    PubMed Central

    Asakawa, Hiroki; Lee, Ka-Ho; Lin, Zhenyang; Yamashita, Makoto

    2014-01-01

    Transition metal reagents and catalysts are generally effective to cleave all three bonds (one σ and two π) in a triple bond despite its high bonding energy. Recently, chemistry of single-bond cleavage by using main-group element compounds is rapidly being developed in the absence of transition metals. However, the cleavage of a triple bond using non-transition-metal compounds is less explored. Here we report that an unsymmetrical diborane(4) compound could react with carbon monoxide and tert-butyl isonitrile at room temperature. In the latter case, the carbon–nitrogen triple bond was completely cleaved in the absence of transition metal as confirmed by X-ray crystallographic analysis, 13C NMR spectroscopy with 13C labelling and DFT calculations. The DFT calculations also revealed the detailed reaction mechanism and indicated that the key for the carbon–nitrogen triple-bond cleavage could be attributed to the presence of nucleophilic nitrogen atom in one of the intermediates. PMID:24967910

  6. Local site selectivity and conformational structures in the glycosidic bond scission of cellobiose.

    PubMed

    Liang, Xiao; Montoya, Alejandro; Haynes, Brian S

    2011-09-15

    Car-Parrinello molecular dynamics combined with metadynamics simulations were used to study the acid-catalyzed hydrolysis of cellobiose (CB) in aqueous solution. The hydrolysis was studied in two steps. Step 1 involves the proton transfer from solvent to CB and dissociation of the glycosidic bond to β-glucose and oxacarbenium ion species. Step 2 involves the formation of α-glucose from oxacarbenium and regeneration of the acid proton species. Step 1 is endothermic, while Step 2 is exothermic. The overall activation free energy of CB hydrolysis is 32.5 kcal mol(-1), and the overall reaction free energy is -5.9 kcal mol(-l), consistent with available experimental data. We observe that a stepwise mechanism generally described in the literature for Step 1 is not significantly favored relative to a concerted β-1,4' linkage dissociation process. PMID:21800820

  7. Competing mechanisms and scaling laws for carbon nanotube scission by ultrasonication

    PubMed Central

    Pagani, Guido; Green, Micah J.; Poulin, Philippe; Pasquali, Matteo

    2012-01-01

    Dispersion of carbon nanotubes (CNTs) into liquids typically requires ultrasonication to exfoliate individuals CNTs from bundles. Experiments show that CNT length drops with sonication time (or energy) as a power law t-m. Yet the breakage mechanism is not well understood, and the experimentally reported power law exponent m ranges from approximately 0.2 to 0.5. Here we simulate the motion of CNTs around cavitating bubbles by coupling Brownian dynamics with the Rayleigh–Plesset equation. We observe that, during bubble growth, CNTs align tangentially to the bubble surface. Surprisingly, we find two dynamical regimes during the collapse: shorter CNTs align radially, longer ones buckle. We compute the phase diagram for CNT collapse dynamics as a function of CNT length, stiffness, and initial distance from the bubble nuclei and determine the transition from aligning to buckling. We conclude that, depending on their length, CNTs can break due to either buckling or stretching. These two mechanisms yield different power laws for the length decay (0.25 and 0.5, respectively), reconciling the apparent discrepancy in the experimental data. PMID:22752305

  8. The ultrasound-assisted oxidative scission of monoenic fatty acids by ruthenium tetroxide catalysis: influence of the mixture of solvents.

    PubMed

    Rup, Sandrine; Zimmermann, François; Meux, Eric; Schneider, Michel; Sindt, Michele; Oget, Nicolas

    2009-02-01

    Carboxylic acids and diacids were synthesized from monoenic fatty acids by using RuO4 catalysis, under ultrasonic irradiation, in various mixtures of solvents. Ultrasound associated with Aliquat 336 have promoted in water, the quantitative oxidative cleavage of the CH=CH bond of oleic acid. A design of experiment (DOE) shows that the optimal mixture of solvents (H2O/MeCN, ratio 1/1, 2.2% RuCl3/4.1 eq. NaIO4) gives 81% azelaic acid and 97% pelargonic acid. With the binary heterogeneous mixture H2O/AcOEt, the oxidation of the oleic acid leads to a third product, the alpha-dione 9,10-dioxostearic acid.

  9. DNA strand-scission by phloroglucinols and lignans from heartwood of Garcinia subelliptica Merr. and Justicia plants.

    PubMed

    Lu, Yi-Huang; Wei, Bai-Luh; Ko, Horng-Huey; Lin, Chun-Nan

    2008-01-01

    Five 2,4,6-prenylated phloroglucinols, garcinielliptones HA (1), HB (2), HC (3), HD (4) and HE (5), were isolated from the heartwood of Garcinia subelliptica Merr. Their structures, including relative configurations, were elucidated by means of spectroscopic data analysis. The ability of phloroglucinols, 1-5 and lignans, tuberculatin (8), justicidin A (9), procumbenoside A (10) and ciliatosides A (11) and B (12), isolated from Justicia ciliata and Justicia procumbens, to induce DNA-cleavage activity was examined using pBR322, a supercoiled, covalently closed circular DNA, and it was analyzed by agarose gel electrophoresis. In the presence of Cu (II), compounds 3, 8, 10 and 11 caused significant breakage of supercoiled plasmid pBR322. The products were relaxed circles with no detectable linear forms. In the Cu(II)-mediated DNA damage of 3 and selective compound 8, Cu(I) was shown not to be an essential intermediate by using the Cu(I)-specific sequestering reagent neocuproine.

  10. Bond Formation and Bond Scission Dynamics in Polyatomic Molecules Revealed by Momentum Imaging Experiments and Electron Scattering Calculations

    NASA Astrophysics Data System (ADS)

    Slaughter, Daniel; Trevisan, Cynthia; Weyland, Marvin; Dorn, Alexander; Douguet, Nicolas; Orel, Ann; Adaniya, Hidehito; McCurdy, Bill; Belkacem, Ali; Rescigno, Tom

    2016-05-01

    We present combined experimental and theoretical studies of dissociative electron attachment (DEA) dynamics in methane and ammonia. DEA in each of these systems proceeds through electronic Feshbach resonances, where a valence electron is excited and captured with the incident electron in the lowest unoccupied orbital. In methane, one triply-degenerate resonance undergoes Jahn-Teller splitting through molecular distortions, leading to four observed final states, each having a 2-body and a 3-body dissociation with anionic products H- and CH2-and neutrals CH3, CH2, H2 or H. In ammonia, one resonance leads to H- + NH2 and NH2-+ H, the latter resulting from non-adiabatic charge transfer. A higher energy resonance leads directly to H- + NH2* and indirectly to NH2-+ H. We examine the dynamics of the transient anion in each of these processes. work supported by Chemical Sciences, Geosciences and Biosciences division of BES/DOE.

  11. Solvent induced channel interference in the two-photon absorption process--a theoretical study with a generalized few-state-model in three dimensions.

    PubMed

    Alam, Md Mehboob; Chattopadhyaya, Mausumi; Chakrabarti, Swapan

    2012-01-21

    For the first time, we report the effect of interference between different optical channels on the two-photon absorption (TPA) process in three dimensions. We have employed response theory as well as a sum-over-states (SOS) approach involving few intermediate states to calculate the TPA parameters like transition probabilities (δ(TP)) and TPA tensor elements. In order to use the limited SOS approach, we have derived a new formula for a generalized few-state-model (GFSM) in three dimensions. Due to the presence of additional terms related to the angle between different transition moment vectors, the channel interference associated with the TPA process in 3D is significantly different and much more complicated than that in 1D and 2D cases. The entire study has been carried out on the two simplest Reichardt's dyes, namely 2- and 4-(pyridinium-1-yl)-phenolate (ortho- and para-betain) in gas phase, THF, CH(3)CN and water solvents. We have meticulously inspected the effect of the additional angle related terms on the overall TPA transition probabilities of the two 3D isomeric molecules studied and found that the interfering terms involved in the δ(TP) expression contribute both constructively and destructively as well to the overall δ(TP) value. Moreover, the interfering term has a more conspicuous role in determining the net δ(TP) associated with charge transfer transition in comparison to that of π-π* transition of the studied systems. Interestingly, our model calculations suggest that, for o- and p-betain, the quenching of destructive interference associated with a particular two-photon process can be done with high polarity solvents while the enhancement of constructive interference will be achieved in solvents having relatively small polarity. All the one- and two-photon parameters are evaluated using a range separated CAMB3LYP functional. PMID:22127437

  12. Solvent-induced O-H vibration red-shifts of oxygen-acids in hydrogen-bonded O-H···base complexes.

    PubMed

    Keinan, Sharon; Pines, Dina; Kiefer, Philip M; Hynes, James T; Pines, Ehud

    2015-01-22

    Infrared spectroscopy has been used to characterize the solvent effect on the OH stretching vibrations νOH of phenol, 1-naphthol, 2-naphthol, 1-hydroxypyrene, and ethanol. We distinguish the dielectric (nonspecific) effect of the solvent on ΔνOH, the observed red-shifts in νOH, from the much larger red-shift caused by direct hydrogen (H)-bonding interactions with the solvents. To isolate the solvent dielectric constant ε effect on νOH, the OH oscillator was also studied when it is already H-bonded with an invariant oxygen base, dimethyl sulfoxide. We find that ΔνOH depends importantly on ΔPA, the difference between the proton affinities of the conjugate base of the proton donor and the proton acceptor. For a given H-bonded complex, νOH tends to vary inversely with ε, exhibiting different slopes for polar and nonpolar solvents, i.e., solvents comprising molecules with and without a permanent dipole moment, respectively. We use a two-state valence-bond-based theory to analyze our experimental data. This demonstrates that the OH oscillator acquires a more ionic-like character in the vibrational excited state, i.e., charge transfer; this results in a stronger H-bond in a more anharmonic potential for the OH vibration. The theory distinguishes between nonpolar and polar solvents and successfully accounts for the observed 1/ε and ΔPA variations. PMID:24975617

  13. An improved AMBER force field for α,α-dialkylated peptides: intrinsic and solvent-induced conformational preferences of model systems.

    PubMed

    Grubišić, Sonja; Brancato, Giuseppe; Barone, Vincenzo

    2013-10-28

    α,α-Dialkylated amino acid residues have acquired considerable importance as effective means for introducing backbone conformation constraints in synthetic peptides. The prototype of such a class of residues, namely Aib (α-aminoisobutyric acid), appears to play a dominant role in determining the preferred conformations of host proteins. We have recently introduced into the standard AMBER force field some new parameters, fitted against high-level quantum mechanical (QM) data, for simulating peptides containing α,α-dialkylated residues with cyclic side chains, such as TOAC (TOAC, 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid) and Ac6c (Ac6c = 1-aminocyclohexaneacetic acid). Here, we show that in order to accurately reproduce the observed conformational geometries and structural fluctuations of linear α,α-dialkylated peptides based on Aib, further improvements of the non-bonding and side chain torsion potential parameters have to be considered, due to the expected larger structural flexibility of linear residues with respect to cyclic ones. To this end, we present an extended set of parameters, which have been optimized by fitting the energies of multiple conformations of the Aib dipeptide analogue to corresponding QM calculations that properly account for dispersion interactions (B3LYP-D3). The quality, transferability and size-consistency of the proposed force field have been assessed both by considering a series of poly-Aib peptides, modeled at the same QM level, and by performing molecular dynamics simulations in solvents with high and low polarity. As a result, the present parameters allow one to reproduce with good reliability the available QM and experimental data, thus representing a notable improvement over current force field especially in the description of the α/310-helix conformational equilibria of α,α-dialkylated peptides with linear and cyclic side chains.

  14. Solvent induced synthesis, structure and properties of coordination polymers based on 5-hydroxyisophthalic acid as linker and 1,10-phenanthroline as auxiliary ligand

    NASA Astrophysics Data System (ADS)

    Kariem, Mukaddus; Yawer, Mohd; Sheikh, Haq Nawaz

    2015-11-01

    Three new coordination polymers [Mn(hip)(phen) (H2O)]n (1), [Co(hip)(phen) (H2O)]n (2), and [Cd(hip) (phen) (H2O)]n (3) (H2hip=5-hydroxyisophthalic acid; phen=1,10-phenanthroline) have been synthesized by solvo-hydrothermal method using diethyl formamide-water (DEF-H2O) as solvent system. Single-crystal X-ray diffraction analysis reveals that all three coordination polymers 1, 2 and 3 crystallize in monoclinic space group P2/n. Metal ions are inter-connected by hydroxyisophthalate anions forming zig-zag 1D chain. 1D chains are further inter-connected by hydrogen bonding and π-π stacking interactions leading to 3D supramolecular architecture. Hydrogen-bonding and π-π stacking provide thermal stability to polymers. Compounds 1 and 2 are paramagnetic at room temperature and variable temperature magnetic moment measurements revealed weak ferromagnetic interactions between metal ions at low temperature. Compound 3 exhibits excellent photoluminescence with large Stokes shift.

  15. Coal liquefaction process using pretreatment with a binary solvent mixture

    DOEpatents

    Miller, Robert N.

    1986-01-01

    An improved process for thermal solvent refining or hydroliquefaction of non-anthracitic coal at elevated temperatures under hydrogen pressure in a hydrogen donor solvent comprises pretreating the coal with a binary mixture of an aromatic hydrocarbon and an aliphatic alcohol at a temperature below 300.degree. C. before the hydroliquefaction step. This treatment generally increases both conversion of coal and yields of oil.

  16. Density functional theory study of O-H and C-H bond scission of methanol catalyzed by a chemisorbed oxygen layer on Cu(111)

    NASA Astrophysics Data System (ADS)

    Li, Jonathan; Zhou, Guangwen

    2016-04-01

    Using the density-functional theory within the generalized gradient approximation, we have studied the partial oxidation of methanol on a Cu(111) surface covered with a chemisorbed oxygen layer that resembles a Cu2O layer. Adsorption energies and geometries were computed for methanol, methoxy, hydroxymethyl and formaldehyde on both clean Cu(111) and Cu2O/Cu(111) and electronic structures were computed for the reaction intermediates on Cu2O/Cu(111). We also calculated the energy barrier for partial oxidation of methanol to formaldehyde on Cu2O/Cu(111). These results show that the Cu2O monolayer slightly lowers the stability of each of the surface adsorbates and the oxygen strongly promotes hydrogen dissociation by lowering the energy barrier of methanol decomposition and causing the spontaneous dissociation of methanol into methoxy.

  17. Reaction pathways of 2-iodoacetic acid on Cu(100): coverage-dependent competition between C-I bond scission and COOH deprotonation and identification of surface intermediates.

    PubMed

    Lin, Yi-Shiue; Lin, Jain-Shiun; Liao, Yung-Hsuan; Yang, Che-Ming; Kuo, Che-Wei; Lin, Hong-Ping; Fan, Liang-Jen; Yang, Yaw-Wen; Lin, Jong-Liang

    2010-06-01

    The chemistry of 2-iodoacetic acid on Cu(100) has been studied by a combination of reflection-absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), temperature-programmed reaction/desorption (TPR/D), and theoretical calculations based on density functional theory for the optimized intermediate structures. In the thermal decomposition of ICH(2)COOH on Cu(100) with a coverage less than a half monolayer, three surface intermediates, CH(2)COO, CH(3)COO, and CCOH, are generated and characterized spectroscopically. Based on their different thermal stabilities, the reaction pathways of ICH(2)COOH on Cu(100) at temperatures higher than 230 K are established to be ICH(2)COOH --> CH(2)COO + H + I, CH(2)COO + H --> CH(3)COO, and CH(3)COO --> CCOH. Theoretical calculations suggest that the surface CH(2)COO has the skeletal plane, with delocalized pi electrons, approximately parallel to the surface. The calculated Mulliken charges agree with the detected binding energies for the two carbon atoms in CH(2)COO on Cu(100). The CCOH derived from CH(3)COO decomposition has a CC stretching frequency at 2025 cm(-1), reflecting its triple-bond character which is consistent with the calculated CCOH structure on Cu(100). Theoretically, CCOH at the bridge and hollow sites has a similar stability and is adsorbed with the molecular axis approximately perpendicular to the surface. The TPR/D study has shown the evolution of the products of H(2), CH(4), H(2)O, CO, CO(2), CH(2)CO, and CH(3)COOH from CH(3)COO decomposition between 500 and 600 K and the formation of H(2) and CO from CCOH between 600 and 700 K. However, at a coverage near one monolayer, the major species formed at 230 and 320 K are proposed to be ICH(2)COO and CH(3)COO. CH(3)COO becomes the only species present on the surface at 400 K. That is, there are two reaction pathways of ICH(2)COOH --> ICH(2)COO + H and ICH(2)COO + H --> CH(3)COO + I (possibly via CH(2)COO), which are different from those observed at lower coverages. Because the C-I bond dissociation of iodoethane on copper single crystal surfaces occurs at approximately 120 K and that the deprotonation of CH(3)COOH on Cu(100) occurs at approximately 220 K, the preferential COOH dehydrogenation of monolayer ICH(2)COOH is an interesting result, possibly due to electronic and/or steric effects.

  18. Color tunable and near white-light emission of two solvent-induced 2D lead(II) coordination networks based on a rigid ligand 1-tetrazole-4-imidazole-benzene.

    PubMed

    Chen, Jun; Zhang, Qing; Liu, Zhi-Fa; Wang, Shuai-Hua; Xiao, Yu; Li, Rong; Xu, Jian-Gang; Zhao, Ya-Ping; Zheng, Fa-Kun; Guo, Guo-Cong

    2015-06-01

    Two new lead(II) coordination polymers, [Pb(NO3)(tzib)]n (1) and [Pb(tzib)2]n (2), were successfully synthesized from the reaction of a rigid ligand 1-tetrazole-4-imidazole-benzene (Htzib) and lead(II) nitrate in different solvents. The obtained polymers have been characterized by single-crystal X-ray diffraction analyses, which show that both polymers feature 2D layer structures. The inorganic anion nitrate in 1 shows a μ2-κO3:κO3 bridging mode to connect adjacent lead ions into a zigzag chain, and then the organic ligands tzib(-) join the neighboring chains into a 2D layer by a μ3-κN1:κN2:κN6 connection mode. In 2, there are two different bridging modes of the tzib(-) ligand: μ3-κN1:κN2:κN6 and μ3-κN1:κN6 to coordinate the lead ions into a 2D layer structure. Interestingly, both polymers displayed broadband emissions covering the entire visible spectra, which could be tunable to near white-light emission by varying excitation wavelengths. PMID:25952460

  19. Time phased alternate blending of feed coals for liquefaction

    DOEpatents

    Schweigharett, Frank; Hoover, David S.; Garg, Diwaker

    1985-01-01

    The present invention is directed to a method for reducing process performance excursions during feed coal or process solvent changeover in a coal hydroliquefaction process by blending of feedstocks or solvents over time. ,

  20. Coal liquefaction process using pretreatment with a binary solvent mixture

    DOEpatents

    Miller, R.N.

    1986-10-14

    An improved process for thermal solvent refining or hydroliquefaction of non-anthracitic coal at elevated temperatures under hydrogen pressure in a hydrogen donor solvent comprises pretreating the coal with a binary mixture of an aromatic hydrocarbon and an aliphatic alcohol at a temperature below 300 C before the hydroliquefaction step. This treatment generally increases both conversion of coal and yields of oil. 1 fig.

  1. Ambient pressure XPS and IRRAS investigation of ethanol steam reforming on Ni-CeO2(111) catalysts: an in situ study of C-C and O-H bond scission.

    PubMed

    Liu, Zongyuan; Duchoň, Tomáš; Wang, Huanru; Grinter, David C; Waluyo, Iradwikanari; Zhou, Jing; Liu, Qiang; Jeong, Beomgyun; Crumlin, Ethan J; Matolín, Vladimír; Stacchiola, Dario J; Rodriguez, José A; Senanayake, Sanjaya D

    2016-06-22

    Ambient-Pressure X-ray Photoelectron Spectroscopy (AP-XPS) and Infrared Reflection Absorption Spectroscopy (AP-IRRAS) have been used to elucidate the active sites and mechanistic steps associated with the ethanol steam reforming reaction (ESR) over Ni-CeO2(111) model catalysts. Our results reveal that surface layers of the ceria substrate are both highly reduced and hydroxylated under reaction conditions while the small supported Ni nanoparticles are present as Ni(0)/NixC. A multifunctional, synergistic role is highlighted in which Ni, CeOx and the interface provide an ensemble effect in the active chemistry that leads to H2. Ni(0) is the active phase leading to both C-C and C-H bond cleavage in ethanol and it is also responsible for carbon accumulation. On the other hand, CeOx is important for the deprotonation of ethanol/water to ethoxy and OH intermediates. The active state of CeOx is a Ce(3+)(OH)x compound that results from extensive reduction by ethanol and the efficient dissociation of water. Additionally, we gain an important insight into the stability and selectivity of the catalyst by its effective water dissociation, where the accumulation of surface carbon can be mitigated by the increased presence of surface OH groups. The co-existence and cooperative interplay of Ni(0) and Ce(3+)(OH)x through a metal-support interaction facilitate oxygen transfer, activation of ethanol/water as well as the removal of coke. PMID:27095305

  2. Ambient pressure XPS and IRRAS investigation of ethanol steam reforming on Ni-CeO2(111) catalysts: an in situ study of C-C and O-H bond scission.

    PubMed

    Liu, Zongyuan; Duchoň, Tomáš; Wang, Huanru; Grinter, David C; Waluyo, Iradwikanari; Zhou, Jing; Liu, Qiang; Jeong, Beomgyun; Crumlin, Ethan J; Matolín, Vladimír; Stacchiola, Dario J; Rodriguez, José A; Senanayake, Sanjaya D

    2016-06-22

    Ambient-Pressure X-ray Photoelectron Spectroscopy (AP-XPS) and Infrared Reflection Absorption Spectroscopy (AP-IRRAS) have been used to elucidate the active sites and mechanistic steps associated with the ethanol steam reforming reaction (ESR) over Ni-CeO2(111) model catalysts. Our results reveal that surface layers of the ceria substrate are both highly reduced and hydroxylated under reaction conditions while the small supported Ni nanoparticles are present as Ni(0)/NixC. A multifunctional, synergistic role is highlighted in which Ni, CeOx and the interface provide an ensemble effect in the active chemistry that leads to H2. Ni(0) is the active phase leading to both C-C and C-H bond cleavage in ethanol and it is also responsible for carbon accumulation. On the other hand, CeOx is important for the deprotonation of ethanol/water to ethoxy and OH intermediates. The active state of CeOx is a Ce(3+)(OH)x compound that results from extensive reduction by ethanol and the efficient dissociation of water. Additionally, we gain an important insight into the stability and selectivity of the catalyst by its effective water dissociation, where the accumulation of surface carbon can be mitigated by the increased presence of surface OH groups. The co-existence and cooperative interplay of Ni(0) and Ce(3+)(OH)x through a metal-support interaction facilitate oxygen transfer, activation of ethanol/water as well as the removal of coke.

  3. Catalysts for coal liquefaction processes

    DOEpatents

    Garg, D.

    1986-10-14

    Improved catalysts for catalytic solvent refining or hydroliquefaction of non-anthracitic coal at elevated temperatures under hydrogen pressure in a hydrogen donor solvent comprise a combination of zinc or copper, or a compound thereof, and a Group VI or non-ferrous Group VIII metal, or a compound thereof.

  4. Catalytic coal liquefaction process

    DOEpatents

    Garg, D.; Sunder, S.

    1986-12-02

    An improved process for catalytic solvent refining or hydroliquefaction of non-anthracitic coal at elevated temperatures under hydrogen pressure in a solvent comprises using as catalyst a mixture of a 1,2- or 1,4-quinone and an alkaline compound, selected from ammonium, alkali metal, and alkaline earth metal oxides, hydroxides or salts of weak acids. 1 fig.

  5. Catalysts for coal liquefaction processes

    DOEpatents

    Garg, Diwakar

    1986-01-01

    Improved catalysts for catalytic solvent refining or hydroliquefaction of non-anthracitic coal at elevated temperatures under hydrogen pressure in a hydrogen donor solvent comprise a combination of zinc or copper, or a compound thereof, and a Group VI or non-ferrous Group VIII metal, or a compound thereof.

  6. Catalytic coal liquefaction process

    DOEpatents

    Garg, Diwakar; Sunder, Swaminathan

    1986-01-01

    An improved process for catalytic solvent refining or hydroliquefaction of non-anthracitic coal at elevated temperatures under hydrogen pressure in a solvent comprises using as catalyst a mixture of a 1,2- or 1,4-quinone and an alkaline compound, selected from ammonium, alkali metal, and alkaline earth metal oxides, hydroxides or salts of weak acids.

  7. Bioactive prenylated flavonoids from the stem bark of Artocarpus kemando.

    PubMed

    Seo, Eun-Kyoung; Lee, Dongho; Shin, Young Geun; Chai, Hee-Byung; Navarro, Hernán A; Kardono, Leonardus B S; Rahman, Ismail; Cordell, Geoffrey A; Farnsworth, Norman R; Pezzuto, John M; Kinghorn, A Douglas; Wani, Mansukh C; Wall, Monroe E

    2003-02-01

    Four known prenylated flavonoids, artonins E (1) and O (2), artobiloxanthone (3), and cycloartobiloxanthone (4), were isolated from the stem bark of Artocarpus kemando by bioassay-guided fractionation using the DNA strand-scission and the KB cytotoxicity assays as monitors. Compounds 1 and 3 exhibited strong DNA strand-scission activity, and all four compounds were found to be cytotoxic.

  8. Dynamical simulation of energy dissipation in asymmetric heavy-ion induced fission of {sup 200}Pb, {sup 213}Fr, and {sup 251}Es

    SciTech Connect

    Mirfathi, S. M.; Pahlavani, M. R.

    2008-12-15

    The dynamical model based on the asymmetric mass division has been applied to calculate pre-scission neutron multiplicity from heavy-ion induced fusion-fission reactions. Links between the pre-scission neutron multiplicity, excitation energy, and asymmetric mass distribution are clarified based on the Monte Carlo simulation and Langevin dynamics. The pre-scission neutron multiplicity is calculated and compared with the respective experimental data over a wide range of excitation energy and nonconstant viscosity. The analysis indicates a different effect for the application of asymmetric mass division in different energy regions of such processes.

  9. Viscoelastic behavior of polymers undergoing crosslinking reactions.

    NASA Technical Reports Server (NTRS)

    Moacanin, J.; Aklonis, J. J.

    1971-01-01

    Previously a method was developed for predicting the viscoelastic response of polymers undergoing scission reactions. These results are now extended to include crosslinking reactions. As for scission, at any given time the character of the network chains is determined by the instantaneous crosslink density. For scission all chains were assumed to carry the same stress; for crosslinking, however, the stress is distributed between the 'new' and 'old' chains. Equations for calculating the creep response of a system which experiences a step increase in crosslink density are derived.

  10. Structure properties of {sup 226}Th and {sup 256,258,260}Fm fission fragments: Mean-field analysis with the Gogny force

    SciTech Connect

    Dubray, N.; Goutte, H.; Delaroche, J.-P.

    2008-01-15

    The constrained Hartree-Fock-Bogoliubov method is used with the Gogny interaction D1S to calculate potential energy surfaces of fissioning nuclei {sup 226}Th and {sup 256,258,260}Fm up to very large deformations. The constraints employed are the mass quadrupole and octupole moments. In this subspace of collective coordinates, many scission configurations are identified ranging from symmetric to highly asymmetric fragmentations. Corresponding fragment properties at scission are derived yielding fragment deformations, deformation energies, energy partitioning, neutron binding energies at scission, neutron multiplicities, charge polarization, and total fragment kinetic energies.

  11. Fission Fragment Properties from a Microscopic Approach

    SciTech Connect

    Dubray, N.; Goutte, H.; Delaroche, J.-P.

    2008-04-17

    We calculate potential energy surfaces in the elongation-asymmetry plane, up to very large deformations, with the Hartree-Fock-Bogoliubov method and the Gogny nucleon-nucleon effective interaction DIS, for the {sup 226}Th and {sup 256,258,260}Fm fissioning systems. We then define a criterion based on the nuclear density, in order to discriminate between pre- and post-scission configurations. Using this criterion, many scission configurations are identified, and are used for the calculation of several fragment properties, like fragment deformations, deformation energies, energy partitioning, neutron binding energies at scission, charge polarization, total fragment kinetic energies and neutron multiplicities.

  12. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, April--June 1993

    SciTech Connect

    Song, Chunshan; Parfitt, D.P.; Schobert, H.H.

    1993-08-01

    The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular precursors, that can be used in low concentrations (hydroliquefaction of coals under temperature-programmed conditions. Several heterometallic complexes consisting of two transition metals, Mo and Co, and sulfur in a single molecule were synthesized and tested as precursors of bimetallic dispersed catalysts for liquefaction of a Montana subbituminous coal (DECS-9) at the loading level of 0.5 wt% Mo on dmmf coal. It was found that the structure of the precursors, in particular the ligands to the metal species, affect the activity of the resulting catalyst significantly. Among the M-M` type precursors tested, Mo-Co thiocubane, Mo{sub 2}Co{sub 2}S{sub 4}(Cp){sub 2}(CO){sub 2} [Cp = cyclopentadiene], designated as MoCo-TC2, produced in-situ the best catalyst The performance of the Mo-Co bimetallic catalyst was further enhanced by using temperature programmed (TPL) conditions consisting of a low temperature soaking at 200{degrees}C, programmed heat-up to 400 or 425{degrees}C followed by a 30 minutes hold. The pro ed heat-up serves as an in-situ activation of catalyst and coal pretreatment, which contributes to more effective hydrogenation of reactive fragments at high temperature.

  13. Experimental laboratory measurement of thermophysical properties of selected coal types

    NASA Technical Reports Server (NTRS)

    Lloyd, W. G.

    1979-01-01

    A number of bituminous coals of moderate to high plasticity were examined, along with portions of their extrudates from the JPL 1.5-inch 850 F screw extruder. Portions of the condensed pyrolysis liquids released during extrusion, and of the gaseous products formed during extrusion were also analyzed. In addition to the traditional determinations, the coals and extrudates were examined in terms of microstructure (especially extractable fractions), thermal analysis (especially that associated with the plastic state), and reactivity towards thermal and catalyzed hydroliquefaction. The process of extrusion increases the fixed carbon content of coals by about 5% and tends to increase the surface area. Coals contaning 25% or more DMF-extractable material show an increase in extractables as a result of extrusion; those initially containing less than 20% extractables show a decrease as a result of extrusion. Both the raw and extruded samples of Kentucky #9 coal are highly reactive towards hydroliquefaction, undergoing conversions of 75 to 80% in 15 min and 85-94% in 60 min in a stirred clave.

  14. Measurement of neutron multiplicity from fission of {sup 228}U and nuclear dissipation

    SciTech Connect

    Singh, Hardev; Behera, B. R.; Singh, Gulzar; Govil, I. M.; Golda, K. S.; Jhingan, Akhil; Singh, R. P.; Sugathan, P.; Chatterjee, M. B.; Datta, S. K.; Pal, Santanu; Ranjeet; Mandal, S.; Shidling, P. D.; Viesti, G.

    2009-12-15

    Pre- and post-scission neutron multiplicities are measured at different excitation energies of the compound nucleus {sup 228}U populated using the {sup 19}F+{sup 209}Bi reaction. The measured yield of pre-scission and total neutrons are compared with the statistical model calculation for the decay of a compound nucleus. The statistical model calculations are performed using the Bohr-Wheeler transition state fission width as well as the dissipative dynamical fission width due to Kramers. Comparison between the measured and the calculated values shows that, while the Bohr-Wheeler fission width grossly underestimates the pre-scission neutron yield, a large amount of dissipation is required in the Kramers width to fit the experimental pre-scission multiplicities. Various factors contributing to the large excitation energy dependence of the fitted values of the dissipation coefficient are discussed.

  15. Catalytic conversion of polycyclic aromatic hydrocarbons: Mechanistic investigations of hydrogen transfer from an iron-based catalyst to alkylarenes

    SciTech Connect

    Autrey, T.; Linehan, J.C.; Camaioni, D.M.

    1995-12-31

    The mechanisms of hydrogen transfer from iron/sulfur-based catalysts to a series of coal model compounds have been investigated. The iron oxyhydroxides catalyst precursors are produced by the RTDS method with the actual catalytic species, an iron/sulfur catalyst, generated in situ by addition of sulfur and a hydrogen donor solvent. These catalysts promote the selective scission of thermally stable carbon-carbon bonds. Both the rate and the selectivity of catalytic induced bond scission are enhanced relative to the thermal hydrogen transfer pathways in 9,10-dihydrophenanthrene donor solvent. The reactivity of alkylated diphenylmethanes and derivatives of 1,2-diphenylethanol support a non-ionic free radical hydrogen transfer pathway. The selectivity of catalytic engendered bond scission is rationalized by an ipso displacement mechanism competing with a back-hydrogen transfer to the catalytic surface. This mechanism explains the scission of thermal stable coal linkages without the formation of light gases.

  16. Microscopic Calculations of 240Pu Fission

    SciTech Connect

    Younes, W; Gogny, D

    2007-09-11

    Hartree-Fock-Bogoliubov calculations have been performed with the Gogny finite-range effective interaction for {sup 240}Pu out to scission, using a new code developed at LLNL. A first set of calculations was performed with constrained quadrupole moment along the path of most probable fission, assuming axial symmetry but allowing for the spontaneous breaking of reflection symmetry of the nucleus. At a quadrupole moment of 345 b, the nucleus was found to spontaneously scission into two fragments. A second set of calculations, with all nuclear moments up to hexadecapole constrained, was performed to approach the scission configuration in a controlled manner. Calculated energies, moments, and representative plots of the total nuclear density are shown. The present calculations serve as a proof-of-principle, a blueprint, and starting-point solutions for a planned series of more comprehensive calculations to map out a large set of scission configurations, and the associated fission-fragment properties.

  17. Process and analytical studies of enhanced low severity co-processing using selective coal pretreatment. Final technical report

    SciTech Connect

    Baldwin, R.M.; Miller, R.L.

    1991-12-01

    The findings in the first phase were as follows: 1. Both reductive (non-selective) alkylation and selective oxygen alkylation brought about an increase in liquefaction reactivity for both coals. 2. Selective oxygen alkylation is more effective in enhancing the reactivity of low rank coals. In the second phase of studies, the major findings were as follows: 1. Liquefaction reactivity increases with increasing level of alkylation for both hydroliquefaction and co-processing reaction conditions. 2. the increase in reactivity found for O-alkylated Wyodak subbituminous coal is caused by chemical changes at phenolic and carboxylic functional sites. 3. O-methylation of Wyodak subbituminous coal reduced the apparent activation energy for liquefaction of this coal.

  18. Process and analytical studies of enhanced low severity co-processing using selective coal pretreatment

    SciTech Connect

    Baldwin, R.M.; Miller, R.L.

    1991-12-01

    The findings in the first phase were as follows: 1. Both reductive (non-selective) alkylation and selective oxygen alkylation brought about an increase in liquefaction reactivity for both coals. 2. Selective oxygen alkylation is more effective in enhancing the reactivity of low rank coals. In the second phase of studies, the major findings were as follows: 1. Liquefaction reactivity increases with increasing level of alkylation for both hydroliquefaction and co-processing reaction conditions. 2. the increase in reactivity found for O-alkylated Wyodak subbituminous coal is caused by chemical changes at phenolic and carboxylic functional sites. 3. O-methylation of Wyodak subbituminous coal reduced the apparent activation energy for liquefaction of this coal.

  19. Ruthenium ion-catalyzed oxidation of Shenfu coal and its residues

    SciTech Connect

    Yao-Guo Huang; Zhi-Min Zong; Zi-Shuo Yao; Yu-Xuan Zheng; Jie Mou; Guang-Feng Liu; Jin-Pei Cao; Ming-Jie Ding; Ke-Ying Cai; Feng Wang; Wei Zhao; Zhi-Lin Xia; Lin Wu; Xian-Yong Wei

    2008-05-15

    Shenfu coal (SFC), its liquefaction residue (RL), and carbon disulfide (CS{sub 2})/tetrahydrofuran (THF)-inextractable matter (RE) were subject to ruthenium ion-catalyzed oxidation to understand the differences in structural features among the above three samples. The results suggest that SFC is rich in long-chain arylalkanes and {alpha}. {omega}-diarylalkanes (DAAs) with carbon number of methylene linkage from 2 to 4 and that long-chain arylalkanes and DAAs are reactive toward hydroliquefaction and soluble in a CS{sub 2}/THF mixed solvent, whereas highly condensed aromatic species in SFC show poor solubility in the CS{sub 2}/THF mixed solvent. 29 refs., 6 figs., 4 tabs.

  20. New approach to immobilization of coal-model compounds on silica using a calcium carboxylate linkage

    SciTech Connect

    Ramakrishnan, S.; Guthrie, R.D.; Britt, P.F.; Buchanan, A.C. III; Davis, B.H.

    1995-12-31

    In an earlier report, the authors described efforts to study the hydrothermolysis of surface-immobilized coal model compounds by attaching 1-(4{prime}-hydroxyphenyl)-2-phenylethane to the surface of fumed silica via a Si-OAr linkage using procedures developed by Buchanan, Poutsma and coworkers and heating the resultant material (SiO-DPE) under D{sub 2} pressure. Despite the successes noted here, they sought to find a method for constructing links between silica and organic materials which might better survive hydroliquefaction conditions. Attachment of long-chain aliphatic carboxylic acids to silica through Mg{sup ++} or Ca{sup ++} ions is a patented method for silica flotation which they thought might be adapted to their purposes. This preprint is a preliminary report on the preparation, thermolysis and hydrothermolysis of materials believed to have the general structure, SiO{sup {minus}}Ca{sup ++}{sup {minus}}O{sub 2}CAr.

  1. Some consideration on potentials of coal organic materials for chemicals

    SciTech Connect

    Nomura, Masakatsu; Artok, Levent; Su, Yan; Murata, Satoru

    1998-12-31

    According to the recent structural studies on bituminous coals, the presence of condensed aromatic nuclei and alicyclic portion in coal is considered to be more abundant than believed so far. Based on these data consideration of the potential of coal for chemical production is made by referring to the results on sodium dichromate-oxidation of Akabira coal and detailed analysis of vacuum residue from Illinois No.6 coal derived liquid. It is also stressed that to select the appropriate coal samples for either flash pyrolysis or hydroliquefaction based on their detailed structural index is important to attain their effective conversion. Three methods occurs in the minds of coal chemists, pyrolysis, direct liquefaction and indirect liquefaction. In this paper, the authors focus on the former two methods because indirect liquefaction makes use of carbon monoxide and hydrogen obtained in coal gasification, being not fitted in the present context of potentials of coal organic materials.

  2. The chemistry and technology of synthetic fuels

    NASA Astrophysics Data System (ADS)

    Schriesheim, A.; Kirshenbaum, I.

    1981-10-01

    The variety of methods by which crude oil residua, coal and oil shale may be converted to synthetic fuels are considered, with attention to the chemical conversion processes that must be implemented on a large industrial scale. Among the technologies highlighted are (1) Flexicoking, in which residuum, preheated to 300 C, is sprayed into a reactor containing a fluidized solids bed of hot coke; the resulting thermal cracking of the residuum at 525 C forming gaseous and liquid products for conventional processing; (2) coal pyrolysis, a carbon rejection process that produces liquids, tars and coke; (3) hydroliquefaction, in which coal is liquefied directly by treatment with hydrogen at 450 C and pressures in the 70-200 atmospheres range; and (4) oil shale retorting, which is seen as requiring considerable further development before commercial feasibility is reached.

  3. Fabrication of nanochannels on polystyrene surface

    PubMed Central

    Li, Dongqing

    2015-01-01

    Solvent-induced nanocrack formation on polystyrene surface is investigated experimentally. Solubility parameter and diffusion coefficient of alcohols are employed to elucidate the swelling and cracking processes as well as the crack size. Experimental results show that the crack size increases with the heating temperature, heating time, and the concentration and volume of the alcohols. A guideline on fabricating single smaller nanocracks on polymers by solvent-induced method is provided. Nanocracks of approximately 64 nm in width and 17.4 nm in depth were created and replicated onto PDMS (polydimethylsiloxane) slabs to form nanochannels. PMID:25945143

  4. Degradation of poly(methylmethacrylate) by deep ultraviolet, x-ray, electron beam, and proton beam irradiations

    SciTech Connect

    Choi, J.O.; Moore, J.A.; Corelli, J.C.; Silverman, J.P.; Bakhru, H.

    1988-11-01

    The chemical changes in poly(methylmethacrylate) (PMMA) caused by irradiation with deep ultraviolet (UV), x-ray, electron, and proton beams were studied by gel permeation chromatography, Fourier-transform infrared, and UV spectroscopy. The quantitative analysis of spectroscopic changes (Beer's law) demonstrated a 1:1 correspondence between the disappearance of ester groups and the generation of double bonds in the polymer chain by all types of radiation. The ratio of main chain scission to changes in the number of ester groups and unsaturated bonds was compared to determine the characteristics of degradation of PMMA by the different types of radiation. This ratio for deep UV data was very close to the quantum yield of main chain scission of PMMA as reported in the literature. High-energy radiation was /similar to/0 x more efficient than deep UV in causing main chain scission with removal of fewer ester groups. Protons induced more main chain scission than electrons. X-ray irradiation was the most efficient at causing main chain scission of the four different types of radiation.

  5. Degradation of poly(methyl methacrylate) by deep uv (ultraviolet), x-ray, e-beam, and proton irradiations. Technical report

    SciTech Connect

    Moore, J.A.; Choi, J.O .; Corelli, J.C.; Silverman, J.P.; Bakhru, H.

    1988-01-01

    The chemical changes in poly (methylmethacrylate) (PMMA) caused by irradiation with deep ultraviolet (UV), x-ray, electron, and proton beams were studied by gel permeation chromatography, Fourier-transform infrared, and UV spectroscopy. The quantitative analysis of spectroscopic changes (Beer's law) demonstrated a 1:1 correspondence between the disappearance of ester groups and the generation of double bonds in the polymer chain by all types of radiation. The ratio of main chain scission to changes in the number of ester groups and unsaturated bonds was compared to determine the characteristics of degradation of PMMA by the different types of radiation. This ratio for deep UV data was very close to the quantum yield of main chain scission of PMMA as reported in the literature. High-energy radiation was approx. 10 X more efficient than deep UV in a causing main chain scission with removal of fewer ester groups. Protons induced more main-chain scission the electrons. X-ray irradiation was the most efficient at causing main-chain scission of the four different types of radiation.

  6. Degradation of poly(lactide-co-glycolide) (PLGA) and poly(L-lactide) (PLLA) by electron beam radiation.

    PubMed

    Loo, J S C; Ooi, C P; Boey, F Y C

    2005-04-01

    This paper seeks to examine the effects of electron beam (e-beam) radiation on biodegradable polymers (PLGA and PLLA), and to understand their radiation-induced degradation mechanisms. PLGA (80:20) and PLLA polymer films were e-beam irradiated at doses from 2.5 to 50 Mrad and the degradation of these films were studied by measuring the changes in their molecular weights, FTIR spectra, thermal and morphological properties. The dominant effect of e-beam irradiation on both PLGA and PLLA is chain scission. Chain scission occurs first through scission of the polymer main chain, followed by hydrogen abstraction. Chain scission, though responsible for the reduction in the average molecular weight, Tc, Tg and Tm of both polymers, encourages crystallization in PLGA. PLLA also undergoes chain scission upon irradiation but to a lesser degree compared to PLGA. The higher crystallinity of PLLA is the key factor in its greater stability to e-beam radiation compared to PLGA. A linear relationship is also established between the decrease in molecular weight with respect to radiation dose. PMID:15482823

  7. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction

    SciTech Connect

    Song, Chunshan; Schobert, H.H.

    1993-02-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on the development of novel bimetallic dispersed catalysts for temperature-programmed liquefaction. The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular that can be used in low precursors concentrations (< 1 %) but exhibit high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. The major technical approaches are, first, to prepare the desired heteronuclear organometallic molecules as catalyst precursors that contain covalently bound, two different metal atoms and sulfur in a single molecule. Such precursors will generate finely dispersed bimetallic catalysts such as Fe-Mo, Co-Mo and Ni-Mo binary sulfides upon thermal decomposition. The second major technical approach is to perform the liquefaction of coals unpregnated with the organometallic precursors under temperature-programmed conditions, where the programmed heat-up serves as a step for both catalyst activation and coal pretreatment or preconversion. Two to three different complexes for each of the Fe-Mo, Co-Mo, and Ni-Mo combinations will be prepared. Initial catalyst screening tests will be conducted using a subbituminous coal and a bituminous coal. Effects of coal rank and solvents will be examined with the selected bimetallic catalysts which showed much higher activity than the dispersed catalysts from conventional precursors.

  8. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, October--December 1992

    SciTech Connect

    Song, Chunshan; Schobert, H.H.

    1993-02-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on the development of novel bimetallic dispersed catalysts for temperature-programmed liquefaction. The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular that can be used in low precursors concentrations (< 1 %) but exhibit high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. The major technical approaches are, first, to prepare the desired heteronuclear organometallic molecules as catalyst precursors that contain covalently bound, two different metal atoms and sulfur in a single molecule. Such precursors will generate finely dispersed bimetallic catalysts such as Fe-Mo, Co-Mo and Ni-Mo binary sulfides upon thermal decomposition. The second major technical approach is to perform the liquefaction of coals unpregnated with the organometallic precursors under temperature-programmed conditions, where the programmed heat-up serves as a step for both catalyst activation and coal pretreatment or preconversion. Two to three different complexes for each of the Fe-Mo, Co-Mo, and Ni-Mo combinations will be prepared. Initial catalyst screening tests will be conducted using a subbituminous coal and a bituminous coal. Effects of coal rank and solvents will be examined with the selected bimetallic catalysts which showed much higher activity than the dispersed catalysts from conventional precursors.

  9. Viscoelastic properties of vis-breaking polypropylenes

    NASA Astrophysics Data System (ADS)

    Nobile, Maria Rossella; Moad, Graeme; Habsuda, Jana; Li, Guoxin; Nichols, Lance; Dagley, Ian; Simon, George P.

    2015-12-01

    In this work hydrogen peroxide is used as a green initiator to cause scissioning of polypropylene (PP) with water as the only by-product replacing the organic peroxides that are usually used. The rheological properties of a commercial polypropylene and of the scissioned samples are determined by dynamic rheology and an inversion procedure for converting the linear viscoelastic data into molar mass distribution has been adopted. The results presented show that the molar mass distribution of the PP polymer is narrowed on scissioning. The process is found to produce polymers similar in molecular architecture and behavior to organic peroxide cleaved materials, the results of which are given as a comparison in this work.

  10. Electron beam irradiation of maltodextrin and cinnamyl alcohol mixtures: influence of glycerol on cross-linking.

    PubMed

    Khandal, Dhriti; Aggarwal, Manjeet; Suri, Gunjan; Coqueret, Xavier

    2015-03-01

    The influence of glycerol on the electron beam-induced changes in maltodextrins-cinnamyl alcohol (CA) blends is examined with respect to its influence on the degree of chain scission, grafting, and cross-linking. The study is relevant to radiation-induced polysaccharide modification, specifically in the perspective of using blended starch as a thermoplastic material, where glycerol is commonly used as a plasticizer. In the absence of CA, glycerol protects maltodextrin from chromophore formation onto the main chain, but also induces more chain scission. The presence of CA provides efficient radiation-protection against scission. Glycerol is shown to affect the interaction between maltodextrin and CA, most likely in the form of an inclusion complex when glycerol is absent. The global behavior under radiation is therefore governed by the physical interactions between the blend constituents rather than on the role of glycerol role as a plasticizer, or as an OH˙ radical scavenger.

  11. Radiochemical Ageing of Aromatic Polymers PEEK, PSU and Kapton registered

    SciTech Connect

    Richaud, E.; Audouin, L.; Colin, X.; Verdu, J.; Monchy-Leroy, C.

    2010-06-02

    This article deals with degradation mechanism of three aromatic polymers submitted to gamma-rays in air at 60 deg. C. T{sub g} measurements and GPC results indicated that thin samples (thickness lower than 200 mum) undergo mostly chain scission whereas sol gel analysis and rheometric measurements showed that thicker ones undergo mainly crosslinking. Both results are explained by oxygen diffusion control of oxidation resulting in the formation of a superficial oxidized layer experimentally observed by muATR InfraRed in which oxidative processes orientate rather to chain scission than crosslinking. Experimental results also allowed discussing relative oxidative stability, sensitivity of T{sub g} to chain scission concentration, and crosslinking mechanism (Y or H).

