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Sample records for reglering utslaepp och

  1. OCH Strap Model Test

    SciTech Connect

    Weber, K.; /Fermilab

    1987-08-26

    The OCH Model was stacked using the appropriate spacers between each absorber plate. Steel bars measuring 3-inch wide by 1/4-inch thick were welded, using 1/8-inch fillet weld, along all the corner edges, except the outer radius edges. On the outer radius, the straps were bolted to the end plates and to plates 9 and 17. The straps on the outer radius were also set in towards the center by approximately 3-inches. The spacers were then knocked out. Twelve strain gauges were mounted on the model. See figure 1 and the OCH strap Model log book for locations. Each rosette was centered in the gap between two absorber plates. The finite element plate model can predict the primary deformations of the OH module in both the cantilever and crushing modes to within 11% of the measured values. The primary stresses away from the support plate for the cantilever mode can be predicted to within 13% by this model. Near the support plate where large shear stresses exists, ANSYS will overpredict the measured stresses substantially. This is probably due to the models inherent inability to allow for shear stress concentrations at the welds. The same over-prediction was seen in the side straps during the OH crush test comparison and is probably attributable to the high shear force in this mode. The simple finite element plate model will provide suitable model of OH module stiffness for use in the analysis of the module assembly. The calculation of shear stresses can be improved by applying the ANSYS calculated inter-element forces to traditional weld strength calculations

  2. OCH Button Test

    SciTech Connect

    Kurita, C.H.; /Fermilab

    1987-05-01

    A test was conducted to make a check on the yield stress of the copper spacer buttons to be used in OCH. The tested button was made from Copper no. 110, cold drawn rod, which has a documented yield stress value of 48,000 psi. The button was put into compression with the load applied to the face of the button. The resulting deflection vs. the applied cross load was then charted with the width of the chart having a 10,000 kg scale. While the chart speed was set at 1 cm/min, the cross head speed was set at .05 cm/min. To find a value of Young's Modulus for the OCH button, the compression test was run again with a chart width scale of 5,000 kg. The chart speed was set at 10 cm/min and the cross head speed at .05 cm/min. The curve generated on the chart was linear in nature until the button reached its yield point. Here, the slope of the curve began to change, increasing over a small area until a new linear curve was established. The point at which the slope changed would be considered the yielding point of the material, but here, there was no single distinct point. Instead there was a smooth transition between the two linear portions of the curve. In order to find where the yield point would occur, two lines were drawn, representing the best fit of each of the two slopes of the curve (before and after the yield point). The intersection of these lines was taken to be the point from which the yield stress could be calculated.

  3. Phil Ochs: No Place in This World

    ERIC Educational Resources Information Center

    Doughty, Howard A.

    2005-01-01

    Phil Ochs was a prominent topical songwriter and singer in the 1960s. He was conventionally considered second only to Bob Dylan in terms of popularity, creativity and influence in the specific genre of contemporary folk music commonly known as "protest music." Whereas Dylan successfully reinvented himself many times in terms of his musical style…

  4. Atmospheric chemistry of CF3CF2OCH3

    NASA Astrophysics Data System (ADS)

    Østerstrøm, Freja F.; Nielsen, Ole John; Wallington, Timothy J.

    2016-06-01

    Smog chamber Fourier transform infrared techniques were used to investigate the kinetics of the reaction of CF3CF2OCH3 with Cl atoms and OH radicals: k(Cl + CF3CF2OCH3) = (1.09 ± 0.16) × 10-13 and k(OH + CF3CF2OCH3) = (1.28 ± 0.19) × 10-14 cm3 molecule-1 s-1 in 700 Torr total pressure of N2/O2 at 296 ± 2 K. The Cl-initiated oxidation of CF3CF2OCH3 gives CF3CF2OCHO in a yield indistinguishable from 100%. An estimate of k(Cl + CF3CF2OCHO) = (1.18 ± 0.34) × 10-14 cm3 molecule-1 s-1 is provided. Based on the OH reaction rate, the atmospheric lifetime of CF3CF2OCH3 is estimated to be 5.0 years. The 100-year time horizon global warming potential of CF3CF2OCH3 is estimated to be 585. The atmospheric impact of CF3CF2OCH3 is discussed.

  5. Crystallization-induced dynamic resolution R-epimer from 25-OCH3-PPD epimeric mixture.

    PubMed

    Zhang, Sainan; Tang, Yun; Cao, Jiaqing; Zhao, Chen; Zhao, Yuqing

    2015-11-15

    25-OCH3-PPD is a promising antitumor dammarane sapogenin isolated from the total saponin-hydrolyzed extract of Panax ginseng berry and Panax notoginseng leaves. 20(R)-25-OCH3-PPD was more potent as an anti-cancer agent than 20(S)-25-OCH3-PPD and epimeric mixture of 25-OCH3-PPD. This paper describes the rapid separation process of the R-epimer of 25-OCH3-PPD from its epimeric mixture by crystallization-induced dynamic resolution (CIDR). The optimized CIDR process was based on single factor analysis and nine well-planned orthogonal design experiments (OA9 matrix). A rapid and sensitive reverse phase high-performance liquid chromatographic (HPLC) method with evaporative light-scattering detector (ELSD) was developed and validated for the quantitation of 25-OCH3-PPD epimeric mixture and crystalline product. Separation and quantitation were achieved with a silica column using a mobile phase consisting of methanol and water (87:13, v/v) at a flow rate of 1.0mL/min. The ELSD detection was performed at 50°C and 3L/min. Under conditions involving 3mL of 95% ethanol, 8% HCl, and a hermetically sealed environment for 72h, the maximum production of 25(R)-OCH3-PPD was achieved with a chemical purity of 97% and a total yield of 87% through the CIDR process. The 25(R)-OCH3-PPD was nearly completely separated from the 220mg 25-OCH3-PPD epimeric mixture. Overall, a simple and steady small-batch purification process for the large-scale production of 25(R)-OCH3-PPD from 25-OCH3-PPD epimeric mixture was developed.

  6. Crystallization-induced dynamic resolution R-epimer from 25-OCH3-PPD epimeric mixture.

    PubMed

    Zhang, Sainan; Tang, Yun; Cao, Jiaqing; Zhao, Chen; Zhao, Yuqing

    2015-11-15

    25-OCH3-PPD is a promising antitumor dammarane sapogenin isolated from the total saponin-hydrolyzed extract of Panax ginseng berry and Panax notoginseng leaves. 20(R)-25-OCH3-PPD was more potent as an anti-cancer agent than 20(S)-25-OCH3-PPD and epimeric mixture of 25-OCH3-PPD. This paper describes the rapid separation process of the R-epimer of 25-OCH3-PPD from its epimeric mixture by crystallization-induced dynamic resolution (CIDR). The optimized CIDR process was based on single factor analysis and nine well-planned orthogonal design experiments (OA9 matrix). A rapid and sensitive reverse phase high-performance liquid chromatographic (HPLC) method with evaporative light-scattering detector (ELSD) was developed and validated for the quantitation of 25-OCH3-PPD epimeric mixture and crystalline product. Separation and quantitation were achieved with a silica column using a mobile phase consisting of methanol and water (87:13, v/v) at a flow rate of 1.0mL/min. The ELSD detection was performed at 50°C and 3L/min. Under conditions involving 3mL of 95% ethanol, 8% HCl, and a hermetically sealed environment for 72h, the maximum production of 25(R)-OCH3-PPD was achieved with a chemical purity of 97% and a total yield of 87% through the CIDR process. The 25(R)-OCH3-PPD was nearly completely separated from the 220mg 25-OCH3-PPD epimeric mixture. Overall, a simple and steady small-batch purification process for the large-scale production of 25(R)-OCH3-PPD from 25-OCH3-PPD epimeric mixture was developed. PMID:26491820

  7. Theoretical investigation on gas-phase reaction of CF3CH2OCH3 with OH radicals and fate of alkoxy radicals (CF3CH(O•)OCH3/CF3CH2OCH2O•).

    PubMed

    Mishra, Bhupesh Kumar; Lily, Makroni; Deka, Ramesh Chandra; Chandra, Asit K

    2014-05-01

    Detailed theoretical investigation has been performed on the mechanism, kinetics and thermochemistry of the gas phase reactions of CF3CH2OCH3 (HFE-263fb2) with OH radicals using ab-initio and DFT methods. Reaction profiles are modeled including the formation of pre-reactive and post-reactive complexes at entrance and exit channels, respectively. Our calculations reveal that hydrogen abstraction from the CH2 group is thermodynamically and kinetically more facile than that from the CH3 group. Using group-balanced isodesmic reactions, the standard enthalpies of formation for CF3CH2OCH3 and radicals (CF3CHOCH3 and CF3CH2OCH2) are also reported for the first time. The calculated bond dissociation energies for the CH bonds are in good agreement with experimental results. At 298K, the calculated total rate coefficient for CF3CH2OCH3+OH reactions is found to be in good agreement with the experimental results. The atmospheric fate of the alkoxy radicals, CF3CH(O)OCH3 and CF3CH2OCH2O are also investigated for the first time using the same level of theory. Out of three plausible decomposition channels, our results clearly point out that reaction with O2 is not the dominant path leading to the formation of CF3C(O)OCH3 for the decomposition of CF3CH(O)OCH3 radical in the atmosphere. This is in accord with the recent report of Osterstrom et al. [CPL 524 (2012) 32] but found to be in contradiction with experimental finding of Oyaro et al. [JPCA 109 (2005) 337].

  8. High Resolution Laser Spectroscopy of SrOCH_3

    NASA Astrophysics Data System (ADS)

    Forthomme, D.; Linton, C.; Tokaryk, D. W.; Adam, A. G.; Granger, A. D.; Downie, L. E.; Hopkins, W. S.

    2011-06-01

    The tilde{A}2E-tilde{X}2A_1 transition of SrOCH_3 was first studied at high resolution by O'Brien et al.footnote{L. C. O'Brien, C. R. Brazier and P. F. Bernath, J. Mol. Spectrosc. 130 (1988) 33-45} using a Broida oven. However lines with typically J≤20 were not observed and congestion prevented them from resolving transitions from the Ω=1/2 component of the upper state. We have studied the tilde{B}2A_1-tilde{X}2A_1 and the tilde{A}2E-tilde{X}2A_1 transitions of SrOCH_3 in a laser ablation molecular jet source, where jet cooling and low Doppler widths greatly simplified the spectra. An optical-optical double resonance technique facilitated definite assignments in a number of the transitions observed. Our analysis of the tilde{A}2E-tilde{X}2A_1 transition was straightforward, but a perturbation was observed in the tilde{B}2A_1 K'=1 F_2 levels. A satisfactory fit was achieved for the tilde{B}2A_1-tilde{X}2A_1 transition when a separate B parameter was used to fit the perturbed levels.

  9. 30. Historic American Buildings Survey SussmanOch, Photographer 1961 FRAGMENT OF ...

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

    30. Historic American Buildings Survey Sussman-Och, Photographer 1961 FRAGMENT OF FIREBACK FOUND IN A HAMPTON OUTBUILDING SHOWING THE 'NORTHAMTON' MARK - Hampton, Mansion, 535 Hampton Lane, Towson, Baltimore County, MD

  10. Protein Production with a Pichia pastoris OCH1 Knockout Strain in Fed-Batch Mode.

    PubMed

    Gmeiner, Christoph; Spadiut, Oliver

    2015-01-01

    The methylotrophic yeast Pichia pastoris is a widely used host organism for recombinant protein production in biotechnology and pharmaceutical industry. However, if the target product describes a glycoprotein, an α-1,6-mannosyltransferase located in the Golgi apparatus of P. pastoris, called OCH1, triggers hypermannosylation of the recombinant protein which significantly impedes following unit operations and hampers biopharmaceutical product applications. A knockout of the och1 gene allows the production of less-glycosylated proteins-however, morphology and physiology of P. pastoris also change, complicating the upstream process. Here, we describe a controlled and efficient bioprocess based on the specific substrate uptake rate (q s) for a recombinant P. pastoris OCH1 knockout strain expressing a peroxidase as model protein. PMID:26082217

  11. Analysis of the Vibrational Spectra of P_3N_3(OCH_2CF_3)_6 and P_4N_4(OCH_2CF_3)_8

    NASA Astrophysics Data System (ADS)

    King, Adrian K.; Plant, David F.; Golding, Peter; Lawson, Michael A.; Davies, Paul B.

    2011-06-01

    The cyclic phosphazene trimer P_3N_3(OCH_2CF_3)_6 and the related cyclic tetramer P_4N_4(OCH_2CF_3)_8 have been proposed as the major low-to-medium temperature pyrolysis products of the parent polyphosphazene (PN(OCH_2CF_3)_2)_n. Recently, both molecules have been synthesized, isolated and their vapour-phase vibrational spectra recorded using a high-resolution FTIR instrument. The interpretation of these spectra is achieved primarily by comparison with the results of high-quality density functional calculations, which enable the principal absorption features to be assigned and conclusions to be drawn regarding the geometries and conformations adopted by both molecules. These in turn allow interesting comparisons to be made with analogous cyclic halo-phosphazenes such as P_3N_3Cl_6 and P_4N_4Cl_8. Work to record in situ the spectra of the vapour-phase pyrolysis products of (PN(OCH_2CF_3)_2)_n and to analyse these results in terms of the tetramer and trimer spectra will also be presented. S. V. Peddada and J. H. Magill Macromolecules 16 (1983) 1258-1264. H. R. Allcock, G. S. McDonnell, G. H. Riding, and I. Manners Chem. Mater. 2 (1990) 425-432. T. R. Manley and D. A. Williams Spectrochimica Acta 23A (1966) 149-165. V. Varma, J. R. Fernandez and C. N. R. Rao J. Mol. Struct. 198 (1989) 403-412.

  12. Atmospheric degradation mechanism of CF{sub 3}OCH{sub 3}

    SciTech Connect

    Christensen, L.K.; Wallington, T.J.; Guschin, A.; Hurley, M.D.

    1999-05-27

    Recognition of the adverse effect of chlorofluorocarbon (CFC) release into the atmosphere has led to an international effort to replace CFCs with environmentally acceptable alternatives. Hydrofluoroethers (HFEs) are a class of compounds which have been developed to replace CFCs in applications such as the cleaning of electronic equipment, heat transfer agents in refrigeration systems, and carrier fluids for lubricant deposition. HFEs are volatile compounds and are released into the atmosphere when used. CF{sub 3}OCH{sub 3} has not been used commercially but is one of the simplest fluoroethers and serves as a model compound for the group of fluorinated ethers. A smog chamber/FTIR technique was used to study the Cl atom initiated oxidation of CF{sub 3}OCH{sub 3} in 700 Torr of N{sub 2}/O{sub 2} at 296 K. Using relative rate techniques it was determined that {kappa}(Cl + CF{sub 3}OCH{sub 3}) = (1.4 {+-} 0.2) {times} 10{sup {minus}13} and {kappa}(Cl + CF{sub 3}OC(O)H) = (9.8 {+-} 1.2) {times} 10{sup {minus}15} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. At 700 Torr of N{sub 2}/O{sub 2} diluent at 296 K reaction with O{sub 2} is the only loss mechanism of the CF{sub 3}OCH{sub 2}O{sup {sm_bullet}} radical. The infrared spectra of the peroxy nitrates CF{sub 3}OCH{sub 2}O{sub 2}NO{sub 2} and CF{sub 3}OC(O)O{sub 2}NO{sub 2} were recorded and compared to the nonfluorinated analogues CH{sub 3}OCH{sub 2}O{sub 2}NO{sub 2} and CH{sub 3}OC(O)O{sub 2}NO{sub 2}. The thermal decomposition rate of CF{sub 3}OC(O)NO{sub 2} is (2.3 {+-} 0.1) {times} 10{sup {minus}4} s{sup {minus}1} in 700 Torr of N{sub 2} at 295.8 K. The reaction of CF{sub 3}OC(O)O{sub 2} radicals with HO{sub 2} radicals gives CF{sub 3}OC(O)H in a yield of (80 {+-} 11)%. The results are discussed with respect to the atmospheric degradation mechanism of CF{sub 3}OCH{sub 3} and other ethers.

  13. A model for Si, SiCH, SiO{sub 2}, SiOCH, and porous SiOCH etch rate calculation in inductively coupled fluorocarbon plasma with a pulsed bias: Importance of the fluorocarbon layer

    SciTech Connect

    Raballand, V.; Cartry, G.; Cardinaud, C.

    2007-09-15

    In a previous paper we showed that selective etching of porous SiOCH with respect to SiO{sub 2} and SiCH is clearly enhanced when using a pulsed bias in inductively coupled fluorocarbon plasma. To understand this pulsed process, a model for etch rate calculation is developed in the present paper. This model explains the etching/deposition threshold shift toward higher bias voltage in pulsed conditions. Rather good confidence is obtained with experimental SiO{sub 2}, Si, SiOCH and SiCH etch rates. Porous SiOCH etching is found to behave slightly differently compared to SiO{sub 2} or SiCH; its chemical etching is assumed to occur even during the beginning of off period. This point could explain why good selectivities between porous SiOCH and SiO{sub 2} and SiCH are obtained.

  14. Vibrational spectra, isolated CH stretching frequencies and CH bond lengths in CH 3OCH 2X compounds (XF, Cl, Br, I)

    NASA Astrophysics Data System (ADS)

    McKean, D. C.; Torto, I.; Morrisson, A. R.

    1983-05-01

    Infrared and Raman spectra are reported for CH 3OCH 2X, CHD 2OCD 2X, CD 3OCHDX (XF, Cl, Br, I) and for CH 3OCD 2Cl and CD 3OCH 2Cl, in various phases. νCHis values are obtained which enable CH bond lengths and dissociation energies to be predicted. The changes in bond lengths from Me 2O to MeOCH 2X and from MeOCH 2F to MeOCH 2Cl are in good agreement with those calculated ab initio and in radical disagreement with microwave-based values. The effect of halogen is to strengthen all the CH bonds present, especially that lying parallel to the CX one. All major features in the spectra are explained if only the gauche skeletal conformer exists in the phases studied. However, two transient bands in solid films of CH 3OCH 2F may indicate the presence of a metastable trans conformer phase. Secure assignments for CH 3OCH 2Cl are based on the CH 3OCD 2Cl and CD 3OCH 2Cl spectra and extended by analogy to most of the vibrations of the F, Br and I compounds.

  15. A General Method for Imine Formation Using B(OCH2CF3)3.

    PubMed

    Reeves, Jonathan T; Visco, Michael D; Marsini, Maurice A; Grinberg, Nelu; Busacca, Carl A; Mattson, Anita E; Senanayake, Chris H

    2015-05-15

    Tris(2,2,2-trifluoroethyl)borate [B(OCH2CF3)3] was found to be a mild and general reagent for the formation of a variety of imines by condensation of amides or amines with carbonyl compounds. N-Sulfinyl, N-toluenesulfonyl, N-(dimethylamino)sulfamoyl, N-diphenylphosphinoyl, N-(α-methylbenzyl), and N-(4-methoxyphenyl) aldimines are all accessible using this reagent at room temperature. The reactions are operationally simple, and the products are obtained without special workup or isolation procedures. PMID:25906082

  16. Mechanism of plasma-induced damage to low-k SiOCH films during plasma ashing of organic resists

    NASA Astrophysics Data System (ADS)

    Takeda, Keigo; Miyawaki, Yudai; Takashima, Seigo; Fukasawa, Masanaga; Oshima, Keiji; Nagahata, Kazunori; Tatsumi, Tetsuya; Hori, Masaru

    2011-02-01

    Plasma-induced damage to porous SiOCH (p-SiOCH) films during organic resist film ashing using dual-frequency capacitively coupled O2 plasmas was investigated using the pallet for plasma evaluation method developed by our group. The damage was characterized by ellipsometry and Fourier-transform infrared spectroscopy. Individual and synergetic damage associated with vacuum ultraviolet (VUV) and UV radiation, radicals, and ions in the O2 plasma were clarified. It was found that the damage was caused not only by radicals but also by synergetic reactions of radicals with VUV and UV radiation emitted by the plasmas. It is noteworthy that the damage induced by plasma exposure without ion bombardment was larger than the damage with ion bombardment. These results differed from those obtained using an H2/N2 plasma for resist ashing. Finally, the mechanism of damage to p-SiOCH caused by O2 and H2/N2 plasma ashing of organic resist films is discussed. These results are very important in understanding the mechanism of plasma-induced damage to p-SiOCH films.

  17. Mechanism of plasma-induced damage to low-k SiOCH films during plasma ashing of organic resists

    SciTech Connect

    Takeda, Keigo; Miyawaki, Yudai; Takashima, Seigo; Fukasawa, Masanaga; Oshima, Keiji; Nagahata, Kazunori; Tatsumi, Tetsuya; Hori, Masaru

    2011-02-01

    Plasma-induced damage to porous SiOCH (p-SiOCH) films during organic resist film ashing using dual-frequency capacitively coupled O{sub 2} plasmas was investigated using the pallet for plasma evaluation method developed by our group. The damage was characterized by ellipsometry and Fourier-transform infrared spectroscopy. Individual and synergetic damage associated with vacuum ultraviolet (VUV) and UV radiation, radicals, and ions in the O{sub 2} plasma were clarified. It was found that the damage was caused not only by radicals but also by synergetic reactions of radicals with VUV and UV radiation emitted by the plasmas. It is noteworthy that the damage induced by plasma exposure without ion bombardment was larger than the damage with ion bombardment. These results differed from those obtained using an H{sub 2}/N{sub 2} plasma for resist ashing. Finally, the mechanism of damage to p-SiOCH caused by O{sub 2} and H{sub 2}/N{sub 2} plasma ashing of organic resist films is discussed. These results are very important in understanding the mechanism of plasma-induced damage to p-SiOCH films.

  18. Analysis of the Pressure and Temperature Dependence of the Complex-Forming Bimolecular Reaction CH3OCH3 + Fe(.).

    PubMed

    Ard, Shaun G; Johnson, Ryan S; Martinez, Oscar; Shuman, Nicholas S; Guo, Hua; Troe, Jürgen; Viggiano, Albert

    2016-07-14

    The kinetics of the reaction CH3OCH3 + Fe(+) has been studied between 250 and 600 K in the buffer gas He at pressures between 0.4 and 1.6 Torr. Total rate constants and branching ratios for the formation of Fe(+)O(CH3)2 adducts and of Fe(+)OCH2 + CH4 products were determined. Quantum-chemical calculations provided the parameters required for an analysis in terms of statistical unimolecular rate theory. The analysis employed a recently developed simplified representation of the rates of complex-forming bimolecular reactions, separating association and chemical activation contributions. Satisfactory agreement between experimental results and kinetic modeling was obtained that allows for an extrapolation of the data over wide ranges of conditions. Possible reaction pathways with or without spin-inversion are discussed in relation to the kinetic modeling results.

  19. Analysis of the Pressure and Temperature Dependence of the Complex-Forming Bimolecular Reaction CH3OCH3 + Fe(.).

    PubMed

    Ard, Shaun G; Johnson, Ryan S; Martinez, Oscar; Shuman, Nicholas S; Guo, Hua; Troe, Jürgen; Viggiano, Albert

    2016-07-14

    The kinetics of the reaction CH3OCH3 + Fe(+) has been studied between 250 and 600 K in the buffer gas He at pressures between 0.4 and 1.6 Torr. Total rate constants and branching ratios for the formation of Fe(+)O(CH3)2 adducts and of Fe(+)OCH2 + CH4 products were determined. Quantum-chemical calculations provided the parameters required for an analysis in terms of statistical unimolecular rate theory. The analysis employed a recently developed simplified representation of the rates of complex-forming bimolecular reactions, separating association and chemical activation contributions. Satisfactory agreement between experimental results and kinetic modeling was obtained that allows for an extrapolation of the data over wide ranges of conditions. Possible reaction pathways with or without spin-inversion are discussed in relation to the kinetic modeling results. PMID:27228310

  20. Atmospheric chemistry of CF{sub 3}C(O)OCH{sub 2}CF{sub 3}: UV spectra and kinetic data for CF{sub 3}C(O)OCH({sm_bullet})CF{sub 3} and CF{sub 3}C(O)OCH(OO{sm_bullet})CF{sub 3} radicals, and atmospheric fate of CF{sub 3}C(O)OCH(O{sm_bullet})CF{sub 3} radicals

    SciTech Connect

    Stein, T.N.N.; Christensen, L.K.; Platz, J.; Sehested, J.; Nielsen, O.J.; Wallington, T.J.

    1999-07-22

    Recognition of the adverse effect of chlorofluorocarbon (CFC) release into the atmosphere has led to an international effort to replace CFCs with environmentally acceptable alternatives. Hydrofluoroethers (HFEs) are fluids designed to replace CFCs in applications such as the cleaning of electronic equipment, heat transfer agents in refrigeration systems, and carrier fluids for lubricant deposition. HFEs are volatile compounds and will be released into the atmosphere during its use. In the atmosphere, photochemical oxidation of HFEs will lead to the formation of fluorinated esters and fluorinated formates. The atmospheric fate of these products is unknown at the present. To improve their understanding of the atmospheric chemistry of esters the authors have studied the atmospheric chemistry of 2,2,2-trifluoroethyltrifluoroacetate CF{sub 3}C(O)OCH{sub 2}CF{sub 3} (bp = 55.0 C). This compound provides insight into the behavior of alkyl, alkyl peroxy, and alkoxy radicals formed {alpha} to the ester functionality. The atmospheric fate of CF{sub 3}C(O)OCH(O{sup {sm_bullet}})CF{sub 3} radicals was investigated in a FTIR smog chamber. Three loss processes for the CF{sub 3}C(O)OCH(O{sup {sm_bullet}})CF{sub 3} radicals were identified at 296 K and 700 Torr total pressure, reaction with O{sub 2} to form CF{sub 3}C(O)OC(O)CF{sub 3}, {alpha}-rearrangement to form CF{sub 3}C(O){sm_bullet} radicals and CF{sub 3}C(O)OH, and decomposition via a mechanism which is unclear. In 760 Torr of air at 296 K, 65% of the CF{sub 3}C(O)OCH(O{sm_bullet})CF{sub 3} radicals react with oxygen, 18% undergo {alpha}-rearrangement, while the fate of the remaining 17% is unclear.

  1. Hydrogen and methanol exchange processes for (TMP)Rh-OCH3(CH3OH) in binary solutions of methanol and benzene.

    PubMed

    Sarkar, Sounak; Li, Shan; Wayland, Bradford B

    2011-04-18

    Tetramesityl porphinato rhodium(III) methoxide ((TMP)Rh-OCH(3)) binds with methanol in benzene to form a 1:1 methanol complex ((TMP)Rh-OCH(3)(CH(3)OH)) (1). Dynamic processes are observed to occur for the rhodium(III) methoxide methanol complex (1) that involve both hydrogen and methanol exchange. Hydrogen exchange between coordinated methanol and methoxide through methanol in solution results in an interchange of the environments for the non-equivalent porphyrin faces that contain methoxide and methanol ligands. Interchange of the environments of the coordinated methanol and methoxide sites in 1 produces interchange of the inequivalent mesityl o-CH(3) groups, but methanol ligand exchange occurs on one face of the porphyrin and the mesityl o-CH(3) groups remain inequivalent. Rate constants for dynamic processes are evaluated by full line shape analysis for the (1)H NMR of the mesityl o-CH(3) and high field methyl resonances of coordinated methanol and methoxide groups in 1. The rate constant for interchange of the inequivalent porphyrin faces is associated with hydrogen exchange between 1 and methanol in solution and is observed to increase regularly with the increase in the mole fraction of methanol. The rate constant for methanol ligand exchange between 1 and the solution varies with the solution composition and fluctuates in a manner that parallels the change in the activation energy for methanol diffusion which is a consequence of solution non-ideality from hydrogen bonded clusters.

  2. Development of a fed-batch process for a recombinant Pichia pastoris Δoch1 strain expressing a plant peroxidase.

    PubMed

    Gmeiner, Christoph; Saadati, Amirhossein; Maresch, Daniel; Krasteva, Stanimira; Frank, Manuela; Altmann, Friedrich; Herwig, Christoph; Spadiut, Oliver

    2015-01-01

    Pichia pastoris is a prominent host for recombinant protein production, amongst other things due to its capability of glycosylation. However, N-linked glycans on recombinant proteins get hypermannosylated, causing problems in subsequent unit operations and medical applications. Hypermannosylation is triggered by an α-1,6-mannosyltransferase called OCH1. In a recent study, we knocked out OCH1 in a recombinant P. pastoris CBS7435 Mut(S) strain (Δoch1) expressing the biopharmaceutically relevant enzyme horseradish peroxidase. We characterized the strain in the controlled environment of a bioreactor in dynamic batch cultivations and identified the strain to be physiologically impaired. We faced cell cluster formation, cell lysis and uncontrollable foam formation.In the present study, we investigated the effects of the 3 process parameters temperature, pH and dissolved oxygen concentration on 1) cell physiology, 2) cell morphology, 3) cell lysis, 4) productivity and 5) product purity of the recombinant Δoch1 strain in a multivariate manner. Cultivation at 30°C resulted in low specific methanol uptake during adaptation and the risk of methanol accumulation during cultivation. Cell cluster formation was a function of the C-source rather than process parameters and went along with cell lysis. In terms of productivity and product purity a temperature of 20°C was highly beneficial. In summary, we determined cultivation conditions for a recombinant P. pastoris Δoch1 strain allowing high productivity and product purity. PMID:25567661

  3. High pressure Raman spectroscopy of H2O-CH3OH mixtures.

    PubMed

    Hsieh, Wen-Pin; Chien, Yu-Hsiang

    2015-02-23

    Complex intra-molecular interactions and the hydrogen-bonding network in H2O-volatile mixtures play critical roles in many dynamics processes in physical chemistry, biology, and Earth and planetary sciences. We used high pressure Raman spectroscopy to study the pressure evolution of vibrational frequencies and bonding behavior in H2O-CH3OH mixtures. We found that the presence of low CH3OH content in H2O increases the transition pressure where water crystallizes to ice VI, but does not significantly change the pressure where ice VI transforms to ice VII. Furthermore, the stiffening rates of C-H stretching frequencies dω/dP in CH3OH significantly decrease upon the crystallization of water, and the softening rates of the O-H stretching frequencies of ice VII are suppressed over a narrow pressure range, after which the frequencies of these modes shift with pressure in ways similar to pure CH3OH and ice VII, respectively. Such complex pressure evolution of Raman frequencies along with pronounced variations in Raman intensities of CH3OH within the sample, and the hysteresis of the water-ice VI phase transition suggest pressure-induced segregation of low content CH3OH from ice VII. These findings indicate the significant influence of volatiles on the crystallization of sub-surface ocean and thermal evolution within large icy planets and satellites.

  4. Astronomical Orientations Of Dragon Houses (Laka Palli, Kapsala, Oche) And Armena Gate (Euboea, Greece)

    NASA Astrophysics Data System (ADS)

    Liritzis, I.; Artelaris, G.

    The preliminary investigation of the astronomical orientation of monuments at Styra, southern Euboea, includes the triple so called 'dragon house' complex at Laka Palli, one dragon house at Kapsala and one on the summit of Mount Oche, and a monumental gate in the megalithic fortification wall at Armena. Recent luminescence testing dates these remains to approximately the Classical period with apparent re-use in Roman and later times. Thus far no definite astronomical orientation has been determined in the layout of the structures and no celestial stone markers or similar features have been found associated with the dragon houses, however, the relationship of significant stars, constellations and solar stands was well known in antiquity, and the limited results presented here suggests the possibility for further investigation. This study, which considered possible orientations related to sun rise and sun set for the summer and winter solstice, as well as, alignments towards equinoxes and major bright stars and constellations, did observe a general preference for a southern orientation at most of the sites and a possible feature for time observations in the dragon house complex at Laka Palli.

  5. Towards understanding intrinsic degradation and breakdown mechanisms in SiOCH low-k dielectrics

    SciTech Connect

    Wu, C. De Wolf, I.; Li, Y.; Ciofi, I.; Kauerauf, Th.; Bömmels, J.; Tőkei, Zs.; Croes, K.

    2015-02-14

    The degradation and breakdown mechanisms of a SiOCH low-k material with k = 2.3 (25% porosity) and thicknesses ranging from 90 nm to 20 nm were investigated. By combining the time dependent dielectric breakdown data at positive/negative bias stress with the thickness scaling results, dielectric failure is proven to be intrinsic and not influenced by copper drift or metal barrier deposition induced dielectric damage. It is shown that stress induced leakage current (SILC) can be used as a measure of dielectric degradation. Therefore, low field lifetimes can be safely estimated using SILC extrapolation. Based on our results, both the impact damage model and the power law model have a good accuracy for low field lifetime prediction. Recovery and anneal experiments are used to study the physical nature causing the observed negative flatband voltage shifts in our metal-insulator-semiconductor planar capacitor structures, where hydrogen induced unstable fast and slow donor type interface states are hypothesized to be the root cause of the observed shifts. We suggest that atomic hydrogen is released from the dielectric during electron injection and migrates to the interfacial region. Our model is further supported by an observed irreversible SILC change during the recovery and anneal studies. The degradation mechanism proposed in this work, supported by the low field lifetime data, provides a feasible explanation for intrinsic low-k dielectric failure.

  6. Role of the host tissue in the anti-invasive activity of the alkyllysophospholipid, ET-18-OCH3, in vitro.

    PubMed

    Schallier, D C; Bruyneel, E A; Storme, G A; Mareel, M M

    1991-01-01

    The alkyllysophospholipid, racemic-l-O-octadecyl-2-O-methylglycero-3- phosphocholine (ET-18-OCH3) was previously shown to inhibit invasion of malignant cells into precultured heart fragments (PHF) in vitro. In particular, pretreatment of PHF with 10 micrograms ET-18-OCH3 for 48 h was sufficient to induce in the host tissue resistance towards invasion by mouse MO4 cells. Resistance was obvious when MO4 cells were confronted either immediately (the pretreatment experiment) or after withdrawal of the drug 7 days prior to confrontation (the reversibility experiment). In the present study, the survival of PHF cells in the pretreatment and reversibility experiments was similar to that of untreated PHF cells as determined by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) test and by the PHF explantation test. The effective anti-invasive concentration was 6 micrograms/ml in the pretreatment experiment while 3 micrograms/ml was sufficient to inhibit invasion in the reversibility experiment. Induction of resistance towards invasion in pretreated PHF was shown to occur not only with MO4 cells but also with mouse LLC-H61 Lewis lung carcinoma and mouse BW-O-Li1 T-lymphoma cells. The increase in molecular weight of N-linked cell surface glycosylpeptides (N-GP) of PHF was apparent in the pretreatment experiment and was enhanced in the reversibility experiment. This effect was completely abolished in cells obtained from pretreated PHF which were converted into a cell suspension and further cultured as a monolayer on tissue culture plastic without drug for 7 days. The results reported here provide additional evidence for the causal involvement of N-GP of the PHF host tissue in the anti-invasive activity of ET-18-OCH3 in vitro.

  7. Investigation of the O+allyl addition/elimination reaction pathways from the OCH(2)CHCH(2) radical intermediate.

    PubMed

    Fitzpatrick, Benjamin L; Lau, Kai-Chung; Butler, Laurie J; Lee, Shih-Huang; Lin, Jim Jr-Min

    2008-08-28

    These experiments study the preparation of and product channels resulting from OCH(2)CHCH(2), a key radical intermediate in the O+allyl bimolecular reaction. The data include velocity map imaging and molecular beam scattering results to probe the photolytic generation of the radical intermediate and the subsequent pathways by which the radicals access the energetically allowed product channels of the bimolecular reaction. The photodissociation of epichlorohydrin at 193.3 nm produces chlorine atoms and c-OCH(2)CHCH(2) radicals; these undergo a facile ring opening to the OCH(2)CHCH(2) radical intermediate. State-selective resonance-enhanced multiphoton ionization (REMPI) detection resolves the velocity distributions of ground and spin-orbit excited state chlorine independently, allowing for a more accurate determination of the internal energy distribution of the nascent radicals. We obtain good agreement detecting the velocity distributions of the Cl atoms with REMPI, vacuum ultraviolet (VUV) photoionization at 13.8 eV, and electron bombardment ionization; all show a bimodal distribution of recoil kinetic energies. The dominant high recoil kinetic energy feature peaks near 33 kcalmol. To elucidate the product channels resulting from the OCH(2)CHCH(2) radical intermediate, the crossed laser-molecular beam experiment uses VUV photoionization and detects the velocity distribution of the possible products. The data identify the three dominant product channels as C(3)H(4)O (acrolein)+H, C(2)H(4)+HCO (formyl radical), and H(2)CO (formaldehyde)+C(2)H(3). A small signal from C(2)H(2)O (ketene) product is also detected. The measured velocity distributions and relative signal intensities at me=27, 28, and 29 at two photoionization energies show that the most exothermic product channel, C(2)H(5)+CO, does not contribute significantly to the product branching. The higher internal energy onset of the acrolein+H product channel is consistent with the relative barriers en route to

  8. Incorporation of a Rovibrational Analysis of OC-H_2O Into 6-D Morphed Potentials of the Complex

    NASA Astrophysics Data System (ADS)

    Rivera-Rivera, Luis A.; Springer, Sean D.; McElmurry, Blake A.; Leonov, Igor I.; Lucchese, Robert R.; Bevan, John W.; Coudert, L. H.

    2016-06-01

    Rovibrational transitions associated with tunneling states in the water bending vibration in OC-H_2O and other available spectroscopic data are included in generation of 6-D morphed potentials of the complex. Six-dimension ab initio interaction potentials are initially calculated for the complex to provided the initial functions for the potential morphing. The available spectroscopic data is then used to fit and generate 6-D morphed potentials. Previous prediction of the D_0 of the complex will be incorporated in the analysis. Finally, intermolecular frequencies of the complex will be predicted using the 6-D morphed potentials involving the CO stretching and the H_2O bending vibrations.

  9. Atmospheric Degradation of CH2═C(CH3)C(O)OCH3 Initiated by OH Radicals: Mechanistic Study and Quantification of CH3C(O)C(O)OCH3 in NOx Free Air.

    PubMed

    Gibilisco, Rodrigo G; Uranga, Jorge G; Santiago, Ana N; Teruel, Mariano A

    2015-08-20

    The product distribution of the gas-phase reaction of OH radicals with methyl methacrylate (CH2═C(CH3)C(O)OCH3, MMA) in the absence of NOx was studied at 298 K and atmospheric pressure of air. The experiments were performed in a Teflon chamber using solid-phase microextraction (SPME) with GC-MS and GC-FID for product identification and quantification, respectively. In the absence of NOx, methyl pyruvate (CH3C(O)C(O)OCH3) was identified with a yield of 76 ± 13% in accordance with the decomposition of the 1,2-hydroxyalkoxy radicals formed. In addition, a detailed quantum chemical study of the degradation of MMA was performed by density functional theory (DFT) methods using the MPWB1K functional. This calculation suggests that formation of methyl pyruvate, from C1-C2 scission of 1,2-hydroxyalkoxy radical, is kinetically and thermodynamically the most favorable reaction path taking into account the electronic properties of reaction intermediates and transition states. The difference observed on the degradation mechanism of MMA in the presence and absence of NOx was explained in terms of the associated thermochemistry. Furthermore, this study propose that reaction between peroxy radical (RO2(•)) and hydroxyl radical (OH) became relevant at NOx-free environments. This statement is in agreement with recent studies concerning small peroxy radicals such as CH3OO(•).

  10. Atmospheric Degradation of CH2═C(CH3)C(O)OCH3 Initiated by OH Radicals: Mechanistic Study and Quantification of CH3C(O)C(O)OCH3 in NOx Free Air.

    PubMed

    Gibilisco, Rodrigo G; Uranga, Jorge G; Santiago, Ana N; Teruel, Mariano A

    2015-08-20

    The product distribution of the gas-phase reaction of OH radicals with methyl methacrylate (CH2═C(CH3)C(O)OCH3, MMA) in the absence of NOx was studied at 298 K and atmospheric pressure of air. The experiments were performed in a Teflon chamber using solid-phase microextraction (SPME) with GC-MS and GC-FID for product identification and quantification, respectively. In the absence of NOx, methyl pyruvate (CH3C(O)C(O)OCH3) was identified with a yield of 76 ± 13% in accordance with the decomposition of the 1,2-hydroxyalkoxy radicals formed. In addition, a detailed quantum chemical study of the degradation of MMA was performed by density functional theory (DFT) methods using the MPWB1K functional. This calculation suggests that formation of methyl pyruvate, from C1-C2 scission of 1,2-hydroxyalkoxy radical, is kinetically and thermodynamically the most favorable reaction path taking into account the electronic properties of reaction intermediates and transition states. The difference observed on the degradation mechanism of MMA in the presence and absence of NOx was explained in terms of the associated thermochemistry. Furthermore, this study propose that reaction between peroxy radical (RO2(•)) and hydroxyl radical (OH) became relevant at NOx-free environments. This statement is in agreement with recent studies concerning small peroxy radicals such as CH3OO(•). PMID:26213280

  11. Theoretical investigation of the gas-phase reactions of CF2ClC(O)OCH3 with the hydroxyl radical and the chlorine atom at 298 K.

    PubMed

    Mishra, Bhupesh Kumar; Chakrabartty, Arup Kumar; Deka, Ramesh Chandra

    2013-08-01

    A Theoretical study on the mechanism of the reactions of CF2ClC(O)OCH3 with the OH radical and Cl atom is presented. Geometry optimization and frequency calculations have been performed at the MPWB1K/6-31+G(d,p) level of theory and energetic information is further refined by calculating the energy of the species using G2(MP2) theory. Transition states are searched on the potential energy surface involved during the reaction channels and each of the transition states are characterized by presence of only one imaginary frequency. The existence of transition states on the corresponding potential energy surface is ascertained by performing intrinsic reaction coordinate (IRC) calculation. Theoretically calculated rate constants at 298 K and atmospheric pressure using the canonical transition state theory (CTST) are found to be in good agreement with the experimentally measured ones. Using group-balanced isodesmic reactions as working chemical reactions, the standard enthalpies of formation for CF2ClC(O)OCH3, CF2ClC(O)OCH2 and CF3C(O)OCH3 are also reported for the first time.

  12. Long persistent near infrared luminescence nanoprobes LiGa5O8:Cr3+-PEG-OCH3 for in vivo imaging

    NASA Astrophysics Data System (ADS)

    Fu, Xiaoyan; Liu, Chunlin; Shi, Junpeng; Man, Huizi; Xu, Jia; Zhang, Hongwu

    2014-09-01

    The Cr3+-doped LiGa5O8 nanoparticles (LGNPs) with long-persistent near-infrared phosphorescence were obtained through a sol-gel approach followed by heat treatment at 800 °C in air. The obtained results reveal that the nanoparticles with an average diameter of 100 nm are well defined and have pure structure of LiGa5O8. After illumination for 3 min using a 254 nm UV lamp, the LGNPs exhibit strong near-infrared peak at ca. 720 nm belonging to tissue transparency window which can last for more than 1 h. Via surface modified with PEG-5000-OCH3, the LGNPs-PEG-OCH3 exhibit excellent biocompatibility and low toxicity. Under in vitro pre-excitation using a 254 nm UV lamp for 3 min, the in vivo distribution of the LGNPs-PEG-OCH3 in the abdomen can be detected in real time for more than 1 h. All the results indicate that the LGNPs-PEG-OCH3 can be used as potential nanoprobes to realize in vivo, real time and long time imaging with high sensitivity.

  13. Effects of different media supplements on the production of an active recombinant plant peroxidase in a Pichia pastoris Δoch1 strain.

    PubMed

    Gmeiner, Christoph; Spadiut, Oliver

    2015-01-01

    Recombinant protein production in microorganisms is one of the most studied areas of research in biotechnology today. In this respect the yeast Pichia pastoris is an important microbial production host due to its capability of secreting the target protein and performing posttranslational modifications. In a recent study, we described the development of a robust bioprocess for a glyco-engineered recombinant P. pastoris strain where the native α-1,6-mannosyltransfrease OCH1 was knocked out (Δoch1 strain). This strain produced the glycosylated enzyme horseradish peroxidase (HRP) with more homogeneous and shorter surface glycans than the respective benchmark strain. However, the recombinant Δoch1 strain was physiologically impaired and thus hard to cultivate. We faced cell cluster formation, cell lysis and consequent intensive foam formation. Thus, we investigated the effects of the 3 process parameters temperature, pH and dissolved oxygen concentration on (1) cell physiology, (2) cell morphology, (3) cell lysis, (4) productivity and (5) product purity in a multivariate manner. However, not only process parameters might influence these characteristics, but also media supplements might have an impact. Here, we describe the effects of different heme-precursors as well as of a protease-inhibitor cocktail on the production of active HRP in therecombinant P. pastoris Δoch1strain.

  14. Induction of apoptosis in human mitogen-activated peripheral blood T-lymphocytes by the ether phospholipid ET-18-OCH3: Involvement of the Fas receptor/ligand system

    PubMed Central

    Cabaner, Christelle; Gajate, Consuelo; Macho, Antonio; Muñoz, Eduardo; Modolell, Manuel; Mollinedo, Faustino

    1999-01-01

    Activated T-cells constitute a target for treatment of autoimmune diseases. We have found that the antitumour ether phospholipid 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3; edelfosine) induced dose- and time-dependent apoptosis in human mitogen-activated peripheral blood T-lymphocytes, but not in resting T-cells. T-lymphocytes were stimulated with phytohemagglutinin and interleukin-2 or with concanavalin A. Apoptosis was assessed by DNA fragmentation through cell cycle and TUNEL analyses, as well as through visualization of internucleosomal DNA fragmentation in agarose gels.The ET-18-OCH3-mediated apoptotic response in activated T-lymphocytes was less intense than in human leukaemic T cell lines, such as Jurkat cells and Peer cells; namely about 25% apoptosis in activated T-cells versus about 46–61% apoptosis in T leukaemic cells after 24 h treatment with 10 μM ET-18-OCH3.The ET-18-OCH3 thioether analogue BM 41.440 (ilmofosine) showed a similar apoptotic capacity to that found with ET-18-OCH3 in activated T-cells, whereas the phospholipid analogue hexadecylphosphocholine (miltefosine) failed to promote this response.The uptake of [3H]-ET-18-OCH3 was much larger in activated T-cells than in resting lymphocytes.Using a cytofluorimetric approach we have found that ET-18-OCH3 induced disruption of the mitochondrial transmembrane potential and production of reactive oxygen species in activated T-cells, but not in resting lymphocytes.ET-18-OCH3 induced an increase in Fas (APO-1/CD95) ligand mRNA expression in activated T-cells, and incubation with a blocking anti-Fas (APO-1/CD95) antibody partially inhibited the ET-18-OCH3-induced apoptosis of activated T-lymphocytes.These results demonstrate that mitogen-activated T-cells, unlike resting lymphocytes, are able to take up significant amounts of ET-18-OCH3, and are susceptible to undergo apoptosis by the ether lipid via, in part, the Fas (APO-1/CD95) receptor/ligand system. This ET-18-OCH3

  15. Characterization of Cu(II) and Cd(II) resistance mechanisms in Sphingobium sp. PHE-SPH and Ochrobactrum sp. PHE-OCH and their potential application in the bioremediation of heavy metal-phenanthrene co-contaminated sites.

    PubMed

    Chen, Chen; Lei, Wenrui; Lu, Min; Zhang, Jianan; Zhang, Zhou; Luo, Chunling; Chen, Yahua; Hong, Qing; Shen, Zhenguo

    2016-04-01

    Soil that is co-contaminated with heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) is difficult to bioremediate due to the ability of toxic metals to inhibit PAH degradation by bacteria. We demonstrated the resistance mechanisms to Cu(II) and Cd(II) of two newly isolated strains of Sphingobium sp. PHE-SPH and Ochrobactrum sp. PHE-OCH and further tested their potential application in the bioremediation of HM-phenanthrene (PhA) co-contaminated sites. The PHE-SPH and PHE-OCH strains tolerated 4.63 and 4.34 mM Cu(II) and also showed tolerance to 0.48 and 1.52 mM Cd(II), respectively. Diverse resistance patterns were detected between the two strains. In PHE-OCH cells, the maximum accumulation of Cu(II) occurred in the cell wall, while the maximum accumulation was in the cytoplasm of PHE-SPH cells. This resulted in a sudden suppression of growth in PHE-OCH and a gradual inhibition in PHE-SPH as the concentration of Cu(II) increased. Organic acid production was markedly higher in PHE-OCH than in PHE-SPH, which may also have a role in the resistance mechanisms, and contributes to the higher Cd(II) tolerance of PHE-OCH. The factors involved in the absorption of Cu(II) or Cd(II) in PHE-SPH and PHE-OCH were identified as proteins and carbohydrates by Fourier transform infrared (FT-IR) spectroscopy. Furthermore, both strains showed the ability to efficiently degrade PhA and maintained this high degradation efficiency under HM stress. The high tolerance to HMs and the PhA degradation capacity make Sphingobium sp. PHE-SPH and Ochrobactrum sp. PHE-OCH excellent candidate organisms for the bioremediation of HM-PhA co-contaminated sites.

  16. Damage by radicals and photons during plasma cleaning of porous low-k SiOCH. II. Water uptake and change in dielectric constant

    SciTech Connect

    Shoeb, Juline; Kushner, Mark J.

    2012-07-15

    Porous dielectric materials provide lower capacitances that reduce RC time delays in integrated circuits. Typical low-k materials include porous SiOCH-silicon dioxide with carbon groups, principally CH{sub 3}, lining the pores. With a high porosity, internally connected pores provide pathways for reactive species to enter into the material. Fluorocarbon plasmas are often used to etch SiOCH, a process that leaves a fluorocarbon polymer on the surface that must later be removed. During cleaning using Ar/O{sub 2} or He/H{sub 2} plasmas, reactions of radicals that diffuse into the SiOCH and photons that penetrate into the SiOCH can remove -CH{sub 3} groups. Due to its higher reactivity, cleaning with Ar/O{sub 2} plasmas removes more -CH{sub 3} groups than He/H{sub 2} plasmas, and so produce more free radical sites, such as -SiO{sub 2} Bullet (a -SiO{sub 2}-CH{sub 3} site with the -CH{sub 3} group removed).Upon exposure to humid air, these free radical sites can chemisorb H{sub 2}O to form hydrophilic Si-OH which can further physisorb H{sub 2}O through hydrogen bonding to form Si-OH(H{sub 2}O). With the high dielectric constant of water, even a small percentage of water uptake can significantly increase the effective dielectric constant of SiOCH. In this paper, we report on results from a computational investigation of the cleaning of SiOCH using Ar/O{sub 2} or He/H{sub 2} plasmas and subsequent exposure to humid air. The authors found that plasma cleaning with He/H{sub 2} mixtures produce less demethylation than cleaning with Ar/O{sub 2} plasmas, as so results in less water uptake, and a smaller increase in dielectric constant. The water that produces the increase in dielectric constant is roughly half chemisorbed and half physisorbed, the latter of which can be removed with mild heating. Sealing the pores with NH{sub 3} plasma treatment reduces water uptake and helps prevent the increase in dielectric constant.

  17. Improving mechanical robustness of ultralow-k SiOCH plasma enhanced chemical vapor deposition glasses by controlled porogen decomposition prior to UV-hardening

    NASA Astrophysics Data System (ADS)

    Urbanowicz, A. M.; Vanstreels, K.; Verdonck, P.; Shamiryan, D.; De Gendt, S.; Baklanov, M. R.

    2010-05-01

    We report a new curing procedure of a plasma enhanced chemical vapor deposited SiCOH glasses for interlayer dielectric applications in microelectronic. It is demonstrated that SiOCH glasses with improved mechanical properties and ultralow dielectric constant can be obtained by controlled decomposition of the porogen molecules used to create nanoscale pores, prior to the UV-hardening step. The Young's modulus (YM) of conventional SiOCH-based glasses with 32% open porosity hardened with porogen is 4.6 GPa, this value is shown to increase up to 5.2 GPa with even 46% open porosity, when the glasses are hardened after porogen removal. This increase in porosity is accompanied by significant reduction in the dielectric constant from 2.3 to 1.8. The increased YM is related to an enhanced molecular-bridging mechanism when film is hardened without porogen that was explained on the base of percolation of rigidity theory and random network concepts.

  18. Conformational and spectroscopic study of xanthogen ethyl formates, ROC(S)SC(O)OCH2CH3. Isolation of CH3CH2OC(O)SH

    NASA Astrophysics Data System (ADS)

    Juncal, Luciana C.; Cozzarín, Melina V.; Romano, Rosana M.

    2015-03-01

    ROC(S)SC(O)OCH2CH3, with R = CH3sbnd , (CH3)2CHsbnd and CH3(CH2)2sbnd , were obtained through the reaction between potassium xanthate salts, ROC(S)SK, and ethyl chloroformate, ClC(O)OCH2CH3. The liquid compounds were identified and characterized by 1H and 13C NMR and mass spectrometry. The conformations adopted by the molecules were studied by DFT methods. 6 conformers were theoretically predicted for R = CH3sbnd and (CH3)2CHsbnd , while the conformational flexibility of the n-propyl substituent increases the total number of feasible rotamers to 21. For the three molecules, the conformers can be associated in 3 groups, being the most stable the AS forms - the Cdbnd S double bond anti (A) with respect to the Csbnd S single bond and the Ssbnd C single bond syn (S) with respect to the Cdbnd O double bond - followed by AA and SS conformers. The vibrational spectra were interpreted in terms of the predicted conformational equilibrium, presenting the ν(Cdbnd O) spectral region signals corresponding to the three groups of conformers. A moderated pre-resonance Raman enhancement of the ν(Cdbnd S) vibrational mode of CH3(CH2)2OC(S)SC(O)OCH2CH3 was detected, when the excitation radiation approaches the energy of a n → π∗ electronic transition associated with the Cdbnd S chromophore. UV-visible spectra in different solvents were measured and interpreted in terms of TD-DFT calculations. The unknown molecule CH3CH2OC(O)SH was isolated by the UV-visible photolysis of CH3OC(S)SC(O)OCH2CH3 isolated in Ar matrix, and also obtained as a side-product of the reaction between potassium xanthate salts, ROC(S)SK, and ethyl chloroformate, ClC(O)OCH2CH3.

  19. Atmospheric Chemistry of (CF3)2CHOCH3, (CF3)2CHOCHO, and CF3C(O)OCH3.

    PubMed

    Østerstrøm, Freja From; Wallington, Timothy J; Sulbaek Andersen, Mads P; Nielsen, Ole John

    2015-10-22

    Smog chambers with in situ FTIR detection were used to measure rate coefficients in 700 Torr of air and 296 ± 2 K of: k(Cl+(CF3)2CHOCH3) = (5.41 ± 1.63) × 10(-12), k(Cl+(CF3)2CHOCHO) = (9.44 ± 1.81) × 10(-15), k(Cl+CF3C(O)OCH3) = (6.28 ± 0.98) × 10(-14), k(OH+(CF3)2CHOCH3) = (1.86 ± 0.41) × 10(-13), and k(OH+(CF3)2CHOCHO) = (2.08 ± 0.63) × 10(-14) cm(3) molecule(-1) s(-1). The Cl atom initiated oxidation of (CF3)2CHOCH3 gives (CF3)2CHOCHO in a yield indistinguishable from 100%. The OH radical initiated oxidation of (CF3)2CHOCH3 gives the following products (molar yields): (CF3)2CHOCHO (76 ± 8)%, CF3C(O)OCH3 (16 ± 2)%, CF3C(O)CF3 (4 ± 1)%, and C(O)F2 (45 ± 5)%. The primary oxidation product (CF3)2CHOCHO reacts with Cl atoms to give secondary products (molar yields): CF3C(O)CF3 (67 ± 7)%, CF3C(O)OCHO (28 ± 3)%, and C(O)F2 (118 ± 12)%. CF3C(O)OCH3 reacts with Cl atoms to give: CF3C(O)OCHO (80 ± 8)% and C(O)F2 (6 ± 1)%. Atmospheric lifetimes of (CF3)2CHOCH3, (CF3)2CHOCHO, and CF3C(O)OCH3 were estimated to be 62 days, 1.5 years, and 220 days, respectively. The 100-year global warming potentials (GWPs) for (CF3)2CHOCH3, (CF3)2CHOCHO, and CF3C(O)OCH3 are estimated to be 6, 121, and 46, respectively. A comprehensive description of the atmospheric fate of (CF3)2CHOCH3 is presented. PMID:26439469

  20. The effect of VUV radiation from Ar/O2 plasmas on low-k SiOCH films

    NASA Astrophysics Data System (ADS)

    Lee, J.; Graves, D. B.

    2011-08-01

    The degradation of porous low-k materials, like SiOCH, under plasma processing continues to be a problem in the next generation of integrated-circuit fabrication. Due to the exposure of the film to many species during plasma treatment, such as photons, ions, radicals, etc, it is difficult to identify the mechanisms responsible for plasma-induced damage. Using a vacuum beam apparatus with a calibrated Xe vacuum ultraviolet (VUV) lamp, we show that 147 nm VUV photons and molecular O2 alone can damage these low-k materials. Using Fourier-transform infrared (FTIR) spectroscopy, we show that VUV/O2 exposure causes a loss of methylated species, resulting in a hydrophilic, SiOx-like layer that is susceptible to H2O absorption, leading to an increased dielectric constant. The effect of VUV radiation on chemical modification of porous SiOCH films in the vacuum beam apparatus and in Ar and O2 plasma exposure was found to be a significant contributor to dielectric damage. Measurements of dielectric constant change using a mercury probe are consistent with chemical modification inferred from FTIR analysis. Furthermore, the extent of chemical modification appears to be limited by the penetration depth of the VUV photons, which is dependent on wavelength of radiation. The creation of a SiOx-like layer near the surface of the material, which grows deeper as more methyl is extracted, introduces a dynamic change of VUV absorption throughout the material over time. As a result, the rate of methyl loss is continuously changing during the exposure. We present a model that attempts to capture this dynamic behaviour and compare the model predictions to experimental data through a fitting parameter that represents the effective photo-induced methyl removal. While this model accurately simulates the methyl loss through VUV exposure by the Xe lamp and Ar plasma, the methyl loss from VUV photons in O2 plasma are only accurately depicted at longer exposure times. We conclude that other

  1. Analysis of the kinetics and yields of OH radical production from the CH3OCH2 + O2 reaction in the temperature range 195-650 K: an experimental and computational study.

    PubMed

    Eskola, A J; Carr, S A; Shannon, R J; Wang, B; Blitz, M A; Pilling, M J; Seakins, P W; Robertson, S H

    2014-08-28

    The methoxymethyl radical, CH3OCH2, is an important intermediate in the low temperature combustion of dimethyl ether. The kinetics and yields of OH from the reaction of the methoxymethyl radical with O2 have been measured over the temperature and pressure ranges of 195-650 K and 5-500 Torr by detecting the hydroxyl radical using laser-induced fluorescence following the excimer laser photolysis (248 nm) of CH3OCH2Br. The reaction proceeds via the formation of an energized CH3OCH2O2 adduct, which either dissociates to OH + 2 H2CO or is collisionally stabilized by the buffer gas. At temperatures above 550 K, a secondary source of OH was observed consistent with thermal decomposition of stabilized CH3OCH2O2 radicals. In order to quantify OH production from the CH3OCH2 + O2 reaction, extensive relative and absolute OH yield measurements were performed over the same (T, P) conditions as the kinetic experiments. The reaction was studied at sufficiently low radical concentrations (∼10(11) cm(-3)) that secondary (radical + radical) reactions were unimportant and the rate coefficients could be extracted from simple bi- or triexponential analysis. Ab initio (CBS-GB3)/master equation calculations (using the program MESMER) of the CH3OCH2 + O2 system were also performed to better understand this combustion-related reaction as well as be able to extrapolate experimental results to higher temperatures and pressures. To obtain agreement with experimental results (both kinetics and yield data), energies of the key transition states were substantially reduced (by 20-40 kJ mol(-1)) from their ab initio values and the effect of hindered rotations in the CH3OCH2 and CH3OCH2OO intermediates were taken into account. The optimized master equation model was used to generate a set of pressure and temperature dependent rate coefficients for the component nine phenomenological reactions that describe the CH3OCH2 + O2 system, including four well-skipping reactions. The rate coefficients were

  2. Disproportionation and thermochemical sulfate reduction reactions in S-H20-Ch4 and S-D2O-CH4 systems from 200 to 340 °C at elevated pressures

    USGS Publications Warehouse

    Yuan, Shunda; Chou, I-Ming; Burruss, Robert A.

    2013-01-01

    Elemental sulfur, as a transient intermediate compound, by-product, or catalyst, plays significant roles in thermochemical sulfate reduction (TSR) reactions. However, the mechanisms of the reactions in S-H2O-hydrocarbons systems are not clear. To improve our understanding of reaction mechanisms, we conducted a series of experiments between 200 and 340 °C for S-H2O-CH4, S-D2O-CH4, and S-CH4-1m ZnBr2 systems in fused silica capillary capsules (FSCC). After a heating period ranging from 24 to 2160 hours (hrs), the quenched samples were analyzed by Raman spectroscopy. Combined with the in situ Raman spectra collected at high temperatures and pressures in the S-H2O and S-H2O-CH4 systems, our results showed that (1) the disproportionation of sulfur in the S-H2O-CH4 system occurred at temperatures above 200 °C and produced H2S, SO42-, and possibly trace amount of HSO4-; (2) sulfate (and bisulfate), in the presence of sulfur, can be reduced by methane between 250 and 340 °C to produce CO2 and H2S, and these TSR temperatures are much closer to those of the natural system (2O-CH4 system may take place simultaneously, with TSR being favored at higher temperatures; and (4) in the system S-D2O-CH4, both TSR and the competitive disproportionation reactions occurred simultaneously at temperatures above 300 °C, but these reactions were very slow at lower temperatures. Our observation of methane reaction at 250 °C in a laboratory time scale suggests that, in a geologic time scale, methane may be destroyed by TSR reactions at temperatures > 200 °C that can be reached by deep drilling for hydrocarbon resources.

  3. Anticancer activity of Panax notoginseng extract 20(S)-25-OCH3-PPD: Targetting beta-catenin signalling.

    PubMed

    Bi, Xiuli; Zhao, Yuqing; Fang, Wenfeng; Yang, Wancai

    2009-11-01

    1. The Wnt/beta-catenin pathway plays a critical role in carcinogenesis and so agents that target Wnt/beta-catenin may have potential in cancer prevention and therapy. The aim of the present study was to evaluate the anticancer activity of the novel natural product dammarane-type triterpene sapogenin (20(S)-25-OCH3-PPD; PPD25) isolated from the leaves of Panax notoginseng. 2. The anticancer activity of PPD25 was evaluated in three colon cancer cell lines and in one lung cancer cell line. The effects of PPD25 to inhibit proliferation and to induce apoptosis were evaluated. In addition, the potential mechanisms underlying the effects of PPD25 were investigated. 3. It was found that the addition of 5 or 25 micromol/L PPD25 to the culture medium significantly inhibited cell proliferation and induced apoptosis in all four cancer cell lines. Mechanistic studies revealed that PPD25 significantly reduced the expression of beta-catenin, a key mediator in the Wnt pathway, as well as transcriptional targets of beta-catenin, namely c-myc, cyclin D1, cdk4 and T cell factor (TCF)-4. In addition, beta-catenin/TCF transcriptional activity was significantly suppressed by PPD25. 4. The data demonstrate that the PPD25 exerts its anticancer effect by targetting beta-catenin signalling, suggesting that PPD25 may have potential as a chemotherapeutic and/or chemopreventive agent for colon and lung cancer. PMID:19413587

  4. Investigation of the O+allyl addition/elimination reaction pathways from the OCH{sub 2}CHCH{sub 2} radical intermediate

    SciTech Connect

    FitzPatrick, Benjamin L.; Lau, K.-C.; Butler, Laurie J.; Lee, S.-H.; Lin, Jim Jr-Min

    2008-08-28

    These experiments study the preparation of and product channels resulting from OCH{sub 2}CHCH{sub 2}, a key radical intermediate in the O+allyl bimolecular reaction. The data include velocity map imaging and molecular beam scattering results to probe the photolytic generation of the radical intermediate and the subsequent pathways by which the radicals access the energetically allowed product channels of the bimolecular reaction. The photodissociation of epichlorohydrin at 193.3 nm produces chlorine atoms and c-OCH{sub 2}CHCH{sub 2} radicals; these undergo a facile ring opening to the OCH{sub 2}CHCH{sub 2} radical intermediate. State-selective resonance-enhanced multiphoton ionization (REMPI) detection resolves the velocity distributions of ground and spin-orbit excited state chlorine independently, allowing for a more accurate determination of the internal energy distribution of the nascent radicals. We obtain good agreement detecting the velocity distributions of the Cl atoms with REMPI, vacuum ultraviolet (VUV) photoionization at 13.8 eV, and electron bombardment ionization; all show a bimodal distribution of recoil kinetic energies. The dominant high recoil kinetic energy feature peaks near 33 kcal/mol. To elucidate the product channels resulting from the OCH{sub 2}CHCH{sub 2} radical intermediate, the crossed laser-molecular beam experiment uses VUV photoionization and detects the velocity distribution of the possible products. The data identify the three dominant product channels as C{sub 3}H{sub 4}O (acrolein)+H, C{sub 2}H{sub 4}+HCO (formyl radical), and H{sub 2}CO (formaldehyde)+C{sub 2}H{sub 3}. A small signal from C{sub 2}H{sub 2}O (ketene) product is also detected. The measured velocity distributions and relative signal intensities at m/e=27, 28, and 29 at two photoionization energies show that the most exothermic product channel, C{sub 2}H{sub 5}+CO, does not contribute significantly to the product branching. The higher internal energy onset of the

  5. A computational study of the addition of ReO3L (L = Cl(-), CH3, OCH3 and Cp) to ethenone.

    PubMed

    Aniagyei, Albert; Tia, Richard; Adei, Evans

    2016-01-01

    The periselectivity and chemoselectivity of the addition of transition metal oxides of the type ReO3L (L = Cl, CH3, OCH3 and Cp) to ethenone have been explored at the MO6 and B3LYP/LACVP* levels of theory. The activation barriers and reaction energies for the stepwise and concerted addition pathways involving multiple spin states have been computed. In the reaction of ReO3L (L = Cl(-), OCH3, CH3 and Cp) with ethenone, the concerted [2 + 2] addition of the metal oxide across the C=C and C=O double bond to form either metalla-2-oxetane-3-one or metalla-2,4-dioxolane is the most kinetically favored over the formation of metalla-2,5-dioxolane-3-one from the direct [3 + 2] addition pathway. The trends in activation and reaction energies for the formation of metalla-2-oxetane-3-one and metalla-2,4-dioxolane are Cp < Cl(-) < OCH3 < CH3 and Cp < OCH3 < CH3 < Cl(-) and for the reaction energies are Cp < OCH3 < Cl(-) < CH3 and Cp < CH3 < OCH3 < Cl CH3. The concerted [3 + 2] addition of the metal oxide across the C=C double of the ethenone to form species metalla-2,5-dioxolane-3-one is thermodynamically the most favored for the ligand L = Cp. The direct [2 + 2] addition pathways leading to the formations of metalla-2-oxetane-3-one and metalla-2,4-dioxolane is thermodynamically the most favored for the ligands L = OCH3 and Cl(-). The difference between the calculated [2 + 2] activation barriers for the addition of the metal oxide LReO3 across the C=C and C=O functionalities of ethenone are small except for the case of L = Cl(-) and OCH3. The rearrangement of the metalla-2-oxetane-3-one-metalla-2,5-dioxolane-3-one even though feasible, are unfavorable due to high activation energies of their rate-determining steps. For the rearrangement of the metalla-2-oxetane-3-one to metalla-2,5-dioxolane-3-one, the trends in activation barriers is found to follow the order OCH3 < Cl(-) < CH3 < Cp. The trends in the activation energies for

  6. Distribution of eukaryotic serine racemases in the bacterial domain and characterization of a representative protein in Roseobacter litoralis Och 149.

    PubMed

    Kubota, Takaaki; Shimamura, Shigeru; Kobayashi, Tohru; Nunoura, Takuro; Deguchi, Shigeru

    2016-01-01

    Two distinct bacterial and eukaryotic serine racemases (SRs) have been identified based on phylogenetic and biochemical characteristics. Although some reports have suggested that marine heterotrophic bacteria have the potential to produce d-serine, the gene encoding bacterial SRs is not found in those bacterial genomes. In this study, using in-depth genomic analysis, we found that eukaryotic SR homologues were distributed widely in various bacterial genomes. Additionally, we selected a eukaryotic SR homologue from a marine heterotrophic bacterium, Roseobacter litoralis Och 149 (RiSR), and constructed an RiSR gene expression system in Escherichia coli for studying the properties of the enzyme. Among the tested amino acids, the recombinant RiSR exhibited both racemization and dehydration activities only towards serine, similar to many eukaryotic SRs. Mg2+ and MgATP enhanced both activities of RiSR, whereas EDTA abolished these enzymatic activities. The enzymatic properties and domain structure of RiSR were similar to those of eukaryotic SRs, particularly mammalian SRs. However, RiSR showed lower catalytic efficiency for L-serine dehydration (kcat/Km=0.094 min(-1) mM(-1)) than those of eukaryotic SRs reported to date (kcat/Km=0.6-21 min(-1) mM(-1)). In contrast, the catalytic efficiency for L-serine racemization of RiSR (kcat/Km=3.14 min(-1) mM(-1)) was 34-fold higher than that of l-serine dehydration. These data suggested that RiSR primarily catalysed serine racemization rather than dehydration.

  7. Chemical and electrochemical oxidation of [Rh(β-diketonato)(CO)(P(OCH2)3CCH3)]: an experimental and DFT study.

    PubMed

    Erasmus, Johannes J C; Conradie, Jeanet

    2013-06-28

    An experimental and computational chemistry study of the reactivity of [Rh(β-diketonato)(CO)(P(OCH2)3CCH3)] complexes towards chemical and electrochemical oxidation shows that more electron withdrawing groups on the β-diketonato ligand reduce electron density on the rhodium atom to a larger extent than electron donating groups. This leads to a slower second-order oxidative addition rate, k1, and a higher electrochemical oxidation potential, E(pa)(Rh), linearly related by ln k1 = -11(1) E(pa)(Rh) - 2.3(5). The reactivity of these complexes can be predicted by their DFT calculated HOMO energies: E(HOMO) = -0.34(8)E(pa)(Rh) - 5.04(4) = 0.032(5) ln k1- 4.96(4). k1 of [Rh(β-diketonato)(CO)(P(OCH2)3CCH3)] complexes is slower than that of related [Rh(β-diketonato)(CO)(PPh3)] and [Rh(β-diketonato)(P(OPh)3)2] complexes due to the better π-acceptor ability of the CO-phosphite-rhodium combination than that of CO-PPh3-rhodium or di-phosphite-rhodium. PMID:23632432

  8. Rotational Spectrum, Conformational Composition, and Quantum Chemical Calculations of Cyanomethyl Formate (HC(O)OCH2C≡N), a Compound of Potential Astrochemical Interest.

    PubMed

    Samdal, Svein; Møllendal, Harald; Carles, Sophie

    2015-08-27

    The rotational spectrum of cyanomethyl formate (HC(O)OCH2C≡N) has been recorded in the 12–123 GHz spectral range. The spectra of two conformers were assigned. The rotamer denoted I has a symmetry plane and two out-of plane hydrogen atoms belonging to the cyanomethyl (CH2CN) moiety. In the conformer called II, the cyanomethyl group is rotated 80.3° out of this plane. Conformer I has an energy that is 1.4(6) kJ/mol lower than the energy of II according to relative intensity measurements. A large number of rotational transitions have been assigned for the ground and vibrationally excited states of the two conformers and accurate spectroscopic constants have been obtained. These constants should predict frequencies of transitions outside the investigated spectral range with a very high degree of precision. It is suggested that cyanomethyl formate is a potential interstellar compound. This suggestion is based on the fact that its congener methyl formate (HC(O)OCH3) exists across a large variety of interstellar environments and the fact that cyanides are very prevalent in the Universe. The experimental work has been augmented by high-level quantum chemical calculations. The CCSD/cc-pVQZ calculations are found to predict structures of the two forms that are very close to the Born–Oppenheimer equilibrium structures. MP2/cc-pVTZ predictions of several vibration–rotation interaction constants were generally found to be rather inaccurate. A gas-phase reaction between methyl formate and the cyanomethyl radical CH2CN to produce a hydrogen atom and cyanomethyl formate was mimicked using MP2/cc-pVTZ calculations. It was found that this reaction is not favored thermodynamically. It is also conjectured that the possible formation of cyanomethyl formate might be catalyzed and take place on interstellar particles. PMID:26207519

  9. Evaluation of a Novel Approach for Peptide Sequencing: Laser-induced Acoustic Desorption Combined with P(OCH3)2+ Chemical Ionization and Collision-activated Dissociation in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer

    PubMed Central

    Somuramasami, Jayalakshmi; Kenttämaa, Hilkka I.

    2007-01-01

    A novel mass spectrometric method has been developed for obtaining sequence information on small peptides. The peptides are desorbed as intact neutral molecules into a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR) by means of laser-induced acoustic desorption (LIAD). Reactions of the neutral peptides with the dimethoxyphosphenium ion, P(OCH3)2+, occur predominantly by addition of the peptide to P(OCH3)2+ followed by the loss of two methanol molecules, thus yielding product ions with the composition (peptide + P − 2H)+. Upon sustained off-resonance irradiation for collision-activated dissociation (SORI-CAD), the (peptide + P − 2H)+ ions undergo successive losses of CO and NH = CHR or H2O, CO, and NH = CHR to yield sequence-related fragment ions in addition to the regular an- and bn-type ions. Under the same conditions, SORI-CAD of the analogous protonated peptides predominantly yields the regular an- and bn-type ions. The mechanisms of the reactions of peptides with P(OCH3)2+ and the dissociation of the (peptide + P − 2H)+ ions were examined by using model peptides and molecular orbital calculations. PMID:17157527

  10. H2O-CH4 and H2S-CH4 complexes: a direct comparison through molecular beam experiments and ab initio calculations.

    PubMed

    Cappelletti, David; Bartocci, Alessio; Frati, Federica; Roncaratti, Luiz F; Belpassi, Leonardo; Tarantelli, Francesco; Lakshmi, Prabha Aiswarya; Arunan, Elangannan; Pirani, Fernando

    2015-11-11

    New molecular beam scattering experiments have been performed to measure the total (elastic plus inelastic) cross sections as a function of the velocity in collisions between water and hydrogen sulfide projectile molecules and the methane target. Measured data have been exploited to characterize the range and strength of the intermolecular interaction in such systems, which are of relevance as they drive the gas phase molecular dynamics and the clathrate formation. Complementary information has been obtained by rotational spectra, recorded for the hydrogen sulfide-methane complex, with a pulsed nozzle Fourier transform microwave spectrometer. Extensive ab initio calculations have been performed to rationalize all the experimental findings. The combination of experimental and theoretical information has established the ground for the understanding of the nature of the interaction and allows for its basic components to be modelled, including charge transfer, in these weakly bound systems. The intermolecular potential for H2S-CH4 is significantly less anisotropic than for H2O-CH4, although both of them have potential minima that can be characterized as 'hydrogen bonded'.

  11. Plasma damage mechanisms for low-k porous SiOCH films due to radiation, radicals, and ions in the plasma etching process

    SciTech Connect

    Uchida, Saburo; Takashima, Seigo; Hori, Masaru; Fukasawa, Masanaga; Ohshima, Keiji; Nagahata, Kazunori; Tatsumi, Tetsuya

    2008-04-01

    Low dielectric constant (low-k) films have been widely used as insulating materials in ultra-large-scale integrated circuits. Low-k films receive heavy damage during the plasma processes of etching or ashing, resulting in an increase in their dielectric constant. In order to realize damage-free plasma processes for low-k films, it is essential to determine the influence of radiation, radicals, and ions emitted in the plasma process on the characteristics of low-k films. We have developed a technique to evaluate the influence of radiation, radicals, ions, and their synergies on films in real plasma processes and have named it pallet for plasma evaluation (PAPE). Using the PAPE, plasma-induced damage on porous SiOCH films were investigated in dual-frequency capacitively coupled H{sub 2}/N{sub 2} plasmas. The damage was characterized by ellipsometry, Fourier-transform infrared spectroscopy, and thermal desorption spectroscopy. On the basis of the results, the damage mechanisms associated with vacuum ultraviolet (VUV) and UV radiation, radicals, and ions were clarified. The damage was caused not only by ions and radicals but also by VUV and UV radiation emitted by the plasmas. Moreover, it was found that the synergy between the radiation and the radicals enhanced the damage.

  12. Investigating the H2-He-H2O-CH4 equation of state in the deep troposphere of Jupiter

    NASA Astrophysics Data System (ADS)

    Karpowicz, Bryan M.; Steffes, Paul G.

    2013-03-01

    In this work, a new equation of state for a H2-He-H2O-CH4 mixture is presented. The equation is optimized for the deep jovian atmosphere (∼100 bars) where the NASA Juno Microwave Radiometer (MWR) will probe. The methodology used is based upon that of Lemmon and Jacobsen (Lemmon, E.W., Jacobsen, R.T. [2004]. J. Phys. Chem. Ref. Data 33, 593-+) and Kunz et al. (Kunz, O., Klimeck, R., Wagner, W., Jaeschke, M. [2006]. Technical Monograph, VDI-Verlag). This methodology is used in combination with available published thermodynamic measurements and with new pressure-Volume-Temperature (pVT) measurements of H2-H2O mixtures conducted with the jovian simulator described in Karpowicz and Steffes (Karpowicz, B.M., Steffes, P.G. [2011]. Icarus 212, 210-223). In addition to being necessary to interpret laboratory measurements, the new equation of state is important in developing temperature pressure profiles of the deep jovian atmosphere. This is demonstrated by incorporating the new equation of state into an updated version of the DeBoer (DeBoer, D.R. [1995]. Ph.D. Thesis, Georgia Institute of Technology) Thermo-Chemical Model (TCM), and viewing its effect on the resulting simulated jovian atmospheric profiles.

  13. Singlet Mechanism for Trans → Cis Photoisomerization of Quaternary Salts of 4-Substituted 4'-Azastilbenes (R = CN, H, CH3, and OCH3) and their Quinolinium Analogues. VIII

    NASA Astrophysics Data System (ADS)

    Görner, H.; Fojtik, A.; Wróblewski, J.; Currell, L. J.

    1985-05-01

    The trans → cis photoisomerization of a series of substituted stilbazolium salts (At+X- , At+: trans-1-alkyl-4-[4-R-styryl]-pyridinium and -quinolinium, R = CN. H, CH3 and OCH3, X- = I and ClO4-) was studied by laser flash photolysis and steady state irradiation measurements. The quantum yields of cis ⇄ trans photoisomerization (ϕc → t and ϕt → c ) and of fluorescence of the trans isomers (ϕf) were determined in several solvents at room temperature and at low temperatures in mixtures of either 2-methyltetrahydrofuran-dichloromethane or ethanolmethanol (E-M). In polar solvents at room temperature ϕt → c is substantial ( ≧ 0.3) and ϕf is small (10-3-10-2). Competition of fluorescence and an activated step in the trans → cis pathway is indicated by the effects of temperature on ϕf and ϕt → c (activation energy: 2 - 3 kcal/mol). A transient, observed only at low temperatures (lifetime τT > 0.5 ms in E-M below -170°C), is assigned to the lowest triplet state with trans configuration. On the basis of the effects of temperature on ϕf, ϕt → c , and the triplet yield and those of quenchers on ϕf and ϕt → c , involvement of the triplet state in the twisting process at room temperature is excluded. Therefore, a singlet mechanism is suggested for the trans → cis photoisomerization of the stilbazolium salts examined. Significant reduction of ϕt → c for iodides in solvents of moderate polarity, where ion pairs are present, is accounted for by photoinduced electron transfer in competition to trans → cis photoisomerization.

  14. Correlation between stress-induced leakage current and dielectric degradation in ultra-porous SiOCH low-k materials

    SciTech Connect

    Wu, C. De Wolf, I.; Li, Y.; Leśniewska, A.; Varela Pedreira, O.; Marneffe, J.-F. de; Ciofi, I.; Verdonck, P.; Baklanov, M. R.; Bömmels, J.; Tőkei, Zs.; Croes, K.

    2015-10-28

    Stress-Induced Leakage Current (SILC) behavior during the dielectric degradation of ultra-porous SiOCH low-k materials was investigated. Under high voltage stress, SILC increases to a critical value before final hard breakdown. This SILC increase rate is mainly driven by the injected charges and is negligibly influenced by temperature and voltage. SILC is found to be transient and shows a t{sup −1} relaxation behavior, where t is the storage time at low voltages. This t{sup −1} transient behavior, described by the tunneling front model, is caused by both electron charging of neutral defects in the dielectric close to the cathode interface and discharging of donor defects close to the anode interface. These defects have a uniform density distribution within the probed depth range, which is confirmed by the observed flat band voltage shift results collected during the low voltage storage. By applying an additional discharging step after the low voltage storage, the trap energies and spatial distributions are derived. In a highly degraded low-k dielectric, the majority of defects have a trap depth between 3.4 eV and 3.6 eV and a density level of 1 × 10{sup 18 }eV{sup −1 }cm{sup −3}. The relation between the defect density N and the total amount of the injected charges Q is measured to be sub-linear, N ∼ Q{sup 0.45±0.07}. The physical nature of these stress-induced defects is suggested to be caused by the degradation of the Si-O based skeleton in the low-k dielectric.

  15. Design of peptides with α, β-dehydro-residues: synthesis and crystal structure of a tripeptide N-benzyloxycarbonyl-ΔVal-ΔPhe- L-Ala-OCH 3

    NASA Astrophysics Data System (ADS)

    Goel, Vijay Kumar; Dey, Sharmistha; Singh, Tej P.

    2005-03-01

    In order to develop the design rules for producing specific conformations of peptides with α, β-dehydro-residues a peptide Cbz-ΔVal-ΔPhe-Ala-OCH 3 was synthesized in solution phase. The crystal structure has been determined by X-ray diffraction method. The structure was refined to an R-value of 0.050. The peptide adopts a type I β-turn conformation with backbone torsion angles of two corner residues, ϕ1=-53.9(6)°, ψ1=-33.0(6)°, ϕ2=-73.7(5)° and ψ2=-12.2(6)°. The conformation is stabilized by an intramolecular 4→1 hydrogen bond involving NH of Ala residue as a donor and carbonyl oxygen atom of Cbz group as an acceptor. The torsion angles, χ11,1=172.8(6) and χ11,2=-6.9(9) of ΔVal residue indicate that its side chain is planar while the torsion angles, χ21=-9.0(9), χ22,1=-43.4(10) and χ22,2=130.1(9) show that the side chain of ΔPhe deviates considerably from the planarity. This is the first sequence in which ΔVal and ΔPhe are introduced at adjacent positions and the structure reveals clearly that the side chain of ΔPhe is a relatively less rigid than that of ΔVal. The molecules are packed in columns parallel to c-axis.

  16. Correlation between stress-induced leakage current and dielectric degradation in ultra-porous SiOCH low-k materials

    NASA Astrophysics Data System (ADS)

    Wu, C.; Li, Y.; Leśniewska, A.; Varela Pedreira, O.; de Marneffe, J.-F.; Ciofi, I.; Verdonck, P.; Baklanov, M. R.; Bömmels, J.; De Wolf, I.; Tőkei, Zs.; Croes, K.

    2015-10-01

    Stress-Induced Leakage Current (SILC) behavior during the dielectric degradation of ultra-porous SiOCH low-k materials was investigated. Under high voltage stress, SILC increases to a critical value before final hard breakdown. This SILC increase rate is mainly driven by the injected charges and is negligibly influenced by temperature and voltage. SILC is found to be transient and shows a t-1 relaxation behavior, where t is the storage time at low voltages. This t-1 transient behavior, described by the tunneling front model, is caused by both electron charging of neutral defects in the dielectric close to the cathode interface and discharging of donor defects close to the anode interface. These defects have a uniform density distribution within the probed depth range, which is confirmed by the observed flat band voltage shift results collected during the low voltage storage. By applying an additional discharging step after the low voltage storage, the trap energies and spatial distributions are derived. In a highly degraded low-k dielectric, the majority of defects have a trap depth between 3.4 eV and 3.6 eV and a density level of 1 × 1018 eV-1 cm-3. The relation between the defect density N and the total amount of the injected charges Q is measured to be sub-linear, N ˜ Q0.45±0.07. The physical nature of these stress-induced defects is suggested to be caused by the degradation of the Si-O based skeleton in the low-k dielectric.

  17. Theoretical studies in local coordination and vibrational spectra of M +CH 3O(CH 2CH 2O) nCH 3 ( n = 2-7) complexes (M = Na, K, Mg and Ca)

    NASA Astrophysics Data System (ADS)

    Dhumal, Nilesh R.; Gejji, Shridhar P.

    2006-04-01

    Solid polymer electrolytes (SPE) comprised of poly(ethylene oxide) (PEO) oligomers complexed with alkali metal salt of weakly coordinating anions have been of a great interest due to their high ionic conductivity. Ion pair formation influence the number of charge carriers and is an important factor underlying the ion transport phenomenon. In this work, the electronic structure and vibrational spectra of the metal ion-PEO oligomer represented by M-CH 3O(CH 2CH 2O) nCH 3 ( n = 2-7) (M = Na +, K +, Mg 2+ and Ca 2+) are obtained by employing the ab initio and hybrid density functional methods. Structural and spectral consequences of PEO oligomers to the alkali- and alkaline earth-metal ion coordination in different chemical environments have been presented. In metal ion-PEO oligomer ion-pairs the Mg 2+ ion binds strongly to ether oxygens of polyether complexes. The density functional calculations predict the heptaglyme ( n = 7 in the above series) binds strongly to the metal ion. The frequency shifts of characteristics vibrations induced by the metal ion-coordination in CH 3O(CH 2CH 2O) nCH 3-M ( n = 2-7) complexes have been discussed.

  18. Fluid evolution in the H 2O-CH 4-CO 2-NaCl system during emerald mineralization at Gravelotte, Murchison Greenstone Belt, Northeast Transvaal, South Africa

    NASA Astrophysics Data System (ADS)

    Nwe, Yin Yin; Morteani, Giulio

    1993-01-01

    Fluid evolution during emerald mineralization at the Gravelotte emerald mine has been studied by microthermometry and laser Raman microprobe spectrometry. The emeralds and associated phenakites occur on the flanks of a highly metasomatised albitite pegmatoid body and in the biotite schists at and near its contact. The fluids lie in the H 2O-CH 4-CO 2-NaCl system and four types of inclusions are characterised based on time of trapping and fluid contents. The earliest type 1 inclusions, found in phenakites and the emeralds which formed from them, are low salinity (<6 wt% NaCl) with up to 18 mol% CH 4. The carbonic phase contains over 93 mol% CH 4 and variable small amounts of CO 2, C 2H 6, N 2, and H 2S. The solvus crest for this system lies at ≈400°C, closer to the H 2O end of the join. With time the fluids become less CH 4 rich and more saline. The type 2 fluids are highly variable in both CH 4-CO 2 contents and salinity, reflecting mixing of type 1 fluids with higher salinity brines. The late type 3 and 4 inclusions are CH 4-CO 2-free high salinity inclusions with up to 38 wt% NaCl. Trapping conditions for the type 1 fluids were around 450-500°C and 4 kb based on model isochores and geologic evidence. During the trapping of type 2 inclusions, fluid pressures probably fluctuated due to opening and resealing of fractures. Approximate P- T ranges of trapping for these and other later inclusions have been defined, minimum trapping temperatures for types 2, 3, and 4 being, respectively, 250, 150, and 240°C, and pressures in the range of 1-4 kb. Calculations of ƒ O 2 show an initial low ƒ O 2 between QFM and the synthetic graphite-CH 4 buffer for the type 1 fluids. This rises to above QFM in the later stages. Such low initial values are uncharacteristic of granitic pegmatite systems, and it is suggested that the phenakites formed in the post-magmatic stage of alkali metasomatism when the albitization took place. In the later stages, phenakite was converted to

  19. Degenerate electrical conductive and excitonic photoluminescence properties of epitaxial films of wide gap p-type layered oxychalcogenides, LnCuOCh (Ln=La, Pr and Nd; Ch=S or Se)

    NASA Astrophysics Data System (ADS)

    Hiramatsu, H.; Ueda, K.; Takafuji, K.; Ohta, H.; Hirano, M.; Kamiya, T.; Hosono, H.

