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Sample records for adjacent aromatic rings

  1. Optimization of low ring polycylic aromatic biodegradation

    NASA Astrophysics Data System (ADS)

    Othman, N.; Abdul-Talib, S.; Tay, C. C.

    2016-07-01

    Polycyclic aromatic hydrocarbons (PAHs) are recalcitrance and persistence that finally turn into problematic environmental contaminants. Microbial degradation is considered to be the primary mechanism of PAHs removal from the environment due to its organic criteria. This study is carried out to optimize degradation process of low ring PAHs. Bacteria used in this study was isolated from sludge collected from Kolej Mawar, Universiti Teknologi MARA, Shah Alam, Selangor. Working condition namely, substrate concentration, bacteria concentration, pH and temperature were optimized. PAHs in the liquid sample was extracted by using solid phase microextractio equipped with a 7 µm polydimethylsiloxane (PDMS) SPME fibr. Removal of PAHs were assessed by measuring PAHs concentration using GC-FID. Results from the optimization study of biodegradation indicated that maximum rate of PAHs removal occurred at 100 mgL-1 of PAHs, 10% bacteria concentration, pH 7.0 and 30°C. These working condition had proved the effectiveness of using bacteria in biodegradation process of PAHs.

  2. Redox shuttles having an aromatic ring fused to a 1,1,4,4-tetrasubstituted cyclohexane ring

    SciTech Connect

    Weng, Wei; Zhang, Zhengcheng; Amine, Khalil

    2015-12-01

    An electrolyte includes an alkali metal salt; an aprotic solvent; and a redox shuttle additive including an aromatic compound having at least one aromatic ring fused with at least one non-aromatic ring, the aromatic ring having two or more oxygen or phosphorus-containing substituents.

  3. Aromatic rings in chemical and biological recognition: energetics and structures.

    PubMed

    Salonen, Laura M; Ellermann, Manuel; Diederich, François

    2011-05-16

    This review describes a multidimensional treatment of molecular recognition phenomena involving aromatic rings in chemical and biological systems. It summarizes new results reported since the appearance of an earlier review in 2003 in host-guest chemistry, biological affinity assays and biostructural analysis, data base mining in the Cambridge Structural Database (CSD) and the Protein Data Bank (PDB), and advanced computational studies. Topics addressed are arene-arene, perfluoroarene-arene, S⋅⋅⋅aromatic, cation-π, and anion-π interactions, as well as hydrogen bonding to π systems. The generated knowledge benefits, in particular, structure-based hit-to-lead development and lead optimization both in the pharmaceutical and in the crop protection industry. It equally facilitates the development of new advanced materials and supramolecular systems, and should inspire further utilization of interactions with aromatic rings to control the stereochemical outcome of synthetic transformations. PMID:21538733

  4. Iterative Reductive Aromatization/Ring-Closing Metathesis Strategy toward the Synthesis of Strained Aromatic Belts.

    PubMed

    Golder, Matthew R; Colwell, Curtis E; Wong, Bryan M; Zakharov, Lev N; Zhen, Jingxin; Jasti, Ramesh

    2016-05-25

    The construction of all sp(2)-hybridized molecular belts has been an ongoing challenge in the chemistry community for decades. Despite numerous attempts, these double-stranded macrocycles remain outstanding synthetic challenges. Prior approaches have relied on late-state oxidations and/or acid-catalyzed processes that have been incapable of accessing the envisaged targets. Herein, we describe the development of an iterative reductive aromatization/ring-closing metathesis approach. Successful syntheses of nanohoop targets containing benzo[k]tetraphene and dibenzo[c,m]pentaphene moieties not only provide proof of principle that aromatic belts can be derived by this new strategy but also represent some of the largest aromatic belt fragments reported to date. PMID:27133789

  5. Interactions between manganese oxides and multiple-ringed aromatic compounds

    SciTech Connect

    Whelan, G. ); Sims, R.C. . Dept. of Civil and Environmental Engineering)

    1992-08-01

    Objective is to determine whether Mn reductive dissolution can oxidize multiple-ringed aromatics, such as PAHs, in an oxic environment Research indicated that certain PAHs (eg, dihydrodiols and diones that form free-radical intermediates) are susceptible to oxidation and polymerization. Over 14 days, 83, 76, 54, 70, and 20% of the Mn was reduced by 2,3-, 1,3-, and 1,4-naphthalenediol, quinizarin, and 1,4-naphthoquinone, respectively. 100, 100, and 65% of the first three PAHs were oxidized, respectively. Aromatics with diol functional groups were more easily oxidized than those with only dione groups. Relatively insoluble compounds like quinizarin can be oxidized; insoluble ''humic-like'' material precipitated, indicating a polymerization-humification process. Results suggest that electron transfer/organic release from the oxide surface is the rate-limiting step.

  6. Interactions between manganese oxides and multiple-ringed aromatic compounds

    SciTech Connect

    Whelan, G.; Sims, R.C.

    1992-08-01

    Objective is to determine whether Mn reductive dissolution can oxidize multiple-ringed aromatics, such as PAHs, in an oxic environment? Research indicated that certain PAHs (eg, dihydrodiols and diones that form free-radical intermediates) are susceptible to oxidation and polymerization. Over 14 days, 83, 76, 54, 70, and 20% of the Mn was reduced by 2,3-, 1,3-, and 1,4-naphthalenediol, quinizarin, and 1,4-naphthoquinone, respectively. 100, 100, and 65% of the first three PAHs were oxidized, respectively. Aromatics with diol functional groups were more easily oxidized than those with only dione groups. Relatively insoluble compounds like quinizarin can be oxidized; insoluble ``humic-like`` material precipitated, indicating a polymerization-humification process. Results suggest that electron transfer/organic release from the oxide surface is the rate-limiting step.

  7. Local aromaticity in naphtho-annelated fluoranthenes: can the five-membered rings be more aromatic than the six-membered rings?

    PubMed

    Radenković, Slavko; Tošović, Jelena; Đurđević Nikolić, Jelena

    2015-05-21

    All Kekulé-structure-based theories predict that the central five-membered ring in fluoranthene and naphtho-annelated fluoranthenes is nonaromatic. In the present work, a detailed study of the local aromaticity in a series of naphtho-annelated fluoranthene derivatives was performed by means of the following aromaticity indices: the energy effect (ef), bond resonance energy (BRE), multicenter delocalization indices (MCI), harmonic oscillator model of aromaticity (HOMA) index, nucleus-independent chemical shifts (NICS), and ring current maps. It was found that, according to the ef, BRE, MCI, and HOMA values, the pentagonal rings in some naphtho-annelated fluoranthenes can be even more aromatic than some hexagonal rings in the respective molecules. The magnetic indices do not support the results obtained by the energetic, electron delocalization, and geometrical aromaticity indices. PMID:25915757

  8. Polycyclic aromatic hydrocarbons in suspended particulate matter and sediments from the Pearl River Estuary and adjacent coastal areas, China.

    PubMed

    Luo, Xiao-Jun; Chen, She-Jun; Mai, Bi-Xian; Yang, Qing-Shu; Sheng, Guo-Ying; Fu, Jia-Mo

    2006-01-01

    The spatial distribution, composition, and sources of polycyclic aromatic hydrocarbons (PAHs) in sediments and suspended particulate matter (SPM) from the Pearl River Estuary and adjacent coastal areas were examined. Total PAH concentrations varied from 189 to 637 ng/g in sediments and 422 to 1,850 ng/g in SPM. PAHs were dominated by 5,6-ring compounds in sediments and by 2,3-ring compounds in SPM samples. Assessment of PAH sources suggested that biomass and coal combustion is the major PAH source to the outer part of the estuary sediments and that petroleum combustion is the major PAH source to the inner part of estuary sediments. As for SPM samples, PAH isomer pair ratios indicated multiple (petroleum, petroleum combustion, and biomass and coal combustion) PAH sources, and significant temporal variations could exist for the sources of water column PAHs in the study area. The distribution of perylene in SPM samples indicated that the river was the dominant source of perylene in SPM and that perylene could be taken as an index to assess the contribution of river inflow to the total PAHs in SPM samples. The high concentration of perylene in the sediment was indicative of an in situ biogenic origin. PMID:15996803

  9. On the question of aromatic ring expansion-contraction for conversions with a ZSM-5 catalyst

    SciTech Connect

    Dabbagh, H.A.; Davis, B.H. )

    1991-01-01

    Toluene, labeled with {sup 14}C in either the methyl position or uniformly in the aromatic ring, did not undergo a measurable amount of either ring expansion-contraction or ring degradation to produce ethene at temperatures up to 350{degrees}C. Ethylbenzene dealkylation and disproportionation and xylene isomerization occur to produce equilibrium mixtures of diethylbenzenes or xylenes under these reaction conditions; hence, ring expansion-contraction must be much slower than these isomerization reactions.

  10. Polyimides with carbonyl and ether connecting groups between the aromatic rings

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Havens, Stephen J. (Inventor)

    1992-01-01

    New polyimides have been prepared from the reaction of aromatic dianhydrides with novel aromatic diamines containing carbonyl and ether connecting groups between the aromatic rings. Several of these polyimides are shown to be semi-crystalline as evidenced by wide angle x ray diffraction and differential scanning calorimetry. Most of the polyimides form tough solvent resistant films with high tensile properties. Several of these materials can be thermally processed to form solvent and base resistant moldings.

  11. A Multistep Synthesis Incorporating a Green Bromination of an Aromatic Ring

    ERIC Educational Resources Information Center

    Cardinal, Pascal; Greer, Brandon; Luong, Horace; Tyagunova, Yevgeniya

    2012-01-01

    Electrophilic aromatic substitution is a fundamental topic taught in the undergraduate organic chemistry curriculum. A multistep synthesis that includes a safer and greener method for the bromination of an aromatic ring than traditional bromination methods is described. This experiment is multifaceted and can be used to teach students about…

  12. Synthesis of Carbazole Alkaloids by Ring-Closing Metathesis and Ring Rearrangement-Aromatization.

    PubMed

    Dhara, Kalyan; Mandal, Tirtha; Das, Joydeb; Dash, Jyotirmayee

    2015-12-21

    Aprocess for the assembly of carbazole alkaloids has been developed on the basis of ring-closing metathesis (RCM) and ringrearrangement-aromatization (RRA) as the key steps. This method is based on allyl Grignard addition to isatin derivatives to provide smooth access to 2,2-diallyl 3-oxindole derivatives through a 1,2-allyl shift. The diallyl derivatives were used as RCM precursors to afford a novel class of spirocyclopentene-3-oxindole derivatives, which underwent a novel RRA reaction to afford carbazole derivatives. The synthetic sequence to carbazoles was shortened by combining the RCM and RRA steps in an orthogonal tandem catalytic process. The utility of this methodology was further demonstrated by the straightforward synthesis of carbazole alkaloids, including amukonal derivative, girinimbilol, heptaphylline, and bis(2-hydroxy-3-methylcarbazole). PMID:26768698

  13. The Misuse of the Circle Notation to Represent Aromatic Rings.

    ERIC Educational Resources Information Center

    Belloli, Robert C.

    1983-01-01

    Discusses the confusion and erroneous conclusions that can result from the overuse and misuse of the circle notation to represent aromaticity in polycylic aromatic hydrocarbons. Includes nature of the problem, textbook treatment, and a possible compromise method of representation. (Author/JN)

  14. Vibrational effects on UV/Vis laser-driven π-electron ring currents in aromatic ring molecules

    NASA Astrophysics Data System (ADS)

    Mineo, H.; Lin, S. H.; Fujimura, Y.

    2014-10-01

    We present the results of a theoretical study of vibrational effects on UV/Vis laser-driven π-electron ring currents in aromatic ring molecules. We consider vibrational effects on both coherent and non-coherent (single quantum state) ring currents. The coherent ring current originates from an excitation of a pair of quasi-degenerate electronic states by an ultrashort linearly polarized UV/Vis laser pulse, while the non-coherent ring current originates from by an excitation of a degenerated electronic state of an aromatic ring molecule with high symmetry by a circularly polarized electric field of a UV/Vis laser pulse. The magnitude of a generated ring current can be expressed as an average of those of the bond currents for both the coherent and non-coherent cases. We derive an analytical expression for the magnitude of the bond currents in the adiabatic approximation. Using the expression, we performed calculations of a non-coherent ring current generated in the optically allowed excited state (1E1U) of benzene and the time evolution of coherent ring current of (P)-2,2-biphenol. Vibrational effects on the non-coherent ring current of benzene were found to be negligibly small. We paid particular attention to the vibrational effects induced by the torsion mode on time evolution of the coherent ring current along the bond bridging between the two aromatic rings of (P)-2,2-biphenol. By comparing the time evolution of the coherent ring current with that in the frozen-nuclear approximation, we found that inclusion of the low-frequency torsion mode brings about modulations in the beating in the ring current. The modulations in the time evolution of the coherent ring current were brought about by contribution of several pairs of the coherently excited vibronic states. Coherent vibronic ring currents generated from pairs of the coherently excited vibronic states interfere each other. The existence of the pairs originates from relatively large potential displacement of the

  15. No-carrier-added (NCA) aryl ([sup 18]F) fluorides via the nucleophilic aromatic substitution of electron rich aromatic rings

    DOEpatents

    Yushin Ding; Fowler, J.S.; Wolf, A.P.

    1993-10-19

    A method for synthesizing no-carrier-added (NCA) aryl [.sup.18 F] fluoride substituted aromatic aldehyde compositions bearing an electron donating group is described. The method of the present invention includes the step of reacting aromatic nitro aldehydes having a suitably protected hydroxyl substitutent on an electron rich ring. The reaction is The U.S. Government has rights in this invention pursuant to Contract Number DE-AC02-76CH00016, between the U.S. Department of Energy and Associated Universities Inc.

  16. No-carrier-added (NCA) aryl (18E) fluorides via the nucleophilic aromatic substitution of electron rich aromatic rings

    DOEpatents

    Ding, Yu-Shin; Fowler, Joanna S.; Wolf, Alfred P.

    1993-01-01

    A method for synthesizing no-carrier-added (NCA) aryl [.sup.18 F] fluoride substituted aromatic aldehyde compositions bearing an electron donating group is described. The method of the present invention includes the step of reacting aromatic nitro aldehydes having a suitably protected hydroxyl substitutent on an electron rich ring. The reaction is The U.S. Government has rights in this invention pursuant to Contract Number DE-AC02-76CH00016, between the U.S. Department of Energy and Associated Universities Inc.

  17. σ-Aromaticity in an unsaturated ring: osmapentalene derivatives containing a metallacyclopropene unit.

    PubMed

    Zhu, Congqing; Zhou, Xiaoxi; Xing, Hongjie; An, Ke; Zhu, Jun; Xia, Haiping

    2015-03-01

    In general, aromaticity can be clarified as π- and σ-aromaticity according to the type of electrons with major contributions. The traditional π-aromaticity generally describes the π-conjugation in fully unsaturated rings whereas σ-aromaticity may stabilize fully saturated rings with delocalization caused by σ-electron conjugation. Reported herein is an example of σ-aromaticity in an unsaturated three-membered ring (3 MR), which is supported by experimental observations and theoretical calculations. Specifically, when the 3 MR in cyclopropaosmapentalene is cleaved by ethane through two isodesmic reactions, both of them are highly endothermic (+29.7 and +35.0 kcal mol(-1)). These positive values are in sharp contrast to the expected exothermicity, thus indicating aromaticity in the 3 MR. Further nucleus-independent chemical shift and anisotropy of the current-induced density calculations reveal the nature of σ-aromaticity in the unsaturated 3 MR. PMID:25656694

  18. Stabilization of anti-aromatic and strained five-membered rings with a transition metal

    NASA Astrophysics Data System (ADS)

    Zhu, Congqing; Li, Shunhua; Luo, Ming; Zhou, Xiaoxi; Niu, Yufen; Lin, Minglian; Zhu, Jun; Cao, Zexing; Lu, Xin; Wen, Tingbin; Xie, Zhaoxiong; Schleyer, Paul V. R.; Xia, Haiping

    2013-08-01

    Anti-aromatic compounds, as well as small cyclic alkynes or carbynes, are particularly challenging synthetic goals. The combination of their destabilizing features hinders attempts to prepare molecules such as pentalyne, an 8π-electron anti-aromatic bicycle with extremely high ring strain. Here we describe the facile synthesis of osmapentalyne derivatives that are thermally viable, despite containing the smallest angles observed so far at a carbyne carbon. The compounds are characterized using X-ray crystallography, and their computed energies and magnetic properties reveal aromatic character. Hence, the incorporation of the osmium centre not only reduces the ring strain of the parent pentalyne, but also converts its Hückel anti-aromaticity into Craig-type Möbius aromaticity in the metallapentalynes. The concept of aromaticity is thus extended to five-membered rings containing a metal-carbon triple bond. Moreover, these metal-aromatic compounds exhibit unusual optical effects such as near-infrared photoluminescence with particularly large Stokes shifts, long lifetimes and aggregation enhancement.

  19. A new aromatic probe - The ring stretching vibration Raman spectroscopy frequency.

    PubMed

    Guo, Yan-Bo; Liu, Zi-Zhong; Liu, Hong-Xia; Zhang, Feng-Ying; Yin, Jun-Qing

    2016-07-01

    A new aromatic criterion is presented to determine the aromatic degree of the high symmetric molecules. Group theory is used to explain the correlation between the aromatic degree and the value of Ring Stretching Vibration Raman Spectroscopic Frequency (RSVRSF). The calculations of the geometrical optimization, nucleus-independent chemical shifts (NICS) and values of the Raman Spectroscopy for the aromatic molecules-LnHn (L=C, Si, Ge, n=3, 5-8) were performed using the Density Functional Theory (DFT) Method, as well as the correlations between the values of their RSVRSF and NICS values by Statistic Package for Social Science (SPSS17.0). There are high positive correlations between the theoretical calculated the NICS values and the value of the RSVRSF (A1g/A1') of the LnHn (L=C, Si, Ge, n=3, 5-8). The bigger the aromatic degree, the bigger the RSVRSF is. The value of the RSVRSF is a new probe of aromaticity. Expectedly, it is predicted that the experimental determination of the aromatic degree can be achieved by the determination of the ring stretching vibration (A1g/A1') Raman spectrum frequencies for the aromatic target molecules. PMID:27085169

  20. A new aromatic probe - The ring stretching vibration Raman spectroscopy frequency

    NASA Astrophysics Data System (ADS)

    Guo, Yan-bo; Liu, Zi-zhong; Liu, Hong-xia; Zhang, Feng-ying; Yin, Jun-qing

    2016-07-01

    A new aromatic criterion is presented to determine the aromatic degree of the high symmetric molecules. Group theory is used to explain the correlation between the aromatic degree and the value of Ring Stretching Vibration Raman Spectroscopic Frequency (RSVRSF). The calculations of the geometrical optimization, nucleus-independent chemical shifts (NICS) and values of the Raman Spectroscopy for the aromatic molecules-LnHn (L = C, Si, Ge, n = 3, 5-8) were performed using the Density Functional Theory (DFT) Method, as well as the correlations between the values of their RSVRSF and NICS values by Statistic Package for Social Science (SPSS17.0). There are high positive correlations between the theoretical calculated the NICS values and the value of the RSVRSF (A1g/A1‧) of the LnHn (L = C, Si, Ge, n = 3, 5-8). The bigger the aromatic degree, the bigger the RSVRSF is. The value of the RSVRSF is a new probe of aromaticity. Expectedly, it is predicted that the experimental determination of the aromatic degree can be achieved by the determination of the ring stretching vibration (A1g/A1‧) Raman spectrum frequencies for the aromatic target molecules.

  1. Δg: The new aromaticity index based on g-factor calculation applied for polycyclic benzene rings

    NASA Astrophysics Data System (ADS)

    Ucun, Fatih; Tokatlı, Ahmet

    2015-02-01

    In this work, the aromaticity of polycyclic benzene rings was evaluated by the calculation of g-factor for a hydrogen placed perpendicularly at geometrical center of related ring plane at a distance of 1.2 Å. The results have compared with the other commonly used aromatic indices, such as HOMA, NICSs, PDI, FLU, MCI, CTED and, generally been found to be in agreement with them. So, it was proposed that the calculation of the average g-factor as Δg could be applied to study the aromaticity of polycyclic benzene rings without any restriction in the number of benzene rings as a new magnetic-based aromaticity index.

  2. A sharp thermal transition of fast aromatic ring dynamics in ubiquitin

    PubMed Central

    Kasinath, Vignesh; Fu, Yinan; Sharp, Kim A.

    2015-01-01

    Aromatic amino acid side chains have a rich role within proteins and are often central to their structure and function. Suitable isotopic labelling strategies enable studies of sub-nanosecond aromatic ring dynamics using solution NMR relaxation methods. Surprisingly, we find that the three aromatic side chains in human ubiquitin show a sharp thermal dynamical transition at ~312 K. Hydrostatic pressure has little effect on the low temperature behaviour but decreases somewhat the amplitude of motion in the high temperature regime. Thus below the transition temperature ring motion is largely librational. Above it complete ring rotation that is most consistent with a continuous rotational diffusion not requiring transient creation of a large activated free volume occurs. Molecular dynamics simulations qualitatively corroborate this view and reinforce the notion that the dynamical character of the protein interior has a much more liquid alkane-like properties than previously appreciated. PMID:25476230

  3. Cobalt-catalyzed one-step assembly of B-ring aromatic steroids from acyclic precursors

    SciTech Connect

    Lecker, S.H.; Nguyen, N.H.; Vollhardt, K.P.C.

    1986-02-19

    Because of their varied physiological activity, steroids are important testing grounds on which to explore the utility of novel synthetic methodology. In this study cobalt, in the form of CpCo(CO)/sub 2/ is used as a matrix around which to assemble natural and unnatural polycyclic products, including the steroid nucleus. In this way, the total synthesis of A-ring aromatic systems of the estrone type was achieved via the D ..-->.. ABCD and A ..-->.. ABCD strategies. An approach is reported here in which all four rings are assembled (0 ..-->.. ABCD) in one step to give B-ring aromatic derivatives with complete control of the crucial stereochemistry of the C,D-ring juncture. This strategy has been accomplished previously only by employing biomimetic cyclizations and not en route to the rate target class of compounds which has never been constructed by total synthesis. 13 references, 1 table.

  4. Aromatic character of planar boron-based clusters revisited by ring current calculations.

    PubMed

    Pham, Hung Tan; Lim, Kie Zen; Havenith, Remco W A; Nguyen, Minh Tho

    2016-04-28

    The planarity of small boron-based clusters is the result of an interplay between geometry, electron delocalization, covalent bonding and stability. These compounds contain two different bonding patterns involving both σ and π delocalized bonds, and up to now, their aromaticity has been assigned mainly using the classical (4N + 2) electron count for both types of electrons. In the present study, we reexplored the aromatic feature of different types of planar boron-based clusters making use of the ring current approach. B3(+/-), B4(2-), B5(+/-), B6, B7(-), B8(2-), B9(-), B10(2-), B11(-), B12, B13(+), B14(2-) and B16(2-) are characterized by magnetic responses to be doubly σ and π aromatic species in which the π aromaticity can be predicted using the (4N + 2) electron count. The triply aromatic character of B12 and B13(+) is confirmed. The π electrons of B18(2-), B19(-) and B20(2-) obey the disk aromaticity rule with an electronic configuration of [1σ(2)1π(4)1δ(4)2σ(2)] rather than the (4N + 2) count. The double aromaticity feature is observed for boron hydride cycles including B@B5H5(+), Li7B5H5 and M@BnHn(q) clusters from both the (4N + 2) rule and ring current maps. The double π and σ aromaticity in carbon-boron planar cycles B7C(-), B8C, B6C2, B9C(-), B8C2 and B7C3(-) is in conflict with the Hückel electron count. This is also the case for the ions B11C5(+/-) whose ring current indicators suggest that they belong to the class of double aromaticity, in which the π electrons obey the disk aromaticity characteristics. In many clusters, the classical electron count cannot be applied, and the magnetic responses of the electron density expressed in terms of the ring current provide us with a more consistent criterion for determining their aromatic character. PMID:26956732

  5. Synthesis of Aromatic Aza-metallapentalenes from Metallabenzene via Sequential Ring Contraction/Annulation

    PubMed Central

    Wang, Tongdao; Han, Feifei; Huang, Haiping; Li, Jinhua; Zhang, Hong; Zhu, Jun; Lin, Zhenyang; Xia, Haiping

    2015-01-01

    The concept of aromaticity has long played an important role in chemistry and continues to fascinate both experimentalists and theoreticians. Among the archetypal aromatic compounds, heteroaromatics are particularly attractive. Recently, substitution of a transition-metal fragment for a carbon atom in the anti-aromatic hydrocarbon pentalene has led to the new heteroaromatic osmapentalenes. However, construction of the aza-homolog of osmapentalenes cannot be accomplished by a similar synthetic manipulation. Here, we report the synthesis of aza-osmapentalenes by sequential ring contraction/annulation reactions of osmabenzenes via osmapentafulvenes. Nuclear magnetic resonance spectra, X-ray crystallographic analysis, and DFT calculations all suggest that these aza-osmapentalenes exhibit aromatic character. Thus, the stepwise transformation of metallabenzenes to metallapentafulvenes and then aza-metallapentalenes provides an efficient and facile synthetic route to these bicyclic heteroaromatics. PMID:25856747

  6. Formylation of electron-rich aromatic rings mediated by dichloromethyl methyl ether and TiCl4: scope and limitations.

    PubMed

    Ramos-Tomillero, Iván; Paradís-Bas, Marta; de Pinho Ribeiro Moreira, Ibério; Bofill, Josep María; Nicolás, Ernesto; Albericio, Fernando

    2015-01-01

    Here the aromatic formylation mediated by TiCl4 and dichloromethyl methyl ether previously described by our group has been explored for a wide range of aromatic rings, including phenols, methoxy- and methylbenzenes, as an excellent way to produce aromatic aldehydes. Here we determine that the regioselectivity of this process is highly promoted by the coordination between the atoms present in the aromatic moiety and those in the metal core. PMID:25822080

  7. Hydrogen/deuterium exchange on aromatic rings during atmospheric pressure chemical ionization mass spectrometry.

    PubMed

    Davies, Noel W; Smith, Jason A; Molesworth, Peter P; Ross, John J

    2010-04-15

    It has been demonstrated that substituted indoles fully labelled with deuterium on the aromatic ring can undergo substantial exchange back to partial and even fully protonated forms during atmospheric pressure chemical ionisation (APCI) liquid chromatography/mass spectrometry (LC/MS). The degree of this exchange was strongly dependent on the absolute quantity of analyte, the APCI desolvation temperature, the nature of the mobile phase, the mobile phase flow rate and the instrument used. Hydrogen/deuterium (H/D) exchange on several other aromatic ring systems during APCI LC/MS was either undetectable (nitrobenzene, aniline) or extremely small (acetanilide) compared to the effect observed for substituted indoles. This observation has major implications for quantitative assays using deuterium-labelled internal standards and for the detection of deuterium-labelled products from isotopically labelled feeding experiments where there is a risk of back exchange to the protonated form during the analysis. PMID:20213724

  8. Secondary Structures in a Freeze-Dried Lignite Humic Acid Fraction Caused by Hydrogen-Bonding of Acidic Protons with Aromatic Rings.

    PubMed

    Cao, Xiaoyan; Drosos, Marios; Leenheer, Jerry A; Mao, Jingdong

    2016-02-16

    A lignite humic acid (HA) was separated from inorganic and non-HA impurities (i.e., aluminosilicates, metals) and fractionated by a combination of dialysis and XAD-8 resin. Fractionation revealed a more homogeneous structure of lignite HA. New and more specific structural information on the main lignite HA fraction is obtained by solid-state nuclear magnetic resonance (NMR) spectroscopy. Quantitative (13)C multiple cross-polarization (multiCP) NMR indicated oxidized phenyl propane structures derived from lignin. MultiCP experiments, conducted on potassium HA salts titrated to pH 10 and pH 12, revealed shifts consistent with carboxylate and phenolate formation, but structural changes associated with enolate formation from aromatic beta keto acids were not detected. Two-dimensional (1)H-(13)C heteronuclear correlation (2D HETCOR) NMR indicated aryl-aliphatic ketones, aliphatic and aromatic carboxyl groups, phenol, and methoxy phenyl ethers. Acidic protons from carboxyl groups in both the lignite HA fraction and a synthetic HA-like polycondensate were found to be hydrogen-bonded with electron-rich aromatic rings. Our results coupled with published infrared spectra provide evidence for the preferential hydrogen bonding of acidic hydrogens with electron-rich aromatic rings rather than adjacent carbonyl groups. These hydrogen-bonding interactions likely result from stereochemical arrangements in primary structures and folding. PMID:26836017

  9. Cation induced electrochromism in 2,4-dinitrophenylhydrazine (DNPH): Tuning optical properties of aromatic rings

    NASA Astrophysics Data System (ADS)

    Sanader, Željka; Brunet, Claire; Broyer, Michel; Antoine, Rodolphe; Dugourd, Philippe; Mitrić, Roland; Bonačić-Koutecký, Vlasta

    2013-05-01

    We have theoretically investigated the influence of protons and noble metal cations on optical properties of 2,4-dinitrophenylhydrazine (DNPH). We show that optical properties of aromatic rings can be tuned by cation-induced electrochromism in DNPH due to binding to specific NO2 groups. Our findings on cation-induced electrochromism in DNPH may open new routes in two different application areas, due to the fact that DNPH can easily bind to biological molecules and surface materials through carbonyl groups.

  10. Differential Degradation of Bicyclics with Aromatic and Alicyclic Rings by Rhodococcus sp. Strain DK17 ▿

    PubMed Central

    Kim, Dockyu; Yoo, Miyoun; Choi, Ki Young; Kang, Beom Sik; Kim, Tai Kyoung; Hong, Soon Gyu; Zylstra, Gerben J.; Kim, Eungbin

    2011-01-01

    The metabolically versatile Rhodococcus sp. strain DK17 is able to grow on tetralin and indan but cannot use their respective desaturated counterparts, 1,2-dihydronaphthalene and indene, as sole carbon and energy sources. Metabolite analyses by gas chromatography-mass spectrometry and nuclear magnetic resonance spectrometry clearly show that (i) the meta-cleavage dioxygenase mutant strain DK180 accumulates 5,6,7,8-tetrahydro-1,2-naphthalene diol, 1,2-indene diol, and 3,4-dihydro-naphthalene-1,2-diol from tetralin, indene, and 1,2-dihydronaphthalene, respectively, and (ii) when expressed in Escherichia coli, the DK17 o-xylene dioxygenase transforms tetralin, indene, and 1,2-dihydronaphthalene into tetralin cis-dihydrodiol, indan-1,2-diol, and cis-1,2-dihydroxy-1,2,3,4-tetrahydronaphthalene, respectively. Tetralin, which is activated by aromatic hydroxylation, is degraded successfully via the ring cleavage pathway to support growth of DK17. Indene and 1,2-dihydronaphthalene do not serve as growth substrates because DK17 hydroxylates them on the alicyclic ring and further metabolism results in a dead-end metabolite. This study reveals that aromatic hydroxylation is a prerequisite for proper degradation of bicyclics with aromatic and alicyclic rings by DK17 and confirms the unique ability of the DK17 o-xylene dioxygenase to perform distinct regioselective hydroxylations. PMID:21965391

  11. Comparison of Intramolecular Forces in Dipeptides with Two Aromatic Rings: does Dispersion Dominate?

    NASA Astrophysics Data System (ADS)

    Thomas, Jessica A.

    2015-06-01

    IR/UV double resonance spectroscopy has shown that the structure of the capped dipeptide Ac-Trp-Tyr-NH2 is dominated by a hydrophobic interaction between the aromatic rings on the side chains. Using the same method, a similar molecule, Ac-Phe-Phe-NH2, had three experimentally observed conformers including one similar to that of Ac-Trp-Tyr-NH2. In this work, calculations were performed on additional dipeptides containing two aromatic rings to determine if the dispersion-dominated structure was among the lowest energy structures in all such cases. The B3LYP-DCP method developed by DiLabio and Torres was used to calculate the conformations of each dipeptide. Appending dispersion correction potentials (DCP) to B3LYP input files improves results for systems containing dispersion interactions without significantly increasing the calculation time. This method was used first on Ac-Trp-Tyr-NH2 and Ac-Phe-Phe-NH2 to confirm that it successfully identified the experimentally observed structures among the lowest energy results and was then applied to other capped dipeptides containing two aromatic rings including Ac-Phe-Tyr-NH2 and Ac-Tyr-Phe-NH2.

  12. SYNTHESIS AND BIOLOGICAL ACTIVITY OF CYCLOPENTA EPOXIDES OF PAH (POLYCYCLIC AROMATIC HYDROCARBONS) CONTAINING PERIPHERALLY FUSED CYCLOPENTA RINGS

    EPA Science Inventory

    Polycyclic aromatic hydrocarbons (PAH) containing peripherally fused cyclopenta rings have been identified in soots from many different combustion sources. Metabolism and mutagenicity studies have been reported on the series of four cyclopenta-fused isomers derived from benzanthr...

  13. Distribution and ecological risk assessment of polycyclic aromatic hydrocarbons in water, suspended particulate matter and sediment from Daliao River estuary and the adjacent area, China.

    PubMed

    Zheng, Binghui; Wang, Liping; Lei, Kun; Nan, Bingxu

    2016-04-01

    Polycyclic aromatic hydrocarbons (PAHs) contamination was investigated in concurrently sampled surface water, suspended particulate matter (SPM) and sediment of Daliao River estuary and the adjacent area, China. The total concentrations of PAHs ranged from 71.12 to 4255.43 ng/L in water, from 1969.95 to 11612.21 ng/L in SPM, and from 374.84 to 11588.85 ng/g dry weight (dw) in sediment. Although the 2-3 ring PAHs were main PAH congeners in water and SPM, the 4-6 ring PAHs were also detected and their distribution was site-specific, indicating a very recent PAHs input around the area since they were hydrophobic. The PAHs pollution was identified as mixed combustion and petroleum sources. Based on species sensitivity distribution (SSD), the ecological risk in SPM from 82% stations was found to be higher obviously than that in water. The risk in water was basically ranked as medium, while the risk in SPM was ranked as high. Analysis with sediment quality guidelines (SQGs) indicated that negative eco-risk occasionally occurred in about 50% stations, while negative eco-risk frequently occurred in about 3% stations only caused by Phenanthrene(Phe) and Dibenzo(a,h)anthracene(DBA). Here freshwater acute effects data together with saltwater data were used for SSD model. And this method could quickly give the rational risk information, and achieved our objective that compared the spatial difference of risk levels among three compartments. The results confirmed that the use of freshwater acute effects data from the ECOTOX database together with saltwater effects data is acceptable for risk assessment purposes in estuary. PMID:26855211

  14. Ozonolysis of surface adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

    NASA Astrophysics Data System (ADS)

    O'Neill, E. M.; Kawam, A. Z.; Van Ry, D. A.; Hinrichs, R. Z.

    2013-07-01

    Lignin pyrolysis products, which include a variety of substituted methoxyphenols, constitute a major component of organics released by biomass combustion and may play a central role in the formation of atmospheric brown carbon. Understanding the atmospheric fate of these compounds upon exposure to trace gases is therefore critical to predicting the chemical and physical properties of biomass burning aerosol. We used diffuse reflectance infrared spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol, eugenol, and isoeugenol adsorbed on NaCl and α-Al2O3 substrates. Adsorption of gaseous methoxyphenols onto these substrates produced near monolayer surface concentrations of 3 × 1018 molecules m-2. The subsequent dark heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic ring between the methoxy and phenol groups with the product conclusively identified by GC-MS and 1H-NMR. Kinetic analysis of eugenol and isoeugenol dark ozonolysis also suggested the formation of ring-cleaved products, although ozonolysis of the unsaturated substituent groups forming carboxylic acids and aldehydes was an order of magnitude faster. Average uptake coefficients for NaCl-adsorbed methoxyphenols were γ = 2.3 (±0.8) × 10-7 and 2 (±1) × 10-6 for ozonolysis of the aromatic ring and the unsaturated side chain, respectively, and reactions on α-Al2O3 were approximately two times slower. UV-visible radiation (λ>300 nm) enhanced eugenol ozonolysis of the aromatic ring by a factor of 4(±1) but had no effect on ozonolysis of the alkene side-chain.

  15. Ring expansion reactions of anti-aromatic boroles: a promising synthetic avenue to unsaturated boracycles.

    PubMed

    Barnard, Jonathan H; Yruegas, Sam; Huang, Kexuan; Martin, Caleb D

    2016-08-21

    Conjugated boron heterocycles have emerged as attractive synthetic targets due to their potential in medicinal chemistry and as electronic materials. However, the development of unsaturated boracycles has been hampered by difficulties in their preparation. Recently, a new synthetic avenue to access these species has been developed that takes advantage of the high reactivity of boroles. These five-membered anti-aromatic heterocycles can react with substrates to furnish ring expansion products via the insertion of one, two, or three atoms into the boracyclic ring. The ring expansion can occur via two pathways, the first exploits the activated diene moiety of the heterocycle in Diels-Alder chemistry with the resulting bicyclic species undergoing further rearrangements. The second reaction pathway is initiated by the coordination of the Lewis basic site of a substrate to the highly Lewis acidic boron center rendering the endocyclic B-C bond of the borole nucleophilic, inducing the formation of larger boracycles via attack at the electrophilic site of the substrate. This review summarizes the current state of this chemistry and details the mechanisms leading to the products. The methodologies described herein could very well be extended to other substrates, as well as applied to other anti-aromatic heterocycles. PMID:27345619

  16. Aromatic A-ring analogues of orobanchol, new germination stimulants for seeds of parasitic weeds.

    PubMed

    Malik, Heetika; Kohlen, Wouter; Jamil, Muhammad; Rutjes, Floris P J T; Zwanenburg, Binne

    2011-04-01

    Strigolactones are signaling compounds in plants of increasing importance. In this paper the focus is on their activity as germinating agents for seeds of parasitic weeds. The syntheses of aromatic A-ring analogues of the germination stimulant orobanchol have been described. Starting substrate is the ABC unit of the stimulant GR24. Oxidation at the C-4 position gives a 4-oxo derivative which on subsequent reduction produces two C-4 epimeric alcohols, syn and anti in a ratio of 82 : 3. For practical access of the C-4 anti alcohol, the predominant syn epimer is inverted by a Mitsunobu procedure. The anti C-4 alcohol is then coupled with the D-ring in a one-pot two-step process involving a formylation and a reaction with bromobutenolide to give a mixture of the diastereomeric aromatic A-ring analogues of orobanchol. In contrast, the syn C-4 alcohol cannot be coupled directly with the D-ring. Protection of the C-4 syn OH is a prequisite. The best protecting function is the SEM group as deprotection after coupling with the D-ring can then readily be achieved. The structures of these new analogues have been ascertained by X-ray analyses. Both diastereomers of the C-4 syn as well as the C-4 anti orobanchol analogues have been tested as germination agents of seeds of Striga hermonthica and Orobanche ramosa. In addition, the acetates of both epimeric C-4 alcohols have been prepared and tested. Both diastereomers of the 4-oxo derivative have been prepared and bioassayed as well. The bioassays reveal that the diastereomers having the natural relative configuration are most active. The data also suggest that hydrogen bonding is not an important factor in the binding of the stimulant molecules in the receptor. PMID:21321762

  17. Polymerization of aniline and alkyl ring-substituted anilines in the presence of aromatic additives

    SciTech Connect

    Wei, Yen; Jang, Guangway; Chan, Chicheung; Hsueh, K.F.; Hariharan, R.; Patel, S.A.; Whitecar, C.K. )

    1990-09-20

    A new synthetic method for the preparation of electrically conductive polyaniline and alkyl ring-substituted polyanilines is presented, in which a small amount of aromatic additives is introduced into both chemical and electrochemical polymerization systems. In the presence of the additives, such as p-aminodiphenylamine, benzidine, and p-phenoxyaniline, the rate of polyaniline formation increases greatly; and lower applied potentials, e.g., 0.55 V vs SCE, or milder oxidants, e.g., O{sub 2}, can be effectively employed in the polymerization. All of these additives have lower oxidation potentials than the aniline monomers and at least one sterically accessible aromatic amino group which allow their incorporation into polymer chains as a part of the structural backbones. In contrast, addition of N,N-diphenylamine or hydroquinone to the polymerization system reduces the rate of polymer formation. The results are consistent with the proposed mechanism of polymerization.

  18. Palladium-Catalyzed, Ring-Forming Aromatic C–H Alkylations with Unactivated Alkyl Halides

    PubMed Central

    Venning, Alexander R. O.; Bohan, Patrick T.; Alexanian, Erik J.

    2015-01-01

    A catalytic C–H alkylation using unactivated alkyl halides and a variety of arenes and heteroarenes is described. This ring-forming process is successful with a variety of unactivated primary and secondary alkyl halides, including those with β-hydrogens. In contrast to standard polar or radical cyclizations of aromatic systems, electronic activation of the substrate is not required. The mild, catalytic reaction conditions are highly functional group tolerant and facilitate access to a diverse range of synthetically and medicinally important carbocyclic and heterocyclic systems. PMID:25746442

  19. Influence of Fluorine Atoms and Aromatic Rings on the Acidity of Ethanol

    NASA Astrophysics Data System (ADS)

    Ramírez, Ramsés E.; García-Martínez, Cirilo; Méndez, Francisco

    2009-09-01

    Absolute gas-phase acidities ΔacidG0(OH) and ΔacidG0(CH) were calculated at the B3LYP and MP2 levels using six different standard basis sets for the OH and CH heterolytic bond cleavage of ethanol and twelve derivatives of the type CH3-nFnCHXrOH, where n ranges from zero to three and represents the number of fluorine atoms and r represents hydrogen and the type of aromatic ring, namely: X0 = hydrogen, X1 = phenyl, X2 = 1-naphthyl, and X3 = 9-anthryl. The similarity between calculated and experimental ΔacidG0(OH) values for ethanol (1a), 2-fluoroethanol (1b), 2,2-difluoroethanol (1c), 2,2,2-trifluoroethanol (1d), and 1-phenylethanol (2a) was used to validate the right theoretical method for this study. Substituent partial contributions to hydroxyl-, methylene-, and methine-hydrogen acidities were evaluated by linear combination. Good parameter fittings of the primary and secondary alcohols were obtained and interpreted as additive contribution of the substituent effects. The nonlinear contributions were identified. Calculations prove that fluoroalcohols exhibit C-H acidity, which is usually lower than O-H acidity. In principle, the inversion of this acidity order is possible by the introduction of a large aromatic ring instead to increase the number of fluorine atoms.

  20. Pollution status of polycyclic aromatic hydrocarbons in surface sediments from the Yangtze River Estuary and its adjacent coastal zone.

    PubMed

    Wang, Chenglong; Zou, Xinqing; Gao, Jianhua; Zhao, Yifei; Yu, Wenwen; Li, Yali; Song, Qiaochu

    2016-11-01

    Polycyclic aromatic hydrocarbons (PAHs) are mainly produced by incomplete combustion and are used as indicators of anthropogenic activities on the environment. This study analyses the PAHs level in the Yangtze River Estuary (YRE), an important component of Yangtze River and a developed and populated region in China. Surface sediments were collected from 77 sites at the YRE and its adjacent coastal zone (IACZ) for a comprehensive study of PAHs. Kriging interpolation technology and Positive matrix factorization (PMF) model were applied to explore the spatial distribution and sources of PAHs. Concentrations of 16 PAHs (ΣPAHs) varied from 27.2 ng g(-1) to 621.6 ng g(-1) dry weight, with an average value of 158.2 ng g(-1). Spatially, ΣPAHs exhibited wide fluctuation and exhibited an increasing tendency from north to south. In addition, ΣPAHs exhibited a decreasing trend with increasing distance between the estuary and IACZ. The deposition flux of PAHs indicated that more than 107.8 t a(-1) PAHs was deposited in the study area annually. The results of the PMF model revealed that anthropogenic activities were the main sources of PAHs in the study area. Vehicle emissions and marine engines were the most important sources and accounted for 40.9% of the pollution. Coal combustion, petrogenic sources, and wood combustion were other sources that contributed 23.9%, 23.6%, and 11.5%, respectively. The distribution patterns of PAHs in the YRE and IACZ were influenced by many complicated factors such as sediment grain size, hydrodynamics and so on. PMID:27485799

  1. Computer-aided rational design of novel EBF analogues with an aromatic ring.

    PubMed

    Wang, Shanshan; Sun, Yufeng; Du, Shaoqing; Qin, Yaoguo; Duan, Hongxia; Yang, Xinling

    2016-06-01

    Odorant binding proteins (OBPs) are important in insect olfactory recognition. These proteins bind specifically to insect semiochemicals and induce their seeking, mating, and alarm behaviors. Molecular docking and molecular dynamics simulations were performed to provide computational insight into the interaction mode between AgamOBP7 and novel (E)-β-farnesene (EBF) analogues with an aromatic ring. The ligand-binding cavity in OBP7 was found to be mostly hydrophobic due to the presence of several nonpolar residues. The interactions between the EBF analogues and the hydrophobic residues in the binding cavity increased in strength as the distance between them decreased. The EBF analogues with an N-methyl formamide or ester linkage had higher docking scores than those with an amide linkage. Moreover, delocalized π-π and electrostatic interactions were found to contribute significantly to the binding between the ligand benzene ring and nearby protein residues. To design new compounds with higher activity, four EBF analogues D1-D4 with a benzene ring were synthesized and evaluated based on their docking scores and binding affinities. D2, which had an N-methyl formamide group linkage, exhibited stronger binding than D1, which had an amide linkage. D4 exhibited particularly strong binding due to multiple hydrophobic interactions with the protein. This study provides crucial foundations for designing novel EBF analogues based on the OBP structure. Graphical abstract The design strategy of new EBF analogues based on the OBP7 structure. PMID:27251400

  2. Aromatic Character of Irregular-Shaped Nanographenes.

    PubMed

    Nishina, Naoko; Makino, Masakazu; Aihara, Jun-Ichi

    2016-04-21

    We found that the Clar sextet formula with the maximum number of sextet rings cannot always be defined meaningfully for large irregular-shaped PAHs. It is true that edge structure is always a primary determinant of the PAH aromaticity pattern. In large PAH molecules, every edge structure modifies the aromaticity pattern near the edge, but its influence fades on going away from the edge. It follows that different textures of the aromaticity pattern appear near different edges. As a result, the entire aromaticity pattern does not always match with a single Clar formula or a single weighted superposed Clar formula. Such an unusual feature of aromaticity patterns could not have been observed distinctly if we had not explored the aromaticity patterns of large irregular-shaped PAH molecules systematically. We used the superaromatic stabilization energy (SSE) as a local aromaticity index, which is the only index of this kind not disturbed by the aromaticity of adjacent benzene rings. PMID:27030605

  3. Protonation energies of 1-5-ring polycyclic aromatic nitrogen heterocyclics: comparing experiment and theory.

    PubMed

    Wiseman, Alexander; Sims, Lacey A; Snead, Russell; Gronert, Scott; Maclagan, Robert G A R; Meot-Ner Mautner, Michael

    2015-01-01

    Polycyclic nitrogen heterocyclic compounds (PANHs) can be protonated in the gas phase in mass spectrometry, in solution in acidic and biological environments, and if present, in interstellar clouds. Intrinsic molecular effects on PANH basicities can be observed by their gas phase protonation thermochemistry. We determined the gas phase basicities/proton affinities (GBs/PAs) of prototype one-nitrogen, 3-5-ring PANH compounds of increasing sizes and polarizabilities by kinetic bracketing, using proton transfer reactions to reference bases. The experimental proton affinities increase from 1-ring (pyridine, 222.2); to 2-ring (quinoline, 227.8); to 3-5-ring compounds, 227-234 kcal mol(-1). We also calculated the GB/PA values at the M06-2X/6-311+G**//B3LYP/6-31g* level. The computed PAs agree, within the experimental uncertainty, with the experimental values anchored to the upper range of the NIST GB/PA database. Specifically, the computed PAs are smaller than the experimental values by 1.4 ± 0.9 kcal/mol for nonaromatic nitrogen reference bases and for 1-5-ring PANHs, independently of the number of rings, aromaticity, and molecular size. Therefore, a useful method to calculate proton affinities of PANH compounds can use M06-2X/6-311+G**//B3LYP/6-31g* computational PAs + 1.4 ± 0.9 kcal mol(-1). The agreement with experiment supports the NIST database within this accuracy, in the upper range up to 235 kcal mol(-1), even though there are no direct absolute experimental anchor points in this range. For astrochemical applications, the measured PAs allow calculating the energies of the (PANH)(+•) + H2 → (PANH)H(+) + H(•) reactions that may convert the radical ions to less reactive 11-electron ions. The reactions are endothermic or nearly thermoneutral for the 3-5-ring ions and would be very slow at low temperatures, allowing reactive (PANH)(+•) radical ions to persist in interstellar clouds. PMID:25479250

  4. Compounds having aromatic rings and side-chain amide-functionality and a method for transporting monovalent anions across biological membranes using the same

    DOEpatents

    Davis, Jeffery T.; Sidorov, Vladimir; Kotch, Frank W.

    2008-04-08

    A compound containing at least two aromatic rings covalently bonded together, with each aromatic ring containing at least one oxyacetamide-based side chain, the compound being capable of forming a chloride ion channel across a lipid bilayer, and transporting chloride ion across the lipid bilayer.

  5. Formation of Polycyclic Aromatic Hydrocarbons exhibiting (5,7)-member ring defects in Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Öttl, S.; Huber, S. E.; Kimeswenger, S.; Probst, M.

    2014-04-01

    Polycyclic aromatic hydrocarbons (PAHs) are nowadays widely accepted as one of the carriers of the ubiquitous aromatic infrared (IR) bands. The IR spectra of many planetary nebulae (PNe) are dominated by mid-IR emission features, attributed to the IR fluorescence of PAHs. Recent observations of PNe show the simultaneous presence of mid-IR features attributed to neutral fullerene molecules (i.e. C60) and PAHs (García-Hernández et al. 2010). In general, PNe show evidence of mixed chemistry with emission from PAHs, silicate dust, fullerenes and contributions from other molecular components. The still unidentified IR features seen in PNe require further laboratory and observational investigations. We present a theoretical study of the IR spectra of PAHs containing (5,7)-member ring defects. Using density functional theory, we investigate the effects such defects have on the IR spectra of pyrene (C16H10) and coronene (C24H12). In addition, we explore parts of the potential energy surface of the neutral species and discuss alternative formation pathways, especially in the environment of PNe. Coronene and pyrene can be seen as limiting or prototypical cases in various respects. They are among the smallest hydrocarbons that can exhibit (5,7)-ring defects. Previous work (Yu et al. 2012) has raised the suspicion that effects of such defects might be more intriguing with decreasing size of the PAHs. Our investigations represent the limiting cases with respect to the size of the PAHs. To study these small systems is thought to be an important step towards a substantial understanding of the role of (5,7)-ring defects for the IR spectra of PAHs. The formation of these (5,7)-ring defects in PAHs may be well supported in PNe. The environment strongly enables the transition from the ground state to the defect state. Therefore the knowledge of the IR spectra of these molecules will support the investigations in understanding the unidentified IR emission bands in PNe.

  6. Coordinated Coverage of the Ring Current, Cusp and Adjacent FACs with Cluster and Swarm

    NASA Astrophysics Data System (ADS)

    Xiong, C.; Dunlop, M. W.; Bogdanova, Y.; Yang, J.; Yang, Y.; Shen, C.; Luhr, H.; Olsen, N.; Zhang, Q. H.; Ritter, P.; Kauristie, K.; Masson, A.; Haagmans, R.

    2014-12-01

    We explore the capability of Swarm-Cluster coordination for probing the behavior of the ring current (RC), field aligned currents (FAC) and cusp currents at medium and low orbits. The RC and connecting R2 FACs influence the geomagnetic field at low Earth orbit (LEO) and are sampled in situ by the four Cluster spacecraft every perigee pass. Coordination of the configuration of the three Swarm spacecraft with the constellation of the four Cluster spacecraft has been planned through joint operations; providing a set of distributed, multi-point measurements covering this region. A particularly close coordination of all spacecraft has been achieved during the start of the Swarm operations. We show preliminary study of the morphology and influence of the ring current from the in-situ RC and associated FACs determined directly from the 4-spacecraft Cluster perigee observations. We report here preliminary results of joint science targets, including coordinated cusp encounters; the comparative significance of the connecting R2 FACs, and the use and application of new analysis techniques derived from the calculation of curl B and magnetic gradients to compare estimates of the current distributions. For context, we will report on the coordination of Champ and Cluster data to interpret and resolve the R1 and R2 FACs using Champ derived models of the associated auroral boundaries.

  7. Enantioselective ring-opening of meso-epoxides by aromatic amines catalyzed by a homochiral metal-organic framework.

    PubMed

    Regati, Sridhar; He, Yabing; Thimmaiah, Muralidhara; Li, Peng; Xiang, Shengchang; Chen, Banglin; Zhao, John Cong-Gui

    2013-10-28

    The enantioselective ring-opening of meso-epoxides by aromatic amines was achieved by using a new chiral metal-organic framework . The corresponding α-hydroxyamines were obtained with good yields and ee values (up to 89% ee). PMID:24030658

  8. Study of the Formation of the First Aromatic Rings in the Pyrolysis of Cyclopentene.

    PubMed

    Herbinet, Olivier; Rodriguez, Anne; Husson, Benoit; Battin-Leclerc, Frédérique; Wang, Zhandong; Cheng, Zhanjun; Qi, Fei

    2016-02-11

    The thermal decomposition of cyclopentene was studied in a jet-stirred reactor operated at constant pressure and temperature to provide new experimental information about the formation of the first aromatic rings from cyclic C5 species. Experiments were carried out at a residence time of 1 s, a pressure of 106.7 kPa, temperatures ranging from 773 to 1073 K and under diluted conditions (cyclopentene inlet mole fraction of 0.04). Species were quantified using three analytical methods: gas chromatography, synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS), and single photon laser ionization mass spectrometry (SPI-MS). Several species could be quantified using both methods allowing comparison of experimental data obtained with the three apparatuses. Discrepancies observed in mole fraction profiles of some large aromatics suggest that the direct sampling in the gas phase (with a molecular beam or a capillary tube) provide more reliable results. The main reaction products are 1,3-cyclopentadiene and hydrogen. The formation of many unsaturated C2-C6 olefins, diolefins and alkynes was also observed but in smaller amounts. Benzene, toluene, styrene, indene, and naphthalene were detected from 923 K. SVUV-PIMS data allowed the identification of another C6H6 isomer which is 1,5-hexadien-3-yne rather than fulvene. The quantification of the cyclopentadienyl radical was obtained from SVUV-PIMS and SPI-MS data with some uncertainty induced by the possible contribution to the signal for m/z 65 of a fragment from the decomposition of a larger ion. This is the first time that a radical is quantified in a jet-stirred reactor using non-optical techniques. SPI-MS analyses allowed the detection of species likely being combination products of allyl and cyclopentadienyl radicals. A model was developed for the pyrolysis of cyclopentene. This model includes routes of formation of aromatics from the cyclopentadienyl radical. The comparison of experimental and

  9. Calculated interactions of a nitro group with aromatic rings of crystalline picryl bromide

    PubMed Central

    Huang, Lulu; Massa, Lou; Karle, Jerome

    2008-01-01

    Several crystalline polymorphs have been discovered for picryl bromide. Among the several forces that control the formation of such polymorphs are the interactions among the nitro groups and phenyl rings of those crystals. Although there are >300 structures to be found in the Cambridge Structural Database displaying the nitro-phenyl interaction, nonetheless this interesting, and apparently important, interaction, seems not to have been discussed within any of the papers reporting the structures. In this article, quantum calculations are reported that assess the strength of these nitro-phenyl interactions within a crystal of picryl bromide. The rather flat molecules of picryl bromide are arranged in layered planes within the crystal, and we examine the attractive interactions that occur within a given plane, and between adjacent planes. Calculations of Hartree Fock and Møller Plesset perturbation theory carried to a second-order expansion are used. Both quantum mechanical approximations are implemented with 6–31G* basis functions. PMID:18780785

  10. The aromatic fluctuation index (FLU): A new aromaticity index based on electron delocalization

    NASA Astrophysics Data System (ADS)

    Matito, Eduard; Duran, Miquel; Solà, Miquel

    2005-01-01

    In this work, the aromatic fluctuation index (FLU) that describes the fluctuation of electronic charge between adjacent atoms in a given ring is introduced as a new aromaticity measure. This new electronic criterion of aromaticity is based on the fact that aromaticity is related to the cyclic delocalized circulation of π electrons. It is defined not only considering the amount of electron sharing between contiguous atoms, which should be substantial in aromatic molecules, but also taking into account the similarity of electron sharing between adjacent atoms. For a series of rings in 15 planar polycyclic aromatic hydrocarbons, we have found that, in general, FLU is strongly correlated with other widely used indicators of local aromaticity, such as the harmonic-oscillator model of aromaticity, the nucleus independent chemical shift, and the para-delocalization index (PDI). In contrast to PDI, the FLU index can be applied to study the aromaticity of rings with any number of members and it can be used to analyze both the local and global aromatic character of rings and molecules.

  11. The generation of stationary π-electron rotations in chiral aromatic ring molecules possessing non-degenerate excited states.

    PubMed

    Yamaki, Masahiro; Teranishi, Yoshiaki; Nakamura, Hiroki; Lin, Sheng Hsien; Fujimura, Yuichi

    2016-01-21

    The electron angular momentum is a fundamental quantity of high-symmetry aromatic ring molecules and finds many applications in chemistry such as molecular spectroscopy. The stationary angular momentum or unidirectional rotation of π electrons is generated by the excitation of a degenerated electronic excited state by a circularly-polarized photon. For low-symmetry aromatic ring molecules having non-degenerate states, such as chiral aromatic ring molecules, on the other hand, whether stationary angular momentum can be generated or not is uncertain and has not been clarified so far. We have found by both theoretical treatments and quantum optimal control (QOC) simulations that a stationary angular momentum can be generated even from a low-symmetry aromatic ring molecule. The generation mechanism can be explained in terms of the creation of a dressed-state, and the maximum angular momentum is generated by the dressed state with an equal contribution from the relevant two excited states in a simple three-electronic state model. The dressed state is formed by inducing selective nonresonant transitions between the ground and each excited state by two lasers with the same frequency but having different polarization directions. The selective excitation can be carried out by arranging each photon-polarization vector orthogonal to the electronic transition moment of the other transition. We have successfully analyzed the results of the QOC simulations of (P)-2,2'-biphenol of axial chirality in terms of the analytically determined optimal laser fields. The present findings may open up new types of chemical dynamics and spectroscopy by utilizing strong stationary ring currents and current-induced magnetic fields, which are created at a local site of large compounds such as biomolecules. PMID:26670839

  12. Analysis of the magnetically induced current density of molecules consisting of annelated aromatic and antiaromatic hydrocarbon rings.

    PubMed

    Sundholm, Dage; Berger, Raphael J F; Fliegl, Heike

    2016-06-21

    Magnetically induced current susceptibilities and current pathways have been calculated for molecules consisting of two pentalene groups annelated with a benzene (1) or naphthalene (2) moiety. Current strength susceptibilities have been obtained by numerically integrating separately the diatropic and paratropic contributions to the current flow passing planes through chosen bonds of the molecules. The current density calculations provide novel and unambiguous current pathways for the unusual molecules with annelated aromatic and antiaromatic hydrocarbon moieties. The calculations show that the benzene and naphthalene moieties annelated with two pentalene units as in molecules 1 and 2, respectively, are unexpectedly antiaromatic sustaining only a local paratropic ring current around the ring, whereas a weak diatropic current flows around the C-H moiety of the benzene ring. For 1 and 2, the individual five-membered rings of the pentalenes are antiaromatic and a slightly weaker semilocal paratropic current flows around the two pentalene rings. Molecules 1 and 2 do not sustain any net global ring current. The naphthalene moiety of the molecule consisting of a naphthalene annelated with two pentalene units (3) does not sustain any strong ring current that is typical for naphthalene. Instead, half of the diatropic current passing the naphthalene moiety forms a zig-zag pattern along the C-C bonds of the naphthalene moiety that are not shared with the pentalene moieties and one third of the current continues around the whole molecule partially cancelling the very strong paratropic semilocal ring current of the pentalenes. For molecule 3, the pentalene moieties and the individual five-membered rings of the pentalenes are more antiaromatic than for 1 and 2. The calculated current patterns elucidate why the compounds with formally [4n + 2] π-electrons have unusual aromatic properties violating the Hückel π-electron count rule. The current density calculations also provide

  13. Novel aromatic ring-hydroxylating dioxygenase genes from coastal marine sediments of Patagonia

    PubMed Central

    Lozada, Mariana; Riva Mercadal, Juan P; Guerrero, Leandro D; Di Marzio, Walter D; Ferrero, Marcela A; Dionisi, Hebe M

    2008-01-01

    Background Polycyclic aromatic hydrocarbons (PAHs), widespread pollutants in the marine environment, can produce adverse effects in marine organisms and can be transferred to humans through seafood. Our knowledge of PAH-degrading bacterial populations in the marine environment is still very limited, and mainly originates from studies of cultured bacteria. In this work, genes coding catabolic enzymes from PAH-biodegradation pathways were characterized in coastal sediments of Patagonia with different levels of PAH contamination. Results Genes encoding for the catalytic alpha subunit of aromatic ring-hydroxylating dioxygenases (ARHDs) were amplified from intertidal sediment samples using two different primer sets. Products were cloned and screened by restriction fragment length polymorphism analysis. Clones representing each restriction pattern were selected in each library for sequencing. A total of 500 clones were screened in 9 gene libraries, and 193 clones were sequenced. Libraries contained one to five different ARHD gene types, and this number was correlated with the number of PAHs found in the samples above the quantification limit (r = 0.834, p < 0.05). Overall, eight different ARHD gene types were detected in the sediments. In five of them, their deduced amino acid sequences formed deeply rooted branches with previously described ARHD peptide sequences, exhibiting less than 70% identity to them. They contain consensus sequences of the Rieske type [2Fe-2S] cluster binding site, suggesting that these gene fragments encode for ARHDs. On the other hand, three gene types were closely related to previously described ARHDs: archetypical nahAc-like genes, phnAc-like genes as identified in Alcaligenes faecalis AFK2, and phnA1-like genes from marine PAH-degraders from the genus Cycloclasticus. Conclusion These results show the presence of hitherto unidentified ARHD genes in this sub-Antarctic marine environment exposed to anthropogenic contamination. This information

  14. A dissected ring current model for assessing magnetic aromaticity: a general approach for both organic and inorganic rings.

    PubMed

    Foroutan-Nejad, Cina; Shahbazian, Shant; Feixas, Ferran; Rashidi-Ranjbar, Parviz; Solà, Miquel

    2011-08-01

    A model based on classical electrodynamics is used to measure the strength of ring currents of different molecular orbitals, i.e., σ- and π-orbitals, and characteristics of ring current loops, i.e., ring current radii and height of current loops above/below the ring planes, among a number of organic as well as inorganic molecules. For the π-current, the present model represents an improvement of previous approaches to determine ring current intensity. It is proven that the present model is more precise than previous models as they could not explain presence of the minimum in the plot of NICS(πzz) versus distance close to the ring plane. Variations in the charge of molecules and the types of constituent atoms of each species affect the ring current radii of both σ- and π-current loops as well as the height of π-current loops above/below the ring plane. It is suggested that variation in the distribution of the one-electron density in different systems is the main source of differences of the ring current characteristics. PMID:21598277

  15. No-carrier-added (NCA) aryl [{sup 18}F]fluorides via the nucleophilic aromatic substitution of electron rich aromatic rings

    SciTech Connect

    Ding, Yu-Shin; Fowler, J.S.; Wolf, A.P.

    1991-12-31

    A method for synthesizing no-carrier-added (NCA) aryl [{sup 18}F] fluoride substituted aromatic aldehyde compositions bearing an electron donating group is described. The method includes the step of reacting aromatic nitro aldehydes having a suitably protected hydroxyl substituent on an electron rich ring. The reaction is carried out by nucleophilic aromatic substitution with a no-carrier-added (NCA) [{sup 18}F]fluoride ion. The method can be used to synthesize various no-carrier-added aryl [{sup 18}F]fluoride compositions, including 6-[{sup 18}F]fluoro-L-DOPA, 2-[{sup 18}F]fluorotyrosine, 6-[{sup 18}F]fluoronorepinephrine, and 6-[{sup 18}F]fluorodopamine. In those instances when a racemic mixture of enantiomers is produced by the present invention, such as in the synthesis of 6-[{sup 18}F]fluoronorepinephrine, a preferred method also includes resolution of the racemic mixture on a chiral HPLC column. This procedure results in a high yield of enantiomerically pure [{sup 18}F] labeled isomers, for example [-]-6-[{sup 18}F]fluoronorepinephrine and [+]-6-[{sup 18}F]fluoronorepinephrine.

  16. Importance of Tensor Asymmetry for the Analysis of 2H-NMR Spectra from Deuterated Aromatic Rings

    PubMed Central

    Pulay, Peter; Scherer, Erin M.; van der Wel, Patrick C. A.; Koeppe, Roger E.