  12. Molecular weight changes induced in an anionic polydimethylsiloxane by gamma irradiation in vacuum

    NASA Astrophysics Data System (ADS)

    Satti, Angel J.; Andreucetti, Noemí A.; Ciolino, Andrés E.; Vitale, Cristian; Sarmoria, Claudia; Vallés, Enrique M.

    2010-11-01

    An anionic almost monodisperse linear polydimethylsiloxane (PDMS) was subjected to gamma irradiation under vacuum at room temperature. The molecular weight changes induced by the radiation process have been investigated using size exclusion chromatography (SEC) with refraction index (RI) and multi angle laser light scattering (MALLS) detectors, to obtain the number and weight average molecular weights of the irradiated samples. The analysis of the data indicates that crosslinking reactions predominated over scission reactions. The results obtained by an SEC-RI have confirmed the presence of small, but measurable amounts of scission. A previously developed mathematical model of the irradiation process that accounts for simultaneous scission and crosslinking and allows for both H- and Y-crosslinks, fitted well the measured molecular weight data. This prediction is in accordance with the experimental data obtained by 29Si-Nuclear Magnetic Resonance spectroscopy (NMR) and previously reported data for commercial linear PDMS ( Satti et al., 2008).

  13. Radiochemical Ageing of Aromatic Polymers PEEK, PSU and Kapton®

    NASA Astrophysics Data System (ADS)

    Richaud, E.; Audouin, L.; Colin, X.; Monchy-Leroy, C.; Verdu, J.

    2010-06-01

    This article deals with degradation mechanism of three aromatic polymers submitted to γ-rays in air at 60° C. Tg measurements and GPC results indicated that thin samples (thickness lower than 200 μm) undergo mostly chain scission whereas sol gel analysis and rheometric measurements showed that thicker ones undergo mainly crosslinking. Both results are explained by oxygen diffusion control of oxidation resulting in the formation of a superficial oxidized layer experimentally observed by μATR InfraRed in which oxidative processes orientate rather to chain scission than crosslinking. Experimental results also allowed discussing relative oxidative stability, sensitivity of Tg to chain scission concentration, and crosslinking mechanism (Y or H).

  14. Thermochemistry of C-O, (CO)-O, and (CO)-C bond breaking in fatty acid methyl esters

    SciTech Connect

    Osmont, Antoine; Yahyaoui, Mohammed; Catoire, Laurent; Goekalp, Iskender; Swihart, Mark T.

    2008-10-15

    Density functional theory quantum chemical calculations corrected with empirical atomic increments have been used to examine C-O, (CO)-O, and (CO)-C bond scission enthalpies in gas-phase fatty acid methyl esters (FAMEs) present in biodiesel derived from rapeseed oil methyl ester and soybean oil methyl ester. Mechanistic information, currently not available elsewhere for these large species, is obtained based on thermochemical considerations and compared to thermochemical considerations reported for methyl butanoate, a small methyl ester sometimes used as a model for FAMEs. These results are compared to previously reported C-C and C-H bond scissions in these FAMEs, derived using this same protocol. (author)

  15. Irradiation of linear polyethylene - Partitioning between sol and gel.

    NASA Technical Reports Server (NTRS)

    Rijke, A. M.; Mandelkern, L.

    1971-01-01

    Investigation of the importance of chain-scission processes and of the applicability of the general theory of network formation to polyethylene with respect to critical conditions for gelation, using molecular weight fractions of linear polyethylene irradiated at 133 C. The partitioning between sol and gel was found to adhere to the theory just beyond the gel point. Deviations from theory occurred as the irradiation dosage was increased. It was concluded that main-chain scission at the temperatures concerned is not a significant process.

  16. Molecular weight distributions of irradiated siloxane-based elastomers: A complementary study by statistical modeling and multiple quantum nuclear magnetic resonance

    SciTech Connect

    Dinh, L. N.; Mayer, B. P.; Maiti, A.; Chinn, S. C.; Maxwell, R. S.

    2011-05-01

    The statistical methodology of population balance (PB) has been applied in order to predict the effects of cross-linking and chain-scissioning induced by ionizing radiation on the distribution of molecular weight between cross-links (MWBC) of a siloxane-based elastomer. Effective molecular weight distributions were extracted from the quantification of residual dipolar couplings via multiple quantum nuclear magnetic resonance (MQ-NMR) measurements and are taken to reflect actual MWBC distributions. The PB methodology is then applied to the unirradiated MWBC distribution and considers both chain-scissioning and the possibility of the formation of three types of cross-links: random recombination of scissioned-chain ends (end-linking), random covalent bonds of free radicals on scissioned-chain ends (Y-cross-linking), and the formation of random cross-links from free radicals on side groups (H-cross-linking). The qualitative agreement between the statistical modeling approach and the NMR data confirms that it is possible to predict trends for the evolution of the distribution of MWBC of polymers under irradiation. The approach described herein can also discern heterogeneities in radiation effects in different structural motifs in the polymer network.

  17. On the degelation of networks - Case of the radiochemical degradation of methyl methacrylate - ethylene glycol dimethacrylate copolymers

    NASA Astrophysics Data System (ADS)

    Richaud, Emmanuel; Gilormini, Pierre; Verdu, Jacques

    2016-05-01

    Methyl methacrylate networks were synthetized and submitted to radiochemical degradation. Ageing was monitored by means of sol-gel analysis and glass transition temperature measurements. Networks were shown to undergo exclusively chain scission process leading to the degelation of network. The critical conversion degree corresponding to degelation (loss of all elastically active chains) is discussed regarding a statistical theory.

  18. Imaging single endocytic events reveals diversity in clathrin, dynamin and vesicle dynamics.

    PubMed

    Mattheyses, Alexa L; Atkinson, Claire E; Simon, Sanford M

    2011-10-01

    The dynamics of clathrin-mediated endocytosis can be assayed using fluorescently tagged proteins and total internal reflection fluorescence microscopy. Many of these proteins, including clathrin and dynamin, are soluble and changes in fluorescence intensity can be attributed either to membrane/vesicle movement or to changes in the numbers of individual molecules. It is important for assays to discriminate between physical membrane events and the dynamics of molecules. Two physical events in endocytosis were investigated: vesicle scission from the plasma membrane and vesicle internalization. Single vesicle analysis allowed the characterization of dynamin and clathrin dynamics relative to scission and internalization. We show that vesicles remain proximal to the plasma membrane for variable amounts of time following scission, and that uncoating of clathrin can occur before or after vesicle internalization. The dynamics of dynamin also vary with respect to scission. Results from assays based on physical events suggest that disappearance of fluorescence from the evanescent field should be re-evaluated as an assay for endocytosis. These results illustrate the heterogeneity of behaviors of endocytic vesicles and the importance of establishing suitable evaluation criteria for biophysical processes.

  19. THE EFFECT OF MOLECULAR SIZE ON HUMIC ACID ASSOCIATIONS (R822832)

    EPA Science Inventory

    Abstract

    Aqueous solutions of two humic acids were subjected to UV photolysis, resulting in chain scission of the solute. The molecular fragments were found to have diminished detergent properties, indicated by a reduced tendency to associate with small hydrophobic spe...

  20. Repeatable mechanochemical activation of dynamic covalent bonds in thermoplastic elastomers.

    PubMed

    Imato, Keiichi; Kanehara, Takeshi; Nojima, Shiki; Ohishi, Tomoyuki; Higaki, Yuji; Takahara, Atsushi; Otsuka, Hideyuki

    2016-08-18

    Repeated mechanical scission and recombination of dynamic covalent bonds incorporated in segmented polyurethane elastomers are demonstrated by utilizing a diarylbibenzofuranone-based mechanophore and by the design of the segmented polymer structures. The repeated mechanochemical reactions can accompany clear colouration and simultaneous fading.

  1. Aqueous-phase hydrogenation of acetic acid over transition metal catalysts

    SciTech Connect

    Olcay, Hakan; Xu, Lijun; Xu, Ye; Huber, George

    2010-01-01

    Catalytic hydrogenation of acetic acid to ethanol has been carried out in aqueous phase on several metals, with ruthenium being the most active and selective. DFT calculations suggest that the initial CO bond scission yielding acetyl is the key step and that the intrinsic reactivity of the metals accounts for the observed activity.

  2. Radical [1,3] Rearrangements of Breslow Intermediates.

    PubMed

    Alwarsh, Sefat; Xu, Yi; Qian, Steven Y; McIntosh, Matthias C

    2016-01-01

    Breslow intermediates that bear radical-stabilizing N substituents, such as benzyl, cinnamyl, and diarylmethyl, undergo facile homolytic C-N bond scission under mild conditions to give products of formal [1,3] rearrangement rather than benzoin condensation. EPR experiments and computational analysis support a radical-based mechanism. Implications for thiamine-based enzymes are discussed.

  3. Stress-induced colouration and crosslinking of polymeric materials by mechanochemical formation of triphenylimidazolyl radicals.

    PubMed

    Verstraeten, F; Göstl, R; Sijbesma, R P

    2016-06-30

    Under mechanical stress, the hexaarylbiimidazole (HABI) motif can cleave to triphenylimidazolyl radicals when incorporated into a polymer matrix. The mechanically produced coloured radicals can initiate secondary radical reactions yielding polymer networks. Thus, the HABI mechanophore combines optical reporting of bond scission and reinforcement of polymers in a single molecular moiety. PMID:27326922

  4. Repeatable mechanochemical activation of dynamic covalent bonds in thermoplastic elastomers.

    PubMed

    Imato, Keiichi; Kanehara, Takeshi; Nojima, Shiki; Ohishi, Tomoyuki; Higaki, Yuji; Takahara, Atsushi; Otsuka, Hideyuki

    2016-08-18

    Repeated mechanical scission and recombination of dynamic covalent bonds incorporated in segmented polyurethane elastomers are demonstrated by utilizing a diarylbibenzofuranone-based mechanophore and by the design of the segmented polymer structures. The repeated mechanochemical reactions can accompany clear colouration and simultaneous fading. PMID:27424868

  5. Methanol Oxidation on Pt3Sn(111) for Direct Methanol Fuel Cells: Methanol Decomposition.

    PubMed

    Lu, Xiaoqing; Deng, Zhigang; Guo, Chen; Wang, Weili; Wei, Shuxian; Ng, Siu-Pang; Chen, Xiangfeng; Ding, Ning; Guo, Wenyue; Wu, Chi-Man Lawrence

    2016-05-18

    PtSn alloy, which is a potential material for use in direct methanol fuel cells, can efficiently promote methanol oxidation and alleviate the CO poisoning problem. Herein, methanol decomposition on Pt3Sn(111) was systematically investigated using periodic density functional theory and microkinetic modeling. The geometries and energies of all of the involved species were analyzed, and the decomposition network was mapped out to elaborate the reaction mechanisms. Our results indicated that methanol and formaldehyde were weakly adsorbed, and the other derivatives (CHxOHy, x = 1-3, y = 0-1) were strongly adsorbed and preferred decomposition rather than desorption on Pt3Sn(111). The competitive methanol decomposition started with the initial O-H bond scission followed by successive C-H bond scissions, (i.e., CH3OH → CH3O → CH2O → CHO → CO). The Brønsted-Evans-Polanyi relations and energy barrier decomposition analyses identified the C-H and O-H bond scissions as being more competitive than the C-O bond scission. Microkinetic modeling confirmed that the vast majority of the intermediates and products from methanol decomposition would escape from the Pt3Sn(111) surface at a relatively low temperature, and the coverage of the CO residue decreased with an increase in the temperature and decrease in partial methanol pressure.

  6. Thermal stability and degradation of chitosan modified by benzophenone

    NASA Astrophysics Data System (ADS)

    Diab, M. A.; El-Sonbati, A. Z.; Bader, D. M. D.

    2011-09-01

    N-(biphenylmethylidenyl) chitosan polymer was prepared, characterized and thermal stability was compared with chitosan. Thermal degradation products of the modified polymer were identified by GC-MS technique. It seems that the mechanism of degradation of the prepared polymer is characterized by formation of low molecular weight radicals, followed by random scission mechanism along the backbond chain.

  7. Degradation mechanisms of bioresorbable polyesters. Part 2. Effects of initial molecular weight and residual monomer.

    PubMed

    Gleadall, Andrew; Pan, Jingzhe; Kruft, Marc-Anton; Kellomäki, Minna

    2014-05-01

    This paper presents an understanding of how initial molecular weight and initial monomer fraction affect the degradation of bioresorbable polymers in terms of the underlying hydrolysis mechanisms. A mathematical model was used to analyse the effects of initial molecular weight for various hydrolysis mechanisms including noncatalytic random scission, autocatalytic random scission, noncatalytic end scission or autocatalytic end scission. Different behaviours were identified to relate initial molecular weight to the molecular weight half-life and to the time until the onset of mass loss. The behaviours were validated by fitting the model to experimental data for molecular weight reduction and mass loss of samples with different initial molecular weights. Several publications that consider initial molecular weight were reviewed. The effect of residual monomer on degradation was also analysed, and shown to accelerate the reduction of molecular weight and mass loss. An inverse square root law relationship was found between molecular weight half-life and initial monomer fraction for autocatalytic hydrolysis. The relationship was tested by fitting the model to experimental data with various residual monomer contents.

  8. A comparative theoretical study for the methanol dehydrogenation to CO over Pt3 and PtAu2 clusters.

    PubMed

    Zhong, Wenhui; Liu, Yuxia; Zhang, Dongju

    2012-07-01

    The density functional theory (DFT) calculations are carried out to study the mechanism details and the ensemble effect of methanol dehydrogenation over Pt(3) and PtAu(2) clusters, which present the smallest models of pure Pt clusters and bimetallic PtAu clusters. The energy diagrams are drawn out along both the initial O-H and C-H bond scission pathways via the four sequential dehydrogenation processes, respectively, i.e., CH(3)OH → CH(2)OH → CH(2)O → CHO → CO and CH(3)OH → CH(3)O → CH(2)O → CHO → CO, respectively. It is revealed that the reaction kinetics over PtAu(2) is significantly different from that over Pt(3). For the Pt(3)-mediated reaction, the C-H bond scission pathway, where an ensemble composed of two Pt atoms is required to complete methanol dehydrogenation, is energetically more favorable than the O-H bond scission pathway, and the maximum barrier along this pathway is calculated to be 12.99 kcal mol(-1). In contrast, PtAu(2) cluster facilitates the reaction starting from the O-H bond scission, where the Pt atom acts as the active center throughout each elementary step of methanol dehydrogenation, and the initial O-H bond scission with a barrier of 21.42 kcal mol(-1) is the bottom-neck step of methanol decomposition. Importantly, it is shown that the complete dehydrogenation product of methanol, CO, can more easily dissociate from PtAu(2) cluster than from Pt(3) cluster. The calculated results over the model clusters provide assistance to some extent for understanding the improved catalytic activity of bimetal PtAu catalysts toward methanol oxidation in comparison with pure Pt catalysts. PMID:22160734

  9. Ethanol decomposition on a Pd(110) surface: a density functional theory investigation.

    PubMed

    Guo, Wenyue; Li, Ming; Lu, Xiaoqing; Zhu, Houyu; Li, Yang; Li, Shaoren; Zhao, Lianming

    2013-02-14

    Ethanol decomposition on Pd(110) is comprehensively investigated using self-consistent periodic density functional theory. Geometries and energies for all the intermediates involved are analyzed, and the decomposition network is mapped out to illustrate the reaction mechanism. On Pd(110), the most stable adsorption of the involved species tends to follow the gas-phase bond order rules, wherein C is tetravalent and O is divalent with the missing H atoms replaced by metal atoms. The most likely decomposition pathway of ethanol on Pd(110) is CH(3)CH(2)OH → CH(3)CH(2)O → CH(3)CHO → CH(3)CO → CH(3) + CO → CO + H + CH(4) + C, in which the initial dehydrogenation is the rate-limited step. No C-O scission pathway is identified. Comparing with ethanol decomposition on Pd(111) [Langmuir, 2010, 26, 1879-1888], Pd(110) characterizes relatively high activity and different selectivity. Two crucial factors controlling the variations of reactivity and selectivity from Pd(111) to Pd(110), i.e., the local electronic effect of the metals and the geometrical effect of the relevant transition states, are identified. Four distinct Brønsted-Evans-Polanyi (BEP) relations are identified for the three types of bond scission (C-H, C-O, and C-C) if we consider Pd(111) and Pd(110) as a whole, one for C-H bond scission, one for C-O bond scission, and two for C-C bond scission. PMID:23169574

  10. Multilevel fitting of {sup 235}U resonance data sensitive to Bohr-and Brosa-fission channels

    SciTech Connect

    Moore, M.S.

    1995-05-01

    The recent determination of the K, J dependence of the neutron induced fission cross section of {sup 235}U by the Dubna group has led to a renewed interest in the mechanism of fission from saddle to scission. The K quantum numbers designate the so-called Bohr fission channels, which describe the fission properties at the saddle point. Certain other fission properties, e.g., the fragment mass and kinetic-energy distribution, are related to the properties of the scission point. The neutron energy dependence of the fragment kinetic energies has been measured by Hambsch et al., who analyzed their data according to a channel description of Brosa et al. How these two channel descriptions, the saddle-point Bohr channels and the scission-point Brosa channels, relate to one another is an open question, and is the subject matter of the present paper. We use the correlation coefficient between various data sets, in which variations are reported from resonance to resonance, as a measure of both-the statistical reliability of the data and of the degree to which different scission variables relate to different Bohr channels. We have carried out an adjustment of the ENDF/B-VI multilevel evaluation of the fission cross section of {sup 235}U, one that provides a reasonably good fit to the energy dependence of the fission, capture, and total cross sections below 100 eV, and to the Bohr-channel structure deduced from an earlier measurement by Pattenden and Postma. We have also further explored the possibility of describing the data of Hambsch et al. in the Brosa-channel framework with the same set of fission-width vectors, only in a different reference system. While this approach shows promise, it is clear that better data are also needed for the neutron energy variation of the scission-point variables.

  11. Comparative Investigation of Benzene Steam Reforming over Spinel Supported Rh and Ir Catalysts

    SciTech Connect

    Mei, Donghai; Lebarbier, Vanessa M.; Rousseau, Roger; Glezakou, Vassiliki-Alexandra; Albrecht, Karl O.; Kovarik, Libor; Flake, Matt; Dagle, Robert A.

    2013-06-07

    In a combined experimental and first-principles density functional theory (DFT) study, benzene steam reforming (BSR) over MgAl2O4 supported Rh and Ir catalysts was investigated. Experimentally, it has been found that both highly dispersed Rh and Ir clusters (1-2 nm) on the MgAl2O4 spinel support are stable during the BSR in the temperature range of 700-850°C. Compared to the Ir/MgAl2O4 catalyst, the Rh/MgAl2O4 catalyst is more active with higher benzene turnover frequency and conversion. At typical steam conditions with the steam-to-carbon ratio > 12, the benzene conversion is only a weak function of the H2O concentration in the feed. This suggests that the initial benzene decomposition step rather than the benzene adsorption is most likely the rate-determined step in BSR over supported Rh and Ir catalysts. In order to understand the differences between the two catalysts, we followed with a comparative DFT study of initial benzene decomposition pathways over two representative model systems for each supported metal (Rh and Ir) catalysts. A periodic terrace (111) surface and an amorphous 50-atom metal cluster with a diameter of 1.0 nm were used to represent the two supported model catalysts under low and high dispersion conditions. Our DFT results show that the decreasing catalyst particle size enhances the benzene decomposition on supported Rh catalysts by lowering both C-C and C-H bond scission. The activation barriers of the C-C and the C-H bond scission decrease from 1.60 and 1.61 eV on the Rh(111) surface to 1.34 and 1.26 eV on the Rh50 cluster. For supported Ir catalysts, the decreasing particle size only affects the C-C scission. The activation barrier of the C-C scission of benzene decreases from 1.60 eV on the Ir(111) surface to 1.35 eV on the Ir50 cluster while the barriers of the C-H scission are practically the same. The experimentally measured higher BSR

  12. Effects of angiotensin, vasopressin and atrial natriuretic peptide on intraocular pressure in anesthetized rats

    NASA Technical Reports Server (NTRS)

    Palm, D. E.; Shue, S. G.; Keil, L. C.; Balaban, C. D.; Severs, W. B.

    1995-01-01

    The effects of atrial natriuretic peptide (ANP), vasopressin (AVP) and angiotensin (ANG) on blood and intraocular pressures of pentobarbital anesthetized rats were evaluated following intravenous, intracerebroventricular or anterior chamber routes of administration. Central injections did not affect intraocular pressure. Equipressor intravenous infusions of ANG raised, whereas AVP decreased, intraocular pressure. Direct infusions of a balanced salt solution (0.175 microliter/min) raised intraocular pressure between 30 and 60 min. Adding ANG or ANP slightly reduced this solvent effect but AVP was markedly inhibitory. An AVP-V1 receptor antagonist reversed the blunting of the solvent-induced rise by the peptide, indicating receptor specificity. Acetazolamide pretreatment lowered intraocular pressure, but the solvent-induced rise in intraocular pressure and inhibition by AVP still occurred without altering the temporal pattern. Thus, these effects appear unrelated to aqueous humor synthesis rate. The data support the possibility of intraocular pressure regulation by peptides acting from the blood and aqueous humor.

  13. Three-Dimensional Molecular Theory of Solvation Coupled with Molecular Dynamics in Amber

    SciTech Connect

    Luchko, T.; Simmerling, C.; Gusarov, S.; Roe, D.R., Case, D.A.; Tuszynski, J.; Kovalenko, A.

    2010-02-01

    We present the three-dimensional molecular theory of solvation (also known as 3D-RISM) coupled with molecular dynamics (MD) simulation by contracting solvent degrees of freedom, accelerated by extrapolating solvent-induced forces and applying them in large multiple time steps (up to 20 fs) to enable simulation of large biomolecules. The method has been implemented in the Amber molecular modeling package and is illustrated here on alanine-dipeptide and protein-G.

  14. Simple, benign, aqueous-based amination of polycarbonate surfaces

    SciTech Connect

    VanDelinder, Virginia; Wheeler, David R.; Small, Leo J.; Brumbach, Michael T.; Spoerke, Erik D.; Henderson, Ian; Bachand, George D.

    2015-03-18

    Here we report a simple, safe, environmentally-friendly aqueous method that uses diamines to functionalize a polycarbonate surface with amino groups. We demonstrate the ability of this facile method to serve as a foundation upon which other functionalities may be attached, including anti-fouling coatings and oriented membrane proteins. The use of water as the solvent for the functionalization ensures that solvent induced swelling does not affect the optical or mechanical properties of the polycarbonate.

  15. Three-dimensional molecular theory of solvation coupled with molecular dynamics in Amber

    PubMed Central

    Luchko, Tyler; Gusarov, Sergey; Roe, Daniel R.; Simmerling, Carlos; Case, David A.; Tuszynski, Jack; Kovalenko, Andriy

    2010-01-01

    We present the three-dimensional molecular theory of solvation (also known as 3D-RISM) coupled with molecular dynamics (MD) simulation by contracting solvent degrees of freedom, accelerated by extrapolating solvent-induced forces and applying them in large multi-time steps (up to 20 fs) to enable simulation of large biomolecules. The method has been implemented in the Amber molecular modeling package, and is illustrated here on alanine dipeptide and protein G. PMID:20440377

  16. Self-healing Microencapsulation of Biomacromolecules without Organic Solvents**

    PubMed Central

    Reinhold, Samuel E.; Desai, Kashappa-Goud H.; Zhang, Li; Olsen, Karl F.

    2012-01-01

    Microencapsulation of biomacromolecules in PLGA is routinely performed with organic solvent through multiple complex steps deleterious to the biomacromolecule. The new self-healing based PLGA microencapsulation obviates micronization- and organic solvent-induced protein damage, provides very high encapsulation efficiency, exhibit stabilization and slow release of labile tetanus protein antigen, and provides long-term testosterone suppression in rats following a single injection of encapsulated leuprolide. PMID:23011773

  17. Superhydrophobic and superoleophilic PVDF membranes for effective separation of water-in-oil emulsions with high flux.

    PubMed

    Zhang, Wenbin; Shi, Zhun; Zhang, Feng; Liu, Xia; Jin, Jian; Jiang, Lei

    2013-04-11

    A superhydrophobic-superoleophilic PVDF membrane is fabricated via an inert solvent-induced phase inversion for effective separation of both micrometer and nanometer-sized surfactant-free and surfactant-stabilized water-in-oil emulsions solely driven by gravity, with high separation efficiency (oil purity in filtrate after separation > 99.95 wt%) and high flux, which is several times higher than those of commercial filtration membranes and reported materials with similar permeation properties. PMID:23418068

  18. Effect of pretreating of host oil on coprocessing

    SciTech Connect

    Hajdu, P.E.; Tierney, J.W.; Wender, I.

    1995-12-31

    The principal objective of this research was to determine if coprocessing performance (i.e., coal conversion and oil yield) could be significantly improved by pretreating the heavy resid prior to reacting it with coal. For this purpose, two petroleum vacuum resids (1000{degrees}F+), one from the Amoco Co. and another from the Citgo Co., were used as such and after they had been pretreated by catalytic hydrogenation and hydrocracking reactions. The pretreatments were aimed at improving the host oil by; (1) converting any aromatic structures in the petroleum to hydroaromatic compounds capable of donating hydrogen, (2) cracking the heavy oil to lower molecular weight material that might serve as a better solvent, (3) reducing the coking propensity of the heavy oil through the hydrogenation of polynuclear aromatic compounds, and (4) removing metals and heteroatoms that might poison a coprocessing catalyst. Highly dispersed catalysts, including fine particle Fe- and Mo-based, and dicobalt octacarbonyl, Co{sub 2}(CO){sub 8}, were used in this study. The untreated and pretreated resids were extensively characterized in order to determine chemical changes brought about by the pretreatments. The modified heavy oils were then coprocessed with an Illinois No. 6 coal as well as with a Wyodak coal, and compared to coprocessing with untreated resids under the same hydroliquefaction conditions. The amount of oil derived from coal was estimated by measuring the level of phenolic oxygen (derived mainly from coal) present in the oil products. Results are presented and discussed.

  19. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Final report

    SciTech Connect

    Chunshan Song; Schobert, H.H.; Parfitt, D.P.

    1997-11-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that dispersed catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on exploring novel bimetallic dispersed catalysts for coal liquefaction and the effectiveness of temperature-programmed liquefaction using dispersed catalysts. The primary objective of this research was to explore novel bimetallic dispersed catalysts from organometallic molecular precursors, that could be used in low concentrations but exhibit relatively high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. We have synthesized and tested various catalyst precursors in liquefaction of subbituminous and bituminous coals and in model compound studies to examine how do the composition and structure of the catalytic precursors affect their effectiveness for coal liquefaction under different reaction conditions, and how do these factors affect their catalytic functions for hydrogenation of polyaromatic hydrocarbons, for cleavage of C-C bonds in polycyclic systems such as 4-(1-naphthylmethyl)bibenzyl, for hydrogenolysis of C-O bond such as that in dinaphthylether, for hydrodeoxygenation of phenolic compounds and other oxygen-containing compounds such as xanthene, and for hydrodesulfurization of polycyclic sulfur compounds such as dibenzothiophene. The novel bimetallic and monometallic precursors synthesized and tested in this project include various Mo- and Fe-based compounds.

  20. Progress of fossil fuel science

    SciTech Connect

    Demirbas, M.F.

    2007-07-01

    Coal is the most abundant and widely distributed fossil fuel. More than 45% of the world's electricity is generated from coal, and it is the major fuel for generating electricity worldwide. The known coal reserves in the world are enough for more than 215 years of consumption, while the known oil reserves are only about 39 times of the world's consumption and the known natural gas reserves are about 63 times of the world's consumption level in 1998. In recent years, there have been effective scientific investigations on Turkish fossil fuels, which are considerable focused on coal resources. Coal is a major fossil fuel source for Turkey. Turkish coal consumption has been stable over the past decade and currently accounts for about 24% of the country's total energy consumption. Lignite coal has had the biggest share in total fossil fuel production, at 43%, in Turkey. Turkish researchers may investigate ten broad pathways of coal species upgrading, such as desulfurization and oxydesulfurization, pyrolysis and hydropyrolysis, liquefaction and hydroliquefaction, extraction and supercritical fluid extraction, gasification, oxidation, briquetting, flotation, and structure identification.

  1. Evaporation residue cross sections for the {sup 64}Ni + {sup 144,154}Sm reaction -- Energy dissipation in hot nuclei

    SciTech Connect

    Back, B.B.; Blumenthal, D.J.; Davids, C.N.

    1995-08-01

    The fission hindrance of hot nuclei was deduced recently from an enhanced emission of GDR {gamma} rays, neutrons and charged particles prior to scission of heavy nuclei. In the most recent experiments addressing this topic, namely new measurements of the pre-scission {gamma} rays and evaporation residues from the {sup 32}S + {sup 184}W reaction, a rather sharp transition from negligible to full one-body dissipation occurs over the excitation energy region E{sub exc} = 60-100 MeV. However, the cross section does not appear to level out or start to decline again at the upper end of the energy range as expected in this interpretation. It is therefore clearly desirable to extend the excitation energy range to look for such an effect in order to either corroborate or refute this interpretation.

  2. Histone Modification via Rapid Cleavage of C4′-Oxidized Abasic Sites in Nucleosome Core Particles

    PubMed Central

    Zhou, Chuanzheng; Sczepanski, Jonathan T.; Greenberg, Marc M.

    2013-01-01

    The C4′-oxidized abasic site is produced in DNA by a variety of oxidizing agents, including potent cytotoxic antitumor agents. Independent generation of this alkali-labile lesion at defined positions within nucleosome core particles reveals that the histone proteins increase strand scission between 130 and 550-fold. Strand scission proceeds via a Schiff base intermediate but the DNA protein cross-links are unstable. The oxidized abasic site is removed in its entirety from the DNA and transferred to the lysine rich tail region of the proximal histone protein in the form of a lactam. The modification is distributed over several residues within the amino terminal tail of the proximal histone. Transfer of DNA damage to histones could affect gene regulation. PMID:23531104

  3. Effects of nuclear deformation in dinuclear systems: Application to the fission process

    SciTech Connect

    Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.; Ivanova, S. P. Scheid, W.

    2006-02-15

    The relative yields of fission fragments, the mean values of their total kinetic energy, and the variances of their distributions with respect to the total kinetic energy are described within the improved scission-point model. It is shown that, for fixed charge and mass numbers of fragments, the potential energy of the precision configuration as a function of the deformation parameters of the fragments has several minima. The scission at these minima leads to a relative enhancement of the yields of the fragments that have the corresponding values of the total kinetic energy and to the appearance of a fine structure in the mass-energy distribution, this structure being different from that induced by the even-odd effect.

  4. A Density Functional Theory Analysis of Trends in Glycerol Decomposition on Close-Packed Transition Metal Surfaces

    SciTech Connect

    Liu, Bin; Greeley, Jeffrey P.

    2013-05-07

    We describe an accelerated density functional theory (DFT)-based computational strategy to determine trends in the decomposition of glycerol via elementary dehydrogenation, C–C, and C–O bond scission reactions on close-packed transition metal surfaces. Beginning with periodic DFT calculations on Pt(111), the thermochemistry of glycerol dehydrogenation on Pd(111), Rh(111), Cu(111) and Ni(111) is determined using a parameter-free, bond order-based scaling relationship. By combining the results with Brønsted–Evans–Polanyi (BEP) relationships to estimate elementary reaction barriers, free energy diagrams are developed on the respective metal surfaces, and trends concerning the relative selectivity and activity for C–C and C–O bond scission in glycerol on the various metals are obtained. The results are consistent with available theoretical and experimental literature and demonstrate that scaling relationships are capable of providing powerful insights into the catalytic chemistry of complex biomolecules.

  5. New experimental approaches to investigate the fission dynamics

    NASA Astrophysics Data System (ADS)

    Benlliure, J.; Rodríguez-Sánchez, J. L.; Alvarez-Pol, H.; Audouin, L.; Ayyad, Y.; Bélier, G.; Boutoux, G.; Casarejos, E.; Chatillon, A.; Cortina-Gil, D.; Gorbinet, T.; Heinz, A.; Kelić-Heil, A.; Laurent, B.; Martin, J.-F.; Paradela, C.; Pellereau, E.; Pietras, B.; Ramos, D.; Rodríguez-Tajes, C.; Rossi, D. M.; Simon, H.; Taïeb, J.; Vargas, J.; Voss, B.

    2016-07-01

    The first ever achieved full identification of both fission fragments, in atomic and mass number, made it possible to define new observables sensitive to the fission dynamics along the fission path up to the scission point. Moreover, proton-induced fission of 208Pb at high energies offers optimal conditions for the investigation of dissipative, and transient effects, because of the high-excitation energy of the fissioning nuclei, its low angular momentum, and limited shape distortion by the reaction. In this work we show that the charge distribution of the final fission fragments can constrain the ground-to-saddle dynamics while the mass distribution is sensitive to the dynamics until the scission point.

  6. A comparison of electrochemical and gas-phase decomposition of methanol on platinum surfaces

    SciTech Connect

    Franaszczuk, K.; Herrero, E.; Zelenay, P.

    1992-10-15

    By using electrochemical and ultrahigh-vacuum (UHV) techniques, combined with an isotope substitution method, it is found that the mechanism of methanol decomposition on platinum in the electrochemical environment is different than that in the UHV. In the UHV, the first step in the decomposition process is the scission of an O-H bond to yield a methoxy intermediate, whereas in the electrochemical environment, the first step is the scission of a C-H bond. The difference in the decomposition mechanism is discussed in terms of differences in the local electric field at the surface and in terms of methanol hydrophobic/hydrophilic interactions in solution. The latter affect methanol-water near-surface conformation and predetermine the destiny of the individual methanolic bonds in the catalytic splitting. 51 refs., 11 figs., 4 tabs.

  7. Modeling Initial Stage of Ablation Material Pyrolysis: Graphitic Precursor Formation and Interfacial Effects

    NASA Technical Reports Server (NTRS)

    Desai, Tapan G.; Lawson, John W.; Keblinski, Pawel

    2010-01-01

    Reactive molecular dynamics simulations are used to study initial stage of pyrolysis of ablation materials and their composites with carbon nanotubes and carbon fibers. The products formed during pyrolysis are characterized and water is found as the primary product in all cases. The water formation mechanisms are analyzed and the value of the activation energy for water formation is estimated. A detailed study on graphitic precursor formation reveals the presence of two temperature zones. In the lower temperature zone (less than 2000 K) polymerization occurs resulting in formation of large, stable graphitic precursors, and in the high temperature zone (greater than 2000 K) polymer scission results in formation of short polymer chains/molecules. Simulations performed in the high temperature zone on the phenolic resin composites (with carbon nanotubes and carbon fibers) shows that the presence of interfaces had no substantial effect on the chain scission rate or the activation energy value for water formation.

  8. Stability of a salicylate-based poly(anhydride-ester) to electron beam and gamma radiation

    PubMed Central

    Rosario-Meléndez, Roselin; Lavelle, Linda; Bodnar, Stanko; Halperin, Frederick; Harper, Ike; Griffin, Jeremy; Uhrich, Kathryn E.

    2011-01-01

    The effect of electron beam and gamma radiation on the physicochemical properties of a salicylate-based poly(anhydride-ester) was studied by exposing polymers to 0 (control), 25 and 50 kGy. After radiation exposure, salicylic acid release in vitro was monitored to assess any changes in drug release profiles. Molecular weight, glass transition temperature and decomposition temperature were evaluated for polymer chain scission and/or crosslinking as well as changes in thermal properties. Proton nuclear magnetic resonance and infrared spectroscopies were also used to determine polymer degradation and/or chain scission. In vitro cell studies were performed to identify cytocompatibility following radiation exposure. These studies demonstrate that the physicochemical properties of the polymer are not substantially affected by exposure to electron beam and gamma radiation. PMID:21909173

  9. Mass spectrometry investigation of the degradation of polyethylene terephtalate induced by low-energy (<100 eV) electrons

    NASA Astrophysics Data System (ADS)

    Massey, Sylvain; Cloutier, Pierre; Sanche, Léon; Roy, Denis

    2008-07-01

    Polyethylene terephtalate (PET) thin films were damaged by low-energy (0-100 eV) electron irradiation to simulate the degradation of this polymer in electronic devices. The products formed were analyzed by mass spectrometry. The emission of anions from the polymer surface is associated with dissociative electron attachment (DEA) and dipolar dissociation (DD) for H -, and with DD for O -. The monotonic emission rise in O - desorption as a function of incident electron energy is produced by mid-chain C-O-C cleavage, leading to chain scission. The signal of the positive mass fragments showed only a monotonic increase with electron energy. In this case, chemical recombination with hydrogen atoms also leads to chain scission.

  10. Oxidation of amylose and amylopectin by hydroxyl radicals assessed by electrospray ionisation mass spectrometry.

    PubMed

    Simões, Joana; Moreira, Ana S P; da Costa, Elisabete; Evtyugin, Dmitry; Domingues, Pedro; Nunes, Fernando M; Coimbra, Manuel A; Domingues, M Rosário M

    2016-09-01

    The hydroxyl radicals (HO) are one of the most reactive oxygen species (ROS) involved in the oxidative damage of biological molecules, including carbohydrates. During the industrial processing of food, ROS can be formed. In order to identify the structural changes induced in starch by oxidation, amylose, amylopectin, and maltotriose, an oligosaccharide structurally related to these polysaccharides, were subjected to oxidation with HO generated under Fenton reaction conditions (Fe(2+)/H2O2). The oxidised polysaccharides were hydrolysed by α-amylase and the obtained oligosaccharides were fractionated by ligand-exchange/size-exclusion chromatography. Both acidic and neutral α-amylase resistant oligosaccharides were characterized by mass spectrometry. In oxidised neutral products, new keto, hydroxyl, and hydroperoxy moieties, and oxidative ring scission were observed at the reducing end of the oligosaccharides. The acid sugar residues occurred at the reducing end and included gluconic and glucuronic acid derivatives, and acids formed by oxidative ring scission, namely, arabinonic, erythronic, glyceric and glycolic acids.

  11. Creep behavior of epoxy resin during irradiation at cryogenic temperature

    NASA Astrophysics Data System (ADS)

    Nishiura, Tetsuya; Nishijima, Shigehiro; Okada, Toichi

    1999-11-01

    Creep tests of an epoxy resin during bending and irradiation have been carried out to investigate the synergistic effects of radiation and stress on mechanical properties of the resin. Simultaneous application of stress and irradiation on the epoxy resin enhanced creep rates in comparison with the application of stress on an irradiated sample. In order to clarify the mechanism of the radiation-induced creep, measurements of solvent swelling of specimens have been performed. The swelling increased with the dose and the increase of the swelling corresponds to the increase of the chain scission. The mechanism of increased deformation of the resin during irradiation is proposed to be caused by increased chain scission following the release of the local strain energy.

  12. Irradiation of linear polyethylene - Partitioning between sol and gel.

    NASA Technical Reports Server (NTRS)

    Rijke, A. M.; Mandelkern, L.

    1971-01-01

    Molecular weight fractions of linear polyethylene were irradiated at 133 C, in the completely molten and highly crystalline states, for the purpose of assessing the importance of chain-scission processes and establishing the critical conditions for gelation. The partitioning between sol and gel in either state was found to adhere to the theory for the intermolecular cross-linking of monodisperse species for dosages just beyond the gel point. Deviations from theory occurred as the dosage was increased further. It was concluded that main-chain scission, at these temperatures, is not a significant process. High molecular weight samples in the completely molten state obeyed the Flory-Stockmayer condition for critical gelation.

  13. Characterization of electron-irradiated biaxially-oriented polypropylene films

    SciTech Connect

    Hammoud, A.N.; Laghari, J.R.; Krishnakumar, B.

    1988-06-01

    Post-radiation changes in the electrical and mechanical properties of capacitor-grade isotactic polypropylene films exposed to electron radiation were reported in a previous paper. Based on the data obtained, it was suggested that crosslinking, chain scission and oxidative degradation were responsible for the radiation-induced changes in the film. In the present investigations, additional electrical characterizations that included the dc breakdown voltage and ac conductivity measurements were performed. Effects of the electron radiation on the physical and chemical properties were also evaluated so as to identify the actual degradation mechanisms. These studies included scanning electron microscopy, X-ray diffraction, infrared spectroscopy and sol gel measurements. The results obtained confirm that crosslinking and chain scission of the polymer are responsible for the changes in the lower dose range, whereas oxidative degradation become predominant at higher dose levels.

  14. Membrane Fission Is Promoted by Insertion of Amphipathic Helices and Is Restricted by Crescent BAR Domains

    PubMed Central

    Boucrot, Emmanuel; Pick, Adi; Çamdere, Gamze; Liska, Nicole; Evergren, Emma; McMahon, Harvey T.; Kozlov, Michael M.

    2012-01-01

    Summary Shallow hydrophobic insertions and crescent-shaped BAR scaffolds promote membrane curvature. Here, we investigate membrane fission by shallow hydrophobic insertions quantitatively and mechanistically. We provide evidence that membrane insertion of the ENTH domain of epsin leads to liposome vesiculation, and that epsin is required for clathrin-coated vesicle budding in cells. We also show that BAR-domain scaffolds from endophilin, amphiphysin, GRAF, and β2-centaurin limit membrane fission driven by hydrophobic insertions. A quantitative assay for vesiculation reveals an antagonistic relationship between amphipathic helices and scaffolds of N-BAR domains in fission. The extent of vesiculation by these proteins and vesicle size depend on the number and length of amphipathic helices per BAR domain, in accord with theoretical considerations. This fission mechanism gives a new framework for understanding membrane scission in the absence of mechanoenzymes such as dynamin and suggests how Arf and Sar proteins work in vesicle scission. PMID:22464325

  15. The radiation chemistry of polymer composites

    NASA Astrophysics Data System (ADS)

    Dole, Malcolm

    With the use of plastics in the construction of space satellites which may be exposed in geosynchronous orbit to 100 MGy (10,000 Mrad) of high-energy radiation in 30 years of use, the effect of these radiations on the polymer becomes of practical importance. To understand the effects we consider first various radiation-resistant groups that are incorporated into the polymer and their relative effectiveness in reducing molecular scissions due to the radiation. The location of such groups in the polymer is also discussed. Next the chemical structures of a number of resins such as epoxies, polyimides, etc. are described followed by a detailed account of methods of improving the radiation resistance of plastics by the incorporation of carbon or glass fibers. Finally, the role of oxygen in causing chain scissions and other effects during irradiation which reduce the mechanical strength of the plastics and the fiber resin composites are also considered.

  16. On-line and post irradiation analysis of swift heavy ion induced modification of PMMA (polymethyl-methacrylate)

    NASA Astrophysics Data System (ADS)

    Hossain, U. H.; Lima, V.; Baake, O.; Severin, D.; Bender, M.; Ensinger, W.

    2014-05-01

    The present work is part of a research program studying the swift heavy ion induced modification of aliphatic polymers with some comparable side groups, here polymethyl-methacrylate (PMMA). This paper presents a study on Fourier-transform-infrared spectroscopy (FTIR), residual gas analysis (RGA), and Ultraviolet-Visible (UV-Vis) spectroscopy of the transformations of a PMMA film under gold (Au) and uranium (U) ion irradiation in the MeV/u range in vacuum to fluences up to 3 × 1011 ions per cm2. The results show a general ion induced degradation of the polymer, with release of volatile fragments, scission of side chains and polymeric backbone, formation of conjugated double bonds, and the resulting increased absorption of the UV part in the UV-Vis spectral region. A molecular scission mechanism which explains the main degradation products is proposed.

  17. Pt/MgO as catalyst for hydrogenolysis reactions of C[sub 5] and C[sub 6] hydrocarbons: Evidence for metal-support interactions

    SciTech Connect

    Clarke, J.K.A.; Bradley, M.J. ); Garvie, L.A.J.; Craven, A.J.; Baird, T. )

    1993-09-01

    Pt/magnesia catalysts having high metal dispersion (av. dia. 21 [angstrom]) have been prepared employing nonaqueous impregnating solutions and an incipient wetness technique. Both chlorine-free and residual-chlorine-containing catalysts were studied, the latter being prepared from platinum (IV) chloride. Both types of catalyst are of negligible sulphur content (<2ppm). Comparison of hydrogen chemisorption and transmission electron microscopy results for both [open quotes]chlorine-free[close quotes] and chlorine-containing Pt/MgO catalysts showed that (i) chemisorption capacity was substantially as expected from TEM-derived particle size following a reduction temperature of 593 K (LTR), and (ii) chemisorption was depressed to 40% or less of expectation when a reduction temperature of 753 K (HTR) was used. Reactions of saturated hydrocarbons in a flow of hydrogen (p[sub hydrocarbon] = 8-16 Torr, balance to 760 Torr hydrogen) showed hydrogenolysis to be a prominent reaction. With LTR chlorine-free catalysts, hydrogenolysis of n-pentane was almost exclusively by central scission. The chlorine-containing HTR catalyst yielded largely terminal scission. HTR chlorine-free catalysts and LTR chlorine-containing catalysts gave an intermediate behavior. Thus, both higher reduction temperature and presence of chlorine act to move scission of the C-C chain from the center to the ends. Hydrogenolysis of neohexane showed increased direct demethanation to give n-butane with the presence of chlorine in the catalyst. Ring scission of methylcyclopentane depressed hydrogen chemisorption and the carbanionic reactivity in these cracking reactions are interpreted in terms of a moderately strong metal-support interaction with a shift of negative charge from the magnesia O[sup 2[minus

  18. Economic efficiency and effectiveness of ways of separating materials electro diamond processing

    NASA Astrophysics Data System (ADS)

    Khafizov, I. I.

    2016-06-01

    Purveying operations on the division of all types of materials include a hand and machine scission on the equipment of the different setting. In an engineer there is reliable information about the mastered methods, their maximum possibilities and defects. With the increase of stake of expenses there was a problem of research of new types of division of materials on materials, especially it touched scarce and expensive alloys.

  19. The Microscopic Theory of Fission

    SciTech Connect

    Younes, W; Gogny, D

    2009-06-09

    Fission-fragment properties have been calculated for thermal neutron-induced fission on a {sup 239}Pu target, using constrained Hartree-Fock-Bogoliubov calculations with a finite-range effective interaction. A quantitative criterion based on the interaction energy between the nascent fragments is introduced to define the scission configurations. The validity of this criterion is benchmarked against experimental measurements of the kinetic energies and of multiplicities of neutrons emitted by the fragments.

  20. Protection in radiolysis of n-hexadecane—I. Radiolysis of pure liquid n-hexadecane

    NASA Astrophysics Data System (ADS)

    Soebianto, Yanti S.; Yamaguchi, Tetsuro; Katsumura, Yosuke; Ishigure, Kenkichi; Kubo, Junichi; Koizumi, Takeo

    Radiolysis of pure liquid n-hexadecane under vacuum has been studied to obtain greater understanding about the effect of radiation on open chain polymers such as polyethylene. Gas chromatography, gel permeation chromatography and mass spectrometry have been used to analyze the radiolysis products and their yields have been determined. The gas products mainly contain H 2, the condensed products contain saturated and unsaturated scission products, hexadecene and crosslink products. Mass analysis of the condensed products shows unsaturations in the crosslink products.

  1. Conjugation-Driven "Reverse Mars-van Krevelen"-Type Radical Mechanism for Low-Temperature C-O Bond Activation.

    PubMed

    Mironenko, Alexander V; Vlachos, Dionisios G

    2016-07-01

    C-O bond activation on monofunctional catalysts (metals, carbides, and oxides) is challenging due to activity constraints imposed by energy scaling relationships. Yet, contrary to predictions, recently discovered multifunctional metal/metal oxide catalysts (e.g., Rh/ReOx, Rh/MoOx, Ir/VOx) demonstrate unusually high C-O scission activity at moderate temperatures. Herein, we use extensive density functional theory calculations, first-principles microkinetic modeling, and electronic structure analysis to elucidate the metal/metal oxide synergy in the Ru/RuO2 catalyst, which enables up to 76% yield of the C-O scission product (2-methyl furan) in catalytic transfer hydrogenolysis of furfural at low temperatures. Our key mechanistic finding is a facile radical-mediated C-O bond activation on RuO2 oxygen vacancies, which directly leads to a weakly bound final product. This is the first time the radical reduction mechanism is reported in heterogeneous catalysis at temperatures <200 °C. We attribute the unique catalytic properties to the formation of a conjugation-stabilized furfuryl radical upon C-O bond scission, the strong hydroxyl affinity of oxygen vacancies due to the metallic character of RuO2, and the acid-base heterogeneity of the oxide surface. The conjugation-driven radical-assisted C-O bond scission applies to any catalytic surface that preserves the π-electron system of the reactant and leads to C-O selectivity enhancement, with notable examples including Cu, H-covered Pd, self-assembled monolayers on Pd, and oxygen-covered Mo2C. Furthermore, we reveal the cooperativity of active sites in multifunctional catalysts. The mechanism is fully consistent with kinetic studies and isotopic labeling experiments, and the insights gained might prove useful more broadly in overcoming activity constraints induced by energy scaling relationships.