    Electrical and photoluminescence properties were investigated for epitaxial films of layered oxychalcogenides, LnCuOCh (Ln=La, Pr, and Nd, Ch=S or Se). Epitaxial films of Mg 10 at.% doped LaCuOS1-xSex are the first demonstration of degenerate conduction with high hole concentration >1020 cm-3 in wide gap p-type semiconductors. Ion substitution varied the excitonic emission energy from 3.21 eV to 2.89 eV while lanthanide and chalcogenide ion substitutions displayed the opposite tendency against cell volume. These unique properties are discussed with respect to the electronic structure originating from the layered crystal structure.

  20. Transfer of Amide and 2-Methoxyethoxy Groups and Sodium Encapsulation in the Reaction of TaCl3[N(TMS)2]2 with Sodium Bis(2-methoxyethoxy)aluminum Hydride: X-ray Structure of [NaAl{N(TMS)2}(OCH2CH2OMe)3]2

    SciTech Connect

    Huang, Shih-Huang Huang; Wang, Xiaoping; Richmond, Michael G.

    2009-01-01

    The reaction between the tantalum compound TaCl3[N(TMS)2]2 and the hydridic reducing agent sodium bis(2-methoxyethoxy)aluminum hydride (Vitride) has been investigated in toluene solution at room temperature and found to afford the dimeric aluminate complex [NaAl{N(TMS)2}(OCH2CH2OMe)3]2 as the sole isolable product. The molecular structure of the product establishes the existence of a four-coordinate aluminum atom and the formal transfer of the 2-methoxyethoxy and bis(trimethylsilyl)amide groups to the aluminate product. The aggregation of two NaAl{N(TMS)2}(OCH2CH2OMe)3 units serves to bind the two sodium cations in a crown-ether fashion through six ancillary oxygen atoms.

  1. VAPOR PRESSURES, LIQUID MOLAR VOLUMES, VAPOR NON- IDEALITIES, AND CRITICAL PROPERTIES OF SOME FLUORINATED ETHERS: CF3OCF2OCF3, CF3OCF2 CF2H, c-CF2CF2CF2O, CF3OCF2H, AND CF3OCH3; AND OF CCl3F AND CF2ClH

    EPA Science Inventory

    Vapor pressures, compressibilities, expansivities, and molar volumes of the liquid phase have been measured between room temperature and the critical temperature for a series of fluorinated ethers: CF3OCF2OCF3, CF3OCF2CF2H, c-CF2CF2CF2O, CF3OCF2H, and CF3OCH3. Vapor-phase non-ide...

  2. [Ni(OH)3W6O18(OCH2)3CCH2OH]4–: the first tris-functionalized Anderson-type heteropolytungstate† †Electronic supplementary information (ESI) available: Experimental procedures, synthesis details, characterization data, including IR, ESI-MS, TGA, elemental analysis and X-ray crystallography with CIF file. CCDC 1477611. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6cc04326g Click here for additional data file. Click here for additional data file.

    PubMed Central

    Gumerova, Nadiia I.; Roller, Alexander

    2016-01-01

    Na2[TMA]2[Ni(OH)3W6O18(OCH2)3CCH2OH]·9H2O represents the first covalent tris-functionalized Anderson-type heteropolytungstate and was characterized by single-crystal X-ray diffraction, electrospray ionization mass spectrometry, TGA and IR spectroscopy. Zeta potential measurements in solutions containing human serum albumin were performed to investigate electrostatic interactions with [Ni(OH)3W6O18(OCH2)3CCH2OH]4–. PMID:27355393

  3. Synthesis and characterization of a new monophosphate (5-Cl-2,4-(OCH{sub 3}){sub 2}C{sub 6}H{sub 2}NH{sub 3})H{sub 2}PO{sub 4}

    SciTech Connect

    Kefi, R.; Abid, S.; Nasr, C. Ben . E-mail: cherif.bennasr@fsb.rnu.tn; Rzaigui, M.

    2007-03-22

    Chemical preparation, crystal structure and NMR spectroscopy of a new organic cation 5-chloro(2,4-dimethoxy)anilinium monophosphate H{sub 2}PO{sub 4} are given. This new compound crystallizes in the monoclinic system, with the space group P2{sub 1}/c and the following parameters: a=5.524(2)A, b=9.303(2)A, c=23.388(2)A, {beta}=90.66(4), V=1201.8(2)A{sup 3}, Z=4 and D{sub x}=1.573gcm{sup -3}. Crystal structure has been determined and refined to R=0.031 and R{sub w}=0.080 using 1702 independent reflections. Structure can be described as an infinite (H{sub 2}PO{sub 4}){sub n}{sup n-} corrugated chains in the a-direction. The organic groups (5-Cl-2,4-(OCH{sub 3}){sub 2}C{sub 6}H{sub 2}NH{sub 3}){sup +} are anchored between adjacent polyanions through multiple hydrogen bonds. This compound is also investigated by IR, thermal, and solid-state, {sup 13}C, {sup 31}P MAS NMR spectroscopies.

  4. Atmospheric oxidation of fluorinated ethers, E143a (CF{sub 3}OCH{sub 3}), E134 (CHF{sub 2}OCHF{sub 2}), and E125 (CHF{sub 2}OCF{sub 3})

    SciTech Connect

    Good, D.A.; Kamboures, M.; Santiano, R.; Francisco, J.S.

    1999-11-18

    Because of the ability of chlorofluorocarbons (CFCs) to deplete stratospheric ozone, many applications have begun to employ hydrofluorocarbons (HFCs) as working fluids. HFCs contain no chlorine and are thus given ozone depletion potentials of essentially zero. Attention is now focused on global warming, with the goal of reducing greenhouse gas emissions. Air conditioners, heat pumps, and refrigeration devices that use refrigerants also use energy. They contribute to global warming both by the release of the refrigerant and by the emission of carbon dioxide and other greenhouse gases in powering the devices. The atmospheric oxidation mechanisms of E143a (CF{sub 3}OCH{sub 3}), E134 (CHF{sub 2}OCHF{sub 2}), and E125 (CHF{sub 2}OCF{sub 3}) have been investigated using experimental and ab initio methodology. The oxidation of E143a produces the stable reservoir species trifluoromethyl formate, CF{sub 3}OCOH, which further oxidizes to CF{sub 2}O and CO{sub 2}. Oxidation of E134 and E125 shows the presence of only CF{sub 2}O under the condition of high O{sub 2} concentrations. Carbonyl fluoride can be formed from two competing pathways involving the halogenated alkyl radicals formed from hydrogen abstraction of E134 and E125. CO bond fission reactions and O{sub 2} addition reactions compete to produce carbonyl fluoride and a CF{sub x}H{sub 3{minus}x} radical fragment. Computational modeling of the reaction pathways provides insight into the molecular steps of the degradation process.

  5. Structure of the puf operon of the obligately aerobic, bacteriochlorophyll alpha-containing bacterium Roseobacter denitrificans OCh114 and its expression in a Rhodobacter capsulatus puf puc deletion mutant.

    PubMed Central

    Kortlüke, C; Breese, K; Gad'on, N; Labahn, A; Drews, G

    1997-01-01

    Roseobacter denitrificans (Erythrobacter species strain OCh114) synthesizes bacteriochlorophyll a (BChl) and the photosynthetic apparatus only in the presence of oxygen and is unable to carry out primary photosynthetic reactions and to grow photosynthetically under anoxic conditions. The puf operon of R. denitrificans has the same five genes in the same order as in many photosynthetic bacteria, i.e., pufBALMC. PufC, the tetraheme subunit of the reaction center (RC), consists of 352 amino acids (Mr, 39,043); 20 and 34% of the total amino acids are identical to those of PufC of Chloroflexus aurantiacus and Rubrivivax gelatinosus, respectively. The N-terminal hydrophobic domain is probably responsible for anchoring the subunit in the membrane. Four heme-binding domains are homologous to those of PufC in several purple bacteria. Sequences similar to pufQ and pufX of Rhodobacter capsulatus were not detected on the chromosome of R. denitrificans. The puf operon of R. denitrificans was expressed in trans in Escherichia coli, and all gene products were synthesized. The Roseobacter puf operon was also expressed in R. capsulatus CK11, a puf puc double-deletion mutant. For the first time, an RC/light-harvesting complex I core complex was heterologously synthesized. The strongest expression of the R. denitrificans puf operon was observed under the control of the R. capsulatus puf promoter, in the presence of pufQ and pufX and in the absence of pufC. Charge recombination between the primary donor P+ and the primary ubiquinone Q(A)- was observed in the transconjugant, showing that the M and L subunits of the RC were correctly assembled. The transconjugants did not grow photosynthetically under anoxic conditions. PMID:9286973

  6. Electronic structure of the members of the electron transfer series [NiL](z) (z = 3+, 2+, 1+, 0) and [NiL(X)](n) (X = Cl, CO, P(OCH(3))(3)) species containing a tetradentate, redox-noninnocent, Schiff base macrocyclic ligand L: an experimental and density functional theoretical study.

    PubMed

    Ghosh, Meenakshi; Weyhermüller, Thomas; Wieghardt, Karl

    2010-02-28

    The electronic structure of the four members of the electron transfer series [NiL](z) (z = 3+, 2+, 1+, 0) have been established experimentally (EPR spectroscopy and X-ray crystallography) and by density functional theoretical (DFT) calculations using the B3LYP functional in conjunction with a conductor-like screening model (COSMO) for acetonitrile solvent effects. L represents a generic designation of the tetradentate macrocycle 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]-heptadeca-1(17),2,11,13,15-pentane where the true oxidation level is not specified; (L(Ox))(0) represents its neutral form, (L )(1-) is the one-electron reduced pi radical anion, and (L(Red))(2-) is the singlet (or triplet) diradical dianion of this ligand. It is shown that the above series consists of square planar [Ni(III)(L(Ox))](3+) (S = 1/2), [Ni(II)(L(Ox))](2+) (S = 0), [Ni(II)(L )](1+) (S = 1/2), [Ni(II)(L(Red))](0) (S = 0). The structure of [Ni(II)(L(Red))](0) has been determined by X-ray crystallography. The electrochemistry of [Ni(II)(L(Ox))](PF(6))(2) in the presence of hard chloride anions shows the presence of trans-[Ni(III)(L(Ox))Cl(2)](+), the EPR spectrum of which has been recorded and calculated, and of trans-[Ni(II)(L(Ox))Cl(2)](0) (S = 1). Upon further reduction the coordinated Cl(-) ligands dissociate and [Ni(II)(L )](1+) and [Ni(II)(L(Red))](0) are successively generated. Similarly, in the presence of good pi-acceptor ligands such as CO or P(OCH(3))(3) the following five-coordinate, square base pyramidal species are found to be stable: [Ni(I)(L(Ox))(X)](1+) (S = 1/2), [Ni(I)(L )(X)](0) (S = 0, 1) (X = CO, P(OCH(3))(3)). As shown by EPR spectroscopy in the work of J. Lewis and M. Schröder, J. Chem. Soc., Dalton Trans., 1982, 1085, the monocations consist of a central nickel(i) ion (d(9), S(Ni) = 1/2). These spectra have been faithfully reproduced by the calculations. The neutral complexes [Ni(I)(L )(X)](0) are singlet or triplet diradicals comprising a central nickel

  7. Synthesis, characterization, structural and biological aspects of copper(II) dithiocarbamate complexes - Part II, [Cu{S2CN(Me)(R1)}2], [Cu{S2CN(Me)(R2)}2] and [Cu{S2CN(R3)(R4)}2] {R1 = CH2CH(OMe)2, R2 = 2-methyl-1,3-dioxolane, R3 = CH2(CH2)2NCHPhOCH2Ph and R4 = CH2CH2OH}

    NASA Astrophysics Data System (ADS)

    Ferreira, Isabella P.; de Lima, Geraldo M.; Paniago, Eucler B.; Takahashi, Jacqueline A.; Krambrock, Klaus; Pinheiro, Carlos B.; Wardell, James L.; Visentin, Lorenzo C.

    2013-09-01

    Three new copper(II) dithiocarbamates (DTC), [Cu{S2CN(Me)(R1)}2] (1), [Cu{S2CN(Me)(R2)}2] (2) and [Cu{S2CN(R3)(R4)}2] (3) with R1 = CH2CH(OMe)2, R2 = 2-methyl-1,3-dioxolane, R3 = CH2(CH2)2NCHPhOCH2Ph and R4 = CH2CH2OH, have been synthesized and characterized by different spectroscopic techniques. Complexes (1) and (2) display typical EPR spectra for separated Cu(II) centers, and the spectrum of (3) is characteristic of two magnetically coupled Cu(II) ions with S = 1. The X-ray crystallographic determination has shown that complexes (1) and (2) crystallise in the triclinic and monoclinic systems. In addition both complexes are monomers in which the geometry at each Cu(II) is square planar. The in vitro antimicrobial activity of the sodium salts of ligands, and of the Cu(II)-DTC complexes have been screened against Aspergillus flavus, Aspergillus niger, Aspergillus parasiticus, Penicillium citrinum and Curvularia senegalensis, as well as Gram positive and Gram negative bacteria. Finally, the toxic effects of complexes (1)-(3) were performed using Chlorella vulgaris.

  8. Dagliga Separationer och Tidig Daghemsstart (Daily Separations and Early Entry into Day Care).

    ERIC Educational Resources Information Center

    Harsman, Ingrid

    The purpose of this thesis [Swedish language with English abstract and summary] was to study the reactions of infants when they started attending day care centers and to elucidate the process of adjustment. The theoretical perspective employed is the J. Bowlby/M. Ainsworth attachment theory. U. Bronfenbrenner's ecological theory of human…

  9. Aetervinning av faerg och ridaevatten med ultrafiltrering (recycling of paint and water curtains with ultrafiltration)

    SciTech Connect

    Fortkamp, U.; Allard, A.S.; Ekengren, O.

    1997-12-01

    Painting in spray booths causes overspray that is collected by a water curtain. The mixture of water and paint is commonly treated by means of precipitation. By means of this method, water can be used again but a paint sludge is created. Within this project, it was investigated how the paint as well as the water can be recycled. Separation by membrane filtration was tested for different paints in laboratory scale (0.2 liter volume). It was possible to separate all tested paints from the water and to concentrate it. At large scale (15 to 75 liters volume), an emulsion paint and a dispersion paint were tested. Under the tested conditions, it was slightly easier to concentrate the emulsion paint than the dispersion paint. It was possible to concentrate the paints to the original dry substance percentage. An important aspect of membrane filtration is cleaning of the membrane when the performance decreases. It was possible to clean all the tested membranes, but in many cases it was difficult. A ceramic membrane and a membrane of polyaramide showed the best results with regard to flux and cleaning of the membrane under the tested conditions. During the performance of the project two new applications of membrane filtration of paint were found. The method can be used for waste minimization by only separating the paint in an easy way at low costs. A third application is treating cleaning water from paint manufacturing.

  10. Sma Barn Pa Daghem: En studie av personalens samspel med barn och foraldrar vid lamning, hamtning och fri lek (Infants at Day Care: A Study of Staff Interaction with Children and Their Parents during Leaving, Collecting and Free Play).

    ERIC Educational Resources Information Center

    Lothigius, Anita Holmstedt

    This thesis presents a picture of how staff interact with infants (age group 1-3 years old) and parents at three day care centers. The study focused on the situations of leaving and collecting the children and the children's time of free play both in and outdoors. The theoretical content has an attachment/psycho-dynamical perspective with emphasis…

  11. Speciallararens Kunskaper Och Kompetens: Intervjuer med tio speciallarare (The Special Teacher's Knowledge and Competence: Interviews with Ten Special Teachers).

    ERIC Educational Resources Information Center

    Vernersson, Inga-Lill

    This thesis reports on a study in which 10 Swedish special education teachers were interviewed concerning the following six topics: (1) personal background and choice of a career; (2) professional knowledge; (3) the role of a special education teacher; (4) educational goals and methods; (5) cooperation; and (6) thoughts about the future.…

  12. Thermal conductivity of H2O-CH3OH mixtures at high pressures: Implications for the dynamics of icy super-Earths outer shells

    NASA Astrophysics Data System (ADS)

    Hsieh, Wen-Pin; Deschamps, Frédéric

    2015-10-01

    Thermal conductivity of H2O-volatile mixtures at extreme pressure-temperature conditions is a key factor to determine the heat flux and profile of the interior temperature in icy bodies. We use time domain thermoreflectance and stimulated Brillouin scattering combined with diamond anvil cells to study the thermal conductivity and sound velocity of water (H2O)-methanol (CH3OH) mixtures to pressures as high as 12 GPa. Compared to pure H2O, the presence of 5-20 wt % CH3OH significantly reduces the thermal conductivity and sound velocity when the mixture becomes ice VI-CH3OH and ice VII-CH3OH phases at high pressures, indicating that the heat transfer is hindered within the icy body. We then apply these results to model the heat transfer through the icy mantles of super-Earths, assuming that these mantles are animated by thermal convection. Our calculations indicate that the decrease of thermal conductivity due to the presence of 10 wt % CH3OH induces a twofold decrease of the power transported by convection.

  13. Att Tolka Barns Signaler: Gravt utvecklingsstorda flerhandikappade barns lek och kommunikation (To Interpret Childrens' Signals: Play and Communication in Profoundly Mentally Retarded and Multiply Handicapped Children).

    ERIC Educational Resources Information Center

    Brodin, Jane

    Written in Swedish with an English-language summary, this report describes a study which examined the interaction between mothers or caregivers and their children with profound mental retardation and multiple disabilities, particularly looking at the function of play in communicative interaction. The six children all had five or six handicaps in…

  14. Hydrogen isotope systematics among H2-H2O-CH4 during the growth of the hydrogenotrophic methanogen Methanothermobacter thermautotrophicus strain ΔH

    NASA Astrophysics Data System (ADS)

    Kawagucci, Shinsuke; Kobayashi, Mariko; Hattori, Shohei; Yamada, Keita; Ueno, Yuichiro; Takai, Ken; Yoshida, Naohiro

    2014-10-01

    Stable hydrogen isotope systematics among H2, H2O, and CH4 during hydrogenotrophic methanogenesis were investigated by growing a thermophilic methanogen, Methanothermobacter thermautotrophicus strain ΔH, in batch cultures spiked with deuterium-labeled H2 and/or H2O. The hydrogen isotope ratio of the product, CH4, reflected not only the isotope ratio of the H2O in the medium but also that of the substrate, H2. The D/H ratios of the CH4 were highest during the early phase of growth, and the growth-phase-dependent changes were greatest in the deuterium-enriched H2 cultures. The hydrogen isotope systematics among H2, H2O, and CH4 during growth of the methanogen could be described with the following equations: δDCH4=a×δDH2O+b×δDH2-c a=0.71-0.55×b 0.17⩽b⩽0.38 c=1000×(a+b-1) The greatest effect of δDH2 on δDCH4 (b = 0.38) was observed during the earliest phase of growth. In contrast to this study, the possible disappearance of the effect (b = 0) has been suggested in a previous study (Valentine et al., 2004a) in which Methanothermobacter marburgensis was cultured and hydrogen isotope systematics during growth was monitored, as was the case in this study. The close phylogenetic relationship between M. thermautotrophicus and M. marburgensis, which likely have similar biochemical pathways, suggests a possibly broad range of the b value, 0-0.38. To explain the observed hydrogen isotope systematics, two cellular mechanisms were proposed. One is that the hydrogen atoms of both H2 and H2O are directly incorporated into the product, CH4. The other is that all four hydrogen atoms in the product, CH4, are derived from intracellular H2O, which consists of a mixture of medium-derived pristine H2O and isotopically distinct H2O derived from methanogenic H2 oxidation. Although we attempted to evaluate the feasibility of these mechanisms, both cellular mechanisms remain hypothetical. The hydrogen isotope systematics shown here contribute to put forward utility of δDCH4 value as a geochemical tracer of the origins of environmental CH4.

  15. Investigation of Methanol Formation Mechanisms in H2O+CH4 Ices Subjected to 5 keV Electrons at a 10-100 K Temperature Range

    NASA Astrophysics Data System (ADS)

    Stelmach, K. B.; Cooper, P. D.

    2014-12-01

    Methane (CH4) and water are one of the most common molecules in both planetary bodies and interstellar dust grains. Another common molecule, methanol (CH3OH), is thought to form in CH4+H2O ices. However, the exact formation mechanisms of methanol from cosmic rays are not well known, especially in the temperatures of interest. Experiments were performed using high energy electrons (5 keV) to irradiate mixtures of 1:10, 1:5, and 1:3 CH4+H2O ices under a temperature range of 10-100 Kelvin with Fourier Transform Infrared (FTIR) spectroscopy being used to identify the products. Isotopologues of the two molecules (D2O and CD4) were used to probe for the mechanisms. Other products were formed as well and their potential mechanisms are identified. The implications of the mechanisms for planetary and interstellar chemistry are discussed.

  16. [BLOODSUCKING MOSQUITOES (DIPTERA: CULICIDAE) IN, THE TULA REGION ARE POTENTIAL VECTORS OF DIROFILARIAS].

    PubMed

    Bogacheva, A S; Ganushkina, L A; Lopatina, Yu V

    2015-01-01

    Bloodsucking mosquitoes were collected in Tula and its Region in May to August 2013-2014. The fauna included 17 species from 5 genera in the subfamily Culicinae and Anopheles maculipennis complex in the subsystem Anophelinae. Ochlerotatus cantans was a dominant species in the collections. The dominant species also included Aedes einereus, Ae. vexans, Ae. geniculatus, Och. diantaeus, Och. intrudens, Och. Cataphylla, and Culex pipiens. The possible value of different mosquito species Dirofilaria repens and D. immitis as vectors of dirofilarasis was discussed.

  17. Synthesis and evaluation of κ(2)-β-diketonate and β-ketoesterate tungsten(vi) oxo-alkoxide complexes as precursors for chemical vapor deposition of WOx thin films.

    PubMed

    Bonsu, Richard O; Bock, Duane C; Kim, Hankook; Korotkov, Roman Y; Abboud, Khalil A; Anderson, Timothy J; McElwee-White, Lisa

    2016-07-01

    Reactions of [WO(OR)4]x (x = 1, 2) complexes with bidentate ligands (LH = acacH, tbacH, dpmH, tbpaH) afforded complexes : [WO(OCH3)3(acac) (); WO(OCH2CH3)3(acac) (); WO(OCH(CH3)2)3(acac) (); WO(OCH3)3(tbac) (); WO(OCH2CH3)3(tbac) (); WO(OCH(CH3)2)3(tbac) (); WO(OCH2CH3)3(dpm) (); WO(OCH(CH3)2)3(dpm) (); WO(OCH2C(CH3)3)3(acac) (); WO(OCH2C(CH3)3)3(tbac) (); WO(OCH2C(CH3)3)3(dpm) (); WO(OCH2C(CH3)3)3(tbpa) (); WO(OC(CH3)3)3(tbac) ()]. The synthesis is facilitated by the lability of the bridging ligands of the [WO(OR)4]2 complexes in solution, which provides a pathway for exchange of L with an alkoxide ligand. Thermogravimetric analysis and the conditions for sublimation or distillation of demonstrate that they have sufficient vapor pressure and thermal stability for volatilization in a conventional Chemical Vapor Deposition (CVD) reactor. High solubility in hydrocarbon and ether solvents establishes that the complexes are also potential candidates for Aerosol-Assisted Chemical Vapor Deposition (AACVD). AACVD from on ITO or bare glass resulted in growth of continuous, dense and amorphous thin films of substoichiometric WOx between 250-350 °C and nanorods of W18O49 above 350 °C. PMID:27160734

  18. Self-assembled nanoparticles based on hydrophobically modified chitosan as carriers for doxorubicin.

    PubMed

    Zhang, Jing; Chen, Xi Guang; Li, Yan Yan; Liu, Cheng Sheng

    2007-12-01

    In this study self-assembled nanoparticles based on oleoyl-chitosan (OCH) were prepared with a mean diameter of 255.3 nm and an almost spherical shape. The toxicity profile of OCH nanoparticles was evaluated in vitro via hemolysis test and MTT assay. The hemolysis rates of OCH nanoparticles tested in different conditions came well within permissible limits (5%). The OCH nanoparticles showed no cytotoxicity to mouse embryo fibroblasts. Doxorubicin (DOX) was efficiently loaded into OCH nanoparticles with an encapsulation efficiency of 52.6%. The drug was rapidly and completely released from the nanoparticles (DOX-OCH nanoparticles) at pH 3.8, whereas at pH 7.4 there was a sustained release after a burst release. The inhibitory rates of DOX-OCH nanoparticle suspension to different human cancer cells (A549, Bel-7402, HeLa, and SGC-7901) significantly outperformed that of DOX solution. These results revealed the potential of OCH nanoparticles as carriers for hydrophobic antitumor agents.

  19. ORGANONICKEL CHEMISTRY IN THE CATALYTIC HYDRODECHLORINATION OF POLYCHLOROBIPHENYLS (PCBS): LIGAND STERIC EFFECTS AND MOLECULAR STRUCTURE OF REACTION INTERMEDIATES. (R823526)

    EPA Science Inventory

    Abstract

    Soluble homogeneous organophosphorus¯¯nickel complexes have been used to detoxify polychlorinated biphenyls (PCBs) by catalyzed hydrodechlorination using NaBH2(OCH2CH2OCH3)2 as the hyd...

  20. Discourse Markers in Chinese Conversational Narrative

    ERIC Educational Resources Information Center

    Xiao, Yang

    2010-01-01

    This study examines the indexicality of discourse markers (DMs) in Chinese conversational narrative. Drawing upon theoretical and methodological principles related to narrative dimensions (Ochs & Capps, 2001), narrative desires (Ochs, 1997, 2004), and narrative positioning (Bamberg, 1997), this work proposes an integrated analytical framework for…

  1. Ecological Functions of Off-Channel Habitats of the Willamette River, Oregon, Database and Documentation (1997-2001)

    EPA Science Inventory

    The database from the Ecological Functions of Off-Channel Habitats of the Willamette River, Oregon project (OCH Project) contains data collected from 1997 through 2001 from multiple research areas of the project, and project documents such as the OCH Research Plan, Quality Assura...

  2. Lysophosphatidylcholine attenuates the cytotoxic effects of the antineoplastic phospholipid 1-O-octadecyl-2-O-methyl-rac-glycero-3- phosphocholine.

    PubMed

    Boggs, K P; Rock, C O; Jackowski, S

    1995-05-12

    A colony-stimulating factor 1-dependent cell line was used to determine the relationship between the inhibition of phospholipid synthesis and the cytotoxic activity of the antineoplastic ether lipid, 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3). ET-18-OCH3 inhibited choline incorporation into phosphatidylcholine as well as total phospholipid synthesis. Exposure to ET-18-OCH3 at the G1/S boundary led to the accumulation of cells in G2, whereas the addition of ET-18-OCH3 in the G1 phase of the cell cycle prevented entry into the S phase. In both cases, ET-18-OCH3 treatment triggered DNA fragmentation and morphological changes associated with apoptosis within 10 h. The addition of lysophosphatidylcholine provided an exogenous source of cellular phospholipid and prevented ET-18-OCH3-dependent accumulation of cells in G2 and apoptosis. However, lysophosphatidylcholine did not overcome the ET-18-OCH3-dependent G1 block, although the growth-arrested cells remained viable. These data indicate that restoring phosphatidylcholine synthesis by supplementation with lysophosphatidylcholine overrides the cytotoxic but not the cytostatic activity of ET-18-OCH3.

  3. Fluid inclusions in the system H sub 2 O-CH sub 4 -NaCl-CO sub 2 from metasomatic tourmaline within the border unit of the Tanco zoned granitic pegmatite, S. E. Manitoba

    SciTech Connect

    Thomas, A.V.; Spooner, E.T. )

    1988-05-01

    Fluid inclusions from the tourmaline phase of alteration of the footwall amphibolite from the Tanco zoned granitic pegmatite lie in the system H{sub 2}O-CH{sub 4}-NaCl-CO{sub 2}. These inclusions contain a liquid and vapor phase at room temperature and develop a second liquid phase on cooling in the range {minus}77 to {minus}95{degree}C: the second liquid and the vapor are methane. Isochores for inclusions showing vapor phase (CH{sub 4}) homogenization were constructed from the equations of Jacobs and Kerrick (1981). The intersections of these isochores with the univariant melting curves for methane clathrate hydrates give estimates of salinity for the inclusions of between 7 and 10 equivalent wt.% NaCl, which are lower than those derived from measurement of the depression of the melting point of ice; a result consistent with salt exclusion by clathrate. The bulk composition of the fluid is estimated to be 91 mol.% H{sub 2}O, 6 mol.% CH{sub 4}, 2 equiv. mol.% NaCl and <1 mol.% CO{sub 2}. Total homogenization temperatures have a mean value of 371{degree}C {plus minus} 36{degree}C. Calculation of f{sub O2} from the bulk inclusion composition gives values near WI at these conditions which is unreasonably low for fluids derived from the pegmatite, which were probably between QFM and HM. The metasomatic fluids may have resulted from fluid mixing in the wall rock immediately adjacent to the pegmatite. The fluid derived from the pegmatite, a H{sub 2}O-CO{sub 2} fluid, introduced the B necessary to form tourmaline in the amphibolite. Supporting evidence is provided by pegmatite wall zone fluids with higher CH{sub 4} than the bulk of the pegmatite H{sub 2}O-CO{sub 2} fluids, suggesting marginal fluid contamination.

  4. Larande I Produktionssytem. En studie av operatorsarbete i hogautomatiserad process--och verkstadsindustri = Learning in Production Systems. A Study of Operator Work in Highly Automated Process and Manufacturing Industry. Linkoping Studies in Education and Psychology, No. 63.

    ERIC Educational Resources Information Center

    Davidson, Bo; Svedin, Per-Olof

    This study of the conditions of developmental on-the-job training and learning for operators in highly automated industries is written in Swedish but contains an English abstract and 18-page summary. The summary begins with the study objectives, which were to determine the following: (1) conditions of developmental on-the-job learning in highly…

  5. Effects of oligochitosan on postharvest Alternaria rot, storage quality, and defense responses in Chinese jujube (Zizyphus jujuba Mill. cv. Dongzao) fruit.

    PubMed

    Yan, Jiaqi; Li, Jian; Zhao, Hongwei; Chen, Ni; Cao, Jiankang; Jiang, Weibo

    2011-05-01

    Effects of oligochitosan (OCH) on postharvest rot caused by Alternaria alternata in Chinese jujube (Zizyphus jujuba Mill. cv. Dongzao) fruit were investigated. An in vitro test indicated that mycelial growth of A. alternata was strongly suppressed by OCH at 0.5, 1, 2, 5, 10, 15, or 20 g/liter. The half-inhibition concentration of OCH against this fungus was 0.76 and 1.69 g/liter on days 4 and 6 of incubation, respectively. Lesion area and disease incidence in the jujube fruit inoculated with A. alternata were remarkably reduced by the OCH treatments at concentrations higher than 1 g/liter, but 5 g/liter OCH was considered the optimal treatment for inhibiting disease development. OCH also significantly reduced postharvest natural decay, promoted fruit firmness, delayed decline in soluble solids and loss of ascorbic acid, and increased total phenolic compounds during storage at 0°C and 85 to 95% relative humidity. Biochemical evaluations revealed that the activities of the main defense-related enzymes in the jujube fruit, including phenylalanine ammonia-lyase, peroxidase, chitinase, and β-1,3-glucanase, were significantly enhanced (P < 0.05) by OCH treatment. OCH increased superoxide dismutase activity but decreased catalase activity and, consequently, elevated hydrogen peroxide levels in the fruit. These results suggest that OCH might trigger several defense mechanisms in the jujube fruit for disease control in addition to its direct antifungal activity. OCH could be a viable alternative to conventional control of postharvest diseases of horticultural products.

  6. Tin(II) alkoxide hydrolysis products for use as base catalysts

    DOEpatents

    Boyle, Timothy J.

    2002-01-01

    Tin alkoxide compounds are provided with accessible electrons. The compounds are a polymeric tin alkoxide, [Sn(OCH.sub.2 C(CH.sub.3).sub.3).sub.2 ].sub.n, and the hydrolysis products Sn.sub.6 O.sub.4 (OCH.sub.2 C(CH.sub.3).sub.3).sub.4 and Sn.sub.5 O.sub.2 (OCH.sub.2 C(CH.sub.3).sub.3).sub.6. The hydrolysis products are formed by hydrolyzing the [Sn(OCH.sub.2 C(CH.sub.3).sub.3).sub.2 ].sub.n in a solvent with controlled amounts of water, between 0.1 and 2 moles of water per mole of the polymeric tin alkoxide.

  7. α-1,6-Mannosylation of N-Linked Oligosaccharide Present on Cell Wall Proteins Is Required for Their Incorporation into the Cell Wall in the Filamentous Fungus Neurospora crassa▿†

    PubMed Central

    Maddi, Abhiram; Free, Stephen J.

    2010-01-01

    The enzyme α-1,6-mannosyltransferase (OCH-1) is required for the synthesis of galactomannans attached to the N-linked oligosaccharides of Neurospora crassa cell wall proteins. The Neurospora crassa och-1 mutant has a tight colonial phenotype and a defective cell wall. A carbohydrate analysis of the och-1 mutant cell wall revealed a 10-fold reduction in the levels of mannose and galactose and a total lack of 1,6-linked mannose residues. Analysis of the integral cell wall protein from wild-type and och-1 mutant cells showed that the mutant cell wall had reduced protein content. The och-1 mutant was found to secrete 18-fold more protein than wild-type cells. Proteomic analysis of the proteins released by the mutant into the growth medium identified seven of the major cell wall proteins. Western blot analysis of ACW-1 and GEL-1 (two glycosylphosphatidylinositol [GPI]-anchored proteins that are covalently integrated into the wild-type cell wall) showed that high levels of these proteins were being released into the medium by the och-1 mutant. High levels of ACW-1 and GEL-1 were also released from the och-1 mutant cell wall by subjecting the wall to boiling in a 1% SDS solution, indicating that these proteins are not being covalently integrated into the mutant cell wall. From these results, we conclude that N-linked mannosylation of cell wall proteins by OCH-1 is required for their efficient covalent incorporation into the cell wall. PMID:20870880

  8. The reactivity of molybdenum pentachloride with ethers: routes to the synthesis of Mo(IV)Cl4 adducts, Mo(V) chlorido-alkoxides and Mo(V) oxydo-chlorides.

    PubMed

    Marchetti, Fabio; Pampaloni, Guido; Zacchini, Stefano

    2013-11-14

    The reactivity of molybdenum pentachloride, 1, with a selection of mono- and diethers was investigated at room temperature in a non-coordinating solvent (dichloromethane). The Mo(IV) complex MoCl4(OMe2)2, 2, was obtained in 75% yield by the reaction of 1 with an excess of Me2O; similarly, MoCl4(κ(2)-L) [L = EtOCH2CH2OEt, 6a; MeOCH2CH(Me)OMe, 6b] were prepared in good yields by 1:1 combination of 1 with the appropriate diether. MoCl5 reacted with OMePh and Et2O affording variable amounts of RCl (R = Me and Et, respectively); MoCl3(OPh)2, 3, was isolated in 60% yield from 1 and OMePh. The reactions of 1 with OMe(t)Bu, O(t)Bu(CH=CH2), MeOCH2CH2OCH2Cl and 1,3-dioxane proceeded with non-selective activation of the organic material. The oxido-complexes Mo2O2Cl4(μ-OMe)2(μ-MeOH), 4, and MoOCl3(MeOH)2, 5, were isolated in modest amounts from 1/OMe(t)Bu, whereas MoOCl3(κ(2)-MeOCH2CH2OCH2Cl), 7, was obtained in 32% yield from 1/MeOCH2CH2OCH2Cl. All of the isolated metal products were characterized by spectroscopic and analytical techniques, and by X-ray diffractometry in the cases of 2, 4, 5, 6b and 7. NMR/GC-MS analyses were carried out in order to outline the fragmentation pathways of the organic reactants. PMID:24005818

  9. Replacement of the carboxylic acid group of prostaglandin F2α with a hydroxyl or methoxy substituent provides biologically unique compounds

    PubMed Central

    Woodward, D F; Krauss, A H-P; Chen, J; Gil, D W; Kedzie, K M; Protzman, C E; Shi, L; Chen, R; Krauss, H A; Bogardus, A; Dinh, H T T; Wheeler, L A; Andrews, S W; Burk, R M; Gac, T; Roof, M B; Garst, M E; Kaplan, L J; Sachs, G; Pierce, K L; Regan, J W; Ross, R A; Chan, M F

    2000-01-01

    Replacement of the carboxylic acid group of PGF2α with the non-acidic substituents hydroxyl (-OH) or methoxy (-OCH3) resulted in an unexpected activity profile.Although PGF2α 1-OH and PGF2α 1-OCH3 exhibited potent contractile effects similar to 17-phenyl PGF2α in the cat lung parenchymal preparation, they were approximately 1000 times less potent than 17-phenyl PGF2α in stimulating recombinant feline and human FP receptors.In human dermal fibroblasts and Swiss 3T3 cells PGF2α 1-OH and PGF2α 1-OCH3 produced no Ca2+ signal until a 1 μM concentration was exceeded. Pretreatment of Swiss 3T3 cells with either 1 μM PGF2α 1-OH or PGF2α 1-OCH3 did not attenuate Ca2+ signal responses produced by PGF2α or fluprostenol. In the rat uterus, PGF2α 1-OH was about two orders of magnitude less potent than 17-phenyl PGF2α whereas PGF2α 1-OCH3 produced only a minimal effect.Radioligand binding studies on cat lung parenchymal plasma membrane preparations suggested that the cat lung parenchyma does not contain a homogeneous population of receptors that equally respond to PGF2α1-OH, PGF2α1-OCH3, and classical FP receptor agonists.Studies on smooth muscle preparations and cells containing DP, EP1, EP2, EP3, EP4, IP, and TP receptors indicated that the activity of PGF2α 1-OH and PGF2α 1-OCH3 could not be ascribed to interaction with these receptors.The potent effects of PGF2α 1-OH and PGF2α 1-OCH3 on the cat lung parenchyma are difficult to describe in terms of interaction with the FP or any other known prostanoid receptor. PMID:10952685

  10. Electrochemical storage cell containing a substituted anisole or di-anisole redox shuttle additive for overcharge protection and suitable for use in liquid organic and solid polymer electrolytes

    DOEpatents

    Kerr, John B.; Tian, Minmin

    2000-01-01

    A electrochemical cell is described comprising an anode, a cathode, a solid polymer electrolyte, and a redox shuttle additive to protect the cell against overcharging and a redox shuttle additive to protect the cell against overcharging selected from the group consisting of: (a) a substituted anisole having the general formula (in an uncharged state): ##STR1## where R.sub.1 is selected from the group consisting of H, OCH.sub.3, OCH.sub.2 CH.sub.3, and OCH.sub.2 phenyl, and R.sub.2 is selected from the group consisting of OCH.sub.3, OCH.sub.2 CH.sub.3, OCH.sub.2 phenyl, and O.sup.- Li.sup.+ ; and (b) a di-anisole compound having the general formula (in an uncharged state): ##STR2## where R is selected from the group consisting of -OCH.sub.3 and -CH.sub.3, m is either 1 or 0, n is either 1 or 0, and X is selected from the group consisting of -OCH.sub.3 (methoxy) or its lithium salt --O.sup.- Li.sup.+. The lithium salt of the di-anisole is the preferred form of the redox shuttle additive because the shuttle anion will then initially have a single negative charge, it loses two electrons when it is oxidized at the cathode, and then moves toward the anode as a single positively charged species where it is then reduced to a single negatively charged species by gaining back two electrons.

  11. The ether lipid 1-octadecyl-2-methyl-rac-glycero-3-phosphocholine induces expression of fos and jun proto-oncogenes and activates AP-1 transcription factor in human leukaemic cells.

    PubMed Central

    Mollinedo, F; Gajate, C; Modolell, M

    1994-01-01

    The ether lipid analogue 1-octadecyl-2-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3) has been recently shown to induce apoptosis in the human leukaemic HL-60 and U937 myeloid cell lines [Mollinedo, Martinez-Dalmau and Modolell (1993) Biochem. Biophys. Res. Commun. 192, 603-609]. We have found that ET-18-OCH3 is also able to promote apoptosis in the human leukaemic Jurkat T lymphoid cell line. This lymphoid cell line as well as the two myeloid HL-60 and U937 cell lines incorporated significant amounts of exogenously added radiolabelled ET-18-OCH3. Addition of ET-18-OCH3 to these human leukaemic cells induced an increase in the steady-state mRNA levels of fos and jun proto-oncogenes, components of the transcription factor AP-1. These increases in fos and jun mRNA levels were associated with the activation of the AP-1 transcription factor after addition of ET-18-OCH3 to human leukaemic cells, as assessed by an enhanced binding activity of transcription factor AP-1 to its cognate DNA sequence as well as by stimulation of transcription from an AP-1 enhancer element. These data demonstrate that the ether lipid ET-18-OCH3 can affect gene expression by inducing expression of fos and jun proto-oncogenes and by modulating the activity of transcription factor AP-1. Images Figure 2 Figure 3 Figure 4 PMID:8092982

  12. Perspectives on Pentaerythritol Tetranitrate (PETN) Decomposition

    SciTech Connect

    Chambers, D; Brackett, C; Sparkman, D O

    2002-07-01

    This report evaluates the large body of work involving the decomposition of PETN and identifies the major decomposition routes and byproducts. From these studies it becomes apparent that the PETN decomposition mechanisms and the resulting byproducts are primarily determined by the chemical environment. In the absence of water, PETN can decompose through the scission of the O-NO{sup 2} bond resulting in the formation of an alkoxy radical and NO{sub 2}. Because of the relatively high reactivity of both these initial byproducts, they are believed to drive a number of autocatalytic reactions eventually forming (NO{sub 2}OCH{sub 2}){sub 3}CCHO, (NO{sub 2}OCH{sub 2}){sub 2}C=CHONO{sub 2}, NO{sub 2}OCH=C=CHONO{sub 2}, (NO{sub 2}OCH{sub 2}){sub 3}C-NO{sub 2}, (NO{sub 2}OCH{sub 2}){sub 2}C(NO{sub 2}){sub 2}, NO{sub 2}OCH{sub 2}C(NO{sub 2}){sub 3}, and C(NO{sub 2}){sub 4} as well as polymer-like species such as di-PEHN and tri-PEON. Surprisingly, the products of many of these proposed autocatalytic reactions have never been analytically validated. Conversely, in the presence of water, PETN has been shown to decompose primarily to mono, di, and tri nitrates of pentaerythritol.

  13. Enthalpy of formation of anisole: implications for the controversy on the O-H bond dissociation enthalpy in phenol.

    PubMed

    Simões, Ricardo G; Agapito, Filipe; Diogo, Hermínio P; da Piedade, Manuel E Minas

    2014-11-20

    Significant discrepancies in the literature data for the enthalpy of formation of gaseous anisole, ΔfHmo(PhOCH3, g), have fueled an ongoing controversy regarding the most reliable enthalpy of formation of the phenoxy radical and of the gas phase O-H bond dissociation enthalpy, DHo(PhO-H), in phenol. In the present work ΔfHmo(PhOCH3, g) was reassessed using a combination of calorimetric determinations and high-level (W2-F12) ab initio calculations. Static-bomb combustion calorimetry led to the standard molar enthalpy of formation of liquid anisole at 298.15 K, ΔfHmo(PhOCH3, l) = −(117.1 ± 1.4) kJ·mol(-1). The corresponding enthalpy of vaporization was obtained as, ΔvapHmo(PhOCH3) = 46.41 ± 0.26 kJ·mol(-1), by Calvet-drop microcalorimetry. These results give ΔfHmo(PhOCH3, g) = −(70.7 ± 1.4) kJ·mol(-1), in excellent agreement with ΔfHmo(PhOCH3, g) = −(70.8 ± 3.2) kJ·mol(-1), obtained from the W2-F12 calculations. The ΔfHmo(PhOCH3, g) here recommended leads to ΔfHmo(PhO•, g) = 55.5 ± 2.4 kJ·mol(-)1 and DH°(PhO-H) = 368.1 ± 2.6 kJ·mol(-1).

  14. Presolvated Electron Reaction with Methylacetoacetate: Electron Localization, Proton-Deuteron Exchange, and H-atom Abstraction

    PubMed Central

    Petrovici, Alex; Adhikary, Amitava; Kumar, Anil; Sevilla, Michael D.

    2015-01-01

    Radiation-produced electrons initiate various reaction processes that are important to radiation damage to biomolecules. In this work, the site of attachment of the prehydrated electrons with methylacetoacetate (MAA, CH3-CO-CH2-CO-OCH3) at 77 K and subsequent reactions of the anion radical (CH3-CO•−-CH2-CO-OCH3) in the temperature range (77 to ca. 170 K) have been investigated in homogeneous H2O and D2O aqueous glasses by electron spin resonance (ESR) spectroscopy. At 77 K, the prehydrated electron attaches to MAA forming the anion radical in which the electron is delocalized over the two carbonyl groups. This species readily protonates to produce the protonated electron adduct radical CH3-C(•)OH-CH2-CO-OCH3. The ESR spectrum of CH3-C(•)OH-CH2-CO-OCH3 in H2O shows line components due to proton hyperfine couplings of the methyl and methylene groups. Whereas, the ESR spectrum of CH3-C(•)OH-CH2-CO-OCH3 in D2O glass shows only the line components due to proton hyperfine couplings of CH3 group. This is expected since the methylen protons in MAA are readily exchangeable in D2O. On stepwise annealing to higher temperatures (ca. 150 to 170 K), CH3-C(•)OH-CH2-CO-OCH3 undergoes bimolecular H-atom abstraction from MAA to form the more stable radical, CH3-CO-CH•-CO-OCH3. Theoretical calculations using density functional theory (DFT) support the radical assignments. PMID:25255751

  15. Retrosynthetic approach to the design of molybdenum-magnesium oxoalkoxides.

    PubMed

    Kuznetsov, Denis A; Fedyanin, Ivan V; Lyssenko, Konstantin A; Bazhenova, Tamara A

    2014-09-14

    The reaction of MoCl5 methanolysis in the presence of magnesium ions was shown to produce an extensive row of heterobimetallic Mg-Mo(V, VI) oxomethoxides of different nuclearity ranging from 4 for [Mg2(CH3OH)4Mo2O2(OCH3)10] (1) to 26 for [Mg(DMF)3(CH3OH)3]2[Mo22Mg4O48(OCH3)28(DMF)6] (2) with the latter possessing a ring morphology. Examination of [Mo6O12(OCH3)16Mg4(CH3OH)6] (3), [Mo6O12(OCH3)12Mg2(DMF)4] (4a), and [Mo6O16(OCH3)4Mg2(DMF)8] (5a) X-ray structures revealed the presence of the well known tetranuclear core {Mo4O8(OCH3)2}(2+) thus similar reactivity patterns leading to their formation were assumed. For convenient synthesis of such heterobimetallic oxoalkoxides, the retrosynthetic approach based on speculative deconstruction of a target molecule onto simpler fragments was suggested and successfully employed. Namely, the reaction of the stoichiometric amounts of appropriately chosen Mo(V), Mo(VI) and Mg(2+) synthons led to their assembling resulting in the formation of heterometallic clusters 3, 5a and [Mo6O12(OCH3)12Mg2(CH3OH)4]·2CH3OH (4b) characterized by means of elemental analysis, UV-Vis, IR spectroscopy, and X-ray crystallography. PMID:25019529

  16. Decreased sensitivity to 1-O-octadecyl-2-O-methyl-glycerophosphocholine in MCF-7 cells adapted for serum-free growth correlates with constitutive association of Raf-1 with cellular membranes.

    PubMed

    Samadder, P; Arthur, G

    1999-10-01

    We have previously shown that inhibition of MCF-7 cell proliferation by 1-O-octadecyl-2-O-methyl-glycerophosphocholine (ET-18-OCH3) is linked to a drug-induced decrease in membrane Raf-1 levels and the subsequent inhibition of mitogen-activated protein (MAP) kinase activation in response to growth factor stimulation. We now report that adaptation of MCF-7 cells for growth in a serum-free formulation results in decreased sensitivity to growth inhibition by ET-18-OCH3. The decrease in ET-18-OCH3 sensitivity occurred progressively during the adaptation process and correlated with the presence of increasing amounts of inactive Raf-1 that stably associated with MCF-7 cell membranes. ET-18-OCH3 sensitivity could be restored by growing the adapted cells in serum-containing medium, which resulted in the loss of membrane-associated Raf-1. In human normal mammary epithelial cells, which are insensitive to ET-18-OCH3, Raf-1 was also associated with membranes in quiescent cells. In both cell types, incubation with ET-18-OCH3 had no effect on the membrane-Raf-1 levels, suggesting that ET-18-OCH3-induced reduction of Raf-1 levels in growth factor-stimulated MCF-7 cells is due to inhibition of Raf translocation. The activation and termination of the MAP kinase pathway in response to growth factors in the adapted MCF-7 cells and HNME cells occurred without changes to membrane Raf-1 levels. Because membrane translocation is not required to activate Raf in these cells, inhibition of Raf translocation by ET-18-OCH3 subsequent to cell stimulation has no effect on the activation of the membrane-bound Raf and, consequently, the activation of the MAP kinase pathway. The ability of the cells to activate the MAP kinase pathway in the presence of the drugs enables them to resist the growth-inhibitory effects of the drug, leading to the observed ET-18-OCH3 insensitivity of the cells.

  17. Structural Basis for piRNA 2-O-methylated 3-end Recognition by Piwi PAZ (Piwi/Argonaute/Awille) Domains

    SciTech Connect

    Y Tian; D Simanshu; J Ma; D Patel

    2011-12-31

    Argonaute and Piwi proteins are key players in the RNA silencing pathway, with the former interacting with micro-RNAs (miRNAs) and siRNAs, whereas the latter targets piwi-interacting RNAs (piRNAs) that are 2'-O-methylated (2'-OCH{sub 3}) at their 3' ends. Germline-specific piRNAs and Piwi proteins play a critical role in genome defense against transposable elements, thereby protecting the genome against transposon-induced defects in gametogenesis and fertility. Humans contain four Piwi family proteins designated Hiwi1, Hiwi2, Hiwi3, and Hili. We report on the structures of Hili-PAZ (Piwi/Argonaute/Zwille) domain in the free state and Hiwi1 PAZ domain bound to self-complementary 14-mer RNAs (12-bp + 2-nt overhang) containing 2'-OCH{sub 3} and 2'-OH at their 3' ends. These structures explain the molecular basis underlying accommodation of the 2'-OCH{sub 3} group within a preformed Hiwi1 PAZ domain binding pocket, whose hydrophobic characteristics account for the preferential binding of 2'-OCH{sub 3} over 2'-OH 3' ends. These results contrast with the more restricted binding pocket for the human Ago1 PAZ domain, which exhibits a reverse order, with preferential binding of 2'-OH over 2'-OCH{sub 3} 3' ends.

  18. Structural basis for piRNA 2'-O-methylated 3'-end recognition by Piwi PAZ (Piwi/Argonaute/Zwille) domains.

    PubMed

    Tian, Yuan; Simanshu, Dhirendra K; Ma, Jin-Biao; Patel, Dinshaw J

    2011-01-18

    Argonaute and Piwi proteins are key players in the RNA silencing pathway, with the former interacting with micro-RNAs (miRNAs) and siRNAs, whereas the latter targets piwi-interacting RNAs (piRNAs) that are 2'-O-methylated (2(')-OCH(3)) at their 3' ends. Germline-specific piRNAs and Piwi proteins play a critical role in genome defense against transposable elements, thereby protecting the genome against transposon-induced defects in gametogenesis and fertility. Humans contain four Piwi family proteins designated Hiwi1, Hiwi2, Hiwi3, and Hili. We report on the structures of Hili-PAZ (Piwi/Argonaute/Zwille) domain in the free state and Hiwi1 PAZ domain bound to self-complementary 14-mer RNAs (12-bp + 2-nt overhang) containing 2(')-OCH(3) and 2'-OH at their 3' ends. These structures explain the molecular basis underlying accommodation of the 2(')-OCH(3) group within a preformed Hiwi1 PAZ domain binding pocket, whose hydrophobic characteristics account for the preferential binding of 2(')-OCH(3) over 2'-OH 3' ends. These results contrast with the more restricted binding pocket for the human Ago1 PAZ domain, which exhibits a reverse order, with preferential binding of 2'-OH over 2(')-OCH(3) 3' ends.

  19. Self-microemulsifying drug-delivery system for improved oral bioavailability of 20(S)-25-methoxyl-dammarane-3β, 12β, 20-triol: preparation and evaluation

    PubMed Central

    Cai, Shuang; Shi, Cai-Hong; Zhang, Xiangrong; Tang, Xiaojiao; Suo, Hao; Yang, Li; Zhao, Yuqing

    2014-01-01

    The objective of this study was to develop a self-microemulsifying drug delivery system (SMEDDS) to enhance the oral bioavailability of the poorly water-soluble compound 20(S)-25-methoxydammarane-3β;12β;20-triol (25-OCH3-PPD). Optimized SMEDDS formulations for 25-OCH3-PPD contained Cremophor® EL (50%) as the surfactant, glycerin (20%) as the cosurfactant, and Labrafil® M1944 (30%) as the oil. The SMEDDS were characterized by morphological observation and mean droplet size. The pharmacokinetics and bioavailability of the 25-OCH3-PPD suspension and SMEDDS were evaluated and compared in rats. The plasma concentrations of 25-OCH3-PPD and its main metabolite, 25-OH-PPD, were determined by ultra performance liquid chromatography-tandem mass spectrometry. The relative bioavailability of SMEDDS was dramatically enhanced by an average of 9.8-fold compared with the suspension. Improved solubility and lymphatic transport may contribute to this enhanced bioavailability. Our studies highlight the promise of SMEDDS for the delivery of 25-OCH3-PPD via the oral route. PMID:24611008

  20. Biological distinctions between juvenile nasopharyngeal angiofibroma and vascular malformation: an immunohistochemical study.

    PubMed

    Zhang, Mengjun; Sun, Xicai; Yu, Huapeng; Hu, Li; Wang, Dehui

    2011-10-01

    The exact nature of juvenile nasopharyngeal angiofibroma (JNA) is still in dispute. In recent years, the main controversy of its nature has focused on hemangioma and vascular malformation. In this study, the immunolocalization of vascular endothelial growth factor (VEGF), VEGF receptor-1/fms-like tyrosine kinase-1 (VEGFR-1/Flt-1), VEGF receptor-2/fetal liver kinase-1 (VEGFR-2/Flk-1), proliferating cell nuclear antigen (PCNA), and CD34 was investigated in 28 cases of JNA and 20 cases of orbital cavernous hemangiomas (OCH). The immunostaining levels of VEGF, Flt-1, and Flk-1 were higher and more frequent in vascular endothelial cells of JNA than those of OCH (p<0.05). The average microvessel density (MVD) marked by CD34 in JNA was (49.3 ± 9.1)/HPF (high power field), which was higher than OCH (29.1 ± 6.7)/HPF (p<0.05). Immunoreactivity of PCNA was localized in both endothelial and stromal cell components of JNA, but was predominantly seen in the stromal cells. However, no PCNA immunoreactivity was identified in any of the stromal and endothelial cells in cases of OCH. The immunostaining levels of CD34, VEGF, Flt-1, Flk-1, and PCNA in JNA were higher than those in OCH. These data support the view that JNA has biological characteristics of an angiogenic histogenetic tumor. In the future, anti-angiogenic therapy may represent a novel treatment strategy for JNA.

  1. Niobium alcoholate clusters with an octahedral arrangement of metal atoms: [K(CH3OH)4]2 [Nb6(OCH3)18] and [Na([18]crown-6)(C2H5OH)2]2 [Nb6(OC2H5)12(NCS)6].

    PubMed

    Flemming, Anke; Köckerling, Martin

    2009-01-01

    Complete exchange: [M(6)X(12)] type cluster compounds with an octahedral M(6) metal atom arrangement, which is completely surrounded by alcoholato ligands, were unknown until now. The first representatives are prepared containing a [Nb(6)(OR)(12)](4+) unit (R = CH(3) or C(2)H(5)). They are accessible at elevated temperatures from strongly basic alcoholate solutions of [Nb(6)Cl(12)](2+)-containing precursors. C gray, H white, K turquoise, Nb blue, O red.

  2. Ochratoxin A displaces claudins from detergent resistant membrane microdomains.

    PubMed

    Lambert, Daniel; Padfield, Philip J; McLaughlin, John; Cannell, Stephanie; O'Neill, Catherine A

    2007-06-29

    Ochratoxin A (OchA) is a food-borne mycotoxin with multiple effects in vivo. Previously, we have demonstrated that the toxin can significantly impair the barrier function of the gut epithelial cell line, Caco-2. Barrier disruption involved loss of claudins 3 and 4, but not claudin 1 from the tight junction complex. In this study, we demonstrate for the first time, that OchA is able to remove claudins 3 and 4 from the detergent insoluble membrane microdomains associated with the tight junctions. However, cholesterol distribution within the microdomain was unaffected by the toxin. In addition, the thiol antioxidant, N-acetyl cysteine, preserved the microdomain localisation of claudins and also the barrier function of Caco-2 cells. This work suggests that OchA-mediated barrier toxicity is due to removal of claudins from detergent insoluble membrane microdomains. Moreover, loss of microdomain association may be due to oxidative events.

  3. C---lH...O and O...H...O bonded intermediates in the dissociation of low energy methyl glycolate radical cations

    NASA Astrophysics Data System (ADS)

    Suh, Dennis; Kingsmill, Carol A.; Ruttink, Paul J. A.; Burgers, Peter C.; Terlouw, Johan K.

    1995-08-01

    Low energy methyl glycolate radical cations HOCH2C(=O)OCH3+, 1, abundantly lose HCO, yielding protonated methyl formate H---C(OH)OCH3+. Tandem mass spectrometry based experiments on 2H, 13C and 18O labelled isotopologues show that this loss is largely (about 75%) atom specific. Analysis of the atom connectivity in the product ions indicates that the reaction proceeds analogously to the loss of HCO and CH3CO from ionized acetol HOCH2C(=O)CH3+ and acetoin HOCH(CH3)C(=O)CH3+, respectively. The mechanism, it is proposed, involves isomerization of 1 to the key intermediate CH2=O... H---C(=O)OCH3+, an H-bridged ion-dipole complex of neutral formaldehyde and ionized methyl formate. Next, charge transfer takes place to produce CH3OC(H)=O...HC(H)=O+, an H-bridged ion-dipole complex of ionized formaldehyde and neutral methyl formate, followed by proton transfer to generate the products. Preliminary ab initio calculations executed at the UMP3/6-31G*//6-31G*+ZPVE level of theory are presented in support of this proposal. The non-specific loss of HCO from 1 (about 25%) is rationalized to occur via the same mechanism, but after communication with isomeric dimethyl carbonate ions CH3OC(=O)OCH3+, 2, via the O...H...O bonded intermediate [CH2=O...H...O=C---OCH3]+. The latter pathway is even more important in the formation of CH2OH+ ions from 1 which, it is shown, is not a simple bond cleavage reaction, but may involve consecutive or concerted losses of CH3 and CO2 from the above O...H...O bonded species. Ionized methyl lactate HOCH(CH3)C(=O)OCH3+, the higher homologue of 1, shows a unimolecular chemistry which is akin to that of 1.

  4. Complex formation between anisole and boron trifluoride: structural and binding properties.

    PubMed

    Lin, Tao; Zhang, Weijiang; Wang, Lichang

    2008-12-25

    The structures, energetics, and binding characteristics of complexes formed between anisole (C(6)H(5)OCH(3)) and boron trifluoride (BF(3)) were investigated using MP2 and B3LYP methods with 6-31+G(d,p) and 6-311+G(d,p) basis sets. Among the complexes with a 1:1 ratio of C(6)H(5)OCH(3) to BF(3), both B3LYP and MP2 methods predict the same structures and relative stability of the isomers; however, the B3LYP binding energies are smaller than the MP2 energies. Furthermore, the weaker the interaction, the greater the discrepancy in binding energy. The charge decomposition analysis (CDA) showed that there are two types of complexes: the Lewis acid-base adduct and the van der Waals complexes. The CDA results also illustrated that there is a significant donation from the oxygen lone pair electrons to the boron vacant orbital in the adduct. The van der Waals complexes were formed through the aromatic ring and BF(3) interaction or through the H and F interactions. The MP2 results showed that the formation of adduct at room temperature is thermodynamically favorable. Among the 1:2 C(6)H(5)OCH(3)-BF(3) complexes, the most stable structure consists of both the Lewis acid-base and van der Waals binding; i.e., one BF(3) binds with C(6)H(5)OCH(3) to form C(6)H(5)OCH(3) x BF(3) adduct, while the other BF(3) binds with this adduct through van der Waals interactions. The calculated binding energy of the 1:1 complex is close to the experimental heat of formation, which suggests that the 1:1 complexes are the most likely species in the C(6)H(5)OCH(3) and BF(3) mixture.

  5. Intracellular Triggering of Fas Aggregation and Recruitment of Apoptotic Molecules into Fas-enriched Rafts in Selective Tumor Cell Apoptosis

    PubMed Central

    Gajate, Consuelo; del Canto-Jañez, Esther; Acuña, A. Ulises; Amat-Guerri, Francisco; Geijo, Emilio; Santos-Beneit, Antonio M.; Veldman, Robert J.; Mollinedo, Faustino

    2004-01-01

    We have discovered a new and specific cell-killing mechanism mediated by the selective uptake of the antitumor drug 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3, Edelfosine) into lipid rafts of tumor cells, followed by its coaggregation with Fas death receptor (also known as APO-1 or CD95) and recruitment of apoptotic molecules into Fas-enriched rafts. Drug sensitivity was dependent on drug uptake and Fas expression, regardless of the presence of other major death receptors, such as tumor necrosis factor (TNF) receptor 1 or TNF-related apoptosis-inducing ligand R2/DR5 in the target cell. Drug microinjection experiments in Fas-deficient and Fas-transfected cells unable to incorporate exogenous ET-18-OCH3 demonstrated that Fas was intracellularly activated. Partial deletion of the Fas intracellular domain prevented apoptosis. Unlike normal lymphocytes, leukemic T cells incorporated ET-18-OCH3 into rafts coaggregating with Fas and underwent apoptosis. Fas-associated death domain protein, procaspase-8, procaspase-10, c-Jun amino-terminal kinase, and Bid were recruited into rafts, linking Fas and mitochondrial signaling routes. Clustering of rafts was necessary but not sufficient for ET-18-OCH3–mediated cell death, with Fas being required as the apoptosis trigger. ET-18-OCH3–mediated apoptosis did not require sphingomyelinase activation. Normal cells, including human and rat hepatocytes, did not incorporate ET-18-OCH3 and were spared. This mechanism represents the first selective activation of Fas in tumor cells. Our data set a framework for the development of more targeted therapies leading to intracellular Fas activation and recruitment of downstream signaling molecules into Fas-enriched rafts. PMID:15289504

  6. Nitroaliphatic difluoroformals

    DOEpatents

    Peters, Howard M.; Simon, Jr., Robert L.

    1978-01-01

    Nitroaliphatic difluoroformals of the formula RCH.sub.2 OCF.sub.2 OCH.sub.2 R' wherein R = FC(NO.sub.2).sub.2 -- and R' = F.sub.2 C(NO.sub.2)-- or CF.sub.3 --; or R = R' = CF.sub.3 OCH.sub.2 C(NO.sub.2).sub.2 --. The compounds are prepared in accordance with the following reaction: ##STR1## carried out at temperatures of from about 95.degree. C to about 150.degree. C. The compounds are especially useful as energetic plasticizers in explosive compositions.

  7. Role of Protein Glycosylation in Candida parapsilosis Cell Wall Integrity and Host Interaction

    PubMed Central

    Pérez-García, Luis A.; Csonka, Katalin; Flores-Carreón, Arturo; Estrada-Mata, Eine; Mellado-Mojica, Erika; Németh, Tibor; López-Ramírez, Luz A.; Toth, Renata; López, Mercedes G.; Vizler, Csaba; Marton, Annamaria; Tóth, Adél; Nosanchuk, Joshua D.; Gácser, Attila; Mora-Montes, Héctor M.

    2016-01-01

    Candida parapsilosis is an important, emerging opportunistic fungal pathogen. Highly mannosylated fungal cell wall proteins are initial contact points with host immune systems. In Candida albicans, Och1 is a Golgi α1,6-mannosyltransferase that plays a key role in the elaboration of the N-linked mannan outer chain. Here, we disrupted C. parapsilosis OCH1 to gain insights into the contribution of N-linked mannosylation to cell fitness and to interactions with immune cells. Loss of Och1 in C. parapsilosis resulted in cellular aggregation, failure of morphogenesis, enhanced susceptibility to cell wall perturbing agents and defects in wall composition. We removed the cell wall O-linked mannans by β-elimination, and assessed the relevance of mannans during interaction with human monocytes. Results indicated that O-linked mannans are important for IL-1β stimulation in a dectin-1 and TLR4-dependent pathway; whereas both, N- and O-linked mannans are equally important ligands for TNFα and IL-6 stimulation, but neither is involved in IL-10 production. Furthermore, mice infected with C. parapsilosis och1Δ null mutant cells had significantly lower fungal burdens compared to wild-type (WT)-challenged counterparts. Therefore, our data are the first to demonstrate that C. parapsilosis N- and O-linked mannans have different roles in host interactions than those reported for C. albicans. PMID:27014229

  8. Polymerizable 2(2-hydroxynaphthyl)2H-benzotriazole compounds

    DOEpatents

    Gomez, Peter M.; Neidlinger, Hermann H.

    1991-01-01

    Benzotriazole compounds having the formula: ##STR1## wherein R.sub.1 is H, Cl, or OCH.sub.3 ; R.sub.2 is a hydroxynaphthyl group; and R.sub.3 is a vinyl unsaturated polymerizable group. Homopolymers or copolymers thereof are effective as UV light stabilizers and absorbers.

  9. Adolescent Tobacco and Cannabis Use: Young Adult Outcomes from the Ontario Child Health Study

    ERIC Educational Resources Information Center

    Georgiades, Katholiki; Boyle, Michael H.

    2007-01-01

    Background: This study examines the longitudinal associations between adolescent tobacco and cannabis use and young adult functioning. Methods: Data for analysis come from the Ontario Child Health Study (OCHS), a prospective study of child health, psychiatric disorder and adolescent substance use in a general population sample that began in 1983,…

  10. Anomalous conformational behavior of poly(ethylene oxide) oligomers in aqueous solutions. A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Bedrov, Dmitry; Smith, Grant D.

    1998-11-01

    Molecular dynamics simulations of 1,2-dimethoxyethane (DME) CH3(OCH2CH2)OCH3 and diglyme CH3(OCH2CH2)2OCH3 in aqueous solution have been performed for several solution compositions. Conformational analysis of these systems shows that the g population of the O-C—C-O dihedral increases with increasing water content. For DME solutions, this increase is monotonic with a tendency to saturate in the extremely dilute (water-rich) regime. For diglyme solutions a distinct maximum in the g population of the O-C—C-O dihedral was observed at mole fraction Xdiglyme=0.03. More detailed analysis of the composition dependence of diglyme conformational populations reveals that the decrease in the O-C—C-O g population in extremely dilute solutions is due to a decrease in the tgt population of the C-O—C—C—O-C conformational triad. This in turn can be related to a decrease in a single conformer of diglyme, namely tgttgt. This conformer is unique in its nearly perfect antiparallel alignment of large triad dipoles. Finally, the anomalous conformational behavior of diglyme at extreme dilution is found to disappear at higher temperature.

  11. Reciprocal Cross-School Attraction in Domestic Educational Policy Borrowing: An Initial Conceptualization

    ERIC Educational Resources Information Center

    Barmeier, Henry

    2012-01-01

    This article presents a novel theoretical framework for the study of educational policy borrowing at the sub-national level. Prior theorizing on educational policy transfer, and on policy "borrowing" in particular, has focused on cross-national processes. In this article the author uses the existing cross-national models of Phillips and Ochs and…

  12. 40 CFR 63.62 - Redefinition of glycol ethers listed as hazardous air pollutants.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., diethylene glycol, and triethylene glycol R-(OCH2CH2)n-OR′. Where: n = 1, 2, or 3; R = alkyl C7 or less; or R = phenyl or alkyl substituted phenyl; R′= H or alkyl C7 or less; or OR′ consisting of carboxylic acid...

  13. 40 CFR 63.62 - Redefinition of glycol ethers listed as hazardous air pollutants.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., diethylene glycol, and triethylene glycol R-(OCH2CH2)n-OR′. Where: n = 1, 2, or 3; R = alkyl C7 or less; or R = phenyl or alkyl substituted phenyl; R′= H or alkyl C7 or less; or OR′ consisting of carboxylic acid...

  14. N-hypermannose glycosylation disruption enhances recombinant protein production by regulating secretory pathway and cell wall integrity in Saccharomyces cerevisiae.

    PubMed

    Tang, Hongting; Wang, Shenghuan; Wang, Jiajing; Song, Meihui; Xu, Mengyang; Zhang, Mengying; Shen, Yu; Hou, Jin; Bao, Xiaoming

    2016-01-01

    Saccharomyces cerevisiae is a robust host for heterologous protein expression. The efficient expression of cellulases in S. cerevisiae is important for the consolidated bioprocess that directly converts lignocellulose into valuable products. However, heterologous proteins are often N-hyperglycosylated in S. cerevisiae, which may affect protein activity. In this study, the expression of three heterologous proteins, β-glucosidase, endoglucanase and cellobiohydrolase, was found to be N-hyperglycosylated in S. cerevisiae. To block the formation of hypermannose glycan, these proteins were expressed in strains with deletions in key Golgi mannosyltransferases (Och1p, Mnn9p and Mnn1p), respectively. Their extracellular activities improved markedly in the OCH1 and MNN9 deletion strains. Interestingly, truncation of the N-hypermannose glycan did not increase the specific activity of these proteins, but improved the secretion yield. Further analysis showed OCH1 and MNN9 deletion up-regulated genes in the secretory pathway, such as protein folding and vesicular trafficking, but did not induce the unfolded protein response. The cell wall integrity was also affected by OCH1 and MNN9 deletion, which contributed to the release of secretory protein extracellularly. This study demonstrated that mannosyltransferases disruption improved protein secretion through up-regulating secretory pathway and affecting cell wall integrity and provided new insights into glycosylation engineering for protein secretion. PMID:27156860

  15. N-hypermannose glycosylation disruption enhances recombinant protein production by regulating secretory pathway and cell wall integrity in Saccharomyces cerevisiae

    PubMed Central

    Tang, Hongting; Wang, Shenghuan; Wang, Jiajing; Song, Meihui; Xu, Mengyang; Zhang, Mengying; Shen, Yu; Hou, Jin; Bao, Xiaoming

    2016-01-01

    Saccharomyces cerevisiae is a robust host for heterologous protein expression. The efficient expression of cellulases in S. cerevisiae is important for the consolidated bioprocess that directly converts lignocellulose into valuable products. However, heterologous proteins are often N-hyperglycosylated in S. cerevisiae, which may affect protein activity. In this study, the expression of three heterologous proteins, β-glucosidase, endoglucanase and cellobiohydrolase, was found to be N-hyperglycosylated in S. cerevisiae. To block the formation of hypermannose glycan, these proteins were expressed in strains with deletions in key Golgi mannosyltransferases (Och1p, Mnn9p and Mnn1p), respectively. Their extracellular activities improved markedly in the OCH1 and MNN9 deletion strains. Interestingly, truncation of the N-hypermannose glycan did not increase the specific activity of these proteins, but improved the secretion yield. Further analysis showed OCH1 and MNN9 deletion up-regulated genes in the secretory pathway, such as protein folding and vesicular trafficking, but did not induce the unfolded protein response. The cell wall integrity was also affected by OCH1 and MNN9 deletion, which contributed to the release of secretory protein extracellularly. This study demonstrated that mannosyltransferases disruption improved protein secretion through up-regulating secretory pathway and affecting cell wall integrity and provided new insights into glycosylation engineering for protein secretion. PMID:27156860

  16. Parental Expectations of the Swedish Municipal School of Arts

    ERIC Educational Resources Information Center

    Lilliedahl, Jonathan; Georgii-Hemming, Eva

    2009-01-01

    This article draws on a study designed to analyse parental expectations of the Swedish municipal school of arts (hereafter MSA) (in Swedish: kommunal musik- och kulturskola). The study is based on in-depth interviews conducted and informed by grounded theory. Although parental expectations are scarcely uniform, the study reveals a hope that the…

  17. Schools Reaching Out: An Introduction.

    ERIC Educational Resources Information Center

    Heleen, Owen

    1990-01-01

    Introduces an issue devoted to the Schools Reaching Out projects at David A. Ellis School in Roxbury (MA) and Adolph S. Ochs School in New York City. Projects attempt to link the schools with parents and their communities to promote the students' academic and social success. (DM)

  18. Polymerizable 2(2-hydroxynaphthyl)2H-benzotriazole compounds

    DOEpatents

    Gomez, P.M.; Neidlinger, H.H.

    1991-07-16

    Benzotriazole compounds having the formula: ##STR1## wherein R.sub.1 is H, Cl, or OCH.sub.3 ; R.sub.2 is a hydroxynaphthyl group; and R.sub.3 is a vinyl unsaturated polymerizable group. Homopolymers or copolymers thereof are effective as UV light stabilizers and absorbers.

  19. A Scientist or Salesman? Identity Construction through Referent Honorifics on a Japanese Shopping Channel Program

    ERIC Educational Resources Information Center

    Cook, Haruko Minegishi

    2013-01-01

    This paper explores how referent honorifics contribute to identity construction on a Japanese TV shopping channel program. Drawing on Ochs' twostep model of indexicality (1993, 1996) and Agah's proposal (1993) that honorifics are not directly linked to social status but index a "relative position within events of discursive…

  20. Co-Construction in Korean Interaction

    ERIC Educational Resources Information Center

    Ju, Hee

    2011-01-01

    This dissertation explores co-construction of a situated activity in a current unit by mainly focusing on hearers' actions. The "co-construction" involves a process of interaction in which speakers and hearers jointly construct the form and the meaning of ongoing utterances even when they disagree with each other (Jacoby & Ochs,…

  1. Social Networking in an Intensive English Program Classroom: A Language Socialization Perspective

    ERIC Educational Resources Information Center

    Reinhardt, Jonathon; Zander, Victoria

    2011-01-01

    This ongoing project seeks to investigate the impact, inside and outside of class, of instruction focused on developing learner awareness of social-networking site (SNS) use in an American Intensive English Program (IEP). With language socialization as an interpretative framework (Duff, in press; Ochs, 1988; Watson-Gegeo, 2004), the project uses a…

  2. Reactions of ruthenium hydrides with ethyl-vinyl sulfide.

    PubMed

    Dahcheh, Fatme; Stephan, Douglas W

    2014-03-01

    The Ru-hydride precursors (Im(OMe)2)(PPh3)2RuHCl () and (Me2Im(OMe)2)(PPh3)2RuHCl () reacted with ethyl-vinyl-sulfide to give ((MeOCH2CH2)C3H2N2(CH2CH(OMe))RuCl(PPh3)2 () and ((MeOCH2CH2)C3Me2N2(CH2CH(OMe))RuCl(PPh3)2 (), respectively. Dissolution of () in C6D6 prompts formation of ((MeOCH2CH2)C5H6N2(CHCH)RuCl(PPh3)2 (). The analogous reactions of the bis-carbene Ru-hydride precursors (Im(OMe)2)(IMes)(PPh3)RuHCl (), (Im(OMe)2)(SIMes)(PPh3)RuHCl () and (Im(OMe)2)(IMes-Cl2)(PPh3)RuHCl () gave ((MeOCH2CH2)C3H2N2(CHCH)RuCl(PPh3)(NHC) (NHC = IMes (), SIMes (), IMes-Cl2 (), respectively. The formation of compounds () and () is thought to go through an initial insertion of the vinyl-fragment into the Ru-H prompting subsequent C-H activation and loss of diethyl sulfide. This yields () and (), while subsequent loss of methanol yields () and (-). PMID:24441082

  3. A Voyage through the Radio Universe

    ERIC Educational Resources Information Center

    Spuck, Timothy

    2004-01-01

    Each year, professionals and amateurs alike make significant contributions to the field of astronomy. High school students can also conduct astronomy research. Since 1992, the Radio Astronomy Research Team from Oil City Area Senior High School (OCHS) in Oil City, Pennsylvania, has traveled each year to the National Radio Astronomy Observatory…

  4. Electron impact cross sections for surrogates of DNA sugar phosphate backbone

    NASA Astrophysics Data System (ADS)

    Bhowmik, Pooja; Joshipura, K. N.; Pandya, Siddharth

    2012-11-01

    Ionization and elastic cross sections by electron impact on H3PO4 and OP(OCH3)3 which are substitutes for the components of DNA phosphate group. We have employed the Complex Scattering Potential-ionization contribution (CSP-ic) formalism to calculate the cross sections in the energy range from ionization threshold to 2000 eV.

  5. Involvement of T-cell immunoregulation by ochnaflavone in therapeutic effect on fungal arthritis due to Candida albicans.

    PubMed

    Lee, Jue-Hee

    2011-07-01

    Arthritis due to pathogenic fungi is a serious disease causing rapid destruction of the joint. In the pathogenesis of arthritis, T lymphocytes are considered to be one of the major immune cells. In present study, we examined the T cell immunoregulatory effect by ochnaflavone (Och), a biflavonoid, on arthritis caused by Candida albicans that is the most commonly associated with fungal arthritis. To examine the effects of ochnaflavonon Candida albicans-caused septic arthritis, an emulsified mixture of C. albicans cell wall and complete Freund's adjuvant (CACW/CFA) was injected into BALB/c mice via hind footpad route on days -3, -2, and -1. On Day 0, Och at 1 or 2 mg/dose/time was intratraperitoneally given to mice with the swollen footpad every other day for 3 times. The footpad-edema was measured for 20 days. Results revealed that Och reduced the edema at all dose levels and furthermore, there was app. 45% reduction of the edema in animals given 2 mg-dose at the peak of septic arthritis (p < 0.05). This anti-arthritic effect was accompanied by the diminishing of the DTH (delayed type hypersensitivity) activity against the CACW and by the provoking of the dominant T helper 2 (Th2) type cytokines production (IL-4 and Il-10), which appeared to result in a suppression of T helper 1 cytokines (IFN-γ and IL-2). Besides the T cell immunoregulatory activity, Och inhibited T cells activation as evidenced by the IL-2 reduction from PMA/ionomycin-stimulated Jurkat cell line and in addition, the compound killed macrophages in a dose-dependent manner (p < 0.05). However, Och caused no hemolysis (p < 0.05). These data implicate that Och, which has anti-arthritic activity based on the Th2 dominance as well as macrophage removal, can be safely administered into the blood circulation for treatment of the arthritis caused by C. albicans. Thus, it can be concluded that Och would be an ideal immunologically evaluated agent for treating of Candida arthritis.

  6. Cyclo- and carbophosphazene-supported ligands for the assembly of heterometallic (Cu2+/Ca2+, Cu2+/Dy3+, Cu2+/Tb3+) complexes: synthesis, structure, and magnetism.

    PubMed

    Chandrasekhar, Vadapalli; Senapati, Tapas; Dey, Atanu; Das, Sourav; Kalisz, Marguerite; Clérac, Rodolphe

    2012-02-20

    The carbophosphazene and cyclophosphazene hydrazides, [{NC(N(CH(3))(2))}(2){NP{N(CH(3))NH(2)}(2)}] (1) and [N(3)P(3)(O(2)C(12)H(8))(2){N(CH(3))NH(2)}(2)] were condensed with o-vanillin to afford the multisite coordination ligands [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-OH)(m-OCH(3))}(2)}] (2) and [{N(2)P(2)(O(2)C(12)H(8))(2)}{NP{N(CH(3))N═CH-C (6)H(3)-(o-OH)(m-OCH(3))}(2)}] (3), respectively. These ligands were used for the preparation of heterometallic complexes [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuCa(NO(3))(2)}] (4), [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{Cu(2)Ca(2)(NO(3))(4)}]·4H(2)O (5), [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuDy(NO(3))(4)}]·CH(3)COCH(3) (6), [{NP(O(2)C(12)H(8))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuDy(NO(3))(3)}] (7), and [{NP(O(2)C(12)H(8))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuTb(NO(3))(3)}] (8). The molecular structures of these compounds reveals that the ligands 2 and 3 possess dual coordination pockets which are used to specifically bind the transition metal ion and the alkaline earth/lanthanide metal ion; the Cu(2+)/Ca(2+), Cu(2+)/Tb(3+), and Cu(2+)/Dy(3+) pairs in these compounds are brought together by phenoxide and methoxy oxygen atoms. While 4, 6, 7, and 8 are dinuclear complexes, 5 is a tetranuclear complex. Detailed magnetic properties on 6-8 reveal that these compounds show weak couplings between the magnetic centers and magnetic anisotropy. However, the ac susceptibility experiments did not reveal any out of phase signal suggesting that in these compounds slow relaxation of magnetization is absent above 1.8 K. PMID:22320309

  7. Environmental risk assessment of hydrofluoroethers (HFEs).

    PubMed

    Tsai, Wen-Tien

    2005-03-17

    Hydrofluoroethers (HFEs) are being used as third generation replacements to chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and perfluorocarbons (PFCs) because of their nearly zero stratospheric ozone depletion and relatively low global warming potential. HFEs have been developed under commercial uses as cleaning solvents (incl., HFE-7500, C7F15OC2H5; HFE-7200, C4F9OC2H5; HFE-7100, C4F9CH3; HFE-7000, n-C3F7OCH3), blowing agents (incl., HFE-245mc, CF3CF2OCH3; HFC-356mec, CF3CHFCF2OCH3), refrigerants (incl., HFE-143a, CF3OCH3; HFE-134, CHF2OCHF2; HFE-245mc, CF3CF2OCH3), and dry etching agents in semiconductor manufacturing, (incl., HFE-227me, CF3OCHFCF3). From the environmental, ecological, and health points of view, it is important to understand their environmental risks for these HFEs from a diversity of commercial applications and industrial processes. This paper aims to introduce these HFEs with respect to physiochemical properties, commercial uses, and environmental hazards (i.e. global warming, photochemical potential, fire and explosion hazard, and environmental partition). Further, it addresses the updated data on the human toxicity, occupational exposure and potential health risk of commercial HFEs. It is concluded that there are few HFEs that still possess some environmental hazards, including global warming, flammability hazard and adverse effect of exposure. The partition coefficient for these HFEs has been estimated using the group contribution method; the values of logKow for commercial HFEs have been estimated to be below 3.5. PMID:15752850

  8. Functionalized arene-ruthenium(II) complexes: dangling vs. tethering side chain.

    PubMed

    Lastra-Barreira, Beatriz; Díez, Josefina; Crochet, Pascale; Fernández, Israel

    2013-04-21

    The reactivity of compounds [RuCl2(η(6)-C6H5OCH2CH2OH)(L)] (L = phosphine or phosphite) towards the chloride abstractor AgSbF6 has been investigated. Thus, the treatment of the triphenylphosphite complex [RuCl2(η(6)-C6H5OCH2CH2OH){P(OPh)3}] with one equivalent of AgSbF6 gave rise to the formation of the dinuclear dichloro-bridged species [{Ru(μ-Cl)(η(6)-C6H5OCH2CH2OH){P(OPh)3}}2](2+) as the hexafluoroantimonate salt. On the other hand, the triphenylphosphine analog [RuCl2(η(6)-C6H5OCH2CH2OH)(PPh3)] led, under the same experimental conditions, to the di-ruthenium derivative [{RuCl(η(6)-C6H5OCH2CH2OH)(PPh3)}2(μ-Cl)][SbF6] containing only one Cl-bridge. In sharp contrast, treatment of precursors [RuCl2(η(6)-C6H5CH2CH2CH2OH)(L)] (L = P(OPh)3, PPh3, P(OEt)3) with AgSbF6 resulted in the clean formation of the tethered compounds [RuCl{η(6):κ(1)(O)-C6H5CH2CH2CH2OH}(L)][SbF6]. The differences in reactivity observed have been rationalized by theoretical calculations.

  9. Gas-phase reactivity of metavanadate [VO3]- towards methanol and ethanol: experiment and theory.

    PubMed

    Waters, Tom; Wedd, Anthony G; O'Hair, Richard A J

    2007-01-01

    The gas-phase reactivity of the metavanadate anion [VO3]- towards methanol and ethanol was examined by a combination of ion-molecule reaction and isotope labelling experiments in a quadrupole ion-trap mass spectrometer. The experimental data were interpreted with the aid of density functional theory calculations. [VO3]- dehydrated methanol to eliminate water and form [VO2(eta2-OCH2)]-, which features an [eta2-C,O-OCH2]2- ligand formed by formal removal of two protons from methanol and which is isoelectronic with peroxide. [VO3]- reacted with ethanol in an analogous manner to form [VO2(eta2-OCHCH3)]-, as well as by loss of ethene to form [VO2(OH)2]-. The calculations predicted that important intermediates in these reactions were the hydroxo alkoxo anions [VO2(OH)(OCH2R)]- (R: H, CH3). These were predicted to undergo intramolecular hydrogen-atom transfer to form [VO(OH)2(eta1-OCHR)]- followed by eta1-O-->eta2-C,O rearrangements to form [VO(OH)2(eta2-OCHR)]-. The latter reacted further to eliminate water and generate the product [VO2(eta2-OCHR)]-. This major product observed for [VO3]- is markedly different from that observed previously for [NbO3]- containing the heavier Group 5 congener niobium. In that case, the major product of the reaction was an ion of stoichiometry [Nb, O3, H2]- arising from the formal dehydrogenation of methanol to formaldehyde. The origin of this difference was examined theoretically and attributed to the intermediate alkoxo anion [NbO2(OH)(OCH3)]- preferring hydride transfer to form [HNbO2(OH)]- with loss of formaldehyde. This contrasts with the hydrogen-atom-transfer pathway observed for [VO2(OH)(OCH3)]-. PMID:17661322

  10. Environmental risk assessment of hydrofluoroethers (HFEs).

    PubMed

    Tsai, Wen-Tien

    2005-03-17

    Hydrofluoroethers (HFEs) are being used as third generation replacements to chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and perfluorocarbons (PFCs) because of their nearly zero stratospheric ozone depletion and relatively low global warming potential. HFEs have been developed under commercial uses as cleaning solvents (incl., HFE-7500, C7F15OC2H5; HFE-7200, C4F9OC2H5; HFE-7100, C4F9CH3; HFE-7000, n-C3F7OCH3), blowing agents (incl., HFE-245mc, CF3CF2OCH3; HFC-356mec, CF3CHFCF2OCH3), refrigerants (incl., HFE-143a, CF3OCH3; HFE-134, CHF2OCHF2; HFE-245mc, CF3CF2OCH3), and dry etching agents in semiconductor manufacturing, (incl., HFE-227me, CF3OCHFCF3). From the environmental, ecological, and health points of view, it is important to understand their environmental risks for these HFEs from a diversity of commercial applications and industrial processes. This paper aims to introduce these HFEs with respect to physiochemical properties, commercial uses, and environmental hazards (i.e. global warming, photochemical potential, fire and explosion hazard, and environmental partition). Further, it addresses the updated data on the human toxicity, occupational exposure and potential health risk of commercial HFEs. It is concluded that there are few HFEs that still possess some environmental hazards, including global warming, flammability hazard and adverse effect of exposure. The partition coefficient for these HFEs has been estimated using the group contribution method; the values of logKow for commercial HFEs have been estimated to be below 3.5.