    2008-01-01

    We have used ab initio calculations to compute all of the tensor elements of the electric field gradient for each carbon-deuterium bond in the ring of deuterated 3-methyl-indole. Previous analyses have ignored the smaller tensor elements perpendicular to principal component Vzz which is aligned with the C-2H bond (local bond z-axis). At each ring position, the smallest element Vxx is in the molecular plane and Vyy is normal to the plane of the ring. The asymmetry parameter η = (|Vyy|-|Vxx|)/|Vzz| ranges from 0.07 at C4 to 0.11 at C2. We used the perpendicular (off-bond) tensor elements, in concert with an improved understanding of the indole ring geometry1, to analyze prototype 2H-NMR spectra from well-oriented, hydrated peptide/lipid samples. For each of the 4 tryptophans of membrane-spanning gramicidin A (gA)2 channels, the inclusion of the perpendicular elements changes the deduced ring tilt by nearly 10° and increases the ring principal order parameter Szz for overall ‘wobble’ with respect to the membrane normal (molecular z-axis). With the improved analysis, the magnitude of Szz for the outermost indole rings of Trp13 and Trp15 is indistinguishable from that observed previously for backbone atoms (0.93 ± 0.03). For the Trp9 and Trp11 rings, which are slightly more buried within the membrane, Szz is slightly lower (0.86 ± 0.03). The results show that the perpendicular elements are important for the detailed analysis of 2H-NMR spectra from aromatic ring systems. PMID:16332101

  17. Non-Markovian response of ultrafast coherent electronic ring currents in chiral aromatic molecules in a condensed phase

    NASA Astrophysics Data System (ADS)

    Mineo, H.; Lin, S. H.; Fujimura, Y.; Xu, J.; Xu, R. X.; Yan, Y. J.

    2013-12-01

    Results of a theoretical study on non-Markov response for femtosecond laser-driven coherent ring currents in chiral aromatic molecules embedded in a condensed phase are presented. Coherent ring currents are generated by coherent excitation of a pair of quasi-degenerated π-electronic excited states. The coherent electronic dynamical behaviors are strongly influenced by interactions between the electronic system and phonon bath in a condensed phase. Here, the bath correlation time is not instantaneous but should be taken to be a finite time in ultrashort time-resolved experiments. In such a case, Markov approximation breaks down. A hierarchical master equation approach for an improved semiclassical Drude dissipation model was adopted to examine the non-Markov effects on ultrafast coherent electronic ring currents of (P)-2,2'-biphenol in a condensed phase. Time evolution of the coherent ring current derived in the hierarchical master equation approach was calculated and compared with those in the Drude model in the Markov approximation and in the static limit. The results show how non-Markovian behaviors in quantum beat signals of ring currents depend on the Drude bath damping constant. Effects of temperatures on ultrafast coherent electronic ring currents are also clarified.

  18. Non-Markovian response of ultrafast coherent electronic ring currents in chiral aromatic molecules in a condensed phase

    SciTech Connect

    Mineo, H.; Lin, S. H.; Fujimura, Y.; Xu, J.; Xu, R. X.; Yan, Y. J.

    2013-12-07

    Results of a theoretical study on non-Markov response for femtosecond laser-driven coherent ring currents in chiral aromatic molecules embedded in a condensed phase are presented. Coherent ring currents are generated by coherent excitation of a pair of quasi-degenerated π-electronic excited states. The coherent electronic dynamical behaviors are strongly influenced by interactions between the electronic system and phonon bath in a condensed phase. Here, the bath correlation time is not instantaneous but should be taken to be a finite time in ultrashort time-resolved experiments. In such a case, Markov approximation breaks down. A hierarchical master equation approach for an improved semiclassical Drude dissipation model was adopted to examine the non-Markov effects on ultrafast coherent electronic ring currents of (P)-2,2{sup ′}-biphenol in a condensed phase. Time evolution of the coherent ring current derived in the hierarchical master equation approach was calculated and compared with those in the Drude model in the Markov approximation and in the static limit. The results show how non-Markovian behaviors in quantum beat signals of ring currents depend on the Drude bath damping constant. Effects of temperatures on ultrafast coherent electronic ring currents are also clarified.

  19. Non-Markovian response of ultrafast coherent electronic ring currents in chiral aromatic molecules in a condensed phase.

    PubMed

    Mineo, H; Lin, S H; Fujimura, Y; Xu, J; Xu, R X; Yan, Y J

    2013-12-01

    Results of a theoretical study on non-Markov response for femtosecond laser-driven coherent ring currents in chiral aromatic molecules embedded in a condensed phase are presented. Coherent ring currents are generated by coherent excitation of a pair of quasi-degenerated π-electronic excited states. The coherent electronic dynamical behaviors are strongly influenced by interactions between the electronic system and phonon bath in a condensed phase. Here, the bath correlation time is not instantaneous but should be taken to be a finite time in ultrashort time-resolved experiments. In such a case, Markov approximation breaks down. A hierarchical master equation approach for an improved semiclassical Drude dissipation model was adopted to examine the non-Markov effects on ultrafast coherent electronic ring currents of (P)-2,2'-biphenol in a condensed phase. Time evolution of the coherent ring current derived in the hierarchical master equation approach was calculated and compared with those in the Drude model in the Markov approximation and in the static limit. The results show how non-Markovian behaviors in quantum beat signals of ring currents depend on the Drude bath damping constant. Effects of temperatures on ultrafast coherent electronic ring currents are also clarified. PMID:24320379

  20. Ozonolysis of surface-adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

    NASA Astrophysics Data System (ADS)

    O'Neill, E. M.; Kawam, A. Z.; Van Ry, D. A.; Hinrichs, R. Z.

    2014-01-01

    Lignin pyrolysis products, which include a variety of substituted methoxyphenols, constitute a major component of organics released by biomass combustion, and may play a central role in the formation of atmospheric brown carbon. Understanding the atmospheric fate of these compounds upon exposure to trace gases is therefore critical to predicting the chemical and physical properties of biomass burning aerosol. We used diffuse reflectance infrared spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol, eugenol, and isoeugenol adsorbed on NaCl and α-Al2O3 substrates. Adsorption of gaseous methoxyphenols onto these substrates produced near-monolayer surface concentrations of 3 × 1018 molecules m-2. The subsequent dark heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic ring between the methoxy and phenol groups with the product conclusively identified by GC-MS and 1H-NMR. Kinetic analysis of eugenol and isoeugenol dark ozonolysis also suggested the formation of ring-cleaved products, although ozonolysis of the unsaturated substituent groups forming carboxylic acids and aldehydes was an order of magnitude faster. Average uptake coefficients for NaCl-adsorbed methoxyphenols were γ = 2.3 (± 0.8) × 10-7 and 2 (± 1) × 10-6 for ozonolysis of the aromatic ring and the unsaturated side chain, respectively, and reactions on α-Al2O3 were approximately two times slower. UV-visible radiation (λ > 300 nm) enhanced eugenol ozonolysis of the aromatic ring by a factor of 4(± 1) but had no effect on ozonolysis of the alkene side chain.

  1. Gaseous polycyclic aromatic hydrocarbon concentrations are higher in urban forests than adjacent open areas during summer but not in winter--Exploratory study.

    PubMed

    Viippola, Viljami; Rantalainen, Anna-Lea; Yli-Pelkonen, Vesa; Tervo, Peatta; Setälä, Heikki

    2016-01-01

    While the potential of plants to uptake polycyclic aromatic hydrocarbons (PAHs) is widely acknowledged, empirical evidence of the effects of this process on local atmospheric PAH concentrations and human health is tenuous. We measured gaseous PAH concentrations using passive samplers in urban tree-covered areas and adjacent open, treeless areas in a near-road environment in Finland to gain information on the ability of urban vegetation to improve air quality. The ability of urban, mostly deciduous, vegetation to affect PAHs was season dependent: during summer, concentrations were significantly higher in tree-covered areas, while in the fall, concentrations in open areas exceeded those in tree-covered areas. During winter, concentrations in tree-covered areas were either lower or did not differ from those in open areas. Results of this study imply that the commonly believed notion that trees unequivocally improve air quality does not apply to PAHs studied here. PMID:26412199

  2. A new classification system for bacterial Rieske non-heme iron aromatic ring-hydroxylating oxygenases

    PubMed Central

    Kweon, Ohgew; Kim, Seong-Jae; Baek, Songjoon; Chae, Jong-Chan; Adjei, Michael D; Baek, Dong-Heon; Kim, Young-Chang; Cerniglia, Carl E

    2008-01-01

    Background Rieske non-heme iron aromatic ring-hydroxylating oxygenases (RHOs) are multi-component enzyme systems that are remarkably diverse in bacteria isolated from diverse habitats. Since the first classification in 1990, there has been a need to devise a new classification scheme for these enzymes because many RHOs have been discovered, which do not belong to any group in the previous classification. Here, we present a scheme for classification of RHOs reflecting new sequence information and interactions between RHO enzyme components. Result We have analyzed a total of 130 RHO enzymes in which 25 well-characterized RHO enzymes were used as standards to test our hypothesis for the proposed classification system. From the sequence analysis of electron transport chain (ETC) components of the standard RHOs, we extracted classification keys that reflect not only the phylogenetic affiliation within each component but also relationship among components. Oxygenase components of standard RHOs were phylogenetically classified into 10 groups with the classification keys derived from ETC components. This phylogenetic classification scheme was converted to a new systematic classification consisting of 5 distinct types. The new classification system was statistically examined to justify its stability. Type I represents two-component RHO systems that consist of an oxygenase and an FNRC-type reductase. Type II contains other two-component RHO systems that consist of an oxygenase and an FNRN-type reductase. Type III represents a group of three-component RHO systems that consist of an oxygenase, a [2Fe-2S]-type ferredoxin and an FNRN-type reductase. Type IV represents another three-component systems that consist of oxygenase, [2Fe-2S]-type ferredoxin and GR-type reductase. Type V represents another different three-component systems that consist of an oxygenase, a [3Fe-4S]-type ferredoxin and a GR-type reductase. Conclusion The new classification system provides the following

  3. Functional Robustness of a Polycyclic Aromatic Hydrocarbon Metabolic Network Examined in a nidA Aromatic Ring-Hydroxylating Oxygenase Mutant of Mycobacterium vanbaalenii PYR-1

    PubMed Central

    Kim, Seong-Jae; Song, Jaekyeong; Kweon, Ohgew; Holland, Ricky D.; Kim, Dae-Wi; Kim, Jongnam; Yu, Li-Rong

    2012-01-01

    In this study, we obtained over 4,000 transposon mutants of Mycobacterium vanbaalenii PYR-1 and analyzed one of the mutants, 8F7, which appeared to lose its ability to degrade pyrene while still being able to degrade fluoranthene. This mutant was identified to be defective in nidA, encoding an aromatic ring-hydroxylating oxygenase (RHO), known to be involved in the initial oxidation step of pyrene degradation. When cultured with pyrene as a sole source of polycyclic aromatic hydrocarbon (PAH), high-pressure liquid chromatography analysis revealed that the nidA mutant showed a significant decrease in the rate of pyrene degradation compared to the wild-type PYR-1, although pyrene was still being degraded. However, when incubated with PAH mixtures including pyrene, phenanthrene, and fluoranthene, the pyrene degradation rate of the mutant was higher than that of the mutant previously incubated with pyrene as a sole source of PAH. There was no significant difference between wild-type PYR-1 and the mutant in the rates of phenanthrene and fluoranthene degradation. From the whole-cell proteome analysis of mutant 8F7 induced by pyrene, we identified expression of a number of RHO enzymes which are suspected to be responsible for pyrene degradation in the nidA mutant, which had no expression of NidA. Taken together, results in this study provide direct evidence for the in vivo functional role of nidA in pyrene degradation at the level of the ring-cleavage-process (RCP) functional module but also for the robustness of the PAH metabolic network (MN) to such a genetic perturbation. PMID:22407691

  4. Functional characterization of diverse ring-hydroxylating oxygenases and induction of complex aromatic catabolic gene clusters in Sphingobium sp. PNB

    PubMed Central

    Khara, Pratick; Roy, Madhumita; Chakraborty, Joydeep; Ghosal, Debajyoti; Dutta, Tapan K.

    2014-01-01

    Sphingobium sp. PNB, like other sphingomonads, has multiple ring-hydroxylating oxygenase (RHO) genes. Three different fosmid clones have been sequenced to identify the putative genes responsible for the degradation of various aromatics in this bacterial strain. Comparison of the map of the catabolic genes with that of different sphingomonads revealed a similar arrangement of gene clusters that harbors seven sets of RHO terminal components and a sole set of electron transport (ET) proteins. The presence of distinctly conserved amino acid residues in ferredoxin and in silico molecular docking analyses of ferredoxin with the well characterized terminal oxygenase components indicated the structural uniqueness of the ET component in sphingomonads. The predicted substrate specificities, derived from the phylogenetic relationship of each of the RHOs, were examined based on transformation of putative substrates and their structural homologs by the recombinant strains expressing each of the oxygenases and the sole set of available ET proteins. The RHO AhdA1bA2b was functionally characterized for the first time and was found to be capable of transforming ethylbenzene, propylbenzene, cumene, p-cymene and biphenyl, in addition to a number of polycyclic aromatic hydrocarbons. Overexpression of aromatic catabolic genes in strain PNB, revealed by real-time PCR analyses, is a way forward to understand the complex regulation of degradative genes in sphingomonads. PMID:24918041

  5. Identification of vitamin d3-based hedgehog pathway inhibitors that incorporate an aromatic a-ring isostere.

    PubMed

    DeBerardinis, Albert M; Banerjee, Upasana; Hadden, M Kyle

    2013-07-11

    Previous structure-activity relationship studies for vitamin D3 (VD3) inhibition of Hedgehog (Hh) signaling directed the design, synthesis, and evaluation of a series of VD3-based analogues that contain an aromatic A-ring mimic. Characterization of these compounds in a series of cellular assays demonstrated their ability to potently and selectively down-regulate Hh pathway signaling. The most active of these, 17, inhibited pathway signaling in Hh-dependent mouse fibroblasts (IC50 = 0.74 ± 0.1 μM) and cultured cancer cells (IC50 values 3.8 ± 0.1 to 5.2 ± 0.2 μM). In addition, 17 demonstrated reduced activation of the vitamin D receptor (VDR) compared to VD3 in these cellular models. These results suggest that VD3-based analogues with an aromatic A-ring are a valid scaffold for the development of more selective and potent Hh pathway inhibitors and identify 17 as an intriguing lead from this class of compounds for further development. In addition, our analysis of Hh pathway inhibitors in cancer cells suggests that the murine basal cell carcinoma cell line ASZ001 and the human medulloblastoma cell line DAOY are appropriate in vitro cancer models for early stage evaluation of pathway inhibition. PMID:24900716

  6. Ring Selective Generation of Isobenzofuran for Divergent Access to Polycyclic Aromatic Compounds.

    PubMed

    Akita, Rie; Kawanishi, Kazuki; Hamura, Toshiyuki

    2015-06-19

    Ring selective generation of isobenzofuran, a formal equivalent to bis-isobenzofuran, was developed. Importantly, selective introduction of functionalities and/or fused rings in the isobenzofuran core by iterative cycloadditions can achieve the divergent construction of polycyclic compounds. This selective approach enables us to prepare a regioisomeric pair of pentacenes. PMID:26057708

  7. Functionalization and kinetic stabilization of the [4]paracyclophane system and aromaticity of its extremely bent benzene ring.

    PubMed

    Tsuji, Takashi; Okuyama, Masahiro; Ohkita, Masakazu; Kawai, Hidetoshi; Suzuki, Takanori

    2003-01-29

    Kinetic stabilization of the [4]paracyclophane skeleton by the introduction of substituents, which serve to sterically hinder reactions at the reactive bridgehead sites, and properties of the resultant [4]paracyclophanes are investigated in this study. Modification of the property of [4]paracyclophane by functionalization is also intended. [4]Paracyclophanes are designed to be derived from the corresponding Dewar benzene isomers via their photochemical aromatization, and the requisite 1,4-bridged Dewar benzenes bearing sterically demanding functional groups are prepared. Irradiation of these precursors under matrix isolation at 77 K leads to the formation of [4]paracyclophanes, which exhibit characteristic electronic absorption spectra. The half-lives of the generated species vary widely from less than 1 min at -90 degrees C to 0.5 h at -20 degrees C, depending on the type of substituents and the pattern of substitution. One of the derivatives, 24, is stable enough and its content in the irradiated mixture is high enough to permit the measurement of the (1)H NMR spectrum. The recorded spectrum, which is reproduced very well by theoretical calculations using the GIAO method at the hybrid HF-DFT (B3LYP/6-31+G*) level, suggests the sustenance of rather strong diatropicity in its severely bent benzene moiety. Calculations on the bent benzene whose geometry is constrained to that calculated for 24 support that aromaticity is retained to a significant extent as compared to that of planar benzene, as judged by the magnetic criteria of aromaticity, that is, diamagnetic susceptibility exaltation and nucleus-independent chemical shift. The reason for the retention of aromaticity despite the severe bending of the benzene ring is discussed. Cyclophane 24 is so strained that it exceeds the corresponding Dewar benzene precursor in energy and thermally reverts to the latter with a half-life of 15 +/- 5 min at -20 degrees C (DeltaG++ = 18.3 +/- 0.3 kcal mol(-1)). PMID:12537493

  8. Identification and quantification of seven fused aromatic rings C26H14peri-condensed benzenoid polycyclic aromatic hydrocarbons in a complex mixture of polycyclic aromatic hydrocarbons from coal tar.

    PubMed

    Oña-Ruales, Jorge O; Ruiz-Morales, Yosadara; Wise, Stephen A

    2016-04-15

    A methodology for the characterization of groups of polycyclic aromatic hydrocarbons (PAHs) using a combination of normal phase liquid chromatography with ultraviolet-visible spectroscopy (NPLC/UV-vis) and gas chromatography with mass spectrometry (GC/MS) was used for the identification and quantification of seven fused aromatic rings C26H14peri-condensed benzenoid polycyclic aromatic hydrocarbons, PAHs, in standard reference material (SRM) 1597a, complex mixture of PAHs from coal tar. The NPLC/UV-vis isolated the fractions based on the number of aromatic carbons and the GC/MS allowed the identification and quantification of five of the nine C26H14 PAH isomers; naphtho[1,2,3,4-ghi]perylene, dibenzo[b,ghi]perylene, dibenzo[b,pqr]perylene, naphtho[8,1,2-bcd]perylene, and dibenzo[cd,lm]perylene using a retention time comparison with authentic reference standards. For the other four benzenoid isomers with no available reference standards the following two approaches were used. First, the annellation theory was used to achieve the potential identification of benzo[qr]naphtho[3,2,1,8-defg]chrysene, and second, the elution distribution in the GC fractions was used to support the potential identification of benzo[qr]naphtho[3,2,1,8-defg]chrysene and to reach the tentative identifications of dibenzo[a,ghi]perylene, naphtho[7,8,1,2,3-pqrst]pentaphene, and anthra[2,1,9,8-opqra]naphthacene. It is the first time that naphtho[1,2,3,4-ghi]perylene, dibenzo[b,ghi]perylene, dibenzo[b,pqr]perylene, naphtho[8,1,2-bcd]perylene, and dibenzo[cd,lm]perylene are quantified, and the first time that benzo[qr]naphtho[3,2,1,8-defg]chrysene is potentially identified, in any sample, in any context. PMID:26976350

  9. Effect of aromatic ring fluorination on CHπ interactions: microwave spectrum and structure of the 1,2-difluorobenzeneacetylene dimer.

    PubMed

    Akmeemana, Anuradha G; Kang, Justin M; Dorris, Rachel E; Nelson, Rebecca D; Anderton, Ashley M; Peebles, Rebecca A; Peebles, Sean A; Seifert, Nathan A; Pate, Brooks H

    2016-09-21

    Rotational spectra for the normal isotopic species and for six additional isotopologues of the 1,2-difluorobenzeneacetylene (C6H4F2HCCH) weakly bound dimer have been assigned in the 6-18 GHz region using chirped-pulse Fourier-transform microwave spectroscopy. This is the third complex in a series of fluorinated benzeneacetylene dimers. In 1,2-difluorobenzeneHCCH, the Hπ distance (2.725(28) Å) is longer by about 0.23 Å, and the estimated binding energy (EB = 2.3(6) kJ mol(-1)) is weaker by about 1.8 kJ mol(-1), than in the previously studied fluorobenzeneHCCH complex. In addition, in 1,2-difluorobenzeneacetylene, HCCH tips ∼46(3)° away from perpendicular to the aromatic ring, with the H nearest the ring moving away from the fluorine atoms along the C2 axis of the monomer, while in the fluorobenzene and benzene complexes HCCH is perpendicular (benzeneHCCH) or nearly perpendicular (fluorobenzeneHCCH, ∼7° tilt) to the ring plane. Results from ab initio and DFT calculations will be compared to an experimental structure determined from rotational constants for the DCCD and five unique (13)C substituted isotopologues. PMID:27530245

  10. A Novel Aromatic-Ring-Hydroxylating Dioxygenase from the Diterpenoid-Degrading Bacterium Pseudomonas abietaniphila BKME-9

    PubMed Central

    Martin, Vincent J. J.; Mohn, William W.

    1999-01-01

    Pseudomonas abietaniphila BKME-9 is able to degrade dehydroabietic acid (DhA) via ring hydroxylation by a novel dioxygenase. The ditA1, ditA2, and ditA3 genes, which encode the α and β subunits of the oxygenase and the ferredoxin of the diterpenoid dioxygenase, respectively, were isolated and sequenced. The ferredoxin gene is 9.2 kb upstream of the oxygenase genes and 872 bp upstream of a putative meta ring cleavage dioxygenase gene, ditC. A Tn5 insertion in the α subunit gene, ditA1, resulted in the accumulation by the mutant strain BKME-941 of the pathway intermediate, 7-oxoDhA. Disruption of the ferredoxin gene, ditA3, in wild-type BKME-9 by mutant-allele exchange resulted in a strain (BKME-91) with a phenotype identical to that of the mutant strain BKME-941. Sequence analysis of the putative ferredoxin indicated that it is likely to be a [4Fe-4S]- or [3Fe-4S]-type ferredoxin and not a [2Fe-2S]-type ferredoxin, as found in all previously described ring-hydroxylating dioxygenases. Expression in Escherichia coli of ditA1A2A3, encoding the diterpenoid dioxygenase without its putative reductase component, resulted in a functional enzyme. The diterpenoid dioxygenase attacks 7-oxoDhA, and not DhA, at C-11 and C-12, producing 7-oxo-11,12-dihydroxy-8,13-abietadien acid, which was identified by 1H nuclear magnetic resonance, UV-visible light, and high-resolution mass spectrometry. The organization of the genes encoding the various components of the diterpenoid dioxygenase, the phylogenetic distinctiveness of both the α subunit and the ferredoxin component, and the unusual Fe-S cluster of the ferredoxin all suggest that this enzyme belongs to a new class of aromatic ring-hydroxylating dioxygenases. PMID:10217753

  11. Structure-property relationships in addition polyimides. 1: Resins from four-ring aromatic diamines containing carbonyl and methylene groups

    NASA Technical Reports Server (NTRS)

    Delvigs, Peter; Klopotek, David L.; Cavano, Paul J.

    1994-01-01

    In an effort to improve the processing characteristics of addition-type polyimide resins the use of flexibilized four-ring aromatic diamine moieties was investigated. A series of 12 diamines containing carbonyl and methylene, as well as oxo and thio bridging groups, was synthesized. The diamines were polymerized with the dimethyl ester of 3.3', 4.4' - benzophenonetetracarboxylic acid (BTDE), using the monomethyl ester of nadic acid (NE) as an end-cap. The effect of diamine structure on the solubility and rheological properties during cure was determined. This paper also describes the effect of diamine structure and formulated molecular weight on the glass transition temperature and thermo-oxidative stability at elevated temperatures after various post-cure regimes. The results indicate that polyimides from some of the diamines containing methylene connecting groups have potential as matrix resins for long-term applications at temperatures up to 300 C.

  12. 1 alpha,25-dihydroxyvitamin D3 analogs featuring aromatic and heteroaromatic rings: design, synthesis, and preliminary biological testing.

    PubMed

    Posner, G H; Li, Z; White, M C; Vinader, V; Takeuchi, K; Guggino, S E; Dolan, P; Kensler, T W

    1995-10-27

    Aromatic compounds 2a-c, analogs of 1 alpha, 25-dihydroxyvitamin (calcitriol, 1), and heteroaromatic compounds 4a-c and 5a-c, analogs of 19-nor-1 alpha, 25-dihydroxyvitamin D3 (3), were designed to simulate the topology of their biologically potent parent compounds while avoiding previtamin D equilibrium. Convergent and facile total syntheses of the analogs (+)-2b, (+)-2c, (-)-4b, and (-)-5b were achieved via carbonyl addition of regiospecifically formed organolithium nucleophiles to the enantiomerically pure C,D-ring ketone (+)-17, characteristic of natural calcitriol (1). Likewise, hybrid analogs 20a-c were prepared to determine whether incorporation of a known potentiating side chain would lead to increased biological activity. Preliminary in vitro biological testing showed that aromatic analogs (+)-2b, (+)-2c, and 20a-c as well as heteroaromatic analogs (-)-4b and (-)-5b have very low affinities for the calf thymus vitamin D receptor but considerable antiproliferative activities in murine keratinocytes at micromolar concentration. No biological advantage was observed in this keratinocyte assay for the doubly modified hybrid analogs 20a-c over the singly modified parent (+)-2b. Analog (+)-2b, but surprisingly not the corresponding analog 20b differing from (+)-2b only in the side chain, showed considerable activity in nongenomic opening of calcium channels in rat osteosarcoma cells. PMID:7473581

  13. Forming a Two-Ring Polycyclic Aromatic Hydrocarbon without a Benzene Intermediate: the Reaction of Propargyl with Acetylene

    NASA Astrophysics Data System (ADS)

    Osborn, David; Savee, John; Selby, Talitha; Welz, Oliver; Taatjes, Craig

    The reaction of acetylene (HCCH) with a resonance-stabilized free radical is a commonly invoked mechanism for the generation of polycyclic aromatic hydrocarbons (PAH), which are likely precursors of soot particles in combustion. In this work, we examine the sequential addition of acetylene to the propargyl radical (H2CCCH) at temperatures of 800 and 1000 K. Using time-resolved multiplexed photoionization mass spectrometry with tunable ionizing radiation, we identified the isomeric forms of the C5H5 and C7H7 intermediates in this reaction sequence, and confirmed that the final C9H8 product is the two-ring aromatic compound indene. We identified two different resonance-stabilized C5H5 intermediates, with different temperature dependencies. Furthermore, the C7H7 intermediate is the tropyl radical (c-C7H7) , not the benzyl radical (C6H5CH2) , as is usually assumed in combustion environments. These experimental results are in general agreement with the latest electronic structure / master equation results of da Silva et al. This work shows a pathway for PAH formation that bypasses benzene / benzyl intermediates.

  14. Particle on a boron disk: ring currents and disk aromaticity in B20(2-).

    PubMed

    Tai, Truong Ba; Havenith, Remco W A; Teunissen, Jos L; Dok, Ahmet R; Hallaert, Simon D; Nguyen, Minh Tho; Ceulemans, Arnout

    2013-09-16

    The B20(2-) cluster is predicted to exhibit a planar sheet-like structure with a circular circumference. Orbital plots and energy correlations demonstrate the close correspondence between the electronic structure of B20(2-) and the Bessel functions describing the waves of a quantum mechanical particle confined to a disk. The π-band of B20(2-), and its B19(-) congener, contains 12 π-electrons, forming a (1σ)(2)(1π)(4)(1δ)(4)(2σ)(2) configuration, which corresponds to a "disk aromaticity" electron count. The analogy not only applies to the π-band, but also extends to the 50 valence σ-electrons. The occupied σ-orbitals are assigned on the basis of radial and angular nodes of the scalar disk waves. The magnetic response of the cluster was examined by Nucleus Independent Chemical Shift (NICS) values and current density calculations based on the ipsocentric model. B20(2-) is found to exhibit a remarkable inner paratropic current in the σ-channel and an outer diatropic current in the π-channel. The orbital excitations responsible for the antiaromaticity in σ and the disk-aromaticity in π are identified. PMID:24011355

  15. Heterologous Expression of Polycyclic Aromatic Hydrocarbon Ring-Hydroxylating Dioxygenase Genes from a Novel Pyrene-Degrading Betaproteobacterium

    PubMed Central

    Hu, Jing; Aitken, Michael D.

    2012-01-01

    A betaproteobacterium within the family Rhodocyclaceae previously identified as a pyrene degrader via stable-isotope probing (SIP) of contaminated soil (designated pyrene group 1 or PG1) was cultivated as the dominant member of a mixed bacterial culture. A metagenomic library was constructed, and the largest contigs were analyzed for genes associated with polycyclic aromatic hydrocarbon (PAH) metabolism. Eight pairs of genes with similarity to the α- and β-subunits of ring-hydroxylating dioxygenases (RHDs) associated with aerobic bacterial PAH degradation were identified and linked to PG1 through PCR analyses of a simplified enrichment culture. In tandem with a ferredoxin and reductase found in close proximity to one pair of RHD genes, six of the RHDs were cloned and expressed in Escherichia coli. Each cloned RHD was tested for activity against nine PAHs ranging in size from two to five rings. Despite differences in their predicted protein sequences, each of the six RHDs was capable of transforming phenanthrene and pyrene. Three RHDs could additionally transform naphthalene and fluorene, and these genotypes were also associated with the ability of the E. coli constructs to convert indole to indigo. Only one of the six cloned RHDs was capable of transforming anthracene and benz[a]anthracene. None of the tested RHDs were capable of significantly transforming fluoranthene, chrysene, or benzo[a]pyrene. PMID:22427500

  16. Protonation at the aromatic ring of samarium benzophenone dianion species. Isolation and structural characterization of a samarium(III) enolate complex

    SciTech Connect

    Hou, Z.; Yoshimura, Takashi; Wakatsuki, Yasuo )

    1994-11-30

    The reduction of aromatic compounds into their dihydro derivatives by dissolving metal/alcohol systems (the Birch reduction) is a useful methodology in organic synthesis. Of particular importance is the reduction of aromatic carbonyl compounds such as aromatic acids, esters, amides, and monoaryl ketones, which usually generates in situ useful metal enolate intermediates that upon further reaction with electrophiles yield a variety of cyclohexadiene derivatives. One of the possible processes to generate these metal enolate intermediates is thought to be the monoprotonation of dianionic species at the para position of the aromatic rings. On the other hand, the reduction of diaryl ketones by alkali metals in liquid ammonia or by lanthanide metals in THF/HMPA or DME has been well known to afford the corresponding ketone dianions. The first X-ray structure of metal ketone dianion complexes, [Yb([mu]-[eta][sup 1],[eta][sup 2]-OCPh[sub 2]) (HMPA)[sub 2

  17. Effects of polycyclic aromatic hydrocarbons on microbial community structure and PAH ring hydroxylating dioxygenase gene abundance in soil.

    PubMed

    Sawulski, Przemyslaw; Clipson, Nicholas; Doyle, Evelyn

    2014-11-01

    Development of successful bioremediation strategies for environments contaminated with recalcitrant pollutants requires in-depth knowledge of the microorganisms and microbial processes involved in degradation. The response of soil microbial communities to three polycyclic aromatic hydrocarbons, phenanthrene (3-ring), fluoranthene (4-ring) and benzo(a)pyrene (5-ring), was examined. Profiles of bacterial, archaeal and fungal communities were generated using molecular fingerprinting techniques (TRFLP, ARISA) and multivariate statistical tools were employed to interpret the effect of PAHs on community dynamics and composition. The extent and rate of PAH removal was directly related to the chemical structure, with the 5-ring PAH benzo(a)pyrene degraded more slowly than phenathrene or fluoranthene. Bacterial, archaeal and fungal communities were all significantly affected by PAH amendment, time and their interaction. Based on analysis of clone libraries, Actinobacteria appeared to dominate in fluoranthene amended soil, although they also represented a significant portion of the diversity in phenanthrene amended and unamended soils. In addition there appeared to be more γ-Proteobacteria and less Bacteroidetes in soil amended with either PAH compared to the control. The soil bacterial community clearly possessed the potential to degrade PAHs as evidenced by the abundance of PAH ring hydroxylating (PAH-RHDα) genes from both gram negative (GN) and gram positive (GP) bacteria in PAH-amended and control soils. Although the dioxygenase gene from GP bacteria was less abundant in soil than the gene associated with GN bacteria, significant (p < 0.001) increases in the abundance of the GP PAH-RHDα gene were observed during phenanthrene and fluoranthene degradation, whereas there was no significant difference in the abundance of the GN PAH-RHDα gene during the course of the experiment. Few studies to-date have examined the effect of pollutants on more than one microbial

  18. Understanding Stacking Interactions between an Aromatic Ring and Nucleobases in Aqueous Solution: Experimental and Theoretical Study.

    PubMed

    Kataev, Evgeny A; Shumilova, Tatiana A; Fiedler, Benjamin; Anacker, Tony; Friedrich, Joachim

    2016-08-01

    Stacking interactions between aromatic compounds and nucleobases are crucial in recognition of nucleotides and nucleic acids, but a comprehensive understanding of the strength and selectivity of these interactions in aqueous solution has been elusive. To this end, model complexes have been designed and analyzed by experiment and theory. For the first time, stacking free energies between five nucleobases and anthracene were determined experimentally from thermodynamic double mutant cycles. Three different experimental methods were proposed and evaluated. The dye prefers to bind nucleobases in the order (kcal/mol): G (1.3) > T (0.9) > U (0.8) > C (0.5) > A (0.3). The respective trend of interaction free energies extracted from DFT calculations correlates to that obtained experimentally. Analysis of the data suggests that stacking interactions dominate over hydrophobic effects in an aqueous solution and can be predicted with DFT calculations. PMID:27314892

  19. Identification and characterization of OSTL (RNF217) encoding a RING-IBR-RING protein adjacent to a translocation breakpoint involving ETV6 in childhood ALL

    PubMed Central

    Fontanari Krause, Luciana M.; Japp, Anna Sophia; Krause, Alexandre; Mooster, Jana; Chopra, Martin; Müschen, Markus; Bohlander, Stefan K.

    2014-01-01

    Genomic aberrations involving ETV6 on band 12p13 are amongst the most common chromosomal abnormalities in human leukemia. The translocation t(6;12)(q23;13) in a childhood B-cell acute lymphoblastic leukemia (ALL) cell line fuses ETV6 with the putative long non-coding RNA gene STL. Linking STL properties to leukemia has so far been difficult. Here, we describe a novel gene, OSTL (annotated as RNF217 in Genbank), which shares the first exon and a CpG island with STL but is transcribed in the opposite direction. Human RNF217 codes for a highly conserved RING finger protein and is mainly expressed in testis and skeletal muscle with different splice variants. RNF217 shows regulated splicing in B cell development, and is expressed in a number of human B cell leukemia cell lines, primary human chronic myeloid leukemia, acute myeloid leukemia with normal karyotype and acute T-ALL samples. Using a yeast two-hybrid screen, we identified the anti-apoptotic protein HAX1 to interact with RNF217. This interaction could be mapped to the C-terminal RING finger motif of RNF217. We propose that some of the recurring aberrations involving 6q might deregulate the expression of RNF217 and result in imbalanced apoptosis signalling via HAX1, promoting leukemia development. PMID:25298122

  20. A Porous Aromatic Framework Constructed from Benzene Rings Has a High Adsorption Capacity for Perfluorooctane Sulfonate

    PubMed Central

    Luo, Qin; Zhao, Changwei; Liu, Guixia; Ren, Hao

    2016-01-01

    A low-cost and easily constructed porous aromatic framework (PAF-45) was successfully prepared using the Scholl reaction. PAF-45 was, for the first time, used to remove perfluorooctane sulfonate (PFOS) from aqueous solution. Systematic experiments were performed to determine the adsorption capacity of PAF-45 for PFOS and to characterize the kinetics of the adsorption process. The adsorption of PFOS onto PAF-45 reached equilibrium in 30 min, and the adsorption capacity of PAF-45 for PFOS was excellent (5847 mg g−1 at pH 3). The amount of PFOS adsorbed by PAF-45 increased significantly as the cation (Na+, Mg2+, or Fe3+) concentration increased, which probably occurred because the cations enhanced the interactions between the negatively charged PFOS molecules and the positively charged PAF-45 surface. The cations Na+, Mg2+, and Fe3+ were found to form complexes with PFOS anions in solution. Density functional theory was used to identify the interactions between PFOS and Na+, Mg2+, and Fe3+. We expect that materials of the same type as PAF-45 could be useful adsorbents for removing organic pollutants from industrial wastewater and contaminated surface water. PMID:26843015

  1. A Porous Aromatic Framework Constructed from Benzene Rings Has a High Adsorption Capacity for Perfluorooctane Sulfonate.

    PubMed

    Luo, Qin; Zhao, Changwei; Liu, Guixia; Ren, Hao

    2016-01-01

    A low-cost and easily constructed porous aromatic framework (PAF-45) was successfully prepared using the Scholl reaction. PAF-45 was, for the first time, used to remove perfluorooctane sulfonate (PFOS) from aqueous solution. Systematic experiments were performed to determine the adsorption capacity of PAF-45 for PFOS and to characterize the kinetics of the adsorption process. The adsorption of PFOS onto PAF-45 reached equilibrium in 30 min, and the adsorption capacity of PAF-45 for PFOS was excellent (5847 mg g(-1) at pH 3). The amount of PFOS adsorbed by PAF-45 increased significantly as the cation (Na(+), Mg(2+), or Fe(3+)) concentration increased, which probably occurred because the cations enhanced the interactions between the negatively charged PFOS molecules and the positively charged PAF-45 surface. The cations Na(+), Mg(2+), and Fe(3+) were found to form complexes with PFOS anions in solution. Density functional theory was used to identify the interactions between PFOS and Na(+), Mg(2+), and Fe(3+). We expect that materials of the same type as PAF-45 could be useful adsorbents for removing organic pollutants from industrial wastewater and contaminated surface water. PMID:26843015

  2. A Porous Aromatic Framework Constructed from Benzene Rings Has a High Adsorption Capacity for Perfluorooctane Sulfonate

    NASA Astrophysics Data System (ADS)

    Luo, Qin; Zhao, Changwei; Liu, Guixia; Ren, Hao

    2016-02-01

    A low-cost and easily constructed porous aromatic framework (PAF-45) was successfully prepared using the Scholl reaction. PAF-45 was, for the first time, used to remove perfluorooctane sulfonate (PFOS) from aqueous solution. Systematic experiments were performed to determine the adsorption capacity of PAF-45 for PFOS and to characterize the kinetics of the adsorption process. The adsorption of PFOS onto PAF-45 reached equilibrium in 30 min, and the adsorption capacity of PAF-45 for PFOS was excellent (5847 mg g-1 at pH 3). The amount of PFOS adsorbed by PAF-45 increased significantly as the cation (Na+, Mg2+, or Fe3+) concentration increased, which probably occurred because the cations enhanced the interactions between the negatively charged PFOS molecules and the positively charged PAF-45 surface. The cations Na+, Mg2+, and Fe3+ were found to form complexes with PFOS anions in solution. Density functional theory was used to identify the interactions between PFOS and Na+, Mg2+, and Fe3+. We expect that materials of the same type as PAF-45 could be useful adsorbents for removing organic pollutants from industrial wastewater and contaminated surface water.

  3. Photochromic Diarylethenes with Heterocyclic Aromatic Rings: Correlation between Thermal Bistability and Geometrical Characters of Transition States.

    PubMed

    Li, Xin; Zou, Qi; Ågren, Hans

    2015-08-27

    We present a density functional theory study on the thermal bistability of a number of photochromic diarylethenes, with emphasis on the free energy barrier of the ground-state ring-opening process. We found that the free energy barrier is correlated with the geometrical and vibrational character of the transition state, in particular the distance between the two reactive carbon atoms, the out-of-plane angles of the methyl groups at the reactive carbon atoms, and the imaginary vibrational frequency. Based on these relationships we propose a linear fitting expression for the free energy barrier in terms of the three aforementioned transition-state quantities and obtained a correlation coefficient of R(2) = 0.971. In this way quantum chemical calculations may provide insight and structure-property relationships, which can be applied in the development of novel photochromic materials. PMID:26267793

  4. Initial Steps of Aromatic Ring Formation in a Laminar Premixed Fuel-Rich Cyclopentene Flame†

    SciTech Connect

    Hansen, N.; Kasper, T.; Klippenstein, S. J.; Westmoreland, P. R.; Law, M. E.; Taatjes, C. A.; Kohse-Höinghaus, K.; Wang, J.; Cool, T. A.

    2007-05-01

    A fuel-rich, nonsooting, premixed laminar cyclopentene flame (phi = 2.0) at 37.6 Torr (50 mbar) is investigated by flame-sampling photoionization molecular-beam mass spectrometry utilizing vacuum-ultraviolet synchrotron radiation. Mole fractions as a function of distance from the burner are measured for 49 intermediates with ion masses ranging from 2 (H-2) to 106 (C8H10), providing a broad database for flame modeling studies. The isomeric composition is resolved for most species, and the identification of several C4Hx, C7H6, and C7H8 isomers is discussed in detail. The presence of C5H5CCH/C5H4CCH2 and cycloheptatriene is revealed by comparisons between flame-sampled photoionization efficiency data and theoretical simulations, based on calculated ionization energies and Franck-Condon factors. This insight suggests a new potential molecular- weight growth mechanism that is characterized by C-5-C-7 ring enlargement reactions.

  5. Electronic transport properties of molecular junctions based on the direct binding of aromatic ring to electrodes

    NASA Astrophysics Data System (ADS)

    Lan, Tran Nguyen

    2014-01-01

    We have used the non-equilibrium Green's function in combination with the density functional theory to investigate the quantum transport properties of the molecular junctions including a terminated benzene ring directly coupled to surface of metal electrodes (physisorption). The other side of molecule was connected to electrode via thiolate bond (chemisorption). Two different electrodes have been studied, namely Cu and Al. Rectification and negative differential resistance behavior have been observed. We found that the electron transport mechanism is affected by the nature of benzene-electrode coupling. In other words, the transport mechanism depends on the nature of metallic electrode. Changing from sp- to sd-metallic electrode, the molecular junction changes from the Schottky to p-n junction-like diode. The transmission spectra, projected density of state, molecular projected self-consistent Hamiltonian, transmission eigenchannel, and Muliken population have been analyzed for explanation of electronic transport properties. Understanding the transport mechanism in junction having direct coupling of π-conjugate to electrode will be useful to design the future molecular devices.

  6. Construction of sole benzene ring porous aromatic frameworks and their high adsorption properties.

    PubMed

    Li, Lina; Cai, Kun; Wang, Pengyuan; Ren, Hao; Zhu, Guangshan

    2015-01-14

    Porous organic frameworks (POFs), with their excellent performance in catalysis, electricity, sensor, gas storage, and separation, have attracted a great deal of attention from researchers all over the world. Generally, the monomers of POF materials require a rigid three-dimensional molecule configuration together with special functional groups, as well as being triggered by noble metal catalysts. Here we report a low-cost and easy-construction strategy for synthesizing PAF materials. A series of flat multi-benzene compounds are selected as building units, and those phenyl rings could couple together to form polymeric skeletons. The BET surface areas of resulting PAFs are moderate, ranging from 777 to 972 m(2) g(-1). However, they unexpectedly exhibit superior gas sorption capacities. At 1.0 bar and 77 K, the H2 uptake of PAF-48 reaches 215 cm(3) g(-1). In addition, PAF-49 shows excellent performance in carbon dioxide and methane sorption, with values of 104 and 35 cm(3) g(-1), respectively. With those adsorption properties, these PAF materials could be considered as potential candidates for energetic gas adsorbents. PMID:25495481

  7. Low-pressure effective fluorescence lifetimes and photo-physical rate constants of one- and two-ring aromatics

    NASA Astrophysics Data System (ADS)

    Benzler, Thorsten; Faust, Stephan; Dreier, Thomas; Schulz, Christof

    2015-12-01

    One- and two-ring aromatics such as toluene and naphthalene are frequently used molecular tracer species in laser-induced fluorescence (LIF) imaging diagnostics. Quantifying LIF signal intensities requires knowledge of the photo-physical processes that determine the fluorescence quantum yield. Collision-induced and intramolecular energy transfer processes in the excited electronic state closely interact under practical conditions. They can be separated through experiments at variable low pressures. Effective fluorescence lifetimes of gaseous toluene, 1,2,4-trimethylbenzene, anisole, naphthalene, and 1-methylnaphthalene diluted in CO2 were measured after picosecond laser excitation at 266 nm and time-resolved detection of fluorescence intensities. Measurements in an optically accessible externally heated cell between 296 and 475 K and 0.010-1 bar showed that effective fluorescence lifetimes generally decrease with temperature, while the influence of the bath-gas pressure depends on the respective target species and temperature. The results provide non-radiative and fluorescence rate constants and experimentally validate the effect of photo-induced cooling.

  8. Isolation and characterization of a Mycobacterium species capable of degrading three- and four-ring aromatic and aliphatic hydrocarbons

    SciTech Connect

    Churchill, S.A.; Harper, J.P.; Churchill, P.F.

    1999-02-01

    Mycobacterium sp. strain CH1 was isolated from polycyclic aromatic hydrocarbon (PAH)-contaminated freshwater sediments and identified by analysis of 16S rDNA sequences. Strain CH1 was capable of mineralizing three- and four-ring PAHs including phenanthrene, pyrene, and fluoranthene. In addition, strain CH1 could utilize phenanthrene or pyrene as a sole carbon and energy source. A lag phase of at least 3 days was observed during pyrene mineralization. This lag phase decreased to less than 1 day when strain CH1 was grown in the presence of phenanthrene or fluoranthene. Strain CH1 also was capable of using a wide range of alkanes as sole carbon and energy sources. No DNA hybridization was detected with the nahAc gene probe, indicating that enzymes involved in PAH metabolism are not related to the well-characterized naphthalene dioxygenase gene. DNA hybridization was not detected when the alkB gene from Pseudomonas oleovorans was used under high-stringency conditions. However, there was slight but detectable hybridization under low-stringency conditions. This suggests a distant relationship between genes involved in alkane oxidation.

  9. Isolation and Characterization of a Mycobacterium Species Capable of Degrading Three- and Four-Ring Aromatic and Aliphatic Hydrocarbons

    PubMed Central

    Churchill, Sharon A.; Harper, Jennifer P.; Churchill, Perry F.

    1999-01-01

    Mycobacterium sp. strain CH1 was isolated from polycyclic aromatic hydrocarbon (PAH)-contaminated freshwater sediments and identified by analysis of 16S rDNA sequences. Strain CH1 was capable of mineralizing three- and four-ring PAHs including phenanthrene, pyrene, and fluoranthene. In addition, strain CH1 could utilize phenanthrene or pyrene as a sole carbon and energy source. A lag phase of at least 3 days was observed during pyrene mineralization. This lag phase decreased to less than 1 day when strain CH1 was grown in the presence of phenanthrene or fluoranthene. Strain CH1 also was capable of using a wide range of alkanes as sole carbon and energy sources. No DNA hybridization was detected with the nahAc gene probe, indicating that enzymes involved in PAH metabolism are not related to the well-characterized naphthalene dioxygenase gene. DNA hybridization was not detected when the alkB gene from Pseudomonas oleovorans was used under high-stringency conditions. However, there was slight but detectable hybridization under low-stringency conditions. This suggests a distant relationship between genes involved in alkane oxidation. PMID:9925581

  10. The relationship between developmental toxicity and aromatic-ring class profile of high-boiling petroleum substances.

    PubMed

    Murray, F Jay; Roth, Randy N; Nicolich, Mark J; Gray, Thomas M; Simpson, Barry J

    2013-11-01

    In response to the US EPA HPV Challenge Program, this study was conducted to: (1) evaluate the relationship between PAC content and the developmental toxicity of high-boiling petroleum substances (HBPS) and (2) develop mathematical models to predict the developmental toxicity of similar untested substances based on their aromatic ring class (ARC) profiles. For this investigation, 68 developmental toxicity studies were reviewed. The ARC models relied on data from 21 rat dermal developmental toxicity studies conducted with similar experimental designs to ensure a consistent data set for comparison. The most sensitive general endpoints of developmental toxicity (i.e., decreased fetal survival and growth) were chosen for modeling. The ARC models demonstrated a strong correlation between the predicted vs. observed values for specific sensitive endpoints of these developmental toxicities (percent resorptions, r=0.99; live fetuses per litter, r=0.98; fetal body weight, r=0.94). Such associations provide a promising approach for predicting the developmental toxicity of untested HBPS. Efforts to corroborate the ARC models using test substances that were not used to build the ARC models produced mixed results, and further development and refinement of the ARC models is recommended before they can be reliably applied to all HBPS. PMID:23680405

  11. Structure-plant phytotoxic activity relationship of 7,7'-epoxylignanes, (+)- and (-)-verrucosin: simplification on the aromatic ring substituents.

    PubMed

    Yamauchi, Satoshi; Nakayama, Kumiko; Nishiwaki, Hisashi; Shuto, Yoshihiro

    2014-10-15

    The synthesized 7-aryl derivatives of (7R,7'S,8S,8'S)-(+)-verrucosin were applied to growth inhibitory activity test against ryegrass at 1mM. 7-(3-Ethoxy-4-hydroxyphenyl) derivative 12 and 7-(2-hydroxyphenyl) derivative 4 showed comparable activity to those of (+)-verrucosin against the root (-95%) and the shoot (-60%), respectively. The growth inhibitory activity test against lettuce using synthesized 7-aryl derivatives of (7S,7'R,8R,8'R)-(-)-verrucosin at 1mM showed that the activities of 7-(3-hydroxyphenyl) derivative 20 and 7-(3-ethoxy-4-hydroxyphenyl) derivative 28 are similar to that of (-)-verrucosin against the root (-95%). Against the shoot, 7-(3-hydroxyphenyl) derivative 20 showed higher activity (-80%) than that of (-)-verrucosin (-60%). As the next step, (7S,7'R,8R,8'R)-7-(3-hydroxyphenyl)-7'-aryl-(-)-verrucosin derivatives, in which the most effective 3-hydroxyphenyl group is employed as 7-aromatic ring, were synthesized for the assay against lettuce. In this experiment, 7'-(2-hydroxyphenyl) derivative 37 and 7'-(3-hydroxyphenyl) derivative 38 showed similar activity to that of derivative 20. The effect of 7- and 7'-aryl structures of 7,7'-epoxylignanes on the plant growth inhibitory activity was clarified. The 7- and 7'-aryl structures were simplified to show comparable activity to or higher activity than that of (-)-verrucosin. The plant growth inhibitory activity of a nutmeg component, (+)-fragransin C3b, was estimated as -80% inhibition at 1mM against ryegrass roots. PMID:25248684

  12. Positioning a Carbon-Fluorine Bond over the π Cloud of an Aromatic Ring: A Different Type of Arene Activation.

    PubMed

    Holl, Maxwell Gargiulo; Struble, Mark D; Singal, Prakhar; Siegler, Maxime A; Lectka, Thomas

    2016-07-11

    It is known that the fluoro group has only a small effect on the rates of electrophilic aromatic substitutions. Imagine instead a carbon-fluorine (C-F) bond positioned tightly over the π cloud of an aryl ring-such an orthogonal, noncovalent arrangement could instead stabilize a positively charged arene intermediate or transition state, giving rise to novel electrophilic aromatic substitution chemistry. Herein, we report the synthesis and study of molecule 1, containing a rigid C-F⋅⋅⋅Ar interaction that plays a prominent role in both its reaction chemistry and spectroscopy. For example, we established that the C-F⋅⋅⋅Ar interaction can bring about a >1500 fold increase in the relative rate of an aromatic nitration reaction, affording functionalization on the activated ring exclusively. Overall, these results establish fluoro as a through-space directing/activating group that complements the traditional role of fluorine as a slightly deactivating aryl substituent in nitrations. PMID:27145463

  13. Extreme projection of a proton into the pi-cloud of an aromatic ring: record shielding of an aromatic proton in trans-10b-methyl-10c-(1-naphthyl)-10b,10c-dihydropyrene.

    PubMed

    Ting, Yuhua; Lai, Yee-Hing

    2004-01-28

    A synthetic sequence involving dithiametacyclophane --> metacyclophanediene --> dihydropyrene was employed to prepare trans-10b-methyl-10c-(2-naphthyl)- and trans-10b-methyl-10c-(1-naphthyl)-10b,10c-dihydropyrene 5 and 6, respectively. Both exhibit a strong diamagnetic ring current despite the introduction of an internal bulky substituent within the pi-electron cloud. Their electronic spectra suggest interaction between the two near-perpendicular naphthyl and dihydropyrenyl pi systems, resulting in red shift and band broadening. All naphthyl protons are well resolved in their 1H NMR spectra due to a strong shielding effect of the dihydropyrene ring. The most shielded protons in 5 and 6 are H1' and H2' at delta 2.47 and 1.42, respectively, being 5.25 and 5.95 ppm shifted from those of reference protons. There is evidence for free rotation on the NMR time scale of the 2-naphthyl ring in 5 with a preference for a particular conformer, whereas the 1-naphthyl ring in 6 is conformationally rigid with its H2' projecting deeply into the pi-cloud, thus accounting for the most shielded aromatic proton (H2' in 6) reported to date. PMID:14733567

  14. Two-dimensional inorganic–organic hybrid semiconductors composed of double-layered ZnS and monoamines with aromatic and heterocyclic aliphatic rings: Syntheses, structures, and properties

    SciTech Connect

    Wang, Sujing; Li, Jing

    2015-04-15

    As an addition to the II–VI based inorganic–organic hybrid semiconductor family, five new two-dimensional (2D) double-layered structures have been synthesized employing monoamines with different aromatic or heterocyclic aliphatic rings. Zn{sub 2}S{sub 2}(bza) (1), Zn{sub 2}S{sub 2}(mbza) (2), Zn{sub 2}S{sub 2}(fbza) (3), Zn{sub 2}S{sub 2}(pca) (4), and Zn{sub 2}S{sub 2}(thfa) (5) (bza=benzylamine, mbza=4-methoxybenzylamine, fbza=4-flurobenzylamine, pca=3-picolylamine, and thfa=tetrahydrofurfurylamine) are prepared by solvothermal reactions and characterized by different analytical methods, including powder X-ray diffraction, optical diffuse reflection, thermogravimetric analysis and photoluminescence spectroscopy. The powder X-ray diffraction patterns show that all five compounds adopt 2D double-layered structures. Optical diffuse reflectance spectra of these compounds suggest that they have notably lower band gaps than those of the similar compounds composed of aliphatic alkyl amines. Their photoluminescence properties and thermal stability are also analyzed. - Graphical abstract: Five new members of two-dimensional double-layered 2D-Zn{sub 2}S{sub 2}(L) (L=Ligand) structures employing monoamines with different aromatic or heterocyclic aliphatic rings have been designed, synthesized, and characterized. - Highlights: • A new sub-family of II-VI based hybrid semiconductors are designed, synthesized, and structurally characterized using amines with aromatic or aliphatic cyclic rings. • These compounds have notably lower band gaps than those made of aliphatic alkyl amines, greatly broadening the range of band gaps of this material family. • They emit strongly with systematically tunable emission intensity and energy.

  15. Rings

    SciTech Connect

    Davis, R.L.

    1989-01-01

    The essence of vortex physics is that at certain low-energy scales elementary excitations of a point particle theory can behave like strings rather than particles. Vortices are the resulting string-like solutions; their thickness sets the distance scale beyond which physics is string-like rather than particle-like. String degrees of freedom are massless in the sense that excitations on a string can have an arbitrarily low frequency. Non-string degrees of freedom correspond to massive particles and are absent from the low energy spectrum. This article considers only field theories with vortices at low energies. The possible existence of a class of solitons in these vortex theories will be discussed. They are vortex rings: they are localized and finite in energy, and able to carry the quantum numbers of point particles. Rings are thus particle-like solutions of a vortex theory, which is itself a limit of a point particle field theory.

  16. Distributions and sources of petroleum, aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) in surface sediments from Bohai Bay and its adjacent river, China.

    PubMed

    Wang, Min; Wang, Chuanyuan; Hu, Xiaoke; Zhang, Haijiang; He, Shijie; Lv, Shuangyan

    2015-01-15

    Surface sediment samples from Bohai Bay and its adjacent river, China, were analyzed for aliphatic hydrocarbon, PAHs and biomarkers in order to determine the distribution, composition and source of organic matter in a coastal environment. Results suggested that the input of organic matter from anthropogenic activities has a more significant influence on its distribution than that from natural processes. Petroleum contamination, mainly from offshore oil exploration and discharge of pollutants from rivers, was the main source of n-alkanes. PAHs were mostly of pyrogenic origin; while some sites in Yellow River Estuary were derived mainly from the petrogenic sources. The toxic assessment suggested that the PAHs in surface sediments will not cause immediately adverse biological effects in sediments from Bohai Bay and its adjacent river, China. PMID:25499964

  17. Supramolecular aromaticity

    NASA Astrophysics Data System (ADS)

    Karabıyık, Hande; Sevinçek, Resul; Karabıyık, Hasan

    2014-05-01

    We report experimental and theoretical evidences for supramolecular aromaticity as a new concept to be widely used in researches about molecular crystals. CSD survey regarding frequently encountered resonance-assisted H-bonds (RAHBs) in formic acid, formamide, formimidamide, formic acid-formamide, and formamide-formimidamide dimers shows that supramolecular quasirings formed by RAHBs have remarkable electronic delocalization within themselves, which is reminiscent of aromaticity at supramolecular level. This study criticizes and reevaluates the validity of conventional judgment which states that ring systems formed by intermolecular H-bonds cannot be aromatic. Thus, the term aromaticity can be extended to supramolecular systems formed by RAHBs. Supramolecular aromaticity has a multi-fold nature involving both σ- and π-delocalization, and σ-delocalization through RAHBs takes on a task of compensating σ-deficiency within quasirings. Atomic composition in donor-acceptor set of the dimers is descriptive for supramolecular aromaticity. We revised bond-valence parameters for RAHBs and they suggest that hypervalent character of H atoms is more pronounced than their hypovalent character in RAHBs. The σ-delocalized bonding within H-bonded quasirings necessitates hypervalent character of H atoms. Quantum chemical calculations based on adiabatic Hydrogen Atom Transfer (HAT) between the monomers reveal that topological parameters at ring critical points (RCPs) of the quasirings correlate well with Shannon's entropic aromaticity index. The presence of additional LP orbital on O atoms implying more diffused LP-orbitals in donor-acceptor set leads to the formation of resonance-disabling states reducing supramolecular aromaticity of a quasiring and energetic cost of the electron transfer between the monomers. There is a nonignorable electron transfer between the monomers even in the cases where H atoms are close to donor or acceptor atom. NBO analyses have revealed that

  18. Double aromaticity in transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8)

    NASA Astrophysics Data System (ADS)

    Xu, Chang; Cheng, Longjiu; Yang, Jinlong

    2014-09-01

    It is well known that double-ring boron clusters have got the special double aromaticity with delocalized π orbitals in two directions (tangential and radial), which are potential ligands centered by a transition metal. In this article, the transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8) are theoretically investigated by density functional theory calculations. These endohedral compounds have also got double aromaticity in both tangential and radial directions. Interestingly, the tangential delocalized π orbitals of boron ligands following the Huckle's (4n + 2) rule do not interact with the central metal, while the radial π orbitals of boron ligands are bonded with the central mental to form spd-π endohedral bonding. The spd-π endohedral bonding follows the 18e-principle in Ni@B14 and Fe@B16. However, due to the flat shape of the compounds, 14e (Cr@B14) and 16e (Ni@B12) can also be electronically very stable where the energy levels of the spd-π orbitals delocalized in z-direction rise up. This intriguing bonding model makes sense in further study of the boron chemistry.

  19. Pleiotropic and Epistatic Behavior of a Ring-Hydroxylating Oxygenase System in the Polycyclic Aromatic Hydrocarbon Metabolic Network from Mycobacterium vanbaalenii PYR-1

    PubMed Central

    Kweon, Ohgew; Kim, Seong-Jae; Kim, Dae-Wi; Kim, Jeong Myeong; Kim, Hyun-lee; Ahn, Youngbeom; Sutherland, John B.

    2014-01-01

    Despite the considerable knowledge of bacterial high-molecular-weight (HMW) polycyclic aromatic hydrocarbon (PAH) metabolism, the key enzyme(s) and its pleiotropic and epistatic behavior(s) responsible for low-molecular-weight (LMW) PAHs in HMW PAH-metabolic networks remain poorly understood. In this study, a phenotype-based strategy, coupled with a spray plate method, selected a Mycobacterium vanbaalenii PYR-1 mutant (6G11) that degrades HMW PAHs but not LMW PAHs. Sequence analysis determined that the mutant was defective in pdoA2, encoding an aromatic ring-hydroxylating oxygenase (RHO). A series of metabolic comparisons using high-performance liquid chromatography (HPLC) analysis revealed that the mutant had a lower rate of degradation of fluorene, anthracene, and pyrene. Unlike the wild type, the mutant did not produce a color change in culture media containing fluorene, phenanthrene, and fluoranthene. An Escherichia coli expression experiment confirmed the ability of the Pdo system to oxidize biphenyl, the LMW PAHs naphthalene, phenanthrene, anthracene, and fluorene, and the HMW PAHs pyrene, fluoranthene, and benzo[a]pyrene, with the highest enzymatic activity directed toward three-ring PAHs. Structure analysis and PAH substrate docking simulations of the Pdo substrate-binding pocket rationalized the experimentally observed metabolic versatility on a molecular scale. Using information obtained in this study and from previous work, we constructed an RHO-centric functional map, allowing pleiotropic and epistatic enzymatic explanation of PAH metabolism. Taking the findings together, the Pdo system is an RHO system with the pleiotropic responsibility of LMW PAH-centric hydroxylation, and its epistatic functional contribution is also crucial for the metabolic quality and quantity of the PAH-MN. PMID:25070740

  20. Catalytic trimerization of aromatic nitriles and triaryl-s-triazine ring cross-linked high temperature resistant polymers and copolymers made thereby

    NASA Technical Reports Server (NTRS)

    Hsu, L. C. (Inventor)

    1979-01-01

    Triazine compounds and cross-linked polymer compositions are made by heating aromatic nitriles to a temperature in the range of from about 100 C to about 700 C, and preferably in the range of from about 200 C to about 350 C, in the presence of a catalyst or mixture of catalysts selected from one or more of the following groups: (1) organic sulfonic and sulfinic acids, (2) organic phosphonic and phosphinic acids, and (3)metallic acetylacetonates, at a pressure in the range of from about atmospheric pressure to about 10,000 psi and preferably in the range of from about 200 psi to about 750 psi. Aromatic nitrile-modified (terminated and/or appended) imide, benzimidazole, imidazopyrrolone, quinoxaline, and other condensation type prepolymers or their precopolymers are made which are trimerized with or without a filler by the aforementioned catalytic trimerization process into triaryl-s-triazine ring containing or cross-linked polymeric or copolymeric products useful in applications requiring high thermal-oxidative stability and high performance structural properties at elevated temperatures.

  1. Aromatic Ring Currents Illustrated--NMR Spectra of Tin(IV) Porphyrin Complexes. An Advanced Undergraduate Experiment.

    ERIC Educational Resources Information Center

    Arnold, Dennis P.

    1988-01-01

    Attempts to show that in the closed loops of cyclic structures the protons situated in conic regions above and below the ring will be shielded. Uses the diamagnetic and air stable octahedral tin(IV) complexes of porphyrins for study. Notes complexes crystallize easily and offer spectacular purple colors. (MVL)

  2. Substrate-dependent aromatic ring fission of catechol and 2-aminophenol with O2 catalyzed by a nonheme iron complex of a tripodal N4 ligand.