  2. Lipid-protein interactions as agents of quality deterioration in intermediate moisture meats: An appraisal.

    PubMed

    Obanu, Z A; Ledward, D A; Lawrie, R A

    1980-04-01

    The literature on lipid-protein interactions which lead to loss of solubility, complex formation, chain scission and loss of specific amino acids in intermediate moisture foods is reviewed. This knowledge is used to explain reported observations on the quality and nutritive value of proteins in intermediate moisture meats as well as the conflicting reports on the significance of oxidative rancidity and non-enzymic browning in intermediate moisture food systems. PMID:22055615

  3. Vac7p, a novel vacuolar protein, is required for normal vacuole inheritance and morphology.

    PubMed Central

    Bonangelino, C J; Catlett, N L; Weisman, L S

    1997-01-01

    During cell division, the vacuole of Saccharomyces cerevisiae partitions between mother and daughter cells. A portion of the parental vacuole membrane moves into the bud, and ultimately membrane scission divides the vacuole into two separate structures. Here we characterize two yeast mutations causing defects in vacuole membrane scission, vac7-1 and vac14-1. A third mutant, afab1-2 strain, isolated in a nonrelated screen (A. Yamamoto et al., Mol. Biol. Cell 6:525-539, 1995) shares the vacuolar phenotypes of the vac7-1 and vac14-1 strains. Unlike the wild type, mutant vacuoles are not multilobed structures; in many cases, a single vacuole spans both the mother and bud, with a distinct gap in the mother-bud neck. Thus, even where the membranes are closely opposed, vacuole fission is arrested. Simply enlarging the vacuole does not produce this mutant phenotype. An additional common phenotype of these mutants is a defect in vacuole acidification; however, vacuole scission in most other vacuole acidification mutants is normal. An alteration in vacuole membrane lipids could account for both the vacuole membrane scission and acidification defects. Because a directed screen has not identified additional class III complementation groups, it is likely that all three genes are involved in a similar process. Interestingly, FAB1, was previously shown to encode a putative phosphatidylinositol-4-phosphate 5-kinase. Moreover, overexpression of FAB1 suppresses the vac14-1 mutation, which suggests that VAC14 and FAB1 act at a common step. VAC7 encodes a novel 128-kDa protein that is localized at the vacuole membrane. This location of Vac7p is consistent with its involvement in vacuole morphology and inheritance. PMID:9372916

  4. Conjugation-Driven "Reverse Mars-van Krevelen"-Type Radical Mechanism for Low-Temperature C-O Bond Activation.

    PubMed

    Mironenko, Alexander V; Vlachos, Dionisios G

    2016-07-01

    C-O bond activation on monofunctional catalysts (metals, carbides, and oxides) is challenging due to activity constraints imposed by energy scaling relationships. Yet, contrary to predictions, recently discovered multifunctional metal/metal oxide catalysts (e.g., Rh/ReOx, Rh/MoOx, Ir/VOx) demonstrate unusually high C-O scission activity at moderate temperatures. Herein, we use extensive density functional theory calculations, first-principles microkinetic modeling, and electronic structure analysis to elucidate the metal/metal oxide synergy in the Ru/RuO2 catalyst, which enables up to 76% yield of the C-O scission product (2-methyl furan) in catalytic transfer hydrogenolysis of furfural at low temperatures. Our key mechanistic finding is a facile radical-mediated C-O bond activation on RuO2 oxygen vacancies, which directly leads to a weakly bound final product. This is the first time the radical reduction mechanism is reported in heterogeneous catalysis at temperatures <200 °C. We attribute the unique catalytic properties to the formation of a conjugation-stabilized furfuryl radical upon C-O bond scission, the strong hydroxyl affinity of oxygen vacancies due to the metallic character of RuO2, and the acid-base heterogeneity of the oxide surface. The conjugation-driven radical-assisted C-O bond scission applies to any catalytic surface that preserves the π-electron system of the reactant and leads to C-O selectivity enhancement, with notable examples including Cu, H-covered Pd, self-assembled monolayers on Pd, and oxygen-covered Mo2C. Furthermore, we reveal the cooperativity of active sites in multifunctional catalysts. The mechanism is fully consistent with kinetic studies and isotopic labeling experiments, and the insights gained might prove useful more broadly in overcoming activity constraints induced by energy scaling relationships. PMID:27281043

  5. Efficient conversion of carbohydrates into 1-C-alditols: application to the synthesis of chiral gamma-substituted butenolides and bicyclic alkaloid analogues.

    PubMed

    Boto, Alicia; Hernández, Dácil; Hernández, Rosendo

    2008-07-18

    Readily available sugar derivatives were transformed in a few steps into valuable, more complex products. The tandem radical scission of carbohydrates-oxidation reaction gave acetoxy acetals, which were converted into a variety of chiral C-alditols in good global yields and excellent 1,2-trans stereoselectivity. The reaction was the key step in the synthesis of hydroxylated gamma-substituted butenolides and bicyclic alkaloid analogues.

  6. Orientation of fission fragments and anisotropy of {gamma}-Quanta emission

    SciTech Connect

    Barabanov, A.L.

    1994-07-01

    Experimental data on angular distributions of {gamma}-quanta emitted by fragments of binary and ternary spontaneous fission of {sup 252}Cf are analyzed. Their difference indicates that the fragment alignment is higher in ternary fission than that in binary fission. Consequences of a possible relation between the ternary fission mechanism and the excitation of collective modes at the stage of descent from the barrier to the scission point are discussed. 19 refs., 5 figs.

  7. The role of carbon-carbon phenyl migration in the pyrolysis mechanism of beta-O-4 lignin model compounds: phenethyl phenyl ether and alpha-hydroxy phenethyl phenyl ether

    SciTech Connect

    Beste, Ariana; Buchanan III, A C

    2012-01-01

    We investigate phenyl shift and subsequent beta-scission reactions for PhCHXCHOPh [X = H, OH], which are part of the pyrolysis mechanism of phenethyl phenyl ether (PPE) and alpha-hydroxy PPE. PPE and its derivatives are model compounds for the most common linkage in lignin, the beta-O-4 linkage. We use density functional theory to locate transition states and equilibrium structures, and kinetic Monte Carlo in combination with transition state theory for kinetic simulations. Oxygen-carbon and carbon-carbon phenyl shift reactions proceed through cyclic intermediates with similar barriers. But, while subsequent beta-scission of the oxygen-carbon shift products proceeds with virtually no barrier, the activation energy for beta-scission of the carbon-carbon shift products exceeds 15 kcal/mol. We found that about 15 % of beta-radical conversion can be attributed to carbon-carbon shift for PPE and alpha-hydroxy PPE at 618 K. Whereas the oxygen-carbon shift reaction has been established as an integral part of the pyrolysis mechanism of PPE and its derivatives, participation of the carbon-carbon shift reaction has not been shown previously.

  8. Phosphorylation Regulates the Endocytic Function of the Yeast Dynamin-Related Protein Vps1.

    PubMed

    Smaczynska-de Rooij, Iwona I; Marklew, Christopher J; Allwood, Ellen G; Palmer, Sarah E; Booth, Wesley I; Mishra, Ritu; Goldberg, Martin W; Ayscough, Kathryn R

    2016-03-01

    The family of dynamin proteins is known to function in many eukaryotic membrane fusion and fission events. The yeast dynamin-related protein Vps1 functions at several stages of membrane trafficking, including Golgi apparatus to endosome and vacuole, peroxisomal fission, and endocytic scission. We have previously shown that in its endocytic role, Vps1 functions with the amphiphysin heterodimer Rvs161/Rvs167 to facilitate scission and release of vesicles. Phosphoproteome studies of Saccharomyces cerevisiae have identified a phosphorylation site in Vps1 at serine 599. In this study, we confirmed this phosphorylation event, and we reveal that, like Rvs167, Vps1 can be phosphorylated by the yeast cyclin-associated kinase Pho85 in vivo and in vitro. The importance of this posttranslational modification was revealed when mutagenesis of S599 to a phosphomimetic or nonphosphorylatable form caused defects in endocytosis but not in other functions associated with Vps1. Mutation to nonphosphorylatable valine inhibited the Rvs167 interaction, while both S599V and S599D caused defects in vesicle scission, as shown by both live-cell imaging and electron microscopy of endocytic invaginations. Our data support a model in which phosphorylation and dephosphorylation of Vps1 promote distinct interactions and highlight the importance of such regulatory events in facilitating sequential progression of the endocytic process. PMID:26711254

  9. Irradiation effects on polymer-model compounds

    NASA Astrophysics Data System (ADS)

    Seguchi, Tadao; Katsumura, Yosuke; Hayashi, Nariyuki; Hayakawa, Naohiro; Tamura, Naoyuki; Tabata, Yoneho

    Irradiation effects on n-paraffins and squalane, used as models of polymers, were investigated by product analysis. Four n-paraffins, C 20H 42, C 21H 44, C 23H 48 and C 24H 50, and squalane (C 30H 62) were γ-irradiated under vacuum in liquid, crystalline and glassy states. The evolved gases were analyzed by gas chromatography and changes in molecular weight were analyzed by liquid chromatography and mass spectroscopy. G-values for crosslinking of n-paraffins were 1.2 for crystalline states (at 25°C) and 1.7 for liquid states (at 55°C), and showed no difference between odd and even carbon numbers. The G-value of liquid squalane was 1.7; it was 1.3 for the glassy state at low temperature (-77°C). Double bonds were common in the crosslinked products, especially after liquid-phase irradiation. The probability of chain scission was estimated as being negligible, though a small number of chain-scission products (which were products of scission at chain-ends or side chains) were observed by gas analysis.

  10. Detection of irradiated food by the changes in protein molecular mass distribution

    NASA Astrophysics Data System (ADS)

    Nićiforović, A.; Radojčić, M.; Milosavljević, B. H.

    1999-08-01

    Protein constituents were extracted from chicken drumstick and chicken white meat, separated according to the molecular mass (Mm), using discontinuous SDS-polyacrylamide electrophoresis (SDS-PAGE) and quantified by scanning densitometry. The obtained profiles were compared with the profiles corresponding to the meat samples which were irradiated at -20, +4, and +20°c. It was observed that the irradiation of chicken white meat led to protein scission which was partially unselective (e.g. the amount of proteins whose Mm>20 kDa decreased, while the amount of those whose Mm<20 kDa increased), and partially selective (e.g. the appearance of Mm≌16 kDa fragment). In the case of chicken drumstick meat the irradiation caused both protein scission and protein cross-linking (unselective and selective, and appearance of 16 kDa fragment). However, in the case of aerated dehydrated egg white proteins, irradiation led only to unselective protein scission. The obtained results are discussed in view of possible application of discontinuous analytical SDS-PAGE combined with laser scanning densitometry for detection of previously irradiated foodstuff.

  11. The effect of environmental humidity on radiation-induced degradation of carrageenans.

    PubMed

    Sen, Murat; Toprak, Deniz; Güven, Olgun

    2014-12-19

    Better understanding of the chemistry of radiation-induced degradation is becoming of increasing importance on account of the utilization of polymeric materials in a variety of radiation environments as well as beneficial uses of degraded polymers. In this report the importance of environmental humidity on the degrading effect of radiation has been considered from the point of view of controlling the molecular weights of kappa- and iota-carrageenans. These two polysaccharides were irradiated in solid form under strictly controlled environmental humidity conditions by incubating and later irradiating the samples over saturated aqueous salt solutions of NaCl, NaNO3 and MgCl2. The degradation was followed in detail by a careful gel permeation chromatographic analysis of their respective molecular weights before and after irradiation. The chain scission yield values G(S) were found to decrease with the water adsorbed from environment at every absorbed dose in the range of 5-100 kGy. On the other hand at very high water uptakes the yield of chain scission again increases especially at low doses. The decrease in degradation yield was attributed to the plastifying effect of water trapped in between the polymer chains facilitating the macroradical recombinations thus reducing the extent of chain scission. This study showed that although carrageenans were irradiated in solid form, the difference in their water uptake from changing environmental humidity has a profound effect in controlling their molecular weights by irradiation with ionizing radiation.

  12. A New Role for Myosin II in Vesicle Fission

    PubMed Central

    Cabeza, Jose M.; Acosta, Jorge; Ramirez-Ponce, Pilar; Ales, Eva

    2014-01-01

    An endocytic vesicle is formed from a flat plasma membrane patch by a sequential process of invagination, bud formation and fission. The scission step requires the formation of a tubular membrane neck (the fission pore) that connects the endocytic vesicle with the plasma membrane. Progress in vesicle fission can be measured by the formation and closure of the fission pore. Live-cell imaging and sensitive biophysical measurements have provided various glimpses into the structure and behaviour of the fission pore. In the present study, the role of non-muscle myosin II (NM-2) in vesicle fission was tested by analyzing the kinetics of the fission pore with perforated-patch clamp capacitance measurements to detect single vesicle endocytosis with millisecond time resolution in peritoneal mast cells. Blebbistatin, a specific inhibitor of NM-2, dramatically increased the duration of the fission pore and also prevented closure during large endocytic events. Using the fluorescent markers FM1-43 and pHrodo Green dextran, we found that NM-2 inhibition greatly arrested vesicle fission in a late phase of the scission event when the pore reached a final diameter of ∼ 5 nm. Our results indicate that loss of the ATPase activity of myosin II drastically reduces the efficiency of membrane scission by making vesicle closure incomplete and suggest that NM-2 might be especially relevant in vesicle fission during compound endocytosis. PMID:24959909

  13. Role of carbon-carbon phenyl migration in the pyrolysis mechanism of β-O-4 lignin model compounds: phenethyl phenyl ether and α-hydroxy phenethyl phenyl ether.

    PubMed

    Beste, Ariana; Buchanan, A C

    2012-12-20

    We investigate phenyl shift and subsequent β-scission reactions for PhCHXCH·OPh [X = H, OH], which are part of the pyrolysis mechanism of phenethyl phenyl ether (PPE) and α-hydroxy PPE. PPE and its derivatives are model compounds for the most common linkage in lignin, the β-O-4 linkage. We use density functional theory to locate transition states and equilibrium structures and kinetic Monte Carlo in combination with transition-state theory for kinetic simulations. Oxygen-carbon and carbon-carbon phenyl shift reactions proceed through cyclic intermediates with similar barriers. However, while subsequent β-scission of the oxygen-carbon shift products proceeds with virtually no barrier, the activation energy for β-scission of the carbon-carbon shift products exceeds 15 kcal/mol. We found that about 15% of β-radical conversion can be attributed to carbon-carbon shift for PPE and α-hydroxy PPE at 618 K. Whereas the oxygen-carbon shift reaction has been established as an integral part of the pyrolysis mechanism of PPE and its derivatives, participation of the carbon-carbon shift reaction has not been shown previously.

  14. Aging studies of Kevlar 49 fibers

    SciTech Connect

    Morgan, R.J.; Pruneda, C.O.; Kong, F.M.

    1983-11-01

    The aging mechanisms in service environment of Kevlar 49 fibers, E.I. duPont, (poly(p-phenylene)terephthalamide) are reviewed. The principal aging mechanisms considered are (i) u.v.-, (ii) hydrolytic- and (iii) stress-induced macromolecular chain scission and microvoid growth. U.V.-induced strength degradation can be significant as a result of photo-oxidative and photodegradative radical formation but in Kevlar 49-epoxy composites only the exterior yarn layer is deteriorated. Hydrolytic chain scission of the amide linkage and corresponding fiber strength deterioration is considered in terms of R.H., time, temperature and stress level. The rates of hydrolytic degradation at 100% R.H. in the 100 to 200/sup 0/C range are reported. The estimated rates of fiber degradation in various service environment conditions are also reported and shown not to be serious. The stress-induced aging of Kevlar 49 fibers is considered in terms of the growth and coalescence of inherent microvoids along the fiber axis together with the generation of new microvoids. (These growth processes involve no detectable macromolecular chain scission or deterioration in fiber strength.) At a critical microvoid volume fraction catastrophic failure occurs by interconnection of such voids.

  15. Electron induced fracture of polymeric materials

    SciTech Connect

    Klakken, M.L.

    1986-01-01

    The application of high energy electrons onto a polymeric sample is known to induce electronic excitations that cause many reactions including dissociation, bond scissions, and chemical reactions. Dissociation and bond scission tend to weaken the material while the chemical reactions tend to strengthen the material. It is hypothesized that the introduction of energetic electrons onto a stressed sample causes a decrease in the effective bond energy of the polymers main chains. The effect of electron bombardment was studied on the following materials: polyisoprene, polybutadiene, polyethylene, BAMO/THF (an energetic elastomer), butyl rubber, Kapton-H, and Teflon. The techniques used in the study are: (1) measurement of the mechanical response of a sample mounted in a tension mode due to the electron application, (2) measurement of the change in the tear energy of an elastic material due to the electron beam and (3) generating the observed responses using a molecular dynamics computer simulation method. It was found that the force required to cause crack propagation in a sample mounted in tension decreased when the applied electron current was increased. Periodic patterns were also observed on the fracture surfaces of many of the materials which indicates that both crosslinking and chain scissions occurred in the induced fracture process.

  16. The influence of gamma radiation on the molecular weight and glass transition of PLLA and HAp/PLLA nanocomposite

    NASA Astrophysics Data System (ADS)

    Milicevic, D.; Trifunovic, S.; Dojcilovic, J.; Ignjatovic, N.; Suljovrujic, E.

    2010-09-01

    The influence of gamma radiation on the molecular weight and glass transition behaviour of poly- L-lactide (PLLA) and hydroxyapatite/poly- L-lactide (HAp/PLLA) nanocomposite has been studied. Since PLLA exposed to high-energy radiation in the presence of air is prone to chain scission reactions and large degradation, changes in molecular weight were obtained by gel permeation chromatography (GPC). Alterations in the glass transition behaviour were investigated by differential scanning calorimetry (DSC). The apparent activation energy (Δ H∗) for glass transition was determined on the basis of the heating rate dependence of the glass transition temperature ( T g). Our findings support the fact that chain scission is the main reason for the decrease of T g and Δ H∗ with the absorbed dose. Furthermore, more intensive chain scission degradation of PLLA was observed in HAp/PLLA and can only be ascribed to the presence of HAp nanoparticles. Consequently, initial differences in the glass transition temperature and/or apparent activation energy of PLLA and HAp/PLLA became more pronounced with absorbed dose. This study reveals that radiation-induced changes in molecular weight and glass transition temperature occur in a predictable and fairly accurate manner. Therefore, gamma radiation can be used not only for sterilization but also for tailoring desirable end-use properties of these biomaterials.

  17. Phosphorylation Regulates the Endocytic Function of the Yeast Dynamin-Related Protein Vps1

    PubMed Central

    Smaczynska-de Rooij, Iwona I.; Marklew, Christopher J.; Allwood, Ellen G.; Palmer, Sarah E.; Booth, Wesley I.; Mishra, Ritu; Goldberg, Martin W.

    2015-01-01

    The family of dynamin proteins is known to function in many eukaryotic membrane fusion and fission events. The yeast dynamin-related protein Vps1 functions at several stages of membrane trafficking, including Golgi apparatus to endosome and vacuole, peroxisomal fission, and endocytic scission. We have previously shown that in its endocytic role, Vps1 functions with the amphiphysin heterodimer Rvs161/Rvs167 to facilitate scission and release of vesicles. Phosphoproteome studies of Saccharomyces cerevisiae have identified a phosphorylation site in Vps1 at serine 599. In this study, we confirmed this phosphorylation event, and we reveal that, like Rvs167, Vps1 can be phosphorylated by the yeast cyclin-associated kinase Pho85 in vivo and in vitro. The importance of this posttranslational modification was revealed when mutagenesis of S599 to a phosphomimetic or nonphosphorylatable form caused defects in endocytosis but not in other functions associated with Vps1. Mutation to nonphosphorylatable valine inhibited the Rvs167 interaction, while both S599V and S599D caused defects in vesicle scission, as shown by both live-cell imaging and electron microscopy of endocytic invaginations. Our data support a model in which phosphorylation and dephosphorylation of Vps1 promote distinct interactions and highlight the importance of such regulatory events in facilitating sequential progression of the endocytic process. PMID:26711254

  18. Kinetics of a Collagen-Like Polypeptide Fragmentation after Mid-IR Free-Electron Laser Ablation

    PubMed Central

    Zavalin, Andrey; Hachey, David L.; Sundaramoorthy, Munirathinam; Banerjee, Surajit; Morgan, Steven; Feldman, Leonard; Tolk, Norman; Piston, David W.

    2008-01-01

    Tissue ablation with mid-infrared irradiation tuned to collagen vibrational modes results in minimal collateral damage. The hypothesis for this effect includes selective scission of protein molecules and excitation of surrounding water molecules, with the scission process currently favored. In this article, we describe the postablation infrared spectral decay kinetics in a model collagen-like peptide (Pro-Pro-Gly)10. We find that the decay is exponential with different decay times for other, simpler dipeptides. Furthermore, we find that collagen-like polypeptides, such as (Pro-Pro-Gly)10, show multiple decay times, indicating multiple scission locations and cross-linking to form longer chain molecules. In combination with data from high-resolution mass spectrometry, we interpret these products to result from the generation of reactive intermediates, such as free radicals, cyanate ions, and isocyanic acid, which can form cross-links and protein adducts. Our results lead to a more complete explanation of the reduced collateral damage resulting from infrared laser irradiation through a mechanism involving cross-linking in which collagen-like molecules form a network of cross-linked fibers. PMID:18441025

  19. Dynamin-Actin Cross Talk Contributes to Phagosome Formation and Closure.

    PubMed

    Marie-Anaïs, Florence; Mazzolini, Julie; Herit, Floriane; Niedergang, Florence

    2016-05-01

    Phagocytosis is a mechanism used by macrophages to internalize and eliminate microorganisms or cellular debris. It relies on profound rearrangements of the actin cytoskeleton that is the driving force allowing plasma membrane extension around the particle. The closure step of phagocytosis, however, remains poorly defined. We used a dedicated experimental setup with Total Internal Reflection Fluorescence Microscopy (TIRFM) to monitor phagosome formation and closure in three dimensions in living cells. We show that dynamin-2, which mediates the scission of endocytic vesicles, was recruited early and concomitantly with actin during phagosome formation. Dynamin-2 accumulated at the site of phagosome closure in living macrophages. Inhibition of its activity with dominant negative mutants or drugs demonstrated that dynamin-2 is implicated in actin dynamics and pseudopod extension. Depolymerization of actin led to impaired dynamin-2 recruitment or activity. Finally, we show that dynamin-2 plays a critical role in the effective scission of the phagosome from the plasma membrane. Thus, we establish that a cross talk between actin and dynamin takes place for phagosome formation and closure before dynamin functions for scission. PMID:26847957

  20. Coulomb and even-odd effects in cold and super-asymmetric fragmentation for thermal neutron induced fission of 235U

    NASA Astrophysics Data System (ADS)

    Montoya, M.

    2016-07-01

    Even-odd effects of the maximal total kinetic energy (Kmax) as a function of charge (Z) and mass (A) of fragments from thermal neutron induced fission of actinides are questioned by other authors. In this work, visiting old results on thermal neutron induced fission of 235U, those even-odd effects are reconfirmed. The cases seeming to contradict even-odd effects are interpreted with the Coulomb effect hypothesis. According to Coulomb effect hypothesis, Kmax is equal to the Coulomb interaction energy of the most compact scission configuration. As a consequence, between two isobaric charge splits with similar Q-values, the more asymmetrical one will get the more compact scission configuration and then it will reach the higher Kmax-value. In some cases, the more asymmetrical charge split corresponds, by coincidence, to an odd charge split; consequently its higher Kmax-value may be misinterpreted as anti-even-odd effect. Another experimental result reported in the literature is the increasing of even-odd effects on charge distribution on the more asymmetrical fragmentations region. In this region, the difference between Kmax and Q-values increases with asymmetry, which means that the corresponding scission configuration needs higher total deformation energy to occur. Higher deformation energy of the fragments implies lower free energy to break nucleon pairs. Consequently, in the asymmetric fragmentation region, the even-odd effects of the distribution of proton number and neutron number must increase with asymmetry.

  1. Explicit solvent simulations of the aqueous oxidation potential and reorganization energy for neutral molecules: gas phase, linear solvent response, and non-linear response contributions.

    PubMed

    Guerard, Jennifer J; Tentscher, Peter R; Seijo, Marianne; Samuel Arey, J

    2015-06-14

    First principles simulations were used to predict aqueous one-electron oxidation potentials (Eox) and associated half-cell reorganization energies (λaq) for aniline, phenol, methoxybenzene, imidazole, and dimethylsulfide. We employed quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations of the oxidized and reduced species in an explicit aqueous solvent, followed by EOM-IP-CCSD computations with effective fragment potentials for diabatic energy gaps of solvated clusters, and finally thermodynamic integration of the non-linear solvent response contribution using classical MD. A priori predicted Eox and λaq values exhibit mean absolute errors of 0.17 V and 0.06 eV, respectively, compared to experiment. We also disaggregate Eox into several well-defined free energy properties, including the gas phase adiabatic free energy of ionization (7.73 to 8.82 eV), the solvent-induced shift in the free energy of ionization due to linear solvent response (-2.01 to -2.73 eV), and the contribution from non-linear solvent response (-0.07 to -0.14 eV). The linear solvent response component is further apportioned into contributions from the solvent-induced shift in vertical ionization energy of the reduced species (ΔVIEaq) and the solvent-induced shift in negative vertical electron affinity of the ionized species (ΔNVEAaq). The simulated ΔVIEaq and ΔNVEAaq are found to contribute the principal sources of uncertainty in computational estimates of Eox and λaq. Trends in the magnitudes of disaggregated solvation properties are found to correlate with trends in structural and electronic features of the solute. Finally, conflicting approaches for evaluating the aqueous reorganization energy are contrasted and discussed, and concluding recommendations are given.

  2. CH 2 Cl 2 + OH - Reaction in Aqueous Solution: A Combined Quantum Mechanical and Molecular Mechanics Study

    SciTech Connect

    Wang, Dunyou; Valiev, Marat; Garrett, Bruce C.

    2011-03-03

    The CH2Cl2 + OH- reaction in aqueous solution was investigated using combined quantum mechanical and molecular mechanics approach. We present analysis of the reactant, transition, and product state structures, and calculate the free energy reaction profile through the CCSD(T) level of the theory for the reactive region. Our results show that the aqueous environment has a significant impact on the reaction process raising the reaction barrier by ~17 kcal/mol and the reaction energy by ~20 kcal/mol. While solvation effects play a predominant role, we also find sizable contributions from solvent-induced polarization effects.

  3. Correlation of 1JCH spin-spin coupling constants and their solvent sensitivities

    NASA Astrophysics Data System (ADS)

    Shahkhatuni, Astghik A.; Sahakyan, Aleksandr B.; Shahkhatuni, Aleksan G.; Mamyan, Suren S.; Panosyan, Henry A.

    2012-07-01

    The solvent induced changes of one-bond spin-spin coupling constants (SSCC) of several substituted methanes are investigated in solvents with different polarities. The correlation between solute SSCC and solvent dielectric constant is used to estimate the solvent effect-free ('pure') values of SSCCs by linear extrapolation to zero in reaction field coordinates. The obtained 'pure' SSCCs are close to the values, measured by gas phase NMR spectroscopy or predicted by quantum chemical calculations for isolated molecules. The slopes of SSCC dependencies, interpreted as solvent sensitivities of each molecule, are linearly correlated with the 'pure' values of SSCC.

  4. Effect of the ortho alkylation of perylene bisimides on the alignment and self-assembly properties.

    PubMed

    Dasgupta, Debarshi; Kendhale, Amol M; Debije, Michael G; Ter Schiphorst, Jeroen; Shishmanova, Ivelina K; Portale, Giuseppe; Schenning, Albertus P H J

    2014-08-01

    The effect of the ortho alkylation of perylene bisimides on the alignment and self-assembly properties has been studied. It was found that the dichroic properties of perylene bisimides in a liquid crystal host can be reversed with a single synthetic step by ortho alkylation. Furthermore, a solvent-induced growth of ultralong organic n-type semiconducting fibrils from non-ortho-alkylated perylene bisimide was observed. Ortho substitution of the perylene bisimide core alters the mode of fibrillar growth, leading to isotropic crystallization.

  5. Effect of the Ortho Alkylation of Perylene Bisimides on the Alignment and Self-Assembly Properties

    PubMed Central

    Dasgupta, Debarshi; Kendhale, Amol M; Debije, Michael G; ter Schiphorst, Jeroen; Shishmanova, Ivelina K; Portale, Giuseppe; Schenning, Albertus P H J

    2014-01-01

    The effect of the ortho alkylation of perylene bisimides on the alignment and self-assembly properties has been studied. It was found that the dichroic properties of perylene bisimides in a liquid crystal host can be reversed with a single synthetic step by ortho alkylation. Furthermore, a solvent-induced growth of ultralong organic n-type semiconducting fibrils from non-ortho-alkylated perylene bisimide was observed. Ortho substitution of the perylene bisimide core alters the mode of fibrillar growth, leading to isotropic crystallization. PMID:25478308

  6. Advancement of flash hydrogasification. Quarterly technical progress report, January-March 1984

    SciTech Connect

    Falk, A.Y.

    1984-06-25

    This first quarterly report documents technical progress during the period 31 December 1983 through 30 March 1984. The technical effort is 17 months in duration and is divided into two major technical tasks: Task VII, Hardware Fabrication and PDU Modifications, and Task VIII, Performance Testing. The design of test hardware and process development unit modifications had been previously completed as part of Task VI of the current contract. Task VII involves the fabrication of test hardware and modification of an existing 1-ton/h hydroliquefaction PDU at Rockwell's facilities for use as a hydrogasifier test facility. During this report period, fabrication of the test hardware and modifications to the PDU were initiated. Test hardware fabrication is now approximately 80% complete and should be completed by the end of May 1984. PDU modifications are progressing well and should be completed by the end of June 1984. The completed test hardware fabrication and PDU modifications will allow the conduct of short duration (1 to 2 h) hydrogasification tests along with preburner assembly performance evaluation tests in order to fulfill the test program objectives. Separate supplies of hydrogen, oxygen, methane, carbon monoxide, and water (for steam generation) are provided for this purpose. The modified facility is designed to accommodate both 10- and 20-ft-long hydrogasifier reactors so that residence times will be in the range of 2 to 6 s when coal is fed at a nominal 1/2 ton/h into reactors at 1000 psia pressure. Provisions are being made for real-time analysis of the product gases using an on-line gas chromatograph system. Test planning was the only Task VIII effort active during this report period. An initial (preliminary) test matrix has been defined. Preparation of a data analysis plan is underway, and data reduction programs are being programmed. 17 references, 25 figures, 6 tables.

  7. Lummus clean fuels from coal

    SciTech Connect

    Gantt, J.E.; Hefferan, J.K.; Chorba, W.F.; Schachtschneider, A.B.; Schulze, J.R.

    1980-12-01

    This report compares two direct, catalytic, hydroliquefaction processes - H-Coal and Lummus Clean Fuels From Coal (LCFFC). These processes are compared for two sets of operating conditions. In the first, the reactors are operated to produce a product suitable for use as fuel oil (fuel oil mode). In the second, the operating conditions are more severe, so the resulting product slates more closely resemble crude oil (syncrude mode). The comparisons are performed using conceptual designs based on single point run data, with a design basis of 25,000 tpd (moisture-free basis) of Illinois No. 6 coal. Although all cost comparisons are well within the estimated 25% accuracy of the estimates, LCFFC shows generally lower costs. Three types of economic evaluation are performed: computation of internal rate of return (IRR) with product values set to estimated market value, computation of overall average product cost ($/MM Btu) with the discount rate set at 20%, and calculation of average product cost with naphtha credited at estimated market value and the discount rate set at 20%. H-Coal has a lower cost only in the fuel oil mode analysis with naphtha valued at market price. The processes are also compared with respect to the potential for commercialization and anticipated operability differences. It is concluded that the lower hydrogen content of LCFFC product may offset its advantage of lower cost if it is used as refinery feed, and that the design of the LCFFC reactor may make it harder to control. Suggestions for future research are presented.

  8. Fundamentals of coal depolymerization: an experimental and statistical correlative model of the effects of temperature and solvent on free radicals in coal. Quarterly report, October 1-December 31, 1980

    SciTech Connect

    Petrakis, L; Grandy, D W; Jones, G L

    1981-01-01

    In this project we are attempting to develop information as to the nature and possible role of free radicals in the depolymerization of coal under hydroliquefaction conditions. It is generally assumed that free radical chemistry plays an important role in the liquefaction of coal. Central in our work has been the use of a specially designed high pressure/high temperature electron spin resonance cavity that allows us to quantitatively monitor free radicals in coal 2 to 4 minutes after the heating cycle is initiated. The free radical concentration has been measured quantitatively and repetitively at these various sets of conditions. The heating time has been restricted to three minutes, gas pressure to 1600 psi and the gas used is hydrogen. The main conclusions from this work include the following: in general, the coal free radicals are quenched in the naphthalene < SRC-II heavy distillate < tetralin. The observed free radical concentration depends on the competing effects of free radical formation and free radical quenching, the latter being both temperature and solvent dependent. The free radical concentration of the liquefaction slurry generally increases with increasing temperature. The rate of quenching of free radicals by SRC-II heavy distillate is closer to that of tetralin at lower temperatures and approaches that of naphthalene at the higher temperature. From the results of the full correlative model, we find that temperature, solvent and residence time and their interactions account for about 90% of the effects noted in the free radical concentration. The correlative model represents the experimental results within the reproducibility of the data.

  9. Advanced direct liquefaction concepts for PETC generic units. [Mainly, the effect of preteatment of coal with carbon monoxide and steam

    SciTech Connect

    Not Available

    1992-08-01

    CAER/UK: Detail coal and starting solvents from Wilsonville were analyzed to develop the data necessary to conduct process studies in the CO Pretreatment and Catalyst Evaluation segment of this program. A comparison of the solvent separation analysis with the distillation/separation used at Wilsonville showed that the residual solvent components contained a large amount of residual pentane soluble products. The ashy resid contained 3% iron and 400 ppM molybdenum. Although the iron content in the distillate and deashed resid was much less, namely about 200 ppM., the molybdenum concentrations in these fractions were not significantly reduced over the concentration in the ashy resid, i.e., 200 ppM in each. The pretreatment of coal with CO/H{sub 2}O in the presence of NaOH and Na{sub 2}CO{sub 3} has been shown to give a product which is lower in oxygen content and higher in hydrogen content compared to the raw coal. The atomic H/C ratios of the H{sub 2}O-insolubles, THF insolubles and the PA+A fractions of the products-together with the hydrogen consumption data suggested that the raw coal has been substantially depolymerized and hydrogenated via the WGS reaction during the pretreatment process. The extensive amount of molecular reconstruction that has occurred in the solid product was evident from the ease of solubilization of the product into pyridine. The result of the pretreatment process is a product which is highly reactive under hydroliquefaction conditions at 400{degrees}C. Reaction rates seem to be much faster than the raw coal, especially at shorter reaction times, providing the opportunity for major reductions in plant vessel sizes, and preliminary data has led us to believe that better efficiency in hydrogen utilization is achieved.

  10. Advanced direct liquefaction concepts for PETC generic units. Quarterly technical progress report, April 1992--June 1992

    SciTech Connect

    Not Available

    1992-08-01

    CAER/UK: Detail coal and starting solvents from Wilsonville were analyzed to develop the data necessary to conduct process studies in the CO Pretreatment and Catalyst Evaluation segment of this program. A comparison of the solvent separation analysis with the distillation/separation used at Wilsonville showed that the residual solvent components contained a large amount of residual pentane soluble products. The ashy resid contained 3% iron and 400 ppM molybdenum. Although the iron content in the distillate and deashed resid was much less, namely about 200 ppM., the molybdenum concentrations in these fractions were not significantly reduced over the concentration in the ashy resid, i.e., 200 ppM in each. The pretreatment of coal with CO/H{sub 2}O in the presence of NaOH and Na{sub 2}CO{sub 3} has been shown to give a product which is lower in oxygen content and higher in hydrogen content compared to the raw coal. The atomic H/C ratios of the H{sub 2}O-insolubles, THF insolubles and the PA+A fractions of the products-together with the hydrogen consumption data suggested that the raw coal has been substantially depolymerized and hydrogenated via the WGS reaction during the pretreatment process. The extensive amount of molecular reconstruction that has occurred in the solid product was evident from the ease of solubilization of the product into pyridine. The result of the pretreatment process is a product which is highly reactive under hydroliquefaction conditions at 400{degrees}C. Reaction rates seem to be much faster than the raw coal, especially at shorter reaction times, providing the opportunity for major reductions in plant vessel sizes, and preliminary data has led us to believe that better efficiency in hydrogen utilization is achieved.

  11. Superacid Catalyzed Depolymerization and Conversion of Coals. Final Technical Report. [HF:BF{sub 2}/H{sub 2}

    DOE R&D Accomplishments Database

    Olah, G.

    1980-01-01

    We were interested in applying superacid catalyzed cleavage-depolymerization and ionic hydrogenation low temperature conversion of coal to liquid hydrocarbon, as well as obtaining information about the reactions involved and the structure of intermediates of the coal liquefaction process. In order to show the feasibility of our proposed research we have carried out preliminary investigation in these areas. Preceding our work there was no practical application of a superacid system to coal liquefaction. We carried out an extensive study of the potential of the HF:BF{sub 3}/H{sub 2} system for coal hydroliquefaction. Under varying conditions of reactant ratio, reaction time and temperature, we were able to obtain over 95% pyridine extractible product by treating coal in HF:BF{sub 3}:H{sub 2} system at approx. 100 degrees C for 4 hours. The coal to acid ratio was 1:5 and FB{sub 3} at 900 psi and H{sub 2} at 500 psi were used. These are extremely encouraging results in that the conditions used are drastically milder than those used in any known process, such as Exxon donor solvent and related processes. The cyclohexane extractibility of the treated coal was as high as 27% and the yield of liquid distillate at 400 degrees C/5 x 10{sup -3}/sup torr/ was approx. 30%. The infrared spectrum of product coal, extracts and distillates were distinctly different from the starting coal and show a significant increase in the amount of saturates. The {sup 1}H NMR spectrum of cyclohexane extract of the treated coal shows essentially all aliphatic photons. The spectra of other treated coal extracts show increased amounts and types of aliphatic protons as well as significant amounts of protons bound to unsaturated sites. This again indicates that the HF-BF{sub 3} system is depolymerizing the coal to small fragments which are soluble in non-polar solvents.

  12. Unusually low fragment energies in the symmetric fission of /sup 259/Md

    SciTech Connect

    Wild, J.F.; Hulet, E.K.; Lougheed, R.W.; Baisden, P.A.; Landrum, J.H.; Dougan, R.J.; Mustafa, M.G.

    1982-10-01

    The 103-min isotope /sup 259/Md has been identified as the daughter of an electron-capture decay branch of /sup 259/No produced via the /sup 248/Cm(/sup 18/O,..cap alpha..3n) reaction. Chemical separations were used to confirm the identity of /sup 259/Md, which decays by spontaneous fission. The kinetic energies of coincident fission fragments were measured, corresponding to a fragment mass which is highly symmetric, similar to those of /sup 258/Fm and /sup 259/Fm. However, the total kinetic energy distribution for /sup 259/Md is considerably broader (FWHM approx.60 MeV) than those of /sup 258/Fm and /sup 259/Fm, and peaks at 201 MeV, about 35--40 MeV lower in energy. Furthermore, the maximum total Kinetic energy of 215 MeV for mass-symmetric events is about 30 MeV lower than for similar events from the spontaneous fission of /sup 258/Fm and /sup 259/Fm. A hypothesis that this energy difference resulted from the emission of light, hydrogen-like particles at scission in a large fraction of /sup 259/Md spontaneous fission decays was shown to be unfounded. From experiments to observe such particles with counter telescopes, an upper limit of 5% was determined for the fraction of fission events accompanied by light-particle emission. The total kinetic energy deficit at mass symmetry must, therefore, be distributed between internal excitation energy and fragment deformation energy at scission. Although the presence of a large amount of fragment deformation energy seems incompatible with symmetric fission into spherical Sn-like fragments, we prefer this explanation because the low total kinetic energy suggests a lowered Coulomb energy resulting from greater separation of the charge centers of deformed fragments at scission.

  13. Thermochemistry and Kinetic Analysis of the Unimolecular Oxiranyl Radical Dissociation Reaction: A Theoretical Study.

    PubMed

    Wang, Heng; Bozzelli, Joseph W

    2016-07-01

    Oxirane structures are important in organic synthesis, and they are important initial products in the oxidation reactions of alkyl radicals. The thermochemical properties (enthalpy of formation, entropy, and heat capacity) for the reaction steps of the unimolecular oxiranyl radical dissociation reaction are determined and compared with the available literature. The overall ring opening and subsequent steps involve four types of reactions: β-scission ring opening, intramolecular hydrogen transfer, β-scission hydrogen elimination, and β-scission methyl radical elimination. The enthalpies of formation of the transition states are determined and evaluated using six popular Density Functional Theory (DFT) calculation methods (B3LYP, B2PLYP, M06, M06-2X, ωB97X, ωB97XD), each combined with three different basis sets. The DFT enthalpy values are compared with five composite calculation methods (G3, G4, CBS-QB3, CBS-APNO, W1U), and by CCSD(T)/aug-cc-pVTZ. Kinetic parameters are determined versus pressure and temperature for the unimolecular dissociation pathways of an oxiranyl radical, which include the chemical activation reactions of the ring-opened oxiranyl radical relative to the ring-opening barrier. Multifrequency quantum Rice Ramsperger Kassel (QRRK) analysis is used to determine k(E) with master equation analysis for falloff. The major overall reaction pathway at lower combustion temperatures is oxiranyl radical dissociation to a methyl radical and carbon monoxide. Oxiranyl radical dissociation to a ketene and hydrogen atom is the key reaction path above 700 K. PMID:26990491

  14. Mechanistic Analysis and Thermochemical Kinetic Simulation of the Pathways for Volatile Product Formation from Pyrolysis of Polystyrene, Especially of the Dimer

    SciTech Connect

    Poutsma, Marvin L

    2006-01-01

    Simulations of the initial distribution of volatiles from pyrolysis of polystyrene were based on propagation rate constants estimated by thermochemical kinetic procedures. The voluminous database exhibits a disturbing lack of consistency with respect to effects of conversion level, temperature, and reactor type. It therefore remains difficult to assign the true primary distribution of the major products, styrene, 2,4-diphenyl-1-butene (''dimer''), 2,4,6-triphenyl-1-hexene (''trimer''), 1,3-diphenylpropane, and toluene, and its dependence on conditions. Probable perturbations by secondary reactions and selective evaporation are considered. The rate constant for 1,3-hydrogen shift appears much too small to accommodate the commonly proposed ''back-biting'' mechanism for dimer formation. Dimer more likely arises by addition of benzyl radical to olefinic chain-ends, followed by {beta}-scission, although ambiguities remain in assigning rate constants for the addition and {beta}-scission steps. With this modification, the major products can be successfully associated with decay of the sec-benzylic chain-end radical. In contrast, the minimal formation of allylbenzene, 2,4-diphenyl-1-pentene, and 2,4,6-triphenyl-1-heptene suggests a minimal chain-propagating role for the prim chain-end radical. Compared with polyethylene, the much enhanced ''unzipping'' to form monomer from polystyrene and the more limited depth of ''back-biting'' into the chain arise from an enthalpy-driven acceleration of {beta}-scission coupled with a kinetically driven deceleration of intramolecular hydrogen transfer. In contrast, the greater ''unzipping'' of poly(isobutylene) compared with polyethylene is proposed to result from relief of steric strain.

  15. Hydroxyalkoxy radicals: importance of intramolecular hydrogen bonding on chain branching reactions in the combustion and atmospheric decomposition of hydrocarbons.

    PubMed

    Davis, Alexander C; Francisco, Joseph S

    2014-11-20

    During both the atmospheric oxidation and combustion of volatile organic compounds, sequential addition of oxygen can lead to compounds that contain multiple hydrogen-bonding sites. The presence of two or more of these sites on a hydrocarbon introduces the possibility of intramolecular H-bonding, which can have a stabilizing effect on the reactants, products, and transition states of subsequent reactions. The present work compares the absolute energies of two sets of conformations, those that contain intramolecular H-bonds and those that lack intramolecular H-bonds, for each reactant, product, and transition state species in the 1,2 through 1,7 H-migrations and Cα-Cβ, Cα-H, and Cα-OH-bond scission reactions in the n-hydroxyeth-1-oxy through n-hydroxyhex-1-oxy radicals, for n ranging from 1 to 6. The difference in energy between the two conformations represents the balance between the stabilizing effects of H-bonds and the steric cost of bringing the two H-bonding sites together. The effect of intramolecular H-bonding and the OH group is assessed by comparing the net intramolecular H-bond stabilization energies, the reaction enthalpies, and barrier heights of the n-hydroxyalkoxy radical reactions with the corresponding alkoxy radicals values. The results suggest that there is a complex dependence on the location of the two H-bonding groups, the location of the abstraction or bond scission, and the shape of the transition state that dictates the extent to which intramolecular H-bonding effects the relative importance of H-migration and bond scission reactions for each n-hydroxyalkoxy radical. These findings have important implications for future studies on hydrocarbons with multiple H-bonding sites.

  16. Thermochemistry and Kinetic Analysis of the Unimolecular Oxiranyl Radical Dissociation Reaction: A Theoretical Study.

    PubMed

    Wang, Heng; Bozzelli, Joseph W

    2016-07-01

    Oxirane structures are important in organic synthesis, and they are important initial products in the oxidation reactions of alkyl radicals. The thermochemical properties (enthalpy of formation, entropy, and heat capacity) for the reaction steps of the unimolecular oxiranyl radical dissociation reaction are determined and compared with the available literature. The overall ring opening and subsequent steps involve four types of reactions: β-scission ring opening, intramolecular hydrogen transfer, β-scission hydrogen elimination, and β-scission methyl radical elimination. The enthalpies of formation of the transition states are determined and evaluated using six popular Density Functional Theory (DFT) calculation methods (B3LYP, B2PLYP, M06, M06-2X, ωB97X, ωB97XD), each combined with three different basis sets. The DFT enthalpy values are compared with five composite calculation methods (G3, G4, CBS-QB3, CBS-APNO, W1U), and by CCSD(T)/aug-cc-pVTZ. Kinetic parameters are determined versus pressure and temperature for the unimolecular dissociation pathways of an oxiranyl radical, which include the chemical activation reactions of the ring-opened oxiranyl radical relative to the ring-opening barrier. Multifrequency quantum Rice Ramsperger Kassel (QRRK) analysis is used to determine k(E) with master equation analysis for falloff. The major overall reaction pathway at lower combustion temperatures is oxiranyl radical dissociation to a methyl radical and carbon monoxide. Oxiranyl radical dissociation to a ketene and hydrogen atom is the key reaction path above 700 K.