  11. Multiple bonds between transition metals and main-group elements. 73. Synthetic routes to rhenium(V) alkyl and rhenium(VII) alkylidyne complexes. X-ray crystal structures of (. eta. sup 5 -C sub 5 Me sub 5 )Re( double bond O)(CH sub 3 )(CH sub 2 C(CH sub 3 ) sub 3 ) and (. eta. sup 5 -C sub 5 Me sub 5 )(Br) sub 3 Re triple bond CC(CH sub 3 ) sub 3

    SciTech Connect

    Herrmann, W.A.; Felixberger, J.K.; Anwander, R.; Herdtweck, E.; Kiprof, P.; Riede, J. )

    1990-05-01

    Dialkyloxo({eta}{sup 5}pentamethylcyclopentadienyl)rhenium(V) complexes ({eta}{sup 5}-C{sub 5}Me{sub 5})Re({double bond}O)(CH{sub 3})R{prime}(R{prime} = C{sub 2}H{sub 5}, CH{sub 2}Si(CH{sub 3}){sub 3}, CH{sub 2}C(CH{sub 3}){sub 3}), 1c-e, have become accessible through alkylation of ({eta}{sup 5}-C{sub 5}Me{sub 5})Re({double bond}O)(Cl)(CH{sub 3}) (7) with R{prime}MgCl. 1c-e are the first rhenium complexes containing different alkyl ligands. The neopentyl derivative 1e (R{prime} = CH{sub 2}C(CH{sub 3}){sub 3}) crystallizes in the orthorhombic space group Pbca with a = 960.7 (2), b = 2.844.5 (4), c = 1,260.7 (2) pm, and Z = 8. The X-ray crystal structure was refined to R{sub W} = 3.9%. The chiral molecule shows a distorted tetrahedral geometry around the rhenium center. The tribromide 3b has been structurally characterized. Brown crystals of 3b belong to space group P2{sub 1}/c with unit cell dimensions a = 1,311.5 (2), b = 723.0 (1), c = 1,901.6 (2) pm, {beta} = 92.68 (1){degree}, and Z = 4. The structure exhibits a four-legged piano stool geometry with no trans influence of the neopentylidyne ligand to the bromine atom.

  12. Progress of the Proton-Ion Medical Machine Study (PIMMS).

    PubMed

    Bryant, P J

    1999-06-01

    The Proton-Ion Medical Machine Study (PIMMS) was set up following an agreement between Professor M. Regler of the Med-AUSTRON (Austria) and Professor U. Amaldi of the TERA Foundation (Italy) to join their efforts in the design of a medical synchrotron that could later be adapted to individual national needs. CERN agreed to host this study inside its PS Division and to contribute one full-time member to the study team. The study group has worked in collaboration with GSI (Germany) and was more recently joined by Onkologie 2000 (Czech Republic). Work started in January 1996 and is expected to finish during 1998. The agreed aim of the study was to investigate and design a generic facility that would allow the direct clinical comparison of protons and carbon ions for cancer treatment. The accelerator was to be designed primarily for high-precision active beam scanning with both protons and ions, but was also to be capable of delivering proton beams with passive spreading. PMID:10394382

  13. Unusual room temperature activation of 1,2-dialkoxyalkanes by niobium and tantalum pentachlorides.

    PubMed

    Marchetti, Fabio; Pampaloni, Guido; Zacchini, Stefano

    2008-12-28

    The outcome of the reactions of MCl(5) (M = Nb, 1a; M = Ta, 1b) with 1,2-dialkoxyalkanes [i.e. MeO(CH(2))(2)OMe (dme), EtO(CH(2))(2)OEt, MeOCH(2)CH(Me)OMe, MeO(CH(2))(2)OCH(2)Cl, MeO(CH(2))(2)O(CH(2))(2)OMe (diglyme)] depends strictly on the stoichiometry. In the 1 : 1 molar ratio reactions, single C-O bond cleavage occurs, resulting in formation of alkyl chloride and of the complexes [upper bond 1 start]MCl(4)[O(R)CH(R')CH(2)O][upper bond 1 end] [M = Nb, R = Me, R' = H, 3a; M = Ta, R = Me, R' = H, 3b; M = Nb, R = Et, R' = H, 5; M = Nb, R = R' = Me, 6; M = Nb, R = CH(2)Cl, R' = H, 7; M = Nb, R = (CH(2))(2)O(Me)NbCl(5), R' = H, 8], which have been characterized spectroscopically. Moreover, minor amounts of the oxo-bridged adducts MOCl(3)(dme)MCl(5) (M = Nb, 4a; M = Ta, 4b) have been isolated in the reactions involving dme. On the other hand, compounds react with two (or more) equivalents of dme mainly via a multiple C-O bond cleavage process, affording MOCl(3)(dme) (M = Nb, 2a; M = Ta, 2b), 1,4-dioxane and methyl chloride. The oxychloride compounds MOCl(3) (M = Nb, 11a; M = Ta, 11b) have been efficiently obtained by addition of TiCl(4) to 2. Compound 2a is reduced in high yield to the Nb(III) species NbCl(3)(dme), 12, upon treatment with SnBu(3)H. The oxychloride NbOCl(3)(diglyme), 9, 1,4-dioxane, CH(3)Cl and the hexachloroniobate salt [MeOCH(2)CH(2)OCH(2)CH(2)O(H)Me][NbCl(6)], 10, have been identified as products of the reaction of 1a with two equivalents of diglyme. The 1 : 2 molar ratio reaction of 1a with MeOCH(2)CH(Me)OMe gives 2,5-dimethyl-1,4-dioxane. Compound 1a reacts with two equivalents of EtO(CH(2))(2)OEt or MeO(CH(2))(2)OCH(2)Cl yielding Cl(CH(2))(2)OCH(2)CH(3) or O(CH(2)Cl)(2) and diglyme, respectively, but not dioxane, suggesting that fragmentation pathways different from that found for dme are operating. The X-ray molecular structures of 4a, 4b and 10 have been determined.

  14. Unusual room temperature activation of 1,2-dialkoxyalkanes by niobium and tantalum pentachlorides.

    PubMed

    Marchetti, Fabio; Pampaloni, Guido; Zacchini, Stefano

    2008-12-28

    The outcome of the reactions of MCl(5) (M = Nb, 1a; M = Ta, 1b) with 1,2-dialkoxyalkanes [i.e. MeO(CH(2))(2)OMe (dme), EtO(CH(2))(2)OEt, MeOCH(2)CH(Me)OMe, MeO(CH(2))(2)OCH(2)Cl, MeO(CH(2))(2)O(CH(2))(2)OMe (diglyme)] depends strictly on the stoichiometry. In the 1 : 1 molar ratio reactions, single C-O bond cleavage occurs, resulting in formation of alkyl chloride and of the complexes [upper bond 1 start]MCl(4)[O(R)CH(R')CH(2)O][upper bond 1 end] [M = Nb, R = Me, R' = H, 3a; M = Ta, R = Me, R' = H, 3b; M = Nb, R = Et, R' = H, 5; M = Nb, R = R' = Me, 6; M = Nb, R = CH(2)Cl, R' = H, 7; M = Nb, R = (CH(2))(2)O(Me)NbCl(5), R' = H, 8], which have been characterized spectroscopically. Moreover, minor amounts of the oxo-bridged adducts MOCl(3)(dme)MCl(5) (M = Nb, 4a; M = Ta, 4b) have been isolated in the reactions involving dme. On the other hand, compounds react with two (or more) equivalents of dme mainly via a multiple C-O bond cleavage process, affording MOCl(3)(dme) (M = Nb, 2a; M = Ta, 2b), 1,4-dioxane and methyl chloride. The oxychloride compounds MOCl(3) (M = Nb, 11a; M = Ta, 11b) have been efficiently obtained by addition of TiCl(4) to 2. Compound 2a is reduced in high yield to the Nb(III) species NbCl(3)(dme), 12, upon treatment with SnBu(3)H. The oxychloride NbOCl(3)(diglyme), 9, 1,4-dioxane, CH(3)Cl and the hexachloroniobate salt [MeOCH(2)CH(2)OCH(2)CH(2)O(H)Me][NbCl(6)], 10, have been identified as products of the reaction of 1a with two equivalents of diglyme. The 1 : 2 molar ratio reaction of 1a with MeOCH(2)CH(Me)OMe gives 2,5-dimethyl-1,4-dioxane. Compound 1a reacts with two equivalents of EtO(CH(2))(2)OEt or MeO(CH(2))(2)OCH(2)Cl yielding Cl(CH(2))(2)OCH(2)CH(3) or O(CH(2)Cl)(2) and diglyme, respectively, but not dioxane, suggesting that fragmentation pathways different from that found for dme are operating. The X-ray molecular structures of 4a, 4b and 10 have been determined. PMID:19050789

  15. FTIR gas-phase kinetic study on the reactions of OH radicals and Cl atoms with unsaturated esters: Methyl-3,3-dimethyl acrylate, (E)-ethyl tiglate and methyl-3-butenoate

    NASA Astrophysics Data System (ADS)

    Colomer, Juan P.; Blanco, María B.; Peñéñory, Alicia B.; Barnes, Ian; Wiesen, Peter; Teruel, Mariano A.

    2013-11-01

    The relative-rate technique has been used to obtain rates coefficients for the reactions of the unsaturated esters methyl-3,3-dimethyl acrylate, (E)-ethyl tiglate and methyl-3-butenoate with OH radicals and chlorine atoms at (298 ± 2) K in synthetic air at a total pressure of (760 ± 10) Torr. The experiments were performed in an environmental chamber using in situ FTIR detection to monitor the decay of the esters relative to different reference compounds. The following room temperature rate coefficients (in units of cm3 molecule-1 s-1) were obtained: k1(OH + (CH3)2Cdbnd CHC(O)OCH3) = (4.46 ± 1.05) × 10-11, k2(Cl + (CH3)2Cdbnd CHC(O)OCH3) = (2.78 ± 0.46) × 10-10, k3(OH + CH3CHdbnd C(CH3)C(O)OCH2CH3) = (8.32 ± 1.93) × 10-11, k4(Cl + CH3CHdbnd C(CH3)C(O)OCH2CH3) = (2.53 ± 0.35) × 10-10, k5(OH + CH2dbnd CHCH2C(O)OCH3) = (3.16 ± 0.57) × 10-11, k4(Cl + CH2dbnd CHCH2C(O)OCH3) = (2.10 ± 0.35) × 10-10. With the exception of the reaction of Cl with methyl-3,3-dimethyl acrylate (k2), for which one determination exists in the literature, this study is the first kinetic study for these reactions under atmospheric pressure. Reactivity trends are discussed in terms of the effect of the alkyl and ester groups attached to the double bond on the overall rate coefficients towards OH radicals. The atmospheric implications of the reactions were assessed by the estimation of the tropospheric lifetimes of the title reactions.

  16. Method for synthesizing thin film electrodes

    DOEpatents

    Boyle, Timothy J.

    2007-03-13

    A method for making a thin-film electrode, either an anode or a cathode, by preparing a precursor solution using an alkoxide reactant, depositing multiple thin film layers with each layer approximately 500 1000 .ANG. in thickness, and heating the layers to above 600.degree. C. to achieve a material with electrochemical properties suitable for use in a thin film battery. The preparation of the anode precursor solution uses Sn(OCH.sub.2C(CH.sub.3).sub.3).sub.2 dissolved in a solvent in the presence of HO.sub.2CCH.sub.3 and the cathode precursor solution is formed by dissolving a mixture of (Li(OCH.sub.2C(CH.sub.3).sub.3)).sub.8 and Co(O.sub.2CCH.sub.3).H.sub.2O in at least one polar solvent.

  17. Differentiation of neotropical fish species with statistical analysis of fourier transform infrared photoacoustic spectroscopy data.

    PubMed

    Almeida, Francylaine S; Lima, Sandro M; Andrade, Luis H C; Súarez, Yzel R

    2012-07-01

    Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) was applied to nineteen fish species in Brazil's Upper Paraná River basin to identify differences in the structural composition of their scales. To differentiate the species, a canonical discriminant analysis was used to indicate the most important absorption peaks in the mid-infrared region. Significant differences were found in the chemical composition of scales among the studied fish species, with Wilk's lambda = 5.2 × 10(-6), F((13,18,394)) = 37.57, and P < 0.001, indicating that O-CH(2) wag at 1396 cm(-1) can be used as a biomarker of this species group. The species could be categorized into four groups according to phylogenetic similarity, suggesting that the O-CH(2) 1396 cm(-1) absorbance is related to the biological traits of each species. This procedure can also be used to complement evolutionary studies.

  18. High resolution electronic spectra of anisole and anisole-water in the gas phase: hydrogen bond switching in the S1 state.

    PubMed

    Ribblett, J W; Sinclair, W E; Borst, D R; Yi, J T; Pratt, D W

    2006-02-01

    Rotationally resolved S(1)<--S(0) electronic spectra of anisole and its hydrogen bonded complex containing one water molecule have been obtained. The results provide evidence for an "in-plane" complex in which the water molecule is attached via two hydrogen bonds to the anisole molecule, a donor O-H- - -O(CH(3)) bond and an acceptor H-O- - -H(ring) bond. Analysis of the subbands that appear in the spectrum of the complex suggests that hydrogen bond "switching" occurs when the complex absorbs light. The former O-H- - -O(CH(3)) bond is stronger in the ground (S(0)) state, whereas the latter H-O- - -H(ring) bond is stronger in the excited (S(1)) state. Dynamical consequences of this phenomenon are discussed.

  19. The Synthesis and Characterization of Aromatic Hybrid Anderson-Evans POMs and their Serum Albumin Interactions: The Shift from Polar to Hydrophobic Interactions.

    PubMed

    Al-Sayed, Emir; Blazevic, Amir; Roller, Alexander; Rompel, Annette

    2015-12-01

    Four aromatic hybrid Anderson polyoxomolybdates with Fe(3+) or Mn(3+) as the central heteroatom have been synthesized by using a pre-functionalization protocol and characterized by using single-crystal X-ray diffraction, FTIR, ESI-MS, (1) H NMR spectroscopy, and elemental analysis. Structural analysis revealed the formation of (TBA)3 [FeMo6 O18 {(OCH2 )3 CNHCOC6 H5 }2 ]⋅3.5 ACN (TBA-FeMo6 -bzn; TBA=tetrabutylammonium, ACN=acetonitrile, bzn=TRIS-benzoic acid alkanolamide, TRISR=(HOCH2 )3 CR)), (TBA)3 [FeMo6 O18 {(OCH2 )3 CNHCOC8 H7 }2 ]⋅2.5 ACN (TBA-FeMo6 -cin; cin=TRIS-cinnamic acid alkanolamide), (TBA)3 [MnMo6 O18 {(OCH2 )3 CNHCOC6 H5 }2 ]⋅3.5 ACN (TBA-MnMo6 -bzn), and (TBA)3 [MnMo6 O18 {(OCH2 )3 CNHCOC8 H7 }2 ]⋅2.5 ACN (TBA-MnMo6 -cin). To make these four compounds applicable in biological systems, an ion exchange was performed that gave the water-soluble (up to 80 mM) sodium salts Na3 [FeMo6 O18 {(OCH2 )3 CNHCOC6 H5 }2 ] (Na-FeMo6 -bzn), Na3 [FeMo6 O18 {(OCH2 )3 CNHCOC8 H7 }2 ] (Na-FeMo6 -cin), Na3 [MnMo6 O18 {(OCH2 )3 CNHCOC6 H5 }2 ] (Na-MnMo6 -bzn), and Na3 [MnMo6 O18 {(OCH2 )3 CNHCOC8 H7 }2 ] (Na-MnMo6 -cin). The hydrolytic stability of the sodium salts was examined by applying ESI-MS in the pH range of 4 to 9. Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that human and bovine serum albumin (HSA and BSA) remain intact in solutions that contain up to 100 equivalents of the sodium salts over more than 4 d at 20 °C. Tryptophan (Trp) fluorescence quenching was applied to study the interactions between the sodium salts and HSA and BSA at pH 5.5 and 7.4. The quenching constants were extracted by using Stern-Volmer analysis, which suggested the formation of a 1:1 POM-protein complex in all samples. It is suggested that the aromatic hybrid POM approaches subdomain IIA of HSA and exhibits hydrophobic interactions with its hydrophobic tails, whereas the Anderson core is stabilized through electrostatic

  20. Increasing the activity and enantioselectivity of lipases by sol-gel immobilization: further advancements of practical interest.

    PubMed

    Tielmann, Patrick; Kierkels, Hans; Zonta, Albin; Ilie, Adriana; Reetz, Manfred T

    2014-06-21

    The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of the sol-gel approach.

  1. Langmuir monolayers and thin films of amphifilic thiacalix[4]arenes. Properties and matrix for the immobilization of cytochrome c.

    PubMed

    Solovieva, Svetlana E; Safiullin, Roman A; Kochetkov, Evgeni N; Melnikova, Nina B; Kadirov, Marsil K; Popova, Elena V; Antipin, Igor S; Konovalov, Alexander I

    2014-12-23

    Formation and properties of Langmuir films of thiacalix[4]arene (TCA) derivatives containing N-donor groups on the lower rim (Y═O(CH2)3CN; OCH2CN; NH2; OCH2ArCN-p) in 1,3-alternate conformation on aqueous subphase and solid substrates have been studied. Only tetra-cyanopropoxy-p-tert-butylthiacalix[4]arene 1 forms a typical monomolecular layer with perpendicular orientation of the macrocycle relative to the water-air interface that is able to immobilize cytochrome c in the entire range of the surface pressure. Obtained monolayers were transferred by Langmuir-Schaefer technique onto quartz, indium-tin oxide (ITO), and silicon. It was demonstrated that protein activity is retained after immobilization on the substrate. PMID:25435075

  2. Global seamless network demonstrator: carrier grade automatic switched transport network implementation in realistic telecom field environment

    NASA Astrophysics Data System (ADS)

    Foisel, Hans-Martin; Hanik, Norbert; Braun, Ralf-Peter; Lehr, Georg; Gladisch, Andreas

    2004-04-01

    The Global Seamless Network (GSN) Demonstrator is presented, a joint effort of system vendors and Deutsche Telekom Group R&D to demonstrate network functions and management integration and enable, for the first time, experiences with a carrier grade Automatically Switched Transport Network (ASTN) implementation and the envisaged main ASTN clients, IP and Ethernet. For end-to-end monitoring capability, integrating the view on the ASTN and Ethernet-MAN configuration, an UMS (Upper Monitoring System) is being developed. Furthermore broadband application were implemented to visualise the network functions. The ASTN backbone consists of four cross connects and an ULH-WDM system with 3x 10Gbit/s channels (OCh) between Berlin and Darmstadt, whereby each OCh is treated as a virtual fibre.

  3. Estimation of the catalytic centre in double metal cyanide catalysts by XAS

    NASA Astrophysics Data System (ADS)

    Lawniczak-Jablonska, Krystyna; Chrusciel, Arkadiusz

    2016-05-01

    Double metal cyanide (DMC) catalysts are commonly applied at industrial ring opening polymerization of epoxides. Nevertheless, the knowledge on the molecular nature of their high activity and selectivity is limited. XAS studies were performed to look for the possible catalytic centre in this family of catalysts. DMC catalysts were synthesized from ZnCl2 and potassium hexacyanocobaltate(III) solution, in the presence of the different organic ligands and show significant fraction of the non-crystalline structure. Two ligands were analysed (tert-butanol ( t BuOH) or glyme (CH3OCH2CH2OCH3)). EXAFS analysis established that only Zn atoms are the active metallic centers in DMC regardless the used ligand. The coordination around Zn was changed from octahedral in reference non catalytic material to tetrahedral in catalysts, and Cl atoms were detected near some of Zn atoms.

  4. The Synthesis and Characterization of Aromatic Hybrid Anderson–Evans POMs and their Serum Albumin Interactions: The Shift from Polar to Hydrophobic Interactions

    PubMed Central

    Al-Sayed, Emir; Blazevic, Amir; Roller, Alexander; Rompel, Annette

    2015-01-01

    Four aromatic hybrid Anderson polyoxomolybdates with Fe3+ or Mn3+ as the central heteroatom have been synthesized by using a pre-functionalization protocol and characterized by using single-crystal X-ray diffraction, FTIR, ESI-MS, 1H NMR spectroscopy, and elemental analysis. Structural analysis revealed the formation of (TBA)3[FeMo6O18{(OCH2)3CNHCOC6H5}2]⋅3.5 ACN (TBA-FeMo6-bzn; TBA=tetrabutylammonium, ACN=acetonitrile, bzn=TRIS-benzoic acid alkanolamide, TRIS–R=(HOCH2)3C–R)), (TBA)3[FeMo6O18{(OCH2)3CNHCOC8H7}2]⋅2.5 ACN (TBA-FeMo6-cin; cin=TRIS-cinnamic acid alkanolamide), (TBA)3[MnMo6O18{(OCH2)3CNHCOC6H5}2]⋅3.5 ACN (TBA-MnMo6-bzn), and (TBA)3[MnMo6O18{(OCH2)3CNHCOC8H7}2]⋅2.5 ACN (TBA-MnMo6-cin). To make these four compounds applicable in biological systems, an ion exchange was performed that gave the water-soluble (up to 80 mm) sodium salts Na3[FeMo6O18{(OCH2)3CNHCOC6H5}2] (Na-FeMo6-bzn), Na3[FeMo6O18{(OCH2)3CNHCOC8H7}2] (Na-FeMo6-cin), Na3[MnMo6O18{(OCH2)3CNHCOC6H5}2] (Na-MnMo6-bzn), and Na3[MnMo6O18{(OCH2)3CNHCOC8H7}2] (Na-MnMo6-cin). The hydrolytic stability of the sodium salts was examined by applying ESI-MS in the pH range of 4 to 9. Sodium dodecylsulfate–polyacrylamide gel electrophoresis (SDS-PAGE) showed that human and bovine serum albumin (HSA and BSA) remain intact in solutions that contain up to 100 equivalents of the sodium salts over more than 4 d at 20 °C. Tryptophan (Trp) fluorescence quenching was applied to study the interactions between the sodium salts and HSA and BSA at pH 5.5 and 7.4. The quenching constants were extracted by using Stern–Volmer analysis, which suggested the formation of a 1:1 POM–protein complex in all samples. It is suggested that the aromatic hybrid POM approaches subdomain IIA of HSA and exhibits hydrophobic interactions with its hydrophobic tails, whereas the Anderson core is stabilized through electrostatic interactions with polar amino acid side chains from, for example

  5. A Polyurethane Surface Modifier: Contrasting Amphiphilic and Contraphilic Surfaces Driven by block and random Soft Blocks having Trifluoroethoxymethyl and PEG Side Chains

    PubMed Central

    Zhang, Wei; Fujiwara, Tomoko; Taşkent, Hűmeyra; Zheng, Ying; Brunson, Kennard; Gamble, Lara; Wynne, Kenneth J.

    2013-01-01

    A conventional MDI-BD-PTMO polyurethane was modified using 2 wt.% polyurethanes (U) having copolyoxetane soft blocks with hydrophobic 3F, CF3CH2OCH2- and hydrophilic MEn, CH3O(CH2CH2O)nCH2-, n = 3, 7) side chains. In contrast to neat 3F-co-MEn-U, 2 wt.% 3F-co-MEn-U compositions have physically stable morphologies and wetting behavior. Surface composition (XPS) and amphiphilic or contraphilic wetting are controlled by the 3F-co-MEn polyoxetane soft block architecture and MEn side chain length. Importantly, θrec can be tuned for 2 wt.% 3F-co-MEn-U compositions independent of swelling, which is controlled by the bulk polyurethane. AFM imaging led to a new morphological model whereby fluorous/PEG-hard block nano-aggregates combine to form near surface features culminating in micron scale texturing. PMID:24204100

  6. Langmuir monolayers and thin films of amphifilic thiacalix[4]arenes. Properties and matrix for the immobilization of cytochrome c.

    PubMed

    Solovieva, Svetlana E; Safiullin, Roman A; Kochetkov, Evgeni N; Melnikova, Nina B; Kadirov, Marsil K; Popova, Elena V; Antipin, Igor S; Konovalov, Alexander I

    2014-12-23

    Formation and properties of Langmuir films of thiacalix[4]arene (TCA) derivatives containing N-donor groups on the lower rim (Y═O(CH2)3CN; OCH2CN; NH2; OCH2ArCN-p) in 1,3-alternate conformation on aqueous subphase and solid substrates have been studied. Only tetra-cyanopropoxy-p-tert-butylthiacalix[4]arene 1 forms a typical monomolecular layer with perpendicular orientation of the macrocycle relative to the water-air interface that is able to immobilize cytochrome c in the entire range of the surface pressure. Obtained monolayers were transferred by Langmuir-Schaefer technique onto quartz, indium-tin oxide (ITO), and silicon. It was demonstrated that protein activity is retained after immobilization on the substrate.

  7. Anderson-like alkoxo-polyoxovanadate clusters serving as unprecedented second building units to construct metal-organic polyhedra.

    PubMed

    Zhang, Yu-Teng; Wang, Xin-Long; Li, Shuang-Bao; Gong, Ya-Ru; Song, Bai-Qiao; Shao, Kui-Zhan; Su, Zhong-Min

    2016-08-11

    Unprecedented Anderson-like alkoxo-polyoxovanadate [V6O6(OCH3)9(μ6-SO4)(COO)3](2-) polyanions can serve as 3-connected second building units (SBUs) that assemble with dicarboxylate or tricarboxylate ligands to form a new family of metal organic tetrahedrons of V4E6 and V4F4 type (V = vertex, E = edge, and F = face). To our knowledge, this alkoxo-polyoxovanadate-based SBU is the first ever reported. PMID:27363544

  8. Unimolecular thermal decomposition of dimethoxybenzenes

    SciTech Connect

    Robichaud, David J. Mukarakate, Calvin; Nimlos, Mark R.; Scheer, Adam M.; Ormond, Thomas K.; Buckingham, Grant T.; Ellison, G. Barney

    2014-06-21

    The unimolecular thermal decomposition mechanisms of o-, m-, and p-dimethoxybenzene (CH{sub 3}O-C{sub 6}H{sub 4}-OCH{sub 3}) have been studied using a high temperature, microtubular (μtubular) SiC reactor with a residence time of 100 μs. Product detection was carried out using single photon ionization (SPI, 10.487 eV) and resonance enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry and matrix infrared absorption spectroscopy from 400 K to 1600 K. The initial pyrolytic step for each isomer is methoxy bond homolysis to eliminate methyl radical. Subsequent thermolysis is unique for each isomer. In the case of o-CH{sub 3}O-C{sub 6}H{sub 4}-OCH{sub 3}, intramolecular H-transfer dominates leading to the formation of o-hydroxybenzaldehyde (o-HO-C{sub 6}H{sub 4}-CHO) and phenol (C{sub 6}H{sub 5}OH). Para-CH{sub 3}O-C{sub 6}H{sub 4}-OCH{sub 3} immediately breaks the second methoxy bond to form p-benzoquinone, which decomposes further to cyclopentadienone (C{sub 5}H{sub 4}=O). Finally, the m-CH{sub 3}O-C{sub 6}H{sub 4}-OCH{sub 3} isomer will predominantly follow a ring-reduction/CO-elimination mechanism to form C{sub 5}H{sub 4}=O. Electronic structure calculations and transition state theory are used to confirm mechanisms and comment on kinetics. Implications for lignin pyrolysis are discussed.

  9. A selenium-based ionic liquid as a recyclable solvent for the catalyst-free synthesis of 3-selenylindoles.

    PubMed

    Zimmermann, Everton G; Thurow, Samuel; Freitas, Camilo S; Mendes, Samuel R; Perin, Gelson; Alves, Diego; Jacob, Raquel G; Lenardão, Eder J

    2013-04-05

    The ionic liquid 1-butyl-3-methylimidazolium methylselenite, [bmim][SeO2(OCH3)], was successfully used as solvent in the catalyst-free preparation of 3-arylselenylindoles by the reaction of indole with ArSeCl at room temperature. The products were obtained selectively in good yields without the need of any additive and the solvent was easily reused for several cycles with good results.

  10. Towards a synthetic glycoconjugate vaccine against Neisseria meningitidis A.

    PubMed

    Berkin, Ali; Coxon, Bruce; Pozsgay, Vince

    2002-10-01

    Albumin conjugates of synthetic fragments of the capsular polysaccharide of the Gram-negative bacterium Neisseria meningitidis serogroup A were prepared. The fragments include monosaccharides 1 [alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)] and 2 [6-O-P(O)(O(-))(2)-alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)], disaccharide 3 [alpha-D-ManpNAc-[1-->O-P(O)(O(-))-->6]-alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)], and trisaccharide 4 [alpha-D-ManpNAc-[1-->O-P(O)(O(-))-->6]-alpha-D-ManpNAc-[1-->O-P(O)(O(-))-->6]-alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)]. Two monosaccharide blocks were employed as key intermediates. The reducing-end mannose unit featured the NHAc group at C-2, and contained the aminoethyl spacer as the aglycon for the final bioconjugation. The interresidual phosphodiester linkages were fashioned from an anomerically positioned H-phosphonate group in a 2-azido-mannose building block. The spacer-linked saccharides 1-4 were N-acylated with hepta-4,6-dienoic acid and the resulting conjugated diene-equipped saccharides were subjected to Diels-Alder-type addition with maleimidobutyryl-group functionalized human serum albumin to form covalent conjugates containing up to 26 saccharide haptens per albumin molecule. Complete (1)H, (13)C, and (31)P NMR assignments for 1-4 are given. Antigenicity of the neoglycoconjugates containing 1-4 was demonstrated by a double immunodiffusion assay which indicated that a fragment as small as a monosaccharide is recognized by a polyclonal meningococcus group A antiserum and that the O-acetyl group(s) present in the natural capsular material is not essential for antigenicity. PMID:12355530

  11. Structures of the gauche conformers of somE substituted dimethyl ethers. Effect of adjacent atom lone pairs on methyl group asymmetry

    NASA Astrophysics Data System (ADS)

    Boggs, James E.; Altman, Michael; Cordell, Floyd R.; Dai, Yuanfang

    The complete equilibrium structures of CH 3OCH 3 and of the gauche conformers of CH 30CH 2F, HOCH,F, CH,OCH,Cl and CH,OCH,CN have been determined by ab initio gradient computation at the Hartree-Fock, double zeta-plus-polarization level. The very large asymmetries in CH bond distances previously reported from microwave substitution structures are shown to be non-existent in the equilibrium structures and are presumably artifacts. Small differences, different in direction from those reported from the experiments and nearly an order of magnitude smaller in size, do exist. They reflect three factors: (1) a lengthening of a CH bond which is trans to a lone pair on an adjacent atom, (2) a general shortening of CH bonds originating at a carbon atom bearing a highly electronegative substituent, and (3) a specific interaction in which a CX substituent shortens the nearly parallel CH bond on the other methyl group. The last interaction, not previously reported, is mediated by withdrawal of electron density from the oxygen lone pair which is trans to both groups. Other structural features derived from the microwave studies are supported by the new results. Inclusion of polarization functions in the basis set for oxygen is essential for correct determination of the COC angle and the dihedral angles. The dihedral angles of CH 3OCH 2F and HOCH 2F are not correctly determined by the computation even at this level, although the computed values are improved when d functions are used for oxygen and still more by use of two sets of oxygen d functions. Polarization functions on carbon or on fluorine have no effect on the computed torsional angles. There is no problem in computing the correct dihedral angles with the CI or CN derivatives.

  12. Multilingual Affordances in a Swedish Preschool: An Action Research Project

    ERIC Educational Resources Information Center

    Ljunggren, Åsa

    2016-01-01

    This article summarizes the work and the main findings of an action research project that was conducted in an early childhood education and care setting in the city of Malmö, Sweden in the autumn of 2013 and spring 2014. Rönnerman's model (Aktionsforskning i praktiken: förskola och skola på vetenskaplig grund [Action research in practice:…

  13. Theoretical spectroscopic characterization at low temperatures of S-methyl thioformate and O-methyl thioformate.

    PubMed

    Senent, M L; Puzzarini, C; Hochlaf, M; Domínguez-Gómez, R; Carvajal, M

    2014-09-14

    Highly correlated ab initio methods are employed to determine spectroscopic properties at low temperatures of two S-analogs of methyl formate: S-methyl thioformate CH3-S-CHO (MSCHO) and O-methyl thioformate CH3-O-CHS (MOCHS). Both species are detectable and they are expected to play an important role in Astrochemistry. Molecular properties are compared with those of the O-analog, methyl formate. Both isomers present two conformers cis and trans. cis-CH3-S-CHO represents the most stable structure lying 4372.2 cm(-1) below cis-CH3-O-CHS. The energy difference between the cis and trans forms is drastically lower for MSCHO (1134 cm(-1)) than for MOCHS (1963.6 cm(-1)). Harmonic and anharmonic fundamentals and the corresponding intensities, as well as the rotational constants for the ground vibrational and first excited torsional states and the centrifugal distortions constants, are provided. Low torsional energy levels have been obtained by solving variationally a two dimensional Hamiltonian expressed in terms of the two torsional degrees of freedom. The corresponding 2D potential energy surfaces have been computed at the CCSD(T)/aug-cc-pVTZ level of theory. The methyl torsional barriers V3(cis) are determined to be 139.7 cm(-1) (CH3-S-CHO) and 670.4 cm(-1) (CH3-O-CHS). The A/E splitting of ground torsional state has been estimated to be 0.438 cm(-1) for CH3-S-CHO and negligible for CH3-O-CHS.

  14. Theoretical spectroscopic characterization at low temperatures of S-methyl thioformate and O-methyl thioformate.

    PubMed

    Senent, M L; Puzzarini, C; Hochlaf, M; Domínguez-Gómez, R; Carvajal, M

    2014-09-14

    Highly correlated ab initio methods are employed to determine spectroscopic properties at low temperatures of two S-analogs of methyl formate: S-methyl thioformate CH3-S-CHO (MSCHO) and O-methyl thioformate CH3-O-CHS (MOCHS). Both species are detectable and they are expected to play an important role in Astrochemistry. Molecular properties are compared with those of the O-analog, methyl formate. Both isomers present two conformers cis and trans. cis-CH3-S-CHO represents the most stable structure lying 4372.2 cm(-1) below cis-CH3-O-CHS. The energy difference between the cis and trans forms is drastically lower for MSCHO (1134 cm(-1)) than for MOCHS (1963.6 cm(-1)). Harmonic and anharmonic fundamentals and the corresponding intensities, as well as the rotational constants for the ground vibrational and first excited torsional states and the centrifugal distortions constants, are provided. Low torsional energy levels have been obtained by solving variationally a two dimensional Hamiltonian expressed in terms of the two torsional degrees of freedom. The corresponding 2D potential energy surfaces have been computed at the CCSD(T)/aug-cc-pVTZ level of theory. The methyl torsional barriers V3(cis) are determined to be 139.7 cm(-1) (CH3-S-CHO) and 670.4 cm(-1) (CH3-O-CHS). The A/E splitting of ground torsional state has been estimated to be 0.438 cm(-1) for CH3-S-CHO and negligible for CH3-O-CHS. PMID:25217912

  15. Theoretical spectroscopic characterization at low temperatures of S-methyl thioformate and O-methyl thioformate

    SciTech Connect

    Senent, M. L.; Puzzarini, C.; Hochlaf, M.; Domínguez-Gómez, R.; Carvajal, M.

    2014-09-14

    Highly correlated ab initio methods are employed to determine spectroscopic properties at low temperatures of two S-analogs of methyl formate: S-methyl thioformate CH{sub 3}-S-CHO (MSCHO) and O-methyl thioformate CH{sub 3}-O-CHS (MOCHS). Both species are detectable and they are expected to play an important role in Astrochemistry. Molecular properties are compared with those of the O-analog, methyl formate. Both isomers present two conformers cis and trans. cis-CH{sub 3}-S-CHO represents the most stable structure lying 4372.2 cm{sup −1} below cis-CH{sub 3}-O-CHS. The energy difference between the cis and trans forms is drastically lower for MSCHO (1134 cm{sup −1}) than for MOCHS (1963.6 cm{sup −1}). Harmonic and anharmonic fundamentals and the corresponding intensities, as well as the rotational constants for the ground vibrational and first excited torsional states and the centrifugal distortions constants, are provided. Low torsional energy levels have been obtained by solving variationally a two dimensional Hamiltonian expressed in terms of the two torsional degrees of freedom. The corresponding 2D potential energy surfaces have been computed at the CCSD(T)/aug-cc-pVTZ level of theory. The methyl torsional barriers V{sub 3}(cis) are determined to be 139.7 cm{sup −1} (CH{sub 3}-S-CHO) and 670.4 cm{sup −1} (CH{sub 3}-O-CHS). The A/E splitting of ground torsional state has been estimated to be 0.438 cm{sup −1} for CH{sub 3}-S-CHO and negligible for CH{sub 3}-O-CHS.

  16. Influence of molybdenum on the accumulation and composition of the water-soluble polysaccharides of Plantago psyllium

    SciTech Connect

    Lichino, I.P.; Gomanova, M.I.; Milenysheva, L.I.; Yakovlev, A.I.

    1986-07-01

    The authors have studied the dynamics of the accumulation of polysaccharides in flaxseed plantain when it is given a foliar top dressing with molybdenum, and also their monosaccaride composition and physicochemical properties. The amounts of galacturonic acid were determined by potentiometric titration. The results of the investigations permit the conclusions that molybdenum somewhat decreases the amounts of total monosaccaride complex and of galacturonic acid while considerably raising the amount of -OCH/sub 3/.

  17. Photoassisted reduction of molecular oxygen to hydrogen peroxide catalyzed by oxoalkoxomolybdenum(V) porphyrin

    SciTech Connect

    Ledon, H.J.; Bonnet, M.; Galland, D.

    1981-10-07

    Formation of the oxomolybdenum (IV) porphyrin O = M/sub 0//sup IV/(TPP)-OCH/sub 3/(2), by photoinduced hemolysis of the Mo-OCH/sub 3/ bond was confirmed by EPR spectroscopy and spin-trapping experiments. When an oxygen-free benzene solution of 0 = M/sub 0//sup V/(TPP)-OCH/sub 3/(1) was irradiated directly in the cavity of an EPR spectrometer, the intensity of the characteristic nine-line spectra of 1 slowly diminished with time but again was fully restored when the cell was open to air and one drop of methanol was added, confirming the formation of a diamagnetic molybdoporphyrin complex upon irradiation. The reoxidation of O = Mo/sup IV/(TPP)(2) in a benzene-methanol mixture was monitored by uv-visible spectrometry, which showed the reaction to follow strict second-order kinetics. This second dependence on molybdenum suggests a two-electron reduction of molecular oxygen to hydrogen peroxide which was actually identified in separate experiments. In order to evaluate the efficiency and possible uses of the photoreduction of 1, a catalytic cycle was devised by coupling the reactions described. The results of these studies clearly established the ability of molybdenum porphyrins to harvest solar energy to produce reactive intermediates by redox processes.

  18. Co-occurrence of a cerebral cavernous malformation and an orbital cavernous hemangioma in a patient with seizures and visual symptoms: Rare crossroads for vascular malformations

    PubMed Central

    Choudhri, Omar; Feroze, Abdullah H.; Lad, Eleonora M.; Kim, Jonathan W.; Plowey, Edward D.; Karamchandani, Jason R.; Chang, Steven D.

    2014-01-01

    Background: Cerebral cavernous malformations (CCMs) are angiographically occult vascular malformations of the central nervous system. As a result of hemorrhage and mass effect, patients may present with focal neurologic deficits, seizures, and other symptoms necessitating treatment. Once symptomatic, most often from hemorrhage, CCMs are treated with microsurgical resection. Orbital cavernous hemangiomas (OCHs) are similar but distinct vascular malformations that present within the orbital cavity. Even though CCMs and OCHs are both marked by dilated endothelial-lined vascular channels, they are infrequently seen in the same patient. Case Description: We provide a brief overview of the two related pathologies in the context of a patient presenting to our care with concomitant lesions, which were both resected in full without complication. Conclusion: This is the first known report that describes a case of concomitant CCM and OCH and explores the origins of two pathologies that are rarely encountered together in neurosurgical practice. Recognition of disparate symptomatologies is important for properly managing these patients. PMID:25071938

  19. Cross-conjugated hexaphyrins and their bis-rhodium complexes.

    PubMed

    Naoda, Koji; Sung, Young Mo; Lim, Jong Min; Kim, Dongho; Osuka, Atsuhiro

    2014-06-16

    A cross-conjugated hexaphyrin that carries two meso-oxacyclohexadienylidenyl (OCH) groups 9 was synthesized from the condensation of 5,10-bis(pentafluorophenyl)tripyrrane with 3,5-di-tert-butyl-4-hydroxybenzaldehyde. The reduction of 9 with NaBH4 afforded the Möbius aromatic [28]hexaphyrin 10. Bis-rhodium complex 11, prepared from the reaction of 10 with [{RhCl(CO)2}2], displays strong Hückel antiaromatic character because of the 28 π electrons that occupy the conjugated circuit on the enforced planar structure. The oxidation of 11 with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) yielded complexes 12 and 13 depending upon the reaction conditions. Both 12 and 13 are planar owing to bis-rhodium metalation. Although complex 12 bears two meso-OCH groups at the long sides and is quinonoidal and nonaromatic in nature, complex 13 bears 3,5-di-tert-butyl-4-hydroxyphenyl and OCH groups and exhibits a moderate diatropic ring current despite its cross-conjugated electronic circuit. The diatropic ring current increases upon increasing the solvent polarity, most likely due to an increased contribution of an aromatic zwitterionic resonance hybrid. PMID:24805261

  20. Photoelectron velocity-map imaging spectroscopic and theoretical study on the reactivity of the gold atom toward CH3SH, CH3OH, and H2O.

    PubMed

    Qin, Zhengbo; Cong, Ran; Wu, Xia; Liu, Zhiling; Xie, Hua; Tang, Zichao; Jiang, Ling; Fan, Hongjun

    2013-07-21

    Photoelectron velocity-map imaging spectroscopy has been used to study the reaction of the anionic gold atom with the HR (R = SCH3, OCH3, OH) molecules. The solvated [Au···HR](-) and inserted [HAuR](-) products have been experimentally observed for R = SCH3, whereas only solvated [Au⋯HR](-) products were found for R = OCH3 and OH. This significant difference in the photoelectron spectra suggests the different reactivity of the Au(-) toward the CH3SH, CH3OH, and H2O molecules. Second order Møller-Plesset perturbation theory and coupled-cluster single double triple excitation calculations have been performed to aid the structural assignment of the spectra and to explore the reaction mechanism. Activation energies for the isomerizations of the solvated structures to the inserted ones in the Au(-)∕Au + HR reactions (R = OCH3 and OH) are predicted to be much higher than those for the Au(-)∕Au + CH3SH reactions, supporting the experimental observation. Theoretical calculations provide the evidence that the intriguing [HAuSCH3](-) product may be formed by the attachment of the electron onto the neutral HAuSCH3 species or the isomerization from the anionic [Au···HSCH3](-) one. These findings should be helpful for understanding the feature that the thiols are able to form the staple motifs, whereas CH3OH and H2O are not.

  1. Synthesis and characterisation of new types of side chain cholesteryl polymers.

    PubMed

    Wang, Bin; Du, Haiyan; Zhang, Junhua

    2011-01-01

    A series of cholesterol derivatives have been synthesised via the alkylation reaction of the 3-hydroxyl group with the aliphatic bromide compounds with different chain lengths, namely 3β-alkyloxy-cholesterol. The double bond between the C5 and C6 positions in these cholesterol derivatives was oxidised into epoxy, followed by an epoxy-ring-opening reaction with the treatment with acrylic acid, resulting in a series of 3β-alkyloxy-5α-hydroxy-6β-acryloyloxycholesterol, C(n)OCh (n=1, 2, 4, 6, 8, 10, 12), The acrylate group is connected to the C6 position, which is confirmed by the single crystal structure analysis. The corresponding polymers, PC(n)OCh, were prepared via free radical polymerisation. The structure of monomers and the resulting polymers were characterised with nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). The thermal properties of PC(n)OCh were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). To determine the secondary structure of polymers, circular dichroism (CD) spectra were performed. It was found that not all monomers produce high-molecular-weight polymers because of steric hindrance. However, all polymers have a helical structure, which can be enhanced by increasing the alkoxy chain length. In addition, increasing the alkoxy chain length decreases the glass transition temperature and increases the decomposition temperature of the polymers. PMID:21070795

  2. Methyl-perfluoroheptene-ethers (CH3OC7F13): measured OH radical reaction rate coefficients for several isomers and enantiomers and their atmospheric lifetimes and global warming potentials.

    PubMed

    Jubb, Aaron M; Gierczak, Tomasz; Baasandorj, Munkhbayar; Waterland, Robert L; Burkholder, James B

    2014-05-01

    Mixtures of methyl-perfluoroheptene-ethers (CH3OC7F13, MPHEs) are currently in use as replacements for perfluorinated alkanes (PFCs) and poly-ether heat transfer fluids, which are persistent greenhouse gases with lifetimes >1000 years. At present, the atmospheric processing and environmental impact from the use of MPHEs is unknown. In this work, rate coefficients at 296 K for the gas-phase reaction of the OH radical with six key isomers (including stereoisomers and enantiomers) of MPHEs used commercially were measured using a relative rate method. Rate coefficients for the six MPHE isomers ranged from ∼ 0.1 to 2.9 × 10(-12) cm(3) molecule(-1) s(-1) with a strong stereoisomer and -OCH3 group position dependence; the (E)-stereoisomers with the -OCH3 group in an α- position relative to the double bond had the greatest reactivity. Rate coefficients measured for the d3-MPHE isomer analogues showed decreased reactivity consistent with a minor contribution of H atom abstraction from the -OCH3 group to the overall reactivity. Estimated atmospheric lifetimes for the MPHE isomers range from days to months. Atmospheric lifetimes, radiative efficiencies, and global warming potentials for these short-lived MPHE isomers were estimated based on the measured OH rate coefficients along with measured and theoretically calculated MPHE infrared absorption spectra. Our results highlight the importance of quantifying the atmospheric impact of individual components in an isomeric mixture.

  3. Solid Electrolyte Interphase Growth and Capacity Loss in Silicon Electrodes.

    PubMed

    Michan, Alison L; Divitini, Giorgio; Pell, Andrew J; Leskes, Michal; Ducati, Caterina; Grey, Clare P

    2016-06-29

    The solid electrolyte interphase (SEI) of the high capacity anode material Si is monitored over multiple electrochemical cycles by (7)Li, (19)F, and (13)C solid-state nuclear magnetic resonance spectroscopies, with the organics dominating the SEI. Homonuclear correlation experiments are used to identify the organic fragments -OCH2CH2O-, -OCH2CH2-, -OCH2CH3, and -CH2CH3 contained in both oligomeric species and lithium semicarbonates ROCO2Li, RCO2Li. The SEI growth is correlated with increasing electrode tortuosity by using focused ion beam and scanning electron microscopy. A two-stage model for lithiation capacity loss is developed: initially, the lithiation capacity steadily decreases, Li(+) is irreversibly consumed at a steady rate, and pronounced SEI growth is seen. Later, below 50% of the initial lithiation capacity, less Si is (de)lithiated resulting in less volume expansion and contraction; the rate of Li(+) being irreversibly consumed declines, and the Si SEI thickness stabilizes. The decreasing lithiation capacity is primarily attributed to kinetics, the increased electrode tortuousity severely limiting Li(+) ion diffusion through the bulk of the electrode. The resulting changes in the lithiation processes seen in the electrochemical capacity curves are ascribed to non-uniform lithiation, the reaction commencing near the separator/on the surface of the particles.

  4. Duplex stabilities of phosphorothioate, methylphosphonate, and RNA analogs of two DNA 14-mers.

    PubMed Central

    Kibler-Herzog, L; Zon, G; Uznanski, B; Whittier, G; Wilson, W D

    1991-01-01

    The duplex stabilities of various phosphorothioate, methylphosphonate, RNA and 2'-OCH3 RNA analogs of two self-complementary DNA 14-mers are compared. Phosphorothioate and/or methylphosphonate analogs of the two sequences d(TAATTAATTAATTA) [D1] and d(TAGCTAATTAGCTA) [D2] differ in the number, position, or chirality (at the 5' terminal linkage) of the modified phosphates. Phosphorothioate derivatives of D1 are found to be less destabilized when the linkage modified is between adenines rather than between thymines. Surprisingly, no base sequence effect on duplex stabilization is observed for any methylphosphonate derivatives of D1 or D2. Highly modified phosphorothioates or methylphosphonates are less stable than their partially modified counterparts which are less stable than the unmodified parent compounds. The 'normal' (2'-OH) RNA analog of duplex D1 is slightly destabilized, whereas the 2'-OCH3 RNA derivative is significantly stabilized relative to the unmodified DNA. For the D1 sequence, at approximately physiological salt concentration, the order of duplex stability is 2'-OCH3 RNA greater than unmodified DNA greater than 'normal' RNA greater than methylphosphonate DNA greater than phosphorothioate DNA. D2 and the various D2 methylphosphonate analogs investigated all formed hairpin conformations at low salt concentrations. PMID:1711677

  5. Synthesis and characterisation of new types of side chain cholesteryl polymers.

    PubMed

    Wang, Bin; Du, Haiyan; Zhang, Junhua

    2011-01-01

    A series of cholesterol derivatives have been synthesised via the alkylation reaction of the 3-hydroxyl group with the aliphatic bromide compounds with different chain lengths, namely 3β-alkyloxy-cholesterol. The double bond between the C5 and C6 positions in these cholesterol derivatives was oxidised into epoxy, followed by an epoxy-ring-opening reaction with the treatment with acrylic acid, resulting in a series of 3β-alkyloxy-5α-hydroxy-6β-acryloyloxycholesterol, C(n)OCh (n=1, 2, 4, 6, 8, 10, 12), The acrylate group is connected to the C6 position, which is confirmed by the single crystal structure analysis. The corresponding polymers, PC(n)OCh, were prepared via free radical polymerisation. The structure of monomers and the resulting polymers were characterised with nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). The thermal properties of PC(n)OCh were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). To determine the secondary structure of polymers, circular dichroism (CD) spectra were performed. It was found that not all monomers produce high-molecular-weight polymers because of steric hindrance. However, all polymers have a helical structure, which can be enhanced by increasing the alkoxy chain length. In addition, increasing the alkoxy chain length decreases the glass transition temperature and increases the decomposition temperature of the polymers.

  6. Substituent effects on hydrogen bonding of aromatic amide-carboxylate.

    PubMed

    Sen, Ibrahim; Kara, Hulya; Azizoglu, Akın

    2016-10-01

    N-(p-benzoyl)-anthranilic acid (BAA) derivatives have been synthesized with different substituents (X: Br, Cl, OCH3, CH3), and their crystal structures have been analyzed in order to understand the variations in their molecular geometries with respect to the substituents by using (1)H NMR, (13)C NMR, IR and X-ray single-crystal diffraction. The carboxylic acid group forms classic OH⋯O hydrogen bonded dimers in a centrosymmetric R2(2)(8) ring motifs for BAA-Br and BAA-Cl. However, no carboxylic acid group forms classic OH⋯O hydrogen bonded dimers in BAA-OCH3 and BAA-CH3. The asymmetric unit consists of two crystallographically independent molecules in BAA-OCH3. DFT computations show that the interaction energies between monomer and dimer are in the range of 0.5-3.8kcal/mol with the B3LYP/6-31+G*, B3LYP/6-31++G*, B3LYP/6-31++G**, and B3LYP/AUG-cc-pVDZ levels of theory. The presence of different hydrogen bond patterns is also governed by the substrate. For monomeric compounds studied herein, theoretical calculations lead to two low-energy conformers; trans (a) and cis (b). Former one is more stable than latter by about 4kcal/mol. PMID:27239947

  7. Solid Electrolyte Interphase Growth and Capacity Loss in Silicon Electrodes.

    PubMed

    Michan, Alison L; Divitini, Giorgio; Pell, Andrew J; Leskes, Michal; Ducati, Caterina; Grey, Clare P

    2016-06-29

    The solid electrolyte interphase (SEI) of the high capacity anode material Si is monitored over multiple electrochemical cycles by (7)Li, (19)F, and (13)C solid-state nuclear magnetic resonance spectroscopies, with the organics dominating the SEI. Homonuclear correlation experiments are used to identify the organic fragments -OCH2CH2O-, -OCH2CH2-, -OCH2CH3, and -CH2CH3 contained in both oligomeric species and lithium semicarbonates ROCO2Li, RCO2Li. The SEI growth is correlated with increasing electrode tortuosity by using focused ion beam and scanning electron microscopy. A two-stage model for lithiation capacity loss is developed: initially, the lithiation capacity steadily decreases, Li(+) is irreversibly consumed at a steady rate, and pronounced SEI growth is seen. Later, below 50% of the initial lithiation capacity, less Si is (de)lithiated resulting in less volume expansion and contraction; the rate of Li(+) being irreversibly consumed declines, and the Si SEI thickness stabilizes. The decreasing lithiation capacity is primarily attributed to kinetics, the increased electrode tortuousity severely limiting Li(+) ion diffusion through the bulk of the electrode. The resulting changes in the lithiation processes seen in the electrochemical capacity curves are ascribed to non-uniform lithiation, the reaction commencing near the separator/on the surface of the particles. PMID:27232540

  8. Fluorine in drug design: a case study with fluoroanisoles.

    PubMed

    Xing, Li; Blakemore, David C; Narayanan, Arjun; Unwalla, Ray; Lovering, Frank; Denny, R Aldrin; Zhou, Huanyu; Bunnage, Mark E

    2015-04-01

    Anisole and fluoroanisoles display distinct conformational preferences, as evident from a survey of their crystal structures. In addition to altering the free ligand conformation, various degrees of fluorination have a strong impact on physicochemical and pharmacokinetic properties. Analysis of anisole and fluoroanisole matched molecular pairs in the Pfizer corporate database reveals interesting trends: 1) PhOCF3 increases log D by ~1 log unit over PhOCH3 compounds; 2) PhOCF3 shows lower passive permeability despite its higher lipophilicity; and 3) PhOCF3 does not appreciably improve metabolic stability over PhOCH3 . Emerging from the investigation, difluoroanisole (PhOCF2 H) strikes a better balance of properties with noticeable advantages of log D and transcellular permeability over PhOCF3 . Synthetic assessment illustrates that the routes to access difluoroanisoles are often more straightforward than those for trifluoroanisoles. Whereas replacing PhOCH3 with PhOCF3 is a common tactic to optimize ADME properties, our analysis suggests PhOCF2 H may be a more attractive alternative, and greater exploitation of this motif is recommended.

  9. Substituent effects on hydrogen bonding of aromatic amide-carboxylate

    NASA Astrophysics Data System (ADS)

    Sen, Ibrahim; Kara, Hulya; Azizoglu, Akın

    2016-10-01

    N-(p-benzoyl)-anthranilic acid (BAA) derivatives have been synthesized with different substituents (X: Br, Cl, OCH3, CH3), and their crystal structures have been analyzed in order to understand the variations in their molecular geometries with respect to the substituents by using 1H NMR, 13C NMR, IR and X-ray single-crystal diffraction. The carboxylic acid group forms classic Osbnd H ⋯ O hydrogen bonded dimers in a centrosymmetric R22(8) ring motifs for BAA-Br and BAA-Cl. However, no carboxylic acid group forms classic Osbnd H ⋯ O hydrogen bonded dimers in BAA-OCH3 and BAA-CH3. The asymmetric unit consists of two crystallographically independent molecules in BAA-OCH3. DFT computations show that the interaction energies between monomer and dimer are in the range of 0.5-3.8 kcal/mol with the B3LYP/6-31 + G*, B3LYP/6-31 ++G*, B3LYP/6-31 ++G**, and B3LYP/AUG-cc-pVDZ levels of theory. The presence of different hydrogen bond patterns is also governed by the substrate. For monomeric compounds studied herein, theoretical calculations lead to two low-energy conformers; trans (a) and cis (b). Former one is more stable than latter by about 4 kcal/mol.

  10. Saccharomyces Cerevisiae Hoc1, a Suppressor of Pkc1, Encodes a Putative Glycosyltransferase

    PubMed Central

    Neiman, A. M.; Mhaiskar, V.; Manus, V.; Galibert, F.; Dean, N.

    1997-01-01

    The Saccharomyces cerevisiae gene PKC1 encodes a protein kinase C isozyme that regulates cell wall synthesis. Here we describe the characterization of HOC1, a gene identified by its ability to suppress the cell lysis phenotype of pkc1-371 cells. The HOC1 gene (Homologous to OCH1) is predicted to encode a type II integral membrane protein that strongly resembles Och1p, an α-1,6-mannosyltransferase. Immunofluorescence studies localized Hoc1p to the Golgi apparatus. While overexpression of HOC1 rescued the pkc1-371 temperature-sensitive cell lysis phenotype, disruption of HOC1 lowered the restrictive temperature of the pkc1-371 allele. Disruption of HOC1 also resulted in hypersensitivity to Calcofluor White and hygromycin B, phenotypes characteristic of defects in cell wall integrity and protein glycosylation, respectively. The function of HOC1 appears to be distinct from that of OCH1. Taken together, these results suggest that HOC1 encodes a Golgi-localized putative mannosyltransferase required for the proper construction of the cell wall. PMID:9055074

  11. Comments on the ring-opening polymerization of morpholine-2,5-dione derivatives by various metal catalysts and characterization of the products formed in the reactions involving R2SnX2, where X = OPr(i) and NMe2 and R = Bu(n), Ph and p-Me2NC6H4.

    PubMed

    Chisholm, M H; Galucci, J; Krempner, C; Wiggenhorn, C

    2006-02-14

    (3S,6S)-3-Isopropyl-6-methyl-morpholine-2,5-dione (1), and (3S,6S)-3,6-dimethyl-morpholine-2,5-dione (2), do not enter into ring-opening polymerization reactions with metal catalyst precursors commonly employed for lactides, and with Sn(II) octanoate, only low molecular weight oligomers are obtained. Reactions with R2SnX2 compounds, where R = Ph, Bu(n) and p-Me2NC6H4 and X = OPr(i) or NMe2, reveal that ring-opening of the morpholine-2,5-diones does occur, but that polymerization is terminated by the formation of kinetically-inert products such as {Ph2Sn[mu,eta(3)-OCH(Me)CONCH(Pr(i))COOPr(i)]}2 (3), and {[Bu(n))2Sn[mu,eta(3)-OCH(Me)CONCH(Me)CONMe2]}2 (4), with elimination of HX. Ph3SnOPr(i) is seen to react reversibly with morpholine-2,5-diones in toluene-d8 by 1H NMR spectroscopy while (Bu(n))3SnNMe2 reacts by ring opening to give (Bu(n))3SnOCH(Me)C(O)NHCHMeC(O)NMe2. The new organotin compounds have been characterized by 1H, 13C{1H} and 118Sn NMR spectroscopy and compounds 1, 2, 3 and 4 by single crystal X-ray crystallography.

  12. [Dependence of the operation stress degree from the kind of operative intervention for an acute cholecystitis in the patients with high operative-anesthesiological risk].

    PubMed

    Bezruchko, M V; Malyk, S V; Kravchenko, S P; Osipov, O S; Sytnik, D A

    2013-03-01

    The results of comparison between the operation stress degree in various kinds of surgical interventions, performed for an acute cholecystitis, using determination of cortizol, prolactin and glucose content before the operation, intraoperatively and postoperatively in 50 patients, are adduced. There was established, that the largest (in 5.3 times) and the most durable (more than 24 hours) intr erative raising of the cortizol level in the blood serum was noted in patients, to whom open cholecystectomy (OCH) was done, and the minimal (in 2.2 times) and the least durable (up to 1 hour)--while performing transcutaneous transhepatic draining (TTD) of gallbladder under ultrasonographic control. While performance of laparoscopic cholecystectomy (LCH) there was noted the most pronounced intraoperative raising of prolactin level (in 3.6 times) and more rapid its lowering (during 24 hours) in comparison with such while the OCH performance (during 72 hours). In TTD there was observed the minimal intraoperative inhancing of the prolactin level (in 2.3 times) and its duration (during 1 hour) postoperatively. The above mentioned have witnessed, that while TTD of gallbladder performance stimulation of the anterior hypophysis is significantly lesser, than while LCH and OCH.

  13. Preparation and characterization of oligochitosan-tragacanth nanoparticles as a novel gene carrier.

    PubMed

    Fattahi, Ali; Sadrjavadi, Komail; Golozar, Mohammad Ali; Varshosaz, Jaleh; Fathi, Mohammad-Hossein; Mirmohammad-Sadeghi, Hamid

    2013-09-12

    The nanoparticles of oligochitosan-water soluble tragacanth (OCH-WST) as novel gene carriers have been prepared and their transfection efficiency has been investigated on Hela and HepG2 cell lines. Different OCH:WST weight ratios were prepared to obtain particles with low size distribution and high surface charge, and also in range of below 200 nm. Nanoparticles with 132.5 ± 6.77 nm size, polydispersity index 1.92 ± 0.061, surface charge 30.45 ± 1.84 and spherical morphology, have been chosen as gene carrier. Nanoparticle-DNA complexes (nanoplexes) showed better transfection efficiency in both Hela and HepG2 cells than chitosan polyplexes, with 1.26 × 10(6) versus 9.05 × 10(5) and 7.76 × 10(5) versus 2.16 × 10(5), respectively. Higher transfection efficiency of nanoplexes could be attributed to their weaker complexation. Decreasing of transfection in presence of galactose in HepG2 cells, indicated receptor mediated endocytosis of nanoplexes. These properties all together, make OCH-WST nanoparticles as potential gene carrier for active gene delivery into cells containing sugar receptors.

  14. Comments on the ring-opening polymerization of morpholine-2,5-dione derivatives by various metal catalysts and characterization of the products formed in the reactions involving R2SnX2, where X = OPr(i) and NMe2 and R = Bu(n), Ph and p-Me2NC6H4.

    PubMed

    Chisholm, M H; Galucci, J; Krempner, C; Wiggenhorn, C

    2006-02-14

    (3S,6S)-3-Isopropyl-6-methyl-morpholine-2,5-dione (1), and (3S,6S)-3,6-dimethyl-morpholine-2,5-dione (2), do not enter into ring-opening polymerization reactions with metal catalyst precursors commonly employed for lactides, and with Sn(II) octanoate, only low molecular weight oligomers are obtained. Reactions with R2SnX2 compounds, where R = Ph, Bu(n) and p-Me2NC6H4 and X = OPr(i) or NMe2, reveal that ring-opening of the morpholine-2,5-diones does occur, but that polymerization is terminated by the formation of kinetically-inert products such as {Ph2Sn[mu,eta(3)-OCH(Me)CONCH(Pr(i))COOPr(i)]}2 (3), and {[Bu(n))2Sn[mu,eta(3)-OCH(Me)CONCH(Me)CONMe2]}2 (4), with elimination of HX. Ph3SnOPr(i) is seen to react reversibly with morpholine-2,5-diones in toluene-d8 by 1H NMR spectroscopy while (Bu(n))3SnNMe2 reacts by ring opening to give (Bu(n))3SnOCH(Me)C(O)NHCHMeC(O)NMe2. The new organotin compounds have been characterized by 1H, 13C{1H} and 118Sn NMR spectroscopy and compounds 1, 2, 3 and 4 by single crystal X-ray crystallography. PMID:16437180

  15. Reactions of Monomeric [1,2,4-(Me3C)3C5H2]2CeH and CO with orwithout H2:An Experimental and Computational Study

    SciTech Connect

    Werkema, Evan L.; Maron, Laurent; Eisenstein, Odile; Andersen,Richard A.

    2006-09-07

    Addition of CO to [1,2,4-(Me3C)3C5H2]2CeH, Cp'2CeH, intoluene yields the cis (Cp'2Ce)2(mu-OCHCHO), in which the cis enediolategroup bridges the two metallocene fragments. The cis enediolatequantitatively isomerizes intramolecularly to the trans-enediolate inC6D6 at 100oC over seven months. When the solvent is pentane,Cp'2Ce(OCH2)CeCp'2 forms, in which the oxomethylene group or theformaldehyde dianion bridges the two metallocene fragments. The cisenediolate is suggested to form by insertion of CO into the Ce-C bond ofCp'2Ce(OCH2)CeCp'2 generating Cp'2CeOCH2COCeCp'2. The stereochemistry ofthe cis-enediolate is determined by a 1,2-hydrogen shift in the OCH2COfragment that has the OC(H2) bond anti periplanar relative to the carbenelone pair. The bridging oxomethylene complex reacts with H2, but not withCH4, to give Cp'2CeOMe, which is also the product of the reaction betweenCp'2CeH and a mixture of CO and H2. The oxomethylene complex reacts withCO to give the cis enediolate complex. DFT calculations on C5H5 modelmetallocenes show that the reaction of Cp2CeH with CO and H2 to giveCp2CeOMe is exoergic by 50 kcal mol-1. The net reaction proceeds by aseries of elementary reactions that occur after the formyl complex,Cp2Ce(eta-2 CHO), is formed by further reaction with H2. The key pointthat emerges from the calculated potential energy surface is thebifunctional nature of the metal formyl in which the carbon atom behavesas a donor and acceptor. Replacing H2 by CH4 increases the activationenergy barrier by 17 kcal mol-1.

  16. Direct Formation of the C5′-Radical in the Sugar-Phosphate Backbone of DNA by High Energy Radiation

    PubMed Central

    Adhikary, Amitava; Becker, David; Palmer, Brian J.; Heizer, Alicia N.; Sevilla, Michael D.

    2012-01-01

    Neutral sugar radicals formed in DNA sugar-phosphate backbone are well-established as precursors of biologically important damage such as DNA-strand scission and crosslinking. In this work, we present electron spin resonance (ESR) evidence showing that the sugar radical at C5′ (C5′•) is one of the most abundant (ca. 30%) sugar radicals formed by γ- and Ar ion-beam irradiated hydrated DNA samples. Taking dimethyl phosphate as a model of sugar-phosphate backbone, ESR and theoretical (DFT) studies of γ-irradiated dimethyl phosphate were carried out. CH3OP(O2−)OCH2• is formed via deprotonation from the methyl group of directly ionized dimethyl phosphate at 77 K. Formation of CH3OP(O2−)OCH2• is independent of dimethyl phosphate concentration (neat or in aqueous solution) or pH. ESR spectra of C5′• found in DNA and of CH3OP(O2−)OCH2• do not show an observable β-phosphorous hyperfine coupling (HFC). Further, C5′• found in DNA does not show a significant C4′-H β–proton HFC. Applying the DFT/B3LYP/6-31G(d) method, a study of conformational dependence of the phosphorous HFC in CH3OP(O2−)OCH2• shows that in its minimum energy conformation, CH3OP(O2−)OCH2• has a negligible β-phosphorous HFC. Based on these results, formation of radiation-induced C5′• is proposed to occur via a very rapid deprotonation from the directly ionized sugar-phosphate backbone and rate of this deprotonation must be faster than that of energetically downhill transfer of the unpaired spin (hole) from ionized sugar-phosphate backbone to the DNA bases. Moreover, C5′• in irradiated DNA is found to be in a conformation that does not exhibit β proton or β phosphorous HFCs. PMID:22553971

  17. High temperature shock tube and theoretical studies on the thermal decomposition of dimethyl carbonate and its bimolecular reactions with H and D-atoms.

    PubMed

    Peukert, S L; Sivaramakrishnan, R; Michael, J V

    2013-05-01

    The shock tube technique was used to study the high temperature thermal decomposition of dimethyl carbonate, CH3OC(O)OCH3 (DMC). The formation of H-atoms was measured behind reflected shock waves by using atomic resonance absorption spectrometry (ARAS). The experiments span a T-range of 1053-1157 K at pressures ∼0.5 atm. The H-atom profiles were simulated using a detailed chemical kinetic mechanism for DMC thermal decomposition. Simulations indicate that the formation of H-atoms is sensitive to the rate constants for the energetically lowest-lying bond fission channel, CH3OC(O)OCH3 → CH3 + CH3OC(O)O [A], where H-atoms form instantaneously at high temperatures from the sequence of radical β-scissions, CH3OC(O)O → CH3O + CO2 → H + CH2O + CO2. A master equation analysis was performed using CCSD(T)/cc-pv∞z//M06-2X/cc-pvtz energetics and molecular properties for all thermal decomposition processes in DMC. The theoretical predictions were found to be in good agreement with the present experimentally derived rate constants for the bond fission channel (A). The theoretically derived rate constants for this important bond-fission process in DMC can be represented by a modified Arrhenius expression at 0.5 atm over the T-range 1000-2000 K as, kA(T) = 6.85 × 10(98)T (-24.239) exp(-65250 K/T) s(-1). The H-atom temporal profiles at long times show only minor sensitivity to the abstraction reaction, H + CH3OC(O)OCH3 → H2 + CH3OC(O)OCH2 [B]. However, H + DMC is an important fuel destruction reaction at high temperatures. Consequently, measurements of D-atom profiles using D-ARAS allowed unambiguous rate constant measurements for the deuterated analog of reaction B, D + CH3OC(O)OCH3 → HD + CH3OC(O)OCH2 [C]. Reaction C is a surrogate for H + DMC since the theoretically predicted kinetic isotope effect at high temperatures (1000 - 2000K) is close to unity, kC ≈ 1.2 kB. TST calculations employing CCSD(T)/cc-pv∞z//M06-2X/cc-pvtz energetics and molecular properties

  18. On the structural and electronic considerations concerning the reactivity of metal-metal multiple bonds

    NASA Astrophysics Data System (ADS)

    Glasgow, Katherine Campbell

    2000-10-01

    The previously known compound W2(OCH2tBu) 6(py)2 is crystallographically characterized. Its solid state structure is described and compared with other M2(OR)6L 2 complexes. Upon treatment with isoprene, the complex W2(OCH 2tBu)6(py)(mu-isoprene) forms. The solid state structure is disordered with respect to the orientation of the diene; two different configurations are seen in the crystal structure. These two isomers are in equilibrium in solution and are visible by 1H NMR spectroscopy. Multidimensional NMR experiments are used to assign the structures of the two isomers in solution. Through the use of spin magnetization transfer, it has been determined that the two isomers interconvert through the loss of isoprene. The DeltaH° and DeltaS° values for the equilibrium are determined. The starting material W2(OCH2tBu) 6(py)2 had been previously determined to be an olefin hydrogenation catalyst. It has been determined that cyclic olefins are hydrogenated in a cis manner, and a kinetic isotope effect of 1.7 has been measured. It has been determined that olefins which form isolable adducts with W 2(OCH2tBu)6(py)2, such as isoprene, undergo hydrogenation at approximately the same rate as olefins which do not show evidence of adduct formation. The complex W2(OCH2tBu)6(py) 2had been found to couple aldehydes and ketones stoichiometrically to give olefins. The reaction was found to proceed in a stepwise manner through the alkylidene intermediate W2(OCH2tBu) 6(py)(O)(mu-CHR), allowing the selective cross coupling of aldehydes and ketones. More studies have been undertaken to help determine the scope of the reaction. Competition experiments have been performed to determine reaction preferences. Unsaturated and functionalized aldehydes have been studied to determine the tolerance of the reaction to certain chemical groups. The role of pyridine in this reaction has been studied, especially concerning its reactivity with the alkylidene intermediate. The dimetal tetracarboxylate

  19. Exploring the intrinsic polar [4+2(+)] cycloaddition reactivity of gaseous carbosulfonium and carboxonium ions.

    PubMed

    Basher, Muftah M; Corilo, Yuri E; Sparrapan, Regina; Benassi, Mario; Augusti, Rodinei; Eberlin, Marcos N; Riveros, José M

    2012-11-01

    Gas-phase reactions of model carbosulfonium ions (CH(3)-S(+)=CH(2;) CH(3)CH(2)-S(+)=CH(2) and Ph-S(+)=CH(2)) and an O-analogue carboxonium ion (CH(3)-O(+)=CH(2)) with acyclic (isoprene, 1,3-butadiene, methyl vinyl ketone) and cyclic (1,3-cyclohexadiene, thiophene, furan) conjugated dienes were systematically investigated by pentaquadrupole mass spectrometry. As corroborated by B3LYP/6-311 G(d,p) calculations, the carbosulfonium ions first react at large extents with the dienes forming adducts via simple addition. The nascent adducts, depending on their stability and internal energy, react further via two competitive channels: (1) in reactions with acyclic dienes via cyclization that yields formally [4+2(+)] cycloadducts, or (2) in reactions with the cyclic dienes via dissociation by HSR loss that yields methylenation (net CH(+) transfer) products. In great contrast to its S-analogues, CH(3)-O(+)=CH(2) (as well as C(2)H(5)-O(+)=CH(2) and Ph-O(+)=CH(2) in reactions with isoprene) forms little or no adduct and proton transfer is the dominant reaction channel. Isomerization to more acidic protonated aldehydes in the course of reaction seems to be the most plausible cause of the contrasting reactivity of carboxonium ions. The CH(2)=CH-O(+)=CH(2) ion forms an abundant [4+2(+)] cycloadduct with isoprene, but similar to the behavior of such α,β-unsaturated carboxonium ions in solution, seems to occur across the C=C bond. PMID:23147832

  20. Searching for trans ethyl methyl ether in Orion KL★,★★

    PubMed Central

    Tercero, B.; Cernicharo, J.; López, A.; Brouillet, N.; Kolesniková, L.; Motiyenko, R. A.; Margulès, L.; Alonso, J. L.; Guillemin, J.-C.

    2015-01-01

    We report on the tentative detection of trans ethyl methyl ether (tEME), t-CH3CH2OCH3, through the identification of a large number of rotational lines from each one of the spin states of the molecule towards Orion KL. We also search for gauche-trans-n-propanol, Gt-n-CH3CH2CH2OH, an isomer of tEME in the same source. We have identified lines of both species in the IRAM 30 m line survey and in the ALMA Science Verification data. We have obtained ALMA maps to establish the spatial distribution of these species. Whereas tEME mainly arises from the compact ridge component of Orion, Gt-n-propanol appears at the emission peak of ethanol (south hot core). The derived column densities of these species at the location of their emission peaks are ≤(4.0 ± 0.8) × 1015 cm−2 and ≤(1.0 ± 0.2)× 1015 cm−2 for tEME and Gt-n-propanol, respectively. The rotational temperature is ~100 K for both molecules. We also provide maps of CH3OCOH, CH3CH2OCOH, CH3OCH3, CH3OH, and CH3CH2OH to compare the distribution of these organic saturated O-bearing species containing methyl and ethyl groups in this region. Abundance ratios of related species and upper limits to the abundances of non-detected ethers are provided. We derive an abundance ratio N(CH3OCH3)/N(tEME) ≥ 150 in the compact ridge of Orion. PMID:26869726

  1. Intracluster ion-molecule reactions of Ti+ with ether clusters

    NASA Astrophysics Data System (ADS)

    Koo, Young-Mi; Kim, Min-Kyung; Jung, Kwang-Woo

    2005-05-01

    The intracluster ion-molecule reactions of Ti+(CH3OR)n (R = CH3, n-C3H7, n-C4H9, t-C4H9) complexes produced by the mixing of laser-vaporized plasmas and pulsed supersonic beams were investigated using a reflectron time-of-flight mass spectrometer (RTOFMS). The reactions of Ti+ with dimethyl ether clusters were found to be dominated by the CH3 elimination reaction, which produces Ti+(OCH3)m(CH3OCH3)n clusters (m = 1-3). The mass spectra resulting from the reactions of Ti+ with the other ether clusters indicate the formation of major sequences of heterocluster ions with the formula Ti+(OCH3)x(OR)y(CH3OR)n, where x = 1-3 and y = 0-2. These sequences are attributed to the insertion of Ti+ ions into the CO bonds of the ether molecules within the heteroclusters, followed by alkyl radical elimination. The prevalence of radical elimination of longer alkyl groups rather than of CH3 radicals suggests that R elimination from the [CH3OTi+R] intermediate is the preferred decomposition pathway after the selective insertion of a Ti+ ion into the CO bond of an OR group. Our results also indicate that consecutive insertions of a Ti+ ion can occur for up to three precursor molecules. The experiments also show that the molecular eliminations of H2 and alkanes, resulting from CH and CC bond insertion, respectively, play an increasingly important role as the size of the alkyl group (R) in the ether molecule increases. The reaction energetics and the formation mechanisms of the observed heterocluster ions are also discussed.

  2. Kinetics of the degradation of sulfur mustard on ambient and moist concrete.

    PubMed

    Brevett, Carol A S; Sumpter, Kenneth B; Nickol, Robert G

    2009-02-15

    The rate of degradation of the chemical warfare agent sulfur mustard, bis(2-chloroethyl) sulfide, was measured on ambient and moist concrete using (13)C Solid State Magic Angle Spinning Nuclear Magnetic Resonance (SSMAS NMR). Three samples of concrete made by the same formulation, but differing in age and alkalinity were used. The sulfur mustard eventually degraded to thiodiglycol and 1,4-oxathiane via the intermediate sulfonium ions CH-TG, H-TG, H-2TG and O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH on all of the concrete samples, and in addition formed 8-31% vinyl moieties on the newer, more alkaline concrete samples. This is the first observation of the formation of O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH on a solid substrate. The addition of 2-chloroethanol to concrete on which mustard had fully degraded to thiodiglycol and 1,4-oxathiane resulted in the formation of O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH, thus demonstrating the reversibility of sulfur mustard degradation pathways. The sulfur mustard degradation half-lives on ambient concrete at 22 degrees C ranged from 3.5 to 54 weeks. When the substrates were moistened, the degradation half-lives at 22 degrees C ranged from 75 to 350h. The degradation of sulfur mustard occurred more quickly at elevated temperatures and with added water. The non-volatile toxic sulfonium ions persisted for months to years on concrete at 22 degrees C and weeks to months on concrete at 35 degrees C, before decomposing to the relatively non-toxic compounds thiodiglycol and 1,4-oxathiane. PMID:18584953

  3. Phospholipase C and myosin light chain kinase inhibition define a common step in actin regulation during cytokinesis

    PubMed Central

    Wong, Raymond; Fabian, Lacramioara; Forer, Arthur; Brill, Julie A

    2007-01-01

    Background Phosphatidylinositol 4,5-bisphosphate (PIP2) is required for successful completion of cytokinesis. In addition, both PIP2 and phosphoinositide-specific phospholipase C (PLC) have been localized to the cleavage furrow of dividing mammalian cells. PLC hydrolyzes PIP2 to yield diacylglycerol (DAG) and inositol trisphosphate (IP3), which in turn induces calcium (Ca2+) release from the ER. Several studies suggest PIP2 must be hydrolyzed continuously for continued cleavage furrow ingression. The majority of these studies employ the N-substituted maleimide U73122 as an inhibitor of PLC. However, the specificity of U73122 is unclear, as its active group closely resembles the non-specific alkylating agent N-ethylmaleimide (NEM). In addition, the pathway by which PIP2 regulates cytokinesis remains to be elucidated. Results Here we compared the effects of U73122 and the structurally unrelated PLC inhibitor ET-18-OCH3 (edelfosine) on cytokinesis in crane-fly and Drosophila spermatocytes. Our data show that the effects of U73122 are indeed via PLC because U73122 and ET-18-OCH3 produced similar effects on cell morphology and actin cytoskeleton organization that were distinct from those caused by NEM. Furthermore, treatment with the myosin light chain kinase (MLCK) inhibitor ML-7 caused cleavage furrow regression and loss of both F-actin and phosphorylated myosin regulatory light chain from the contractile ring in a manner similar to treatment with U73122 and ET-18-OCH3. Conclusion We have used multiple inhibitors to examine the roles of PLC and MLCK, a predicted downstream target of PLC regulation, in cytokinesis. Our results are consistent with a model in which PIP2 hydrolysis acts via Ca2+ to activate myosin via MLCK and thereby control actin dynamics during constriction of the contractile ring. PMID:17509155

  4. Hydrogen-bonding Interactions between Apigenin and Ethanol/Water: A Theoretical Study

    PubMed Central

    Zheng, Yan-Zhen; Zhou, Yu; Liang, Qin; Chen, Da-Fu; Guo, Rui; Lai, Rong-Cai

    2016-01-01

    In this work, hydrogen-bonding interactions between apigenin and water/ethanol were investigated from a theoretical perspective using quantum chemical calculations. Two conformations of apigenin molecule were considered in this work. The following results were found. (1) For apigenin monomer, the molecular structure is non-planar, and all of the hydrogen and oxygen atoms can be hydrogen-bonding sites. (2) Eight and seven optimized geometries are obtained for apigenin (I)–H2O/CH3CH2OH and apigenin (II)–H2O/CH3CH2OH complexes, respectively. In apigenin, excluding the aromatic hydrogen atoms in the phenyl substituent, all other hydrogen atoms and the oxygen atoms form hydrogen-bonds with H2O and CH3CH2OH. (3) In apigenin–H2O/CH3CH2OH complexes, the electron density and the E(2) in the related localized anti-bonding orbital are increased upon hydrogen-bond formation. These are the cause of the elongation and red-shift of the X−H bond. The sum of the charge change transfers from the hydrogen-bond acceptor to donor. The stronger interaction makes the charge change more intense than in the less stable structures. (4) Most of the hydrogen-bonds in the complexes are electrostatic in nature. However, the C4−O5···H, C9−O4···H and C13−O2···H hydrogen-bonds have some degree of covalent character. Furthermore, the hydroxyl groups of the apigenin molecule are the preferred hydrogen-bonding sites. PMID:27698481

  5. CNN pincer ruthenium catalysts for hydrogenation and transfer hydrogenation of ketones: experimental and computational studies.

    PubMed

    Baratta, Walter; Baldino, Salvatore; Calhorda, Maria José; Costa, Paulo J; Esposito, Gennaro; Herdtweck, Eberhardt; Magnolia, Santo; Mealli, Carlo; Messaoudi, Abdelatif; Mason, Sax A; Veiros, Luis F

    2014-10-13

    Reaction of [RuCl(CNN)(dppb)] (1-Cl) (HCNN=2-aminomethyl-6-(4-methylphenyl)pyridine; dppb=Ph2 P(CH2 )4 PPh2 ) with NaOCH2 CF3 leads to the amine-alkoxide [Ru(CNN)(OCH2 CF3 )(dppb)] (1-OCH2 CF3 ), whose neutron diffraction study reveals a short RuO⋅⋅⋅HN bond length. Treatment of 1-Cl with NaOEt and EtOH affords the alkoxide [Ru(CNN)(OEt)(dppb)]⋅(EtOH)n (1-OEt⋅n EtOH), which equilibrates with the hydride [RuH(CNN)(dppb)] (1-H) and acetaldehyde. Compound 1-OEt⋅n EtOH reacts reversibly with H2 leading to 1-H and EtOH through dihydrogen splitting. NMR spectroscopic studies on 1-OEt⋅n EtOH and 1-H reveal hydrogen bond interactions and exchange processes. The chloride 1-Cl catalyzes the hydrogenation (5 atm of H2 ) of ketones to alcohols (turnover frequency (TOF) up to 6.5×10(4) h(-1) , 40 °C). DFT calculations were performed on the reaction of [RuH(CNN')(dmpb)] (2-H) (HCNN'=2-aminomethyl-6-(phenyl)pyridine; dmpb=Me2 P(CH2 )4 PMe2 ) with acetone and with one molecule of 2-propanol, in alcohol, with the alkoxide complex being the most stable species. In the first step, the Ru-hydride transfers one hydrogen atom to the carbon of the ketone, whereas the second hydrogen transfer from NH2 is mediated by the alcohol and leads to the key "amide" intermediate. Regeneration of the hydride complex may occur by reaction with 2-propanol or with H2 ; both pathways have low barriers and are alcohol assisted. PMID:25195979

  6. Kinetics of the degradation of sulfur mustard on ambient and moist concrete.

    PubMed

    Brevett, Carol A S; Sumpter, Kenneth B; Nickol, Robert G

    2009-02-15

    The rate of degradation of the chemical warfare agent sulfur mustard, bis(2-chloroethyl) sulfide, was measured on ambient and moist concrete using (13)C Solid State Magic Angle Spinning Nuclear Magnetic Resonance (SSMAS NMR). Three samples of concrete made by the same formulation, but differing in age and alkalinity were used. The sulfur mustard eventually degraded to thiodiglycol and 1,4-oxathiane via the intermediate sulfonium ions CH-TG, H-TG, H-2TG and O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH on all of the concrete samples, and in addition formed 8-31% vinyl moieties on the newer, more alkaline concrete samples. This is the first observation of the formation of O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH on a solid substrate. The addition of 2-chloroethanol to concrete on which mustard had fully degraded to thiodiglycol and 1,4-oxathiane resulted in the formation of O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH, thus demonstrating the reversibility of sulfur mustard degradation pathways. The sulfur mustard degradation half-lives on ambient concrete at 22 degrees C ranged from 3.5 to 54 weeks. When the substrates were moistened, the degradation half-lives at 22 degrees C ranged from 75 to 350h. The degradation of sulfur mustard occurred more quickly at elevated temperatures and with added water. The non-volatile toxic sulfonium ions persisted for months to years on concrete at 22 degrees C and weeks to months on concrete at 35 degrees C, before decomposing to the relatively non-toxic compounds thiodiglycol and 1,4-oxathiane.

  7. Hydrogen-bonding Interactions between Apigenin and Ethanol/Water: A Theoretical Study

    NASA Astrophysics Data System (ADS)

    Zheng, Yan-Zhen; Zhou, Yu; Liang, Qin; Chen, Da-Fu; Guo, Rui; Lai, Rong-Cai

    2016-10-01

    In this work, hydrogen-bonding interactions between apigenin and water/ethanol were investigated from a theoretical perspective using quantum chemical calculations. Two conformations of apigenin molecule were considered in this work. The following results were found. (1) For apigenin monomer, the molecular structure is non-planar, and all of the hydrogen and oxygen atoms can be hydrogen-bonding sites. (2) Eight and seven optimized geometries are obtained for apigenin (I)–H2O/CH3CH2OH and apigenin (II)–H2O/CH3CH2OH complexes, respectively. In apigenin, excluding the aromatic hydrogen atoms in the phenyl substituent, all other hydrogen atoms and the oxygen atoms form hydrogen-bonds with H2O and CH3CH2OH. (3) In apigenin–H2O/CH3CH2OH complexes, the electron density and the E(2) in the related localized anti-bonding orbital are increased upon hydrogen-bond formation. These are the cause of the elongation and red-shift of the X‑H bond. The sum of the charge change transfers from the hydrogen-bond acceptor to donor. The stronger interaction makes the charge change more intense than in the less stable structures. (4) Most of the hydrogen-bonds in the complexes are electrostatic in nature. However, the C4‑O5···H, C9‑O4···H and C13‑O2···H hydrogen-bonds have some degree of covalent character. Furthermore, the hydroxyl groups of the apigenin molecule are the preferred hydrogen-bonding sites.

  8. Inositol triphosphate participates in an oestradiol nongenomic signalling pathway involved in accelerated oviductal transport in cycling rats.

    PubMed

    Orihuela, Pedro A; Parada-Bustamante, Alexis; Zuñiga, Lidia M; Croxatto, Horacio B

    2006-03-01

    Oestradiol (E(2)) accelerates oviductal transport of oocytes in cycling rats through a nongenomic pathway that involves the cAMP-PKA signalling cascade. Here we examined the role of the inositol triphosphate (IP3) and mitogen-activated protein kinase (MAPK) signalling cascades in this nongenomic pathway. Oestrous rats were injected with E(2) s.c. and intrabursally (i.b) with the selective inhibitors of phospholipase C (PLC) ET-18-OCH(3) or MAPK PD98059. The number of eggs in the oviduct assessed 24 h later showed that ET-18-OCH(3) blocked E(2)-induced egg transport acceleration, whereas PD98059 had no effect. Other oestrous rats were treated with E(2) s.c. and 1, 3 or 6 h later oviducts were excised and the levels of IP3 and phosphorylated MAPK p44/42 (activated) were determined by radioreceptor assay and western blot, respectively. Oestradiol administration increased IP3 level at 1 and 6 h after treatment, whereas activated MAPK p44/42 level was unchanged. Finally, we explored whether cAMP-PKA and PLC-IP3 signalling cascades are coupled. Inhibition of adenylyl cyclase by i.b. injection of SQ 22536 blocked the increase of IP3 levels induced by E(2), while inhibition of PLC by ET-18-OCH(3) had no effect on E(2)-induced PKA activity. Furthermore, activation of adenylyl cyclase by Forskolin increased oviductal IP3 levels. Thus, activation of PLC-IP3 by E(2) requires previous stimulation of cAMP-PKA. We conclude that the nongenomic pathway utilised by E(2) to accelerate oviductal transport of oocytes in cycling rats involves successive activation of the cAMP-PKA and PLC-IP3 signalling cascades and does not require activation of MAPK. These findings clearly illustrate a non-genomic pathway triggered by E(2) that regulates a complex physiologic process accomplished by an entire organ.

  9. Preventing and curing citrulline-induced autoimmune arthritis in a humanized mouse model using a Th2-polarizing iNKT cell agonist.