    PubMed

    Lakshman, Triloke Ranjan; Chatterjee, Sayanti; Chakraborty, Biswarup; Paine, Tapan Kanti

    2016-06-01

    The catalytic reactivity of an iron(ii) complex [(TPA)Fe(II)(CH3CN)2](2+) (1) (TPA = tris(2-pyridylmethyl)amine) towards oxygenative aromatic C-C bond cleavage of catechol and 2-aminophenol is presented. Complex 1 exhibits catalytic and regioselective C-C bond cleavage of 3,5-di-tert-butylcatechol (H2DBC) to form intradiol products, whereas it catalyzes extradiol-type C-C bond cleavage of 2-amino-4,6-di-tert-butylphenol (H2AP). The catalytic reactions are found to be pH-dependent and the complex exhibits maximum turnovers at pH 5 in acetonitrile-phthalate buffer. An iron(iii)-catecholate complex [(TPA)Fe(III)(DBC)](+) (2) is formed in the ring cleavage of catechol. In the extradiol-type cleavage of H2AP, an iron(iii)-2-iminobenzosemiquinonate complex [(TPA)Fe(III)(ISQ)](2+) (3) (ISQ = 4,6-di-tert-butyl-2-iminobenzosemiquinonate radical anion) is observed in the reaction pathway. This work shows the importance of the nature of 'redox non-innocent' substrates in governing the mode of ring fission reactivity. PMID:27148606

  3. Solid-State Nuclear Magnetic Resonance Studies Delineate the Role of the Protein in Activation of Both Aromatic Rings of Thiamin

    PubMed Central

    Balakrishnan, Anand; Paramasivam, Sivakumar; Chakraborty, Sumit; Polenova, Tatyana; Jordan, Frank

    2011-01-01

    Knowledge of the state of ionization and tautomerization of hetero-aromatic cofactors when enzyme-bound is essential for formulating a detailed stepwise mechanism via proton transfers, the most commonly observed contribution to enzyme catalysis. In the bi-functional coenzyme, thiamin diphosphate (ThDP), both aromatic rings participate in catalysis, the thiazolium ring as an electrophilic covalent catalyst, the 4’-aminopyrimidine as acid-base catalyst involving its 1’,4’-iminopyrimidine tautomeric form. Two of four ionization and tautomeric states of ThDP are well characterized via circular dichroism spectral signatures on several ThDP superfamily members. Yet, the method is incapable of providing information about specific proton locations, which in principle may be accessible via NMR studies. To determine the precise ionization/tautomerization states of ThDP during various stages of the catalytic cycle (exemplified in Scheme 1), we report the first application of solid-state NMR spectroscopy to ThDP enzymes, whose large mass (160,000–250,000 Da) precludes solution NMR approaches. Three de novo synthesized analogs, [C2,C6’-13C2]ThDP, [C2-13C]ThDP and [N4’-15N]ThDP used with three enzymes revealed that: (a) Binding to the enzymes activates both the 4'-aminopyrimidine (via pKa elevation) and the thiazolium rings (pKa suppression), (b) Detection of a predecarboxylation intermediate analog using [C2,C6’-13C2]ThDP, enables both confirmation of covalent bond formation, and response in 4’-aminopyrimidine ring’s tautomeric state to intermediate formation, supporting the mechanism postulated in Scheme 1B. (c) The chemical shift of bound [N4’-15N]ThDP provides plausible models for the participation of the 1’,4’-iminopyrimidine tautomer in the mechanism. Unprecedented detail is achieved about proton positions on this bi-functional coenzyme on large enzymes in their active states. PMID:22092024

  4. A comparative study of the aromaticity of pyrrole, furan, thiophene, and their aza-derivatives.

    PubMed

    Najmidin, Kalbinur; Kerim, Ablikim; Abdirishit, Paruza; Kalam, Horigul; Tawar, Tursungul

    2013-09-01

    The relative aromaticity of pyrrole, furan, thiophene, and their aza-derivatives has been examined using TRE (topological resonance energy), MRE (magnetic resonance energy), ring current (RC), and ring current diamagnetic susceptibility (χG) methods. The results obtained were compared with results obtained by others who used the energetic method ASE (aromatic stabilization energy), the geometric method HOMA (harmonic oscillator model of aromaticity), and the magnetic method NICS(1) (nucleus-independent chemical shift). The impact of nitrogen atoms on the aromaticity of the aza-derivatives of pyrrole, furan, and thiophene is discussed. An excellent correlation was found between the energetic (TRE, MRE) and magnetic (RC and χG) criteria of aromaticity for all compounds. It was expected that inclusion of a heteroatom would decrease the aromaticity relative to the cyclopentadienyl anion. Our results show that the type of the first heteroatom, which donates two electrons to the system, as well as the number of nitrogen atoms and their positions in the molecule have a strong effect on aromaticity. In general, aromaticity is enhanced when the nitrogen atom is adjacent to the first heteroatom. The magnitude of aromaticity is related closely with the uniformity of distribution of π-electrons in the molecule. PMID:23716174

  5. Coprophagy by wild ring-tailed lemurs (Lemur catta) in human-disturbed locations adjacent to the Beza Mahafaly Special Reserve, Madagascar.

    PubMed

    Fish, Krista D; Sauther, Michelle L; Loudon, James E; Cuozzo, Frank P

    2007-06-01

    Coprophagy occurs in a number of animal species, including nonhuman primates. During the 2003-2004 dry seasons at the Beza Mahafaly Special Reserve, Madagascar, we observed wild ring-tailed lemurs (Lemur catta) consuming dried fecal matter from three different species. Ring-tailed lemurs consumed human feces on 12 occasions, cattle feces twice, and feral dog feces once. Coprophagy in this population may be a behavioral adaptation that provides animals access to energy and nutrients and may be an important nutritional source for older, and/or dentally impaired individuals during the dry season. PMID:17253614

  6. Insights into the Reaction Mechanism of Aromatic Ring Cleavage by Homogentisate Dioxygenase: A Quantum Mechanical/Molecular Mechanical Study.

    PubMed

    Qi, Yue; Lu, Jiarui; Lai, Wenzhen

    2016-05-26

    To elucidate the reaction mechanism of the ring cleavage of homogentisate by homogentisate dioxygenase, quantum mechanical/molecular mechanical (QM/MM) calculations were carried out by using two systems in different protonation states of the substrate C2 hydroxyl group. When the substrate C2 hydroxyl group is ionized (the ionized pathway), the superoxo attack on the substrate is the rate-limiting step in the catalytic cycle, with a barrier of 15.9 kcal/mol. Glu396 was found to play an important role in stabilizing the bridge species and its O-O cleavage product by donating a proton via a hydrogen-bonded water molecule. When the substrate C2 hydroxyl group is not ionized (the nonionized pathway), the O-O bond cleavage of the bridge species is the rate-limiting step, with a barrier of 15.3 kcal/mol. The QM/MM-optimized geometries for the dioxygen and alkylperoxo complexes using the nonionized model (for the C2 hydroxyl group) are in agreement with the experimental crystal structures, suggesting that the C2 hydroxyl group is more likely to be nonionized. PMID:27119315

  7. The stability of biradicaloid versus closed-shell [E(μ-XR)]2 (E = P, As; X = N, P, As) rings. Does aromaticity play a role?

    PubMed

    Grande-Aztatzi, Rafael; Mercero, Jose M; Ugalde, Jesus M

    2016-04-28

    High-level multiconfigurational self-consistent field calculations, supplemented with multiconfigurational quasi-degenerate perturbation theory ab initio calculations with the aug-cc-pVTZ basis set, demonstrate that the [E(μ-XH)]2 (E = P, As; X = N, P, As) compounds possess one planar and one butterfly-like isomer. The calculations predict that for X = N, planar isomers, which bear substantial biradicaloid character, are more stable than their butterfly-like counterpart isomers, which feature closed-shell electronic structures. This has been ascribed to the fact that the increased bond angle strain at E-N-E is not compensated by the E-E σ (deformed) bond formation in the butterfly-like isomers, yielding the planar structures, which hold wider E-N-E bond angles, as the most stable isomers. As N is substituted by heavier atoms, either P or As, the E-P(As)-E bond angle strain is released and, additionally, as the formed E-E σ-bond is less deformed, the butterfly isomer becomes the most stable isomer. Subsequent evaluation of the normalized Giambiagi multicenter electron delocalization indices revealed no sign of electron delocalization in the four-membered rings and consequently, it is concluded that aromaticity does not play any role in the stabilization of the planar isomers. PMID:26911902

  8. Cardiac toxicity of 5-ring polycyclic aromatic hydrocarbons is differentially dependent on the aryl hydrocarbon receptor 2 isoform during zebrafish development

    SciTech Connect

    Incardona, John P. Linbo, Tiffany L.; Scholz, Nathaniel L.

    2011-12-15

    Petroleum-derived compounds, including polycyclic aromatic hydrocarbons (PAHs), commonly occur as complex mixtures in the environment. Recent studies using the zebrafish experimental model have shown that PAHs are toxic to the embryonic cardiovascular system, and that the severity and nature of this developmental cardiotoxicity varies by individual PAH. In the present study we characterize the toxicity of the relatively higher molecular weight 5-ring PAHs benzo[a]pyrene (BaP), benzo[e]pyrene (BeP), and benzo[k]fluoranthene (BkF). While all three compounds target the cardiovascular system, the underlying role of the ligand-activated aryl hydrocarbon receptor (AHR2) and the tissue-specific induction of the cytochrome p450 metabolic pathway (CYP1A) were distinct for each. BaP exposure (40 {mu}M) produced AHR2-dependent bradycardia, pericardial edema, and myocardial CYP1A immunofluorescence. By contrast, BkF exposure (4-40 {mu}M) caused more severe pericardial edema, looping defects, and erythrocyte regurgitation through the atrioventricular valve that were AHR2-independent (i.e., absent myocardial or endocardial CYP1A induction). Lastly, exposure to BeP (40 {mu}M) yielded a low level of CYP1A+ signal in the vascular endothelium of the head and trunk, without evident toxic effects on cardiac function or morphogenesis. Combined with earlier work on 3- and 4-ring PAHs, our findings provide a more complete picture of how individual PAHs may drive the cardiotoxicity of mixtures in which they predominate. This will improve toxic injury assessments and risk assessments for wild fish populations that spawn in habitats altered by overlapping petroleum-related human impacts such as oil spills, urban stormwater runoff, or sediments contaminated by legacy industrial activities. -- Highlights: Black-Right-Pointing-Pointer PAH compounds with 5 rings in different arrangements caused differential tissue-specific patterns of CYP1A induction in zebrafish embryos. Black

  9. Systematic Introduction of Aromatic Rings to Diphosphine Ligands for Emission Color Tuning of Dinuclear Copper(I) Iodide Complexes.

    PubMed

    Okano, Yuka; Ohara, Hiroki; Kobayashi, Atsushi; Yoshida, Masaki; Kato, Masako

    2016-06-01

    We have newly synthesized two solution-stable luminescent dinuclear copper(I) complexes, [Cu2(μ-I)2(dpppy)2] (Cu-py) and [Cu2(μ-I)2(dpppyz)2] (Cu-pyz), where dpppy = 2,3-bis(diphenylphosphino)pyridine and dpppyz = 2,3-bis(diphenylphosphino)pyrazine, using chelating diphosphine ligands composed of N-heteroaromatic rings. X-ray analysis clearly indicates that the molecular structures of Cu-py and Cu-pyz are almost identical with that of the parent complex, [Cu2(μ-I)2(dppb)2] [Cu-bz; dppb = 2,3-bis(diphenylphosphino)benzene]. Complexes Cu-py and Cu-pyz exhibit luminescence [emission quantum yield (Φem) = 0.48 and 0.02, respectively] in the solid state at 298 K. A wide emission color tuning, from 497 to 638 nm (energy = 0.55 eV, with an emission color ranging from green to reddish-orange), was achieved in the solid state by the introduction of pyridinic N atoms into the bridging phenyl group between the two diphenylphosphine groups. Density functional theory calculations suggest that the emission could originate from the effective combination of the metal-to-ligand charge-transfer excited state with the halide-to-ligand charge-transfer excited state. Thus, the emission color change is due to stabilization of the π* levels of the central aryl group in the diphosphine ligand. Furthermore, these copper(I) complexes exhibit thermally activated delayed fluorescence at 298 K because of the small singlet-triplet energy difference (ΔE = 523 and 564 cm(-1) for Cu-py and Cu-pyz, respectively). The stability of these complexes in chloroform, due to the rigid bonds between the diphosphine ligands and the Cu(I) ions, enables the preparation of emissive poly(methyl methacrylate) films by the solution-doping technique. PMID:27152774

  10. Polynuclear aromatic hydrocarbons for fullerene synthesis in flames

    DOEpatents

    Alford, J. Michael; Diener, Michael D.

    2006-12-19

    This invention provides improved methods for combustion synthesis of carbon nanomaterials, including fullerenes, employing multiple-ring aromatic hydrocarbon fuels selected for high carbon conversion to extractable fullerenes. The multiple-ring aromatic hydrocarbon fuels include those that contain polynuclear aromatic hydrocarbons. More specifically, multiple-ring aromatic hydrocarbon fuels contain a substantial amount of indene, methylnapthalenes or mixtures thereof. Coal tar and petroleum distillate fractions provide low cost hydrocarbon fuels containing polynuclear aromatic hydrocarbons, including without limitation, indene, methylnapthalenes or mixtures thereof.

  11. Substrate Specificity and Structural Characteristics of the Novel Rieske Nonheme Iron Aromatic Ring-Hydroxylating Oxygenases NidAB and NidA3B3 from Mycobacterium vanbaalenii PYR-1

    PubMed Central

    Kweon, Ohgew; Kim, Seong-Jae; Freeman, James P.; Song, Jaekyeong; Baek, Songjoon; Cerniglia, Carl E.

    2010-01-01

    The Rieske nonheme iron aromatic ring-hydroxylating oxygenases (RHOs) NidAB and NidA3B3 from Mycobacterium vanbaalenii PYR-1 have been implicated in the initial oxidation of high-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs), forming cis-dihydrodiols. To clarify how these two RHOs are functionally different with respect to the degradation of HMW PAHs, we investigated their substrate specificities to 13 representative aromatic substrates (toluene, m-xylene, phthalate, biphenyl, naphthalene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, benzo[a]pyrene, carbazole, and dibenzothiophene) by enzyme reconstitution studies of Escherichia coli. Both Nid systems were identified to be compatible with type V electron transport chain (ETC) components, consisting of a [3Fe-4S]-type ferredoxin and a glutathione reductase (GR)-type reductase. Metabolite profiles indicated that the Nid systems oxidize a wide range of aromatic hydrocarbon compounds, producing various isomeric dihydrodiol and phenolic compounds. NidAB and NidA3B3 showed the highest conversion rates for pyrene and fluoranthene, respectively, with high product regiospecificity, whereas other aromatic substrates were converted at relatively low regiospecificity. Structural characteristics of the active sites of the Nid systems were investigated and compared to those of other RHOs. The NidAB and NidA3B3 systems showed the largest substrate-binding pockets in the active sites, which satisfies spatial requirements for accepting HMW PAHs. Spatially conserved aromatic amino acids, Phe-Phe-Phe, in the substrate-binding pockets of the Nid systems appeared to play an important role in keeping aromatic substrates within the reactive distance from the iron atom, which allows each oxygen to attack the neighboring carbons. PMID:20714442

  12. Near-infrared continuum and 3.3 micrometer(s) polycyclic aromatic hydrocarbon imaging of the starburst ring in the type 1 Seyfert galaxy NGC 7469

    NASA Technical Reports Server (NTRS)

    Mazzarella, J. M.; Voit, G. M.; Soifer, B. T.; Matthews, K.; Graham, J. R.; Armus, L.; Shupe, D.

    1994-01-01

    High resolution near-infrared images of the type 1 Seyfert galaxy NGC 7469 have been obtained to probe its dusty nuclear environment. Direct J, H, and K images are relatively featureless, but residual images created by subtracting a smooth model based on best-fitting elliptical isophotes reveal a tight inner spiral whose high surface-brightness portions correspond to a previously detected 3 sec (1 kpc) diameter ring of radio continuum emission. The inner infrared spiral arms extended approximately equal to 4 sec NW and SE from the nucleus, and the NW arm joins up with large-scale spiral structure visible in the R band. The residual images also show a bar-like structure aligned with the brightest infrared/radio hotspots at PA approximately equal to 50 deg. Three infrared hotspots are detected which align remarkably well with 6 cm radio continuum sources. The near-infrared ring and the hotspots are visible in the residual images, and in a high-resolution direct K-band image restored to an effective resolution of 0.65 sec (FWHM) using the Richardson-Lucy algorithm. The infrared hotspots have luminosities of nuL(sub nu) (2.2 micrometer(s)) approximately equal to 10(exp 8) solar luminosity (M(sub k) approximately equal to -16 mag), suggesting they are either giant H II regions or individual supernovae. The two brightest regions may be associated with enhanced star formation triggered by orbit crowding of gas where spiral arms emerge from an inner bar. Narrowband (delta lambda/lambda approximately 1.5%) imaging in the 3.28 micrometer(s) dust emission feature and surrounding continuum confirms the 3 sec diameter 3.28 micrometer(s) emission region detected previously using multiaperture photometry. The extended polycyclic aromatic hydrocarbon (PAH) emission is slightly elongated and aligned with published 1O III1 line emission and 12.5 micrometer(s) continuum emission, apparently tracing the starburst. The presence of approximately equal to 25% of the total 3.28 micrometer

  13. Aromaticity effects on the profiles of the lowest triplet-state potential-energy surfaces for rotation about the C=C bonds of olefins with five-membered ring substituents: an example of the impact of Baird's rule.

    PubMed

    Zhu, Jun; Fogarty, Heather A; Möllerstedt, Helene; Brink, Maria; Ottosson, Henrik

    2013-08-01

    A density functional theory study on olefins with five-membered monocyclic 4n and 4n+2 π-electron substituents (C4H3X; X=CH(+), SiH(+), BH, AlH, CH2, SiH2, O, S, NH, and CH(-)) was performed to assess the connection between the degree of substituent (anti)aromaticity and the profile of the lowest triplet-state (T1) potential-energy surface (PES) for twisting about olefinic C=C bonds. It exploited both Hückel's rule on aromaticity in the closed-shell singlet ground state (S0) and Baird's rule on aromaticity in the lowest ππ* excited triplet state. The compounds CH2=CH(C4H3X) were categorized as set A and set B olefins depending on which carbon atom (C2 or C3) of the C4H3X ring is bonded to the olefin. The degree of substituent (anti)aromaticity goes from strongly S0 -antiaromatic/T1 -aromatic (C5H4 (+)) to strongly S0 -aromatic/T1- antiaromatic (C5H4(-)). Our hypothesis is that the shapes of the T1 PESs, as given by the energy differences between planar and perpendicularly twisted olefin structures in T1 [ΔE(T1)], smoothly follow the changes in substituent (anti)aromaticity. Indeed, correlations between ΔE(T1) and the (anti)aromaticity changes of the C4 H3 X groups, as measured by the zz-tensor component of the nucleus-independent chemical shift ΔNICS(T1;1)zz , are found both for sets A and B separately (linear fits; r(2) =0.949 and 0.851, respectively) and for the two sets combined (linear fit; r(2) =0.851). For sets A and B combined, strong correlations are also found between ΔE(T1) and the degree of S0 (anti)aromaticity as determined by NICS(S0,1)zz (sigmoidal fit; r(2) =0.963), as well as between the T1 energies of the planar olefins and NICS(S0,1)zz (linear fit; r(2) =0.939). Thus, careful tuning of substituent (anti)aromaticity allows for design of small olefins with T1 PESs suitable for adiabatic Z/E photoisomerization. PMID:23794153

  14. Quantification of carcinogenic 4- to 6-ring polycyclic aromatic hydrocarbons in human urine by solid-phase microextraction gas chromatography-isotope dilution mass spectrometry.

    PubMed

    Campo, Laura; Fustinoni, Silvia; Bertazzi, Pieralberto

    2011-08-01

    Polycyclic aromatic hydrocarbons (PAHs) are pollutants found in living and working environments. The aim of this study was to develop a solid-phase microextraction (SPME) gas chromatography (GC)-isotope dilution mass spectrometry method for the quantification of 10 four- to six-ring PAHs in urine samples. Seven of the selected PAHs have been classified as carcinogenic. Under the final conditions, analytes were sampled with a 100-μm polydimethylsiloxane SPME fibre for 60 min at 80 °C and desorbed in the injection port of the GC at 270 °C. Fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene were separated using a highly arylene-modified phase capillary column and quantified by MS using eight deuterated PAHs as surrogate internal standards. Limits of quantification (LOQ) were in the 0.5- to 2.2-ng/L range. Validation showed linear dynamic ranges up to 340 ng/L, inter- and intra-run precisions <20%, and accuracies within 20% of spiked concentrations. Matrix effect evaluation and the use of control charts to monitor process performances showed that the isotope dilution approach allowed for the control of bias sources. Urinary PAHs were above or equal to LOQ, depending on different compounds, in 58-100% (min-max), 40-100% and 5-39% of samples from coke oven workers (n = 12), asphalt workers (n = 10) and individuals not occupationally exposed to PAHs (n = 18), respectively. Chrysene was the most abundant PAH determined with median levels of 62.6, 6.9 and <0.6 ng/L, respectively. These results show that the method is suitable for quantifying carcinogenic PAHs in specimens from individuals with different levels of PAH exposure. PMID:21626187

  15. Developmental toxicity of 4-ring polycyclic aromatic hydrocarbons in zebrafish is differentially dependent on AH receptor isoforms and hepatic cytochrome P4501A metabolism

    SciTech Connect

    Incardona, John P. . E-mail: john.incardona@noaa.gov; Day, Heather L.; Collier, Tracy K.; Scholz, Nathaniel L.

    2006-12-15

    Polycyclic aromatic hydrocarbons (PAHs) derived from fossil fuels are ubiquitous contaminants and occur in aquatic habitats as highly variable and complex mixtures of compounds containing 2 to 6 rings. For aquatic species, PAHs are generally accepted as acting through either of two modes of action: (1) 'dioxin-like' toxicity mediated by activation of the aryl hydrocarbon receptor (AHR), which controls a battery of genes involved in PAH metabolism, such as cytochrome P4501A (CYP1A) and (2) 'nonpolar narcosis', in which tissue uptake is dependent solely on hydrophobicity and toxicity is mediated through non-specific partitioning into lipid bilayers. As part of a systematic analysis of mechanisms of PAH developmental toxicity in zebrafish, we show here that three tetracyclic PAHs (pyrene, chrysene, and benz[a]anthracene) activate the AHR pathway tissue-specifically to induce distinct patterns of CYP1A expression. Using morpholino knockdown of ahr1a, ahr2, and cyp1a, we show that distinct embryolarval syndromes induced by exposure to two of these compounds are differentially dependent on tissue-specific activation of AHR isoforms or metabolism by CYP1A. Exposure of embryos with and without circulation (silent heart morphants) resulted in dramatically different patterns of CYP1A induction, with circulation required to deliver some compounds to internal tissues. Therefore, biological effects of PAHs cannot be predicted simply by quantitative measures of AHR activity or a compound's hydrophobicity. These results indicate that current models of PAH toxicity in fish are greatly oversimplified and that individual PAHs are pharmacologically active compounds with distinct and specific cellular targets.

  16. Effect of electron-donating substituent groups on aromatic ring on photoluminescence properties of complexes of benzoic acid-functionalized polysulfone with Eu(III) ions.

    PubMed

    Gao, Baojiao; Chen, Lulu; Chen, Tao

    2015-10-14

    By molecular design and via polymer reactions, methoxybenzoic acid (MOBA) and hydroxybenzoic acid (HBA) were bonded onto the side chains of polysulfone (PSF) for preparing two benzoic acid-functionalized PSFs, PSF-MOBA and PSF-HBA, respectively. Based on full characterization of their structures, the two macromolecule ligands were made to coordinate to Eu(3+) ions, and two binary polymer-rare earth complexes, PSF-(MOBA)3-Eu(III) and PSF-(HBA)3-Eu(III), were obtained. At the same time, using phenanthroline (Phen) as a second small-molecule ligand, the corresponding two ternary complexes, PSF-(MOBA)3-Eu(III)-Phen1 and PSF-(HBA)3-Eu(III)-Phen1, were also prepared. The photo physical behaviors of these complexes were examined in depth, and the luminescent properties of these prepared polymer-rare earth complexes were mainly investigated. The experimental results show that the two electron-donating substituent groups on the aromatic ring of the bonded benzoic acid significantly affect the luminescence properties of these complexes of benzoic acid-functionalized PSF and Eu(III) ions, and they can effectively strengthen the fluorescence emission intensities of the complexes. The possible reason is that through the p-π conjugative effect, the two electron-donating substituent groups can remarkably decline the triplet state energy levels of the bonded ligand MOBA and HBA, and strengthen the matching degree of energy between the triplet state energy level of the ligand and the resonant energy level of Eu(III) ions, resulting in the enhancement of fluorescence emission intensities of the complexes. Besides, the fluorescence emissions of the binary complexes are stronger than those of the corresponding ternary complexes because of the synergistic coordination effect of Phen with the macromolecular ligand. PMID:26355714

  17. The chemistry of aromatic osmacycles.

    PubMed

    Cao, Xiao-Yu; Zhao, Qianyi; Lin, Zhiqun; Xia, Haiping

    2014-02-18

    ring planarity and the characteristic bond lengths between a single and double bond, but the osma-aromatics we have prepared also exhibit good stability towards air, water, and heat. Indeed, some seemingly unstable species proved stable, and their stability made it possible to study their optical, electrochemical, and magnetic properties. The stability of these compouds results from their aromaticity and the phosphonium substituents on the aromatic plane: most of our osma-aromatics carry at least one phosphonium group. The phosphonium group offers stability via both electronic and steric mechanisms. The phosphonium acts as an electron reservoir, allowing the circulation of electron pairs along metallacycles and lowering the electron density of the aromatic rings. Meanwhile, the bulky phosphonium groups surrounding the aromatic metallacycle prevent most reactions that could decompose the skeleton. PMID:24224464

  18. Magnetic criteria of aromaticity.

    PubMed

    Gershoni-Poranne, Renana; Stanger, Amnon

    2015-09-21

    This review describes the current state of magnetic criteria of aromaticity. The introduction contains the fundamentals of ring currents in aromatic and antiaromatic systems, followed by a brief description of experimental and computational tools: NMR, diamagnetic susceptibility exaltation, current density analyses (CDA) and nucleus independent chemical shifts (NICS). This is followed by more comprehensive chapters: NMR - focusing on the work of R. Mitchell - NICS and CDA - describing the progress and development of the methods to their current state and presenting some examples of representative work. PMID:26035305

  19. An insight into the aromaticity of fullerene anions: experimental evidence for diamagnetic ring currents in the five-membered rings of C(60)(6-) and C(70)(6-).

    PubMed

    Sternfeld, Tamar; Thilgen, Carlo; Hoffman, Roy E; Del Rosario Colorado Heras, María; Diederich, François; Wudl, Fred; Scott, Lawrence T; Mack, James; Rabinovitz, Mordecai

    2002-05-22

    Reduction of the two "closed" [6,6] methanofullerenes, [6,6]C(61)H(2) (1) and [6,6]C(71)H(2) (5), to the corresponding hexaanions with lithium metal causes the bridgehead-bridgehead bonds to open, at least partially, and this change gives rise to diamagnetic ring currents in the resulting homoconjugated six-membered rings (6-MRs). These new ring currents shield the overlying hydrogen atoms on the methylene bridge and induce upfield shifts of 1.60 and 0.11 ppm in their (1)H NMR resonances, respectively. Analogous reduction of the already "open" [5,6]methanofullerenes, [5,6]C(61)H(2) (2) and [5,6]C(71)H(2) (3 and 4), only slightly enhances the shielding of the hydrogen atoms over the homoconjugated 6-MRs (upfield shifts of 0.13, 0.68, and 0.14 ppm, respectively) but leads to exceptionally strong diamagnetic ring currents in the homoconjugated five- membered rings (5-MRs), as evidenced by dramatic shielding of the hydrogen atoms situated over them (upfield shift of 5.01, 6.78, and 1.63 ppm, respectively). The strongest shielding is seen for the hydrogen atom sitting over the 5-MR at the pole of C(71)H(2)(6)(-) (delta = -0.255 ppm) indicating that the excess charge density is concentrated at the poles. PMID:12010047

  20. Two Aromatic Rings Coupled a Sulfur-Containing Group to Favor Protein Electron Transfer by Instantaneous Formations of π∴S:π↔π:S∴π or π∴π:S↔π:π∴S Five-Electron Bindings

    PubMed Central

    Sun, Weichao; Ren, Haisheng; Tao, Ye; Xiao, Dong; Qin, Xin; Deng, Li; Shao, Mengyao; Gao, Jiali; Chen, Xiaohua

    2015-01-01

    The cooperative interactions among two aromatic rings with a S-containing group are described, which may participate in electron hole transport in proteins. Ab initio calculations reveal the possibility for the formations of the π∴S:π↔π:S∴π and π∴π:S↔π:π∴S five-electron bindings in the corresponding microsurrounding structures in proteins, both facilitating electron hole transport as efficient relay stations. The relay functionality of these two special structures comes from their low local ionization energies and proper binding energies, which varies with the different aromatic amino acids, S-containing residues, and the arrangements of the same aromatic rings according to the local microsurroundings in proteins. PMID:26120374

  1. Synthesis of tetra- and octa-aurated heteroaryl complexes towards probing aromatic indoliums

    PubMed Central

    Yuan, Jun; Sun, Tingting; He, Xin; An, Ke; Zhu, Jun; Zhao, Liang

    2016-01-01

    Polymetalated aromatic compounds are particularly challenging synthetic goals because of the limited thermodynamic stability of polyanionic species arising from strong electrostatic repulsion between adjacent carbanionic sites. Here we describe a facile synthesis of two polyaurated complexes including a tetra-aurated indole and an octa-aurated benzodipyrrole. The imido trinuclear gold(I) moiety exhibits nucleophilicity and undergoes an intramolecular attack on a gold(I)-activated ethynyl to generate polyanionic heteroaryl species. Their computed magnetic properties reveal the aromatic character in the five-membered ring. The incorporation of the aurated substituents at the nitrogen atom can convert non-aromaticity in the parent indolium into aromaticity in the aurated one because of hyperconjugation. Thus, the concept of hyperconjugative aromaticity is extended to heterocycles with transition metal substituents. More importantly, further analysis indicates that the aurated substituents can perform better than traditional main-group substituents. This work highlights the difference in aromaticity between polymetalated aryls and their organic prototypes. PMID:27186982

  2. Synthesis of tetra- and octa-aurated heteroaryl complexes towards probing aromatic indoliums.

    PubMed

    Yuan, Jun; Sun, Tingting; He, Xin; An, Ke; Zhu, Jun; Zhao, Liang

    2016-01-01

    Polymetalated aromatic compounds are particularly challenging synthetic goals because of the limited thermodynamic stability of polyanionic species arising from strong electrostatic repulsion between adjacent carbanionic sites. Here we describe a facile synthesis of two polyaurated complexes including a tetra-aurated indole and an octa-aurated benzodipyrrole. The imido trinuclear gold(I) moiety exhibits nucleophilicity and undergoes an intramolecular attack on a gold(I)-activated ethynyl to generate polyanionic heteroaryl species. Their computed magnetic properties reveal the aromatic character in the five-membered ring. The incorporation of the aurated substituents at the nitrogen atom can convert non-aromaticity in the parent indolium into aromaticity in the aurated one because of hyperconjugation. Thus, the concept of hyperconjugative aromaticity is extended to heterocycles with transition metal substituents. More importantly, further analysis indicates that the aurated substituents can perform better than traditional main-group substituents. This work highlights the difference in aromaticity between polymetalated aryls and their organic prototypes. PMID:27186982

  3. Concentric ring flywheel without expansion separators

    DOEpatents

    Kuklo, T.C.

    1999-08-24

    A concentric ring flywheel wherein the adjacent rings are configured to eliminate the need for differential expansion separators between the adjacent rings. This is accomplished by forming a circumferential step on an outer surface of an inner concentric ring and forming a matching circumferential step on the inner surface of an adjacent outer concentric ring. During operation the circumferential steps allow the rings to differentially expand due to the difference in the radius of the rings without the formation of gaps therebetween, thereby eliminating the need for expansion separators to take up the gaps formed by differential expansion. 3 figs.

  4. Concentric ring flywheel without expansion separators

    DOEpatents

    Kuklo, Thomas C.

    1999-01-01

    A concentric ring flywheel wherein the adjacent rings are configured to eliminate the need for differential expansion separators between the adjacent rings. This is accomplished by forming a circumferential step on an outer surface of an inner concentric ring and forming a matching circumferential step on the inner surface of an adjacent outer concentric ring. During operation the circumferential steps allow the rings to differentially expand due to the difference in the radius of the rings without the formation of gaps therebetween, thereby eliminating the need for expansion separators to take up the gaps formed by differential expansion.

  5. Identification of a Novel Metabolite in the Degradation of Pyrene by Mycobacterium sp. Strain AP1: Actions of the Isolate on Two- and Three-Ring Polycyclic Aromatic Hydrocarbons

    PubMed Central

    Vila, Joaquim; López, Zaira; Sabaté, Jordi; Minguillón, Cristina; Solanas, Anna M.; Grifoll, Magdalena

    2001-01-01

    Mycobacterium sp. strain AP1 grew with pyrene as a sole source of carbon and energy. The identification of metabolites accumulating during growth suggests that this strain initiates its attack on pyrene by either monooxygenation or dioxygenation at its C-4, C-5 positions to give trans- or cis-4,5-dihydroxy-4,5-dihydropyrene, respectively. Dehydrogenation of the latter, ortho cleavage of the resulting diol to form phenanthrene 4,5-dicarboxylic acid, and subsequent decarboxylation to phenanthrene 4-carboxylic acid lead to degradation of the phenanthrene 4-carboxylic acid via phthalate. A novel metabolite identified as 6,6′-dihydroxy-2,2′-biphenyl dicarboxylic acid demonstrates a new branch in the pathway that involves the cleavage of both central rings of pyrene. In addition to pyrene, strain AP1 utilized hexadecane, phenanthrene, and fluoranthene for growth. Pyrene-grown cells oxidized the methylenic groups of fluorene and acenaphthene and catalyzed the dihydroxylation and ortho cleavage of one of the rings of naphthalene and phenanthrene to give 2-carboxycinnamic and diphenic acids, respectively. The catabolic versatility of strain AP1 and its use of ortho cleavage mechanisms during the degradation of polycyclic aromatic hydrocarbons (PAHs) give new insight into the role that pyrene-degrading bacterial strains may play in the environmental fate of PAH mixtures. PMID:11722898

  6. Aromatic Gain in a Supramolecular Polymer.

    PubMed

    Saez Talens, Victorio; Englebienne, Pablo; Trinh, Thuat T; Noteborn, Willem E M; Voets, Ilja K; Kieltyka, Roxanne E

    2015-09-01

    The synergy of aromatic gain and hydrogen bonding in a supramolecular polymer is explored. Partially aromatic bis(squaramide) bolaamphiphiles were designed to self-assemble through a combination of hydrophobic, hydrogen-bonding, and aromatic effects into stiff, high-aspect-ratio fibers. UV and IR spectroscopy show electron delocalization and geometric changes within the squaramide ring indicative of strong hydrogen bonding and aromatic gain of the monomer units. The aromatic contribution to the interaction energy was further supported computationally by nucleus-independent chemical shift (NICS) and harmonic oscillator model of aromaticity (HOMA) indices, demonstrating greater aromatic character upon polymerization: at least 30% in a pentamer. The aromatic gain-hydrogen bonding synergy results in a significant increase in thermodynamic stability and a striking difference in aggregate morphology of the bis(squaramide) bolamphiphile compared to isosteres that cannot engage in this effect. PMID:26179942

  7. A Gene Expression Study of the Activities of Aromatic Ring-Cleavage Dioxygenases in Mycobacterium gilvum PYR-GCK to Changes in Salinity and pH during Pyrene Degradation

    PubMed Central

    Badejo, Abimbola Comfort; Badejo, Adegoke Olugboyega; Shin, Kyung Hoon; Chai, Young Gyu

    2013-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are toxic pollutants found in the environment which can be removed through the use of physical and biological agents. The rate of PAH biodegradation is affected by environmental conditions of pH, salinity and temperature. Adaptation of the pyrene degrading bacteria, Mycobacterium gilvum PYR-GCK, to fluctuating environmental conditions during pyrene biodegrading activity was studied using the quantitative real time – Polymerase Chain Reaction (qRT-PCR) technique. Four aromatic ring-cleavage dioxygenase genes: phdF, phdI, pcaG and pcaH; critical to pyrene biodegradation, were studied in pH states of 5.5, 6.5, 7.5 and NaCl concentrations 0 M, 0.17 M, 0.5 M, 0.6 M, 1 M. First, we conducted a residual pyrene study using gas chromatography and flame ionization technologies. Central to a gene expression study is the use of a valid endogenous reference gene, making its determination our next approach, using the geNorm/NormFinder algorithms. Armed with a valid control gene, rpoB, we applied it to a gene expression study, using the comparative critical threshold (2ΔΔCT) quantification method. The pyrene degrading activity of the strain was strongly functional in all the NaCl concentration states, with the least activity found at 1M (∼70% degraded after 48 hours of cultivation). The transcripts quantification of three genes backed this observation with high expression levels. The gene expression levels also revealed pH 6.5 as optimal for pyrene degradation and weak degradation activity at pH of 5.5, corroborating the residual pyrene analysis. The expression of these genes as proteins has already been studied in our laboratory using proteomics techniques and this validates our current study. PMID:23469141

  8. A gene expression study of the activities of aromatic ring-cleavage dioxygenases in Mycobacterium gilvum PYR-GCK to changes in salinity and pH during pyrene degradation.

    PubMed

    Badejo, Abimbola Comfort; Badejo, Adegoke Olugboyega; Shin, Kyung Hoon; Chai, Young Gyu

    2013-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are toxic pollutants found in the environment which can be removed through the use of physical and biological agents. The rate of PAH biodegradation is affected by environmental conditions of pH, salinity and temperature. Adaptation of the pyrene degrading bacteria, Mycobacterium gilvum PYR-GCK, to fluctuating environmental conditions during pyrene biodegrading activity was studied using the quantitative real time - Polymerase Chain Reaction (qRT-PCR) technique. Four aromatic ring-cleavage dioxygenase genes: phdF, phdI, pcaG and pcaH; critical to pyrene biodegradation, were studied in pH states of 5.5, 6.5, 7.5 and NaCl concentrations 0 M, 0.17 M, 0.5 M, 0.6 M, 1 M. First, we conducted a residual pyrene study using gas chromatography and flame ionization technologies. Central to a gene expression study is the use of a valid endogenous reference gene, making its determination our next approach, using the geNorm/NormFinder algorithms. Armed with a valid control gene, rpoB, we applied it to a gene expression study, using the comparative critical threshold (2(ΔΔCT)) quantification method. The pyrene degrading activity of the strain was strongly functional in all the NaCl concentration states, with the least activity found at 1M (∼70% degraded after 48 hours of cultivation). The transcripts quantification of three genes backed this observation with high expression levels. The gene expression levels also revealed pH 6.5 as optimal for pyrene degradation and weak degradation activity at pH of 5.5, corroborating the residual pyrene analysis. The expression of these genes as proteins has already been studied in our laboratory using proteomics techniques and this validates our current study. PMID:23469141

  9. Molecular and functional analysis of the TOL plasmid pWWO from Pseudomonas putida and cloning of genes for the entire regulated aromatic ring meta cleavage pathway.

    PubMed Central

    Franklin, F C; Bagdasarian, M; Bagdasarian, M M; Timmis, K N

    1981-01-01

    The genetic organization of the Pseudomonas putida plasmid pWWO-161, which encodes enzymes for the degradation of toluene and related aromatic hydrocarbons, has been investigated by transposition mutagenesis and gene cloning. Catabolic genes were localized to two clusters, one for upper pathway (hydrocarbon leads to carboxylic acid) enzymes and the other for lower pathway (carboxylic acid leads to tricarboxylic acid cycle) enzymes, that are separated by a 14-kilobase DNA segment. The physical organization of the catabolic genes thus reflects their functional organization into two regulatory blocks. The pWWO-161 DNA fragments Sst I fragment C and fragment D were cloned in a broad host range vector to produce plasmid pKT530. This hybrid encodes toluate oxygenase and all meta cleavage pathway enzymes, and it enables P. putida mt-2 and Escherichia coli K-12 cells to grow on m-toluate as sole carbon source. The pKT530 plasmid also carries xylS (a gene whose product has been postulated to regulate expression of the lower pathway genes) and the control sequences of the pathway that interact with this product, because catechol 2,3-oxygenase synthesis is specifically induced by m-toluate in both P. putida and E. coli. Evidence is presented that suggests the promoter operator of the meta pathway gene functions less effectively with the RNA polymerase or xylS product of E. coli than with the enzyme or product of P. putida. PMID:6950388

  10. Evidence for intramolecular aromatic-ring stacking in the physiological pH range of the monodeprotonated xanthine residue in mixed-ligand complexes containing xanthosinate 5'-monophosphate (XMP).

    PubMed

    Sigel, Helmut; Operschall, Bert P; Massoud, Salah S; Song, Bin; Griesser, Rolf

    2006-12-14

    The stability constants of the mixed-ligand complexes formed between Cu(Arm)2+ [Arm = 2,2'-bipyridine (Bpy) or 1,10-phenanthroline (Phen)], and the di- or trianion of xanthosine 5'-monophosphoric acid [= XMP(2-) or (XMP - H)(3-)] were determined by potentiometric pH titration in aqueous solution (25 degrees C; I = 0.1 M, NaNO3). Those for the monoanion, i.e., the Cu(Arm)(H;XMP)+ complexes, could only be estimated; for these species it is concluded that the metal ion is overwhelmingly bound at N7 and the proton resides at the phosphate group. Similarly, in the Cu(Arm)(XMP)+/- [= Cu(Arm)(X - H.MP.H)+/-] complexes Cu(Arm)2+ is also at N7 but the xanthine residue has lost a proton whereas the phosphate group still carries one, i.e., stacking plays, if at all, only a very minor role, yet, the N7-bound Cu(Arm)2+ appears to form an outer-sphere macrochelate with P(O)2(OH)-, its formation degree being about 60%. All this is different in the Cu(Arm)(XMP - H)- complexes, which are formed by the (XMP - H)(3-) species, that occur at the physiological pH of 7.5 and for which previously evidence has been provided that in a tautomeric equilibrium the xanthine moiety loses a proton either from (N1)H or (N3)H. In Cu(Arm)(XMP - H)- the phosphate group is the primary binding site for Cu(Arm)2+ and the observed increased complex stability is mainly due to intramolecular stack (st) formation between the aromatic-ring systems of Phen or Bpy and the monodeprotonated xanthine residue of (XMP - H)(3-); e.g., the stacked Cu(Phen)(XMP - H) isomer occurs with approximately 76%. Regarding biological systems the most important result is that at physiological pH the xanthine moiety has lost a proton from the (N1)H/(N3)H sites forming (XMP - H)(3-) and that its anionic xanthinate residue is able to undergo aromatic-ring stacking. PMID:17117222

  11. Metabolic activation of N-hydroxy arylamines, N-hydroxy heterocyclic amines and ring-hydroxymethyl polycyclic aromatic hydrocarbons by human sulfotransferases

    SciTech Connect

    Chou, H.C.

    1993-01-01

    Arylamines and polycyclic aromatic hydrocarbons (PAHs) are two major classes of chemical carcinogens. N-Hydroxylation of arylamines is regarded to be a necessary process for their mutagenicity and carcinogenicity, while alkyl-hydroxylation is the major metabolic pathway for alkyl-substituted PAHs. Evidence has been presented that sulfation of several N-hydroxy arylamines and hydroxymethyl PAHs is an important pathway leading to the formation of ultimate carcinogens in experiment animals. Sulfation of these chemicals forms putative sulfuric acid ester intermediates that can rearrange to electrophilic nitrenium or carbenium ions capable of forming covalent adducts with important cellular macromolecules. In order to study the metabolic activation by sulfotransferase(s) in various human tissue preparations an in vitro enzymatic assay was established. A metabolic phenotyping method was also developed for thermostable phenolsulfotransferase (TS-PST) in platelet homogenates (correlated with TS-PST activity in other tissues) based on a simple colorimetric assay using 2-naphthol as substrate. By using a PAPS-regenerating system to supply the activated sulfate and calf thymus DNA to trap the reactive metabolites, we found that N-hydroxy derivatives of the carcinogens, 4-aminobiphenyl (4-ABP), 4,4[prime]-methylene-bis(2-chloroaniline) (MOCA), 2-acetylaminofluorene (2-AAF), 2-aminofluorene (2-AF), 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP), and 2-amino-6-methyldipyrido [1,2-1:3[prime],2[prime]-d]imidazole (Glu-P-1) were metabolically activated by human TS-PST. On the other hand, three methyl-hydroxylated derivatives (7-OH, 12-OH, and 7,12-diOH) of 7, 12-dimethylbenz[a]anthracene (DMBA) were metabolically activated by human steroid sulfotransferase. Human sulfotransferase(s)-mediated activation of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) or 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) was not observed.

  12. Presence and potential significance of aromatic-ketone groups in aquatic humic substances

    USGS Publications Warehouse

    Leenheer, J.A.; Wilson, M.A.; Malcolm, R.L.

    1987-01-01

    Aquatic humic- and fulvic-acid standards of the International Humic Substances Society were characterized, with emphasis on carbonyl-group nature and content, by carbon-13 nuclear-magnetic-resonance spectroscopy, proton nuclear-magnetic-resonance spectroscopy, and infrared spectroscopy. After comparing spectral results of underivatized humic and fulvic acids with spectral results of chemically modified derivatives, that allow improved observation of the carbonyl group, the data clearly indicated that aromatic ketone groups comprised the majority of the carbonyl-group content. About one ketone group per monocyclic aromatic ring was determined for both humic and fulvic acids. Aromatic-ketone groups were hypothesized to form by photolytic rearrangements and oxidation of phenolic ester and hydrocarbon precursors; these groups have potential significance regarding haloform formation in water, reactivity resulting from active hydrogen of the methyl and methylene adjacent to the ketone groups, and formation of hemiketal and lactol structures. Aromatic-ketone groups also may be the point of attachment between aliphatic and aromatic moieties of aquatic humic-substance structure. ?? 1987.

  13. "Carbo-aromaticity" and novel carbo-aromatic compounds.

    PubMed

    Cocq, Kévin; Lepetit, Christine; Maraval, Valérie; Chauvin, Remi

    2015-09-21

    While the concept of aromaticity is being more and more precisely delineated, the category of "aromatic compounds" is being more and more expanded. This is illustrated by an introductory highlight of the various types of "aromaticity" previously invoked, and by a focus on the recently proposed "aromatic character" of the "two-membered rings" of the acetylene and butatriene molecules. This serves as a general foundation for the definition of "carbo-aromaticity", the relevance of which is surveyed through recent results in the synthetic, physical, and theoretical chemistry of carbo-mers and in particular macrocyclic-polycyclic representatives constituting a natural family of "novel aromatic compounds". With respect to their parent molecules, carbo-mers are constitutionally defined as "carbon-enriched", and can also be functionally regarded as "π-electron-enriched". This is exemplified by recent experimental and theoretical results on functional, aromatic, rigid, σ,π-macrocyclic carbo-benzene archetypes of various substitution patterns, with emphasis on the quadrupolar pattern. For the purpose of comparison, several types of non-aromatic references of carbo-benzenes are then considered, i.e. freely rotating σ,π-acyclic carbo-n-butadienes and flexible σ-cyclic, π-acyclic carbo-cyclohexadienes, and to "pro-aromatic" congeners, i.e. rigid σ,π-macrocyclic carbo-quinoids. It is shown that functional carbo-mers are entering the field of "molecular materials" for properties such as linear or nonlinear optical properties (e.g. dichromism and two-photon absorption) and single molecule conductivity. Since total or partial carbo-mers of aromatic carbon-allotropes of infinite size such as graphene (graphynes and graphdiynes) and graphite ("graphitynes") have long been addressed at the theoretical or conceptual level, recent predictive advances on the electrical, optical and mechanical properties of such carbo-materials are surveyed. Very preliminary experimental results

  14. Soil Type-Dependent Responses to Phenanthrene as Revealed by Determining the Diversity and Abundance of Polycyclic Aromatic Hydrocarbon Ring-Hydroxylating Dioxygenase Genes by Using a Novel PCR Detection System▿ †

    PubMed Central

    Ding, Guo-Chun; Heuer, Holger; Zühlke, Sebastian; Spiteller, Michael; Pronk, Geertje Johanna; Heister, Katja; Kögel-Knabner, Ingrid; Smalla, Kornelia

    2010-01-01

    A novel PCR primer system that targets a wide range of polycyclic aromatic hydrocarbon ring-hydroxylating dioxygenase (PAH-RHDα) genes of both Gram-positive and Gram-negative bacteria was developed and used to study their abundance and diversity in two different soils in response to phenanthrene spiking. The specificities and target ranges of the primers predicted in silico were confirmed experimentally by cloning and sequencing of PAH-RHDα gene amplicons from soil DNA. Cloning and sequencing showed the dominance of phnAc genes in the contaminated Luvisol. In contrast, high diversity of PAH-RHDα genes of Gram-positive and Gram-negative bacteria was observed in the phenanthrene-spiked Cambisol. Quantitative real-time PCR based on the same primers revealed that 63 days after phenanthrene spiking, PAH-RHDα genes were 1 order of magnitude more abundant in the Luvisol than in the Cambisol, while they were not detected in both control soils. In conclusion, sequence analysis of the amplicons obtained confirmed the specificity of the novel primer system and revealed a soil type-dependent response of PAH-RHDα gene-carrying soil bacteria to phenanthrene spiking. PMID:20495045

  15. Description of aromaticity in porphyrinoids.

    PubMed

    Wu, Judy I; Fernández, Israel; Schleyer, Paul v R

    2013-01-01

    Like the larger nonplanar Möbius rings, porphyrinoid aromaticity is not due primarily to the macrocyclic π conjugation of the corresponding annulene perimeters. The block-localized wave function (BLW)-derived aromatic stabilization energies (ASE) of several porphyrinoids reveal that, on a per atom basis, the appended 6π electron heterocycles of porphyrinoids confer aromaticity much more effectively than the macrocyclic 4n+2 π electron conjugations. There is no direct relationship between thermochemical stability of porphyrinoids and their macrocyclic 4n or 4n+2 π electron counts. Porphyrinoids having an "antiaromatic" macrocyclic 4n+2 π electron conjugation pathway (e.g., 4) as well as those having no macrocyclic conjugation (e.g., 9) can be stabilized by aromaticity. Computed nucleus independent chemical shifts (NICS) and the anisotropy of the induced current density (ACID) disclose the intricate local versus macrocyclic circulation interplay for several porphyrinoids. PMID:23205604

  16. Adjacent segment disease.

    PubMed

    Virk, Sohrab S; Niedermeier, Steven; Yu, Elizabeth; Khan, Safdar N

    2014-08-01

    EDUCATIONAL OBJECTIVES As a result of reading this article, physicians should be able to: 1. Understand the forces that predispose adjacent cervical segments to degeneration. 2. Understand the challenges of radiographic evaluation in the diagnosis of cervical and lumbar adjacent segment disease. 3. Describe the changes in biomechanical forces applied to adjacent segments of lumbar vertebrae with fusion. 4. Know the risk factors for adjacent segment disease in spinal fusion. Adjacent segment disease (ASD) is a broad term encompassing many complications of spinal fusion, including listhesis, instability, herniated nucleus pulposus, stenosis, hypertrophic facet arthritis, scoliosis, and vertebral compression fracture. The area of the cervical spine where most fusions occur (C3-C7) is adjacent to a highly mobile upper cervical region, and this contributes to the biomechanical stress put on the adjacent cervical segments postfusion. Studies have shown that after fusion surgery, there is increased load on adjacent segments. Definitive treatment of ASD is a topic of continuing research, but in general, treatment choices are dictated by patient age and degree of debilitation. Investigators have also studied the risk factors associated with spinal fusion that may predispose certain patients to ASD postfusion, and these data are invaluable for properly counseling patients considering spinal fusion surgery. Biomechanical studies have confirmed the added stress on adjacent segments in the cervical and lumbar spine. The diagnosis of cervical ASD is complicated given the imprecise correlation of radiographic and clinical findings. Although radiological and clinical diagnoses do not always correlate, radiographs and clinical examination dictate how a patient with prolonged pain is treated. Options for both cervical and lumbar spine ASD include fusion and/or decompression. Current studies are encouraging regarding the adoption of arthroplasty in spinal surgery, but more long

  17. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Esposito, Larry

    2014-03-01

    Preface: a personal view of planetary rings; 1. Introduction: the allure of the ringed planets; 2. Studies of planetary rings 1610-2013; 3. Diversity of planetary rings; 4. Individual ring particles and their collisions; 5. Large-scale ring evolution; 6. Moons confine and sculpt rings; 7. Explaining ring phenomena; 8. N-body simulations; 9. Stochastic models; 10. Age and evolution of rings; 11. Saturn's mysterious F ring; 12. Uranus' rings and moons; 13. Neptune's partial rings; 14. Jupiter's ring-moon system after Galileo and New Horizons; 15. Ring photometry; 16. Dusty rings; 17. Concluding remarks; Afterword; Glossary; References; Index.

  18. Influence of methoxy- and nitro-substitutions in the aromatic ring on proton donation ability in hydrogen bond and on the amino group parameters of free and H-bonded molecules of 2-aminopyrimidine

    NASA Astrophysics Data System (ADS)

    Borisenko, V. E.; Krekov, S. A.; Fomenko, M. Yu.; Koll, A.; Lipkovski, P.

    2008-06-01

    Amino- and imino- forms of pyrimidine are widely presented as part of antibiotics, corrective medications for heart failures and metabolic stimulators. Hydrogen bonding is one of the fundamental interactions between biologically active molecules. This type of interactions provides flexibility, speed and variety of the biochemical processes. Proton donation properties of aminopyrimidines significantly depend on the position, number and kind of the substituent in its aromatic ring. In present work we studied the influence of the methoxy- and nitro-substitutions in the phenyl radical of pyridine and pyrimidine cycles on the proton donation ability of the amino group in hydrogen bonds as well as on its geometrical, force, electro-optical and thermodynamical characteristics in free and H-bonded (1:1 and 1:2, with various proton acceptors) molecules of primary aromatic amines. Acetonitrile, dioxane, tetrahydrofourane, dimethylformamide, dimethylsulfoxide and hexamethylphosphoramide (whose proton accepting properties vary within a wide range) were used as proton acceptors in our research. In the region of the amino group stretching and deformation vibrations the IR spectra of free and H-bonded (1:1) molecules of 2-amino-4,6-dimethoxy- and 2-amino-5-nitropyrimidine were studied in complexes with proton acceptors in CCl 4 within the temperature range 288-328 K. The spectra of 1:2 complexes were studied in undiluted aprotic solvents. The following spectral characteristics of absorption bands in amino group stretching vibrations were determined: M(0) (zero spectral moment, integrated intensity B); M(1) (first spectral moment, band "centre of gravity"); effective half width, related to the second central moment (Δ ν1/2) eff = 2( M(2)) 1/2, frequencies of the deformation vibrations δ(HNH) of free and H-bonded molecules. It was shown that changes of the absorption band spectral characteristics of the amino group stretching and deformation vibrations in the analyzed

  19. Method of upgrading oils containing hydroxyaromatic hydrocarbon compounds to highly aromatic gasoline

    DOEpatents

    Baker, E.G.; Elliott, D.C.

    1993-01-19

    The present invention is a multi-stepped method of converting an oil which is produced by various biomass and coal conversion processes and contains primarily single and multiple ring hydroxyaromatic hydrocarbon compounds to highly aromatic gasoline. The single and multiple ring hydroxyaromatic hydrocarbon compounds in a raw oil material are first deoxygenated to produce a deoxygenated oil material containing single and multiple ring aromatic compounds. Then, water is removed from the deoxygenated oil material. The next step is distillation to remove the single ring aromatic compounds as gasoline. In the third step, the multiple ring aromatics remaining in the deoxygenated oil material are cracked in the presence of hydrogen to produce a cracked oil material containing single ring aromatic compounds. Finally, the cracked oil material is then distilled to remove the single ring aromatics as gasoline.

  20. Method of upgrading oils containing hydroxyaromatic hydrocarbon compounds to highly aromatic gasoline

    DOEpatents

    Baker, Eddie G.; Elliott, Douglas C.

    1993-01-01

    The present invention is a multi-stepped method of converting an oil which is produced by various biomass and coal conversion processes and contains primarily single and multiple ring hydroxyaromatic hydrocarbon compounds to highly aromatic gasoline. The single and multiple ring hydroxyaromatic hydrocarbon compounds in a raw oil material are first deoxygenated to produce a deoxygenated oil material containing single and multiple ring aromatic compounds. Then, water is removed from the deoxygenated oil material. The next step is distillation to remove the single ring aromatic compouns as gasoline. In the third step, the multiple ring aromatics remaining in the deoxygenated oil material are cracked in the presence of hydrogen to produce a cracked oil material containing single ring aromatic compounds. Finally, the cracked oil material is then distilled to remove the single ring aromatics as gasoline.

  1. Reinforcement core facilitates O-ring installation

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Reinforcement core holds O-ring in place within a structure while adjacent parts are being assembled. The core in the O-ring adds circumferential rigidity to the O-ring material. This inner core does not appreciably affect the sectional elasticity or gland-sealing characteristics of the O-ring.

  2. Optically active aromatic amino acids. Part VI. Synthesis and properties of (Leu5)-enkephalin analogues containing O-methyl-L-tyrosine1 with ring substitution at position 3'.

    PubMed

    Arnold, Z S; Schiller, P W

    2000-06-01

    Twelve new [Tyr(Me)1, Leu5]-enkephalin analogues with substituents at position 3' of the Tyr ring have been synthesized using traditional solution methods. The substituents were -CO2H, -CONH2, -CO2Me, -(E)-CH=NOH, -(E)-CH=NOMe and CH2OH. The analogues were C-terminated with methyl esters, amides or as free acids. In the in vitro biological assays a remarkable agonist activity to the opiate receptor mu in guinea pig ileum (GPI) relative to Leu-ENK was shown by the following: Leu-ENK, 100; [Tyr(Me)(3'-CO2Me)1, Leu-OMe5]-ENK (I), 8.1; [Tyr(Me)(3'-(E)-CH=NOH)1, Leu-OMe5]-ENK (VI), 26.2; [Tyr(Me)(3'-(E)-CH=NOH)1, Leu-OH5]-ENK (VII), 2.9; [Tyr(Me)(3'-(E)-CH=NOH)1, Leu-NH2(5)]-ENK (VIII), 4.7; and [Tyr(Me)(3'-CH2OH)1, Leu-OMe5]-ENK (X), 5.6. The agonist effect was naltrexone- or naloxone-reversible. The masking of the hydroxyl group in (E)-hydroxyiminomethyl group of analogue (VI) by O-methylation has totally abolished its GPI agonist activity. It seems that the (E)-CH=NOH group shows affinity and plays an analogous role to the phenol group Tyr1 in leucine-enkephalin and in the tyramine group of the opiate alkaloids. The analogues: [Tyr(Me)(3'-CO2Me)1, Leu-OMe5]-ENK (I), [Tyr(Me)(3'-CO2H)1, Leu-OMe5]-ENK (II), [Tyr(Me)(3'-CO2Me)1, Leu-NH2(5)]-ENK (III), [Tyr(Me)(3'-CO2H)1, Leu-NH2(5)]-ENK (IV), [Tyr(Me)(3'-CONH2)1, Leu-NH2(5)]-ENK (V), [Tyr(Me)(3'-(E)-CH=NOH)1, Leu-OMe5]-ENK (VI), [Tyr(Me)(3'-(E)-CH=NOH)1, Leu-OH5]-ENK (VII), [Tyr(Me)(3'-(E)-CH=NOH)1, Leu-NH2(5)]-ENK (VIII), [Tyr(Me)(3'-(E)-CH=NOMe)1, Leu-OMe5]-ENK (IX), [Tyr(Me)(3'-CH2OH)1, Leu-OMe5]-ENK (X), [Tyr(Me)(3'-CH2OH)1, Leu-OH5]-ENK (XI) and [Tyr(Me)(3'-CH2OH)1, Leu-NH2(5)]-ENK (XII) under testing had no significant agonist activity to the enkephalinergic receptor in mouse vas deferens (MVD). All methyl esters of synthesized analogues of [Leu5]-ENK showed higher activity to mu receptors than structurally identical C-terminal amides. It is a surprising result since usually C-terminate amides are stronger

  3. Are nucleus-independent (NICS) and 1H NMR chemical shifts good indicators of aromaticity in π-stacked polyfluorenes?

    NASA Astrophysics Data System (ADS)

    Osuna, Sílvia; Poater, Jordi; Bofill, Josep M.; Alemany, Pere; Solà, Miquel

    2006-09-01

    We have analyzed the change of local aromaticity in a series of polyfluorene compounds with the increase of the number of π-stacked layers. The local aromaticity of the aromatic and non-aromatic rings of polyfluorenes remains unchanged when going from one to four layers of π-stacked rings according to HOMA, PDI, and FLU aromaticity descriptors. On the contrary, experimental 1H NMR chemical shifts indicate a reduction of the aromaticity of π-stacked rings with the increase of the number of layers. Calculated NICS also show a change of aromaticity, but opposite to the tendency given by the 1H NMR chemical shifts. We show that this increase (decrease) of local aromaticity in superimposed aromatic rings indicated by NICS ( 1H NMR) is not real but the result of the coupling between the magnetic fields generated by the π-stacked rings.

  4. AMHB: (Anti)aromaticity-Modulated Hydrogen Bonding.

    PubMed

    Kakeshpour, Tayeb; Wu, Judy I; Jackson, James E

    2016-03-16

    This in silico survey shows that changes in the (anti)aromatic character of π-conjugated heterocycles can be used to fine-tune their hydrogen (H-)bond strengths. Upon H-bonding dimerization, the π-electrons of these rings can be polarized to reinforce or disrupt their (anti)aromatic π-conjugated circuits (πCCs) and stabilize or destabilize the resulting H-bonded complexes. H-bonding interactions that enhance aromaticity or relieve antiaromaticity are fortified, whereas those that intensify antiaromaticity or disrupt aromaticity are weakened, relative to analogues lacking full π-circuits. Computed dissected nucleus-independent chemical shifts, NICS(1)(zz), reveal a uniform pattern and document changes in the magnetic (anti)aromatic character of the heterocycles considered. Recognition of this (anti)aromaticity-modulated H-bonding (AMHB) phenomenon offers insights into a range of fields from organocatalysis and self-assembly to pharmaceutical chemistry and molecular biology. PMID:26860619

  5. Intramolecular "Aryl-metal chelate ring" pi,pi-interactions as structural evidence for metalloaromaticity in (aromatic alpha,alpha'-diimine)-copper(II) chelates: molecular and crystal structure of aqua(1,10-phenanthroline)(2-benzylmalonato)copper(II) three-hydrate.

    PubMed

    Castiñeiras, A; Sicilia-Zafra, A G; González-Pérez, J M; Choquesillo-Lazarte, D; Niclós-Gutiérrez, J

    2002-12-30

    By reaction of Cu(2)CO(3)(OH)(2), 2-benzylmalonic acid (H(2)Bzmal), and 1,10-phenanthroline (phen), [Cu(Bzmal)(phen)(H(2)O)] x 3H(2)O (compound 1) has been obtained and characterized by thermal, spectral, magnetic, and X-ray diffraction methods. The molecular structure of 1 is remarkably similar to that of [Cu(Bzmal)(bipy)(H(2)O)] x 2H(2)O (compound 2, bipy = 2,2'-bipyridine). In both complexes, the aryl(Bzmal) ring produces an unexpected pi,pi-stacking interaction with the Cu(II)-(aromatic alpha,alpha'-diimine) chelate ring, at an average distance d(pi)(-)(pi) of 3.40 A, involving roughly parallel and smoothly slipped rings. This insight is discussed as new structural evidence for metalloaromaticity of Cu(II)-(aromatic alpha,alpha'-diimine) chelate rings. Interestingly, 1 recognizes itself by a weak intermolecular pi,pi-stacking interaction between aryl(Bzmal) ligands to give pairs of complex molecules. In contrast, there is an intermolecular pyridyl-pyridyl pi,pi-stacking interaction also forming pairs of complex molecules in 2. PMID:12495333

  6. Novel Approach for Evaluating Secondary Organic Aerosol from Aromatic Hydrocarbons: Unified Method for Predicting Aerosol Composition and Formation.

    PubMed

    Li, Lijie; Tang, Ping; Nakao, Shunsuke; Kacarab, Mary; Cocker, David R

    2016-06-21

    Innovative secondary organic aerosol (SOA) composition analysis methods normalizing aerosol yield and chemical composition on an aromatic ring basis are developed and utilized to explore aerosol formation from oxidation of aromatic hydrocarbons. SOA yield and chemical composition are revisited using 15 years of University of California, Riverside/CE-CERT environmental chamber data on 17 aromatic hydrocarbons with HC:NO ranging from 11.1 to 171 ppbC:ppb. SOA yield is redefined in this work by normalizing the molecular weight of all aromatic precursors to the molecular weight of the aromatic ring [Formula: see text], where i is the aromatic hydrocarbon precursor. The yield normalization process demonstrates that the amount of aromatic rings present is a more significant driver of aerosol formation than the vapor pressure of the precursor aromatic. Yield normalization also provided a basis to evaluate isomer impacts on SOA formation. Further, SOA elemental composition is explored relative to the aromatic ring rather than on a classical mole basis. Generally, four oxygens per aromatic ring are observed in SOA, regardless of the alkyl substitutes attached to the ring. Besides the observed SOA oxygen to ring ratio (O/R ∼ 4), a hydrogen to ring ratio (H/R) of 6 + 2n is observed, where n is the number of nonaromatic carbons. Normalization of yield and composition to the aromatic ring clearly demonstrates the greater significance of aromatic ring carbons compared with alkyl carbon substituents in determining SOA formation and composition. PMID:27177154

  7. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Esposito, Larry W.