  17. Relationship between hydroperoxide concentration and average molar mass in thermo-oxidized polyethylene

    NASA Astrophysics Data System (ADS)

    Da Cruz, Manuela; Van Schoors, Laetitia; Colin, Xavier; Benzarti, Karim

    2014-05-01

    The aim of this research project is to investigate the oxidation mechanism of high density polyethylene (HDPE) used in outdoor applications, in order to establish in a near future, a non-empirical kinetic model for lifetime prediction. The present paper focuses on the changes in the hydroperoxide (POOH) concentration induced by thermo-oxidative ageing, and on their relationship with the evolution of the weight average molar mass (Mw) due both to chain scission and crosslinking processes. Thin HDPE films were aged at 110 and 140°C in air under atmospheric pressure. In a first part, changes in the POOH concentration versus ageing time were assessed by three different analytical methods previously reported in the literature: modulated differential scattering calorimetry (MDSC), Fourier transform Infra-Red spectrometry after chemical derivatization treatment with gaseous sulfur dioxide (SO2-FTIR), and iodometry. A comparison of experimental results revealed that these three methods provide very similar quantitative data on POOH accumulation, whereas iodometry tends to strongly underestimate the subsequent stage of POOH decomposition. It was thus suspected that iodometry does not only titrate POOH, but also other chemical species (presumably double bonds) formed when POOH decompose. Therefore, only MDSC and SO2-FTIR were considered as relevant methods for POOH titration. In a second part, changes in Mw versus ageing time were monitored by size exclusion chromatography (SEC). A sharp drop of Mw was first observed at the beginning of exposure, which was assigned to an intensive chain scission process. Then, in a second stage, a stabilization or even a substantial re-increase in Mw was observed, suggesting a competition between chain scission and crosslinking processes. As this second stage starts at the same time as POOH decomposition, it was concluded that there is a strong correlation between both phenomena, occurring respectively at the macromolecular and molecular

  18. Actin-cytoskeleton rearrangement modulates proton-induced uptake

    SciTech Connect

    Ben-Dov, Nadav; Korenstein, Rafi

    2013-04-15

    Recently it has been shown that elevating proton concentration at the cell surface stimulates the formation of membrane invaginations and vesicles accompanied by an enhanced uptake of macromolecules. While the initial induction of inward membrane curvature was rationalized in terms of proton-based increase of charge asymmetry across the membrane, the mechanisms underlying vesicle formation and its scission are still unknown. In light of the critical role of actin in vesicle formation during endocytosis, the present study addresses the involvement of cytoskeletal actin in proton-induced uptake (PIU). The uptake of dextran-FITC is used as a measure for the factual fraction of inward invaginations that undergo scission from the cell's plasma membrane. Our findings show that the rate of PIU in suspended cells is constant, whereas the rate of PIU in adherent cells is gradually increased in time, saturating at the level possessed by suspended cells. This is consistent with pH induced gradual degradation of stress-fibers in adherent cells. Wortmannin and calyculin-A are able to elevate PIU by 25% in adherent cells but not in suspended cells, while cytochalasin-D, rapamycin and latrunculin-A elevate PIU both in adherent and suspended cells. However, extensive actin depolymerization by high concentrations of latrunculin-A is able to inhibit PIU. We conclude that proton-induced membrane vesiculation is restricted by the actin structural resistance to the plasma membrane bending. Nevertheless, a certain degree of cortical actin restructuring is required for the completion of the scission process. - Highlights: ► Acidification of cells' exterior enhances uptake of macromolecules by the cells. ► Disruption of actin stress fibers leads to enhancement of proton induced uptake. ► Extensive depolymerization of cellular actin attenuates proton-induced uptake.

  19. Local even-odd effect based on the number of configurations of pre-formed and formed fragmentations in a fissioning nucleus

    NASA Astrophysics Data System (ADS)

    Tudora, A.; Hambsch, F.-J.; Giubega, G.

    2016-09-01

    The present paper proposes a modeling of the local even-odd effect based on the number of configurations in a nucleus undergoing fission at two stages along its fission path. One is the fissioning nucleus stage just after passing through the outer saddle point when the fragments are considered as pre-formed and the intrinsic energy is not yet shared. The other stage is at the end of the fission path when the scission is imminent. Then the intrinsic energy is already partitioned and the fragments are completely formed. The probability that a pre-formed fragmentation arrives at the end of the fission path (i.e. at scission) when the fragmentation is completely formed is expressed by the ratio of the number of configurations of the formed fragmentation to the one of pre-formed fragmentation. The local even-odd effect is defined as half of the difference between these normalized ratios corresponding to even-Z and odd-Z fragmentations. Both numbers of configurations in the fissioning nucleus, in which the fragments are pre-formed and completely formed, are calculated using level densities described by the constant temperature function (justified by the small values of the intrinsic energy before scission). The obtained local even-odd effect results describe well the experimental data, including the increase at asymmetry values corresponding to fragmentations in which one of the fragments is magic or double magic (i.e. fragmentations in which ZH = 50 and/or NH = 82 and very asymmetric fragmentations in which ZL = 28).

  20. Probing fusion-fission dynamics in Bi203

    NASA Astrophysics Data System (ADS)

    Mukul, Ish; Nath, S.; Golda, K. S.; Jhingan, A.; Gehlot, J.; Prasad, E.; Kalkal, Sunil; Naik, M. B.; Banerjee, Tathagata; Varughese, T.; Sugathan, P.; Madhavan, N.; Pal, Santanu

    2015-11-01

    Background: Complete fusion between two massive nuclei after capture inside the potential barrier is inhibited by competing fission-like processes. The target-projectile composite system may reseparate after capture without proceeding towards formation of the compound nucleus (CN), which is equilibrated in all degrees of freedom. The nature of these non-CN fission (NCNF) processes and factors that affect them are not completely known yet. Purpose: The nuclear mass regions from where NCNF processes begin to manifest themselves are not clearly demarcated. This work aims to study the onset of NCNF, if any, in the mass region ˜200 . Methods: Fission fragment (FF) mass and angular distribution (MAD) and pre-scission and post-scission neutron multiplicities were measured for the reaction +W184F19 at a laboratory energy (Elab) range of 84-125 MeV. The measurements were carried out using two multiwire proportional counters (MWPC) to detect the FFs in coincidence and four neutron detectors to measure neutron time of flight (TOF). Statistical model (SM) calculation was performed. Results: No significant mass-angle correlation was observed in the MAD plots. Extracted mass ratio distributions were single-peaked and of Gaussian shape. Measured pre-scission neutron multiplicity values indicated dissipative nature of CN decay for this reaction. Conclusions: No clear signatures of NCNF were observed in the studied reaction, indicating that the target-projectile composite system predominantly proceeds towards formation of the CN after capture.

  1. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    NASA Astrophysics Data System (ADS)

    See, Tian Long; Liu, Zhu; Li, Lin; Zhong, Xiang Li

    2016-02-01

    This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser-material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (Fth = 0.087 J/cm2) than that for the femtosecond laser ablation of ABS (Fth = 1.576 J/cm2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α-1 = 223 nm) than that for femtosecond laser ablation (α-1 = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the Cdbnd C bond completely through the chain scission process whereas Cdbnd C bond is partially eliminated through the femtosecond laser treatment due to the difference in photon energy of the two laser beams. A reduction in the Cdbnd C bond through the chain scission process creates free radical carbons which then form crosslinks with each other or react with oxygen, nitrogen and water in air producing oxygen-rich (Csbnd O and Cdbnd O bond) and nitrogen-rich (Csbnd N) functional groups.

  2. Crosslinking of metallocenic α-olefin propylene copolymers by vacuum gamma irradiation

    NASA Astrophysics Data System (ADS)

    Satti, A. J.; Andreucetti, N. A.; Quijada, R.; Vallés, E. M.

    2012-12-01

    Metallocenic polypropylene and copolymers with 3.7, and 9.2 mol% of hexene and 3.0 mol% of octadecene comonomer content were synthesized without the presence of additives and irradiated with 60Co gamma radiation under vacuum at room temperature. Size Exclusion Cromatography and gel extraction data showed that scission reactions predominate over crosslinking in the homopolymer and that there is a dose from where crosslinking started to increase considerably, in the irradiated copolymers. Rheology also showed evidence of chain-enlargements on the copolymers by means of an increase in the viscoelastic properties of the irradiated material.

  3. Possible origin of transition from symmetric to asymmetric fission

    NASA Astrophysics Data System (ADS)

    Paşca, H.; Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.

    2016-09-01

    The charged distributions of fragments produced in the electromagnetic-induced fission of the even-even isotopes of Rn, Ra, Th, and U are described within an improved scission-point model and compared with the available experimental data. The three-equal-peaked charge distributions are predicted for several fissioning nuclei with neutron number N = 136. The possible explanation of the transition from a symmetric fission mode to an asymmetric one around N ∼ 136 is presented. The excitation energy dependencies of the asymmetric and symmetric fission modes are anticipated.

  4. Initial Stages of Pyrolysis of Polyethylene

    NASA Astrophysics Data System (ADS)

    Popov, Konstantin V.

    Combustion and flammability of plastics are important topics of practical interest directly related to fire safety and recycling of polymeric materials; pyrolysis of the solid is the initial step of its combustion. One of the main ways to study such complicated processes is through detailed mechanistic modeling, in which the process is represented by a set of many elementary reactions. Mechanistic modeling of combustion of plastics is considerably hindered by the lack of necessary kinetic data. In virtually all existing models of polymer pyrolysis the majority of kinetic data used are derived from the corresponding gas phase values of smaller species. The use of gas phase rate constants is, generally, not justified without an experimental justification. In the first part of the work the influence of condensed phase on the rate of scission of a carbon-carbon bond (the reaction that initiates pyrolysis and combustion) in polyethylene (PE) was studied using the method of Reactive Molecular Dynamics (RMD). A method based on a two-step kinetic mechanism was developed to decouple the cage effect from the kinetics of the reaction under study. It was observed that under the conditions of condensed phase the rate constant of C-C bond scission in PE decreased by an order of magnitude compared to that obtained in vacuum. It was also shown that under the conditions of polymer melt the rate constant does not depend on the length of the polymer chain. In the second part of the work the kinetics of liquid phase and gas phase products of PE pyrolysis were studied experimentally using Gas Chromatography and Nuclear Magnetic Resonance. Based on the assumption of applicability of gas phase kinetic data for C-C scission reaction and beta-scission reaction under the conditions of polymer melt, rate constants of hydrogen transfer, radical addition to double bonds, and radical recombination were determined via kinetic modeling of the experimental results. The obtained values of the rate

  5. Fission fragment mass distribution studies in 30Si +180Hf reaction

    NASA Astrophysics Data System (ADS)

    Shamlath, A.; Shareef, M.; Prasad, E.; Sugathan, P.; Thomas, R. G.; Jhingan, A.; Appannababu, S.; Nasirov, A. K.; Vinodkumar, A. M.; Varier, K. M.; Yadav, C.; Babu, B. R. S.; Nath, S.; Mohanto, G.; Mukul, Ish; Singh, D.; Kailas, S.

    2016-01-01

    Fission fragment mass-angle and mass ratio distributions have been measured for the 30Si + 180Hf reaction in the beam energy range 128-148 MeV. Quasifission signature is observed in this reaction, forming the compound system 210Rn. The results are compared with a very asymmetric reaction 16O + 194Pt, forming the same compound nucleus. Calculations assuming saddle point, scission point and DNS models have been performed to interpret the experimental results. The results strongly suggest the entrance channel dependence of quasifission in heavy ion collisions.

  6. Application of the dinuclear system model to fission process

    NASA Astrophysics Data System (ADS)

    Andreev, A. V.; Shneidman, T. M.; Ventura, A.

    2016-01-01

    A theoretical evaluation of the collective excitation spectra of nucleus at large deformations is possible within the framework of the dinuclear system model, which treats the wave function of the fissioning nucleus as a superposition of a mononucleus configuration and two-cluster configurations in a dynamical way, permitting exchange of nucleons between clusters. In this work the method of calculation of the potential energy and the collective spectrum of fissioning nucleus at scission point is presented. Combining the DNS model calculations and the statistical model of fission we calculate the mass, total kinetic energy, and angular distribution of fission fragments for the neutron-induced fission of 239Pu.

  7. Macroscopic and microscopic aspects in nuclear fission

    NASA Astrophysics Data System (ADS)

    Strutinsky, V.

    1989-10-01

    Nuclear macroscopic properties are determined as statistical averages and it is then recognized that several levels of macroscopic descriptions may exist. By zooming the averaging scale the gross shell structures are distinguished from the macroscopic background and a theory can be formed consistently combining both the macroscopic and microscopic features. The shell structure varies in the fissioning nucleus on its way to scission leading to a double-humped shape of the fission barrier. This is due to modifications of the classical periodic paths responsible for the quantal non-uniformity of the single-particle phase space. Briefly results of the combined theory for the fission process are outlined.

  8. Nuclear-deformation energies according to a liquid-drop model with a sharp surface

    SciTech Connect

    Blocki, J.; Swiatecki, W.J.

    1982-05-01

    We present an atlas of 665 deformation-energy maps and 150 maps of other properties of interest, relevant for nuclear systems idealized as uniformly charged drops endowed with a surface tension. The nuclear shapes are parametrized in terms of two spheres modified by a smoothly fitted quadratic surface of revolution and are specified by three variables: asymmetry, sphere separation, and a neck variable (that goes over into a fragment-deformation variable after scission). The maps and related tables should be useful for the study of macroscopic aspects of nuclear fission and of collisions between any two nuclei in the periodic table.

  9. Desorption of Hydrogen from Si(111) by Resonant Excitation of the Si-H Vibrational Stretch Mode

    SciTech Connect

    Liu, Zhiheng; Feldman, Leonard C.; Tolk, Norman; Zhang, Zhenyu; Cohen, Philip I

    2006-01-01

    Past efforts to achieve selective bond scission by vibrational excitation have been thwarted by energy thermalization. Here we report resonant photodesorption of hydrogen from a Si(111) surface using tunable infrared radiation. The wavelength dependence of the desorption yield peaks at 0.26 electron volt: the energy of the Si-H vibrational stretch mode. The desorption yield is quadratic in the infrared intensity. A strong H/D isotope effect rules out thermal desorption mechanisms, and electronic effects are not applicable in this low-energy regime. A molecular mechanism accounting for the desorption event remains elusive.

  10. Constitutive equations of ageing polymeric materials

    NASA Technical Reports Server (NTRS)

    Peng, S. T. J.

    1985-01-01

    The constitutive equation for the relaxation behavior of time-dependent, chemically unstable materials developed by Valanis and Peng (1983), which used the irreversible thermodynamics of internal variables in Eyring's absolute reaction theory and yielded a theoretical expression for the effect of chemical crosslink density on the relaxation rate, is presently applied to the creep behavior of a network polymer which is undergoing a scission process. In particular, two equations are derived which may for the first time show the relations between mechanical models and internal variables in the creep expressions, using a three-element model with a Maxwell element.

  11. Chemo-physical properties of renal capsules under ultraviolet-c exposure

    SciTech Connect

    Baghapour, Sh.; Parvin, P. Mokhtari, S.; Reyhani, A.; Mortazavi, S. Z.; Amjadi, A.

    2014-08-07

    The renal capsule tissue of lamb was irradiated with ultraviolet-C light and the treated samples were analyzed by uniaxial tensile test, dynamic mechanical analysis, attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements. It was shown that the skin cross-linking is dominant in low doses in accordance with the contact angle assessment. Conversely, the strong bulk degradation takes place at high doses. Similarly, the bulk cross-linking affects the mechanical tests as to enhance the stiffness at low doses, whereas strong degradation occurs at high doses that mainly arises from the strong bulk chain scission.

  12. Novel ESCRT functions in cell biology: spiraling out of control?

    PubMed

    Campsteijn, Coen; Vietri, Marina; Stenmark, Harald

    2016-08-01

    The endosomal sorting complex required for transport (ESCRT), originally identified for its role in endosomal protein sorting and biogenesis of multivesicular endosomes (MVEs), has proven to be a versatile machinery for involution and scission of narrow membrane invaginations filled with cytosol. Budding of enveloped viruses and cytokinetic abscission were early described functions for the ESCRT machinery, and recently a number of new ESCRT functions have emerged. These include cytokinetic abscission checkpoint control, plasma membrane repair, exovesicle release, quality control of nuclear pore complexes, neuron pruning, and sealing of the newly formed nuclear envelope. Here we review these novel ESCRT mechanisms and discuss similarities and differences between the various ESCRT-dependent activities.

  13. Failure modes and durability of kevlar/epoxy composites

    SciTech Connect

    Morgan, R.J.; Mones, E.T.; Steele, W.J.; Deutscher, S.B.

    1981-04-01

    The fracture topographies of Kevlar 49/epoxy composite strands and multilayer composites in the form of pressure vessels are discussed in terms of the microscopic deformation and failure processes of the composites. The effect of resin ductility and fiber-matrix interfacial bond strength on mechanisms of fiber damage are considered. The failure of the Kevlar 49 fibers by a splitting process and the parameters, such as fiber fibrillation and macromolecular chain scission, that control such a process are discussed in relation to fiber and composite performance.

  14. Failure modes and durability of Kevlar/epoxy composites

    SciTech Connect

    Morgan, R.J.; Mones, E.T.; Steele, W.J.; Deutscher, S.B.

    1980-06-04

    The fracture topographies of Kevlar 49/epoxy composite strands and multilayer composites in the form of pressure vessels are discussed in terms of the microscopic deformation and failure processes of the composites. The effect of resin ductility and fiber-matrix interfacial bond strength on mechanisms of fiber damage are considered. The failure of the Kevlar 49 fibers by a splitting process and the parameters, such as fiber fibrillation and macromolecular chain scission, that control such a process, are discussed in relation to fiber and composite performance.

  15. Effect of transverse vibrations of fissile nuclei on the angular and spin distributions of low-energy fission fragments

    NASA Astrophysics Data System (ADS)

    Bunakov, V. E.; Kadmensky, S. G.; Lyubashevsky, D. E.

    2016-05-01

    It is shown that A. Bohr's classic theory of angular distributions of fragments originating from low-energy fission should be supplemented with quantum corrections based on the involvement of a superposition of a very large number of angular momenta L m in the description of the relative motion of fragments flying apart along the straight line coincidentwith the symmetry axis. It is revealed that quantum zero-point wriggling-type vibrations of the fissile system in the vicinity of its scission point are a source of these angular momenta and of high fragment spins observed experimentally.

  16. Prompt muon-induced fission: A probe for nuclear friction in large-amplitude collective motion

    SciTech Connect

    Oberacker, V.E.; Umar, A.S.; Wells, J.C.; Strayer, M.R.; Maruhn, J.A.; Reinhard, P.G.

    1998-01-01

    Excited muonic atoms in the actinide region may induce prompt fission by inverse internal conversion, i.e. the excitation energy of the muonic atom is transferred to the nucleus. The authors solve the time dependent Dirac equation for the muonic spinor wave function in the Coulomb field of the fissioning nucleus on a 3-dimensional lattice and demonstrate that the muon attachment probability to the light fission fragment is a measure of the nuclear energy dissipation between the outer fission barrier and the scission point.

  17. Microscopic modeling of mass and charge distributions in the spontaneous fission of 240Pu

    NASA Astrophysics Data System (ADS)

    Sadhukhan, Jhilam; Nazarewicz, Witold; Schunck, Nicolas

    2016-01-01

    We propose a methodology to calculate microscopically the mass and charge distributions of spontaneous fission yields. We combine the multidimensional minimization of collective action for fission with stochastic Langevin dynamics to track the relevant fission paths from the ground-state configuration up to scission. The nuclear potential energy and collective inertia governing the tunneling motion are obtained with nuclear density functional theory in the collective space of shape deformations and pairing. We obtain a quantitative agreement with experimental data and find that both the charge and mass distributions in the spontaneous fission of 240Pu are sensitive both to the dissipation in collective motion and to adiabatic fission characteristics.

  18. A transfection reporter for the prevention of false-negative results in molecular beacon experiments.

    PubMed

    Toga, Tatsuya; Kuraoka, Isao; Yasui, Akira; Iwai, Shigenori

    2013-09-01

    We previously developed a molecular beacon-type probe to detect the strand scission in cellular base excision repair and found that the phosphodiester linkages in the fluorophore/quencher linkers were cleaved. This reaction was applied to a transfection reporter, which contained the unmodified phosphodiester in the linker to another type of fluorophore. After cotransfection of cells with the probe and the reporter, the signals were used to detect the incision and to confirm the proper transfection, respectively. This method will contribute to the prevention of false-negative results in experiments using molecular beacon-type probes.

  19. Radiation-induced physical changes in UHMWPE implant components.

    PubMed

    Naidu, S H; Bixler, B L; Moulton, M J

    1997-02-01

    Post-irradiation aging of ultra-high molecular weight polyethylene (UHMWPE) is not well understood. Retrieval studies and in vitro aged specimens have shown oxidative changes along with increases in crystallinity. Critical analysis and review of the polymer science and polymer physics literature shows that while oxidation may be important during the first year post-irradiation, subsequent aging occurs because of initial gamma radiation-induced chain scission leading to eventual isothermal crystallization of polymer chains in the amorphous regions of the UHMWPE bulk. Mechanical properties of aged UHMWPE are not as yet clear and, until such data become available, gamma irradiation sterilization must be used with caution.

  20. Catalytic Carbocation Generation Enabled by the Mesolytic Cleavage of Alkoxyamine Radical Cations.

    PubMed

    Zhu, Qilei; Gentry, Emily C; Knowles, Robert R

    2016-08-16

    A new catalytic method is described to access carbocation intermediates via the mesolytic cleavage of alkoxyamine radical cations. In this process, electron transfer between an excited state oxidant and a TEMPO-derived alkoxyamine substrate gives rise to a radical cation with a remarkably weak C-O bond. Spontaneous scission results in the formation of the stable nitroxyl radical TEMPO(.) as well as a reactive carbocation intermediate that can be intercepted by a wide range of nucleophiles. Notably, this process occurs under neutral conditions and at comparatively mild potentials, enabling catalytic cation generation in the presence of both acid sensitive and easily oxidized nucleophilic partners. PMID:27403637

  1. Silver ion beam irradiation effects on poly(lactide-co-glycolide) (PLGA)/clay nanocomposites

    NASA Astrophysics Data System (ADS)

    Kaur, Manpreet; Singh, Surinder; Mehta, Rajeev

    2014-12-01

    Swift heavy ions induced modification of thin films of blends of poly(lactide-co-glycolide) (PLGA) (50:50) with organically modified nanoclay (Cloisite® 30B) has been studied, using optical, structural and surface morphological analysis. Presence of nanoclay is found to enhance the properties of this degradable copolymer by reducing the rate of degradation even at high irradiation fluence. Optical and structural analysis of the polymer nanocomposites suggests that both the cross-linking and chain scission phenomenon are caused by swift heavy ion irradiation. XRD measurements show intercalation of PLGA in the clay galleries. Surface morphology of a nanocomposite indicates significant changes after irradiation at various fluences.

  2. Thermal decomposition pathway and desorption study of isopropanol and tert-butanol on Si(100)

    NASA Astrophysics Data System (ADS)

    Kim, Jaehyun; Kim, Kwansoo; Yong, Kijung

    2002-09-01

    Thermal decomposition pathway and desorption of isopropanol (IPA) and tert-butanol on Si(100) were studied using temperature programed desorption. Adsorbed alcohols studied were decomposed into atomic hydrogen and alkoxy on the surface. During heating the sample up to 1000 K, acetone, propylene, and hydrogen were desorbed as decomposition products of IPA on Si(100). Desorption pathways of IPA on Si(100) were largely consistent with those on metal surfaces: beta-hydride elimination reaction to acetone and C-O scission to propylene. For tert-butanol, which has no beta-hydrogen, isobutene and hydrogen were observed as main desorption products. copyright 2002 American Vacuum Society.

  3. C-O cleavage of aromatic oxygenates over ruthenium catalysts. A computational study of reactions at step sites.

    PubMed

    Chiu, Cheng-chau; Genest, Alexander; Borgna, Armando; Rösch, Notker

    2015-06-21

    We studied the C-O cleavage of phenolate and catecholate at step sites of a Ru catalyst using periodic DFT methods at the GGA level. Both C-O scission steps are associated with activation barriers of about 75 kJ mol(-1), hence are significantly more facile than the analogous reactions on Ru terraces. With these computational results, we offer an interpretation of recent experiments on the hydrodeoxygenation of guaiacol (2-methoxyphenol) over Ru/C. We hypothesize that the experimentally observed dependency of the product selectivity on the H2 pressure is related to the availability of step sites on a Ru catalyst.

  4. Vacuum thermal degradation of poly(ethylene oxide).

    PubMed

    Choukourov, Andrei; Grinevich, Andrey; Polonskyi, Oleksandr; Hanus, Jan; Kousal, Jaroslav; Slavinska, Danka; Biederman, Hynek

    2009-03-12

    Thermal degradation of poly(ethylene oxide) (PEO) was studied under vacuum conditions. PEO macromolecules degrade predominantly by random chain scission of a backbone with elimination of oligomer fragments. The reactions include the mechanism of radical termination by disproportionation. The eliminated fragments form thin film deposits which have chemical composition close to the original PEO. Activation of the evaporated flux with a glow discharge leads to further fragmentation and recombination of the released species and can be used to tune the properties of the resulting thin films. PMID:19708261

  5. Reactivity of aminophosphonic acids. Oxidative dephosphonylation of 1-aminoalkylphosphonic acids by aqueous halogens.

    PubMed

    Drabowicz, Józef; Jordan, Frank; Kudzin, Marcin H; Kudzin, Zbigniew H; Stevens, Christian V; Urbaniak, Paweł

    2016-02-01

    The reactions of 1-aminoalkylphosphonic acids with bromine-water, chlorine-water and iodine-water were investigated. The formation of phosphoric(v) acid, as a result of a halogen-promoted cleavage of the Cα-P bond, accompanied by nitrogen release, was observed. The dephosphonylation of 1-aminoalkylphosphonic acids was found to occur quantitatively. In the reactions of 1-aminoalkylphosphonic acids with other halogen-water reagents investigated by (31)P NMR, scission of the Cα-P bond was also observed, the reaction rates being comparable for bromine and chlorine, but much slower for iodine.

  6. Between complexity of modelling and modelling of complexity: An essay on econophysics

    NASA Astrophysics Data System (ADS)

    Schinckus, C.

    2013-09-01

    Econophysics is an emerging field dealing with complex systems and emergent properties. A deeper analysis of themes studied by econophysicists shows that research conducted in this field can be decomposed into two different computational approaches: “statistical econophysics” and “agent-based econophysics”. This methodological scission complicates the definition of the complexity used in econophysics. Therefore, this article aims to clarify what kind of emergences and complexities we can find in econophysics in order to better understand, on one hand, the current scientific modes of reasoning this new field provides; and on the other hand, the future methodological evolution of the field.

  7. Study of asymmetric fission yield behavior from neutron-deficient Hg isotope

    SciTech Connect

    Perkasa, Y. S.; Waris, A. Kurniadi, R. Su'ud, Z.

    2014-09-30

    A study of asymmetric fission yield behavior from a neutron-deficient Hg isotope has been conducted. The fission yield calculation of the neutron-deficient Hg isotope using Brownian Metropolis shape had showed unusual result at decreasing energy. In this paper, this interesting feature will be validated by using nine degree of scission shapes parameterization from Brosa model that had been implemented in TALYS nuclear reaction code. This validation is intended to show agreement between both model and the experiment result. The expected result from these models considered to be different due to dynamical properties that implemented in both models.

  8. The ubiquitous hammerhead ribozyme

    PubMed Central

    Hammann, Christian; Luptak, Andrej; Perreault, Jonathan; de la Peña, Marcos

    2012-01-01

    The hammerhead ribozyme is a small catalytic RNA motif capable of endonucleolytic (self-) cleavage. It is composed of a catalytic core of conserved nucleotides flanked by three helices, two of which form essential tertiary interactions for fast self-scission under physiological conditions. Originally discovered in subviral plant pathogens, its presence in several eukaryotic genomes has been reported since. More recently, this catalytic RNA motif has been shown to reside in a large number of genomes. We review the different approaches in discovering these new hammerhead ribozyme sequences and discuss possible biological functions of the genomic motifs. PMID:22454536

  9. Mutagenicity of the nuclease activity of 1,10-phenanthroline-copper ion

    SciTech Connect

    Feig, A.L.; Thederahn, T.; Sigman, D.S.

    1988-08-30

    The nuclease activity of 1,10-phenanthroline-copper functions intracellularly. This was shown by its mutagenicity in the Ames Test using the tester strain TA 102 and the in vivo nicking of plasmids derived from this strain. In vivo DNA strand scission requires all the components essential for the in vitro activity: 1,10-phenanthroline, cupric ion, thiol and hydrogen peroxide. Although /sup 60/Co gamma radiation potentiates the nuclease activity of 1,10-phenanthroline-copper ion in vitro via a superoxide dependent pathway, it does not promote significant mutagenesis in vivo at exposure levels below cytotoxicity.

  10. First Principles Simulations of Hydrocarbon Conversion Processes in Functionalized Zeolitic Materials

    NASA Astrophysics Data System (ADS)

    Mazar, Mark Nickolaus

    is responsible for the largest activation energy of the catalytic cycle. This assessment is similar to the findings of alkane metathesis studies on alumina/silica supports and indicates that the entire AM cycle can be performed in zeolites by isolated single-atom transition metal hydrides. Performed over acid form zeolites, MTH is used in the conversion of methanol into a broad range of hydrocarbons, including alkenes, alkanes, and aromatics. For reasons that are not yet rigorously quantified, product selectivities vary dramatically based on the choice of catalyst and reaction conditions. The methylation of species containing double bonds (i.e., co-catalysts) is central to the overall process. Distinct structure-function relationships were found with respect to the elementary steps in the methylation and beta-scission of olefins. In Chapter 4, the role of zeolite topology in the step-wise methylation of ethene by surface methoxides is investigated. Elementary steps are studied across multiple frameworks (i.e., BEA, CHA, FER, MFI, and MOR) constituting a wide variety of confinement environments. The reaction of surface methoxides with ethene is found to require a transition state containing a primary carbocation. The barrier height is found to decrease nearly monotonically with respect to the degree of dispersion interactions stabilizing the primary carbocationic species in the transition state. In addition, quantification of the ``local'' dispersion energy indicates that confinement effects can not be simply correlated to pore size. The beta-scission of olefins plays an important role in the product selectivities of many important chemical processes, including MTH. In Chapter 5, beta-scission modes involving C6 and C8 isomers are investigated at a single, isolated Bronsted acid site within H-ZSM-5. We find that the relative enthalpic barriers of beta-scission elementary steps can be rationalized by the substitution order of the two different carbocationic carbon

  11. Interplay between compound and fragments aspects of nuclear fission and heavy-ion reaction

    SciTech Connect

    Moller, Peter; Iwamoto, A; Ichikawa, I

    2010-09-10

    The scission point in nuclear fission plays a special role where one-body system changes to two-body system. Inverse of this situation is realized in heavy-ion fusion reaction where two-body system changes to one body system. Among several peculiar phenomena expected to occur during this change, we focus our attention to the behavior of compound and fragments shell effects. Some aspects of the interplay between compound and fragments shell effect are discussed related to the topics of the fission valleys in the potential energy surface of actinide nuclei and the fusion-like trajectory found in the cold fusion reaction leading to superheavy nuclei.

  12. Colloid Coalescence with Focused X Rays

    SciTech Connect

    Weon, B. M.; Kim, J. T.; Je, J. H.; Yi, J. M.; Wang, S.; Lee, W.-K.

    2011-07-01

    We show direct evidence that focused x rays enable us to merge polymer colloidal particles at room temperature. This phenomenon is ascribed to the photochemical scission of colloids with x rays, reducing the molecular weight, glass transition temperature, surface tension, and viscosity of colloids. The observation of the neck bridge growth with time shows that the x-ray-induced colloid coalescence is analogous to viscoelastic coalescence. This finding suggests a feasible protocol of photonic nanofabrication by sintering or welding of polymers, without thermal damage, using x-ray photonics.

  13. Free Volume Related Fluorescence Properties of Electron Irradiated Chalcone Doped PMMA Films

    SciTech Connect

    Ravindrachary, Ismayil V.; Bhajantri, R. F.; Harisha, A.; Praveena, S. D.

    2011-07-15

    Effect of electron irradiation on free volume related fluorescence properties of chalcone doped Poly(methyl methacrylate)(PMMA) composite films have been studied using Positron Annihilation and Fluorescence spectroscopic techniques. In this polymer composite, enhancement of fluorescence at lower doses and reduction at higher doses has been observed under electron irradiation. From Positron annihilation studies suggests that at lower doses of irradiation induced crosslinking which affect the free volume properties and inturn hinders the chalcone molecular rotation. At higher doses chain scission process affect matrix relaxation. Under the restricted condition the chromophore molecules likely to emit enhanced fluorescence and its mobility is directly related to the free volume around it.

  14. Energy dependence of mass, charge, isotopic, and energy distributions in neutron-induced fission of 235U and 239Pu

    NASA Astrophysics Data System (ADS)

    Pasca, H.; Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.; Kim, Y.

    2016-05-01

    The mass, charge, isotopic, and kinetic-energy distributions of fission fragments are studied within an improved scission-point statistical model in the reactions 235U+n and 239Pu+n at different energies of the incident neutron. The charge and mass distributions of the electromagnetic- and neutron-induced fission of 214,218Ra, 230,232,238U are also shown. The available experimental data are well reproduced and the energy-dependencies of the observable characteristics of fission are predicted for future experiments.

  15. The effects of metals and inhibitors on thermal oxidative degradation reactions of unbranched perfluoroalkylethers

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Paciorek, K. J. L.; Harris, D. H. L.; Smythe, M. E.; Kratzer, R. H.

    1983-01-01

    Thermal oxidative degradation studies were performed on unbranched perfluoroalkylethers at 288 C in oxygen. Metals and alloys studied included Ti, Al, and Ti (4 Al, 4 Mn). The mechanism of degradation was by chain scission. Ti and Al promoted less degradation than Ti (4 Al, 4 Mn). The two inhibitors investigated (a perfluorophenyl phosphine and a phosphatriazine) reduced degradation rates by several orders of magnitude. Both inhibitors were effective for the same duration (75 to 100 hours). The phosphatriazine appeared to provide more surface protection.

  16. Resynchronization in neuronal network divided by femtosecond laser processing.

    PubMed

    Hosokawa, Chie; Kudoh, Suguru N; Kiyohara, Ai; Taguchi, Takahisa

    2008-05-01

    We demonstrated scission of a living neuronal network on multielectrode arrays (MEAs) using a focused femtosecond laser and evaluated the resynchronization of spontaneous electrical activity within the network. By an irradiation of femtosecond laser into hippocampal neurons cultured on a multielectrode array dish, neurites were cut at the focal point. After the irradiation, synchronization of neuronal activity within the network drastically decreased over the divided area, indicating diminished functional connections between neurons. Cross-correlation analysis revealed that spontaneous activity between the divided areas gradually resynchronized within 10 days. These findings indicate that hippocampal neurons have the potential to regenerate functional connections and to reconstruct a network by self-assembly. PMID:18418255

  17. Atomistic mechanisms of moisture-induced fracture at copper-silica interfaces

    NASA Astrophysics Data System (ADS)

    Vijayashankar, Dandapani; Zhu, Hong; Garg, Saurabh; Teki, Ranganath; Ramprasad, R.; Lane, Michael W.; Ramanath, Ganpati

    2011-09-01

    Tailoring the chemo-mechanical properties of metal-dielectric interfaces is crucial for many applications including nanodevice wiring, packaging, composites, and catalysis. Here, we combine moisture-induced fracture tests, electron spectroscopy, and density functional theory calculations to reveal fracture toughness partitioning and atomistic delamination mechanisms at copper-silica interfaces. Copper plasticity is supported above a threshold work of adhesion and delamination occurs by moisture-induced Cu-O bond scission in Cu-O-Si bridges. These results provide insights into the effects of the nature of metal-oxygen bonding on moisture-induced delamination of metal-dielectric interfaces.

  18. Kinetics of oxidation of vanadium(IV) by alkyl hydroperoxides in acidic, aqueous solution

    SciTech Connect

    Ma, Rong; Bakac, A.; Espenson, J.H. )

    1992-05-13

    The title reactions produce VO[sub 2][sup +] and products derived from [beta]-scission of alkoxy radicals, largely acetone, ethane, and methane (tert-butyl hydroperoxide) or ethane, ethylene, and n-butane (tert-amyl hydroperoxide). The minor amounts of methane from the first reaction and the excess amount of ethane from the second suggest a small contribution from the oxidation of VO[sup 2+] by [sm bullet]CH[sub 3] and [sm bullet]C[sub 2]H[sub 5], respectively. The kinetic dependence of the main reaction upon [H[sup +

  19. Report on ASC project degradation of organic materials.

    SciTech Connect

    Thompson, Aidan Patrick; Curro, John G.; Rottach, Dana R.; Grest, Gary Stephen; Lo, Chi S; Budzien, Joanne L.

    2006-09-01

    Using molecular dynamics simulations, a constitutive model for the chemical aging of polymer networks was developed. This model incorporates the effects on the stress from the chemical crosslinks and the physical entanglements. The independent network hypothesis has been modified to account for the stress transfer between networks due to crosslinking and scission in strained states. This model was implemented in the finite element code Adagio and validated through comparison with experiment. Stress relaxation data was used to deduce crosslinking history and the resulting history was used to predict permanent set. The permanent set predictions agree quantitatively with experiment.

  20. Constitutive modeling of Radiation effects on the Permanent Set in a silicone elastomer

    SciTech Connect

    Maiti, A; Gee, R; Weisgraber, T; Chinn, S; Maxwell, R

    2008-03-10

    When a networked polymeric composite under high stress is subjected to irradiation, the resulting chemical changes like chain scissioning and cross-link formation can lead to permanent set and altered elastic modulus. Using a commercial silicone elastomer as a specific example we show that a simple 2-stage Tobolsky model in conjunction with Fricker's stress-transfer function can quantitatively reproduce all experimental data as a function of radiation dosage and the static strain at which radiation is turned on, including permanent set, stress-strain response, and net cross-linking density.

  1. Cluster aspects of binary fission

    NASA Astrophysics Data System (ADS)

    Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.

    2013-04-01

    With the improved scission-point model the mass distributions are calculated for induced fission of different Hg isotopes with even mass numbers A =180, 184, 188, 192, 196, 198. The calculated mass distribution and mean total kinetic energy of fission fragments are in a good agreement with the existing experimental data. The change in the shape of the mass distribution from asymmetric to more symmetric is revealed with increasing A of the fissioning AHg nucleus, and the reactions are proposed to verify this prediction experimentally.

  2. Radiation resistance of electro-optic polymer-based modulators

    SciTech Connect

    Taylor, Edward W.; Nichter, James E.; Nash, Fazio D.; Haas, Franz; Szep, Attila A.; Michalak, Richard J.; Flusche, Brian M.; Cook, Paul R.; McEwen, Tom A.; McKeon, Brian F.; Payson, Paul M.; Brost, George A.; Pirich, Andrew R.; Castaneda, Carlos; Tsap, Boris; Fetterman, Harold R.

    2005-05-16

    Mach-Zehnder interferometric electro-optic polymer modulators composed of highly nonlinear phenyltetraene bridge-type chromophores within an amorphous polycarbonate host matrix were investigated for their resistance to gamma rays and 25.6 MeV protons. No device failures were observed and the majority of irradiated modulators exhibited decreases in half-wave voltage and optical insertion losses compared to nonirradiated control samples undergoing aging processes. Irradiated device responses were attributed to scission, cross-linking, and free volume processes. The data suggests that strongly poled devices are less likely to de-pole under the influence of ionizing radiation.

  3. Catalytic Ring-Opening of Cyclic Alcohols Enabled by PCET Activation of Strong O-H Bonds.

    PubMed

    Yayla, Hatice G; Wang, Huaiju; Tarantino, Kyle T; Orbe, Hudson S; Knowles, Robert R

    2016-08-31

    We report a new photocatalytic protocol for the redox-neutral isomerization of cyclic alcohols to linear ketones via C-C bond scission. Mechanistic studies demonstrate that key alkoxy radical intermediates in this reaction are generated via the direct homolytic activation of alcohol O-H bonds in an unusual intramolecular PCET process, wherein the electron travels to a proximal radical cation in concert with proton transfer to a weak Brønsted base. Effective bond strength considerations are shown to accurately forecast the feasibility of alkoxy radical generation with a given oxidant/base pair. PMID:27515494

  4. Integral Equation Theory for the Conformation of Polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Shew, C.-Y.; Yethiraj, A.

    1996-03-01

    The equilibrium conformation properties of polyelectrolyes are explored using the integral equation theory. The polymer molecules are modeled as freely-jointed beads that interact via a hard sphere plus screened Coulomb potential. To obtain the intramolecuar correlation function ( and hence the chain conformations) the many chain system is replaced by a single chain whose beads interact via the bare interaction plus a solvent-induced potential, which approximately accounts for the presence of the other molecules. Since this solvent induced potential is a functional of the intramolecular correlations it is obtained iteratively in a self-consistent fashion. The intramolecular correlation functions for a given solvation potential are obtained via Monte Carlo simulation of a single chain. A thread model of the polymer molecules is also investigated, in which case the single chain conformations are obtained using a variational method. The predictions of the theory for these two models are similar. For single chains ~ N^2 ( is the mean square end-to-end distance and N is the degree of polymerization) in salt free solutions, and ~ N^1.2 in high salt solutions. At high polymer concentration ~ N. The theory provides a means of interpolating between these limiting cases. An interesting feature is that there is a very sharp drop in polymer size at very low concentrations which happens because the overlap threshold concentration in polyelectrolytes solutions is very small.

  5. Thermal stability of poly(ethylene-co-vinyl acetate) based materials

    DOE PAGESBeta

    Patel, Mogon; Pitts, Simon; Beavis, Peter; Robinson, Mathew; Morrell, Paul; Khan, Niaz; Khan, Imran; Pockett, Nicola; Letant, Sonia; Von White, Gregory; et al

    2013-03-26

    The thermal stability properties of poly (ethylene-co-vinyl acetate) composites have been studied in support of our core programmes in materials qualification and life assessment. The material is used as a binder phase for boron particles in highly filled (70 wt %) composites. Our studies show that the uncured resin readily accumulates acetic acid through hydrolysis of the pendent acetate groups which alters the acidity (pH) of the material. Thermal desorption studies in combination with gas-chromatography-mass spectrometry show that the resin readily evolves acetic acid when thermally aged to temperatures up to 75°C. Gel Permeation Chromatography (GPC) suggests that thermal ageingmore » induces a gradual reduction in resin molecular weight and confirms the susceptibility of the material to chain scission. Heating at elevated temperatures in excess of 300oC is required to induce significant changes in the carbon skeleton through deacetylation and dehydration processes and the production of unsaturated main chain double bonds. Overall, the mechanical response of these filled composites are found to be relatively complex with the extent of polymer-filler interactions possibly playing an important role in determining key engineering properties. Mechanical property studies confirm a small but significant decrease in modulus presumably linked to thermally induced chain scission of the EVA binder.« less

  6. Investigations into crazing in glassy amorphous polymers through molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Venkatesan, Sudarkodi; Basu, Sumit

    2015-04-01

    In many glassy amorphous polymers, localisation of deformation during loading leads to crazes. Crazes are crack like features whose faces are bridged either by fibrils or a cellular network of voids and fibrils. While formation of crazes is aided by the presence of surface imperfections and embedded dust particles, in this work, we focus on intrinsic crazes that form spontaneously in the volume of the material. We perform carefully designed molecular dynamics simulations on well equilibrated samples of a model polymer with a view to gaining insights into certain incompletely understood aspects of the crazing process. These include genesis of the early nanovoids leading to craze nucleation, mechanisms of stabilising the cellular or fibrillar structure and the competition between chain scission and chain disentanglement in causing the final breakdown of the craze. Additionally, we identify and enumerate clusters of entanglement points with high functionality as effective topological constraints on macromolecular chains. We show that regions with low density of entanglement clusters serve as sites for nanovoid nucleation under high mean stress. Growth occurs by the repeated triggering of cavitation instabilities above a growing void. The growth of the void is aided by disentanglement in and flow of entanglements away from the cavitating region. Finally, for the chain lengths chosen, scission serves to supply short chains to the growing craze but breakdown occurs by complete disentanglement of the chains. In fact, most of the energy supplied to the material seems to be used in causing disentanglements and very little energy is required to create a stable fibril.

  7. Transfer-induced fission in inverse kinematics: Impact on experimental and evaluated nuclear data bases

    NASA Astrophysics Data System (ADS)

    Farget, F.; Caamaño, M.; Ramos, D.; Rodrıguez-Tajes, C.; Schmidt, K.-H.; Audouin, L.; Benlliure, J.; Casarejos, E.; Clément, E.; Cortina, D.; Delaune, O.; Derkx, X.; Dijon, A.; Doré, D.; Fernández-Domınguez, B.; Gaudefroy, L.; Golabek, C.; Heinz, A.; Jurado, B.; Lemasson, A.; Paradela, C.; Roger, T.; Salsac, M. D.; Schmitt, C.

    2015-12-01

    Inverse kinematics is a new tool to study nuclear fission. Its main advantage is the possibility to measure with an unmatched resolution the atomic number of fission fragments, leading to new observables in the properties of fission-fragment distributions. In addition to the resolution improvement, the study of fission based on nuclear collisions in inverse kinematics beneficiates from a larger view with respect to the neutron-induced fission, as in a single experiment the number of fissioning systems and the excitation energy range are widden. With the use of spectrometers, mass and kinetic-energy distributions may now be investigated as a function of the proton and neutron number sharing. The production of fissioning nuclei in transfer reactions allows studying the isotopic yields of fission fragments as a function of the excitation energy. The higher excitation energy resulting in the fusion reaction leading to the compound nucleus 250Cf at an excitation energy of 45MeV is also presented. With the use of inverse kinematics, the charge polarisation of fragments at scission is now revealed with high precision, and it is shown that it cannot be neglected, even at higher excitation energies. In addition, the kinematical properties of the fragments inform on the deformation configuration at scission.

  8. In vitro evolution of preferred topoisomerase II DNA cleavage sites.

    PubMed

    Burden, D A; Osheroff, N

    1999-02-19

    Topoisomerase II is an essential enzyme that is the target for several clinically important anticancer drugs. Although this enzyme must create transient double-stranded breaks in the genetic material in order to carry out its indispensable DNA strand passage reaction, the factors that underlie its nucleotide cleavage specificity remain an enigma. Therefore, to address the critical issue of enzyme specificity, a modified systematic evolution of ligands by exponential enrichment (SELEX) protocol was employed to select/evolve DNA sequences that were preferentially cleaved by Drosophila melanogaster topoisomerase II. Levels of DNA scission rose substantially (from 3 to 20%) over 20 rounds of SELEX. In vitro selection/evolution converged on an alternating purine/pyrmidine sequence that was highly AT-rich (TATATATACATATATATA). The preference for this sequence was more pronounced for Drosophila topoisomerase II over other species and was increased in the presence of DNA cleavage-enhancing anticancer drugs. Enhanced cleavage appeared to be based on higher rates of DNA scission rather than increased binding affinity or decreased religation rates. The preferred sequence for topoisomerase II-mediated DNA cleavage is dramatically overrepresented ( approximately 10,000-fold) in the euchromatic genome of D. melanogaster, implying that it may be a site for the physiological action of this enzyme.

  9. Heme-thiolate ferryl of aromatic peroxygenase is basic and reactive

    PubMed Central

    Wang, Xiaoshi; Ullrich, René; Hofrichter, Martin; Groves, John T.

    2015-01-01

    A kinetic and spectroscopic characterization of the ferryl intermediate (APO-II) from APO, the heme-thiolate peroxygenase from Agrocybe aegerita, is described. APO-II was generated by reaction of the ferric enzyme with metachloroperoxybenzoic acid in the presence of nitroxyl radicals and detected with the use of rapid-mixing stopped-flow UV-visible (UV-vis) spectroscopy. The nitroxyl radicals served as selective reductants of APO-I, reacting only slowly with APO-II. APO-II displayed a split Soret UV-vis spectrum (370 nm and 428 nm) characteristic of thiolate ligation. Rapid-mixing, pH-jump spectrophotometry revealed a basic pKa of 10.0 for the FeIV−O−H of APO-II, indicating that APO-II is protonated under typical turnover conditions. Kinetic characterization showed that APO-II is unusually reactive toward a panel of benzylic C−H and phenolic substrates, with second-order rate constants for C−H and O−H bond scission in the range of 10–107 M−1⋅s−1. Our results demonstrate the important role of the axial cysteine ligand in increasing the proton affinity of the ferryl oxygen of APO intermediates, thus providing additional driving force for C−H and O−H bond scission. PMID:25759437

  10. Influence of ionizing radiation on physical properties of native and chemically modified starches

    NASA Astrophysics Data System (ADS)

    Henry, F.; Costa, L. C.; Aymes-Chodur, C.

    2010-01-01

    Cationic and anionic starches (chemically modified) and native starch (non-modified) were exposed to electron-beam irradiation at doses of 25, 75 and 150 kGy. The increasing solubility in water, due to chain scission and creation of polar groups as already mentioned in the literature, has been confirmed using several physical methodologies. Impedance Spectroscopy (IS) on water solutions was carried out in order to calculate the relaxation parameters of the Cole-Cole model and α and β parameters of the Jones-Dole equation, which show the influence of radiation dose on increasing polarity, decreasing of molecular mass and increasing of electrostatic attraction between chains. Infra-red spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC) confirm the formation of polar groups that retain water. The aim of this work was to confirm that the control of chain scission and functionalization of starches with irradiation could then be used in a future work to create nanoparticles by complex coacervation in an aqueous base.