    PubMed

    Walker, Kyle M; Rytelewski, Mateusz; Mazzuca, Delfina M; Meilleur, Shannon A; Mannik, Lisa A; Yue, David; Brintnell, William C; Welch, Ian; Cairns, Ewa; Haeryfar, S M Mansour

    2012-07-01

    Invariant natural killer T (iNKT) cells are innate lymphocytes with unique reactivity to glycolipid antigens bound to non-polymorphic CD1d molecules. They are capable of rapidly releasing pro- and/or anti-inflammatory cytokines and constitute attractive targets for immunotherapy of a wide range of diseases including autoimmune disorders. In this study, we have explored the beneficial effects of OCH, a Th2-polarizing glycolipid agonist of iNKT cells, in a humanized mouse model of rheumatoid arthritis (RA) in which citrullinated human proteins are targeted by autoaggressive immune responses in mice expressing an RA susceptibility human leukocyte antigen (HLA) DR4 molecule. We found for the first time that treatment with OCH both prevents and cures citrulline-induced autoimmune arthritis as evidenced by resolved ankle swelling and reversed histopathological changes associated with arthritis. Also importantly, OCH treatment blocked the arthritogenic capacity of citrullinated antigen-experienced splenocytes without compromising their global responsiveness or altering the proportion of splenic naturally occurring CD4(+)CD25(+)FoxP3(+) regulatory T cells. Interestingly, administering the Th1-promoting iNKT cell glycolipid ligand α-C-galactosylceramide into HLA-DR4 transgenic mice increased the incidence of arthritis in these animals and exacerbated their clinical symptoms, strongly suggesting a role for Th1 responses in the pathogenesis of citrulline-induced arthritis. Therefore, our findings indicate a role for Th1-mediated immunopathology in citrulline-induced arthritis and provide the first evidence that iNKT cell manipulation by Th2-skewing glycolipids may be of therapeutic value in this clinically relevant model, a finding that is potentially translatable to human RA. PMID:21912419

  10. Metallacryptate single-molecule magnets: effect of lower molecular symmetry on blocking temperature.

    PubMed

    Zaleski, Curtis M; Depperman, Ezra C; Dendrinou-Samara, Catherine; Alexiou, Maria; Kampf, Jeff W; Kessissoglou, Dimitris P; Kirk, Martin L; Pecoraro, Vincent L

    2005-09-21

    The structural characterization of complexes [Mn(II)4Mn(III)22(pdol)12(OCH3)12(O)16(N3)6] (1) and [Mn(II)4Mn(III)22(pdol)12(OCH3)12(O)16(OH)2(H3O)(OCH3)3].ClO4.5CH3OH (2), where pdol(2-) is di-2-pyridyl methanediol, reveals that each has a metallacryptand shell that encapsulates a manganese oxide core. Variable-temperature direct current magnetic susceptibility measurements on 2 indicate a paramagnetic ground state that results from an overall antiferromagnetic interaction in the cluster, with chiT values decreasing from 300 K (51.2 cm3 K mol(-1)) to 2 K (19.8 cm3 K mol(-1)). Variable-temperature alternating current magnetic susceptibility measurements imply that both 1 and 2 behave as single-molecule magnets. Fitting the frequency-dependent out-of-phase magnetic susceptibility to the Arrhenius equation yields an effective energy barrier, Ueff, to magnetization relaxation of 16.5 +/- 0.7 K (11.5 +/- 0.5 cm(-1)) for 1 and 36.2 +/- 2.0 K (25.1 +/- 1.4 cm(-1)) for 2. The larger value for 2 is in agreement with the lower molecular symmetry, larger magnetoanisotropy, and higher ground spin state of 2 compared to those of 1. This observation suggests a new strategy for increasing the blocking temperatures in high-nuclearity manganese clusters.

  11. Detection and Identification of the Keto-Hydroperoxide (HOOCH2OCHO) and Other Intermediates during Low-Temperature Oxidation of Dimethyl Ether.

    PubMed

    Moshammer, Kai; Jasper, Ahren W; Popolan-Vaida, Denisia M; Lucassen, Arnas; Diévart, Pascal; Selim, Hatem; Eskola, Arkke J; Taatjes, Craig A; Leone, Stephen R; Sarathy, S Mani; Ju, Yiguang; Dagaut, Philippe; Kohse-Höinghaus, Katharina; Hansen, Nils

    2015-07-16

    In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxymethyl formate, HPMF, HOOCH2OCHO) and other partially oxidized intermediate species arising from the low-temperature (540 K) oxidation of dimethyl ether (DME). These observations were made possible by coupling a jet-stirred reactor with molecular-beam sampling capabilities, operated near atmospheric pressure, to a reflectron time-of-flight mass spectrometer that employs single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation. On the basis of experimentally observed ionization thresholds and fragmentation appearance energies, interpreted with the aid of ab initio calculations, we have identified HPMF and its conceivable decomposition products HC(O)O(O)CH (formic acid anhydride), HC(O)OOH (performic acid), and HOC(O)OH (carbonic acid). Other intermediates that were detected and identified include HC(O)OCH3 (methyl formate), cycl-CH2-O-CH2-O- (1,3-dioxetane), CH3OOH (methyl hydroperoxide), HC(O)OH (formic acid), and H2O2 (hydrogen peroxide). We show that the theoretical characterization of multiple conformeric structures of some intermediates is required when interpreting the experimentally observed ionization thresholds, and a simple method is presented for estimating the importance of multiple conformers at the estimated temperature (∼100 K) of the present molecular beam. We also discuss possible formation pathways of the detected species: for example, supported by potential energy surface calculations, we show that performic acid may be a minor channel of the O2 + ĊH2OCH2OOH reaction, resulting from the decomposition of the HOOCH2OĊHOOH intermediate, which predominantly leads to the HPMF.

  12. Detection and Identification of the Keto-Hydroperoxide (HOOCH2OCHO) and Other Intermediates during Low-Temperature Oxidation of Dimethyl Ether.

    PubMed

    Moshammer, Kai; Jasper, Ahren W; Popolan-Vaida, Denisia M; Lucassen, Arnas; Diévart, Pascal; Selim, Hatem; Eskola, Arkke J; Taatjes, Craig A; Leone, Stephen R; Sarathy, S Mani; Ju, Yiguang; Dagaut, Philippe; Kohse-Höinghaus, Katharina; Hansen, Nils

    2015-07-16

    In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxymethyl formate, HPMF, HOOCH2OCHO) and other partially oxidized intermediate species arising from the low-temperature (540 K) oxidation of dimethyl ether (DME). These observations were made possible by coupling a jet-stirred reactor with molecular-beam sampling capabilities, operated near atmospheric pressure, to a reflectron time-of-flight mass spectrometer that employs single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation. On the basis of experimentally observed ionization thresholds and fragmentation appearance energies, interpreted with the aid of ab initio calculations, we have identified HPMF and its conceivable decomposition products HC(O)O(O)CH (formic acid anhydride), HC(O)OOH (performic acid), and HOC(O)OH (carbonic acid). Other intermediates that were detected and identified include HC(O)OCH3 (methyl formate), cycl-CH2-O-CH2-O- (1,3-dioxetane), CH3OOH (methyl hydroperoxide), HC(O)OH (formic acid), and H2O2 (hydrogen peroxide). We show that the theoretical characterization of multiple conformeric structures of some intermediates is required when interpreting the experimentally observed ionization thresholds, and a simple method is presented for estimating the importance of multiple conformers at the estimated temperature (∼100 K) of the present molecular beam. We also discuss possible formation pathways of the detected species: for example, supported by potential energy surface calculations, we show that performic acid may be a minor channel of the O2 + ĊH2OCH2OOH reaction, resulting from the decomposition of the HOOCH2OĊHOOH intermediate, which predominantly leads to the HPMF. PMID:25695304

  13. Inference of nitrogen cycling in three watersheds of northern Florida, USA, by multivariate statistical analysis

    NASA Astrophysics Data System (ADS)

    Fu, Ji-Meng; Winchester, John W.

    1994-03-01

    Nitrogen in fresh waters of three rivers in northern Florida - the Apalachicola-Chattahoochee-Flint (ACF) River system, Ochlockonee (Och), and Sopchoppy (Sop) - is inferred to be derived mostly from atmospheric deposition. Because the N:P mole ratios in the rivers are nearly three times higher than the Redfield ratio for aquatic photosynthesis, N is saturated in the ecosystems, not a limiting nutrient, although it may be chemically transformed. Absolute principal component analysis (APCA), a receptor model, was applied to many years of monitoring data for Apalachicola River water and rainfall over its basin in order to better understand aquatic chemistry of nitrogen in the watershed. The APCA model describes the river water as mainly a mixture of components with compositions resembling fresh rain, aged rain, and groundwater. In the fresh rain component, the ratio of atmospheric nitrate to sulfate is close to that in rainwater, as if some samples had been collected following very recent rainfall. The aged rain component of the river water is distinguished by a low NO 3-/SO 42- ratio, signifying an atmospheric source but with most of its nitrate having been lost or transformed. The groundwater component, inferred from its concentration to contribute on average about one fourth of the river water, contains abundant Ca 2+ but no detectable nitrogen. Results similar to ACF were obtained for Sop and Och, though Och exhibits some association of NO 3- with the Ca 2+-rich component. Similar APCA of wet precipitation resolves mainly components that represent acid rain, with NO 3-, SO 42- and NH 4+ and sea salt, with Na +, Cl - and Mg 2+. Inland, the acid rain component is relatively more prominent and Cl - is depleted, while at atmospheric monitoring sites nearer the coastal region sea salt tends to be more prominent.

  14. Multiheteromacrocycles that Complex Metal Ions. Second Progress Report, 1 May 1975 -- 30 April 1976

    DOE R&D Accomplishments Database

    Cram, D. J.

    1976-01-15

    Objective is to develop cyclic and polycyclic host organic compounds to complex and lipophilize metal ions. Macrorings were synthesized: (OCH{sub 2} CH{sub 2} O CH{sub 2}COCH{sub 2} COCH{sub 2}){sub 2} and (OCH{sub 2} CH{sub 2} O CH{sub 2} COCH{sub 2} COCH{sub 2}){sub 3}. The smaller ring complexes divalent metals 10{sup 1+9} times better than the open-chain model CH{sub 3} O CH{sub 2} CO CH{sub 2} COCH{sub 2} O CH{sub 3}, and the order in which metal ions are complexed is Cu{sup 2+}, UO{sub 2}{sup 2+} greater than Ni{sup 2+} greater than Fe{sup 2+}, Co{sup 2+}, Zn{sup 2+}, Cd{sup 2+} greater than Mn{sup 2+}. The UO{sub 2}{sup 2+} and Cu{sup 2+} complexes were isolated and characterized. The larger ring complexes trivalent metals 10{sup 0.9-1.7} times better than the open- chain model compound, and the order is La{sup 3+}, Ce{sup 3+} greater than Cr{sup 3+}. Five other macrocycles were also synthesized, and their binding constants with Na, K, NH{sub 4}, and Cs picrates were measured. Six compounds containing one macroring and two inward-pointing ArOH or ArOCH{sub 3} groups were also prepared and tested for binding of Li, Na, K, Rb, and NH{sub 4} picrates. Racemic compounds containing two binaphthyls and its sulfur analog were prepared. Cage-shaped multiheteromacrocycles containing ten O ligand sites or four S and six O ligand sites were prepared and the binding capability of the first compound for picrates studied. Two ring systems with phosphonate ester groups were also prepared. (DLC)

  15. The effect of solution chemistry on the preparation of MgAl{sub 2}O{sub 4} by hydrothermal-assisted sol-gel processing

    SciTech Connect

    Amini, M.M. . E-mail: m-pouramini@cc.sbu.ac.ir; Mirzaee, M.; Sepanj, N.

    2007-03-22

    Preparation of magnesium aluminate spinel powder by hydrothermal-assisted sol-gel processing from MgAl{sub 2}(OCH{sub 2}CH{sub 2}OR){sub 8}, R=CH{sub 3} (1), CH{sub 2}CH{sub 2}OCH{sub 3} (2), MgAl{sub 2}[OCH(CH{sub 3}){sub 2}]{sub 8} (3) and MgAl{sub 2}(O- {sup s}Bu){sub 8} (4) in toluene and parent alcohol has been investigated. Coordination status of aluminum atom in precursors was determined by {sup 27}Al NMR and correlation between coordination number of aluminum and development of spinel phase in hydrothermal-assisted sol-gel processing has been studied. The gels obtained from hydrothermal-assisted hydrolysis of magnesium-aluminum alkoxides that contain six-coordinated aluminum atoms in solution (1 and 2) after calcination at 700 deg. C resulted in the formation of pure spinel phase, whereas in similar hydrolysis and calcination processes of precursors that contain four-coordinated aluminum (3 and 4) spinel phase forms along with some Al{sub 2}O{sub 3} and MgO. Selected powders obtained from hydrothermal-assisted sol-gel processing were characterized by thermal analysis (TGA/DSC), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Results indicate that the coordination status of aluminum in the precursor is very crucial for the formation of pure phase spinel. The morphology of prepared spinels was studied by SEM and the results showed that the solvent in hydrothermal-assisted sol-gel processing has a marked effect on the morphology of the resulting MgAl{sub 2}O{sub 4}. In hydrothermal-assisted sol-gel processing of aluminum-magnesium alkoxides in hydrophobic solvent, spherical particles are formed, while in the parent alcohol, non-spherical powders are formed.

  16. FTIR gas-phase kinetic study on the reactions of some acrylate esters with OH radicals and Cl atoms.

    PubMed

    Moreno, A; Gallego-Iniesta, M P; Taccone, R; Martín, M P; Cabañas, B; Salgado, M S

    2014-10-01

    Acrylate esters are α,β-unsaturated esters that contain vinyl groups directly attached to the carbonyl carbon. These compounds are widely used in the production of plastics and resins. Atmospheric degradation processes of these compounds are currently not well understood. The kinetics of the gas phase reactions of OH radicals with methyl 3-methylacrylate and methyl 3,3-dimethylacrylate were determined using the relative rate technique in a 50 L Pyrex photoreactor using in situ FTIR spectroscopy at room temperature (298 ± 2 K) and atmospheric pressure (708 ± 8 Torr) with air as the bath gas. Rate coefficients obtained were (in units cm(3) molecule(-1) s(-1)): (3.27 ± 0.33) × 10(-11) and (4.43 ± 0.42) × 10(-11), for CH3CH═CHC(O)OCH3 and (CH3)2CH═CHC(O)OCH3, respectively. The same technique was used to study the gas phase reactions of hexyl acrylate and ethyl hexyl acrylate with OH radicals and Cl atoms. In the experiments with Cl, N2 and air were used as the bath gases. The following rate coefficients were obtained (in cm(3) molecule(-1) s(-1)): k3 (CH2═CHC(O)O(CH2)5CH3 + Cl) = (3.31 ± 0.31) × 10(-10), k4(CH2═CHC(O)OCH2CH(CH2CH3)(CH2)3CH3 + Cl) = (3.46 ± 0.31) × 10(-10), k5(CH2═CHC(O)O(CH2)5CH3 + OH) = (2.28 ± 0.23) × 10(-11), and k6(CH2═CHC(O)OCH2CH(CH2CH3)(CH2)3CH3 + OH) = (2.74 ± 0.26) × 10(-11). The reactivity increased with the number of methyl substituents on the double bond and with the chain length of the alkyl group in -C(O)OR. Estimations of the atmospheric lifetimes clearly indicate that the dominant atmospheric loss process for these compounds is their daytime reaction with the hydroxyl radical. In coastal areas and in some polluted environments, Cl atom-initiated degradation of these compounds can be significant, if not dominant. Maximum Incremental Reactivity (MIR) index and global warming potential (GWP) were also calculated, and it was concluded that these compounds have significant MIR values, but they do

  17. (R)-2,2'-Bis(meth-oxy-meth-oxy)-1,1'-binaphth-yl.

    PubMed

    Zhou, Liang; Eli, Wumanjiang

    2012-05-01

    The asymmetric unit of the title compound, C(24)H(22)O(4), contains two independent mol-ecules in both of which the naphthalene ring systems adopts a transoid arrangement. The dihedral angles between the naphthalene ring system in the two mol-ecules are 83.0 (1) and 89.0 (1)°. There are slight differences in the C(H(3))-O-C(H(2))-O- torsion angles of the eqivalent meth-oxy-meth-oxy groups. In the crystal, weak C-H⋯O hydrogen bonds are present.

  18. Atmospheric chemistry of a model biodiesel fuel, CH3C(O)O(CH2)2OC(O)CH3: kinetics, mechanisms, and products of Cl atom and OH radical initiated oxidation in the presence and absence of NOx.

    PubMed

    Hurley, M D; Ball, J C; Wallington, T J; Toft, A; Nielsen, O J; Bertman, S; Perkovic, M

    2007-04-01

    Relative rate techniques were used to study the kinetics of the reactions of Cl atoms and OH radicals with ethylene glycol diacetate, CH3C(O)O(CH2)2OC(O)CH3, in 700 Torr of N2/O2 diluent at 296 K. The rate constants measured were k(Cl + CH3C(O)O(CH2)2OC(O)CH3) = (5.7 +/- 1.1) x 10(-12) and k(OH + CH3C(O)O(CH2)2OC(O)CH3) = (2.36 +/- 0.34) x 10(-12) cm3 molecule-1 s-1. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the absence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)CH2OC(O)CH3, CH3C(O)OC(O)H, and CH3C(O)OH. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the presence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)H and CH3C(O)OH. The CH3C(O)OCH2O* radical is formed during the Cl atom initiated oxidation of ethylene glycol diacetate, and two loss mechanisms were identified: reaction with O2 to give CH3C(O)OC(O)H and alpha-ester rearrangement to give CH3C(O)OH and HC(O) radicals. The reaction of CH3C(O)OCH2O2* with NO gives chemically activated CH3C(O)OCH2O* radicals which are more likely to undergo decomposition via the alpha-ester rearrangement than CH3C(O)OCH2O* radicals produced in the peroxy radical self-reaction.

  19. Propenyl ether monomers for photopolymerization

    DOEpatents

    Crivello, James V.

    1996-01-01

    Propenyl ether monomers of formula V A(OCH.dbd.CHCH.sub.3).sub.n wherein n is an integer from one to six and A is selected from cyclic ethers, polyether and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of formula V together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  20. Process for making propenyl ethers and photopolymerizable compositions containing them

    DOEpatents

    Crivello, James V.

    1996-01-01

    Propenyl ether monomers of formula V A(OCH.dbd.CHCH.sub.3).sub.n wherein n is an integer from one to six and A is selected from cyclic ethers, polyether and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of formula V together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  1. Characterization of supramolecular (H2O)18 water morphology and water-methanol (H2O)15(CH3OH)3 clusters in a novel phosphorus functionalized trimeric amino acid host.

    PubMed

    Raghuraman, Kannan; Katti, Kavita K; Barbour, Leonard J; Pillarsetty, Nagavarakishore; Barnes, Charles L; Katti, Kattesh V

    2003-06-11

    Phosphorus functionalized trimeric alanine compounds (l)- and (d)-P(CH(2)NHCH(CH(3))COOH)(3) 2 are prepared in 90% yields by the Mannich reaction of Tris(hydroxymethyl)phosphine 1 with (l)- or (d)- Alanine in aqueous media. The hydration properties of (l)-2 and (d)-2 in water and water-methanol mixtures are described. The crystal structure analysis of (l)-2.4H(2)O, reveals that the alanine molecules pack to form two-dimensional bilayers running parallel to (001). The layered structural motif depicts two closely packed monolayers of 2 each oriented with its phosphorus atoms projected at the center of the bilayer and adjacent monolayers are held together by hydrogen bonds between amine and carboxylate groups. The water bilayers are juxtaposed with the H-bonded alanine trimers leading to 18-membered (H(2)O)(18) water rings. Exposure of aqueous solution of (l)-2 and (d)-2 to methanol vapors resulted in closely packed (l)-2 and (d)-2 solvated with mixed water-methanol (H(2)O)(15)(CH(3)OH)(3) clusters. The O-O distances in the mixed methanol-water clusters of (l)-2.3H(2)O.CH(3)OH and (d)-2.3H(2)O.CH(3)OH (O-O(average) = 2.857 A) are nearly identical to the O-O distance observed in the supramolecular (H(2)O)(18) water structure (O-O(average) = 2.859 A) implying the retention of the hydrogen bonded structure in water despite the accommodation of hydrophobic methanol groups within the supramolecular (H(2)O)(15)(CH(3)OH)(3) framework. The O-O distances in (l)-2.3H(2)O.CH(3)OH and (d)-2.3H(2)O.CH(3)OH and in (H(2)O)(18) are very close to the O-O distance reported for liquid water (2.85 A).

  2. New sandwich-type lanthanide complexes based on closed-macrocyclic Schiff base and phthalocyanine molecules.

    PubMed

    Gao, Feng; Feng, Xiaowan; Yang, Liu; Chen, Xiaoyu

    2016-04-25

    Two new sandwich-type lanthanide complexes with the general formula [(Pc)2Ln3(L)(OAc)(OCH3)2] (Ln(3+) = Dy(3+) () and Er(3+) ()) were successfully synthesized and structurally characterized based on closed-macrocyclic Schiff base and phthalocyanine molecules. The magnetic properties and structure-property relationship in this multi-decker system were investigated. Interestingly, the corresponding dysprosium complex shows typical single-molecule magnetic behavior with ferromagnetic dipole-dipole interactions and the slow relaxation of magnetization. PMID:27044594

  3. Increasing the activity and enantioselectivity of lipases by sol-gel immobilization: further advancements of practical interest

    NASA Astrophysics Data System (ADS)

    Tielmann, Patrick; Kierkels, Hans; Zonta, Albin; Ilie, Adriana; Reetz, Manfred T.

    2014-05-01

    The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of the sol-gel approach.The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of

  4. Theoretical study of the pyrolysis of vanillin as a model of secondary lignin pyrolysis

    NASA Astrophysics Data System (ADS)

    Wang, Meng; Liu, Chao; Xu, Xiaoxiao; Li, Qibin

    2016-06-01

    The unimolecular and bimolecular decomposition reactions in processes of vanillin pyrolysis were theoretically investigated by employing density functional theory (DFT) method at M06-2X/6-31 G+(d,p) level. The result shows that the homolytic cleavage of O-CH3 bond could be the dominant initial step in the pyrolysis of vanillin. The hydrogen abstractions from functional groups of vanillin by the formed radicals play important roles in the formation of main products. Both formyl, hydroxyl and methoxyl group contribute to the formation of CO. Benzene is formed from the hydrogen addition reaction between hydrogen radical and phenol at high temperature.

  5. FTIR gas-phase kinetic study on the reactions of some acrylate esters with OH radicals and Cl atoms.

    PubMed

    Moreno, A; Gallego-Iniesta, M P; Taccone, R; Martín, M P; Cabañas, B; Salgado, M S

    2014-10-01

    Acrylate esters are α,β-unsaturated esters that contain vinyl groups directly attached to the carbonyl carbon. These compounds are widely used in the production of plastics and resins. Atmospheric degradation processes of these compounds are currently not well understood. The kinetics of the gas phase reactions of OH radicals with methyl 3-methylacrylate and methyl 3,3-dimethylacrylate were determined using the relative rate technique in a 50 L Pyrex photoreactor using in situ FTIR spectroscopy at room temperature (298 ± 2 K) and atmospheric pressure (708 ± 8 Torr) with air as the bath gas. Rate coefficients obtained were (in units cm(3) molecule(-1) s(-1)): (3.27 ± 0.33) × 10(-11) and (4.43 ± 0.42) × 10(-11), for CH3CH═CHC(O)OCH3 and (CH3)2CH═CHC(O)OCH3, respectively. The same technique was used to study the gas phase reactions of hexyl acrylate and ethyl hexyl acrylate with OH radicals and Cl atoms. In the experiments with Cl, N2 and air were used as the bath gases. The following rate coefficients were obtained (in cm(3) molecule(-1) s(-1)): k3 (CH2═CHC(O)O(CH2)5CH3 + Cl) = (3.31 ± 0.31) × 10(-10), k4(CH2═CHC(O)OCH2CH(CH2CH3)(CH2)3CH3 + Cl) = (3.46 ± 0.31) × 10(-10), k5(CH2═CHC(O)O(CH2)5CH3 + OH) = (2.28 ± 0.23) × 10(-11), and k6(CH2═CHC(O)OCH2CH(CH2CH3)(CH2)3CH3 + OH) = (2.74 ± 0.26) × 10(-11). The reactivity increased with the number of methyl substituents on the double bond and with the chain length of the alkyl group in -C(O)OR. Estimations of the atmospheric lifetimes clearly indicate that the dominant atmospheric loss process for these compounds is their daytime reaction with the hydroxyl radical. In coastal areas and in some polluted environments, Cl atom-initiated degradation of these compounds can be significant, if not dominant. Maximum Incremental Reactivity (MIR) index and global warming potential (GWP) were also calculated, and it was concluded that these compounds have significant MIR values, but they do

  6. Reactions of alkoxysilanes on metal oxide surfaces: decomposition of tetraethoxysilane on MgO(100) and Al 2O 3(0001)

    NASA Astrophysics Data System (ADS)

    Danner, J. B.; Vohs, J. M.

    1993-12-01

    The thermal decomposition of tetraethoxysilane (TEOS) on MgO(100) and Al 2O 3(0001) surfaces was investigated using temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and high-resolution electron energy-loss spectroscopy (HREELS). TEOS was found to dissociate on both MgO(100) and Al 2O 3(0001) to form ethoxysilane species, Si(OCH 2CH 3) n, n=2, 3. The ethoxysilanes are stable to a temperature of 600 K at which point they decompose, liberating ethanol, ethylene and ethyl radicals and depositing SiO 2.

  7. The Formation of N- and O-Heterocycles from the Irradiation of Benzene and Naphthalene in H2O/NH3- Containing Ices

    NASA Technical Reports Server (NTRS)

    Sandford, S. A.; Materese, C. K.; Nuevo, M.

    2015-01-01

    Aromatic hydrocarbons are an important class of molecules for both astrochemistry and astrobiology (Fig. 1). Within this class of molecules, polycyclic aromatic hydrocarbons (PAHs) are known to be ubiquitous in many astrophysical environments, and are likely present in interstellar clouds and protostellar disks. In dense clouds, PAHs are expected to condense onto grains as part of mixed molecular ice mantles dominated by small molecules like H2O,CH3OH, NH3, CO, and CO2. These ices are exposed to ionizing radiation in the form of cosmic rays and ambient high-energy X-ray and UV photons.

  8. Synthesis of elusive chloropnictenium ions.

    PubMed

    Hering-Junghans, Christian; Thomas, Max; Villinger, Alexander; Schulz, Axel

    2015-04-27

    This work describes the synthesis and full characterization of elusive chloropnictenium ion salts of the type [(R)Ar*N(SiMe)ECl][A] ((R)Ar* = 2,6-(CHPh2)-4-R-C6H2, R = Me, tBu; E = Sb, Bi; A(-) = GaCl4, Al(OCH(CF3)2)4). In these species the cation is significantly stabilized by weak arene interactions to flanking phenyl groups of the (R)Ar* moiety. In this context the bonding situation has been studied by computational means and the reactivity towards the Lewis base 4-dimethylaminopyridine (dmap) was investigated.

  9. [INFECTION OF BLOOD-SUCKING MOSQUITOES (DIPTERA: CULICIDAE) WITH DIROFILARIAE (SPIRURIDA, ONCHOCERCIDAE) IN THE TULA REGION].

    PubMed

    Bogacheva, A S; Ganushkina, L A; Lopatina, Yu V

    2016-01-01

    Blood-sucking mosquitoes (n = 2277) collected in Tula and its Region in 2013-2014 were examined using a PCR assay for dirofilariae. A total of 12 species from 4 genera (Culiseta, Aedes, Ochlerotatus [foreign character] Culex) out of 18 found mosquito species were infected with Dirofilaria immitis and D. repens. The proportion of the infected mosquitoes was 2.5% (D. immitis, 1.5%; D.repens, 1%). According to preliminary data, the most efficient Dirofilaria vectors, in the Tula Region may be Ae. vexans, Ae. geniculatus, Och. cantans, and Cx. pipiens. PMID:27405207

  10. Process for making propenyl ethers and photopolymerizable compositions containing them

    DOEpatents

    Crivello, J.V.

    1996-01-23

    Propenyl ether monomers of formula A(OCH{double_bond}CHCH{sub 3}){sub n} (V) wherein n is an integer from one to six and A is selected from cyclic ethers, polyether, and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of formula V together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  11. Propenyl ether monomers for photopolymerization

    DOEpatents

    Crivello, J.V.

    1996-10-22

    Propenyl ether monomers of formula A(OCH{double_bond}CHCH{sub 3}){sub n} wherein n is an integer from one to six and A is selected from cyclic ethers, polyether and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of the above formula together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  12. Differentiation of Boc-protected alpha,delta-/delta,alpha- and beta,delta-/delta,beta-hybrid peptide positional isomers by electrospray ionization tandem mass spectrometry.

    PubMed

    Raju, G; Ramesh, V; Srinivas, R; Sharma, G V M; Shoban Babu, B

    2010-06-01

    Two new series of Boc-N-alpha,delta-/delta,alpha- and beta,delta-/delta,beta-hybrid peptides containing repeats of L-Ala-delta(5)-Caa/delta(5)-Caa-L-Ala and beta(3)-Caa-delta(5)-Caa/delta(5)-Caa-beta(3)-Caa (L-Ala = L-alanine, Caa = C-linked carbo amino acid derived from D-xylose) have been differentiated by both positive and negative ion electrospray ionization (ESI) ion trap tandem mass spectrometry (MS/MS). MS(n) spectra of protonated isomeric peptides produce characteristic fragmentation involving the peptide backbone, the Boc-group, and the side chain. The dipeptide positional isomers are differentiated by the collision-induced dissociation (CID) of the protonated peptides. The loss of 2-methylprop-1-ene is more pronounced for Boc-NH-L-Ala-delta-Caa-OCH(3) (1), whereas it is totally absent for its positional isomer Boc-NH-delta-Caa-L-Ala-OCH(3) (7), instead it shows significant loss of t-butanol. On the other hand, second isomeric pair shows significant loss of t-butanol and loss of acetone for Boc-NH-delta-Caa-beta-Caa-OCH(3) (18), whereas these are insignificant for its positional isomer Boc-NH-beta-Caa-delta-Caa-OCH(3) (13). The tetra- and hexapeptide positional isomers also show significant differences in MS(2) and MS(3) CID spectra. It is observed that 'b' ions are abundant when oxazolone structures are formed through five-membered cyclic transition state and cyclization process for larger 'b' ions led to its insignificant abundance. However, b(1)(+) ion is formed in case of delta,alpha-dipeptide that may have a six-membered substituted piperidone ion structure. Furthermore, ESI negative ion MS/MS has also been found to be useful for differentiating these isomeric peptide acids. Thus, the results of MS/MS of pairs of di-, tetra-, and hexapeptide positional isomers provide peptide sequencing information and distinguish the positional isomers.

  13. [INFECTION OF BLOOD-SUCKING MOSQUITOES (DIPTERA: CULICIDAE) WITH DIROFILARIAE (SPIRURIDA, ONCHOCERCIDAE) IN THE TULA REGION].

    PubMed

    Bogacheva, A S; Ganushkina, L A; Lopatina, Yu V

    2016-01-01

    Blood-sucking mosquitoes (n = 2277) collected in Tula and its Region in 2013-2014 were examined using a PCR assay for dirofilariae. A total of 12 species from 4 genera (Culiseta, Aedes, Ochlerotatus [foreign character] Culex) out of 18 found mosquito species were infected with Dirofilaria immitis and D. repens. The proportion of the infected mosquitoes was 2.5% (D. immitis, 1.5%; D.repens, 1%). According to preliminary data, the most efficient Dirofilaria vectors, in the Tula Region may be Ae. vexans, Ae. geniculatus, Och. cantans, and Cx. pipiens.

  14. Reactions of 3-OXETANONE at High Temperatures

    NASA Astrophysics Data System (ADS)

    Wright, Emily; Warner, Brian; Foreman, Hannah; Urness, Kimberly N.; McCunn, Laura R.

    2015-06-01

    The pyrolysis of 3-oxetanone, O(CH2)2CO, has been studied in a resistively heated SiC tubular reactor at 400-1200 °C. Products of pyrolysis were identified via matrix-isolation FTIR spectroscopy and photoionization mass spectrometry in separate experiments. While 3-oxetanone is expected to dissociate into ketene and formaldehyde, these experiments show that ethylene oxide and carbon monoxide are also produced. Methyl radical and ethylene were observed as additional products and are thought to be the result of reactions involving ethylene oxide.

  15. Exposures of preschool children to chlorpyrifos, diazinon, pentachlorophenol, and 2,4-dichlorophenoxyacetic acid over 3 years from 2003 to 2005: A longitudinal model.

    PubMed

    Wilson, Nancy K; Strauss, Warren J; Iroz-Elardo, Nicole; Chuang, Jane C

    2010-09-01

    The impact of the US EPA-required phase-outs starting in 2000-2001 of residential uses of the organophosphate (OP) pesticides chlorpyrifos (CPF) and diazinon (DZN) on preschool children's pesticide exposures was investigated over 2003-2005, in the Raleigh-Durham-Chapel Hill area of North Carolina. Data were collected from 50 homes, each with a child initially of age 3 years (OCh) and a younger child (YCh). Environmental samples (indoor and outdoor air, dust, soil) and child-specific samples (hand surface residue, urine, diet) were collected annually over 24-h periods at each home. Child time-activity diaries and household pesticide use information were also collected. Analytes included CPF and DZN; pentachlorophenol (PCP); 2,4-dichlorophenoxyacetic acid (2,4-D); the CPF metabolite 3,5,6-trichloro-2-pyridinol (TCP); and the DZN metabolite 2-isopropyl-6-methyl-4-pyrimidinol (IMP). Exposures (ng/day) through the inhalation, dietary ingestion, and indirect ingestion were calculated. Aggregate potential doses in ng/kg body weight per day (ng/kg/day) were obtained by summing the potential doses through the three routes of exposure. Geometric mean aggregate potential doses decreased from 2003 to 2005 for both OCh and YCh, with the exception of 2,4-D. Child-specific longitudinal modeling indicated significant declines across time of the potential doses of CPF, DZN, and PCP for both children; declines of IMP for both children, significant only for OCh; a decline of TCP for OCh but an increase of TCP for YCh; and no significant change of 2,4-D for either child. Age-adjusted modeling indicated significant effects of the child's age for all except CPF, and of time for all except PCP and 2,4-D. Within-home variability was small compared with that between homes; variability was smallest for 2,4-D, both within and between homes. The aggregate potential doses of CPF and DZN were well below published reference dose values. These findings show the success of the US EPA restrictions

  16. Artocarpin-galactomannan interaction: characterization of combining site of artocarpin.

    PubMed

    Chowdhury, S; Chatterjee, B P

    1993-01-01

    Artocarpin, a lectin purified from Artocarpus lakoocha seeds, precipitates well several galactomannans having terminal D-Gal-alpha-(1-6)-residues. Quantitative precipitin-inhibition studies using various haptens suggest that the -OCH2-group at C-1 and hydroxyl groups at C-4, and partially at C-6, in the alpha-glycoside of D-galactose configuration are necessary for lectin-sugar interaction. The formation of an artocarpin-fenugreek galactomannan complex was dependent on temperature, pH, ionic strength and the number of hydroxy groups of alditols added to the medium.

  17. Two tri-spin complexes based on gadolinium and nitronyl nitroxide radicals: Structure and ferromagnetic interactions

    SciTech Connect

    Zhou Na; Ma Yue; Wang Chao; Xu Gongfeng; Tang Jinkui; Yan Shiping; Liao Daizheng

    2010-04-15

    Three Radical-Ln(III)-Radical complexes based on nitronyl nitroxide radicals have been synthesized, structurally and magnetically characterized: [Gd(hfac){sub 3}(NITPhOEt){sub 2}] (1) (hfac=hexafluoroacetylacetonate, and NITPhOEt=4'-ethoxy-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), [Gd(hfac){sub 3}(NITPhOCH{sub 2}Ph){sub 2}] (2) (NITPhOCH{sub 2}Ph=4'-benzyloxy-phenyl-4,4,5, 5-tetramethylimidazoline-1-oxyl-3-oxide) and [Lu(hfac){sub 3}(NITPhOCH{sub 2}Ph){sub 2}] (3). The X-ray crystal structure analyses show that the structures of the three compounds are similar and all consist of the isolated molecules, in which central ions Gd{sup III} or Lu{sup III} are coordinated by six oxygen atoms from three hfac and two oxygen atoms from nitronyl radicals. The magnetic studies show that in both of the two Gd{sup III} complexes, there are ferromagnetic Gd{sup III}-Rad interactions and antiferro-magnetic Rad-Rad interactions in the molecules (with J{sub Rad-Gd}=0.27 cm{sup -1}, j{sub Rad-Rad}=-2.97 cm{sup -1} for 1: and J{sub Rad-Gd}=0.62 cm{sup -1}, j{sub Rad-Rad}=-7.01 cm{sup -1} for 2). An analogous complex of [Lu(hfac){sub 3} (NITPhOCH{sub 2}Ph){sub 2}] (3) containing diamagnetic Lu{sup III} ions has also been introduced for further demonstrating the nature of magnetic coupling between radicals. - Graphical abstract: Two tri-spin complexes based on gadolinium-radical have been synthesized and characterized, the magnetic studies show that in the two complexes the Gd-radical interaction is ferromagnetic and the radical-radical interaction is antiferromagnetic. An analogous complex containing the diamagnetic Lu{sup III} ions has also been synthesized to further demonstrate the nature of the magnetic coupling between radicals.

  18. New secoiridoids from the fruits of Ligustrum lucidum Ait with triglyceride accumulation inhibitory effects.

    PubMed

    Zhang, Yi; Liu, Lili; Gao, Jing; Wu, Chunhua; Han, Lifeng; Liu, Erwei; Shi, Pingping; Gao, Xiumei; Wang, Tao

    2013-12-01

    Five new secoiridoids, nuzhenal C (1), 6'-O-trans-cinnamoyl iso-8-epikingisidic acid (2), ligulucidumosides A (3), B (4), and C (5), were obtained from the fruits of Ligustrum lucidum Ait. Their structures were elucidated by chemical and spectroscopic methods (UV, IR, HRESI-TOF-MS, 1D and 2D NMR). Among them, compound 3 is the first 1-OCH3 substituent secoiridoid obtained from plant kingdom. Furthermore, activity screening results showed that all of the isolates had triglyceride accumulation inhibitory effects in HepG2 cells. PMID:24001714

  19. Gas-phase reactions of [VO2(OH)2]- and [V2O5(OH)]- with methanol: experiment and theory.

    PubMed

    Harris, Benjamin L; Waters, Tom; Khairallah, George N; O'Hair, Richard A J

    2013-02-14

    The gas-phase reactivity of the vanadium hydroxides [VO(2)(OH)(2)](-) and [V(2)O(5)(OH)](-) toward methanol was examined using a combination of ion-molecule reactions (IMRs) and collision-induced dissociation (CID) in a quadrupole ion trap mass spectrometer. Isotope-labeling experiments with CD(3)OH, (13)CH(3)OH, and CH(3)(18)OH were used to confirm the stoichiometry of ions and the observed sequence of reactions. The experimental data were interpreted with the aid of density functional theory calculations, carried out at the B3LYP/SDD6-311++G** level of theory. While [VO(2)(OH)(2)](-) is unreactive, [V(2)O(5)(OH)](-) undergoes a metathesis reaction to yield [V(2)O(5)(OCH(3))](-). The DFT calculations reveal that the metathesis reaction of methanol with [VO(2)(OH)(2)](-) suffers from a barrier of +0.52 eV (relative to separated reactants) but that the reaction of [V(2)O(5)(OH)](-) with methanol readily proceeds via addition/elimination reactions with both transition states being below the energy of the separated reactants. CID of [V(2)O(5)(OCH(3))](-) (m/z 213) yields three ions arising from activation of the methoxo ligand: [V(2), O(6), C, H](-) (m/z 211); [V(2), O(5), H](-) (m/z 183); and [V(2), O(4), H](-) (m/z 167). Additional experiments and DFT calculations suggest that these ions arise from losses of H(2), formaldehyde and the sequential losses of H(2) and CO(2), respectively. The use of an (18)O-labeled methoxo ligand in [V(2)O(5)((18)OCH(3))](-) (m/z 215) showed the competing losses of H(2)C(16)O and H(2)C(18)O and [H(2) and C(16)O(18)O] and [H(2) and C(16)O(2)], highlighting that (16)O/(18)O exchange between the methoxo ligand and the vanadium oxide occurs prior to the subsequent fragmentation of the ligand. DFT calculations reveal that a key step involves hydrogen atom transfer from the methoxo ligand to the oxo ligand of the same vanadium center, producing the intermediate [V(2)O(4)(OH)(OCH(2))](-) containing a ketyl radical ligand and a hydroxo ligand

  20. Insight into selected reactions in low-temperature dimethyl ether combustion from Born-Oppenheimer molecular dynamics.

    PubMed

    Andersen, Amity; Carter, Emily A

    2006-02-01

    Dimethyl ether is under consideration as an alternative diesel fuel. Its combustion chemistry is as yet ill-characterized. Here we use Born-Oppenheimer molecular dynamics (BOMD) based on DFT-B3LYP forces to investigate the short-time dynamics of selected features of the low-temperature dimethyl ether (DME) oxidation potential energy surface. Along the chain propagation pathway, we run BOMD simulations from the transition state involving the decomposition of (*)CH(2)OCH(2)OOH to two CH(2)=O and an (*)OH radical. We predict that formaldehyde C-O stretch overtones are excited, consistent with laser photolysis experiments. We also predict that O-H overtones are excited for the (*)OH formed from (*)CH(2)OCH(2)OOH dissociation. We also investigate short-time dynamics involved in chain branching. First, we examine the isomerization transition state of (*)OOCH(2)OCH(2)OOH --> HOOCH(2)OCHOOH. The latter species is predicted to be a short-lived metastable radical that decomposes within 500 fs to hydroperoxymethyl formate (HPMF; HOOCH(2)OC(=O)H) and the first (*)OH of chain branching. The dissociation of HOOCH(2)OCHOOH exhibits non-RRKM behavior in its lifetime profile, which may be due to conformational constraints or slow intramolecular vibrational energy transfer (IVR) from the nascent H-O bond to the opposite end of the radical, where O-O scission occurs to form HPMF and (*)OH. In a few trajectories, we see HOOCH(2)OCHOOH recross back to (*)OOCH(2)OCH(2)OOH because the isomerization is endothermic, with only an 8 kcal/mol barrier to recrossing. Therefore, some inhibition of chain-branching may be due to recrossing. Second, trajectories run from the transition state leading to the direct decomposition of HPMF (an important source of the second (*)OH radical in chain branching) to HCO, (*)OH, and HC(=O)OH show that these products can recombine to form many other possible products. These products include CH(2)OO + HC(=O)OH, H(2)O + CO + HC(=O)OH, HC(=O)OH + HC(=O)OH, and HC

  1. Non-strinking siloxane polymers

    DOEpatents

    Loy, Douglas A.; Rahimian, Kamyar

    2001-01-01

    Cross-linked polymers formed by ring-opening polymerization of a precursor monomer of the general formula R[CH.sub.2 CH(Si(CH.sub.3).sub.2).sub.2 O].sub.2, where R is a phenyl group or an alkyl group having at least two carbon atoms. A cross-linked polymer is synthesized by mixing the monomer with a co-monomer of the general formula CH.sub.2 CHR.sup.2 (SiMe.sub.2).sub.2 O in the presence of an anionic base to form a cross-linked polymer of recurring units of the general formula R(Me.sub.2 SiOCH.sub.2 CHSiMe.sub.2).sub.2 [CH.sub.2 CHR.sup.2 (SiMe.sub.2).sub.2 O].sub.n, where R.sup.2 is hydrogen, phenyl, ethyl, propyl or butyl. If the precursor monomer is a liquid, the polymer can be directly synthesized in the presence of an anionic base to a cross-linked polymer containing recurring units of the general formula R(Me.sub.2 SiOCH.sub.2 CHSiMe.sub.2).sub.2. The polymers have approximately less than 1% porosity and are thermally stable at temperatures up to approximately 500.degree. C. The conversion to the cross-linked polymer occurs by ring opening polymerization and results in shrinkage of less than approximately 5% by volume.

  2. A noticeable phenomenon: thiol terminal PEG enhances the immunogenicity of PEGylated emulsions injected intravenously or subcutaneously into rats.

    PubMed

    Wang, Chunling; Cheng, Xiaobo; Sui, Yue; Luo, Xiang; Jiang, Gongping; Wang, Yu; Huang, Zhenjun; She, Zhennan; Deng, Yihui

    2013-11-01

    Repeated intravenous injection of long-circulating methoxy-polyethylene glycol (PEG)-liposomes alters the pharmacokinetics and biodistribution of the second administration, regarded as the "accelerated blood clearance (ABC) phenomenon." Nevertheless, the effect of terminal groups of distearoylphosphatidylethanolamine-polyethylene glycol (DSPE-PEG) on the induction of the ABC phenomenon had not been reported previously. In this study, rats were injected intravenously or subcutaneously with PEG coated emulsions (DE) which were prepared using PEG terminated with either the methoxyl (OCH3), hydroxyl (OH), amino (NH2), carboxyl (COOH), or thiol (SH) group. DE-OCH3 demonstrated the longest prolonged half-life in vivo after a single intravenous injection, followed by DE-SH and DE-COOH. In contrast, DE-OH was rapidly removed from the blood circulation, as was DE-NH2. Moreover, we observed a strong positive relationship between the circulation time of initially injected PEGylated emulsions and the extent to which the ABC phenomenon was induced, but a exception of DE-SH increasing the ABC effect. Furthermore, the present study suggested that thiols might stimulate the proliferation and differentiation of B cells to induce the fastest clearance of the second intravenous administration by inducing the synthesis of the cell membrane and cytosolic proteins or reacting with follicular dendritic cells. The results strongly suggested that thiol groups played a stimulatory role in the immune response and provided a considerable implication for multiple drug therapy of thiol groups. PMID:24129310

  3. Reactive Capture of Gold Nanoparticles by Strongly Physisorbed Monolayers on Graphite

    SciTech Connect

    Wei, Xiaoliang; Tong, Wenjun; Fidler, Vlastimil; Zimmt, Matthew B.

    2012-12-01

    Anthracene Diels Alder adducts (DAa) bearing two long side chains (H-(CH2)22O(CH2)6OCH2-) at the 1- and 5-positions form self-assembled monolayers (SAMs) at the phenyloctane - highly oriented pyrolytic graphite (HOPG) interface. The long DAa side chains promote strong physisorption of the monolayer to HOPG and maintain the monolayer morphology upon rinsing or incubation in ethanol and air-drying of the substrate. Incorporating a carboxylic acid group on the DAa core enables capture of 1 - 4 nm diameter gold nanoparticles (AuNP) provided (i) the monolayer containing DAa-carboxylic acids is treated with Cu2+ ions and (ii) the organic coating on the AuNP contains carboxylic acids (11-mercaptoundecanoic acid, MUA-AuNP). AuNP capture by the monolayer proceeds with formation of Cu2+ - carboxylate coordination complexes. The captured AuNP appear as mono- and multi-layered clusters at high coverage on HOPG. The surface density of the captured AuNPs can be adjusted from AuNP multi-layers to isolated AuNPs by varying incubation times, MUA-AuNP concentration, the number density of carboxylic acids in the monolayer, the number of MUA per AuNP, and the post-incubation treatments.

  4. Insight into the evolution, redox, and metal binding properties of dissolved organic matter from municipal solid wastes using two-dimensional correlation spectroscopy.

    PubMed

    He, Xiao-Song; Xi, Bei-Dou; Zhang, Zong-Yong; Gao, Ru-Tai; Tan, Wen-Bing; Cui, Dong-Yu

    2014-12-01

    Two-dimensional correlation spectroscopy was employed to investigate the evolution, redox, and metal binding properties of dissolved organic matter (DOM) from municipal solid wastes (MSWs) during composting. The results showed that the DOM was degraded during composting in the order of aliphatic substances > proteinaceous compounds > cellulose, hemicellulose and lignin, while humic substances transformed during the process in the order of fulvic-like matter > humic-like substances > protein-like matter. The fulvic- and humic-like substances originated from lignin and polysaccharide-like substances with the function groups of CH3, CCH2, CCH, OCH3, OCH, O--C--O, aromatic C, and COO, while the protein-like matter was derived from aliphatic and proteinaceous compounds with the functional groups of CCH3 and N--C==O. The aromatic C and COO were responsible for the oxidation capacity of the MSW-derived DOM, while the O--C--O and COO accounted for the Cu and Zn binding capacity of the DOM.

  5. Conformational, electronic and antioxidant properties of lucidone, linderone and methyllinderone: DFT, QTAIM and NBO studies

    NASA Astrophysics Data System (ADS)

    Kabanda, Mwadham M.; Tan Tran, Van; Seema, Kamogelo M.; Serobatse, Kemoabetswe R. N.; Tsiepe, Tshepiso J.; Tran, Quoc Tri; Ebenso, Eno E.

    2015-04-01

    Theoretical studies on lucidone, linderone and methyllinderone were performed to investigate factors that contribute to structural stability and to elucidate the antioxidant properties and mechanisms. The study was performed in different media utilising the density functional theory with different functionals and the 6-311+ G(d,p) basis set. The antioxidant activity has been considered through the electron transfer and metal chelation mechanisms. The results show that the stability of the tautomers and conformers is due to the presence of several intramolecular hydrogen bonds. The ionisation potential values suggest that the antiradical activity increases with the increase in the number of OCH3 groups substituted on the cyclopentene-1,3-dione ring. In vacuo, the spin density of the Fe(II) cation upon ligand coordination decreases to 3.0-3.5, whereas the ligand spin density approaches 1, indicating that it is oxidised to a radical cation. The metal ion affinity (MIA) is influenced by the position and number of OCH3 substituted on the acylcyclopentene-1,3-dione ring. A very favourable MIA, in vacuo, is obtained when Fe(II) is chelated between the sp2 O and sp3 O atoms. An estimation of MIA in an aqueous solution shows a remarkable decrease with respect to the results in vacuo.

  6. Synthesis and biological evaluation of pyrazolylthiazole carboxylic acids as potent anti-inflammatory-antimicrobial agents.

    PubMed

    Khloya, Poonam; Kumar, Satish; Kaushik, Pawan; Surain, Parveen; Kaushik, Dhirender; Sharma, Pawan K

    2015-03-15

    Current Letter presents design, synthesis and biological evaluation of a novel series of pyrazolylthiazole carboxylates 1a-1p and corresponding acid derivatives 2a-2p. All 32 novel compounds were tested for their in vivo anti-inflammatory activity by carrageenan-induced rat paw edema method as well as for in vitro antimicrobial activity. All the tested compounds exhibited excellent AI activity profile. Three compounds 1p (R=Cl, R(1)=Cl), 2c (R=H, R(1)=F) and 2n (R=Cl, R(1)=OCH3) were identified as potent anti-inflammatory agents exhibiting edema inhibition of 93.06-89.59% which is comparable to the reference drug indomethacin (91.32%) after 3h of carrageenan injection while most of the other compounds displayed inhibition ⩾80%. In addition, pyrazolylthiazole carboxylic acids (2a-2p) also showed good antimicrobial profile. Compound 2h (R=OCH3, R(1)=Cl) showed excellent antimicrobial activity (MIC 6.25μg/mL) against both Gram positive bacteria comparable with the reference drug ciprofloxacin (MIC 6.25μg/mL).

  7. Mechanistic study of atomic layer deposition of Al{sub x}Si{sub y}O thin film via in-situ FTIR spectroscopy

    SciTech Connect

    Cho, Jea; Kim, Taeseung; Seegmiller, Trevor; Chang, Jane P.

    2015-09-15

    A study of surface reaction mechanism on atomic layer deposition (ALD) of aluminum silicate (Al{sub x}Si{sub y}O) was conducted with trimethylaluminum (TMA) and tetraethoxysilane (TEOS) as precursors and H{sub 2}O as the oxidant. In-situ Fourier transform infrared spectroscopy (FTIR) was utilized to elucidate the underlying surface mechanism that enables the deposition of Al{sub x}Si{sub y}O by ALD. In-situ FTIR study revealed that ineffective hydroxylation of the surface ethoxy (–OCH{sub 2}CH{sub 3}) groups prohibits ALD of SiO{sub 2} by TEOS/H{sub 2}O. In contrast, effective desorption of the surface ethoxy group was observed in TEOS/H{sub 2}O/TMA/H{sub 2}O chemistry. The presence of Al-OH* group in vicinity of partially hydroxylated ethoxy (–OCH{sub 2}CH{sub 3}) group was found to propagate disproportionation reaction, which results in ALD of Al{sub x}Si{sub y}O. The maximum thickness from incorporation of SiO{sub x} from alternating exposures of TEOS/H{sub 2}O chemistry in Al{sub x}Si{sub y}O was found to be ∼2 Å, confirmed by high resolution transmission electron microscopy measurements.

  8. Catalyst Structure-Performance Relationship Identified by High-Throughput Operando Method: New Insight for Silica-Supported Vanadium Oxide for Methanol Oxidation

    SciTech Connect

    Li, Guosheng; Hu, Dehong; Xia, Guanguang; Zhang, Z Conrad

    2010-02-01

    A prototype high throughput operando reactor, that integrates FT-IR imaging for rapid reaction product analysis and parallel Raman imaging for catalyst characterization, has been designed to accelerate catalyst discovery and, concurrently, fundamental research toward reliable correlations between catalyst active sites and catalyst performance for at-line real catalytic conditions. This reactor, consisting of six parallel reaction channels, is demonstrated for methanol oxidation using silica supported vanadium oxide catalysts at various reaction conditions. The results of semi-quantitative analysis of a large array of operando Raman scattering bands, specifically for C-H bonds in Si-OCH3 and V-OCH3 surface intermediates, obtained simultaneously on multiple catalyst surfaces with a time resolution of 60s for each set at different temperatures, reveal for the first time methanol activation at surface vanadium oxide cluster edge on silica support at lower reaction temperatures, <175°C. This activation phenomenon is not observed at a higher reaction temperature, 225°C.

  9. Mechanistic understanding of hydrogenation of acetaldehyde on Au(111): A DFT investigation

    NASA Astrophysics Data System (ADS)

    Meng, Qingsen; Shen, Yongli; Xu, Jing; Ma, Xinbin; Gong, Jinlong

    2012-11-01

    This paper describes the reaction pathways for hydrogenation of acetaldehyde on atomic hydrogen pre-adsorbed Au(111) employing density functional theory (DFT) calculations. All the surface species involved in the reaction scheme have low diffusion barriers, suggesting that the rearrangement and movement of these species on the surface are facile under reaction condition. The hydroxyethyl is proposed to be the intermediate for the hydrogenation of acetaldehyde, and the activation energy for its formation is 0.37 eV. Additionally, the coupling reaction of hydroxyethyl and acetaldehyde - resulting in the formation of the ethylidene ethylene glycol (CH3C*HOCH(CH3)OH) species - also readily occurs at the reaction condition. Two-dimensional (2-D) polyacetaldehyde ((CH3CHO)2) can be easily hydrogenated to ethylidene ethylene glycol or ethoxy hemiacetal (CH3CH2OCH(CH3)O*); the latter can be converted to ethanol and acetaldehyde via further hydrogenation. As the hydrogenation products of ethylidene ethylene glycol and ethoxy hemiacetal, ethoxyethanol (CH3CH2OCH(CH3)OH) can be deeply hydrogenated to hydroxyethyl and ethanol. Our calculations also suggest that the formation of an ethoxyl intermediate is not likely, which agrees with the experimental observation that no deuterated acetaldehydes have been detected in isotopic measurements.

  10. Rational discovery and development of a mitochondria-targeted antioxidant based on cinnamic acid scaffold.

    PubMed

    Teixeira, José; Soares, Pedro; Benfeito, Sofia; Gaspar, Alexandra; Garrido, Jorge; Murphy, Michael P; Borges, Fernanda

    2012-05-01

    A novel mitochondria-targeted antioxidant (TPP-OH) was synthesized by attaching the natural hydrophilic antioxidant caffeic acid to an aliphatic lipophilic carbon chain containing a triphenylphosphonium (TPP) cation. This compound has similar antioxidant activity to caffeic acid as demonstrated by measurement of DPPH/ABTS radical quenching and redox potentials, but is significantly more hydrophobic than its precursor as indicated by the relative partition coefficients. The antioxidant activity of both compounds was intrinsic related to the ortho-catechol system, as the methoxylation of the phenolic functions, namely in TPP-OCH(3) and dimethoxycinnamic acid, gave compounds with negligible antioxidant action. The incorporation of the lipophilic TPP cation to form TTP-OH and TPP-OCH(3) allowed the cinnamic derivatives to accumulate within mitochondria in a process driven by the membrane potential. However, only TPP-OH was an effective antioxidant: TPP-OH protected cells against H(2)O(2) and linoleic acid hydroperoxide-induced oxidative stress. As mitochondrial oxidative damage is associated with a number of clinical disorders, TPP-OH may be a useful lead that could be added to the family of mitochondria-targeted antioxidants that can decrease mitochondrial oxidative damage.

  11. Ion-molecule reactions involving HCO+ and N2H+: Isotopologue equilibria from new theoretical calculations and consequences for interstellar isotope fractionation

    NASA Astrophysics Data System (ADS)

    Mladenović, M.; Roueff, E.

    2014-06-01

    Aims: We revisit with new augmented accuracy the theoretical dynamics of basic isotope exchange reactions involved in the 12C/13C, 16O/18O, and 14N/15N balance because these reactions have already been studied experimentally in great detail. Methods: Electronic structure methods were employed to explore potential energy surfaces, full-dimensional rovibrational calculations to compute rovibrational energy levels that are numerically exact, and chemical network models to estimate the abundance ratios under interstellar conditions. Results: New exothermicities, derived for HCO+ reacting with CO, provide rate coefficients markedly different from previous theoretical values in particular at low temperatures, resulting in new abundance ratios relevant for carbon chemistry networks. In concrete terms, we obtain a reduction in the abundance of H12C18O+ and an increase in the abundance of H13C16O+ and D13C16O+. In all studied cases, the reaction of the ion with a neutral polarizable molecule proceeds through the intermediate proton-bound complex found to be very stable. For the complexes OCH+··· CO, OCH+··· OC, COHOC+, N2··· HCO+, N2H+··· OC, and N2HN2+, we also calculated vibrational frequencies and dissociation energies. Conclusions: The linear proton-bound complexes possess sizeable dipole moments, which may facilitate their detection.

  12. Competing Noncovalent Host-guest Interactions and H/D Exchange: Reactions of Benzyloxycarbonyl-Proline Glycine Dipeptide Variants with ND3

    NASA Astrophysics Data System (ADS)

    Miladi, Mahsan; Olaitan, Abayomi D.; Zekavat, Behrooz; Solouki, Touradj

    2015-11-01

    A combination of density functional theory calculations, hydrogen/deuterium exchange (HDX) reactions, ion mobility-mass spectrometry, and isotope labeling tandem mass spectrometry was used to study gas-phase "host-guest" type interactions of a benzyloxycarbonyl (Z)-capped proline (P) glycine (G) model dipeptide (i.e., Z-PG) and its various structural analogues with ND3. It is shown that in a solvent-free environment, structural differences between protonated and alkali metal ion (Na+, K+, or Cs+)-complexed species of Z-PG affect ND3 adduct formation. Specifically, [Z-PG + H]+ and [Z-PG-OCH3 + H]+ formed gas-phase ND3 adducts ([Z-PG (or Z-PG-OCH3) + H + ND3]+) but no ND3 adducts were observed for [Z-PG + alkali metal]+ or [Z-PG + H - CO2]+. Experimentally measured and theoretically calculated collision cross sections (CCSs) of protonated and alkali metal ion-complexed Z-PG species showed similar trends that agreed with the observed structural differences from molecular modeling results. Moreover, results from theoretical ND3 affinity calculations were consistent with experimental HDX observations, indicating a more stable ND3 adduct for [Z-PG + H]+ compared to [Z-PG + alkali metal]+ species. Molecular modeling and experimental MS results for [Z-PG + H]+ and [Z-PG + alkali metal]+ suggest that optimized cation-π and hydrogen bonding interactions of carbonyl groups in final products are important for ND3 adduct formation.

  13. Dechlorination of hazardous wastes Ca/NH{sub 3}, Na/NH{sub 3} and borohydride reductions and by thermolysis over solid bases

    SciTech Connect

    Pittman, C.U. Jr.

    1996-10-01

    The dechlorination of PCBs, pentachlorophenol, CAHs, and pesticides has been carried out at 35{degrees}C by Ca/NH{sub 3} or Na/NH{sub 3} and at 68{degrees}C by NaBH{sub 2}(OCH{sub 2}CH{sub 2}OCH{sub 3}){sub 2}/NiX{sub 2} salts in THF. Remarkably, PCB-contaminated soils (clay, sandy loam) are remediated within one min at 35{degrees}C (99.9+% PCB destruction) by solvated electrons present in soil/Ca/NH{sub 3} slurries. Wet soils (>25% H{sub 2}O) are decontaminated using Ca stoichiometries far lower than the H{sub 2}O present. Alternatively, PCBs, for example, can be dechlorinated to polyhydroxylatedbiphenols by heating at 250-400{degrees}C over solid CaO/Ca(OH){sub 2}, MgO/Mg(OH){sub 2}, BaO/Ba(OH){sub 2}, KOH or Na{sub 2}CO{sub 3}. The benzyne mechanism was implicated at 375{degrees}C. More highly chlorinated congeners are destroyed more rapidly while the 2,2{prime}-dichloro- and 2-chloro-congeners are most resistant.

  14. Amphiphilic ferrocenylated alkylpyridinium: the formation of micelles and hydrogels and their disaggregation induced by an external stimulus.

    PubMed

    Suzaki, Yuji; Endo, Hirotaka; Kojima, Takahiro; Osakada, Kohtaro

    2013-12-01

    Ferrocene-containing amphiphiles [py-N-(CH2)nOCH2Fc]Cl (n = 6 (1a), 8 (1b), 10 (1c); py = C5H5N, Fc = Fe(C5H4)(C5H5)) were synthesized. The absorption spectra of 1a-1c in the presence of a small amount of dye (Nile red and pyrene) in aqueous media suggested the formation of micelles which encapsulated the dye molecules. Two critical micelle concentrations were observed at 1.1 mM and 2.3 mM at 20 °C. Compounds 1a and 1c showed a single CMC for each, while the formation of two kinds of micelles, the spherical and rod-like ones, depended on the concentrations. The addition of an oxidant, NaOCl, to the aqueous solution of the micelles of 1b turned ferrocene to ferrocenium and caused the disaggregation of the micelles. The addition of α-cyclodextrin (α-CD) to 2b caused the disaggregation of the micelle and the formation of water-soluble [2]- and [3]pseudorotaxane [{py-N-(CH2)8OCH2Fc}(α-CD)m]Cl (1b(α-CD)m) (m = 1, 2), while mixing 1c and α-CD in water formed the rotaxane gel. The addition of NaOCl to the hydrogel of 1c and α-CD changed the gel to sol. PMID:24141739

  15. Reaction of singlet-excited 2,3-diazabicyclo[2.2.2]oct-2-ene and tert-butoxyl radicals with aryl-substituted benzofuranones.

    PubMed

    Lundgren, Cecilia Vannesjö; Koner, Apurba L; Tinkl, Michael; Pischel, Uwe; Nau, Werner M

    2006-03-01

    5,7-Di-tert-butyl-3-aryl-3H-benzofuran-2-ones are lactones with potential antioxidant activity, owing to their abstractable benzylic C-H hydrogens. The fluorescence quenching of the azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO), an established probe for the hydrogen-donor propensity of chain-breaking antioxidants, was investigated for 16 aryl-substituted benzofuranone derivatives [m,m-(CF3)2, p-CN, m-CN, p-CF3, p-COOCH3, m-CF3, p-Cl, p-F, H, m-CH3, p-CH3, m,p-(CH3)2, p-OCH3, o-CH3, o-CF3, o,m-(CH3)2]. Analysis of the rate data in terms of a linear free energy relationship yielded a reaction constant of rho = +0.35. This implies that n,pi*-excited DBO acts as nucleophilic species. In contrast, hydrogen abstraction of tert-butoxyl radicals from the benzofuranones was accelerated by electron-donating substituents (rho = -0.23), in conformity with the electrophilic character of oxygen-centered alkoxyl radicals. Possible implications for the optimization of the hydrogen-donor propensity of antioxidants through structural variation are discussed.

  16. Forces on the Middle EC Module Connections Resulting From Assembly Sequence A

    SciTech Connect

    Wands, R.; /Fermilab

    1986-09-23

    The ANSYS superelement model representing the sequential assembly of the ec modules has been used to calculate the maximum forces experienced at any interface between middle modules during assembly. The assembly sequence used was devised by GTM and is referred to as Sequence A. Fig. 1 shows the assembled model and support. One-half symmetry is assumed. The superelement model supported the OCH modules at theta = 56.25 in such a way that the support was allowed to translate freely in the horizontal direction, and rotate freely about the longitudinal (beam) axis. This produces 'worst case' module connecting forces, and is justified given the importance of these connections. The middle modules were supported within the OCH arch only through theta = 56.25. Each middle module interface contained six connection points in the fmite element model through which the forces were transmitted between modules. In presenting the results here, the forces at the three connection locations at the inner radius of each interface were summed, and the largest value found. This was also done for the outer radius. In applying these results to the design of the actual connections, the forces presented here should be divided by the actual number of connection points used.

  17. T helper type 2-polarized invariant natural killer T cells reduce disease severity in acute intra-abdominal sepsis

    PubMed Central

    Anantha, R V; Mazzuca, D M; Xu, S X; Porcelli, S A; Fraser, D D; Martin, C M; Welch, I; Mele, T; Haeryfar, S M M; McCormick, J K

    2014-01-01

    Sepsis is characterized by a severe systemic inflammatory response to infection that is associated with high morbidity and mortality despite optimal care. Invariant natural killer T (iNK T) cells are potent regulatory lymphocytes that can produce pro- and/or anti-inflammatory cytokines, thus shaping the course and nature of immune responses; however, little is known about their role in sepsis. We demonstrate here that patients with sepsis/severe sepsis have significantly elevated proportions of iNK T cells in their peripheral blood (as a percentage of their circulating T cells) compared to non-septic patients. We therefore investigated the role of iNK T cells in a mouse model of intra-abdominal sepsis (IAS). Our data show that iNK T cells are pathogenic in IAS, and that T helper type 2 (Th2) polarization of iNK T cells using the synthetic glycolipid OCH significantly reduces mortality from IAS. This reduction in mortality is associated with the systemic elevation of the anti-inflammatory cytokine interleukin (IL)-13 and reduction of several proinflammatory cytokines within the spleen, notably interleukin (IL)-17. Finally, we show that treatment of sepsis with OCH in mice is accompanied by significantly reduced apoptosis of splenic T and B lymphocytes and macrophages, but not natural killer cells. We propose that modulation of iNK T cell responses towards a Th2 phenotype may be an effective therapeutic strategy in early sepsis. PMID:24965554

  18. 2-Methoxyphenyl isocyanate and 2-Methoxyphenyl isothiocyanate: conformers, vibration structure and multiplet Fermi resonance.

    PubMed

    Yenagi, Jayashree; Nandurkar, Anita R; Tonannavar, J

    2012-06-01

    IR and Raman spectral measurements in the region 3500-400/50 cm(-1) have been made for the liquid samples of 2-Methoxyphenyl isocyanate and 2-Methoxyphenyl isothiocyanate. A complete assignment of the measured bands has been proposed as aided by conformational and vibration analyses at B3LYP/6-311++G** level of calculations. Three conformers for 2-Methoxyphenyl isocyanate and two for 2-Methoxyphenyl isothiocyanate have been determined. The tilt of the isocyanate (NCO) and isothiocyanate (NCS) moieties with respect to phenyl ring are in broad agreement with their parents. Stretching mode frequencies of methyl group (-OCH(3)) in 2-Methoxyphenyl isocyanate have been lowered in the 2900-2800 cm(-1); deformation asymmetric modes are IR strong and symmetric one Raman strong. In 2-Methoxyphenyl isothiocyanate, a similar pattern is true for stretching modes but deformation asymmetric modes are IR strong and symmetric mode has not been observed. Multiplet absorption band system near 2200 cm(-1) in 2-Methoxyphenyl isocyanate has been interpreted to be caused by Fermi resonance. A similar pattern in absorption near 2100 cm(-1) in 2-Methoxyphenyl isothiocyanate but more complex Raman band pattern has also been explained through Fermi resonance from heuristic stand-point. Many Raman modes in 1300-1100 cm(-1) are intensified apparently owing to isothiocyanate than isocyanate moiety. Phenyl ring breathing mode is shifted to 1040 cm(-1) as strong Raman; the symmetric stretching mode of O-CH(3) near 1023 cm(-1) as strong absorption.

  19. Leishmania amazonensis: heme stimulates (Na(+)+K(+))ATPase activity via phosphatidylinositol-specific phospholipase C/protein kinase C-like (PI-PLC/PKC) signaling pathways.

    PubMed

    Almeida-Amaral, Elmo Eduardo; Cardoso, Viviane Carrozino; Francioli, Fernanda Gomes; Meyer-Fernandes, José Roberto

    2010-04-01

    In the present paper we studied the involvement of the phosphatidylinositol-specific PLC (PI-PLC)/protein kinase C (PKC) pathway in (Na(+)+K(+))ATPase stimulation by heme in Leishmania amazonensis promastigotes. Heme stimulated the PKC-like activity with a concentration of 50nM. Interestingly, the maximal stimulation of the PKC-like activity promoted by phorbol ester was of the same magnitude promoted by heme. However, the stimulatory effect of heme is completely abolished by ET-18-OCH(3) and U73122, specific inhibitors of PI-PLC. (Na(+)+K(+))ATPase activity is increased in the presence of increased concentrations of heme, being maximally affected at 50nM. This effect was completely reversed by 10nM calphostin C, an inhibitor of PKC. Thus, the effect of 50nM heme on (Na(+)+K(+))ATPase activity is completely abolished by ET-18-OCH(3) and U73122. Taken together, these results demonstrate that the heme receptor mediates the stimulatory effect of heme on the (Na(+)+K(+))ATPase activity through a PI-PLC/PKC signaling pathway. PMID:20045694

  20. The MAPKKK Ste11 regulates vegetative growth through a kinase cascade of shared signaling components.

    PubMed

    Lee, B N; Elion, E A

    1999-10-26

    In haploid Saccharomyces cerevisiae, the mating and invasive growth (IG) pathways use the same mitogen-activated protein kinase kinase kinase kinase (MAPKKKK, Ste20), MAPKKK (Ste11), MAPKK (Ste7), and transcription factor (Ste12) to promote either G(1) arrest and fusion or foraging in response to distinct stimuli. This exquisite specificity is the result of pathway-specific receptors, G proteins, scaffold protein, and MAPKs. It is currently not thought that the shared signaling components function under the basal conditions of vegetative growth. We tested this hypothesis by searching for mutations that cause lethality when the STE11 gene is deleted. Strikingly, we found that Ste11, together with Ste20, Ste7, Ste12, and the IG MAPK Kss1, functions in a third pathway that promotes vegetative growth and is essential in an och1 mutant that does not synthesize mannoproteins. We term this pathway the STE vegetative growth (SVG) pathway. The SVG pathway functions, in part, to promote cell wall integrity in parallel with the protein kinase C pathway. During vegetative growth, the SVG pathway is inhibited by the mating MAPK Fus3. By contrast, the SVG pathway is constitutively activated in an och1 mutant, suggesting that it senses intracellular changes arising from the loss of mannoproteins. We predict that general proliferative functions may also exist for other MAPK cascades thought only to perform specialized functions. PMID:10535982

  1. Surface chemistry of boron-doped SiO{sub 2} CVD: Enhanced uptake of tetraethyl orthosilicate by hydroxyl groups bonded to boron

    SciTech Connect

    Bartram, M.E.; Moffat, H.K.

    1993-12-31

    Insight into how dopants can enhance deposition rates has been obtained by comparing reactivities of tetraethyl orthosilicate (TEOS, Si(OCH{sub 2}CH{sub 3}){sub 4}) with silanol and boranol groups on SiO{sub 2}. This comparison is relevant for boron-doped SiO{sub 2} film growth from TEOS and trimethyl borate (TMB, B(OCH{sub 3}){sub 3}) sources since boranols and silanols are expected to be present on surface during the (CVD). A silica substrate having coadsorbed deuterated silanols (SIOD) and boranols (BOD) was reacted with TEOS in a cold-wall reactor in the mTorr pressure regime at 1000K. Reactions were followed with Fourier transform infrared spectroscopy. Use of deuterated hydroxyls allowed consumption of hydroxyls by TEOS chemisorption to be distinguished from concurrent formation of SIOH and BOH that results from TEOS decomposition. It was found that TEOS reacts with BOD at twice the rate observed for SIOD demonstrating that hydroxyl groups bonded to boron increase the rate of TEOS chemisorption. Surface ethoxy groups produced by chemisorption of TEOS decompose at a slower rate in the presence of TMB decomposition products. Possible dependencies on reactor geometries and other deposition conditions may determine which of these two competing effects will control deposition rates. This may explain (in part) why the rate enhancement effect is not always observed in boron-doped SiO{sub 2} CVD processes.

  2. Femtosecond laser spectroscopy and DFT studies of photochromic dithizonatomercury complexes.

    PubMed

    von Eschwege, Karel G; Bosman, Gurthwin; Conradie, Jeanet; Schwoerer, Heinrich

    2014-02-01

    The ultrafast dynamics of the photochromic reaction of dithizonatophenylmercury(II) was recently reported. For purpose of investigating the effect of electronically different substituents (X = o-F, m-F, p-F, p-Cl, o-CH3, m-CH3, p-CH3, m,p-diCH3, p-OCH3, o-SCH3, and p-SCH3) on this reaction, a series of phenyl-substituted dithizones were synthesized and complexed with phenylmercury(II). A variation of more than 3 ps in ground state repopulation times was observed, with the o-methyl derivative absorbing both at shortest wavelength and having the fastest repopulation time, while the p-S-methyl derivative lies at the opposite extremity. An increase in both decay times and λmax values is generally reflected by an increase in electron density in the chromophore. Ultrafast rates also proved to be dependent on solvent polarity, while a profound solvatochromic effect was observed in the transition state absorbance. Density functional theory realistically simulated isomer stabilities, electronic spectra and molecular orbitals. Increased electron density enhances stability in the photoexcited blue isomer relative to the orange resting state, as seen from a comparison between orange and blue isomer total bonding energies. A linear trend between computed HOMO energies and experimental λmax of related aliphatic substituted derivatives was found. PMID:24422764

  3. The New World whirligig beetles of the genus Dineutus Macleay, 1825 (Coleoptera, Gyrinidae, Gyrininae, Dineutini).

    PubMed

    Gustafson, Grey T; Miller, Kelly B

    2015-01-01

    All New World members of the whirligig beetle genus Dineutus Macleay, 1825 are treated. The New World Dineutus are found to be composed of 18 species and 6 subspecies: one species, Dineutusmexicanus Ochs, 1925, stat. n. is elevated from subspecies to species rank, and the subspecies Dineutuscarolinusmutchleri Ochs, 1925, syn. n. is synonymized here with the typical form. Lectotypes are designated for Dineutusdiscolor Aubé, 1838, Dineutesmetallicus Aubé, 1838, Dineutussolitarius Aubé, 1838, Dineutesanalis Régimbart, 1883, and Gyrinuslongimanus Olivier, 1795. Each taxonomic unit is provided with a taxonomic history, type locality, diagnosis, distribution, habitat information, and a discussion section. The aedeagus and male mesotarsal claws are illustrated, and dorsal and ventral habitus images of both sexes, for each species and subspecies are provided. General distribution maps are provided for all taxonimc units. A key to the genera of New World Gyrinidae, as well as all the New World Dineutus species is provided. General Dineutus anatomy as well as a clarification of homology and anatomical terms is included.

  4. The New World whirligig beetles of the genus Dineutus Macleay, 1825 (Coleoptera, Gyrinidae, Gyrininae, Dineutini)

    PubMed Central

    Gustafson, Grey T.; Miller, Kelly B.

    2015-01-01

    Abstract All New World members of the whirligig beetle genus Dineutus Macleay, 1825 are treated. The New World Dineutus are found to be composed of 18 species and 6 subspecies: one species, Dineutus mexicanus Ochs, 1925, stat. n. is elevated from subspecies to species rank, and the subspecies Dineutus carolinus mutchleri Ochs, 1925, syn. n. is synonymized here with the typical form. Lectotypes are designated for Dineutus discolor Aubé, 1838, Dineutes metallicus Aubé, 1838, Dineutus solitarius Aubé, 1838, Dineutes analis Régimbart, 1883, and Gyrinus longimanus Olivier, 1795. Each taxonomic unit is provided with a taxonomic history, type locality, diagnosis, distribution, habitat information, and a discussion section. The aedeagus and male mesotarsal claws are illustrated, and dorsal and ventral habitus images of both sexes, for each species and subspecies are provided. General distribution maps are provided for all taxonimc units. A key to the genera of New World Gyrinidae, as well as all the New World Dineutus species is provided. General Dineutus anatomy as well as a clarification of homology and anatomical terms is included. PMID:25685002

  5. Isotope Fractionation Associated with the Indirect Photolysis of Substituted Anilines in Aqueous Solution.

    PubMed

    Ratti, Marco; Canonica, Silvio; McNeill, Kristopher; Bolotin, Jakov; Hofstetter, Thomas B

    2015-11-01

    Organic micropollutants containing aniline substructures are susceptible to different light-induced transformation processes in aquatic environments and water treatment operations. Here, we investigated the magnitude and variability of C and N isotope fractionation during the indirect phototransformation of four para-substituted anilines in aerated aqueous solutions. The model photosensitizers, namely 9,10-anthraquinone-1,5-disulfonate and methylene blue, were used as surrogates for dissolved organic matter chromophores generating excited triplet states in sunlit surface waters. The transformation of aniline, 4-CH3-, 4-OCH3-, and 4-Cl-aniline by excited triplet states of the photosensitizers was associated with inverse and normal N isotope fractionation, whereas C isotope fractionation was negligible. The apparent 15N kinetic isotope effects (AKIE) were almost identical for both photosensitizers, increased from 0.9958±0.0013 for 4-OCH3-aniline to 1.0035±0.0006 for 4-Cl-aniline, and correlated well with the electron donating properties of the substituent. N isotope fractionation is pH-dependent in that H+ exchange reactions dominate below and N atom oxidation processes above the pKa value of the substituted aniline's conjugate acid. Correlations of C and N isotope fractionation for indirect phototransformation were different from those determined previously for the direct photolysis of chloroanilines and offer new opportunities to distinguish between abiotic degradation pathways. PMID:26418612

  6. Fluorinated microemulsions: A study of the phase behavior and structure

    SciTech Connect

    LoNostro, P.; Choi, S.M.; Chen, S.H.; Ku, C.Y.

    1999-06-24

    Fluorinated surfactants have been studied for their peculiar property to form micellar aggregates in water and oils (hydrocarbons or fluorocarbons) and to produce stable microemulsions. Because of their capacity to dissolve large amounts of gases (such as oxygen and carbon dioxide) and for their characteristic physicochemical properties, fluorocarbons have been tested for specific medical purposes, and their microemulsions are among the most promising candidates for the production of suitable blood substitutes and other biocompatible fluids. The authors have synthesized a new partially fluorinated nonionic surfactant, namely, F(CF{sub 2}){sub 7}-CO-(OCH{sub 2}CH{sub 2}){sub 7.2}OCH{sub 3} (I), that forms stable microemulsions with water and perfluorocarbons such as perfluorooctane (PFO). In this paper the authors describe for the first time the phase behaviors of perfluorooctanoic acid (PFOA) in water/PFH and in water/PFO, and that of ester I in water/PFO. Small-angle neutron-scattering (SANS) experiments provide a detailed description of the microstructure of the H{sub 2}O/PFO/PFOA ternary system.

  7. Lewis acid-base adducts of group 13 elements: synthesis, structure and reactivity toward benzaldehyde.

    PubMed

    Ganesamoorthy, C; Matthias, M; Bläser, D; Wölper, C; Schulz, S

    2016-07-28

    Lewis acid-base adducts [LGa-M(C6F5)3] (M = B 1, Al 2, Ga 3) were prepared by the reaction of gallanediyl LGa {L = HC[C(Me)N(2,6-i-Pr2C6H3)]2} with the Lewis acids M(C6F5)3 (M = B, Al, Ga). Benzaldehyde reacts with [LGa-M(C6F5)3] (M = B 1, Al 2) at room temperature with the insertion and formation of [LGa(C6F5){CH(Ph)(OB(C6F5)2)}] (4) and the zwitterionic species [LGa(C6F5){CH(Ph)(OAl(C6F5)2)}] (5), respectively, which was found to decompose at 80 °C with the formation of {(C6F5)2Al(OCH2Ph)}2 (6). Any attempts to isolate the insertion complex of [LGa-Ga(C6F5)3] with benzaldehyde failed and only {(C6F5)2Ga(OCH2Ph)}2 (7) was isolated at elevated temperatures. 2-5 and 7 were structurally characterized by heteronuclear NMR spectroscopy and single crystal X-ray diffraction.

  8. Capsaicin, a tasty free radical scavenger: mechanism of action and kinetics.

    PubMed

    Galano, Annia; Martínez, Ana

    2012-01-26

    The free radical scavenging activity of capsaicin (CAP), which is the pungent component of hot chili peppers, has been studied in aqueous and lipid solutions, using the density functional theory. Different mechanisms of reaction have been considered: single electron transfer (SET), hydrogen transfer (HT), and radical adduct formation (RAF). Rate constants and branching ratios of the different channels of reaction are provided, as well as an interpretation of the UV-vis spectra. CAP is predicted to react faster in aqueous solution than in nonpolar media with oxygenated free radicals, and it was found to be a more efficient scavenger than melatonin and caffeine. It was also found that while SET does not contribute to the overall reactivity of CAP toward (•)OOH, (•)OOCH(3), and (•)OCH(3) radicals, it might be important for the reactions with more electrophilic radicals such as (•)OH, (•)OCCl(3), and (•)OOCCl(3). The main process, responsible for the peroxyl scavenging activity of CAP, was found to be the HT from the OH phenolic group. For the reaction with (•)OCH(3), on the other hand, the HT from allylic sites are predicted to be the main channels of reaction. In this particular case a wider product distribution is predicted. This supports the role of the reacting free radical on the preponderant mechanism of action of free radical scavengers. PMID:22188587

  9. Design of peptides with α,β-dehydro-residues: syntheses, crystal structures and molecular conformations of two ΔPhe-Trp containing peptides

    NASA Astrophysics Data System (ADS)

    Vijayaraghavan, R.; Makker, J.; Kumar, P.; Dey, S.; Singh, T. P.

    2003-06-01

    The ΔPhe-Trp is a newly designed moiety that was found inducing a unique conformation in peptides. The peptides Boc-L-Val-ΔPhe-L-Trp-OCH 3 (I) and Boc-L-Leu-ΔPhe-L-Trp-OCH 3 (II) were synthesized by azlactone method in solution phase. The peptide (I) was crystallized from its solution in ethanol-water mixture in orthorhombic space group P2 12 12 1 with a=10.663(3) Å, b=11.204(3) Å, c=26.516(10) Å and peptide (II) was crystallized from its solution in acetone in a monoclinic space group P2 1 with a=9.354(1)Å, b=11.218(4)Å, c=15.633(1)Å and β=101.83(1)°. The structures were determined by direct methods. Peptide (I) was refined to an R value of 0.059 for 1554 observed reflections [ I≥2 σ (I)] and peptide (II) was refined to an R value of 0.043 for 2920 observed reflections [ I≥2 σ (I)]. The structures of peptides (I) and (II) were found to be identical. They formed an unusual type VIa β-turn conformation which is observed for the first time with a ΔPhe residue at ( i+2) position indicating a unique influence of ΔPhe-Trp moiety in inducing a reproducible new structure in peptides.

  10. OH Production from Reactions of Organic Peroxy Radicals with HO2 : Recent Studies on Ether-Derived Peroxy Radicals

    NASA Astrophysics Data System (ADS)

    Orlando, J. J.; Tyndall, G. S.; Kegley Owen, C. S.; Reynoldson, N.

    2013-12-01

    There is now ample evidence supporting significant formation of OH radicals in the reaction of HO2 with certain organic peroxy radicals (RO2). These reaction channels serve to promote radical propagation, and thus have the potential to alter HOx budgets and partitioning and hence tropospheric oxidative capacity. While much focus has been placed on OH production from reactions involving carbonyl-containing RO2 species, it is also the case that other oxygen- substituted peroxy species (e.g., CH3OCH2OO, HOCH2OO) likely generate OH in their reactions with HO2 (see ref. 1 and refs therein). In this work, the Cl-atom-initiated oxidation of two ethers, diethyl and diisopropyl ether, is investigated over ranges of conditions in an environmental chamber, using both FTIR and GC-FID methods for product quantification. Preliminary analysis suggests that significant OH production is occurring in the reaction of HO2 with CH3CH2OCH(OO)CH3, and also provides evidence for a rapid unimolecular reaction of diisopropyl ether-derived peroxy radicals. Details of these and other results will be described. 1. Orlando, J. J., and G. S. Tyndall, 2012: Laboratory studies of organic peroxy radical chemistry: an overview with emphasis on recent issues of atmospheric significance, Chemical Society Reviews, 41, 6294-6317, doi: 10.1039/C2CS35166H.

  11. Molecular properties of protonated homogeneous and mixed carbon oxide and carbon dioxide clusters

    NASA Astrophysics Data System (ADS)

    Szymczak, Jaroslaw J.; Roszak, Szczepan; Gora, Robert W.; Leszczynski, Jerzy

    2003-10-01

    The molecular structures and characteristics of CO and CO2 protonated homogeneous and mixed complexes were studied by theoretical, ab initio calculations. The thermodynamics, vibrational properties, charge distribution, and interaction energy decomposition components are investigated as a function of the increasing size of clusters. The study reveals the similarities and differences between homogeneous protonated carbon oxide and protonated carbon dioxide clusters. In the first-order approximation the structural differences between (CO)nH+ and (CO2)nH+ clusters are the consequence of the electronic charge distribution in the protonated OCH+ and OCOH+ core fragments. The symmetry of protonated dimers, constituting the cationic core of clusters is the second important factor in determining the overall structure of extended complexes. The OCH+ as well as the OCOH+ fragments are stabilized by cluster formation. The structures and energetics of complexes emerge as a balance between competing electrostatic, exchange, and covalent interactions. The directional covalent forces prevail and enforce the structure of the complexes, however. A universal approach is proposed which allows for the computation of interaction energies for chemical reactions involving significant relaxation of the reactants.

  12. (Acetonitrile){2-[bis-(pyridin-2-ylmethyl-κ(2)N)amino-κN]-N-(2,6-dimethyl-phen-yl)acetamide-κO}(perchlorato-κO)zinc (acetonitrile){2-[bis-(pyridin-2-ylmethyl-κ(2)N)amino-κN]-N-(2,6-dimethyl-phen-yl)acetamide-κO}zinc tris-(perchlorate).