    2011-07-01

    Preface; 1. Introduction: the allure of ringed planets; 2. Studies of planetary rings 1610-2004; 3. Diversity of planetary rings; 4. Individual ring particles and their collisions; 5. Large-scale ring evolution; 6. Moons confine and sculpt rings; 7. Explaining ring phenomena; 8. N-Body simulations; 9. Stochastic models; 10. Age and evolution of rings; 11. Saturn's mysterious F ring; 12. Neptune's partial rings; 13. Jupiter's ring-moon system after Galileo; 14. Ring photometry; 15. Dusty rings; 16. Cassini observations; 17. Summary: the big questions; Glossary; References; Index.

  8. Aromaticity of the doubly charged [8]circulenes.

    PubMed

    Baryshnikov, Gleb V; Valiev, Rashid R; Karaush, Nataliya N; Sundholm, Dage; Minaev, Boris F

    2016-04-01

    Magnetically induced current densities and current pathways have been calculated for a series of fully annelated dicationic and dianionic tetraphenylenes, which are also named [8]circulenes. The gauge including magnetically induced current (GIMIC) method has been employed for calculating the current density susceptibilities. The aromatic character and current pathways are deduced from the calculated current density susceptibilities showing that the neutral [8]circulenes have two concentric pathways with aromatic and antiaromatic character, respectively. The inner octatetraene core (the hub) is found to sustain a paratropic (antiaromatic) ring current, whereas the ring current along the outer part of the macrocycle (the rim) is diatropic (aromatic). The neutral [8]circulenes can be considered nonaromatic, because the sum of the ring-current strengths of the hub and the rim almost vanishes. The aromatic character of the doubly charged [8]circulenes is completely different: the dianionic [8]circulenes and the OC-, CH-, CH2-, SiH-, GeH-, SiH2-, and GeH2-containing dicationic species sustain net diatropic ring currents i.e., they are aromatic, whereas the O-, S-, Se-, NH-, PH- and AsH-containing dicationic [8]circulenes are strongly antiaromatic. The present study also shows that GIMIC calculations on the [8]circulenes provide more accurate information about the aromatic character than that obtained using local indices such as nuclear-independent chemical shifts (NICSs) and (1)H NMR chemical shifts. PMID:26964752

  9. Can the positive aromatic ring be as π-electron donor in π-halogen bond? A MP2 theoretical investigation on the unusual π-halogen bond interaction between three-membered ring (BNN)₃⁺ and X1X2 (X1, X2 = F, Cl, Br).

    PubMed

    Qi, Hai-Tao; Ren, Fu-de; Zhang, Jing-Lin; Wang, Jing-Yu

    2011-05-01

    The unusual π-halogen bond interactions are investigated between (BNN)₃⁺ and X1X2 (X1, X2 = F, Cl, Br) employing MP2 at 6-311 + G(2d) and aug-cc-pVDZ levels according to the "CP (counterpoise) corrected potential energy surface (PES)" method. The order of the π-halogen bond interactions and stabilities of the complexes are obtained to be (BNN)₃⁺... F₂ < (BNN)₃⁺... ClF < (BNN)₃⁺... Cl₂ < (BNN)₃⁺... BrCl < (BNN)₃⁺... Br₂ < (BNN)₃⁺ ... BrF. at MP2/aug-cc-pVDZ level. The analyses of the Mulliken charge transfer, natural bond orbital (NBO), atoms in molecules (AIM) theory and electron density shifts reveal that the nature of the π-halogen bond interaction in the complexes of ClF, BrF and BrCl might partly be charge transfer from the delocalized π-HOMO orbital of (BNN)₃⁺ to X1X2. This result suggests that the positive aromatic ring (BNN)₃⁺ might act as a π-electron donor to form the π-halogen bond. PMID:20607330

  10. Critical analysis of the local aromaticity concept in polyaromatic hydrocarbons.

    PubMed

    Bultinck, Patrick

    2007-01-01

    A large number of local aromaticity indices for the benzenoid rings in polyaromatic hydrocarbons is computed. The results are interpreted, supporting Clar's hypothesis, and mutual correlations are investigated. It is shown that there are good correlations between all indices that strictly allow comparing benzenoid character. Poor correlations are found with NICS. A rationale is offered, yielding the conclusion that NICS and ring current maps follow a fundamentally different path to local aromaticity. In this sense the lack of correlation is not due to a real multidimensional character of aromaticity but rather to confusion and vagueness of the aromaticity concept. PMID:17328438

  11. Aromatic graphene

    NASA Astrophysics Data System (ADS)

    Das, D. K.; Sahoo, S.

    2016-04-01

    In recent years graphene attracts the scientific and engineering communities due to its outstanding electronic, thermal, mechanical and optical properties and many potential applications. Recently, Popov et al. [1] have studied the properties of graphene and proved that it is aromatic but without fragrance. In this paper, we present a theory to prepare graphene with fragrance. This can be used as scented pencils, perfumes, room and car fresheners, cosmetics and many other useful household substances.

  12. The boron-carbon-nitrogen heterocyclic rings

    NASA Astrophysics Data System (ADS)

    Srivastava, Ambrish Kumar; Misra, Neeraj

    2015-04-01

    The heterocyclic rings containing B, C and N atoms, also known as azaborines, are systematically studied. The electronic properties of these BCN rings are explored by using second order perturbation theory and their aromaticity is discussed by the nucleus independent chemical shifts. These heterocyclic rings are found to be chemically more reactive than benzene and borazine, due to smaller HOMO-LUMO gap and non-zero dipole moment. However, the aromaticity of these BCN rings is less than benzene but two or three times that of borazine.

  13. Ladder supported ring bar circuit

    NASA Technical Reports Server (NTRS)

    Kosmahl, H. G. (Inventor)

    1983-01-01

    An improved slow wave circuit especially useful in backward wave oscillators includes a slow wave circuit in a waveguide. The slow wave circuit is comprised of rings disposed between and attached to respective stubs. The stubs are attached to opposing sidewalls of the waveguide. To the end that opposed, interacting magnetic fields will be established to provide a very high coupling impedance for the slow wave structure, axially orientated bars are connected between rings in alternate spaces and adjacent to the attachment points of stubs. Similarly, axial bars are connected between rings in the spaces which do not include bars and at points adjacent to the attachment of bars.

  14. Fluorescent aromatic sensors and their methods of use

    NASA Technical Reports Server (NTRS)

    Meador, Michael A. (Inventor); Tyson, Daniel S. (Inventor); Ilan, Ulvi F. (Inventor)

    2012-01-01

    Aromatic molecules that can be used as sensors are described. The aromatic sensors include a polycyclic aromatic hydrocarbon core with a five-membered imide rings fused to the core and at least two pendant aryl groups. The aromatic sensor molecules can detect target analytes or molecular strain as a result of changes in their fluorescence, in many cases with on-off behavior. Aromatic molecules that fluoresce at various frequencies can be prepared by altering the structure of the aromatic core or the substituents attached to it. The aromatic molecules can be used as sensors for various applications such as, for example, the detection of dangerous chemicals, biomedical diagnosis, and the detection of damage or strain in composite materials. Methods of preparing aromatic sensor molecules are also described.

  15. Hexacoordinate bonding and aromaticity in silicon phthalocyanine.

    PubMed

    Yang, Yang

    2010-12-23

    Si-E bondings in hexacoordinate silicon phthalocyanine were analyzed using bond order (BO), energy partition, atoms in molecules (AIM), electron localization function (ELF), and localized orbital locator (LOL). Bond models were proposed to explain differences between hexacoordinate and tetracoordinate Si-E bondings. Aromaticity of silicon phthalocyanine was investigated using nucleus-independent chemical shift (NICS), harmonic oscillator model of aromaticity (HOMA), conceptual density functional theory (DFT), ring critical point (RCP) descriptors, and delocalization index (DI). Structure, energy, bonding, and aromaticity of tetracoordinate silicon phthalocyanine were studied and compared with hexacoordinate one. PMID:21105726

  16. Assessing Uncertainty of Interspecies Correlation Estimation Models for Aromatic Compounds

    EPA Science Inventory

    We developed Interspecies Correlation Estimation (ICE) models for aromatic compounds containing 1 to 4 benzene rings to assess uncertainty in toxicity extrapolation in two data compilation approaches. ICE models are mathematical relationships between surrogate and predicted test ...

  17. Evaluation of antibacterial activity of synthetic aliphatic and aromatic monoacylglycerols.

    PubMed

    Batovska, Daniela; Todorova, Iva; Parushev, Stoyan; Tsvetkova, Iva; Najdenski, Hristo; Ubukata, Makoto

    2008-01-01

    The antibacterial activity of synthetic aliphatic and aromatic monoacylglycerols (MAGs) was studied against two human pathogens: Staphylococcus aureus and Escherichia coli. The active compounds inhibited selectively S. aureus. The most active compounds amongst them were those with medium size aliphatic chain and aromatic MAGs with electron withdrawing substituents at the aryl ring. The introduction of one or two-carbon spacer between the aryl ring and the carboxylic function did not influence antibacterial effectiveness. PMID:19004249

  18. Planetary rings

    SciTech Connect

    Greenberg, R.; Brahic, A.

    1984-01-01

    Among the topics discussed are the development history of planetary ring research, the view of planetary rings in astronomy and cosmology over the period 1600-1900, the characteristics of the ring systems of Saturn and Uranus, the ethereal rings of Jupiter and Saturn, dust-magnetosphere interactions, the effects of radiation forces on dust particles, the collisional interactions and physical nature of ring particles, transport effects due to particle erosion mechanisms, and collision-induced transport processes in planetary rings. Also discussed are planetary ring waves, ring particle dynamics in resonances, the dynamics of narrow rings, the origin and evolution of planetary rings, the solar nebula and planetary disk, future studies of the planetary rings by space probes, ground-based observatories and earth-orbiting satellites, and unsolved problems in planetary ring dynamics.

  19. Novel Approach for Evaluating Secondary Organic Aerosol from Aromatic Hydrocarbons: SOA Yield and Chemical Composition

    NASA Astrophysics Data System (ADS)

    Li, Lijie; Tang, Ping; Nakao, Shunsuke; Qi, Li; Kacarab, Mary; Cocker, David

    2016-04-01

    Aromatic hydrocarbons account for 20%-30% of urban atmospheric VOCs and are major contributors to anthropogenic secondary organic aerosol (SOA). However, prediction of SOA from aromatic hydrocarbons as a function of structure, NOx concentration, and OH radical levels remains elusive. Innovative SOA yield and chemical composition evaluation approaches are developed here to investigate SOA formation from aromatic hydrocarbons. SOA yield is redefined in this work by adjusting the molecular weight of all aromatic precursors to the molecular weight of benzene (Yield'= Yieldi×(MWi/MWBenzene); i: aromatic hydrocarbon precursor). Further, SOA elemental ratio is calculated on an aromatic ring basis rather than the classic mole basis. Unified and unique characteristics in SOA formed from aromatic hydrocarbons with different alkyl groups (varying in carbon number and location on aromatic ring) are explored by revisiting fifteen years of UC Riverside/CE-CERT environmental chamber data on 129 experiments from 17 aromatic precursors at urban region relevant low NOx conditions (HC:NO 11.1-171 ppbC:ppb). Traditionally, SOA mass yield of benzene is much greater than that of other aromatic species. However, when adjusting for molecular weight, a similar yield is found across the 17 different aromatic precursors. More importantly, four oxygens per aromatic ring are observed in the resulting SOA regardless of the alkyl substitutes attached to the ring, which majorly affect H/C ratio in SOA. Therefore, resulting SOA bulk composition from aromatic hydrocarbons can be predicted as C6+nH6+2nO4 (n: alkyl substitute carbon number). Further, the dominating role of the aromatic ring carbons is confirmed by studying the chemical composition of SOA formed from the photooxidation of an aromatic hydrocarbon with a 13C isotopically labeled alkyl carbon. Overall, this study unveils the similarity in SOA formation from aromatic hydrocarbons enhancing the understanding of SOA formation from

  20. Experimental and modeling investigation of aromatic and polycyclic aromatic hydrocarbon formation in a premixed ethylene flame

    SciTech Connect

    Castaldi, M.J.; Marinov, N.M.; Melius, C.F.

    1996-02-01

    Experimental and detailed chemical kinetic modeling has been performed to investigate aromatic and polyaromatic hydrocarbon formation pathways in a rich, sooting, ethylene-oxygen-argon premixed flame. An atmospheric pressure, laminar flat flame operated at an equivalence ratio of 2.5 was used to acquire experimental data for model validation. Gas composition analysis was conducted by an on-line gas chromatograph/mass spectrometer (GC/MS) technique. Measurements were made in the flame and post-flame zone for a number of low molecular weight species, aliphatics, aromatics and polycyclic aromatic hydrocarbons (PAHs) ranging from two to five-aromatic fused rings. The modeling results show the key reaction sequences leading to aromatic and polycyclic aromatic hydrocarbon growth involve the combination of resonantly stabilized radicals. In particular, propargyl and 1-methylallenyl combination reactions lead to benzene and methyl substituted benzene formation, while polycyclic aromatics are formed from cyclopentadienyl radicals and fused rings that have a shared C{sub 5} side structure. Naphthalene production through the reaction step of cyclopentadienyl self-combination and phenanthrene formation from indenyl and cyclopentadienyl combination were shown to be important in the flame modeling study. The removal of phenyl by O{sub 2} leading to cyclopentadienyl formation is expected to play a pivotal role in the PAH or soot precursor growth process under fuel-rich oxidation conditions.

  1. Nucleophilic fluorination of aromatic compounds

    DOEpatents

    Satyamurthy, Nagichettiar; Barrio, Jorge R

    2014-03-18

    Iodylbenzene derivatives substituted with electron donating as well as electron withdrawing groups on the aromatic ring are used as precursors in aromatic nucleophilic substitution reactions. The iodyl group (IO.sub.2) is regiospecifically substituted by nucleophilic fluoride to provide the corresponding fluoroaryl derivatives. No-carrier-added [F-18]fluoride ion derived from anhydrous [F-18](F/Kryptofix, [F-18]CsF or a quaternary ammonium fluoride (e.g., Me.sub.4NF, Et.sub.4NF, n-Bu.sub.4NF, (PhCH.sub.2).sub.4NF) exclusively substitutes the iodyl moiety in these derivatives and provides high specific activity F-18 labeled fluoroaryl analogs. Iodyl derivatives of a benzothiazole analog and 6-iodyl-L-dopa derivatives have been synthesized as precursors and have been used in the preparation of no-carrier-added [F-18]fluorobenzothiazole as well as 6-[F-18]fluoro-L-dopa.

  2. Synthesis and characterization, novel across adjacent ring formed phthalocyanine.

    PubMed

    Elmali, Dilek; Altindal, Ahmet; Ozkaya, Ali Riza; Salih, Bekir; Bekaroğlu, Ozer

    2011-01-21

    Novel mononuclear Zn(ii) 4, Co(ii) 5 and Cu(ii) 6 metallophthalocyanines have been synthesized from 4,4'(ethane-1,1-p-phenol-2,2-p-phenoxy)phthalonitrile 3, which can be obtained by the reaction of 4-nitrophthalonitrile 1 with 1,1,2,2-tetrakis(p-hydroxy-phenyl)-ethane 2. The target water-soluble derivatives of 7-9 were acquired from a boiling suspension of the compounds in aqueous 20% KOH solution. The synthesized complexes have been characterized by UV-vis, IR, (1)H NMR and MALDI-TOF-mass spectroscopies. In addition, the geometric and electronic structures of 2-6 were investigated by ab initio/DFT quantum mechanical calculations using the Gaussian 03 program with HF theory at the B3LYP/3-21G level. The redox properties of the complexes 4-6 were examined by cyclic voltammetry on platinum in DMSO/TBAP. These complexes displayed one-electron metallophthalocyanine-based and multi-electron hydroxyphenyl-based redox processes. The effect of temperature on the d.c. conductivity and impedance spectra of spin coated films of compounds were investigated at the temperatures between 300-452 K and in the frequency range of 40-105 Hz. Thermally activated conductivity dependence on temperature was observed for all compounds. A.c. results indicated that conduction mechanism can be explained by classical hopping barriers mechanism for all films. PMID:21125131

  3. Saturn's rings

    NASA Technical Reports Server (NTRS)

    2000-01-01

    When seen from the unlit side, the rings of Saturn present a much different appearance from that familiar to telescopic observers. Relatively opaque areas like the B Ring turn black, while lightly populated zones, such as the C Ring and the Cassini Division, prove to excellent diffuse transmitters of sunlight. The A Ring, with intermediate opacity, is at an intermediate level of brightness.

  4. Fusing porphyrins with polycyclic aromatic hydrocarbons and heterocycles for optoelectronic applications

    SciTech Connect

    Thompson, Mark E.; Diev, Viacheslav; Hanson, Kenneth; Forrest, Stephen R.

    2015-08-18

    A compound that can be used as a donor material in organic photovoltaic devices comprising a non-activated porphyrin fused with one or more non-activated polycyclic aromatic rings or one or more non-activated heterocyclic rings can be obtained by a thermal fusion process. The compounds can include structures of Formula I: ##STR00001## By heating the reaction mixture of non-activated porphyrins with non-activated polycyclic aromatic rings or heterocyclic rings to a fusion temperature and holding for a predetermined time, fusion of one or more polycyclic rings or heterocyclic rings to the non-activated porphyrin core in meso,.beta. fashion is achieved resulting in hybrid structures containing a distorted porphyrin ring with annulated aromatic rings. The porphyrin core can be olygoporphyrins.

  5. Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Cuzzi, J. N.

    2014-12-01

    The rings are changing before our eyes; structure varies on all timescales and unexpected things have been discovered. Many questions have been answered, but some answers remain elusive (see Cuzzi et al 2010 for a review). Here we highlight the major ring science progress over the mission to date, and describe new observations planned for Cassini's final three years. Ring Composition and particle sizes: The rings are nearly all water ice with no other ices - so why are they reddish? The C Ring and Cassini Division are "dirtier" than the more massive B and A Rings, as shown by near-IR and, recently, microwave observations. Particle sizes, from stellar and radio occultations, vary from place to place. Ring structure, micro and macro: numerous spiral density waves and ubiquitous "self-gravity wakes" reveal processes which fostered planet formation in the solar system and elsewhere. However, big puzzles remain regarding the main ring divisions, the C Ring plateau structures, and the B Ring irregular structure. Moonlets, inside and out, seen and unseen: Two gaps contain sizeable moonlets, but more gaps seem to contain none; even smaller embedded "propeller" objects wander, systematically or randomly, through the A ring. Rubble pile ringmoons just outside the rings may escaped from the rings, and the recently discovered "Peggy" may be trying this as we watch. Impact bombardment of the rings: Comet fragments set the rings to rippling on century-timescales, and boulders crash through hourly; meanwhile, the constant hail of infalling Kuiper belt material has a lower mass flux than previously thought. Origin and Age of the Rings: The ring mass and bombardment play key roles. The ring mass is well known everywhere but in the B Ring (where most of it is). New models suggest how tidal breakup of evolving moons may have formed massive ancient rings, of which the current ring is just a shadow. During its last three years, the Cassini tour profile will allow entirely new

  6. Five-membered heterocycles. Part III. Aromaticity of 1,3-imidazole in 5+ n hetero-bicyclic molecules

    NASA Astrophysics Data System (ADS)

    Mrozek, Agnieszka; Karolak-Wojciechowska, Janina; Kieć-Kononowicz, Katarzyna

    2003-08-01

    The aromaticity (in the form of HOMA index) of 1,3-imidazole ring and its bicyclic derivatives was studied on the basis of statistical data from Cambridge Structural Database and X-ray investigations performed by authors. As a starting point, aromaticity of the 1,3-imidazoles with exocyclic X substituent at C2 (XN, O or S) was calculated. Subsequently, the HOMA index was calculated for various 5+ n bicyclic skeletons with N, O, and S as endocyclic heteroatoms in the second ring. For the isolated 1,3-imidazole ring, aromaticity depends on exocyclic substituent at C2 and decreases in sequence N, S, O. For bicyclic derivatives it was found that both rings are aromatic and coplanar in very few molecules (17% of investigated ones), and positive charge—located on endocyclic heteroatom—increases the aromaticity. For remaining compounds, presence of sp 3 carbons excludes possibility of aromatic ring existence.

  7. Concentric ring flywheel with hooked ring carbon fiber separator/torque coupler

    DOEpatents

    Kuklo, Thomas C.

    1999-01-01

    A concentric ring flywheel with expandable separators, which function as torque couplers, between the rings to take up the gap formed between adjacent rings due to differential expansion between different radius rings during rotation of the flywheel. The expandable separators or torque couplers include a hook-like section at an upper end which is positioned over an inner ring and a shelf-like or flange section at a lower end onto which the next adjacent outer ring is positioned. As the concentric rings are rotated the gap formed by the differential expansion there between is partially taken up by the expandable separators or torque couplers to maintain torque and centering attachment of the concentric rings.

  8. Concentric ring flywheel with hooked ring carbon fiber separator/torque coupler

    DOEpatents

    Kuklo, T.C.

    1999-07-20

    A concentric ring flywheel with expandable separators, which function as torque couplers, between the rings to take up the gap formed between adjacent rings due to differential expansion between different radius rings during rotation of the flywheel. The expandable separators or torque couplers include a hook-like section at an upper end which is positioned over an inner ring and a shelf-like or flange section at a lower end onto which the next adjacent outer ring is positioned. As the concentric rings are rotated the gap formed by the differential expansion there between is partially taken up by the expandable separators or torque couplers to maintain torque and centering attachment of the concentric rings. 2 figs.

  9. Vascular ring

    MedlinePlus

    ... with aberrant subclavian and left ligamentum ateriosus; Congenital heart defect - vascular ring; Birth defect heart - vascular ring ... accounts for less than 1% of all congenital heart problems. The condition occurs as often in males ...

  10. Neptune's rings

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This 591-second exposure of the rings of Neptune were taken with the clear filter by the Voyager 2 wide-angle camera. The two main rings are clearly visible and appear complete over the region imaged. Also visible in this image is the inner faint ring and the faint band which extends smoothly from the ring roughly halfway between the two bright rings. Both of these newly discovered rings are broad and much fainter than the two narrow rings. The bright glare is due to over-exposure of the crescent on Neptune. Numerous bright stars are evident in the background. Both bright rings have material throughout their entire orbit, and are therefore continuous. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications.

  11. Mechanism of aromatic hydrocarbon formation in FCC naphtha

    SciTech Connect

    Mota, C.J.A.; Rawet, R.

    1995-12-01

    A microactivity test study of the FCC naphtha composition at increasing conversions was carried out. At low conversions (ca. 10--20%), the naphtha is rich in olefinic and aromatic hydrocarbons. As the conversion increases, the composition changes dramatically. The olefins initially increase and then decrease sharply. The paraffins increase continually, and the aromatics initially decrease and then increase slightly. The naphthenics remain constant in the conversion range studied. These results indicate that, at low conversions, the aromatics in the gasoline are mainly formed by dealkylation of heavy aromatic molecules present in the feed. At higher conversions, however, the aromatics in the naphtha are mainly formed by cyclization followed by hydrogen transfer of the olefins formed during cracking. This reaction also increases the relative concentration of paraffinic hydrocarbons. The distribution of C9 aromatics showed that, as the conversion increases, there occurs an isomerization of the alkyl chain, to increase the branching of the ring.

  12. Infrared spectroscopy of matrix-isolated polycyclic aromatic hydrocarbon cations. 4. The tetracyclic PAH isomers chrysene and 1,2-benzanthracene.

    PubMed

    Hudgins, D M; Allamandola, L J

    1997-05-01

    The mid-infrared spectra of the polycyclic aromatic hydrocarbon (PAH) cations of the tetracyclic isomers chrysene (C18H12+) and 1,2-benzanthracene (C18H12+) are presented. As with previous PAH cations studied to date, the CC stretching and CH in-plane bending mode absorptions are about an order of magnitude stronger than the aromatic CH out-of-plane bending absorptions and nearly 2 orders of magnitude more intense than the corresponding bands in the neutral molecule. The CH bands arising from the out-of-plane bends in the cation are slightly weaker than the corresponding bands in the neutral species. The strongest cation bands of these species fall between 1300 and 1330 cm-1, close to the peak of the most intense interstellar emission feature in HII regions and reflection nebulae. A strong PAH cation band at slightly higher frequency than 1300 cm-1 may be associated with an asymmetric CC stretching vibration involving rings adjacent to the kink in the chain of aromatic rings. PMID:11541094

  13. Role of alkyl group in the aromatic extraction using pyridinium-based ionic liquids.

    PubMed

    Kim, Min Ji; Shin, Seung Hoon; Kim, Young Jin; Cheong, Minserk; Lee, Je Seung; Kim, Hoon Sik

    2013-11-27

    The performance of N-alkylpyridinium-based ionic liquids with a SCN anion (PyILs) was evaluated for the selective extraction of aromatics from aliphatic hydrocarbons. The aromatic extraction ability of PyILs was greatly enhanced by the presence of a methyl group on the pyridinium ring at the 3- or 4-position, whereas the solubility of the aromatics in the PyILs decreased with increasing the number of methyl groups on the benzene ring. The FT-IR studies revealed that the solubility of an aromatic compound in a PyIL is closely correlated with the degree of aromatic C-H bending frequency shift observed during the dissolution of the aromatic compound in the PyIL: the larger the shift, the higher the solubility. The computational calculations on the dispersion interactions between aromatics and PyILs demonstrated that the anion-aromatic interaction is much more important than the cation-aromatic interaction in determining the aromatic solubility in PyILs, and such anion-aromatic interaction can be enhanced by introducing a methyl group at the carbon atom of the pyridinium ring. PMID:24180561

  14. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Gordon, M. K.; Araki, S.; Black, G. J.; Bosh, A. S.; Brahic, A.; Brooks, S. M.; Charnoz, S.; Colwell, J. E.; Cuzzi, J. N.; Dones, L.; Durisen, R. H.; Esposito, L. W.; Ferrari, C.; Festou, M.; French, R. G.; Giuliatti-Winter, S. M.; Graps, A. L.; Hamilton, D. P.; Horanyi, M.; Karjalainen, R. M.; Krivov, A. V.; Krueger, H.; Larson, S. M.; Levison, H. F.; Lewis, M. C.; Lissauer, J. J.; Murray, C. D.; Namouni, F.; Nicholson, P. D.; Olkin, C. B.; Poulet, F.; Rappaport, N. J.; Salo, H. J.; Schmidt, J.; Showalter, M. R.; Spahn, F.; Spilker, L. J.; Srama, R.; Stewart, G. R.; Yanamandra-Fisher, P.

    2002-08-01

    The past two decades have witnessed dramatic changes in our view and understanding of planetary rings. We now know that each of the giant planets in the Solar System possesses a complex and unique ring system. Recent studies have identified complex gravitational interactions between the rings and their retinues of attendant satellites. Among the four known ring systems, we see elegant examples of Lindblad and corotation resonances (first invoked in the context of galactic disks), electromagnetic resonances, spiral density waves and bending waves, narrow ringlets which exhibit internal modes due to collective instabilities, sharp-edged gaps maintained via tidal torques from embedded moonlets, and tenuous dust belts created by meteoroid impact onto, or collisions between, parent bodies. Yet, as far as we have come, our understanding is far from complete. The fundamental questions confronting ring scientists at the beginning of the twenty-first century are those regarding the origin, age and evolution of the various ring systems, in the broadest context. Understanding the origin and age requires us to know the current ring properties, and to understand the dominant evolutionary processes and how they influence ring properties. Here we discuss a prioritized list of the key questions, the answers to which would provide the greatest improvement in our understanding of planetary rings. We then outline the initiatives, missions, and other supporting activities needed to address those questions, and recommend priorities for the coming decade in planetary ring science.

  15. Influence of quantum dots on the aromaticity of thiosalicylic acid.

    PubMed

    Guan, Qiumei

    2013-12-01

    When ligands are coordinated to quantum dots (QDs), the ring current of the ligand strongly influences the applications of the QDs, for example in solar cell technology. The Raman spectrum of the ligand can be used to probe and identify ions or measure ion concentrations. Here, we investigated, using a theoretical method, the aromaticities and Raman spectra of CdTe, CdSe, and CdS QDs coordinated with thiosalicylic acid ligands. We found that the aromaticity of the benzene ring in free thiosalicylic acid increased when it was used as a QD ligand. The ring currents of the benzene rings in the CdTe-ligand, CdSe-ligand, and CdS-ligand systems were stronger than the ring current of the benzene ring in free thiosalicylic acid; in other words, the QDs influence the ring current--they enhance the electron transfer rate of the benzene ring. We also discovered that the CdTe-ligand and CdSe-ligand systems have stronger ring currents than the CdS-ligand system. The high electronegativity and vacant d orbital of the sulfur atom influence the ring current of the ligand in the CdS-ligand system. Further, the Raman spectrum of free thiosalicylic acid was different from the spectra of the ligands in the QD-ligand systems: the Raman spectra of COO(-) in each QD-ligand system was enhanced compared with that of the COO(-) in free thiosalicylic acid. PMID:23934301

  16. Properties of the indole ring in metal complexes. A comparison with the phenol ring.

    PubMed

    Shimazaki, Yuichi; Yajima, Tatsuo; Yamauchi, Osamu

    2015-07-01

    Tryptophan (Trp), an essential amino acid, has an indole ring with a high electron density and is frequently seen at the proximal position of the metal site in metalloproteins. For example, the indole ring of Trp has been reported to interact weakly with Cu(I) in a Cu chaperone CusF. Another aromatic amino acid, tyrosine (Tyr), has a phenol ring, which is an important metal binding site in various metalloproteins. Although the structures of the aromatic rings are different, they both have a weakly acidic moiety and perform some similar roles in biological systems, such as radical formation and electron transfer. In this review, we focus on these and other properties of the indole and phenol rings in metal-containing systems. PMID:25817198

  17. Interatomic magnetizability: a QTAIM-based approach toward deciphering magnetic aromaticity.

    PubMed

    Foroutan-Nejad, Cina

    2011-11-17

    Interatomic magnetizability provides insight into the extent of electronic current density between two adjacent atomic basins. By studying a number of well-known aromatic, nonaromatic, and antiaromatic molecules, it is demonstrated that interatomic magnetizability (bond magnetizability) not only is able to verify the exact nature of aromaticity/antiaromaticity among different molecules, but also can distinguish the correct aromaticity order among sets of aromatic/antiaromatic molecules. The interatomic magnetizability is a direct measure of the current flux between two adjacent atomic basins and is the first QTAIM-derived index that evaluates aromaticity based on a response property, that is, magnetizability. Bond magnetizability is easy to compute, straightforward to interpret, and can be employed to evaluate the pure π- or σ-orbital contributions to magnetic aromaticity. PMID:21739973

  18. Effect of intercalated aromatic sulfonates on uptake of aromatic compounds from aqueous solutions by modified Mg-Al layered double hydroxide

    SciTech Connect

    Kameda, Tomohito; Yamazaki, Takashi; Yoshioka, Toshiaki

    2010-06-15

    In this study, we utilized Mg-Al layered double hydroxide (Mg-Al LDH) modified by intercalation with three aromatic sulfonates-2,7-naphthalene disulfonate (2,7-NDS{sup 2-}), benzenesulfonate (BS{sup -}), and benzenedisulfonate (BDS{sup 2-})-for the uptake of two aromatics-1,3-dinitrobenzene (DNB) and anisole (AS)-from aqueous solution and determined the effect of the aromatic sulfonates on the uptake of these aromatics. We found that the electron-rich aromatic ring of the intercalated aromatic sulfonates such as 2,7-NDS{sup 2-} undergoes strong {pi}-{pi} stacking interactions with the electron-poorer benzene ring of DNB in aqueous solution, and these interactions result in a higher uptake of DNB by the modified Mg-Al LDHs. In contrast, the electron-poor aromatic ring of the aromatic sulfonates such as BDS{sup 2-} undergoes weak {pi}-{pi} stacking interactions with the electron-poorer benzene ring of DNB, and these interactions result in a lower uptake of DNB by the modified Mg-Al LDHs.

  19. Planetary Rings

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.

    1994-01-01

    Just over two decades ago, Jim Pollack made a critical contribution to our understanding of planetary ring particle properties, and resolved a major apparent paradox between radar reflection and radio emission observations. At the time, particle properties were about all there were to study about planetary rings, and the fundamental questions were, why is Saturn the only planet with rings, how big are the particles, and what are they made of? Since then, we have received an avalanche of observations of planetary ring systems, both from spacecraft and from Earth. Meanwhile, we have seen steady progress in our understanding of the myriad ways in which gravity, fluid and statistical mechanics, and electromagnetism can combine to shape the distribution of the submicron-to-several-meter size particles which comprise ring systems into the complex webs of structure that we now know them to display. Insights gained from studies of these giant dynamical analogs have carried over into improved understanding of the formation of the planets themselves from particle disks, a subject very close to Jim's heart. The now-complete reconnaissance of the gas giant planets by spacecraft has revealed that ring systems are invariably found in association with families of regular satellites, and there is ark emerging perspective that they are not only physically but causally linked. There is also mounting evidence that many features or aspects of all planetary ring systems, if not the ring systems themselves, are considerably younger than the solar system

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

    PubMed

    Kita, Yasuyuki; Dohi, Toshifumi

    2015-10-01

    We started our hypervalent iodine research about 30 years ago in the mid-1980s. We soon successfully developed the single-electron-transfer oxidation ability of a hypervalent iodine reagent, specifically, phenyliodine(III) bis(trifluoroacetate) (PIFA), toward aromatic rings of phenyl ethers for forming aromatic cation radicals. This was one of the exciting and unexpected events in our research studies so far, and the discovery was reported in 1991. It also led to the next challenge, developing the metal-free oxidative couplings for C-H functionalizations and direct couplings between the C-H bonds of valuable aromatic compounds in organic synthesis. In order to realize the effective oxidative coupling, pioneering new aromatic ring activations was essential and several useful methodologies have been found for oxidizable arenes. The achievements regarding this objective obtained in our continuous research are herein summarized with classification of the aromatic ring activation strategies. PMID:26223195

  1. Birds and polycyclic aromatic hydrocarbons

    USGS Publications Warehouse

    Albers, P.H.

    2006-01-01

    Polycyclic aromatic hydrocarbons (PAH) are present throughout the global environment and are produced naturally and by activities of humans. Effects of PAH on birds have been determined by studies employing egg injection, egg immersion, egg shell application, single and multiple oral doses, subcutaneous injection, and chemical analysis of field-collected eggs and tissue. The four-to six-ring aromatic compounds are the most toxic to embryos, young birds, and adult birds. For embryos, effects include death, developmental abnormalities, and a variety of cellular and biochemical responses. For adult and young birds, effects include reduced egg production and hatching, increased clutch or brood abandonment, reduced growth, increased organweights, and a variety of biochemical responses. Trophic level accumulation is unlikely. Environmental exposure to PAH in areas of high human population or habitats affected by recent petroleum spills might be sufficient to adversely affect reproduction. Evidence of long-term effects of elevated concentrations of environmental PAH on bird populations is very limited and the mechanisms of effect are unclear.

  2. Development of Enantiospecific Coupling of Secondary and Tertiary Boronic Esters with Aromatic Compounds.

    PubMed

    Odachowski, Marcin; Bonet, Amadeu; Essafi, Stephanie; Conti-Ramsden, Philip; Harvey, Jeremy N; Leonori, Daniele; Aggarwal, Varinder K

    2016-08-01

    The stereospecific cross-coupling of secondary boronic esters with sp(2) electrophiles (Suzuki-Miyaura reaction) is a long-standing problem in synthesis, but progress has been achieved in specific cases using palladium catalysis. However, related couplings with tertiary boronic esters are not currently achievable. To address this general problem, we have focused on an alternative method exploiting the reactivity of a boronate complex formed between an aryl lithium and a boronic ester. We reasoned that subsequent addition of an oxidant or an electrophile would remove an electron from the aromatic ring or react in a Friedel-Crafts-type manner, respectively, generating a cationic species, which would trigger 1,2-migration of the boron substituent, creating the new C-C bond. Elimination (preceded by further oxidation in the former case) would result in rearomatization giving the coupled product stereospecifically. Initial work was examined with 2-furyllithium. Although the oxidants tested were unsuccessful, electrophiles, particularly NBS, enabled the coupling reaction to occur in good yield with a broad range of secondary and tertiary boronic esters, bearing different steric demands and functional groups (esters, azides, nitriles, alcohols, and ethers). The reaction also worked well with other electron-rich heteroaromatics and 6-membered ring aromatics provided they had donor groups in the meta position. Conditions were also found under which the B(pin)- moiety could be retained in the product, ortho to the boron substituent. This protocol, which created a new C(sp(2))-C(sp(3)) and an adjacent C-B bond, was again applicable to a range of secondary and tertiary boronic esters. In all cases, the coupling reaction occurred with complete stereospecificity. Computational studies verified the competing processes involved and were in close agreement with the experimental observations. PMID:27384259

  3. Vascular rings.

    PubMed

    Backer, Carl L; Mongé, Michael C; Popescu, Andrada R; Eltayeb, Osama M; Rastatter, Jeffrey C; Rigsby, Cynthia K

    2016-06-01

    The term vascular ring refers to congenital vascular anomalies of the aortic arch system that compress the esophagus and trachea, causing symptoms related to those two structures. The most common vascular rings are double aortic arch and right aortic arch with left ligamentum. Pulmonary artery sling is rare and these patients need to be carefully evaluated for frequently associated tracheal stenosis. Another cause of tracheal compression occurring only in infants is the innominate artery compression syndrome. In the current era, the diagnosis of a vascular ring is best established by CT imaging that can accurately delineate the anatomy of the vascular ring and associated tracheal pathology. For patients with a right aortic arch there recently has been an increased recognition of a structure called a Kommerell diverticulum which may require resection and transfer of the left subclavian artery to the left carotid artery. A very rare vascular ring is the circumflex aorta that is now treated with the aortic uncrossing operation. Patients with vascular rings should all have an echocardiogram because of the incidence of associated congenital heart disease. We also recommend bronchoscopy to assess for additional tracheal pathology and provide an assessment of the degree of tracheomalacia and bronchomalacia. The outcomes of surgical intervention are excellent and most patients have complete resolution of symptoms over a period of time. PMID:27301603

  4. Tunable Control of Polyproline Helix (PPII) Structure via Aromatic Electronic Effects: An Electronic Switch of Polyproline Helix

    PubMed Central

    2015-01-01

    Aromatic rings exhibit defined interactions via the unique aromatic π face. Aromatic amino acids interact favorably with proline residues via both the hydrophobic effect and aromatic–proline interactions, C−H/π interactions between the aromatic π face and proline ring C–H bonds. The canonical aromatic amino acids Trp, Tyr, and Phe strongly disfavor a polyproline helix (PPII) when they are present in proline-rich sequences because of the large populations of cis amide bonds induced by favorable aromatic–proline interactions (aromatic–cis-proline and proline–cis-proline–aromatic interactions). We demonstrate the ability to tune polyproline helix conformation and cis–trans isomerism in proline-rich sequences using aromatic electronic effects. Electron-rich aromatic residues strongly disfavor polyproline helix and exhibit large populations of cis amide bonds, while electron-poor aromatic residues exhibit small populations of cis amide bonds and favor polyproline helix. 4-Aminophenylalanine is a pH-dependent electronic switch of polyproline helix, with cis amide bonds favored as the electron-donating amine, but trans amide bonds and polyproline helix preferred as the electron-withdrawing ammonium. Peptides with block proline–aromatic PPXPPXPPXPP sequences exhibited electronically switchable pH-dependent structures. Electron-poor aromatic amino acids provide special capabilities to integrate aromatic residues into polyproline helices and to serve as the basis of aromatic electronic switches to change structure. PMID:25075447

  5. Transformations of Aromatic Compounds by Nitrosomonas europaea

    PubMed Central

    Keener, William K.; Arp, Daniel J.

    1994-01-01

    Benzene and a variety of substituted benzenes inhibited ammonia oxidation by intact cells of Nitrosomonas europaea. In most cases, the inhibition was accompanied by transformation of the aromatic compound to a more oxidized product or products. All products detected were aromatic, and substituents were often oxidized but were not separated from the benzene ring. Most transformations were enhanced by (NH4)2SO4 (12.5 mM) and were prevented by C2H2, a mechanism-based inactivator of ammonia monooxygenase (AMO). AMO catalyzed alkyl substituent hydroxylations, styrene epoxidation, ethylbenzene desaturation to styrene, and aniline oxidation to nitrobenzene (and unidentified products). Alkyl substituents were preferred oxidation sites, but the ring was also oxidized to produce phenolic compounds from benzene, ethylbenzene, halobenzenes, phenol, and nitrobenzene. No carboxylic acids were identified. Ethylbenzene was oxidized via styrene to two products common also to oxidation of styrene; production of styrene is suggestive of an electron transfer mechanism for AMO. Iodobenzene and 1,2-dichlorobenzene were oxidized slowly to halophenols; 1,4-dichlorobenzene was not transformed. No 2-halophenols were detected as products. Several hydroxymethyl (-CH2OH)-substituted aromatics and p-cresol were oxidized by C2H2-treated cells to the corresponding aldehydes, benzaldehyde was reduced to benzyl alcohol, and o-cresol and 2,5-dimethylphenol were not depleted. PMID:16349282

  6. Storage Rings

    SciTech Connect

    Fischer, W.

    2011-01-01

    Storage rings are circular machines that store particle beams at a constant energy. Beams are stored in rings without acceleration for a number of reasons (Tab. 1). Storage rings are used in high-energy, nuclear, atomic, and molecular physics, as well as for experiments in chemistry, material and life sciences. Parameters for storage rings such as particle species, energy, beam intensity, beam size, and store time vary widely depending on the application. The beam must be injected into a storage ring but may not be extracted (Fig. 1). Accelerator rings such as synchrotrons are used as storage rings before and after acceleration. Particles stored in rings include electrons and positrons; muons; protons and anti-protons; neutrons; light and heavy, positive and negative, atomic ions of various charge states; molecular and cluster ions, and neutral polar molecules. Spin polarized beams of electrons, positrons, and protons were stored. The kinetic energy of the stored particles ranges from 10{sup -6} eV to 3.5 x 10{sup 12} eV (LHC, 7 x 10{sup 12} eV planned), the number of stored particles from one (ESR) to 1015 (ISR). To store beam in rings requires bending (dipoles) and transverse focusing (quadrupoles). Higher order multipoles are used to correct chromatic aberrations, to suppress instabilities, and to compensate for nonlinear field errors of dipoles and quadrupoles. Magnetic multipole functions can be combined in magnets. Beams are stored bunched with radio frequency systems, and unbunched. The magnetic lattice and radio frequency system are designed to ensure the stability of transverse and longitudinal motion. New technologies allow for better storage rings. With strong focusing the beam pipe dimensions became much smaller than previously possible. For a given circumference superconducting magnets make higher energies possible, and superconducting radio frequency systems allow for efficient replenishment of synchrotron radiation losses of large current electron or

  7. High performance liquid chromatographic separation of polycyclic aromatic hydrocarbons on microparticulate pyrrolidone and application to the analysis of shale oil

    SciTech Connect

    Mourey, T.H.; Siggia, S.; Uden, P.C.; Crowley, R.J.

    1980-05-01

    A chemically bonded pyrrolidone substrate is used for the high performance liquid chromatographic separation of polycyclic aromatic hydrocarbons. The cyclic amide phase interacts electronically with the polycyclic aromatic hydrocarbons in both the normal and reversed phase modes. Separation is effected according to the number of aromatic rings and the type of ring condensation. Information obtained is very different from that observed on hydrocarbon substrates, and thus these phases can be used in a complementary fashion to give a profile of polycyclic aromatics in shale oil samples. 7 figures, 1 table.

  8. Nucleophilic Aromatic Substitution.

    ERIC Educational Resources Information Center

    Avila, Walter B.; And Others

    1990-01-01

    Described is a microscale organic chemistry experiment which demonstrates one feasible route in preparing ortho-substituted benzoic acids and provides an example of nucleophilic aromatic substitution chemistry. Experimental procedures and instructor notes for this activity are provided. (CW)

  9. Trimerization of aromatic nitriles

    NASA Technical Reports Server (NTRS)

    Hsu, L. C. (Inventor)

    1977-01-01

    Triazine compounds and cross-linked polymer compositions were made by heating aromatic nitriles to a temperature in the range of about 100 C to about 700 C, in the presence of a catalyst or mixture of catalysts. Aromatic nitrile-modified (terminated and/or appended) imide, benzimidazole, imidazopyrrolone, quinoxaline, and other condensation type prepolymers or their precopolymers were made which were trimerized with or without a filler by the aforementioned catalytic trimerization process.

  10. Annulation of Aromatic Imines via Directed C-H BondActivation

    SciTech Connect

    Thalji, Reema K.; Ahrendt, Kateri A.; Bergman, Robert G.; Ellman,Jonathan A.

    2005-04-14

    A directed C-H bond activation approach to the synthesis of indans, tetralins, dihydrofurans, dihydroindoles, and other polycyclic aromatic compounds is presented. Cyclization of aromatic ketimines and aldimines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using (PPh{sub 3}){sub 3}RhCl (Wilkinson's catalyst). The cyclization of a range of aromatic ketimines and aldimines provides bi- and tricyclic ring systems with good regioselectivity. Different ring sizes and substitution patterns can be accessed through the coupling of monosubstituted, 1,1- or 1,2-disubstituted, and trisubstituted alkenes bearing both electron-rich and electron-deficient functionality.

  11. Annulation of aromatic imines via directed C-H bond activation.

    PubMed

    Thalji, Reema K; Ahrendt, Kateri A; Bergman, Robert G; Ellman, Jonathan A

    2005-08-19

    A directed C-H bond activation approach to the synthesis of indans, tetralins, dihydrofurans, dihydroindoles, and other polycyclic aromatic compounds is presented. Cyclization of aromatic ketimines and aldimines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using (PPh3)3RhCl (Wilkinson's catalyst). The cyclization of a range of aromatic ketimines and aldimines provides bi- and tricyclic ring systems with good regioselectivity. Different ring sizes and substitution patterns can be accessed through the coupling of monosubstituted, 1,1- or 1,2-disubstituted, and trisubstituted alkenes bearing both electron-rich and electron-deficient functionality. PMID:16095296

  12. Aromatic Polyimide Foam

    NASA Technical Reports Server (NTRS)

    Weiser, Erik S. (Inventor); St.Clair, Terry L. (Inventor); Echigo, Yoshiaki (Inventor); Kaneshiro, Hisayasu (Inventor)

    2000-01-01

    A mechanically undensified aromatic polyimide foam is made from an aromatic polyimide precursor solid residuum and has the following combination of properties: a density according to ASTM D-3574A of about 0.5 pounds/cu.ft to about 20 pounds/cu.ft; a compression strength according to ASTM D-3574C of about 1.5 psi to about 1500 psi; and a limiting oxygen index according to ASTM D-2863 of about 35% oxygen to about 75% oxygen at atmospheric pressure. The aromatic polyimide foam has no appreciable solid inorganic contaminants which are residues of inorganic blowing agents. The aromatic polyimide which constitutes the aromatic polyimide foam has a glass transition temperature (Tg) by differential scanning calorimetry of about 235 C to about 400 C; and a thermal stability of 0 to about 1% weight loss at 204 C as determined by thermogravinietric analysis (TGA). The aromatic polyimide foam has utility as foam insulation and as structural foam, for example, for aeronautical, aerospace and maritime applications.

  13. Ring Galaxies

    NASA Astrophysics Data System (ADS)

    Dennefeld, M.; Materne, J.

    1980-09-01

    Among the 338 exotic, intriguing and/or fascinating objects contained in Arp's catalogue of peculiar galaxies, two, Arp 146 and 147, are calling special attention as a presumably separate class of objects displaying closed rings with almost empty interior. It is difficult to find out when, historically speaking, attention was called first to this type of object as a peculiar class, but certainly ga1axies with rings were widely found and recognized in the early sixties, ul}der others by Vorontsov-Velyaminov (1960), Sandage (1961) in the Hubble Atlas or de Vaucouleurs (1964) in the first reference catalogue of ga1axies. The most recent estimates by Arp and Madore (1977) from a search on about 200 Schmidt plates covering 7,000 square degrees give 3.6 per cent of ring galaxies among 2,784 peculiar galaxies found. However, despite the mythological perfection associated with a circle, some ordering is necessary before trying to understand the nature of such objects. This is particularly true because a large fraction of those galaxies with rings are probably normal spiral galaxies of type RS or S(r) as defined by de Vaucouleurs, where the spiral arms are simply "closing the circle". A good example of such "ordinary" galaxy is NGC 3081 in the Hubble Atlas .

  14. Anaerobic biodegradation of aromatic compounds.

    PubMed

    Jothimani, P; Kalaichelvan, G; Bhaskaran, A; Selvaseelan, D Augustine; Ramasamy, K

    2003-09-01

    Many aromatic compounds and their monomers are existing in nature. Besides they are introduced into the environment by human activity. The conversion of these aromatic compounds is mainly an aerobic process because of the involvement of molecular oxygen in ring fission and as an electron acceptor. Recent literatures indicated that ring fission of monomers and obligomers mainly occurs in anaerobic environments through anaerobic respiration with nitrate, sulphate, carbon dioxide or carbonate as electron acceptors. These anaerobic processes will help to work out the better situation for bioremediation of contaminated environments. While there are plenty of efforts to reduce the release of these chemicals to the environment, already contaminated sites need to be remediated not only to restore the sites but to prevent the leachates spreading to nearby environment. Basically microorganisms are better candidates for breakdown of these compounds because of their wider catalytic mechanisms and the ability to act even in the absence of oxygen. These microbes can be grouped based on their energy mechanisms. Normally, the aerobic counterparts employ the enzymes like mono-and-dioxygenases. The end product is basically catechol, which further may be metabolised to CO2 by means of quinones reductases cycles. In the absense of reductases compounds, the reduced catechols tend to become oxidised to form many quinone compounds. The quinone products are more recalcitrant and lead to other aesthetic problems like colour in water, unpleasant odour, etc. On the contrary, in the reducing environment this process is prevented and in a cascade of pathways, the cleaved products are converted to acetyl co-A to be integrated into other central metabolite paths. The central metabolite of anaerobic degradation is invariably co-A thio-esters of benzoic acid or hydroxy benzoic acid. The benzene ring undergoes various substitution and addition reactions to form chloro-, nitro-, methyl- compounds

  15. Synthetic fuel aromaticity and staged combustion

    SciTech Connect

    Longanbach, J. R.; Chan, L. K.; Levy, A.

    1982-11-15

    Samples of middle and heavy SRC-II distillates were distilled into 50 C boiling point range fractions. These were characterized by measurements of their molecular weight, elemental analysis and basic nitrogen content and calculation of average molecular structures. The structures typically consisted of 1 to 3 aromatic rings fused to alicyclic rings with short, 1 to 3 carbon aliphatic side chains. The lower boiling fractions contained significant amounts (1 atom/molecule) of oxygen while the heavier fractions contained so few heteroatoms that they were essentially hydrocarbons. Laboratory scale oxidative-pyrolysis experiments were carried out at pyrolysis temperatures of 500 to 1100 C and oxygen concentrations from 0 to 100 percent of stoichiometry. Analysis of liquid products, collected in condensers cooled with liquid nitrogen showed that aromatization is a major reaction in the absence of oxygen. The oxygen-containing materials (phenolics) seem to be more resistant to thermal pyrolysis than unsubstituted aromatics. Nitrogen converts from basic to nonbasic forms at about 500 C. The nonbasic nitrogen is more stable and survives up to 700 C after which it is slowly removed. A recently constructed 50,000 Btu/hr staged combustor was used to study the chemistry of the nitrogen and aromatics. SRC II combustion was studied under fuel-rich, first-stage conditions at air/fuel ratios from 0.6 to 1.0 times stoichiometric. The chemistry of the fuel during combustion calls for further investigation in order to examine the mechanism by which HCN is evolved as a common intermediate for the formation of the nitrogen-containing gaseous combustion products. 25 references, 45 figures, 25 tables.

  16. Structure-activity relationships of aromatic diamines in the Ames Salmonella typhimurium assay. Part II.

    PubMed

    Kalopissis, G

    1992-09-01

    Structure-activity relationships in the case of aromatic monoamines, diversely substituted on the ring, using the mutagenic activity in the Ames test were studied in part I. This part II is based on the same general principles but applied to phenylene diamines (ortho, para and meta) diversely substituted on the ring. PMID:1381475

  17. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  18. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  19. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  20. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  1. Metabolism of aromatic compounds by Caulobacter crescentus

    SciTech Connect

    Chatterjee, D.K.; Bourquin, A.W.

    1987-05-01

    Cultures of Caulobacter crescentus were found to grow on a variety of aromatic compounds. Degradation of benzoate, p-hydroxybenzoate, and phenol was found to occur via ..beta..-ketoadipate. The induction of degradative enzymes such as benzoate 1,2-dioxygenase, the ring cleavage enzyme catechol 1,2-dioxygenase, and cis,cis-muconate lactonizing enzyme appeared similar to the control mechanism present in Pseudomonas spp. Both benzoate 1,2-dioxygenase and catechol 1,2-dioxygenase had stringent specificities, as revealed by their action toward substituted benzoates and substituted catechols, respectively.

  2. Overview of Polycyclic Aromatic Compounds (PAC)

    PubMed Central

    Achten, Christine; Andersson, Jan T.

    2015-01-01

    The chemical group of polycyclic aromatic compounds (PAC), including the better-known subgroup of polycyclic aromatic hydrocarbons (PAH) and the heterocyclic aromatic compounds (NSO-PAC, heterocycles), comprise several thousand individual compounds. It is hard to find a comprehensive overview in the literature of these PACs that includes a substantial amount of relevant properties. Here an attempt is made to summarize the most studied but also some less well-known PACs. In addition to basic data such as recommended names, abbreviations, CAS numbers, molecular formulas, chemical structures, and exact mono-isotopic molecular weights, physico-chemical properties taken from the literature like boiling points, vapor pressures, water solubilities, Henry's Law constants, n-octanol-water partition coefficients (log KOW), and pKa are summarized. Selected toxicological data are listed indicating carcinogenic and mutagenic activity or effects on different organisms. PAC nomenclature is a complex topic, so suggestions for practical use are made. Regarding available data, estimated (instead of measured) values should be used with caution because considerable deviations from experimentally determined values can occur. For an enhanced understanding of the behavior of single PACs in comparison with each other, some of the properties mentioned above are plotted vs. the number of rings or the degree of alkylation. Also, some physico-chemical data are correlated with different functional groups as substituents of the PAHs. This article reveals that rather little is known about the less common PACs, e.g., higher molecular weight compounds, alkylated or otherwise substituted aromatics, for instance, keto-, oxo-, amino-, nitro-, cyano-PAHs, or some heterocyclic aromatic compounds, including their derivatives. It mirrors the limited state of knowledge about the variety of PACs that do not belong to the 16 EPA PAHs. PMID:26823644

  3. Role of methyl group number on SOA formation from monocyclic aromatic hydrocarbons photooxidation under low-NOx conditions

    NASA Astrophysics Data System (ADS)

    Li, L.; Tang, P.; Nakao, S.; Chen, C.-L.; Cocker, D. R., III

    2016-02-01

    Substitution of methyl groups onto the aromatic ring determines the secondary organic aerosol (SOA) formation from the monocyclic aromatic hydrocarbon precursor (SOA yield and chemical composition). This study links the number of methyl groups on the aromatic ring to SOA formation from monocyclic aromatic hydrocarbons photooxidation under low-NOx conditions (HC/NO > 10 ppbC : ppb). Monocyclic aromatic hydrocarbons with increasing numbers of methyl groups are systematically studied. SOA formation from pentamethylbenzene and hexamethylbenzene are reported for the first time. A decreasing SOA yield with increasing number of methyl groups is observed. Linear trends are found in both f44 vs. f43 and O / C vs. H / C for SOA from monocyclic aromatic hydrocarbons with zero to six methyl groups. An SOA oxidation state predictive method based on benzene is used to examine the effect of added methyl groups on aromatic oxidation under low-NOx conditions. Further, the impact of methyl group number on density and volatility of SOA from monocyclic aromatic hydrocarbons is explored. Finally, a mechanism for methyl group impact on SOA formation is suggested. Overall, this work suggests that, as more methyl groups are attached on the aromatic ring, SOA products from these monocyclic aromatic hydrocarbons become less oxidized per mass/carbon on the basis of SOA yield or chemical composition.

  4. The oxidation degradation of aromatic compounds

    NASA Technical Reports Server (NTRS)

    Brezinsky, Kenneth; Glassman, Irvin

    1987-01-01

    A series of experiments were conducted which focused on understanding the role that the O atom addition to aromatic rings plays in the oxidation of benzene and toluene. Flow reactor studies of the oxidation of toluene gave an indication of the amount of O atoms available during an oxidation and the degree to which the O atom adds to the ring. Flow reactor studies of the oxidation of toluene and benzene to which NO2 was added, have shown that NO2 appears to suppress the formation of O atoms and consequently reduce the amount of phenols and cresols formed by O atom addition. A high temperature pyrolysis study of phenol has confirmed that the major decomposition products are carbon monoxide and cyclopentadiene. A preliminary value for the overall decomposition rate constant was also obtained.

  5. (Hetero)aromatics from dienynes, enediynes and enyne-allenes.

    PubMed

    Raviola, Carlotta; Protti, Stefano; Ravelli, Davide; Fagnoni, Maurizio

    2016-08-01

    The construction of aromatic rings has become a key objective for organic chemists. While several strategies have been developed for the functionalization of pre-formed aromatic rings, the direct construction of an aromatic core starting from polyunsaturated systems is yet a less explored field. The potential of such reactions in the formation of aromatics increased at a regular pace in the last few years. Nowadays, there are reliable and well-established procedures to prepare polyenic derivatives, such as dienynes, enediynes, enyne-allenes and hetero-analogues. This has stimulated their use in the development of innovative cycloaromatizations. Different examples have recently emerged, suggesting large potential of this strategy in the preparation of (hetero)aromatics. Accordingly, this review highlights the recent advancements in this field and describes the different conditions exploited to trigger the process, including thermal and photochemical activation, as well as the use of transition metal catalysis and the addition of electrophiles/nucleophiles or radical species. PMID:27263976

  6. Reduction of Aromatic Hydrocarbons by Zero-Valent Iron and Palladium Catalyst

    SciTech Connect

    Kim, Young-Hun; Shin, Won Sik; Ko, Seok-Oh; Kim, Myung-Chul

    2004-03-31

    Permeable reactive barrier (PRB) is an alternative technology for soil and groundwater remediation. Zero valent iron, which is the most popular PRB material, is only applicable to halogenated aliphatic organics and some heavy metals. The objective of this study was to investigate reductive dechlorination of halogenated compounds and reduction of non-halogenated aromatic hydrocarbons using zero valent metals (ZVMs) and catalysts as reactive materials for PRBs. A group of small aromatic hydrocarbons such as monochlorophenols, phenol and benzene were readily reduced with palladium catalyst and zero valent iron. Poly-aromatic hydrocarbons (PAHs) were also tested with the catalysts and zero valent metal combinations. The aromatic rings were reduced and partly reduced PAHs were found as the daughter compounds. The current study demonstrates reduction of aromatic compounds by ZVMs and modified catalysts and implicates that PRB is applicable not only for halogenated organic compounds but nonhalogenated aromatic compounds such as PAHs.

  7. Oxidative aromatic coupling of meso-arylamino-porphyrins.

    PubMed

    Nowak-Król, Agnieszka; Gryko, Daniel T

    2013-11-15

    Strategic placement of the bis-arylamino group at the meso-position of porphyrins allowed fusion of these two moieties via aromatic dehydrogenation. By placing two di(naphthalene-2-yl)amine or bis(3,5-dimethoxyphenyl)amine groups at positions 5 and 15 of the porphyrin, the oxidative aromatic coupling was directed toward closing one six-membered ring. The extension of the porphyrin chromophore leads to significant change in linear optical properties, such as a bathochromic shift of absorption and broadening of the Q-band. PMID:24168727

  8. Ringing wormholes

    SciTech Connect

    Konoplya, R.A.; Molina, C.

    2005-06-15

    We investigate the response of traversable wormholes to external perturbations through finding their characteristic frequencies and time-domain profiles. The considered solution describes traversable wormholes between the branes in the two brane Randall-Sundrum model and was previously found within Einstein gravity with a conformally coupled scalar field. The evolution of perturbations of a wormhole is similar to that of a black hole and represents damped oscillations (ringing) at intermediately late times, which are suppressed by power-law tails (proportional to t{sup -2} for monopole perturbations) at asymptotically late times.

  9. Polybenzimidazole via aromatic nucleophilic displacement

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Hergenrother, Paul M. (Inventor); Smith, Joseph G. (Inventor)

    1994-01-01

    Di(hydroxyphenyl)benzimidazole monomers were prepared from phenyl-4-hydroxybenzoate and aromatic bis(o-diamine)s. These monomers were used in the synthesis of soluble polybenzimidazoles. The reaction involved the aromatic nucleophilic displacement of various di(hydroxyphenyl)benzimidazole monomers with activated aromatic dihalides or activated aromatic dinitro compounds in the presence of an alkali metal base. These polymers exhibited lower glass transition temperatures, improved solubility, and better compression moldability over their commercial counterparts.

  10. Aromatic site description of soot particles

    SciTech Connect

    Celnik, Matthew; Raj, Abhijeet; West, Richard; Patterson, Robert; Kraft, Markus

    2008-10-15

    A new, advanced soot particle model is developed that describes soot particles by their aromatic structure, including functional site descriptions and a detailed surface chemistry mechanism. A methodology is presented for the description of polyaromatic hydrocarbon (PAH) structures by their functional sites. The model is based on statistics that describe aromatic structural information in the form of easily computed correlations, which were generated using a kinetic Monte Carlo algorithm to study the growth of single PAH molecules. A comprehensive surface reaction mechanism is presented to describe the growth and desorption of aromatic rings on PAHs. The model is capable of simulating whole particle ensembles which allows bulk properties such as soot volume fraction and number density to be found, as well as joint particle size and surface area distributions. The model is compared to the literature-standard soot model [J. Appel, H. Bockhorn, M. Frenklach, Combust. Flame 121 (2000) 122-136] in a plug-flow reactor and is shown to predict well the experimental results of soot mass, average particle size, and particle size distributions at different flow times. Finally, the carbon/hydrogen ratio and the distribution of average PAH sizes in the ensemble, as predicted by the model, are discussed. (author)

  11. In vitro metabolism of aromatic nitriles.

    PubMed

    Markus, B; Kwon, C H

    1994-12-01

    Studies on the metabolic fate of aromatic nitriles, in contrast to their aliphatic counterparts, have been minimal and the subject of controversy. The in vitro metabolic fate of several aromatic nitriles with varying substituents was investigated by using rat liver subcellular fractions, with a particular emphasis on the nitrile moiety. Benzonitriles and 4-cyanophenols underwent oxidative metabolism to produce ring-hydroxylated metabolites. On the other hand, 2-cyanophenol was resistant to metabolism. o-Tolunitrile was metabolized and produced o-cyanobenzyl alcohol and phthalide. Phthalide, however, was chemically derived from o-cyanobenzyl alcohol, the initial metabolite. 4-Nitrobenzonitrile was resistant to oxidation on the ring, but was readily reduced to the corresponding amine metabolite under both aerobic and anaerobic conditions. Nitroxynil (3-iodo-4-hydroxy-5-nitrobenzonitrile) was metabolized to produce 3-iodo-4-hydroxy-5-nitrobenzamide and 3-iodo-4-hydroxy-5-nitrobenzoic acid. The enzyme(s) responsible for this hydrolytic metabolism was primarily localized in the cytosol. Among the nitriles tested, o-tolunitrile and nitroxynil produced metabolites in which the nitrile moiety was modified. Nitroxynil, however, was the only compound that was directly metabolized on the nitrile moiety by the rat liver enzyme(s). PMID:7891302

  12. Structural basis of enzymatic benzene ring reduction.

    PubMed

    Weinert, Tobias; Huwiler, Simona G; Kung, Johannes W; Weidenweber, Sina; Hellwig, Petra; Stärk, Hans-Joachim; Biskup, Till; Weber, Stefan; Cotelesage, Julien J H; George, Graham N; Ermler, Ulrich; Boll, Matthias

    2015-08-01

    In chemical synthesis, the widely used Birch reduction of aromatic compounds to cyclic dienes requires alkali metals in ammonia as extremely low-potential electron donors. An analogous reaction is catalyzed by benzoyl-coenzyme A reductases (BCRs) that have a key role in the globally important bacterial degradation of aromatic compounds at anoxic sites. Because of the lack of structural information, the catalytic mechanism of enzymatic benzene ring reduction remained obscure. Here, we present the structural characterization of a dearomatizing BCR containing an unprecedented tungsten cofactor that transfers electrons to the benzene ring in an aprotic cavity. Substrate binding induces proton transfer from the bulk solvent to the active site by expelling a Zn(2+) that is crucial for active site encapsulation. Our results shed light on the structural basis of an electron transfer process at the negative redox potential limit in biology. They open the door for biological or biomimetic alternatives to a basic chemical synthetic tool. PMID:26120796

  13. Analogs of solid nanoparticles as precursors of aromatic hydrocarbons

    NASA Astrophysics Data System (ADS)

    Gadallah, K. A. K.; Mutschke, H.; Jäger, C.