  11. Elastic yielding after γ-irradiation of cold-drawn polymer glasses

    NASA Astrophysics Data System (ADS)

    Lin, Panpan; Xu, Quan; Joy, Abraham; Wang, Shi-Qing

    Elastic yielding shows up when a considerable retractive stress rises from a piece of cold-drawn polymer glass during annealing at temperatures above storage temperature .............. This phenomenon indicates significant chain tension built up during cold drawing. To explore the role of chain networking, we applied γ-irradiation to produce chain scission and cause partial breakdown of the chain network in the pre-necked polymer glasses. To demonstrate universality, four different glasses, i.e., polycarbonate (PC), polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(2,6-dimethyl-1,4-phenylene oxide) (PPE) were first subjected to uniaxial extension at room temperature before the irradiation. Our data shows that the retractive stress significantly decreases in magnitude with increasing dosage of the γ-irradiation. The diminishing elastic yielding effect may be due to the loss of chain tension by chain scission brought about by the irradiation. This work is support, in part, by ACS-PRF (54047-ND7).

  12. INTERACTION OF BENZO(A)PYRENE DIOL EPOXIDE WITH SVAO MINICHROMOSOMES

    SciTech Connect

    Gamper, Howard B.; Yokota, Hisao A.; Bartholomew, James C.

    1980-03-01

    SV40 minichromosomes were reacted with (+)7{beta},8{alpha}-dihydroxy-9{alpha},10{alpha}-epoxy- 7,8,9,10-tetrahydrobenzo[a]pyrene (BaP diol epoxide). Low levels of modification (< 5 DNA adducts/minichromosome) did not detectably alter the structure of the minichromosomes but high levels (> 200 DNA adducts/minichromosome) led to extensive fragmentation. Relative to naked SV40 DNA BaP diol epoxide induced alkylation and strand scission of minichromosomal DNA was reduced or enhanced by factors of 1.5 and 2.0, respectively. The reduction in covalent binding was attributed to the presence of histones, which competed with DNA for the hydrocarbon and reduced the probability of BaP diol epoxide intercalation by tightening the helix. The enhancement of strand scission was probably due to the catalytic effect of histones on the rate of S-elimination at apurinic sites, although an altered adduct profile or the presence of a repair endonuclease were not excluded. Staphylococcal nuclease digestion indicated that BaP dial epoxide randomly alkylated the minichromosomal DNA. This is in contrast to studies with cellular chromatin where internucleosomal DNA was preferentially modified. Differences in the minichromosomal protein complement were responsible for this altered susceptibility.

  13. Silane cross-linkable ethylene-propylene elastomer compositions prepared by reactive processing

    NASA Astrophysics Data System (ADS)

    Kozawa, Eiji; Nakajima, Yasuo; Kim, Jae Kyung

    2015-05-01

    Thermoplastic Elastomers (TPEs) have received attention as the alternative materials of EPDM due to an advantage for mass production. In recent years, by the progress of polymerization technology, Ethylene-propylene Elastomer (EP), one of the TPEs, is beginning to be applied to many products because of its good properties as rubber. However, as much as a complete replacement for EPDM, it is not provided with sufficient properties. In such circumstance, we found that EP's performance properties can be further enhanced via chemical modification such as cross-linking. The advent of a newer technique, involving the grafting of organo-functional silane onto the polymer chain in the reaction extrusion process is more attractive due to various industrial advantages. Although the functionalization of the EP by silane grafting through reactive processing is very useful, the silane grafting process of EP has a difficulty. It is most likely a consequence of the nature of the PP chain scission (β-scission), which is the dominant reaction in PP when subjected to free radicals at elevated temperature during processing. Therefore, the objective of our current work is to investigate a reactive extrusion process for the silane cross-linkable EP while minimizing the degradation, as well as evaluate the properties of the modified polymer.

  14. The potential of diffuse reflectance FTIR spectroscopy in the examination of small chemical changes in polyethylene and dry foods

    NASA Astrophysics Data System (ADS)

    Hrebičik, M.; Suchánek, M.; Volka, K.; Novák, P.; Scotter, C. N. G.

    1995-03-01

    Irradiation of some materials by low doses of gamma radiation, as a mean of disinfection or sterilization, has been increasingly used in the last few years. Food is usually irradiated with an absorbed dose up to 10 kGy; higher absorbed doses (25 kGy) are required for sterilization (the quantity of the absorbed dose is defined as the mean energy imparted by ionizing radiation to the matter in a volume element divided by the mass of the matter in that volume element. The unit gray (Gy) is defined as: 1 Gy = 1 J/kg = 100 rd = 6.24 × 10 18eV/kg). This paper addresses what chemical changes are caused by these doses and which method is most suitable for their monitoring. These questions are not only of interest to chemists but also to state organizations allowing or prohibiting this means of disinfection. The major chemical changes that are caused in polymers by ionizing radiation are [1]: simultaneous scission and cross-linking of the polymeric chains, formation of gases and low molecular weight radiolysis products and formation of unsaturated bonds. In the presence of oxygen, there is additional oxidative chain scission, and oxidation of the polymer, leading to the formation of peroxide, alcohol, and carbonyl functions, and of CO, CO 2, and various oxygen-containing low molecular weight compounds. Free radicals created by irradiation may remain trapped in the polymer and cause post-irradiation "aging".

  15. A theoretical study on the complete dehydrogenation of methanol on Pd (100) surface

    NASA Astrophysics Data System (ADS)

    Jiang, Zhao; Wang, Bin; Fang, Tao

    2016-02-01

    Density functional theory (DFT) method was employed to investigate the adsorption and decomposition mechanisms of CH3OH on Pd (100) surface. Different kinds of possible adsorption modes of relevant intermediates on the surface were identified. It was found that CH3OH and CH2OH prefers to adsorb on the top site, CH3O, CHOH and CO occupy preferentially on the bridge site, while CH2O, CHO, COH and H species adsorb on the hollow site. The adsorption energies of all species exhibit the following trend: CH3OH < CH2O < CH3O < CO < CH2OH < H < CHO < CHOH < COH. Subsequently, four possible dissociation pathways of CH3OH via initial Osbnd H and Csbnd H bond scissions were proposed and studied systematically. The transition states, energy barriers and reaction energies were calculated to explore the dehydrogenation mechanisms of CH3OH on Pd (100) surface. It was indicated that the scission of Csbnd H bond is more favorable for CH3OH and CH2OH and the Hsbnd O bond cleavage is easier for CHOH. The path 2 (CH3OHsbnd CH2OHsbnd CHOHsbnd CHOsbnd CO) is the most possible dehydrogenation pathway, where the highest energy barrier of CH3OH dissociation makes it to be the rate-determining step of the whole dehydrogenation reaction.

  16. Development of Branched Polycarbonate by an Ultrasound-Assisted Melt Mixing Process with Multifunctional Agents

    NASA Astrophysics Data System (ADS)

    Hwang, Tae Yong; Kim, Heejung; Kim, Hyungsu; Lee, Jae Wook

    2008-07-01

    The chain structure of polymer molecules is an important characteristic of polymers. In the polymer industry, in-situ processing during polymerization or a post-processing is applied to alter the chain structure as an attempt to produce polymers with tailored properties. Among various methods to control the chain structure, ultrasound-induced polymer chain scission is a useful route which can either be used as a post-processing step or can be used during ultrasound-induced polymerization. In our previous studies, we intended to induce degradation of polymer melts in a sonicated intensive mixer and extruder. By combining high intensity ultrasound which causes chain scission of polymer molecules and a multifunctional agent (MFA) having double bonds at its ends, we were able to modify the molecular structure of polycarbonate (PC) from linear to branched structure during melt processing. The three double bonds in chain ends of MFA were expected to act as sites for trapping macroradicals of PC during the course of ultrasound-assisted mixing process. The transformation of molecular structure of PC was confirmed by the measurements of rheological properties of the modified PC.

  17. Structural analysis and modeling reveals new mechanisms governing ESCRT-III spiral filament assembly.

    PubMed

    Shen, Qing-Tao; Schuh, Amber L; Zheng, Yuqing; Quinney, Kyle; Wang, Lei; Hanna, Michael; Mitchell, Julie C; Otegui, Marisa S; Ahlquist, Paul; Cui, Qiang; Audhya, Anjon

    2014-09-15

    The scission of biological membranes is facilitated by a variety of protein complexes that bind and manipulate lipid bilayers. ESCRT-III (endosomal sorting complex required for transport III) filaments mediate membrane scission during the ostensibly disparate processes of multivesicular endosome biogenesis, cytokinesis, and retroviral budding. However, mechanisms by which ESCRT-III subunits assemble into a polymer remain unknown. Using cryogenic electron microscopy (cryo-EM), we found that the full-length ESCRT-III subunit Vps32/CHMP4B spontaneously forms single-stranded spiral filaments. The resolution afforded by two-dimensional cryo-EM combined with molecular dynamics simulations revealed that individual Vps32/CHMP4B monomers within a filament are flexible and able to accommodate a range of bending angles. In contrast, the interface between monomers is stable and refractory to changes in conformation. We additionally found that the carboxyl terminus of Vps32/CHMP4B plays a key role in restricting the lateral association of filaments. Our findings highlight new mechanisms by which ESCRT-III filaments assemble to generate a unique polymer capable of membrane remodeling in multiple cellular contexts. PMID:25202029

  18. Mechanism of dissipation in heavy-ion reactions

    SciTech Connect

    Nix, J.R.; Sierk, A.J.

    1987-01-01

    We discuss a new surface-plus-window mechanism for the conversion of nuclear collective energy into internal degrees of freedom at intermediate excitation energies. This novel dissipation mechanism, which results from the long mean free path of nucleons inside a nucleus, involves interactions of either one or two nucleons with the moving nuclear surface and also, for dumbbell-like shapes encountered in heavy-ion reactions and fission, the transfer of nucleons through the window separating the two portions of the system. To illustrate the effect of surface-plus-window dissipation on heavy-ion-fusion reactions we present dynamical calculations for values of the dissipation strength corresponding to 27% and 100% of the Swiatecki wall-formula value, as well as for no dissipation. In addition to dynamical thresholds for compound-nucleus formation in heavy-ion reactions, our new picture describes such other phenomena as experimental mean fission-fragment kinetic energies for the fission of nuclei throughout the periodic system, enhancement in neutron emission prior to fission, short scission-to-scission times in sequential ternary fission, widths of mass and charge distributions in deep-inelastic heavy-ion reactions, and widths of isoscalar giant quadrupole and giant octupole resonances. 32 refs., 2 figs.

  19. Structure and function of the ESCRT-II-III interface in multivesicular body biogenesis

    SciTech Connect

    Im, Young Jun; Wollert, Thomas; Boura, Evzen; Hurley, James H.

    2009-09-08

    The ESCRT-II-ESCRT-III interaction coordinates the sorting of ubiquitinated cargo with the budding and scission of intralumenal vesicles into multivesicular bodies. The interacting regions of these complexes were mapped to the second winged helix domain of human ESCRT-II subunit VPS25 and the first helix of ESCRT-III subunit VPS20. The crystal structure of this complex was determined at 2.0 {angstrom} resolution. Residues involved in structural interactions explain the specificity of ESCRT-II for Vps20, and are critical for cargo sorting in vivo. ESCRT-II directly activates ESCRT-III-driven vesicle budding and scission in vitro via these structural interactions. VPS20 and ESCRT-II bind membranes with nanomolar affinity, explaining why binding to ESCRT-II is dispensable for the recruitment of Vps20 to membranes. Docking of the ESCRT-II-VPS202 supercomplex reveals a convex membrane-binding surface, suggesting a hypothesis for negative membrane curvature induction in the nascent intralumenal vesicle.

  20. Fragmentation of molecular adsorbates by electron and ion bombardment: methoxy chemistry on Al(111)

    SciTech Connect

    Basu, P.; Chen, J.G.; Ng, L.; Colaianni, M.L.; Yates, J.T.

    1988-08-15

    High-resolution electron-energy-loss spectroscopy (HR)EELS has been used successfully to provide direct spectroscopic evidence regarding details of the molecular fragmentation of methoxy (CH3O) on Al(lll) caused by energetic electron and ion beams. Chemisorbed methoxy on Al(lll) is produced by heating of absorbed CH3OH. Irradiation of CH3O(a) by either energetic (approx 300 eV) electrons or Ar+ ions results in C-O and C-H bond scission with simultaneous formation of Al-O and Al-C bonds. During electron stimulated desorption the CH3O(a) species undergo sequential fragmentation first to CHx groups that are captured by the surface and in the final decay process to adsorbed carbon. C-O bonds in CH3O9a) are depleted preferentially compared to C-H bonds in CHx(a) species. The electron-induced sequential fragmentation of the patent CH3 group (from methoxy) to resultant CHx(a) occurs with an efficiency approx. 3 orders of magnitude greater than the subsequent process of CHx(a)=C(a). Cross sections for various bond scission processes in electron and ion bombardment have been estimated.

  1. a Viscoelastic Fracture Model for Simulation of Solid Propellant Impacts

    NASA Astrophysics Data System (ADS)

    Matheson, E. R.; Nguyen, D. Q.

    2007-12-01

    A viscoelastic kinetics (VEK) model for deformation and damage in solid rocket propellant has been previously developed and correlated to an extensive set of experiments to determine mechanical properties. Ultimately, VEK will be extended to perform coupled damage and reaction modeling of XDT during propellant impacts. There are two types of damage considered in VEK: 1) decohesion at particle/binder interfaces, and 2) scission of the binder. The first type of damage leads to formation of essentially spherical voids around the decohered particles, and development of a model for the surface area that supports combustion is rather straightforward. The second type of damage leads to formation of propellant rubble, and the fineness depends on the impact stresses. Thus, a kinetic fracture model describing surface area generation due to scission damage has been added to the VEK model. To obtain data on the surface area generated, 25 mm L/D = 1 propellant samples were fired into steel target plates at various velocities, and the resultant fragments were collected and burned in a combustion bomb. The total surface area generated was then estimated for each impacted sample. The upgraded VEK model is used to simulate the 25 mm impact experiments and is correlated to the combustion bomb data.

  2. A Viscoelastic Fracture Model for Simulation of Solid Propellant Impacts

    NASA Astrophysics Data System (ADS)

    Matheson, Erik R.

    2007-06-01

    A viscoelastic kinetics (VEK) model for deformation and damage in solid rocket propellant has been previously developed and correlated to an extensive set of experiments to determine mechanical properties. Ultimately, VEK will be extended to perform coupled damage and reaction modeling of XDT during propellant impacts. There are two types of damage considered in VEK: 1) decohesion at particle/binder interfaces, and 2) scission of the binder. The first type of damage leads to formation of essentially spherical voids around the decohered particles, and development of a model for the surface area that supports combustion is rather straightforward. The second type of damage leads to formation of propellant rubble, and the fineness depends on the impact stresses. Thus, a kinetic fracture model describing surface area generation due to scission damage has been added to the VEK model. To obtain data on the surface area generated, 25 mm L/D=1 propellant samples were fired into steel target plates at various velocities, and the resultant fragments were collected and burned in a combustion bomb. The total surface area generated was then estimated for each impacted sample. The upgraded VEK model is used to simulate the 25 mm impact experiments and is correlated to the combustion bomb data.

  3. Methylamine adsorption and decomposition on B12N12 nanocage: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Esrafili, Mehdi D.; Nurazar, Roghaye

    2014-08-01

    Density functional theory calculations are performed to investigate the adsorption and decomposition of methylamine (CH3NH2) on the surface of a B12N12 fullerene-like nanocage. Two adsorption types and two reaction channels are identified. It is found that the electrical conductivity of the nanocage can be modified upon the adsorption of CH3NH2. The pathways of CH3NH2 decomposition via bond scission of the Csbnd N and Nsbnd H bonds are examined. The results indicate that Nsbnd H bond scission is the most favorable pathway on the B12N12 surface. The side reaction that generates CH3 and NH2 fragments is endothermic by 15.6 kcal/mol with an energy-barrier height of 81.5 kcal/mol. For the CH3NH2 decomposition on the B12N12 surface, the rate-determining step appears to be as the following reaction: CH3NH → CH3N + H.

  4. Characterization of Kevlar 49 fibers by electron paramagnetic resonance. Final report, 20 May 1981-20 June 1982. [Radicals induced by ultraviolet or fracture

    SciTech Connect

    Brown, I.M.; Sandreczki, T.C.

    1982-06-20

    EPR was used to investigate the free radicals created in Kevlar 49 fibers by stress-induced and photo-induced macromolecular chain scissions. Mn/sup +2/ ions were identified from the EPR spectrum of frozen solutions of concentrated sulfuric acid containing Kevlar 49. Other ions present are Cu/sup +2/, and possibly Fe/sup +3/, Cr/sup +3/, and Ti/sup +3/. EPR lineshape anisotropy indicates that some of the metal ions and first coordinate spheres are oriented. The concentration of stress-induced radicals (2 x 10/sup 10/ per filament) suggest that chain scission occurs in more weak planes than are estimated to exist in the fracture surfaces of the fiber core. These radicals are unstable in air and have some aromatic character. Several different types of radicals were obtained following uv irradiations of the Kevlar 49 fibers in vacuum (photodegradative radicals) and in air (photo-oxidative radicals). The photodegradative radicals are identified with primary radicals involved in the photo-Fries rearrangement reaction, secondary radicals formed as a result of a hydrogen atom abstraction by the primary radical, and/or ketyl radicals produced as a result of uv irradiation of the photo-Fries rearrangement product. The photo-oxidative radicals are identified with the uv irradiation products of a peroxide intermediate. Lineshape anisotropy indicates that both radical types are oriented. 31 figures.

  5. The dynamics of polymer bridge formation and disruption and its effect on the bulk rheology of suspensions.

    PubMed

    Bhosale, Prasad S; Berg, John C

    2012-12-11

    Bridge-flocculated colloidal gels are used in many important processes and products such as gel casting for advanced ceramics, precursor inks for 3D printing, and waste treatment strategies. An important aspect of polymer bridged gels that makes them excellent candidates for these applications is the precise control it affords for control of rheological properties. Recent studies have shown that adhesion between bridged surfaces increases with time as the number of polymer bridges formed grows. However, the consequences of the dynamics of these processes toward bulk rheological properties have not been studied. Here we investigate the link between the dynamics of polymer bridging and disruption and bulk rheology in dense colloidal silica particle suspensions flocculated by polyethylene oxide (PEO). Microscale pull-off force measurements using atomic force microscope (AFM) show that upon repeated disruption and establishment of bridged contact, the adhesion between the surfaces is reduced. During contact disruption, the polymer chains bridging the two surfaces are stretched leading to chain scission. On the re-establishment of contact, these fragmented polymer chains are unable to fully re-establish the adhesion. Macroscale measurements using oscillatory rheology show that this reduced adhesion results in reduction of both the storage modulus and the yield stress. If the slurry is subjected to high shear for long periods, polymer chain scission is amplified, and the fragmented polymer chains are unable to bridge the particles again, resulting in free-flowing slurries. PMID:23152979

  6. Thermal stability of poly(ethylene-co-vinyl acetate) based materials

    SciTech Connect

    Patel, Mogon; Pitts, Simon; Beavis, Peter; Robinson, Mathew; Morrell, Paul; Khan, Niaz; Khan, Imran; Pockett, Nicola; Letant, Sonia; Von White, Gregory; Labouriau, Andrea

    2013-03-26

    The thermal stability properties of poly (ethylene-co-vinyl acetate) composites have been studied in support of our core programmes in materials qualification and life assessment. The material is used as a binder phase for boron particles in highly filled (70 wt %) composites. Our studies show that the uncured resin readily accumulates acetic acid through hydrolysis of the pendent acetate groups which alters the acidity (pH) of the material. Thermal desorption studies in combination with gas-chromatography-mass spectrometry show that the resin readily evolves acetic acid when thermally aged to temperatures up to 75°C. Gel Permeation Chromatography (GPC) suggests that thermal ageing induces a gradual reduction in resin molecular weight and confirms the susceptibility of the material to chain scission. Heating at elevated temperatures in excess of 300oC is required to induce significant changes in the carbon skeleton through deacetylation and dehydration processes and the production of unsaturated main chain double bonds. Overall, the mechanical response of these filled composites are found to be relatively complex with the extent of polymer-filler interactions possibly playing an important role in determining key engineering properties. Mechanical property studies confirm a small but significant decrease in modulus presumably linked to thermally induced chain scission of the EVA binder.

  7. Occurence and implications of radiation dose-rate effects for material aging studies

    NASA Astrophysics Data System (ADS)

    Gillen, Kenneth T.; Clough, Roger L.

    A number of commercial cable materials, including ethylene propylene rubber and crosslinked polyolefin insulations and chloroprene and chlorosulfonated polyethylene jackets have been radiation aged in air and nitrogen at radiation dose rates ranging from approximately 10 3 to 10 6{rad}/{hr}. Material degradation was followed using ultimate tensile properties (elongation and tensile strength), swelling measurements and infrared spectroscopy. The tensile results indicate that in air environments radiation dose rate effects are important for all four materials, with more mechanical damage occurring as the dose rate is lowered. These results are interpreted as coming from a competition between crosslinking and oxidative scission in which scission becomes more important as the dose rate is lowered. The swelling results offer direct evidence in support of this interpretation. In addition the infrared results show increased carbonyl content at lower dose rates, also indicative of increased oxidation. The conclusions of this study have important implications for the qualification of elastomeric materials for nuclear applications, since they clearly indicate that the mechanism of degradation is quite different (and the amount usually more severe) under low dose rate exposures compared to the mechanism occurring under the high dose rate exposures normally utilized for stimulating the natural aging.

  8. Stability of Organically Modified Montmorillonites and Their Polystyrene Nanocomposites After Prolonged Thermal Treatment

    SciTech Connect

    Frankowski,D.; Capracotta, M.; Martin, J.; Khan, S.; Spontak, R.

    2007-01-01

    Melt intercalation of montmorillonite (MMT) into polymeric matrices to improve the mechanical properties of polymers has evolved into a subject of tremendous fundamental and technological interest. The thermal treatment experienced during processing or end use can substantially affect the clay and diminish the target properties of polymer/clay nanocomposites (NCs) because of deintercalation or degradation of surface modifiers. In this work, changes in morphology, chemistry, and thermal stability of organically modified (OM) MMT after annealing in O{sub 2}-rich and N{sub 2} environments are investigated. Degradation of the alkyl ammonium cation occurs at temperatures as low as 105 {sup o}C upon prolonged exposure in an O{sub 2}-rich environment. X-ray diffractometry (XRD) performed in situ establishes the response of two OM-MMTs to elevated temperatures at short times, whereas ex situ XRD provides insight into high-temperature exposure at long times. Active sites on the silicate surfaces are found to induce scission of, as well as chemical interaction with, the chains comprising a polystyrene (PS) matrix. Size-exclusion chromatography indicates that PS chain scission occurs primarily after relatively short annealing times, whereas branching and cross-linking are more prevalent after long exposure times in an O{sub 2}-rich environment.

  9. Fundamental Kinetics of Supercritical Coal Liquefaction: Effect of Catalysts and Hydrogen-Donor Solvents.

    SciTech Connect

    McCoy, B.J.; Smith, J.M.

    1997-07-21

    Most research on polymer degradation is for single polymers, even though the thermal decomposition of polymer mixtures is of interest both practically and theoretically. Polymer degradation rates depend on the mixture type, and adding a polymer can increase, decrease, or leave unchanged the degradation rate of the first polymer. We show how distribution-kinetics theory, based on molecular-weight distributions (MWDs), provides expressions for degradation rates of binary polymer mixtures. The approach accounts for initiation, termination, hydrogen abstraction, and radical chain scission in the governing equations for MWDS. Molecular-weight moments yield expressions for molar and mass concentrations and rate coefficients for combinations of random and chain-end scission. Experimental data show the concentration effect of poly((x-methyl styrene)) (PAMS) on the degradation of polystyrene dissolved in mineral oil at 275 {degrees}C in a batch reactor. Samples analyzed by gel permeation chromatography yielded the time evolution of the MD. The results indicated that, owing to the interaction of mixed radicals with polymer by hydrogen abstraction, polystyrene degradation rate decreases with increasing PAMS concentration.

  10. Reactions of allylic radicals that impact molecular weight growth kinetics.

    PubMed

    Wang, Kun; Villano, Stephanie M; Dean, Anthony M

    2015-03-01

    The reactions of allylic radicals have the potential to play a critical role in molecular weight growth (MWG) kinetics during hydrocarbon oxidation and/or pyrolysis. Due to their stability (when compared to alkyl radicals), they can accumulate to relatively high concentrations. Thus, even though the rate coefficients for their various reactions are small, the rates of these reactions may be significant. In this work, we use electronic structure calculations to examine the recombination, addition, and abstraction reactions of allylic radicals. For the recombination reaction of allyl radicals, we assign a high pressure rate rule that is based on experimental data. Once formed, the recombination product can potentially undergo an H-atom abstraction reaction followed by unimolecular cyclization and β-scission reactions. Depending upon the conditions (e.g., higher pressures) these pathways can lead to the formation of stable MWG species. The addition of allylic radicals to olefins can also lead to MWG species formation. Once again, cyclization of the adduct followed by β-scission is an important energy accessible route. Since the recombination and addition reactions produce chemically-activated adducts, we have explored the pressure- and temperature-dependence of the overall rate constants as well as that for the multiple product channels. We describe a strategy for estimating these pressure-dependencies for systems where detailed electronic structure information is not available. We also derive generic rate rules for hydrogen abstraction reactions from olefins and diolefins by methyl and allyl radicals.

  11. Comparative study on catalytic hydrodehalogenation of halogenated aromatic compounds over Pd/C and Raney Ni catalysts

    PubMed Central

    Ma, Xuanxuan; Liu, Sujing; Liu, Ying; Gu, Guodong; Xia, Chuanhai

    2016-01-01

    Catalytic hydrodehalogenation (HDH) has proved to be an efficient approach to dispose halogenated aromatic compounds (HACs). Liquid-phase HDH of single and mixed halobenzenes/4-halophenols with H2 over 5% Pd/C and Raney Ni catalyst are investigated and compared. For liquid-phase HDH of single HACs, hydrogenolytic scission reactivity of C-X bonds decreases in order of C-Br > C-Cl > C-I > C-F over Pd/C catalyst, and in order of C-I > C-Br > C-Cl > C-F over Raney Ni catalyst. To clarify the reason why hydrogenolytic scission reactivity of C-X bonds over Pd/C and Raney Ni catalysts exhibits different trends, liquid-phase HDH of mixed HACs over Pd/C and Raney Ni catalysts were studied, and catalysts are characterized by SEM, EDX, and XRD techniques. It was found that the high adsorption of iodoarenes on Pd/C catalyst caused the HDH reactivity of iodoarenes to be lower than that of chloroarenes and bromoarenes in the HDH of single HACs. Moreover, the adsorption of in situ produced iodine ion (I−) to catalyst surface would result in the decline of catalytic activity, which might be the main reason why the HDH reactivity of HACs in the presence of NaI is rather low. PMID:27113406

  12. Active sites and mechanisms for H2O2 decomposition over Pd catalysts

    PubMed Central

    Plauck, Anthony; Stangland, Eric E.; Dumesic, James A.; Mavrikakis, Manos

    2016-01-01

    A combination of periodic, self-consistent density functional theory (DFT-GGA-PW91) calculations, reaction kinetics experiments on a SiO2-supported Pd catalyst, and mean-field microkinetic modeling are used to probe key aspects of H2O2 decomposition on Pd in the absence of cofeeding H2. We conclude that both Pd(111) and OH-partially covered Pd(100) surfaces represent the nature of the active site for H2O2 decomposition on the supported Pd catalyst reasonably well. Furthermore, all reaction flux in the closed catalytic cycle is predicted to flow through an O–O bond scission step in either H2O2 or OOH, followed by rapid H-transfer steps to produce the H2O and O2 products. The barrier for O–O bond scission is sensitive to Pd surface structure and is concluded to be the central parameter governing H2O2 decomposition activity. PMID:27006504

  13. Germination and microwave processing of barley (Hordeum vulgare L) changes the structural and physicochemical properties of β-d-glucan & enhances its antioxidant potential.

    PubMed

    Ahmad, Mudasir; Gani, Adil; Shah, Asima; Gani, Asir; Masoodi, F A

    2016-11-20

    The nutraceutical potential of β-d-glucan is largely dependent on its structure, size and viscosity. The present study analyzed the effect of germination and microwave processing of barley on the structural, size, antioxidant and thermal characteristics of β-d-glucan. The molecular weight and viscosity of β-d-glucan obtained from germinated barley (GGB) were the lowest (144kDa and 37.33cp) as compared to β-d-glucan from microwave processed barley (GMB) and unprocessed barley (GUB). The GGB exhibited higher antioxidant potential than GMB and GUB. The Structural elucidation by ATR-FTIR revealed scission in polymeric chain and β glycosydic linkage of β-d-glucan obtained from processed barley. The highest peak intensity at glycosydic linkage in GGB confirms more scission in the molecule. The DSC curve of GGB showed the highest transition temperature. It was concluded that germination of barley can be a good approach for enhancing the antioxidant potential of β-d-glucan. PMID:27561541

  14. Coarse-grained molecular dynamics simulations of the tensile behavior of a thermosetting polymer

    NASA Astrophysics Data System (ADS)

    Yang, Shaorui; Qu, Jianmin

    2014-07-01

    Using a previously developed coarse-grained model, we conducted large-scale (˜85×85×85nm3) molecular dynamics simulations of uniaxial-strain deformation to study the tensile behavior of an epoxy molding compound, epoxy phenol novolacs (EPN) bisphenol A (BPA). Under the uniaxial-strain deformation, the material is found to exhibit cavity nucleation and growth, followed by stretching of the ligaments separated by the cavities, until the ultimate failure through ligament scissions. The nucleation sites of cavities are rather random and the subsequent cavity growth accounts for much (87%) of the volumetric change during the uniaxial-strain deformation. Ultimate failure of the materials occurs when the cavity volume fraction reaches ˜60%. During the entire deformation process, polymer strands in the network are continuously extended to their linear states and broken in the postyielding strain hardening stage. When most of the strands are stretched to their taut configurations, rapid scission of a large number of strands occurs within a small strain increment, which eventually leads to fracture. Finally, through extensive numerical simulations of various loading conditions in addition to uniaxial strain, we find that yielding of the EPN-BPA can be described by the pressure-modified von Mises yield criterion.

  15. Mechanism of antioxidant interaction on polymer oxidation by thermal and radiation ageing

    NASA Astrophysics Data System (ADS)

    Seguchi, Tadao; Tamura, Kiyotoshi; Shimada, Akihiko; Sugimoto, Masaki; Kudoh, Hisaaki

    2012-11-01

    The mechanism of polymer oxidation by radiation and thermal ageing was investigated for the life evaluation of cables installed in radiation environments. The antioxidant as a stabilizer was very effective for thermal oxidation with a small content in polymers, but was not effective for radiation oxidation. The ionizing radiation induced the oxidation to result in chain scission even at low temperature, because the free radicals were produced and the antioxidant could not stop the oxidation of radicals with the chain scission. A new mechanism of antioxidant effect for polymer oxidation was proposed. The effect of antioxidant was not the termination of free radicals in polymer chains such as peroxy radicals, but was the depression of initial radical formation in polymer chains by thermal activation. The antioxidant molecule was assumed to delocalize the activated energy in polymer chains by the Boltzmann statics (distribution) to result in decrease in the probability of radical formation at a given temperature. The interaction distance (delocalization volume) by one antioxidant molecule was estimated to be 5-10 nm by the radius of sphere in polymer matrix, though the value would depend on the chemical structure of antioxidant.

  16. gamma-Irradiation of PEGd,lPLA and PEG-PLGA multiblock copolymers. I. Effect of irradiation doses.

    PubMed

    Dorati, R; Colonna, C; Serra, M; Genta, I; Modena, T; Pavanetto, F; Perugini, P; Conti, B

    2008-01-01

    To evaluate the effects of different gamma irradiation doses on PEGd,lPLA and PEG-PLGA multiblock copolymers. The behaviour of the multiblock copolymers to irradiation was compared to that of PLA, PLGA polymers. PEGd,lPLA, PEG-PLGA, PLA and PLGA polymers were irradiated by using a (60)Co irradiation source at 5, 15, 25 and 50 kGy total dose. Characterization was performed on all samples before and after irradiation, by nuclear magnetic resonance (NMR), infrared absorption spectrophotometry (FTIR) and gel permeation chromatography (GPC). The effect of gamma irradiation on polymer stability was also evaluated. Results of NMR and FTIR suggest an increase in -OH and -COOH groups, attributed to scission reactions induced by irradiation treatment. Data of GPC analysis showed that the weight average molecular weight (Mw) of polymer samples decreased with increasing irradiation dose. The extent of Mw degradation expressed as percentage of Mw reduction was more prominent for polymers with high molecular weight as PEGd,lPLA and PLA. The dominant effect of gamma-irradiation on both polymer samples was chain scission. The multiblock copolymer PEGd,lPLA presented higher sensitivity to irradiation treatment with respect to PLA, likely due to the presence of PEG in the matrix. The effect of gamma irradiation continues over a much longer period of time after gamma irradiation has been performed. It is suggested that the material reacts with oxygen to form peroxyl free radicals, which may further undergo degradation reactions during storage after irradiation. PMID:18528761

  17. Kinetics of virus entry by endocytosis

    NASA Astrophysics Data System (ADS)

    Zhdanov, Vladimir P.

    2015-04-01

    Entry of virions into the host cells is either endocytotic or fusogenic. In both cases, it occurs via reversible formation of numerous relatively weak bonds resulting in wrapping of a virion by the host membrane with subsequent membrane rupture or scission. The corresponding kinetic models are customarily focused on the formation of bonds and do not pay attention to the energetics of the whole process, which is crucially dependent, especially in the case of endocytosis, on deformation of actin filaments forming the cytoskeleton of the host cell. The kinetic model of endocytosis, proposed by the author, takes this factor into account and shows that the whole process can be divided into a rapid initial transient stage and a long steady-state stage. The entry occurs during the latter stage and can be described as a first-order reaction. Depending on the details of the dependence of the grand canonical potential on the number of bonds, the entry can be limited either by the interplay of bond formation and membrane rupture (or scission) or by reaching a maximum of this potential.

  18. Effect of gamma radiation on chlorobutyl rubber vulcanized by three different crosslinking systems

    NASA Astrophysics Data System (ADS)

    Scagliusi, Sandra R.; Cardoso, Elisabeth L. C.; Lugao, Ademar B.

    2012-09-01

    The development of halogenated butyl rubber (chlorobutyl) in the 1950s and 1960s greatly extended the usefulness of butyl. Their properties allowed the development of more durable tubeless tires with the air retaining innerliner, chemically bonded to the body of the tire. Tire innerliners are by far the largest application for halobutyl. When polymers are subjected to high energy radiation, a number of chemical reactions may occur following the initial ionization and excitation events. These reactions lead to changes in the molecular weight of the polymer through scission (S) and crosslinking (X) of the molecules and affect the physical and mechanical properties. In the halobutyl rubbers the chain scission may predominate. This work aims to show effects of gamma radiation in properties of chlorobutyl rubbers vulcanized with sulfur, sulfur donor and phenolic resin. The butyl rubber has been already studied by us previously. The samples were characterized before and after irradiation. Gamma radiation doses used were: 25 kGy, 50 kGy, 100 kGy, 150 kGy and 200 kGy, in order to identify which cure system is the most stable under irradiation. In this study we observed that the properties of all samples were affected irrespective of the vulcanization system.

  19. Quantification of radiation induced crosslinking in a commercial, toughened silicone rubber, TR-55, by 1H MQ-NMR

    SciTech Connect

    Maxwell, R; Chinn, S; Alviso, C; Harvey, C A; Giuliani, J; Wilson, T; Cohenour, R

    2008-11-10

    Radiation induced degradation in a commercial, filled silicone composite has been studied by SPME/GC-MS, DMA, DSC, swelling, and Multiple Quantum NMR. Analysis of volatile and semivolatile species indicates degradation via decomposition of the peroxide curing catalyst and radiation induced backbiting reactions. DMA, swelling, and spin-echo NMR analysis indicate a increase in crosslink density of near 100% upon exposure to a cumulative dose of 250 kGray. Analysis of the sol-fraction via Charlseby-Pinner analysis indicates a ratio of chain scission to crosslinking yields of 0.38, consistent with the dominance of the crosslinking observed by DMA, swelling and spin-echo NMR and the chain scissioning reactions observed by MS analysis. Multiple Quantum NMR has revealed a bimodal distribution of residual dipolar couplings near 1 krad/sec and 5 krad/sec in an approximately 90:10 ratio, consistent with bulk network chains and chains associated with the filler surface. Upon exposure to radiation, the mean {Omega}{sub d} for both domains and the width of both domains both increased. The MQ NMR analysis provided increase insight into the effects of ionizing radiation on the network structure of silicone polymers.

  20. Influence of γ-irradiation and temperature on the mechanical properties of EPDM cable insulation

    NASA Astrophysics Data System (ADS)

    Šarac, T.; Quiévy, N.; Gusarov, A.; Konstantinović, M. J.

    2016-08-01

    The mechanical properties of EPDM polymers, degraded as a result of extensive thermal and radiochemical aging treatment, are studied. The focus is given to dose rate effects in polymer insulation materials extracted from industrial cables in use in Belgian nuclear power plants. All studied mechanical characteristics such as the ultimate tensile stress, the Young's modulus, and the total elongation (or elongation at break) are found to be strongly affected by the irradiation dose. The ultimate tensile stress and Young's modulus are clearly exhibiting the dose rate effect, which originated from oxidation mediated interplay of polymer cross-linking and chain scission processes. The change of crossover between these two processes is found to be gradual, without critical dose rate or temperature values. On the contrary, the total elongation is observed not to be sensitive neither to irradiation temperature nor to the dose rate. Both cross-linking and chain scission seem to affect the total elongation in a similar way by reducing the average polymers chain length. This idea is confirmed by the model which shows that all total elongation data as a function of irradiation time can be reproduced by varying a single parameter, the pre-exponential factor of the irradiation rate constant.

  1. Autocatalytic-Assisted Photorelease of a Sensitizer Drug Bound to a Silica Support

    PubMed Central

    Bartusik, Dorota; Minnis, Mihaela; Ghosh, Goutam; Greer, Alexander

    2013-01-01

    The photorelease of a sensitizer from a fluorinated silica surface occurs by a reaction of singlet oxygen with the vinyl ether bond linking with scission of a dioxetane intermediate. Irradiation of the released sensitizer generates singlet oxygen, which accelerates the release of more sensitizer via an autocatalytic reaction. Sigmoidal behavior of sensitizer release in n-butanol and n-octanol occurs at the optimal temperature of 20 °C. The photorelease efficiency was reduced at low temperatures, where the sensitizer was retained on the surface due to a long-lived dioxetane with inefficient scission; and also reduced at high temperatures, due to a slower reaction of 1O2 with the vinyl ether bond. Immediate acceleration is a result of released sensitizer being used as a dopant to eliminate the induction step further implicating an autocatalytic mechanism. However, the sigmoidal sensitizer release was not correlated to solvent viscosity, heat or light from the dioxetane decomposition, or to minor O2 solubility enhancements caused by the fluorinated silica. The mechanistic information collected here can be used to help control the pace of drug release; however, it remains to be seen whether an autocatalytic-based drug delivery system has an advantage to those with non-sigmoidal kinetics. PMID:23899089

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

    SciTech Connect

    Melius, C F; Piqueras, M C

    2001-12-11

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

  3. Germination and microwave processing of barley (Hordeum vulgare L) changes the structural and physicochemical properties of β-d-glucan & enhances its antioxidant potential.

    PubMed

    Ahmad, Mudasir; Gani, Adil; Shah, Asima; Gani, Asir; Masoodi, F A

    2016-11-20

    The nutraceutical potential of β-d-glucan is largely dependent on its structure, size and viscosity. The present study analyzed the effect of germination and microwave processing of barley on the structural, size, antioxidant and thermal characteristics of β-d-glucan. The molecular weight and viscosity of β-d-glucan obtained from germinated barley (GGB) were the lowest (144kDa and 37.33cp) as compared to β-d-glucan from microwave processed barley (GMB) and unprocessed barley (GUB). The GGB exhibited higher antioxidant potential than GMB and GUB. The Structural elucidation by ATR-FTIR revealed scission in polymeric chain and β glycosydic linkage of β-d-glucan obtained from processed barley. The highest peak intensity at glycosydic linkage in GGB confirms more scission in the molecule. The DSC curve of GGB showed the highest transition temperature. It was concluded that germination of barley can be a good approach for enhancing the antioxidant potential of β-d-glucan.

  4. Correlating electronic structure and chemical durability of sulfonated poly(arylene ether sulfone)s

    NASA Astrophysics Data System (ADS)

    Lawrence, Jimmy; Yamashita, Koichi; Yamaguchi, Takeo

    2015-04-01

    Many different proton-conducting polymeric materials have been developed for polymer electrolyte membrane fuel cells (PEMFCs). The development of perfluorosulfonic acid-based, polymer electrolyte membranes (PFSA-PEMs) was followed by aromatic hydrocarbon-based PEMs (HC-PEMs), which allow for tailored design and optimization of their molecular structures. Although many new PFSA-PEMs and HC-PEMs have shown promising proton conductivity and thermal stability, chemical degradation of these materials in an oxidizing environment remains a significant technical barrier in PEMFC development. Here, we used accelerated degradation tests and electronic structure analysis to examine the chemical stability of sulfonated poly(arylene ether sulfone) (SPES) copolymers, a highly thermally stable HC-PEM. HOMO levels, the presence of main chain-protecting steric groups, and HOMO-LUMO location along the main chain have significant effects on the chain scission modes and degradation rate of SPES copolymers. Rational design of HC-PEMs to suppress midpoint scission can open many opportunities in the development of highly robust polymer electrolytes for fuel cell and other energy storage applications.

  5. Neutral and acidic products derived from hydroxyl radical-induced oxidation of arabinotriose assessed by electrospray ionisation mass spectrometry.

    PubMed

    Moreira, Ana S P; da Costa, Elisabete V; Evtuguin, Dmitry V; Coimbra, Manuel A; Nunes, Fernando M; Domingues, M Rosário M

    2014-04-01

    The oxidation of α-(1 → 5)-L-arabinotriose (Ara3), an oligosaccharide structurally related to side chains of coffee arabinogalactans, was studied in reaction with hydroxyl radicals generated under conditions of Fenton reaction (Fe(2+)/H2O2). The acidic and neutral oxidation products were separated by ligand exchange/size-exclusion chromatography, subsequently identified by electrospray ionisation mass spectrometry (ESI-MS) and structurally characterised by tandem MS (ESI-MS/MS). In acidic fraction were identified several oxidation products containing an acidic residue at the corresponding reducing end of Ara3, namely arabinonic acid, and erythronic, glyceric and glycolic acids formed by oxidative scission of the furanose ring. In neutral fractions were identified derivatives containing keto, hydroxy and hydroperoxy moieties, as well as derivatives resulting from the ring scission at the reducing end of Ara3. In both acidic and neutral fractions, beyond the trisaccharide derivatives, the corresponding di- and monosaccharide derivatives were identified indicating the occurrence of oxidative depolymerisation. The structural characterisation of these oxidation products by ESI-MS/MS allowed the differentiation of isobaric and isomeric species of acidic and neutral character. The species identified in this study may help in detection of roasting products associated with the free radical-mediated oxidation of coffee arabinogalactans.

  6. Thermal aging of interfacial polymer chains in ethylene-propylene-diene terpolymer/aluminum hydroxide composites: solid-state NMR study.

    PubMed

    Gabrielle, Brice; Lorthioir, Cédric; Lauprêtre, Françoise

    2011-11-01

    The possible influence of micrometric-size filler particles on the thermo-oxidative degradation behavior of the polymer chains at polymer/filler interfaces is still an open question. In this study, a cross-linked ethylene-propylene-diene (EPDM) terpolymer filled by aluminum trihydrate (ATH) particles is investigated using (1)H solid-state NMR. The time evolution of the EPDM network microstructure under thermal aging at 80 °C is monitored as a function of the exposure time and compared to that of an unfilled EPDM network displaying a similar initial structure. While nearly no variations of the topology are observed on the neat EPDM network over 5 days at 80 °C, a significant amount of chain scission phenomena are evidenced in EPDM/ATH. A specific surface effect induced by ATH on the thermodegradative properties of the polymer chains located in their vicinity is thus pointed out. Close to the filler particles, a higher amount of chain scissions are detected, and the characteristic length scale related to these interfacial regions displaying a significant thermo-oxidation process is determined as a function of the aging time.

  7. Alternatives to chemical amplification for 193nm lithography

    NASA Astrophysics Data System (ADS)

    Baylav, Burak; Zhao, Meng; Yin, Ran; Xie, Peng; Scholz, Chris; Smith, Bruce; Smith, Thomas; Zimmerman, Paul

    2010-04-01

    Research has been conducted to develop alternatives to chemically amplified 193 nm photoresist materials that will be able to achieve the requirements associated with sub-32 nm device technology. New as well as older photoresist design concepts for non-chemically amplified 193 nm photoresists that have the potential to enable improvements in line edge roughness while maintaining adequate sensitivity, base solubility, and dry etch resistance for high volume manufacturing are being explored. The particular platforms that have been explored in this work include dissolution inhibitor photoresist systems, chain scissioning polymers, and photoresist systems based on polymers incorporating formyloxyphenyl functional groups. In studies of two-component acidic polymer/dissolution inhibitor systems, it was found that compositions using ortho-nitrobenzyl cholate (NBC) as the dissolution inhibitor and poly norbornene hexafluoro alcohol (PNBHFA) as the base resin are capable of printing 90 nm dense line/space patterns upon exposure to a 193 nm laser. Studies of chain scission enhancement in methylmethacrylate copolymers showed that incorporating small amounts of absorptive a-cleavage monomers significantly enhanced sensitivity with an acceptable increase in absorbance at 193 nm. Specifically, it was found that adding 3 mol% of α-methyl styrene (α-MS) reduced the dose to clear of PMMA-based resist from 1400 mJ/cm2 to 420 mJ/cm2. Preliminary data are also presented on a direct photoreactive design concept based on the photo-Fries reaction of formyloxyphenyl functional groups in acrylic copolymers.

  8. Hydrolytic degradation and morphologic study of poly-p-dioxanone.

    PubMed

    Lin, H L; Chu, C C; Grubb, D

    1993-02-01

    The in vitro hydrolytic degradation of 2-0 size PDS monofilament suture was studied for the purpose of revealing its morphologic structure and degradation mechanism. The sutures were immersed in phosphate buffer of pH 7.44 for up to 120 days at 37 degrees C. These hydrolyzed sutures were examined by the changes in tensile properties, weight, thermal properties, x-ray diffraction structure, surface morphology, and dye diffusion phenomena. It was found that hydrolysis had significant effects on the change of PDS fiber morphology and properties. Hydrolysis, however, had no significant effect on overall molecular orientation of the fiber until the very late stage. PDS suture fibers retained their skeleton throughout the earlier periods of hydrolysis concurrent with mass and tensile strength losses. PDS sutures exhibited an absorption delay of 120 days. Both heat of fusion and melting point exhibited a maximum function of hydrolysis time. Hydrolysis of PDS suture fibers proceeded through two stages: random scission of chain segments located in the amorphous regions of microfibrils and intermicrofibrillar space, followed by stepwise scission of chain segments located in the crystalline regions of microfibrils. Dye diffusion data showed that the passage along the longitudinal direction of the fiber was relatively easier than the lateral direction as evident in the diffusion coefficient, activation energy, and flexibility of chain segments. Swiss-cheese model of fiber structure appears to describe the observed dye diffusion phenomena and their dependence on hydrolysis time and dying temperature. PMID:8436572

  9. Breaking action of ascorbic acid on nucleic acids.

    PubMed

    Omura, H; Iiyama, S; Tomita, Y; Narazaki, Y; Shinohara, K

    1975-01-01

    The lowering of the viscosity of DNA solution was caused by the action of AsA or EA and facilitated in the presence of CU2+. However, the action of AsA-3-P was very weak. By sucrose density gradient centrifugation, it was observed that single- and double-strand scissions of DNA were provoked by AsA or EA and enhanced with Cu2+, while only a single-strand scission was caused by AsA-3-P and Cu2+. Similar action of AsA or AsA-3-P was also observed for RNA. Thus, the result indicates that the enediol group of AsA takes an essential part in the breakage of nucleic acids, and Cu2+ enhances the action. It was shown that Apu was mainly decomposed by AsA, whereas Apy not, suggesting that some pyrimidine cluster may be one of the regions attacked by AsA. During the reaction with DNA, the reducing activity of AsA decreased first to some extent and then increased, whereas the reducing activity of AsA-3-P was much lower than that of AsA and decreased steadily. The priming activity of DNA for DNA polymerase was changed after treatment with AsA according to the condition. It was enhanced when DNA was treated under mild conditions but decreased with severer action.