    PubMed

    Astrand, Ove Alexander Høgmoen; Görbitz, Carl Henrik; Kristoffersen, Kenneth Aase; Rongved, Pål

    2013-02-01

    In the title salt, [Zn(C(22)H(24)N(4)O)(CH(3)CN)][Zn(ClO(4))(C(22)H(24)N(4)O)(CH(3)CN)](ClO(4))(3), two differently coordinated zinc cations occur. In the first complex, the metal ion is coordinated by the N,N',N'',O-tetra-dentate acetamide ligand and an acetonitrile N atom, generating an approximate trigonal-bipyramidal coordination geometry, with the O atom in an equatorial site and the acetonitrile N atom in an axial site. In the second complex ion, a perchlorate ion is also bonded to the zinc ion, generating a distorted trans-ZnO(2)N(4) octa-hedron. Of the uncoordinating perchlorate ions, one lies on a crystallographic twofold axis and one lies close to a twofold axis and has a site occupancy of 0.5. N-H⋯O and N-H⋯(O,O) hydrogen bonds are observed in the crystal. Disordered solvent mol-ecules occupy about 11% of the unit-cell volume; their contribution to the scattering was removed with the SQUEEZE routine of the PLATON program [Spek (2009 ▶). Acta Cryst. D65, 148-155.]. PMID:23424407

  13. Isotope Fractionation Associated with the Indirect Photolysis of Substituted Anilines in Aqueous Solution.

    PubMed

    Ratti, Marco; Canonica, Silvio; McNeill, Kristopher; Bolotin, Jakov; Hofstetter, Thomas B

    2015-11-01

    Organic micropollutants containing aniline substructures are susceptible to different light-induced transformation processes in aquatic environments and water treatment operations. Here, we investigated the magnitude and variability of C and N isotope fractionation during the indirect phototransformation of four para-substituted anilines in aerated aqueous solutions. The model photosensitizers, namely 9,10-anthraquinone-1,5-disulfonate and methylene blue, were used as surrogates for dissolved organic matter chromophores generating excited triplet states in sunlit surface waters. The transformation of aniline, 4-CH3-, 4-OCH3-, and 4-Cl-aniline by excited triplet states of the photosensitizers was associated with inverse and normal N isotope fractionation, whereas C isotope fractionation was negligible. The apparent 15N kinetic isotope effects (AKIE) were almost identical for both photosensitizers, increased from 0.9958±0.0013 for 4-OCH3-aniline to 1.0035±0.0006 for 4-Cl-aniline, and correlated well with the electron donating properties of the substituent. N isotope fractionation is pH-dependent in that H+ exchange reactions dominate below and N atom oxidation processes above the pKa value of the substituted aniline's conjugate acid. Correlations of C and N isotope fractionation for indirect phototransformation were different from those determined previously for the direct photolysis of chloroanilines and offer new opportunities to distinguish between abiotic degradation pathways.

  14. Pyrolysis of silica-immobilized benzyl phenyl ether: Competing radical rearrangement pathways under restricted diffusion

    SciTech Connect

    Buchanan, A.C. III; Britt, P.F.; Skeen, J.T.; Struss, J.A.; Elam, C.L.

    1998-12-25

    Pyrolysis studies of silica-immobilized benzyl phenyl ether ({approx}PhOCH{sub 2}Ph or {approx}BPE), a model for related ether structures in fuel resources, have been conducted at 275--325 C to examine the impact of restricted mass transport on the pyrolysis mechanism compared with previous studies in fluid phases. Significant rearrangement chemistry is observed for {approx}BPE occurring through two competitive free-radical pathways that are both promoted by the diffusional constraints. One path involves recombination of incipient benzyl and surface-bound phenoxy radicals to form benzylphenol isomers, 10. The second, previously unreported rearrangement path for {approx}BPE involves a 1,2-phenyl shift in an intermediate radical, {approx}PhOCH{center_dot}Ph, leading to formation of benzhydrol (8) and benzophenone (9) as principal products. The rearrangement products 8--10 typically account for ca. 50% of the pyrolysis products. However, the path selectivity is a sensitive function of {approx}BPE surface coverage and the presence of spacer molecules that either facilitate or hinder hydrogen atom transfer steps on the surface.

  15. Capsaicin, a tasty free radical scavenger: mechanism of action and kinetics.

    PubMed

    Galano, Annia; Martínez, Ana

    2012-01-26

    The free radical scavenging activity of capsaicin (CAP), which is the pungent component of hot chili peppers, has been studied in aqueous and lipid solutions, using the density functional theory. Different mechanisms of reaction have been considered: single electron transfer (SET), hydrogen transfer (HT), and radical adduct formation (RAF). Rate constants and branching ratios of the different channels of reaction are provided, as well as an interpretation of the UV-vis spectra. CAP is predicted to react faster in aqueous solution than in nonpolar media with oxygenated free radicals, and it was found to be a more efficient scavenger than melatonin and caffeine. It was also found that while SET does not contribute to the overall reactivity of CAP toward (•)OOH, (•)OOCH(3), and (•)OCH(3) radicals, it might be important for the reactions with more electrophilic radicals such as (•)OH, (•)OCCl(3), and (•)OOCCl(3). The main process, responsible for the peroxyl scavenging activity of CAP, was found to be the HT from the OH phenolic group. For the reaction with (•)OCH(3), on the other hand, the HT from allylic sites are predicted to be the main channels of reaction. In this particular case a wider product distribution is predicted. This supports the role of the reacting free radical on the preponderant mechanism of action of free radical scavengers.

  16. Mechanistic and kinetic study on the reactions of coumaric acids with reactive oxygen species: a DFT approach.

    PubMed

    Garzón, Andrés; Bravo, Iván; Barbero, Antonio J; Albaladejo, José

    2014-10-01

    The mechanism and kinetics of reactions between coumaric acids and a series of reactive oxygen species ((•)OX) was studied through the density functional theory (DFT). H atom abstraction from -OH and -COOH groups and addition to the nonaromatic double bond were the most representative reaction pathways chosen for which free energy barriers and rate constants were calculated within the transition state theory (TST) framework. From these calculations, it was estimated that (•)OH > (•)OCH3 > (•)OOH > (•)OOCH3 is the order of reactivity of (•)OX with any coumaric acid. The highest rate constant was estimated for p-coumaric acid + (•)OH reaction, whereas the rest of the (•)OX species are more reactive with o-coumaric acid. On the basis of the calculated rate constants, H abstraction from a -OH group should be the main mechanism for the reactions involving (•)OCH3, (•)OOH, and (•)OOCH3 radicals. Nevertheless, the addition mechanism, which sometimes is not considered in theoretical studies on reactions of phenolic compounds with electrophilic species, could play a relevant role in the global mechanism of coumaric acid + (•)OH reactions.

  17. Model biogas steam reforming in a thin Pd-supported membrane reactor to generate clean hydrogen for fuel cells

    NASA Astrophysics Data System (ADS)

    Iulianelli, A.; Liguori, S.; Huang, Y.; Basile, A.

    2015-01-01

    Steam reforming of a model biogas mixture is studied for generating clean hydrogen by using an inorganic membrane reactor, in which a composite Pd/Al2O3 membrane separates part of the produced hydrogen through its selective permeation. The characteristics of H2 perm-selectivity of the fresh membrane is expressed in terms of H2/N2 ideal selectivity, in this case equal to 4300. Concerning biogas steam reforming reaction, at 380 °C, 2.0 bar H2O:CH4 = 3:1, GHSV = 9000 h-1 the permeate purity of the recovered hydrogen is around 96%, although the conversion (15%) and hydrogen recovery (>20%) are relatively low; on the contrary, at 450 °C, 3.5 bar H2O:CH4 = 4:1, GHSV = 11000 h-1 the conversion is increased up to more than 30% and the recovery of hydrogen to about 70%. This novel work constitutes a reference study for new developments on biogas steam reforming reaction in membrane reactors.

  18. Immobilization of nanobeads on a surface to control the size, shape and distribution of pores in electrochemically generated sol-gel films

    PubMed Central

    Ciabocco, Michela; Berrettoni, Mario; Zamponi, Silvia

    2015-01-01

    Electrochemically assisted deposition of an ormosil film at a potential where hydrogen ion is generated as the catalyst yields insulating films on electrodes. When the base electrode is modified with 20-nm poly(styrene sulfonate), PSS, beads bound to the surface with 3-aminopropyltriethoxysilane (APTES) and using (CH3)3SiOCH3 as the precursor, the resulting film of organically modified silica (ormosil) has cylindrical channels that reflect both the diameter of the PSS and the distribution of the APTES-PSS on the electrode. At an electrode modified by a 20-min immersion in 0.5 mmol dm-3 APTES followed by a 30-s immersion in PSS, a 20-min electrolysis at 1.5 V in acidified (CH3)3SiOCH3 resulted in an ormosil film with 20-nm pores separated by 100 nm. Cyclic voltammetry of Ru(CN)64- at scan rates above 5 mVs-1 yielded currents controlled primarily by linear diffusion. Below 5 mVs-1, convection rather than the expected factor, radial diffusion, apparently limited the current. PMID:26167128

  19. Mechanism and kinetic properties of OH-initiated atmospheric oxidation degradation of methamidophos in the presence of O2/NO

    NASA Astrophysics Data System (ADS)

    Shi, Xiangli; Zhang, Ruiming; Zhang, Qingzhu; Wang, Wenxing

    2016-05-01

    Methamidophos is a member of the organophosphorus insecticides. In the present work, the mechanism of the OH radical-initiated atmospheric oxidation degradation of methamidophos and the possible degradation products were investigated with the aid of quantum chemical calculations. The geometrical parameters and vibrational frequencies were calculated at the MPWB1K/6-31+G(d,p) level. The energies of all the stationary points were carried out at the MPWB1K/6-311+G(3df,2p) level of theory. The rate constants of key elementary steps involved in the OH radical-initiated atmospheric degradation of methamidophos were calculated by meaning of the canonical variation transition-state (CVT) theory with the small curvature tunneling (SCT) correction over the possible atmospheric temperature range of 273-333 K. The rate-temperature formulas were fitted for the first time. The pre-exponential factor and the activation energy were obtained. Studies show that the OH additions from the trans-positions of the NH2 and OCH3 groups, the H abstractions from the SCH3 and OCH3 groups as well as the substitution reaction resulting in the products of CH3OP(O)OHNH2 and SCH3 are thermodynamically favorable reaction pathways for the reaction of methamidophos with OH radicals due to the low barrier and strong exothermicity.

  20. The antiproliferative effect of hexadecylphosphocholine toward HL60 cells is prevented by exogenous lysophosphatidylcholine.

    PubMed

    Boggs, K; Rock, C O; Jackowski, S

    1998-01-01

    The mechanisms that account for the anti-proliferative properties of the biologically active lysophospholipid analog hexadecylphosphocholine (HexPC) were investigated in HL60 cells. HexPC inhibited the incorporation of choline into phosphatidylcholine and the pattern of accumulation of soluble choline-derived metabolites pinpointed CTP:phosphocholine cytidylyltransferase (CT) as the inhibited step in vivo. HexPC also inhibited recombinant CT in vitro. HexPC treatment led to accumulation of cells in G2/M phase, triggered DNA fragmentation and caused morphological changes associated with apoptosis. The supplementation of HexPC-treated cells with exogenous lysophosphatidylcholine (LPC) completely reversed the cytotoxic effects of HexPC and restored HL60 cell proliferation in the presence of the drug. LPC provided an alternate pathway for phosphatidylcholine synthesis via the acylation of exogenous LPC. This result contrasted with the response of HL60 cells to 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3) where LPC overcame the cytotoxic effects but did not support continued cell proliferation. Morphological integrity, DNA stability and cell viability were maintained in cells treated with LPC plus either antineoplastic agent. Thus the inhibition of phosphatidylcholine biosynthesis at the CT step accounts for the cytotoxicity of both HexPC and ET-18-OCH3 which is overridden by providing an alternate pathway for phosphatidylcholine synthesis via the acylation of exogenous LPC.

  1. Visible-Light-Induced Olefin Activation Using 3D Aromatic Boron-Rich Cluster Photooxidants.

    PubMed

    Messina, Marco S; Axtell, Jonathan C; Wang, Yiqun; Chong, Paul; Wixtrom, Alex I; Kirlikovali, Kent O; Upton, Brianna M; Hunter, Bryan M; Shafaat, Oliver S; Khan, Saeed I; Winkler, Jay R; Gray, Harry B; Alexandrova, Anastassia N; Maynard, Heather D; Spokoyny, Alexander M

    2016-06-01

    We report a discovery that perfunctionalized icosahedral dodecaborate clusters of the type B12(OCH2Ar)12 (Ar = Ph or C6F5) can undergo photo-excitation with visible light, leading to a new class of metal-free photooxidants. Excitation in these species occurs as a result of the charge transfer between low-lying orbitals located on the benzyl substituents and an unoccupied orbital delocalized throughout the boron cluster core. Here we show how these species, photo-excited with a benchtop blue LED source, can exhibit excited-state reduction potentials as high as 3 V and can participate in electron-transfer processes with a broad range of styrene monomers, initiating their polymerization. Initiation is observed in cases of both electron-rich and electron-deficient styrene monomers at cluster loadings as low as 0.005 mol%. Furthermore, photo-excitation of B12(OCH2C6F5)12 in the presence of a less activated olefin such as isobutylene results in the production of highly branched poly(isobutylene). This work introduces a new class of air-stable, metal-free photo-redox reagents capable of mediating chemical transformations. PMID:27186856

  2. Cu(II) complexes bearing the 2,2,2-tris(1-pyrazolyl)ethanol or 2,2,2-tris(1-pyrazolyl)ethyl methanesulfonate scorpionates. X-Ray structural characterization and application in the mild catalytic peroxidative oxidation of cyclohexane.

    PubMed

    Silva, Telma F S; Mishra, Gopal S; da Silva, M Fátima Guedes; Wanke, Riccardo; Martins, Luísa M D R S; Pombeiro, Armando J L

    2009-11-14

    Reactions between CuCl2 and the functionalized scorpionate 2,2,2-tris(1-pyrazolyl)ethanol HOCH2C(pz)3 1 (pz = pyrazolyl) or 2,2,2-tris(1-pyrazolyl)ethyl methanesulfonate CH3SO2OCH2C(pz)3 2 yield the corresponding water soluble CuII complexes [CuCl2{HOCH2C(pz)3}] 3 or [CuCl2{CH3SO2OCH2C(pz)3}]2 4. In 3 the scorpionate ligand shows the typical N,N,N-coordination mode, whereas in the dinuclear complex 4 it binds the metal as a bidentate species. Compounds 1-4 have been characterized by IR, far-IR, elemental analysis and (for 2-4) single crystal X-ray diffraction. The new scorpionate complexes 3 and 4 are shown to act as catalyst precursors for the peroxidative oxidation of cyclohexane to cyclohexanol (main product) and cyclohexanone, under mild conditions (at room temperature and using an aqueous solution of H2O2) reaching TON values up to 186 in NCMe/H2O. Their hydrosolubility allows them to operate also in pure aqueous media (without any organic solvent, although less effectively), a rare feature of significance towards a green alkane oxidation process. PMID:20449198

  3. One-pot solvothermal synthesis of a well-ordered layered sodium aluminoalcoholate complex: a useful precursor for the preparation of porous Al2O3 particles

    SciTech Connect

    Li, XS; Michaelis, VK; Ong, TC; Smith, SJ; McKay, I; Muller, P; Griffin, RG; Wang, EN

    2014-01-01

    One-pot solvothermal synthesis of a robust tetranuclear sodium hexakis(glycolato)tris(methanolato)aluminate complex Na-3[Al-4(OCH3)(3)(OCH2CH2O)(6)] via a modified yet rigorous base-catalyzed transesterification mechanism is presented here. Single crystal X-ray diffraction (SCXRD) studies indicate that this unique Al complex contains three pentacoordinate Al3+ ions, each bound to two bidentate ethylene glycolate chelators and one monodentate methanolate ligand. The remaining fourth Al3+ ion is octahedrally coordinated to one oxygen atom from each of the six surrounding glycolate chelators, effectively stitching the three pentacoordinate Al moieties together into a novel tetranuclear Al complex. This aluminate complex is periodically self-assembled into well-ordered layers normal to the [110] axis with the intra-/inter-layer bonding involving extensive ionic bonds from the three charge-counterbalancing Na+ cations rather than the more typical hydrogen bonding interactions as a result of fewer free hydroxyl groups present in its structure. It can also serve as a valuable precursor toward the facile synthesis of high-surface-area alumina powders using a very efficient rapid pyrolysis technique.

  4. Electronic Structure and Optical Properties of Boron Difluoride Dibenzoylmethane Derivatives.

    PubMed

    Tikhonov, Sergey A; Vovna, Vitaliy I; Gelfand, Natalia A; Osmushko, Ivan S; Fedorenko, Elena V; Mirochnik, Anatoliy G

    2016-09-22

    Electronic structure and optical properties of boron difluoride dibenzoylmethanate BF2Dbm and its four derivatives were studied using X-ray photoelectron spectroscopy, absorption and luminescence spectroscopy, and quantum chemistry (DFT and TDDFT). In a series of the studied compounds, the relationship of molecular design and optical properties has been revealed. At the transition from BF2Dbm to BF2Dbm(OCH3)2, the HOMO-LUMO energy gap decreases, resulting in a bathochromic shift of the optical spectra. Substitution of one methoxy group by the nitro group in BF2Dbm(OCH3)2 causes a decrease in the contribution of the chelate ring π-orbital in the LUMO, resulting in a lower value of charge transfer from the substituents to the chelate ring in the case of the first excited state, which determines the characteristics of the main absorption bands. The nitro group transition from the m- to p-position of the benzene ring causes a change in the nature of the main bands of the optical spectra due to the increase of the splitting value of the LUMO and LUMO+1 levels. The main band in the optical spectra of the complex containing the C10H7 group is associated with the charge transfer transitions. PMID:27580170

  5. The effect of a paramagnetic metal ion within a molecule: comparison of the structurally identical paramagnetic [3,3-Fe(1,2-C2B9H11)2]- with the diamagnetic [3,3-Co(1,2-C2B9H11)2]- sandwich complexes.

    PubMed

    Cioran, Ana M; Teixidor, Francesc; Viñas, Clara

    2015-02-14

    Derivatives of the ferrabisdicarbollide [3,3'-Fe(1,2-C(2)B(9)H(11))(2)](-) have been produced starting from the zwitterion [3,3'-Fe(8-(OCH(2)CH(2))(2)-1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))], 1, upon reaction with nucleophiles: alkoxides, halides and hydrosulfide ions HS(-). The result has been the preparation of [3,3'-Fe(8-(OCH(2)CH(2))(2)R/X-1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))] (R = OMe, [2](-); OEt, [3](-); OCH(2)CH(2)OCH(3), [4](-); and X = Cl, [5](-); Br, [6](-); I, [7](-); and SH, [8](-)). The reaction behavior of is comparable to the well-studied cobalt equivalent, [3,3'-Co(8-(OCH(2)CH(2))2-1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))], and the yields and stability of the resulting complexes are similar. These results are relevant taking into account that [3,3'-Fe(1,2-C(2)B(9)H(11))(2))(-) is a paramagnetic anion. Implications of this are observed in the (11)B-, (1)H and (13)C NMR spectra of [3,3'-Co(1,2-C(2)B(9)H(11))(2)](-) and [3,3'-Fe(1,2-C(2)B(9)H(11))(2)](-) that having identical sandwich molecular structures and the same negative charge have absolutely different widths of the NMR field, between 15 and -25 ppm for [3,3'-Co(1,2-C(2)B(9)H(11))(2)](-) and in the range 150 to -550 ppm for [3,3'-Fe(1,2-C(2)B(9)H(11))(2)](-). The sharpness of both spectra is on the other hand comparable, although no B-H couplings are observed in the Fe metallacarborane or its derivatives. Remarkable is the comparative influence vs. [3,3'-Co(1,2-C(2)B(9)H(11))(2)](-) of replacing Co by Fe on the elements of the cluster layer nearest to the metal. The two equivalent C cluster (Cc) atoms are influenced at 36 840 Hz, the two equivalent B atoms that are adjacent to the two Cc are influenced at 38 157 Hz and the single B that is adjacent to the two B atoms is influenced at 44 062 Hz. Remarkable is the similar influence on B and on C, taking into account that the values have been obtained from two distinct NMR spectra of (11)B and (13)C. The {(11)B-(11)B} COSY NMR and {(1)H

  6. Study of the photon-induced formation and subsequent desorption of CH3OH and H2CO in interstellar ice analogs

    NASA Astrophysics Data System (ADS)

    Martín-Doménech, R.; Muñoz Caro, G. M.; Cruz-Díaz, G. A.

    2016-05-01

    Context. Methanol and formaldehyde are two simple organic molecules that are ubiquitously detected in the interstellar medium, in both the solid and gaseous phases. An origin in the solid phase and a subsequent nonthermal desorption into the gas phase is often invoked to explain their abundances in some of the environments where they are found. Experimental simulations under astrophysically relevant conditions have been carried out in the past four decades in order to find a suitable mechanism for that process. Aims: In particular, photodesorption from pure methanol ice (and presumably from pure formaldehyde ice) has been found to be negligible in previous works, probably because both molecules are very readily dissociated by vacuum-UV photons. Therefore, we explore the in situ formation and subsequent photon-induced desorption of these species, studying the UV photoprocessing of pure ethanol ice, and a more realistic binary H2O:CH4 ice analog. Methods: Experimental simulations were performed in an ultra-high vacuum chamber. Pure ethanol and binary H2O:CH4 ice samples deposited onto an infrared transparent window at 8 K were UV-irradiated using a microwave-discharged hydrogen flow lamp. Evidence of photochemical production of these two species and subsequent UV-photon-induced desorption into the gas phase were searched for by means of a Fourier transform infrared spectrometer and a quadrupole mass spectrometer, respectively. After irradiation, ice samples were warmed up to room temperature until complete sublimation was attained for detection of volatile products. Results: Formation of CH3OH was only observed during photoprocessing of the H2O:CH4 ice analog, accounting for ~4% of the initial CH4 ice column density, but no photon-induced desorption was detected. Photochemical production of H2CO was observed in both series of experiments. Formation of formaldehyde accounted for ≤45% conversion of the initial ethanol ice, but it could not be quantified during

  7. Photochemical ozone creation potentials for oxygenated volatile organic compounds: sensitivity to variations in kinetic and mechanistic parameters

    NASA Astrophysics Data System (ADS)

    Jenkin, Michael E.; Hayman, Garry D.

    , and new schemes are incorporated for dimethoxy methane (CH 3OCH 2OCH 3) and dimethyl carbonate (CH 3OC(O)OCH 3), which are proposed fuel additives. New or updated POCP values are calculated for all 37 oxygenated VOCs and, where applicable, these are compared with the previous POCP values and reported Maximum Incremental Reactivity (MIR) values.

  8. Searching for trans ethyl methyl ether in Orion KL⋆

    NASA Astrophysics Data System (ADS)

    Tercero, B.; Cernicharo, J.; López, A.; Brouillet, N.; Kolesniková, L.; Motiyenko, R. A.; Margulès, L.; Alonso, J. L.; Guillemin, J.-C.

    2015-10-01

    We report on the tentative detection of trans ethyl methyl ether (tEME), t-CH3CH2OCH3, through the identification of a large number of rotational lines from each one of the spin states of the molecule towards Orion KL. We also search for gauche-trans-n-propanol, Gt-n-CH3CH2CH2OH, an isomer of tEME in the same source. We have identified lines of both species in the IRAM 30 m line survey and in the ALMA Science Verification data. We have obtained ALMA maps to establish the spatial distribution of these species. Whereas tEME mainly arises from the compact ridge component of Orion, Gt-n-propanol appears at the emission peak of ethanol (south hot core). The derived column densities of these species at the location of their emission peaks are ≤(4.0 ± 0.8) × 1015 cm-2 and ≤(1.0 ± 0.2) × 1015 cm-2 for tEME and Gt-n-propanol, respectively. The rotational temperature is ~100 K for both molecules. We also provide maps of CH3OCOH, CH3CH2OCOH, CH3OCH3, CH3OH, and CH3CH2OH to compare the distribution of these organic saturated O-bearing species containing methyl and ethyl groups in this region. Abundance ratios of related species and upper limits to the abundances of non-detected ethers are provided. We derive an abundance ratio N(CH3OCH3)/N(tEME) ≥ 150 in the compact ridge of Orion. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.00009.SV. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan) with NRC (Canada), NSC, and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. This work was also based on observations carried out with the IRAM 30-m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).Appendix A is available in electronic form at http://www.aanda.org

  9. Thermal Decomposition Mechanisms of Lignin Model Compounds: From Phenol to Vanillin

    NASA Astrophysics Data System (ADS)

    Scheer, Adam Michael

    Lignin is a complex, aromatic polymer abundant in cellulosic biomass (trees, switchgrass etc.). Thermochemical breakdown of lignin for liquid fuel production results in undesirable polycyclic aromatic hydrocarbons that lead to tar and soot byproducts. The fundamental chemistry governing these processes is not well understood. We have studied the unimolecular thermal decomposition mechanisms of aromatic lignin model compounds using a miniature SiC tubular reactor. Products are detected and characterized using time-of-flight mass spectrometry with both single photon (118.2 nm; 10.487 eV) and 1 + 1 resonance-enhanced multiphoton ionization (REMPI) as well as matrix isolation infrared spectroscopy. Gas exiting the heated reactor (300 K--1600 K) is subject to a free expansion after a residence time of approximately 100 micros. The expansion into vacuum rapidly cools the gas mixture and allows the detection of radicals and other highly reactive intermediates. By understanding the unimolecular fragmentation patterns of phenol (C6H5OH), anisole (C6H 5OCH3) and benzaldehyde (C6H5CHO), the more complicated thermocracking processes of the catechols (HO-C 6H4-OH), methoxyphenols (HO-C6H4-OCH 3) and hydroxybenzaldehydes (HO-C6H4-CHO) can be interpreted. These studies have resulted in a predictive model that allows the interpretation of vanillin, a complex phenolic ether containing methoxy, hydroxy and aldehyde functional groups. This model will serve as a guide for the pyrolyses of larger systems including lignin monomers such as coniferyl alcohol. The pyrolysis mechanisms of the dimethoxybenzenes (H3C-C 6H4-OCH3) and syringol, a hydroxydimethoxybenzene have also been studied. These results will aid in the understanding of the thermal fragmentation of sinapyl alcohol, the most complex lignin monomer. In addition to the model compound work, pyrolyisis of biomass has been studied via the pulsed laser ablation of poplar wood. With the REMPI scheme, aromatic lignin decomposition

  10. Effects of methanol on the thermodynamics of iron(III) [tetrakis(pentafluorophenyl)]porphyrin chloride dissociation and the creation of catalytically active species for the epoxidation of cyclooctene.

    PubMed

    Stephenson, Ned A; Bell, Alexis T

    2006-07-10

    In a previous study, the authors showed that iron(III) [tetrakis(pentafluorophenyl)]porphyrin chloride [(F20TPP)FeCl] is catalytically inactive for cyclooctene epoxidation by hydrogen peroxide in acetonitrile but is catalytically active if the solvent contains methanol. It was suggested that the precursor to the active species is (F20TPP)Fe(OCH3) in methanol-containing solvents. The present study was aimed at evaluating this hypothesis. (F20TPP)Fe(OCH3) was synthesized and characterized by 1H NMR but was found to be inactive in both acetonitrile and methanol. Further investigation of the interactions of (F20TPP)FeCl with methanol in acetonitrile/methanol mixtures was then carried out using NMR. Two species, characterized by 1H NMR resonances at 82 and 65 ppm, were observed. The first resonance is attributed to the beta-pyrrole protons on molecularly dissolved (F20TPP)FeCl, whereas the second is attributed to beta-pyrrole protons of [(F20TPP)Fe]+ cations that are stabilized by coordination with a molecule of methanol, viz., [(F20TPP)Fe(CH3OH)]+. The relative concentration of [(F20TPP)Fe(CH3OH)]+ increases as the fraction of methanol in the solvent increases, suggesting that methanol facilitates the dissociation of (F20TPP)FeCl into cations and anions. A thermodynamic model of the dissociation is proposed and found to describe successfully the experimental observation over a range of solvent compositions, porphyrin concentrations, and temperatures. UV-visible spectroscopy was also used to validate the developed model. In addition, the observed rate constant for cyclooctene epoxidation was found to be proportional to the concentration of [(F20TPP)Fe(CH3OH)]+ calculated using the thermodynamic model, suggesting that this intermediate is a precursor to the species that catalyzes olefin epoxidation. The catalytic activity of [(F20TPP)Fe(CH3OH)]+ was further confirmed through experiments in which (F20TPP)Fe(OCH3) dissolved in methanol was reacted with HCl(aq). This

  11. Schiff base mediated sol-gel polymerization

    SciTech Connect

    Lindquist, D.A.; Harrison, C.M.; Williams, B.; Morris, R.D.

    1996-12-31

    Formation of a Schiff base imine by reacting a primary amine with either an aldehyde or ketone was initiated by an aluminum compound acting as a Lewis acid catalyst. The water byproduct of the reaction then was used as an in situ reagent for subsequent hydrolysis and sol-gel condensation of the aluminum species. These reactions yielded a gel network containing the entrained Schiff base. Two examples of this synthetic approach are described with two different aluminum catalyst/reagents: a diethylaluminum diethylphosphate ester [(CH{sub 3}CH{sub 2}){sub 2}Al-O-P(O)(OCH{sub 2}CH{sub 3}){sub 2}] and triethyl aluminum [Al(CH{sub 3}CH{sub 2}){sub 3}]. Anhydrous ammonia and acetone were used as the Schiff base precursors.

  12. Synthesis and Fluorescence Properties of Eu(3+), Tb(3+) Complexes with Schiff Base Derivatives.

    PubMed

    Liu, Yanhong; Kong, Weihua; Yang, Zehui; Dai, Ming; Shi, Ling; Guo, Dongcai

    2016-03-01

    Novel Schiff base ligands derived from N'-benzylidene-benzohydrazide (substituted by -H, -CH3, -OCH3, -Cl) and 2-chloro-N-phenylacetamide were synthesized. The solid complexes of rare earth (Eu, Tb) nitrate with these Schiff base ligands were synthesized and characterized by elemental analysis, EDTA titrimetric analysis, thermal analysis, infrared spectra and UV-Vis spectra analysis. The fluorescence properties of rare earth (Eu, Tb) complexes in solid were studied. Under the excitation of ultraviolet light, these complexes exhibited characteristic emission of europium and terbium ions. The results showed that the ligand favored energy transfer to the emitting energy of Eu and Tb ions. Effects of different ligands on the fluorescence intensity of rare earth (Eu, Tb) complexes had been discussed. The electrochemical properties of rare earth (Eu, Tb) complexes were also investigated.

  13. Dispersive Stabilization of Liquid Crystal-in-Water with Acrylamide Copolymer/Surfactant Mixture: Nematic Curvilinear Aligned Phase Composite Film.

    PubMed

    Park; Lee

    1999-11-01

    The effect of nonionic surfactant, (H(OCH(2)-CH(2))(8)-OC(6)H(4)-C(9)H(19)), on the dispersion stabilization of liquid crystal (LC)-in-water with acrylamide copolymer containing the related nonylphenyl groups was studied. It was observed that the addition of nonionic surfactant increases the stability of LC dispersions and improves the electrooptical properties of the nematic curvilinear aligned phase (NCAP) composite film. On the basis of the surface tension, reduced viscosity, cloud point, and coalescence time measurements, it was proposed that formation of an integrated structure induced by interactions between hydrophobic groups in the polymer chains is probably important to fabrication of a polymer composite film made of LC and polymer matrix. Copyright 1999 Academic Press.

  14. Synthesis and properties of salicyladehyde salicyhydrazone derivatives and their europium complexes.

    PubMed

    Meng, Defen; Liu, Fen; Lian, Xiaomei; Yang, Zehui; Guo, Dongcai

    2014-11-01

    Four novel salicyladehyde salicyhydrazone derivatives and their corresponding europium (Eu(3+)) complexes were synthesized and characterized. The formulas of the complexes were [EuL(a-d)(NO3)2](NO3) · H2O. The investigatoin of fluoresence properties of the Eu(3+) complexes showed that the salicyladehyde salicyhydrazone derivatives were efficient sensitizers for the fluoresence of Eu(3+) ions. The fluorescence intensity of the complex substituted by methyl (-CH3) was the strongest among all the Eu(3+) complexes. The exploration of the electrochemical properties of the Eu(3+) complexes showed that the introduction of electron-donating groups methyl and methoxyl (-CH3 and -OCH3) could increase the oxidation potential and the highest occupied molecular orbital (HOMO) energy level of the Eu(3+) complex; however, the results of introduction of electron-withdrawing group were just opposite.

  15. Syntheses and spectroscopy of germanium and tin compounds with biorelevant ligands

    NASA Astrophysics Data System (ADS)

    Breitinger, D. K.; Grützner, T.; Wick, H.; Schimmer, O.; Eschelbach, H.

    1997-06-01

    The germanium and tin compounds diaquabis(glycolato)germanium(IV) Ge(OCH 2COO) 2(H 2O) 2 ( 1), bis(thioglycolato)-, bis(thiolactato)-, and bis(thiohydracrylato)-germanium(IV) Ge(SJCOO) 2 (J = CH 2 ( 2), CH(CH 3) ( 3), CH 2CH 2 ( 4)), as well as the tetrakis(alkylthioglycolato)tetrels Tt(SCH 2COOR) 4 (Tt = Ge ( 5, 6) and Sn ( 7, 8); R = Me, i-Pr, respectively), under study for their antimutagenic properties, were studied by vibrational spectrometry. Some of the skeletal vibrations of the octahedral 1 and otherwise tetrahedral compounds were assigned. Data from 1H- and 13C- NMR spectra and from mass spectra are also reported.

  16. p-type transparent conducting oxides

    NASA Astrophysics Data System (ADS)

    Sheng, Su; Fang, Guojia; Li, Chun; Xu, Sheng; Zhao, Xingzhong

    2006-06-01

    The recent advance of p-type transparent conductive oxide thin films is reviewed. The focus is on p-type transparent oxide semiconductors CuAlO2, CuGaO2, CuInO2, SrCu2O2, and LaCuOCh (Ch = chalcogen). These materials and related device applications are then shown as examples. Room temperature operation of current injection emission from ultraviolet light-emitting diodes based on p-SCO/n-ZnO p-n junctions has been demonstrated. This changed with the discovery of p-type transparent conducting oxides, thereby opening up the possibility for all-oxide transparent electronics.

  17. Radical scavenging of white tea and its flavonoid constituents by electron paramagnetic resonance (EPR) spectroscopy.

    PubMed

    Azman, Nurul A M; Peiró, Sara; Fajarí, Lluís; Julià, Luis; Almajano, Maria Pilar

    2014-06-25

    White tea (WT) presents high levels of catechins, which are known to reduce oxidative stress. WT is the least processed tea, unfermented and prepared only from very young tea leaves. The subject of this paper is the use of the spin trap method and electron paramagnetic resonance (EPR) spectroscopy as the analytical tool to measure, for the first time, the radical scavenging activity of WT and its major catechin components, epicatechin (EC), epicatechin-3-gallate (ECG), epigallocatechin (EGC), and epigallocatechin-3-gallate (EGCG), against the methoxy radical, using ferulic acid as antioxidant pattern. The antioxidant activity has been measured by the decrease of the intensity of the spectral bands of the adduct DMPO-OCH3 in the EPR with the amount of antioxidant in the reactive mixture. Tea leaves and buds were extracted with waterless methanol. It has been proved that tea compounds with more antiradical activity against methoxy radical are those with the gallate group, EGCG and ECG. PMID:24885813

  18. Fluorescence quenching in an organic donor-acceptor dyad: a first principles study.

    PubMed

    Körzdörfer, T; Tretiak, S; Kümmel, S

    2009-07-21

    Perylene bisimide and triphenyl diamine are prototypical organic dyes frequently used in organic solar cells and light emitting devices. Recent Forster-resonant-energy-transfer experiments on a bridged organic dyad consisting of triphenyl diamine as an energy-donor and perylene bisimide as an energy-acceptor revealed a strong fluorescence quenching on the perylene bisimide. This quenching is absent in a solution of free donors and acceptors and thus attributed to the presence of the saturated CH(2)O(CH(2))(12)-bridge. We investigate the cause of the fluorescence quenching as well as the special role of the covalently bound bridge by means of time dependent density functional theory and molecular dynamics. The conformational dynamics of the bridged system leads to a charge transfer process between donor and acceptor that causes the acceptor fluorescence quenching. PMID:19624200

  19. Synthesis and biological evaluation of 1-phenyl-1,2,3,4-dihydroisoquinoline compounds as tubulin polymerization inhibitors.

    PubMed

    Zheng, Can-Hui; Chen, Jun; Liu, Jia; Zhou, Xiao-Tian; Liu, Na; Shi, Duo; Huang, Jing-Jing; Lv, Jia-Guo; Zhu, Ju; Zhou, You-Jun

    2012-06-01

    A series of 1-phenyl-3,4-dihydroisoquinoline derivatives and several 1-phenyl-1,2,3,4-tetrahydroisoquinoline, 1-phenyl-isoquinoline analogues were synthesized, and their cytotoxicity and tubulin polymerization inhibitory activity were evaluated. The 1-phenyl-3,4-dihydroisoquinoline compounds were found to be potential tubulin polymerization inhibitors. Compound 5n, bearing a 3'-OH and 4'-OCH(3) substituted 1-phenyl B-ring, was shown to confer optimal bioactivity. The single-crystal structure of 5n was further determined by X-ray diffraction, and the binding mode of 5n to tubulin was obtained by molecular docking, which can explain the structure-activity relationships. The studies presented here provide a new structural type for the development of novel antitumor agents.

  20. Induced cholesteric systems based on some cyano derivatives as host phases

    NASA Astrophysics Data System (ADS)

    Shkolnikova, Natalya I.; Kutulya, Lidiya A.; Vashchenko, V. V.; Fedoryako, A. P.; Lapanik, V. I.; Posledovich, N. R.

    2002-12-01

    Macroscopical properties of some induced cholesteric compositions based on 4-pentyl-4'-cyano derivatives of biphenyl and phenylcyclohexane as host phases have been investigated. The series of N-arylidene derivatives of (S)-1-phenylethylamine with varied both rigid moiety of the N-arylidene fragment and terminal substituent was used as chiral dopants. The influence of the chiral dopant molecular structure as well as of physical properties of the host phases used on the helical twisting power, the temperature dependence of the induced helical pitch and the N* mesophase thermal stability has been characterized. It has been concluded that the distinctions in properties of the LC systems containing the OCH2 and COO linking groups are caused by their different conformational states.

  1. Extraction processes and solvents for recovery of cesium, strontium, rare earth elements, technetium and actinides from liquid radioactive waste

    DOEpatents

    Zaitsev, Boris N.; Esimantovskiy, Vyacheslav M.; Lazarev, Leonard N.; Dzekun, Evgeniy G.; Romanovskiy, Valeriy N.; Todd, Terry A.; Brewer, Ken N.; Herbst, Ronald S.; Law, Jack D.

    2001-01-01

    Cesium and strontium are extracted from aqueous acidic radioactive waste containing rare earth elements, technetium and actinides, by contacting the waste with a composition of a complex organoboron compound and polyethylene glycol in an organofluorine diluent mixture. In a preferred embodiment the complex organoboron compound is chlorinated cobalt dicarbollide, the polyethylene glycol has the formula RC.sub.6 H.sub.4 (OCH.sub.2 CH.sub.2).sub.n OH, and the organofluorine diluent is a mixture of bis-tetrafluoropropyl ether of diethylene glycol with at least one of bis-tetrafluoropropyl ether of ethylene glycol and bis-tetrafluoropropyl formal. The rare earths, technetium and the actinides (especially uranium, plutonium and americium), are extracted from the aqueous phase using a phosphine oxide in a hydrocarbon diluent, and reextracted from the resulting organic phase into an aqueous phase by using a suitable strip reagent.

  2. Synthesis and In-vitro Cytotoxicity Assessment of N-(5-(Benzylthio)-1,3,4- thiadiazol-2-yl)-2-(4-(trifluoromethyl)phenyl)acetamide with Potential Anticancer Activity

    PubMed Central

    Aliabadi, Alireza; Hasanvand, Zaman; Kiani, Amir; Mirabdali, Seyed Saber

    2013-01-01

    Cancer is the second leading cause of death in the world. Despite advances in the diagnosis and treatment, overall survival of patients still remains poor. Hence, there is an urgent need for development of new anticancer agents. Considering promising biological activity of 1,3,4-thiadiazole derivatives, in the present study, synthesis and cytotoxicity assessment of new derivatives of this ring was done. All synthesized compounds were characterized by NMR, IR and MS spectroscopic methods. Obtained data from MTT assay showed that all compounds 3a- 3l had better anticancer activity against MDA(breast cancer) compared to PC3(prostate cancer) and U87(Glioblastoma). Compound 3 g with m-OCH3 moiety on the phenyl ring was the most potent one in this series with IC50 = 9 μM against MDA breast cell line in comparison with imatinib (IC50 = 20 μM) as reference drug. PMID:24523748

  3. Formaldehyde mediated proton-transport catalysis in the ketene-water radical cation CH2C(O)OH2+

    NASA Astrophysics Data System (ADS)

    Lee, Richard; Ruttink, Paul J. A.; Burgers, Peter C.; Terlouw, Johan K.

    2006-09-01

    Previous studies have shown that the solitary ketene-water ion CH2C(O)OH2+ (1) does not isomerize into CH2C(OH)2+ (2), its more stable hydrogen shift isomer. Tandem mass spectrometry based collision experiments reveal that this isomerization does take place in the CH2O loss from low-energy 1,3-dihydroxyacetone ions (HOCH2)2CO+. A mechanistic analysis using the CBS-QB3 model chemistry shows that such molecular ions rearrange into hydrogen-bridged radical cations [CH2C(O)O(H)-H...OCH2]+ in which the CH2O molecule catalyzes the transformation 1 --> 2 prior to dissociation. The barrier for the unassisted reaction, 29 kcal mol-1, is reduced to a mere 0.6 kcal mol-1 for the catalysed transformation. Formaldehyde is an efficient catalyst because its proton affinity meets the criterion for facile proton-transport catalysis.

  4. The use of a vanadium species as a catalyst in photoinduced water oxidation.

    PubMed

    Santoni, Marie-Pierre; La Ganga, Giuseppina; Mollica Nardo, Viviana; Natali, Mirco; Puntoriero, Fausto; Scandola, Franco; Campagna, Sebastiano

    2014-06-11

    The first water oxidation catalyst containing only vanadium atoms as metal centers is reported. The compound is the mixed-valence [(V(IV)5V(V)1)O7(OCH3)12](-) species, 1. Photoinduced water oxidation catalyzed by 1, in the presence of Ru(bpy)3(2+) (bpy = 2,2'-bipyridine) and Na2S2O8, in acetonitrile/aqueous phosphate buffer takes place with a quantum yield of 0.20. A hole scavenging reaction between the photochemically generated Ru(bpy)3(3+) and 1 occurs with a bimolecular rate constant of 2.5 × 10(8) M(-1) s(-1). The time-resolved formation of the oxidized molecular catalyst 1(+) in bimolecular reactions is also evidenced for the first time by transient absorption spectroscopy. This result opens the way to the use of less expensive vanadium clusters as water oxidation catalysts in artificial photosynthesis schemes.

  5. α-Tocopherol impact on oxy-radical induced free radical decomposition of DMSO: Spin trapping EPR and theoretical studies

    NASA Astrophysics Data System (ADS)

    Jerzykiewicz, Maria; Ćwieląg-Piasecka, Irmina; Witwicki, Maciej; Jezierski, Adam

    2011-05-01

    EPR spin trapping and theoretical methods such as density functional theory (DFT) as well as combined DFT and quadratic configuration interaction approach (DFT/QCISD) were used to identify the radicals produced in the reaction of oxy-radicals and dimethyl sulfoxide (DMSO) in the presence and absence of α-tocopherol. Additionally, the mixtures of α-tocopherol with linolenic acid and glyceryl trilinoleate as well as bioglycerols (glycerol fractions from biodiesel production) were tested. α-Tocopherol inhibited oxidation of the main decomposition product of DMSO, •CH 3 to •OCH 3 but did not prevent the transformation process of N-t-butyl- α-phenylnitrone (PBN) into 2-methyl-2-nitrosopropane (MNP). Theoretical investigations confirmed the structures of proposed spin adducts and allowed to correlate the EPR parameters observed in the experiment with the spin adducts electronic structure.

  6. Process for treating radioactive waste

    SciTech Connect

    Chino, K.; Kawamura, F.; Kikuchi, M.; Yusa, H.

    1982-11-30

    N-beta-(Aminoethyl)-gamma-aminopropyltrimethoxysilane (NH2(CH2)2NH(CH2)3SI(OCH3)3) as a silane coupling agent and SiO(2 -x)(ONa)x/2(OH)x/2 as colloidal silica are mixed into a radioactive liquid waste containing sodium sulfate as a main component, coming from a boiling water-type, nuclear power plant as an effluent. The resulting mixed radioactive liquid waste is supplied into a vessel provided with a rotating shaft with blades. The rotating shaft is revolved while heating the radioactive liquid waste in the vessel, thereby making the radioactive liquid waste into powder. The resulting powder containing the silane coupling agent and the colloidal silica is shaped into pellets by a pelletizer. The pellets having a low hygroscopicity and a high strength are obtained.

  7. Luminescence from Vacuum-Ultraviolet-Irradiated Cosmic Ice Analogs and Residues

    NASA Technical Reports Server (NTRS)

    Gudipati, Murthy S.; Dworkin, Jason P.; Chillier, Xavier D. F.; Allamandola, Louis J.

    2003-01-01

    Here we report a study of the optical luminescent properties for a variety of vacuum-ultraviolet (VUV)- irradiated cosmic ice analogs and the complex organic residues produced. Detailed results are presented for the irradiated, mixed molecular ice: H2O:CH3OH:NH3:CO (100:50:1:1), a realistic representation for an interstellar/precometary ice that reproduces all the salient infrared spectral features associated with interstellar ices. The irradiated ices and the room-temperature residues resulting from this energetic processing have remarkable photoluminescent properties in the visible (520-570 nm). The luminescence dependence on temperature, thermal cycling, and VUV exposure is described. It is suggested that this type of luminescent behavior might be applicable to solar system and interstellar observations and processes for various astronomical objects with an ice heritage. Some examples include grain temperature determination and vaporization rates, nebula radiation balance, albedo values, color analysis, and biomarker identification.

  8. 5-Methoxysalicylic Acid Matrix for Ganglioside Analysis with Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Lee, Dongkun; Cha, Sangwon

    2015-03-01

    In this note, we report that high quality ganglioside profiles with minimal loss of sialic acid residues can be obtained in the positive ion mode by using a 5-methoxysalicylic acid (MSA) matrix for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Our results showed that MSA produced much less sialic acid losses from gangliosides than DHB, although MSA and DHB are differ only by their functional groups at their 5-positions (-OH for DHB and -OCH3 for MSA). Furthermore, our data also demonstrated that addition of an alkali metal additive was effective for simplifying ganglioside profiles, but not necessary for stabilizing glycosidic bonds of gangliosides if MSA was used as a matrix. This suggests that MALDI MS with MSA has a potential to gain additional benefits from the positive-ion mode analyses without losing performance in ganglioside profiling.

  9. Theoretical study on the intracluster elimination channels for Mg+(CH3OH), Ca+(CH3OH), Mg+(NH3), and Ca+(NH3).

    PubMed

    Chan, Ka Wai; Wu, Yang; Liu, Zhi-Feng

    2008-09-18

    The intracluster elimination reactions in solvated alkaline earth metal monocation clusters, M (+)L n , are known to be size-dependent, indicating links between chemical reactivity and the solvation environment controlled by the cluster size. For the methanol and ammonia clusters, there are a number of competing elimination channels involving the breaking of O-H, C-H, O-CH 3, or N-H bond. In this report, we focus on the four clusters with only one solvent molecule and systematically map out the reaction paths and intermediates. The interaction between the metal ion and the departing H atom or CH 3 group varies considerably, depending on the interaction between the metal ion and the remaining group. The understanding of the nature of these interactions and the evaluation of various theoretical levels in treating these reactions provide a solid base for the investigation of the solvation effects on the chemical reactivity of the larger clusters.

  10. Methanol in dark clouds

    NASA Technical Reports Server (NTRS)

    Friberg, P.; Hjalmarson, A.; Madden, S. C.; Irvine, W. M.

    1988-01-01

    The first observation of methanol in cold dark clouds TMC 1, L 134 N, and B 335 is reported. In all three clouds, the relative abundance of methanol was found to be in the range of 10 to the -9th (i.e., almost an order of magnitude more abundant than acetaldehyde), with no observable variation between the clouds. Methanol emission showed a complex velocity structure; in TMC 1, clear indications of non-LTE were observed. Dimethyl ether was searched for in L 134 N; the upper limit of the column density of dimethyl ether in L 134 N was estimated to be 4 x 10 to the 12th/sq cm, assuming 5 K rotation temperature and LTE. This limit makes the abundance ratio (CH3)2O/CH3OH not higher than 1/5, indicating that dimethyl ether is not overabundant in this dark cloud.

  11. Interactions between alkaline earth cations and oxo ligands. DFT study of the affinity of the Mg²+ cation for phosphoryl ligands.

    PubMed

    da Costa, Leonardo Moreira; de Mesquita Carneiro, José Walkimar; Paes, Lilian Weitzel Coelho

    2011-08-01

    DFT (B3LYP/6-31+G(d)) calculations of Mg(2+) affinities for a set of phosphoryl ligands were performed. Two types of ligands were studied: a set of trivalent [O = P(R)] and a set of pentavalent phosphoryl ligands [O = P(R)(3)] (R = H, F, Cl, Br, OH, OCH(3), CH(3), CN, NH(2) and NO(2)), with R either bound directly to the phosphorus atom or to the para position of a phenyl ring. The affinity of the Mg(2+) cation for the ligands was quantified by means of the enthalpy for the substitution of one water molecule in the [Mg(H(2)O)(6)](2+) complex for a ligand. The enthalpy of substitution was correlated with electronic and geometric parameters. Electron-donor groups increase the interaction between the cation and the ligand, while electron-acceptor groups decrease the interaction enthalpy. PMID:21161556

  12. Crystal structure and C—H⋯F hydrogen bonding in the fluorinated bis-benzoxazine: 3,3′-(ethane-1,2-di­yl)bis­(6-fluoro-3,4-di­hydro-2H-1,3-benzoxazine)

    PubMed Central

    Rivera, Augusto; Rojas, Jicli José; Ríos-Motta, Jaime; Bolte, Michael

    2016-01-01

    The title fluorinated bis­benzoxazine, C18H18F2N2O2, crystallizes with one half-mol­ecule in the asymmetric unit, which is completed by inversion symmetry. The fused oxazine ring adopts an approximately half-chair conformation. The two benzoxazine rings are oriented anti to one another around the central C—C bond. The dominant inter­molecular inter­action in the crystal structure is a C—H⋯F hydrogen bond between the F atoms and the axial H atoms of the OCH2N methyl­ene group in the oxazine rings of neighbouring mol­ecules. C—H⋯π contacts further stabilize the crystal packing. PMID:27746952

  13. In situ formation of cobalt oxide nanocubanes as efficient oxygen evolution catalysts.

    PubMed

    Hutchings, Gregory S; Zhang, Yan; Li, Jian; Yonemoto, Bryan T; Zhou, Xinggui; Zhu, Kake; Jiao, Feng

    2015-04-01

    Oxygen evolution from water poses a significant challenge in solar fuel production because it requires an efficient catalyst to bridge the one-electron photon capture process with the four-electron oxygen evolution reaction (OER). Here, a new strategy was developed to synthesize nonsupported ultrasmall cobalt oxide nanocubanes through an in situ phase transformation mechanism using a layered Co(OH)(OCH3) precursor. Under sonication, the precursor was exfoliated and transformed into cobalt oxide nanocubanes in the presence of NaHCO3-Na2SiF6 buffer solution. The resulting cobalt catalyst with an average particle size less than 2 nm exhibited a turnover frequency of 0.023 per second per cobalt in photocatalytic water oxidation. X-ray absorption results suggested a unique nanocubane structure, where 13 cobalt atoms fully coordinated with oxygen in an octahedral arrangement to form 8 Co4O4 cubanes, which may be responsible for the exceptionally high OER activity.

  14. Structural studies of methyl brevifolincarboxylate in solid state by means of NMR spectroscopy and DFT calculations

    NASA Astrophysics Data System (ADS)

    Wolniak, Michał; Tomczyk, Michał; Gudej, Jan; Wawer, Iwona

    2006-12-01

    Methyl brevifolincarboxylate isolated from the herb of Potentilla argentea L. (Rosaceae) is a representative of the naturally occurring polyphenols. The compound is of pharmaceutical interest mainly because of its antiviral and antioxidant properties. 13C NMR spectra were recorded for solution and solid phase. 13C CPMAS spectra were assigned by comparison with solution data, dipolar dephasing and short contact time experiments. The correctness of assignments was verified by GIAO DFT calculations of shielding constants. The differences between the solution and solid state chemical shift values were explained in terms of orientation of OH groups and intramolecular hydrogen bonds. The splitting of the C1 dbnd O resonance shows that there exists a polymorphism in the solid phase, which might be due to the formation of intramolecular hydrogen bond involving carbonyl or methoxy oxygen (i.e. C10 sbnd OH⋯O dbnd C or C10 sbnd OH⋯OCH 3).

  15. Comparative Study of Ether-Based Electrolytes for Application in Lithium-Sulfur Battery.

    PubMed

    Carbone, Lorenzo; Gobet, Mallory; Peng, Jing; Devany, Matthew; Scrosati, Bruno; Greenbaum, Steve; Hassoun, Jusef

    2015-07-01

    Herein, we report the characteristics of electrolytes using various ether-solvents with molecular composition CH3O[CH2CH2O]nCH3, differing by chain length, and LiCF3SO3 as the lithium salt. The electrolytes, considered as suitable media for lithium-sulfur batteries, are characterized in terms of thermal properties (TGA, DSC), lithium ion conductivity, lithium interface stability, cyclic voltammetry, self-diffusion properties of the various components, and lithium transference number measured by NMR. Furthermore, the electrolytes are characterized in lithium cells using a sulfur-carbon composite cathode by galvanostatic charge-discharge tests. The results clearly evidence the influence of the solvent chain length on the species mobility within the electrolytes that directly affects the behavior in lithium sulfur cell. The results may effectively contribute to the progress of an efficient, high-energy lithium-sulfur battery.

  16. Vibration-Rotation Spectrum of Formic Acid Dimer in the 7.3μm Region

    NASA Astrophysics Data System (ADS)

    Duan, Chuanxi

    2016-06-01

    The vibration-rotation-tunneling spectrum of formic acid dimer, (HCOOH)2, in the spectral region 1369-1375 wn has been measured by a multi-step rapid-can method in a slit jet expansion using a distributed-feedback quantum cascade laser. The observed spectrum is assigned to the O-C-H bending fundamental band. The tunneling splitting in the vibrational excited state is determined to be about 0.005 wn, which is much smaller than that in the ground state, 0.0165 wn (Goroya et al.,J. Chem. Phys. 140, 164311 (2014)). Strong local perturbations involving transitions with J > 9, K = 0 and 1 are identified in the observed spectrum. The deperturbation analysis will be presented.

  17. B-Decachloro-o-carborane Derivatives suitable for the preparation of boron-labeled biological macromolecules.

    PubMed

    Gabel, D; Walczyna, R

    1982-10-01

    B-decachloro-o-carborane derivatives in which one of the carbon atoms was substituted by -CH2CH2CO2H (I), -CH2CHOHCH2-O-CH2CH=CH2 (II) and -CH2CHOHCH2-O-p-C6H4NHCOOC(CH3)3 (III) were prepared from decachloro-o-carborane and the corresponding bromo (I) or epoxi (II and III) derivatives under alkaline conditions. II could be epoxidized and bound to dextran, Concanavalin A, and human IgG, with a boron content of 4.3, 4.8, and 4.9% (w/w), respectively. III could be converted to the corresponding amine and further to the isothiocyanate. Such boron derivatives could be suitable compounds for neutron capture therapy of tumors, as they are well water soluble and could be attached to tumor specific antibodies.

  18. 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.

  19. Variation of electronic transitions and reduction potentials of cerium(IV) complexes.

    PubMed

    Williams, Ursula J; Schneider, David; Dorfner, Walter L; Maichle-Mössmer, Cäcilia; Carroll, Patrick J; Anwander, Reiner; Schelter, Eric J

    2014-11-21

    The trivalent compound K[Ce[N(SiHMe2)2]4] was synthesized and oxidized, providing a convenient route to the reported cerium(IV) compound Ce[N(SiHMe2)2]4. Protonolysis reactions of Ce[N(SiHMe2)2]4 with tert-butanol, substituted benzyl alcohols, and 2,6-diphenylphenol yielded the neutral tetravalent compounds Ce(O(t)Bu)4(py)2, Ce2(OCH2C6R5)8(thf)2 (R = Me, F), and Ce(Odpp)4 (dpp = 2,6-(C6H5)2-C6H3). Spectroscopic and electrochemical characterization of the monometallic cerium(IV) silylamide, alkoxide, and aryloxide compounds revealed variable ligand-to-metal charge transfer transitions and metal-based reduction potentials. Computational bonding analyses were performed to complement the physical characterization of the complexes.

  20. Electromagnetic radiation absorbers and modulators comprising polyaniline

    DOEpatents

    Epstein, Arthur J.; Ginder, John M.; Roe, Mitchell G.; Hajiseyedjavadi, Hamid

    1992-01-01

    A composition for absorbing electromagnetic radiation, wherein said electromagnetic radiation possesses a wavelength generally in the range of from about 1000 Angstroms to about 50 meters, wherein said composition comprises a polyaniline composition of the formula ##STR1## where y can be equal to or greater than zero, and R.sup.1 and R.sup.2 are independently selected from the group containing of H, --OCH.sub.3, --CH.sub.3, --F, --Cl, --Br, --I, NR.sup.3 .sub.2, --NHCOR.sup.3, --OH, --O.sup.-, SR.sup.3, --OCOR.sup.3, --NO.sub.2, --COOH, --COOR.sup.3, --COR.sup.3, --CHO, and --CN, where R.sup.3 is a C.sub.1 to C.sub.8 alkyl, aryl or aralkyl group.

  1. Lignin pyrolysis products, lignans, and resin acids as specific tracers of plant classes in emissions from biomass combustion

    SciTech Connect

    Simoneit, B.R.T. ); Rogge, W.F.; Cass, G.R. ); Mazurek, M.A. ); Standley, L.J. ); Hildemann, L.M. )

    1993-11-01

    Biomass smoke aerosols contain thermally unaltered and partially altered biomarker compounds from major vegetation taxa. These compounds range from C[sub 8] to C[sub 31] and include phytosterols, lignans, phenolic products from lignin, and diterpenoids from resins. Certain of the higher molecular weight biomarkers are vaporized from the parent plant material and subsequently condense unaltered into the particle phase. Other compounds undergo pyrolytic alteration and possibly dimerization. In both cases it is possible to assign many of these compounds to the plant taxa of the unburned fuel. The diterpenoids are good indicators for smoke from burning of gymnosperm wood. The relative distribution of the OH/OCH[sub 3] substituent patterns on the phenolic products indicates the plant class of the biomass that was burned. Application of these relationships to the interpretation of ambient smoke aerosols may permit further evaluation of the sources that contribute to regional biomass burning. 80 refs., 5 figs., 1 tab.

  2. Efficient Room-Temperature Methane Activation by the Closed-Shell, Metal-Free Cluster [OSiOH](+) : A Novel Mechanistic Variant.

    PubMed

    Sun, Xiaoyan; Zhou, Shaodong; Schlangen, Maria; Schwarz, Helmut

    2016-09-26

    The closed-shell cluster ion [OSiOH](+) is generated in the gas phase and its reactivity towards the thermal activation of CH4 has been examined using Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry in conjunction with state-of-the-art quantum chemical calculations. Quite unexpectedly at room temperature, [OSiOH](+) efficiently mediates C-H bond activation, giving rise to [SiOH](+) and [SiOCH3 ](+) with the concomitant formation of methanol and water, respectively. Mechanistic aspects for this unprecedented reactivity pattern are presented, and the properties of the [OSiOH](+) /CH4 couple are compared with those of the closed-shell systems [OCOH](+) /CH4 and [MgOH](+) /CH4 ; the last two couples exhibit an entirely different reactivity scenario. PMID:27515768

  3. Side Group Addition to the PAH Coronene by UV Photolysis in Cosmic Ice Analogs

    NASA Technical Reports Server (NTRS)

    Bernstein, Max P.; Elsila, Jamie E.; Dworkin, Jason P.; Sandford, Scott A.; Allamandola, Louis J.; Zare, Richard N.; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    Ultraviolet photolysis of various ice mixtures at low temperature and pressure caused the addition of amino (-NH2), methyl (-CH3), methoxy (-OCH3), and cyano (-CN) functional groups to the polycyclic aromatic hydrocarbon (PAH) coronene (C22H12). The implications of these results for interstellar and meteoritic chemistry are discussed. Previously only simple PAH photo-oxidation had been reported. This work represents the first experimental evidence that ice photochemistry may have contributed to aromatics bearing carbon and nitrogen containing side groups that are detected in primitive meteorites and interplanetary dust particles. Furthermore, these results suggest a wider range of modified PAHs should be expected in interstellar lees and materials predating solar system formation.

  4. Role of water and carbonates in photocatalytic transformation of CO{sub 2} to CH{sub 4} on titania.

    SciTech Connect

    Dimitrijevic, N. M.; Vijayan, B. K.; Poluektov, O. G.; Rajh, T.; Gray, K. A.; He, H.; Zapol, P.

    2011-02-24

    Using the electron paramagnetic resonance technique, we have elucidated the multiple roles of water and carbonates in the overall photocatalytic reduction of carbon dioxide to methane over titania nanoparticles. The formation of H atoms (reduction product) and {center_dot}OH radicals (oxidation product) from water, and CO{sub 3}{sup -} radical anions (oxidation product) from carbonates, was detected in CO{sub 2}-saturated titania aqueous dispersion under UV illumination. Additionally, methoxyl, {center_dot}OCH{sub 3}, and methyl, {center_dot}CH{sub 3}, radicals were identified as reaction intermediates. The two-electron, one-proton reaction proposed as an initial step in the reduction of CO{sub 2} on the surface of TiO{sub 2} is supported by the results of first-principles calculations.

  5. Role of Water and Carbonates in Photocatalytic Transformation of CO2 to CH4 on Titania

    SciTech Connect

    Dimitrijevic, Nada; Vijayan, Baiju K.; Poluektov, Oleg G.; Rajh, Tijana; Gray, Kimberley A.; He, Haiying; Zapol, Peter

    2011-03-23

    Using the electron paramagnetic resonance technique, we have elucidated the multiple roles of water and carbonates in the overall photocatalytic reduction of carbon dioxide to methane over titania nanoparticles. The formation of H atoms (reduction product) and {sm_bullet}OH radicals (oxidation product) from water, and CO{sub 3}{sup -} radical anions (oxidation product) from carbonates, was detected in CO{sub 2}-saturated titania aqueous dispersion under UV illumination. Additionally, methoxyl, {sm_bullet}OCH{sub 3}, and methyl, {sm_bullet}CH{sub 3}, radicals were identified as reaction intermediates. The two-electron, one-proton reaction proposed as an initial step in the reduction of CO{sub 2}, on the surface of TiO{sub 2}, is supported by the results of first-principles calculations.

  6. Computational Study of Monosubstituted Azo(tetrazolepentazolium)-Based Ionic Dimers.

    PubMed

    Pimienta, Ian S O

    2015-06-01

    The structures of monosubstituted azo(tetrazolepentazolium) cations (N11CHR(+)), oxygen-rich anions such as N(NO2)2(-), NO3(-), and ClO4(-), and the corresponding ion pairs are investigated using ab initio quantum chemistry calculations. The substituents (R) used are H, F, CH3, CN, NH2, OH, OCH3, N3, NF2, and C2H3. The stability of the protonated cation is explored by examining the decomposition pathway of the protonated cation (N11CH2(+)) to yield molecular N2 fragments. The heats of formation of these cations, which are based on isodesmic (bond type conserving) reactions, are dependent on the nature of the substituents. Ionic dimer structures are obtained, but side reactions including proton transfer, binding, and hydrogen bonding are observed in the gas phase. Implicit solvation studies are performed to determine the solution properties of the ion pairs.

  7. Synthesis and Fluorescence Properties of Eu(3+), Tb(3+) Complexes with Schiff Base Derivatives.

    PubMed

    Liu, Yanhong; Kong, Weihua; Yang, Zehui; Dai, Ming; Shi, Ling; Guo, Dongcai

    2016-03-01

    Novel Schiff base ligands derived from N'-benzylidene-benzohydrazide (substituted by -H, -CH3, -OCH3, -Cl) and 2-chloro-N-phenylacetamide were synthesized. The solid complexes of rare earth (Eu, Tb) nitrate with these Schiff base ligands were synthesized and characterized by elemental analysis, EDTA titrimetric analysis, thermal analysis, infrared spectra and UV-Vis spectra analysis. The fluorescence properties of rare earth (Eu, Tb) complexes in solid were studied. Under the excitation of ultraviolet light, these complexes exhibited characteristic emission of europium and terbium ions. The results showed that the ligand favored energy transfer to the emitting energy of Eu and Tb ions. Effects of different ligands on the fluorescence intensity of rare earth (Eu, Tb) complexes had been discussed. The electrochemical properties of rare earth (Eu, Tb) complexes were also investigated. PMID:26658796

  8. Orthopedic application of spikenard herbal rhizome decorated microstructured polymer biocomposites and their in vitro cytotoxicity.

    PubMed

    Priya, Sahariya; Jeya Jothi, Gabriel

    2016-09-01

    The present study explores the synthesis of highly potential polymer biocomposite from Nardostachys jatamansi rhizome extract. The polymer biocomposites were synthesized from methyl methacrylate by free radical polymerization. ATR-IR enunciate the functional groups attributed at 956 cm(-1) (aromatic), a peak appeared at 1685 cm(-1) (-C 000000000000 000000000000 000000000000 111111111111 000000000000 111111111111 000000000000 000000000000 000000000000 O), 1186 cm(-1) (-O-CH3), 1149 cm(-1) (-C-O-C) framework and 1279 cm(-1) (-C-O), which are good agreement for the formation composites. The quantitative evaluations of antimicrobial studies were analyzed by serial dilution method and also improved activity in orthopedic infection pathogens. Cytocompatibility was analyzed by keratinocyte cell lines and it may be used for various biomedical applications. PMID:27408493

  9. Conformations of solid 2-methyl-4-( p-X-phenylazo)imidazoles by 13C CP MAS NMR spectroscopy and PM3 semi-empirical calculations

    NASA Astrophysics Data System (ADS)

    Maciejewska, Dorota

    1999-03-01

    Solid 2-methyl-4-( p-X-phenylazo)imidazoles form hydrogen bonded chains with N-H⋯N bonds and C-H⋯O or C-H⋯N interaction. Depending on the nature and orientation of the substituents X it was possible to identify one tautomer if XH ( 2), Br ( 3), NO 2 ( 4) and the two, a- and b-tautomers in the crystal unit if XOCH 3 ( 1). The 13C CP MAS NMR spectra of ( 4) indicate the presence of phenyl ring dynamics. A preferred structure present in the solid state is that with different lengths of C1'-N and C4-N bonds and with higher dipole moment.

  10. Bis(O-n-butyl dithio­carbonato-κ2 S,S′)bis­(pyridine-κN)manganese(II)

    PubMed Central

    Alam, Naveed; Ehsan, Muhammad Ali; Zeller, Matthias; Mazhar, Muhammad; Arifin, Zainudin

    2011-01-01

    The structure of the title manganese complex, [Mn(C5H9OS2)2(C5H5N)2] or [Mn(S2CO-n-Bu)2(C5H5N)2], consists of discrete monomeric entities with Mn2+ ions located on centres of inversion. The metal atom is coordinated by a six-coordinate trans-N2S4 donor set with the pyridyl N atoms located in the apical positions. The observed slight deviations from octa­hedral geometry are caused by the bite angle of the bidentate κ2-S2CO-n-Bu ligands [69.48 (1)°]. The O(CH2)3(CH3) chains of the O-n-butyl dithio­carbonate units are disordered over two sets of sites with an occupancy ratio of 0.589 (2):0.411 (2). PMID:22090847

  11. Cross-Linking the Fibers of Supramolecular Gels Formed from a Tripodal Terpyridine Derived Ligand with d-Block Metal Ions.

    PubMed

    Kotova, Oxana; Daly, Ronan; dos Santos, Cidália M G; Kruger, Paul E; Boland, John J; Gunnlaugsson, Thorfinnur

    2015-08-17

    The tripodal terpyridine ligand, L, forms 1D helical supramolecular polymers/gels in H2O-CH3OH solution mediated through hydrogen bonding and π-π interactions. These gels further cross-link into 3D supramolecular metallogels with a range of metal ions (M) such as Fe(II), Ni(II), Cu(II), Zn(II), and Ru(III); the cross-linking resulting in the formation of colored or colorless gels. The fibrous morphology of these gels was confirmed using scanning electron microscopy (SEM); while the self-assembly processes between L and M were investigated by absorbance and emission spectroscopy from which their binding constants were determined by using a nonlinear regression analysis. PMID:26222397

  12. VizieR Online Data Catalog: Dimethyl ether laboratory spectra up to 2.1THz (Endres+, 2009)

    NASA Astrophysics Data System (ADS)

    Endres, C. P.; Drouin, B. J.; Pearson, J. C.; Muller, H. S. P.; Lewen, F.; Schlemmer, S.; Giesen, T. F.

    2009-07-01

    Dimethyl ether (CH3OCH3) is one of the largest or detected in the interstellar medium. As an asymmetric top molecule with two methyl groups which undergo large amplitude motions and a dipole moment of mub=1.3D it conveys a dense spectrum throughout the terahertz region and contributes to the spectral line confusion in astronomical observations at these frequencies. Rotational spectra of dimethyl ether in its ground vibrational states are presented in this paper, which have been measured in the laboratory and analyzed covering frequencies up to 2.1THz. The analysis is based on an effective Hamiltonian for a symmetric two-top rotor and includes experimental data published so far. Frequency predictions are presented up to 2.5THz for astronomical applications with accuracies better than 1MHz. (1 data file).

  13. Heterobimetallic dinuclear lanthanide alkoxide complexes as acid-base difunctional catalysts for transesterification.

    PubMed

    Zeng, Ruijie; Sheng, Hongting; Zhang, Yongcang; Feng, Yan; Chen, Zhi; Wang, Junfeng; Chen, Man; Zhu, Manzhou; Guo, Qingxiang

    2014-10-01

    A practical lanthanide(III)-catalyzed transesterification of carboxylic esters, weakly reactive carbonates, and much less-reactive ethyl silicate with primary and secondary alcohols was developed. Heterobimetallic dinuclear lanthanide alkoxide complexes [Ln2Na8{(OCH2CH2NMe2)}12(OH)2] (Ln = Nd (I), Sm (II), and Yb (III)) were used as highly active catalysts for this reaction. The mild reaction conditions enabled the transesterification of various substrates to proceed in good to high yield. Efficient activation of transesterification may be endowed by the above complexes as cooperative acid-base difunctional catalysts, which is proposed to be responsible for the higher reactivity in comparison with simple acid/base catalysts.

  14. A novel fluorocyclophosphazene as bifunctional additive for safer lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Xia, Lan; Xia, Yonggao; Liu, Zhaoping

    2015-03-01

    A high-efficiency flame-retarding additive, (Ethoxy)pentafluorocyclotriphosphazene (N3P3F5OCH2CH3, PFPN), has been synthesized and explored as a safer protection additive for rechargeable lithium batteries. The flammability tests indicate that only the addition of 5 wt% PFPN can make the electrolyte be totally non-flammable. As far as we know, the PFPN additive is the most efficient one of any flame-retarding additive ever synthesized and reported in the literature. The charge-discharge results demonstrate that the PFPN additive shows a good electrochemical compatibility on the graphitic anode and LiCoO2 cathode. Meanwhile, the incorporated PFPN additive can greatly improve the cyclic performance of LiCoO2 electrode at a high cut-off voltage of 4.5 V, showing a prospective flame-retarding additive for the applications in high-voltage lithium ion batteries.

  15. Organic solids produced from simple C/H/O/N ices by charged particles - Applications to the outer solar system

    SciTech Connect

    Khare, B.N.; Thompson, W.R.; Chyba, C.F.; Sagan, C.; Arakawa, E.T.

    1989-01-01

    The effects of charged particle irradiation by cold plasma discharge on surfaces of H2O:CH4 clathrate with a 200:1 ratio and on ices composed of H2O and C2H6 or C2H2 are examined. The molecules studies are found in Comet Halley and are plausible constituents in icy outer solar system objects. The IR transmission spectra of four ice-tholin residues obtained in the laboratory are compared with spectra produced by irradiation of gases and ices containing simple hydrocarbons. The similarities between CH4 clathrate residue and Halley organic grains, and the surface transport or atmospheric replenishment activity on Triton and Pluto are discussed. 56 refs.

  16. Solvated Electrons in Clusters: Magic Numbers for the Photoelectron Anisotropy.

    PubMed

    West, Adam H C; Yoder, Bruce L; Luckhaus, David; Signorell, Ruth

    2015-12-17

    This paper reports on a curiosity concerning magic numbers in neutral molecular clusters, namely on magic numbers related to the photoelectron anisotropy in angle-resolved photoelectron spectra. With a combination of density functional calculations and experiment, we search for magic numbers in Na(H2O)n, Na(NH3)n, Na(CH3OH)n, and Na(CH3OCH3)n clusters. In clusters of high symmetry, the highest occupied molecular orbital can be delocalized over an extended region, forming a symmetric charge distribution of high s character, which results in a pronounced anisotropy in the photoelectron angular distribution. We find magic numbers at n = 6 and 4 for sodium-doped dimethyl ether and ammonia clusters, respectively, but not for sodium-doped water and methanol clusters, which is likely a consequence of the degree of hydrogen bonding and the number of structural isomers.

  17. Intramolecular structure and dynamics of mequinol and guaiacol in the gas phase: Rotationally resolved electronic spectra of their S{sub 1} states

    SciTech Connect

    Ruiz-Santoyo, José Arturo; Rodríguez-Matus, Marcela; Álvarez-Valtierra, Leonardo E-mail: gmerino@mda.cinvestav.mx; Cabellos, José Luis; Merino, Gabriel E-mail: gmerino@mda.cinvestav.mx; Yi, John T.; Pratt, David W.; Schmitt, Michael

    2015-09-07

    The molecular structures of guaiacol (2-methoxyphenol) and mequinol (4-methoxyphenol) have been studied using high resolution electronic spectroscopy in a molecular beam and contrasted with ab initio computations. Mequinol exhibits two low frequency bands that have been assigned to electronic origins of two possible conformers of the molecule, trans and cis. Guaiacol also shows low frequency bands, but in this case, the bands have been assigned to the electronic origin and vibrational modes of a single conformer of the isolated molecule. A detailed study of these bands indicates that guaiacol has a vibrationally averaged planar structure in the ground state, but it is distorted along both in-plane and out-of-plane coordinates in the first electronically excited state. An intramolecular hydrogen bond involving the adjacent   –OH and   –OCH{sub 3} groups plays a major role in these dynamics.

  18. Electrohydrodynamic convective heat transfer in a square duct.

    PubMed

    Grassi, Walter; Testi, Daniele

    2009-04-01

    Laminar to weakly turbulent forced convection in a square duct heated from the bottom is strengthened by ion injection from an array of high-voltage points opposite the heated strip. Both positive and negative ion injection are activated within the working liquid HFE-7100 (C(4)F(9)OCH(3)), with transiting electrical currents on the order of 0.1 mA. Local temperatures on the heated wall are measured by liquid crystal thermography. The tests are conducted in a Reynolds number range from 510 to 12,100. In any case, heat transfer is dramatically augmented, almost independently from the flow rate. The pressure drop increase caused by the electrohydrodynamically induced flow is also measured. A profitable implementation of the technique in the design of heat sinks and heat exchangers is foreseen; possible benefits are pumping power reduction, size reduction, and heat exchange capability augmentation. PMID:19426338

  19. Synthesis of nano grade hollow silica sphere via a soft template method.

    PubMed

    Tsai, Ming-Shyong; Li, Miao Ju; Yen, Fu-Hsu

    2008-06-01

    The nano grade hollow silica sphere (HSS) was synthesized by a novel soft template method. We found that the precipitate of aluminate had a porous structure that could be the soft template for HSS. After mixing the colloidal silica with the aluminate precipitate, the bubble trapped in this porous structure could form the nano grade HSS. The aluminate precipitate was removed by adjusting the pH of the slurry to approximately 1. The outside diameter, the specific surface, and the mean pore size diameter of the forming HSS were 60-90 nm, 571 m2/g, and 3 nm, respectively. The formed HSS was collected by modifying the surface with Si(OCH3)3CHCH2 (VTMO) and then filtrating the precipitated gel in the n-butanol and ethanol solvent system.

  20. Environmentally harmonized CF{sub 3}I plasma for low-damage and highly selective low-k etching

    SciTech Connect

    Samukawa, Seiji; Ichihashi, Yoshinari; Ohtake, Hiroto; Soda, Eiichi; Saito, Shuichi

    2008-03-01

    Low-damage, high-rate, and highly selective low-k etching can be simultaneously satisfied using a plasma with an environmentally harmonized gas chemistry (CF{sub 3}I). Such a CF{sub 3}I plasma can drastically reduce the irradiation damage by ultraviolet (UV) photons during low-k etching, because the intensity of UV in CF{sub 3}I plasma is much lower than that in conventional CF{sub 4} plasma. The etching selectivity of SiOCH to a photoresist can be drastically improved by using CF{sub 3}I plasma because of reducing F radical generation. In addition, pulse-time-modulated CF{sub 3}I plasma causes a drastic increase in the etching rate because a large amount of negative ions can be generated. These results show that CF{sub 3}I plasma is a very promising candidate for low-damage and highly selective low-k etching.

  1. Microwave Spectroscopy of Trans-Ethyl Methyl Ether in the Torsionally Excited State 3

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kaori; Murata, Keigo; Tsunekawa, Shozo; Ohashi, Nobukimi

    2010-06-01

    The trans-ethyl methyl ether molecule (CH_3CH_2OCH_3) has two methyl group internal rotors which are equivalent to the two vibrational motions, ν28 and ν29. There is another low-lying torsional motion which is a skeltal torsion (ν30) and does not cause splitting. The microwave spectra of the trans-ethyl methyl ether molecule in the ν28 = 1, ν29 = 1, and ν30 = 1 have been studied and interactions between these states were discussed. In this paper we report results on the ν30 = 2, and 3 state. The analysis based on Hougen's tunneling matrix formulation considering two methyl groups are used. We try to interpret tunneling parameters obtained in the present analysis quantitatively from the viewpoint of torsion-torsion interaction.

  2. Di-ionizable p-tert-butylcalix[4]arene-1,2-crown-3 ligands in cone and 1,2-alternate conformations: synthesis and metal ion extraction.

    PubMed

    Zhang, Dongmei; Cao, Xiaodan; Purkiss, David W; Bartsch, Richard A

    2007-04-21

    Novel di-ionizable p-tert-butylcalix[4]arene-1,2-crown-3 ligands in cone and 1,2-alternate conformations were prepared as potential metal ion extractants. Selective bridging of proximal hydroxyl groups of the calix[4]arene platform by a crown-3 polyether unit was achieved under Mitsunobu reaction conditions. In addition to the carboxylic acid group, the acidity tunable N-(X)sulfonyl oxyacetamide functions [OCH(2)C(O)NHSO(2)X] with X group variation from methyl to phenyl to p-nitrophenyl to trifluomethyl were used as the proton-ionizable groups. Conformations and regioselectivities of the new ligands were established by (1)H and (13)C NMR spectroscopy. Competitive solvent extractions of alkali metal cations and of alkaline earth metal cations from aqueous solutions into chloroform were performed, as were single species extractions of lead(ii) and mercury(ii).

  3. The influence of oxygen on the surface chemistry of 1,2-propanediol on Pd(111)

    NASA Astrophysics Data System (ADS)

    Williams, Rhea M.; Medlin, J. Will

    2014-01-01

    The surface chemistry of 1,2-propanediol (PDO) has been studied on oxygen precovered Pd(111) using temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). Adsorbed 1,2-propanedioxy (-OCH(CH3)CH2O-) forms from the activation of the O-H bonds. When the concentration of O(a) is large compared to 1,2-propanedioxy, no H2 is produced and the dialkoxide reacts to form H2O, CO through decarbonylation, and CO2 through decarboxylation. Unreacted oxygen also desorbs as O2 at high temperature. Conversely, when the concentration of O(a) is small relative to 1,2-propanedioxy, the dialkoxide reacts to form decomposition products (H2, CO), oxidation products (H2O, glyoxal, methylglyoxal, formaldehyde) and deoxygenation products (ethylene, propylene). Co-adsorbed oxygen increases the overall coverage of PDO that can undergo decomposition, which in turn strongly influences decomposition activation barriers and products.

  4. H-D exchange in metal carbene complexes: Structure of cluster (μ-H)(μ-OCD3)Os3(CO)9{:C(CD3)NC2H8O}

    NASA Astrophysics Data System (ADS)

    Savkov, Boris; Maksakov, Vladimir; Kuratieva, Natalia

    2015-10-01

    X-ray and spectroscopic data for the new complex (μ-H)(μ-OCH3)Os3(CO)9{:C(CD3)NC2H8O} (2) obtained in the reaction of the (μ-H)(μ-Cl)Os3(CO)9{:C(CH3)NC2H8O} (1) with NaOCD3 in CD3OD solution are reported. It is shown that cluster 1 has the property of CH-acidity inherent of Fisher type carbenes. This had demonstrated using hydrogen deuterium exchange reaction in the presence of a strong base. Bridging chlorine to metoxide ligand substitution takes place during the reaction. The molecular structure of 2 is compared with known analogues.

  5. Comparative Study of Ether-Based Electrolytes for Application in Lithium-Sulfur Battery.

    PubMed

    Carbone, Lorenzo; Gobet, Mallory; Peng, Jing; Devany, Matthew; Scrosati, Bruno; Greenbaum, Steve; Hassoun, Jusef

    2015-07-01

    Herein, we report the characteristics of electrolytes using various ether-solvents with molecular composition CH3O[CH2CH2O]nCH3, differing by chain length, and LiCF3SO3 as the lithium salt. The electrolytes, considered as suitable media for lithium-sulfur batteries, are characterized in terms of thermal properties (TGA, DSC), lithium ion conductivity, lithium interface stability, cyclic voltammetry, self-diffusion properties of the various components, and lithium transference number measured by NMR. Furthermore, the electrolytes are characterized in lithium cells using a sulfur-carbon composite cathode by galvanostatic charge-discharge tests. The results clearly evidence the influence of the solvent chain length on the species mobility within the electrolytes that directly affects the behavior in lithium sulfur cell. The results may effectively contribute to the progress of an efficient, high-energy lithium-sulfur battery. PMID:26057152

  6. Preparative separation of glycoalkaloids α-solanine and α-chaconine by centrifugal partition chromatography.

    PubMed

    Attoumbré, Jacques; Lesur, David; Giordanengo, Philippe; Baltora-Rosset, Sylvie

    2012-11-01

    The main glycoalkaloids of a commercial potato cultivar, α-chaconine and α-solanine, were extracted from sprouts of Solanum tuberosum cv. Pompadour by a mixture of MeOH/H(2)O/CH(3)COOH (400/100/50, v/v/v). In these conditions, 2.8±0.62g of crude extract were obtained from 50g of fresh sprouts and the total glycoalkaloid content was determined by analytical HPLC at 216.5mg/100g. α-Chaconine and α-solanine were separated in a preparative scale using centrifugal partition chromatography (CPC). In a solvent system composed of a mixture of ethyl acetate/butanol/water (15/35/50, v/v/v), α-chaconine (54mg) and α-solanine (15mg) were successfully isolated from the crude extract in one step of purification. The purity of isolated compounds was determined to be higher than 92% by HPLC analysis.

  7. Infrared Spectra and Hydrogen Bonds of Biologically Active Benzaldehydes

    NASA Astrophysics Data System (ADS)

    Tolstorozhev, G. B.; Skornyakov, I. V.; Belkov, M. V.; Shimko, A. N.; Shadyro, O. I.; Brinkevich, S. D.; Samovich, S. N.

    2013-09-01

    IR-Fourier spectra of solutions and crystals of biologically active benzaldehyde derivatives were studied. Specific features of the formation of intra- and intermolecular hydrogen bonds were analyzed. Spectral signatures that characterized participation of the hydroxyl OH group and also the OCH3 and C=O groups in the formation of intramolecular hydrogen bonds of the three different types O-H···O-H, O-H···O-CH3, and O-H···O=C were revealed. Intramolecular hydrogen bonds of the types O-H···O-H and O-H···O-CH3 were absent for benzaldehyde derivatives in the crystal phase. Only hydroxyl and carbonyl groups participated in intermolecular interactions. This resulted in the formation of linear intermolecular dimers. Seven various configurations of the linear dimers were identified in solutions and crystals.

  8. Luminescence from VUV Irradiated Cosmic Ice Analogs and Organic Residues

    NASA Technical Reports Server (NTRS)

    Gudipati, Murthy S.; Dworkin, Jason P.; Chillier, Xavier; Allamandola, Louis J.; DeVincenzi, Donald (Technical Monitor)

    2002-01-01

    The optical luminescent properties for a variety of vacuum-ultraviolet (VUV) irradiated cosmic ice analogs and the complex organic residues produced from irradiation might be applicable to Solar System and interstellar observations and processes for various astronomical objects with an ice heritage. Some examples include grain temperature determination and vaporization rates, nebula radiation balance, albedo values, color analysis, and biomarker identification. Detailed results are presented for the mixed molecular ice: H2O:CH3OH:NH3:CO (100:50:1:1), a realistic representation for an interstellar/precometary ice. The irradiated ices and the room-temperature residues resulting from this energetic processing have remarkable photoluminescent properties in the visible (520-570 nm). The luminescence dependence on temperature, thermal cycling, and VUV exposure of the residue is described.

  9. Two-photon imaging of a magneto-fluorescent indicator for 3D optical magnetometry.

    PubMed

    Lee, Hohjai; Brinks, Daan; Cohen, Adam E

    2015-10-19

    We developed an optical method to visualize the three-dimensional distribution of magnetic field strength around magnetic microstructures. We show that the two-photon-excited fluorescence of a chained donor-bridge-acceptor compound, phenanthrene-(CH2)12-O-(CH2)2-N,N-dimethylaniline, is sensitive to ambient magnetic field strength. A test structure is immersed in a solution of the magneto-fluorescent indicator and a custom two-photon microscope maps the fluorescence of this compound. The decay kinetics of the electronic excited state provide a measure of magnetic field that is insensitive to photobleaching, indicator concentration, or local variations in optical excitation or collection efficiency. PMID:26480460

  10. Galanthamine, Plicamine, and Secoplicamine Alkaloids from Zephyranthes candida and Their Anti-acetylcholinesterase and Anti-inflammatory Activities.