    2013-06-01

    Context. Aromatic =CH and C=C vibrational bands have been observed within shocked interstellar regions, indicating the presence of aromatic emission carriers such as PAHs, which may have been created from adjacent molecular cloud material by interaction with a shock front. Aims: We investigate the evolution of the aromatic =CH and C=C vibrational modes at 3.3 and 6.2 μm wavelength in heated HAC materials, PAHs and mixed PAHs and HACs, respectively, aiming at an explanation of the evolution of carbonaceous dust grains in the shocked regions. Methods: Materials used in these analogs (HAC and PAH materials) were prepared by the laser ablation and the laser pyrolysis methods, respectively. The transmission electron microscopy (TEM) in high-resolution mode was used as an analytical technique to characterize the aromatic layers in HACs. Spectroscopic analysis was prformed in the mid-IR range. Results: A remarkable destruction of aliphatic structures in HACs has been observed with the thermal processing, while aromatic structures become dominating by increasing the diameters of the graphene layers. The aromatic bands at 3.3 and 6.2 μm, observed in the laboratory spectra of PAHs and of the combination of the PAHs and HAC materials, are also clearly observed in the spectrum of the heated HACs. These bands agree with those of aromatic bands observed in astronomical observations. Conclusions: Aromatization of HACs could be a pre-stage in the decomposition process of hydrocarbons that form PAH-clusters in such hot interstellar medium.

  14. Ab initio theoretical study of non-covalent adsorption of aromatic molecules on boron nitride nanotubes.

    PubMed

    Zhao, Yu; Wu, Xiaojun; Yang, Jinlong; Zeng, Xiao Cheng

    2011-06-28

    We have studied non-covalent functionalization of boron nitride nanotubes (BNNTs) with benzene molecule and with seven other different heterocyclic aromatic rings (furan, thiophene, pyrrole, pyridine, pyrazine, pyrimidine, and pyridazine, respectively). A hybrid density functional theory (DFT) method with the inclusion of dispersion correction is employed. The structural and electronic properties of the functionalized BNNTs are obtained. The DFT calculation shows that upon adsorption to the BNNT, the center of aromatic rings tend to locate on top of the nitrogen site. The trend of adsorption energy for the aromatic rings on the BNNTs shows marked dependence on different intermolecular interactions, including the dispersion interaction (area of the delocalized π bond), the dipole-dipole interaction (polarization), and the electrostatic repulsion (lone pair electrons). The DFT calculation also shows that non-covalent functionalization of BNNTs with aromatic rings can give rise to new impurity states within the band gap of pristine BNNTs, suggesting possible carrier doping of BNNTs via selective adsorption of aromatic rings. PMID:21603684

  15. Disordered organic electronic materials based on non-benzenoid 1,6-methano[10]annulene rings

    SciTech Connect

    Tovar, John D; Streifel, Benjamin C; Peart, Patricia A

    2014-10-07

    Conjugated polymers and small molecules including the nonplanar aromatic 1,6-methano[10]annulene ring structure along with aromatic subunits, such as diketopyrrolopyrrole, and 2,1,3-benzothiadiazole, substituted with alkyl chains in a "Tail In," "Tail Out," or "No Tail" regiochemistry are disclosed.

  16. Phenylalanyl-Glycyl-Phenylalanine Tripeptide: A Model System for Aromatic-Aromatic Side Chain Interactions in Proteins

    SciTech Connect

    Valdes, Haydee; Pluhackova, Kristyna; Hobza, Pavel

    2009-09-08

    The performance of a wide range of quantum chemical calculations for the ab initio study of realistic model systems of aromatic-aromatic side chain interactions in proteins (in particular those π-π interactions occurring between adjacent residues along the protein sequence) is here assessed on the phenylalanyl-glycyl-phenylalanine (FGF) tripeptide. Energies and geometries obtained at different levels of theory are compared with CCSD(T)/CBS benchmark energies and RI-MP2/cc-pVTZ benchmark geometries, respectively. Consequently, a protocol of calculation alternative to the very expensive CCSD(T)/CBS is proposed. In addition to this, the preferred orientation of the Phe aromatic side chains is discussed and compared with previous results on the topic.

  17. Basin-ring spacing on the Moon, Mercury, and Mars

    USGS Publications Warehouse

    Pike, R.J.; Spudis, P.D.

    1987-01-01

    Radial spacing between concentric rings of impact basins that lack central peaks is statistically similar and nonrandom on the Moon, Mercury, and Mars, both inside and outside the main ring. One spacing interval, (2.0 ?? 0.3)0.5D, or an integer multiple of it, dominates most basin rings. Three analytical approaches yield similar results from 296 remapped or newly mapped rings of 67 multi-ringed basins: least-squares of rank-grouped rings, least-squares of rank and ring diameter for each basin, and averaged ratios of adjacent rings. Analysis of 106 rings of 53 two-ring basins by the first and third methods yields an integer multiple (2 ??) of 2.00.5D. There are two exceptions: (1) Rings adjacent to the main ring of multi-ring basins are consistently spaced at a slightly, but significantly, larger interval, (2.1 ?? 0.3)0.5D; (2) The 88 rings of 44 protobasins (large peak-plus-inner-ring craters) are spaced at an entirely different interval (3.3 ?? 0.6)0.5D. The statistically constant and target-invariant spacing of so many rings suggests that this characteristic may constrain formational models of impact basins on the terrestrial planets. The key elements of such a constraint include: (1) ring positions may not have been located by the same process(es) that formed ring topography; (2) ring location and emplacement of ring topography need not be coeval; (3) ring location, but not necessarily the mode of ring emplacement, reflects one process that operated at the time of impact; and (4) the process yields similarly-disposed topographic features that are spatially discrete at 20.5D intervals, or some multiple, rather than continuous. These four elements suggest that some type of wave mechanism dominates the location, but not necessarily the formation, of basin rings. The waves may be standing, rather than travelling. The ring topography itself may be emplaced at impact by this and/or other mechanisms and may reflect additional, including post-impact, influences. ?? 1987

  18. Aromatic Structure in Simulates Titan Aerosol

    NASA Technical Reports Server (NTRS)

    Trainer, Melissa G.; Loeffler, M. J.; Anderson, C. M.; Hudson, R. L.; Samuelson, R. E.; Moore, M. A.

    2011-01-01

    Observations of Titan by the Cassini Composite Infrared Spectrometer (CIRS) between 560 and 20 per centimeter (approximately 18 to 500 micrometers) have been used to infer the vertical variations of Titan's ice abundances, as well as those of the aerosol from the surface to an altitude of 300 km [1]. The aerosol has a broad emission feature centered approximately at 140 per centimeter (71 micrometers). As seen in Figure 1, this feature cannot be reproduced using currently available optical constants from laboratory-generated Titan aerosol analogs [2]. The far-IR is uniquely qualified for investigating low-energy vibrational motions within the lattice structures of COITIDlex aerosol. The feature observed by CIRS is broad, and does not likely arise from individual molecules, but rather is representative of the skeletal movements of macromolecules. Since Cassini's arrival at Titan, benzene (C6H6) has been detected in the atmosphere at ppm levels as well as ions that may be polycyclic aromatic hydrocarbons (PAHs) [3]. We speculate that the feature may be a blended composite that can be identified with low-energy vibrations of two-dimensional lattice structures of large molecules, such as PAHs or nitrogenated aromatics. Such structures do not dominate the composition of analog materials generated from CH4 and N2 irradiation. We are performing studies forming aerosol analog via UV irradiation of aromatic precursors - specifically C6H6 - to understand how the unique chemical architecture of the products will influence the observable aerosol characteristics. The optical and chemical properties of the aromatic analog will be compared to those formed from CH4/N2 mixtures, with a focus on the as-yet unidentified far-IR absorbance feature. Preliminary results indicate that the photochemically-formed aromatic aerosol has distinct chemical composition, and may incorporate nitrogen either into the ring structure or adjoined chemical groups. These compositional differences are

  19. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 1 2014-10-01 2014-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR...-managing agencies on adjacent lands (both public and private)....

  20. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 1 2013-10-01 2013-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR...-managing agencies on adjacent lands (both public and private)....

  1. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of off-road vehicle use on Reclamation lands will...

  2. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 1 2012-10-01 2011-10-01 true Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR...-managing agencies on adjacent lands (both public and private)....

  3. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of...

  4. Proton nuclear magnetic resonance characterization of the aromatic residues in the variant-3 neurotoxin from Centruroides sculpturatus Ewing

    SciTech Connect

    Krishna, N.R.; Nettesheim, D.G.; Klevit, R.E.; Drobny, G.; Watt, D.D.; Bugg, C.E. )

    1989-02-21

    The amino acid sequence for the variant-3 (CsE-v3) toxin from the venom of the scorpion Centruroides sculpturatus Ewing contains eight aromatic residues. By use of 2D NMR spectroscopic methods, the resonances from the individual protons (NH, C{sup alpha}H, C{sup beta}H{prime}, H{double prime}, and the ring) for each of the individual aromatic residues have been completely assigned. The spatial arrangement of the aromatic ring systems with respect to each other has been qualitatively analyzed by 2D-NOESY techniques. The results show that Trp-47, Tyr-4, and Tyr-42 are in close spatial proximity to each other. The NOESY contacts and the ring current induced shifts in the resonances of the individual protons of Tyr-4 and Trp-47 suggest that the aromatic ring planes of these residues are in an orthogonal arrangement. A comparison with the published crystal structure suggests that there is a minor rearrangement of the aromatic rings in the solution phase. No 2D-NOESY contacts involving Phe-44 and Tyr-14 to any other aromatic ring protons have been observed. The pH dependence of the aromatic ring proton chemical shifts has also been studied. These results suggest that the Tyr-58 phenolic group is experiencing a hydrogen-bonding interaction with a positively charged group, while Tyr-4, -14, -38, and -40 are experiencing through-space interactions with proximal negatively charged groups. These studies define the microenvironment of the aromatic residues in the variant-3 neurotoxin in aqueous solution.

  5. 32P-postlabelling analysis of small aromatic and of bulky non-aromatic DNA adducts.

    PubMed

    Reddy, M V

    1993-01-01

    The 32P-postlabelling methodology for analysis of DNA adducts derived from carcinogens containing one aromatic ring (e.g., safrole, styrene oxide, benzene metabolites, 1-nitrosoindole-3-acetonitrile) or a bulky non-aromatic moiety (e.g., mitomycin C, diaziquone) is reviewed. Six steps are involved: digestion of DNA to 3'-nucleotides, enrichment of adducts, 32P-labelling of adducts, separation of labelled adducts by TLC, detection, and quantitation. The first step, DNA digestion with micrococcal nuclease and spleen phosphodiesterase, is applicable to DNA modified with most carcinogens independent of their size and structure. Of the two commonly used procedures for enrichment of aromatic adducts in DNA digests, the nuclease P1 treatment is substantially more effective than butanol extraction for small aromatic and bulky non-aromatic adducts. For initial purification of these adducts from unadducted material after 32P-labelling, multi-directional polyethyleneimine (PEI)-cellulose TLC using 1 M sodium phosphate, pH 6.0, as the D1 solvent is not suitable, because they are not retained on PEI-cellulose under these conditions. A higher concentration of sodium phosphate (e.g., 2.3 M) or development with D1 and D3 solvents in the same direction helps to retain adducts of safrole and of benzene metabolites. Also, transfer of adducts from multiple cut-outs above the origin after D1 chromatography, as adopted for analysis of I-compounds, is potentially applicable. However, initial purification by reverse-phase TLC, followed by in situ transfer and resolution by PEI-cellulose TLC has been found to be most effective for these adducts. Reverse-phase TLC at 4 degrees C or in a stronger salt solution further improves retention of some adducts (e.g., mitomycin C and diaziquone adducts). For adduct separation by PEI-cellulose TLC, salt solutions with or without urea are used. PMID:8225492

  6. The Phylogenetic Signature Underlying ATP Synthase c-Ring Compliance.

    PubMed

    Pandini, Alessandro; Kleinjung, Jens; Taylor, Willie R; Junge, Wolfgang; Khan, Shahid

    2015-09-01

    The proton-driven ATP synthase (FOF1) is comprised of two rotary, stepping motors (FO and F1) coupled by an elastic power transmission. The elastic compliance resides in the rotor module that includes the membrane-embedded FO c-ring. Proton transport by FO is firmly coupled to the rotation of the c-ring relative to other FO subunits (ab2). It drives ATP synthesis. We used a computational method to investigate the contribution of the c-ring to the total elastic compliance. We performed principal component analysis of conformational ensembles built using distance constraints from the bovine mitochondrial c-ring x-ray structure. Angular rotary twist, the dominant ring motion, was estimated to show that the c-ring accounted in part for the measured compliance. Ring rotation was entrained to rotation of the external helix within each hairpin-shaped c-subunit in the ring. Ensembles of monomer and dimers extracted from complete c-rings showed that the coupling between collective ring and the individual subunit motions was independent of the size of the c-ring, which varies between organisms. Molecular determinants were identified by covariance analysis of residue coevolution and structural-alphabet-based local dynamics correlations. The residue coevolution gave a readout of subunit architecture. The dynamic couplings revealed that the hinge for both ring and subunit helix rotations was constructed from the proton-binding site and the adjacent glycine motif (IB-GGGG) in the midmembrane plane. IB-GGGG motifs were linked by long-range couplings across the ring, while intrasubunit couplings connected the motif to the conserved cytoplasmic loop and adjacent segments. The correlation with principal collective motions shows that the couplings underlie both ring rotary and bending motions. Noncontact couplings between IB-GGGG motifs matched the coevolution signal as well as contact couplings. The residue coevolution reflects the physiological importance of the dynamics that may

  7. Efficient Route to Deuterated Aromatics by the Deamination of Anilines.

    PubMed

    Burglova, Kristyna; Okorochenkov, Sergei; Hlavac, Jan

    2016-07-15

    One-step replacement of NH2 groups in ring-substituted anilines by deuterium is reported. Approaches comprising both solid-phase and solution-phase syntheses can be used on a large variety of substrates. The method uses diazotization in a mixture of water and either dichloromethane or chloroform, which serve as a source of hydrogen. This protocol can be used as a general method for fast and easy incorporation of deuterium into an aromatic system using deuterated chloroform. PMID:27378277

  8. New insights into aromatic pathways of carbachlorins and carbaporphyrins based on calculations of magnetically induced current densities.

    PubMed

    Benkyi, Isaac; Fliegl, Heike; Valiev, Rashid R; Sundholm, Dage

    2016-04-28

    Magnetically induced current densities have been calculated and analyzed for a number of synthesized carbachlorins and carbaporphyrins using density functional theory and the gauge including magnetically induced current (GIMIC) method. Aromatic properties have been determined by using accurate numerical integration of the current flow yielding reliable current strengths and pathways that are related to the degree of aromaticity and the aromatic character of the studied molecules. All investigated compounds are found to be aromatic. However, the obtained aromatic pathways differ from those previously deduced from spectroscopic data and magnetic shielding calculations. For all studied compounds, the ring current divides into an outer and an inner branch at each pyrrolic subring, showing that all π-electrons of the pyrrolic rings take part in the delocalization pathway. The calculations do not support the common notion that the main share of the current takes the inner route at the pyrrolic rings without an inner hydrogen and follows an 18π aromatic pathway. The aromatic pathways of the investigated carbaporphyrins and carbachlorins are very similar, since the current strength via the Cβ[double bond, length as m-dash]Cβ' bond of the cyclopentadienyl ring of the carbaporphyrins is almost as weak as the current density passing the corresponding saturated Cβ-Cβ' bond of the carbachlorins. PMID:26974190

  9. Mechanical seal having a double-tier mating ring

    DOEpatents

    Khonsari, Michael M.; Somanchi, Anoop K.

    2005-09-13

    An apparatus and method to enhance the overall performance of mechanical seals in one of the following ways: by reducing seal face wear, by reducing the contact surface temperature, or by increasing the life span of mechanical seals. The apparatus is a mechanical seal (e.g., single mechanical seals, double mechanical seals, tandem mechanical seals, bellows, pusher mechanical seals, and all types of rotating and reciprocating machines) comprising a rotating ring and a double-tier mating ring. In a preferred embodiment, the double-tier mating ring comprises a first and a second stationary ring that together form an agitation-inducing, guided flow channel to allow for the removal of heat generated at the seal face of the mating ring by channeling a coolant entering the mating ring to a position adjacent to and in close proximity with the interior surface area of the seal face of the mating ring.

  10. Asymmetric dipolar ring

    DOEpatents

    Prosandeev, Sergey A.; Ponomareva, Inna V.; Kornev, Igor A.; Bellaiche, Laurent M.

    2010-11-16

    A device having a dipolar ring surrounding an interior region that is disposed asymmetrically on the ring. The dipolar ring generates a toroidal moment switchable between at least two stable states by a homogeneous field applied to the dipolar ring in the plane of the ring. The ring may be made of ferroelectric or magnetic material. In the former case, the homogeneous field is an electric field and in the latter case, the homogeneous field is a magnetic field.

  11. Polyimidazoles via aromatic nucleophilic displacement

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Hergenrother, Paul M. (Inventor)

    1991-01-01

    Polyimidazoles (Pl) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenyl)imidazole monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The reactions are carried out in polar aprotic solvents such as N,N-dimethylacetamide, sulfolane, N-methylpyrroldinone, dimethylsulfoxide, or diphenylsulfone using alkali metal bases such as potassium carbonate at elevated temperature under nitrogen. The di(hydroxyphenyl)imidazole monomers are prepared by reacting an aromatic aldehyde with a dimethoxybenzil or by reacting an aromatic dialdehyde with a methoxybenzil in the presence of ammonium acetate. The di(methoxyphenyl)imidazole is subsequently treated with aqueous hydrobromic acid to give the di(hydroxyphenyl)imidazole monomer. This synthetic route has provided high molecular weight Pl of new chemical structure, is economically and synthetically more favorable than other routes, and allows for facile chemical structure variation due to the availability of a large variety of activated aromatic dihalides and dinitro compounds.

  12. Polyimidazoles via aromatic nucleophilic displacement

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Hergenrother, Paul M. (Inventor)

    1992-01-01

    Polyimidazoles (PI) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenyl) imidazole monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The reactions are carried out in polar aprotic solvents such as N,N-dimethyl acetamide, sulfolane, N-methylpyrrolidinone, dimethylsulfoxide, or diphenylsulfone using alkali metal bases such as potassium carbonate at elevated temperatures under nitrogen. The di(hydroxyphenyl) imidazole monomers are prepared by reacting an aromatic aldehyde with a dimethoxybenzil or by reacting an aromatic dialdehyde with a methoxybenzil in the presence of ammonium acetate. The di(methoxyphenyl) imidazole is subsequently treated with aqueous hydrobromic acid to give the di(hydroxphenyl) imidazole monomer. This synthetic route has provided high molecular weight PI of new chemical structure, is economically and synthetically more favorable than other routes, and allows for facile chemical structure variation due to the availability of a large variety of activated aromatic dihalides and dinitro compounds.

  13. Biomimetic diversity-oriented synthesis of benzannulated medium rings via ring expansion

    PubMed Central

    Bauer, Renato A.; Wenderski, Todd A.; Tan, Derek S.

    2012-01-01

    Nature has exploited medium-sized 8- to 11-membered rings in a variety of natural products to address diverse and challenging biological targets. However, due to the limitations of conventional cyclization-based approaches to medium-ring synthesis, these structures remain severely underrepresented in current probe and drug discovery efforts. To address this problem, we have established an alternative, biomimetic ring expansion approach to the diversity-oriented synthesis of medium-ring libraries. Oxidative dearomatization of bicyclic phenols affords polycyclic cyclohexadienones that undergo efficient ring expansion to form benzannulated medium-ring scaffolds found in natural products. The ring expansion reaction can be induced using three complementary reagents that avoid competing dienone–phenol rearrangements and is driven by rearomatization of a phenol ring adjacent to the scissile bond. Cheminformatic analysis of the resulting first-generation library confirms that these molecules occupy chemical space overlapping with medium-ring natural products and distinct from that of synthetic drugs and drug-like libraries. PMID:23160003

  14. Contorted polycyclic aromatics.

    PubMed

    Ball, Melissa; Zhong, Yu; Wu, Ying; Schenck, Christine; Ng, Fay; Steigerwald, Michael; Xiao, Shengxiong; Nuckolls, Colin

    2015-02-17

    CONSPECTUS: This Account describes a body of research in the design, synthesis, and assembly of molecular materials made from strained polycyclic aromatic molecules. The strain in the molecular subunits severely distorts the aromatic molecules away from planarity. We coined the term "contorted aromatics" to describe this class of molecules. Using these molecules, we demonstrate that the curved pi-surfaces are useful as subunits to make self-assembled electronic materials. We have created and continue to study two broad classes of these "contorted aromatics": discs and ribbons. The figure that accompanies this conspectus displays the three-dimensional surfaces of a selection of these "contorted aromatics". The disc-shaped contorted molecules have well-defined conformations that create concave pi-surfaces. When these disc-shaped molecules are substituted with hydrocarbon side chains, they self-assemble into columnar superstructures. Depending on the hydrocarbon substitution, they form either liquid crystalline films or macroscopic cables. In both cases, the columnar structures are photoconductive and form p-type, hole- transporting materials in field effect transistor devices. This columnar motif is robust, allowing us to form monolayers of these columns attached to the surface of dielectrics such as silicon oxide. We use ultrathin point contacts made from individual single-walled carbon nanotubes that are separated by a few nanometers to probe the electronic properties of short stacks of a few contorted discs. We find that these materials have high mobility and can sense electron-deficient aromatic molecules. The concave surfaces of these disc-shaped contorted molecules form ideal receptors for the molecular recognition and assembly with spherical molecules such as fullerenes. These interfaces resemble ball-and-socket joints, where the fullerene nests itself in the concave surface of the contorted disc. The tightness of the binding between the two partners can be

  15. Cracking of long-chain alkyl aromatics on USY zeolite catalysts

    SciTech Connect

    Corma, A. ); Miguel, P.J.; Orchilles, A.V. ); Koermer, G.S. )

    1992-05-01

    Long-chain alkyl aromatics are important precursors for FCC gasoline. It is well known that for short-chain alkyl aromatics like cumene the dominant cracking process is simple alkyl aryl cleavage. In contrast the authors have found that for long-chain alkyl aromatics like 1-phenylheptane, cracking over in situ USY catalysts is much more complex. Cracking in a long alkyl side chain results in a carbenium ion that isomerizes easily and gives self-alkylation of the aromatic ring. Self-alkylation produces coke precursors and heavy gasoline aromatics. Product selectivities vary with zeolite unit cell size in ways that are rationalized on the basis of decreasing acid site density and zeolite adsorption properties.

  16. Aromatic molecules as spintronic devices

    SciTech Connect

    Ojeda, J. H.; Orellana, P. A.; Laroze, D.

    2014-03-14

    In this paper, we study the spin-dependent electron transport through aromatic molecular chains attached to two semi-infinite leads. We model this system taking into account different geometrical configurations which are all characterized by a tight binding Hamiltonian. Based on the Green's function approach with a Landauer formalism, we find spin-dependent transport in short aromatic molecules by applying external magnetic fields. Additionally, we find that the magnetoresistance of aromatic molecules can reach different values, which are dependent on the variations in the applied magnetic field, length of the molecules, and the interactions between the contacts and the aromatic molecule.

  17. Polycyclic aromatic hydrocarbons profiles of spent drilling fluids deposited at Emu-Uno, Delta State, Nigeria.

    PubMed

    Iwegbue, Chukwujindu M A

    2011-10-01

    The concentrations and profiles of polycyclic aromatic hydrocarbons were determined in spent drilling fluid deposited at Emu-Uno, Delta State of Nigeria. The total concentrations of polycyclic aromatic hydrocarbons in the spent drilling fluid deposits ranged between 40 and 770 μg kg(-1). The PAHs profile were predominantly 2- and 3-rings with acenaphthalene, phenanthrene, fluorene being the predominant PAHs. The prevalence of 2- and 3-rings PAHs in the spent drilling fluid deposits indicate contamination of the drilling fluids with crude oil during drilling. Incorporation of spent drilling fluids into the soil has serious implication for soil, surface water and groundwater quality. PMID:21809098

  18. Fluorinated aromatic diamine

    NASA Technical Reports Server (NTRS)

    Jones, Robert J. (Inventor); O'Rell, Michael K. (Inventor); Hom, Jim M. (Inventor)

    1980-01-01

    This invention relates to a novel aromatic diamine and more particularly to the use of said diamine for the preparation of thermally stable high-molecular weight polymers including, for example, polyamides, polyamideimides, polyimides, and the like. This diamine is obtained by reacting a stoichometric amount of a disodium salt of 2,2-bis(4-hydroxyphenyl) hexafluoropropane with 4-chloronitrobenzene to obtain an intermediate, 2,2-bis[4-(4-nitrophenoxy)phenyl] hexafluoropropane, which is reduced to the corresponding 2,2-bis[4-(4-aminophenoxy)phenyl] hexafluoropropane.

  19. Mechanistic Investigation into the Decarboxylation of Aromatic Carboxylic Acids

    SciTech Connect

    Britt, P F; Buchanan, III, A C; Eskay, T P; Mungall, W S

    1999-08-22

    It has been proposed that carboxylic acids and carboxylates are major contributors to cross-linking reactions in low-rank coals and inhibit its thermochemical processing. Therefore, the thermolysis of aromatic carboxylic acids was investigated to determine the mechanisms of decarboxylation at temperatures relevant to coal processing, and to determine if decarboxylation leads to cross-linking (i.e., formation of more refractory products). From the thcrmolysis of simple and polymeric coal model compounds containing aromatic carboxylic acids at 250-425 °C, decarboxylation was found to occur primarily by an acid promoted ionic pathway. Carboxylate salts were found to enhance the decarboxylation rate, which is consistent with the proposed cationic mechanism. Thermolysis of the acid in an aromatic solvent, such as naphthalene, produced a small amount of arylated products (~5 mol%)), which constitute a low-temperature cross-link. These arylated products were formed by the rapid decomposition of aromatic anhydrides, which are in equilibrium with the acid. These anhydrides decompose by a free radical induced decomposition pathway to form atyl radicals that can add to aromatic rings to form cross-links or abstract hydrogen. Large amounts of CO were formed in the thennolysis of the anhydrides which is consistent with the induced decomposition pathway. CO was also formed in the thermolysis of the carboxylic acids in aromatic solvents which is consistent with the formation and decomposition of the anhydride. The formation of anhydride linkages and cross-links was found to be very sensitive to the reactions conditions. Hydrogen donor solvents, such as tetralin, and water were found to decrease the formation of arylated products. Silar reaction pathways were also found in the thermolysis of a polymeric model that contained aromatic carboxylic acids. In this case, anhydride formation and decomposition produced an insoluble polymer, while the O-methylated polymer and the non

  20. Saturn's Spectacular Ring System

    NASA Technical Reports Server (NTRS)

    Lissauer, Jack J.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    Saturn's beautiful rings have fascinated astronomers since they were first observed by Galileo in 1610. The main rings consist of solid particles mostly in the 1 cm - 10 m range, composed primarily of water ice. The ring disk is exceptionally thin - the typical local thickness of the bright rings is tens of meters, whereas the diameter of the main rings is 250,000 km! The main rings exhibit substantial radial variations "ringlets", many of which are actively maintained via gravitational perturbations from Saturn's moons. Exterior to the main rings lie tenuous dust rings, which have little mass but occupy a very large volume of space. This seminar will emphasize the physics of ring-moon interactions, recent advances in our understanding of various aspects of the rings obtained from observations taken during 1995 when the rings appeared edge-on to the Earth and then to the Sun, and observations in subsequent years from HST.

  1. Saturn's Ring Images/Dynamics by Cassini

    NASA Astrophysics Data System (ADS)

    Burns, J. A.; Tiscareno, M. S.

    2005-12-01

    Since its orbit insertion in mid-2004, the Cassini spacecraft has been able to view Saturn's magnificent rings at various phase and elevation angles, with resolutions ranging from ~200 m on orbit insertion, through a km or two during typical closest approaches, up to many tens of km at distant apoapses. Significant changes have occurred in isolated regions of the rings between the Voyager encounters a quarter century ago and the continuing observations over the last eighteen months. This talk will focus on observations and understandings of the past year. As time permits, we will discuss bending and density wave structures (emphasizing the changes in those caused by the switching orbits of Janus and Epimetheus); features that are temporally variable over short times (F ring, Encke ringlets, ring edges) and longer (D and G rings); odd patterns (short streaks, "straw", "knots" and "turbulence"); and interactions with adjacent satellites, especially those embedded in the Encke and Keeler gaps. Since the spacecraft will spend most of Fall 2005 near the ring plane, we anticipate few discoveries during this period; this should allow us time to do a better job at interpreting those data currently in hand. As J. C. Maxwell wrote in 1857, we are "still grinding at Saturn's rings."

  2. Paleozoic oil in Uzbekistan and adjacent territories

    SciTech Connect

    Ryzhkov, O.A.; Khaimov, R.N.; Vitchinkin, M.M.; Zuev, Yu.N.

    1983-01-01

    Direct evidence of the presence of oil in the region is characteristically widespread within a broad stratigraphic span as well as territorially. This Paleozoic oil is of the naphthene aromatic type, in contrast with the Mesozoic and Tertiary oils of Uzbekistan, suggesting a justifiable hypothesis of an independent Paleozoic cycle of oleogenesis involving accumulation of hydrocarbons.

  3. Ultrahigh Molecular Weight Aromatic Siloxane Polymers

    NASA Technical Reports Server (NTRS)

    Ludwick, L. M.

    1983-01-01

    Silphenylene-siloxane polymers can be prepared by a condensation reaction of a diol 1,4-bis(hydroxydimethylsilyl)benzene and a silane bis(dimethylamino)dimethylsilane. Using a stepwise condensation technique, a polymer (R=CH3) with a molecular weight in excess of 1.0 x 1 million has been produced. The polymer exhibits increased thermal stability, compared to a methyl siloxane polymer without the aromatic phenyl ring in the backbone. The use of bis(dimethylamino)methylvinylsilane should allow for ready crosslinking at the vinyl sites (R=-CH=CH2) introduced into the backbone. However, under the conditions of the reaction system a high molecular weight polymer was not obtained or the polymer underwent a crosslinking process during the synthesis.

  4. The biodegradation vs. biotransformation of fluorosubstituted aromatics.

    PubMed

    Kiel, Martina; Engesser, Karl-Heinrich

    2015-09-01

    Fluoroaromatics are widely and--in recent years--increasingly used as agrochemicals, starting materials for chemical syntheses and especially pharmaceuticals. This originates from the special properties the carbon-fluorine bond is imposing on organic molecules. Hence, fluoro-substituted compounds more and more are considered to be important potential environmental contaminants. On the other hand, the microbial potentials for their transformation and mineralization have received less attention in comparison to other haloaromatics. Due to the high electronegativity of the fluorine atom, its small size, and the extraordinary strength of the C-F bond, enzymes and mechanisms known to facilitate the degradation of chloro- or bromoarenes are not necessarily equally active with fluoroaromatics. Here, we review the literature on the microbial degradation of ring and side-chain fluorinated aromatic compounds under aerobic and anaerobic conditions, with particular emphasis being placed on the mechanisms of defluorination reactions. PMID:26216240

  5. Stirling engine piston ring

    DOEpatents

    Howarth, Roy B.

    1983-01-01

    A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

  6. Molecular dynamics studies of aromatic hydrocarbon liquids

    SciTech Connect

    McLaughlin, E.; Gupta, S.

    1990-01-01

    This project mainly involves a molecular dynamics and Monte Carlo study of the effect of molecular shape on thermophysical properties of bulk fluids with an emphasis on the aromatic hydrocarbon liquids. In this regard we have studied the modeling, simulation methodologies, and predictive and correlating methods for thermodynamic properties of fluids of nonspherical molecules. In connection with modeling we have studied the use of anisotropic site-site potentials, through a modification of the Gay-Berne Gaussian overlap potential, to successfully model the aromatic rings after adding the necessary electrostatic moments. We have also shown these interaction sites should be located at the geometric centers of the chemical groups. In connection with predictive methods, we have shown two perturbation type theories to work well for fluids modeled using one-center anisotropic potentials and the possibility exists for extending these to anisotropic site-site models. In connection with correlation methods, we have studied, through simulations, the effect of molecular shape on the attraction term in the generalized van der Waals equation of state for fluids of nonspherical molecules and proposed a possible form which is to be studied further. We have successfully studied the vector and parallel processing aspects of molecular simulations for fluids of nonspherical molecules.

  7. Actin Rings of Power.

    PubMed

    Schwayer, Cornelia; Sikora, Mateusz; Slováková, Jana; Kardos, Roland; Heisenberg, Carl-Philipp

    2016-06-20

    Circular or ring-like actin structures play important roles in various developmental and physiological processes. Commonly, these rings are composed of actin filaments and myosin motors (actomyosin) that, upon activation, trigger ring constriction. Actomyosin ring constriction, in turn, has been implicated in key cellular processes ranging from cytokinesis to wound closure. Non-constricting actin ring-like structures also form at cell-cell contacts, where they exert a stabilizing function. Here, we review recent studies on the formation and function of actin ring-like structures in various morphogenetic processes, shedding light on how those different rings have been adapted to fulfill their specific roles. PMID:27326928

  8. New Dust Belts of Uranus: One Ring, Two Ring, Red Ring, Blue Ring

    SciTech Connect

    de Pater, I; Hammel, H B; Gibbard, S G; Showalter, M R

    2006-02-02

    We compare near-infrared observations of the recently discovered outer rings of Uranus with HST results. We find that the inner ring, R/2003 U 2, is red, whereas the outer ring, R/2003 U 1, is very blue. Blue is an unusual color for rings; Saturn's enigmatic E ring is the only other known example. By analogy to the E ring, R/2003 U 1 is probably produced via impacts into the embedded moon Mab, which apparently orbits at a location where non-gravitational perturbations favor the survival and spreading of sub-micron sized dust. R/2003 U 2 more closely resembles Saturn's G ring.

  9. Electronic Structure Principles and Aromaticity

    ERIC Educational Resources Information Center

    Chattaraj, P. K.; Sarkar, U.; Roy, D. R.

    2007-01-01

    The relationship between aromaticity and stability in molecules on the basis of quantities such as hardness and electrophilicity is explored. The findings reveal that aromatic molecules are less energetic, harder, less polarizable, and less electrophilic as compared to antiaromatic molecules, as expected from the electronic structure principles.

  10. Aromatic hydrocarbons of mineral oil origin in foods: method for determining the total concentration and first results.

    PubMed

    Biedermann, Maurus; Fiselier, Katell; Grob, Koni

    2009-10-14

    An online normal phase high-performance liquid chromatography (HPLC)-gas chromatography (GC)-flame ionization detection (FID) method was developed for the determination of the total concentration of the aromatic hydrocarbons of mineral oil origin with up to at least five rings in edible oils and other foods. For some samples, the olefins in the food matrix were epoxidized to increase their polarity and remove them from the fraction of the aromatic hydrocarbons. This reaction was carefully optimized, because also some aromatics tend to react. To reach a detection limit of around 1 mg kg(-1) in edible oils, an off-line enrichment was introduced. Some foods contained elevated concentrations of white paraffin oils (free of aromatics), but the majority of the mineral oils detected in foods were of technical grade with 20-30% aromatic hydrocarbons. Many foods contained mineral aromatic hydrocarbons in excess of 1 mg kg(-1). PMID:19728727

  11. Bacterial Degradation of Aromatic Compounds

    PubMed Central

    Seo, Jong-Su; Keum, Young-Soo; Li, Qing X.

    2009-01-01

    Aromatic compounds are among the most prevalent and persistent pollutants in the environment. Petroleum-contaminated soil and sediment commonly contain a mixture of polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatics. Aromatics derived from industrial activities often have functional groups such as alkyls, halogens and nitro groups. Biodegradation is a major mechanism of removal of organic pollutants from a contaminated site. This review focuses on bacterial degradation pathways of selected aromatic compounds. Catabolic pathways of naphthalene, fluorene, phenanthrene, fluoranthene, pyrene, and benzo[a]pyrene are described in detail. Bacterial catabolism of the heterocycles dibenzofuran, carbazole, dibenzothiophene, and dibenzodioxin is discussed. Bacterial catabolism of alkylated PAHs is summarized, followed by a brief discussion of proteomics and metabolomics as powerful tools for elucidation of biodegradation mechanisms. PMID:19440284

  12. On the time-course of adjacent and non-adjacent transposed-letter priming

    PubMed Central

    Ktori, Maria; Kingma, Brechtsje; Hannagan, Thomas; Holcomb, Phillip J.; Grainger, Jonathan

    2014-01-01

    We compared effects of adjacent (e.g., atricle-ARTICLE) and non-adjacent (e.g., actirle-ARTICLE) transposed-letter (TL) primes in an ERP study using the sandwich priming technique. TL priming was measured relative to the standard double-substitution condition. We found significantly stronger priming effects for adjacent transpositions than non-adjacent transpositions (with 2 intervening letters) in behavioral responses (lexical decision latencies), and the adjacent priming effects emerged earlier in the ERP signal, at around 200 ms post-target onset. Non-adjacent priming effects emerged about 50 ms later and were short-lived, being significant only in the 250-300 ms time-window. Adjacent transpositions on the other hand continued to produce priming in the N400 time-window (300-500 ms post-target onset). This qualitatively different pattern of priming effects for adjacent and non-adjacent transpositions is discussed in the light of different accounts of letter transposition effects, and the utility of drawing a distinction between positional flexibility and positional noise. PMID:25364497

  13. The AHA Moment: Assessment of the Redox Stability of Ionic Liquids Based on Aromatic Heterocyclic Anions (AHAs) for Nuclear Separations and Electric Energy Storage.

    PubMed

    Shkrob, Ilya A; Marin, Timothy W

    2015-11-19

    Because of their extended conjugated bond network, aromatic compounds generally have higher redox stability than less saturated compounds. We conjectured that ionic liquids (ILs) consisting of aromatic heterocyclic anions (AHAs) may exhibit improved radiation and electrochemical stability. Such properties are important in applications of these ILs as diluents in radionuclide separations and electrolytes in the electric energy storage devices. In this study, we systematically examine the redox chemistry of the AHAs. Three classes of these anions have been studied: (i) simple 5-atom ring AHAs, such as the pyrazolide and triazolides, (ii) AHAs containing an adjacent benzene ring, and (iii) AHAs containing electron-withdrawing groups that were introduced to reduce their basicity and interaction with metal ions. It is shown that fragmentation in the reduced and oxidized states of these AHAs does not generally occur, and the two main products, respectively, are the H atom adduct and the imidyl radical. The latter species occurs either as an N σ-radical or as an N π-radical, depending on the length of the N-N bond, and the state that is stabilized in the solid matrix is frequently different from that having the lowest energy in the gas phase. In some instances, the formation of the sandwich π-stack dimer radical anions has been observed. For trifluoromethylated anions, H adduct formation did not occur; instead, there was facile loss of fluoride from their fluorinated groups. The latter can be problematic in nuclear separations, but beneficial in batteries. Overall, our study suggests that AHA-based ILs are viable candidates for use as radiation-exposed diluents and electrolytes. PMID:26506410

  14. Two- and three-dimensional rings in drugs.

    PubMed

    Aldeghi, Matteo; Malhotra, Shipra; Selwood, David L; Chan, Ah Wing Edith

    2014-04-01

    Using small, flat aromatic rings as components of fragments or molecules is a common practice in fragment-based drug discovery and lead optimization. With an increasing focus on the exploration of novel biological and chemical space, and their improved synthetic accessibility, 3D fragments are attracting increasing interest. This study presents a detailed analysis of 3D and 2D ring fragments in marketed drugs. Several measures of properties were used, such as the type of ring assemblies and molecular shapes. The study also took into account the relationship between protein classes targeted by each ring fragment, providing target-specific information. The analysis shows the high structural and shape diversity of 3D ring systems and their importance in bioactive compounds. Major differences in 2D and 3D fragments are apparent in ligands that bind to the major drug targets such as GPCRs, ion channels, and enzymes. PMID:24472495

  15. Two- and Three-dimensional Rings in Drugs

    PubMed Central

    Aldeghi, Matteo; Malhotra, Shipra; Selwood, David L; Chan, Ah Wing Edith

    2014-01-01

    Using small, flat aromatic rings as components of fragments or molecules is a common practice in fragment-based drug discovery and lead optimization. With an increasing focus on the exploration of novel biological and chemical space, and their improved synthetic accessibility, 3D fragments are attracting increasing interest. This study presents a detailed analysis of 3D and 2D ring fragments in marketed drugs. Several measures of properties were used, such as the type of ring assemblies and molecular shapes. The study also took into account the relationship between protein classes targeted by each ring fragment, providing target-specific information. The analysis shows the high structural and shape diversity of 3D ring systems and their importance in bioactive compounds. Major differences in 2D and 3D fragments are apparent in ligands that bind to the major drug targets such as GPCRs, ion channels, and enzymes. PMID:24472495

  16. Graphene Layer Growth: Collision of Migrating Five-MemberRings

    SciTech Connect

    Whitesides, Russell; Kollias, Alexander C.; Domin, Dominik; Lester Jr., William A.; Frenklach, Michael

    2005-12-02

    A reaction pathway is explored in which two cyclopenta groups combine on the zigzag edge of a graphene layer. The process is initiated by H addition to a five-membered ring, followed by opening of that ring and the formation of a six-membered ring adjacent to another five-membered ring. The elementary steps of the migration pathway are analyzed using density functional theory to examine the region of the potential energy surface associated with the pathway. The calculations are performed on a substrate modeled by the zigzag edge of tetracene. Based on the obtained energetics, the dynamics of the system are analyzed by solving the energy transfer master equations. The results indicate energetic and reaction-rate similarity between the cyclopenta combination and migration reactions. Also examined in the present study are desorption rates of migrating cyclopenta rings which are found to be comparable to cyclopenta ring migration.

  17. Optimizing Thomson's jumping ring

    NASA Astrophysics Data System (ADS)

    Tjossem, Paul J. H.; Brost, Elizabeth C.

    2011-04-01

    The height to which rings will jump in a Thomson jumping ring apparatus is the central question posed by this popular lecture demonstration. We develop a simple time-averaged inductive-phase-lag model for the dependence of the jump height on the ring material, its mass, and temperature and apply it to measurements of the jump height for a set of rings made by slicing copper and aluminum alloy pipe into varying lengths. The data confirm a peak jump height that grows, narrows, and shifts to smaller optimal mass when the rings are cooled to 77 K. The model explains the ratio of the cooled/warm jump heights for a given ring, the reduction in optimal mass as the ring is cooled, and the shape of the mass resonance. The ring that jumps the highest is found to have a characteristic resistance equal to the inductive reactance of the set of rings.

  18. Substituent effects on the energetics and aromaticity of aminomethylbenzoic acids.

    PubMed

    Lima, Carlos F R A C; Gomes, Lígia R; Santos, Luís M N B F

    2007-10-25

    The standard (p0 = 0.1 MPa) molar enthalpies of combustion of six aminomethylbenzoic acids were measured at T = 298.15 K by static bomb calorimetry. With these values, the standard molar enthalpies of formation in the crystalline state were obtained. Combining these results with the standard molar enthalpies of sublimation, the standard molar enthalpies of formation in the gaseous phase were derived. For the 10 possible isomers, the obtained experimental results were compared to and correlated with the relative stability obtained by ab initio calculations at the B3LYP/6-311++G(d,p) level of theory. Seeking a better understanding of the aromatic behavior and energetics of aminomethylbenzoic acids in the gas phase, calculations of NICS values, HOMA indices, and dihedral angles between the aromatic carbon and the amino group, Phi(Ar-NHH), were also performed computationally. The significant differences observed in the energetics, as well as in the NICS values, HOMA indices, and Phi(Ar-NHH) dihedral angles for these 10 isomers suggest a strong dependency on the identity and relative position of the three substituents on the benzene ring. This study points out a marked tendency for a decrease of the ring aromaticity, accompanied by an increase in the respective system stability, as the conjugation between the substituents becomes more extensive. PMID:17914759

  19. Theory of radio occultation by Saturn's rings

    NASA Technical Reports Server (NTRS)

    Marouf, E. A.; Tyler, G. L.; Eshleman, V. R.

    1982-01-01

    The radio occultation technique, as applied to Saturn's rings, is developed as a new method for the study of the physical properties of planetary ring systems. The rings are treated as a Doppler-spread radar target composed of an ensemble of discrete scatterers. The mathematical formulation of the received signal as a random-phasor-sum process is carried out following a conventional radar theory approach, providing a convenient starting point for deriving coherent signal parameters. A classical result is rederived for the equivalent refractive index of the medium. The analysis is generalized to include ringlets of arbitrary width and it is shown that when the width is such that two adjacent rays are differentially perturbed in phase, ray bending that causes focusing of the coherent signal may result. The diffuse component is also treated in detail.

  20. Jupiter's Main Ring/Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (28.5 miles) per picture element (pixel) along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun; the ring was approximately 2.3 million kilometers (1.4 million miles) away. The arc on the far right of the image is produced when sunlight is scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts - - a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, outside the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the figure's far left side. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa (top image). A faint mist of particles can be seen above and below the main rings. This vertically extended 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. To accentuate faint features in the bottom image of the ring halo, different brightnesses are shown through color. Brightest features are white or yellow and the

  1. On semi ring bornologies

    NASA Astrophysics Data System (ADS)

    Imran, A. N.; Rakhimov, I. S.; Husain, Sh. K. Said

    2016-06-01

    Our main focus in this work is to introduce new structure bornological semi rings. This generalizes the theory of algebraic semi rings from the algebraic setting to the framework of bornological sets. We give basic properties for this new structure. As well as, We study the fundamental construction of bornological semi ring as product, inductive limits and projective limits and their extensions on bornological semi ring. Additionally, we introduce the category of bornological semi rings and study product and pullback (fiber product) in the category of bornological semi rings.

  2. Synthesis of aromatic secondary diamines

    NASA Technical Reports Server (NTRS)

    Wolfe, J. F.; Greenwood, T. D.; Kahley, R. A.

    1979-01-01

    A series of N-methyl substituted aromatic polyamides derived from the secondary aromatic diamines, 4,4'-bis(methylamino)diphenylmethane, 3,3'-bis(methylamino) diphenylmethane, 4,4'-bis(methylamino)benzophenone or 3,3'-bis(methylamino)benzophenone and isophthaloyl dichloride, terphthaloyl dichloride or 3,3'diphenylmethane dicarboxylic acid dichloride was prepared by high temperature solution polymerization in s-tetrachloroethane. Compared to analogous unsubstituted and partially N-methylated aromatic polyamides, the full N-methylated polyamides exhibited significantly lower glass transition temperatures, reduced crystallinity, improved thermal stability and good solubility in chlorinated solvents.

  3. Atomic-phase interference devices based on ring-shaped Bose-Einstein condensates: Two-ring case

    SciTech Connect

    Anderson, B.P.; Dholakia, K.; Wright, E.M.

    2003-03-01

    We theoretically investigate the ground-state properties and quantum dynamics of a pair of adjacent ring-shaped Bose-Einstein condensates that are coupled via tunneling. This device, which is the analog of a symmetric superconducting quantum interference device, is the simplest version of what we term an atomic-phase interference device (APHID). The two-ring APHID is shown to be sensitive to rotation.

  4. SOLIDS TRANSPORT BETWEEN ADJACENT CAFB FLUIDIZED BEDS

    EPA Science Inventory

    The report gives results of an experimental investigation of a pulsed, dense-phase pneumatic transport system for controlled circulation between adjacent fluidized beds. A model was developed to predict performance. The program provides technical support for EPA's program to demo...

  5. Border separation for adjacent orthogonal fields

    SciTech Connect

    Werner, B.L.; Khan, F.M.; Sharma, S.C.; Lee, C.K.; Kim, T.H. )

    1991-06-01

    Field border separations for adjacent orthogonal fields can be calculated geometrically, given the validity of some important assumptions such as beam alignment and field uniformity. Thermoluminescent dosimetry (TLD) measurements were used to investigate dose uniformity across field junctions as a function of field separation and, in particular, to review the CCSG recommendation for the treatment of medulloblastoma with separate head and spine fields.

  6. Environment influences on the aromatic character of nucleobases and amino acids

    PubMed Central

    Szefler, Beata

    2010-01-01

    Geometric (HOMA) and magnetic (NICS) indices of aromaticity were estimated for aromatic rings of amino acids and nucleobases. Cartesian coordinates were taken directly either from PDB files deposited in public databases at the finest resolution available (≤1.5 Å), or from structures resulting from full gradient geometry optimization in a hybrid QM/MM approach. Significant environmental effects imposing alterations of HOMA values were noted for all aromatic rings analysed. Furthermore, even extra fine resolution (≤1.0 Å) is not sufficient for direct estimation of HOMA values based on Cartesian coordinates provided by PDB files. The values of mean bond errors seem to be much higher than the 0.05 Å often reported for PDB files. The use of quantum chemistry geometry optimization is strongly advised; even a simple QM/MM model comprising only the aromatic substructure within the QM region and the rest of biomolecule treated classically within the MM framework proved to be a promising means of describing aromaticity inside native environments. According to the results presented, three consequences of the interaction with the environment can be observed that induce changes in structural and magnetic indices of aromaticity. First, broad ranges of HOMA or NICS values are usually obtained for different conformations of nearest neighborhood. Next, these values and their means can differ significantly from those characterising isolated monomers. The most significant increase in aromaticities is expected for the six-membered rings of guanine, thymine and cytosine. The same trend was also noticed for all amino acids inside proteins but this effect was much smaller, reaching the highest value for the five-membered ring of tryptophan. Explicit water solutions impose similar changes on HOMA and NICS distributions. Thus, environment effects of protein, DNA and even explicit water molecules are non-negligible sources of aromaticity changes appearing in the rings of

  7. PERSONAL EXPOSURE TO FINE PARTICLE POLYCYCLIC AROMATIC HYDROCARBONS: OUTDOOR SOURCE TRACERS

    EPA Science Inventory


    The most carcinogenic and toxic polycyclic aromatic hydrocarbons (PAH) are the 4-5 ring PAH found preferentially adsorbed to the fine particles (<2.54u in urban ambient air and personal air. Personal exposure to the carcinogenic particle bound PAH is also highly correlated ...

  8. Internal dynamics of proteins. Short time and long time motions of aromatic sidechains in PTI.

    PubMed Central

    Karplus, M; Gelin, B R; McCammon, J A

    1980-01-01

    Theoretical approaches to the internal dynamics of proteins are outlined and illustrated by application to the aromatic sidechain motions of tyrosines in the bovine pancreatic trypsin inhibitor. High frequency torsional oscillations are obtained from a molecular dynamics simulation, while the longer time ring rotations are analyzed by use of adiabatic energy minimization and special transition-state trajectory techniques. PMID:7248464

  9. Spin-orbit effects on electronic delocalization. Aromaticity in a discrete square tetrapalladium sandwich complex

    NASA Astrophysics Data System (ADS)

    Muñoz-Castro, A.; Mac-Leod Carey, D.; Arratia-Pérez, R.

    2010-04-01

    In this article, we report the relativistic electronic structure, including spin-orbit interaction, employing all-electron density functional theory calculations on the multimetallic sandwich compound [(CNT)Pd4(COT)]1+ (1), which can be considered as a [Pd4]2+ fragment flanked by two ring-ligands, namely, cyclononatetraenyl (CNT1-) and cyclooctatetraene (COT), as well as the dimer of 1, hereafter 2. The calculations suggest that the Pd4-ligand interaction is mainly electrostatic, being the main responsible term for the stabilization of the almost fully occupied 4d shell [Pd4]2+ fragment. The ring currents and electronic delocalization estimated via the nuclear independent chemical shifts indices and electron localization function, allow us to describe a significant σ-aromaticity at the center of the Pd4 square in 1, which in conjunction with the aromaticity arising from the ligands induce considerable aromatic character inside of the multimetallic metallocene.

  10. Quantification of Aromaticity Based on Interaction Coordinates: A New Proposal.

    PubMed

    Pandey, Sarvesh Kumar; Manogaran, Dhivya; Manogaran, Sadasivam; Schaefer, Henry F

    2016-05-12

    Attempts to establish degrees of aromaticity in molecules are legion. In the present study, we begin with a fictitious fragment arising from only those atoms contributing to the aromatic ring and having a force field projected from the original system. For example, in benzene, we adopt a fictitious C6 fragment with a force field projected from the full benzene force field. When one bond or angle is stretched and kept fixed, followed by a partial optimization for all other internal coordinates, structures change from their respective equilibria. These changes are the responses of all other internal coordinates for constraining the bond or angle by unit displacements and relaxing the forces on all other internal coordinates. The "interaction coordinate" derived from the redundant internal coordinate compliance constants measures how a bond (its electron density) responds for constrained optimization when another bond or angle is stretched by a specified unit (its electron density is perturbed by a finite amount). The sum of interaction coordinates (responses) of all bonded neighbors for all internal coordinates of the fictitious fragment is a measure of the strength of the σ and π electron interactions leading to aromatic stability. This sum, based on interaction coordinates, appears to be successful as an aromaticity index for a range of chemical systems. Since the concept involves analyzing a fragment rather than the whole molecule, this idea is more general and is likely to lead to new insights. PMID:27074522

  11. Solid Phase Synthesis of Helically Folded Aromatic Oligoamides.

    PubMed

    Dawson, S J; Hu, X; Claerhout, S; Huc, I

    2016-01-01

    Aromatic amide foldamers constitute a growing class of oligomers that adopt remarkably stable folded conformations. The folded structures possess largely predictable shapes and open the way toward the design of synthetic mimics of proteins. Important examples of aromatic amide foldamers include oligomers of 7- or 8-amino-2-quinoline carboxylic acid that have been shown to exist predominantly as well-defined helices, including when they are combined with α-amino acids to which they may impose their folding behavior. To rapidly iterate their synthesis, solid phase synthesis (SPS) protocols have been developed and optimized for overcoming synthetic difficulties inherent to these backbones such as low nucleophilicity of amine groups on electron poor aromatic rings and a strong propensity of even short sequences to fold on the solid phase during synthesis. For example, acid chloride activation and the use of microwaves are required to bring coupling at aromatic amines to completion. Here, we report detailed SPS protocols for the rapid production of: (1) oligomers of 8-amino-2-quinolinecarboxylic acid; (2) oligomers containing 7-amino-8-fluoro-2-quinolinecarboxylic acid; and (3) heteromeric oligomers of 8-amino-2-quinolinecarboxylic acid and α-amino acids. SPS brings the advantage to quickly produce sequences having varied main chain or side chain components without having to purify multiple intermediates as in solution phase synthesis. With these protocols, an octamer could easily be synthesized and purified within one to two weeks from Fmoc protected amino acid monomer precursors. PMID:27586338

  12. New dust belts of Uranus: one ring, two ring, red ring, blue ring.

    PubMed

    de Pater, Imke; Hammel, Heidi B; Gibbard, Seran G; Showalter, Mark R

    2006-04-01

    We compared near-infrared observations of the recently discovered outer rings of Uranus with Hubble Space Telescope results. We find that the inner ring, R/2003 U 2, is red, whereas the outer ring, R/2003 U 1, is very blue. Blue is an unusual color for rings; Saturn's enigmatic E ring is the only other known example. By analogy to the E ring, R/2003 U 1 is probably produced by impacts into the embedded moon Mab, which apparently orbits at a location where nongravitational perturbations favor the survival and spreading of submicron-sized dust. R/2003 U 2 more closely resembles Saturn's G ring, which is red, a typical color for dusty rings. PMID:16601188

  13. Polyimidazoles Via Aromatic Nucleophilic Displacement

    NASA Technical Reports Server (NTRS)

    Connell, John W.; Hergenrother, Paul M.

    1990-01-01

    Experiments show variety of polyimidazoles prepared by aromatic nucleophilic displacement, from reactions of bisphenol imidazoles with activated difluoro compounds. Polyimidazoles have good mechanical properties making them suitable for use as films, moldings, and adhesives.

  14. Polybenzimidazoles via aromatic nucleophilic displacement

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Hergenrother, Paul M. (Inventor); Smith, Joseph G., Jr. (Inventor)

    1995-01-01

    Novel molecular weight controlled and endcapped polybenzimidazoles (PBI) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenyl benzimidazole) monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The PBI are endcapped with mono(hydroxyphenyl) benzimidazoles. The polymerizations are carried out in polar aprotic solvents such as N-methyl-2-pyrrolidinone or N,N-dimethylacetamide using alkali metal bases such as potassium carbonate at elevated temperatures under nitrogen. Mono(hydroxyphenyl) benzimidazoles are synthesizedby reacting phenyl-4-hydroxybenzoate with aromatic (o-diamine)s in diphenylsulfone. Molecular weight controlled and endcapped PBI of new chemical structures are prepared that exhibit a favorable combination of physical and mechanical properties.

  15. Polybenzimidazoles Via Aromatic Nucleophilic Displacement

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Hergerrother, Paul M. (Inventor); Smith, Joseph G., Jr. (Inventor)

    1997-01-01

    Novel molecular weight controlled and endcapped polybenzimidazoles (PBI) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenylbenzimidazole) monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The PBI are endcapped with mono(hydroxyphenyl)benzimidazoles. The polymerizations are carried out in polar aprotic solvents such as N-methyl-2-pyrrolidinone or N,N-dimethylacetamide using alkali metal bases such as potassium carbonate at elevated temperatures under nitrogen. Mono(hydroxyphenyl)benzimidazoles are synthesized by reacting phenyl-4-hydroxybenzoate with aromatic (o-diamine)s in diphenylsulfone. Molecular weight controlled and endcapped PBI of new chemical structures are prepared that exhibit a favorable combination of physical and mechanical properties.

  16. Formation of polycyclic aromatic hydrocarbons in circumstellar envelopes

    NASA Astrophysics Data System (ADS)

    Frenklach, Michael; Feigelson, Eric D.

    1989-06-01

    Production of polycyclic aromatic hydrocarbons in carbon-rich circumstellar envelopes was investigated using a kinetic approach. A detailed chemical reaction mechanism of gas-phase PAH formation and growth, containing approximately 100 reactions of 40 species, was numerically solved under the physical conditions expected in cool stellar winds. The chemistry is based on studies of soot production in hydrocarbon pyrolysis and combustion. Several first-ring and second-ring cyclization processes were considered. A linear lumping algorithm was used to describe PAH growth beyond the second aromatic ring. PAH production using this mechanism was examined with respect to a grid of idealized constant velocity stellar winds as well as several published astrophysical models. The basic result is that the onset of PAH production in the interstellar envelopes is predicted to occur within the temperature interval of 1100 to 900 K. The absolute amounts of the PAHs formed, however, are very sensitive to a number of parameters, both chemical and astrophysical, whose values are not accurately known. Astrophysically meaningful quantities of PAHs require particularly dense and slow stellar winds and high initial acetylene abundance. It is suggested that most of the PAHs may be produced in a relatively small fraction of carbon-rich red giants.

  17. Saturn's F-Ring

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This narrow-angle camera image of Saturn's F Ring was taken through the Clear filter while at a distance of 6.9 million km from Saturn on 8 November 1980. The brightness variations of this tightly-constrained ring shown here indicate that the ring is less uniform in makeup than the larger rings. JPL managed the Voyager Project for NASA's Office of Space Science

  18. Neptune - full ring system

    NASA Technical Reports Server (NTRS)

    1989-01-01

    This pair of Voyager 2 images (FDS 11446.21 and 11448.10), two 591-s exposures obtained through the clear filter of the wide angle camera, show the full ring system with the highest sensitivity. Visible in this figure are the bright, narrow N53 and N63 rings, the diffuse N42 ring, and (faintly) the plateau outside of the N53 ring (with its slight brightening near 57,500 km).

  19. Bioassay of polycyclic aromatic hydrocarbons

    SciTech Connect

    Van Kirk, E.A.

    1980-08-01

    A positive relationship was found between the photodynamic activity of 24 polycyclic aromatic hydrocarbons versus published results on the mutagenicity, carcinogenicity, and initiation of unscheduled DNA synthesis. Metabolic activation of benzo(a)pyrene resulted in detection of increased mutagenesis in Paramecium tetraurelia as found also in the Ames Salmonella assay. The utility of P. tetraurelia as a biological detector of hazardous polycyclic aromatic hydrocarbons is discussed.

  20. Polycyclic aromatic hydrocarbons in the atmospheres of Titan and Jupiter.

    PubMed

    Sagan, C; Khare, B N; Thompson, W R; McDonald, G D; Wing, M R; Bada, J L; Vo-Dinh, T; Arakawa, E T

    1993-09-01

    Polycyclic aromatic hydrocarbons (PAHs) are important components of the interstellar medium and carbonaceous chondrites, but have never been identified in the reducing atmospheres of the outer solar system. Incompletely characterized complex organic solids (tholins) produced by irradiating simulated Titan atmospheres reproduce well the observed UV/visible/IR optical constants of the Titan stratospheric haze. Titan tholin and a tholin generated in a crude simulation of the atmosphere of Jupiter are examined by two-step laser desorption/multiphoton ionization mass spectrometry. A range of two- to four-ring PAHs, some with one to four alkylation sites are identified, with net abundance approximately 10(-4) g g-1 (grams per gram) of tholins produced. Synchronous fluorescence techniques confirm this detection. Titan tholins have proportionately more one- and two-ring PAHs than do Jupiter tholins, which in turn have more four-ring and larger PAHs. The four-ringed PAH chrysene, prominent in some discussions of interstellar grains, is found in Jupiter tholins. Solid state 13C NMR spectroscopy suggests approximately equal to 25% of the total C in both tholins is tied up in aromatic and/or aliphatic alkenes. IR spectra indicate an upper limit in both tholins of approximately equal to 6% by mass in benzenes, heterocyclics, and PAHs with more than four rings. Condensed PAHs may contribute at most approximately 10% to the observed detached limb haze layers on Titan. As with interstellar PAHs, the synthesis route of planetary PAHs is likely to be via acetylene addition reactions. PMID:11539501

  1. Isotopic exchange of hydrogen in aromatic amino acids

    SciTech Connect

    Pshenichnikova, A.B.; Karnaukhova, E.N.; Mitsner, B.I.

    1993-10-20

    The kinetics of the isotopic replacement of hydrogen in the aromatic amino acids L-tryptophan, L-tyrosine, and L-phenylalanine in solutions of deuterochloric and deuterosulfuric acids in deuterium oxide were investigated by PMR spectroscopy. The reactions were shown to be of first orders with respect both to the concentration of the substrate and to the activity of the deuterium ion. The isotopic effects of hydrogen and the values of the activation energy of H-D exchange in different positions of the aromatic ring in tryptophan and tyrosine were determined. The effect of properties of the medium on the rate of the isotopic exchange of hydrogen is discussed. 17 refs., 2 figs., 2 tabs.

  2. Saturn's F-Ring

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This narrow-angle camera image of Saturn's F Ring was taken through the Clear filter while at a distance of 0.75 million km from Saturn on 12 November 1980. The kinks and braids of this tightly-constrained ring are visible along with the outer edge of the A Ring. JPL managed the Voyager Project for NASA's Office of Space Science.

  3. The Jumping Ring Experiment

    ERIC Educational Resources Information Center

    Baylie, M.; Ford, P. J.; Mathlin, G. P.; Palmer, C.

    2009-01-01

    The jumping ring experiment has become central to liquid nitrogen shows given as part of the outreach and open day activities carried out within the University of Bath. The basic principles of the experiment are described as well as the effect of changing the geometry of the rings and their metallurgical state. In general, aluminium rings are…

  4. Rings Around Uranus

    ERIC Educational Resources Information Center

    Maran, Stephen P.

    1977-01-01

    Events leading up to the discovery of the rings of Uranus are described. The methods used and the logic behind the methods are explained. Data collected to prove the existence of the rings are outlined and theories concerning the presence of planetary rings are presented. (AJ)

  5. Polybenzoxazole via aromatic nucleophilic displacement

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor)

    1993-01-01

    Polybenzoxazoles (PBO) are heterocyclic macromolecules which were first synthesized in a two-step process by the initial formation of aromatic diacid chlorides with bis(o-aminophenol)s through solution condensation of aromatic diacid chlorides with bis(o-aminophenol)s followed by thermal cyclodehydration. Since then several methods were utilized in their synthesis. The most common synthetic method for PBO involves a polycondensation of bis(o-aminophenol)s with aromatic diacid diphenyl esters. Another preparative route involves the solution polycondensation of the hydrochloride salts of bis(o-amino phenol)s with aromatic diacids in polyphosphoric acid. Another synthetic method involves the initial formation of poly(o-hydroxy amide)s from silylated bis(o-aminophenol)s with aromatic diacid chlorides followed by thermal cyclodehydration to PBO. A recent preparative route involves the reaction of aromatic bisphenols with bis(fluorophenyl) benzoxazoles by the displacement reaction to form PBO. The novelty of the present invention is that high molecular weight PBO of new chemical structures are prepared that exhibit a favorable combination of physical and mechanical properties.