  10. The dynamics of polymer bridge formation and disruption and its effect on the bulk rheology of suspensions.

    PubMed

    Bhosale, Prasad S; Berg, John C

    2012-12-11

    Bridge-flocculated colloidal gels are used in many important processes and products such as gel casting for advanced ceramics, precursor inks for 3D printing, and waste treatment strategies. An important aspect of polymer bridged gels that makes them excellent candidates for these applications is the precise control it affords for control of rheological properties. Recent studies have shown that adhesion between bridged surfaces increases with time as the number of polymer bridges formed grows. However, the consequences of the dynamics of these processes toward bulk rheological properties have not been studied. Here we investigate the link between the dynamics of polymer bridging and disruption and bulk rheology in dense colloidal silica particle suspensions flocculated by polyethylene oxide (PEO). Microscale pull-off force measurements using atomic force microscope (AFM) show that upon repeated disruption and establishment of bridged contact, the adhesion between the surfaces is reduced. During contact disruption, the polymer chains bridging the two surfaces are stretched leading to chain scission. On the re-establishment of contact, these fragmented polymer chains are unable to fully re-establish the adhesion. Macroscale measurements using oscillatory rheology show that this reduced adhesion results in reduction of both the storage modulus and the yield stress. If the slurry is subjected to high shear for long periods, polymer chain scission is amplified, and the fragmented polymer chains are unable to bridge the particles again, resulting in free-flowing slurries.

  11. Tensile Fracture of Welded Polymer Interfaces: Miscibility, Entanglements, and Crazing

    DOE PAGESBeta

    Ge, Ting; Grest, Gary S.; Robbins, Mark O.

    2014-09-26

    Large-scale molecular simulations are performed to investigate tensile failure of polymer interfaces as a function of welding time t. Changes in the tensile stress, mode of failure and interfacial fracture energy GI are correlated to changes in the interfacial entanglements as determined from Primitive Path Analysis. Bulk polymers fail through craze formation, followed by craze breakdown through chain scission. At small t welded interfaces are not strong enough to support craze formation and fail at small strains through chain pullout at the interface. Once chains have formed an average of about one entanglement across the interface, a stable craze ismore » formed throughout the sample. The failure stress of the craze rises with welding time and the mode of craze breakdown changes from chain pullout to chain scission as the interface approaches bulk strength. The interfacial fracture energy GI is calculated by coupling the simulation results to a continuum fracture mechanics model. As in experiment, GI increases as t1/2 before saturating at the average bulk fracture energy Gb. As in previous studies of shear strength, saturation coincides with the recovery of the bulk entanglement density. Before saturation, GI is proportional to the areal density of interfacial entanglements. Immiscibiltiy limits interdiffusion and thus suppresses entanglements at the interface. Even small degrees of immisciblity reduce interfacial entanglements enough that failure occurs by chain pullout and GI << Gb.« less

  12. Study of the fission process of 200Pb and 197Tl produced in fusion reactions with the modified statistical model and multidimensional dynamical model

    NASA Astrophysics Data System (ADS)

    Eslamizadeh, H.

    2015-09-01

    The fission probability, pre-scission neutron, proton and alpha multiplicities, anisotropy of fission fragment angular distribution and the fission time have been calculated for the compound nuclei 200Pb and 197Tl based on the modified statistical model and four-dimensional dynamical model. In dynamical calculations, dissipation was generated through the chaos weighted wall and window friction formula. The projection of the total spin of the compound nucleus to the symmetry axis, K, was considered as the fourth-dimension in Langevin dynamical calculations. In our dynamical calculations, we have used a constant dissipation coefficient of K, {γ }K=0.077{({{MeV}} {{zs}})}-{1/2}, and a non-constant dissipation coefficient to reproduce the above-mentioned experimental data. Comparison of the theoretical results of the fission probability and pre-scission particle multiplicities with the experimental data showed that the difference between the results of both dynamical models is small whereas, for the anisotropy of fission fragment angular distribution, it is slightly large. Furthermore, comparison of the results of the modified statistical model with the above-mentioned experimental data showed that with choosing appropriate values of the temperature coefficient of the effective potential, λ , and the scaling factor of the fission-barrier height, {r}s, the experimental data were satisfactorily reproduced.

  13. A constitutive law for degrading bioresorbable polymers.

    PubMed

    Samami, Hassan; Pan, Jingzhe

    2016-06-01

    This paper presents a constitutive law that predicts the changes in elastic moduli, Poisson's ratio and ultimate tensile strength of bioresorbable polymers due to biodegradation. During biodegradation, long polymer chains are cleaved by hydrolysis reaction. For semi-crystalline polymers, the chain scissions also lead to crystallisation. Treating each scission as a cavity and each new crystal as a solid inclusion, a degrading semi-crystalline polymer can be modelled as a continuum solid containing randomly distributed cavities and crystal inclusions. The effective elastic properties of a degrading polymer are calculated using existing theories for such solid and the tensile strength of the degrading polymer is predicted using scaling relations that were developed for porous materials. The theoretical model for elastic properties and the scaling law for strength form a complete constitutive relation for the degrading polymers. It is shown that the constitutive law can capture the trend of the experimental data in the literature for a range of biodegradable polymers fairly well. PMID:26971070

  14. Eukaryotic-Like Virus Budding in Archaea

    PubMed Central

    Quemin, Emmanuelle R. J.; Chlanda, Petr; Sachse, Martin; Forterre, Patrick

    2016-01-01

    ABSTRACT Similar to many eukaryotic viruses (and unlike bacteriophages), viruses infecting archaea are often encased in lipid-containing envelopes. However, the mechanisms of their morphogenesis and egress remain unexplored. Here, we used dual-axis electron tomography (ET) to characterize the morphogenesis of Sulfolobus spindle-shaped virus 1 (SSV1), the prototype of the family Fuselloviridae and representative of the most abundant archaea-specific group of viruses. Our results show that SSV1 assembly and egress are concomitant and occur at the cellular cytoplasmic membrane via a process highly reminiscent of the budding of enveloped viruses that infect eukaryotes. The viral nucleoprotein complexes are extruded in the form of previously unknown rod-shaped intermediate structures which have an envelope continuous with the host membrane. Further maturation into characteristic spindle-shaped virions takes place while virions remain attached to the cell surface. Our data also revealed the formation of constricted ring-like structures which resemble the budding necks observed prior to the ESCRT machinery-mediated membrane scission during egress of various enveloped viruses of eukaryotes. Collectively, we provide evidence that archaeal spindle-shaped viruses contain a lipid envelope acquired upon budding of the viral nucleoprotein complex through the host cytoplasmic membrane. The proposed model bears a clear resemblance to the egress strategy employed by enveloped eukaryotic viruses and raises important questions as to how the archaeal single-layered membrane composed of tetraether lipids can undergo scission. PMID:27624130

  15. Surface Modification of Polymer Substrates by Oxygen Ion Irradiation

    SciTech Connect

    Takaoka, G. H.; Ryuto, H.; Araki, R.; Yakushiji, T.

    2008-11-03

    Oxygen cluster ions and/or monomer ions were used for the sputtering and the surface modification of polymers such as polycarbonate (PC) and polyethylene terephthalate (PET). For the case of oxygen cluster ion irradiation, the sputtered depth increased with increase of the acceleration voltage, and the sputtering yield was much larger than that by the monomer ion irradiation. The sputtered particles represented the polymer structure, which indicated that the bond scission by the cluster ion irradiation resulted in an ejection of monomer molecule through the intermolecular collision. On the other hand, for the oxygen monomer ion irradiation, the implanted depth increased with increase of the acceleration voltage, and the bond scission occurred at the deep region through the binary collision with the high energetic ions. Therefore, the sputtering yield for the polymer surfaces decreased, and the sputtering effect became very small. Furthermore, the simultaneous use of oxygen cluster and monomer ions was more effective for oxidation of the PET surfaces rather than the monomer ion irradiation or the cluster ion irradiation. As a result, the contact angle measurement showed that the wettability of the PET surfaces irradiated by the simultaneous use of oxygen cluster and monomer ions was much enhanced.

  16. Combustion modeling and kinetic rate calculations for a stoichiometric cyclohexane flame. 1. Major reaction pathways.

    PubMed

    Zhang, Hongzhi R; Huynh, Lam K; Kungwan, Nawee; Yang, Zhiwei; Zhang, Shaowen

    2007-05-17

    The Utah Surrogate Mechanism was extended in order to model a stoichiometric premixed cyclohexane flame (P = 30 Torr). Generic rates were assigned to reaction classes of hydrogen abstraction, beta scission, and isomerization, and the resulting mechanism was found to be adequate in describing the combustion chemistry of cyclohexane. Satisfactory results were obtained in comparison with the experimental data of oxygen, major products and important intermediates, which include major soot precursors of C2-C5 unsaturated species. Measured concentrations of immediate products of fuel decomposition were also successfully reproduced. For example, the maximum concentrations of benzene and 1,3-butadiene, two major fuel decomposition products via competing pathways, were predicted within 10% of the measured values. Ring-opening reactions compete with those of cascading dehydrogenation for the decomposition of the conjugate cyclohexyl radical. The major ring-opening pathways produce 1-buten-4-yl radical, molecular ethylene, and 1,3-butadiene. The butadiene species is formed via beta scission after a 1-4 internal hydrogen migration of 1-hexen-6-yl radical. Cascading dehydrogenation also makes an important contribution to the fuel decomposition and provides the exclusive formation pathway of benzene. Benzene formation routes via combination of C2-C4 hydrocarbon fragments were found to be insignificant under current flame conditions, inferred by the later concentration peak of fulvene, in comparison with benzene, because the analogous species series for benzene formation via dehydrogenation was found to be precursors with regard to parent species of fulvene. PMID:17388269

  17. Fundamental study on dissolution behavior of poly(methyl methacrylate) by quartz crystal microbalance

    NASA Astrophysics Data System (ADS)

    Konda, Akihiro; Yamamoto, Hiroki; Yoshitake, Shusuke; Kozawa, Takahiro

    2016-03-01

    Ionizing radiations such as extreme ultraviolet (EUV) and electron beam (EB) are the most promising exposure source for next-generation lithographic technology. In the realization of high resolution lithography, it is necessary for resist materials to improve the trade-off relationship among sensitivity, resolution, and line width roughness (LWR). In order to overcome them, it is essential to understand basic chemistry of resist matrices in resist processes. In particular, the dissolution process of resist materials is a key process. Therefore, it is essential for next-generation resist design for ionizing radiation to clarify the dissolution behavior of the resist film into developer. However, the details in dissolution process of EUV and EB resist films have not been investigated thus far. In this study, main chain scission and dissolution behavior of poly(methyl methacrylate) (PMMA) as main chain scission type resist was investigated using quartz crystal microbalance (QCM) method and gel permeation chromatography (GPC) in order to understand the relationship between the degree of PMMA degradation and dissolution behavior. The relationship between the molecular weight after irradiation and the swelling behavior was clarified.

  18. Solvent effects on the nonlinear optical responses of anil derivatives

    NASA Astrophysics Data System (ADS)

    Plaquet, Aurélie; Bogdan, Elena; Antonov, Liudmil; Rodriguez, Vincent; Ducasse, Laurent; Champagne, Benoıît; Castet, Frédéric

    2015-01-01

    This contribution addresses the solvent effects on the second-order nonlinear optical responses of three representative anil derivatives, and in particular on their variations upon switching between the enol-imine and keto-amine forms. The impact of solute-solvent interactions is investigated by means of ab initio and DFT calculations in which solvent effects are included through the polarizable continuum model. In addition, for one of the compounds, Hyper-Rayleigh Scattering experiments and ab initio calculations are combined to highlight the impact of the solvent-induced equilibrium displacement. These studies show that the global solvent effect on the nonlinear optical responses originates from both the displacement of the tautomeric equilibrium and from the modification of the second-order nonlinear optical response of the individual tautomeric forms.

  19. Preparation of Polyvinylidene Fluoride (PVDF) Hollow Fiber Hemodialysis Membranes

    PubMed Central

    Zhang, Qinglei; Lu, Xiaolong; Zhao, Lihua

    2014-01-01

    In this study, the polyvinylidene fluoride (PVDF) hollow fiber hemodialysis membranes were prepared by non-solvent induced phase separation (NIPS). The influences of PVDF membrane thickness and polyethylene glycol (PEG) content on membrane morphologies, pore size, mechanical and permeable performance were investigated. It was found that membrane thickness and PEG content affected both the structure and performance of hollow fiber membranes. The tensile strength and rejection of bovine serum albumin (BSA) increased with increasing membrane thickness, while the Ultrafiltration flux (UF) flux of pure water was the opposite. The tensile strength, porosity and rejection of BSA increased with increasing PEG content within a certain range. Compared with commercial F60S membrane, the PVDF hollow fiber membrane showed higher mechanical and permeable performance. It was proven that PVDF material had better hydrophilicity and lower BSA adsorption, which was more suitable for hemodialysis. All the results indicate that PVDF hollow fiber membrane is promising as a hemodialysis membrane. PMID:24957122

  20. Photoconductive and supramolecularly engineered organic field-effect transistors based on fibres from donor-acceptor dyads.

    PubMed

    Treier, Matthias; Liscio, Andrea; Mativetsky, Jeffrey M; Kastler, Marcel; Müllen, Klaus; Palermo, Vincenzo; Samorì, Paolo

    2012-03-01

    We report on the formation of photoconductive self-assembled fibres by solvent induced precipitation of a HBC-PMI donor-acceptor dyad. Kelvin Probe Force Microscopy revealed that upon illumination with white light the surface potential of the fibres shifted to negative values due to a build-up of negative charge. When integrated in a field-effect transistor (FET) configuration, the devices can be turned 'on' much more efficiently using light than conventional bias triggered field-effect, suggesting that these structures could be used for the fabrication of light sensing devices. Such a double gating represents an important step towards bi-functional organic FETs, in which the current through the junction can be modulated both optically (by photoexcitation) and electrically (by gate control).

  1. Highly Efficient Conjugated Polymer/Fulleren Solar Cells

    NASA Astrophysics Data System (ADS)

    Brabec, Christoph J.

    2001-03-01

    The increase of mobility of hole conducting polmyers upon different processing is also reflected in the improved performance of photovoltaic bulk heterojunction cells, in our case, based on organic blends of MDMO-PPV and [6,6]PCBM. The field-effect hole mobilities of pristine MDMO-PPV have been measured to be 4.8 * 10-6 cm2/Vs and 3.3 * 10-5 cm2/Vs respectively, depending on the solvent-induced modification of the polymer morphology. The performance of such "bulk heterojunction" photovoltaic devices is further critically depending on the formation of the interpenetrating network between the fullerene and the polymer. We discuss the optimization of the photocurrent in thin bulk heterojunctions solar cells where the diffusion/drift lengths are in the order of the device thickness. Solar cells with a power efficiency higher than 2.5illumination and an external quantum efficiency higher than 50

  2. Misusing volatile substances for their hallucinatory effects: a qualitative pilot study with Mexican teenagers and a pharmacological discussion of their hallucinations.

    PubMed

    Cruz, Silvia L; Domínguez, Mario

    2011-01-01

    This work describes the solvent-induced hallucinatory experiences of 10 male and seven female teenagers in Mexico City from 1998 to 2000. The youth were recruited from public schools through a combined snowball and convenience sampling procedure. Inclusion criteria were: 13-18 years of age, school attendance, living with family, and weekly toluene-based solvent misuse. Interested students were interviewed and transcripts were analyzed. Hallucinations and illusions were common, including changes in color perception, visual, somatic, auditory, and tactile hallucinations. Some users described their hallucinatory experience as being able to be shared by a group and modulated by their environment. The pharmacological linkages with hallucinations are discussed. The study's limitations are noted. PMID:21609151

  3. Fabrication of polydimethylsiloxane (PDMS) nanofluidic chips with controllable channel size and spacing.

    PubMed

    Peng, Ran; Li, Dongqing

    2016-10-01

    The ability to create reproducible and inexpensive nanofluidic chips is essential to the fundamental research and applications of nanofluidics. This paper presents a novel and cost-effective method for fabricating a single nanochannel or multiple nanochannels in PDMS chips with controllable channel size and spacing. Single nanocracks or nanocrack arrays, positioned by artificial defects, are first generated on a polystyrene surface with controllable size and spacing by a solvent-induced method. Two sets of optimal working parameters are developed to replicate the nanocracks onto the polymer layers to form the nanochannel molds. The nanochannel molds are used to make the bi-layer PDMS microchannel-nanochannel chips by simple soft lithography. An alignment system is developed for bonding the nanofluidic chips under an optical microscope. Using this method, high quality PDMS nanofluidic chips with a single nanochannel or multiple nanochannels of sub-100 nm width and height and centimeter length can be obtained with high repeatability. PMID:27539019

  4. Selective fluorescence sensors for detection of nitroaniline and metal Ions based on ligand-based luminescent metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Yu, Zongchao; Wang, Fengqin; Lin, Xiangyi; Wang, Chengmiao; Fu, Yiyuan; Wang, Xiaojun; Zhao, Yongnan; Li, Guodong

    2015-12-01

    Metal-organic frameworks (MOFs) are porous crystalline materials with high potential for applications in fluorescence sensors. In this work, two solvent-induced Zn(II)-based metal-organic frameworks, Zn3L3(DMF)2 (1) and Zn3L3(DMA)2(H2O)3 (2) (L=4,4‧-stilbenedicarboxylic acid), were investigated as selective sensing materials for detection of nitroaromatic compounds and metal ions. The sensing experiments show that 1 and 2 both exhibit selective fluorescence quenching toward nitroaniline with a low detection limit. In addition, 1 exhibits high selectivity for detection of Fe3+ and Al3+ by significant fluorescence quenching or enhancement effect. While for 2, it only exhibits significant fluorescence quenching effect for Fe3+. The results indicate that 1 and 2 are both promising fluorescence sensors for detecting and recognizing nitroaniline and metal ions with high sensitivity and selectivity.

  5. Free energy surface for Brønsted acid-catalyzed glucose ring-opening in aqueous solution.

    PubMed

    Qian, Xianghong

    2013-10-01

    Car-Parrinello-based molecular dynamics coupled with metadynamics simulations were used to determine the mechanism and associated free energy surface for opening the ring structure of cyclic glucopyranose in acidic aqueous solutions. The ring-opening process is initiated by the protonation of the ring oxygen atom and the breakage of the C1-O5 bond. The barrier for this process is about 25 kcal/mol, in good agreement with experimental measurements. Moreover, the glucose cyclic conformation is found to be more stable than the open chain form. The barrier for proton-catalyzed ring-opening in aqueous solution appears to be largely solvent induced due to the high affinity of water molecules for protons. PMID:23992399

  6. Mechanisms and energetics for acid catalyzed β-D-glucose conversion to 5-hydroxymethylfurfurl.

    PubMed

    Qian, Xianghong

    2011-10-27

    Car-Parrinello based ab initio molecular dynamics (CPMD) coupled with metadynamics (MTD) simulations were carried out to investigate the mechanism and energetics for acid-catalyzed β-d-glucose conversion to 5-hydroxymethylfurfurl (HMF) in water. HMF is a critical intermediate for biomass conversion to biofuels. It was found that protonation of the C2-OH on glucose, the breakage of the C2-O2 bond, and the formation of the C2-O5 bond is the critical rate-limiting step for the direct glucose conversion to HMF without converting to fructose first, contrary to the wide-spread assumption in literature that fructose is the main intermediate for glucose conversion to HMF. The calculated reaction barrier of 30-35 kcal/mol appears to be solvent-induced and is in excellent agreement with experimental observations. PMID:21916465

  7. Phycocyanobilin in solution--a solvent triggered molecular switch.

    PubMed

    Watermann, Tobias; Elgabarty, Hossam; Sebastiani, Daniel

    2014-04-01

    We present a computational investigation of the conformational response of phycocyanobilin (PCB) to the ability of solvents to form hydrogen bonds. PCB is the chromophore of several proteins in light harvesting complexes. We determine the conformational distributions in different solvents (methanol and hexamethylphosphoramide HMPT) by means of ab initio molecular dynamics simulations and characterize them via ab initio calculations of NMR chemical shift patterns. The computed trajectories and spectroscopic fingerprints illustrate that the energy landscape is very complex and exhibits various conformations of similar energy. We elucidate the strong influence of the solvent characteristics on the structural and spectroscopic parameters. Specifically, we predict a cis-trans isomerization of phycocyanobilin upon switching from the aprotic to the protic solvent, which explains an experimentally observed change in the NMR patterns. In the context of technological molecular recognition, solvent induced conformational switching can be considered a precursor mechanism to the recognition of single molecules. PMID:24561966

  8. Nightmare from which you will never awake: Electronic to vibrational spectra!

    SciTech Connect

    De Silva, Nuwon

    2013-01-01

    The theoretical background of ab initio methods and density functional theory is provided. The anharmonicity associated with weakly bound metal cation dihydrogen complexes is examined using the vibrational self-consistent field (VSCF) method and the interaction between a hydrogen molecule and a metal cation is characterized. A study of molecular hydrogen clustering around the lithium cation and their accompanied vibrational anharmonicity employing VSCF is illustrated. A qualitative interpretation is provided of solvent-induced shifts of amides and simulated electronic absorption spectra using the combined time-dependent density functional theory/effective fragment potential method (TDDFT/EFP). An excited-state solvent assisted quadruple hydrogen atom transfer reaction of a coumarin derivative is elucidated using micro solvated quantum mechanical (QM) water and macro solvated EFP water. A dispersion correction to the QM-EFP1 interaction energy is presented.

  9. Fluorine-Free Oil Absorbents Made from Cellulose Nanofibril Aerogels.

    PubMed

    Mulyadi, Arie; Zhang, Zhe; Deng, Yulin

    2016-02-01

    Aerogels based on cellulose nanofibrils (CNFs) have been of great interest as absorbents due to their high absorption capacity, low density, biodegradability, and large surface area. Hydrophobic aerogels have been designed to give excellent oil absorption tendency from water. Herein, we present an in situ method for CNF surface modification and hydrophobic aerogel preparation. Neither solvent exchange nor fluorine chemical is used in aerogel preparations. The as-prepared hydrophobic aerogels exhibit low density (23.2 mg/cm(-3)), high porosity (98.5%), good flexibility, and solvent-induced shape recovery property. Successful surface modification was confirmed through field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and water contact angle measurements. The hydrophobic aerogels show high absorption capacities for various oils, depending on liquid density, up to 47× their original weight but with low water uptake (<0.5 g/g aerogel). PMID:26761377

  10. Study of the solvent effects on the molecular structure and Cdbnd O stretching vibrations of flurbiprofen

    NASA Astrophysics Data System (ADS)

    Tekin, Nalan; Pir, Hacer; Sagdinc, Seda

    2012-12-01

    The effects of 15 solvents on the C=O stretching vibrational frequency of flurbiprofen (FBF) were determined to investigate solvent-solute interactions. Solvent effects on the geometry and C=O stretching vibrational frequency, ν(C=O), of FBF were studied theoretically at the DFT/B3LYP and HF level in combination with the polarizable continuum model and experimentally using attenuated total reflection infrared spectroscopy (ATR-IR). The calculated C=O stretching frequencies in the liquid phase are in agreement with experimental values. Moreover, the wavenumbers of ν(C=O) of FBF in different solvents have been obtained and correlated with the Kirkwood-Bauer-Magat equation (KBM), the solvent acceptor numbers (ANs), and the linear solvation energy relationships (LSERs). The solvent-induced stretching vibrational frequency shifts displayed a better correlation with the LSERs than with the ANs and KBM.

  11. Influence of Bridgehead Substitution and Ring Annelation on the Photophysical Properties of Polycyclic DBO-Type Azoalkanes.

    PubMed

    Adam, Waldemar; Nikolaus, Achim; Sauer, Jürgen

    1999-05-14

    The photophysical data for the polycyclic, bridgehead-substituted derivatives 1-10 of the photoreluctant diazabicyclo[2.2.2]oct-2-ene (DBO) are presented. Substitution on the bridgehead positions with radical-stabilizing substituents enhances the photoreactivity (Phi(r)) and decreases the fluorescence quantum yields (Phi(f)) and lifetimes (tau) compared to the parent DBO. The annelated rings have no influence on the photoreactivity, except when steric interactions with an alpha substituent hinder the optimal radical-stabilizing conformation. The fused rings and some of the bridgehead substituents reduce the solvent-induced quenching of the singlet-excited azo chromophore by steric shielding of the azo group and, thus, increase the fluorescence quantum yields and lifetimes.

  12. Solvent effects on metal-to-ligand charge-transfer bands in ortho-metalated complexes of iridium(III): Estimates of transition dipole moments

    SciTech Connect

    Wilde, A.P.; Watts, R.J. )

    1991-01-24

    Shifts in the absorption and emission maxima of several ortho-metalated complexes of Ir(III) in a series of solvents are reported. These complexes contain combinations of the ortho-metalating ligands 2-phenylpyridine or benzo(h)quinoline and the chelating ligands 2,2{prime}-bipyridine or 1,10-phenanthroline bonded to the Ir(III). The solvent-induced shifts are interpreted in terms of theoretical treatments due to McRae and to Marcus. Each of these treatments leads to estimates of transition dipoles associated with absorption, and the sign and magnitude of the transition dipole indicate that the direction of the excited-state dipole is opposite that of the ground-state dipole. This result is consistent with prior assignments of the absorption band to a metal-to-ligand charge-transfer excited state associated with the chelating ligand.

  13. International SAMPE Symposium and Exhibition, 34th, Reno, NV, May 8-11, 1989, Proceedings. Books 1 2

    SciTech Connect

    Zakrzewski, G.A.; Peters, S.T.; Dean, C.D.; Mazenko, D.

    1989-01-01

    The present conference on advanced materials discusses the curing of thick laminates with internal heat sources, the use of wide-angle X-ray scattering to determine solvent-induced polymer matrix crystallization, long-term degradation of fibrous silica composites, cyanate ester matrix resins, the 977 family of toughened epoxies, an all-thermoplastic matrix composite fighter forward fuselage, a high-temperature BMI matrix system for composite structures, and the design and analysis of elevated-temperature aerospace structures. Also discussed are on-orbit fabrication of Space Station structures, a novel infiltration process for metal-matrix composites, Boeing 360 helicopter honeycomb sandwich primary structures, recent advancements in honeycomb structures, thermoplastic-toughened epoxy resins, the LARC-CPI semicrystalline polyimide, torsion in filament-wound tubes, monolithic graphite tooling, stitching for laminate damage-tolerance improvement, and advanced composite structures for cryogenic applications.

  14. Development of flash nanoprecipitation as a scalable platform for production of hybrid polymer-inorganic Janus particles

    NASA Astrophysics Data System (ADS)

    Lee, Victoria E.; Prud'Homme, Robert K.; Priestley, Rodney D.

    Polymer Janus particles, containing two or more distinct domains, can act as supports for inorganic nanoparticles, stabilizing them against aggregation and templating anisotropic functionalization of the microparticles. This anisotropy can be advantageous for applications such as biofuel upgrading, bionanosensors, and responsive materials. Here, we introduce flash nanoprecipitation (FNP) as a scalable, fast process to create hybrid polymer-inorganic Janus particles with control of particle size and anisotropy. During FNP, polymer Janus particles form by rapid intermixing of a polymer solution with a poor solvent, inducing polymer precipitation and phase separation. Inorganic nanoparticles are then adsorbed selectively onto one domain of the polymer support by exploiting electrostatic interactions between the charged particles. By tuning polymer concentration and ratio in the feed stream, the particle size and anisotropy can be controlled. We further demonstrate that these hybrid particles can simultaneously stabilize emulsions and selectively catalyze the degradation of dye in one phase. With support from the Princeton Imaging Analysis Center.

  15. High mobility organic field-effect transistor based on water-soluble deoxyribonucleic acid via spray coating

    SciTech Connect

    Shi, Wei; Han, Shijiao; Huang, Wei; Yu, Junsheng

    2015-01-26

    High mobility organic field-effect transistors (OFETs) by inserting water-soluble deoxyribonucleic acid (DNA) buffer layer between electrodes and pentacene film through spray coating process were fabricated. Compared with the OFETs incorporated with DNA in the conventional organic solvents of ethanol and methanol: water mixture, the water-soluble DNA based OFET exhibited an over four folds enhancement of field-effect mobility from 0.035 to 0.153 cm{sup 2}/Vs. By characterizing the surface morphology and the crystalline structure of pentacene active layer through atomic force microscope and X-ray diffraction, it was found that the adoption of water solvent in DNA solution, which played a key role in enhancing the field-effect mobility, was ascribed to both the elimination of the irreversible organic solvent-induced bulk-like phase transition of pentacene film and the diminution of a majority of charge trapping at interfaces in OFETs.

  16. A Photo-Triggered Traceless Staudinger-Bertozzi Ligation Reaction.

    PubMed

    Hu, Peng; Feng, Tianshi; Yeung, Chi-Chung; Koo, Chi-Kin; Lau, Kai-Chung; Lam, Michael H W

    2016-08-01

    The use of light to control the course of a chemical/biochemical reaction is an attractive idea because of its ease of administration with high precision and fine spatial resolution. Staudinger ligation is one of the commonly adopted conjugation processes that involve a spontaneous reaction between azides and arylphosphines to form iminophosphoranes, which further hydrolyze to give stable amides. We designed an anthracenylmethyl diphenylphosphinothioester (1) that showed promising Staudinger ligation reactivity upon photo-excitation. Broadband photolysis at 360-400 nm in aqueous organic solvents induced heterolytic cleavage of its anthracenylmethyl-phosphorus bond, releasing a diphenylphosphinothioester (2) as an efficient traceless Staudinger-Bertozzi ligation reagent. The quantum yield of such a photo-induced heterolytic bond-cleavage at the optimal wavelength of photolysis (376 nm) at room temperature is ≥0.07. This work demonstrated the feasibility of photocaging arylphosphines to realize the photo-triggering of the Staudinger ligation reaction.

  17. Excited-state intramolecular proton transfer of 2-acetylindan-1,3-dione studied by ultrafast absorption and fluorescence spectroscopy

    PubMed Central

    Verma, Pramod Kumar; Steinbacher, Andreas; Schmiedel, Alexander; Nuernberger, Patrick; Brixner, Tobias

    2015-01-01

    We employ transient absorption from the deep-UV to the visible region and fluorescence upconversion to investigate the photoinduced excited-state intramolecular proton-transfer dynamics in a biologically relevant drug molecule, 2-acetylindan-1,3-dione. The molecule is a ß-diketone which in the electronic ground state exists as exocyclic enol with an intramolecular H-bond. Upon electronic excitation at 300 nm, the first excited state of the exocyclic enol is initially populated, followed by ultrafast proton transfer (≈160 fs) to form the vibrationally hot endocyclic enol. Subsequently, solvent-induced vibrational relaxation takes place (≈10 ps) followed by decay (≈390 ps) to the corresponding ground state. PMID:26798837

  18. Theoretical aspects of pressure and solute denaturation of proteins: A Kirkwood-buff-theory approach

    NASA Astrophysics Data System (ADS)

    Ben-Naim, Arieh

    2012-12-01

    A new approach to the problem of pressure-denaturation (PD) and solute-denaturation (SD) of proteins is presented. The problem is formulated in terms of Le Chatelier principle, and a solution is sought in terms of the Kirkwood-Buff theory of solutions. It is found that both problems have one factor in common; the excluded volumes of the folded and the unfolded forms with respect to the solvent molecules. It is shown that solvent-induced effects operating on hydrophilic groups along the protein are probably the main reason for PD. On the other hand, the SD depends on the preferential solvation of the folded and the unfolded forms with respect to solvent and co-solvent molecules.

  19. Misusing volatile substances for their hallucinatory effects: a qualitative pilot study with Mexican teenagers and a pharmacological discussion of their hallucinations.

    PubMed

    Cruz, Silvia L; Domínguez, Mario

    2011-01-01

    This work describes the solvent-induced hallucinatory experiences of 10 male and seven female teenagers in Mexico City from 1998 to 2000. The youth were recruited from public schools through a combined snowball and convenience sampling procedure. Inclusion criteria were: 13-18 years of age, school attendance, living with family, and weekly toluene-based solvent misuse. Interested students were interviewed and transcripts were analyzed. Hallucinations and illusions were common, including changes in color perception, visual, somatic, auditory, and tactile hallucinations. Some users described their hallucinatory experience as being able to be shared by a group and modulated by their environment. The pharmacological linkages with hallucinations are discussed. The study's limitations are noted.

  20. Fabrication of polydimethylsiloxane (PDMS) nanofluidic chips with controllable channel size and spacing.

    PubMed

    Peng, Ran; Li, Dongqing

    2016-10-01

    The ability to create reproducible and inexpensive nanofluidic chips is essential to the fundamental research and applications of nanofluidics. This paper presents a novel and cost-effective method for fabricating a single nanochannel or multiple nanochannels in PDMS chips with controllable channel size and spacing. Single nanocracks or nanocrack arrays, positioned by artificial defects, are first generated on a polystyrene surface with controllable size and spacing by a solvent-induced method. Two sets of optimal working parameters are developed to replicate the nanocracks onto the polymer layers to form the nanochannel molds. The nanochannel molds are used to make the bi-layer PDMS microchannel-nanochannel chips by simple soft lithography. An alignment system is developed for bonding the nanofluidic chips under an optical microscope. Using this method, high quality PDMS nanofluidic chips with a single nanochannel or multiple nanochannels of sub-100 nm width and height and centimeter length can be obtained with high repeatability.

  1. A QM/MM-MD study on protein electronic properties: Circular dichroism spectra of oxytocin and insulin

    NASA Astrophysics Data System (ADS)

    Kitagawa, Yuya; Akinaga, Yoshinobu; Kawashima, Yukio; Jung, Jaewoon; Ten-no, Seiichiro

    2012-06-01

    A QM/MM (quantum-mechanical/molecular-mechanical) molecular-dynamics approach based on the generalized hybrid-orbital (GHO) method, in conjunction with the second-order perturbation (MP2) theory and the second-order approximate coupled-cluster (CC2) model, is employed to calculate electronic property accounting for a protein environment. Circular dichroism (CD) spectra originating from chiral disulfide bridges of oxytocin and insulin at room temperature are computed. It is shown that the sampling of thermal fluctuation of molecular geometries facilitated by the GHO-MD method plays an important role in the obtained spectra. It is demonstrated that, while the protein environments in an oxytocin molecule have significant electrostatic influence on its chiral center, it is compensated by solvent induced charges. This gives a reasonable explanation to experimental observations. GHO-MD simulations starting from different experimental structures of insulin indicate that existence of the disulfide bridges with negative dihedral angles is crucial.

  2. Clustering mechanism of ethanol-water mixtures investigated with photothermal microfluidic cantilever deflection spectroscopy

    PubMed Central

    Ghoraishi, M. S.; Hawk, J. E.; Phani, Arindam; Khan, M. F.; Thundat, T.

    2016-01-01

    The infrared-active (IR) vibrational mode of ethanol (EtOH) associated with the asymmetrical stretching of the C-C-O bond in pico-liter volumes of EtOH-water binary mixtures is calorimetrically measured using photothermal microfluidic cantilever deflection spectroscopy (PMCDS). IR absorption by the confined liquid results in wavelength dependent cantilever deflections, thus providing a complementary response to IR absorption revealing a complex dipole moment dependence on mixture concentration. Solvent-induced blue shifts of the C-C-O asymmetric vibrational stretch for both anti and gauche conformers of EtOH were precisely monitored for EtOH concentrations ranging from 20–100% w/w. Variations in IR absorption peak maxima show an inverse dependence on induced EtOH dipole moment (μ) and is attributed to the complex clustering mechanism of EtOH-water mixtures. PMID:27046089

  3. Free energy barrier for dissociation of the guanosine monophosphate anion in water

    NASA Astrophysics Data System (ADS)

    Cornetta, Lucas M.; Coutinho, Kaline; Canuto, Sylvio; Varella, Márcio T. do N.

    2016-08-01

    We report free energy barriers for the ground-state dissociation of the guanosine nucleotide anion in solution, employing implicit and explicit solvation models. The latter was based on the Free Energy Perturbation technique and Monte Carlo simulations. For the lowest-energy structure, both solvation models indicate a solvent-induced transition from a dipole-bound state in the gas phase to a π∗ valence state in solution. The free barrier estimates obtained from explicit and implicit solvation are in fair agreement with each other, although significantly overestimated in comparison to a previously reported explicit solvation model based on ab initio molecular dynamics simulations. Accounting for corrections related to the different DFT functionals used in the present and previous studies significantly improves the agreement. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  4. A new model for pressure-induced shifts of electronic absorption bands as applied to neat CS sub 2 and CS sub 2 in n-hexane and dichloromethane solutions

    SciTech Connect

    Agnew, S.F.; Swanson, B.I. )

    1990-01-25

    The authors propose a model for the pressure dependence of electronic absorption spectra and apply it to the authors data on CS{sub 2} both in neat phase and in hexane and dichloromethane solid solutions. They believe that their data represent a rather severe test of this model and argue that any model for the pressure dependence of electronic absorption spectra must include certain minimal effects - dispersive or dielectric and repulsive or volume effects - in order to adequately represent the data. They discuss previous models at some length in order to delineate the limits of their applicability. They further acknowledge and define the limits of the applicability of their model to solvent-induced shifts in general.

  5. Effect of Water Hydrogen Bonding on the Solvent-Mediated "Oscillatory" Repulsion of C60 Fullerenes in Water.

    PubMed

    Djikaev, Yuri S; Ruckenstein, Eli

    2015-05-01

    The solvent-mediated interaction of C60 fullerenes in liquid water is examined by using the combination of the probabilistic hydrogen bond model with the density functional theory. This combination allows one to take into account the effect of hydrogen bonding between water molecules on their interaction with fullerenes and to construct an approximation for the distribution of water molecules in the system, which provides an efficient foundation for studying hydrophobic phenomena. Our numerical evaluations predict the solvent-induced interaction of two C60 fullerenes in water at 293 K to have an oscillatory-repulsive character (previously observed in molecular dynamics simulations) only when the vicinal water-water hydrogen bonds are slightly weaker than bulk ones. Besides indicating the direction of the energetic alteration of water-water hydrogen bonds near C60 fullerenes, our model also suggests that the hydrogen bonding ability of water plays a defining role in the solvent-mediated C60-C60 repulsion.

  6. Synthesis, crystal structure and catalytic behavior of homo- and heteronuclear coordination polymers [M(tdc)(bpy)] (M2+ = Fe2+, Co2+, Zn2+, Cd2+; tdc2- = 2,5-thiophenedicarboxylate).

    PubMed

    Kettner, Florian; Worch, Christian; Moellmer, Jens; Gläser, Roger; Staudt, Reiner; Krautscheid, Harald

    2013-08-01

    A series of isostructural 3D coordination polymers (3)∞[M(tdc)(bpy)] (M(2+) = Zn(2+), Cd(2+), Co(2+), Fe(2+); tdc(2-) = 2,5-thiophenedicarboxylate; bpy = 4,4'-bipyridine) was synthesized and characterized by X-ray diffraction, thermal analysis, and gas adsorption measurements. The materials show high thermal stability up to approximately 400 °C and a solvent induced phase transition. Single crystal X-ray structure determination was successfully performed for all compounds after the phase transition. In the zinc-based coordination polymer, various amounts of a second type of metal ions such as Co(2+) or Fe(2+) could be incorporated. Furthermore, the catalytic behavior of the homo- and heteronuclear 3D coordination polymers in an oxidation model reaction was investigated.

  7. Simple, benign, aqueous-based amination of polycarbonate surfaces.

    PubMed

    VanDelinder, Virginia; Wheeler, David R; Small, Leo J; Brumbach, Michael T; Spoerke, Erik D; Henderson, Ian; Bachand, George D

    2015-03-18

    Polycarbonate is a desirable material for many applications due to its favorable mechanical and optical properties. Here, we report a simple, safe, environmentally friendly aqueous method that uses diamines to functionalize a polycarbonate surface with amino groups. The use of water as the solvent for the functionalization ensures that solvent induced swelling does not affect the optical or mechanical properties of the polycarbonate. We characterize the efficacy of the surface amination using X-ray photo spectroscopy, Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and contact angle measurements. Furthermore, we demonstrate the ability of this facile method to serve as a foundation upon which other functionalities may be attached, including antifouling coatings and oriented membrane proteins.

  8. Recurrent Acute Liver Failure Because of Acute Hepatitis Induced by Organic Solvents: A Case Report.

    PubMed

    Ito, Daisuke; Tanaka, Tomohiro; Akamatsu, Nobuhisa; Ito, Kyoji; Hasegawa, Kiyoshi; Sakamoto, Yoshihiro; Nakagawa, Hayato; Fujinaga, Hidetaka; Kokudo, Norihiro

    2016-01-01

    The authors present a case of recurrent acute liver failure because of occupational exposure to organic solvents. A 35-year-old man with a 3-week history of worsening jaundice and flu-like symptoms was admitted to our hospital. Viral hepatitis serology and autoimmune factors were negative. The authors considered liver transplantation, but the patient's liver function spontaneously recovered. Liver biopsy revealed massive infiltration of neutrophils, but the cause of the acute hepatitis was not identified. Four months after discharge, the patient's liver function worsened again. The authors considered the possibility of antinuclear antibody-negative autoimmune hepatitis and initiated steroid treatment, which was effective. Four months after discharge, the patient was admitted for repeated liver injury. The authors started him on steroid pulse therapy, but this time it was not effective. Just before the first admission, he had started his own construction company where he was highly exposed to organic solvents, and thus the authors considered organic solvent-induced hepatitis. Although urine test results for organic solvents were negative, a second liver biopsy revealed severe infiltration of neutrophils, compatible with toxic hepatitis. Again, his liver function spontaneously improved. Based on the pathology and detailed clinical course, including the patient's high exposure to organic solvents since just before the first admission, and the spontaneous recovery of his liver damage in the absence of the exposure, he was diagnosed with toxic hepatitis. The authors strongly advised him to avoid organic solvents. Since then, he has been in good health without recurrence. This is the first report of recurrent acute liver failure because of exposure to organic solvents, which was eventually diagnosed through a meticulous medical history and successfully recovered by avoiding the causative agents. In acute liver failure with an undetermined etiology, clinicians should rule

  9. Recurrent Acute Liver Failure Because of Acute Hepatitis Induced by Organic Solvents

    PubMed Central

    Ito, Daisuke; Tanaka, Tomohiro; Akamatsu, Nobuhisa; Ito, Kyoji; Hasegawa, Kiyoshi; Sakamoto, Yoshihiro; Nakagawa, Hayato; Fujinaga, Hidetaka; Kokudo, Norihiro

    2016-01-01

    Abstract The authors present a case of recurrent acute liver failure because of occupational exposure to organic solvents. A 35-year-old man with a 3-week history of worsening jaundice and flu-like symptoms was admitted to our hospital. Viral hepatitis serology and autoimmune factors were negative. The authors considered liver transplantation, but the patient's liver function spontaneously recovered. Liver biopsy revealed massive infiltration of neutrophils, but the cause of the acute hepatitis was not identified. Four months after discharge, the patient's liver function worsened again. The authors considered the possibility of antinuclear antibody-negative autoimmune hepatitis and initiated steroid treatment, which was effective. Four months after discharge, the patient was admitted for repeated liver injury. The authors started him on steroid pulse therapy, but this time it was not effective. Just before the first admission, he had started his own construction company where he was highly exposed to organic solvents, and thus the authors considered organic solvent-induced hepatitis. Although urine test results for organic solvents were negative, a second liver biopsy revealed severe infiltration of neutrophils, compatible with toxic hepatitis. Again, his liver function spontaneously improved. Based on the pathology and detailed clinical course, including the patient's high exposure to organic solvents since just before the first admission, and the spontaneous recovery of his liver damage in the absence of the exposure, he was diagnosed with toxic hepatitis. The authors strongly advised him to avoid organic solvents. Since then, he has been in good health without recurrence. This is the first report of recurrent acute liver failure because of exposure to organic solvents, which was eventually diagnosed through a meticulous medical history and successfully recovered by avoiding the causative agents. In acute liver failure with an undetermined etiology, clinicians

  10. Photoconductive and supramolecularly engineered organic field-effect transistors based on fibres from donor-acceptor dyads

    NASA Astrophysics Data System (ADS)

    Treier, Matthias; Liscio, Andrea; Mativetsky, Jeffrey M.; Kastler, Marcel; Müllen, Klaus; Palermo, Vincenzo; Samorì, Paolo

    2012-02-01

    We report on the formation of photoconductive self-assembled fibres by solvent induced precipitation of a HBC-PMI donor-acceptor dyad. Kelvin Probe Force Microscopy revealed that upon illumination with white light the surface potential of the fibres shifted to negative values due to a build-up of negative charge. When integrated in a field-effect transistor (FET) configuration, the devices can be turned `on' much more efficiently using light than conventional bias triggered field-effect, suggesting that these structures could be used for the fabrication of light sensing devices. Such a double gating represents an important step towards bi-functional organic FETs, in which the current through the junction can be modulated both optically (by photoexcitation) and electrically (by gate control).We report on the formation of photoconductive self-assembled fibres by solvent induced precipitation of a HBC-PMI donor-acceptor dyad. Kelvin Probe Force Microscopy revealed that upon illumination with white light the surface potential of the fibres shifted to negative values due to a build-up of negative charge. When integrated in a field-effect transistor (FET) configuration, the devices can be turned `on' much more efficiently using light than conventional bias triggered field-effect, suggesting that these structures could be used for the fabrication of light sensing devices. Such a double gating represents an important step towards bi-functional organic FETs, in which the current through the junction can be modulated both optically (by photoexcitation) and electrically (by gate control). Electronic supplementary information (ESI) available: Experimental details and photoresponse on spin-coated film (3 pages). See DOI: 10.1039/c2nr11635a

  11. Entropic screening preserves non-equilibrium nature of nematic phase while enthalpic screening destroys it.

    PubMed

    Dan, K; Roy, M; Datta, A

    2016-02-14

    The present manuscript describes the role of entropic and enthalpic forces mediated by organic non-polar (hexane) and polar (methanol) solvents on the bulk and microscopic phase transition of a well known nematic liquid crystalline material MBBA (N-(4-methoxybenzylidene)-4-butylaniline) through Differential Scanning calorimetry (DSC), UV-Visible (UV-Vis), and Fourier Transform Infrared (FTIR) spectroscopy. DSC study indicates continuous linear decreases in both nematic-isotropic (N-I) phase transition temperature and enthalpy of MBBA in presence of hexane while both these parameters show a saturation after an initial decay in methanol. These distinct transitional behaviours were explained in terms of the "depletion force" model for entropic screening in hexane and "screening-self-screening" model for methanol. Heating rate dependent DSC studies find that non-Arrhenius behaviour, characteristic of pristine MBBA and a manifestation of non-equilibrium nature [Dan et al., J. Chem. Phys. 143, 094501 (2015)], is preserved in presence of entropic screening in the hexane solution, while it changes to Arrhenius behaviour (signifying equilibrium behaviour) in presence of enthalpic screening in methanol solution. FTIR spectra show similar dependence on the solvent induced screening in the intensities of the imine (-C = N) stretch and the out-of-plane distortion vibrations of the benzene rings of MBBA with hexane and methanol as in DSC, further establishing our entropic and enthalpic screening models. UV-Vis spectra of the electronic transitions in MBBA as a function of temperature also exhibit different dependences of intensities on the solvent induced screening, and an exponential decrease is observed in presence of hexane while methanol completely changes the nature of interaction to follow a linear dependence. PMID:26874498

  12. Mesoscale aggregation properties of C60 in toluene and chlorobenzene.

    PubMed

    Guo, Rong-Hao; Hua, Chi-Chung; Lin, Po-Chang; Wang, Ting-Yu; Chen, Show-An

    2016-07-20

    The mesoscale aggregation properties of C60 in two distinct aromatic solvents (toluene and chlorobenzene) and a practical range of concentrations (c = 1-2 and c = 1-5 mg mL(-1), respectively) were systematically explored by static/dynamic light scattering (SLS/DLS), small angle X-ray scattering (SAXS), depolarized dynamic light scattering (DDLS), and cryogenic transmission electron microscopy (cryo-TEM) analyses. The central observations were as follows: (1) aggregate species of sizes in the range of several hundred nanometers have been independently revealed by SLS, DLS, and DDLS analyses for both solvent systems. (2) DDLS and cryo-TEM measurements further revealed that while C60 clusters are notably anisotropic (rod-like) in chlorobenzene, they are basically isotropic (spherical) in toluene. (3) Detailed analyses of combined SLS and SAXS profiles suggested that varied, yet self-similar, solvent-induced aggregate units were responsible for the distinct (mesoscale) aggregation features noted above. (4) From a dynamic perspective, specially commissioned DLS measurements ubiquitously displayed two relaxation modes (fast and slow mode), with the second (slow) mode being q (wave vector) independent. While the fast mode in both solvent systems was basically diffusive by nature and leads to geometrical features in good agreement with the above static analyses, the slow mode was analyzed and tentatively suggested to reflect the effect of mutual confinement. (5) Micron-scale aggregate morphology of drop-cast thin films displays similar contrasting features for the two solvent media used. Overall, this study suggests that solvent-induced, nanoscale, aggregate units may be a promising factor to control a hierarchy of microscopic aggregation properties of C60 solutions and thin films.