    PubMed

    Zhan, Guanqun; Zhou, Junfei; Liu, Rong; Liu, Tingting; Guo, Guoli; Wang, Jianping; Xiang, Ming; Xue, Yongbo; Luo, Zengwei; Zhang, Yonghui; Yao, Guangmin

    2016-04-22

    Sixteen new alkaloids belonging to the galanthamine (1-6), plicamine (7-14), and secoplicamine (15 and 16) classes, together with eight known analogues (17-24), were isolated from Zephyranthes candida. The structures of 1-16 were determined by extensive spectroscopic analyses, and the absolute configurations of 1, 2, 7, 8, and 17 were confirmed by single-crystal X-ray diffraction analysis. The orientation of 3-OCH3 in N-methyl-5,6-dihydroplicane (22) was revised. Alkaloids 3, 12-14, and 18-21 exhibited anti-acetylcholinesterase activities with IC50 values ranging from 0.48 to 168.7 μM. Compounds 10-12, 14, and 16 showed in vitro anti-inflammatory activities with IC50 values ranging from 7.50 to 23.55 μM. PMID:26913788

  11. Synthesis and Structures of [LCu(I)(SSi(i)Pr3)] (L = triphos, carbene) and Related Compounds.

    PubMed

    Ferrara, Skylar J; Wang, Bo; Haas, Elaine; Wright LeBlanc, Karry; Mague, Joel T; Donahue, James P

    2016-09-19

    The mononuclear Cu(I) complexes [LCu(I)(SSi(i)Pr3)] (L = 1,1,1-tris(diphenylphosphinomethyl)ethane (triphos), 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes)) have been prepared by ligand displacement from [LCu(I)Cl] with (i)Pr3SiS(-). Both compounds are colorless, diamagnetic species and have been characterized structurally by X-ray crystallography. The compounds [(IMes)Cu(η(1)κ(S)-SC(O)CH3)] and [(triphos)Cu(η(1)κ(S)-SC(S)OCH3)] have been prepared in the context of synthesis aimed at [LCu(η(1)κ(S)-SCOS)] and [LCu(η(1)κ(S)-SCS2)] complexes, which are intended as synthons toward an analogue of the Mo(μ-OSCO)Cu intermediate proposed as occurring in the catalytic cycle of carbon monoxide dehydrogenase (CODH). PMID:27579711

  12. Treatment of dilute clusters of methanol and water by ab initio quantum mechanical calculations.

    PubMed

    Ruckenstein, Eli; Shulgin, Ivan L; Tilson, Jeffrey L

    2005-02-10

    Large molecular clusters can be considered as intermediate states between gas and condensed phases, and information about them can help us understand condensed phases. In this paper, ab initio quantum mechanical methods have been used to examine clusters formed of methanol and water molecules. The main goal was to obtain information about the intermolecular interactions and the structure of methanol/water clusters at the molecular level. The large clusters (CH(4)O...(H(2)O)(12) and H(2)O...(CH(4)O)(10)) containing one molecule of one component (methanol or water) and many (12, 10) molecules of the other component were considered. Møller-Plesset perturbation theory (MP2) was used in the calculations. Several representative cluster geometries were optimized, and nearest-neighbor interaction energies were calculated for the geometries obtained in the first step. The results of the calculations were compared to the available experimental information regarding the liquid methanol/water mixtures and to the molecular dynamics and Monte Carlo simulations, and good agreement was found. For the CH(4)O...(H(2)O)(12) cluster, it was shown that the molecules of water can be subdivided into two classes: (i) H bonded to the central methanol molecule and (ii) not H bonded to the central methanol molecule. As expected, these two classes exhibited striking energy differences. Although they are located almost the same distance from the carbon atom of the central methanol molecule, they possess very different intermolecular interaction energies with the central molecule. The H bonding constitutes a dominant factor in the hydration of methanol in dilute aqueous solutions. For the H(2)O...(CH(4)O)(10) cluster, it was shown that the central molecule of water has almost three H bonds with the methanol molecules; this result differs from those in the literature that concluded that the average number of H bonds between a central water molecule and methanol molecules in dilute solutions of

  13. Photoswitchable azobenzene-appended iridium(iii) complexes.

    PubMed

    Pérez-Miqueo, J; Altube, A; García-Lecina, E; Tron, A; McClenaghan, N D; Freixa, Z

    2016-09-21

    Iridium(iii) cyclometalated complexes have been used as models to study the effect that extended conjugation and substitution pattern has on the photochromic behavior of azobenzene-appended 2-phenylpyridyl (ppy) ligands. For this purpose four azobenzene-containing ppy ligands were synthesized. With these ligands, nine iridium(iii) complexes containing up to three appended azobenzenes were synthesized. Analysis of their photochromic behaviour by means of UV-vis and (1)H-NMR spectroscopy permitted us to conclude that the light-induced trans-to-cis isomerization of the azobenzene was strongly inhibited upon coordination to the Ir(iii) cation when the electronic conjugation was extended along the whole ligand. The use of an aliphatic spacer unit (either -CH2- or -OCH2-) between the azobenzene and the ppy fragment of the ligand sufficed to disrupt the electronic communication, and obtain photochromic organometallic complexes. PMID:27460186

  14. Ni (II), Cu (II) and Zn (II) Metal Chelates With Some Thiazole Derived Schiff-Bases: Their Synthesis, Characterization and Bactericidal Properties

    PubMed Central

    Chohan, Zahid H.

    1999-01-01

    A number of thiazole derived tridentate Schiff-bases (LH) and its metal chelates of the type [M(L)2X] where M=Ni(II), Cu(II) and Zn(II), L=substituted salicylaldehyde (5-H, 5-CH3, 5-OCH3, 5-NO2 and 5-Cl) and X=CI have been synthesized and characterized with the help of elemental analyses, conductivity measurements, magnetic moments, UV-Vis, IR and NMR spectral data. An octahedral structure for Ni(II) and Zn(II) and a distorted octahedral structure for Cu(II) chelates have been proposed. All the Schiff-bases and their metal chelates have been screened for their biological activity against Escherichia coli, Staphylococcus aureous , Pseudomonas aeruginosa and Klebsiella pneumonae and in comparison, the metal chelates have been shown to possess more antibacterial activity than the uncomplexed Schiff-bases. PMID:18475884

  15. Site reactivity in the free radicals induced damage to leucine residues: a theoretical study.

    PubMed

    Medina, M E; Galano, A; Alvarez-Idaboy, J R

    2015-02-21

    Several recent computational studies have tried to explain the observed selectivity in radical damage to proteins. In this work we use Density Functional Theory and Transition State Theory including tunnelling corrections, reaction path degeneracy, the effect of diffusion, and the role of free radicals to get further insights into this important topic. The reaction between a leucine derivative and free radicals of biological significance, in aqueous and lipid media, has been investigated. Both thermochemical and kinetic analyses, in both hydrophilic and hydrophobic environments, have been carried out. DPPH, ˙OOH, ˙OOCH3, ˙OOCH2Cl, ˙OOCHCl2 and ˙OOCHCH2 radicals do not react with the target molecule. The reactions are proposed to be kinetically controlled. The leucine gamma site was the most reactive for the reactions with ˙N3, ˙OOCCl3, ˙OCH3, ˙OCH2Cl, and ˙OCHCl2 radicals, with rate constants equal to 1.97 × 10(5), 3.24 × 10(4), 6.68 × 10(5), 5.98 × 10(6) and 8.87 × 10(8) M(-1) s(-1), respectively, in aqueous solution. The ˙Cl, ˙OH and ˙OCCl3 radicals react with leucine at the beta, gamma, and delta positions at rates close to the diffusion limit with the alpha position which is the slowest path and the most thermodynamically favored. The presented results confirm that the Bell-Evans-Polanyi principle does not apply for the reactions between amino acid residues and free radicals. Regarding the influence of the environment on the reactivity of the studied series of free radicals towards leucine residues, it is concluded that hydrophilic media slightly lower the reactivity of the studied radicals, compared to hydrophobic ones, albeit the trends in reactivity are very similar.

  16. Synthesis of formamide and isocyanic acid after ion irradiation of frozen gas mixtures

    NASA Astrophysics Data System (ADS)

    Kaňuchová, Z.; Urso, R. G.; Baratta, G. A.; Brucato, J. R.; Palumbo, M. E.; Strazzulla, G.

    2016-01-01

    Context. Formamide (NH2HCO) and isocyanic acid (HNCO) have been observed as gaseous species in several astronomical environments such as cometary comae and pre- and proto-stellar objects. A debate is open on the formation route of those molecules, in particular if they are formed by chemical reactions in the gas phase and/or on grains. In this latter case it is relevant to understand if the formation occurs through surface reactions or is induced by energetic processing. Aims: We present arguments that support the formation of formamide in the solid phase by cosmic-ion-induced energetic processing of ices present as mantles of interstellar grains and on comets. Formamides, along with other molecules, are expelled in the gas phase when the physical parameters are appropriate to induce the desorption of ices. Methods: We have performed several laboratory experiments in which ice mixtures (H2O:CH4:N2, H2O:CH4:NH3, and CH3OH:N2) were bombarded with energetic (30-200 keV) ions (H+ or He+). FTIR spectroscopy was performed before, during, and after ion bombardment. In particular, the formation of HNCO and NH2HCO was measured quantiatively. Results: Energetic processing of ice can quantitatively reproduce the amount of NH2HCO observed in cometary comae and in many circumstellar regions. HNCO is also formed, but additional formation mechanisms are requested to quantitatively account for the astronomical observations. Conclusions: We suggest that energetic processing of ices in the pre- and proto-stellar regions and in comets is the main mechanism to produce formamide, which, once it is released in the gas phase because of desorption of ices, is observed in the gas phase in these astrophysical environments.

  17. Enantioselective DNA condensation induced by heptameric lanthanum helical supramolecular enantiomers.

    PubMed

    Bao, Fei-Fei; Xu, Xin-Xin; Zhou, Wen; Pang, Chun-Yan; Li, Zaijun; Gu, Zhi-Guo

    2014-09-01

    DNA condensation induced by a pair of heptameric La(III) helical enantiomers M-[La7(S-L)6(CO3)(NO3)6(OCH3)(CH3OH)7]·2CH3OH·5H2O and P-[La7(R-L)6(CO3)(NO3)6(OCH3)(CH3OH)5(H2O)2]·2CH3OH·4H2O (M-La and P-La, L=2-(2-hydroxybenzylamino)-3-carbamoylpropanoic acid) has been investigated by UV/vis spectroscopy, fluorescence spectroscopy, CD spectroscopy, EMSA, RALS, DLS, and SEM. The enantiomers M-La and P-La could induce CT-DNA condensation at a low concentration as observed in UV/vis spectroscopy. DNA condensates possessed globular nanoparticles with nearly homogeneous sizes in solid state determined by SEM (ca. 250 nm for M-La and ca. 200 nm for P-La). The enantiomers bound to DNA through electrostatic attraction and hydrogen bond interactions in a major groove, and rapidly condensed free DNA into its compact state. DNA decompaction has been acquired by using EDTA as disassembly agent, and analyzed by UV/vis spectroscopy, CD spectroscopy and EMSA. Moreover, the enantiomers M-La and P-La displayed discernible discrimination in DNA interaction and DNA condensation, as well as DNA decondensation. Our study suggested that lanthanum(III) enantiomers M-La and P-La were efficient DNA packaging agents with potential applications in gene delivery.

  18. High diversity of microcystins in a Microcystis bloom from an Algerian lake.

    PubMed

    Bouhaddada, Ratiba; Nélieu, Sylvie; Nasri, Hichem; Delarue, Ghislaine; Bouaïcha, Noureddine

    2016-09-01

    Microcystins (MCs) are cyanobacterial heptapeptides, produced by several genera and species of cyanobacteria, which have been involved in poisoning of animals throughout the world and have also been implicated in human health problems. They are regarded as the most frequently occurring and widespread of the cyanotoxins, with more than 100 MC variants reported to date including the present study. The lake des Oiseaux is a shallow permanent freshwater lake located in north-eastern Algeria. It is an important natural reserve playing a major role for the migratory birds after the crossing of the Mediterranean Sea and from the Sahara desert. In recent years, possibly related to increased eutrophication of the lake, massive blooms of cyanobacteria identified as Microcystis spp. have been observed. A bloom sample collected in September 2013 was analyzed by the serine/threonine phosphatase PP2A inhibition assay and liquid chromatography-mass spectrometry to determine respectively, the total concentration of MCs and the different variants of these toxins present. The results revealed that the Microcystis spp. bloom sample contained microcystins of which 21 putatively congeners were detected. Among these, 12 known microcystins (MC-RR, MC-LR, MC-FR, MC-WR, MC-YR, MC-LA, MC-(H4)YR, MC-HilR, [Asp(3)]MC-RAba, and [Glu(OCH3)(6)]MC-LR) and two new congeners ([Asp(3)]MC-HarAba and [Glu(OCH3)(6)]MC-FR) were characterized, considering their molecular mass and the fragment ions produced by collision-induced dissociation of the [M+H](+) ions. MC-RR was the major (43.4%) in the bloom sample. PMID:27394081

  19. Highly proton conductive phosphoric acid-nonionic surfactant lyotropic liquid crystalline mesophases and application in graphene optical modulators.

    PubMed

    Tunkara, Ebrima; Albayrak, Cemal; Polat, Emre O; Kocabas, Coskun; Dag, Ömer

    2014-10-28

    Proton conducting gel electrolytes are very important components of clean energy devices. Phosphoric acid (PA, H(3)PO(4) · H2O) is one of the best proton conductors, but needs to be incorporated into some matrix for real device applications, such as into lyotropic liquid crystalline mesophases (LLCMs). Herein, we show that PA and nonionic surfactant (NS, C(12)H(25)(OCH(2)CH(2))(10)OH, C(12)E(10)) molecules self-assemble into PANS-LLCMs and display high proton conductivity. The content of the PANS-LLCM can be as high 75% H(3)PO(4) · H2O and 25% 10-lauryl ether (C(12)H(25)(OCH(2)CH(2))(10)OH, C(12)E(10)), and the mesophase follows the usual LLC trend, bicontinuous cubic (V1)-normal hexagonal (H1)-micelle cubic (I1), by increasing the PA concentration in the media. The PANS-LLCMs are stable under ambient conditions, as well as at high (up to 130 °C) and low (-100 °C) temperatures with a high proton conductivity, in the range of 10(-2) to 10(-6) S/cm. The mesophase becomes a mesostructured solid with decent proton conductivity below -100 °C. The mesophase can be used in many applications as a proton-conducting media as well as a phosphate source for the synthesis of various metal phosphates. As an application, we demonstrate a graphene-based optical modulator using supercapacitor structure formed by graphene electrodes and a PANS electrolyte. A PANS-LLC electrolyte-based supercapacitor enables efficient optical modulation of graphene electrodes over a range of wavelengths, from 500 nm to 2 μm, under ambient conditions.

  20. New 7-arylpiperazinylalkyl-8-morpholin-4-yl-purine-2,6-dione derivatives with anxiolytic activity - Synthesis, crystal structure and structure-activity study

    NASA Astrophysics Data System (ADS)

    Chłoń-Rzepa, Grażyna; Żmudzki, Paweł; Pawłowski, Maciej; Wesołowska, Anna; Satała, Grzegorz; Bojarski, Andrzej J.; Jabłoński, Mateusz; Kalinowska-Tłuścik, Justyna

    2014-06-01

    On the basis of our earlier studies with serotonin (5-HT) receptor ligands in the group of long-chain arylpiperazines (LCAPs), a new series of 7-arylpiperazinylalkyl-8-morpholin-4-yl-purine-2,6-dione derivatives (5-12) has been designed, synthesised and studied in vitro for their affinity for 5-HT1A, 5-HT2A, 5-HT6 and 5-HT7 receptors. The introduction of o-OCH3 and m-Cl into the phenylpiperazinyl moiety as well as the elongation of the linker between purine-2,6-dione core and arylpiperazine fragment modified the affinity for the tested 5-HT receptors. The structures of compounds 9-11 (hydrochloride salts) were confirmed by an X-ray diffraction method. All molecules adopted a different conformation in the crystal. The strongest observed type of interaction is a charge assisted hydrogen bond N+-H⋯Cl-. Additionally, the π-π interactions between 1,3-dimethyl-3,7-dihydropurine-2,6-dione cores of the neighbouring molecules were also observed. As it is observed in the presented crystal structures, the morpholine ring (a potential donor and acceptor of the hydrogen bonds) seems to be an attractive substituent, that may support binding to the non-specific sites of 5-HT receptors. Another interesting feature is the mutual orientation of rings in the arylpiperazine fragment, with plausible influence on ligand-receptor recognition. For compound 10, with strong 5-HT1A binding affinity, the mutual orientation of rings is determined by the intramolecular weak C-H⋯O hydrogen bond. This observation may contribute to a better understanding of the more selective binding of o-OCH3 arylpiperazine derivatives to the 5-HT1A receptor.

  1. Effect of several analogs of 2,4,6-triphenyldioxane-1,3 on CYP2B induction in mouse liver.

    PubMed

    Pustylnyak, Vladimir; Kazakova, Yuliya; Yarushkin, Andrei; Slynko, Nikolai; Gulyaeva, Lyudmila

    2011-11-15

    2,4,6-Triphenyldioxane-1,3 (TPD) is a highly effective inducer of CYP2В in rats, but not in mice. Several analogs of TPD were synthesized. All substituents were entered into the same position of TPD (R=H, cisTPD and transTPD; R=N(CH(3))(2), transpDMA; R=NO(2), transpNO(2); R=F, transpF; R=OCH(3), transpMeO). The purpose of the present study was to investigate the effect of TPD analogs on CYP2B induction in mouse livers. Among the six test compounds, four (R=-N(CH(3))(2), -NO(2), -F, -OCH(3)) demonstrated a dose-dependent induction of mouse CYP2B. To further characterize the compounds, we determined ED50s using sigmoidal dose-response curves. The dose-response study has shown that all active compounds have similar potencies to induce CYP2B in mouse livers. Western-blot analysis and multiplex RT-PCR have shown that the increase of CYP2B activity in mouse liver is related to the high content of CYP2B proteins and paralleled the increase of cyp2b10 mRNA level. ChIP results have demonstrated that the transcriptional enhancement of cyp2b10 gene in response to compounds is accompanied by the increased recruitment of the constitutive androstane receptor (CAR) to its specific binding site (PBREM) on the target gene. Thus, minor structural changes in TPD cause dramatic changes in its ability to induce mouse CYP2B, and it is likely several TPD analogs act by activation of mouse CAR. PMID:21982821

  2. Modelization of structural changes in ultra low k materials during ultraviolet cure

    NASA Astrophysics Data System (ADS)

    Imbert, G.; Vo-Than, D.; Trouiller, C.; Lorut, F.

    2013-12-01

    As of 45 nm node, ultralow k (ULK) materials (ɛr < 2.55) are widely used in microelectronic interconnects to reduce signal propagation delay. In order to get such low dielectric constant, most of these ULK are obtained using subtractive method: after co-deposition of matrix and porogen a UV cure process is used to remove labile species (porogen). During this process, porosity is created and films are densified as shrinkage increases. This paper presents an in-depth study of the UV cure process. Two kinetic models are presented to describe shrinkage rate: the nth order and the autocatalytic model. These models also used to describe photo-polymerization shrinkage-strain of dental composite, gives predictions that are in good agreement with experimental data. We find that nth-order model is best suited to describe ULK transformations during UV cure process. CHx bonds loss and carbon content can also be modeled using same kinetic model. In order to be able to build the model, initial SiOCH-CxHy film has to be over-cured to determine the maximum conversion that film can reach when submitted to extra-long cure times. Results show that such SiOCH materials have to be cured more than 250 times their nominal cure time to reach maximum shrinkage (˜50%) and a complete loss of carbon, making them looking like SiO2. When structural changes are observed at different temperature, activation energy of reactions can be determined. In this way, shrinkage reaction has an activation energy close to 1000-1100 kJ/mol and CHx bonds or carbon loss reactions have activation energy in the range of 250-400 kJ/mol, which is pretty close to C-H binding energy.

  3. Perinatal exposure of female rats to 2,3,7,8-tetrachlorodibenzo-p-dioxin induces central precocious puberty in the offspring.

    PubMed

    Kakeyama, Masaki; Sone, Hideko; Tohyama, Chiharu

    2008-05-01

    Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) during the fetal and neonatal periods has been indicated to alter the development of the offspring later in life. In this study, we determined whether perinatal exposure to a low dose of TCDD affects the onset of puberty in the female offspring of Long-Evans hooded rats. On day 15 of gestation, pregnant female rats were administered TCDD by gavage at a single dose of 0 (vehicle), 200, or 800 ng/kg b.w. In the female offspring born to dams administered with TCDD at either 200 or 800 ng/kg b.w., the vaginal opening and first estrus occurred approximately 4-7 days earlier than in the offspring born to vehicle-treated animals. The ovarian weight gain was also accelerated following exposure to TCDD in a dose-dependent manner. We next examined the ovarian compensatory hypertrophy (OCH) as an indicator of the maturation of the LH/GnRH-generating system in the pituitary and the hypothalamus. Exposure to TCDD accelerated the onset of OCH in the female offspring in a dose-dependent manner. In particular, in the offspring born to the dams exposed to TCDD at 800 ng/kg b.w., hypertrophy, which is characterized by hyperovulation and a marked increase in the weight of the remaining ovary after hemi-ovariectomy, was observed on postnatal days 27-30, which was 10 days earlier than in the offspring born to the vehicle-treated dams. These results indicate that perinatal exposure to a low dose of TCDD induces precocious puberty, including early maturation of the hypothalamic-pituitary axis, the gonads and genitals, in female Long-Evans hooded rats.

  4. Formation of hydroxyacetonitrile (HOCH2CN) and polyoxymethylene (POM)-derivatives in comets from formaldehyde (CH2O) and hydrogen cyanide (HCN) activated by water.

    PubMed

    Danger, Grégoire; Rimola, Albert; Abou Mrad, Ninette; Duvernay, Fabrice; Roussin, Gaël; Theule, Patrice; Chiavassa, Thierry

    2014-02-28

    Studying chemical reactivity is an important way to improve our understanding of the origin of organic matter in astrophysical environments such as molecular clouds, protoplanetary disks, and possibly, as a final destination, in our solar system bodies such as in comets. Laboratory simulations on the reactivity of ice analogs can provide important insights into this complex reactivity. Here, the role of water as a catalytic agent is investigated under the conditions of simulated interstellar and cometary grains in the formation of complex organic molecules: the hydroxyacetonitrile (HOCH2CN) and formaldehyde polymers (polyoxymethylene POM). Using infrared spectroscopy and mass spectrometry, we show that HCN reacts with CH2O only in the presence of H2O, whereas in the absence of H2O, HCN is not sufficiently reactive to promote this reaction. Furthermore, depending on the dilution of CH2O and HCN in the water matrix, 1-cyanopolyoxymethylene polymers can also be formed (H-(O-CH2)n-CN, POM-CN), as confirmed by mass spectrometry using the HC(15)N isotopologue. Moreover, quantum chemical calculations allowed us to suggest mechanistic proposals for these reactions, the first step being the activation of HCN by water forming H3O(+) and CN(-), which subsequently condense on a neighbouring CH2O promoting the formation of (-)OCH2CN. Once (-)OCH2CN is formed, it can either recover a proton by reacting with H3O(+) or condense on CH2O molecules leading to POM-CN structures. Implications of this work for the forthcoming Rosetta mission are also addressed. PMID:24202268

  5. Kinetics and mechanism of (CF3)2CHOCH3 reaction with OH radicals in an environmental reaction chamber.

    PubMed

    Chen, L; Kutsuna, S; Tokuhashi, K; Sekiya, A; Tamai, R; Hibino, Y

    2005-06-01

    The atmospheric chemistry of (CF3)2CHOCH3, a possible HCFC/HFC alternative, was studied using a smog chamber/FT-IR technique. OH radicals were prepared by the photolysis of ozone in a 200-Torr H2O/O3/O2 gas mixture held in an 11.5-dm3 temperature-controlled chamber. The rate constant, k1, for the reaction of (CF3)2CHOCH3 with OH radicals was determined to be (1.40 +/- 0.28) x 10(-12) exp[(-550 +/- 60)/T] cm3 molecule(-1) s(-1) by means of a relative rate method at 253-328 K. The value of k1 at 298 K was (2.25 +/- 0.04) x 10(-13) cm3 molecule(-1) s(-1). The random errors are reported with +/-2 standard deviations, and potential systematic errors of 15% could increase k(1). In considering OH-radical reactions, we estimated the tropospheric lifetime of (CF3)2CHOCH3 to be 2.0 months using the rate constant at 288 K. The degradation mechanism of (CF3)2CHOCH3 initiated by OH radicals was also investigated using FT-IR spectroscopy at 298 K. Products (CF3)2CHOC(O)H, CF3C(OH)2CF3, CF3C(O)OCH3, and COF(2) were identified and quantified. The branching ratio, k1a/k1b, was estimated to be 2.1:1 for reactions (CF3)2CHOCH3 + OH --> (CF3)2CHOCH2*+ H2O (k1a) and (CF3)2CHOCH3 + OH --> (CF3)2C*OCH3 + H2O (k1b). PMID:16833819

  6. Evaluation of multistep derivatization methods for identification and quantification of oxygenated species in organic aerosol.

    PubMed

    Flores, Rosa M; Doskey, Paul V

    2015-10-30

    Two, 3-step methods for derivatizing mono- and multi-functional species with carbonyl (CO), carboxylic acid (-COOH), and alcohol (-OH) moieties were compared and optimized. In Method 1, the CO, -COOH, and -OH moieties were converted (1) to methyloximes (R-CN-OCH3) with O-methylhydroxylamine hydrochloride (MHA), (2) to methyl esters (OC-R-OCH3) with (trimethylsilyl)diazomethane in methanol (TMSD/MeOH), and (3) to trimethylsilyl ethers [R-OSi(CH3)3] with N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA) containing 1% trimethylchlorosilane (TMCS), respectively. Steps 1 and 3 of both methods were identical; however, in Step 2 of Method 2, -COOH moieties were derivatized with 10% (v/v) boron trifluoride (BF3) in MeOH or n-butanol (n-BuOH). The BF3/MeOH and BF3/n-BuOH were ineffective at converting species with more than 2-OH moieties. Average standard deviations for derivatization of 36 model compounds by the 3-step methods using TMSD/MeOH and BF3/(MeOH) were 7.4 and 14.8%, respectively. Average derivatization efficiencies for Methods 1 and 2 were 88.0 and 114%, respectively. Despite the lower average derivatization efficiency of Method 1, distinct advantages included a greater certainty of derivatization yield for the entire suite of mono- and multi-functional species and fewer processing steps for sequential derivatization. Detection limits for Method 1 using GC×GC-ToF-MS were 0.3-54pgm(-3). Approximately 100 oxygenated organic species were identified and quantified in aerosol filtered from 39m(3) of air in an urban location. Levels of species were 0.013-17ngm(-3) and were nearly all above the Method 1 limit of detection. PMID:26427323

  7. Impact of water on the cis-trans photoisomerization of hydroxychalcones.

    PubMed

    Leydet, Yoann; Batat, Pinar; Jonusauskas, Gediminas; Denisov, Sergey; Lima, João Carlos; Parola, A Jorge; McClenaghan, Nathan D; Pina, Fernando

    2013-05-23

    The photochromism of a 2-hydroxychalcone has been studied in CH3CN and H2O/CH3OH (1/1, v/v), as well as in analogous deuterated solvents using steady-state (UV-vis absorption, (1)H and (13)C NMR) and time-resolved (ultrafast transient absorption and nanosecond flow flash photolysis) spectroscopies. Whereas the irradiation of trans-chalcone (Ct) under neutral pH conditions leads to the formation of the same final chromene derivative (B) in both media, two distinct photochemical mechanisms are proposed in agreement with thermodynamic and kinetic properties of the chemical reaction network at the ground state. Following light excitation, the first steps are identical in acetonitrile and aqueous solution: the Franck-Condon excited state rapidly populates the trans-chalcone singlet excited state (1)Ct* (LE), which evolves into a twisted state (1)P*. This excited state is directly responsible for the photochemistry in acetonitrile in the nanosecond time scale (16 ns) leading to the formation of cis-chalcone (Cc) through a simple isomerization process. The resulting cis-chalcone evolves into the chromene B through a tautomerization process in the ground state (τ = 10 ms). Unlike in acetonitrile, in H2O/CH3OH (1/1, v/v), the P* state becomes unstable and evolves into a new state attributed to the tautomer (1)Q*. This state directly evolves into B in one photochemical step through a consecutive ultrafast tautomerization process followed by electrocyclization. This last case represents a new hypothesis in the photochromism of 2-hydroxychalcone derivatives.

  8. Formation of hydroxyacetonitrile (HOCH2CN) and polyoxymethylene (POM)-derivatives in comets from formaldehyde (CH2O) and hydrogen cyanide (HCN) activated by water.

    PubMed

    Danger, Grégoire; Rimola, Albert; Abou Mrad, Ninette; Duvernay, Fabrice; Roussin, Gaël; Theule, Patrice; Chiavassa, Thierry

    2014-02-28

    Studying chemical reactivity is an important way to improve our understanding of the origin of organic matter in astrophysical environments such as molecular clouds, protoplanetary disks, and possibly, as a final destination, in our solar system bodies such as in comets. Laboratory simulations on the reactivity of ice analogs can provide important insights into this complex reactivity. Here, the role of water as a catalytic agent is investigated under the conditions of simulated interstellar and cometary grains in the formation of complex organic molecules: the hydroxyacetonitrile (HOCH2CN) and formaldehyde polymers (polyoxymethylene POM). Using infrared spectroscopy and mass spectrometry, we show that HCN reacts with CH2O only in the presence of H2O, whereas in the absence of H2O, HCN is not sufficiently reactive to promote this reaction. Furthermore, depending on the dilution of CH2O and HCN in the water matrix, 1-cyanopolyoxymethylene polymers can also be formed (H-(O-CH2)n-CN, POM-CN), as confirmed by mass spectrometry using the HC(15)N isotopologue. Moreover, quantum chemical calculations allowed us to suggest mechanistic proposals for these reactions, the first step being the activation of HCN by water forming H3O(+) and CN(-), which subsequently condense on a neighbouring CH2O promoting the formation of (-)OCH2CN. Once (-)OCH2CN is formed, it can either recover a proton by reacting with H3O(+) or condense on CH2O molecules leading to POM-CN structures. Implications of this work for the forthcoming Rosetta mission are also addressed.

  9. The Search for a Complex Molecule in a Selected Hot Core Region: A Rigorous Attempt to Confirm Trans-ethyl Methyl Ether toward W51 e1/e2

    NASA Astrophysics Data System (ADS)

    Carroll, P. Brandon; McGuire, Brett A.; Blake, Geoffrey A.; Apponi, A. J.; Ziurys, L. M.; Remijan, Anthony

    2015-01-01

    An extensive search has been conducted to confirm transitions of trans-ethyl methyl ether (tEME, C2H5OCH3), toward the high-mass star forming region W51 e1/e2 using the 12 m Telescope of the Arizona Radio Observatory at wavelengths from 2 mm and 3 mm. In short, we cannot confirm the detection of tEME toward W51 e1/e2 and our results call into question the initial identification of this species by Fuchs et al. Additionally, re-evaluation of the data from the original detection indicates that tEME is not present toward W51 e1/e2 in the abundance reported by Fuchs and colleagues. Typical peak-to-peak noise levels for the present observations of W51 e1/e2 were between 10 and 30 mK, yielding an upper limit of the tEME column density of <=1.5 × 1015 cm-2. This would make tEME at least a factor of two times less abundant than dimethyl ether (CH3OCH3) toward W51 e1/e2. We also performed an extensive search for this species toward the high-mass star forming region Sgr B2(N-LMH) with the National Radio Astronomy Observatory 100 m Green Bank Telescope. No transitions of tEME were detected and we were able to set an upper limit to the tEME column density of <=4 × 1014 cm-2 toward this source. Thus, we are able to show that tEME is not a new molecular component of the interstellar medium and that an exacting assessment must be carried out when assigning transitions of new molecular species to astronomical spectra to support the identification of large organic interstellar molecules.

  10. NMR shielding calculations across the periodic table: diamagnetic uranium compounds. 2. Ligand and metal NMR.

    PubMed

    Schreckenbach, Georg

    2002-12-16

    In this and a previous article (J. Phys. Chem. A 2000, 104, 8244), the range of application for relativistic density functional theory (DFT) is extended to the calculation of nuclear magnetic resonance (NMR) shieldings and chemical shifts in diamagnetic actinide compounds. Two relativistic DFT methods are used, ZORA ("zeroth-order regular approximation") and the quasirelativistic (QR) method. In the given second paper, NMR shieldings and chemical shifts are calculated and discussed for a wide range of compounds. The molecules studied comprise uranyl complexes, [UO(2)L(n)](+/-)(q); UF(6); inorganic UF(6) derivatives, UF(6-n)Cl(n), n = 0-6; and organometallic UF(6) derivatives, UF(6-n)(OCH(3))(n), n = 0-5. Uranyl complexes include [UO(2)F(4)](2-), [UO(2)Cl(4)](2-), [UO(2)(OH)(4)](2-), [UO(2)(CO(3))(3)](4-), and [UO(2)(H(2)O)(5)](2+). For the ligand NMR, moderate (e.g., (19)F NMR chemical shifts in UF(6-n)Cl(n)) to excellent agreement [e.g., (19)F chemical shift tensor in UF(6) or (1)H NMR in UF(6-n)(OCH(3))(n)] has been found between theory and experiment. The methods have been used to calculate the experimentally unknown (235)U NMR chemical shifts. A large chemical shift range of at least 21,000 ppm has been predicted for the (235)U nucleus. ZORA spin-orbit appears to be the most accurate method for predicting actinide metal chemical shifts. Trends in the (235)U NMR chemical shifts of UF(6-n)L(n) molecules are analyzed and explained in terms of the calculated electronic structure. It is argued that the energy separation and interaction between occupied and virtual orbitals with f-character are the determining factors.

  11. Comparison of the crystal structures of methyl 4-bromo-2-(meth-oxy-meth-oxy)benzoate and 4-bromo-3-(meth-oxy-meth-oxy)benzoic acid.

    PubMed

    Suchetan, P A; Suneetha, V; Naveen, S; Lokanath, N K; Krishna Murthy, P

    2016-04-01

    The title compounds, C10H11BrO4, (I), and C9H9BrO4, (II), are derivatives of bromo-hy-droxy-benzoic acids. Compound (II) crystallizes with two independent mol-ecules (A and B) in the asymmetric unit. In both (I) and (II), the O-CH2-O-CH3 side chain is not in its fully extended conformation; the O-C-O-C torsion angle is 67.3 (3) ° in (I), and -65.8 (3) and -74.1 (3)° in mol-ecules A and B, respectively, in compound (II). In the crystal of (I), mol-ecules are linked by C-H⋯O hydrogen bonds, forming C(5) chains along [010]. The chains are linked by short Br⋯O contacts [3.047 (2) Å], forming sheets parallel to the bc plane. The sheets are linked via C-H⋯π inter-actions, forming a three-dimensional architecture. In the crystal of (II), mol-ecules A and B are linked to form R 2 (2)(8) dimers via two strong O-H⋯O hydrogen bonds. These dimers are linked into ⋯A-B⋯A-B⋯A-B⋯ [C 2 (2)(15)] chains along [011] by C-H⋯O hydrogen bonds. The chains are linked by slipped parallel π-π inter-actions [inter-centroid distances = 3.6787 (18) and 3.8431 (17) Å], leading to the formation of slabs parallel to the bc plane. PMID:27375868

  12. Functional disubstituted polyacetylenes: Synthesis, liquid crystallinity, light emission, and fluorescent photopatterning of biphenyl-containing poly(1-phenyl-octyne)s with different functional bridges.

    PubMed

    Lam, Jacky W Y; Qin, Anjun; Dong, Yuping; Lai, Lo Ming; Häussler, Matthias; Dong, Yongqiang; Tang, Ben Zhong

    2006-11-01

    Biphenyl (Biph)-containing 1-phenyl-1-octynes and their polymers are synthesized, and the effects of functional bridge groups on the mesomorphic and optical properties of the polymers are studied. The nonmesomorphic disubstituted acetylene monomers (C6H13)C[triple bond]C(C6H4)O(CH2)12O-Biph-OC7H15 (1), (C6H13)C[triple bond]C(C6H4)O(CH2)11OOC-Biph-OC7H15 (2), and (C6H13)C[triple bond]C(C6H4)CO2(CH2)12OOC-Biph-OC7H15 (3) are prepared by multistep reaction routes and converted into their corresponding polymers P1-P3 by a WCl6-Ph4Sn catalyst. The structures and properties of the polymers are characterized and evaluated by NMR, TGA, DSC, POM, XRD, UV, and PL analyses. The mesogenic pendants have endowed the polymers with high thermal stability (> or =400 degrees C). While P1 exhibits no liquid crystallinity, P2 and P3 form enantiotropic S(A) phase with a monolayer structure. Upon photoexcitation, the polymers emit blue and blue-green lights of 460 and 480 nm, respectively, in THF with quantum efficiencies larger than 30%. UV irradiation of a thin film of P2 through a mask oxidizes and quenches the light emission of the exposed regions, generating a two-dimensional luminescent photoimage.

  13. Theoretical studies on kinetics, mechanism and thermochemistry of gas-phase reactions of HFE-449mec-f with OH radicals and Cl atom.

    PubMed

    Deka, Ramesh Chandra; Mishra, Bhupesh Kumar

    2014-09-01

    A theoretical study on the mechanism and kinetics of the gas phase reactions of CF3CHFCF2OCH2CF3 (HFE-449mec-f) with the OH radicals and Cl atom have been performed using meta-hybrid modern density functional M06-2X using 6-31+G(d,p) basis set. Two conformers have been identified for CF3CHFCF2OCH2CF3 and the most stable one is considered for detailed study. Reaction profiles for OH-initiated hydrogen abstraction are modeled including the formation of pre-reactive and post-reactive complexes at entrance and exit channels. Our calculations reveal that hydrogen abstraction from the CH2 group is thermodynamically and kinetically more facile than that from the CHF group. Using group-balanced isodesmic reactions, the standard enthalpies of formation for HFE-449mecf and radicals generated by hydrogen abstraction, are also reported. The calculated bond dissociation energies for CH bonds are in good agreement with experimental results. The rate constants of the two reactions are determined for the first time in a wide temperature range of 250-450K. The calculated rate constant values are found to be 9.10×10(-15) and 4.77×10(-17)cm(3)molecule(-1)s(-1) for reactions with OH radicals and Cl atom, respectively. At 298K, the total calculated rate coefficient for reactions with OH radical is in good agreement with the experimental results. The atmospheric life time of HFE-449mec-f is estimated to be 0.287 years.

  14. Separating chemical and excluded volume interactions of polyethylene glycols with native proteins: Comparison with PEG effects on DNA helix formation.

    PubMed

    Shkel, Irina A; Knowles, D B; Record, M Thomas

    2015-09-01

    Small and large PEGs greatly increase chemical potentials of globular proteins (μ2), thereby favoring precipitation, crystallization, and protein-protein interactions that reduce water-accessible protein surface and/or protein-PEG excluded volume. To determine individual contributions of PEG-protein chemical and excluded volume interactions to μ2 as functions of PEG molality m3 , we analyze published chemical potential increments μ23  = dμ2/dm3 quantifying unfavorable interactions of PEG (PEG200-PEG6000) with BSA and lysozyme. For both proteins, μ23 increases approximately linearly with the number of PEG residues (N3). A 1 molal increase in concentration of PEG -CH2 OCH2 - groups, for any chain-length PEG, increases μBSA by ∼2.7 kcal/mol and μlysozyme by ∼1.0 kcal/mol. These values are similar to predicted chemical interactions of PEG -CH2 OCH2 - groups with these protein components (BSA ∼3.3 kcal/mol, lysozyme ∼0.7 kcal/mol), dominated by unfavorable interactions with amide and carboxylate oxygens and counterions. While these chemical effects should be dominant for small PEGs, larger PEGS are expected to exhibit unfavorable excluded volume interactions and reduced chemical interactions because of shielding of PEG residues in PEG flexible coils. We deduce that these excluded volume and chemical shielding contributions largely compensate, explaining why the dependence of μ23 on N3 is similar for both small and large PEGs. PMID:25924886

  15. Combustion characterization of methylal in reciprocating engines

    SciTech Connect

    Dodge, L.; Naegeli, D.

    1994-06-01

    Methylal, CH{sub 3}OCH{sub 2}OCH{sub 3}, also known as dimethoxy-methane, is unique among oxygenates in that it has a low autoignition temperature, no carbon-carbon bonds, and is soluble in middle distillate fuels. Because of these properties, methylal has been shown to be a favorable fuel additive for reducing smoke in diesel engines. Recent measurements of ignition delay times indicate that methylal has a cetane number in the range of 45-50, which is compatible with diesel fuels. Engine tests have shown that adding methylal to diesel fuel significantly reduces smoke emissions. Gaseous emissions and combustion efficiencies obtained with methylal/diesel fuel blends remain essentially the same as those measured using neat diesel fuel. Lubricity measurements of methylal/diesel fuel blends with a ball on cylinder lubrication evaluator (BOCLE) show that methylal improves the lubricity of diesel fuel. Even though additions of methylal lower the fuel viscosity, the results of the BOCLE tests indicate that the methylal/diesel fuel blends cause less pump wear than neat diesel fuel. The one drawback is that methylal has a low boiling point (42{degrees}C) and a relatively high vapor pressure. As a result, it lowers the flash point of diesel fuel and causes a potential fuel tank flammability hazard. One solution to this increased volatility is to make polyoxymethylenes with the general formula of CH{sub 3}O(CH{sub 2}O){sub x}CH{sub 3} where x > 2. The molecules are similar to methylal, but have higher molecular weights and thus higher viscosities and substantially lower vapor pressures. Therefore, their flash points will be compatible with regular diesel fuel. The polyoxymethylenes are expected to have combustion properties similar to methylal. It is theorized that by analogy with hydrocarbons, the ignition quality (i.e., cetane number) of the polyoxymethylenes will be better than that of methylal.

  16. New structural information on a humic acid from two-dimensional 1H-13C correlation solid-state nuclear magnetic resonance.

    PubMed

    Mao, J D; Xing, B; Schmidt-Rohr, K

    2001-05-15

    New information on the chemical structure of a peat humic acid has been obtained using a series of two-dimensional 1H-13C heteronuclear correlation solid-state NMR (HETCOR) experiments with different contact times and with spectral editing by dipolar dephasing and 13C transverse relaxation filtering. Carbon-bonded methyl groups (C-CH3) are found to be near both aliphatic and O-alkyl but not aromatic groups. The spectra prove that most OCH3 groups are connected directly with the aromatic rings, as is typical in lignin. As a result, about one-third of the aromatic C-O groups is not phenolic C-OH but C-OCH3. Both protonated and unprotonated anomeric O-C-O carbons are identified in the one- and two-dimensional spectra. COO groups are found predominantly in OCHn-COO environments, but some are also bonded to aromatic rings and aliphatic groups. All models of humic acids in the literature lack at least some of the features observed here. Compositional heterogeneity was studied by introducing 1H spin diffusion into the HETCOR experiment. Comparison with data for a synthetic polymer, polycarbonate, indicates that the separation between O-alkyl and aromatic groups in the humic acid is less than 1.5 nm. However, transverse 13C relaxation filtering under 1H decoupling reveals heterogeneity on a nanometer scale, with the slow-relaxing component being rich in lignin-like aromatic-C-O-CH3 moieties and poor in COO groups.

  17. Histidine 352 (His352) and Tryptophan 355 (Trp355) Are Essential for Flax UGT74S1 Glucosylation Activity toward Secoisolariciresinol

    PubMed Central

    Ghose, Kaushik; McCallum, Jason; Sweeney-Nixon, Marva; Fofana, Bourlaye

    2015-01-01

    Flax secoisolariciresinol diglucoside (SDG) lignan is a natural phytoestrogen for which a positive role in metabolic diseases is emerging. Until recently however, much less was known about SDG and its monoglucoside (SMG) biosynthesis. Lately, flax UGT74S1 was identified and characterized as an enzyme sequentially glucosylating secoisolariciresinol (SECO) into SMG and SDG when expressed in yeast. However, the amino acids critical for UGT74S1 glucosyltransferase activity were unknown. A 3D structural modeling and docking, site-directed mutagenesis of five amino acids in the plant secondary product glycosyltransferase (PSPG) motif, and enzyme assays were conducted. UGT74S1 appeared to be structurally similar to the Arabidopsis thaliana UGT72B1 model. The ligand docking predicted Ser357 and Trp355 as binding to the phosphate and hydroxyl groups of UDP-glucose, whereas Cys335, Gln337 and Trp355 were predicted to bind the 7-OH, 2-OCH3 and 17-OCH3 of SECO. Site-directed mutagenesis of Cys335, Gln337, His352, Trp355 and Ser357, and enzyme assays revealed an alteration of these binding sites and a significant reduction of UGT74S1 glucosyltransferase catalytic activity towards SECO and UDP-glucose in all mutants. A complete abolition of UGT74S1 activity was observed when Trp355 was substituted to Ala355 and Gly355 or when changing His352 to Asp352, and an altered metabolite profile was observed in Cys335Ala, Gln337Ala, and Ser357Ala mutants. This study provided for the first time evidence that Trp355 and His352 are critical for UGT74S1’s glucosylation activity toward SECO and suggested the possibility for SMG production in vitro. PMID:25714779

  18. Stereoelectronic effects on 1H nuclear magnetic resonance chemical shifts in methoxybenzenes.

    PubMed

    Lambert, Maja; Olsen, Lars; Jaroszewski, Jerzy W

    2006-12-01

    Investigation of all O-methyl ethers of 1,2,3-benzenetriol and 4-methyl-1,2,3-benzenetriol (3-16) by 1H NMR spectroscopy and density-functional calculations disclosed practically useful conformational effects on 1H NMR chemical shifts in the aromatic ring. While the conversion of phenol (2) to anisole (1) causes only small positive changes of 1H NMR chemical shifts (Delta delta < 0.08 ppm) that decrease in the order Hortho > Hmeta > Hpara, the experimental O-methylation induced shifts in ortho-disubstituted phenols are largest for Hpara, Delta delta equals; 0.19 +/- 0.02 ppm (n = 11). The differences are due to different conformational behavior of the OH and OCH3 groups; while the ortho-disubstituted OH group remains planar in polyphenols due to hydrogen bonding and conjugative stabilization, the steric congestion in ortho-disubstituted anisoles outweighs the conjugative effects and forces the Ar-OCH3 torsion out of the ring plane, resulting in large stereoelectronic effects on the chemical shift of Hpara. Conformational searches and geometry optimizations for 3-16 at the B3LYP/6-31G** level, followed by B3LYP/6-311++G(2d,2p) calculations for all low-energy conformers, gave excellent correlation between computed and observed 1H NMR chemical shifts, including agreement between computed and observed chemical shift changes caused by O-methylation. The observed regularities can aid structure elucidation of partly O-methylated polyphenols, including many natural products and drugs, and are useful in connection with chemical shift predictions by desktop computer programs. PMID:17137372

  19. Reaching and abandoning the furthest ice extent during the Last Glacial Maximum in the Alps

    NASA Astrophysics Data System (ADS)

    Ivy-Ochs, Susan; Wirsig, Christian; Zasadni, Jerzy; Hippe, Kristina; Christl, Marcus; Akçar, Naki; Schluechter, Christian

    2016-04-01

    During the Last Glacial Maximum (LGM) in the European Alps (late Würm) local ice caps and extensive ice fields in the high Alps fed huge outlet glaciers that occupied the main valleys and extended onto the forelands as piedmont lobes. Records from numerous sites suggest advance of glaciers beyond the mountain front by around 30 ka (Ivy-Ochs 2015 and references therein). Reaching of the maximum extent occurred by about 27-26 ka, as exemplified by dates from the Rhein glacier area (Keller and Krayss, 2005). Abandonment of the outermost moraines at sites north and south of the Alps was underway by about 24 ka. In the high Alps, systems of transection glaciers with transfluences over many of the Alpine passes dominated, for example, at Grimsel Pass in the Central Alps (Switzerland). 10Be exposure ages of 23 ± 1 ka for glacially sculpted bedrock located just a few meters below the LGM trimline in the Haslital near Grimsel Pass suggest a pulse of ice surface lowering at about the same time that the foreland moraines were being abandoned (Wirsig et al., 2016). Widespread ice surface lowering in the high Alps was underway by no later than 18 ka. Thereafter, glaciers oscillated at stillstand and minor re-advance positions on the northern forelands for several thousand years forming the LGM stadial moraines. Final recession back within the mountain front took place by 19-18 ka. Recalculation to a common basis of all published 10Be exposure dates for boulders situated on LGM moraines suggests a strong degree of synchrony for the timing of onset of ice decay both north and south of the Alps. Ivy-Ochs, S., 2015, Cuadernos de investigación geográfica 41: 295-315. Keller, O., Krayss, E., 2005, Vierteljahrschr. Naturforsch. Gesell. Zürich 150: 69-85. Wirsig, C. et al., 2016, J. Quat. Sci. 31: 46-59.

  20. Low-energy (<20 eV) and high-energy (1000 eV) electron-induced methanol radiolysis of astrochemical interest

    NASA Astrophysics Data System (ADS)

    Sullivan, Kristal K.; Boamah, Mavis D.; Shulenberger, Katie E.; Chapman, Sitara; Atkinson, Karen E.; Boyer, Michael C.; Arumainayagam, Christopher R.

    2016-07-01

    We report the first infrared study of the low-energy (<20 eV) electron-induced reactions of condensed methanol. Our goal is to simulate processes which occur when high-energy cosmic rays interact with interstellar and cometary ices, where methanol, a precursor of several prebiotic species, is relatively abundant. The interactions of high-energy radiation, such as cosmic rays (Emax ˜ 1020 eV), with matter produce large numbers of low-energy secondary electrons, which are known to initiate radiolysis reactions in the condensed phase. Using temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRAS), we have investigated low-energy (5-20 eV) and high-energy (˜1000 eV) electron-induced reactions in condensed methanol (CH3OH). IRAS has the benefit that it does not require thermal processing prior to product detection. Using IRAS, we have found evidence for the formation of ethylene glycol (HOCH2CH2OH), formaldehyde (CH2O), dimethyl ether (CH3OCH3), methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), and the hydroxyl methyl radical (·CH2OH) upon both low-energy and high-energy electron irradiation of condensed methanol at ˜85 K. Additionally, TPD results, presented herein, are similar for methanol films irradiated with both 1000 eV and 20 eV electrons. These IRAS and TPD findings are qualitatively consistent with the hypothesis that high-energy condensed phase radiolysis is mediated by low-energy electron-induced reactions. Moreover, methoxymethanol (CH3OCH2OH) could serve as a tracer molecule for electron-induced reactions in the interstellar medium. The results of experiments such as ours may provide a fundamental understanding of how complex organic molecules are synthesized in cosmic ices.

  1. Structural changes of humic acids from sinking organic matter and surface sediments investigated by advanced solid-state NMR: Insights into sources, preservation and molecularly uncharacterized components

    NASA Astrophysics Data System (ADS)

    Mao, Jingdong; Tremblay, Luc; Gagné, Jean-Pierre

    2011-12-01

    Knowledge of the structural changes that particulate organic matter (POM) undergoes in natural systems is essential for determining its reactivity and fate. In the present study, we used advanced solid-state NMR techniques to investigate the chemical structures of sinking particulate matter collected at different depths as well as humic acids (HAs) extracted from these samples and underlying sediments from the Saguenay Fjord and the St. Lawrence Lower Estuary (Canada). Compared to bulk POM, HAs contain more non-polar alkyls, aromatics, and aromatic C-O, but less carbohydrates (or carbohydrate-like structures). In the two locations studied, the C and N contents of the samples (POM and HAs) decreased with depth and after deposition onto sediments, leaving N-poor but O-enriched HAs and suggesting the involvement of partial oxidation reactions during POM microbial degradation. Advanced NMR techniques revealed that, compared to the water-column HAs, sedimentary HAs contained more protonated aromatics, non-protonated aromatics, aromatic C-O, carbohydrates (excluding anomerics), anomerics, OC q, O-C q-O, OCH, and OCH 3 groups, but less non-polar alkyls, NCH, and mobile CH 2 groups. These results are consistent with the relatively high reactivity of lipids and proteins or peptides. In contrast, carbohydrate-like structures were selectively preserved and appeared to be involved in substitution and copolymerization reactions. Some of these trends support the selective degradation (or selective preservation) theory. The results provide insights into mechanisms that likely contribute to the preservation of POM and the formation of molecules that escape characterization by traditional methods. Despite the depletion of non-polar alkyls with depth in HAs, a significant portion of their general structure survived and can be assigned to a model phospholipid. In addition, little changes in the connectivities of different functional groups were observed. Substituted and copolymerized

  2. Sources of nitrogen in three watersheds of northern Florida, USA: Mainly atmospheric deposition

    SciTech Connect

    Fu, Ji-Meng; Winchester, J.W. )

    1994-03-01

    Atmospheric deposition is estimated to be the principal source of N in water that flows to the Apalachicola river from the Chattahoochee and Flint Rivers (ACF) as well as in two nearby small rivers, Ochlockonee (Och) and Sopchoppy (Sop), that drain watersheds with different land use characteristics. By mass balance and descriptive statistics of hundreds of rainfall and river water samples from monitoring programs since the 1960s, the average nitrate and ammonium deposition flux from the atmosphere is sufficient to account for N that flows toward Apalachicola Bay, an estuary in which N may be a limiting nutrient. Urban and agricultural sources of N in the three watersheds ACF, Och, and Sop appear to be relatively smaller. The work was based on long-term data bases from the National Atmospheric Deposition Program (NADP) rain chemistry monitoring network and the U.S. Geological Survey (USGS) water monitoring program. Average atmospheric N depositions to the three river watersheds are nearly the same as river fluxes of N in all forms monitored. Nitrogen is not likely to be a limiting nutrient in the three watersheds, since river water N:P exceeds the Redfield ratio. An estimate of largest possible input of urban sewage is several times lower than the atmospheric flux of N to the ACF watershed. And N from N-fertilizer, comparable to the atmospheric deposition flux of N, is likely to be smaller if mostly retained in crops or farmland before it reaches the estuary. Annual nitrogen export from the Apalachicola River to the estuary, 1.22 x 10[sup 9] moles N yr[sup [minus]1], consists of organic nitrogen 60%, nitrate 34%, and NH[sup +][sub 4]6%. Atmospheric nitrate and sulfate depositions are highly correlated, both being principally from fossil fuel combustion. Hydrologic conditions, which exhibit variations on seasonal and longer time scales, play an important role in the transport of nutrients and other species in the rivers.

  3. Sources of nitrogen in three watersheds of northern Florida, USA: Mainly atmospheric deposition

    NASA Astrophysics Data System (ADS)

    Fu, Ji-Meng; Winchester, John W.

    1994-03-01

    Atmospheric deposition is estimated to be the principal source of N in water that flows to the Apalachicola River from the Chattahoochee and Flint Rivers (ACF) as well as in two nearby small rivers, Ochlockonee (Och) and Sopchoppy (Sop), that drain watersheds with different land use characteristics. By mass balance and descriptive statistics of hundreds of rainfall and river water samples from monitoring programs since the 1960s, the average nitrate and ammonium deposition flux from the atmosphere is sufficient to account for N that flows toward Apalachicola Bay, an estuary in which N may be a limiting nutrient. Urban and agricultural sources of N in the three watersheds ACF, Och and Sop appear to be relatively smaller. The work was based on long-term data bases from the National Atmospheric Deposition Program (NADP) rain chemistry monitoring network and the U.S. Geological Survey (USGS) water monitoring program. Average atmospheric N depositions to the three river watersheds are nearly the same as river fluxes of N in all forms monitored. Nitrogen is not likely to be a limiting nutrient in the three watersheds, since river water N:P exceeds the Redfield ratio. An estimate of largest possible input of urban sewage is several times lower than the atmospheric flux of N to the ACF watershed. And N from N-fertilizer, comparable to the atmospheric deposition flux of N, is likely to be smaller if mostly retained in crops or farmland before it reaches the estuary. Annual nitrogen export from the Apalachicola River to the estuary, 1.22 × 10 9 moles N yr -1, consists of organic nitrogen 60%, nitrate 34% and NH 4+ 6%. Atmospheric nitrate and sulfate depositions are highly correlated, both being principally from fossil fuel combustion. Hydrologie conditions, which exhibit variations on seasonal and longer time scales, play an important role in the transport of nutrients and other species in the rivers.

  4. Synthesis, characterization of Ag(I), Pd(II) and Pt(II) complexes of a triazine-3-thione and their interactions with bovine serum albumin.

    PubMed

    Zhang, Xiuying; Li, Shuyan; Yang, Lin; Fan, Changqing

    2007-11-01

    Ag(I), Pd(II) and Pt(II) complexes of 5-methoxy-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]triazine-3-thione (LH(2)OCH(3)) have been synthesized and characterized by elemental analysis, molar conductance, (1)H NMR, IR spectra, UV spectra and thermal analysis (TG-DTA). The components of the three complexes are [Ag(C(15)H(10)N(3)S)](6), Pd(C(15)H(10)N(3)S)(2) and Pt(C(15)H(10)N(3)S)(2).C(3)H(6)O.2H(2)O, respectively. All the complexes are nonelectrolyte and have high thermodynamic stability. The ligand may act as bidentate NS donor for Pd(II) and Pt(II) complexes, while it seems to be bidentate NS bridging via sulphur atom for Ag(I) complex. A planar quadrangular structure is proposed for Pd(II) and Pt(II) complexes and Ag(I) complex may be a hexanuclear cluster. Their interactions with bovine serum albumin (BSA) are investigated using steady state fluorescence technology. It is observed that all of them can quench the intrinsic fluorescence of BSA through static quenching procedure. The binding constants (K(A)) at different temperatures, thermodynamic parameters enthalpy changes (DeltaH) and entropy changes (DeltaS) between BSA and the compounds are calculated. Based on the values of DeltaH and DeltaS, it is judged that the main acting force of PtL(2).C(3)H(6)O.2H(2)O with BSA may be electrostatic interaction, and for the LH(2)OCH(3), Ag(6)L(6) and PdL(2), hydrophobic and electrostatic interactions may be involved in their binding processes.

  5. Palladium(II) and platinum(II) complexes with tridentate iminophosphine ligands; synthesis and structural studies.

    PubMed

    Ní Dhubhghaill, Orla M; Lennon, Joanne; Drew, Michael G B

    2005-10-01

    The previously synthesised Schiff-base ligands 2-(2-Ph(2)PC(6)H(4)N[double bond, length as m-dash]CH)-R'-C(6)H(3)OH (R'= 3-OCH(3), HL(1); 5-OCH(3), HL(2); 5-Br, HL(3); 5-Cl, HL(4)) were prepared by a faster, more efficient route involving a microwave assisted co-condensation of 2-(diphenylphosphino)aniline with the appropriate substituted salicylaldehyde. HL(1-4) react directly with M(II)Cl(2)(M = Pd, Pt) or Pt(II)I(2)(cod) affording neutral square-planar complexes of general formula [M(II)Cl(eta(3)-L(1-4))](M = Pd, Pt, 1-8) and [Pt(II)I(eta(3)-L(1-4))](M = Pd, Pt, 9-12). Reaction of complexes 1-4 with the triarylphosphines PR(3)(R = Ph, p-tolyl) gave the novel ionic complexes [Pd(II)(PR(3))(eta(3)-L(1-4))]ClO(4)(13-20). Substituted platinum complexes of the type [Pt(II)(PR(3))(eta(3)-L(1-4))]ClO(4)(R = P(CH(2)CH(2)CN)(3)21-24) and [Pt(II)(P(p-tolyl)(3))(eta(3)-L(3,4))]ClO(4)( 25 and 26 ) were synthesised from the appropriate [Pt(II)Cl(eta(3)-L(1-4))] complex (5-8) and PR(3). The complexes are characterised by microanalytical and spectroscopic techniques. The crystal structures of 3, 6, 10, 15, 20 and 26 were determined and revealed the metal to be in a square-planar four-coordinate environment containing a planar tridentate ligand with an O,N,P donor set together with one further atom which is trans to the central nitrogen atom. PMID:16172647

  6. Peptidyl inverse esters of p-methoxybenzoic acid: a novel class of potent inactivator of the serine proteases.

    PubMed Central

    Lynas, J; Walker, B

    1997-01-01

    A series of novel synthetic peptides, containing a C-terminal beta-amino alcohol linked to p-methoxybenzoic acid via an ester linkage, have been prepared and tested as inhibitors against typical members of the serine protease family. For example, the sequences Ac-Val-Pro-NH-CH-(CH2-C6H5)-CH2O-CO-C6H4-OCH3 (I) and Ac-Val-Pro-NH-CH-[CH-(CH3)2]-CH2O-CO-C6H4-OCH3 (II), which fulfil the known primary and secondary specificity requirements of chymotrypsin and elastase respectively, have been found to behave as exceptionally potent irreversible inactivators of their respective target protease. Thus I was found to inactivate chymotrypsin with an overall second-order rate constant (k2/Ki) of approx. 6.6x10(6) M-1. s-1, whereas II is an even more potent inactivator of human neutrophil elastase, exhibiting a second-order rate constant of inactivation of approx. 1.3x10(7) M-1.s-1. These values represent the largest rate constants ever reported for the inactivation of these proteases with synthetic peptide-based inactivators. On prolonged incubation in substrate-containing buffers, samples of the inactivated proteases were found to regain activity slowly. The first-order rate constants for the regeneration of enzymic activity from chymotrypsin and human neutrophil elastase inactivated by I and II respectively were determined to be approx. 5.8x10(-5) s-1 and approx. 4.3x10(-4) s-1. We believe that the most likely mechanism for the inactivation and regeneration of enzymic activity involves the formation and subsequent slow hydrolysis of long-lived acyl enzyme intermediates. PMID:9271079

  7. 4-Aryl-1,3,2-oxathiazolylium-5-olates as pH-controlled NO-donors: the next generation of S-nitrosothiols.

    PubMed

    Lu, Dongning; Nadas, Janos; Zhang, Guisheng; Johnson, Wesley; Zweier, Jay L; Cardounel, Arturo J; Villamena, Frederick A; Wang, Peng George

    2007-05-01

    S-Nitrosothiols (RSNOs) are important exogenous and endogenous sources of nitric oxide (NO) in biological systems. A series of 4-aryl-1,3,2-oxathiazolylium-5-olates derivatives with varying aryl para-substituents (-CF3, -H, -Cl, and -OCH3) were synthesized. These compounds were found to release NO under acidic condition (pH = 5). The decomposition pathway of the aryloxathiazolyliumolates proceeded via an acid-catalyzed ring-opening mechanism after which NO was released and an S-centered radical was generated. Electron paramagnetic resonance (EPR) spin trapping studies were performed to detect NO and the S-centered radical using the spin traps of iron(II) N-methyl-D-glucamine dithiocarbamate [(MGD)2-FeII] and 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Also, EPR spin trapping and UV-vis spectrophotometry were used to analyze the effect of aryl para substitution on the NO-releasing property of aryloxathiazolyliumolates. The results showed that the presence of an electron-withdrawing substituent such as -CF3 enhanced the NO-releasing capability of the aryloxathiazolyliumolates, whereas an electron-donating substituent like methoxy (-OCH3) diminished it. Computational studies using density functional theory (DFT) at the PCM/B3LYP/6-31+G**//B3LYP/6-31G* level were used to rationalize the experimental observations. The aryloxathiazolyliumolates diminished susceptibility to reduction by ascorbate or gluthathione, and their capacity to cause vasodilation as compared to other S-nitrosothiols suggests potential application in biological systems. PMID:17419627

  8. Experimental and Theoretical Insight into Electrocatalytic Hydrogen Evolution with Nickel Bis(aryldithiolene) Complexes as Catalysts.

    PubMed

    Zarkadoulas, Athanasios; Field, Martin J; Papatriantafyllopoulou, Constantina; Fize, Jennifer; Artero, Vincent; Mitsopoulou, Christiana A

    2016-01-19

    A series of neutral and monoanionic nickel dithiolene complexes with p-methoxyphenyl-substituted 1,2-dithiolene ligands have been prepared and characterized with physicochemical methods. Two of the complexes, the monoanion of the symmetric [Ni{S2C2(Ph-p-OCH3)2}2] (3(-)) with NBu4(+) as a counterion and the neutral asymmetric [Ni{S2C2(Ph)(Ph-p-OCH3)}2] (2), have been structurally characterized by single-crystal X-ray crystallography. All complexes have been employed as proton-reducing catalysts in N,N-dimethylformamide with trifluoroacetic acid as the proton source. The complexes are active catalysts with good faradaic yields, reaching 83% for 2 but relatively high overpotential requirements (0.91 and 1.55 V measured at the middle of the catalytic wave for two processes observed depending on the different routes of the mechanism). The similarity of the experimental data regardless of whether the neutral or anionic form of the complexes is used indicates that the neutral form acts as a precatalyst. On the basis of detailed density functional theory calculations, the proposed mechanism reveals two different main routes after protonation of the dianion of the catalyst in accordance with the experimental data, indicating the role of the concentration of the acid and the influence of the methoxy groups. Protonation at sulfur seems be more favorable than that at the metal, which is in marked contrast with the catalytic mechanism proposed for analogous cobalt dithiolene complexes. PMID:26645557

  9. Substituent Effects on the Formation and Nucleophile Selectivity of Ring-Substituted Phenonium Ions in Aqueous Solution.

    PubMed

    Tsuji, Yutaka; Ogawa, Shin; Richard, John P

    2013-12-01

    The reaction of 2-(4-methyphenyl)ethyl tosylate (Me-1-OTs) in 50/50 (v/v) trifluoroethanol/water at 25 °C is first-order in the concentration of azide anion nucleophile. A carbon-13 NMR analysis of the products of the reactions of Me-1-[α-(13)C]OTs in 50/50 (v/v) trifluoroethanol/water at 25 °C shows the formation of Me-1-[β-(13)C]OH, Me-1-[β-(13)C]OCH2CF3 and Me-1-[β-(13)C]N3 from the trapping of a symmetrical 4-methylphenonium ion reaction intermediate Me-2 (+). The formation of Me-1-[α-(13)C]N3 by concerted bimolecular displacement of azide ion at Me-1-[α-(13)C]OTs (k N = 3.8 × 10(-6) M(-1) s(-1)) and of Me-1-[α-(13)C]OH and Me-1-[α-(13)C]OCH2CF3 by concerted bimolecular displacement of solvent (k solv = 1.8 × 10(-8) s(-1)) is also observed. An analysis of the rate and product data provides a value of k az/k s = 32 M(-1) for partitioning of Me-2 (+) between addition of azide ion and solvent that is nearly 3-fold smaller than k az/k s = 83 M(-1) reported in an earlier study on the partitioning of MeO-2 (+) [J. Org. Chem. 2011, 76, 9568]. This change is attributed to a decrease in nucleophile selectivity with increasing electrophile reactivity for the activation-limited addition of solvent and azide anion to X-2 (+). These data set a limit of 1/k s ≥ 10(-7) s for the lifetime of Me-2 (+) in aqueous solution.

  10. Histidine 352 (His352) and tryptophan 355 (Trp355) are essential for flax UGT74S1 glucosylation activity toward secoisolariciresinol.

    PubMed

    Ghose, Kaushik; McCallum, Jason; Sweeney-Nixon, Marva; Fofana, Bourlaye

    2015-01-01

    Flax secoisolariciresinol diglucoside (SDG) lignan is a natural phytoestrogen for which a positive role in metabolic diseases is emerging. Until recently however, much less was known about SDG and its monoglucoside (SMG) biosynthesis. Lately, flax UGT74S1 was identified and characterized as an enzyme sequentially glucosylating secoisolariciresinol (SECO) into SMG and SDG when expressed in yeast. However, the amino acids critical for UGT74S1 glucosyltransferase activity were unknown. A 3D structural modeling and docking, site-directed mutagenesis of five amino acids in the plant secondary product glycosyltransferase (PSPG) motif, and enzyme assays were conducted. UGT74S1 appeared to be structurally similar to the Arabidopsis thaliana UGT72B1 model. The ligand docking predicted Ser357 and Trp355 as binding to the phosphate and hydroxyl groups of UDP-glucose, whereas Cys335, Gln337 and Trp355 were predicted to bind the 7-OH, 2-OCH3 and 17-OCH3 of SECO. Site-directed mutagenesis of Cys335, Gln337, His352, Trp355 and Ser357, and enzyme assays revealed an alteration of these binding sites and a significant reduction of UGT74S1 glucosyltransferase catalytic activity towards SECO and UDP-glucose in all mutants. A complete abolition of UGT74S1 activity was observed when Trp355 was substituted to Ala355 and Gly355 or when changing His352 to Asp352, and an altered metabolite profile was observed in Cys335Ala, Gln337Ala, and Ser357Ala mutants. This study provided for the first time evidence that Trp355 and His352 are critical for UGT74S1's glucosylation activity toward SECO and suggested the possibility for SMG production in vitro.

  11. Competing noncovalent host-guest interactions and H/D exchange: reactions of benzyloxycarbonyl-proline glycine dipeptide variants with ND3.

    PubMed

    Miladi, Mahsan; Olaitan, Abayomi D; Zekavat, Behrooz; Solouki, Touradj

    2015-11-01

    A combination of density functional theory calculations, hydrogen/deuterium exchange (HDX) reactions, ion mobility-mass spectrometry, and isotope labeling tandem mass spectrometry was used to study gas-phase "host-guest" type interactions of a benzyloxycarbonyl (Z)-capped proline (P) glycine (G) model dipeptide (i.e., Z-PG) and its various structural analogues with ND3. It is shown that in a solvent-free environment, structural differences between protonated and alkali metal ion (Na(+), K(+), or Cs(+))-complexed species of Z-PG affect ND3 adduct formation. Specifically, [Z-PG + H](+) and [Z-PG-OCH3 + H](+) formed gas-phase ND3 adducts ([Z-PG (or Z-PG-OCH3) + H + ND3](+)) but no ND3 adducts were observed for [Z-PG + alkali metal](+) or [Z-PG + H - CO2](+). Experimentally measured and theoretically calculated collision cross sections (CCSs) of protonated and alkali metal ion-complexed Z-PG species showed similar trends that agreed with the observed structural differences from molecular modeling results. Moreover, results from theoretical ND3 affinity calculations were consistent with experimental HDX observations, indicating a more stable ND3 adduct for [Z-PG + H](+) compared to [Z-PG + alkali metal](+) species. Molecular modeling and experimental MS results for [Z-PG + H](+) and [Z-PG + alkali metal](+) suggest that optimized cation-π and hydrogen bonding interactions of carbonyl groups in final products are important for ND3 adduct formation. Graphical Abstract ᅟ. PMID:26289383

  12. Hydrothermal synthesis of copper selenides with controllable phases and morphologies from an ionic liquid precursor

    NASA Astrophysics Data System (ADS)

    Liu, Xiaodi; Duan, Xiaochuan; Peng, Peng; Zheng, Wenjun

    2011-12-01

    Cu2-xSe nanocrystals and CuSe nanoflakes are successfully synthesized through a convenient hydrothermal method from an ionic liquid precursor 1-n-butyl-3-ethylimidazolium methylselenite ([BMIm][SeO2(OCH3)]). The phases and morphologies of the copper selenides can be controlled by simply changing the atom ratio of Cu/Se in the reactants and reaction temperature. Furthermore, it is found that the [BMIm][SeO2(OCH3)] not only serves as Se source but also has influence on the shapes of CuSe nanoflakes. The adsorption of alkyl imidazolium rings ([BMIm]+) onto the (0001) facets of covellite CuSe prohibits the growth in the [0001] direction, and CuSe nuclei growth mainly processes along the six symmetric directions (+/-[01&cmb.macr;11], +/-[101&cmb.macr;1&cmb.macr;], and +/-[1&cmb.macr;100]) to form flakelike CuSe. The obtained copper selenides are characterized by XRD, SEM, EDS, XPS, TEM, and HRTEM. The results indicate that the Cu2-xSe nanocrystals are nearly spherical particles with an average diameter of about 20 nm, the hexagonal CuSe nanoflakes are single crystals with an edge length of 100-400 nm and a thickness of 25-50 nm. The potential formation mechanism of the copper selenides is also proposed.Cu2-xSe nanocrystals and CuSe nanoflakes are successfully synthesized through a convenient hydrothermal method from an ionic liquid precursor 1-n-butyl-3-ethylimidazolium methylselenite ([BMIm][SeO2(OCH3)]). The phases and morphologies of the copper selenides can be controlled by simply changing the atom ratio of Cu/Se in the reactants and reaction temperature. Furthermore, it is found that the [BMIm][SeO2(OCH3)] not only serves as Se source but also has influence on the shapes of CuSe nanoflakes. The adsorption of alkyl imidazolium rings ([BMIm]+) onto the (0001) facets of covellite CuSe prohibits the growth in the [0001] direction, and CuSe nuclei growth mainly processes along the six symmetric directions (+/-[01&cmb.macr;11], +/-[101&cmb.macr;1&cmb.macr;], and +/-[1

  13. Towards H2-rich gas production from unmixed steam reforming of methane: Thermodynamic modeling

    NASA Astrophysics Data System (ADS)

    Lima da Silva, Aline; Müller, Iduvirges Lourdes

    2011-10-01

    In this work, the Gibbs energy minimization method is applied to investigate the unmixed steam reforming (USR) of methane to generate hydrogen for fuel cell application. The USR process is an advanced reforming technology that relies on the use of separate air and fuel/steam feeds to create a cyclic process. Under air flow (first half of the cycle), a bed of Ni-based material is oxidized, providing the heat necessary for the steam reforming that occurs subsequently during fuel/steam feed stage (second half of the cycle). In the presence of CaO sorbent, high purity hydrogen can be produced in a single reactor. In the first part of this work, it is demonstrated that thermodynamic predictions are consistent with experimental results from USR isothermal tests under fuel/steam feed. From this, it is also verified that the reacted NiO to CH4 (NiOreacted/CH4) molar ratio is a very important parameter that affects the product gas composition and decreases with time. At the end of fuel/steam flow, the reforming reaction is the most important chemical mechanism, with H2 production reaching ∼75 mol%. On the other hand, at the beginning of fuel/steam feed stage, NiO reduction reactions dominate the equilibrium system, resulting in high CO2 selectivity, negative steam conversion and low concentrations of H2. In the second part of this paper, the effect of NiOreacted/CH4 molar ratio on the product gas composition and enthalpy change during fuel flow is investigated at different temperatures for inlet H2O/CH4 molar ratios in the range of 1.2-4, considering the USR process operated with and without CaO sorbent. During fuel/steam feed stage, the energy demand increases as time passes, because endothermic reforming reaction becomes increasingly important as this stage nears its end. Thus, the duration of the second half of the cycle is limited by the conditions under which auto-thermal operation can be achieved. In absence of CaO, H2 at concentrations of approximately 73 mol% can

  14. Pb(II)-promoted amide cleavage: mechanistic comparison to a Zn(II) analogue.

    PubMed

    Elton, Eric S; Zhang, Tingting; Prabhakar, Rajeev; Arif, Atta M; Berreau, Lisa M

    2013-10-01

    Two new Pb(II) complexes of the amide-appended nitrogen/sulfur epppa (N-((2-ethylthio)ethyl)-N-((6-pivaloylamido-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine) chelate ligand, [(epppa)Pb(NO3)2] (4-NO3) and [(epppa)Pb(ClO4)2] (4-ClO4), were prepared and characterized. In the solid state, 4-NO3 exhibits κ(5)-epppa chelate ligand coordination as well as the coordination of two bidentate nitrate ions. In acetonitrile, 4-NO3 is a 1:1 electrolyte with a coordinated NO3(-), whereas 4-ClO4 is a 1:2 electrolyte. Treatment of 4-ClO4 with 1 equiv Me4NOH·5H2O in CH3CN:CH3OH (3:5) results in amide methanolysis in a reaction that is akin to that previously reported for the Zn(II) analogue [(epppa)Zn](ClO4)2 (3-ClO4). (1)H NMR kinetic studies of the amide methanolysis reactions of 4-ClO4 and 3-ClO4 as a function of temperature revealed free energies of activation of 21.3 and 24.5 kcal/mol, respectively. The amide methanolysis reactions of 4-ClO4 and 3-ClO4 differ in terms of the effect of the concentration of methanol (saturation kinetics for 4-ClO4; second-order behavior for 3-ClO4), the observation of a small solvent kinetic isotope effect (SKIE) only for the reaction of the Zn(II)-containing 3-ClO4, and the properties of an initial intermediate isolated from each reaction upon treatment with Me4NOH·5H2O. These experimental results, combined with computational studies of the amide methanolysis reaction pathways of 4-ClO4 and 3-ClO4, indicate that the Zn(II)-containing 3-ClO4 initially undergoes amide deprotonation upon treatment with Me4NOH·5H2O. Subsequent amide protonation from coordinated methanol yields a structure containing a coordinated neutral amide and methoxide anion from which amide cleavage can then proceed. The rate-determining step in this pathway is either amide protonation or protonation of the leaving group. The Pb(II)-containing 4-ClO4 instead directly forms a neutral amide-containing, epppa-ligated Pb(II)-OH/Pb(II)-OCH3 equilibrium mixture upon treatment

  15. Climate change and control of the southeastern Bering Sea pelagic ecosystem

    NASA Astrophysics Data System (ADS)

    Hunt, George L., Jr.; Stabeno, Phyllis; Walters, Gary; Sinclair, Elizabeth; Brodeur, Richard D.; Napp, Jeffery M.; Bond, Nicholas A.

    2002-12-01

    We propose a new hypothesis, the Oscillating Control Hypothesis (OCH), which predicts that pelagic ecosystem function in the southeastern Bering Sea will alternate between primarily bottom-up control in cold regimes and primarily top-down control in warm regimes. The timing of spring primary production is determined predominately by the timing of ice retreat. Late ice retreat (late March or later) leads to an early, ice-associated bloom in cold water (e.g., 1995, 1997, 1999), whereas no ice, or early ice retreat before mid-March, leads to an open-water bloom in May or June in warm water (e.g., 1996, 1998, 2000). Zooplankton populations are not closely coupled to the spring bloom, but are sensitive to water temperature. In years when the spring bloom occurs in cold water, low temperatures limit the production of zooplankton, the survival of larval/juvenile fish, and their recruitment into the populations of species of large piscivorous fish, such as walleye pollock ( Theragra chalcogramma), Pacific cod ( Gadus macrocephalus) and arrowtooth flounder ( Atheresthes stomias). When continued over decadal scales, this will lead to bottom-up limitation and a decreased biomass of piscivorous fish. Alternatively, in periods when the bloom occurs in warm water, zooplankton populations should grow rapidly, providing plentiful prey for larval and juvenile fish. Abundant zooplankton will support strong recruitment of fish and will lead to abundant predatory fish that control forage fish, including, in the case of pollock, their own juveniles. Piscivorous marine birds and pinnipeds may achieve higher production of young and survival in cold regimes, when there is less competition from large piscivorous fish for cold-water forage fish such as capelin ( Mallotus villosus). Piscivorous seabirds and pinnipeds also may be expected to have high productivity in periods of transition from cold regimes to warm regimes, when young of large predatory species of fish are numerous enough to

  16. The reactivity of 1,1-dialkoxyalkanes with niobium and tantalum pentahalides. Formation of coordination compounds, C-H and C-C bond activation and the X-ray structure of the stable carboxonium species [Me(2)C=CHC(=OMe)Me][NbCl(5)(OMe)].

    PubMed

    Marchetti, Fabio; Pampaloni, Guido; Zacchini, Stefano

    2009-10-14

    The reactions of the pentahalides NbX5 (X = Cl, Br) with the 1,1-dialkoxyalkanes CHR'(OEt)2 or 1,3-dioxolane yield the coordination adducts NbX5[kappa1-(OEt)CHR'(OEt)] (X = Cl, R' = H, 2a; X = Br, R' = H, 2b; X = Cl, R' = Me, 2c; X = Br, R' = Me, 2d) or NbCl5(kappa1-right angle OCH2OCH2C right angle H2), 3, respectively. Compounds 2a-c and 3 are stable at room temperature, while 2d slowly converts into the alkoxide NbBr4[OCH(Me)OEt], 4. Room-temperature fragmentations are observed upon reacting CH2(OMe)2, CHMe(OMe)2 and CMe2(OMe)2 with MX5 (M = Nb, Ta; X = Cl, Br). The complexes MX5[O(Me)(CH2X)], 5, and [MX3(OMe)2]2, 6, form selectively from MX5/CH2(OMe)2 (M = Nb, Ta; X = Cl, Br), while mixtures of [NbX4(OMe)]2 (X = Cl, 8a; X = Br, 8b) and organic halides are obtained from NbX5/CHMe(OMe)2. Instead, the reaction of NbCl5 with CMe2(OMe)2 affords the stable carboxonium species [Me2C=CHC(=OMe)Me][NbCl5(OMe)], 7, as prevalent product. Furthermore, 1,1-dialkoxyalkanes are generally activated by MF5 (M = Nb, Ta) at room temperature: according to the cases, alcohols, ethers, esters and ketones have been detected in the reaction mixtures after hydrolysis. In agreement with NMR data, the carboxonium ion [Me2C=CHC(=OMe)Me]+ is produced from NbF5/CMe2(OMe)2. The complexes NbF5[OEt(Me)], 9a, and NbF5[O=CH(OEt)], 9b, obtained by addition of CH2(OEt)2 to NbF5, have been characterised by NMR spectroscopy. Trimethyl formate, CH(OMe)3, reacts with NbX5 (X = Cl, Br) with formation of the alkoxides 6 and 8, in admixture with NbX5[O=CH(OMe)] and MeX; otherwise, MF5[O=CH(OMe)] and MF5(OMe2) have been synthesised from MF5/CH(OMe)3 (M = Nb, Ta). Complete screening of the organic fragments produced in the distinct reactions has been carried out by both GC-MS and NMR analyses on the reaction mixtures, after treatment with water. The solid state structures of the mixed halo-alkoxy complexes [TaX3(OMe)(mu-OMe)]2 (X = Cl, 6c; X = Br, 6d) and of the stable alkylated ketone containing species 7

  17. Selective transformation of carbonyl ligands to organic molecules. Progress report, September 1, 1989--November 14, 1992

    SciTech Connect

    Cutler, A.R.

    1992-05-12

    Studies on the carbonylation of ({eta}{sup 5}-indenyl)(L)(CO)Ru-R complexes (L = CO, PPh{sub 3}; R = CH{sub 2}OMe, CH{sub 3}) have been completed. Particularly noteworthy is that the methoxymethyl complexes readily transform to their acyl derivatives under mild conditions that leave their iron congeners inert towards CO. Surprisingly, even ({eta}{sup 5}-indenyl)(PPh{sub 3}){sub 2}Ru-CH{sub 3} carbonylates and gives ({eta}{sup 5}-indenyl)(PPh{sub 3})(CO)Ru-C(O)CH{sub 3}. Mechanistic studies on the ``non catalyzed`` hydrosilation of the manganese acyls (CO){sub 5}Mn-C(O)CH{sub 2}R (R = H, OCH{sub 3}, CH{sub 3}) with Et{sub 3}SiH and of cobalt acetyls (CO){sub 3}(PR{sub 3})CoC(O)CH{sub 3} with several monohydrosilanes have been completed. The cobalt acetyls cleanly give ethoxysilanes (not acetaldehyde), and the manganese acyls provide {alpha}-siloxyvinyl complexes Z-(CO){sub 5}Mn-C(OSiEt{sub 3})=CHR (R = H, CH{sub 3}, OCH{sub 3}). Carbonylation and protolytic cleavage of the latter generate pyruvoyl complexes (CO){sub 5}Mn-COCOR (R = CH{sub 3}, CH{sub 2}CH{sub 3}), formally the products of net ``double carbonylation`` sequences. Studies in progress are concerned with how manganese complexes as diverse as (CO){sub 5}Mn-Y [Y = C(O)R, R, BR - but not SiMe{sub 3} or Mn(CO){sub 5}] and ({eta}{sup 3}-C{sub 3}H{sub 5})Mn(CO){sub 2}L [but not CpMn(CO){sub 3} or CpMn(CO){sub 2}({eta}{sup 2}HSiR{sub 3})] function as efficient hydrosilation catalysts towards Cp(CO){sub 2}FeC(O)CH{sub 3}, for example. These reactions cleanly afford fully characterized {alpha}-siloxyethyl complexes Fp-CH(OSiR{sub 3})CH{sub 3} under conditions where typically Rh(1) hydrosilation catalysts are inactive. Several of these manganese complexes also catalytically hydrosilate organic esters, including lactones, to their ethers R-CH{sub 2}OR; these novel ester reductions occur quantitatively at room temperature and appear to be general in scope.

  18. Selective transformation of carbonyl ligands to organic molecules

    SciTech Connect

    Cutler, A.R.

    1992-05-12

    Studies on the carbonylation of ({eta}{sup 5}-indenyl)(L)(CO)Ru-R complexes (L = CO, PPh{sub 3}; R = CH{sub 2}OMe, CH{sub 3}) have been completed. Particularly noteworthy is that the methoxymethyl complexes readily transform to their acyl derivatives under mild conditions that leave their iron congeners inert towards CO. Surprisingly, even ({eta}{sup 5}-indenyl)(PPh{sub 3}){sub 2}Ru-CH{sub 3} carbonylates and gives ({eta}{sup 5}-indenyl)(PPh{sub 3})(CO)Ru-C(O)CH{sub 3}. Mechanistic studies on the non catalyzed'' hydrosilation of the manganese acyls (CO){sub 5}Mn-C(O)CH{sub 2}R (R = H, OCH{sub 3}, CH{sub 3}) with Et{sub 3}SiH and of cobalt acetyls (CO){sub 3}(PR{sub 3})CoC(O)CH{sub 3} with several monohydrosilanes have been completed. The cobalt acetyls cleanly give ethoxysilanes (not acetaldehyde), and the manganese acyls provide {alpha}-siloxyvinyl complexes Z-(CO){sub 5}Mn-C(OSiEt{sub 3})=CHR (R = H, CH{sub 3}, OCH{sub 3}). Carbonylation and protolytic cleavage of the latter generate pyruvoyl complexes (CO){sub 5}Mn-COCOR (R = CH{sub 3}, CH{sub 2}CH{sub 3}), formally the products of net double carbonylation'' sequences. Studies in progress are concerned with how manganese complexes as diverse as (CO){sub 5}Mn-Y (Y = C(O)R, R, BR - but not SiMe{sub 3} or Mn(CO){sub 5}) and ({eta}{sup 3}-C{sub 3}H{sub 5})Mn(CO){sub 2}L (but not CpMn(CO){sub 3} or CpMn(CO){sub 2}({eta}{sup 2}HSiR{sub 3})) function as efficient hydrosilation catalysts towards Cp(CO){sub 2}FeC(O)CH{sub 3}, for example. These reactions cleanly afford fully characterized {alpha}-siloxyethyl complexes Fp-CH(OSiR{sub 3})CH{sub 3} under conditions where typically Rh(1) hydrosilation catalysts are inactive. Several of these manganese complexes also catalytically hydrosilate organic esters, including lactones, to their ethers R-CH{sub 2}OR; these novel ester reductions occur quantitatively at room temperature and appear to be general in scope.

  19. Interstellar ice analogs: H2O ice mixtures with CH3OH and NH3 in the far-IR region

    NASA Astrophysics Data System (ADS)

    Giuliano, B. M.; Martín-Doménech, R.; Escribano, R. M.; Manzano-Santamaría, J.; Muñoz Caro, G. M.

    2016-08-01

    Context. New spectroscopic observations in the far-infrared (IR) range are expected from future planned missions. Although water ice is the only species detected so far in interstellar ices in this range, the presence of ice mixtures requires laboratory characterization of the corresponding spectra. Aims: We present an investigation on far-IR spectra of binary ice mixtures relevant in various astrophysical environments. The foremost goal is to compare the spectroscopic features of the ice mixtures to those of pure ices, and to search for changes in peak frequencies, intensities, and band strengths of the main bands. Methods: Mixtures H2O:CH3OH and H2O:NH3 of different ratios have been deposited on a diamond substrate at astrophysically relevant conditions. We measured the spectra in the near- and mid-IR regions to derive ice column densities that were subsequently used to calculate the apparent band strengths in the far-IR region. We also designed theoretical models to study these mixtures and to predict their spectra. Results: We recorded spectra of amorphous phases for H2O:CH3OH mixtures of different compositions, that is 1:1, 3:1, and 10:1 at 8 K, and compared these mixtures to those obtained after warming. This process involves the appearance of new spectral features and changes in band shapes and band strengths. We also compared the spectra to those of the pure species and to theoretical predictions. We measured apparent band strengths for all the observed features. For H2O:NH3 mixtures, the ratios selected were 3:1, 1:1, and 1:3. In this case the spectral variations are even more marked than for the water:methanol samples. Conclusions: Band strengths in the far-IR are missing in astrophysics literature for ice mixtures. The results presented here are valuable for detecting the presence and composition of such mixtures from future space observations in this spectral region.

  20. Palladium complexes of a phosphorus ylide with two stabilizing groups: synthesis, structure, and DFT study of the bonding modes.

    PubMed

    Falvello, Larry R; Ginés, Juan Carlos; Carbó, Jorge J; Lledós, Agustí; Navarro, Rafael; Soler, Tatiana; Urriolabeitia, Esteban P

    2006-08-21

    The phosphorus ylide ligand [Ph3P=C(CO2Me)C(=NPh)CO2Me] (L1) has been prepared and fully characterized by spectroscopic, crystallographic, and density functional theory (DFT) methods (B3LYP level). The reactivity of L1 toward several cationic Pd(II) and Pt(II) precursors, with two vacant coordination sites, has been studied. The reaction of [M(C/\\X)(THF)2]ClO4 with L1 (1:1 molar ratio) gives [M(C/\\X)(L1)]ClO4 [M = Pd, C/\\X = C6H4CH2NMe2 (1), S-C6H4C(H)MeNMe2 (2), CH2-8-C9H6N (3), C6H4-2-NC5H4 (4), o-CH2C6H4P(o-tol)2 (6), eta3-C3H5 (7); M = Pt, C/\\X = o-CH2C6H4P(o-tol)2 (5); M(C/\\X) = Pd(C6F5)(SC4H8) (8), PdCl2 (9)]. In complexes 1-9, the ligand L1 bonds systematically to the metal center through the iminic N and the carbonyl O of the stabilizing CO2Me group, as is evident from the NMR data and from the X-ray structure of 3. Ligand L1 can also be orthopalladated by reaction with Pd(OAc)2 and LiCl, giving the dinuclear derivative [Pd(mu-Cl)(C6H4-2-PPh2=C(CO2Me)C(CO2Me)=NPh)]2 (10). The X-ray crystal structure of 10 is also reported. In none of the prepared complexes 1-10 was the C(alpha) atom found to be bonded to the metal center. DFT calculations and Bader analysis were performed on ylide L1 and complex 9 and its congeners in order to assess the preference of the six-membered N,O metallacycle over the four-membered C,N and five-membered C,O rings. The presence of two stabilizing groups at the ylidic C causes a reduction of its bonding capabilities. The increasing strength of the Pd-C, Pd-O, and Pd-N bonds along with other subtle effects are responsible for the relative stabilities of the different bonding modes. PMID:16903737

  1. Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment.