  6. [Determination of aromatics in light petroleum products by comprehensive two-dimensional gas chromatography].

    PubMed

    Li, Yanyan

    2006-07-01

    In recent years, comprehensive two-dimensional gas chromatography (GC x GC) have been used widely, and the applications of this technique to many fields have already been reported. In the standard method of oil analysis, the concentrations of aromatics and naphthalene hydrocarbons in light petroleum products must be detected by more than two methods. Mono-aromatics, di-aromatics etc. in light petroleum products were detected only by comprehensive two-dimensional gas chromatography. After the proper selection of column system and optimization of chromatographic conditions, the method can achieve the group separations of paraffins, olefins, naphthenes, aromatics with 1 to 2 rings and some target components in light petroleum products with good reproducibility and good precision. The recoveries of standard compounds were 89.5% - 106.1%, and the relative standard deviations of repeatedly detecting the components were all lower than 5.8%. It took only 30 min to finish a determination. PMID:17017165

  7. Infrared Signature of the Cation-π Interaction between Calcite and Aromatic Hydrocarbons.

    PubMed

    Wang, Haitao; Grant, Daniel J; Burns, Peter C; Na, Chongzheng

    2015-06-01

    The cation-π interaction is proposed as an important mechanism for the adsorption of aromatic hydrocarbons having non-zero quadrupole moments by mineral surfaces. Direct evidence supporting such a mechanism is, however, limited. Using the model mineral calcite, we probe the cation-π interaction with adsorbed benzene, toluene, and ethylbenzene (BTE) molecules using attenuated total reflectance Fourier transform infrared spectroscopy. We show that the presence of calcite increases the energy required to excite the synchronized bending of aromatic C-H bonds of BTE molecules. The unique conformation of this vibrational mode indicates that the planar aromatic rings of BTE molecules are constrained in a tilted face-down position by the cation-π interaction, as further confirmed by density functional theory calculations. Our results suggest that the shift of the excitation energy of the aromatic C-H bending may be used as an infrared signature for the cation-π interaction occurring on mineral surfaces. PMID:25974679

  8. Aromatic-aromatic interaction of amitriptyline: implication of overdosed drug detoxification.

    PubMed

    Lee, Dong-Won; Flint, Jason; Morey, Timothy; Dennis, Donn; Partch, Richard; Baney, Ronald

    2005-02-01

    The objectives of this work are to explore the pi-pi complexation of amitriptyline with pi electron-deficient aromatic rings and demonstrate the feasibility of pi-pi complexation for overdosed drug detoxification. Water-soluble oligochitosan was chemically modified with dinitrobenzenesulfonyl groups to induce selective binding toward amitriptyline through pi-pi complexation. NMR studies showed that benzenesulfonyl and dinitrobenzenesulfonyl protons were upfield shifted by the addition of amitriptyline, indicating the formation of pi-pi complexes. The pi-pi complexation of amitriptyline is driven primarily by a desolvation driving force, whereas the magnitude of interaction is dictated by the complementrary electrostatic interaction. Isolated rat heart tests revealed that dinitrobenzenesulfonyl oligochitosan prevented the amitriptyline-induced cardiotoxicity and was itself not cardiotoxic. PMID:15614810

  9. Adjacent Segment Pathology after Lumbar Spinal Fusion.

    PubMed

    Lee, Jae Chul; Choi, Sung-Woo

    2015-10-01

    One of the major clinical issues encountered after lumbar spinal fusion is the development of adjacent segment pathology (ASP) caused by increased mechanical stress at adjacent segments, and resulting in various radiographic changes and clinical symptoms. This condition may require surgical intervention. The incidence of ASP varies with both the definition and methodology adopted in individual studies; various risk factors for this condition have been identified, although a significant controversy still exists regarding their significance. Motion-preserving devices have been developed, and some studies have shown their efficacy of preventing ASP. Surgeons should be aware of the risk factors of ASP when planning a surgery, and accordingly counsel their patients preoperatively. PMID:26435804

  10. Search for aromatic anions in the P2E3(-) (E = N, P, As, Sb, Bi) series.

    PubMed

    Nizovtsev, Anton S

    2016-06-28

    We report a systematic computational study focused on the global minimum and low-lying isomer search for the P2E3(-) (E = N, P, As, Sb, Bi) series of anions. We found nine planar five-membered rings and proved their aromatic character by various quantum chemical techniques. The possible use of two different P2N3(-) aromatic anions as ligands in a number of sandwich complexes was also studied. PMID:27250818

  11. Synthesis and crystal structure of a chiral aromatic amine chloride salt (C8H12N)Cl

    NASA Astrophysics Data System (ADS)

    Ben Salah, A. M.; Naїli, H.; Mhiri, T.; Bataille, T.

    2015-12-01

    The new organic chloride salt incorporating an aromatic primary amine with a chiral functional group, (S)-α-methylbenzylammonium), has been synthesized by slow evaporation method at room temperature. The crystals are trigonal with non-centrosymmetric sp. gr. R3. The crystal packing is determined by N-H···Cl hydrogen bonds and C-H···π interactions between the aromatic rings of the organic moieties, resulting in supramolecular architecture.

  12. Jovian Ring System Mosaic

    NASA Technical Reports Server (NTRS)

    2000-01-01

    NASA's Galileo spacecraft acquired this mosaic of Jupiter's ring system (top) when the spacecraft was in Jupiter's shadow looking back toward the Sun. Jupiter's ring system (inset diagram) is composed of three parts: an outermost gossamer ring, a flat main ring, and an innermost donut-shaped halo. These rings are made up of dust-sized particles that are blasted off of the nearby inner satellites by small impacts. This image was taken on November 9, 1996 at a distance of 2.3 million kilometers (1.4 million miles).

  13. Adjacent Segment Pathology after Anterior Cervical Fusion

    PubMed Central

    Chung, Jae Yoon; Park, Jong-Beom; Seo, Hyoung-Yeon

    2016-01-01

    Anterior cervical fusion has become a standard of care for numerous pathologic conditions of the cervical spine. However, subsequent development of clinically significant disc disease at levels adjacent to fused discs is a serious long-term complication of this procedure. As more patients live longer after surgery, it is foreseeable that adjacent segment pathology (ASP) will develop in increasing numbers of patients. Also, ASP has been studied more intensively with the recent popularity of motion preservation technologies like total disc arthroplasty. The true nature and scope of ASP remains poorly understood. The etiology of ASP is most likely multifactorial. Various factors including altered biomechanical stresses, surgical disruption of soft tissue and the natural history of cervical disc disease contribute to the development of ASP. General factors associated with disc degeneration including gender, age, smoking and sports may play a role in the development of ASP. Postoperative sagittal alignment and type of surgery are also considered potential causes of ASP. Therefore, a spine surgeon must be particularly careful to avoid unnecessary disruption of the musculoligamentous structures, reduced risk of direct injury to the disc during dissection and maintain a safe margin between the plate edge and adjacent vertebrae during anterior cervical fusion. PMID:27340541

  14. Adjacent Segment Pathology after Anterior Cervical Fusion.

    PubMed

    Chung, Jae Yoon; Park, Jong-Beom; Seo, Hyoung-Yeon; Kim, Sung Kyu

    2016-06-01

    Anterior cervical fusion has become a standard of care for numerous pathologic conditions of the cervical spine. However, subsequent development of clinically significant disc disease at levels adjacent to fused discs is a serious long-term complication of this procedure. As more patients live longer after surgery, it is foreseeable that adjacent segment pathology (ASP) will develop in increasing numbers of patients. Also, ASP has been studied more intensively with the recent popularity of motion preservation technologies like total disc arthroplasty. The true nature and scope of ASP remains poorly understood. The etiology of ASP is most likely multifactorial. Various factors including altered biomechanical stresses, surgical disruption of soft tissue and the natural history of cervical disc disease contribute to the development of ASP. General factors associated with disc degeneration including gender, age, smoking and sports may play a role in the development of ASP. Postoperative sagittal alignment and type of surgery are also considered potential causes of ASP. Therefore, a spine surgeon must be particularly careful to avoid unnecessary disruption of the musculoligamentous structures, reduced risk of direct injury to the disc during dissection and maintain a safe margin between the plate edge and adjacent vertebrae during anterior cervical fusion. PMID:27340541

  15. Polycyclic Aromatic Hydrocarbons

    NASA Technical Reports Server (NTRS)

    Salama, Farid

    2010-01-01

    Carbonaceous materials play an important role in space. Polycyclic Aromatic Hydrocarbons (PAHs) are a ubiquitous component of the carbonaceous materials. PAHs are the best-known candidates to account for the IR emission bands. They are also thought to be among the carriers of the diffuse interstellar absorption bands (DIBs). PAH ionization states reflect the ionization balance of the medium while PAH size, composition, and structure reflect the energetic and chemical history of the medium. A major challenge is to reproduce in the laboratory the physical conditions that exist in the emission and absorption interstellar zones. The harsh physical conditions of the ISM -low temperature, collisionless, strong UV radiation fields- are simulated in the laboratory by associating a molecular beam with an ionizing discharge to generate a cold plasma expansion. PAH ions and radicals are formed from the neutral precursors in an isolated environment at low temperature and probed with high-sensitivity cavity ringdown spectroscopy in the NUV-NIR range. Carbon nanoparticles are also formed during the short residence time of the precursors in the plasma and are characterized with time-offlight mass spectrometry. These experiments provide unique information on the spectra of large carbonaceous molecules and ions in the gas phase that can now be directly compared to interstellar and circumstellar observations (IR emission bands, DIBs, extinction curve). These findings also hold great potential for understanding the formation process of interstellar carbonaceous grains. We will review recent progress in the experimental and theoretical studies of PAHs, compare the laboratory data with astronomical observations and discuss the global implications.

  16. The Dependence of Carbohydrate-Aromatic Interaction Strengths on the Structure of the Carbohydrate.

    PubMed

    Hsu, Che-Hsiung; Park, Sangho; Mortenson, David E; Foley, B Lachele; Wang, Xiaocong; Woods, Robert J; Case, David A; Powers, Evan T; Wong, Chi-Huey; Dyson, H Jane; Kelly, Jeffery W

    2016-06-22

    Interactions between proteins and carbohydrates are ubiquitous in biology. Therefore, understanding the factors that determine their affinity and selectivity are correspondingly important. Herein, we have determined the relative strengths of intramolecular interactions between a series of monosaccharides and an aromatic ring close to the glycosylation site in an N-glycoprotein host. We employed the enhanced aromatic sequon, a structural motif found in the reverse turns of some N-glycoproteins, to facilitate face-to-face monosaccharide-aromatic interactions. A protein host was used because the dependence of the folding energetics on the identity of the monosaccharide can be accurately measured to assess the strength of the carbohydrate-aromatic interaction. Our data demonstrate that the carbohydrate-aromatic interaction strengths are moderately affected by changes in the stereochemistry and identity of the substituents on the pyranose rings of the sugars. Galactose seems to make the weakest and allose the strongest sugar-aromatic interactions, with glucose, N-acetylglucosamine (GlcNAc) and mannose in between. The NMR solution structures of several of the monosaccharide-containing N-glycoproteins were solved to further understand the origins of the similarities and differences between the monosaccharide-aromatic interaction energies. Peracetylation of the monosaccharides substantially increases the strength of the sugar-aromatic interaction in the context of our N-glycoprotein host. Finally, we discuss our results in light of recent literature regarding the contribution of electrostatics to CH-π interactions and speculate on what our observations imply about the absolute conservation of GlcNAc as the monosaccharide through which N-linked glycans are attached to glycoproteins in eukaryotes. PMID:27249581

  17. IMPACT OF MAGNETIC FIELD INTERFERENCE IN THE SNS RING.

    SciTech Connect

    PAPAPHILIPPOU,Y.; LEE,Y.Y.; MENG,W.

    2001-06-18

    The modest size of the SNS accumulator ring and the use of short, large aperture magnets makes unavoidable the overlapping between the magnetic end fields of the quadrupoles with the adjacent multipole correctors. This interference effect can be quantified through magnetic field simulations and measurements. The impact to the beam dynamics is finally discussed.

  18. Saturn's largest ring.

    PubMed

    Verbiscer, Anne J; Skrutskie, Michael F; Hamilton, Douglas P

    2009-10-22

    Most planetary rings in the Solar System lie within a few radii of their host body, because at these distances gravitational accelerations inhibit satellite formation. The best known exceptions are Jupiter's gossamer rings and Saturn's E ring, broad sheets of dust that extend outward until they fade from view at five to ten planetary radii. Source satellites continuously supply the dust, which is subsequently lost in collisions or by radial transport. Here we report that Saturn has an enormous ring associated with its outer moon Phoebe, extending from at least 128R(S) to 207R(S) (Saturn's radius R(S) is 60,330 km). The ring's vertical thickness of 40R(S) matches the range of vertical motion of Phoebe along its orbit. Dynamical considerations argue that these ring particles span the Saturnian system from the main rings to the edges of interplanetary space. The ring's normal optical depth of approximately 2 x 10(-8) is comparable to that of Jupiter's faintest gossamer ring, although its particle number density is several hundred times smaller. Repeated impacts on Phoebe, from both interplanetary and circumplanetary particle populations, probably keep the ring populated with material. Ring particles smaller than centimetres in size slowly migrate inward and many of them ultimately strike the dark leading face of Iapetus. PMID:19812546

  19. Linear heterocyclic aromatic fluorescence compounds having various donor-acceptor spacers prepared by the combination of carbon-carbon bond and carbon-nitrogen bond cross-coupling reactions.

    PubMed

    Hu, Bin; Fu, Shu-Jun; Xu, Feng; Tao, Tao; Zhu, Hao-Yu; Cao, Kou-Sen; Huang, Wei; You, Xiao-Zeng

    2011-06-01

    A family of novel linear 1,10-phenanthroline-based (A-D-A-D-A) and oligothiophene-based (A-D-D-D-(D)-A) heterocyclic aromatic fluorescence compounds having N-containing imidazole and pyridine tails with effective π-conjugated systems, prepared by the combination of carbon-carbon (C-C) bond and carbon-nitrogen (C-N) bond cross-coupling reactions, is described. They have molecular lengths of more than 2.30 nm in the cases of 4, 6, 9, and 26, various D-A spacers, and certain N-coordination sites (phen, imidazole, and pyridine). X-ray single-crystal structures of 13 compounds reveal a variety of trans and cis configurations with different dihedral angles between adjacent aromatic heterocycles. Synthetic, computational, and spectral studies have been made to reveal the differences between cross-coupling approaches on the C-C bond and C-N bond formation as well as band gaps and energy levels and optical and electrochemical properties for related compounds. The influences of introducing a β-methyl group to the thiophene ring on reaction activity, solubility, and conformation of related compounds have also been discussed. PMID:21513323

  20. A ring-source model for jet noise

    NASA Technical Reports Server (NTRS)

    Maestrello, L.

    1978-01-01

    A model consisting of two ring sources was developed to study the direct radiation of jet noise in terms of correlation, coherence, and phase and also to aid in solving the inverse radiation problem of determining the noise source in terms of far-field measurements. The rings consist of discrete sources which are either monopoles or quadrupoles with Gaussian profiles. Only adjacent sources, both within the rings and between rings, are correlated. Results show that from the far-field information can be used to determine when the sources are compact or noncompact with respect to the acoustic wavelength and to distinguish between the types of sources. In addition, from the inverse radiation approach, the center of mass, the location and separation distance of the ring, and the diameters can be recovered.

  1. Bacterial degradation of monocyclic aromatic amines

    PubMed Central

    Arora, Pankaj K.

    2015-01-01

    Aromatic amines are an important group of industrial chemicals, which are widely used for manufacturing of dyes, pesticides, drugs, pigments, and other industrial products. These compounds have been considered highly toxic to human beings due to their carcinogenic nature. Three groups of aromatic amines have been recognized: monocyclic, polycyclic, and heterocyclic aromatic amines. Bacterial degradation of several monocyclic aromatic amines has been studied in a variety of bacteria, which utilizes monocyclic aromatic amines as their sole source of carbon and energy. Several degradation pathways have been proposed and the related enzymes and genes have also been characterized. Many reviews have been reviewed toxicity of monocyclic aromatic amines; however, there is lack of review on biodegradation of monocyclic aromatic amines. The aim of this review is to summarize bacterial degradation of monocyclic aromatic amines. This review will increase our current understanding of biochemical and molecular basis of bacterial degradation of monocyclic aromatic amines. PMID:26347719

  2. Dust and Planetary Rings

    NASA Astrophysics Data System (ADS)

    Siddiqui, Muddassir

    ABSTRACT Space is not empty it has comic radiations (CMBR), dust etc. Cosmic dust is that type of dust which is composed of particles in space which vary from few molecules to 0.1micro metres in size. This type of dust is made up of heavier atoms born in the heart of stars and supernova. Mainly it contains dust grains and when these dust grains starts compacting then it turns to dense clouds, planetary ring dust and circumstellar dust. Dust grains are mainly silicate particles. Dust plays a major role in our solar system, for example in zodiacal light, Saturn's B ring spokes, planetary rings at Jovian planets and comets. Observations and measurements of cosmic dust in different regions of universe provide an important insight into the Universe's recycling processes. Astronomers consider dust in its most recycled state. Cosmic dust have radiative properties by which they can be detected. Cosmic dusts are classified as intergalactic dusts, interstellar dusts and planetary rings. A planetary ring is a ring of cosmic dust and other small particles orbiting around a planet in flat disc shape. All of the Jovian planets in our solar system have rings. But the most notable one is the Saturn's ring which is the brightest one. In March 2008 a report suggested that the Saturn's moon Rhea may have its own tenuous ring system. The ring swirling around Saturn consists of chunks of ice and dust. Most rings were thought to be unstable and to dissipate over course of tens or hundreds of millions of years but it now appears that Saturn's rings might be older than that. The dust particles in the ring collide with each other and are subjected to forces other than gravity of its own planet. Such collisions and extra forces tend to spread out the rings. Pluto is not known to have any ring system but some Astronomers believe that New Horizons probe might find a ring system when it visits in 2015.It is also predicted that Phobos, a moon of Mars will break up and form into a planetary ring

  3. Traceable Ring Signature

    NASA Astrophysics Data System (ADS)

    Fujisaki, Eiichiro; Suzuki, Koutarou

    The ring signature allows a signer to leak secrets anonymously, without the risk of identity escrow. At the same time, the ring signature provides great flexibility: No group manager, no special setup, and the dynamics of group choice. The ring signature is, however, vulnerable to malicious or irresponsible signers in some applications, because of its anonymity. In this paper, we propose a traceable ring signature scheme. A traceable ring scheme is a ring signature except that it can restrict “excessive” anonymity. The traceable ring signature has a tag that consists of a list of ring members and an issue that refers to, for instance, a social affair or an election. A ring member can make any signed but anonymous opinion regarding the issue, but only once (per tag). If the member submits another signed opinion, possibly pretending to be another person who supports the first opinion, the identity of the member is immediately revealed. If the member submits the same opinion, for instance, voting “yes” regarding the same issue twice, everyone can see that these two are linked. The traceable ring signature can suit to many applications, such as an anonymous voting on a BBS. We formalize the security definitions for this primitive and show an efficient and simple construction in the random oracle model.

  4. Sunset on Saturn's Rings

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This is a rare view of Saturn's rings seen just after the Sun has set below the ring plane, taken with the Hubble Space Telescope on Nov. 21, 1995.

    This perspective is unusual because the Earth is slightly above (2.7 degrees latitude) Saturn's rings and the Sun is below them. Normally we see the rings fully illuminated by the Sun.

    The photograph shows three bright ring features: the F Ring, the Cassini Division, and the C Ring (moving from the outer rings to the inner). The low concentration of material in these rings allows light from the Sun to shine through them. The A and B rings are much denser, which limits the amount of light that penetrates through them. Instead, they are faintly visible because they reflect light from Saturn's disk.

    Scientists believe that the F Ring is slightly warped because it disappears part way around on the right (West) side. Hubble's high resolution shows the that A Ring's shadow obscures part of the F ring (right).

    The image was assembled from 20 exposures taken with Wide Field Planetary Camera-2 over 8 hours.

    The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.

    This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

  5. Gas and Particulate Sampling of Airborne Polycyclic Aromatic Compounds

    SciTech Connect

    Lane, D.A.; Gundel, L.A.

    1995-10-01

    The denuder surfaces of the gas and particle (GAP) sampler (developed at the Atmospheric Environment Service of Environment Canada) have been modified by coating with XAD-4 resin, using techniques developed at Lawrence Berkeley National Laboratory (LBNL) for the lower capacity integrated organic vapor/particle sampler (IOVPS). The resulting high capacity integrated organic gas and particle sampler (IOGAPS) has been operated in ambient air at 16.7 L min{sup -1} for a 24-hour period in Berkeley, California, USA. Simultaneous measurements were made at the same collection rate with a conventional sampler that used a filter followed by two sorbent beds. Gas and particle partition measurements were determined for 13 polycyclic aromatic hydrocarbons (PAH) ranging from 2-ring to 6-ring species. The IOGAPS indicated a higher particle fraction of these compounds than did the conventional sampler, suggesting that the conventional sampler suffered from 'blow-off' losses from the particles collected on the filter.

  6. Reconstructing genome mixtures from partial adjacencies.

    PubMed

    Mahmoody, Ahmad; Kahn, Crystal L; Raphael, Benjamin J

    2012-01-01

    Many cancer genome sequencing efforts are underway with the goal of identifying the somatic mutations that drive cancer progression. A major difficulty in these studies is that tumors are typically heterogeneous, with individual cells in a tumor having different complements of somatic mutations. However, nearly all DNA sequencing technologies sequence DNA from multiple cells, thus resulting in measurement of mutations from a mixture of genomes. Genome rearrangements are a major class of somatic mutations in many tumors, and the novel adjacencies (i.e. breakpoints) resulting from these rearrangements are readily detected from DNA sequencing reads. However, the assignment of each rearrangement, or adjacency, to an individual cancer genome in the mixture is not known. Moreover, the quantity of DNA sequence reads may be insufficient to measure all rearrangements in all genomes in the tumor. Motivated by this application, we formulate the k-minimum completion problem (k-MCP). In this problem, we aim to reconstruct k genomes derived from a single reference genome, given partial information about the adjacencies present in the mixture of these genomes. We show that the 1-MCP is solvable in linear time in the cases where: (i) the measured, incomplete genome has a single circular or linear chromosome; (ii) there are no restrictions on the chromosomal content of the measured, incomplete genome. We also show that the k-MCP problem, for k ≥ 3 in general, and the 2-MCP problem with the double-cut-and-join (DCJ) distance are NP-complete, when there are no restriction on the chromosomal structure of the measured, incomplete genome. These results lay the foundation for future algorithmic studies of the k-MCP and the application of these algorithms to real cancer sequencing data. PMID:23282028

  7. Detection of chlorinated aromatic compounds

    DOEpatents

    Ekechukwu, Amy A.

    1996-01-01

    A method for making a composition for measuring the concentration of chloated aromatic compounds in aqueous fluids, and an optical probe for use with the method. The composition comprises a hydrophobic polymer matrix, preferably polyamide, with a fluorescent indicator uniformly dispersed therein. The indicator fluoresces in the presence of the chlorinated aromatic compounds with an intensity dependent on the concentration of these compounds in the fluid of interest, such as 8-amino-2-naphthalene sulfonate. The probe includes a hollow cylindrical housing that contains the composition in its distal end. The probe admits an aqueous fluid to the probe interior for exposure to the composition. An optical fiber transmits excitation light from a remote source to the composition while the indicator reacts with chlorinated aromatic compounds present in the fluid. The resulting fluorescence light signal is reflected to a second optical fiber that transmits the light to a spectrophotometer for analysis.

  8. Detection of chlorinated aromatic compounds

    DOEpatents

    Ekechukwu, A.A.

    1996-02-06

    A method for making a composition for measuring the concentration of chlorinated aromatic compounds in aqueous fluids, and an optical probe for use with the method are disclosed. The composition comprises a hydrophobic polymer matrix, preferably polyamide, with a fluorescent indicator uniformly dispersed therein. The indicator fluoresces in the presence of the chlorinated aromatic compounds with an intensity dependent on the concentration of these compounds in the fluid of interest, such as 8-amino-2-naphthalene sulfonate. The probe includes a hollow cylindrical housing that contains the composition in its distal end. The probe admits an aqueous fluid to the probe interior for exposure to the composition. An optical fiber transmits excitation light from a remote source to the composition while the indicator reacts with chlorinated aromatic compounds present in the fluid. The resulting fluorescence light signal is reflected to a second optical fiber that transmits the light to a spectrophotometer for analysis. 5 figs.

  9. Actions of a versatile fluorene-degrading bacterial isolate on polycyclic aromatic compounds.

    PubMed Central

    Grifoll, M; Selifonov, S A; Gatlin, C V; Chapman, P J

    1995-01-01

    Pseudomonas cepacia F297 grew with fluorene as a sole source of carbon and energy; its growth yield corresponded to an assimilation of about 40% of fluorene carbon. The accumulation of a ring meta-cleavage product during growth and the identification of 1-indanone in growth media and washed-cell suspensions suggest that strain F297 metabolizes fluorene by mechanisms analogous to those of naphthalene degradation. In addition to fluorene, strain F297 utilized for growth a wide variety of polycyclic aromatic compounds (PACs), including naphthalene, 2,3-dimethylnaphthalene, phenanthrene, anthracene, and dibenzothiophene. Fluorene-induced cells of the strain also transformed 2,6-dimethylnaphthalene, biphenyl, dibenzofuran, acenaphthene, and acenaphthylene. The identification of products formed from those substrates (by gas chromatography-mass spectrometry) in washed-cell suspensions indicates that P. cepacia F297 carries out the following reactions: (i) aromatic ring oxidation and cleavage, apparently using the pyruvate released for growth, (ii) methyl group oxidations, (iii) methylenic oxidations, and (iv) S oxidations of aromatic sulfur heterocycles. Strain F297 grew with a creosote-PAC mixture, producing an almost complete removal of all aromatic compounds containing 2 to 3 rings in 14 days, as demonstrated by gas chromatography analysis of the remaining PACs recovered from cultures. The identification of key chemicals confirmed that not only are certain compounds depleted but also the anticipated reaction products are found. PMID:7487007

  10. The Phylogenetic Signature Underlying ATP Synthase c-Ring Compliance

    SciTech Connect

    Pandini, Alessandro; Kleinjung, Jens; Taylor, Willie R.; Junge, Wolfgang; Khan, Shahid

    2015-09-01

    The proton-driven ATP synthase (FOF1) is comprised of two rotary, stepping motors (FO and F1) coupled by an elastic power transmission. The elastic compliance resides in the rotor module that includes the membrane-embedded FO c-ring. Proton transport by FO is firmly coupled to the rotation of the c-ring relative to other FO subunits (ab2). It drives ATP synthesis. We used a computational method to investigate the contribution of the c-ring to the total elastic compliance. We performed principal component analysis of conformational ensembles built using distance constraints from the bovine mitochondrial c-ring x-ray structure. Angular rotary twist, the dominant ring motion, was estimated to show that the c-ring accounted in part for the measured compliance. Ring rotation was entrained to rotation of the external helix within each hairpin-shaped c-subunit in the ring. Ensembles of monomer and dimers extracted from complete c-rings showed that the coupling between collective ring and the individual subunit motions was independent of the size of the c-ring, which varies between organisms. Molecular determinants were identified by covariance analysis of residue coevolution and structural-alphabet-based local dynamics correlations. The residue coevolution gave a readout of subunit architecture. The dynamic couplings revealed that the hinge for both ring and subunit helix rotations was constructed from the proton-binding site and the adjacent glycine motif (IB-GGGG) in the midmembrane plane. IB-GGGG motifs were linked by long-range couplings across the ring, while intrasubunit couplings connected the motif to the conserved cytoplasmic loop and adjacent segments. The correlation with principal collective motions shows that the couplings underlie both ring rotary and bending motions. Noncontact couplings between IB-GGGG motifs matched the coevolution signal as well as contact couplings

  11. Evaluation of the aromaticity of non-planar and bowl-shaped molecules by NICS criterion.

    PubMed

    Reisi-Vanani, Adel; Rezaei, Ali Asghar

    2015-09-01

    Nucleus independent chemical shift (NICS) criterion was used to gauge the amount of aromaticity in a lot of publications in two last decades. Non-planar molecules with many polygons in different sheets that make angle together have not been studied by this criterion. Perhaps, one ascribes this deficiency to NICS index, but we think it is concern to depauperation in evaluation methods. Therefore, in this work, we try to evaluate aromaticity of two fullerene substructures bowl-shaped molecules, namely corannulene and sumanene as typical non-planar molecules by using of the NICSzz-scan method. The gauge-independent atomic orbital (GIAO) NMR calculations were done at B3LYP/6-311+G(d) level of theory. Energetic criterion as another tool for evaluation of the aromaticity of compounds was used and discussed. Results shows that pentagon and hexagon rings in corannulene have antiaromatic and aromatic character, respectively and in sumanene, pentagon and outer hexagon rings have antiaromatic and aromatic character, respectively. However, the picture obtained based on the NICS computations did not provide any insight towards the real nature of current density in the corannulene and sumanene. PMID:26188797

  12. Telomere length in hepatocellular carcinoma and paired adjacent non-tumor tissues by quantitative PCR.

    PubMed

    Zhang, Yujing; Shen, Jing; Ming-Whei; Lee, Yu Po-Huang; Santella, Regina M

    2007-12-01

    Telomere shortening limits the proliferative capacity of human cells, restrains the regenerative capacity of organ systems during chronic diseases and aging and also induces chromosomal instability as well as initiation of cancer. Previous studies demonstrated that telomeres are often significantly shorter in tumor tissue, including hepatocellular carcinoma (HCC), compared to the surrounding tissue, but telomere length in HCC tissues was not correlated with several clinical parameters, such as age, sex, HBV or HCV infections and tumor size. In the present study, the telomere length ratio of 36 paired HCC, and their adjacent non-tumor tissues was measured by quantitative PCR (Q-PCR). The mean telomere lengths (SD) for HCC and adjacent non-tumor tissues were 0.26 (0.10) and 0.47 (0.20) respectively (t = 6.22, P < 0.0001). There was a large difference in the distribution of subjects based on telomere length in tumor and adjacent non-tumor tissues. The number of tumors with telomere length shorter than 0.50 was much higher than that of adjacent non-tumor tissues; more than 90% of the tissues with telomere length > or = 0.50 were adjacent non-tumor tissues. The correlations between telomere length and aflatoxin B1- and polycyclic aromatic hydrocarbon-DNA adducts level, p53 mutations and p16 hypermethylation status were also tested, but no significant associations were found. The relationship between telomere length shortening, chemical carcinogen exposure, and genetic and epigenetic changes in hepatocarcinogenesis needs further investigation. PMID:18058461

  13. Features in Saturn's rings

    NASA Technical Reports Server (NTRS)

    Esposito, Larry W.; Harris, Craig C.; Simmons, Karen E.

    1987-01-01

    A systematic, uniform search of Voyage 2 photopolarimeter system (PSS) data set for all significant features of Saturn's rings is described. On August 25, 1981, the PSS observed the occultation of the star Delta Scorpii by the rings of Saturn, and the timing of the data taking was rapid enough that the spatial resolution in the radial direction in the ring plane was better than 100 m. Tabular information and figures for 216 significant features that were found are presented.

  14. Radioactive gold ring dermatitis

    SciTech Connect

    Miller, R.A.; Aldrich, J.E. )

    1990-08-01

    A superficial squamous cell carcinoma developed in a woman who wore a radioactive gold ring for more than 30 years. Only part of the ring was radioactive. Radiation dose measurements indicated that the dose to basal skin layer was 2.4 Gy (240 rad) per week. If it is assumed that the woman continually wore her wedding ring for 37 years since purchase, she would have received a maximum dose of approximately 4600 Gy.

  15. MONITORING THE SUCCESS OF SEDIMENT REMEDIATION AT A SITE CONTAMINATED WITH CHLORINATED PESTICIDES, POLYNUCLEAR AROMATIC HYDROCARBONS AND ARSENIC

    EPA Science Inventory

    Monitoring the Success of Sediment Remediation at a Site Contaminated with Chlorinated Pesticides, Polynuclear Aromatic Hydrocarbons and Arsenic (Baird & McGuire Superfund Site, Holbrook, MA) Contaminated sediment in the Cochato River adjacent to the Baird & McGuire Superfund Sit...

  16. Computer Simulations Reveal Multiple Functions for Aromatic Residues in Cellulase Enzymes (Fact Sheet)

    SciTech Connect

    Not Available

    2012-07-01

    NREL researchers use high-performance computing to demonstrate fundamental roles of aromatic residues in cellulase enzyme tunnels. National Renewable Energy Laboratory (NREL) computer simulations of a key industrial enzyme, the Trichoderma reesei Family 6 cellulase (Cel6A), predict that aromatic residues near the enzyme's active site and at the entrance and exit tunnel perform different functions in substrate binding and catalysis, depending on their location in the enzyme. These results suggest that nature employs aromatic-carbohydrate interactions with a wide variety of binding affinities for diverse functions. Outcomes also suggest that protein engineering strategies in which mutations are made around the binding sites may require tailoring specific to the enzyme family. Cellulase enzymes ubiquitously exhibit tunnels or clefts lined with aromatic residues for processing carbohydrate polymers to monomers, but the molecular-level role of these aromatic residues remains unknown. In silico mutation of the aromatic residues near the catalytic site of Cel6A has little impact on the binding affinity, but simulation suggests that these residues play a major role in the glucopyranose ring distortion necessary for cleaving glycosidic bonds to produce fermentable sugars. Removal of aromatic residues at the entrance and exit of the cellulase tunnel, however, dramatically impacts the binding affinity. This suggests that these residues play a role in acquiring cellulose chains from the cellulose crystal and stabilizing the reaction product, respectively. These results illustrate that the role of aromatic-carbohydrate interactions varies dramatically depending on the position in the enzyme tunnel. As aromatic-carbohydrate interactions are present in all carbohydrate-active enzymes, the results have implications for understanding protein structure-function relationships in carbohydrate metabolism and recognition, carbon turnover in nature, and protein engineering strategies for

  17. Volatile profiles of aromatic and non-aromatic rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rice is enjoyed by many people as a staple food because of its flavor and texture. Some scented varieties command a premium in the marketplace because of their distinctive aroma and flavor. The compound most commonly associated with the popcorn or nutty scent of aromatic rice is 2-acetyl-1-pyrroline...

  18. Jupiter's Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow.

    A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest

  19. Integrated semiconductor ring lasers

    NASA Astrophysics Data System (ADS)

    Jezierski, A. F.; Laybourn, P. J. R.

    1988-02-01

    Ring-waveguide and pill-box structures down to 12 microns in diameter, made in GaAs/GaAlAs heterostructure material, have been designed with output stripe waveguides coupled to the rings via Y-junctions. The waveguides were defined by reactive ion etching, although the inner boundaries of some of the ring waveguides relied on stress and carrier confinement. Lasing has been observed with pulsed drive current, and has been shown to correspond to resonances in the rings, although other resonances have been observed in some of the structures. This type of structure is suitable for use as a light source in monolithic integrated optics.

  20. Viscosity in Saturn's rings

    NASA Technical Reports Server (NTRS)

    Lissauer, J. J.; Shu, F. H.; Cuzzi, J. N.

    1982-01-01

    The technique of estimating the viscosity in Saturn's rings from the damping rate of waves observed to be propagating within the rings is discussed. The wavetrains of attempts using spiral density waves as a diagnostic suffer significant complications that compromise the interpretations. A method that considers the damping of spiral bending waves was used to deduce a kinematic viscosity of 260 (+150, -100) sqcm/sec for the middle of the A ring where bending waves are excited by the 5:3 vertical resonance with Mimas. This value implies upper limits on the particle velocity dispersion and local ring thickness of 0.4 cm/sec and 30 m, respectively.

  1. Efficient Route to Highly Water-Soluble Aromatic Cyclic Hydroxamic Acid Ligands

    SciTech Connect

    Seitz, Michael; Raymond, Kenneth N.

    2008-02-06

    2-Hydroxyisoquinolin-1-one (1,2-HOIQO) is a new member of the important class of aromatic cyclic hydroxamic acid ligands which are widely used in metal sequestering applications and metal chelating therapy. The first general approach for the introduction of substituents at the aromatic ring of the chelating moiety is presented. As a useful derivative, the highly water-soluble sulfonic acid has been synthesized by an efficient route that allows general access to 1,2-HOQIO 3-carboxlic acid amides, which are the most relevant for applications.

  2. Stereoselective Arene-Forming Aldol Condensation: Synthesis of Axially Chiral Aromatic Amides.

    PubMed

    Fäseke, Vincent C; Sparr, Christof

    2016-06-13

    The increasing awareness of the importance of amide atropisomers prompts the development of novel strategies for their selective preparation. Described herein is a method for the enantioselective synthesis of atropisomeric aromatic amides by an amine-catalyzed arene-forming aldol condensation. The high reactivity of the glyoxylic amide substrates enables a remarkably efficient construction of a new aromatic ring, which proceeds within minutes at ambient temperature to afford products with excellent stereoselectivity. The high rotational barriers of the reduced products highlight the utility of this stable, spatially organized chiral scaffold. PMID:27166995

  3. Atmospheric chemistry of gas-phase polycyclic aromatic hydrocarbons: formation of atmospheric mutagens.

    PubMed Central

    Atkinson, R; Arey, J

    1994-01-01

    The atmospheric chemistry of the 2- to 4-ring polycyclic aromatic hydrocarbons (PAH), which exist mainly in the gas phase in the atmosphere, is discussed. The dominant loss process for the gas-phase PAH is by reaction with the hydroxyl radical, resulting in calculated lifetimes in the atmosphere of generally less than one day. The hydroxyl (OH) radical-initiated reactions and nitrate (NO3) radical-initiated reactions often lead to the formation of mutagenic nitro-PAH and other nitropolycyclic aromatic compounds, including nitrodibenzopyranones. These atmospheric reactions have a significant effect on ambient mutagenic activity, indicating that health risk assessments of combustion emissions should include atmospheric transformation products. PMID:7821285

  4. Concise synthesis of 2-amino-4(3H)-quinazolinones from simple (Hetero)aromatic amines.

    PubMed

    Zeghida, Walid; Debray, Julien; Chierici, Sabine; Dumy, Pascal; Demeunynck, Martine

    2008-03-21

    A novel and simple method of preparation of 2-alkylaminoquinazolin-4-ones with fused heteroaromatic rings from easily accessible (hetero)aromatic amines is described. The method is very efficient, and the 2-alkylaminoquinazolinone derivatives are obtained in three steps without chromatographic purification. The key step is the ring closure of the N-protected guanidine intermediates by intramolecular Friedel-Craft's type substitution. PMID:18290665

  5. THE PHOTOTOXICITY OF POLYCYCLIC AROMATIC HYDROCARBONS

    EPA Science Inventory

    The U.S. Environmental Protection Agency (EPA) continues to be interested in developing methods for the detection of polycyclic aromatic hydrocarbons (PAHS) in the environment. Polycyclic aromatic hydrocarbons (PAHS) are common contaminants in our environment. Being major product...

  6. Structural and functional characterization of solute binding proteins for aromatic compounds derived from lignin: p-coumaric acid and related aromatic acids

    PubMed Central

    Tan, Kemin; Chang, Changsoo; Cuff, Marianne; Osipiuk, Jerzy; Landorf, Elizabeth; Mack, Jamey C.; Zerbs, Sarah; Joachimiak, Andrzej; Collart, Frank R.

    2013-01-01

    Lignin comprises 15.25% of plant biomass and represents a major environmental carbon source for utilization by soil microorganisms. Access to this energy resource requires the action of fungal and bacterial enzymes to break down the lignin polymer into a complex assortment of aromatic compounds that can be transported into the cells. To improve our understanding of the utilization of lignin by microorganisms, we characterized the molecular properties of solute binding proteins of ATP.binding cassette transporter proteins that interact with these compounds. A combination of functional screens and structural studies characterized the binding specificity of the solute binding proteins for aromatic compounds derived from lignin such as p-coumarate, 3-phenylpropionic acid and compounds with more complex ring substitutions. A ligand screen based on thermal stabilization identified several binding protein clusters that exhibit preferences based on the size or number of aromatic ring substituents. Multiple X-ray crystal structures of protein-ligand complexes for these clusters identified the molecular basis of the binding specificity for the lignin-derived aromatic compounds. The screens and structural data provide new functional assignments for these solute.binding proteins which can be used to infer their transport specificity. This knowledge of the functional roles and molecular binding specificity of these proteins will support the identification of the specific enzymes and regulatory proteins of peripheral pathways that funnel these compounds to central metabolic pathways and will improve the predictive power of sequence-based functional annotation methods for this family of proteins. PMID:23606130

  7. Structural and functional characterization of solute binding proteins for aromatic compounds derived from lignin: p-coumaric acid and related aromatic acids.

    PubMed

    Tan, Kemin; Chang, Changsoo; Cuff, Marianne; Osipiuk, Jerzy; Landorf, Elizabeth; Mack, Jamey C; Zerbs, Sarah; Joachimiak, Andrzej; Collart, Frank R

    2013-10-01

    Lignin comprises 15-25% of plant biomass and represents a major environmental carbon source for utilization by soil microorganisms. Access to this energy resource requires the action of fungal and bacterial enzymes to break down the lignin polymer into a complex assortment of aromatic compounds that can be transported into the cells. To improve our understanding of the utilization of lignin by microorganisms, we characterized the molecular properties of solute binding proteins of ATP-binding cassette transporter proteins that interact with these compounds. A combination of functional screens and structural studies characterized the binding specificity of the solute binding proteins for aromatic compounds derived from lignin such as p-coumarate, 3-phenylpropionic acid and compounds with more complex ring substitutions. A ligand screen based on thermal stabilization identified several binding protein clusters that exhibit preferences based on the size or number of aromatic ring substituents. Multiple X-ray crystal structures of protein-ligand complexes for these clusters identified the molecular basis of the binding specificity for the lignin-derived aromatic compounds. The screens and structural data provide new functional assignments for these solute-binding proteins which can be used to infer their transport specificity. This knowledge of the functional roles and molecular binding specificity of these proteins will support the identification of the specific enzymes and regulatory proteins of peripheral pathways that funnel these compounds to central metabolic pathways and will improve the predictive power of sequence-based functional annotation methods for this family of proteins. PMID:23606130

  8. The energetics of tetrahydrocarbazole aromatization over Pd(111): A computational analysis

    NASA Astrophysics Data System (ADS)

    Crawford, P.; Burch, R.; Hardacre, C.; Hindle, K. T.; Hu, P.; Rooney, D. W.

    2008-03-01

    The carbazole moiety is a component of many important pharmaceuticals including anticancer and anti-HIV agents and is commonly utilized in the production of modern polymeric materials with novel photophysical and electronic properties. Simple carbazoles are generally produced via the aromatization of the respective tetrahydrocarbazole (THCZ). In this work, density functional theory calculations are used to model the reaction pathway of tetrahydrocarbazole aromatization over Pd(111). The geometry of each of the intermediate surface species has been determined and how each structure interacts with the metal surface addressed. The reaction energies and barriers of each of the elementary surface reactions have also been calculated, and a detailed analysis of the energetic trends performed. Our calculations have shown that the surface intermediates remain fixed to the surface via the aromatic ring in a manner similar to that of THCZ. Moreover, the aliphatic ring becomes progressively more planer with the dissociation of each subsequent hydrogen atom. Analysis of the reaction energy profile has revealed that the trend in reaction barriers is determined by the two factors: (i) the strength of the dissociating ring-H bond and (ii) the subsequent gain in energy due to the geometric relaxation of the aliphatic ring.

  9. Ring Around a Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Space Telescope Science Institute astronomers are giving the public chances to decide where to aim NASA's Hubble Space Telescope. Guided by 8,000 Internet voters, Hubble has already been used to take a close-up, multi-color picture of the most popular object from a list of candidates, the extraordinary 'polar-ring' galaxy NGC 4650A. Located about 130 million light-years away, NGC 4650A is one of only 100 known polar-ring galaxies. Their unusual disk-ring structure is not yet understood fully. One possibility is that polar rings are the remnants of colossal collisions between two galaxies sometime in the distant past, probably at least 1 billion years ago. What is left of one galaxy has become the rotating inner disk of old red stars in the center. Meanwhile, another smaller galaxy which ventured too close was probably severely damaged or destroyed. The bright bluish clumps, which are especially prominent in the outer parts of the ring, are regions containing luminous young stars, examples of stellar rebirth from the remnants of an ancient galactic disaster. The polar ring appears to be highly distorted. No regular spiral pattern stands out in the main part of the ring, and the presence of young stars below the main ring on one side and above on the other shows that the ring is warped and does not lie in one plane. Determining the typical ages of the stars in the polar ring is an initial goal of our Polar Ring Science Team that can provide a clue to the evolution of this unusual galaxy. The HST exposures were acquired by the Hubble Heritage Team, consisting of Keith Noll, Howard Bond, Carol Christian, Jayanne English, Lisa Frattare, Forrest Hamilton, Anne Kinney and Zolt Levay, and guest collaborators Jay Gallagher (University of Wisconsin-Madison), Lynn Matthews (National Radio Astronomy Observatory-Charlottesville), and Linda Sparke (University of Wisconsin-Madison).

  10. The Phylogenetic Signature Underlying ATP Synthase c-Ring Compliance

    DOE PAGESBeta

    Pandini, Alessandro; Kleinjung, Jens; Taylor, Willie R.; Junge, Wolfgang; Khan, Shahid

    2015-09-01

    The proton-driven ATP synthase (FOF1) is comprised of two rotary, stepping motors (FO and F1) coupled by an elastic power transmission. The elastic compliance resides in the rotor module that includes the membrane-embedded FO c-ring. Proton transport by FO is firmly coupled to the rotation of the c-ring relative to other FO subunits (ab2). It drives ATP synthesis. We used a computational method to investigate the contribution of the c-ring to the total elastic compliance. We performed principal component analysis of conformational ensembles built using distance constraints from the bovine mitochondrial c-ring x-ray structure. Angular rotary twist, the dominant ringmore » motion, was estimated to show that the c-ring accounted in part for the measured compliance. Ring rotation was entrained to rotation of the external helix within each hairpin-shaped c-subunit in the ring. Ensembles of monomer and dimers extracted from complete c-rings showed that the coupling between collective ring and the individual subunit motions was independent of the size of the c-ring, which varies between organisms. Molecular determinants were identified by covariance analysis of residue coevolution and structural-alphabet-based local dynamics correlations. The residue coevolution gave a readout of subunit architecture. The dynamic couplings revealed that the hinge for both ring and subunit helix rotations was constructed from the proton-binding site and the adjacent glycine motif (IB-GGGG) in the midmembrane plane. IB-GGGG motifs were linked by long-range couplings across the ring, while intrasubunit couplings connected the motif to the conserved cytoplasmic loop and adjacent segments. The correlation with principal collective motions shows that the couplings underlie both ring rotary and bending motions. Noncontact couplings between IB-GGGG motifs matched the coevolution signal as well as contact couplings. The residue coevolution reflects the physiological importance of the dynamics

  11. Polybenzimidazoles Via Aromatic Nucleophilic Displacement

    NASA Technical Reports Server (NTRS)

    Connell, John W.; Hergenrother, Paul M.; Smith, Joseph G.

    1994-01-01

    Soluble polybenzimidazoles (PBI's) synthesized by nucleophilic displacement reaction of di(hydroxyphenyl)-benzimidazole monomers with activated aromatic difluoride compounds in presence of anhydrous potassium carbonate. These polymers exhibit good thermal, thermo-oxidative, and chemical stability, and high mechanical properties. Using benzimidazole monomers, more economical, and new PBI's processed more easily than commercial PBI, without loss of desirable physical properties.

  12. Smoke Ring Physics

    ERIC Educational Resources Information Center

    Huggins, Elisha

    2011-01-01

    The behavior of smoke rings, tornados, and quantized vortex rings in superfluid helium has many features in common. These features can be described by the same mathematics we use when introducing Ampere's law in an introductory physics course. We discuss these common features. (Contains 7 figures.)

  13. Illustration of Saturn's Rings

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This illustration shows a close-up of Saturn's rings. These rings are thought to have formed from material that was unable to form into a Moon because of tidal forces from Saturn, or from a Moon that was broken up by Saturn's tidal forces.

  14. Lower esophageal ring (Schatzki)

    MedlinePlus

    ... narrowed area to stretch the ring. Sometimes, a balloon is placed in the area and inflated, to help widen the ring. Outlook (Prognosis) Swallowing problems may return. You may need repeat treatment. When to Contact a Medical Professional Call your health care provider if you ...

  15. EBT ring physics

    SciTech Connect

    Uckan, N.A.

    1980-04-01

    This workshop attempted to evaluate the status of the current experimental and theoretical understanding of hot electron ring properties. The dominant physical processes that influence ring formation, scaling, and their optimal behavior are also studied. Separate abstracts were prepared for each of the 27 included papers. (MOW)

  16. Contactless Magnetic Slip Ring

    NASA Technical Reports Server (NTRS)

    Kumagai, Hiroyuki (Inventor); Deardon, Joe D. (Inventor)

    1997-01-01

    A contactless magnetic slip ring is disclosed having a primary coil and a secondary coil. The primary and secondary coils are preferably magnetically coupled together, in a highly reliable efficient manner, by a magnetic layered core. One of the secondary and primary coils is rotatable and the contactless magnetic slip ring provides a substantially constant output.

  17. The Fermilab recycler ring

    SciTech Connect

    Martin Hu

    2001-07-24

    The Fermilab Recycler is a permanent magnet storage ring for the accumulation of antiprotons from the Antiproton Source, and the recovery and cooling of the antiprotons remaining at the end of a Tevatron store. It is an integral part of the Fermilab III luminosity upgrade. The following paper describes the design features, operational and commissioning status of the Recycler Ring.

  18. Exchange coupling between laterally adjacent nanomagnets.

    PubMed

    Dey, H; Csaba, G; Bernstein, G H; Porod, W

    2016-09-30

    We experimentally demonstrate exchange-coupling between laterally adjacent nanomagnets. Our results show that two neighboring nanomagnets that are each antiferromagnetically exchange-coupled to a common ferromagnetic bottom layer can be brought into strong ferromagnetic interaction. Simulations show that interlayer exchange coupling effectively promotes ferromagnetic alignment between the two nanomagnets, as opposed to antiferromagnetic alignment due to dipole-coupling. In order to experimentally demonstrate the proposed scheme, we fabricated arrays of pairs of elongated, single-domain nanomagnets. Magnetic force microscopy measurements show that most of the pairs are ferromagnetically ordered. The results are in agreement with micromagnetic simulations. The presented scheme can achieve coupling strengths that are significantly stronger than dipole coupling, potentially enabling far-reaching applications in Nanomagnet Logic, spin-wave devices and three-dimensional storage and computing. PMID:27535227

  19. Seismicity in Azerbaijan and Adjacent Caspian Sea

    SciTech Connect

    Panahi, Behrouz M.

    2006-03-23

    So far no general view on the geodynamic evolution of the Black Sea to the Caspian Sea region is elaborated. This is associated with the geological and structural complexities of the region revealed by geophysical, geochemical, petrologic, structural, and other studies. A clash of opinions on geodynamic conditions of the Caucasus region, sometimes mutually exclusive, can be explained by a simplified interpretation of the seismic data. In this paper I analyze available data on earthquake occurrences in Azerbaijan and the adjacent Caspian Sea region. The results of the analysis of macroseismic and instrumental data, seismic regime, and earthquake reoccurrence indicate that a level of seismicity in the region is moderate, and seismic event are concentrated in the shallow part of the lithosphere. Seismicity is mostly intra-plate, and spatial distribution of earthquake epicenters does not correlate with the plate boundaries.

  20. Boundary Layers of Air Adjacent to Cylinders

    PubMed Central

    Nobel, Park S.

    1974-01-01

    Using existing heat transfer data, a relatively simple expression was developed for estimating the effective thickness of the boundary layer of air surrounding cylinders. For wind velocities from 10 to 1000 cm/second, the calculated boundary-layer thickness agreed with that determined for water vapor diffusion from a moistened cylindrical surface 2 cm in diameter. It correctly predicted the resistance for water vapor movement across the boundary layers adjacent to the (cylindrical) inflorescence stems of Xanthorrhoea australis R. Br. and Scirpus validus Vahl and the leaves of Allium cepa L. The boundary-layer thickness decreased as the turbulence intensity increased. For a turbulence intensity representative of field conditions (0.5) and for νwindd between 200 and 30,000 cm2/second (where νwind is the mean wind velocity and d is the cylinder diameter), the effective boundary-layer thickness in centimeters was equal to [Formula: see text]. PMID:16658855

  1. Telemetry carrier ring and support

    NASA Technical Reports Server (NTRS)

    Wakeman, Thomas G. (Inventor)

    1992-01-01

    A telemetry carrier ring for use in a gas turbine engine includes an annular support ring connected to the engine and an annular carrier ring coupled to the support ring, each ring exhibiting different growth characteristics in response to thermal and mechanical loading. The carrier ring is coupled to the support ring by a plurality of circumferentially spaced web members which are relatively thin in an engine radial direction to provide a predetermined degree of radial flexibility. the web members have a circumferential width and straight axial line of action selected to transfer torque and thrust between the support ring and the carrier ring without substantial deflection. The use of the web members with radial flexibility provides compensation between the support ring and the carrier ring since the carrier ring grows at a different rate than the supporting ring.

  2. Jupiter's Gossamer Rings Explained.

    NASA Astrophysics Data System (ADS)

    Hamilton, D. P.

    2003-05-01

    Over the past several years, Galileo measurements and groundbased imaging have drastically improved our knowledge of Jupiter's faint ring system. We now recognize that the ring consists of four components: a main ring 7000km wide, whose inner edge blossoms into a vertically-extended halo, and a pair of more tenuous Gossamer rings, one associated with each of the small moons Thebe and Amalthea. When viewed edge on, the Gossamer rings appear as diaphanous disks whose thicknesses agree with the vertical excursions of the inclined satellites from the equatorial plane. In addition, the brightness of each Gossamer ring drops off sharply outside the satellite orbits. These correlations allowed Burns etal (1999, Science, 284, 1146) to argue convincingly that the satellites act as sources of the dusty ring material. In addition, since most material is seen inside the orbits of the source satellites, an inwardly-acting dissipative force such as Poynting-Robertson drag is implicated. The most serious problem with this simple and elegant picture is that it is unable to explain the existence of a faint swath of material that extends half a jovian radius outward from Thebe. A key constraint is that this material has the same thickness as the rest of the Thebe ring. In this work, we identify the mechanism responsible for the outward extension: it is a shadow resonance, first investigated by Horanyi and Burns (1991, JGR, 96, 19283). When a dust grain enters Jupiter's shadow, photoelectric processes shut down and the grain's electric charge becomes more negative. The electromagnetic forces associated with the varying charge cause periodic oscillations in the orbital eccentricity and semimajor axis as the orbital pericenter precesses. This results in a ring which spreads both inward and outward of its source satellite while preserving its vertical thickness - just as is observed for the Thebe ring. Predictions of the model are: i) gaps of micron-sized material interior to Thebe and

  3. Environmental diagnostic analysis of ground water bacteria and their involvement in utilization of aromatic compounds

    SciTech Connect

    Wear, J.E. Jr.

    1993-05-01

    The objective of this study was to examine the hypothesis that select functional groups of bacteria from pristine sites have an innate ability to degrade synthetic aromatics that often contaminate groundwater environments,due to exposure to naturally occurring recalcitrant aromatics in their environment. This study demonstrates that subsurface microbial communities are capable of utilizing lignin and humic acid breakdown products. Utilizers of these compounds were found to be present in most all the wells tested. Even the deepest aquifer tested had utilizers present for all six of the aromatics tested. Highest counts for the aromatics tested were observed with the naturally occurring breakdown products of either lignin or humic acid. Carboxylic acids were found to be an important sole carbon source for groundwater bacteria possibly explained by the fact that they are produced by the oxidative cleavage of aromatic ring structures. The carbohydrate sole carbon sources that demonstrated the greatest densities were ones commonly associated with humics. This study indicates that utilization of naturally occurring aromatic compounds in the subsurface is an important nutritional source for groundwater bacteria. In addition, it suggests that adaptation to naturally occurring recalcitrant substrates is the origin of degradative pathways for xenobiotic compounds with analogous structure. This work has important implications for in situ bioremediation as a method of environmental cleanup.

  4. Jupiter's Rings: Sharpest View

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The New Horizons spacecraft took the best images of Jupiter's charcoal-black rings as it approached and then looked back at Jupiter. The top image was taken on approach, showing three well-defined lanes of gravel- to boulder-sized material composing the bulk of the rings, as well as lesser amounts of material between the rings. New Horizons snapped the lower image after it had passed Jupiter on February 28, 2007, and looked back in a direction toward the sun. The image is sharply focused, though it appears fuzzy due to the cloud of dust-sized particles enveloping the rings. The dust is brightly illuminated in the same way the dust on a dirty windshield lights up when you drive toward a 'low' sun. The narrow rings are confined in their orbits by small 'shepherding' moons.

  5. STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED ...

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

    STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED BY ARCHITECTURAL FINISH. TENSION RING ROLLER SUPPORT AT COLUMN OBSCURED BY COLUMN COVERINGS. - Houston Astrodome, 8400 Kirby Drive, Houston, Harris County, TX

  6. 30 CFR 56.9103 - Clearance on adjacent tracks.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Clearance on adjacent tracks. 56.9103 Section..., Hauling, and Dumping Traffic Safety § 56.9103 Clearance on adjacent tracks. Railcars shall not be left on side tracks unless clearance is provided for traffic on adjacent tracks....

  7. 30 CFR 57.9103 - Clearance on adjacent tracks.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Clearance on adjacent tracks. 57.9103 Section..., Hauling, and Dumping Traffic Safety § 57.9103 Clearance on adjacent tracks. Railcars shall not be left on side tracks unless clearance is provided for traffic on adjacent tracks....

  8. 30 CFR 56.9103 - Clearance on adjacent tracks.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Clearance on adjacent tracks. 56.9103 Section..., Hauling, and Dumping Traffic Safety § 56.9103 Clearance on adjacent tracks. Railcars shall not be left on side tracks unless clearance is provided for traffic on adjacent tracks....

  9. 30 CFR 57.9103 - Clearance on adjacent tracks.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Clearance on adjacent tracks. 57.9103 Section..., Hauling, and Dumping Traffic Safety § 57.9103 Clearance on adjacent tracks. Railcars shall not be left on side tracks unless clearance is provided for traffic on adjacent tracks....

  10. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  11. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  12. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  13. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  14. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  15. The Enceladus Ring

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] The Enceladus Ring (labeled)

    This excellent view of the faint E ring -- a ring feature now known to be created by Enceladus -- also shows two of Saturn's small moons that orbit within the ring, among a field of stars in the background.

    The E ring extends from three to eight Saturn radii -- about 180,000 kilometers (118,000 miles) to 482,000 kilometers (300,000 miles). Its full extent is not visible in this view.

    Calypso (22 kilometers, or 14 miles across) and Helene (32 kilometers, or 20 miles across) orbit within the E ring's expanse. Helene skirts the outer parts of the E ring, but here it is projected in front of a region deeper within the ring.

    Calypso and Helene are trojan satellites, or moons that orbit 60 degrees in front or behind a larger moon. Calypso is a Tethys trojan and Helene is a trojan of Dione.

    An interesting feature of note in this image is the double-banded appearance of the E-ring, which is created because the ring is somewhat fainter in the ringplane than it is 500-1,000 kilometers (300-600 miles) above and below the ringplane. This appearance implies that the particles in this part of the ring have nonzero inclinations (a similar affect is seen in Jupiter's gossamer ring). An object with a nonzero inclination does not orbit exactly at Saturn's ringplane. Instead, its orbit takes it above and below the ringplane. Scientists are not entirely sure why the particles should have such inclinations, but they are fairly certain that the reason involves Enceladus.

    One possible explanation is that all the E ring particles come from the plume of icy material that is shooting due south out of the moon's pole. This means all of the particles are created with a certain velocity out of the ringplane, and then they orbit above and below that plane.

    Another possible explanation is that Enceladus produces particles with a range of speeds, but the moon gravitationally

  16. Earth: A Ringed Planet?

    NASA Astrophysics Data System (ADS)

    Hancock, L. O.; Povenmire, H.

    2010-12-01

    Among the most beautiful findings of the Space Age have been the discoveries of planetary rings. Not only Saturn but also Jupiter, Uranus and Neptune have rings; Saturn’s ring system has structures newly discovered; even Saturn's moon Rhea itself has a ring. All these are apparently supplied by material from the planetary moons (Rhea's ring by Rhea itself). The question naturally arises, why should the Earth not have a ring, and on the other hand, if it does, why has it not been observed? No rings have yet been observed in the inner solar system, but after all, rings in the inner solar system might simply tend to be fainter and more transient than those of the outer solar system: the inner solar system is more affected by the solar wind, and the Sun’s perturbing gravitational influence is greater. J.A. O’Keefe first suggested (1980) that Earth might have a ring system of its own. An Earth ring could account for some climate events. O’Keefe remarked that formation or thickening of a ring system in Earth’s equatorial plane could drive glaciation by deepening the chill of the winter hemisphere. (It is very well established that volcanic dust is an effective agent for the extinction of sunlight; this factor can be overwhelmingly apparent in eclipse observations.) O’Keefe died in 2000 and the speculation was not pursued, but the idea of an Earth ring has a prima facie reasonableness that calls for its renewed consideration. The program of this note is to hypothesize that, as O’Keefe proposed: (a) an Earth ring system exists; (b) it affects Earth's weather and climate; (c) the tektite strewn fields comprise filaments of the ring fallen to Earth's surface on various occasions of disturbance by comets or asteroids. On this basis, and drawing on the world's weather records, together with the Twentieth Century Reanalysis by NCEP/CIRES covering the period 1870-2010 and the geology of the tektite strewn fields, we herein propose the hypothesized Earth ring

  17. Comments on the Treatment of Aromaticity and Acid-Base Character of Pyridine and Pyrrole in Contemporary Organic Chemistry Textbooks

    NASA Astrophysics Data System (ADS)

    Anderson, Hugh J.; Bauer, Ludwig

    1999-08-01

    Presentations of aromaticity and acid-base character of pyridine and pyrrole in 18 contemporary organic chemistry textbooks were surveyed. Superficially, each of these two monoaza aromatic heterocycles retains an electron pair on its sp2-hybridized ring nitrogen, ostensibly available for neutralization with a proton to form a salt. The two nonbonded electrons in pyridine, in an sp2-hybridized orbital outside the ring, are not interacting with the 6p-electron aromatic sextet and thus are fully available for neutralization to form an N+-H pyridinium cation. However, in pyrrole, the nonbonded electron pair on nitrogen is part of the aromatic 6p- electron sextet and is not available for NH salt formation, since this would generate an aliphatic (highly reactive) diene imminium cation, which would destroy pyrrole's aromaticity. However, electrophilic attack of a proton in an irreversible manner attacks C-2 of pyrrole to form a resonance-stabilized cationic intermediate capable of further transformations. Pyridine is classified correctly as a weak base, while pyrrole in aqueous solutions is classified essentially neutral. In reality, pyrrole is a weak acid, neutralized by strong bases to generate a stable aromatic and highly reactive nucleophilic anion. Most authors fail to stress the acidic property of pyrrole and some organic texts need revision to eliminate some misconceptions and omissions.

  18. Seal ring installation tool

    NASA Technical Reports Server (NTRS)

    Haselmaier, L. Haynes (Inventor)

    2004-01-01

    A seal ring tool that allows an installer to position a primary seal ring between hub ends of pipe flanges that are being assembled together. The tool includes a pivoting handle member and extension arms attached to the pivoting handle member. The ends of the arms have side indentation type longitudinal grooves angled toward one another for holding the primary seal ring in place between the hubs of respective pipes that are to be attached together. The arms of the tool can also have flat sides that can be used to abut against an optional second larger seal that is supported within a groove in one of the hub ends so that the second hub end can then be moved against the other side of the primary seal ring. Once the seal ring is positioned between the pipe hubs, the pipe hubs can be moved about the seal ring due to the flat sides of the arms of the tool. The tool eliminates the chances of damaging and contaminating seal rings being installed within pipe hubs that are being attached to one another.

  19. Hot piston ring tests

    NASA Technical Reports Server (NTRS)

    Allen, David J.; Tomazic, William A.

    1987-01-01

    As part of the DOE/NASA Automotive Stirling Engine Project, tests were made at NASA Lewis Research Center to determine whether appendix gap losses could be reduced and Stirling engine performance increased by installing an additional piston ring near the top of each piston dome. An MTI-designed upgraded Mod I Automotive Stirling Engine was used. Unlike the conventional rings at the bottom of the piston, these hot rings operated in a high temperature environment (700 C). They were made of a high temperature alloy (Stellite 6B) and a high temperature solid lubricant coating (NASA Lewis-developed PS-200) was applied to the cylinder walls. Engine tests were run at 5, 10, and 15 MPa operating pressure over a range of operating speeds. Tests were run both with hot rings and without to provide a baseline for comparison. Minimum data to assess the potential of both the hot rings and high temperature low friction coating was obtained. Results indicated a slight increase in power and efficiency, an increase over and above the friction loss introduced by the hot rings. Seal leakage measurements showed a significant reduction. Wear on both rings and coating was low.