  13. Mesoscale aggregation properties of C60 in toluene and chlorobenzene.

    PubMed

    Guo, Rong-Hao; Hua, Chi-Chung; Lin, Po-Chang; Wang, Ting-Yu; Chen, Show-An

    2016-07-20

    The mesoscale aggregation properties of C60 in two distinct aromatic solvents (toluene and chlorobenzene) and a practical range of concentrations (c = 1-2 and c = 1-5 mg mL(-1), respectively) were systematically explored by static/dynamic light scattering (SLS/DLS), small angle X-ray scattering (SAXS), depolarized dynamic light scattering (DDLS), and cryogenic transmission electron microscopy (cryo-TEM) analyses. The central observations were as follows: (1) aggregate species of sizes in the range of several hundred nanometers have been independently revealed by SLS, DLS, and DDLS analyses for both solvent systems. (2) DDLS and cryo-TEM measurements further revealed that while C60 clusters are notably anisotropic (rod-like) in chlorobenzene, they are basically isotropic (spherical) in toluene. (3) Detailed analyses of combined SLS and SAXS profiles suggested that varied, yet self-similar, solvent-induced aggregate units were responsible for the distinct (mesoscale) aggregation features noted above. (4) From a dynamic perspective, specially commissioned DLS measurements ubiquitously displayed two relaxation modes (fast and slow mode), with the second (slow) mode being q (wave vector) independent. While the fast mode in both solvent systems was basically diffusive by nature and leads to geometrical features in good agreement with the above static analyses, the slow mode was analyzed and tentatively suggested to reflect the effect of mutual confinement. (5) Micron-scale aggregate morphology of drop-cast thin films displays similar contrasting features for the two solvent media used. Overall, this study suggests that solvent-induced, nanoscale, aggregate units may be a promising factor to control a hierarchy of microscopic aggregation properties of C60 solutions and thin films. PMID:27376417

  14. Entropic screening preserves non-equilibrium nature of nematic phase while enthalpic screening destroys it

    NASA Astrophysics Data System (ADS)

    Dan, K.; Roy, M.; Datta, A.

    2016-02-01

    The present manuscript describes the role of entropic and enthalpic forces mediated by organic non-polar (hexane) and polar (methanol) solvents on the bulk and microscopic phase transition of a well known nematic liquid crystalline material MBBA (N-(4-methoxybenzylidene)-4-butylaniline) through Differential Scanning calorimetry (DSC), UV-Visible (UV-Vis), and Fourier Transform Infrared (FTIR) spectroscopy. DSC study indicates continuous linear decreases in both nematic-isotropic (N-I) phase transition temperature and enthalpy of MBBA in presence of hexane while both these parameters show a saturation after an initial decay in methanol. These distinct transitional behaviours were explained in terms of the "depletion force" model for entropic screening in hexane and "screening-self-screening" model for methanol. Heating rate dependent DSC studies find that non-Arrhenius behaviour, characteristic of pristine MBBA and a manifestation of non-equilibrium nature [Dan et al., J. Chem. Phys. 143, 094501 (2015)], is preserved in presence of entropic screening in the hexane solution, while it changes to Arrhenius behaviour (signifying equilibrium behaviour) in presence of enthalpic screening in methanol solution. FTIR spectra show similar dependence on the solvent induced screening in the intensities of the imine (—C = N) stretch and the out-of-plane distortion vibrations of the benzene rings of MBBA with hexane and methanol as in DSC, further establishing our entropic and enthalpic screening models. UV-Vis spectra of the electronic transitions in MBBA as a function of temperature also exhibit different dependences of intensities on the solvent induced screening, and an exponential decrease is observed in presence of hexane while methanol completely changes the nature of interaction to follow a linear dependence.

  15. Chiromers: conformation-driven mirror-image supramolecular chirality isomerism identified in a new class of helical rosette nanotubes

    NASA Astrophysics Data System (ADS)

    Hemraz, Usha D.; El-Bakkari, Mounir; Yamazaki, Takeshi; Cho, Jae-Young; Beingessner, Rachel L.; Fenniri, Hicham

    2014-07-01

    Rosette nanotubes are biologically inspired nanostructures, formed through the hierarchical organization of a hybrid DNA base analogue (G∧C), which features hydrogen-bonding arrays of guanine and cytosine. Several twin-G∧C motifs functionalized with chiral moieties, which undergo a self-assembly process under methanolic and aqueous conditions to produce helical rosette nanotubes (RNTs), were synthesized and characterized. The built-in molecular chirality in the twin-G∧C building blocks led to the supramolecular chirality exhibited by the RNTs, as evidenced by the CD activity. Depending on the motifs and environmental conditions, mirror-image supramolecular chirality due to absolute molecular chirality, solvent-induced and structure-dependent supramolecular chirality inversion, and pH-controlled chiroptical switching were observed.Rosette nanotubes are biologically inspired nanostructures, formed through the hierarchical organization of a hybrid DNA base analogue (G∧C), which features hydrogen-bonding arrays of guanine and cytosine. Several twin-G∧C motifs functionalized with chiral moieties, which undergo a self-assembly process under methanolic and aqueous conditions to produce helical rosette nanotubes (RNTs), were synthesized and characterized. The built-in molecular chirality in the twin-G∧C building blocks led to the supramolecular chirality exhibited by the RNTs, as evidenced by the CD activity. Depending on the motifs and environmental conditions, mirror-image supramolecular chirality due to absolute molecular chirality, solvent-induced and structure-dependent supramolecular chirality inversion, and pH-controlled chiroptical switching were observed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00340c

  16. /sup 18/O isotope effect in /sup 13/C nuclear magnetic resonance spectroscopy. Part 9. Hydrolysis of benzyl phosphate by phosphatase enzymes and in acidic aqueous solutions

    SciTech Connect

    Parente, J.E.; Risley, J.M.; Van Etten, R.L.

    1984-12-26

    The /sup 18/O isotope-induced shifts in /sup 13/C and /sup 31/P nuclear magnetic resonance (NMR) spectroscopy were used to establish the position of bond cleavage in the phosphatase-catalyzed and acid-catalyzed hydrolysis reactions of benzyl phosphate. The application of the /sup 18/O-isotope effect in NMR spectroscopy affords a continuous, nondestructive assay method for following the kinetics and position of bond cleavage in the hydrolytic process. The technique provides advantages over most discontinuous methods in which the reaction components must be isolated and converted to volatile derivatives prior to analysis. In the present study, (..cap alpha..-/sup 13/C,ester-/sup 18/O)benzyl phosphate and (ester-/sup 18/O)benzyl phosphate were synthesized for use in enzymatic and nonenzymatic studies. Hydrolysis reactions catalyzed by the alkaline phosphatase from E. coli and by the acid phosphatases isolated from human prostate and human liver were all accompanied by cleavage of the substrate phosphorus-oxygen bond consistent with previously postulated mechanisms involving covalent phosphoenzyme intermediates. An extensive study of the acid-catalyzed hydrolysis of benzyl phosphate at 75/sup 0/C revealed that the site of bond cleavage is dependent on pH. At pH less than or equal to 1.3, the hydrolysis proceeds with C-O bond cleavage; at 1.3 < pH < 2.0, there is a mixture of C-O and P-O bond scission, the latter progressively predominating as the pH is raised; at pH greater than or equal to 2.0, the hydrolysis proceeds with exclusive P-O bond scission. (S)-(+)-(..cap alpha..-/sup 2/H)Benzyl phosphate was also synthesized. Hydrolysis of this chiral benzyl derivative demonstrated that the acid-catalyzed C-O bond scission of benzyl phosphate proceeds by an A-1 (S/sub N/1) mechanism with 70% racemization and 30% inversion at carbon. 37 references, 4 figures, 2 tables.

  17. Hybrid resist systems based on α-substituted acrylate copolymers

    NASA Astrophysics Data System (ADS)

    Ito, Hiroshi; Sundberg, Linda K.; Bozano, Luisa; Lofano, Elizabeth M.; Yamanaka, Kazuhiro; Terui, Yoshiharu; Fujiwara, Masaki

    2009-03-01

    Classical electron-beam resists such as poly(methyl methacrylate) (PMMA) and Nippon Zeon's ZEP function as high resolution and low roughness positive resists on the basis of radiation induced main chain scission to reduce the molecular weight while chemical amplification resists utilized in device manufacturing function on the basis of acidcatalyzed deprotection to change the polarity. In an attempt to increase the resolution and reduce the line roughness of chemical amplification resists, we prepared copolymers that undergo radiation induced main chain scission and acidcatalyzed deprotection. In another word, we wanted to increase the sensitivity of the PMMA resist by incorporating the acid-catalyzed deprotection mechanism in polymers that undergo main chain scission, maintaining the high resolution and low roughness of PMMA. To synthesize such hybrid resist polymers, we selected α-substituted acrylates and α- substituted styrenes. The former included methyl methacrylate (MMA), t-butyl methacrylate (TBMA), methyl α- fluoroacrylate (MFA), t-butyl α-fluoroacrylate (TBFA), and t-butyl α-trifluoromethylacrylate (TBTFMA) and the latter α-methylstyrene (αMEST), α-methyleneindane (αMEIN), and α-methylenetetralin (αMETL). The α-substituted tbutyl acrylic esters were copolymerized with the methyl esters and also with α-substituted styrenic monomers using 2, 2'-azobis(isobutyronitrile) (AIBN). Hybrid resists were formulated by adding a photochemical acid generator and a base quencher to the copolymers and developers were selected by studying the dissolution behavior of unexposed and 254 nm exposed resist films using a quartz crystal microbalance (QCM). In addition to the difference in the imaging mechanism, PMMA and ZEP differ from the chemical amplification resists in developers; organic solvent vs. aqueous base. We were interested in looking also into the influence of the developer on the lithographic performance. Contrast curves were generated by exposing

  18. Characteristics of liquid product from the pyrolysis of waste plastic mixture at low and high temperatures: Influence of lapse time of reaction

    SciTech Connect

    Lee, Kyong-Hwan . E-mail: khwanlee@kier.re.kr; Shin, Dae-Hyun

    2007-07-01

    Pyrolysis of a waste plastic mixture (high-density polyethylene: low-density polyethylene: polypropylene: polystyrene = 3:2:3:1) into a liquid product was carried out in a stirred semi-batch reactor at low (350 deg. C) and high (400 deg. C) temperatures. The effect of lapse time of reaction in the reactor and also degradation temperature on the characteristics of the liquid product from pyrolysis of the mixture was investigated. Liquid products were described by cumulative amount distribution, paraffin, olefin, naphthene and aromatic (PONA) distribution and molecular weight distribution. Their characteristic was quite differed with a lapse time of reaction and also at a low and high degradation temperatures, because of the different physicochemical properties of the plastic types in the mixture. With increase of lapse time of reaction, the order for the main products in PONA components obtained at 350 deg. C was firstly aromatic products and then olefin products, while at 400 deg. C the order was firstly aromatic products, then olefin products and finally paraffin products. The experiments also showed from the molecular weight distribution of liquid PONA components that the paraffin and olefin products had a wide distribution by mainly random scission of polymer, but in the case of olefin products were produced by an end-chain scission mechanism as well as random scission mechanism, as evidenced by much more light olefin products. This phenomenon was evident at a higher degradation temperature. Also, both the light olefin and naphthene products with a molecular weight of around 120, as a main product, showed a similar trend as a function of lapse time, which had a maximum fraction at 343 min (at 350 deg. C) and 83 min (at 400 deg. C). Among PONA components, the highest concentrations of aromatic products were obtained with a molecular weight of around 100 at the fastest lapse time of reaction, regardless of degradation temperature. It was concluded that the

  19. Physical and mechanical properties of poly(hydroxybutyrate-co-hydroxyvalerate) and its pineapple fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Luo, Shuiyuan

    2000-10-01

    Recently, there has been considerable research on biodegradable polymers because of the complex plastic waste management created by the mostly non-degradable polymers and polymer-based composites. In this dissertation, physical and mechanical properties of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), a degradable polymer, and its pineapple fiber-reinforced composites are discussed. CHAPTER ONE introduces the PHBV polymer, natural cellulose fibers, and polymeric composites including the fiber/matrix interface. The degradability of PHBV is also briefly discussed. CHAPTER TWO describes the effects of thermal processing time on the properties of PHBV. At processing conditions of 180°C and 140 MPa, PHBV underwent significant, random chain scission. As a result, tensile properties deteriorated. DSC and SAXS results show that thermally degraded PHBVs had different thermal properties and lamellar morphology. CHAPTER THREE reports the effects of 60Co gamma-radiation on the properties of PHBV. Under 60Co gamma-radiation random chain scission but no cross-linking occurred in PHBV. Chain scission occurs probably in the amorphous region. As a result, thermal and tensile properties are significantly affected. CHAPTER FOUR describes properties of pineapple fibers, the interface between pineapple fiber and PHBV, and properties of pineapple fiber-reinforced PHBV "green" composites. Pineapple fiber has enough strength to be used as reinforcement in composites with intermediate strength. Interfacial shear strength was moderate. The mechanical properties of PHBV were significantly improved, and were comparable to some woods. CHAPTER FIVE presents the mechanical and thermal properties of unidirectional, degradable, environment-friendly "green" composites made from pineapple fibers and PHBV resin. Tensile and flexural properties of the "green" composites with different fiber contents were investigated. The presence of pineapple fibers did not affect the non

  20. Reaction kinetics of cellulose hydrolysis in subcritical and supercritical water

    NASA Astrophysics Data System (ADS)

    Olanrewaju, Kazeem Bode

    The uncertainties in the continuous supply of fossil fuels from the crisis-ridden oil-rich region of the world is fast shifting focus on the need to utilize cellulosic biomass and develop more efficient technologies for its conversion to fuels and chemicals. One such technology is the rapid degradation of cellulose in supercritical water without the need for an enzyme or inorganic catalyst such as acid. This project focused on the study of reaction kinetics of cellulose hydrolysis in subcritical and supercritical water. Cellulose reactions at hydrothermal conditions can proceed via the homogeneous route involving dissolution and hydrolysis or the heterogeneous path of surface hydrolysis. The work is divided into three main parts. First, the detailed kinetic analysis of cellulose reactions in micro- and tubular reactors was conducted. Reaction kinetics models were applied, and kinetics parameters at both subcritical and supercritical conditions were evaluated. The second major task was the evaluation of yields of water soluble hydrolysates obtained from the hydrolysis of cellulose and starch in hydrothermal reactors. Lastly, changes in molecular weight distribution due to hydrothermolytic degradation of cellulose were investigated. These changes were also simulated based on different modes of scission, and the pattern generated from simulation was compared with the distribution pattern from experiments. For a better understanding of the reaction kinetics of cellulose in subcritical and supercritical water, a series of reactions was conducted in the microreactor. Hydrolysis of cellulose was performed at subcritical temperatures ranging from 270 to 340 °C (tau = 0.40--0.88 s). For the dissolution of cellulose, the reaction was conducted at supercritical temperatures ranging from 375 to 395 °C (tau = 0.27--0.44 s). The operating pressure for the reactions at both subcritical and supercritical conditions was 5000 psig. The results show that the rate-limiting step in

  1. The role of alkoxy radicals in the heterogeneous reaction of two structural isomers of dimethylsuccinic acid.

    PubMed

    Cheng, Chiu Tung; Chan, Man Nin; Wilson, Kevin R

    2015-10-14

    A key challenge in understanding the transformation chemistry of organic aerosols is to quantify how changes in molecular structure alter heterogeneous reaction mechanisms. Here we use two model systems to investigate how the relative locations of branched methyl groups control the heterogeneous reaction of OH with two isomers of dimethylsuccinic acid (C6H10O4). 2,2-Dimethylsuccinic acid (2,2-DMSA) and 2,3-dimethylsuccinic acid (2,3-DMSA) differ only in the location of the two branched methyl groups, thus enabling a closer inspection of how the distribution of carbon reaction sites impacts the chemical evolution of the aerosol. The heterogeneous reaction of OH with 2,3-DMSA (reactive OH uptake coefficient, γ = 0.99 ± 0.16) is found to be ∼2 times faster than that of 2,2-DMSA (γ = 0.41 ± 0.07), which is attributed to the larger stability of the tertiary alkyl radical produced by the initial OH abstraction reaction. While changes in the average aerosol oxidation state (OSC) and the carbon number (NC) are similar for both isomers upon reaction, significant differences are observed in the underlying molecular distribution of reaction products. The reaction of OH with the 2,3-DMSA isomer produces two major reaction products: a product containing a new alcohol functional group (C6H10O5) formed by intermolecular hydrogen abstraction and a C5 compound formed via carbon-carbon (C-C) bond scission. Both of these reaction products are explained by the formation and subsequent reaction of a tertiary alkoxy radical. In contrast, the OH reaction with the 2,2-DMSA isomer forms four dominant reaction products, the majority of which are C5 scission products. The difference in the quantity of C-C bond scission products for these two isomers is unexpected since decomposition is assumed to be favored for the isomer with the most tertiary carbon sites (i.e. 2,3-DMSA). For both isomers, there is a much larger abundance of C6 alcohol relative to C6 ketone products, which suggests

  2. Seminar on Fission VI

    NASA Astrophysics Data System (ADS)

    Wagemans, Cyriel; Wagemans, Jan; D'Hondt, Pierre

    2008-04-01

    Topical reviews. Angular momentum in fission / F. Gönnenwein ... [et al.]. The processes of fusion-fission and quasi-fission of heavy and super-heavy nuclei / M. G. Itkis ... [et al.] -- Fission cross sections and fragment properties. Minor-actinides fission cross sections and fission fragment mass yields via the surrogate reaction technique / B. Jurado ... [et al.]. Proton-induced fission on actinide nuclei at medium energy / S. Isaev ... [et al.]. Fission cross sections of minor actinides and application in transmutation studies / A. Letourneau ... [et al.]. Systematics on even-odd effects in fission fragments yields: comparison between symmetric and asymmetric splits / F. Rejmund, M Caamano. Measurement of kinetic energy distributions, mass and isotopic yields in the heavy fission products region at Lohengrin / A. Bail ... [et al.] -- Ternary fission. On the Ternary [symbol] spectrum in [symbol]Cf(sf) / M. Mutterer ... [et al.]. Energy degrader technique for light-charged particle spectroscopy at LOHENGRIN / A. Oberstedt, S. Oberstedt, D. Rochman. Ternary fission of Cf isotopes / S. Vermote ... [et al.]. Systematics of the triton and alpha particle emission in ternary fission / C. Wagemans, S. Vermote, O. Serot -- Neutron emission in fission. Scission neutron emission in fission / F.-J. Hambsch ... [et al.]. At and beyond the Scission point: what can we learn from Scission and prompt neutrons? / P. Talou. Fission prompt neutron and gamma multiplicity by statistical decay of fragments / S. Perez-Martin, S. Hilaire, E. Bauge -- Fission theory. Structure and fission properties of actinides with the Gogny force / H. Goutte ... [et al.]. Fission fragment properties from a microscopic approach / N. Dubray, H. Goutte, J.-P. Delaroche. Smoker and non-smoker neutron-induced fission rates / I. Korneev ... [et al.] -- Facilities and detectors. A novel 2v2E spectrometer in Manchester: new development in identification of fission fragments / I. Tsekhanovich ... [et al

  3. Reduction of Influenza Virus Envelope's Fusogenicity by Viral Fusion Inhibitors.

    PubMed

    Rowse, Michael; Qiu, Shihong; Tsao, Jun; Yamauchi, Yohei; Wang, Guoxin; Luo, Ming

    2016-01-01

    During cell entry of an enveloped virus, the viral membrane must be fused with the cellular membrane. The virus envelope has a unique structure consisting of viral proteins and a virus-specific lipid composition, whereas the host membrane has its own structure with host membrane proteins. Compound 136 was previously found to bind in close proximity to the viral envelope and inhibit influenza virus entry. We showed here that the 136-treated influenza virus still caused hemolysis. When liposomes were used as the target membrane for 136-treated viruses, aberrant fusion occurred; few liposomes fused per virion, and glycoproteins were not distributed evenly across fusion complexes. Additionally, large fusion aggregates did not form, and in some instances, neck-like structures were found. Based on previous results and hemolysis, fusion inhibition by 136 occurs post-scission but prior to lipid mixing. PMID:27622947

  4. Photoinduced reactions of 1-(dimethylethyl)-2,2-dimethylpropyl and cyclohexyl radicals in low-temperature solids

    NASA Astrophysics Data System (ADS)

    Koizumi, Hitoshi; Takada, Tomoya; Ichikawa, Tsuneki; Lund, Anders

    2001-06-01

    Photoinduced reactions of 1-(dimethylethyl)-2,2-dimethylpropyl and cyclohexyl radicals in 77 K solids were studied by the ESR method. 1-(Dimethylethyl)-2,2-dimethylpropyl is converted to 2,2,4,4-tetramethylpentyl radical with photoirradiation of 254 nm light. A hydrogen atom of methyl groups can hence directly transfer to the radical site at a carbon atom other than an adjacent one in the photoinduced reactions of alkyl radicals. Cyclohexyl radical is converted to cyclopentylmethyl radical with irradiation of 254 nm light. The photolysis of cyclohexyl radical causes C-C bond scission, and results in the formation of 5-hexenyl radical. It is then converted to cyclopentylmethyl radical through intramolecular rearrangement.

  5. RNASEK Is a V-ATPase-Associated Factor Required for Endocytosis and the Replication of Rhinovirus, Influenza A Virus, and Dengue Virus.

    PubMed

    Perreira, Jill M; Aker, Aaron M; Savidis, George; Chin, Christopher R; McDougall, William M; Portmann, Jocelyn M; Meraner, Paul; Smith, Miles C; Rahman, Motiur; Baker, Richard E; Gauthier, Annick; Franti, Michael; Brass, Abraham L

    2015-08-01

    Human rhinovirus (HRV) causes upper respiratory infections and asthma exacerbations. We screened multiple orthologous RNAi reagents and identified host proteins that modulate HRV replication. Here, we show that RNASEK, a transmembrane protein, was needed for the replication of HRV, influenza A virus, and dengue virus. RNASEK localizes to the cell surface and endosomal pathway and closely associates with the vacuolar ATPase (V-ATPase) proton pump. RNASEK is required for endocytosis, and its depletion produces enlarged clathrin-coated pits (CCPs) at the cell surface. These enlarged CCPs contain endocytic cargo and are bound by the scissioning GTPase, DNM2. Loss of RNASEK alters the localization of multiple V-ATPase subunits and lowers the levels of the ATP6AP1 subunit. Together, our results show that RNASEK closely associates with the V-ATPase and is required for its function; its loss prevents the early events of endocytosis and the replication of multiple pathogenic viruses.

  6. Emission turn-on and solubility turn-off in conjugated polymers: one- and two-photon-induced removal of fluorescence-quenching solubilizing groups.

    PubMed

    Schelkle, Korwin M; Becht, Steffy; Faraji, Shirin; Petzoldt, Martin; Müllen, Klaus; Buckup, Tiago; Dreuw, Andreas; Motzkus, Marcus; Hamburger, Manuel

    2015-01-01

    The synthesis of highly efficient two-photon uncaging groups and their potential use in functional conjugated polymers for post-polymerization modification are reported. Careful structural design of the employed nitrophenethyl caging groups allows to efficiently induce bond scission by a two-photon process through a combination of exceptionally high two-photon absorption cross-sections and high reaction quantum yields. Furthermore, π-conjugated polyfluorenes are functionalized with these photocleavable side groups and it is possible to alter their emission properties and solubility behavior by simple light irradiation. Cleavage of side groups leads to a turn-on of the fluorescence while solubility of the π-conjugated materials is drastically reduced.

  7. Effect of high energy electron radiation on MIPB-impregnated polypropylene film

    SciTech Connect

    Hammoud, A.N.; Laghari, J.R.; Krishnakumar, B.

    1988-08-01

    This work examines the effect of impregnating capacitor-grade polypropylene film with an aromatic hydrocarbon fluid with a view towards assessing the response under radiation of the relevant properties of the film. Monoisopropyl biphenyl (MIPB)-impregnated polypropylene film was exposed in air to 1 MeV electrons to different doses and the post-radiation effects on the electrical, mechanical, morphological and chemical properties were evaluated. The results obtained indicate that the oil-impregnated films remain relatively stable even at the highest dose of 10/sup 8/ rads. This is in contrast to the results reported earlier for dry polypropylene films which underwent degradation primarily due to chain scission and oxidation. In the present instance, it is believed that impregnation of the film has inhibited the diffusion of oxygen and consequently favored crosslinking. The chemical characterizations as well as the changes in some of the measured properties of the film seem to corroborate this belief.

  8. [Study of the hydrolytic degradation of a biodegradable copolymer].

    PubMed

    Sabino, Marco A; Morales, Dayanara; Ronca, Gladys; Feijoo, José Luis

    2003-01-01

    The hydrolytic degradation of bioabsorbable Poliglactin 910 was studied in a phosphate buffer solution, pH = 7.4, at 37 degrees C. The degradation was evaluated by analyzing the changes in weight loss, pH, DSC, mechanical properties and morphological changes. After 10 weeks, the weight loss and pH changes suggested diffusion of low molecular weight chain segments into the reaction medium as a consequence of the breaking of ester bonds in the material. Breaking stress and Young Modulus decrease, indicating that chain scission proceeded in two steps: the first occurring in the amorphous regions within the intermicrofibrillar space; the second in the crystalline regions. Surface morphological changes suggest a heterogeneous degradation mechanism by layers.

  9. Low-intensity UV effects on optical constants of PMMA film

    NASA Astrophysics Data System (ADS)

    Rashidian, M.; Dorranian, D.

    2014-04-01

    Effects of low-intensity UV treatment on the optical constants of red BS dye-doped polymethyl methacrylate (PMMA) film including refractive index, extinction coefficient, real and imaginary parts of dielectric constant, band gap energy, Urbach energy, and refractive index dispersion parameters are measured and calculated. Changes in optical constants mainly occurred in the UV-VIS range. Red BS dye, which is used as a UV absorber impurity in PMMA films, generated another energy band gap which was increased by UV treatment. Although some of the optical constants of PMMA are not changed noticeably by the treatment in this low range of UV radiation, our results confirm that polymeric changes such as chain scission and depolymerization can directly affect the optical constants of PMMA.

  10. Fundamental reaction pathways during coprocessing

    SciTech Connect

    Stock, L.M.; Gatsis, J.G.

    1992-12-01

    The objective of this research was to investigate the fundamental reaction pathways in coal petroleum residuum coprocessing. Once the reaction pathways are defined, further efforts can be directed at improving those aspects of the chemistry of coprocessing that are responsible for the desired results such as high oil yields, low dihydrogen consumption, and mild reaction conditions. We decided to carry out this investigation by looking at four basic aspects of coprocessing: (1) the effect of fossil fuel materials on promoting reactions essential to coprocessing such as hydrogen atom transfer, carbon-carbon bond scission, and hydrodemethylation; (2) the effect of varied mild conditions on the coprocessing reactions; (3) determination of dihydrogen uptake and utilization under severe conditions as a function of the coal or petroleum residuum employed; and (4) the effect of varied dihydrogen pressure, temperature, and residence time on the uptake and utilization of dihydrogen and on the distribution of the coprocessed products. Accomplishments are described.

  11. Highest Efficiency Two-Photon Degradable Copolymer for Remote Controlled Release

    PubMed Central

    Olejniczak, Jason; Sankaranarayanan, Jagadis; Viger, Mathieu L.; Almutairi, Adah

    2013-01-01

    To address the scarcity of polymers that degrade upon absorption of near infrared (NIR) light, we introduce a new polymer containing moieties in its backbone capable of highly efficient NIR-triggered photocleavage. The polymer rapidly undergoes backbone scission in response to both UV-Vis and near infrared light via two-photon absorption, as revealed by gel permeation chromatography. Cleavage of photosensitive groups from the backbone is confirmed by 1H NMR. These polymers were successfully formulated into particles encapsulating a dye that was released upon irradiation with UV-Vis and NIR light, as indicated by changes in fluorescence characteristic of increased solvent interaction with cargo. Thus, this new polymer is readily photocleaved by UV-Vis and NIR light, giving it a variety of potential applications in photopatterning and on-demand release. PMID:24044102

  12. Evaluation of the toxic and genotoxic potential of acid mine drainage using physicochemical parameters and bioassays.

    PubMed

    Netto, E; Madeira, R A; Silveira, F Z; Fiori, M A; Angioleto, E; Pich, C T; Geremias, R

    2013-05-01

    Carboniferous activity generates acid mine drainage (AMD) which is capable of unleashing toxic effects on the exposed biota. The aim of this study was to evaluate the toxic and genotoxic potential of untreated-AMD and AMD treated with calcinated sediment, using physicochemical parameters and bioassays. Results revealed that untreated-AMD presented low pH values and elevated concentrations of the metals Fe, Al, Mn, Zn and Cu. High acute toxicity was observed in Artemia sp. and Daphnia magna, and sub-chronic toxicity and genotoxicity in Allium cepa L. as well as scission of plasmid DNA exposed to untreated-AMD. Treatment of AMD with calcinated sediment promoted the reduction of acidity and the removal of metals, as well as a reduction in toxic and genotoxic effects. In conclusion, the calcinated sediment can be used as an alternative AMD treatment.

  13. Improving enzymatic hydrolysis of industrial hemp ( Cannabis sativa L.) by electron beam irradiation

    NASA Astrophysics Data System (ADS)

    Shin, Soo-Jeong; Sung, Yong Joo

    2008-09-01

    The electron beam irradiation was applied as a pretreatment of the enzymatic hydrolysis of hemp biomass with doses of 150, 300 and 450 kGy. The higher irradiation dose resulted in the more extraction with hot-water extraction or 1% sodium hydroxide solution extraction. The higher solubility of the treated sample was originated from the chains scission during irradiation, which was indirectly demonstrated by the increase of carbonyl groups as shown in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra. The changes in the micro-structure of hemp resulted in the better response to enzymatic hydrolysis with commercial cellulases (Celluclast 1.5L and Novozym 342). The improvement in enzymatic hydrolysis by the irradiation was more evident in the hydrolysis of the xylan than in that of the cellulose.

  14. Dynamical effects in fission investigated at high excitation energy

    NASA Astrophysics Data System (ADS)

    Benlliure, J.

    2016-05-01

    The experimental techniques used for the investigation of nuclear fission have progressed considerably during the last decade. Most of this progress is based on the use of the inverse kinematics technique allowing for the first time the complete isotopic and kinematic characterization of both fission fragments. These measurements make possible to characterize the fissioning system at saddle and at scission, and can be used to benchmark fission model calculations. One of the important ingredients in transport models describing the dynamics of the process is the dissipation parameter, governing the coupling between intrinsic and collective degrees of freedom. Recent experiments got access to the magnitude of this parameter and could also investigate its dependence in temperature and deformation.

  15. Two in one or one in two? Pushing off from Jung with Wolfgang Giegerich.

    PubMed

    Saban, Mark

    2015-11-01

    This paper responds to a recent paper by Wolfgang Giegerich entitled 'Two Jungs: apropos a paper by Mark Saban'. Giegerich disputes my assertion that the 'rigorous notion' at the heart of his psychology 'finds no source in Jung's psychology, implicit or explicit'. In order to do this he posits the existence of two Jungs, an exoteric Jung and an esoteric Jung. The implications of Giegerich's binary scission of Jung are explored in this paper, and show that the tendency to exalt one Jung while disparaging the other betrays a comprehensive blindness toward the contradictory complexity of Jung's psychology as a whole. It is suggested that this blindness is the consequence of Giegerich's systematic prioritization of a neo-Hegelian agenda that is in profound conflict with the telos of Jung's psychology. PMID:26499299

  16. Surface band structure of Si(111)2×1

    NASA Astrophysics Data System (ADS)

    Chen, B.; Haneman, D.

    1995-02-01

    The surface band structures of the three-bond scission (TBS) model and the Pandey-chain (PC) model have been computed using an ab initio Hartree-Fock program crystal 92. In the case of the bulk energy bands, the method gives the correct shapes and structure but overestimates the valence-band dispersion by about 50%. For the TBS model, the calculated valence-band dispersion came out about 50% wider than measured experimentally. This would suggest that the model is consistent with optical data. In the case of the PC model, the valence-band dispersion was qualitatively similar to those of previous calculations, but the width discrepancy was large. The method overestimates the surface band gap for both TBS and PC models. The significance is discussed.

  17. Surface Structures on Cleaved Silicon by Cleavage Luminescence Detection

    NASA Astrophysics Data System (ADS)

    Li, Dongguang

    This paper reports on further research into the structure and properties of the cleaved surfaces of silicon, using vacuum cleavage luminescence detection methods. Results show resistance partially recovers during the cleavage process through "crack healing". When the elasticity of the parts transmitting the applied stress temporarily absorbs the initial rupture stress, the crack stops and partially re-closes until the applied force "catches up" and reapplies stress. The high resistance created by the two Schottky barriers prevents resistance recovery from mere surfaces re-contact. Instead, resistance recovery from the atom-to-atom re-closure surface healing is more likely, as expected from a Three Bond Scission Model (TBS) silicon surface structure.

  18. Photostabilizing Efficiency of PVC in the Presence of Schiff Bases as Photostabilizers.

    PubMed

    Yousif, Emad; Al-Amiery, Ahmed A; Kadihum, Abdulhadi; Kadhum, Abdul Amir H; Mohamad, Abu Bakar

    2015-11-04

    The photostabilization of polyvinyl chloride (PVC) films by Schiff bases was investigated. Polyvinyl chloride films containing 0.5 wt % Schiff bases were produced using the same casting method as that used for additive-free PVC films from tetrahydrofuran (THF) solvent. The photostabilization activities of these compounds were determined by monitoring the carbonyl, polyene and hydroxyl indices with irradiation time. The changes in viscosity average molecular weight of PVC with irradiation time were also monitored using THF as a solvent. The quantum yield of chain scission (Φcs) for the studied complexes in PVC was estimated to range between 4.72 and 8.99 × 10(-8). According to the experimental results, several mechanisms were suggested, depending on the structure of the additive. Ultra violet (UV) absorption, peroxide decomposition and radical scavenging were suggested as the photostabilizing mechanisms.

  19. Emergence of Synchronized Beating during the Regrowth of Eukaryotic Flagella

    NASA Astrophysics Data System (ADS)

    Goldstein, Raymond E.; Polin, Marco; Tuval, Idan

    2011-09-01

    A fundamental issue in the biology of eukaryotic flagella is the origin of synchronized beating observed in tissues and organisms containing multiple flagella. Recent studies of the biflagellate unicellular alga Chlamydomonas reinhardtii provided the first evidence that the interflagellar coupling responsible for synchronization is of hydrodynamic origin. To investigate this mechanism in detail, we study here synchronization in Chlamydomonas as its flagella slowly regrow after mechanically induced self-scission. The duration of synchronized intervals is found to be strongly dependent on flagellar length. Analysis within a stochastic model of coupled phase oscillators is used to extract the length dependence of the interflagellar coupling and the intrinsic beat frequencies of the two flagella. Physical and biological considerations that may explain these results are proposed.

  20. Mild cracking of high-molecular-weight hydrocarbons

    SciTech Connect

    Biouri, B.; Hamdan, F.; Herault, D.

    1985-01-01

    Controlled cracking in the liquid phase of n-hexadecane, 6-methyleicosane, 1-phenyldodecane, and C21-C27 paraffins was studied in a stainless steel microreactor between 350 and 440 C for residence times varyin from 0.5 to 4 h at nitrogen or hydrogen pressures of 20 bar. Cracking occurred according to a molecular mechanism, but its kinetic data such as the order of reaction and the activation energy were similar to those of radical type cracking. The rate of formation of cracked gases was extremely small and the experimental and simulated compositions of the cracked liquids, based on a molecular type scission, agreed very well. This type of cracking is very interesting for visbreaking of heavy oils.

  1. Radiation-induced degradation of galactomannan polysaccharides

    NASA Astrophysics Data System (ADS)

    Şen, Murat; Yolaçan, Burcu; Güven, Olgun

    2007-12-01

    In this study, guar gum, tara gum and locust bean gum were irradiated in a gamma cell in the solid state. The change in their molecular weights were determined by size exclusion chromatography analysis and the change in their viscosity values with change of temperature and irradiation dose were determined. Chain scission yield, G( s), and degradation rate values were calculated. The calculated G( s) values is 1.09 ± 0.16, 1.07 ± 0.06, 0.85 ± 0.10 for GG, TG and LBG, respectively. The effect of mannose-galactose ratio and initial molecular weight of these gums on the degradation behavior were discussed.

  2. CO adsorption on (111) and (100) surfaces of the Pt sub 3 Ti alloy. Evidence for parallel binding and strong activation of CO

    NASA Technical Reports Server (NTRS)

    Mehandru, S. P.; Anderson, A. B.; Ross, P. N.

    1985-01-01

    The CO adsorption on a 40 atom cluster model of the (111) surface and a 36 atom cluster model of the (100) surface of the Pt3Ti alloy was studied. Parallel binding to high coordinate sites associated with Ti and low CO bond scission barriers are predicted for both surfaces. The binding of CO to Pt sites occurs in an upright orientation. These orientations are a consequence of the nature of the CO pi donation interactions with the surface. On the Ti sites the orbitals donate to the nearly empty Ti 3d band and the antibonding counterpart orbitals are empty. On the Pt sites, however, they are in the filled Pt 5d region of the alloy band, which causes CO to bond in a vertical orientation by 5 delta donation from the carbon end.

  3. Visible-Light-Triggered Drug Release from TiO2 Nanotube Arrays: A Controllable Antibacterial Platform.

    PubMed

    Xu, Jingwen; Zhou, Xuemei; Gao, Zhida; Song, Yan-Yan; Schmuki, Patrik

    2016-01-11

    In this work, we use a double-layered stack of TiO2 nanotubes (TiNTs) to construct a visible-light-triggered drug delivery system. The key for visible light drug release is a hydrophobic cap on the nanotubes containing Au nanoparticles (AuNPs). The AuNPs allow for a photocatalytic scission of the hydrophobic chain under visible light. To demonstrate this principle, we loaded ampicillin (AMP) into the lower part of the TiO2 nanotube stack, triggered visible-light-induced release, and carried out antibacterial studies. The release from the platform becomes most controllable if the drug is silane-grafted in the hydrophilic bottom layer for drug storage. Thus, visible light photocatalysis can also determine the release kinetics of the active drug from the nanotube wall.

  4. Biochemical analysis of hatchet self-cleaving ribozymes

    PubMed Central

    Li, Sanshu; Lünse, Christina E.; Harris, Kimberly A.; Breaker, Ronald R.

    2015-01-01

    Hatchet RNAs are members of a novel self-cleaving ribozyme class that was recently discovered by using a bioinformatics search strategy. The consensus sequence and secondary structure of this class includes 13 highly conserved and numerous other modestly conserved nucleotides interspersed among bulges linking four base-paired substructures. A representative hatchet ribozyme from a metagenomic source requires divalent ions such as Mg2+ to promote RNA strand scission with a maximum rate constant of ∼4 min−1. As with all other small self-cleaving ribozymes discovered to date, hatchet ribozymes employ a general mechanism for catalysis involving the nucleophilic attack of a ribose 2′-oxygen atom on an adjacent phosphorus center. Kinetic characteristics of the reaction demonstrate that members of this ribozyme class have an essential requirement for divalent metal ions and that they might have a complex active site that employs multiple catalytic strategies to accelerate RNA cleavage by internal phosphoester transfer. PMID:26385510

  5. Molecular basis of fracture in polystyrene films

    SciTech Connect

    Sambasivam, M.; Klein, A.; Thomas, T.N.; Mohammadi, N.; Sperling, L.H.

    1993-12-31

    To understand the molecular mechanisms involved in the fracture of polystyrene films, a custom built dental burr grinding instrument was used. Films were made from latexes, compression molded polystyrene, and by photopolymerization. Latexes were prepared by direct miniemulsification of polystyrene using sodium lauryl sulfate as surfactant and cetyl and stearyl alcohols as co-surfactants. Grinding of various films was carried out at room temperature. GPC was used to determine the molecular weight before and after grinding. From the molecular weight reduction, the number of chain scissions per unit volume was determined. The energy required for the grinding process was also measured. The results are consistent with a model of exciting 300{+-}150 bonds (per chain fracture) to the breaking point. The most probable deformation mode, consuming maximum energy is envisaged as the scissor-like opening of the 109{degrees} -C-C-C bond angle.

  6. Coadsorbed species explain the mechanism of methanol temperature-desorption on CeO2(111)

    DOE PAGESBeta

    Sutton, Jonathan E.; Steven H. Overbury; Beste, Ariana

    2016-03-24

    Here, we have used density functional theory calculations to investigate the temperature-programmed desorption (TPD) of methanol from CeO2(111). For the first time, low-temperature water formation and high-temperature methanol desorption are explained by our calculations. High coverages of methanol, which correspond to experimental conditions, are required to properly describe these features of the TPD spectrum. We identify a mechanism for the low-temperature formation of water involving the dissociation of two methanol molecules on the same surface O atom and filling of the resulting surface vacancy with one of the methoxy products. After water desorption, methoxy groups are stabilized on the surfacemore » and react at higher temperatures to form methanol and formaldehyde by a disproportionation mechanism. Alternatively, the stabilized methoxy groups undergo sequential C–H scission reactions to produce formaldehyde. Calculated energy requirements and methanol/formaldehyde selectivity agree with the experimental data.« less

  7. Ammonia decomposition activity on monolayer Ni supported on Ru, Pt and WC substrates

    NASA Astrophysics Data System (ADS)

    Hansgen, Danielle A.; Vlachos, Dionisios G.; Chen, Jingguang G.

    2011-12-01

    Catalyst design for specific reactions currently involves using atomic or molecular descriptors to identify promising catalysts. In this paper, we explore three surfaces that have similar computed nitrogen binding energies, which is a descriptor for the ammonia decomposition reaction. The surfaces studied include a monolayer of Ni on Pt(111), Ru(0001) and tungsten monocarbide (WC). The activity of these surfaces toward the ammonia decomposition reaction was compared using density functional theory and temperature programmed desorption. It was found that while the NHx-H bond scission is similar on each of the surfaces, the temperature of nitrogen desorption is very different. The differences are explained and the implications for ammonia decomposition activity and catalyst design are discussed.

  8. Decomposition pathways of C2 oxygenates on Rh-modified tungsten carbide surfaces

    NASA Astrophysics Data System (ADS)

    Kelly, Thomas G.; Ren, Hui; Chen, Jingguang G.

    2015-10-01

    Ethanol decomposition on tungsten monocarbide (WC) and Rh-modified WC was investigated using ultrahigh vacuum (UHV) surface science experiments and density functional theory (DFT) calculations. DFT calculations indicated that the binding energies of ethanol and its decomposition intermediates on WC(0001) were modified by Rh, with Rh/WC(0001) showing similar values to those on Rh(111). Through temperature-programmed desorption (TPD) experiments on polycrystalline WC and Rh-modified WC, it was shown that the selectivity for ethanol decomposition was different on these surfaces. On WC, the C-O bond of ethanol was preferentially broken to produce ethylene; on Rh-modified WC, the C-C bond was broken to produce carbon monoxide and methane. Furthermore, high-resolution electron energy loss spectroscopy (HREELS) was used to determine likely surface intermediates. On Rh-modified WC, ethanol first formed ethoxy through O-H scission, then reacted through an aldehyde intermediate to form the C1 products.

  9. Release of polysaccharide by sonication of cells ( Porphyridium sp.)

    NASA Astrophysics Data System (ADS)

    Faerman, V.; Mukmenev, I.; Shreiber, I.

    2009-03-01

    The paper deals with experimental data concerning the interaction of acoustical waves with microbial cell (Porphyridium sp.). The aim of the present paper was to increase the amount of biopolymer released from the microorganisms biomass with the aid ultrasound irradiation without scission or a decrease in the molecular weight. The results indicated that the amount of polysaccharide (for example) released from the cell pellet could be enhanced by ultrasound, depending on the frequency and energy of the ultrasound. The sugar composition remain the same, but the apparent viscosity of polysaccharide aqueous solutions decreased, indicated that some changes in the molecular shape and size occurred. When ultrasound irradiation was applied in the presence of either CO2 or CO2 + H2, the apparent viscosity of polysaccharide aqueous solutions increased (versus usual ultrasound treatment).

  10. Doppler spectroscopy of hydrogen atoms from the photodissociation of saturated hydrocarbons and methyl halides at 157 nm

    SciTech Connect

    Tonokura, K.; Matsumi, Y.; Kawasaki, M. ); Kasatani, K. )

    1991-10-01

    Hydrocarbons (C{sub {ital n}}H{sub 2{ital n}+2}, {ital n}=3, 4, and 6) and methyl halides (CH{sub 3}{ital X}, {ital X}=Cl, Br, I) are photodissociated at 157 nm. The hydrogen atom photofragments are detected by a resonance-enhanced multiphoton ionization technique. The Doppler profiles of the hydrogen atoms from hydrocarbons are well represented by a Gaussian profile, while those from methyl halides by a mixture of a Gaussian and a non-Gaussian profiles. These Doppler profiles are interpreted assuming that (a) hot ethyl photofragments from hydrocarbons result in the formation of hydrogen atoms and (b) methyl halides undergo both direct and indirect photolytic scissions of the C---H bonds at 157 nm.

  11. Two-photon polarization-selective etching of emergent nano-structures on diamond surfaces.

    PubMed

    Lehmann, A; Bradac, C; Mildren, R P

    2014-01-01

    Optical techniques have advanced considerably in recent years to enable processing of surfaces with a resolution less than the wavelength of light. Despite the highly selective nature of light-matter interactions, however, efforts to increase resolution to the scale of single atoms are hampered by rapid and efficient dissipation of the absorbed energy to the surrounding matrix. Here we show that two-photon surface excitation using ultraviolet light provides a method for selectively removing carbon from diamond surfaces. Polished surfaces etched by this method develop ultra-deep subwavelength structures with morphologies dependent on the polarization of the incident laser with respect to the crystal axes. As well as revealing a practical and versatile method for nano-patterning of diamond surfaces, we show that the results comprise mesoscopic evidence for bond scission via a highly localized optical interaction that may lead to the development of new optical approaches for ultra-nanoscale (<10 nm) surface structuring. PMID:24594857

  12. Induced fission of Pu240 within a real-time microscopic framework

    DOE PAGESBeta

    Bulgac, Aurel; Magierski, Piotr; Roche, Kenneth J.; Stetcu, Ionel

    2016-03-25

    Here, we describe the fissioning dynamics of 240Pu from a configuration in the proximity of the outer fission barrier to full scission and the formation of the fragments within an implementation of density functional theory extended to superfluid systems and real-time dynamics. The fission fragments emerge with properties similar to those determined experimentally, while the fission dynamics appears to be quite complex, with many excited shape and pairing modes. The evolution is found to be much slower than previously expected, and the ultimate role of the collective inertia is found to be negligible in this fully nonadiabatic treatment of nuclearmore » dynamics, where all collective degrees of freedom (CDOF) are included (unlike adiabatic treatments with a small number of CDOF).« less

  13. A DNA enzyme with N-glycosylase activity

    NASA Technical Reports Server (NTRS)

    Sheppard, T. L.; Ordoukhanian, P.; Joyce, G. F.