    PubMed

    Liu, Neng; Moumanis, Khalid; Dubowski, Jan J

    2015-11-09

    The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75°. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm(2), respectively, has decreased the CA to near 15°, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer's surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm(2) and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103°. The XPS results indicate ArF laser induced formation of Si-(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

  2. Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment.

    PubMed

    Liu, Neng; Moumanis, Khalid; Dubowski, Jan J

    2015-01-01

    The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75°. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm(2), respectively, has decreased the CA to near 15°, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer's surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm(2) and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103°. The XPS results indicate ArF laser induced formation of Si-(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals. PMID:26575362

  3. Synthesis, characterization and solid-state photoluminescence studies of six alkoxy phenylene ethynylene dinuclear palladium(II) rods.

    PubMed

    Figueira, João; Czardybon, Wojciech; Mesquita, José Carlos; Rodrigues, João; Lahoz, Fernando; Russo, Luca; Valkonen, Arto; Rissanen, Kari

    2015-03-01

    A rare family of six discrete binuclear [PdCl(PEt3)2] phenylene ethynylene rods with alkoxy side chains (methoxy, ethoxy and heptoxy) have been developed, and their solid-state photoluminescence results have been presented and discussed. The shorter bridging ligands are of the general formula H-C≡C-C6H2(R)2-C≡C-H, where R = H, OCH3, OC2H5, and OC7H15, whereas the longer ones are based on H-C≡C-C6H4-C≡C-C6H2(R)2-C≡C-C6H4-C≡C-H, where R = OCH3, OC2H5. These ligands display increasing length in both the main dimension (backbone length) as well as the number of carbons in the side chains (R, alkoxide side chain) that stem from the central phenylene moiety. The X-ray crystal structures of two of the prepared complexes are reported: one corresponds to a shorter rod, 1,4-bis[trans-(PEt3)2ClPd-C≡C]-2,5-diethoxybenzene (6c), while the second one is associated with a longer rod, the binuclear complex 1,4-bis[trans-(PEt3)2ClPd-4-(-C≡C-C6H4-C≡C)]-2,5-diethoxybenzene (7c). All new compounds were characterized by NMR spectroscopy ((1)H, (13)C{(1)H} and (31)P{(1)H}) as well as ESI-MS(TOF), EA, FTIR, UV-Vis, cyclic voltammetry and solid-state photoluminescence. Our work shows the influence of the alkoxy side chains on the electronic structure of the family of binuclear Pd rods by lowering its oxidation potential. In addition to this, the increase of the length of the bridge results in a higher oxidation potential. Solid state photoluminescence results indicate that Pd complexes are characterized by a marked decrease in both the emission intensity and the fluorescence lifetime values as compared to their ligands. This behaviour could be due to some degree of ligand-to-metal charge transfer.

  4. THE SEARCH FOR A COMPLEX MOLECULE IN A SELECTED HOT CORE REGION: A RIGOROUS ATTEMPT TO CONFIRM TRANS-ETHYL METHYL ETHER TOWARD W51 e1/e2

    SciTech Connect

    Carroll, P. Brandon; McGuire, Brett A.; Blake, Geoffrey A.; Apponi, A. J.; Ziurys, L. M.; Remijan, Anthony

    2015-01-20

    An extensive search has been conducted to confirm transitions of trans-ethyl methyl ether (tEME, C{sub 2}H{sub 5}OCH{sub 3}), toward the high-mass star forming region W51 e1/e2 using the 12 m Telescope of the Arizona Radio Observatory at wavelengths from 2 mm and 3 mm. In short, we cannot confirm the detection of tEME toward W51 e1/e2 and our results call into question the initial identification of this species by Fuchs et al. Additionally, re-evaluation of the data from the original detection indicates that tEME is not present toward W51 e1/e2 in the abundance reported by Fuchs and colleagues. Typical peak-to-peak noise levels for the present observations of W51 e1/e2 were between 10 and 30 mK, yielding an upper limit of the tEME column density of ≤1.5 × 10{sup 15} cm{sup –2}. This would make tEME at least a factor of two times less abundant than dimethyl ether (CH{sub 3}OCH{sub 3}) toward W51 e1/e2. We also performed an extensive search for this species toward the high-mass star forming region Sgr B2(N-LMH) with the National Radio Astronomy Observatory 100 m Green Bank Telescope. No transitions of tEME were detected and we were able to set an upper limit to the tEME column density of ≤4 × 10{sup 14} cm{sup –2} toward this source. Thus, we are able to show that tEME is not a new molecular component of the interstellar medium and that an exacting assessment must be carried out when assigning transitions of new molecular species to astronomical spectra to support the identification of large organic interstellar molecules.

  5. 10Be surface exposure dating of rock glaciers in Larstigtal, Tyrol, Austria

    NASA Astrophysics Data System (ADS)

    Ivy-Ochs, S.; Kerschner, H.; Maisch, M.; Christl, M.; Kubik, P. W.; Schluchter, C.

    2009-04-01

    In the context of Lateglacial and Holocene climate change research, rock glaciers (creeping mountain permafrost) also play an important role. They are phenomena of discontinuous alpine permafrost and as such good indicators for the mean annual air temperature for the period they are active. We have 10Be surface exposure dated boulders from two relict rock glaciers in Larstigtal, Austria. This is the type area for a postulated mid-Holocene cold period called the Larstig oscillation. The period of activity was suggested to be of similar age as the mid-Holocene Frosnitz advance of glaciers in the Venediger Mountains farther to the east (Patzelt and Bortenschlager, 1973). For rock glaciers of this size to be active at 2200 m a.s.l. in Larstig valley would have required a significant drop in temperatures, thus a marked mid-Holocene cold pulse, for at least several centuries at around 7.0 ka. In contrast, our exposure dates show that the rock glaciers stabilized during the early Preboreal (Ivy-Ochs et al., submitted). We see no distinct pattern with respect to exposure age and boulder location on the rock glaciers. This implies that for our site the blocks did not acquire inherited 10Be during exposure in the free rock face, in the talus at the base of the slope, or during transport on the rock glaciers. Our data point to final stabilization of the Larstigtal rock glaciers in the earliest Holocene and not in the middle Holocene. Combined with data from other archives (Nicolussi et al., 2005), there appears to have been no time window in the middle Holocene long enough for rock glaciers of the size and at the elevation of the Larstig site to have formed. Ivy-Ochs, S., Kerschner, H., Maisch, M., Christl, M., Kubik, P.W., Schlüchter, C., Latest Pleistocene and Holocene glacier variations in the European Alps. Quaternary Science Reviews (submitted). Nicolussi, K., Kaufmann, M., Patzelt, G., van der Plicht, J., Thurner, A., 2005. Holocene tree-line variability in the Kauner

  6. Comparison of the completely renormalized equation-of-motion coupled-cluster and Quantum Monte Carlo results for the low-lying electronic states of methylene

    NASA Astrophysics Data System (ADS)

    Gour, Jeffrey R.; Piecuch, Piotr; Włoch, Marta

    2010-10-01

    The left-eigenstate completely renormalized (CR) equation-of-motion (EOM) coupled-cluster (CC) method with singles, doubles, and non-iterative triples, abbreviated as CR-EOMCC(2,3) [M. Włoch et al., Mol. Phys. 104, 2149 (2006); P. Piecuch et al., Int. J. Quantum Chem. 109, 3268 (2009)], and the companion ground-state CR-CC(2,3) methodology [P. Piecuch and M. Włoch, J. Chem. Phys. 123, 224105 (2005); P. Piecuch et al., Chem. Phys. Lett. 418, 467 (2006)] are used to determine the total electronic and adiabatic excitation energies corresponding to the ground and lowest three excited states of methylene. The emphasis is on comparing the CR-CC(2,3)/CR-EOMCC(2,3) results obtained with the large correlation-consistent basis sets of the aug-cc-pCV xZ (x = T, Q, 5) quality and the corresponding complete basis set (CBS) limits with the recently published variational and diffusion Quantum Monte Carlo (QMC) data [P. Zimmerman et al., J. Chem. Phys. 131, 124103 (2009)]. It is demonstrated that the CBS CR-CC(2,3)/CR-EOMCC(2,3) results are in very good agreement with the best QMC, i.e. diffusion MC (DMC) data, with errors in the total and adiabatic excitation energies of all calculated states on the order of a few millihartree and less than 0.1 eV, respectively, even for the challenging, strongly multi-reference C 1 A 1 state for which the basic EOMCC approach with singles and doubles completely fails. The agreement between the CBS CR-CC(2,3)/CR-EOMCC(2,3) and variational MC (VMC) results for the total energies is not as good as in the DMC case, but the excitation energies resulting from the CBS CR-CC(2,3)/CR-EOMCC(2,3) and VMC calculations agree very well.

  7. A new method of reconstituting the P-T conditions of fluid circulation in an accretionary prism (Shimanto, Japan) from microthermometry of methane-bearing aqueous inclusions

    NASA Astrophysics Data System (ADS)

    Raimbourg, Hugues; Thiéry, Régis; Vacelet, Maxime; Ramboz, Claire; Cluzel, Nicolas; Le Trong, Emmanuel; Yamaguchi, Asuka; Kimura, Gaku

    2014-01-01

    In paleo-accretionary prisms and the shallow metamorphic domains of orogens, circulating fluids trapped in inclusions are commonly composed of a mixture of salt water and methane, producing two types of fluid inclusions: methane-bearing aqueous and methane-rich gaseous fluid inclusions. In such geological settings, where multiple stages of deformation, veining and fluid influx are prevalent, textural relationships between aqueous and gaseous inclusions are often ambiguous, preventing the microthermometric determination of fluid trapping pressure and temperature conditions. To assess the P-T conditions of deep circulating fluids from the Hyuga unit of the Shimanto paleo-accretionary prism on Kyushu, Japan, we have developed a new computational code, applicable to the H2O-CH4-NaCl system, which allows the characterization of CH4-bearing aqueous inclusions using only the temperatures of their phase transitions estimated by microthermometry: Tmi, the melting temperature of ice; Thyd, the melting temperature of gas hydrate and Th,aq, homogenization temperature. This thermodynamic modeling calculates the bulk density and composition of aqueous inclusions, as well as their P-T isochoric paths in a P-T diagram with an estimated precision of approximatively 10%. We use this computational tool to reconstruct the entrapment P-T conditions of aqueous inclusions in the Hyuga unit, and we show that these aqueous inclusions cannot be cogenetic with methane gaseous inclusions present in the same rocks. As a result, we propose that pulses of a high-pressure, methane-rich fluid transiently percolated through a rock wetted by a lower-pressure aqueous fluid. By coupling microthermometric results with petrological data, we infer that the exhumation of the Hyuga unit from the peak metamorphic conditions was nearly isothermal and ended up under a very hot geothermal gradient. In subduction or collision zones, modeling aqueous fluid inclusions in the ternary H2O-CH4-NaCl system and not

  8. Climate change and the control of energy flow in the southeastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Hunt, George L.; Stabeno, Phyllis J.

    2002-10-01

    We examine how coupling between physical and biological processes influences the production and transfer of energy to upper trophic-level species in the southeastern Bering Sea. We review time series that illustrate changes in the marine climate of the southeastern Bering Sea since the mid-1970s, particularly variability in the persistence of sea ice and the timing of its retreat. Time series (1995 - 2001) from a biophysical mooring in the middle domain of the southeastern shelf support the hypothesis that retreat of the winter sea ice before mid-March (or the failure of ice to be advected into a region) results in an open water bloom in May or June in relatively warm water (≥3°C). Conversely, when ice retreat is delayed until mid-March or later, an ice-associated bloom occurs in cold (≤0°C) water in early spring. These variations are important because the growth and production of zooplankton and the growth and survival of larval and juvenile fish are sensitive to water temperature. The Oscillating Control Hypothesis (OCH) recently proposed by Hunt et al. (2002), predicts that control of the abundance of forage fish, and in the case of walleye pollock ( Theragra chalcogramma), recruitment of large piscivorous fish, will switch from bottom-up limitation in extended periods with late ice retreat to top-down in warmer periods when ice retreat occurs before mid-March. In support of this hypothesis, we review recent data from the southeastern Bering Sea that show 2- to 13-fold changes in copepod abundance with changes in spring water temperatures of 3 to 5°C. We also provide indirect evidence that the abundance of adult pollock on the eastern Bering Sea shelf negatively affects the abundance forage fishes (including juvenile pollock) available to top predators. Although there is evidence that pollock year-class strength is positively related to temperature, we lack the time series of pollock populations in extended periods (8 - 10 years) of cold-water blooms

  9. Left-eigenstate completely renormalized equation-of-motion coupled-cluster methods: Review of key concepts, extension to excited states of open-shell systems, and comparison with electron-attached and ionized approaches

    NASA Astrophysics Data System (ADS)

    Piecuch, Piotr; Gour, Jeffrey R.; Włoch, Marta

    The recently proposed left-eigenstate completely renormalized (CR) coupled-cluster (CC) method with singles, doubles, and noniterative triples, termed CR-CC(2,3) Piecuch and Włoch, J Chem Phys, 2005, 123, 224105; Piecuch et al. Chem Phys Lett, 2006, 418, 467 and the companion CR-EOMCC(2,3) methodology, which has been previously applied to singlet excited states of closed-shell molecular systems Włoch et al. Mol Phys, 2006, 104, 2149 and in which relatively inexpensive noniterative corrections due to triple excitations derived from the biorthogonal method of moments of CC equations (MMCC) are added to the CC singles and doubles (CCSD) or equation-of-motion (EOM) CCSD energies, have been extended to excited states of open-shell species. The resulting highly efficient computer codes for the open-shell CR-EOMCC(2,3) approach exploiting the recursively generated intermediates and fast matrix multiplication routines have been developed and interfaced with the GAMESS package, enabling CR-EOMCC(2,3) calculations for singlet as well as nonsinglet ground and excited states of closed- and open-shell systems using the restricted Hartree-Fock or restricted open-shell Hartree-Fock references. A number of important mathematical and algorithmic details related to formal aspects and computer implementation of the CR-EOMCC(2,3) method have been discussed, in addition to overviewing the key concepts behind the CR-EOMCC(2,3) and biorthogonal MMCC methodologies for ground and excited states, and the numerical results involving low-lying states of the CH, CNC, C2N, N3, and NCO species, including states dominated by two-electron transitions, have been presented. The results of the CR-EOMCC(2,3) calculations have been compared with other CC/EOMCC approaches, including the EOMCCSD and EOMCC singles, doubles, and triples methods, and their full and active-space valence counterparts based on the electron-attached and ionized EOMCC methodologies, and the predecessor of CR-EOMCC(2,3) termed

  10. Alkoxy-1,3,5-triazapentadien(e/ato) copper(II) complexes: template formation and applications for the preparation of pyrimidines and as catalysts for oxidation of alcohols to carbonyl products.

    PubMed

    Kopylovich, Maximilian N; Karabach, Yauhen Yu; da Silva, M Fátima C Guedes; Figiel, Paweł J; Lasri, Jamal; Pombeiro, Armando J L

    2012-01-16

    Template combination of copper acetate (Cu(AcO)(2)⋅H(2)O) with sodium dicyanamide (NaN(C≡N)(2), 2 equiv) or cyanoguanidine (N≡CNHC(=NH)NH(2), 2 equiv) and an alcohol ROH (used also as solvent) leads to the neutral copper(II)-(2,4-alkoxy-1,3,5-triazapentadienato) complexes [Cu{NH=C(OR)NC(OR)=NH}(2)] (R = Me (1), Et (2), nPr (3), iPr (4), CH(2)CH(2)OCH(3) (5)) or cationic copper(II)-(2-alkoxy-4-amino-1,3,5-triazapentadiene) complexes [Cu{NH=C(OR)NHC(NH(2))=NH}(2)](AcO)(2) (R = Me (6), Et (7), nPr (8), nBu (9), CH(2)CH(2)OCH(3) (10)), respectively. Several intermediates of this reaction were isolated and a pathway was proposed. The deprotonation of 6-10 with NaOH allows their transformation to the corresponding neutral triazapentadienates [Cu{NH=C(OR)NC(NH(2))=NH}(2)] 11-15. Reaction of 11, 12 or 15 with acetyl acetone (MeC(=O)CH(2)C(=O)Me) leads to liberation of the corresponding pyrimidines NC(Me)CHC(Me)NCNHC(=NH)OR, whereas the same treatment of the cationic complexes 6, 7 or 10 allows the corresponding metal-free triazapentadiene salts {NH(2)C(OR)=NC(NH(2))=NH(2)}(OAc) to be isolated. The alkoxy-1,3,5-triazapentadiene/ato copper(II) complexes have been applied as efficient catalysts for the TEMPO radical-mediated mild aerobic oxidation of alcohols to the corresponding aldehydes (molar yields of aldehydes of up to 100 % with >99 % selectivity) and for the solvent-free microwave-assisted synthesis of ketones from secondary alcohols with tert-butylhydroperoxide as oxidant (yields of up to 97 %, turnover numbers of up to 485 and turnover frequencies of up to 1170 h(-1)).

  11. Investigation of cellular and protein interactions with model self-assembled monolayer surfaces

    NASA Astrophysics Data System (ADS)

    Tegoulia, Vassiliki Apostolou

    Self-assembled monolayers (SAMs) of alkanethiolates on gold have been used to investigate the effect of substrate surface properties on bacterial and blood cell adhesion in the presence and absence of blood proteins. Protein adsorption and binding strength on SAMs as well as complement activation by these model surfaces were also studied. It is hoped that information gained, regarding factors that influence biological processes, will lead to strategies for designing materials and surfaces that specifically inhibit cell adhesion and protein adsorption. Single component SAMs of the general formula HS(CH2) 10X, where X = CH3, CH2OH. COOH and CH2(OCH 2CH2)3OH, and two component mixed SAMs created from binary solutions of HS(CH2), OCH3 and HS(CH 2)10CH2OH, were used. Adhesion was investigated under well-defined flow conditions. Adhesion was found to be higher for the hydrophobic methyl and minimal for the tri(ethyleneoxide) terminated SAM. Preincubation of the SAMs with fibrinogen led to an increase in cell adhesion for bacteria and a decrease for leukocyte adhesion. The effect of surface chemistry on protein adsorption was studied for three blood proteins, fibrinogen, fibronectin and albumin. Adsorption was found to be higher on the hydrophobic CH3 surface and lower but comparable for the other surfaces while proteins adsorbed strongly on all surfaces. SAMs were also used to evaluate complement activation by foreign surfaces. The hydroxyl rich SAMs were found to activate complement more significantly than the anionic carboxyl and the hydrophobic methyl terminated SAMs. A surface modification was introduced to incorporate a zwitterionic phosphorylcholine (PC) group on a hydroxyl monolayer in an effort to create a biomimetic surface that could minimize cell adhesion and protein adsorption. The good antifouling properties of the phosphorylcholine modified surface led to the synthesis of a novel phosphorylcholine functionalized thiol. Single component and two component

  12. Water and complex organic chemistry in the cold dark cloud Barnard 5: Observations and Models

    NASA Astrophysics Data System (ADS)

    Wirström, Eva; Charnley, Steven B.; Taquet, Vianney; Persson, Carina M.

    2015-08-01

    Studies of complex organic molecule (COM) formation have traditionally been focused on hot cores in regions of massive star formation, where chemistry is driven by the elevated temperatures - evaporating ices and allowing for endothermic reactions in the gas-phase. As more sensitive instruments have become available, the types of objects known to harbour COMs like acetaldehyde (CH3CHO), dimethyl ether (CH3OCH3), methyl formate (CH3OCHO), and ketene (CH2CO) have expanded to include low mass protostars and, recently, even pre-stellar cores. We here report on the first in a new category of objects harbouring COMs: the cold dark cloud Barnard 5 where non-thermal ice desorption induce complex organic chemistry entirely unrelated to local star-formation.Methanol, which only forms efficiently on the surfaces of dust grains, provide evidence of efficient non-thermal desorption of ices in the form of prominent emission peaks offset from protostellar activity and high density tracers in cold molecular clouds. A study with Herschel targeting such methanol emission peaks resulted in the first ever detection of gas-phase water offset from protostellar activity in a dark cloud, at the so called methanol hotspot in Barnard 5.To model the effect a transient injection of ices into the gas-phase has on the chemistry of a cold, dark cloud we have included gas-grain interactions in an existing gas-phase chemical model and connected it to a chemical reaction network updated and expanded to include the formation and destruction paths of the most common COMs. Results from this model will be presented.Ground-based follow-up studies toward the methanol hotspot in B5 have resulted in the detection of a number of COMs, including CH2CO, CH3CHO, CH3OCH3, and CH3OCHO, as well as deuterated methanol (CH2DOH). Observations have also confirmed that COM emission is extended and not localised to a core structure. The implications of these observational and theoretical studies of B5 will be discussed

  13. Carbonylation of ( sup t Bu sub 3 SiNH) sub 3 ZrH and X-ray structural study of ( sup t Bu sub 3 SiNH) sub 3 ZrCH sub 3

    SciTech Connect

    Cummins, C.C.; Van Duyne, G.D.; Schaller, C.P.; Wolczanski, P.T. )

    1991-01-01

    Treatment of ZrCl{sub 4} with 3 equiv of {sup t}Bu{sub 3}SiNHLi afforded ({sup t}Bu{sub 3}SiNH){sub 3}ZrCl (1); alkylation of 1 with MeMgBr gave ({sup t}Bu{sub 3}SiNH){sub 3}ZrMe (2), whose structure was determined via X-ray crystallography. Crystal data: monoclinic, P2{sub 1}/c, a = 22.052 (3) {angstrom}, b = 12.943 (2) {angstrom}, c = 17.320 (2) {angstrom}, {beta} = 108.93 (1){degree}, Z = 4, T = 25C. The methyl derivative 2 exhibits near-tetrahedral coordination with a normal Zr-C distance (2.231 (7) {angstrom}) and virtually indistinguishable amido groups (d(Zr-N){sub av} = 2.039 (7) {angstrom}, {angle}(Zr-N-Si){sub av} = 151.4 (8){degree}). Upon thermolysis of 2 in cyclohexane (95C, 8 h), CH{sub 4} was eliminated via abstraction of an amido hydrogen, generating the transient (({sup t}Bu{sub 3}SiNH){sub 2}Zr{double bond}NSi{sup t}Bu{sub 3}) (3), which was scavenged by H{sub 2} (3 atm) to produce ({sup t}Bu{sub 3}SiNH){sub 3}ZrH (4). The monohydride 4 was shown to reduce CO to provide (({sup t}Bu{sub 3}SiNH){sub 3}Zr){sub 2}({mu}-OCH){sub 2} (6), presumably via monohydride (4) reduction of undetected (({sup t}Bu{sub 3}SiNH){sub 3}Zr(CHO)) (5). Further carbonylation yielded the spectroscopically observable (({sup t}Bu{sub 3}SiNH){sub 3}Zr){sub 2}({mu}-{eta}{sup 1}:{eta}{sup 2}-OCH{sub 2}C{double bond}O) (7) and, ultimately, (({sup t}Bu{sub 3}SiNH){sub 3}Zr){sub 2}(cis-{mu}-O(H)C{double bond}C(H)O) (8). Thermolysis of 6 in THF resulted in the elimination of ({sup t}Bu{sub 3}SiNH){sub 3}ZrOMe (10), leaving the transient 3, which was trapped by solvent to give ({sup t}Bu{sub 3}SiNH){sub 2}(THF)Zr{double bond}NSi{sup t}Bu{sub 3} (9). The addition of LiOMe to 1 provided an alternate route to 10. The mechanism of CO reduction is discussed in relation to other group 4 actinide mono- and dihydride systems.

  14. Ab initio study of the interaction of polyoxymethylene with polyoxymethylene, ammonium perchlorate, and the aluminum (100) surface

    NASA Astrophysics Data System (ADS)

    Seel, M.; Kunz, A. B.; Wadiak, D. T.

    1988-05-01

    Self-consistent restricted and unrestricted Hartree-Fock calculations have been performed for the microscopic interactions in particle-filled polymeric suspensions. First, we have investigated the elongation and the torsion potential of a single infinite polyoxymethylene chain. It is found that the 9/5 helix is ~4.5 kcal/mol lower in energy than the planar zigzag conformation. A Young's modulus of 80+/-20 GPa is obtained for the chain-direction deformation. The potential-energy curve for the van der Waals interaction between two 2/1 helical polyoxymethylene chains has a minimum for a chain separation of ~4.3 Å with a binding energy of ~1.3 kcal per (CH2O)2 translational unit. For the chain-direction slip of two polyoxymethylene chains a barrier of ~5.1 kcal is calculated. To study polymer-particle interactions, cluster calculations for the interaction of polyoxymethylene fragments with ammonium perchlorate and the aluminum (100) surface have been performed. The oxygen in the polyoxymethylene backbone forms a hydrogen bond with ammonium perchlorate. For an O-H distance of 1.62 Å a binding energy of 23.7 kcal is obtained. This strong coordination of the ammonium ion with the oxygen in the polyether backbone is in agreement with the experimentally observed increase in viscosity of polyether lacquers upon dissolution of ammonium perchlorate. The potential energy curve for the bonding of a H3C-O-CH2-O-CH2-O-CH3 fragment at the on-top sites of an Al5 cluster has a minimum for an O-Al separation of 2.3 Å with a binding energy of 17.1 kcal (8.55 kcal per O-Al bonding). This binding energy is of the same order of magnitude as the energy of 4.5 kcal per CH2O unit needed to stretch the polyoxymethylene 9/5 helix to a helix whose next-nearest oxygen atoms are commensurate with the aluminum lattice constant of 4.05 Å. Therefore the coating of aluminum particles with polyoxymethylene polymers is possible. The quantum-mechanical results of these microscopic

  15. Mechanistic aspects of hydrosilylation catalyzed by (ArN=)Mo(H)(Cl)(PMe3)3.

    PubMed

    Khalimon, Andrey Y; Shirobokov, Oleg G; Peterson, Erik; Simionescu, Razvan; Kuzmina, Lyudmila G; Howard, Judith A K; Nikonov, Georgii I

    2012-04-01

    The reaction of (ArN=)MoCl(2)(PMe(3))(3) (Ar = 2,6-diisopropylphenyl) with L-Selectride gives the hydrido-chloride complex (ArN=)Mo(H)(Cl)(PMe(3))(3) (2). Complex 2 was found to catalyze the hydrosilylation of carbonyls and nitriles as well as the dehydrogenative silylation of alcohols and water. Compound 2 does not show any productive reaction with PhSiH(3); however, a slow H/D exchange and formation of (ArN=)Mo(D)(Cl)(PMe(3))(3) (2(D)) was observed upon addition of PhSiD(3). Reactivity of 2 toward organic substrates was studied. Stoichiometric reactions of 2 with benzaldehyde and cyclohexanone start with dissociation of the trans-to-hydride PMe(3) ligand followed by coordination and insertion of carbonyls into the Mo-H bond to form alkoxy derivatives (ArN=)Mo(Cl)(OR)(PMe(2))L(2) (3: R = OCH(2)Ph, L(2) = 2 PMe(3); 5: R = OCH(2)Ph, L(2) = η(2)-PhC(O)H; 6: R = OCy, L(2) = 2 PMe(3)). The latter species reacts with PhSiH(3) to furnish the corresponding silyl ethers and to recover the hydride 2. An analogous mechanism was suggested for the dehydrogenative ethanolysis with PhSiH(3), with the key intermediate being the ethoxy complex (ArN=)Mo(Cl)(OEt)(PMe(3))(3) (7). In the case of hydrosilylation of acetophenone, a D-labeling experiment, i.e., a reaction of 2 with acetophenone and PhSiD(3) in the 1:1:1 ratio, suggests an alternative mechanism that does not involve the intermediacy of an alkoxy complex. In this particular case, the reaction presumably proceeds via Lewis acid catalysis. Similar to the case of benzaldehyde, treatment of 2 with styrene gives trans-(ArN=)Mo(H)(η(2)-CH(2)═CHPh)(PMe(3))(2) (8). Complex 8 slowly decomposes via the release of ethylbenzene, indicating only a slow insertion of styrene ligand into the Mo-H bond of 8.

  16. Cycloaddition reactions of allenylphosphonates and related allenes with dialkyl acetylenedicarboxylates, 1,3-diphenylisobenzofuran, and anthracene.

    PubMed

    Sajna, K V; Kotikalapudi, Ramesh; Chakravarty, Manab; Bhuvan Kumar, N N; Swamy, K C Kumara

    2011-02-01

    Cycloaddition reactions of allenylphosphonates [(RO)(2)P(O)[(R(1))C═C═CR(2)(2)] with dialkyl acetylenedicarboxylates, 1,3-diphenylisobenzofuran, and anthracene have been investigated and compared with those of allenoates [(EtO(2)C)RC═C═CH(2)] and allenylphosphine oxides [Ph(2)P(O)(R(1))C═C═CR(2)(2)] in selected cases. Allenylphosphonates (RO)(2)P(O)(Ar)C═C═CH(2) with an α-aryl group preferentially undergo [4 + 2] cycloaddition with DMAD/DEAD under thermal activation, but in addition to the expected 1:1 (allene: DMAD) product, the reaction also leads to 1:2 as well as 2:1 products that were not reported before. When an extra vinyl group is present at the γ-carbon of allenylphosphonate [e.g., (OCH(2)CMe(2)CH(2)O)P(O)(Ph)C═C═CH(C═CHMe)], [4 + 2] cycloaddition takes place utilizing either the vinylic or the aryl end, but additionally a novel cyclization wherein complete opening of the [β,γ] carbon-carbon double bond of the allene is realized. In contrast to these, the reaction of allenylphosphonate (OCH(2)CMe(2)CH(2)O)P(O)(H)C═C═CMe(2) possessing a terminal ═CMe(2) group with DMAD occurs by both [2 + 2] cycloaddition and ene reaction. While the reaction of ═CH(2) terminal allenylphosphonates as well as allenylphosphine oxides with 1,3-diphenylisobenzofuran afforded preferentially endo-[4 + 2] cycloaddition products via [α,β] attack, the analogous allenoates [(EtO(2)C)RC═C═CH(2)] underwent exo-[4 + 2] cyclization. Under similar conditions, allenylphosphonates with a terminal ═CR(2) group gave only [β,γ]-cycloaddition products. An unusual ring-opening of a [4 + 2] cycloaddition product followed by ring-closing via [4 + 4] cycloaddition, as revealed by (31)P NMR spectroscopy, is reported. Anthracene reacted in a manner similar to 1,3-diphenylisobenzofuran, albeit with lower reactivity. Key products, including a set of exo- and endo- [4 + 2] cycloaddition products, have been characterized by single crystal X-ray crystallography.

  17. The interplay of solvation, molecular conformation and supramolecular assembly in 1,1'-({[(ethane-1,2-diyl)dioxy](1,2-phenylene)}bis(methanylylidene))bis(thiosemicarbazide) and its N,N-dimethylformamide disolvate.

    PubMed

    Mohamed, Shaaban K; Younes, Sabry H H; Abdel-Raheem, Eman M M; Mague, Joel T; Akkurt, Mehmet; Glidewell, Christopher

    2015-11-01

    The wide diversity of applications of thiosemicarbazones and bis(thiosemicarbazones) has seen them used as anticancer and antitubercular agents, and as ligands in metal complexes designed to act as site-specific radiopharmaceuticals. Molecules of 1,1'-({[(ethane-1,2-diyl)dioxy](1,2-phenylene)}bis(methanylylidene))bis(thiosemicarbazide) {alternative name: 2,2'-[ethane-1,2-diylbis(oxy)]dibenzaldehyde bis(thiosemicarbazide)}, C18H20N6O2S2, (I), lie across twofold rotation axes in the space group C2/c, with an O-C-C-O torsion angle of -59.62 (13)° and a trans-planar arrangement of the thiosemicarbazide fragments relative to the adjacent aryl rings. The molecules of (I) are linked by N-H...S hydrogen bonds to form sheets containing R(2)4(38) rings and two types of R(2)2(8) ring. In the N,N-dimethylformamide disolvate, C18H20N6O2S2·2C3H7NO, (II), the independent molecular components all lie in general positions, but one of the solvent molecules is disordered over two sets of atomic sites having occupancies of 0.839 (3) and 0.161 (3). The O-C-C-O torsion angle in the ArOCH2CH2OAr component is -75.91 (14)° and the independent thiosemicarbazide fragments both adopt a cis-planar arrangement relative to the adjacent aryl rings. The ArOCH2CH2OAr components in (II) are linked by N-H...S hydrogen bonds to form deeply puckered sheets containing R(2)2(8), R(2)4(8) and two types of R(2)2(38) rings, and which contain cavities which accommodate all of the solvent molecules in the interior of the sheets. Comparisons are made with some related compounds. PMID:26524167

  18. Tuning the reactivity of Fe(V)(O) toward C-H bonds at room temperature: effect of water.

    PubMed

    Singh, Kundan K; Tiwari, Mrityunjay k; Ghosh, Munmun; Panda, Chakadola; Weitz, Andrew; Hendrich, Michael P; Dhar, Basab B; Vanka, Kumar; Sen Gupta, Sayam

    2015-02-16

    The presence of an Fe(V)(O) species has been postulated as the active intermediate for the oxidation of both C-H and C═C bonds in the Rieske dioxygenase family of enzymes. Understanding the reactivity of these high valent iron-oxo intermediates, especially in an aqueous medium, would provide a better understanding of these enzymatic reaction mechanisms. The formation of an Fe(V)(O) complex at room temperature in an aqueous CH3CN mixture that contains up to 90% water using NaOCl as the oxidant is reported here. The stability of Fe(V)(O) decreases with increasing water concentration. We show that the reactivity of Fe(V)(O) toward the oxidation of C-H bonds, such as those in toluene, can be tuned by varying the amount of water in the H2O/CH3CN mixture. Rate acceleration of up to 60 times is observed for the oxidation of toluene upon increasing the water concentration. The role of water in accelerating the rate of the reaction has been studied using kinetic measurements, isotope labeling experiments, and density functional theory (DFT) calculations. A kinetic isotope effect of ∼13 was observed for the oxidation of toluene and d8-toluene showing that C-H abstraction was involved in the rate-determining step. Activation parameters determined for toluene oxidation in H2O/CH3CN mixtures on the basis of Eyring plots for the rate constants show a gain in enthalpy with a concomitant loss in entropy. This points to the formation of a more-ordered transition state involving water molecules. To further understand the role of water, we performed a careful DFT study, concentrating mostly on the rate-determining hydrogen abstraction step. The DFT-optimized structure of the starting Fe(V)(O) and the transition state indicates that the rate enhancement is due to the transition state's favored stabilization over the reactant due to enhanced hydrogen bonding with water.

  19. Tuning the Reactivity of FeV(O) toward C–H Bonds at Room Temperature: Effect of Water

    PubMed Central

    2016-01-01

    The presence of an FeV(O) species has been postulated as the active intermediate for the oxidation of both C–H and C=C bonds in the Rieske dioxygenase family of enzymes. Understanding the reactivity of these high valent iron–oxo intermediates, especially in an aqueous medium, would provide a better understanding of these enzymatic reaction mechanisms. The formation of an FeV(O) complex at room temperature in an aqueous CH3CN mixture that contains up to 90% water using NaOCl as the oxidant is reported here. The stability of FeV(O) decreases with increasing water concentration. We show that the reactivity of FeV(O) toward the oxidation of C–H bonds, such as those in toluene, can be tuned by varying the amount of water in the H2O/CH3CN mixture. Rate acceleration of up to 60 times is observed for the oxidation of toluene upon increasing the water concentration. The role of water in accelerating the rate of the reaction has been studied using kinetic measurements, isotope labeling experiments, and density functional theory (DFT) calculations. A kinetic isotope effect of ∼13 was observed for the oxidation of toluene and d8-toluene showing that C–H abstraction was involved in the rate-determining step. Activation parameters determined for toluene oxidation in H2O/CH3CN mixtures on the basis of Eyring plots for the rate constants show a gain in enthalpy with a concomitant loss in entropy. This points to the formation of a more-ordered transition state involving water molecules. To further understand the role of water, we performed a careful DFT study, concentrating mostly on the rate-determining hydrogen abstraction step. The DFT-optimized structure of the starting FeV(O) and the transition state indicates that the rate enhancement is due to the transition state’s favored stabilization over the reactant due to enhanced hydrogen bonding with water. PMID:25594114

  20. Morphological and Phase Controlled Tungsten Based Nanoparticles: Synthesis and Characterization of Scheelites, Wolframites, and Oxides Nanomaterials

    PubMed Central

    Hernandez-Sanchez, Bernadette A.; Boyle, Timothy J.; Pratt, Harry D.; Rodriguez, Mark A.; Brewer, Luke N.; Dunphy, Darren R.

    2009-01-01

    For the first time tungsten based nanoparticles (WNPs) of scheelite (MWO4; M = Ca, Sr, Ba, Pb), wolframite (MWO4; M = Mn, Fe, Zn & (Mg0.60Mn0.17Fe0.26)WO4), and the oxide (WO3 and W18O49) were synthesized from solution precipitation (i.e.,trioctylamine or oleic acid) and solvothermal (i.e., benzyl alcohol) routes. The resultant WNPs were prepared directly from tungsten (VI) ethoxide (W(OCH2CH3)6, 1) and stoichiometeric mixtures of the following precursors: [Ca(N(SiMe3)2)2]2 (2), Pb(N(SiMe3)2)2 (3), Mn[(μ-Mes)2Mn(Mes)]2 (4), [Fe(μ-Mes)(Mes)]2 (5), Fe(CO)5 (6), H+[Ba2(μ3-ONep)(μ-ONep)2(ONep)(ONep)3(py)]−2 (7), H+[Sr5(μ4-O)(μ3-ONep)4(μ-ONep)4(ONep)(py)4]− (8), and [Zn(Et)(ONep)(py)]2 (9) where Mes = C6H2(CH3)3-2,4,6, ONep = OCH2CMe3, Et = CH2CH3, and py = pyridine. Through these routes, the WNP morphologies were found to be manipulated by the processing conditions, while precursor selection influenced the final phase observed. For the solution precipitation route, 1 yielded (5 × 100 nm) W18O49 rods while stochiometeric reactions between 1 and (2 – 9) generated homogenous sub 30 nm nano-dots, -diamonds, -rods, and -wires for the MWO4 systems. For the solvothermal route, 1 was found to produce wires of WO3 with aspect ratios of 20 while (1 & 2) formed 10 – 60 nm CaWO4 nanodots. Room temperature photoluminescent (PL) emission properties of select WNPs were also examined with fluorescence spectroscopy (λex = 320 nm). Broad PL emissions = 430, 420, 395, 420 nm were noted for 5 × 100 nm W18O49 rods, 5 × 15 nm, CaWO4 rods, 10 – 30 nm CaWO4 dots, and 10 nm BaWO4 diamonds, respectively. PMID:19911034

  1. Roseibacterium beibuensis sp. nov., a novel member of roseobacter clade isolated from Beibu Gulf in the South China Sea.

    PubMed

    Mao, Yujiao; Wei, Jingjing; Zheng, Qiang; Xiao, Na; Li, Qipei; Fu, Yingnan; Wang, Yanan; Jiao, Nianzhi

    2012-11-01

    A novel aerobic, bacteriochlorophyll-containing bacteria strain JLT1202r(T) was isolated from Beibu Gulf in the South China Sea. Cells were gram-negative, non-motile, and short-ovoid to rod-shaped with two narrower poles. Strain JLT1202r(T) formed circular, opaque, wine-red colonies, and grew optimally at 3-4 % NaCl, pH 7.5-8.0 and 28-30 °C. The strain was catalase, oxidase, ONPG, gelatin, and Voges-Proskauer test positive. In vivo absorption spectrum of bacteriochlorophyll a presented two peaks at 800 and 877 nm. The predominant cellular fatty acid was C(18:1) ω7c and significant amounts of C(16:0), C(18:0), C(10:0) 3-OH, C(16:0) 2-OH, and 11-methyl C(18:1) ω7c were present. Strain JLT1202r(T) contained Q-10 as the major respiratory quinone and the genomic DNA G+C content was 76.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences of various species with validly published names showed that strain JLT1202r(T) fell within the genus Roseibacterium, family Rhodobacteraceae, sharing the highest similarity with Roseibacterium elongatum OCh 323(T) (97.9 % similarity), followed by Dinoroseobacter shibae DFL 12(T) (95.4 % similarity). The phylogenetic distance of pufM genes between strain JLT1202r(T) and R. elongatum OCh 323(T) was 9.4 %, suggesting that strain JLT1202r(T) was distinct from the only strain of the genus Roseibacterium. Based on the variabilities of phylogenetic and phenotypic characteristics, strain JLT1202r(T) stands for a novel species of the genus Roseibacterium and the name R. beibuensis sp. nov. is proposed with JLT1202r(T) as the type strain (=JCM 18015(T) = CGMCC 1.10994(T)).

  2. Schiff's bases of quinazolinone derivatives: Synthesis and SAR studies of a novel series of potential anti-inflammatory and antioxidants.

    PubMed

    Rakesh, K P; Manukumar, H M; Gowda, D Channe

    2015-03-01

    A series of quinazolinone derived Schiff base derivatives 7-28 were synthesized and characterized as novel antioxidants and anti-inflammatory agents. The in vitro antioxidant activities of these compounds were evaluated and compared with commercial antioxidants ascorbic acid (AA), gallic acid (GA), butylatedhydroxytoluene (BHT), butylatedhydroxyanisole (BHA) employing 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay, 2,2-azinobis-(3-ethylbenzothiazoline-6-sufonic acid) (ABTS) assay and N,N-dimethyl-p-phenylenediamine dihydrochloride (DMPD) assay. The results revealed that IC50 of 17, 18, 23, 24, 25, 27 and 28 were lower than the IC50 of standards in all the three performed antioxidant assays indicating good activities of these compounds. In addition, in vitro anti-inflammatory activity of the synthesized compounds were evaluated and the results demonstrate that the compounds 9-12 exhibited excellent anti-inflammatory activity. Preliminary structure-activity relationship revealed that the compounds 17, 18, 23, 24, 25, 27 and 28 with electron donating moiety (OH, OCH3) were found to be excellent antioxidants and compounds 9, 10, 11 and 12 with electron withdrawing moiety (Cl, NO2) were found to be excellent anti-inflammatory agents.

  3. Synthetic cation transporters incorporating crown ethers and calixarenes as headgroups and central relays: a comparison of sodium and chloride selectivity†

    PubMed Central

    Iglesias-Sánchez, José Carlos; Wang, Wei; Ferdani, Riccardo; Prados, Pilar; de Mendoza, Javier

    2009-01-01

    An earlier study showed that a calix[4]arene could function as a central relay unit to form an ion conductance pathway through a phospholipid bilayer membrane. The present study expands the range of compounds from calix[4]arene to calix[6]arene and incorporates them either as central units or as headgroups, substituting one or more diaza-18-crown-6 residues in functioning hydraphiles. Ion release was assayed by detecting either Na+ or Cl− release from phospholipid vesicles. The ion transport activity for calix[4]arenes in either position is modest, but is almost non-existent when calix[6] residues were incorporated either as head groups or central relay units. The poor activity of the calix[6]arenes may result from an inability to penetrate to the midplane of the bilayer or pass entirely through it to form a conductance pathway. The transmembrane “flip-flop” may result from high polarity or steric bulk, or both. A hydraphile incorporating a single –NHCOC6H4OCH2CONH– as a central relay proved to be an excellent Na+ conductor, but less selective for Cl−. The fact that this new hydraphile molecule shows selectivity for Na + over Cl− transport and possesses two secondary amide residues in the central relay suggests a means to control ion selectivity in synthetic ion transporters. PMID:21720497

  4. Coordination Compounds of Strontium. Syntheses, Characterizations, and Crystal Structures of [Sr(u-ONc)(2)(HONc(4))]2 and Sr(5)(u(4)-O)(u(3)-ONep)(4)(u-ONep)(4)(HONep)(solv)(4) (ONc=O(2)CCH(2)CMe(3));Nep=CH(2)CMe(3); solv=tetrahydrofuran or 1-methyl-imida

    SciTech Connect

    Boyle, Timothy J.; Tafoya, Cory J.; Scott, Brian L.; Ziller, Joseph W.

    1999-07-21

    The authors have synthesized and characterized two novel Sr compounds: [Sr({mu}-ONc){sub 2}(HONc){sub 4}]{sub 2} (1, ONc = O{sub 2}CCH{sub 2}CMe{sub 3}), and Sr{sub 5}({mu}{sub 4}-O)({mu}{sub 3}-ONep){sub 4}({mu}-ONep){sub 4}(HONep)(solv){sub 4} [ONep = OCH{sub 2}CMe{sub 3}, solv = tetrahydrofuran (THF), 2a; 1-methyl-imidazole (MeIm), (2b)], that demonstrate increased solubility in comparison to the commercially available Sr precursors. The two metal centers of 1 share 4 unidentate bridging {mu}-ONc ligands and complete their octahedral geometry through the coordination of 4 monodentate terminal HONc ligands. The structure arrangement of the central core of 2a and b are identical, wherein 4 octahedral Sr atoms are arranged in a square geometry around a {mu}{sub 4}-O ligand. An additional 7-coordinated Sr atom sits directly atop the {mu}{sub 4}-O to form a square base pyramidal arrangement of the Sr atoms but the apical Sr-O distance is too long to be considered a bond. In solution, compound 1 is disrupted forming a monomer but 2a and b retain their structures.

  5. Selective surface decoration of corannulene.

    PubMed

    Zabula, Alexander V; Dubceac, Cristina; Filatov, Alexander S; Petrukhina, Marina A

    2011-12-01

    The reaction of corannulene (C(20)H(10)) with 1,2-C(2)H(4)Hal(2) (Hal = Cl or Br) in the presence of AlCl(3) affords stable nonplanar carbocations C(20)H(10)CH(2)CH(2)Hal(+) (Hal = Cl (1) and Br (2)) with an -CH(2)CH(2)Hal moiety attached to the interior carbon atom of the bowl. In the analogous reaction with 1-bromo-2-chloroethane, the selective (up to 98%) abstraction of chloride is observed with the formation of cation 2. The molecular structures of bowl-shaped carbocations 1 and 2 crystallized as salts with AlCl(4)(-) counterions are revealed by single-crystal X-ray diffraction. The reaction of 2 with methanol or ethanol provides further decoration of the nonplanar polyarene upon the nucleophilic addition of alkoxy groups to the exterior carbon atom of the corannulene moiety. The (1)H NMR investigation of the corresponding products, C(20)H(10)(CH(2)CH(2)Br)(OCH(2)R) (R = H (3) and CH(3) (4)), shows the formation of intramolecular H···O and H···Br hydrogen bonds.

  6. New polyoxometalates containing hybrid polymers and their potential for nano-patterning.

    PubMed

    Kalyani, Vishwanath; Satyanarayana, V S V; Singh, Vikram; Pradeep, Chullikkattil P; Ghosh, Subrata; Sharma, Satinder K; Gonsalves, Kenneth E

    2015-01-26

    Two new polyoxometalate (POM)-based hybrid monomers (Bu4 N)5 (H)[P2 V3 W15 O59 {(OCH2 )3 CNHCO(CH3 )CCH2 }] (2) and (S(CH3 )2 C6 H4 OCOC(CH3 )=CH2 )6 [PV  2Mo10 O40 ] (5) were developed by grafting polymerizable organic units covalently or electrostatically onto Wells-Dawson and Keggin-type clusters and were characterized by analytical and spectroscopic techniques including ESI-MS and/or single-crystal X-ray diffraction analyses. Radical initiated polymerization of 2 and 5 with organic monomers (methacryloyloxy)phenyldimethylsulfonium triflate (MAPDST) and/or methylmethacrylate (MMA) yielded a new series of POM/polymer hybrids that were characterized by (1) H, (31) P NMR and IR spectroscopic techniques, gel-permeation chromatography as well as thermal analyses. Preliminary tests were conducted on these POM/polymer hybrids to evaluate their properties as photoresists using electron beam (E-beam)/extreme ultraviolet (EUV) lithographic techniques. It was observed that the POM/polymer hybrid of 2 with MAPDST exhibited improved sensitivity under EUV lithographic conditions in comparison to the MAPDST homopolymer resist possibly due to the efficient photon harvesting by the POM clusters from the EUV source.

  7. In vivo synthesis of mammalian-like, hybrid-type N-glycans in Pichia pastoris.

    PubMed

    Vervecken, Wouter; Kaigorodov, Vladimir; Callewaert, Nico; Geysens, Steven; De Vusser, Kristof; Contreras, Roland

    2004-05-01

    The Pichia pastoris N-glycosylation pathway is only partially homologous to the pathway in human cells. In the Golgi apparatus, human cells synthesize complex oligosaccharides, whereas Pichia cells form mannose structures that can contain up to 40 mannose residues. This hypermannosylation of secreted glycoproteins hampers the downstream processing of heterologously expressed glycoproteins and leads to the production of protein-based therapeutic agents that are rapidly cleared from the blood because of the presence of terminal mannose residues. Here, we describe engineering of the P. pastoris N-glycosylation pathway to produce nonhyperglycosylated hybrid glycans. This was accomplished by inactivation of OCH1 and overexpression of an alpha-1,2-mannosidase retained in the endoplasmic reticulum and N-acetylglucosaminyltransferase I and beta-1,4-galactosyltransferase retained in the Golgi apparatus. The engineered strain synthesized a nonsialylated hybrid-type N-linked oligosaccharide structure on its glycoproteins. The procedures which we developed allow glycan engineering of any P. pastoris expression strain and can yield up to 90% homogeneous protein-linked oligosaccharides. PMID:15128513

  8. Transesterification process to manufacture ethyl ester of rape oil

    SciTech Connect

    Korus, R.A.; Hoffman, D.S.; Bam, N.; Peterson, C.L.; Drown, D.C.

    1993-12-31

    A process for the production of the ethyl ester of winter rape [EEWR] for use as a biodiesel fuel has been studied. The essential part of the process is the transesterification of rape oil with ethanol, in the presence of a catalyst, to yield the ethyl ester of rape oil as a product and glycerin as a by-product. Experiments have been performed to determine the optimum conditions for the preparation of EEWR. The process variables were: (1) temperature, (2) catalyst, (3) rate of agitation, (4) water content of the alcohol used, and (5) the amount of excess alcohol used. The optimum conditions were: (1) room temperature, (2) 0.5% sodium methoxide or 1% potassium hydroxide catalyst by weight of rapeseed oil, (3) extremely vigorous agitation with some splashing during the initial phase of the reaction and agitation was not necessary after the reaction mixture became homogeneous, (4) absolute ethanol was necessary for high conversion, and (5) 50% excess ethanol with NaOCH{sub 3} or 100% excess with KOH gave a maximum conversion. Viscosity, cloud point and pour point of the EEWR were measured. A preliminary break-even cost for the commercial production of EEWR was found to be $0.55/liter [$2.08/US gallon].

  9. Li(+) Local Structure in Li-Tetraglyme Solvate Ionic Liquid Revealed by Neutron Total Scattering Experiments with the (6/7)Li Isotopic Substitution Technique.

    PubMed

    Saito, Soshi; Watanabe, Hikari; Hayashi, Yutaka; Matsugami, Masaru; Tsuzuki, Seiji; Seki, Shiro; Canongia Lopes, José N; Atkin, Rob; Ueno, Kazuhide; Dokko, Kaoru; Watanabe, Masayoshi; Kameda, Yasuo; Umebayashi, Yasuhiro

    2016-07-21

    Equimolar mixtures of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and tetraglyme (G4: CH3O-(CH2CH2O)4-CH3) yield the solvate (or chelate) ionic liquid [Li(G4)][TFSA], which is a homogeneous transparent solution at room temperature. Solvate ionic liquids (SILs) are currently attracting increasing research interest, especially as new electrolytes for Li-sulfur batteries. Here, we performed neutron total scattering experiments with (6/7)Li isotopic substitution to reveal the Li(+) solvation/local structure in [Li(G4)][TFSA] SILs. The experimental interference function and radial distribution function around Li(+) agree well with predictions from ab initio calculations and MD simulations. The model solvation/local structure was optimized with nonlinear least-squares analysis to yield structural parameters. The refined Li(+) solvation/local structure in the [Li(G4)][TFSA] SIL shows that lithium cations are not coordinated to all five oxygen atoms of the G4 molecule (deficient five-coordination) but only to four of them (actual four-coordination). The solvate cation is thus considerably distorted, which can be ascribed to the limited phase space of the ethylene oxide chain and competition for coordination sites from the TFSA anion. PMID:27388117

  10. Self-assembly of hybrid dendrons with complex primary structure into functional helical pores.

    PubMed

    Percec, Virgil; Smidrkal, Jan; Peterca, Mihai; Mitchell, Catherine M; Nummelin, Sami; Dulcey, Andrés E; Sienkowska, Monika J; Heiney, Paul A

    2007-01-01

    The synthesis of three libraries of self-assembling hybrid dendrons containing a primary structure based on the sequence (4-3,4-3,5)12G2-CO(2)CH(3) generated from benzyl ether, biphenyl-4-methyl ether, and AB(2) repeat units constructed from (AB)(y)--AB(2) combinations of benzyl ethers, is reported. The structural and retrostructural analysis of their supramolecular dendrimers facilitated the discovery of new architectural principles that lead to the assembly of functional helical pores. The self-assembly of an example of hybrid dendron containing -H, -CO(2)CH(3), -CH(2)OH, -COOH, -COOK, -CONH(2), -CONHCH(3), -CO(2)(CH(2))(2)OCH(3), -(R) and -(S)-CONHCH(CH(3))C(2)H(5) as X-groups at the apex demonstrated that these self-assembling dendrons provide the simplest strategy for the design and synthesis of porous columns containing a diversity of hydrophilic and hydrophobic functional groups in the inner part of the pore. The results reported here expand the scope and limitations of dendrons available for the self-assembly of functional pores that previously were generated mostly from dendritic dipeptides, to simpler architectures based on hybrid dendrons. PMID:17304597

  11. A multivariate variational objective analysis-assimilation method. Part 2: Case study results with and without satellite data

    NASA Technical Reports Server (NTRS)

    Achtemeier, Gary L.; Kidder, Stanley Q.; Scott, Robert W.

    1988-01-01

    The variational multivariate assimilation method described in a companion paper by Achtemeier and Ochs is applied to conventional and conventional plus satellite data. Ground-based and space-based meteorological data are weighted according to the respective measurement errors and blended into a data set that is a solution of numerical forms of the two nonlinear horizontal momentum equations, the hydrostatic equation, and an integrated continuity equation for a dry atmosphere. The analyses serve first, to evaluate the accuracy of the model, and second to contrast the analyses with and without satellite data. Evaluation criteria measure the extent to which: (1) the assimilated fields satisfy the dynamical constraints, (2) the assimilated fields depart from the observations, and (3) the assimilated fields are judged to be realistic through pattern analysis. The last criterion requires that the signs, magnitudes, and patterns of the hypersensitive vertical velocity and local tendencies of the horizontal velocity components be physically consistent with respect to the larger scale weather systems.

  12. High-altitude radar meteors observed at Jicamarca Radio Observatory using a multibaseline interferometric technique

    NASA Astrophysics Data System (ADS)

    Gao, Boyi; Mathews, John D.

    2015-10-01

    A new unambiguous, multibaseline interferometric technique was recently employed for meteor observations at Jicamarca Radio Observatory (JRO). These observations largely confirm high-altitude radar meteors (HARMs). The 50 MHz JRO array is arranged in contiguous quarter-arrays (Q) each of which is comprised of 4 × 4 sub-arrays (M), which are referred to as square modules in the Ochs' manual. In these observations the radar transmission was from two quarter-arrays sharing a common diagonal. Signal reception was via three, quarter-array (Q) receivers and three adjacent (M) module receivers all of the same polarization. This arrangement offered the usual Q-Q and M-M interferometric baseline-pairs as well as new Q-M baselines that were rotated ˜6° from the Q-Q and M-M baselines. For relatively high signal-to-noise ratio meteors, this arrangement yields ambiguity resolution to the horizon and confirms the existence of HARM events. We report results from 2014 August 4 to 5 observations that include interesting new HARM events and also suggest the meteoric origin of high-altitude, altitude-extended transient events we named `Dragons' in our earlier report (Gao & Mathews 2015a). We hope to extend this new technique with yet more baselines and higher sensitivity in near future observations.

  13. Crystal phase competition by addition of a second metal cation in solid solution metal-organic frameworks.

    PubMed

    Castillo-Blas, C; Snejko, N; de la Peña-O'Shea, V A; Gallardo, J; Gutiérrez-Puebla, E; Monge, M A; Gándara, F

    2016-03-14

    Herein we report a synthetic study focused on the preparation of solid-solution metal-organic frameworks, MOFs, with the use of two kinds of linkers. In particular, we have explored the system composed by zinc, cobalt, 1,2,4-triazole and 4,4′-hexafluoroisopropylidenebisbenzoic acid (H2hfipbb). During this study, four new MOFs have been isolated, denoted TMPF-88 [M3(hfipbb)2(triazole)2(H2O)], TMPF-90 [M2(triazole)3(OCH2CH3)], TMPF-91 [M2(hfipbb)(triazole)2(H2O)] and TMPF-95 [M5(hfipbb)4(triazole)2(H2O)] (TMPF = transition metal polymeric framework, M = Zn, Co, or mixture of them). The study demonstrates that the addition of a second metal element during the MOF synthesis has a major effect in the formation of new phases, even at very high Zn/Co metal ratios. Furthermore, we show that during the MOF formation reaction, there is a competition among different crystal phases, where kinetically favoured phases of various compositions crystallize in short reaction times, precluding the formation of the pure solid-solution phases of other energetically more stable MOFs.

  14. Two new chelidamate complexes with the 4-methoxypyridine: A combined theoretical and experimental study.

    PubMed

    Uçar, İbrahim; Vural, Hatice; Küçük, Ebru

    2015-12-01

    Two new mixed chelidamate complexes, [M(chel)(mhpOCH3)·2H2O]·2H2O [M=Ni(II) (1); Co(II) (2); chel: chelidamate or 4-hydroxypyridine-2,6-dicarboxylate; mhp: 4-methoxypyridine], were prepared and characterized through a combination of X-ray diffraction method, FT-IR and UV-Vis spectroscopy. The central M(II) ion in complex (1) and (2) is coordinated by the mhp nitrogen atom, the chel nitrogen and oxygen atoms and aqua oxygen atoms, forming the distorted octahedral geometry. Intra and intermolecular hydrogen bonds and π-π stacking interactions appear to be effective in the stabilization of the crystal structures. Also, the fully optimized geometries and vibrational frequencies have been calculated using density functional theory (DFT)-B3LYP with 6-31G (d) basis set. The vibrational frequencies were interpreted by means of potential energy distribution (PED). The energetic behaviors of the complexes in methanol solvent were examined using by time-dependent DFT (TD-DFT) method by applying the polarizable continuum model (PCM). The molecular stability and charge delocalization were analyzed using natural bond orbital (NBO) analysis. PMID:26163790

  15. Infrared Spectroscopy of Hydrogen Bonds in Benzoic Acid Derivatives

    NASA Astrophysics Data System (ADS)

    Tolstorozhev, G. B.; Bel‧kov, M. V.; Skornyakov, I. V.; Bazyl, O. K.; Artyukhov, V. Ya.; Mayer, G. V.; Shadyro, O. I.; Kuzovkov, P. V.; Brinkevich, S. D.; Samovich, S. N.

    2014-03-01

    We have measured the Fourier transform IR spectra of CCl4 solutions of benzoic acid and its biologically active derivatives. We investigated the proton-acceptor properties of the studied molecules theoretically by the molecular electrostatic potential method. The calculations are compared with experimental results. Based on an estimate of the proton-acceptor properties, we give an interpretation of the specific features of the IR spectra of benzoic acid and its derivatives in the region of the O-H and C = O vibrations. The mechanisms for interactions of the molecules are determined by the nature of substituents which are added to the benzene ring in positions para and meta to the carboxyl group. We identify the conditions for appearance of intermolecular hydrogen bonds of O-H · · · O = C, O-H · · · O-H types with formation of cyclic and linear dimers. We show that intramolecular hydrogen bonds of the type O-H · · · O-CH3 prevent the hydroxyl groups from participating in intermolecular interactions.

  16. Label-free colorimetric detection of mercury via Hg2+ ions-accelerated structural transformation of nanoscale metal-oxo clusters

    PubMed Central

    Chen, Kun; She, Shan; Zhang, Jiangwei; Bayaguud, Aruuhan; Wei, Yongge

    2015-01-01

    Mercury and its compounds are known to be extremely toxic but widely distributed in environment. Although many works have been reported to efficiently detect mercury, development of simple and convenient sensors is still longed for quick analyzing mercury in water. In this work, a nanoscale metal-oxo cluster, (n-Bu4N)2[Mo5NaO13(OCH3)4(NO)], (MLPOM), organically-derivatized from monolacunary Lindqvist-type polyoxomolybdate, is found to specifically react with Hg2+ in methanol/water via structural transformation. The MLPOM methanol solution displays a color change from purple to brown within seconds after being mixed with an aqueous solution containing Hg2+. By comparing the structure of polyoxomolybdate before and after reaction, the color change is revealed to be the essentially structural transformation of MLPOM accelerated by Hg2+. Based on this discovery, MLPOM could be utilized as a colorimetric sensor to sense the existence of Hg2+, and a simple and label-free method is developed to selectively detect aqueous Hg2+. Furthermore, the colorimetric sensor has been applied to indicating mercury contamination in industrial sewage. PMID:26559602

  17. Dye-doped silica-based nanoparticles for bioapplications

    NASA Astrophysics Data System (ADS)

    Nhung Tran, Hong; Nghiem, Thi Ha Lien; Thuy Duong Vu, Thi; Tan Pham, Minh; Van Nguyen, Thi; Trang Tran, Thu; Chu, Viet Ha; Thuan Tong, Kim; Thuy Tran, Thanh; Le, Thi Thanh Xuan; Brochon, Jean-Claude; Quy Nguyen, Thi; Nhung Hoang, My; Nguyen Duong, Cao; Thuy Nguyen, Thi; Hoang, Anh Tuan; Hoa Nguyen, Phuong

    2013-12-01

    This paper presents our recent research results on synthesis and bioapplications of dye-doped silica-based nanoparticles. The dye-doped water soluble organically modified silicate (ORMOSIL) nanoparticles (NPs) with the size of 15-100 nm were synthesized by modified Stöber method from methyltriethoxysilane CH3Si(OCH3)3 precursor (MTEOS). Because thousands of fluorescent dye molecules are encapsulated in the silica-based matrix, the dye-doped nanoparticles are extremely bright and photostable. Their surfaces were modified with bovine serum albumin (BSA) and biocompatible chemical reagents. The highly intensive luminescent nanoparticles were combined with specific bacterial and breast cancer antigen antibodies. The antibody-conjugated nanoparticles can identify a variety of bacterium, such as Escherichia coli O157:H7, through antibody-antigen interaction and recognition. A highly sensitive breast cancer cell detection has been achieved with the anti-HER2 monoclonal antibody-nanoparticles complex. These results demonstrate the potential to apply these fluorescent nanoparticles in various biodetection systems.

  18. Series of edge-sharing bi-triangle Ln4 clusters with a μ4-NO3- bridge: syntheses, structures, luminescence, and the SMM behavior of the Dy4 analogue.

    PubMed

    Zou, Hua-Hong; Wang, Rong; Chen, Zi-Lu; Liu, Dong-Cheng; Liang, Fu-Pei

    2014-02-14

    A series of Ln4 clusters, [Ln4L2(μ3-OH)2(μ4-NO3)(NO3)4(OCH3)(H2O)]·xMeCN·yMeOH (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5), Yb (6), L = 2-{[2-(2-hydroxy-ethoxy)-ethylimino]-methyl}-6-methoxyphenol), have been synthesized by the reaction of Ln(NO)3 and a Schiff-base ligand formed in situ. The six complexes display similar structures, with an overall metal core comprising two edge-sharing triangular Ln3 units linked by a μ4-NO3(-) bridge. The luminescence spectrum of complex 2 shows the characteristic emission of the Tb(III) ions. The magnetic susceptibility studies reveal that the Ln(III) ions are very weakly interacting in all six compounds. Frequency dependence of the ac-susceptibility was found for 3, suggesting a typical single-molecule magnet (SMM) behavior with an anisotropic barrier of 28 K.

  19. Contrasting retrogressive rearrangement pathways during thermolysis of silica-immobilized benzyl phenyl ether

    SciTech Connect

    Buchanan, A.C. III; Britt, P.F.; Skeen, J.T.

    1997-03-01

    Many coal model compound studies have focused on the mechanisms of bond cleavage reactions, and the means to alter reaction conditions to promote such reactions. However, there has become increasing interest in elucidating mechanisms associated with retrogressive or retrograde reactions in coal processing, which involve the formation of refractory bonds. Retrograde reactions inhibit efficient thermochemical processing of coals into liquid fuels, which has been particularly well-documented for low rank coals where abundant oxygen-containing functional groups are thought to play a key role in the chemistry. Much less is known about retrogressive reactions for ether-containing model compounds. Radical recombination through ring coupling of phenoxy radicals in benzyl phenyl ether (BPE) is known to lead to more refractory diphenylmethane linkages to a limited extent. Since this chemistry may be attributed at least in part to cage recombination, it could be promoted in a diffusionally constrained environment such as in the coal macromolecule. Using silica-immobilization to simulate restricted diffusion in coal, the authors have found that retrogressive reactions can be promoted for certain hydrocarbon model compounds. The authors have now begun an examination of the thermolysis behavior of silica-immobilized benzyl phenyl ether at 275--325 C. The initial results indicate that two retrogressive reaction pathways, radical recombination and molecular rearrangement through Si-O-C linkage to the surface of PhOCH{center_dot}Ph, are promoted by restricted diffusion. Remarkably, the retrograde products typically account for 50 mol% of the thermolysis products.

  20. Highly cytotoxic DNA-interacting copper(II) coordination compounds.

    PubMed

    Brissos, Rosa F; Torrents, Ester; dos Santos Mello, Francyelli Mariana; Carvalho Pires, Wanessa; Silveira-Lacerda, Elisângela de Paula; Caballero, Ana B; Caubet, Amparo; Massera, Chiara; Roubeau, Olivier; Teat, Simon J; Gamez, Patrick

    2014-10-01

    Four new Schiff-base ligands have been designed and prepared by condensation reaction between hydrazine derivatives (i.e. 2-hydrazinopyridine or 2-hydrazinoquinoline) and mono- or dialdehyde (3-tert-butyl-2-hydroxybenzaldehyde and 5-tert-butyl-2-hydroxyisophthalaldehyde, respectively). Six copper(II) coordination compounds of various nuclearities have been obtained from these ligands, which are formulated as [Cu(L1)Cl](CH3OH) (1), [Cu(L2)NO3] (2), [Cu2(L3)(ClO4)2(CH3O)(CH3OH)](CH3OH) (3), [Cu2(L4)(ClO4)(OH)(CH3OH)](ClO4) (4), [Cu8(L3)4(NO3)4(OH)5](NO3)3(CH3OH)5(H2O)8 (5) and [Cu3(HL2')4Cl6](CH3OH)6 (6), as revealed by single-crystal X-ray studies. Their DNA-interacting abilities have been investigated using different characterization techniques, which suggest that the metal complexes act as efficient DNA binders. Moreover, cytotoxicity assays with several cancer cell lines show that some of them are very active, as evidenced by the sub-micromolar IC50 values achieved in some cases. PMID:25096758

  1. Effect of electrolytes on the structure and evolution of the solid electrolyte interphase (SEI) in Li-ion batteries: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Pil; Duin, Adri C. T. van; Shenoy, Vivek B.

    2011-10-01

    We have studied the formation and growth of solid-electrolyte interphase (SEI) for the case of ethylene carbonate (EC), dimethyl carbonate (DMC) and mixtures of these electrolytes using molecular dynamics simulations. We have considered SEI growth on both Li metal surfaces and using a simulation framework that allows us to vary the Li surface density on the anode surface. Using our simulations we have obtained the detailed structure and distribution of different constituents in the SEI as a function of the distance from the anode surfaces. We find that SEI films formed in the presence of EC are rich in Li2CO3 and Li2O, while LiOCH3 is the primary constituent of DMC films. We find that dilithium ethylene dicarbonate, LiEDC, is formed in the presence of EC at low Li surface densities, but it quickly decomposes to inorganic salts during subsequent growth in Li rich environments. The surface films formed in our simulations have a multilayer structure with regions rich in inorganic and organic salts located near the anode surface and the electrolyte interface, respectively, in agreement with depth profiling experiments. Our computed formation potentials 1.0 V vs. Li/Li+ is also in excellent accord with experimental measurements. We have also calculated the elastic stiffness of the SEI films; we find that they are significantly stiffer than Li metal, but are somewhat more compliant compared to the graphite anode.

  2. Effect of Dimethyl Carbonate on the Dynamic Properties and Ionicities of Ionic Liquids with [M(III) (hfip)4 ](-) (M=B, Al) Anions.

    PubMed

    Rupp, Alexander B A; Welle, Sabrina; Klose, Petra; Scherer, Harald; Krossing, Ingo

    2015-06-22

    Several ionic liquids (ILs) comprising [B(hfip)4 ](-) [hfip=OCH(CF3 )2 ] or [Al(hfip)4 ](-) anions and imidazolium or ammonium cations were prepared and mixed with up to 270 mol % of dimethyl carbonate (DMC). The viscosities, conductivities, and self-diffusion constants of these mixtures and, where possible, of the neat ILs were measured and compared with common [NTf2 ](-) based ILs and their mixtures with DMC. A tremendous decrease of the viscosities and a likewise increase of the conductivities and diffusion constants can be achieved for all classes of ILs. However, the order of the conductivities is partially reversed in the diffusion data. This is probably due to the low dielectric constant of DMC and the, thus, favored ion pairing, as evidenced, for example, by the calculated ionicities. Altogether, our data show that the chemically robust, but high-melting and more viscous [B(hfip)4 ](-) ILs might be candidates for electrolytes when mixed with suitable molecular solvents. PMID:25877038

  3. Identification and yield of carbonic acid and formaldehyde in irradiated ices

    NASA Technical Reports Server (NTRS)

    Dellorusso, Neil; Khanna, R. K.; Moore, M. H.

    1993-01-01

    Carbonic acid, (OH)2CO, was tentatively identified in the IR spectrum of a proton irradiated CO2 + H2O ice mixture. In this report, we present additional evidence for a more definitive identification of (OH)2CO with (1) the infrared spectrum of a residue obtained by proton irradiation of CO2 + D2O ice mixture, and (2) the IR spectra of solid phases of formaldehyde (H2CO), acetone (CH3)2CO, and dimethyl carbonate (OCH3)2CO, which are structurally similar to (OH)2CO. IR characteristics (peak frequencies and complex refractive indices of the compounds in point 2) are also reported. In particular, the integrated absorption coefficients for the C-O band for the compounds in point 2 do not vary by more than 20 percent. Based on these values, we estimate the yields of H2CO and (OH)2CO by proton irradiation or ice mixtures. Both H2CO and (OH)2CO are possible irradiation products of cometary and planetary ices.

  4. Identification and yield of carbonic acid and formaldehyde in irradiated ices

    NASA Astrophysics Data System (ADS)

    Dellorusso, N.; Khanna, R. K.; Moore, M. H.

    1993-03-01

    Carbonic acid, (OH)2CO, was tentatively identified in the IR spectrum of a proton irradiated CO2 + H2O ice mixture. In this report, we present additional evidence for a more definitive identification of (OH)2CO with (1) the infrared spectrum of a residue obtained by proton irradiation of CO2 + D2O ice mixture, and (2) the IR spectra of solid phases of formaldehyde (H2CO), acetone (CH3)2CO, and dimethyl carbonate (OCH3)2CO, which are structurally similar to (OH)2CO. IR characteristics (peak frequencies and complex refractive indices of the compounds in point 2) are also reported. In particular, the integrated absorption coefficients for the C-O band for the compounds in point 2 do not vary by more than 20 percent. Based on these values, we estimate the yields of H2CO and (OH)2CO by proton irradiation or ice mixtures. Both H2CO and (OH)2CO are possible irradiation products of cometary and planetary ices.

  5. Synthesis of Formamide and Related Organic Species in the Interstellar Medium via Chemical Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Spezia, Riccardo; Jeanvoine, Yannick; Hase, William L.; Song, Kihyung; Largo, Antonio

    2016-08-01

    We show, by means of direct dynamics simulations, how it is possible to define possible reactants and mechanisms leading to the formation of formamide in the interstellar medium. In particular, different ion-molecule reactions in the gas phase were considered: NH3OH+, NH2OH{}2+, H2COH+, and NH4 + for the ions and NH2OH, H2CO, and NH3 for the partner neutrals. These calculations were combined with high level ab initio calculations to investigate possible further evolution of the products observed. In particular, for formamide, we propose that the NH2OH{}2+ + H2CO reaction can produce an isomer, NH2OCH{}2+, that, after dissociative recombination, can produce neutral formamide, which was observed in space. The direct dynamics do not pre-impose any reaction pathways and in other reactions, we did not observe the formation of formamide or any possible precursor. On the other hand, we obtained other interesting reactions, like the formation of NH2CH{}2+. Finally, some radiative association processes are proposed. All of the results obtained are discussed in light of the species observed in radioastronomy.

  6. West Nile Virus in Mosquitoes of Iranian Wetlands.

    PubMed

    Bagheri, Masoomeh; Terenius, Olle; Oshaghi, Mohammad Ali; Motazakker, Morteza; Asgari, Sassan; Dabiri, Farrokh; Vatandoost, Hassan; Mohammadi Bavani, Mulood; Chavshin, Ali Reza

    2015-12-01

    The West Nile virus (WNV) transmission cycle includes a wide range of migratory wetland birds as reservoirs, mosquitoes as biological vectors, and equines and humans as dead-end hosts. Despite the presence of potential vector species, there is no information about the existence of WNV in mosquito vectors in Iran. The Iranian West Azerbaijan Province is located in the northwestern part of Iran and has borders with Turkey, Iraq, Armenia, and the Republic of Azerbaijan. The current study was conducted to identify the wetland mosquitoes of the West Azerbaijan Province and their infection with WNV. In this study, 2143 specimens were collected, comprising 1541 adults and 602 larvae. Six species belonging to four genera were collected and identified: Anopheles maculipennis sensu lato (s.l.), Culex (Cx.) hortensis, Cx. pipiens s.l., Cx. theileri, Culiseta longiareolata, and Aedes (Ae.) (Ochlerotatus) caspius. In total, 45 pools of mosquitoes were examined. Two of the adult pools collected from the same location showed the presence of WNV in Ae. (Och.) caspius, from Sangar, Makoo County, as confirmed by PCR and sequencing. Due to the discovery of WNV in the mosquito population of the region, and the presence of wetlands and significant populations of migratory birds, the health sector should carefully monitor the factors involved in the cycle of this disease. PMID:26565610

  7. Breaking and Making of Carbon-Carbon Bonds by Lanthanides and Third-Row Transition Metals.

    PubMed

    Zhou, Shaodong; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2016-02-24

    Carbon-atom extrusion from the ipso-position of a halobenzene ring (C6 H5 X; X=F, Cl, Br, I) and its coupling with a methylene ligand to produce acetylene is not confined to [LaCH2 ](+) ; also, the third-row transition-metal complexes [MCH2 ](+) , M=Hf, Ta, W, Re, and Os, bring about this unusual transformation. However, substrates with substituents X=CN, NO2 , OCH3 , and CF3 are either not reactive at all or give rise to different products when reacted with [LaCH2 ](+) . In the thermal gas-phase processes of atomic Ln(+) with C7 H7 Cl substrates, only those lanthanides with a promotion energy small enough to attain a 4f(n) 5d(1) 6s(1) configuration are reactive and form both [LnCl](+) and [LnC5 H5 Cl](+) . Branching ratios and the reaction efficiencies of the various processes seem to correlate with molecular properties, like the bond-dissociation energies of the C-X or M(+) -X bonds or the promotion energies of lanthanides. PMID:26875940

  8. Complete genome sequence of the bacteriochlorophyll a-containing Roseibacterium elongatum type strain (DSM 19469(T)), a representative of the Roseobacter group isolated from Australian coast sand.

    PubMed

    Riedel, Thomas; Fiebig, Anne; Göker, Markus; Klenk, Hans-Peter

    2014-06-15

    Roseibacterium elongatum Suzuki et al. 2006 is a pink-pigmented and bacteriochlorophyll a-producing representative of the Roseobacter group within the alphaproteobacterial family Rhodobacteraceae. Representatives of the marine 'Roseobacter group' were found to be abundant in the ocean and play an important role in global and biogeochemical processes. In the present study we describe the features of R. elongatum strain OCh 323(T) together with its genome sequence and annotation. The 3,555,102 bp long genome consists of one circular chromosome with no extrachromosomal elements and is one of the smallest known Roseobacter genomes. It contains 3,540 protein-coding genes and 59 RNA genes. Genome analysis revealed the presence of a photosynthetic gene cluster, which putatively enables a photoheterotrophic lifestyle. Gene sequences associated with quorum sensing, motility, surface attachment, and thiosulfate and carbon monoxide oxidation could be detected. The genome was sequenced as part of the activities of the Transregional Collaborative Research Centre 51 (TRR51) funded by the German Research Foundation (DFG). PMID:25197467

  9. A Titanium-Organic Framework as an Exemplar of Combining the Chemistry of Metal- and Covalent-Organic Frameworks.

    PubMed

    Nguyen, Ha L; Gándara, Felipe; Furukawa, Hiroyasu; Doan, Tan L H; Cordova, Kyle E; Yaghi, Omar M

    2016-04-01

    A crystalline material with a two-dimensional structure, termed metal-organic framework-901 (MOF-901), was prepared using a strategy that combines the chemistry of MOFs and covalent-organic frameworks (COFs). This strategy involves in situ generation of an amine-functionalized titanium oxo cluster, Ti6O6(OCH3)6(AB)6 (AB = 4-aminobenzoate), which was linked with benzene-1,4-dialdehyde using imine condensation reactions, typical of COFs. The crystal structure of MOF-901 is composed of hexagonal porous layers that are likely stacked in staggered conformation (hxl topology). This MOF represents the first example of combining metal cluster chemistry with dynamic organic covalent bond formation to give a new crystalline, extended framework of titanium metal, which is rarely used in MOFs. The incorporation of Ti(IV) units made MOF-901 useful in the photocatalyzed polymerization of methyl methacrylate (MMA). The resulting polyMMA product was obtained with a high-number-average molar mass (26 850 g mol(-1)) and low polydispersity index (1.6), which in many respects are better than those achieved by the commercially available photocatalyst (P-25 TiO2). Additionally, the catalyst can be isolated, reused, and recycled with no loss in performance.

  10. Doping of vanadium to nanocrystalline diamond films by hot filament chemical vapor deposition.

    PubMed

    Zhang, Yaozhong; Zhang, Liying; Zhao, Jiang; Wang, Liang; Zhao, Gang; Zhang, Yafei

    2012-01-01

    Doping an impure element with a larger atomic volume into crystalline structure of buck crystals is normally blocked because the rigid crystalline structure could not tolerate a larger distortion. However, this difficulty may be weakened for nanocrystalline structures. Diamonds, as well as many semiconductors, have a difficulty in effective doping. Theoretical calculations carried out by DFT indicate that vanadium (V) is a dopant element for the n-type diamond semiconductor, and their several donor state levels are distributed between the conduction band and middle bandgap position in the V-doped band structure of diamond. Experimental investigation of doping vanadium into nanocrystalline diamond films (NDFs) was first attempted by hot filament chemical vapor deposition technique. Acetone/H2 gas mixtures and vanadium oxytripropoxide (VO(OCH2CH2CH3)3) solutions of acetone with V and C elemental ratios of 1:5,000, 1:2,000, and 1:1,000 were used as carbon and vanadium sources, respectively. The resistivity of the V-doped NDFs decreased two orders with the increasing V/C ratios.

  11. Degradation of bare and silanized silicon wafer surfaces by constituents of biological fluids.

    PubMed

    Dekeyser, C M; Buron, C C; Derclaye, S R; Jonas, A M; Marchand-Brynaert, J; Rouxhet, P G

    2012-07-15

    The 24 h stability of bare silicon wafers as such or silanized with CH(3)O-(CH(2)-CH(2)-O)(n)-C(3)H(6)-trichlorosilane (n=6-9) was investigated in water, NaCl, phosphate and carbonate solutions, and in phosphate buffered saline (PBS) at 37 °C (close to biological conditions regarding temperature, high ionic strength, and pH). The resulting surfaces were analyzed using ellipsometry, X-ray Reflectometry (XRR), X-ray Photoelectron Spectroscopy (XPS), and Atomic Force Microscopy (AFM). Incubation of the silanized wafers in phosphate solution and PBS provokes a detachment of the silane layer. This is due to a hydrolysis of Si-O bonds which is favored by the action of phosphate, also responsible for a corrosion of non-silanized wafers. The surface alteration (detachment of silane layer and corrosion of the non-silanized wafer) is also important with carbonate solution, due to a higher pH (8.3). The protection of the silicon oxide layer brought by silane against the action of the salts is noticeable for phosphate but not for carbonate.

  12. Synthesis of Formamide and Related Organic Species in the Interstellar Medium via Chemical Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Spezia, Riccardo; Jeanvoine, Yannick; Hase, William L.; Song, Kihyung; Largo, Antonio

    2016-08-01

    We show, by means of direct dynamics simulations, how it is possible to define possible reactants and mechanisms leading to the formation of formamide in the interstellar medium. In particular, different ion–molecule reactions in the gas phase were considered: NH3OH+, NH2OH{}2+, H2COH+, and NH4 + for the ions and NH2OH, H2CO, and NH3 for the partner neutrals. These calculations were combined with high level ab initio calculations to investigate possible further evolution of the products observed. In particular, for formamide, we propose that the NH2OH{}2+ + H2CO reaction can produce an isomer, NH2OCH{}2+, that, after dissociative recombination, can produce neutral formamide, which was observed in space. The direct dynamics do not pre-impose any reaction pathways and in other reactions, we did not observe the formation of formamide or any possible precursor. On the other hand, we obtained other interesting reactions, like the formation of NH2CH{}2+. Finally, some radiative association processes are proposed. All of the results obtained are discussed in light of the species observed in radioastronomy.

  13. Defectless Monolithic Low-k/Cu Interconnects Produced by Chemically Controlled Chemical Mechanical Polishing Process with In situ End-Point-Detection Technique

    NASA Astrophysics Data System (ADS)

    Ueki, Makoto; Onodera, Takahiro; Ishikawa, Akira; Hoshino, Susumu; Hayashi, Yoshihiro

    2009-04-01

    Defectless monolithic low-k/Cu interconnects have been obtained for low-power LSIs by a chemically controlled local chemical mechanical polishing (CMP) process to remove a Cu/TaN barrier on hydrophobic SiOCH low-k films. In the first step, Cu-CMP, a unique end-point-detection (EDP) method is implemented to detect a very thin Cu layer (˜100 nm) that remains on the TaN barrier by in situ white-light interferometry, which is implemented in the local CMP apparatus where the wafers undergoing polishing are oriented face-up. In the second step, TaN-CMP, a SiO2 hard-mask (HM) layer on the low-k film is selectively removed to reduce the nonuniformity of the Cu line thickness, and accordingly, those of the resistance and capacitance. Here, a CMP slurry with an oxidizer is used to change the low-k surface from a hydrophobic condition to a hydrophilic condition, improving wettability and reducing the number of scratches and abrasive particles. In the post-CMP cleaning, an alkaline rinse solution with an oxidation-reduction potential (ORP) of less than -0.5 V vs a normal hydrogen electrode (NHE) produces a clean low-k surface resulting in monolithic low-k/Cu interconnects with excellent dielectric properties comparable to those of SiO2/Cu interconnects.

  14. Substitution Effects and Linear Free Energy Relationships During Reduction of 4- Benzoyl-n-(4-substituted Benzyl)pyridinium Cations

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas; Zhang, Guo-Hui; Rawashdeh, Abdel-Monem M.; Sotiriou-Leventis, Chariklia; Gray, Hugh R. (Technical Monitor)

    2003-01-01

    In analogy to 4-(para-substituted benzoyl)-N-methylpyridinium cations (1-X's), the title species (2-X's, -X = -OCH3, -CH3, -H, -Br, -COCH3, -NO2) undergo two reversible, well-separated (E(sub 1/2) greater than or equal to 650 mV) one-electron reductions. The effect of substitution on the reduction potentials of 2-X's is much weaker than the effect of the same substituents on 1-X's: the Hammett rho-values are 0.80 and 0.93 for the 1st- and 2nd-e reduction of 2-X's vs. 2.3 and 3.3 for the same reductions of 1-X's, respectively. Importantly, the nitro group of 2-NO2 undergoes reduction before the 2nd-e reduction of the 4-benzoylpyridinium system. These results suggest that the redox potentials of the 4-benzoylpyridinium system can be course-tuned via p-benzoyl substitution and fine-tuned via para-benzyl substitution. Introducing the recently derived substituent constant of the -NO2(sup)- group (sigma para-NO2(sup)- = -0.97) yields an excellent correlation for the 3rd-e reduction of 2- NO2 (corresponding to the reduction of the carbonyl group) with the 2nd-e reduction of the other 2-X's, and confirms the electron donating properties of -NO2(sup)-.

  15. Solvent-free Povarov reaction for synthesizing ferrocenyl quinolines: antioxidant abilities deriving from ferrocene moiety.

    PubMed

    Xi, Gao-Lei; Liu, Zai-Qun

    2014-10-30

    Twenty-two 2-phenyl-4-ferrocenylquinolines are synthesized by Povarov three-component-reaction (3CR) among the substituted anilines, benzaldehydes, and ferrocenylacetylene with Ce(OTf)3 being catalyst in the absence of solvents. The antioxidative effects of the obtained quinolines are estimated by quenching 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS(+·)), 2,2'-diphenyl-1-picrylhydrazyl (DPPH), and galvinoxyl radicals, and by inhibiting Cu(2+)/glutathione (GSH)-, hydroxyl radical (·OH)-, and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidations of DNA. It is found that the ferrocenyl group instead of hydroxyl group generates the antioxidative effect for quinoline to quench radicals and to protect DNA against radical-induced oxidations. The antioxidative effect generated by ferrocenyl group can be further increased by the electron-donating moieties such as furan, -N(CH3)2, -OCH3, and ferrocenyl group, while the electron-withdrawing groups such as -NO2 and -Cl are not beneficial for quinolines to be antioxidants. The ferrocenyl group in quinoline exhibits higher antioxidant activity than hydroxyl group in Trolox.

  16. Transition metal-free olefin polymerization catalyst

    DOEpatents

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

    2001-01-01

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

  17. Factors Affecting the Sealing Efficiency of Low-k Dielectric Surface Pores Using Successive He and Ar/NH3 Plasma Treatment

    NASA Astrophysics Data System (ADS)

    Shoeb, Juline; Kushner, Mark

    2009-10-01

    Sequential treatment of porous SiCOH by He and NH3 plasmas is effective at sealing pores while maintaining the low-k of the dielectric. He plasmas activate surface sites to accelerate the reactions responsible for pore sealing. Additional NH3 plasma treatment completes the sealing through formation of Si-N, C-N and N-N bonds resulting from the adsorption of NHx. To seal pores, sufficient He plasma exposure time is required to break Si-O bonds at SiO2 sites and to activate pore lining CHn groups by removal of H atoms. Sealing efficiency degrades if the pore radius is too large to link the sites of opposite pore walls by Si-N-N-C, Si-N-N-Si or C-N-N-C chains. In this talk, we discuss results from a computational investigation of the sealing efficiency of a porous carbon doped silica films (SiOCH). The Hybrid Plasma Equipment Model provided the fluxes of ions, neutrals and photons onto the surface from He and NH3/Ar ICPs. The sealing mechanism was implemented in the Monte Carlo Feature Profile Model with which profiles of the low-k pores are predicted. Factors affecting the sealing efficiency, such as treatment time, bias, average pore radius and pore radius standard deviation will be discussed.