  20. CATABOLISM OF AROMATIC BIOGENIC AMINES BY 'PSEUDOMONAS AERUGINOSA' PA01 VIA META CLEAVAGE OF HOMOPROTOCATECHUIC ACID (JOURNAL VERSION)

    EPA Science Inventory

    Pseudomonas aruginosa PA01 catabolized the aromatic amines tyramine and octopamine through 4-hydroxyphenylacetic acid and 3,4-dihydroxyphenylacetic acid (HPA). Meta ring cleavage was mediated by 3-4-dihydroxyphenylacetate 2,3-dioxygenase (HPADO), producing 2-hydroxy-5-carboxymeth...

  1. Single kernel method for detection of 2-acetyl-1-pyrroline in aromatic rice germplasm using SPME-GC/MS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    INTRODUCTION Aromatic rice or fragrant rice, (Oryza sativa L.), has a strong popcorn-like aroma due to the presence of a five-membered N-heterocyclic ring compound known as 2-acetyl-1-pyrroline (2-AP). To date, existing methods for detecting this compound in rice require the use of several kernels. ...

  2. Speciation of atmospheric polycyclic aromatic hydrocarbons (PAHs) present during fog time collected submicron particles.

    PubMed

    Singh, Dharmendra Kumar; Sharma, Swati; Habib, Gazala; Gupta, Tarun

    2015-08-01

    Airborne submicron particles (PM1) were collected using PM1 sampler during the fog-dominated days (December 2013-January 2014). PM1 values varied between 58.12 μg/m(3) and 198.75 μg/m(3), and average mass concentration was 162.33 ± 38.25 μg/m(3) while total average concentration of particle-associated polycyclic aromatic hydrocarbon (PAHs) determined was 616.31 ± 30.31 ng/m(3). This is a signal for an alarming high pollution level at this site situated in the Indo-Gangetic Plain (IGP). PAHs were extracted from filters using toluene and acetonitrile. Quantitative measurements of polycyclic aromatic hydrocarbons (PAHs) were carried out using the high performance liquid chromatography (HPLC) technique. The extracts were analyzed for 16 target polycyclic aromatic hydrocarbons (PAHs) including carcinogenic compound benzo(a)pyrene (19.86 ± 38.98 ng/m(3)). Fluoranthene, benzo(a)anthracene, anthracene, and fluorene were the predominant compounds found in the samples collected during foggy days. Based on number of rings, four-ring PAH compounds had maximum contribution (43%) in this fog time collected submicron particles followed by three-ring (21%), five-ring (20%), six-ring (13%), and two-ring (3%), respectively. In winter and foggy days, wood and coal combustion and biomass burning also significantly contribute to the PAH levels. However, diagnostic ratio suggests diesel emissions as the prime source of PAHs at this sampling site. PMID:25903173

  3. Dynamics of the Uranian Rings

    NASA Technical Reports Server (NTRS)

    Dermott, S. F.

    1984-01-01

    Some of the problems of the shepherding satellite model of Goldreich ant tremaine are discussed. The following topics are studied: (1) optical depths of the all the observed narrow rings; (2) satellite and ring separation timescales; (3) ring edge sharpness; (4) shock formation in narrow rings; (5) the existence of small satellites near the Uranian rings; and (6) the apse and node alignments of the eccentric and inclined rings.

  4. Theodolite Ring Lights

    NASA Technical Reports Server (NTRS)

    Clark, David

    2006-01-01

    Theodolite ring lights have been invented to ease a difficulty encountered in the well-established optical-metrology practice of using highly reflective spherical tooling balls as position references. A theodolite ring light produces a more easily visible reflection and eliminates the need for an autocollimating device. A theodolite ring light is a very bright light source that is well centered on the optical axis of the instrument. It can be fabricated, easily and inexpensively, for use on a theodolite or telescope of any diameter.

  5. Dynamics of planetary rings

    NASA Astrophysics Data System (ADS)

    Araki, S.

    1991-02-01

    The modeling of the dynamics of particle collisions within planetary rings is discussed. Particles in the rings collide with one another because they have small random motions in addition to their orbital velocity. The orbital speed is roughly 10 km/s, while the random motions have an average speed of about a tenth of a millimeter per second. As a result, the particle collisions are very gentle. Numerical analysis and simulation of the ring dynamics, performed with the aid of a supercomputer, is outlined.

  6. Alternative parallel ring protocols

    NASA Technical Reports Server (NTRS)

    Mukkamala, R.; Foudriat, E. C.; Maly, Kurt J.; Kale, V.

    1990-01-01

    Communication protocols are know to influence the utilization and performance of communication network. The effect of two token ring protocols on a gigabit network with multiple ring structure is investigated. In the first protocol, a mode sends at most one message on receiving a token. In the second protocol, a mode sends all the waiting messages when a token is received. The behavior of these protocols is shown to be highly dependent on the number of rings as well as the load in the network.

  7. Alkylation of organic aromatic compounds

    DOEpatents

    Smith, L.A. Jr.; Arganbright, R.P.; Hearn, D.

    1993-09-07

    Aromatic compounds are alkylated in a catalytic distillation, wherein the catalyst structure also serves as a distillation component by contacting the aromatic compound with a C[sub 2] to C[sub 10] olefin in the catalyst bed under 0.25 to 50 atmospheres of pressure and at temperatures in the range of 80 C to 500 C, using as the catalyst a molecular sieve characterized as acidic or an acidic cation exchange resin. For example, ethyl benzene is produced by feeding ethylene to about the mid point of the catalyst bed while benzene is conveniently added through the reflux in molar excess to that required to react with ethylene, thereby reacting substantially all of the ethylene and recovering benzene as the principal overhead and ethyl benzene in the bottoms. 1 figures.

  8. Alkylation of organic aromatic compounds

    DOEpatents

    Smith, Jr., Lawrence A.; Arganbright, Robert P.; Hearn, Dennis

    1994-01-01

    Aromatic compounds are alkylated in a catalytic distillation, wherein the catalyst structure also serves as a distillation component by contacting the aromatic compound with a C.sub.2 to C.sub.10 olefin in the catalyst bed under 0.25 to 50 atmospheres of pressure and at temperatures in the range of 80.degree. C. to 500.degree. C., using as the catalyst a mole sieve characterized as acidic or an acidic cation exchange resin. For example, ethyl benzene is produced by feeding ethylene below the catalyst bed while benzene is conveniently added through the reflux in molar excess to that required to react with ethylene, thereby reacting substantially all of the ethylene and recovering benzene as the principal overhead and ethyl benzene in the bottoms.

  9. Alkylation of organic aromatic compounds

    DOEpatents

    Smith, L.A. Jr.; Arganbright, R.P.; Hearn, D.

    1994-06-14

    Aromatic compounds are alkylated in a catalytic distillation, wherein the catalyst structure also serves as a distillation component by contacting the aromatic compound with a C[sub 2] to C[sub 10] olefin in the catalyst bed under 0.25 to 50 atmospheres of pressure and at temperatures in the range of 80 C to 500 C, using as the catalyst a molecular sieve characterized as acidic or an acidic cation exchange resin. For example, ethyl benzene is produced by feeding ethylene below the catalyst bed while benzene is conveniently added through the reflux in molar excess to that required to react with ethylene, thereby reacting substantially all of the ethylene and recovering benzene as the principal overhead and ethyl benzene in the bottoms. 1 fig.

  10. Alkylation of organic aromatic compounds

    DOEpatents

    Smith, Jr., Lawrence A.

    1989-01-01

    Aromatic compounds are alkylated in a catalytic distillation, wherein the catalyst structure also serves as a distillation component by contacting the aromatic compound with a C.sub.2 to C.sub.10 olefin in the catalyst bed under 0.25 to 50 atmospheres of pressure and at temperatures in the range of 80.degree. C. to 500.degree. C., using as the catalyst a mole sieve characterized as acidic or an acidic cation exchange resin. For example, ethyl benzene is produced by feeding ethylene below the catalyst bed while benzene is conveniently added through the reflux in molar excess to that required to react with ethylene, thereby reacting substantially all of the ethylene and recovering benzene as the principal overhead and ethyl benzene in the bottoms.

  11. Alkylation of organic aromatic compounds

    DOEpatents

    Smith, Jr., Lawrence A.; Arganbright, Robert P.; Hearn, Dennis

    1993-01-01

    Aromatic compounds are alkylated in a catalytic distillation, wherein the catalyst structure also serves as a distillation component by contacting the aromatic compound with a C.sub.2 to C.sub.10 olefin in the catalyst bed under 0.25 to 50 atmospheres of pressure and at temperatures in the range of 80.degree. C. to 500.degree. C., using as the catalyst a mole sieve characterized as acidic or an acidic cation exchange resin. For example, ethyl benzene is produced by feeding ethylene to about the mid point of the catalyst bed while benzene is conveniently added through the reflux in molar excess to that required to react with ethylene, thereby reacting substantially all of the ethylene and recovering benzene as the principal overhead and ethyl benzene in the bottoms.

  12. Alkylation of organic aromatic compounds

    DOEpatents

    Smith, L.A. Jr.

    1989-07-18

    Aromatic compounds are alkylated in a catalytic distillation, wherein the catalyst structure also serves as a distillation component by contacting the aromatic compound with a C[sub 2] to C[sub 10] olefin in the catalyst bed under 0.25 to 50 atmospheres of pressure and at temperatures in the range of 80 C to 500 C, using as the catalyst a mole sieve characterized as acidic or an acidic cation exchange resin. For example, ethyl benzene is produced by feeding ethylene below the catalyst bed while benzene is conveniently added through the reflux in molar excess to that required to react with ethylene, thereby reacting substantially all of the ethylene and recovering benzene as the principal overhead and ethyl benzene in the bottoms. 1 fig.

  13. A detailed kinetic modeling study of aromatics formation in laminar premixed acetylene and ethylene flames

    SciTech Connect

    Wang, H.; Frenklach, M.

    1997-07-01

    A computational study was performed for the formation and growth of polycyclic aromatic hydrocarbons (PAHs) in laminar premixed acetylene and ethylene flames. A new detailed reaction mechanism describing fuel pyrolysis and oxidation, benzene formation, and PAH mass growth and oxidation is presented and critically tested. It is shown that the reaction model predicts reasonably well the concentration profiles of major and intermediate species and aromatic molecules in a number of acetylene and ethylene flames reported in the literature. It is demonstrated that reactions of n-C{sub 4}H{sub x} + C{sub 2}H{sub 2} leading to the formation of one-ring aromatics are as important as the propargyl recombination, and hence must be included in kinetic modeling of PAH formation in hydrocarbon flames. It is further demonstrated that the mass growth of PAHs can be accounted for by the previously proposed H-abstraction-C{sub 2}H{sub 2}-addiction mechanism.

  14. Interaction between adjacent lightning discharges in clouds

    NASA Astrophysics Data System (ADS)

    Wang, Yanhui; Zhang, Guangshu; Zhang, Tong; Li, Yajun; Wu, Bin; Zhang, Tinglong

    2013-07-01

    Using a 3D lightning radiation source locating system (LLS), three pairs of associated lightning discharges (two or more adjacent lightning discharges following an arbitrary rule that their space-gap was less than 10 km and their time-gap was less than 800 ms) were observed, and the interaction between associated lightning discharges was analyzed. All these three pairs of associated lightning discharges were found to involve three or more charge regions (the ground was considered as a special charge region). Moreover, at least one charge region involved two lightning discharges per pair of associated lightning discharges. Identified from electric field changes, the subsequent lightning discharges were suppressed by the prior lightning discharges. However, it is possible that the prior lightning discharge provided a remaining discharge channel to facilitate the subsequent lightning discharge. The third case provided evidence of this possibility. Together, the results suggested that, if the charges in the main negative charge region can be consumed using artificial lightning above the main negative charge regions, lightning accidents on the ground could be greatly reduced, on the condition that the height of the main negative charge region and the charge intensity of the lower positive charge region are suitable.

  15. POLYCYCLIC AROMATIC HYDROCARBONS WITH ARMCHAIR EDGES AND THE 12.7 μm BAND

    SciTech Connect

    Candian, A.; Tielens, A. G. G. M.; Sarre, P. J.

    2014-08-10

    In this Letter, we report the results of density functional theory calculations on medium-sized neutral polycyclic aromatic hydrocarbon (PAH) molecules with armchair edges. These PAH molecules possess strong C-H stretching and bending modes around 3 μm and in the fingerprint region (10-15 μm), and also strong ring deformation modes around 12.7 μm. Perusal of the entries in the NASA Ames PAHs Database shows that ring deformation modes of PAHs are common, although generally weak. Therefore, we propose that armchair PAHs with N{sub C} > 65 are responsible for the 12.7 μm aromatic infrared band in H II regions and discuss the astrophysical implications in the context of the PAH life cycle.

  16. Polycyclic Aromatic Hydrocarbons with Armchair Edges and the 12.7 μm Band

    NASA Astrophysics Data System (ADS)

    Candian, A.; Sarre, P. J.; Tielens, A. G. G. M.

    2014-08-01

    In this Letter, we report the results of density functional theory calculations on medium-sized neutral polycyclic aromatic hydrocarbon (PAH) molecules with armchair edges. These PAH molecules possess strong C-H stretching and bending modes around 3 μm and in the fingerprint region (10-15 μm), and also strong ring deformation modes around 12.7 μm. Perusal of the entries in the NASA Ames PAHs Database shows that ring deformation modes of PAHs are common, although generally weak. Therefore, we propose that armchair PAHs with NC > 65 are responsible for the 12.7 μm aromatic infrared band in H II regions and discuss the astrophysical implications in the context of the PAH life cycle.

  17. Intramolecular cycloaddition in 6,6-spiroepoxycyclohexa-2,4-dienone: simple aromatics to (+/-)-platencin.

    PubMed

    Singh, Vishwakarma; Sahu, Bharat Chandra; Bansal, Varsha; Mobin, Shaikh M

    2010-10-01

    A formal total synthesis of platencin from a simple aromatic precursor is described. Transformation of the aromatic compound into reactive spiroepoxycyclohexa-2,4-dienone and intramolecular cycloaddition are the key features of our methodology. 2-Hydroxymethyl-6-(3-hydroxy-hex-5-enyl)-phenol was oxidized with NaIO(4) to give a dimer that, upon a retro-Diels-Alder reaction, generated the spiroepoxycyclohexa-2,4-dienone that underwent intramolecular Diels-Alder reaction to give a tricyclic adduct having a core structure of platencin and appropriately disposed functional groups in a single step. Reduction of the double bond present in the ethano-bridge, manipulation of the oxirane ring and introduction of a double bond in the six-membered ring furnished a tricyclic intermediate which has already been converted into platencin. PMID:20683538

  18. Tough, Soluble, Aromatic, Thermoplastic Copolyimides

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G. (Inventor)

    1998-01-01

    Tough, soluble, aromatic, thermoplastic copolyimides were prepared by reacting 4,4'-oxydiphthalic anhydride, 3,4,3',4'-biphenyltetracarboxylic dianhydride and 3,4'-oxydianiline. These copolyimides were found to be soluble in common amide solvents such as N,N'-dimethyl acetamide, N-methylpyrrolidinone, and dimethylformamide allowing them to be applied as the fully imidized copolymer and to be used to prepare a wide range of articles.

  19. Making Solid Aromatic Polyimide Fibers

    NASA Technical Reports Server (NTRS)

    St. Clair, Anne K.; Ely, Robert M.; Dorogy, William E., Jr.

    1991-01-01

    Improved wet-spinning process makes aromatic polyamic acid fibers containing no voids, and converts to polyimide fibers also free of voids. Elimination of voids found to improve tensile strength and other tensile properties. Improved polyimide fibers prove useful in protective clothing, sealing materials, filters for harsh chemical and/or thermal environments, and other applications taking advantage of excellent chemical resistance, high thermal stability, and good tensile properties.

  20. Analysis of heterocyclic aromatic amines.

    PubMed

    Murkovic, M

    2007-09-01

    Heterocyclic aromatic amines are formed in protein and amino acid-rich foods at temperatures above 150 degrees C. Of more than twenty heterocyclic aromatic amines identified ten have been shown to have carcinogenic potential. As nutritional hazards, their reliable determination in prepared food, their uptake and elimination in living organisms, including humans, and assessment of associated risks are important food-safety issues. The concentration in foods is normally in the low ng g(-1) range, which poses a challenge to the analytical chemist. Because of the complex nature of food matrixes, clean-up and enrichment of the extracts are also complex, usually involving both cation-exchange (propylsulfonic acid silica gel, PRS) and reversed-phase purification. The application of novel solid-phase extraction cartridges with a wettable apolar phase combined with cation-exchange characteristics simplified this process--both the polar and apolar heterocyclic aromatic amines were recovered in one fraction. Copper phthalocyanine trisulfonate bonded to cotton ("blue cotton") or rayon, and molecular imprinted polymers have also been successfully used for one-step sample clean-up. For analysis of the heterocyclic aromatic amines, liquid chromatography with base-deactivated reversed-phase columns has been used, and, recently, semi-micro and capillary columns have been introduced. The photometric, fluorimetric, or electrochemical detectors used previously have been replaced by mass spectrometers. Increased specificity and sub-ppb sensitivities have been achieved by the use of the selected-reaction-monitoring mode of detection of advanced MS instrumentation, for example the triple quadrupole and Q-TOF instrument combination. Gas chromatography, also with mass-selective detection, has been used for specific applications; the extra derivatization step needed for volatilization has been balanced by the higher chromatographic resolution. PMID:17546447

  1. The direct aromatization of methane

    SciTech Connect

    Marcelin, G.; Oukaci, R.; Migone, R.A.; Kazi, A.M.

    1995-12-31

    The thermal decomposition of methane shows significant potential as a process for the production of higher unsaturated and aromatic hydrocarbons when the extent of the reaction is limited. Thermodynamic calculations have shown that when the reaction is limited to the formation of C{sub 2} to C{sub 10} products, yields of aromatics can exceed 40% at temperatures of 1200{degrees}C. Preliminary experiments have shown that when the reaction is limited to the formation of C{sub 2} to C{sub 10} products, yields of aromatics can exceed 40% at temperatures of 1200{degrees}C. Preliminary experiments have shown that cooling the product and reacting gases as the reaction proceeds can significantly reduce or eliminate the formation of solid carbon and heavier (C{sub 10+}) materials. Much work remains to be done in optimizing the quenching process and this is one of the goals of this program. Means to lower the temperature of the reaction are being studied as this result in a more feasible commercial process due to savings realized in energy and material of construction costs. The use of free-radical generators and catalysts will be investigated as a means of lowering the reaction temperature thus allowing faster quenching. It is highly likely that such studies will lead to a successful direct methane to higher hydrocarbon process.

  2. Deuterated polycyclic aromatic hydrocarbons: Revisited

    NASA Astrophysics Data System (ADS)

    Doney, K. D.; Candian, A.; Mori, T.; Onaka, T.; Tielens, A. G. G. M.

    2016-02-01

    Aims: The amount of deuterium locked up in polycyclic aromatic hydrocarbons (PAHs) has to date been an uncertain value. We present a near-infrared (NIR) spectroscopic survey of Hii regions in the Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud obtained with AKARI, which aims to search for features indicative of deuterated PAHs (PAD or Dn-PAH) to better constrain the D/H ratio of PAHs. Methods: Fifty-three Hii regions were observed in the NIR (2.5-5 μm), using the Infrared Camera (IRC) on board the AKARI satellite. Through comparison of the observed spectra with a theoretical model of deuterated PAH vibrational modes, the aromatic and (a)symmetric aliphatic C-D stretch modes were identified. Results: We see emission features between 4.4-4.8 μm, which could be unambiguously attributed to deuterated PAHs in only six of the observed sources, all of which are located in the Milky Way. In all cases, the aromatic C-D stretching feature is weaker than the aliphatic C-D stretching feature, and, in the case of M17b, this feature is not observed at all. Based on the weak or absent PAD features in most of the observed spectra, it is suggested that the mechanism for PAH deuteration in the ISM is uncommon.

  3. Storage Ring EDM Experiments

    NASA Astrophysics Data System (ADS)

    Semertzidis, Yannis K.

    2016-04-01

    Dedicated storage ring electric dipole moment (EDM) methods show great promise advancing the sensitivity level by a couple orders of magnitude over currently planned hadronic EDM experiments. We describe the present status and recent updates of the field.

  4. Heating Saturn's Clumpy Rings

    NASA Astrophysics Data System (ADS)

    Turner, Neal J.; Morishima, Ryuji; Spilker, Linda J.

    2015-11-01

    We model Cassini CIRS data using a Monte Carlo radiative transfer -- thermal balance technique first developed for protostellar disks, with the goals of:1. Exploring whether the A- and B-ring temperatures' variation with viewing angle is consistent with the wake structures suggested by the observed azimuthal asymmetry in optical depth, by analytic arguments, and by numerical N-body modeling.2. Better constraining the shape, size, spacing and optical depths of substructure in the A-ring, using the unexpectedly high temperatures observed at equinox. If the wake features have high enough contrast, Saturn-shine may penetrate the gaps between the wakes and heat thering particles both top and bottom.3. Determining how much of the heating of the A- and B-rings' unlit sides is due to radiative transport and how much is due to particle motions, especially vertical motions. This will help in constraining the rings' surface densities and masses.

  5. Saturn's dynamic D ring

    USGS Publications Warehouse

    Hedman, M.M.; Burns, J.A.; Showalter, M.R.; Porco, C.C.; Nicholson, P.D.; Bosh, A.S.; Tiscareno, M.S.; Brown, R.H.; Buratti, B.J.; Baines, K.H.; Clark, R.

    2007-01-01

    The Cassini spacecraft has provided the first clear images of the D ring since the Voyager missions. These observations show that the structure of the D ring has undergone significant changes over the last 25 years. The brightest of the three ringlets seen in the Voyager images (named D72), has transformed from a narrow, <40-km wide ringlet to a much broader and more diffuse 250-km wide feature. In addition, its center of light has shifted inwards by over 200 km relative to other features in the D ring. Cassini also finds that the locations of other narrow features in the D ring and the structure of the diffuse material in the D ring differ from those measured by Voyager. Furthermore, Cassini has detected additional ringlets and structures in the D ring that were not observed by Voyager. These include a sheet of material just interior to the inner edge of the C ring that is only observable at phase angles below about 60??. New photometric and spectroscopic data from the ISS (Imaging Science Subsystem) and VIMS (Visual and Infrared Mapping Spectrometer) instruments onboard Cassini show the D ring contains a variety of different particle populations with typical particle sizes ranging from 1 to 100 microns. High-resolution images reveal fine-scale structures in the D ring that appear to be variable in time and/or longitude. Particularly interesting is a remarkably regular, periodic structure with a wavelength of ??? 30 ?? km extending between orbital radii of 73,200 and 74,000 km. A similar structure was previously observed in 1995 during the occultation of the star GSC5249-01240, at which time it had a wavelength of ??? 60 ?? km. We interpret this structure as a periodic vertical corrugation in the D ring produced by differential nodal regression of an initially inclined ring. We speculate that this structure may have formed in response to an impact with a comet or meteoroid in early 1984. ?? 2006 Elsevier Inc. All rights reserved.

  6. Mosaic of Saturn's rings

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This detailed mosaic of the underside of the Cassini Division was obtained by Voyager 1 with a resolution of about 10 kilometers. The classical Cassini Division appears here to the right of center as five bright rings with substantial blacks gap on either side. The inner edge of the A Ring, to the left of center, is the brightest part of this image. The fine-scale wave structure in this region has been interpreted as being the result of gravitational density waves.

  7. Saturn's B rings

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This narrow-angle camera image of Saturn's B Ring and Cassini Division was taken through the Clear filter from a distance of 12.6 million km on 3 November 1980. The Cassini Division separating the A and B Rings is clearly not an empty region. The Division shows several substantial well-defined ringlets. JPL managed the Voyager Project for NASA's Office of Space Science.

  8. Concise, aromatization-based approach to an elaborate C2-symmetric pyrenophane.

    PubMed

    Nandaluru, Penchal Reddy; Dongare, Prateek; Kraml, Christina M; Pascal, Robert A; Dawe, Louise N; Thompson, David W; Bodwell, Graham J

    2012-08-11

    A very short synthesis (5 steps), the crystal structure and resolution of an elaborate, inherently chiral [n](1,6)pyrenophane is reported. The synthesis hinges upon two very productive events: a multicomponent reaction and an unprecedented double-McMurry/valence isomerization/dehydrogenation step. Aromatization reactions are involved in the formation of all four of the rings of the pyrene system. PMID:22760162

  9. Saturn's E ring

    NASA Technical Reports Server (NTRS)

    Baum, W. A.; Kreidl, T.; Westphal, J. A.; Danielson, G. E.; Seidelmann, P. K.; Pascu, D.; Currie, D. G.

    1981-01-01

    Observations of the tenuous E ring of Saturn made by an earth-based CCD system at the time of the ring-plane crossing of March 1980 are presented. The observations were made with the CCD system attached to the 1.8-m Perkins reflector at Lowell Observatory using a pupil mask behind a focal plane mask to suppress telescopic diffraction. Photometric analysis of the CCD images reveal the edge-on brightness profile of the ring, beginning at a distance of 3 Saturn radii, to peak sharply in the vicinity of the orbit of Enceladus at about 4 Saturn radii, then decrease to a distance of over 8 Saturn radii. In addition, beyond Enceladus, the edge-on width of the ring is observed to increase with radial distance, reaching nearly 5 arcsec at 7 Saturn radii. Observations suggest, on the one hand, that the E ring is associated with Enceladus and possibly represents material ejected from the satellite, and on the other, that the ring is at an early stage in its evolution.

  10. Carbon deposition from aromatic solvents onto active intact 3d metal surface at ambient conditions.

    PubMed

    Safronov, A P; Kurlyandskaya, G V; Chlenova, A A; Kuznetsov, M V; Bazhin, D N; Beketov, I V; Sanchez-Ilarduya, M B; Martinez-Amesti, A

    2014-03-25

    The process of carbon deposition onto 3d metal surface immersed in aromatic solvents (benzene, toluene, xylene) at ambient conditions was studied for as-prepared magnetic nanoparticles (MNPs) and Fe-based films by thermal analysis, mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, electron microscopy, and energy-dispersive X-ray spectroscopy. The mechanism of the deposition at the interface is likely the heterogeneous Scholl oxidation of the aromatic hydrocarbons, which is the cationic polymerization of the aryl rings. It results in the formation of polycyclic aromatic hydrocarbons (PAH) chemically bonded to the surface of a MNP or thin metallic film. The benzene rings in the polycyclic deposit do not maintain planar aligned structures and do not provide delocalization of the π-electrons in the zone structure. Contrary to the dense graphite layers, the polycyclic layers, although chemically bonded, are not attached tightly to the surface. Such "hairlike" structure of the carboneous deposit might be especially favorable for the applications that imply the enhanced interaction at the surfaces incorporated in the functional matrices (polymeric composites or biosensors). The aromatic chemical nature of the deposit provides strong interaction with most polymers, while its loose structure favors conformational mobility of macromolecular chains at the interface. PMID:24593324

  11. Noncomparative scaling of aromaticity through electron itinerancy

    NASA Astrophysics Data System (ADS)

    Paul, Satadal; Goswami, Tamal; Misra, Anirban

    2015-10-01

    Aromaticity is a multidimensional concept and not a directly observable. These facts have always stood in the way of developing an appropriate theoretical framework for scaling of aromaticity. In the present work, a quantitative account of aromaticity is developed on the basis of cyclic delocalization of π-electrons, which is the phenomenon leading to unique features of aromatic molecules. The stabilization in molecular energy, caused by delocalization of π-electrons is obtained as a second order perturbation energy for archetypal aromatic systems. The final expression parameterizes the aromatic stabilization energy in terms of atom to atom charge transfer integral, onsite repulsion energy and the population of spin orbitals at each site in the delocalized π-electrons. An appropriate computational platform is framed to compute each and individual parameter in the derived equation. The numerical values of aromatic stabilization energies obtained for various aromatic molecules are found to be in close agreement with available theoretical and experimental reports. Thus the reliable estimate of aromaticity through the proposed formalism renders it as a useful tool for the direct assessment of aromaticity, which has been a long standing problem in chemistry.

  12. Noncomparative scaling of aromaticity through electron itinerancy

    SciTech Connect

    Paul, Satadal; Goswami, Tamal; Misra, Anirban

    2015-10-15

    Aromaticity is a multidimensional concept and not a directly observable. These facts have always stood in the way of developing an appropriate theoretical framework for scaling of aromaticity. In the present work, a quantitative account of aromaticity is developed on the basis of cyclic delocalization of π-electrons, which is the phenomenon leading to unique features of aromatic molecules. The stabilization in molecular energy, caused by delocalization of π-electrons is obtained as a second order perturbation energy for archetypal aromatic systems. The final expression parameterizes the aromatic stabilization energy in terms of atom to atom charge transfer integral, onsite repulsion energy and the population of spin orbitals at each site in the delocalized π-electrons. An appropriate computational platform is framed to compute each and individual parameter in the derived equation. The numerical values of aromatic stabilization energies obtained for various aromatic molecules are found to be in close agreement with available theoretical and experimental reports. Thus the reliable estimate of aromaticity through the proposed formalism renders it as a useful tool for the direct assessment of aromaticity, which has been a long standing problem in chemistry.

  13. Planar homotropenylium cation: a transition state with reversed aromaticity.

    PubMed

    Gibson, Christopher M; Havenith, Remco W A; Fowler, Patrick W; Jenneskens, Leonardus W

    2015-02-01

    In contrast to the equilibrium structure of the homoaromatic C(s) homotropenylium cation, C8H9(+) (1), which supports a pinched diatropic ring current, the C(2v) transition state (2) for inversion of the methylene bridge of 1 is antiaromatic and supports a two-lobe paratropic π current, as detected by plotting B3LYP/6-31G** ipsocentric current maps. Participation of the bridge CH bonds is crucial for the change in global character of the current in the transition state, as shown by the quenching of its paratropicity on substitution of H by F. Orbital-based arguments allow rationalization of this transition between homoaromaticity and hyper(conjugative) antiaromaticity. More generally, the hyperconjugative ring current in a family of C(2v) planar-constrained geometries of (CR2)C(N-1)H(N-1)(q) homoannulenes (R = H, F) can be switched from paratropic (antiaromatic) to diatropic (aromatic) by variation of ring size, charge, and bridge substituent. An orbital-based counting rule accounts for these systematic trends. PMID:25526524

  14. Petroleum basins of Sakhalin and adjacent shelf

    SciTech Connect

    Mavrinski, Y.; Koblov, E. )

    1993-09-01

    Sixty-seven oil and gas fields have been discovered on Sakhalin and the adjacent shelf but the distribution of fields is uneven in north Sakhalin, south Sakhalin, and the Tatar basins. The sedimentary cover is composed of sandy, clayey, and siliceous rocks, with volcanogenic and coal-bearing deposits of Upper Cretaceous, Paleogene, and Neogene 8-12 km thick. Marine clayey and siliceous oil source rocks are regionally developed in the section at different stratigraphic levels; the organic matter is of mixed type and the content varies from 0.5 to 1.5%. The upper Oligocene and middle-upper Miocene source rocks in the north Sakhalin basin are typical, and the organic carbon content ranges from 1 to 5%. The level of organic matter catagenesis and conversion into hydrocarbons is high because of the high differential geothermal gradient in the basins, 30-50[degrees]C per km. Porous sandstones in the Miocene form the reservoirs in all fields with the exception of Okruzhnoye, where the pay zone is a siliceous claystone. Growth-fault rollovers and anticlines form the main traps ranging in area from 5 to 300 km[sup 2], with amplitudes between 100 and 600 m. both stratigraphic and structural traps have been identified. Considerable volumes of reserves are associated with the Miocene deposits of north Sakhalin, which are characterized by an optimum combination of oil source rocks, focused migration paths, and thick sequences of reservoirs and cap rocks. Six large fields have been discovered in the past 15 yr. Oil and condensate reserves stand at over 300 million MT, and gas reserves are about 900 billion m[sup 3].

  15. Propellers in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Sremcevic, M.; Stewart, G. R.; Albers, N.; Esposito, L. W.

    2014-04-01

    Theoretical studies and simulations have demonstrated the effects caused by objects embedded in planetary rings [5, 8]. Even if the objects are too small to be directly observed, each creates a much larger gravitational imprint on the surrounding ring material. These strongly depend on the mass of the object and range from "S" like propeller-shaped structures for about 100m-sized icy bodies to the opening of circumferential gaps as in the case of the embedded moons Pan and Daphnis and their corresponding Encke and Keeler Gaps. Since the beginning of the Cassini mission many of these smaller objects (~ 100m in size) have been identified in Saturn's A ring through their propeller signature in the images [10, 7, 9, 11]. Furthermore, recent Cassini observations indicate the possible existence of objects embedded even in Saturn's B and C ring [6, 2]. In this paper we present our new results about by now classical A ring propellers and more enigmatic B ring population. Due to the presence of self-gravity wakes the analysis of propeller brightness in ISS images always bears some ambiguity [7, 9] and consequently the exact morphology of propellers is not a settled issue. In 2008 we obtained a fortunate Cassini Ultraviolet Imaging Spectrograph (UVIS) occultation of the largest A ring propeller Bleriot. Utilizing Cassini ISS images we obtain Bleriot orbit and demonstrate that UVIS Persei Rev42 occultation did cut across Bleriot about 100km downstream from the center. The occultation itself shows a prominent partial gap and higher density outer flanking wakes, while their orientation is consistent with a downstream cut. While in the UVIS occultation the partial gap is more prominent than the flanking wakes, the features mostly seen in Bleriot images are actually flanking wakes. One of the most interesting aspects of the A ring propellers are their wanderings, or longitudinal deviations from a pure circular orbit [11]. We numerically investigated the possibility of simple moon

  16. Aromatic Interactions as Control Elements in Stereoselective Organic Reactions

    PubMed Central

    2012-01-01

    Conspectus This Account describes how attractive interaction of aromatic rings with other groups can influence and control the stereoselectivity of many reactions. Recent developments in theory have led to improved accuracy in the modeling of aromatic interactions. Quantum mechanical modeling can now provide insights into the roles of these interactions at a level of detail not previously accessible, both for ground-state species and for transition states of chemical reactions. In this Account, we show how transition-state modeling led to the discovery of the influence of aryl groups on the stereoselectivities of several types of organic reactions. These reaction types include asymmetric dihydroxylations, transfer hydrogenations, hetero-Diels–Alder reactions, acyl transfers, and Claisen rearrangements. Our recent studies have led to a novel mechanistic picture for two classes of (4+3) cycloadditions, both of which involve reactions of furans with oxyallyl intermediates. The first class of cycloadditions, developed by Hsung, features neutral oxyallyls containing a chiral oxazolidinone auxiliary. Originally, these cycloadditions were thought rely on differential steric crowding of the two faces of a planar intermediate. Computations reveal a different picture and show that cycloadditions with furan takes place preferentially through the more crowded transition state, with furan adding on the same side as the oxazolidinone’s Ph substituent. The crowded transition state is stabilized by a CH–π interaction between furan and Ph, worth about 2.0 kcal/mol. Stereocontrol in a second class of (4+3) cycloadditions, involving chiral alkoxy siloxyallyl cations, also is controlled by attractive interactions with aromatic rings. Alkoxy groups derived from chiral α-methylbenzyl alcohols are found to favor crowded transition states, where a CH–π interaction is again present between furan and Ar. The cationic cycloadditions are stepwise, while the Hsung cycloadditions are

  17. Conjugative transfer of preferential utilization of aromatic compounds from Pseudomonas putida CSV86.

    PubMed

    Basu, Aditya; Phale, Prashant S

    2008-02-01

    Pseudomonas putida CSV86 utilizes naphthalene (Nap), salicylate (Sal), benzyl alcohol (Balc), and methylnaphthalene (MN) preferentially over glucose. Methylnaphthalene is metabolized by ring-hydroxylation as well as side-chain hydroxylation pathway. Although the degradation property was found to be stable, the frequency of obtaining Nap(-)Sal(-)MN(-)Balc(-) phenotype increased to 11% in the presence of curing agents. This property was transferred by conjugation to Stenotrophomonas maltophilia CSV89 with a frequency of 7 x 10(-8) per donor cells. Transconjugants were Nap(+)Sal(+)MN(+)Balc(+) and metabolized MN by ring- as well as side-chain hydroxylation pathway. Transconjugants also showed the preferential utilization of aromatic compounds over glucose indicating transfer of the preferential degradation property. The transferred properties were lost completely when transconjugants were grown on glucose or 2YT. Attempts to detect and isolate plasmid DNA from CSV86 and transconjugants were unsuccessful. Transfer of degradation genes and its subsequent loss from the transconjugants was confirmed by PCR using primers specific for 1,2-dihydroxynaphthalene dioxygenase and catechol 2,3-dioxygenase (C23O) as well as by DNA-DNA hybridizations using total DNA as template and C23O PCR fragment as a probe. These results indicate the involvement of a probable conjugative element in the: (i) metabolism of aromatic compounds, (ii) ring- and side-chain hydroxylation pathways for MN, and (iii) preferential utilization of aromatics over glucose. PMID:17487554

  18. Direct, nonoxidative conversion of methane to ethylene, aromatics, and hydrogen.

    PubMed

    Guo, Xiaoguang; Fang, Guangzong; Li, Gang; Ma, Hao; Fan, Hongjun; Yu, Liang; Ma, Chao; Wu, Xing; Deng, Dehui; Wei, Mingming; Tan, Dali; Si, Rui; Zhang, Shuo; Li, Jianqi; Sun, Litao; Tang, Zichao; Pan, Xiulian; Bao, Xinhe

    2014-05-01

    The efficient use of natural gas will require catalysts that can activate the first C-H bond of methane while suppressing complete dehydrogenation and avoiding overoxidation. We report that single iron sites embedded in a silica matrix enable direct, nonoxidative conversion of methane, exclusively to ethylene and aromatics. The reaction is initiated by catalytic generation of methyl radicals, followed by a series of gas-phase reactions. The absence of adjacent iron sites prevents catalytic C-C coupling, further oligomerization, and hence, coke deposition. At 1363 kelvin, methane conversion reached a maximum at 48.1% and ethylene selectivity peaked at 48.4%, whereas the total hydrocarbon selectivity exceeded 99%, representing an atom-economical transformation process of methane. The lattice-confined single iron sites delivered stable performance, with no deactivation observed during a 60-hour test. PMID:24812398

  19. What's up with witch rings?

    PubMed

    Heard, Priscilla; Phillips, David

    2015-01-01

    'Witch rings' are well-known novelty rings that show a size-change illusion when rotated. We have replicated the illusion of expansion of the reflections in the rings in a variety of contexts with animations, though not as yet so successfully imitated the sense that the whole ring expands and contracts. PMID:26489222

  20. DC-Powered Jumping Ring

    NASA Astrophysics Data System (ADS)

    Jeffery, Rondo N.; Amiri, Farhang

    2016-02-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant differences from the AC case. In particular, the ring does not fly off the core but rises a short distance and then falls back. If the ring jumps high enough, the rising and the falling motion of the ring does not follow simple vertical motion of a projectile. This indicates that there are additional forces on the ring in each part of its motion. Four possible stages of the motion of the ring with DC are identified, which result from the ring current changing directions during the jump in response to a changing magnetic flux through the moving ring.

  1. Steroidal aromatic 'naphthenic acids' in oil sands process-affected water: structural comparisons with environmental estrogens.

    PubMed

    Rowland, Steven J; West, Charles E; Jones, David; Scarlett, Alan G; Frank, Richard A; Hewitt, L Mark

    2011-11-15

    The large volumes, acute toxicity, estrogenicity, and antiandrogenicity of process-affected waters accruing in tailings ponds from the operations of the Alberta oil sands industries pose a significant task for environmental reclamation. Synchronous fluorescence spectra (SFS) suggest that oil sands process-affected water (OSPW) may contain aromatic carboxylic acids, which are among the potentially environmentally important toxicants, but no such acids have yet been identified, limiting interpretations of the results of estrogenicity and other assays. Here we show that multidimensional comprehensive gas chromatography-mass spectrometry (GCxGC-MS) of methyl esters of acids in an OSPW sample produces mass spectra consistent with their assignment as C(19) and C(20) C-ring monoaromatic hydroxy steroid acids, D-ring opened hydroxy and nonhydroxy polyhydrophenanthroic acids with one aromatic and two alicyclic rings and A-ring opened steroidal keto acids. High resolution MS data support the assignment of several of the so-called 'O3' species. When fractions of distilled, esterified, OSPW acid-extractable organics were examined, the putative aromatics were mainly present in a high boiling fraction; when examined by argentation thin layer chromatography, some were present in a fraction with a retardation factor between that of the methyl esters of synthetic monoalicyclic and monoaromatic acids. Ultraviolet absorption spectra of these fractions indicated the presence of benzenoid moieties. SFS of model octahydro- and tetrahydrophenanthroic acids produced emissions at the characteristic excitation wavelengths observed in some OSPW extracts, consistent with the postulations from ultraviolet spectroscopy and mass spectrometry data. We suggest the acids originate from extensive biodegradation of C-ring monoaromatic steroid hydrocarbons and offer a means of differentiating residues at different biodegradation stages in tailings ponds. Structural similarities with estrone and

  2. Mapping Ring Particle Cooling across Saturn's Rings with Cassini CIRS

    NASA Astrophysics Data System (ADS)

    Brooks, Shawn M.; Spilker, L. J.; Edgington, S. G.; Pilorz, S. H.; Deau, E.

    2010-10-01

    Previous studies have shown that the rings' thermal inertia, a measure of their response to changes in the thermal environment, varies from ring to ring. Thermal inertia can provide insight into the physical structure of Saturn's ring particles and their regoliths. Low thermal inertia and quick temperature responses are suggestive of ring particles that have more porous or fluffy regoliths or that are riddled with cracks. Solid, coherent particles can be expected to have higher thermal inertias (Ferrari et al. 2005). Cassini's Composite Infrared Spectrometer has recorded millions of spectra of Saturn's rings since its arrival at Saturn in 2004 (personal communication, M. Segura). CIRS records far infrared radiation between 10 and 600 cm-1 (16.7 and 1000 µm) at focal plane 1 (FP1), which has a field of view of 3.9 mrad. Thermal emission from Saturn's rings peaks in this wavelength range. FP1 spectra can be used to infer ring temperatures. By tracking how ring temperatures vary, we can determine the thermal inertia of the rings. In this work we focus on CIRS observations of the shadowed portion of Saturn's rings. The thermal budget of the rings is dominated by the solar radiation absorbed by its constituent particles. When ring particles enter Saturn's shadow this source of energy is abruptly cut off. As a result, ring particles cool as they traverse Saturn's shadow. From these shadow observations we can create cooling curves at specific locations across the rings. We will show that the rings' cooling curves and thus their thermal inertia vary not only from ring to ring, but by location within the individual rings. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2010 California Institute of Technology. Government sponsorship acknowledged.

  3. Saturn's Other Ring Current

    NASA Astrophysics Data System (ADS)

    Crary, F. J.

    2014-04-01

    Saturn's main rings orbit the planet within an atmosphere and ionosphere of water, oxygen and hydrogen, produced by meteoritic impacts on and ultraviolet photodesorbtion of the ring particles [Johnson et al., 2006; Luhmann et al., 2006; Tseng et al., 2010]. The neutral atmosphere itself has only been tentatively detected through ultraviolet fluorescents of OH [Hall et al., 1996] while the ionosphere was observed in situ by the Cassini spacecraft shortly after orbital insertion [Coates et al.,2005; Tokar et al. 2005, Waite et al. 2005]. Although the plasma flow velocity of this ionosphere is not well-constrained, but the close association with the rings suggests that its speed would be couppled to the keplarian velocity of the rings themselves. As a result, the motion of the plasma through Saturn's magnetic field would produce an induced voltage, oriented away from the planet outside synchronous orbit and towards the planet inside synchronous orbit. Such a potential could result in currents flowing across the ring plane and closeing along magnetic field lines and through Saturn's ionosphere at latitudes between 36o and 48o. Cassini observations of whistler-mode plasma wave emissions [Xin et al.,2006] centered on synchronous orbit (1.76 Rs, mapping to 41o latitude) have been interpreted as a product of field-aligned electron beams associated with such a current. This presentation will investigate the magnitude of these currents and the resulting Joule heating of the ionosphere. An important constraint is that no auroral ultraviolet emissions have been observed at the relevant latitudes. In contrast, Joule heating could affect infrared emissions from H3+. Variations in H3+ emission associated with Saturn's rings have been reported by O'Donoghue et al., 2013, and interpreted as a result of ring "rain", i.e. precipitating water group species from the rings which alter ionosphereic chemistry and H3+ densities. As noted by O'Donoghue et al., this interpretation may be

  4. The effect of aromatization on the isotopic compositions of hydrocarbons during early diagenesis

    NASA Technical Reports Server (NTRS)

    Freeman, K. H.; Boreham, C. J.; Summons, R. E.; Hayes, J. M.

    1994-01-01

    Polycyclic aromatic hydrocarbons with varying degrees of aromatization were isolated from the Eocene Messel Shale (Rheingraben, Germany). The high abundances of these compounds and their structural resemblances to cyclic triterpenoid lipids are consistent with derivation from microbial rather than thermal processes. Compounds structurally related to oleanane contain from five to nine double bonds; those within a series of aromatized hopanoids contain from three to nine. All are products of diagenetic reactions that remove hydrogen or methyl groups, and, in several cases, break carbon-carbon bonds to open rings. Aromatized products are on average depleted in 13C relative to possible precursors by l.2% (range: l.5% enrichment to 4% depletion, n = 9). The dependence of 13C content on the number of double bonds is not, however, statistically significant and it must be concluded that there is no strong evidence for isotopic fractionation accompanying diagenetic aromatization. Isotopic differences between series (structures related to ursane, des-A-ursane, des-A-lupane, des-A-arborane, and possibly, des-A-gammacerane are present) are much greater, indicating that 13C contents are controlled primarily by source effects. Fractionations due to chromatographic isotope effects during HPLC ranged from 0.1 to 2.8%.

  5. Analysis of preference for carbon source utilization among three strains of aromatic compounds degrading Pseudomonas.

    PubMed

    Karishma, M; Trivedi, Vikas D; Choudhary, Alpa; Mhatre, Akanksha; Kambli, Pranita; Desai, Jinal; Phale, Prashant S

    2015-10-01

    Soil isolates Pseudomonas putida CSV86, Pseudomonas aeruginosa PP4 and Pseudomonas sp. C5pp degrade naphthalene, phthalate isomers and carbaryl, respectively. Strain CSV86 displayed a diauxic growth pattern on phenylpropanoid compounds (veratraldehyde, ferulic acid, vanillin or vanillic acid) plus glucose with a distinct second lag-phase. The glucose concentration in the medium remained constant with higher cell respiration rates on aromatics and maximum protocatechuate 3,4-dioxygenase activity in the first log-phase, which gradually decreased in the second log-phase with concomitant depletion of the glucose. In strains PP4 and C5pp, growth profile and metabolic studies suggest that glucose is utilized in the first log-phase with the repression of utilization of aromatics (phthalate or carbaryl). All three strains utilize benzoate via the catechol 'ortho' ring-cleavage pathway. On benzoate plus glucose, strain CSV86 showed preference for benzoate over glucose in contrast to strains PP4 and C5pp. Additionally, organic acids like succinate were preferred over aromatics in strains PP4 and C5pp, whereas strain CSV86 co-metabolizes them. Preferential utilization of aromatics over glucose and co-metabolism of organic acids and aromatics are found to be unique properties of P. putida CSV86 as compared with strains PP4 and C5pp and this property of strain CSV86 can be exploited for effective bioremediation. PMID:26316546

  6. Lignin solubilization and aqueous phase reforming for the production of aromatic chemicals and hydrogen.

    PubMed

    Zakzeski, Joseph; Weckhuysen, Bert M

    2011-03-21

    The solubilization and aqueous phase reforming of lignin, including kraft, soda, and alcell lignin along with sugarcane bagasse, at low temperatures (T≤498 K) and pressures (P≤29 bar) is reported for the first time for the production of aromatic chemicals and hydrogen. Analysis of lignin model compounds and the distribution of products obtained during the lignin aqueous phase reforming revealed that lignin was depolymerized through disruption of the abundant β-O-4 linkages and, to a lesser extent, the 5-5' carbon-carbon linkages to form monomeric aromatic compounds. The alkyl chains contained on these monomeric compounds were readily reformed to produce hydrogen and simple aromatic platform chemicals, particularly guaiacol and syringol, with the distribution of each depending on the lignin source. The methoxy groups present on the aromatic rings were subject to hydrolysis to form methanol, which was also readily reformed to produce hydrogen and carbon dioxide. The composition of the isolated yields of monomeric aromatic compounds and overall lignin conversion based on these isolated yields varied from 10-15% depending on the lignin sample, with the balance consisting of gaseous products and residual solid material. Furthermore, we introduce the use of a high-pressure autoclave with optical windows and an autoclave with ATR-IR sentinel for on-line in situ spectroscopic monitoring of biomass conversion processes, which provides direct insight into, for example, the solubilization process and aqueous phase reforming reaction of lignin. PMID:21246746

  7. Piston Ring Pressure Distribution

    NASA Technical Reports Server (NTRS)

    Kuhn, M.

    1943-01-01

    The discovery and introduction of the internal combustion engine has resulted in a very rapid development in machines utilizing the action of a piston. Design has been limited by the internal components of the engine, which has been subjected to ever increasing thermal and mechanical stresses, Of these internal engine components, the piston and piston rings are of particular importance and the momentary position of engine development is not seldom dependent upon the development of both of the components, The piston ring is a well-known component and has been used in its present shape in the steam engine of the last century, Corresponding to its importance, the piston ring has been a rich field for creative activity and it is noteworthy that in spite of this the ring has maintained its shape through the many years. From the many and complicated designs which have been suggested as a packing between piston and cylinder wall hardly one suggestion has remained which does not resemble the original design of cast iron rectangular ring.

  8. Stacked Corrugated Horn Rings

    NASA Technical Reports Server (NTRS)

    Sosnowski, John B.

    2010-01-01

    This Brief describes a method of machining and assembly when the depth of corrugations far exceeds the width and conventional machining is not practical. The horn is divided into easily machined, individual rings with shoulders to control the depth. In this specific instance, each of the corrugations is identical in profile, and only differs in diameter and outer profile. The horn is segmented into rings that are cut with an interference fit (zero clearance with all machining errors biased toward contact). The interference faces can be cut with a reverse taper to increase the holding strength of the joint. The taper is a compromise between the interference fit and the clearance of the two faces during assembly. Each internal ring is dipped in liquid nitrogen, then nested in the previous, larger ring. The ring is rotated in the nest until the temperature of the two parts equalizes and the pieces lock together. The resulting assay is stable, strong, and has an internal finish that cannot be achieved through other methods.

  9. Compactness Aromaticity of Atoms in Molecules

    PubMed Central

    Putz, Mihai V.

    2010-01-01

    A new aromaticity definition is advanced as the compactness formulation through the ratio between atoms-in-molecule and orbital molecular facets of the same chemical reactivity property around the pre- and post-bonding stabilization limit, respectively. Geometrical reactivity index of polarizability was assumed as providing the benchmark aromaticity scale, since due to its observable character; with this occasion new Hydrogenic polarizability quantum formula that recovers the exact value of 4.5 a03 for Hydrogen is provided, where a0 is the Bohr radius; a polarizability based–aromaticity scale enables the introduction of five referential aromatic rules (Aroma 1 to 5 Rules). With the help of these aromatic rules, the aromaticity scales based on energetic reactivity indices of electronegativity and chemical hardness were computed and analyzed within the major semi-empirical and ab initio quantum chemical methods. Results show that chemical hardness based-aromaticity is in better agreement with polarizability based-aromaticity than the electronegativity-based aromaticity scale, while the most favorable computational environment appears to be the quantum semi-empirical for the first and quantum ab initio for the last of them, respectively. PMID:20480020

  10. Aromatic diglycosides from Cladogynos orientalis.

    PubMed

    Kanchanapoom, Tripetch

    2007-03-01

    Two unusual aromatic diglycosides with galloyl substitution, 4''-O-galloyl-violutoside and 4''-O-galloyl-benzyl-O-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranoside, were isolated from the aerial portion of Cladogynos orientalis along with isovitexin, apigenin 6-C-(2''-O-galloyl)-beta-D-glucopyranoside, apigenin 8-C-(2''-O-galloyl)-beta-D-glucopyranoside, syringic acid beta-D-glucopyranoside, 3,4,5-trimethoxyphenyl beta-D-glucopyranoside, (6S,9R)-roseoside, and violutioside. The structural elucidations were based on analyses of chemical and spectroscopic data by including 1D and 2D NMR analyses. PMID:17161443

  11. Quantum transport through aromatic molecules

    SciTech Connect

    Ojeda, J. H.; Rey-González, R. R.; Laroze, D.

    2013-12-07

    In this paper, we study the electronic transport properties through aromatic molecules connected to two semi-infinite leads. The molecules are in different geometrical configurations including arrays. Using a nearest neighbor tight-binding approach, the transport properties are analyzed into a Green's function technique within a real-space renormalization scheme. We calculate the transmission probability and the Current-Voltage characteristics as a function of a molecule-leads coupling parameter. Our results show different transport regimes for these systems, exhibiting metal-semiconductor-insulator transitions and the possibility to employ them in molecular devices.

  12. Bimolecular photoreduction of aromatic sulfoxides.

    PubMed

    Cubbage, J W; Tetzlaff, T A; Groundwater, H; McCulla, R D; Nag, M; Jenks, W S

    2001-12-14

    Photolysis of aromatic sulfoxides in the presence of alkoxides in alcoholic solvents provides a photochemical route to the corresponding sulfides. Other electron donors also give sulfide with various degrees of success. The reaction could also be carried out using carbazoles as sensitizers, and quantitative yields could be obtained using N-methylcarbazole in methanol. Evidence points toward a hydroxysulfuranyl radical as the key intermediate, and solvent effects point to heterolysis, rather than homolysis, as the step that breaks the S-O bond. PMID:11735547

  13. Rings in the solar system

    SciTech Connect

    Pollack, J.B.; Cuzzi, J.N.

    1981-11-01

    Saturn, Jupiter, and Uranus have rings with different structure and composition. The rings consist of tiny masses in independent orbits. Photographs and data obtained by the Voyager project have aided in the understanding of Saturn's rings. Spokes have been found in B ring and boards, knots, and twist in F ring. Particles on the order of a micrometer in size are believed to occur in F, B, and A rings. The dominant component is water ice. The rings of Uranus are narrow and separated by broad empty regions. The technique used to study them has been stellar occulation. Nothing is known of particle size. The dominant component is believed to be silicates rich in compounds that absorb sunlight. Jupiter's rings consist of 3 main parts: a bright ring, a diffuse disk, and a halo. Use of Pioneer 10 data and other techniques have indicated particle sizes on the order of several micrometers and some at least a centimeter in diameter. The architecture of the ring system results from the interplay of a number of forces. These include gravitational forces due to moons outside the rings and moonlets embedded in them, electromagnetic forces due to the planet's rotating magnetic field, and even the gentle forces exerted by the dilute gaseous medium in which the rings rotate. Each of these forces is discussed. Several alternative explanations of how the rings arose are considered. The primary difference in these hypotheses is the account of the relationship between the ring particles of today and the primordial ring material. (SC)

  14. Physics of planetary rings

    NASA Astrophysics Data System (ADS)

    Gorkavyi, N.

    2007-08-01

    It is difficult to enumerate all the surprises presented by the planetary rings. The Saturnian rings are stratified into thousands of ringlets and the Uranian rings are compressed into narrow streams, which for some reason or other differ from circular orbits like the wheel of an old bicycle. The edge of the rings is jagged and the rings themselves are pegged down under the gravitational pressure of the satellites, bending like a ship's wake. There are spiral waves, elliptical rings, strange interlacing of narrow ringlets, and to cap it all one has observed in the Neptunian ring system three dense, bright arcs - like bunches of sausages on a transparent string. For celestial mechanics this is a spectacle as unnatural as a bear's tooth in the necklace of the English queen. In the dynamics of planetary rings the physics of collective interaction was supplemented by taking collisions between particles into account. One was led to study a kinetic equation with a rather complex collision integral - because the collisions are inelastic - which later on made it possible, both by using the Chapman-Enskog method and by using the solution of the kinetic equation for a plasma in a magnetic field, to reduce it to a closed set of (hydrodynamical) moment equations [1]. The hydrodynamical instabilities lead to the growth of short-wavelength waves and large-scale structures of the Saturnian rings [1]. We have shown that the formation of the existing dense Uranian rings is connected with the capture of positively drifting ring particles in inner Lindblad resonances which arrest this drift [1]. After the formation of dense rings at the positions of satellite resonances the collective interaction between resonant particles is amplified and the rings can leave the resonance and drift away from the planet and the parent resonance. We can expect in the C ring an appreciable positive ballistic particle drift caused by the erosion of the B ring by micrometeorites. It is therefore natural

  15. Reflectance spectroscopy (350-2500 nm) of solid-state polycyclic aromatic hydrocarbons (PAHs)

    NASA Astrophysics Data System (ADS)

    Izawa, M. R. M.; Applin, D. M.; Norman, L.; Cloutis, E. A.

    2014-07-01

    Polycyclic aromatic hydrocarbons (PAHs) are organic compounds based on fused aromatic rings, and are formed in a variety of astrophysical, solar nebula and planetary processes. Polycyclic aromatic hydrocarbons are known or suspected to occur in a wide variety of planetary settings including icy satellites, Titan’s hazes, carbonaceous meteorites, comet nuclei, ring particles; and terrestrial organic-rich lithologies such as coals, asphaltites, and bituminous sands. Relatively few measurements of the visible and near-infrared spectra of PAHs exist, yet this wavelength region (350-2500 nm) is widely used for remote sensing. This study presents detailed analyses of the 350-2500 nm reflectance spectra of 47 fine-grained powders of different high-purity solid-state PAHs. Spectral properties of PAHs change with variations in the number and connectivity of linked aromatic rings and the presence and type of side-groups and heterocycles. PAH spectra are characterized by three strong features near ∼880 nm, ∼1145 nm, and ∼1687 nm due to overtones of νCH fundamental stretching vibrations. Some PAHs are amenable to remote detection due to the presence of diagnostic spectral features, including: Nsbnd H stretching overtones at 1490-1515 nm in NH- and NH2-bearing PAHs, aliphatic or saturated bond Csbnd H overtone vibrations at ∼1180-1280 nm and ∼1700-1860 nm; a broad asymmetric feature between ∼1450 nm and ∼1900 nm due to Osbnd H stretching overtones in aromatic alcohols, Csbnd H and Cdbnd O combinations near ∼2000-2010 nm and ∼2060-2270 nm in acetyl and carboxyl-bearing PAHs. Other substituents such as sulphonyl, thioether ether and carboxyl heterocycles, or cyano, nitrate, and aromatic side groups, do not produce well-resolved diagnostic spectral features but do cause shifts in the positions of the aromatic Csbnd H vibrational overtone features. Fluorescence is commonly suppressed by the presence of heterocycles, side-groups and in many non-alternant PAHs

  16. Rings dominate western Gulf

    NASA Astrophysics Data System (ADS)

    Vidal L., Francisco V.; Vidal L., Victor M. V.; Molero, José María Pérez

    Surface and deep circulation of the central and western Gulf of Mexico is controlled by interactions of rings of water pinched from the gulf's Loop Current. The discovery was made by Mexican oceanographers who are preparing a full-color, 8-volume oceanographic atlas of the gulf.Anticyclonic warm-core rings pinch off the Loop Current at a rate of about one to two per year, the scientists of the Grupo de Estudios Oceanográficos of the Instituto de Investigaciones Eléctricas (GEO-IIE) found. The rings migrate west until they collide with the continental shelf break of the western gulf, almost always between 22° and 23°N latitude. On their westward travel they transfer angular momentum and vorticity to the surrounding water, generating cyclonic circulations and vortex pairs that completely dominate the entire surface and deep circulation of the central and western gulf.

  17. Deployable Fresnel Rings

    NASA Technical Reports Server (NTRS)

    Kennedy, Timothy F.; Fink, Patrick W.; Chu, Andrew W.; Lin, Gregory Y.

    2014-01-01

    Deployable Fresnel rings (DFRs) significantly enhance the realizable gain of an antenna. This innovation is intended to be used in combination with another antenna element, as the DFR itself acts as a focusing or microwave lens element for a primary antenna. This method is completely passive, and is also completely wireless in that it requires neither a cable, nor a connector from the antenna port of the primary antenna to the DFR. The technology improves upon the previous NASA technology called a Tri-Sector Deployable Array Antenna in at least three critical aspects. In contrast to the previous technology, this innovation requires no connector, cable, or other physical interface to the primary communication radio or sensor device. The achievable improvement in terms of antenna gain is significantly higher than has been achieved with the previous technology. Also, where previous embodiments of the Tri-Sector antenna have been constructed with combinations of conventional (e.g., printed circuit board) and conductive fabric materials, this innovation is realized using only conductive and non-conductive fabric (i.e., "e-textile") materials, with the possible exception of a spring-like deployment ring. Conceptually, a DFR operates by canceling the out-of-phase radiation at a plane by insertion of a conducting ring or rings of a specific size and distance from the source antenna, defined by Fresnel zones. Design of DFRs follow similar procedures to those outlined for conventional Fresnel zone rings. Gain enhancement using a single ring is verified experimentally and through computational simulation. The experimental test setup involves a microstrip patch antenna that is directly behind a single-ring DFR and is radiating towards a second microstrip patch antenna. The first patch antenna and DFR are shown. At 2.42 GHz, the DFR improves the transmit antenna gain by 8.6 dB, as shown in Figure 2, relative to the wireless link without the DFR. A figure illustrates the

  18. Resveratrol and para-coumarate serve as ring precursors for coenzyme Q biosynthesis[S

    PubMed Central

    Xie, Letian X.; Williams, Kevin J.; He, Cuiwen H.; Weng, Emily; Khong, San; Rose, Tristan E.; Kwon, Ohyun; Bensinger, Steven J.; Marbois, Beth N.; Clarke, Catherine F.

    2015-01-01

    Coenzyme Q (Q or ubiquinone) is a redox-active polyisoprenylated benzoquinone lipid essential for electron and proton transport in the mitochondrial respiratory chain. The aromatic ring 4-hydroxybenzoic acid (4HB) is commonly depicted as the sole aromatic ring precursor in Q biosynthesis despite the recent finding that para-aminobenzoic acid (pABA) also serves as a ring precursor in Saccharomyces cerevisiae Q biosynthesis. In this study, we employed aromatic 13C6-ring-labeled compounds including 13C6-4HB, 13C6-pABA, 13C6-resveratrol, and 13C6-coumarate to investigate the role of these small molecules as aromatic ring precursors in Q biosynthesis in Escherichia coli, S. cerevisiae, and human and mouse cells. In contrast to S. cerevisiae, neither E. coli nor the mammalian cells tested were able to form 13C6-Q when cultured in the presence of 13C6-pABA. However, E. coli cells treated with 13C6-pABA generated 13C6-ring-labeled forms of 3-octaprenyl-4-aminobenzoic acid, 2-octaprenyl-aniline, and 3-octaprenyl-2-aminophenol, suggesting UbiA, UbiD, UbiX, and UbiI are capable of using pABA or pABA-derived intermediates as substrates. E. coli, S. cerevisiae, and human and mouse cells cultured in the presence of 13C6-resveratrol or 13C6-coumarate were able to synthesize 13C6-Q. Future evaluation of the physiological and pharmacological responses to dietary polyphenols should consider their metabolism to Q. PMID:25681964

  19. Sliding-Ring Catenanes.

    PubMed

    Fernando, Isurika R; Frasconi, Marco; Wu, Yilei; Liu, Wei-Guang; Wasielewski, Michael R; Goddard, William A; Stoddart, J Fraser

    2016-08-17

    Template-directed protocols provide a routine approach to the synthesis of mechanically interlocked molecules (MIMs), in which the mechanical bonds are stabilized by a wide variety of weak interactions. In this Article, we describe a strategy for the preparation of neutral [2]catenanes with sliding interlocked electron-rich rings, starting from two degenerate donor-acceptor [2]catenanes, consisting of a tetracationic cyclobis(paraquat-p-phenylene) cyclophane (CBPQT(4+)) and crown ethers containing either (i) hydroquinone (HQ) or (ii) 1,5-dioxynaphthalene (DNP) recognition units and carrying out four-electron reductions of the cyclophane components to their neutral forms. The donor-acceptor interactions between the CBPQT(4+) ring and both HQ and DNP units present in the crown ethers that stabilize the [2]catenanes are weakened upon reduction of the cyclophane components to their radical cationic states and are all but absent in their fully reduced states. Characterization in solution performed by UV-vis, EPR, and NMR spectroscopic probes reveals that changes in the redox properties of the [2]catenanes result in a substantial decrease of the energy barriers for the circumrotation and pirouetting motions of the interlocked rings, which glide freely through one another in the neutral states. The solid-state structures of the fully reduced catenanes reveal profound changes in the relative dispositions of the interlocked rings, with the glycol chains of the crown ethers residing in the cavities of the neutral CBPQT(0) rings. Quantum mechanical investigations of the energy levels associated with the four different oxidation states of the catenanes support this interpretation. Catenanes and rotaxanes with sliding rings are expected to display unique properties. PMID:27398609

  20. Ius Chasma Tributary Valleys and Adjacent Plains

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This image covers valley tributaries of Ius Chasma, as well as the plains adjacent to the valleys. Ius Chasma is one of several canyons that make up the Valles Marineris canyon system. Valles Marineris likely formed by extension associated with the growth of the large volcanoes and topographic high of Tharsis to the northwest. As the ground was pulled apart, large and deep gaps resulted in the valleys seen in the top and bottom of this HiRISE image. Ice that was once in the ground could have also melted to create additional removal of material in the formation of the valleys. HiRISE is able to see the rocks along the walls of both these valleys and also impact craters in the image. Rock layers that appear lower down in elevation appear rougher and are shedding boulders. Near the top of the walls and also seen in patches along the smooth plains are brighter layers. These brighter layers are not shedding boulders so they must represent a different kind of rock formed in a different kind of environment than those further down the walls. Because they are highest in elevation, the bright layers are youngest in age. HiRISE is able to see dozens of the bright layers, which are perhaps only a meter in thickness. Darker sand dunes and ripples cover most of the plains and fill the floors of impact craters.