    2000-01-01

    In vitro evolution was used to develop a DNA enzyme that catalyzes the site-specific depurination of DNA with a catalytic rate enhancement of about 10(6)-fold. The reaction involves hydrolysis of the N-glycosidic bond of a particular deoxyguanosine residue, leading to DNA strand scission at the apurinic site. The DNA enzyme contains 93 nucleotides and is structurally complex. It has an absolute requirement for a divalent metal cation and exhibits optimal activity at about pH 5. The mechanism of the reaction was confirmed by analysis of the cleavage products by using HPLC and mass spectrometry. The isolation and characterization of an N-glycosylase DNA enzyme demonstrates that single-stranded DNA, like RNA and proteins, can form a complex tertiary structure and catalyze a difficult biochemical transformation. This DNA enzyme provides a new approach for the site-specific cleavage of DNA molecules.

  14. Surface Modification of Polyimide Film by Dielectric Barrier Discharge at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Peng, Shi; Li, Lingjun; Li, Wei; Wang, Chaoliang; Guo, Ying; Shi, Jianjun; Zhang, Jing

    2016-04-01

    In this paper, polyimide (PI) films are modified using an atmospheric pressure plasma generated by a dielectric barrier discharge (DBD) in argon. Surface performance of PI film and its dependence on exposure time from 0 s to 300 s are investigated by dynamic water contact angle (WCA), field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy in attenuated total multiple reflection mode (FTIR-ATR). The study demonstrates that dynamic WCA exhibits a minimum with 40 s plasma treatment, and evenly distributed nano-dots and shadow concaves appeared for 40 s and 12 s Ar plasma treatment individually. A short period of plasma modification can contribute to the scission of the imide ring and the introduction of C-O and C=O (-COOH) by detailed analysis of FTIR-ATR.

  15. Selective hydrogenation of 1,3-butadiene on platinum–copper alloys at the single-atom limit

    PubMed Central

    Lucci, Felicia R.; Liu, Jilei; Marcinkowski, Matthew D.; Yang, Ming; Allard, Lawrence F.; Flytzani-Stephanopoulos, Maria; Sykes, E. Charles H.

    2015-01-01

    Platinum is ubiquitous in the production sectors of chemicals and fuels; however, its scarcity in nature and high price will limit future proliferation of platinum-catalysed reactions. One promising approach to conserve platinum involves understanding the smallest number of platinum atoms needed to catalyse a reaction, then designing catalysts with the minimal platinum ensembles. Here we design and test a new generation of platinum–copper nanoparticle catalysts for the selective hydrogenation of 1,3-butadiene,, an industrially important reaction. Isolated platinum atom geometries enable hydrogen activation and spillover but are incapable of C–C bond scission that leads to loss of selectivity and catalyst deactivation. γ-Alumina-supported single-atom alloy nanoparticle catalysts with <1 platinum atom per 100 copper atoms are found to exhibit high activity and selectivity for butadiene hydrogenation to butenes under mild conditions, demonstrating transferability from the model study to the catalytic reaction under practical conditions. PMID:26449766

  16. Asymmetric Desymmetrization via Metal-Free C-F Bond Activation: Synthesis of 3,5-Diaryl-5-fluoromethyloxazolidin-2-ones with Quaternary Carbon Centers.

    PubMed

    Tanaka, Junki; Suzuki, Satoru; Tokunaga, Etsuko; Haufe, Günter; Shibata, Norio

    2016-08-01

    We disclose the first asymmetric activation of a non-activated aliphatic C-F bond in which a conceptually new desymmetrization of 1,3-difluorides by silicon-induced selective C-F bond scission is a key step. The combination of a cinchona alkaloid based chiral ammonium bifluoride catalyst and N,O-bis(trimethylsilyl)acetoamide (BSA) as the silicon reagent enabled the efficient catalytic cycle of asymmetric Csp3 -F bond cleavage under mild conditions with high enantioselectivities. The ortho effect of the aryl group at the prostereogenic center is remarkable. This concept was applied for the asymmetric synthesis of promising agrochemical compounds, 3,5-diaryl-5-fluoromethyloxazolidin-2-ones bearing a quaternary carbon center.

  17. Microscopic modeling of mass and charge distributions in the spontaneous fission of 240Pu

    DOE PAGESBeta

    Sandhukhan, Jhilam; Nazarewicz, Witold; Schunck, Nicolas

    2016-01-20

    We propose a methodology to calculate microscopically the mass and charge distributions of spontaneous fission yields. We combine the multidimensional minimization of collective action for fission with stochastic Langevin dynamics to track the relevant fission paths from the ground-state configuration up to scission. The nuclear potential energy and collective inertia governing the tunneling motion are obtained with nuclear density functional theory in the collective space of shape deformations and pairing. As a result, we obtain a quantitative agreement with experimental data and find that both the charge and mass distributions in the spontaneous fission of 240Pu are sensitive both tomore » the dissipation in collective motion and to adiabatic fission characteristics.« less

  18. Alcohol-Induced C-N Bond Cleavage of Cyclometalated N-Heterocyclic Carbene Ligands with a Methylene-Linked Pendant Imidazolium Ring.

    PubMed

    Zhong, Wei; Fei, Zhaofu; Scopelliti, Rosario; Dyson, Paul J

    2016-08-16

    Reaction of the pentamethylcyclopentadienyl rhodium iodide dimer [Cp*RhI2 ]2 with 1,1'-diphenyl-3,3'-methylenediimidazolium diiodide in non-alcohol solvents, in the presence of base, led to the formation of bis-carbene complex [Cp*Rh(bis-NHC)I]I (bis-NHC=1,1'-diphenyl-4,4'-methylenediimidazoline-5,5'-diylidene). In contrast, when employing alcohols as the solvent in the same reaction, cleavage of a methylene C-N bond is observed, affording ether-functionalized (cyclometalated) carbene ligands coordinated to the metal center and the concomitant formation of complexes with a coordinated imidazole ligand. Studies employing other 1,1'-diimidazolium salts indicate that the cyclometalation step is a prerequisite for the activation/scission of the C-N bond and, based on additional experimental data, a SN 2 mechanism for the reaction is tentatively proposed. PMID:27412824

  19. Measurement of DNA damage induced by irradiation with gamma-rays from a TRIGA Mark II research reactor in human cells using Fast Micromethod.

    PubMed

    Hassanein, Hamdy; Müller, Claudia I; Schlösser, Dietmar; Kratz, Karl-Ludwig; Senyuk, Olga F; Schröder, Heinz C

    2002-06-01

    The Fast Micromethod is a novel quick and convenient microplate assay for determination of DNA single-strand breaks. This method measures the rate of unwinding of cellular DNA upon exposure to alkaline conditions using a fluorescent dye which preferentially binds to double-stranded DNA. Here we applied this method to determine the levels of DNA single-strand breaks in HeLa cells induced by y-irradiation deriving from fission isotopes and activation products at the TRIGA Mark II research reactor in Mainz. An increased strand scission factor (SSF) value, which is indicative for DNA damage, was found at doses of 1 Gy and higher. A similar increase in SSF value, which further increased in a dose-dependent manner, was found in human peripheral blood mononuclear cells after irradiation with 6 MV X-rays from a linear accelerator to give a total exposure of 0.5 to 10 Gy.

  20. Metal modified tungsten carbide (WC) for catalytic and electrocatalytic applications

    NASA Astrophysics Data System (ADS)

    Mellinger, Zachary J.

    that the binding energies for methanol and methoxy as well as ethanol and ethoxy on one monolayer (ML) Pd/WC are more similar to Pd than to WC. This predicts that the ML Pd/WC surface should have catalytic properties more similar to Pd than to WC. Ultra--high vacuum (UHV) experiments were then performed to determine the reaction products and pathways for methanol and ethanol on Pd(111), WC, and Pd/WC surfaces. These studies showed that the WC surface was very active toward the O--H bond cleavage to produce a methoxy intermediate, although WC was also undesirable because it was active for C--O bond scission and less active for the C--H bond scission. Adding Pd on WC enhanced the scission of the C--H bonds of methoxy while removing the C--O bond scission reaction pathway, suggesting a synergistic effect of using Pd/WC as electrocatalysts for methanol and ethanol decomposition. Dissociation of water, which is important for CO tolerance, was also investigated using UHV techniques with the conclusion that both the WC and Pd/WC surfaces dissociated water. The predictions from UHV studies was verified in electrochemical experiments using cyclic voltammetry (CV) and chronoamperometry (CA) measurements of electro--oxidation of methanol and ethanol in an alkaline environment. These experiments showed that Pd/WC was electrochemically active towards methanol and ethanol decomposition and has greater electrochemical stability over time than pure Pd, potentially due to higher CO tolerance for Pd/WC.

  1. The Mitochondrial Fission Receptor MiD51 Requires ADP as a Cofactor

    PubMed Central

    Losón, Oliver C.; Liu, Raymond; Rome, Michael E.; Meng, Shuxia; Kaiser, Jens T.; Shan, Shu-ou; Chan, David C.

    2014-01-01

    SUMMARY Mitochondrial fission requires recruitment of dynamin-related protein 1 (Drp1) to the mitochondrial surface and activation of its GTP-dependent scission function. The Drp1 receptors MiD49 and MiD51 recruit Drp1 to facilitate mitochondrial fission, but their mechanism of action is poorly understood. Using X-ray crystallography, we demonstrate that MiD51 contains a nucleotidyl transferase domain that binds ADP with high affinity. MiD51 recruits Drp1 via a surface loop that functions independently of ADP binding. However, in the absence of nucleotide binding, the recruited Drp1 cannot be activated for fission. Purified MiD51 strongly inhibits Drp1 assembly and GTP hydrolysis in the absence of ADP. Addition of ADP relieves this inhibition and promotes Drp1 assembly into spirals with enhanced GTP hydrolysis. Our results reveal ADP as an essential cofactor for MiD51 during mitochondrial fission. PMID:24508339

  2. Hydrolytic degradation of Kevlar 49 fibers

    SciTech Connect

    Morgan, R.J.; Pruneda, C.O.; Butler, N.; Kong, F.M.; Caley, L.; Moore, R.L.

    1983-12-05

    The hydrolytic degradation of Kevlar 49 fibers and the principal parameters that control this degradation are presented. Hydrolytic chain scission of the amide linkage and corresponding fiber strength deterioration are considered in terms of RH, time, temperature and stress level. The rates of hydrolytic degradation at 100% RH in the 100 to 200/sup 0/C range are reported. The estimated rates of fiber degradation in various service environment conditions are also reported and shown not to be serious. The impurities present in Kevlar 49 fibers and their effect on hydrolytic degradation are also discussed. In addition, the aging of Kevlar 49 fibers as a result of exposure to uv and stress are reviewed.

  3. An ESR and NMR study of the radiolysis of n-alkanes: Crystal structure dependence

    NASA Astrophysics Data System (ADS)

    Toriyama, K.; Okazaki, M.; Nunome, K.; Matsuura, K.

    The process of radiation damage for long-chain n-alkanes was investigated to elucidate that for polyethylene. Chain-end alkyl radicals were preferentially formed not only through primary C-H scission but also through a hydrogen atom reaction in odd- n-alkane, as was shown by analysis of the ESR spectra for isotopic mixtures of tridecane- h28/tridecane- d28 and nonadecane- h40/nonadecane- d40. To elucidate the mode of alkyl radical migration in solids through intermolecular hydrogen atom abstraction, D/H exchange was detected in mixed crystals of eicosane- d42/eicosane- h42. The chain-end region was found to be more reactive than the inner region for radical site migration. In addition, formation of a microscopic amorphous island by destruction of the crystal lattice was also detected. The influences of molecular packing were large in all cases.

  4. Copper-obatoclax derivative complexes mediate DNA cleavage and exhibit anti-cancer effects in hepatocellular carcinoma.

    PubMed

    Su, Jung-Chen; Chang, Jung-Hua; Huang, Jui-Wen; Chen, Peter P-Y; Chen, Kuen-Feng; Tseng, Ping-Hui; Shiau, Chung-Wai

    2015-02-25

    Obatoclax is an indole-pyrrole compound that induces cancer cell apoptosis through targeting the anti-apoptotic Bcl-2 protein family. Previously, we developed a series of obatoclax derivatives and studied their STAT3 inhibition-dependent activity against cancer cell lines. The obatoclax analog, prodigiosin, has been reported to mediate DNA cleavage in cancer cells by coordinating with copper complexes. To gain an understanding of copper-obatoclax complex activity, we applied obatoclax derivatives to examine their copper-mediated nuclease activity as a means to establish a basis for structure activity relationship. Replacement of the indole ring of obatoclax with furanyl, thiophenyl or Boc-indolyl rings reduced the DNA cleavage ability. The same effect was achieved through the replacement of the obatoclax pyrrolyl ring with thiazolidinedione and thioacetal. Among the compounds tested, we demonstrated that the complex of obatoclax or compound 7 with copper exhibited potent DNA strand scission which correlated with HCC cell growth inhibition.

  5. Mixing Efficiency, Coarsening, and Self-Compatibilization in Immiscible Polymer Blends Processed via Solid-State Shear Pulverization

    NASA Astrophysics Data System (ADS)

    Davydov, Albert; Khait, Klementina; Torkelson, John

    2000-03-01

    Solid-state shear pulverization (SSSP) is a continuous, mechanical alloying process employing simultaneous effects of high pressure and shear deformation to pulverize and mix polymers. Under certain conditions SSSP can result in limited chain scission and polymeric radical formation. In immiscible blends, these radicals may be able to recombine in interfacial regions or regions of high mixing resulting in block copolymer formation and compatibilization. The effects of SSSP on amorphous polyamide (PA)/polystyrene (PS) and PS/low density polyethylene (LDPE) blends have been studied. As compared to melt-mixed blends, SSSP yields blends with enhanced blend morphology refinement or dispersion, and in certain cases enhanced bulk mechanical properties, particularly elongation at break and impact strength. Comparisons of dispersed-phase coarsening during high temperature, liquid-state annealing of the SSSP - processed and conventionally melt-mixed blends will be discussed in terms of the potential for achieving effective compatibilization of particular blends via SSSP.

  6. Induced Fission of (240)Pu within a Real-Time Microscopic Framework.

    PubMed

    Bulgac, Aurel; Magierski, Piotr; Roche, Kenneth J; Stetcu, Ionel

    2016-03-25

    We describe the fissioning dynamics of ^{240}Pu from a configuration in the proximity of the outer fission barrier to full scission and the formation of the fragments within an implementation of density functional theory extended to superfluid systems and real-time dynamics. The fission fragments emerge with properties similar to those determined experimentally, while the fission dynamics appears to be quite complex, with many excited shape and pairing modes. The evolution is found to be much slower than previously expected, and the ultimate role of the collective inertia is found to be negligible in this fully nonadiabatic treatment of nuclear dynamics, where all collective degrees of freedom (CDOF) are included (unlike adiabatic treatments with a small number of CDOF).

  7. The mitochondrial fission receptor MiD51 requires ADP as a cofactor.

    PubMed

    Losón, Oliver C; Liu, Raymond; Rome, Michael E; Meng, Shuxia; Kaiser, Jens T; Shan, Shu-ou; Chan, David C

    2014-03-01

    Mitochondrial fission requires recruitment of dynamin-related protein 1 (Drp1) to the mitochondrial surface and activation of its GTP-dependent scission function. The Drp1 receptors MiD49 and MiD51 recruit Drp1 to facilitate mitochondrial fission, but their mechanism of action is poorly understood. Using X-ray crystallography, we demonstrate that MiD51 contains a nucleotidyl transferase domain that binds ADP with high affinity. MiD51 recruits Drp1 via a surface loop that functions independently of ADP binding. However, in the absence of nucleotide binding, the recruited Drp1 cannot be activated for fission. Purified MiD51 strongly inhibits Drp1 assembly and GTP hydrolysis in the absence of ADP. Addition of ADP relieves this inhibition and promotes Drp1 assembly into spirals with enhanced GTP hydrolysis. Our results reveal ADP as an essential cofactor for MiD51 during mitochondrial fission.

  8. Two in one or one in two? Pushing off from Jung with Wolfgang Giegerich.

    PubMed

    Saban, Mark

    2015-11-01

    This paper responds to a recent paper by Wolfgang Giegerich entitled 'Two Jungs: apropos a paper by Mark Saban'. Giegerich disputes my assertion that the 'rigorous notion' at the heart of his psychology 'finds no source in Jung's psychology, implicit or explicit'. In order to do this he posits the existence of two Jungs, an exoteric Jung and an esoteric Jung. The implications of Giegerich's binary scission of Jung are explored in this paper, and show that the tendency to exalt one Jung while disparaging the other betrays a comprehensive blindness toward the contradictory complexity of Jung's psychology as a whole. It is suggested that this blindness is the consequence of Giegerich's systematic prioritization of a neo-Hegelian agenda that is in profound conflict with the telos of Jung's psychology.

  9. Mechanochemical strengthening of a synthetic polymer in response to typically destructive shear forces.

    PubMed

    Ramirez, Ashley L Black; Kean, Zachary S; Orlicki, Joshua A; Champhekar, Mangesh; Elsakr, Sarah M; Krause, Wendy E; Craig, Stephen L

    2013-09-01

    High shear stresses are known to trigger destructive bond-scission reactions in polymers. Recent work has shown that the same shear forces can be used to accelerate non-destructive reactions in mechanophores along polymer backbones, and it is demonstrated here that such mechanochemical reactions can be used to strengthen a polymer subjected to otherwise destructive shear forces. Polybutadiene was functionalized with dibromocyclopropane mechanophores, whose mechanical activation generates allylic bromides that are crosslinked in situ by nucleophilic substitution reactions with carboxylates. The crosslinking is activated efficiently by shear forces both in solvated systems and in bulk materials, and the resulting covalent polymer networks possess moduli that are orders-of-magnitude greater than those of the unactivated polymers. These molecular-level responses and their impact on polymer properties have implications for the design of materials that, like biological materials, actively remodel locally as a function of their physical environment. PMID:23965677

  10. Mechanochemical strengthening of a synthetic polymer in response to typically destructive shear forces

    NASA Astrophysics Data System (ADS)

    Ramirez, Ashley L. Black; Kean, Zachary S.; Orlicki, Joshua A.; Champhekar, Mangesh; Elsakr, Sarah M.; Krause, Wendy E.; Craig, Stephen L.

    2013-09-01

    High shear stresses are known to trigger destructive bond-scission reactions in polymers. Recent work has shown that the same shear forces can be used to accelerate non-destructive reactions in mechanophores along polymer backbones, and it is demonstrated here that such mechanochemical reactions can be used to strengthen a polymer subjected to otherwise destructive shear forces. Polybutadiene was functionalized with dibromocyclopropane mechanophores, whose mechanical activation generates allylic bromides that are crosslinked in situ by nucleophilic substitution reactions with carboxylates. The crosslinking is activated efficiently by shear forces both in solvated systems and in bulk materials, and the resulting covalent polymer networks possess moduli that are orders-of-magnitude greater than those of the unactivated polymers. These molecular-level responses and their impact on polymer properties have implications for the design of materials that, like biological materials, actively remodel locally as a function of their physical environment.

  11. Mechanochemical strengthening of a synthetic polymer in response to typically destructive shear forces

    PubMed Central

    Black Ramirez, Ashley L.; Kean, Zachary S.; Orlicki, Joshua A.; Champhekar, Mangesh; Elsakr, Sarah M.; Krause, Wendy E.; Craig, Stephen L.

    2014-01-01

    High shear stresses are known to trigger destructive bond-scission reactions in polymers. Recent work has shown that the same shear forces can be used to accelerate non-destructive reactions in mechanophores along polymer backbones, and it is demonstrated here that such mechanochemical reactions can be used to strengthen a polymer subjected to otherwise destructive shear forces. Polybutadiene was functionalized with dibromocyclopropane mechanophores, whose mechanical activation generates allylic bromides that are crosslinked in situ by nucleophilic substitution reactions with carboxylates. The crosslinking is activated efficiently by shear forces both in solvated systems and in bulk materials, and the resulting covalent polymer networks possess moduli that are orders-of-magnitude greater than those of the unactivated polymers. These molecular-level responses and their impact on polymer properties have implications for the design of materials that, like biological materials, actively remodel locally as a function of their physical environment. PMID:23965677

  12. Adsorption of metal ions by carboxymethylchitin and carboxymethylchitosan hydrogels

    NASA Astrophysics Data System (ADS)

    Wasikiewicz, Jaroslaw M.; Nagasawa, Naotsugu; Tamada, Masao; Mitomo, Hiroshi; Yoshii, Fumio

    2005-07-01

    Radiation cross-linking of CM-chitin and CM-chitosan has been investigated. Such parameters of radiation cross-linking as gelation doses, cross-linking and degradation radiation yields and ratios of scission to cross-linking has been determined for both polymers. The absorption ability of various metal ions into EB-radiation cross-linked carboxymethylchitin and carboxymethylchitosan has been investigated. The highest adsorption of scandium and gold has been obtained for carboxymethylchitin (CMCht) and carboxymethylchitosan (CMChts), respectively. Kinetic studies showed that adsorption of most of the metal ions occur in a relatively short period of time (2 h). Detail investigation of adsorption of gold ions has been carried out for both hydrogels. The maximum uptake of Au cations, based on Langmuir equation was determined to be 37.59 for CM-chitosan and 11.86 for CM-chitin. Both hydrogels indicate favorable adsorption of gold cations.

  13. Transition State Features in the Hepatitis Delta Virus (HDV) Ribozyme Reaction Revealed by Atomic Perturbations

    PubMed Central

    Koo, Selene C.; Lu, Jun; Li, Nan-Sheng; Leung, Edward; Das, Subha R.; Harris, Michael E.; Piccirilli, Joseph A.

    2016-01-01

    Endonucleolytic ribozymes constitute a class of non-coding RNAs that catalyze single strand RNA scission. With crystal structures available for all of the known ribozymes, a major challenge involves relating functional data to the physically observed RNA architecture. In the case of the HDV ribozyme, there are three high-resolution crystal structures, the product state of the reaction and two precursor variants, with distinct mechanistic implications. Here, we develop new strategies to probe the structure and catalytic mechanism of a ribozyme. First, we use double mutant cycles to distinguish differences in functional group proximity implicated by the crystal structures. Second, we use a corrected form of the Brønsted equation to assess the functional significance of general acid catalysis in the system. Our results delineate the functional relevance of atomic interactions inferred from structure, and suggest that the HDV ribozyme transition state resembles the cleavage product in the degree of proton transfer to the leaving group. PMID:26125657

  14. A DFT study on the possibility of using boron nitride nanotubes as a dehydrogenation catalyst for methanol

    NASA Astrophysics Data System (ADS)

    Esrafili, Mehdi D.; Nurazar, Roghaye

    2014-09-01

    The adsorption and subsequent dissociative dehydrogenation reaction of methanol (CH3OH) on (6,0) zigzag boron nitride nanotube (BNNT) are investigated using the density functional theory calculations. Five adsorption types and four reaction channels are identified. The calculated adsorption energies range from -1.4 to -21.9 kcal/mol. The results indicate that O-H bond scission is the most favorable pathway on the tube surface. It is predicted that on the surface of the BNNT, the rate-determining step is the dehydrogenation of adsorbed OCH3. The activation energy barrier for generation of a H2 molecule and its subsequent desorption from the surface is approximately 28 kcal/mol. The side reaction that generates CH3 and OH fragments is exothermic by -1.6 kcal/mol with an energy-barrier height of 58 kcal/mol.

  15. Quantitative comparison of wear debris from UHMWPE that has and has not been sterilised by gamma irradiation.

    PubMed

    Besong, A A; Tipper, J L; Ingham, E; Stone, M H; Wroblewski, B M; Fisher, J

    1998-03-01

    Ultra-high-molecular-weight polyethylene (UHMWPE) components for total joint replacement generate wear particles which cause adverse biological tissue reactions leading to osteolysis and loosening. Sterilisation of UHMWPE components by gamma irradiation in air causes chain scissions which initiate a long-term oxidative process that degrades the chemical and mechanical properties of the polyethylene. Using a tri-pin-on-disc tribometer we studied the effect of ageing for ten years after gamma irradiation in air on the volumetric wear, particle size distribution and the number of particles produced by UHMWPE when sliding against a stainless-steel counterface. The aged and irradiated material produced six times more volumetric wear and 34 times more wear particles per unit load per unit sliding distance than non-sterilised UHMWPE. Our findings indicate that oxidative degradation of polyethylene after gamma irradiation in air with ageing produces more wear.

  16. Migration and sensory changes of packaging materials caused by ionising radiation

    NASA Astrophysics Data System (ADS)

    Welle, Frank; Mauer, Alexandra; Franz, Roland

    2002-03-01

    Irradiation of packaging materials—in most cases plastics—generally lead to a formation of free radicals and ions, with secondary effects such as cross-linking as well as oxidative chain scission. These effects result in a formation of volatile radiolysis products which may induce off-odours in the polymers and may change the migration characteristics of packaging materials. Irradiation affect also polymer additives which change the specific migration behaviour of polymer additives and additive related decomposition products. Migration and sensory changes of pre-sterilised packaging materials have consequences on the quality of packaged goods and consumer's safety. Therefore, migration and sensory properties of packaging materials have specific regulations. Within this paper the effects of the formation of radiolysis products on overall migration, specific migration of food additives or radiolysis products as well as on sensory changes are discussed in view of current European food law.

  17. Actinide-Catalyzed Intermolecular Addition of Alcohols to Carbodiimides.

    PubMed

    Batrice, Rami J; Kefalidis, Christos E; Maron, Laurent; Eisen, Moris S

    2016-02-24

    The unprecedented actinide-catalyzed addition of alcohols to carbodiimides is presented. This represents a rare example of thorium-catalyzed transformations of an alcoholic substrate and the first example of uranium complexes showing catalytic reactivity with alcohols. Using the uranium and thorium amides U[N(SiMe3)2]3 and [(Me3Si)2N]2An[κ(2)-(N,C)-CH2Si(CH3)2N(SiMe3)] (An = Th or U), alcohol additions to unsaturated carbon-nitrogen bonds are achieved in short reaction times with excellent selectivities and high to excellent yields. Computational studies, supported by experimental thermodynamic data, suggest plausible models of the profile of the reaction which allow the system to overcome the high barrier of scission of the actinide-oxygen bond. Accompanied by experimentally determined kinetic parameters, a plausible mechanism is proposed for the catalytic cycle. PMID:26844823

  18. Fission dynamics at low excitation energy

    NASA Astrophysics Data System (ADS)

    Aritomo, Y.; Chiba, S.; Ivanyuk, F.

    2014-11-01

    The mass asymmetry in the fission of 236U at low excitation energy is clarified by the analysis of the trajectories obtained by solving the Langevin equations for the shape degrees of freedom. It is demonstrated that the position of the peaks in the mass distribution of fission fragments is determined mainly by the saddle point configuration originating from the shell correction energy. The width of the peaks, on the other hand, results from the shape fluctuations close to the scission point caused by the random force in the Langevin equation. We have found out that the fluctuations between elongated and compact shapes are essential for the fission process. According to our results the fission does not occur with continuous stretching in the prolate direction, similarly to that observed in starch syrup, but is accompanied by the fluctuations between elongated and compact shapes. This picture presents a new viewpoint of fission dynamics and the splitting mechanism.

  19. Use of molecular beacons for the rapid analysis of DNA damage induced by exposure to an atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Kurita, Hirofumi; Miyachika, Saki; Yasuda, Hachiro; Takashima, Kazunori; Mizuno, Akira

    2015-12-01

    A rapid method for evaluating the damage caused to DNA molecules upon exposure to plasma is demonstrated. Here, we propose the use of a molecular beacon for rapid detection of DNA strand breaks induced by atmospheric pressure plasma jet (APPJ) irradiation. Scission of the molecular beacon by APPJ irradiation leads to separation of the fluorophore-quencher pair, resulting in an increase in fluorescence that directly correlates with the DNA strand breaks. The results show that the increase in fluorescence intensity is proportional to the exposure time and the rate of fluorescence increase is proportional to the discharge power. This simple and rapid method allows the estimation of DNA damage induced by exposure to a non-thermal plasma.

  20. Shell energy and the level-density parameter of hot nuclei

    SciTech Connect

    Nerlo-Pomorska, Bozena; Pomorski, Krzysztof; Bartel, Johann

    2006-09-15

    Macroscopic-microscopic calculations have been performed with the Yukawa folded mean field for 134 spherical even-even nuclei and 6 deformed ones at temperatures 0{<=}T{<=}5 MeV and elongations ranging from oblate shapes to the scission configuration of fissioning nuclei. The Strutinsky type free-energy shell corrections for this sample of nuclei and their temperature and deformation dependence are found by a folding procedure in particle-number space. The average dependence of the single-particle level-density parameter on mass number A and isospin I is determined and compared with previous estimates obtained using the relativistic mean-field theory, the Hartree-Fock approximation with the Skyrme effective interaction, and the phenomenological Thomas-Fermi approach adjusted to experimental data. The estimates for the level-density parameter obtained for different deformations are fitted by a liquid-drop type expression.

  1. Thermal Stability of Fluorinated Polydienes Synthesized by Addition of Difluorocarbene

    SciTech Connect

    Huang, Tianzi; Wang, Xiaojun; Malmgren, Thomas W; Hong, Kunlun; Mays, Jimmy

    2012-01-01

    Linear PCHD and polyisoprenes with different microstructures and molecular weights are synthesized and chemically modified to improve their thermal and chemical stability by forming a three-membered ring structure containing two C-F bonds. Pyrolysis of these fluorinated polydienes proceeds through a two-stage decomposition involving chain scission, crosslinking, dehydrogenation, and dehalogenation. The pyrolysis leads to graphite-like residues, whereas their polydiene precursors decompose completely under the same conditions. The fluorination of PCHD enhances its thermal stability. The stronger C-F bond along with high strain of the three-membered ring structure and formation of relatively stable free radicals play an important role in the thermal stability of fluorinated polydienes.

  2. Selective hydrogenation of 1,3-butadiene on platinum–copper alloys at the single-atom limit

    SciTech Connect

    Lucci, Felicia R.; Liu, Jilei; Marcinkowski, Matthew D.; Yang, Ming; Allard, Lawrence F.; Flytzani-Stephanopoulos, Maria; Sykes, E. Charles H.

    2015-10-09

    Platinum is ubiquitous in the production sectors of chemicals and fuels; however, its scarcity in nature and high price will limit future proliferation of platinum-catalysed reactions. One definite approach to conserve platinum involves understanding the smallest number of platinum atoms needed to catalyse a reaction, then designing catalysts with the minimal platinum ensembles. Here we design and test a new generation of platinum–copper nanoparticle catalysts for the selective hydrogenation of 1,3-butadiene,, an industrially important reaction. Isolated platinum atom geometries enable hydrogen activation and spillover but are incapable of C–C bond scission that leads to loss of selectivity and catalyst deactivation. γ-Alumina-supported single-atom alloy nanoparticle catalysts with <1 platinum atom per 100 copper atoms are found to exhibit high activity and selectivity for butadiene hydrogenation to butenes under mild conditions, demonstrating transferability from the model study to the catalytic reaction under practical conditions.

  3. Low-energy irradiation effects in cellulose

    SciTech Connect

    Polvi, Jussi; Nordlund, Kai

    2014-01-14

    Using molecular dynamics simulations, we determined the threshold energy for creating defects as a function of the incident angle for all carbon and oxygen atoms in the cellulose monomer. Our analysis shows that the damage threshold energy is strongly dependent on the initial recoil direction and on average slightly higher for oxygen atoms than for carbon atoms in cellulose chain. We also performed cumulative bombardment simulations mimicking low-energy electron irradiation (such as TEM imaging) on cellulose. Analyzing the results, we found that formation of free molecules and broken glucose rings were the most common forms of damage, whereas cross-linking and chain scission were less common. Pre-existing damage was found to increase the probability of cross-linking.

  4. Mechanically triggered heterolytic unzipping of a low-ceiling-temperature polymer

    NASA Astrophysics Data System (ADS)

    Diesendruck, Charles E.; Peterson, Gregory I.; Kulik, Heather J.; Kaitz, Joshua A.; Mar, Brendan D.; May, Preston A.; White, Scott R.; Martínez, Todd J.; Boydston, Andrew J.; Moore, Jeffrey S.

    2014-07-01

    Biological systems rely on recyclable materials resources such as amino acids, carbohydrates and nucleic acids. When biomaterials are damaged as a result of aging or stress, tissues undergo repair by a depolymerization-repolymerization sequence of remodelling. Integration of this concept into synthetic materials systems may lead to devices with extended lifetimes. Here, we show that a metastable polymer, end-capped poly(o-phthalaldehyde), undergoes mechanically initiated depolymerization to revert the material to monomers. Trapping experiments and steered molecular dynamics simulations are consistent with a heterolytic scission mechanism. The obtained monomer was repolymerized by a chemical initiator, effectively completing a depolymerization-repolymerization cycle. By emulating remodelling of biomaterials, this model system suggests the possibility of smart materials where aging or mechanical damage triggers depolymerization, and orthogonal conditions regenerate the polymer when and where necessary.

  5. Mechanically triggered heterolytic unzipping of a low-ceiling-temperature polymer.

    PubMed

    Diesendruck, Charles E; Peterson, Gregory I; Kulik, Heather J; Kaitz, Joshua A; Mar, Brendan D; May, Preston A; White, Scott R; Martínez, Todd J; Boydston, Andrew J; Moore, Jeffrey S

    2014-07-01

    Biological systems rely on recyclable materials resources such as amino acids, carbohydrates and nucleic acids. When biomaterials are damaged as a result of aging or stress, tissues undergo repair by a depolymerization-repolymerization sequence of remodelling. Integration of this concept into synthetic materials systems may lead to devices with extended lifetimes. Here, we show that a metastable polymer, end-capped poly(o-phthalaldehyde), undergoes mechanically initiated depolymerization to revert the material to monomers. Trapping experiments and steered molecular dynamics simulations are consistent with a heterolytic scission mechanism. The obtained monomer was repolymerized by a chemical initiator, effectively completing a depolymerization-repolymerization cycle. By emulating remodelling of biomaterials, this model system suggests the possibility of smart materials where aging or mechanical damage triggers depolymerization, and orthogonal conditions regenerate the polymer when and where necessary.

  6. Ultrastructural Imaging of Endocytic Sites in Saccharomyces cerevisiae by Transmission Electron Microscopy and Immunolabeling

    PubMed Central

    Buser, Christopher; Drubin, David G.

    2014-01-01

    Defining the ultrastructure of endocytic sites and localization of endocytic proteins in Saccharomyces cerevisiae by immunoelectron microscopy is central in understanding the mechanisms of membrane deformation and scission during endocytosis. We show that an improved sample preparation protocol based on high-pressure freezing, freeze substitution, and low-temperature embedding allows us to maintain the cellular fine structure and to immunolabel green fluorescent protein–tagged endocytic proteins or actin in the same sections. Using this technique we analyzed the stepwise deformation of endocytic membranes and immuno-localized the endocytic proteins Abp1p, Sla1p, Rvs167p, and actin, and were able to draw a clear ultrastructural distinction between endocytic sites and eisosomes by immunolocalizing Pil1p. In addition to defining the geometry and the fine structure of budding yeast endocytic sites, we observed associated actin filaments forming a cage-like meshwork around the endocytic membrane. PMID:23458500

  7. Mutants of the EcoRI endonuclease with promiscuous substrate specificity implicate residues involved in substrate recognition.

    PubMed Central

    Heitman, J; Model, P

    1990-01-01

    The EcoRI restriction endonuclease cleaves DNA molecules at the sequence GAATTC. We devised a genetic screen to isolate EcoRI mutants with altered or broadened substrate specificity. In vitro, the purified mutant enzymes cleave both the wild-type substrate and sites which differ from this by one nucleotide (EcoRI star sites). These mutations identify four residues involved in substrate recognition and catalysis that are different from the amino acids proposed to recognize the substrate based on the EcoRI-DNA co-crystal structure. In fact, these mutations suppress EcoRI mutants altered at some of the proposed substrate binding residues (R145, R200). We argue that these mutations permit cleavage of additional DNA sequences either by perturbing or removing direct DNA-protein interactions or by facilitating conformational changes that allosterically couple substrate binding to DNA scission. Images Fig. 2. Fig. 3. Fig. 4. Fig. 5. PMID:2209548

  8. Effect of low doses of 14 MeV neutrons on polymers.

    PubMed

    Rivaton, Agnès; Arnold, Jack; Dos Santos, Morgane; Bussière, Pierre-Olivier; Taviot-Gueho, Christine

    2010-11-01

    The structural modifications of polymers irradiated with 14 MeV neutrons were studied. Two elastomers, a polypropylene-type polymer and poly(ethylene oxide) were exposed to low doses of fast neutrons in the range of 0.3-14 Gy. The radiation damages were observed at the molecular scale by infrared spectroscopy. The morphological changes were investigated by steric exclusion chromatography, insoluble fraction measurements, differential scanning calorimetry and X-ray diffraction. It was found that neutrons provoked oxidation processes accompanied by modifications in the polymer architecture, including chain scissions, crosslinking reactions and changes in the crystallinity. Moreover, the conventional antioxidants were shown to be inefficient in inhibiting the aging of the polymers. These results also suggest that the radiation damages could be used successfully for dosimetry applications using an easily implementable protocol.

  9. The Electrochemical Fluorination of Organosilicon Compounds

    NASA Technical Reports Server (NTRS)

    Seaver, Robert E.

    1961-01-01

    The electrochemical fluorination of tetramethylsilane, hexamethyl-disiloxane, diethyldichlorosilane, amyltrichlorosilane, and phenyltri-chlorosilane was conducted in an Inconel cell equipped with nickel electrodes. A potential of approximately 5.0 volts and a current of approximately 1.0 ampere were used for the electrolysis reaction. In all cases the fluorinations resulted in considerable scission of the carbon-silicon bonds yielding hydrogen and the various fluorinated decomposition products; no fluoroorganosilicon compounds were identified. The main decomposition products were silicon tetrafluoride, the corresponding fluorinated carbon compounds, and the various organofluorosilanes. It is suggested that this is due to the nucleophilic attack of the fluoride ion (or complex fluoride ion) on the carbon-silicon bond.

  10. Use of molecular beacons for the rapid analysis of DNA damage induced by exposure to an atmospheric pressure plasma jet

    SciTech Connect

    Kurita, Hirofumi E-mail: mizuno@ens.tut.ac.jp; Miyachika, Saki; Yasuda, Hachiro; Takashima, Kazunori; Mizuno, Akira E-mail: mizuno@ens.tut.ac.jp

    2015-12-28

    A rapid method for evaluating the damage caused to DNA molecules upon exposure to plasma is demonstrated. Here, we propose the use of a molecular beacon for rapid detection of DNA strand breaks induced by atmospheric pressure plasma jet (APPJ) irradiation. Scission of the molecular beacon by APPJ irradiation leads to separation of the fluorophore-quencher pair, resulting in an increase in fluorescence that directly correlates with the DNA strand breaks. The results show that the increase in fluorescence intensity is proportional to the exposure time and the rate of fluorescence increase is proportional to the discharge power. This simple and rapid method allows the estimation of DNA damage induced by exposure to a non-thermal plasma.

  11. The influence of electron-beam irradiation on the chemical and the structural properties of medical-grade polyurethane

    NASA Astrophysics Data System (ADS)

    Shin, Sukyoung; Lee, Soonhyouk

    2015-07-01

    Thermo plastic polyurethane (TPU) provides excellent bio-compatibility, flexibility and good irradiation resistance; however, extremely high irradiation doses can alter the structure and the function of macromolecules, resulting in oxidation, chain scission and cross-linking. In this study, the effects of e-beam irradiation on the medical-grade thermo plastic polyurethane were studied. Changes in the chain length and their distribution, as well as changes in the molecular structure were studied. The GPC (gel permeation chromatography) results show that the oxidative decomposition is followed by a decrease in the molecular mass and an increase in polydispersity. This indicates a very inhomogeneous degradation, which is a consequence of the specific course and of the intensity of oxidative degradation. This was confirmed by means of mechanical property measurements. Overall, this study demonstrated that medical-grade TPU was affected by radiation exposure, particularly at high irradiation doses.

  12. Metabolism of proctolin, a pentapeptide neurotransmitter in insects

    SciTech Connect

    Quistad, G.B.; Adams, M.E.; Scarborough, R.M.; Carney, R.L.; Schooley, D.A.

    1984-02-06

    The in vitro metabolism of (tyrosyl-3,5-/sup 3/H)proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH) was studied in the following tissues from the American cockroach, Periplaneta americana: proctodeum, midgut, hemolymph, brain, terminal ganglion, and coxal depressor muscles. In all tissues assayed, the Tyr-Leu bond is the primary cleavage site, but scission of the Arg-Tyr bond is also significant. Greater than 90% of the degradative activity is found in the 100,000 X g supernatant from homogenates. In vivo studies with the tobacco hornworm, Manduca sexta, show that topically applied proctolin does not penetrate larval cuticle; proctolin is readily degraded to constituent amino acds (at least to Tyr) upon ingestion.

  13. Immobilization and orientation of Photosystem I reaction centers on solid surfaces. Final report

    SciTech Connect

    1998-01-20

    The overall objective of this project was to test the potential for immobilization and orientation of Photosystem I reaction center protein on solid surfaces. In order to maximize the resources available for this work, bleomycin complexes were used as a test substrate. The reaction of [(H{sub 2}O)(NH{sub 3}){sub 5}Ru{sup II}]{sup 2+} with bleomycin forms at least two stable products following oxidation to the Ru(III) analog. Spectroscopic and electrochemical measurements indicate monodentate binding of [(NH{sub 3}){sub 5}Ru{sup III}] to the imidazole and pyrimidine moieties, with coordination to the latter involving the exocyclic amine nitrogen. DNA cleavage studies show the complexes to be ineffective in DNA strand scission.

  14. Chemistry and Biology of Self-Cleaving Ribozymes.

    PubMed

    Jimenez, Randi M; Polanco, Julio A; Lupták, Andrej

    2015-11-01

    Self-cleaving ribozymes were discovered 30 years ago, but their biological distribution and catalytic mechanisms are only beginning to be defined. Each ribozyme family is defined by a distinct structure, with unique active sites accelerating the same transesterification reaction across the families. Biochemical studies show that general acid-base catalysis is the most common mechanism of self-cleavage, but metal ions and metabolites can be used as cofactors. Ribozymes have been discovered in highly diverse genomic contexts throughout nature, from viroids to vertebrates. Their biological roles include self-scission during rolling-circle replication of RNA genomes, co-transcriptional processing of retrotransposons, and metabolite-dependent gene expression regulation in bacteria. Other examples, including highly conserved mammalian ribozymes, suggest that many new biological roles are yet to be discovered. PMID:26481500

  15. Synthesis of full-length oligonucleotides: cleavage of apurinic molecules on a novel support.

    PubMed Central

    Kwiatkowski, M; Nilsson, M; Landegren, U

    1996-01-01

    The synthesis of oligodeoxynucleotides is marred by several problems that contribute to the formation of defective molecules. This in turn seriously limits the usefulness of such reagents in DNA diagnostics, molecular cloning, DNA structural analysis and in antisense therapy. In particular, depurination reactions during the cyclical steps of synthesis lead to strand scission during cleavage of the completed molecules from the support. Here we present a remedy to this problem: a novel disiloxyl linkage that connects oligonucleotides to the support withstands reaction conditions that allow the removal of the 5' parts of any depurinated molecules. This ensures that all molecules that preserve the 5' protecting group when cleaved from the support will have both correct 3'- and 5'-ends. We demonstrate the application of the support for synthesis of padlock probe molecules. PMID:8972847

  16. A molecular fraction method for measuring personnel radiation doses

    NASA Astrophysics Data System (ADS)

    Fadel, M. A.; Khalil, W. A.; Krodja, R. P.; Sheta, N.; Abd El-Baset, M. S.

    1987-02-01

    This work represents a development in fast and albedo neutron and gamma ray dosimetry, using cellulose nitrate, as a tissue equivalent material, in which radiation damage was registered. The changes in molecular fractions of the polymer were measured after irradiation with neutron fluences from a 252Cf source in the range 10 5-10 10 n/cm 2 and gamma doses in the range 10 -4-10 -1 Gy through the use of gel filtration chromatography. Effects of irradiation on phantom, phantom to dosimeter distance, phantom thickness and storage at extreme environmental conditions were studied on the detector response and readout. The results showed that main chain scission followed by formation of new molecular configurations is the predominant effect of radiation on the polymer. The method enables measurements of neutron fluences and gamma doses in mixed radiation fields. Empirical formulae for calculating the absorbed dose from the measured changes in molecular fraction intensities are given.

  17. The effects of electron and gamma radiation on epoxy-based materials

    NASA Technical Reports Server (NTRS)

    Fornes, R. E.; Memory, J. D.; Gilbert, R. D.; Long, E. R., Jr.

    1982-01-01

    Specimens of graphite/epoxy composites and epoxy resins were exposed to electron and gamma radiation, followed by mechanical property and fundamental measurements. Measurement techniques included: scanning electron microscopy, X-ray diffraction analysis, and electron spin resonance spectroscopic analysis. Results indicate little or no change in flexural properties of miniature specimens of a graphite/epoxy composite and no change in failure mode at the fiber-resin interface and in the crystallinity of the fiber and the resin. Some doubt in the observation of stable flexural properties is cast by electron paramagnetic resonance spectra of a relatively large number of radiation-generated radicals. These generally lead to a change in cross-linking and in chain-scissioning which should alter mechanical properties.

  18. Effect of radiation on the structure of ultrahigh molecular weight polyethylene

    NASA Astrophysics Data System (ADS)

    Kamel, Ihab; Finegold, Leonard

    Radiation sterilization of ultrahigh molecular weight polyethylene (UHMW-PE) was recently found to cause changes in crystallinity, contradicting earlier observations on linear polyethylene of lower molecular weight. In this study, UHMW-PE (Hercules 1900) was gamma-irradiated up to 21 Mrad. Changes in melting and crystallization temperatures, enthalpies of melting and of crystallization, determined by differential scanning calorimetry, are reported. In particular, the temperature at the onset of crystallization provided a clearer view of the radiation damage to the polymer chains. A mechanism based on chain scission is proposed to explain the observed increase in crystallinity in agreement with recent findings. The crystallization temperature may be useful as an indicator of radiation and/or other damage to the UHMW-PE.

  19. Product analysis for polyethylene degradation by radiation and thermal ageing

    NASA Astrophysics Data System (ADS)

    Sugimoto, Masaki; Shimada, Akihiko; Kudoh, Hisaaki; Tamura, Kiyotoshi; Seguchi, Tadao

    2013-01-01

    The oxidation products in crosslinked polyethylene for cable insulation formed during thermal and radiation ageing were analyzed by FTIR-ATR. The products were composed of carboxylic acid, carboxylic ester, and carboxylic anhydride for all ageing conditions. The relative yields of carboxylic ester and carboxylic anhydride increased with an increase of temperature for radiation and thermal ageing. The carboxylic acid was the primary oxidation product and the ester and anhydride were secondary products formed by the thermally induced reactions of the carboxylic acids. The carboxylic acid could be produced by chain scission at any temperature followed by the oxidation of the free radicals formed in the polyethylene. The results of the analysis led to formulation of a new oxidation mechanism which was different from the chain reactions via peroxy radicals and peroxides.

  20. Determining the extent of heparan sulfate depolymerisation following heparin lyase treatment.

    PubMed

    Carnachan, Susan M; Bell, Tracey J; Sims, Ian M; Smith, Raymond A A; Nurcombe, Victor; Cool, Simon M; Hinkley, Simon F R

    2016-11-01

    The depolymerisation of porcine mucosal heparan sulfate under the action of heparin lyases and analysis by size-exclusion chromatography (SEC) is described. Heparan sulfate treated to enzymic bond scission producing a Δ4,5 double-bond and quantified by SEC with ultraviolet-visible (UV) spectroscopic detection (230nm) indicated that the majority of the biopolymer (>85%) was reduced to disaccharides (degree of polymerisation (DP)=2). However, analysis of the SEC eluant using refractive index (RI), which reflects the mass contribution of the oligosaccharides rather than the molar response of a UV chromophore, indicated that a considerable proportion of the digested HS, up to 43%, was present with DP >2. This was supported by a mass balance analysis. These results contradict the accepted literature where "complete digestion" is routinely reported. Herein we report on the composition and methodology utilised to ascertain the extent of depolymerization and disaccharide composition of this important biopolymer. PMID:27516308