  18. Atomistic simulation of CO2 solubility in poly(ethylene oxide) oligomers

    NASA Astrophysics Data System (ADS)

    Hong, Bingbing; Panagiotopoulos, Athanassios Z.

    2014-06-01

    We have performed atomistic molecular dynamics simulations coupled with thermodynamic integration to obtain the excess chemical potential and pressure-composition phase diagrams for CO2 in poly(ethylene oxide) oligomers. Poly(ethylene oxide) dimethyl ether, CH3O(CH2CH2O)nCH3 (PEO for short) is a widely applied physical solvent that forms the major organic constituent of a class of novel nanoparticle-based absorbents. Good predictions were obtained for pressure-composition-density relations for CO2 + PEO oligomers (2 ≤ n ≤ 12), using the Potoff force field for PEO [J. Chem. Phys. 136, 044514 (2012)] together with the TraPPE model for CO2 [AIChE J. 47, 1676 (2001)]. Water effects on Henry's constant of CO2 in PEO have also been investigated. Addition of modest amounts of water in PEO produces a relatively small increase in Henry's constant. Dependence of the calculated Henry's constant on the weight percentage of water falls on a temperature-dependent master curve, irrespective of PEO chain length.

  19. Alkyl CH Stretch Vibrations as a Probe of Conformational Preferences

    NASA Astrophysics Data System (ADS)

    Sibert, Edwin L. Sibert, Iii; Buchanan, Evan G.; Zwier, Timothy S.

    2013-06-01

    Theoretical IR spectra of 1,2-diphenoxyethane (C_6H_5-O-CH_2-CH_2-O-C_6H_5 DPOE) and 1,2-diphenylethane (C_6H_5-CH_2-CH_2-C_6H_5 DPE) are presented and compared to results of single-conformation spectroscopy of jet cooled molecules. The theoretical transition energies and intensites are obtained from a model based on a local mode Hamiltonian that includes all local cubic stretch-bend couplings that are then projected onto the normal modes. The model parameters are obtained from density functional theory methods. Full dimensional calculations are compared to those of reduced dimensions that include anharmonic CH streches Fermi coupled to scissor modes. Excellent agreement is found. Scale factors of select terms in the reduced dimensional Hamiltonian are determined by fitting the theoretical Hamiltonian to the anti DPE spectrum. Using the same scaling, Hamiltonians for other conformers of the above molecules are generated and used to predict structures by comparing to experimentally determined spectra in the alkyl CH stretch region. The level patterns in the resulting spectra are elucidated in terms of the model parameters. The model results are extended to interpret the spectra of more complicated macrocycles containing multiple -CH_2CH_2- ethano bridges such as the dibenzo-15-crown-5 ether and 2,2,2-paracyclophane.

  20. Atmospheric fate of nitramines: an experimental and theoretical study of the OH reactions with CH3NHNO2 and (CH3)2NNO2.

    PubMed

    Maguta, Mihayo Musabila; Aursnes, Marius; Bunkan, Arne Joakim Coldevin; Edelen, Katie; Mikoviny, Tomáš; Nielsen, Claus Jørgen; Stenstrøm, Yngve; Tang, Yizhen; Wisthaler, Armin

    2014-05-15

    The rates of CH3NHNO2 and (CH3)2NNO2 reaction with OH radicals were determined relative to CH3OCH3 and CH3OH at 298 ± 2 K and 1013 ± 10 hPa in purified air by long path FTIR spectroscopy, and the rate coefficients were determined to be k(OH+CH3NHNO2) = (9.5 ± 1.9) × 10(-13) and k(OH+(CH3)2NNO2) = (3.5 ± 0.7) × 10(-12) (2σ) cm(3) molecule(-1) s(-1). Ozone was found to react very slowly with the two nitramines, k(O3+nitramine) < 10(-21) cm(3) molecule(-1) s(-1). Product formation in the photo-oxidation of CH3NHNO2 and (CH3)2NNO2 was studied by FTIR, PTR-ToF-MS, and quantum chemistry calculations; the major products in the OH-initiated degradation are the corresponding imines, CH2═NH and CH3N═CH2, and N-nitro amides, CHONHNO2 and CHON(CH3)NO2. Atmospheric degradation mechanisms are presented. PMID:24766577

  1. Macroradical reaction in ultra-high molecular weight polyethylene in the presence of vitamin E

    NASA Astrophysics Data System (ADS)

    Jahan, M. S.; Walters, B. M.

    2011-02-01

    Free radical measurements in compression molded ultra-high molecular weight polyethylene (UHMWPE), which contained vitamin E (α-tocopherol (α-T)), was performed using electron spin resonance (ESR) technique in air at room temperature following gamma irradiation (25-32 kGy) in N 2. The vitamin E was incorporated into one set of samples by blending UHMWPE resin with vitamin E (1 and 10 wt%), then compression molded into a solid and then irradiated. Another set of samples had vitamin E incorporated into them by diffusing vitamin E at 100 °C for 2 h after irradiation. Compared to a control (with no vitamin E), the vitamin E-containing UHMWPE (α-TPE) samples suffered a partial loss of PE radicals, but this loss only occurred during or immediately after irradiation (before exposure to air). Subsequently, when all blended samples were exposed to air, the remaining radicals in each sample decayed to the well-known OIR, R1 (- rad CH-[CH=CH-] m-) and R2 ( rad OCH-[CH=CH-] m-) radicals. However, because of the initial loss or partial quenching, α-TPE produced a lower concentration of OIR (measured over a four-year period), but no difference was found between 1% and 10% α-TPEs. In the diffused α-TPE, similar OIR was also found when tested after four months of post-treatment exposure to air.

  2. Study of lignin biotransformation by Aspergillus fumigatus and white-rot fungi using /sup 14/C-labeled and unlabeled kraft lignins

    SciTech Connect

    Kadam, K.K.; Drew, S.W.

    1986-01-01

    The biodegradation of lignin by fungi was studied in shake flasks using /sup 14/C-labeled kraft lignin and in a deep-tank fermentor using unlabeled kraft lignin. Among the fungi screened, A. fumigatus - isolated in our laboratories - was most potent in lignin biotransformation. Dialysis-type fermentation, designed to study possible accumulation of low MW lignin-derived products, showed no such accumulation. Recalcitrant carbohydrates like microcrystalline cellulose supported higher lignolytic activity than easily metabolized carbohydrates like cellobiose. An assay developed to distinguish between CO/sub 2/ evolved from lignin and carbohydrate substrates demonstrated no stoichiometric correlation between the metabolism of the two cosubstrates. The submerged fermentations with unlabeled liqnin are difficult to monitor since chemical assays do not give accurate and true results. Lignolytic efficiencies that allowed monitoring of such fermentations were defined. Degraded lignins were clearly superior to C. versicolor in all aspects of lignin degradation; A fumigatus brought about substantial demethoxylation and dehydroxylation, whereas C. versicolor degraded lignins closely resembled undegraded kraft lignin. There was a good agreement among the different indices of lignin degradation, namely, /sup 14/CO evolution, OCH/sub 3/ loss, OH loss, and monomer and dimer yield after permanganate oxidation.

  3. Ab Initio Study of Hydration and Proton Dissociation in Ionomer Membranes

    SciTech Connect

    Idupulapati, Nagesh B.; Devanathan, Ramaswami; Dupuis, Michel

    2010-07-01

    We present a comparative study of proton dissociation in various functional acidic units that are promising candidates as building blocks for polymeric electrolyte membranes. Minimum energy structures for four acidic moieties with clusters of 1-6 water molecules were determined using density functional theory at the B3LYP/6-311G** level starting from chemically rational initial configurations. The perfluoro sulfonyl imide acid group (CF3CF2SO2NHSO2CF3) was observed to be the strongest acid, due to the substantial electron withdrawing effect of both fluorocarbon groups. The hydrophilic functional group (CH3OC6H3OCH3C6H4SO3H) of sulfonated polyetherether ketone (SPEEK) membrane was found to be the strongest base with the acidic proton dissociation requiring the addition of six water molecules and the hydrated proton being more tightly bound to the conjugate base. Even though both perfluoro sulfonyl imides and sulfonic acids (hydrophilic functional groups for sulfonyl imide and Nafion ionomers respectively) required only three water molecules to exhibit spontaneous proton dissociation, the largest possible solvent-separated hydronium ion was attained only for the sulfonyl imide moiety. These results provide a scientific basis for understanding the improved conductivity of perfluorinated sulfonyl imide-based membranes relative to that of the widely-used Nafion membrane.

  4. Support effect in oxide catalysis: methanol oxidation on vanadia/ceria.

    PubMed

    Kropp, Thomas; Paier, Joachim; Sauer, Joachim

    2014-10-15

    Density functional theory is used for periodic models of monomeric vanadia species deposited on the CeO2(111) surface to study dissociative adsorption of methanol and its subsequent dehydrogenation to formaldehyde. Dispersion-corrected PBE+U calculations are performed and compared with HSE and B3LYP results. Dissociative adsorption of methanol at different sites on VO2·CeO2(111) is highly exothermic with adsorption energies of 1.8 to 1.9 eV (HSE+D). Two relevant pathways for desorption of formaldehyde are found with intrinsic barriers for the redox step of 1.0 and 1.4 eV (HSE+D). The calculated desorption temperatures (370 and 495 K) explain the peaks observed in temperature-programmed desorption experiments. Different sites of the supported catalyst system are involved in the two pathways: (i) methanol can chemisorb on the CeO2 surface filling a so-called pseudovacancy and the H atom is transferred to an V-O-Ce interphase bond or (ii) CH3OH may chemisorb at the V-O-Ce interphase bond and form a V-OCH3 species from which H is transferred to the ceria surface, providing evidence for true cooperativity. In both cases, ceria is directly involved in the redox process, as two electrons are accommodated in Ce f states forming two Ce(3+) ions whereas vanadium remains fully oxidized (V(5+)). PMID:25275568

  5. Intracluster Ion Molecule Reactions Following the Generation of Mg+ Within Polar Clusters

    PubMed Central

    Alsharaeh, Edreese H.

    2011-01-01

    In this work we investigated the intracluster ion molecule reactions following the generation of Mg+ within the polar clusters (water, methanol, ether and acetonitrile), using time of flight mass spectrometry. In the case of Mg+/water and Mg+/methanol, dehydrogenation reactions are observed after the addition of five molecules. However, no dehydrogenation reactions are observed in the case of Mg+/ether or Mg+/acetonitrile clusters. This confirms the role of the H atom in (O–H) in the dehydrogenation reaction, and rules out any contribution from the H atom in the CH3 group. In addition, the magic numbers in the time of flight (TOF) mass spectra of the Mg+Xn clusters (X = H2O, CH3OH, CH3OCH3 and CH3CN) have been investigated. Finally, the role of ground electronic magnesium ion Mg+(2S1/2), and excited electronic magnesium ion Mg+(2P1/2) in the dehydrogenation reaction were investigated using Ion Mobility Mass spectrometry. The results offer direct evidence confirming the absence of the electronically excited, Mg+(2P1/2). PMID:22272121

  6. Intracluster ion molecule reactions following the generation of Mg+ within polar clusters.

    PubMed

    Alsharaeh, Edreese H

    2011-01-01

    In this work we investigated the intracluster ion molecule reactions following the generation of Mg(+) within the polar clusters (water, methanol, ether and acetonitrile), using time of flight mass spectrometry. In the case of Mg(+)/water and Mg(+)/methanol, dehydrogenation reactions are observed after the addition of five molecules. However, no dehydrogenation reactions are observed in the case of Mg(+)/ether or Mg(+)/acetonitrile clusters. This confirms the role of the H atom in (O-H) in the dehydrogenation reaction, and rules out any contribution from the H atom in the CH(3) group. In addition, the magic numbers in the time of flight (TOF) mass spectra of the Mg(+)X(n) clusters (X = H(2)O, CH(3)OH, CH(3)OCH(3) and CH(3)CN) have been investigated. Finally, the role of ground electronic magnesium ion Mg(+)((2)S(1/2)), and excited electronic magnesium ion Mg(+)((2)P(1/2)) in the dehydrogenation reaction were investigated using Ion Mobility Mass spectrometry. The results offer direct evidence confirming the absence of the electronically excited, Mg(+)((2)P(1/2)). PMID:22272121

  7. [Inhibitory effect of methyl esters of arginine-containing oligopeptides on thrombin and trypsin].

    PubMed

    Poiarkova, S A; Kibirev, V K; Serebrianyĭ, S B

    1987-01-01

    Stereoisomeric oligopeptides were studied for their inhibitory effect on the hydrolysis of benzoyl-L-arginine methyl ester catalyzed by thrombin and trypsin, as well as on the thrombin-fibrinogen reaction. Comparison of the peptide structures, their conformational flexibility and inhibitory effects on thrombin and trypsin shows the availability of the essential differences in organization and functioning of the subsites S3, S2 and S'1 of these enzymes. In contrast to trypsin, thrombin is shown to be characterized by more pronounced secondary stereospecificity. This manifests in the more vigorous dropping of the catalytic constants of thrombin-catalyzed esterolysis than those of trypsin-catalyzed hydrolysis of the substrates, containing D-amino acids at the subsite P2. It is revealed that the peptide Tos-D-Val-D-Ala-D-Agr-D-Phe-OCH3 is the most powerful inhibitor among studied compounds. It is noteworthy that its antithrombin effect is almost an order of magnitude higher than its antitrypsin effect.

  8. A Comparative study of microwave-induced pyrolysis of lignocellulosic and algal biomass.

    PubMed

    Wang, Nan; Tahmasebi, Arash; Yu, Jianglong; Xu, Jing; Huang, Feng; Mamaeva, Alisa

    2015-08-01

    Microwave (MW) pyrolysis of algal and lignocellulosic biomass samples were studied using a modified domestic oven. The pyrolysis temperature was recorded continuously by inserting a thermocouple into the samples. Temperatures as high as 1170 and 1015°C were achieved for peanut shell and Chlorella vulgaris. The activation energy for MW pyrolysis was calculated by Coats-Redfern method and the values were 221.96 and 214.27kJ/mol for peanut shell and C. vulgaris, respectively. Bio-oil yields reached to 27.7wt.% and 11.0wt.% during pyrolysis of C. vulgaris and peanut shell, respectively. The bio-oil samples from pyrolysis were analyzed by a gas chromatography-mass spectrometry (GC-MS). Bio-oil from lignocellulosic biomass pyrolysis contained more phenolic compounds while that from microalgae pyrolysis contained more nitrogen-containing species. Fourier transform infrared spectroscopy (FTIR) analysis results showed that concentration of OH, CH, CO, OCH3, and CO functional groups in char samples decreased significantly after pyrolysis.

  9. Synthesis and characterization of a series of rubidium alkoxides and rubidium-titanium double alkoxides.

    PubMed

    Bunge, Scott D; Boyle, Timothy J; Pratt III, Harry D; Alam, Todd M; Rodriguez, Mark A

    2004-09-20

    This report investigates the structural aspects of the products isolated from the reactions of a series of titanium alkoxides [[Ti(OR)4]n n = 2, OR = OCH2C(CH3)3 (ONep) (1); n = 1, OC6H3(CH3)2-2,6 (DMP) (2)] with rubidium alkoxides [[Rb(OR)]infinity where OR = (ONep) (3), (DMP) (4), and OC6H3(CH(CH3)2)2-2,6 (DIP) (5)]. The resultant double alkoxides were determined by single crystal X-ray diffraction to be [Rb(mu-ONep)4(py)Ti(ONep)]2 (6), [Rb(mu-DMP)Ti(DMP)4]infinity (7), and [Rb(mu-DMP)2(mu-ONep)2Ti(ONep)]infinity (8). Compound 1 is the previously reported dinculear species with trigonal bipyramidal Ti metal centers whereas compound 2 is a monomer with a tetrahedral Ti center. Suitable X-ray quality crystals of 3 were not isolated. Compounds 4 and 5 demonstrate extended polymeric networks with Rb coordination ranging from two to five utilizing terminal mu- and mu3-OR ligands and pi-interactions of neighboring OAr ligands. The double alkoxide 6 revealed a simple tetranuclear structure with mu-ONep acting as the bridge, terminal ONep ligands on the Ti, and one terminal py on the Rb. For 7 and 8, the pi-interaction facilitated the formation of extended polymeric systems. All complexes were further characterized by FT-IR and multinuclear NMR spectroscopy.

  10. An electro-optical and electron injection study of benzothiazole-based squaraine dyes as efficient dye-sensitized solar cell materials: a first principles study.

    PubMed

    Al-Fahdan, Najat Saeed; Asiri, Abdullah M; Irfan, Ahmad; Basaif, Salem A; El-Shishtawy, Reda M

    2014-12-01

    Squaraine dyes have attracted significant attention in many areas of daily life from biomedical imaging to semiconducting materials. Moreover, these dyes are used as photoactive materials in the field of solar cells. In the present study, we investigated the structural, electronic, photophysical, and charge transport properties of six benzothiazole-based squaraine dyes (Cis-SQ1-Cis-SQ3 and Trans-SQ1-Trans-SQ3). The effect of electron donating (-OCH3) and electron withdrawing (-COOH) groups was investigated intensively. Ground state geometry and frequency calculations were performed by applying density functional theory (DFT) at B3LYP/6-31G** level of theory. Absorption spectra were computed in chloroform at the time-dependent DFT/B3LYP/6-31G** level of theory. The driving force of electron injection (ΔG (inject)), relative driving force of electron injection (ΔG r (inject)), electronic coupling constants (|VRP|) and light harvesting efficiency (LHE) of all six compounds were calculated and compared with previously studied sensitizers. The ΔG (inject), ΔG r (inject) and |VRP| of all six compounds revealed that these sensitizers would be efficient dye-sensitized solar cell materials. Cis/Trans-SQ3 exhibited superior LHE as compared to other derivatives. The Cis/Trans geometric effect was studied and discussed with regard to electro-optical and charge transport properties.

  11. TEOS surface chemistry on SiO{sub 2} at CVD temperatures and pressures

    SciTech Connect

    Bartrarm, M.E.; Moffat, H.K.

    1995-12-31

    We have developed a significantly improved understanding of thermal TEOS (tetraethylorthosilicate, Si(OCH{sub 2}CH{sub 3}){sub 4}) surface chemistry at CVD (chemical vapor deposition) temperatures and pressures. This was accomplished using GCMS (gas chromatography-mass spectroscopy) and FTIR (Fourier transform infrared spectroscopy) to examine how TEOS reaction rates are influenced by factors critical to the heterogeneous reaction. This included determining the TEOS pressure dependence, testing if reaction by-products inhibit TEOS decomposition, evaluating functional groups on the SiO{sub 2} surface as potential reaction sites, and establishing the functional group coverage dependencies. Our results show that TEOS decomposition rates are first-order in TEOS pressure and independent of the surface reaction by-products and the relative coverages of siloxane bridges (Si-O-Si) and hydroxyls on SiO{sub 2}. These conclusions suggest that a precise knowledge of functional group coverages on SiO{sub 2} is not essential for modeling thermal TEOS decomposition rates at 1000K. In the absence of gas-phase reactions, growth rates should be directly proportional to TEOS pressure. Therefore, it is likely that non-uniform SiO{sub 2} depositions observed in thermal TEOS CVD are due to depletion of TEOS in the gas-phase and/or thermal gradients on the surface.

  12. Effects of changes in straw chemical properties and alkaline soils on bacterial communities engaged in straw decomposition at different temperatures

    PubMed Central

    Zhou, Guixiang; Zhang, Jiabao; Zhang, Congzhi; Feng, Youzhi; Chen, Lin; Yu, Zhenghong; Xin, Xiuli; Zhao, Bingzi

    2016-01-01

    Differences in the composition of a bacterial community engaged in decomposing wheat straw in a fluvo-aquic soil at 15 °C, 25 °C, and 35 °C were identified using barcode pyrosequencing. Functional carbon groups in the decomposing wheat straw were evaluated by 13C-NMR (nuclear magnetic resonance). Actinobacteria and Firmicutes were more abundant, whereas Alphaproteobacteria and Bacteroidetes were less abundant, at higher temperatures during the later stages of decomposition. Differences in the chemical properties of straw accounted for 19.3% of the variation in the community composition, whereas soil properties accounted for more (24.0%) and temperature, for less (7.4%). Carbon content of the soil microbial biomass and nitrogen content of straw were significantly correlated with the abundance of Alphaproteobacteria, Actinobacteria, and Bacteroidetes. The chemical properties of straw, especially the NCH/OCH3, alkyl O-C-O, and O-alkyl functional groups, exercised a significant effect on the composition of the bacterial community at different temperatures during decomposition—results that extend our understanding of bacterial communities associated with the decomposition of straw in agro-ecosystems and of the effects of temperature and chemical properties of the decomposing straw and soil on such communities. PMID:26916902

  13. A spectrophotometric and thermodynamic study of the sitting-atop complex formation from reaction between free base meso-tetraarylporphyrins and zirconyl nitrate in chloroform solution

    NASA Astrophysics Data System (ADS)

    Dehghani, Hossein; Mansournia, Mohammad Reza

    2009-10-01

    The sitting-atop complexation of meso-tetraarylporphyrins and its para-substituted derivatives (H 2t(4-X)pp, X:H, Br, Cl, CH(CH 3) 2, OCH 3, CH 3), as electron donors, with zirconyl, as an electron acceptor, have been investigated spectrophotometrically in chloroform. The mole ratio studies based on physicochemical techniques were employed clearly and revealed the formation of 1:1 sitting-atop complexes which was confirmed by UV-vis, 1H NMR and IR spectroscopic data. The value of the formation constant was estimated for each complex using a nonlinear optimization of the complex absorbance vs. mole ratio data by package KINFIT. The results showed that the stability of these complexes decreases with the temperature enhancement. Thermodynamic parameters, Δ G°, Δ H° and Δ S°, of the SAT complexes have been determined from the temperature dependence of formation constants by Van't Hoff equation. Also, the influence of the substituents of the aryl rings in H 2t(4-X)pp on the stability of the SAT complexes is discussed.

  14. A Survey of Large Molecules toward the Protoplanetary Nebula CRL 61 8

    NASA Technical Reports Server (NTRS)

    Remijan, Anthony J.; Wyrowski, Friedrich; Friedel, Douglas N.; Meier, David S.; Snyder, Lewis E.

    2005-01-01

    We present the results of our survey toward the protoplanetary nebula CRL 618 for several large, highly saturated, oxygen bearing organic molecules of biological importance including acetaldehyde (CH3CHO), acetic acid (CH3OOH), dimethyl ether (CH3OCH3), ethanol (CH3CH2OH), formic acid (HCOOH) and methyl formate (HCOOCH3); large carbon chain molecules including methyl cyanide (CH3CN) , methylcyanoacetylene (CH3C3N), cyanoacetylene (HC3N), cyanodiacetylene (HC5N), and C6H; and finally smaller molecules including SO-34, SO2, O(C-34)S and MgNC. No biologically important organic molecules were detected. However, we report the first interferometric detections of CH3CN and vibrationally excited HC3N and HC5N toward this source. The temperature and distribution of CH3CN toward CRL 618 indicates it is formed in the outer envelope surrounding the UC HII region. Furthermore, the P-Cygni line profile and corresponding channel maps of vibrationally excited HC5N supports its distribution in the extended envelope expanding radially from the central star. The detection of vibrationally excited HC3N confirmed the temperature structure and column density of HC3N in the inner envelope found by Wyrowski and colleagues (2003). Finally, our observations clearly indicate that CRL 618 is a good source of large carbon chain species but is a very poor source to detect or produce organic species of biological importance.

  15. Quantum Chemical Study on the Antioxidation Mechanism of Piceatannol and Isorhapontigenin toward Hydroxyl and Hydroperoxyl Radicals.

    PubMed

    Lu, Yang; Wang, AiHua; Shi, Peng; Zhang, Hui; Li, ZeSheng

    2015-01-01

    A systematic study of the antioxidation mechanisms behind hydroxyl (•OH) and hydroperoxyl (•OOH) radical scavenging activity of piceatannol (PIC) and isorhapontigenin (ISO) was carried out using density functional theory (DFT) method. Two reaction mechanisms, abstraction (ABS) and radical adduct formation (RAF), were discussed. A total of 24 reaction pathways of scavenging •OH and •OOH with PIC and ISO were investigated in the gas phase and solution. The thermodynamic and kinetic properties of all pathways were calculated. Based on these results, we evaluated the antioxidant activity of every active site of PIC and ISO and compared the abilities of PIC and ISO to scavenge radicals. According to our results, PIC and ISO may act as effective •OH and •OOH scavengers in organism. A4-hydroxyl group is a very important active site for PIC and ISO to scavenge radicals. The introducing of -OH or -OCH3 group to the ortho-position of A4-hydroxyl group would increase its antioxidant activity. Meanwhile, the conformational effect was researched, the results suggest that the presence and pattern of intramolecular hydrogen bond (IHB) are considerable in determining the antioxidant activity of PIC and ISO.

  16. Electron paramagnetic resonance evidence of hydroxyl radical generation and oxidative damage induced by tetrabromobisphenol A in Carassius auratus.

    PubMed

    Shi, Huahong; Wang, Xiaorong; Luo, Yi; Su, Yan

    2005-09-30

    Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants (BFRs). To confirm its putative oxidative stress-inducing activity, freshwater fish Carassius auratus were injected intraperitoneally with TBBPA. One experiment lasted 3h to 28 days after a single injection of 100mg/kg TBBPA, and the other lasted 24h after a single injection of 0-300 mg/kg TBBPA. Reactive oxygen species (ROS) were trapped by phenyl-tert-butyl nitrone (PBN) and detected by electron paramagnetic resonance (EPR). Protein carbonyl (PCO) and lipid peroxidation product (LPO) content were also determined. A six-line EPR spectrum was detected in the sample prepared in air, and a multiple one was obtained in nitrogen. The observed spectrum in nitrogen fits the simulation one with PBN/OCH(3) and PBN/CH(3) quite well. As compared to the control group, TBBPA significantly induced ROS production marked by the intensity of the prominent spectra in liver and bile. TBBPA (100mg/kg) also significantly increased PCO content in liver starting 24h and LPO content 3 days after injection. Either PCO or LPO content showed significant relation with ROS production. Based on the hyperfine constants and shape of the spectrum, ROS induced by TBBPA was determined as OH. The results clearly indicated that TBBPA could induce OH generation and result in oxidative damage in liver of C. auratus.

  17. Proposal for Laser Cooling of Alkaline Earth Monoalkoxide Free Radicals

    NASA Astrophysics Data System (ADS)

    Baum, Louis; Kozyryev, Ivan; Matsuda, Kyle; Doyle, John M.

    2016-05-01

    Cold samples of polyatomic molecules will open new avenues in physics, chemistry, and quantum science. Non-diagonal Franck-Condon factors, technically challenging wavelengths, and the lack of strong electronic transitions inhibit direct laser cooling of nonlinear molecules. We identify a scheme for optical cycling in certain molecules with six or more atoms. Replacing hydrogen in alcohols with an alkaline earth metal (M) leads to alkaline earth monoalkoxide free radicals (MOR), which have favorable properties for laser cooling. M-O bond is very ionic, so the metal orbitals are slightly affected by the nature of R on the ligand. Diagonal Franck-Condon factors, laser accessible transitions, and a small hyperfine structure make MOR molecules suitable for laser cooling. We explore a scheme for optical cycling on the A - X transition of SrOCH3 . Molecules lost to dark vibrational states will be repumped on the B - X transition. Extension to larger species is possible through expansion of the R group since transitions involve the promotion of the metal-centered nonbonding valence electron. We will detail our estimations of the Franck-Condon factors, simulations of the cooling process and describe progress towards the Doppler cooling of MOR polyatomics.

  18. Synthesis, optical and electrochemical properties of substituted 2-cinnamoyl-1, 3-indandione O-methyl ethers

    NASA Astrophysics Data System (ADS)

    Malina, Ilze; Kampars, Valdis; Turovska, Baiba

    2016-07-01

    Seven new 2-cinnamoyl-1,3-indandione (2CID) O-methyl ethers with different substituents (R = -H, -CH3, -OCH3, -N(C6H5)2, -N(CH2CH2CN)2, julolidyl, -N(CH3)2) in 4-position of the cinnamoyl moiety were synthesized. The methylation with dimethylsulfate occurred at the oxygen atom of the exocyclic enol group with high selectivity. The synthesized compounds were characterized by 1H, 13C NMR, IR, UV-Vis and luminescence spectroscopy, their electrochemical properties were investigated by cyclic voltammetry. The obtained results indicates that introducing an electron donating substituents in the 4-position of cinnamoyl moiety facilitates electrochemical oxidation, remarkably shifts absorption and emission bands to longer wavelengths, simultaneously increases extinction coefficient (ε). O-methyl ethers with strong electron donating groups (R = -N(C6H5)2, -N(CH2CH2CN)2, julolidyl, -N(CH3)2) in molecule are characterized by luminescence with maximum in range from 547 to 647 nm and absolute photoluminescence quantum yields from 0.02 to 0.32. Quantum yield (QY) of chromophore containing julolidyl fragment is solvent dependent. It was 0.32 in chloroform and decreased in other polar (ethanol, acetone) solvents.

  19. Sorption of linear alcohol ethoxylate surfactant homologs to soils

    NASA Astrophysics Data System (ADS)

    Yuan, Ching; Jafvert, Chad T.

    1997-11-01

    Sorption onto five saturated soils of the homologs within the commercial surfactant mixture Brij 35 (registered trademark of ICI Americas) was investigated. Brij 35 is a mixture of linear ethoxylated alcohols, having an average of 23 ethoxy (EO) groups per molecule and alcohol chain of primarily 12 carbons in length (C 12H 25(OCH 2CH 2) 23OH). In experiments, saturated soils were exposed to various concentrations of the surfactant mixture for specified times, the slurries were centrifuged to separate the phases, the aqueous phases were extracted with 1,2-dichloroethane, and the residual homologs were derivatized with 3,5-dinitrobenzoyl chloride and analyzed by normal phase HPLC. Homologs containing 4-43 EO groups were chromatographically separated at near baseline. At aqueous Brij 35 concentrations below the critical micelle concentration (cmc), the proportion of each homolog sorbed to each of the soils increased with increasing EO chain length through the homologous series. As a result, in experiments where a significant proportion of the surfactant adsorbed, significant shifts in the aqueous phase compositions occurred to mixtures with lower mean EO numbers. A sharp break in the adsorption isotherms occurs at the cmc.

  20. Synthesis and In Vitro Pharmacological Evaluation of 5-(Alkoxymethyl)-2-(3-alkylamino-2-hydroxypropoxy)phenylethanones Related to Acebutolol and Celiprolol.

    PubMed

    Bruchatá, Katarína; Némethy, Andrej; Čižmáriková, Ružena; Račanská, Eva; Habala, Ladislav

    2016-09-01

    The structure-activity relationships of 13 analogs of aryloxyaminopropanol type derived from 2-hydroxyphenylethanone as potential β-blockers are described. The synthesized compounds possess an isopropyl or a tert-butyl group in the hydrophilic part of the molecule and an alkoxymethyl substitution in the lipophilic moiety. The target compounds were prepared by an established four-step method and their structures were confirmed by interpretation of their UV, IR, (1) H NMR and (13) C NMR spectra, and by elemental analysis. The β-adrenolytic efficacy of the prepared racemic compounds was determined on isolated guinea pig atria (β1 ) and trachea (β2 ) and expressed as pA2 values against isoprenaline tachycardia. The assumed cardioselectivity was expressed as β1 /β2 ratio and the values of compounds with an alkoxy group (CH3 O, iC3 H5 O, C5 H11 O, CH2 CHCH2 O, CH3 OCH2 CH2 O) in the lipophilic part and with tert-butyl in the hydrophilic part of the molecule were found to be comparable or higher than those of the standards acebutolol and celiprolol. All evaluated substances at a concentration of 10(-7)  mol/dm(3) showed also negative chronotropic effects. PMID:27417385

  1. IR/UV and UV/UV double-resonance study of guaiacol and eugenol dimers

    NASA Astrophysics Data System (ADS)

    Longarte, Asier; Redondo, Carolina; Fernández, José A.; Castaño, Fernando

    2005-04-01

    Guaiacol (2-methoxyphenol) and eugenol (4-allyl-2-methoxyphenol) molecules are biologically active phenol derivatives with an intramolecular -OH⋯OCH3 hydrogen bond (H bond). Pulsed supersonic expansions of mixtures of either of the two molecules with He yield weakly bound homodimers as well as other higher-order complexes. A number of complementary and powerful laser spectroscopic techniques, including UV-UV and IR-UV double resonances, have been employed to interrogate the species formed in the expansion in order to get information on their structures and spectroscopic properties. The interpretation of the spectra of eugenol dimer is complex and required a previous investigation on a similar but simpler molecule both to gain insight into the possible structures and support the conclusions. Guaiacol (2-methoxyphenol) has been used for that purpose. The combination of the broad laser study combined with ab initio calculations at the Becke 3 Lee-Yang-Parr/6-31+G(d) level has provided the isomer structures, the potential-energy wells, and shed light on the inter- and intramolecular interactions involved. Guaiacol homodimer has been shown to have a single isomer whereas eugenol dimer has at least two. The comparison between the computed geometries of the dimers, their respective energies, and the vibrational normal modes permits the identification of the spectra.

  2. Molecular modification of coumarin dyes for more efficient dye sensitized solar cells

    SciTech Connect

    Sanchez-de-Armas, Rocio; San-Miguel, Miguel A.; Oviedo, Jaime; Sanz, Javier Fdez.

    2012-05-21

    In this work, new coumarin based dyes for dye sensitized solar cells (DSSC) have been designed by introducing several substituent groups in different positions of the NKX-2311 structure. Two types of substitutions have been considered: the introduction of three electron-donating groups (-OH, -NH{sub 2}, and -OCH{sub 3}) and two different substituents with steric effect: -CH{sub 2}-CH{sub 2}-CH{sub 2}- and -CH{sub 2}-HC=CH-. The electronic absorption spectra (position and width of the first band and absorption threshold) and the position of the LUMO level related to the conduction band have been used as theoretical criteria to evaluate the efficiency of the new dyes. The introduction of a -NH{sub 2} group produces a redshift of the absorption maximum position and the absorption threshold, which could improve the cell efficiency. In contrast, the introduction of -CH{sub 2}-CH{sub 2}-CH{sub 2}- does not modify significantly the electronic structure of NKX-2311, but it might prevent aggregation. Finally, -CH{sub 2}-HC=CH- produces important changes both in the electronic spectrum and in the electronic structure of the dye, and it would be expected as an improvement of cell efficiency for these dyes.

  3. Chemical Reactivity of Formaldehyde in FeAlP0{sub 4} Sieve

    SciTech Connect

    Yeom, Young-Hoon; Ulagappan, Nagappan; Frei, Heinz

    2001-03-12

    Formaldehyde gas loaded into framework Fe aluminophosphate sieve (FeAlP O4-5) at 250 K was found to react with adsorbed H2O, CH3OH, H2O2, or lattice OH groups to yield the corresponding addition product, namely CH2(OH)2, CH3OCH2OH, HO 2CH2OH, or POCH2OH, respectively. Reactions were monitored in situ by static FT-IR spectroscopy, and assignments are based on experiments with CD2=0 and CD3OD. Most efficient was the reaction with H2O2 as indicated by the fact that HO2CH2OH was formed at the exclusion of CH2(OH)2 and POCH2OH when adsorbing formaldehyde onto a sieve loaded with H2O2 and H2O. Methoxymethanol, methanediol, and POCH2OH were stable at 250 K, but dissociated above 0 degrees C under release of formaldehyde. Hydromethyl hydroperoxide disproportionates to formic acid and water. Under 355 nm irradiation in FeAlPO4 sieve, HO2CH2OH was found to undergo efficient photofragmentation.

  4. DISCOVERY OF THE METHOXY RADICAL, CH{sub 3}O, TOWARD B1: DUST GRAIN AND GAS-PHASE CHEMISTRY IN COLD DARK CLOUDS

    SciTech Connect

    Cernicharo, J.; Jimenez-Escobar, A.; Munoz Caro, G. M.; Marcelino, N.; Roueff, E.; Gerin, M.

    2012-11-10

    We report on the discovery of the methoxy radical (CH{sub 3}O) toward the cold and dense core B1-b based on the observation, with the IRAM 30 m radio telescope, of several lines at 3 and 2 mm wavelengths. Besides this new molecular species we also report on the detection of many lines arising from methyl mercaptan (CH{sub 3}SH), formic acid (HCOOH), propynal (HCCCHO), acetaldehyde (CH{sub 3}CHO), dimethyl ether (CH{sub 3}OCH{sub 3}), methyl formate (CH{sub 3}OCOH), and the formyl radical (HCO). The column density of all these species is {approx_equal}10{sup 12} cm{sup -2}, corresponding to abundances of {approx_equal}10{sup -11}. The similarity in abundances for all these species strongly suggest that they are formed on the surface of dust grains and ejected to the gas phase through non-thermal desorption processes, most likely cosmic rays or secondary photons. Nevertheless, laboratory experiments indicate that the CH{sub 3}O isomer released to the gas phase is CH{sub 2}OH rather than the methoxy one. Possible gas-phase formation routes to CH{sub 3}O from OH and methanol are discussed.

  5. Barrierless proton transfer across weak CH⋯O hydrogen bonds in dimethyl ether dimer

    SciTech Connect

    Yoder, Bruce L. West, Adam H. C.; Signorell, Ruth; Bravaya, Ksenia B.; Bodi, Andras; Sztáray, Bálint

    2015-03-21

    We present a combined computational and threshold photoelectron photoion coincidence study of two isotopologues of dimethyl ether, (DME − h{sub 6}){sub n} and (DME − d{sub 6}){sub n}n = 1 and 2, in the 9–14 eV photon energy range. Multiple isomers of neutral dimethyl ether dimer were considered, all of which may be present, and exhibited varying C–H⋯O interactions. Results from electronic structure calculations predict that all of them undergo barrierless proton transfer upon photoionization to the ground electronic state of the cation. In fact, all neutral isomers were found to relax to the same radical cation structure. The lowest energy dissociative photoionization channel of the dimer leads to CH{sub 3}OHCH{sub 3}{sup +} by the loss of CH{sub 2}OCH{sub 3} with a 0 K appearance energy of 9.71 ± 0.03 eV and 9.73 ± 0.03 eV for (DME − h{sub 6}){sub 2} and deuterated (DME − d{sub 6}){sub 2}, respectively. The ground state threshold photoelectron spectrum band of the dimethyl ether dimer is broad and exhibits no vibrational structure. Dimerization results in a 350 meV decrease of the valence band appearance energy, a 140 meV decrease of the band maximum, thus an almost twofold increase in the ground state band width, compared with DME − d{sub 6} monomer.

  6. Dip-pen-based direct writing of conducting silver dots.

    PubMed

    Gilles, Sandra; Tuchscherer, André; Lang, Heinrich; Simon, Ulrich

    2013-09-15

    Direct fabrication of micro- and nanoscale metallic structures is advantageous for many applications. Here, we use dip-pen lithography with silver(I) carboxylate [AgO2C(CH2OCH2)3H] in diethylene glycol as precursor ink for the generation of conducting metal structures. After annealing the written dots, solid silver structures are generated. We investigate the influence of several parameters such as substrate functionalization and ink composition on the pattern formation. We found that a substrate coating with perfluorinated silane is necessary, if diethylene glycol will be used as ink carrier. By variation in ink concentration and ink carrier composition, structures with diameters ranging from ~20 μm to ~2 μm and with metal fractions ranging from ~5% to ~80% were fabricated. After gold enhancement of the written patterns, resistivities in the range of 4×10(-5) Ωm on the structures were determined. The ink system introduced here appears promising for the direct fabrication of various metal or metal oxide patterns. PMID:23796451

  7. New polyoxometalates containing hybrid polymers and their potential for nano-patterning.

    PubMed

    Kalyani, Vishwanath; Satyanarayana, V S V; Singh, Vikram; Pradeep, Chullikkattil P; Ghosh, Subrata; Sharma, Satinder K; Gonsalves, Kenneth E

    2015-01-26

    Two new polyoxometalate (POM)-based hybrid monomers (Bu4 N)5 (H)[P2 V3 W15 O59 {(OCH2 )3 CNHCO(CH3 )CCH2 }] (2) and (S(CH3 )2 C6 H4 OCOC(CH3 )=CH2 )6 [PV  2Mo10 O40 ] (5) were developed by grafting polymerizable organic units covalently or electrostatically onto Wells-Dawson and Keggin-type clusters and were characterized by analytical and spectroscopic techniques including ESI-MS and/or single-crystal X-ray diffraction analyses. Radical initiated polymerization of 2 and 5 with organic monomers (methacryloyloxy)phenyldimethylsulfonium triflate (MAPDST) and/or methylmethacrylate (MMA) yielded a new series of POM/polymer hybrids that were characterized by (1) H, (31) P NMR and IR spectroscopic techniques, gel-permeation chromatography as well as thermal analyses. Preliminary tests were conducted on these POM/polymer hybrids to evaluate their properties as photoresists using electron beam (E-beam)/extreme ultraviolet (EUV) lithographic techniques. It was observed that the POM/polymer hybrid of 2 with MAPDST exhibited improved sensitivity under EUV lithographic conditions in comparison to the MAPDST homopolymer resist possibly due to the efficient photon harvesting by the POM clusters from the EUV source. PMID:25431365

  8. Characterization of the Intestinal Absorption of Seven Flavonoids from the Flowers of Trollius chinensis Using the Caco-2 Cell Monolayer Model

    PubMed Central

    Zhao, Can; Wu, Xiuwen; Wang, Rufeng; Liu, Chen

    2015-01-01

    The human Caco-2 cell monolayer model was used to investigate the absorption property, mechanism, and structure-property relationship of seven representative flavonoids, namely, orientin, vitexin, 2”-O-β-L-galactopyranosylorientin, 2”-O-β-L-galactopyranosylvitexin, isoswertisin, isoswertiajaponin, and 2”-O-(2”‘-methylbutanoyl)isoswertisin from the flowers of Trollius chinensis. The results showed that these flavonoids were hardly transported through the Caco-2 cell monolayer. The compounds with 7-OCH3 including isoswertisin, isoswertiajaponin and 2”-O-(2”‘-methylbutanoyl)isoswertisin were absorbed in a passive diffusion manner, and their absorbability was increased in the same order as their polarity. The absorption of the remaining compounds with 7-OH including orientin, vitexin, 2”-O-β-L-galactopyranosylorientin, and 2”-O-β-L-galactopyranosylvitexin involved transporter mediated efflux in addition to passive diffusion. Among the four compounds with 7-OH, those with a free hydroxyl group at C-2” such as orientin and vitexin were the substrates of P-glycoprotein (P-gp) and that with a free hydroxyl group at C-2’ such as 2”-O-β-L-galactopyranosylorientin was the substrate of multidrug resistance protein 2 (MRP2). The results of this study also implied that the absorbability of the flavonoids should be taken into account when estimating the effective components of T. chinensis. PMID:25789809

  9. n-ZnO nanorods/p+-Si (111) heterojunction light emitting diodes

    PubMed Central

    2012-01-01

    In this study, we report the effects of thermal annealing in nitrogen ambient on the optical and electrical properties of zinc oxide (ZnO) nanorod (NR) arrays for the application in light emission diodes (LED). The single-crystalline ZnO NR array was synthesized on p+-Si (111) substrate without seed layer using simple, low-cost, and low-temperature hydrothermal method. The substrate surface was functionalized by hydrofluoric acid and self-assembled monolayer of octadecyltrimethoxysilane ((CH3 (CH2)17Si(OCH3)3). ZnO NRs were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and micro-photoluminescence (micro-PL). The results of FESEM and XRD indicate that single crystalline ZnO NRs with (002) preferred orientation along the substrate surface is successfully grown on functionalized p+-Si (111) substrate. The current–voltage and electroluminescence (EL) characteristics of the LED show that the most suitable annealing temperature ranges from 400°C to 600°C. Both PL and EL spectra show broadband emissions, ultraviolet and visible (green-yellow) light. The white-like light emission is able to be observed by naked eyes. PMID:23216651

  10. Comparison of Microcystis aeruginosa (PCC7820 and PCC7806) growth and intracellular microcystins content determined by liquid chromatography-mass spectrometry, enzyme-linked immunosorbent assay anti-Adda and phosphatase bioassay.

    PubMed

    Ríos, V; Moreno, I; Prieto, A I; Soria-Díaz, M E; Frías, J E; Cameán, A M

    2014-03-01

    Cyanobacteria are able to produce several metabolites that have toxic effects on humans and animals. Among these cyanotoxins, the hepatotoxic microcystins (MC) occur frequently. The intracellular MC content produced by two strains of Microcystis aeruginosa, PCC7806 and PCC7820, and its production kinetics during the culture time were studied in order to elucidate the conditions that favour the growth and proliferation of these toxic strains. Intracellular MC concentrations measured by liquid chromatography (LC) coupled to electrospray ionization mass spectrometer (MS) were compared with those obtained by enzyme-linked immunosorbent assay (ELISA) anti-Adda and protein phosphatase 2A (PP2A) inhibition assays. It has been demonstrated there are discrepancies in the quantification of MC content when comparing ELISA and LC-MS results. However, a good correlation has been obtained between PP2A inhibition assay and LC-MS. Three MC were identified using LC-MS in the PCC7806 strain: MC-LR, demethylated MC-LR and a new variant detected for the first time in this strain, [L-MeSer(7)] MC-LR. In PCC7820, MC-LR, D-Asp(3)-MCLR, Dglu(OCH3)-MCLR, MC-LY, MC-LW and MC-LF were identificated. The major one was MC-LR in both strains, representing 81 and 79% of total MC, respectively. The total MC content in M. aeruginosa PCC7820 was almost three-fold higher than in PCC7806 extracts.

  11. Silicon-containing bis-azomethines: synthesis, structural characterization, evaluation of the photophysical properties and biological activity.

    PubMed

    Zaltariov, Mirela-Fernanada; Vlad, Angelica; Cazacu, Maria; Avadanei, Mihaela; Vornicu, Nicoleta; Balan, Mihaela; Shova, Sergiu

    2015-03-01

    A new diamine, (dimethylsilanediyl)bis(methylene)bis(4-aminobenzoate) (1), containing dimethylsilane spacer, was prepared by the condensation of p-aminobenzoic acid with bis(chloromethyl)dimethylsilane. This was subsequently reacted with salicylaldehyde, 3-hydroxy-salicylaldehyde, and 3-methoxy-salicyladehyde, when corresponding Schiff bases (E)-(dimethylsilanediyl)bis(methylene)bis(4-((E)-(2-hydroxybenzilidene)amino)benzoate (2), (E)-(dimethylsilanediyl)bis(methylene)bis(4-((E)-(2-hydroxybenzilidene)amino)benzoate (3), and (E)-(dimethylsilanediyl)bis(methylene) bis(4-((E)-(2-hydroxy-3-methoxybenzilidene)amino)benzoate (4), respectively were formed. All the obtained compounds were structurally characterized by spectral (FT-IR, (1)HNMR, (13)CNMR) analyses and single crystal X-ray diffraction. Photophysical studies revealed that the new prepared Schiff bases are good UV light absorbing and fluorescent materials. Thus, they exhibit strong UV/Vis-absorption at 250-400nm and violet or orange emission, in sensitive dependence on the polarity of the solvents and the nature of the substituent (H, OH and OCH3) at the aromatic ring. The antimicrobial activity of these compounds was first studied in vitro by the disk diffusion assay against two species of bacteria and three fungi. The minimum inhibitory concentration was then determined with the reference of standard compounds. The results displayed that Schiff bases 3 and 4 having hydroxy- and methoxy-substituents on the aromatic ring were better inhibitors of both types of species (bacteria and fungi) than standard compounds, Caspofungin and Kanamycin. PMID:25437843

  12. Facile fabrication of biomimetic superhydrophobic surface with anti-frosting on stainless steel substrate

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Bai, Yuan; Jin, Jingfu; Tian, Limei; Han, Zhiwu; Ren, Luquan

    2015-11-01

    Inspired by typical plant surfaces with super-hydrophobic character such as lotus leaves and rose petals, a superhydrophobic surface was achieved successfully by a chemical immersion process. Here, 304 SS (stainless steel) was used as substrates and a micro-nano hierarchical structure was obtained by chemical etching with a mixed solution containing ferric chloride. The results showed that the water contact angle (WAC) decreased obviously due to surface morphology changing after chemical etching process. However, we obtained a superhydrophobic surface with a WAC of 158.3 ± 2.8° after modification by DTS (CH3(CH2)11Si(OCH3)3). Furthermore, the superhydrophobic surface showed an excellent anti-frosting character compared to pure staining steel. The surface morphology, chemical composition and wettability are characterized by means of SEM, XPS and water contact angle measurements. This method could provide a facile, low-cost and stable route to fabricate a large-area superhydrophobic surface with anti-frosting for application in various environments including in humid condition.

  13. The effect of substituted 1,2,4-triazole moiety on the emission, phosphorescent properties of the blue emitting heteroleptic iridium(III) complexes and the OLED performance: a theoretical study.

    PubMed

    Srivastava, Ruby; Joshi, Laxmikanth Rao

    2014-08-28

    A series of neutral heteroleptic mononuclear iridium(III) complexes was investigated using the density functional theory/time-dependent density functional theory approach to determine the effect of the substituted 1,2,4-triazole moiety on the electronic structures, emission, and phosphorescent properties and the organic light emitting diode (OLED) performance. The results reveal that substitution of the free position in the triazole ring by -PhOCH3 (2) provides a higher emission energy and a lower oscillator strength, leading to longer radiative lifetime values mainly due to the ligand-to-ligand charge transfer transition character. The evaluation, based on one-center spin-orbit coupling, results in higher kr values for the substituent -F5Ph (5) and a lower ΔE(S-T) value. Furthermore, we also investigated the performance of the OLED device, including the charge injection/transport/balance ability, increases in the Förster energy transfer rate and triplet exciton confinement for host and guest materials of blue emitting Ir(III) complexes. Finally, we hope that our investigations will help in the design of highly efficient phosphorescent materials.

  14. An empirical equation with tables of smoothed solubilities of methane in water and aqueous sodium chloride solutions up to 25 weight percent, 360 degrees C, and 138 MPa

    USGS Publications Warehouse

    Haas, John L.

    1978-01-01

    The total pressure for the system H2O-CH 4 is given by p(total) = P(H2O,t) + exp10[log x(CH 4) - a - b x(CH4)], where P(H2O,t) is the vapor pressure of H2O liquid at the temperature t (?C) and x(CH 4) is the molal concentration of methane in the solution. The terms a and b are functions of temperature only. Where the total pressure and temperature are known, the concentration of methane, x(CH4), is found by iteration. The concentration of methane in a sodium chloride brine, y(CH4), is estimated using the function log y(CH4) = log x(CH4) - A I, where A is the salting out constant and I is the ionic strength. For sodium chloride solutions, the ionic strength is equal to the molality of the salt. The equations are valid to 360?C, 138 MPa, and 25 weight percent sodium chloride.

  15. Pancreatic Stenting Reduces Post-ERCP Pancreatitis and Biliary Sepsis in High-Risk Patients: A Randomized, Controlled Study

    PubMed Central

    Wu, Hai-En; Li, Qi-Xiang; Wang, Wei; Ou, Wei-Lin; Xia, Harry Hua-Xiang

    2016-01-01

    Background. Endoscopic retrograde cholangiopancreatography (ERCP) is an established treatment modality for bile duct disorders, but patients have a risk of post-ERCP pancreatitis (PEP) and biliary sepsis. Aim. To evaluate the effectiveness and safety of pancreatic stent for prophylaxis of PEP and biliary sepsis in high-risk patients with complicating common bile duct (CBD) disorders. Methods. Two hundred and six patients with complicating confirmed or suspected CBD disorders were randomly assigned to receive ERCP with pancreatic stenting (experimental group) or without stenting (control group). Primary outcome measure was frequency of PEP, and secondary outcome measures included operative time, blood loss, postoperative recovery times, and other ERCP-associated morbidities. Results. Baseline age, sex, CBD etiology, concomitant medical/surgical conditions, cannulation difficulty, and ERCP success were comparable between the two groups (all P > 0.05). Compared to the control group, the experimental group had a significantly lower frequency of PEP (7.7% versus 17.7%, P < 0.05) and positive bile microbial culture (40.4% versus 62.7%, P < 0.05). However, the two groups were similar in operative time, blood loss, postoperative recovery times, and other ERCP-associated morbidities (all P > 0.05). Conclusions. Pancreatic stenting can reduce the occurrence of PEP and biliary sepsis in high-risk patients with complicating CBD disorders but does not increase other ERCP-associated morbidities. This trial is registered with the Chinese Clinical Trial Registry (registration identifier ChiCTR-OCH-14005134). PMID:27057161

  16. Self-organized tubular structures as platforms for quantum dots.

    PubMed

    Makki, Rabih; Ji, Xin; Mattoussi, Hedi; Steinbock, Oliver

    2014-04-30

    The combination of top-down and bottom-up approaches offers great opportunities for the production of complex materials and devices. We demonstrate this approach by incorporating luminescent CdSe-ZnS nanoparticles into macroscopic tube structures that form as the result of externally controlled self-organization. The 1-2 mm wide hollow tubes consist of silica-supported zinc oxide/hydroxide and are formed by controlled injection of aqueous zinc sulfate into a sodium silicate solution. The primary growth region at the top of the tube is pinned to a robotic arm that moves upward at constant speed. Dispersed within the injected zinc solution are 3.4 nm CdSe-ZnS quantum dots (QDs) capped by DHLA-PEG-OCH3 ligands. Fluorescence measurements of the washed and dried tubes reveal the presence of trapped QDs at an estimated number density of 10(10) QDs per millimeter of tube length. The successful inclusion of the nanoparticles is further supported by electron microscopy and energy dispersive X-ray spectroscopy, with the latter suggesting a nearly homogeneous QD distribution across the tube wall. Exposure of the samples to copper sulfate solution induces quenching of about 90% of the tubes' fluorescence intensity. This quenching shows that the large majority of the QDs is chemically accessible within the microporous, about 15-μm-wide tube wall. We suggest possible applications of such QD-hosting tube systems as convenient sensors in microfluidic and related applications. PMID:24702437

  17. Degradation of methamidophos by Hyphomicrobium species MAP-1 and the biochemical degradation pathway.

    PubMed

    Wang, Li; Wen, Yang; Guo, Xinqing; Wang, Guangli; Li, Shunpeng; Jiang, Jiandong

    2010-07-01

    Methamidophos is one of the most widely used organophosphorus insecticides usually detectable in the environment. A facultative methylotroph, Hyphomicrobium sp. MAP-1, capable of high efficiently degrading methamidophos, was isolated from methamidophos-contaminated soil in China. It was found that the addition of methanol significantly promoted the growth of strain MAP-1 and enhanced its degradation of methamidophos. Further, this strain could utilize methamidophos as its sole carbon, nitrogen and phosphorus source for growth and could completely degrade 3,000 mg l(-1) methamidophos in 84 h under optimal conditions (pH 7.0, 30 degrees C). The enzyme responsible for methamidophos degradation was mainly located on the cell inner membrane (90.4%). During methamidophos degradation, three metabolites were detected and identified based on tandem mass spectrometry (MS/MS) and gas chromatography-mass spectrometry (GC-MS) analysis. Using this information, a biochemical degradation pathway of methamidophos by Hyphomicrobium sp. MAP-1 was proposed for the first time. Methamidophos is first cleaved at the P-N bond to form O,S-dimethyl hydrogen thiophosphate and NH(3). Subsequently, O,S-dimethyl hydrogen thiophosphate is hydrolyzed at the P-O bond to release -OCH(3) and form S-methyl dihydrogen thiophosphate. O,S-dimethyl hydrogen thiophosphate can also be hydrolyzed at the P-S bond to release -SCH(3) and form methyl dihydrogen phosphate. Finally, S-methyl dihydrogen thiophosphate and methyl dihydrogen phosphate are likely transformed into phosphoric acid. PMID:19960233

  18. Synthesis and in vitro evaluation of novel rhodanine derivatives as potential cholinesterase inhibitors.

    PubMed

    Krátký, Martin; Štěpánková, Šárka; Vorčáková, Katarína; Vinšová, Jarmila

    2016-10-01

    Based on a broad spectrum of biological activities of rhodanines, we synthesized aromatic amides and esters of 2-(4-oxo-2-thioxothiazolidin-3-yl)acetic acid (rhodanine-3-acetic acid) via carbodiimide- or PCl3-mediated coupling. Both esters and amides were investigated for their in vitro inhibitory potency and selectivity against acetylcholinesterase (AChE) from electric eel and butyrylcholinesterase (BChE) from equine serum using Ellman's spectrophotometric method. The derivatives exhibited mostly a moderate activity against both cholinesterases. IC50 values for AChE were in a closer concentration range of 24.05-86.85μM when compared to BChE inhibition (7.92-227.19μM). The esters caused the more efficient inhibition of AChE than amides and parent acid. The esterification and amidation of the rhodanine-3-acetic acid increased inhibition of BChE, even up to 26 times. Derivatives of 4-nitroaniline/phenol showed the activity superior to other substituents (H, Cl, CH3, OCH3, CF3). Rhodanines produced a balanced inhibition of both cholinesterases. Seven derivatives produced the more potent inhibition of AChE than rivastigmine, a clinically used drug; additional three compounds were comparable. Two amides exceeded inhibitory potency of rivastigmine towards BChE. Importantly, this is the first evidence that rhodanine-based compounds are able to inhibit BChE.

  19. Acaricidal activities of apiol and its derivatives from Petroselinum sativum seeds against Dermatophagoides pteronyssinus, Dermatophagoides farinae, and Tyrophagus putrescentiae.

    PubMed

    Song, Ha Yun; Yang, Ji Yeon; Suh, Joo Won; Lee, Hoi Seon

    2011-07-27

    The acaricidal effects of an active constituent derived from Petroselinum sativum seeds and its derivatives were determined using impregnated fabric disk bioassay against Dermatophagoides farinae , Dermatophagoides pteronyssinus , and Tyrophagus putrescentiae and compared with that of synthetic acaricide. The acaricidal constituent of P. sativum was isolated by various chromatographic techniques and identified as apiol. On the basis of LD(50) values against D. farinae and D. pteronyssinus, apiol (0.81 and 0.94 μg/cm(2)) was 12.4 and 10.2 times more toxic than benzyl benzoate (10.0 and 9.58 μg/cm(2)), respectively. In acaricidal studies of apiol derivatives, 3,4-methylenedioxybenzonitrile (0.04, 0.03, and 0.59 μg/cm(2)) was 250, 319, and 20.7 times more toxic than benzyl benzoate (10.0, 9.58, and 12.2 μg/cm(2)) against D. farinae, D. pteronyssinus, and T. putrescentiae. In structure-activity relationships, the acaricidal activities of apiol derivatives could be related to allyl (-C(3)H(5)) and methoxy (-OCH(3)) functional groups. Furthermore, apiol and its derivatives could be useful for natural acaricides against these three mite species.

  20. Tolerance-like innate immunity and spleen injury: a novel discovery via the weekly administrations and consecutive injections of PEGylated emulsions

    PubMed Central

    Wang, Long; Wang, Chunling; Jiao, Jiao; Su, Yuqing; Cheng, Xiaobo; Huang, Zhenjun; Liu, Xinrong; Deng, Yihui

    2014-01-01

    There has been an increasing interest in the study of the innate immune system in recent years. However, few studies have focused on whether innate immunity can acquire tolerance. Therefore, in this study, we investigated tolerance in the innate immune system via the consecutive weekly and daily injections of emulsions modified with polyethylene glycol (PEG), referred to as PEGylated emulsions (PE). The effects of these injections of PE on pharmacokinetics and biodistribution were studied in normal and macrophage-depleted rats. Additionally, we evaluated the antigenic specificity of immunologic tolerance. Immunologic tolerance against PE developed after 21 days of consecutive daily injections or the fourth week of PE administration. Compared with a single administration, it was observed that the tolerant rats had a lower rate of PE clearance from the blood, which was independent of the stress response. In addition, weekly PE injections caused injury to the spleen. Furthermore, the rats tolerant to PEs with the methoxy group (–OCH3) of PEG, failed to respond to the PEs with a different terminal group of PEG or to non-PEG emulsions. Innate immunity tolerance was induced by PE, regardless of the mode of administration. Further study of this mechanism suggested that monocytes play an essential role in the suppression of innate immunity. These findings provide novel insights into the understanding of the innate immune system. PMID:25120362

  1. Simultaneous quantification of 19 ginsenosides in black ginseng developed from Panax ginseng by HPLC-ELSD.

    PubMed

    Sun, Bai-Shen; Gu, Li-Juan; Fang, Zhe-Ming; Wang, Chun-yan; Wang, Zhen; Lee, Mi-Ra; Li, Zheng; Li, Jing-Jie; Sung, Chang-Keun

    2009-08-15

    A high-performance liquid chromatographic method with evaporative light scattering detection (HPLC-ELSD) has been developed to identify and quantify 19 ginsenosides (Rg(1), Re, Rf, Rb(1), Rc, Rb(2), Rd, F(4), Rg(6), Rk(3), Rh(4), 20(S)-, 20(R)-Rg(3), 20(S)-, 20(R)-Rs(3), Rk(1), Rg(5), Rs(4), and Rs(5)) in black ginseng (BG, Korean white ginseng that was subjected to nine cycles of steam treatment). Ultrasonication is employed for sample preparation, and the analysis is achieved on a Discovery C(18) column using gradient elution of CH(3)CN-H(2)O-CH(3)COOH without buffer in 40min. The method was validated by linearity (r(2)> or =0.9994), precision (92.0-107.5%), intra- and inter-day accuracy (R.S.D.<3.21%), and limit of detection (LOD< or =93ng). The quantification method was applied to analyze the composition of ginsenosides in Korean white, red, and black ginsengs. During the preparatory process of BG, ginsenosides transform into constituents of low polarity by hydrolysis, isomerization, and dehydration at C-20, and hydrolysis also occurs at C-3 or C-6. The validated HPLC method is expected to provide the basis for the quality assessment of ginseng products.

  2. Multiplicity Difference between Heavy and Light Quark Jets Revisited

    SciTech Connect

    Fabbri, Fabrizio

    2006-04-11

    A peculiar prediction of perturbative QCD, obtained within the Local Parton Hadron Duality (LPHD) framework, is that the multiplicity difference {delta}Ql between heavy and light quark jets produced in e+e- annihilation is energy independent. In the Modified Leading Logarithmic Approximation (MLLA) the corresponding constant is derived in terms of a few experimentally measurable quantities. While the energy independence of {delta}Ql has been successfully verified experimentally for b-quarks up to the highest LEP2 energy, its numerical prediction ({delta}{sub bl}{sup MLLA} = 5.5 {+-} 0.8) overestimates the experimental results. The work presented in this talk, done in collaboration with Yuri L. Dokshitzer, Valery A. Khoze and Wolfgang Ochs, shows that in the light of new experimental results and the improvement in the understanding of the experimental data, this prediction needs indeed a revision. We now find {delta}bl = 4.4 {+-} 0.4, in better agreement with experiment, and we shaw that the remaining difference can be attributed largely to next-to-MLLA contributions, an important subset of which are identified and evaluated. The situation with charmed quarks is also reviewed.

  3. Characterization of associated proteins and phospholipids in natural rubber latex.

    PubMed

    Sansatsadeekul, Jitlada; Sakdapipanich, Jitladda; Rojruthai, Porntip

    2011-06-01

    Non-rubber components present in natural rubber (NR) latex, such as proteins and phospholipids, are presumed to be distributed in the serum fraction as well as surrounding the rubber particle surface. The phospholipid-protein layers covering the rubber particle surface are especially interesting due to their ability to enhance the colloidal stability of NR latex. In this study, we have characterized the components surrounding the NR particle surface and investigated their role in the colloidal stability of NR particles. Proteins from the cream fraction were proteolytically removed from the NR latex and compare to those from the serum fractions using SDS-polyacrylamide gel electrophoresis revealing that both fractions contained similar proteins in certain molecular weights such as 14.5, 25 and 27 kDa. Phospholipids removed from latex by treatment with NaOH were analyzed using (1)H-NMR spectroscopy and several major signals were assignable to -(CH(2))(n)-, -CH(2)OP, -CH(2)OC═O and -OCH(2)CH(2)NH-. These signals are important evidence that indicates phospholipids associate with the rubber chain. The colloidal behavior of rubber lattices before and after removal of protein-lipid membrane was evaluated by zeta potential analysis and scanning electron microscope (SEM). The lowest zeta potential value of NR particles was observed at pH 10, consequently leading to the highest stability of rubber particles. Additionally, SEM micrographs clearly displayed a gray ring near the particle surface corresponding to the protein-lipid membrane layer.

  4. Kinetic modeling of Pt-catalyzed glycolaldehyde decomposition to syngas.

    PubMed

    Salciccioli, Michael; Vlachos, Dionisios G

    2012-05-10

    Fundamental knowledge of the elementary reaction mechanisms involved in oxygenate decomposition on transition metal catalysts can facilitate the optimization of future catalyst and reactor systems for biomass upgrade to fuels and chemicals. Pt-catalyzed decomposition of glycolaldehyde, as the smallest oxygenate with alcohol and aldehyde functionality, was studied via a DFT-based microkinetic model. It was found that two decomposition pathways exist. Under conditions of low hydrogen surface coverage, the initial C-H bond breaking reaction to HOCH(2)CO* is prevalent, while under conditions of high hydrogen coverage, the rather unexpected O-H bond forming reaction to HOCH(2)CHOH* is more active (subsequent decomposition is energetically favorable from HOCH(2)CHOH*). Our results indicate the possibility that (de)hydrogenation chemistry is rate-controlling in many small polyoxygenate biomass derivatives, and suitable catalysts are needed. Finally, DFT was used to understand the increased decomposition activity observed on the surface segregated Ni-Pt-Pt bimetallic catalyst. It was found that the initial O-H bond breaking of glycolaldehyde to OCH(2)CHO* has an activation barrier of just 0.21 eV. This barrier is lower than that of any glycolaldehyde consuming reaction on Pt. These computational predictions are in qualitative agreement with experimental results. PMID:22483365

  5. RSM Based Optimization of Chemical and Enzymatic Transesterification of Palm Oil: Biodiesel Production and Assessment of Exhaust Emission Levels

    PubMed Central

    Mumtaz, Muhammad Waseem; Anwar, Farooq; Saari, Nazamid

    2014-01-01

    Current study presents RSM based optimized production of biodiesel from palm oil using chemical and enzymatic transesterification. The emission behavior of biodiesel and its blends, namely, POB-5, POB-20, POB-40, POB-50, POB-80, and POB-100 was examined using diesel engine (equipped with tube well). Optimized palm oil fatty acid methyl esters (POFAMEs) yields were depicted to be 47.6 ± 1.5, 92.7 ± 2.5, and 95.4 ± 2.0% for chemical transesterification catalyzed by NaOH, KOH, and NaOCH3, respectively, whereas for enzymatic transesterification reactions catalyzed by NOVOZYME-435 and A. n. lipase optimized biodiesel yields were 94.2 ± 3.1 and 62.8 ± 2.4%, respectively. Distinct decrease in particulate matter (PM) and carbon monoxide (CO) levels was experienced in exhaust emissions from engine operating on biodiesel blends POB-5, POB-20, POB-40, POB-50, POB-80, and POB-100 comparative to conventional petroleum diesel. Percentage change in CO and PM emissions for different biodiesel blends ranged from −2.1 to −68.7% and −6.2 to −58.4%, respectively, relative to conventional diesel, whereas an irregular trend was observed for NOx emissions. Only POB-5 and POB-20 showed notable reductions, whereas all other blends (POB-40 to POB-100) showed slight increase in NOx emission levels from 2.6 to 5.5% comparative to petroleum diesel. PMID:25162053

  6. Vapor pressures of a homologous series of polyethylene glycols as a reference data set for validating vapor pressure measurement techniques.

    NASA Astrophysics Data System (ADS)

    Krieger, Ulrich; Marcolli, Claudia; Siegrist, Franziska

    2015-04-01

    The production of secondary organic aerosol (SOA) by gas-to-particle partitioning is generally represented by an equilibrium partitioning model. A key physical parameter which governs gas-particle partitioning is the pure component vapor pressure, which is difficult to measure for low- and semivolatile compounds. For typical atmospheric compounds like e.g. citric acid or tartaric acid, vapor pressures have been reported in the literature which differ by up to six orders of magnitude [Huisman et al., 2013]. Here, we report vapor pressures of a homologous series of polyethylene glycols (triethylene glycol to octaethylene glycol) determined by measuring the evaporation rate of single, levitated aerosol particles in an electrodynamic balance. We propose to use those as a reference data set for validating different vapor pressure measurement techniques. With each addition of a (O-CH2-CH2)-group the vapor pressure is lowered by about one order of magnitude which makes it easy to detect the lower limit of vapor pressures accessible with a particular technique down to a pressure of 10-8 Pa at room temperature. Reference: Huisman, A. J., Krieger, U. K., Zuend, A., Marcolli, C., and Peter, T., Atmos. Chem. Phys., 13, 6647-6662, 2013.

  7. Role of Solvent and Effect of Substituent on Azobenzene Isomerization by Using Room-Temperature Ionic Liquids as Reaction Media.

    PubMed

    Angelini, Guido; Canilho, Nadia; Emo, Mélanie; Kingsley, Molly; Gasbarri, Carla

    2015-08-01

    The effects of a para substituent, as the electron-donating -OCH3 and -OtBu groups and the electron-withdrawing -Br and -F atoms, on azobenzene isomerization have been investigated in a series of imidazolium ionic liquids (BMIM PF6, BMIM BF4, BMIM Tf2N, EMIM Tf2N, BM2IM Tf2N, and HMIM Tf2N). The thermal cis-trans conversion tends to be improved in the presence of the substituent, as pointed out by the first-order rate constants measured at 25 °C. Both the rotation and the inversion mechanisms occur in BMIM Tf2N, EMIM Tf2N, and HMIM Tf2N, as highlighted by typical V-shape Hammett plots, but only rotation takes place in BMIM PF6, BMIM BF4, and BM2IM Tf2N. The possible interactions between the cation and the anion of the solvent and both the isomers of the azobenzene derivatives have been studied by small-wide-angle X-ray scattering (SWAXS). The calculated cis population in the photostationary state and the hardness parameter η of the trans isomer show that azobenzene and F-azobenzene are the less reactive molecules for the trans-cis conversion in all the investigated ionic liquids.

  8. Validation of the Behavioral Risk Factor Surveillance System Sleep Questions

    PubMed Central

    Jungquist, Carla R.; Mund, Jaime; Aquilina, Alan T.; Klingman, Karen; Pender, John; Ochs-Balcom, Heather; van Wijngaarden, Edwin; Dickerson, Suzanne S.

    2016-01-01

    Study Objective: Sleep problems may constitute a risk for health problems, including cardiovascular disease, depression, diabetes, poor work performance, and motor vehicle accidents. The primary purpose of this study was to assess the validity of the current Behavioral Risk Factor Surveillance System (BRFSS) sleep questions by establishing the sensitivity and specificity for detection of sleep/ wake disturbance. Methods: Repeated cross-sectional assessment of 300 community dwelling adults over the age of 18 who did not wear CPAP or oxygen during sleep. Reliability and validity testing of the BRFSS sleep questions was performed comparing to BFRSS responses to data from home sleep study, actigraphy for 14 days, Insomnia Severity Index, Epworth Sleepiness Scale, and PROMIS-57. Results: Only two of the five BRFSS sleep questions were found valid and reliable in determining total sleep time and excessive daytime sleepiness. Conclusions: Refinement of the BRFSS questions is recommended. Citation: Jungquist CR, Mund J, Aquilina AT, Klingman K, Pender J, Ochs-Balcom H, van Wijngaarden E, Dickerson SS. Validation of the behavioral risk factor surveillance system sleep questions. J Clin Sleep Med 2016;12(3):301–310. PMID:26446246

  9. A Mini-Twister Variant and Impact of Residues/Cations on the Phosphodiester Cleavage of this Ribozyme Class

    PubMed Central

    Ren, Aiming; Flür, Sara; Wunderlich, Christoph; Mairhofer, Elisabeth; Vušurović, Nikola; Seikowski, Jan; Breuker, Kathrin; Höbartner, Claudia; Patel, Dinshaw J.; Kreutz, Christoph; Micura, Ronald

    2015-01-01

    Nucleolytic ribozymes catalyze site-specific cleavage of their phosphodiester backbones. A minimal version of the twister ribozyme is reported that lacks the phylogenetically conserved stem P1 while retaining wild-type activity. Atomic mutagenesis revealed that nitrogen atoms N1 and N3 of the adenine-6 at the cleavage site are indispensable for cleavage. By NMR spectroscopy, a pKa value of 5.1 was determined for a 13C2-labeled adenine at this position in the twister ribozyme, which is significantly shifted compared to the pKa of the same adenine in the substrate alone. This finding pinpoints at a potential role for adenine-6 in the catalytic mechanism besides the previously identified invariant guanine-48 and a Mg2+ ion, both of which are directly coordinated to the non-bridging oxygen atoms of the scissile phosphate; for the latter, additional evidence stems from the observation that Mn2+ or Cd2+ accelerated cleavage of phosphorothioate substrates. The relevance of this metal ion binding site is further emphasized by a new 2.6 Å X-ray structure of a 2′-OCH3-U5 modified twister ribozyme. PMID:26473980

  10. Electronic and optical excitations in building blocks of the metal organic framework MOF-5

    NASA Astrophysics Data System (ADS)

    Shi, Bin; Hung, Linda; Yildirim, Taner; Ogut, Serdar

    Metal organic frameworks (MOFs) are a relatively new class of materials which are made of metal-oxide clusters linked by organic bridging ligands. In recent years, MOFs have received considerable attention due to their widely tunable structural, chemical and physical properties. We investigate one of the well characterized MOFs, MOF-5, whose framework consists of tetrahedral [Zn40]6+ units linked by rigid arylcarboxylate ligands. We use many-body perturbation (GW +BSE) and time-dependent DFT methods in real space to examine the electronic and optical excitations in the building blocks of MOF-5, such as Zn4O(COOH)6, basic zinc acetate [Zn4O(CH3COO)6], and tetranuclear zinc benzoate [Zn4O(C6H5COO)6]. The calculated spectra are compared with available experimental measurements and existing calculations to shed light on the controversy regarding the nature (metal-ligand versus ligand-ligand) of low-energy electronic and optical excitations in MOF-5. Supported by DOE Grant No. DE-SC0001853.

  11. Energy level alignment and quantum conductance of functionalized metal-molecule junctions: Density functional theory versus GW calculations

    SciTech Connect

    Jin, Chengjun; Markussen, Troels; Thygesen, Kristian S.; Strange, Mikkel; Solomon, Gemma C.

    2013-11-14

    We study the effect of functional groups (CH{sub 3}*4, OCH{sub 3}, CH{sub 3}, Cl, CN, F*4) on the electronic transport properties of 1,4-benzenediamine molecular junctions using the non-equilibrium Green function method. Exchange and correlation effects are included at various levels of theory, namely density functional theory (DFT), energy level-corrected DFT (DFT+Σ), Hartree-Fock and the many-body GW approximation. All methods reproduce the expected trends for the energy of the frontier orbitals according to the electron donating or withdrawing character of the substituent group. However, only the GW method predicts the correct ordering of the conductance amongst the molecules. The absolute GW (DFT) conductance is within a factor of two (three) of the experimental values. Correcting the DFT orbital energies by a simple physically motivated scissors operator, Σ, can bring the DFT conductances close to experiments, but does not improve on the relative ordering. We ascribe this to a too strong pinning of the molecular energy levels to the metal Fermi level by DFT which suppresses the variation in orbital energy with functional group.

  12. Development and validation of a liquid chromatography-mass spectrometric method for the determination of DPC 423, an antithrombotic agent, in rat and dog plasma.

    PubMed

    Chi, Cecilia; Liang, Li; Padovani, Patty; Unger, Steve

    2003-01-01

    A sensitive and selective LC-MS-MS method for the determination of DPC 423 (I), an antithrombotic agent, is described. This method used a solid-phase extraction from 0.1 ml plasma with an Isolute C(2) cartridge. HPLC separation was carried out on a YMC ODS-AQ C(18) column (50x2 mm) at a flow-rate of 300 microliter/min with an analysis time of 5 min. Compounds were eluted using a mobile phase of H(2)O/CH(3)CN/HCOOH: 66:34:0.1 (v/v/v), pH 4.0. A structural analogue of I was used as the internal standard to account for variations in recovery and instrument response. Mass spectrometric detection was carried out with a PE Sciex API III(+) triple quadrupole mass spectrometer equipped with a Turbo IonSpray source as the LC-MS interface. Good intra-day and inter-day assay precision (<10% CV) and accuracy (<10% difference) were observed over a concentration range of 0.005-2.5 microM in plasma. The extraction recoveries were approximately 90% and the method was found to be linear for the assay (r(2)>0.999). The method has been successfully applied to discovery and preclinical pharmacokinetic studies, including a dose range-finding study and toxicokinetic exposure studies in rat and dog. PMID:12450535

  13. In situ simple method for measuring size and density of nanoparticles in reactive plasmas

    SciTech Connect

    Nunomura, Shota; Kita, Makoto; Koga, Kazunori; Shiratani, Masaharu; Watanabe, Yukio

    2006-04-15

    A laser-light-scattering (LLS) method for measuring the size and density of nanoparticles generated in reactive plasmas has been developed. The size and density of the nanoparticles are determined from their thermal coagulation that takes place after turning off the discharge. The measurable size and density range of the LLS method is n{sub p} x 10{sup 13} (m{sup -3/2})xd{sub p}{sup -5/2}L{sup -2}n{sub g}{sup -1}, where n{sub p}, d{sub p}, L, and n{sub g} are the density, size, and diffusion length of the nanoparticles, and the density of a background gas, respectively. The method has been demonstrated by measurement of the size and density of nanoparticles formed by the radio-frequency discharge of dimethyldimethoxysilane Si(CH{sub 3}){sub 2}(OCH{sub 3}){sub 2} diluted with Ar. Using a simple optical setup for the LLS measurement, nanoparticles are detected down to {approx_equal}1 nm in size when they are generated at a density of {approx_equal}10{sup 12} cm{sup -3}. The developed method is widely applicable to other systems in which thermal coagulation takes place.

  14. Temperature-Dependent Rate Constants and Substituent Effects for the Reactions of Hydroxyl Radicals With Three Partially Fluorinated Ethers

    NASA Technical Reports Server (NTRS)

    Hsu, K.-J.; DeMore, W. B.

    1995-01-01

    Rate constants and temperature dependencies for the reactions of OH with CF3OCH3 (HFOC-143a), CF2HOCF2H (HFOC-134), and CF3OCF2H (HFOC-125) were studied using a relative rate technique in the temperature range 298-393 K. The following absolute rate constants were derived: HFOC-143a, 1.9E-12 exp(-1555/T); HFOC-134, 1.9E-12 exp(-2006/T); HFOC-125, 4.7E-13 exp(-2095/T). Units are cm(exp 3)molecule(exp -1) s(exp -1). Substituent effects on OH abstraction rate constants are discussed, and it is shown that the CF3O group has an effect on the OH rate constants similar to that of a fluorine atom. The effects are related to changes in the C-H bond energies of the reactants (and thereby the activation energies) rather than changes in the preexponential factors. On the basis of a correlation of rate constants with bond energies, the respective D(C-H) bond strengths in the three ethers are found to be 102, 104, and 106 kcal/mol, with an uncertainty of about 1 kcal/mol.

  15. The surface chemistry of nanocrystalline MgO catalysts for FAME production: An in situ XPS study of H2O, CH3OH and CH3OAc adsorption

    NASA Astrophysics Data System (ADS)

    Montero, J. M.; Isaacs, M. A.; Lee, A. F.; Lynam, J. M.; Wilson, K.

    2016-04-01

    An in situ XPS study of water, methanol and methyl acetate adsorption over as-synthesised and calcined MgO nanocatalysts is reported with a view to gaining insight into the surface adsorption of key components relevant to fatty acid methyl esters (biodiesel) production during the transesterification of triglycerides with methanol. High temperature calcined NanoMgO-700 adsorbed all three species more readily than the parent material due to the higher density of electron-rich (111) and (110) facets exposed over the larger crystallites. Water and methanol chemisorb over the NanoMgO-700 through the conversion of surface O2 - sites to OH- and coincident creation of Mg-OH or Mg-OCH3 moieties respectively. A model is proposed in which the dissociative chemisorption of methanol occurs preferentially over defect and edge sites of NanoMgO-700, with higher methanol coverages resulting in physisorption over weakly basic (100) facets. Methyl acetate undergoes more complex surface chemistry over NanoMgO-700, with C-H dissociation and ester cleavage forming surface hydroxyl and acetate species even at extremely low coverages, indicative of preferential adsorption at defects. Comparison of C 1s spectra with spent catalysts from tributyrin transesterification suggest that ester hydrolysis plays a key factor in the deactivation of MgO catalysts for biodiesel production.

  16. Fritz Reiche and the Emergency Committee in Aid of Displaced Foreign Scholars

    NASA Astrophysics Data System (ADS)

    Bederson, Benjamin

    2005-12-01

    I discuss the family background and early life of the German theoretical physicist Fritz Reiche (1883 1969) in Berlin; his higher education at the University of Berlin under Max Planck (1858 1947); his subsequent work at the University of Breslau with Otto Lummer (1860 1925); his return to Berlin in 1911, where he completed his Habilitation thesis in 1913, married Bertha Ochs the following year, became a friend of Albert Einstein (1879 1955), and worked during and immediately after the Great War. In 1921 he was appointed as ordentlicher Professor of Theoretical Physics at the University of Breslau and worked there until he was dismissed in 1933. He spent the academic year 1934 1935 as a visiting professor at the German University in Prague and then returned to Berlin, where he remained until, with the crucial help of his friend Rudolf Ladenburg (1882 1952) and vital assistance of the Emergency Committee in Aid of Displaced Foreign Scholars, he, his wife Bertha, and their daughter Eve were able to emigrate to the United States in 1941 (their son Hans had already emigrated to England in 1939).From 1941 1946 he held appointments at the New School for Social Research in New York, the City College of New York, and Union College in Schenectady, New York, and then was appointed as an Adjunct Professor of Physics at New York University, where his contract was renewed year-by-year until his retirement in 1958.

  17. "You produce while I clean up", a strategy revealed by exoproteomics during Synechococcus-Roseobacter interactions.

    PubMed

    Christie-Oleza, Joseph A; Scanlan, David J; Armengaud, Jean

    2015-10-01

    Most of the energy that is introduced into the oceans by photosynthetic primary producers is in the form of organic matter that then sustains the rest of the food web, from micro to macro-organisms. However, it is the interactions between phototrophs and heterotrophs that are vital to maintaining the nutrient balance of marine microbiomes that ultimately feed these higher trophic levels. The primary produced organic matter is mostly remineralized by heterotrophic microorganisms but, because most of the oceanic dissolved organic matter is in the form of biopolymers, and microbial membrane transport systems operate with molecules <0.6 kDa, it must be hydrolyzed outside the cell before a microorganism can acquire it. As a simili of the marine microbiome, we analyzed, using state-of-the-art proteomics, the exoproteomes obtained from synthetic communities combining specific Roseobacter (Ruegeria pomeroyi DSS-3, Roseobacter denitrificans OCh114, and Dinoroseobacter shibae DFL-12) and Synechococcus strains (WH7803 and WH8102). This approach identified the repertoire of hydrolytic enzymes secreted by Roseobacter, opening up the black box of heterotrophic transformation/remineralization of biopolymers generated by marine phytoplankton. As well as highlighting interesting exoenzymes this strategy also allowed us to infer clues on the molecular basis of niche partitioning.

  18. Complex molecule formation around massive young stellar objects.

    PubMed

    Oberg, Karin I; Fayolle, Edith C; Reiter, John B; Cyganowski, Claudia

    2014-01-01

    Interstellar complex organic molecules were first identified in the hot inner regions of massive young stellar objects (MYSOs), but have more recently been found in many colder sources, indicating that complex molecules can form at a range of temperatures. However, individually these observations provide limited constraints on how complex molecules form, and whether the same formation pathways dominate in cold, warm and hot environments. To address these questions, we use spatially resolved observations from the Submillimeter Array of three MYSOs together with mostly unresolved literature data to explore how molecular ratios depend on environmental parameters, especially temperature. Towards the three MYSOs, we find multiple complex organic emission peaks characterized by different molecular compositions and temperatures. In particular, CH3CCH and CH3CN seem to always trace a lukewarm (T = 60 K) and a hot (T > 100 K) complex chemistry, respectively. These spatial trends are consistent with abundance-temperature correlations of four representative complex organics--CH3CCH, CH3CN, CH3OCH3 and CH3CHO--in a large sample of complex molecule hosts mined from the literature. Together, these results indicate a general chemical evolution with temperature, i.e. that new complex molecule formation pathways are activated as a MYSO heats up. This is qualitatively consistent with model predictions. Furthermore, these results suggest that ratios of complex molecules may be developed into a powerful probe of the evolutionary stage of a MYSO, and may provide information about its formation history. PMID:25302375

  19. Atomic vapour deposition (AVD) of SrBi 2Ta 2O 9 using an all alkoxide precursor

    NASA Astrophysics Data System (ADS)

    Chalker, Paul R.; Potter, Richard J.; Roberts, John L.; Jones, Anthony C.; Smith, Lesley M.; Schumacher, Marcus

    2004-12-01

    A "single-source" Sr-Ta heterometal alkoxide precursor, Sr[Ta(OEt) 5(dmae)] 2 (dmae=OCH 2CH 2NMe 2), has been used for atomic vapour deposition (AVD) of SrBi 2Ta 2O 9 (SBT). This single-source precursor is designed to alleviate the mismatch between conventional Sr and Ta sources. Strontium tantalate thin films were deposited on silicon using the Sr[Ta(OEt) 5(dmae)] 2, and the optimum temperatures for deposition of strontium tantalate with a Sr:Ta ratio of 0.5 was found to be ˜510 °C. Deposition of Bi-oxide films using Bi(mmp) 3 (mmp=OCMe 2CH 2OMe) indicates similar decomposition behaviour to the Sr-Ta alkoxide precursor, demonstrating its suitability as a complementary source of Bi for SBT. The co-incorporation of Bi and Sr within the SBT films is promoted through the deposition of bismuth oxide/strontium tantalate super lattices. After post-growth annealing the super lattices are converted to strontium bismuth tantalate thin films.

  20. The two faces of hydrogen-bond strength on triple AAA-DDD arrays.

    PubMed

    Lopez, Alfredo Henrique Duarte; Caramori, Giovanni Finoto; Coimbra, Daniel Fernando; Parreira, Renato Luis Tame; da Silva, Éder Henrique

    2013-12-01

    Systems that are connected through multiple hydrogen bonds are the cornerstone of molecular recognition processes in biology, and they are increasingly being employed in supramolecular chemistry, specifically in molecular self-assembly processes. For this reason, the effects of different substituents (NO2, CN, F, Cl, Br, OCH3 and NH2) on the electronic structure, and consequently on the magnitude of hydrogen bonds in triple AAA-DDD arrays (A=acceptor, D=donor) were evaluated in the light of topological [electron localization function (ELF) and quantum theory of atoms in molecules (QTAIM)], energetic [Su-Li energy-decomposition analysis (EDA) and natural bond orbital analysis (NBO)], and geometrical analysis. The results based on local H-bond descriptors (geometries, QTAIM, ELF, and NBO) indicate that substitutions with electron-withdrawing groups on the AAA module tend to strengthen, whereas electron-donating substituents tend to weaken the covalent character of the AAA-DDD intermolecular H-bonds, and also indicate that the magnitude of the effect is dependent on the position of substitution. In contrast, Su-Li EDA results show an opposite behavior when compared to local H-bond descriptors, indicating that electron-donating substituents tend to increase the magnitude of H-bonds in AAA-DDD arrays, and thus suggesting that the use of local H-bond descriptors describes the nature of H bonds only partially, not providing enough insight about the strength of such H bonds.