    Image PSP_001351_1715 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 9, 2006. The complete image is centered at -8.3 degrees latitude, 275.4 degrees East longitude. The range to the target site was 254.3 km (158.9 miles). At this distance the image scale ranges from 25.4 cm/pixel (with 1 x 1 binning) to 101.8 cm/pixel (with 4 x 4 binning). The image shown here has been map-projected to 25 cm/pixel and north is up. The image was taken at a local Mars time of 3:32 PM and the scene is illuminated from the west with a solar incidence angle of 59 degrees, thus the sun was about

  1. GUARD RING SEMICONDUCTOR JUNCTION

    DOEpatents

    Goulding, F.S.; Hansen, W.L.

    1963-12-01

    A semiconductor diode having a very low noise characteristic when used under reverse bias is described. Surface leakage currents, which in conventional diodes greatly contribute to noise, are prevented from mixing with the desired signal currents. A p-n junction is formed with a thin layer of heavily doped semiconductor material disposed on a lightly doped, physically thick base material. An annular groove cuts through the thin layer and into the base for a short distance, dividing the thin layer into a peripheral guard ring that encircles the central region. Noise signal currents are shunted through the guard ring, leaving the central region free from such currents. (AEC)

  2. Ringed Accretion Disks: Instabilities

    NASA Astrophysics Data System (ADS)

    Pugliese, D.; Stuchlík, Z.

    2016-04-01

    We analyze the possibility that several instability points may be formed, due to the Paczyński mechanism of violation of mechanical equilibrium, in the orbiting matter around a supermassive Kerr black hole. We consider a recently proposed model of a ringed accretion disk, made up by several tori (rings) that can be corotating or counter-rotating relative to the Kerr attractor due to the history of the accretion process. Each torus is governed by the general relativistic hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. We prove that the number of the instability points is generally limited and depends on the dimensionless spin of the rotating attractor.

  3. Unidirectional ring lasers

    DOEpatents

    Hohimer, J.P.; Craft, D.C.

    1994-09-20

    Unidirectional ring lasers formed by integrating nonreciprocal optical elements into the resonant ring cavity is disclosed. These optical elements either attenuate light traveling in a nonpreferred direction or amplify light traveling in a preferred direction. In one preferred embodiment the resonant cavity takes the form of a circle with an S-shaped crossover waveguide connected to two points on the interior of the cavity such that light traveling in a nonpreferred direction is diverted from the cavity into the crossover waveguide and reinjected out of the other end of the crossover waveguide into the cavity as light traveling in the preferred direction. 21 figs.

  4. Unidirectional ring lasers

    DOEpatents

    Hohimer, John P.; Craft, David C.

    1994-01-01

    Unidirectional ring lasers formed by integrating nonreciprocal optical elements into the resonant ring cavity. These optical elements either attenuate light traveling in a nonpreferred direction or amplify light traveling in a preferred direction. In one preferred embodiment the resonant cavity takes the form of a circle with an S-shaped crossover waveguide connected to two points on the interior of the cavity such that light traveling in a nonpreferred direction is diverted from the cavity into the crossover waveguide and reinjected out of the other end of the crossover waveguide into the cavity as light traveling in the preferred direction.

  5. The covariant chiral ring

    NASA Astrophysics Data System (ADS)

    Bourget, Antoine; Troost, Jan

    2016-03-01

    We construct a covariant generating function for the spectrum of chiral primaries of symmetric orbifold conformal field theories with N = (4 , 4) supersymmetry in two dimensions. For seed target spaces K3 and T 4, the generating functions capture the SO(21) and SO(5) representation theoretic content of the chiral ring respectively. Via string dualities, we relate the transformation properties of the chiral ring under these isometries of the moduli space to the Lorentz covariance of perturbative string partition functions in flat space.

  6. Saturn's Rings, the Yarkovsky Effects, and the Ring of Fire

    NASA Technical Reports Server (NTRS)

    Rubincam, David Parry

    2004-01-01

    The dimensions of Saturn's A and B rings may be determined by the seasonal Yarkovsky effect and the Yarkovsky-Schach effect; the two effects confine the rings between approximately 1.68 and approximately 2.23 Saturn radii, in reasonable agreement with the observed values of 1.525 and 2.267. The C ring may be sparsely populated because its particles are transients on their way to Saturn; the infall may create a luminous Ring of Fire around Saturn's equator. The ring system may be young: in the past heat flow from Saturn's interior much above its present value would not permit rings to exist.

  7. Transport of Polycyclic Aromatic Hydrocarbons in Unsaturated Porous Media

    NASA Astrophysics Data System (ADS)

    Chahal, Maninder; Flury, Markus

    2016-04-01

    Polycyclic aromatic hydrocarbons (PAHs) are complex organic molecules containing 2 or more fused benzene rings. Being hydrophobic and non-polar, PAHs tend to partition to the organic matter in the soil from bulk aqueous phase. Though transport of these contaminants has been well studied in saturated environment, interactive mechanisms of these fluorescent compounds in unsaturated (identified by presence of air-water interface) porous media is still not well understood. We studied is the transport of fluoranthene in unsaturated porous media as facilitated by moving air-water interfaces. Confocal microscopy was used to visualize the interactions of fluoranthene particles in a glass channel packed with quartz glass beads. The packed glass channel was used to mimic a porous media and effects of an advancing and receding capillary fringe on the detachment of fluoranthene.

  8. From Möbius aromaticity to gapped spin liquids

    NASA Astrophysics Data System (ADS)

    Chen, Cheng-Chien; Muechler, Lukas; Neupert, Titus; Maciejko, Joseph; Car, Roberto

    Motivated by the concept of Möbius aromatics in organic chemistry, the Hubbard model on ring-shaped molecules has been shown previously to support a fragile Mott insulator (FMI) ground state, which is distinct from a conventional insulator through its nontrivial transformation properties under point-group symmetry operations. In this talk, we discuss two-dimensional lattices of weakly-coupled FMI molecules belonging to multi-dimensional irreducible representations of the molecular point group. The low-energy effective Hamiltonians map onto quantum compass models with broken spin SU(2) symmetry. On the triangular lattice, the ground state develops long-range magnetism, which corresponds to a charge-ordered state of the molecules. On the honeycomb lattice, interestingly, we find a non-degenerate gapped spin-liquid ground state that preserves all spatial symmetries but transforms nontrivially under point-group operations. Our microscopic model therefore realizes an intrinsically interacting fermionic symmetry protected topological (SPT) phase.

  9. Biomimetic oxidative dimerization of anodically generated stilbene radical cations: effect of aromatic substitution on product distribution and reaction pathways.

    PubMed

    Hong, Fong-Jiao; Low, Yun-Yee; Chong, Kam-Weng; Thomas, Noel F; Kam, Toh-Seok

    2014-05-16

    A systematic study of the electrochemical oxidation of 1,2-diarylalkenes was carried out with the focus on detailed product studies and variation of product type as a function of aromatic substitution. A reinvestigation of the electrochemical oxidation of 4,4'-dimethoxystilbene under various conditions was first carried out, and all products formed were fully characterized and quantitated. This was followed by a systematic investigation of the effect of aromatic substitution on the nature and distribution of the products. The aromatic substituents were found to fall into three main categories, viz., substrates in which the nature and position of the aromatic substituents gave rise to essentially the same products as 4,4'-dimethoxystilbene, for example, tetraaryltetrahydrofurans, dehydrotetralins, and aldehydes (p-MeO or p-NMe2 on one ring and X on the other ring, where X = o-MeO or p-alkyl, or m- or p-EWG; e.g., 4-methoxy-4'-trifluoromethylstilbene); those that gave rise to a mixture of indanyl (or tetralinyl) acetamides and dehydrotetralins (or pallidols) (both or one ring substituted by alkyl groups, e.g., 4,4'-dimethylstilbene); and those where strategic placement of donor groups, such as OMe and OH, led to the formation of ampelopsin F and pallidol-type carbon skeletons (e.g., 4,3',4'-trimethoxystilbene). Reaction pathways to rationalize the formation of the different products are presented. PMID:24754525

  10. View of north side from exterior stairs of adjacent building, ...

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

    View of north side from exterior stairs of adjacent building, bottom cut off by fringed buildings, view facing south-southwest - U.S. Naval Base, Pearl Harbor, Industrial X-Ray Building, Off Sixth Street, adjacent to and south of Facility No. 11, Pearl City, Honolulu County, HI

  11. Learning Non-Adjacent Regularities at Age 0 ; 7

    ERIC Educational Resources Information Center

    Gervain, Judit; Werker, Janet F.

    2013-01-01

    One important mechanism suggested to underlie the acquisition of grammar is rule learning. Indeed, infants aged 0 ; 7 are able to learn rules based on simple identity relations (adjacent repetitions, ABB: "wo fe fe" and non-adjacent repetitions, ABA: "wo fe wo", respectively; Marcus et al., 1999). One unexplored issue is…

  12. Delayed Acquisition of Non-Adjacent Vocalic Distributional Regularities

    ERIC Educational Resources Information Center

    Gonzalez-Gomez, Nayeli; Nazzi, Thierry

    2016-01-01

    The ability to compute non-adjacent regularities is key in the acquisition of a new language. In the domain of phonology/phonotactics, sensitivity to non-adjacent regularities between consonants has been found to appear between 7 and 10 months. The present study focuses on the emergence of a posterior-anterior (PA) bias, a regularity involving two…

  13. Aromatic Anchor at an Invariant Hormone-Receptor Interface

    PubMed Central

    Pandyarajan, Vijay; Smith, Brian J.; Phillips, Nelson B.; Whittaker, Linda; Cox, Gabriella P.; Wickramasinghe, Nalinda; Menting, John G.; Wan, Zhu-li; Whittaker, Jonathan; Ismail-Beigi, Faramarz; Lawrence, Michael C.; Weiss, Michael A.

    2014-01-01

    Crystallographic studies of insulin bound to fragments of the insulin receptor have recently defined the topography of the primary hormone-receptor interface. Here, we have investigated the role of PheB24, an invariant aromatic anchor at this interface and site of a human mutation causing diabetes mellitus. An extensive set of B24 substitutions has been constructed and tested for effects on receptor binding. Although aromaticity has long been considered a key requirement at this position, MetB24 was found to confer essentially native affinity and bioactivity. Molecular modeling suggests that this linear side chain can serve as an alternative hydrophobic anchor at the hormone-receptor interface. These findings motivated further substitution of PheB24 by cyclohexanylalanine (Cha), which contains a nonplanar aliphatic ring. Contrary to expectations, [ChaB24]insulin likewise exhibited high activity. Furthermore, its resistance to fibrillation and the rapid rate of hexamer disassembly, properties of potential therapeutic advantage, were enhanced. The crystal structure of the ChaB24 analog, determined as an R6 zinc-stabilized hexamer at a resolution of 1.5 Å, closely resembles that of wild-type insulin. The nonplanar aliphatic ring exhibits two chair conformations with partial occupancies, each recapitulating the role of PheB24 at the dimer interface. Together, these studies have defined structural requirements of an anchor residue within the B24-binding pocket of the insulin receptor; similar molecular principles are likely to pertain to insulin-related growth factors. Our results highlight in particular the utility of nonaromatic side chains as probes of the B24 pocket and suggest that the nonstandard Cha side chain may have therapeutic utility. PMID:25305014

  14. Large Abundances of Polycyclic Aromatic Hydrocarbons in Titan's Upper Atmosphere

    NASA Technical Reports Server (NTRS)

    Lopez-Puertas, M.; Dinelli, B. M.; Adriani, A.; Funke, B.; Garcia-Comas, M.; Moriconi, M. L.; D'Aversa, E.; Boersma, C.; Allamandola, L. J.

    2013-01-01

    In this paper, we analyze the strong unidentified emission near 3.28 micron in Titan's upper daytime atmosphere recently discovered by Dinelli et al.We have studied it by using the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbons (PAHs), after absorbing UV solar radiation, are able to emit strongly near 3.3 micron. By using current models for the redistribution of the absorbed UV energy, we have explained the observed spectral feature and have derived the vertical distribution of PAH abundances in Titan's upper atmosphere. PAHs have been found to be present in large concentrations, about (2-3) × 10(exp 4) particles / cubic cm. The identified PAHs have 9-96 carbons, with a concentration-weighted average of 34 carbons. The mean mass is approx 430 u; the mean area is about 0.53 sq. nm; they are formed by 10-11 rings on average, and about one-third of them contain nitrogen atoms. Recently, benzene together with light aromatic species as well as small concentrations of heavy positive and negative ions have been detected in Titan's upper atmosphere. We suggest that the large concentrations of PAHs found here are the neutral counterpart of those positive and negative ions, which hence supports the theory that the origin of Titan main haze layer is located in the upper atmosphere.

  15. Are aromatic carbon donor hydrogen bonds linear in proteins?

    PubMed

    Nanda, Vikas; Schmiedekamp, Ann

    2008-02-01

    Proteins fold and maintain structure through the collective contributions of a large number of weak, noncovalent interactions. The hydrogen bond is one important category of forces that acts on very short distances. As our knowledge of protein structure continues to expand, we are beginning to appreciate the role that weak carbon-donor hydrogen bonds play in structure and function. One property that differentiates hydrogen bonds from other packing forces is propensity for forming a linear donor-hydrogen-acceptor orientation. To ascertain if carbon-donor hydrogen bonds are able to direct acceptor linearity, we surveyed the geometry of interactions specifically involving aromatic sidechain ring carbons in a data set of high resolution protein structures. We found that while donor-acceptor distances for most carbon donor hydrogen bonds were tighter than expected for van der Waals packing, only the carbons of histidine showed a significant bias for linear geometry. By categorizing histidines in the data set into charged and neutral sidechains, we found only the charged subset of histidines participated in linear interactions. B3LYP/6-31G**++ level optimizations of imidazole and indole-water interactions at various fixed angles demonstrates a clear orientation dependence of hydrogen bonding capacity for both charged and neutral sidechains. We suggest that while all aromatic carbons can participate in hydrogen bonding, only charged histidines are able to overcome protein packing forces and enforce linear interactions. The implications for protein modeling and design are discussed. PMID:17705268

  16. Alkyl polycyclic aromatic hydrocarbons emissions in diesel/biodiesel exhaust

    NASA Astrophysics Data System (ADS)

    Casal, Carina S.; Arbilla, Graciela; Corrêa, Sergio M.

    2014-10-01

    Polycyclic aromatic hydrocarbons (PAHs) are widely studied in environmental matrices, such as air, water, soil and sediment, because of their toxicity, mutagenicity and carcinogenicity. Because of these properties, the environmental agencies of developed countries have listed sixteen PAHs as priority pollutants. Few countries have limits for these compounds for ambient air, but they only limit emissions from stationary and mobile sources and occupational areas. There are several studies to specifically address the 16 priority PAHs and very little for the alkyl PAHs. These compounds are more abundant, more persistent and frequently more toxic than the non-alkylated PAHs, and the toxicity increases with the number of alkyl substitutions on the aromatic ring. In this study, a method was developed for the analysis of PAHs and alkyl PAHs by using a GC-MS and large injection volume injection coupled with program temperature vaporisation, which allows for limits of detection below 1.0 ng μL-1. Several variables were tested, such as the injection volume, injection velocity, injector initial temperature, duration of the solvent split and others. This method was evaluated in samples from particulate matter from the emissions of engines employing standard diesel, commercial diesel and biodiesel B20. Samples were collected on a dynamometer bench for a diesel engine cycle and the results ranged from 0.5 to 96.9 ng mL-1, indicating that diesel/biodiesel makes a significant contribution to the formation of PAHs and alkyl PAHs.

  17. A Nonaromatic thiophene-fused heptalene and its aromatic dianion.

    PubMed

    Oshima, Hiroya; Fukazawa, Aiko; Sasamori, Takahiro; Yamaguchi, Shigehiro

    2015-06-22

    Heptalene, a nonaromatic, bicyclic 12 π-electron system with a twisted structure, is of great interest with regard to its potential Hückel aromaticity in the two-electron oxidized or reduced forms. The synthesis of thiophene-fused heptalene 5 from the reductive transannular cyclization of bisdehydro[12]annulene 4, and its solid-state structure, which was confirmed by X-ray crystallographic analysis, is presented. Chemical reduction of 5 readily generated the corresponding dianion, which was successfully isolated as [(K[2.2.2]cryptand)(+) ]2 5(2-) . The X-ray crystallographic analysis of the dianion revealed a shallower saddle structure for the heptalene moiety and a lesser degree of bond alternation relative to 5. (1) H NMR spectroscopy exposed the effect of a diamagnetic ring current on dianion 5(2-) , which was corroborated by nucleus-independent chemical shift (NICS) calculations. These results demonstrate that the heptalene dianion, containing 14 π-electrons, does indeed exhibit pronounced degrees of Hückel aromaticity. PMID:25969146

  18. LARGE ABUNDANCES OF POLYCYCLIC AROMATIC HYDROCARBONS IN TITAN'S UPPER ATMOSPHERE

    SciTech Connect

    Lopez-Puertas, M.; Funke, B.; Garcia-Comas, M.; Dinelli, B. M.; Adriani, A.; D'Aversa, E.; Moriconi, M. L.; Boersma, C.; Allamandola, L. J.

    2013-06-20

    In this paper, we analyze the strong unidentified emission near 3.28 {mu}m in Titan's upper daytime atmosphere recently discovered by Dinelli et al. We have studied it by using the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbons (PAHs), after absorbing UV solar radiation, are able to emit strongly near 3.3 {mu}m. By using current models for the redistribution of the absorbed UV energy, we have explained the observed spectral feature and have derived the vertical distribution of PAH abundances in Titan's upper atmosphere. PAHs have been found to be present in large concentrations, about (2-3) Multiplication-Sign 10{sup 4} particles cm{sup -3}. The identified PAHs have 9-96 carbons, with a concentration-weighted average of 34 carbons. The mean mass is {approx}430 u; the mean area is about 0.53 nm{sup 2}; they are formed by 10-11 rings on average, and about one-third of them contain nitrogen atoms. Recently, benzene together with light aromatic species as well as small concentrations of heavy positive and negative ions have been detected in Titan's upper atmosphere. We suggest that the large concentrations of PAHs found here are the neutral counterpart of those positive and negative ions, which hence supports the theory that the origin of Titan main haze layer is located in the upper atmosphere.

  19. Theoretical studies of the structures and local aromaticity of conjugated polycyclic hydrocarbons using three aromatic indices

    NASA Astrophysics Data System (ADS)

    Sakai, Shogo; Kita, Yuki

    2013-07-01

    The structures and local aromaticity of some conjugated polycyclic hydrocarbons (from the butadienoid, acene, and phenylene series) are studied using ab initio MO and density functional methods. The aromaticities of the molecules are estimated using three indices: the nucleus-independent chemical shift (NICS), the harmonic oscillator model of aromaticity (HOMA), and the index of deviation from aromaticity (IDA). Assessment of the relationships between the structures and the aromatic indices shows that the IDA values correspond best to the characteristics of the conjugated polycyclic hydrocarbon structures.

  20. Bunching for shorter damping rings for the ILC

    SciTech Connect

    Neuffer, D.; /Fermilab

    2005-05-01

    A variant rearrangement of the bunch trains for the ILC that enables much shorter damping rings is presented. In a particular example the {approx}2820 bunches are regrouped into {approx}550 subtrains of five adjacent bunches. These subtrains are extracted from the damping rings at {approx}1.8 {micro}s intervals, obtaining the 1ms macrobunch length of the baseline TESLA collider scenario. If the baseline damping rf frequency is 325 MHz and the kicker rise and fall times are {approx}20 ns, a ring circumference of {approx}5.8km is required. Variations of the scheme could easily reduce the circumference to {approx}4km, and faster kickers could reduce it even further.

  1. Bunching for shorter damping rings for the ILC

    SciTech Connect

    Neuffer, David; /Fermilab

    2004-12-01

    A variant rearrangement of the bunch trains for the ILC that enables much shorter damping rings is presented. In a particular example the {approx}2280 bunches are regrouped into {approx}450 subtrains of five adjacent bunches. These subtrains are extracted from the damping rings at {approx}2.2 {micro}s intervals, obtaining the 1ms macrobunch length of the baseline TESLA collider scenario. If the baseline damping rf frequency is 325 MHz and the kicker rise and fall times are {approx}20 ns, a ring circumference of {approx}4.5km is required. Variations of the scheme could easily reduce the circumference to {approx}3km, and faster kickers could reduce it even further.

  2. Genetics Home Reference: aromatic l-amino acid decarboxylase deficiency

    MedlinePlus

    ... aromatic l-amino acid decarboxylase deficiency aromatic l-amino acid decarboxylase deficiency Enable Javascript to view the expand/ ... PDF Open All Close All Description Aromatic l-amino acid decarboxylase (AADC) deficiency is an inherited disorder that ...

  3. Reading, Writing, and Rings!

    ERIC Educational Resources Information Center

    Aschbacher, Pamela; Li, Erika; Hammon, Art

    2008-01-01

    "Reading, Writing, and Rings!" was created by a team of elementary teachers, literacy experts, and scientists in order to integrate science and literacy. These free units bring students inside NASA's Cassini-Huygens mission to Saturn. The authors--a science teacher and education outreach specialist and two evaluators of educational programs--have…

  4. Field reversed ion rings

    SciTech Connect

    Sudan, R.N.; Omelchenko, Y.A.

    1995-09-01

    In typical field-reversed ion ring experiments, an intense annular ion beam is injected across a plasma-filled magnetic cusp region into a neutral gas immersed in a ramped solenoidal magnetic field. Assuming the characteristic ionization time is much shorter than the long ({ital t}{approx_gt}2{pi}/{Omega}{sub {ital i}}) beam evolution time scale, we investigate the formation of an ion ring in the background plasma followed by field reversal, using a 21/2-D hybrid, PIC code FIRE, in which the beam and background ions are treated as particles and the electrons as a massless fluid. We show that beam bunching and trapping occurs downstream in a ramped magnetic field for an appropriate set of experimental parameters. We find that a compact ion ring is formed and a large field reversal {zeta}={delta}{ital B}/{ital B}{approx_gt}1 on axis develops. We also observe significant deceleration of the ring on reflection due to the transfer of its axial momentum to the background ions, which creates favorable trapping conditions. {copyright} {ital 1995 American Institute of Physics.}

  5. Models of planetary rings

    NASA Technical Reports Server (NTRS)

    Esposito, L. W.; Brophy, T. G.; Stewart, Glen R.; Yanamandra-Fisher, P. A.

    1991-01-01

    The Voyager occultations provide several uniform and high quality data sets for Saturn, Uranus, and Neptune. These data are intercompared, and theoretical models for the particle sizes and the particle transport are developed. The major topics covered include: ring size distribution, torques and resonances, and satellite wakes.

  6. Tool Support Ring

    NASA Technical Reports Server (NTRS)

    Smith, D. F.

    1984-01-01

    Tool support ring requires only single repositioning to give broaching tool access to series of 66 holes located on circle. Permits use of tools designed for hand-held use (such as electric drill) where less portable setup (such as milling machine) otherwise required.

  7. Flushing Ring for EDM

    NASA Technical Reports Server (NTRS)

    Earwood, L.

    1985-01-01

    Removing debris more quickly lowers cutting time. Operation, cutting oil and pressurized air supplied to ring placed around workpiece. Air forces oil through small holes and agitates oil as it flows over workpiece. High flow rate and agitation dislodge and remove debris. Electrical discharge removes material from workpiece faster.

  8. Ring of Stellar Death

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This false-color image from NASA's Spitzer Space Telescope shows a dying star (center) surrounded by a cloud of glowing gas and dust. Thanks to Spitzer's dust-piercing infrared eyes, the new image also highlights a never-before-seen feature -- a giant ring of material (red) slightly offset from the cloud's core. This clumpy ring consists of material that was expelled from the aging star.

    The star and its cloud halo constitute a 'planetary nebula' called NGC 246. When a star like our own Sun begins to run out of fuel, its core shrinks and heats up, boiling off the star's outer layers. Leftover material shoots outward, expanding in shells around the star. This ejected material is then bombarded with ultraviolet light from the central star's fiery surface, producing huge, glowing clouds -- planetary nebulas -- that look like giant jellyfish in space.

    In this image, the expelled gases appear green, and the ring of expelled material appears red. Astronomers believe the ring is likely made of hydrogen molecules that were ejected from the star in the form of atoms, then cooled to make hydrogen pairs. The new data will help explain how planetary nebulas take shape, and how they nourish future generations of stars.

    This image composite was taken on Dec. 6, 2003, by Spitzer's infrared array camera, and is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

  9. Ring laser scatterometer

    DOEpatents

    Ackermann, Mark; Diels, Jean-Claude

    2005-06-28

    A scatterometer utilizes the dead zone resulting from lockup caused by scatter from a sample located in the optical path of a ring laser at a location where counter-rotating pulses cross. The frequency of one pulse relative to the other is varied across the lockup dead zone.

  10. Exotic damping ring lattices

    SciTech Connect

    Palmer, R.B.

    1987-05-01

    This paper looks at, and compares three types of damping ring lattices: conventional, wiggler lattice with finite ..cap alpha.., wiggler lattice with ..cap alpha.. = 0, and observes the attainable equilibrium emittances for the three cases assuming a constraint on the attainable longitudinal impedance of 0.2 ohms. The emittance obtained are roughly in the ratio 4:2:1 for these cases.

  11. Making Molecular Borromean Rings

    ERIC Educational Resources Information Center

    Pentecost, Cari D.; Tangchaivang, Nichol; Cantrill, Stuart J.; Chichak, Kelly S.; Peters, Andrea J.; Stoddart, Fraser J.

    2007-01-01

    A procedure that requires seven 4-hour blocks of time to allow undergraduate students to prepare the molecular Borromean rings (BRs) on a gram-scale in 90% yield is described. The experiment would serve as a nice capstone project to culminate any comprehensive organic laboratory course and expose students to fundamental concepts, symmetry point…

  12. Ring species as demonstrations of the continuum of species formation.

    PubMed

    Pereira, Ricardo J; Wake, David B

    2015-11-01

    In the mid-20th century, Ernst Mayr (1942) and Theodosius Dobzhansky (1958) championed the significance of 'circular overlaps' or 'ring species' as the perfect demonstration of the gradual nature of species formation. As an ancestral species expands its range, wrapping around a geographic barrier, derived taxa within the ring display interactions typical of populations, such as genetic and morphological intergradation, while overlapping taxa at the terminus of the ring behave largely as sympatric, reproductively isolated species. Are ring species extremely rare or are they just difficult to detect? What conditions favour their formation? Modelling studies have attempted to address these knowledge gaps by estimating the biological parameters that result in stable ring species (Martins et al. 2013), and determining the necessary topographic parameters of the barriers encircled (Monahan et al. 2012). However, any generalization is undermined by a major limitation: only a handful of ring species are known to exist in nature. In addition, many of them have been broken into multiple species presumed to be evolving independently, usually obscuring the evolutionary dynamics that generate diversity. A paper in this issue of Molecular Ecology by Fuchs et al. (2015), focused on the entire genealogy of a bulbul (Alophoixus) species complex, offers key insights into the evolutionary processes underlying diversification of this Indo-Malayan bird. Their findings fulfil most of the criteria that can be expected for ring species (Fig. ): an ancestor has colonized the mainland from Sundaland, expanded along the forested habitat wrapping around Thailand's lowlands, adjacent taxa intergrade around the ring distribution, and terminal taxa overlap at the ring closure. Although it remains unclear whether ring divergence has resulted in restrictive gene flow relative to that observed around the ring, their results suggest that circular overlaps might be more common in nature than

  13. Beyond organic chemistry: aromaticity in atomic clusters.

    PubMed

    Boldyrev, Alexander I; Wang, Lai-Sheng

    2016-04-28

    We describe joint experimental and theoretical studies carried out collaboratively in the authors' labs for understanding the structures and chemical bonding of novel atomic clusters, which exhibit aromaticity. The concept of aromaticity was first discovered to be useful in understanding the square-planar unit of Al4 in a series of MAl4(-) bimetallic clusters that led to discoveries of aromaticity in many metal cluster systems, including transition metals and similar cluster motifs in solid compounds. The concept of aromaticity has been found to be particularly powerful in understanding the stability and bonding in planar boron clusters, many of which have been shown to be analogous to polycyclic aromatic hydrocarbons in their π bonding. Stimulated by the multiple aromaticity in planar boron clusters, a design principle has been proposed for stable metal-cerntered aromatic molecular wheels of the general formula, M@Bn(k-). A series of such borometallic aromatic wheel complexes have been produced in supersonic cluster beams and characterized experimentally and theoretically, including Ta@B10(-) and Nb@B10(-), which exhibit the highest coordination number in two dimensions. PMID:26864511

  14. Reaction mechanisms in aromatic hydrocarbon formation involving the C{sub 5}H{sub 5} cyclopentadienyl moiety

    SciTech Connect

    Melius, C.F.; Colvin, M.E.; Marinov, N.M.; Pitz, W.J.; Senkan, S.M.

    1996-02-01

    The quantum chemical BAC-MP4 and BAC-MP2 methods have been used to investigate the reaction mechanisms leading to polycyclic aromatic hydrocarbon (PAH) ring formation. In particular the authors have determined the elementary reaction steps in the conversion of two cyclopentadienyl radicals to naphthalene. This reaction mechanism is shown to be an extension of the mechanism occurring in the H atom-assisted conversion of fulvene to benzene. The net reaction involves the formation of dihydrofulvalene, which eliminates a hydrogen atom and then rearranges to form naphthalene through a series of ring closures and openings. The importance of forming the {single_bond}CR({center_dot}){single_bond}CHR{single_bond}CR{prime}{double_bond}CR{double_prime}-moiety, which can undergo rearrangement to form three-carbon-atom ring structures, is illustrated with the C{sub 4}H{sub 7} system. The ability of hydrogen atoms to migrate around the cyclopentadienyl moiety is illustrated both for methyl-cyclopentadiene, C{sub 5}H{sub 5}CH{sub 3}, and dihydrofulvalene, C{sub 5}H{sub 5}C{sub 5}H{sub 5}, as well as for their radical species, C{sub 6}H{sub 7} and C{sub 5}H{sub 5}C{sub 5}H{sub 4}. The mobility of hydrogen in the cyclopentadienyl moiety plays an important role both in providing resonance-stabilized radical products and in creating the {single_bond}CR({center_dot}){single_bond}CHR{single_bond}CR{prime}{double_bond}CR{double_prime}-moiety for ring formation. The results illustrate the radical pathway for converting five-membered rings to aromatic six-membered rings. Furthermore, the results indicate the important catalytic role of H atoms in the aromatic ring formation process.

  15. Aromatic Difluoroboron β-Diketonate Complexes: Effects of π-Conjugation and Media on Optical Properties

    PubMed Central

    Xu, Songpan; Evans, Ruffin E.; Liu, Tiandong; Zhang, Guoqing; Demas, J. N.; Trindle, Carl O.; Fraser, Cassandra L.

    2013-01-01

    Aromatic difluoroboron β-diketonate complexes (BF2bdks) are classic fluorescent molecules that have been explored as photochemical reagents, two-photon dyes, and oxygen sensors. To gain a better understanding of their emissive properties in both solution and polymer matrices, BF2bdks with varying aromatic groups were synthesized and their photophysical properties were investigated in both methylene chloride and poly(lactic acid) (PLA). Absorption spectra showed systematic variations that are well correlated with structural features, including the size of the aryl substituent and the presence of a para electron donating methoxy substituent. Computational modeling of the absorption spectra with the TD-B3LYP/6-311+G(d)//B3LYP/6-31G(d) formulation of density functional theory and a polarizable continuum model of dichloromethane solvent shows that all systems show intense π–π* one-electron excitations, usually from one of the highest occupied MOs (HOMO-k, k=0, 1, 2) to the lowest unoccupied MO (LUMO). Emission properties are sensitive to the dye structure and medium. Based on spectroscopic and lifetime studies, BF2bdks exhibit comparable fluorescence properties in both solutions and polymers when the diketonate group is functionalized with smaller aromatic ring systems such as benzene. For BF2bdks with larger arene ring systems, such as anthracene, emission from a strong intramolecular charge-transfer (ICT) state was also noted in both solution and in PLA. There are differences in relative intensities of peaks arising from π-π* and ICT excitations depending upon dye loading in PLA. Substituent effects were also observed. Electron-donating methoxyl groups on the aromatic rings lead to enhanced fluorescence quantum yields. For certain dyes, phosphorescence is detected at low temperature or under a nitrogen atmosphere in PLA matrices. PMID:23510181

  16. Do tree ring chronologies have missing rings that distort volcanic cooling signal?: Tree ring records not distorted by missing rings

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2013-09-01

    Tree ring records are often used as a proxy for past climate. Trees form a new growth ring each year, and ring widths are related to temperature and other conditions at cold sites. Some recent studies have noted that tree ring width chronologies and resulting climate reconstructions do not appear to show the widespread cooling in the past millennium that would be expected following large volcanic eruptions. One hypothesis suggests that regional cooling after a volcanic eruption could be so severe that many trees do not form a ring at all, which leads researchers to misdate the tree ring chronology.

  17. A DFT study on dihydropyrazine annulated linear polyacenes: aromaticity, stability and HOMO-LUMO energy modulation.

    PubMed

    Rakhi, Ramachandran; Suresh, Cherumuttathu H

    2016-09-21

    Linear polyacenes (LPAs) beyond pentacene are highly unstable and their application potential in the optoelectronics field is very limited. On the basis of theoretical studies at the M06L/6-311++G(d,p) level of DFT, we show that annulating dihydropyrazine units to LPA cores can yield large LPA mimics. This strategy enhances the aromaticity of the LPA core and also provides a way to modulate the HOMO-LUMO energy gap by choosing an appropriate LPA core and extending dihydropyrazine annulation. The study is conducted for LPA mimics containing up to six dihydropyrazine units annulated to benzene (pB1-pB6), naphthalene (pN1-pN6), anthracene (pA1-pA6) and tetracene (pT1-pT6) cores. The longest of them pT6 contains 34 linearly connected six-membered rings. The dehydrogenation energy (Edh) of the N-heterocycles of the LPA mimics showed endothermic character and indicated their higher stability than dehydrogenated N-heteroacenes. The total Edh (ΣEdh) is proportional to the increase in the number of heterocycles and the increase in the size of the LPA core. The aromaticity of individual rings of all the LPA mimics is assessed on the basis of the harmonic oscillator model of aromaticity (HOMA) and nucleus independent chemical shift (NICS) parameters. Both parameters showed strong linear correlation with ΣEdh, confirming the geometric, magnetic and energetic criteria of aromaticity. The electronic features of the LPA mimics assessed by analysing molecular electrostatic potential topography and molecular orbitals have shown that the LPA cores retain the reactivity of the parent LPA. Furthermore, significant mixing of the N-lone pairs of the heterocycle with carbon π-orbitals improves aromaticity and decreases the HOMO-LUMO energy gap. PMID:27546099

  18. Ring Bubbles of Dolphins

    NASA Technical Reports Server (NTRS)

    Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since

  19. Rings from Close Encounters

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-09-01

    Weve recently discovered narrow sets of rings around two minor planets orbiting in our solar system. How did these rings form? A new study shows that they could be a result of close encounters between the minor planets and giants like Jupiter or Neptune.Unexpected Ring SystemsPositions of the centaurs in our solar system (green). Giant planets (red), Jupiter trojans (grey), scattered disk objects (tan) and Kuiper belt objects (blue) are also shown. [WilyD]Centaurs are minor planets in our solar system that orbit between Jupiter and Neptune. These bodies of which there are roughly 44,000 with diameters larger than 1 km have dynamically unstable orbits that cross paths with those of one or more giant planets.Recent occultation observations of two centaurs, 10199 Chariklo and 2060 Chiron, revealed that these bodies both host narrow ring systems. Besides our four giant planets, Chariklo and Chiron are the only other bodies in the solar system known to have rings. But how did these rings form?Scientists have proposed several models, implicating collisions, disruption of a primordial satellite, or dusty outgassing. But a team of scientists led by Ryuki Hyodo (Paris Institute of Earth Physics, Kobe University) has recently proposed an alternative scenario: what if the rings were formed from partial disruption of the centaur itself, after it crossed just a little too close to a giant planet?Tidal Forces from a GiantHyodo and collaborators first used past studies of centaur orbits to estimate that roughly 10% of centaurs experience close encounters (passing within a distance of ~2x the planetary radius) with a giant planet during their million-year lifetime. The team then performed a series of simulations of close encounters between a giant planet and a differentiated centaur a body in which the rocky material has sunk to form a dense silicate core, surrounded by an icy mantle.Some snapshots of simulation outcomes (click for a closer look!) for different initial states of

  20. Saturn's Rings, the Yarkovsky Effects, and the Ring of Fire

    NASA Technical Reports Server (NTRS)

    Rubincam, David

    2004-01-01

    Saturn's icy ring particles, with their low thermal conductivity, are almost ideal for the operation of the Yarkovsky effects. The dimensions of Saturn's A and B rings may be determined by a near balancing of the seasonal Yarkovsky effect with the Yarkovsky- Schach effect. The two effects, which are photon thrust due to temperature gradients, may confine the A and B rings to within their observed dimensions. The C ring may be sparsely populated with icy particles because Yarkovsky drag has pulled them into Saturn, leaving the more slowly orbitally decaying rocky particles. Icy ring particles ejected from the B ring and passing through the C ring, as well as some of the slower rocky particles, should fall on Saturn's equator, where they may create a luminous "Ring of Fire" around Saturn's equator. This predicted Ring of Fire may be visible to Cassini's camera. Curiously, the speed of outwards Yarkovsky orbital evolution appears to peak near the Cassini Division. The connection between the two is not clear. D. Nesvorny has speculated that the resonance at the outer edge of the B ring may impede particles from evolving via Yarkovsky across the Division. If supply from the B ring is largely cut off, then Yarkovsky may push icy particles outward, away from the inner edge of the A ring, leaving only the rocky ones in the Division. The above scenarios depend delicately on the properties of the icy particles.

  1. Understanding crystallinity in aromatic polyimides

    NASA Technical Reports Server (NTRS)

    Celarier, Edward A.

    1992-01-01

    Aromatic polyimides are a class of polymers that show remarkable thermal stability, strength, and toughness. These properties make them attractive candidates for use in high-performance carbon fiber composites for airborne and spaceborne structural components. Our research centered on the development of an understanding of the underlying process of crystallite formation in a particular class of aryl polyimides for which there are some x-ray crystallographic data available. The ultimate aim of the project is to be able to develop a model sufficiently flexible to be able, on the basis of the chemical structure of a polymer in this class, to predict: (1) whether it will be prone to form crystallites; (2) crystallographic features of the crystallites; and (3) synthesis and/or processing conditions that will be favorable or unfavorable to crystallite formation. This will provide guidance to the laboratory chemists in their choice of candidate polymers and processing methods.

  2. Tough soluble aromatic thermoplastic copolyimides

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G. (Inventor)

    2000-01-01

    Tough, soluble, aromatic, thermoplastic copolyimides were prepared by reacting 4,4'-oxydiphthalic anhydride, 3,4,3',4'-biphenyltetracarboxylic dianhydride and 3,4'-oxydianiline. Alternatively, these copolyimides may be prepared by reacting 4,4'-oxydiphthalic anhydride with 3,4,3',4'-biphenyltetracarboxylic dianhydride and 3,4'-oxydiisocyanate. Also, the copolyimide may be prepared by reacting the corresponding tetra acid and ester precursors of 4,4'-oxydiphthalic anhydride and 3,4,3',4'-biphenyltetracarboxylic dianhydride with 3,4'-oxydianiline. These copolyimides were found to be soluble in common amide solvents such as N,N'-dimethyl acetamide, N-methylpyrrolidinone, and dimethylformamide allowing them to be applied as the fully imidized copolymer and to be used to prepare a wide range of articles.

  3. Alkylation of organic aromatic compounds

    DOEpatents

    Smith, L.A. Jr.; Arganbright, R.P.; Hearn, D.

    1993-01-05

    Aromatic compounds are alkylated in a combination reactor/distillation column comprising a vessel suitable for operating between 70 C and 500 C and from 0.5 to 20 atmospheres pressure; an inert distillation packing in the lower one-third of said vessel; solid acidic catalytic material such as zeolites or an acidic cation exchange resin supported in the middle one-third of said vessel; and inert distillation packing in the upper one-third of said vessel. A benzene inlet is located near the upper end of the vessel; an olefin inlet is juxtaposed with said solid acidic catalytic material; a bottoms outlet is positioned near the bottom of said vessel for removing said cumene and ethyl benzene; and an overhead outlet is placed at the top of said vessel for removing any unreacted benzene and olefin.

  4. Alkylation of organic aromatic compounds

    DOEpatents

    Smith, Jr., Lawrence A.; Arganbright, Robert P.; Hearn, Dennis

    1993-01-01

    Aromatic compounds are alkylated in a combination reactor/distillation column comprising a vessel suitable for operating between 70.degree. C. and 500.degree. C. and from 0.5 to 20 atmospheres pressure; an inert distillation packing in the lower one-third of said vessel; solid acidic catalytic material such as zeolites or an acidic cation exchange resin supported in the middle one-third of said vessel; and inert distillation packing in the upper one-third of said vessel. A benzene inlet is located near the upper end of the vessel; an olefin inlet is juxtaposed with said solid acidic catalytic material; a bottoms outlet is positioned near the bottom of said vessel for removing said cumene and ethyl benzene; and an overhead outlet is placed at the top of said vessel for removing any unreacted benzene and olefin.

  5. Synthesis of perfluoroalkylene aromatic diamines

    NASA Technical Reports Server (NTRS)

    Paciorek, K. L.; Ito, T. I.; Nakahara, J. H.; Kratzer, R. H.

    1978-01-01

    Analogues of methylene dianilines were synthesized, in which the methylene group between the two aromatic nuclei was replaced by various perfluoroalkylene linkage. The hydrolytic thermal, and thermal oxidative stabilities of PMR Polyimides derived from these diamines were determined. Three types of PMR Polyimide discs were fabricated from the dimethyl ester of 3,3', 4,4'-benzophenonetetracarboxylic acid, the methyl ester of 5-norbornene-2,3-dicarboxylic acid, and one of the following three diamines: methyl dianiline, 1,3-bis(4-aminophenyl)hexafluoropropane, and 2,2-bis(4-aminophenyl)hexafluoropropane. The polyimide based on 2,2-bis(4-aminophenyl)hexafluoropropane exhibited the best hydrolytic, thermal, and thermal oxidative stability as determined by moisture uptake and thermogravimetric analysis.

  6. PRACTICAL SYNTHESIS OF AROMATIC DITHIOCARBAMATES

    PubMed Central

    Padungros, Panuwat; Wei, Alexander

    2015-01-01

    GRAPHICAL ABSTRACT Oxidation-sensitive N,N-diaryl dithiocarbamates (DTCs) are synthesized in good yields by the generation of metal amide salts from N-benzoyl precursors, followed by addition of CS2. para-Substituted diphenylamines are prepared by electrophilic aromatic substitution of diphenylbenzamide and saponification. Deacylation of electron-rich species such as bis(p-dimethylaminophenyl)benzamide is challenging because of the oxidative sensitivity of the anionic intermediate but could be achieved in good yield by using n-BuLi to generate a hemiaminal adduct, prior to acidification. The N,N-diaryl DTCs are stable as alkali salts and can be used to produce densely packed monolayers on gold surfaces. PMID:25999616

  7. Planetary rings: Structure and history

    NASA Astrophysics Data System (ADS)

    Esposito, L.

    The composition and structure of planetary rings provide the key evidence to understand their origin and evolution. Before the first space observations, we were able to maintain an idealized view of the rings around Saturn, the only known ring system at that time. Rings were then discovered around Jupiter, Uranus and Neptune. Saturn's F ring was discovered by Pioneer 11. Our ideal view of circular, planar, symmetric and unchanging rings was shattered by observations of inclined, eccentric rings, waves and wavy edges, and numerous processes acting at rates that give timescales much younger than the solar system. Moons within and near the rings sculpt them and are the likely progenitors of future rings. The moonlet lifetimes are much less than Saturn's age. The old idea of ancient rings gave rise to youthful rings, that are recently created by erosion and destruction of small nearby moons. Although this explanation may work well for most rings, Saturn's massive ring system provides a problem. It is extremely improbable that Saturn's rings were recently created by the destruction of a moon as large as Mimas, or even by the breakup of a large comet that passed too close to Saturn. The history of Saturn's rings has been a difficult problem, now made even more challenging by the close-up Cassini measurements. Cassini observations show unexpected ring variability in time and space. Time variations are seen in ring edges, in the thinner D and F rings, and in the neutral oxygen cloud, which outweighs the E ring in the same region around Saturn. The rings are inhomogeneous, with structures on all scales, sharp gradients and edges. Compositional gradients are sharper than expected, but nonetheless cross structural boundaries. This is evidence for ballistic transport that has not gone to completion. The autocovariance maximizes in the middle of the A ring, with smaller structure near the main rings' outer edge. Density wave locations have a fresher ice composition. The

  8. Connector contact-ring bus

    NASA Technical Reports Server (NTRS)

    Ligon, J.

    1976-01-01

    Use of device eliminates crimp connectors and ferrules, resulting in compact termination assembly and efficient use of back-shell space. Pair of insulator rings, one at each end of assembly, provides spacing between disc caps and contact rings.

  9. Inorganic glass ceramic slip rings

    NASA Technical Reports Server (NTRS)

    Glossbrenner, E. W.; Cole, S. R.

    1972-01-01

    Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours.

  10. Pumping iron to keep fit: modulation of siderophore secretion helps efficient aromatic utilization in Pseudomonas putida KT2440.

    PubMed

    Joshi, Hiren; Dave, Rachna; Venugopalan, V P

    2014-07-01

    Studies of biotechnology applications of Pseudomonas putida KT2440 have been predominantly focused on regulation and expression of the toluene degradation (TOL) pathway. Unfortunately, there is limited information on the role of other physiological factors influencing aromatic utilization. In this report, we demonstrate that P. putida KT2440 increases its siderophore secretion in response to the availability of benzyl alcohol, a model aromatic substrate. It is argued that accelerated siderophore secretion in response to aromatic substrates provides an iron 'boost' which is required for the effective functioning of the iron-dependent oxygenases responsible for ring opening. Direct evidence for the cardinal role of siderophores in aromatic utilization is provided by evaluation of per capita siderophore secretion and comparative growth assessments of wild-type and siderophore-negative mutant strains grown on an alternative carbon source. Accelerated siderophore secretion can be viewed as a compensatory mechanism in P. putida in the context of its inability to secrete more than one type of siderophore (pyoverdine) or to utilize heterologous siderophores. Stimulated siderophore secretion might be a key factor in successful integration and proliferation of this organism as a bio-augmentation agent for aromatic degradation. It not only facilitates efficient aromatic utilization, but also provides better opportunities for iron assimilation amongst diverse microbial communities, thereby ensuring better survival and proliferation. PMID:24742959

  11. Thermoelastic response of thin metal films and their adjacent materials

    SciTech Connect

    Kang, S.; Yoon, Y.; Kim, J.; Kim, W.

    2013-01-14

    A pulsed laser beam applied to a thin metal film is capable of launching an acoustic wave due to thermal expansion. Heat transfer from the thin metal film to adjacent materials can also induce thermal expansion; thus, the properties of these adjacent materials (as well as the thin metal film) should be considered for a complete description of the thermoelastic response. Here, we show that adjacent materials with a small specific heat and large thermal expansion coefficient can generate an enhanced acoustic wave and we demonstrate a three-fold increase in the peak pressure of the generated acoustic wave on substitution of parylene for polydimethylsiloxane.

  12. A ring galaxy in Canes Venatici and related ring galaxies

    SciTech Connect

    Wakamatsu, Ken-ichi; Nishida, M.T. Kobe Women's University )

    1991-04-01

    A spectroscopic observation was made of a ring-shaped object in Canes Venatici. A bright knot at the edge of the ring has a recession velocity of 10,960 + or - 30 km/s and so is confirmed as an extragalactic object. It shows no sign of nuclear activity but appears to be an H II region of intermediate excitation class. The linear diameter of the ring is 14.2 + or - 0.8 kpc, a typical size for ring galaxies. Recession velocities of several other ring galaxies are also given. 24 refs.

  13. Magnetic response properties of gaudiene - a cavernous and aromatic carbocage.

    PubMed

    Rauhalahti, M; Muñoz-Castro, A; Sundholm, D

    2016-07-28

    A spherical and cavernous carbocage molecule exhibiting faces with larger ring sizes than regular fullerenes is a suitable species for investigating how molecular magnetic properties depend on the structure of the molecular framework. The studied all-carbon gaudiene (C72) is a highly symmetrical molecule with three- and four-fold faces formed by twelve membered rings. Here, we attempt to unravel the magnetic response properties of C72 by performing magnetic shielding and current density calculations with the external magnetic field applied in different directions. The obtained results indicate that the induced current density flows mainly along the chemical bonds that are largely perpendicular to the magnetic field direction. However, the overall current strength for different directions of the magnetic field is nearly isotropic differing by only 10% indicating that C72 can to some extent be considered to be a spherical aromatic molecule, whose current density and magnetic shielding are ideally completely isotropic. The induced magnetic field is found to exhibit long-range shielding cones in the field direction with a small deshielding region located perpendicularly to the field outside the molecule. The magnetic shielding is isotropic inside the molecular framework of C72, whereas an orientation-dependent magnetic response appears mainly at the exterior of the molecular cage. PMID:27352814

  14. Uranus: the rings are black.

    PubMed

    Sinton, W M

    1977-11-01

    An upper limit of 0.05 is established for the geometric albedo of the newly discovered rings of Uranus. In view of this very low albedo, the particles of the rings cannot be ice-covered as are those of rings A and B of Saturn. PMID:17842136

  15. Electrostatic forces in planetary rings

    NASA Technical Reports Server (NTRS)

    Goertz, C. K.; Shan, Linhua; Havnes, O.

    1988-01-01

    The average charge on a particle in a particle-plasma cloud, the plasma potential inside the cloud, and the Coulomb force acting on the particle are calculated. The net repulsive electrostatic force on a particle depends on the plasma density, temperature, density of particles, particle size, and the gradient of the particle density. In a uniformly dense ring the electrostatic repulsion is zero. It is also shown that the electrostatic force acts like a pressure force, that even a collisionless ring can be stable against gravitational collapse, and that a finite ring thickness does not necessarily imply a finite velocity dispersion. A simple criterion for the importance of electrostatic forces in planetary rings is derived which involves the calculation of the vertical ring thickness which would result if only electrostatic repulsion were responsible for the finite ring thickness. Electrostatic forces are entirely negligible in the main rings of Saturn and the E and G rings. They may also be negligible in the F ring. However, the Uranian rings and Jupiter's ring seem to be very much influenced by electrostatic repulsion. In fact, electrostatic forces could support a Jovian ring which is an order of magnitude more dense than observed.

  16. DC-Powered Jumping Ring

    ERIC Educational Resources Information Center

    Jeffery, Rondo N.; Farhang, Amiri

    2016-01-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant…

  17. Ringed Accretion Disks: Equilibrium Configurations

    NASA Astrophysics Data System (ADS)

    Pugliese, D.; Stuchlík, Z.

    2015-12-01

    We investigate a model of a ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the general relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can then be determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both corotating and counterrotating rings have to be considered as being a constituent of the ringed disk. We provide constraints on the model parameters for the existence and stability of various ringed configurations and discuss occurrence of accretion onto the Kerr black hole and possible launching of jets from the ringed disk. We demonstrate that various ringed disks can be characterized by a maximum number of rings. We present also a perturbation analysis based on evolution of the oscillating components of the ringed disk. The dynamics of the unstable phases of the ringed disk evolution seems to be promising in relation to high-energy phenomena demonstrated in active galactic nuclei.

  18. PAH and H2 emission in the Ring Nebula

    NASA Astrophysics Data System (ADS)

    Cox, N. L. J.; Pilleri, P.; Berné, O.; Cernicharo, J.; Joblin, C.

    2016-07-01

    This paper presents the Spitzer IRS (Infra Red Spectrograph) detection of mid-infrared polycyclic aromatic hydrocarbon (PAH) emission features and H2 associated with dense knots in the ring of the “oxygen-rich” (C/O∼⃒0.6-0.8) planetary nebula (PN) NGC6720 (Ring Nebula). We explored a further three oxygen-rich extended PNe with similar dataset available. These turned out to be non-detection of PAHs, although two of these do contain H2 emission knots. The presence of PAHs is discussed in the context of a bottom-up formation mechanism, in which first small hydrocarbons, and later PAHs, are formed in warm dense knots inside the ionised regions of PNe.

  19. Saturn Ring Observer

    NASA Technical Reports Server (NTRS)

    Spilker, T. R.

    2001-01-01

    Answering fundamental questions about ring particle characteristics, and individual and group behavior, appears to require close-proximity (a few km) observations. Saturn's magnificent example of a ring system offers a full range of particle sizes, densities, and behaviors for study, so it is a natural choice for such detailed investigation. Missions implementing these observations require post-approach Delta(V) of approximately 10 km/s or more, so past mission concepts called upon Nuclear Electric Propulsion. The concept described here reduces the propulsive Delta(V) requirement to as little as 3.5 km/s, difficult but not impossible for high-performance chemical propulsion systems. Additional information is contained in the original extended abstract.

  20. Satellite Rings Movie

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This brief movie clip (of which the release image is a still frame), taken by NASA's Cassini spacecraft as it approached Jupiter, shows the motions, over a 16 hour-period, of two satellites embedded in Jupiter's ring. The moon Adrastea is the fainter of the two, and Metis the brighter. Images such as these will be used to refine the orbits of the two bodies.

    The movie was made from images taken during a 40-hour sequence of the Jovian ring on December 11, 2000.

    Cassini is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages Cassini for NASA's Office of Space Science, Washington, D.C.

  1. Polycyclic Aromatic Aerosol Components: Chemical Analysis and Reactivity

    NASA Astrophysics Data System (ADS)

    Schauer, C.; Niessner, R.; Pöschl, U.

    Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants in the atmosphere and originate primarily from incomplete combustion of organic matter and fossil fuels. Their main sources are anthropogenic (e.g. vehicle emissions, domes- tic heating or tobacco smoke), and PAHs consisting of more than four fused aromatic rings reside mostly on combustion aerosol particles, where they can react with atmo- spheric trace gases like O3, NOx or OH radicals leading to a wide variety of partially oxidized and nitrated derivatives. Such chemical transformations can strongly affect the activity of the aerosol particles as condensation nuclei, their atmospheric residence times, and consequently their direct and indirect climatic effects. Moreover some poly- cyclic aromatic compounds (PACs = PAHs + derivatives) are known to have a high carcinogenic, mutagenic and allergenic potential, and are thus of major importance in air pollution control. Furthermore PACs can be used as well defined soot model sub- stances, since the basic structure of soot can be regarded as an agglomerate of highly polymerized PAC-layers. For the chemical analysis of polycyclic aromatic aerosol components a new analyti- cal method based on LC-APCI-MS has been developed, and a data base comprising PAHs, Oxy-PAHs and Nitro-PAHs has been established. Together with a GC-HRMS method it will be applied to identify and quantify PAHs and Nitro-PAHs in atmo- spheric aerosol samples, diesel exhaust particle samples and model soot samples from laboratory reaction kinetics and product studies. As reported before, the adsorption and surface reaction rate of ozone on soot and PAH-like particle surfaces is reduced by competitive adsorption of water vapor at low relative humidity (< 25 %). Recent results at higher relative humidities (ca. 50 %), however, indicate re-enhanced gas phase ozone loss, which may be due to absorbtion of ozone into an aqueous surface layer. The interaction of ozone and nitrogen

  2. Translation of an aromatic field image

    NASA Astrophysics Data System (ADS)

    Yastrebov, Anatoliy S.; Makarov, Leonid M.; Protasenya, Sergey V.; Vereshak, Evgeniy V.

    2005-04-01

    As is known, for a person there are possibilities of perception of audio, video, and aromatic information messages by means of touch systems available to him. Such packages of the messages are accepted remotely without direct contact to a message source. Now the direction bound with creation of devices capable to playback aromatic information images is actively developed. Such systems switched on in special transmission channels of information provide adequate perception of information highways describing actual event which happen in the enclosing world. One can present the aromatic-field image through a series of control codes for an aromatic field synthesizer, thereupon it is possible to transmit the image on telecommunication networks. For odor oscillators installation problems in compartments of automobiles, buses as well as of airplanes are widely discussed. In this work we deal with a device for synthesis of an image of an aromatic field which works under the control of a personal computer with an express program. In the given operation, the possibility of remote handle of an image of an aromatic field and, as a corollary, organization of a new tansmission channel for the information on the aromatic-field image through an existing synthesizer is considered.

  3. Polycyclic aromatic hydrocarbon (PAH) formation from benzyl radicals: a reaction kinetics study.

    PubMed

    Sinha, Sourab; Raj, Abhijeet

    2016-03-01

    The role of resonantly stabilized radicals such as propargyl, cyclopentadienyl and benzyl in the formation of aromatic hydrocarbons such as benzene and naphthalene in the high temperature environments has been long known. In this work, the possibility of benzyl recombination to form three-ring aromatics, phenanthrene and anthracene, is explored. A reaction mechanism for it is developed, where reaction energetics are calculated using density functional theory (B3LYP functional with 6-311++G(d,p) basis set) and CBS-QB3, while temperature-dependent reaction kinetics are evaluated using transition state theory. The mechanism begins with barrierless formation of bibenzyl from two benzyl radicals with the release of 283.2 kJ mol(-1) of reaction energy. The further reactions involve H-abstraction by a H atom, H-desorption, H-migration, and ring closure to gain aromaticity. Through mechanism and rate of production analyses, the important reactions leading to phenanthrene and anthracene formation are determined. Phenanthrene is found to be the major product at high temperatures. Premixed laminar flame simulations are carried out by including the proposed reactions for phenanthrene formation from benzyl radicals and compared to experimentally observed species profiles to understand their effects on species concentrations. PMID:26923612

  4. Biodegradation of Aromatic Compounds by Escherichia coli

    PubMed Central

    Díaz, Eduardo; Ferrández, Abel; Prieto, María A.; García, José L.

    2001-01-01

    Although Escherichia coli has long been recognized as the best-understood living organism, little was known about its abilities to use aromatic compounds as sole carbon and energy sources. This review gives an extensive overview of the current knowledge of the catabolism of aromatic compounds by E. coli. After giving a general overview of the aromatic compounds that E. coli strains encounter and mineralize in the different habitats that they colonize, we provide an up-to-date status report on the genes and proteins involved in the catabolism of such compounds, namely, several aromatic acids (phenylacetic acid, 3- and 4-hydroxyphenylacetic acid, phenylpropionic acid, 3-hydroxyphenylpropionic acid, and 3-hydroxycinnamic acid) and amines (phenylethylamine, tyramine, and dopamine). Other enzymatic activities acting on aromatic compounds in E. coli are also reviewed and evaluated. The review also reflects the present impact of genomic research and how the analysis of the whole E. coli genome reveals novel aromatic catabolic functions. Moreover, evolutionary considerations derived from sequence comparisons between the aromatic catabolic clusters of E. coli and homologous clusters from an increasing number of bacteria are also discussed. The recent progress in the understanding of the fundamentals that govern the degradation of aromatic compounds in E. coli makes this bacterium a very useful model system to decipher biochemical, genetic, evolutionary, and ecological aspects of the catabolism of such compounds. In the last part of the review, we discuss strategies and concepts to metabolically engineer E. coli to suit specific needs for biodegradation and biotransformation of aromatics and we provide several examples based on selected studies. Finally, conclusions derived from this review may serve as a lead for future research and applications. PMID:11729263

  5. Oligomeric ferrocene rings.

    PubMed

    Inkpen, Michael S; Scheerer, Stefan; Linseis, Michael; White, Andrew J P; Winter, Rainer F; Albrecht, Tim; Long, Nicholas J

    2016-09-01

    Cyclic oligomers comprising strongly interacting redox-active monomer units represent an unknown, yet highly desirable class of nanoscale materials. Here we describe the synthesis and properties of the first family of molecules belonging to this compound category-differently sized rings comprising only 1,1'-disubstituted ferrocene units (cyclo[n], n = 5-7, 9). Due to the close proximity and connectivity of centres (covalent Cp-Cp linkages; Cp = cyclopentadienyl) solution voltammograms exhibit well-resolved, separated 1e(-) waves. Theoretical interrogations into correlations based on ring size and charge state are facilitated using values of the equilibrium potentials of these transitions, as well as their relative spacing. As the interaction free energies between the redox centres scale linearly with overall ring charge and in conjunction with fast intramolecular electron transfer (∼10(7) s(-1)), these molecules can be considered as uniformly charged nanorings (diameter ∼1-2 nm). PMID:27554408

  6. Swarming rings of bacteria.

    NASA Astrophysics Data System (ADS)

    Brenner, M. P.; Levitov, L. S.

    1996-03-01

    The behavior of bacterii controlled by chemotaxis can lead to a complicated spatial organization, producing swarming rings, and steady or moving aggregates( E. O. Budrene, and H. C. Berg, Complex patterns formed by motile cells of Escherichia coli. Nature 349, 630-633 (1991). ). We present a simple theory that explains the experimentally observed structures, by solving analytically two coupled differential equations, for the densities of bacterii and of chemoattractant. The equations have an interesting relation to the exactly solvable Burgers equation, and admit soliton-like solutions, that can be steady or moving. In addition, we find that there are singular solutions to the equations in which the bacterial density diverges. The theory agrees very well with the experiment: the solitons correspond to the observed travelling rings, the singularities describe formation of aggregates. In particular, the theory explains why the velocity of swarming rings decreases with the increase of the food concentration, the fact apparently not accounted by other existing approaches( L. Tsimring et. al., Phys. Rev. Lett., 75, 1859 (1995); Woodward, et al, Biophysical Journal, 68, 2181-2189 (1995). ).

  7. Role of ring torsion angle in polyaniline: Electronic structure and defect states

    NASA Astrophysics Data System (ADS)

    Ginder, J. M.; Epstein, A. J.

    1990-05-01

    The role of phenyl-ring torsion angle in determining the nature of the ground and charged-defect states of polyaniline is explored. The coupling of the transfer integral between nitrogen atom and phenyl-ring constituents of the polyaniline chain to the dihedral angle of the rings competes with the substantial steric repulsion between adjacent rings in determining the conformation of these systems. The ring conformation of the leucoemeraldine-base (LB) form of polyaniline is described by a novel ring-torsion-angle order parameter. The anharmonicity of the interring steric potential leads to a temperature-dependent mean order parameter, and thus to the prediction of thermochromic effects consistent with experiment. Furthermore, changes in optical spectra accompanying derivatization of the rings can be understood by the response of the substituted polymer to modifications of the steric potential. The existence of two degenerate ring-torsion-angle phases in LB implies that both polaronic and solitonic ring-angle-alternation defect states may be relevant in describing the charged states in polyaniline. As these defects involve substantial changes in ring torsion angle, they are expected to possess large kinetic mass, in agreement with photoinduced absorption experiments on polyaniline. The anticipated Peierls ground state of the oxidized pernigraniline-base form of polyaniline can be regarded in part as a ring-torsion-angle dimerized state; consequently, the charge states of this material are also expected to be massive defects in the ring-rotational order. The importance of ring rotations in other ring-containing electronic polymers, such as poly(paraphenylene sulfide), is discussed.

  8. 73. PASSAGE ADJACENT TO ROOM 232, EAST WING, SECOND FLOOR, ...

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

    73. PASSAGE ADJACENT TO ROOM 232, EAST WING, SECOND FLOOR, LOOKING WEST BY NORTHWEST, SHOWING EASTERNMOST ARCH OF FORMER GREAT HALL NORTH ARCADE - Smithsonian Institution Building, 1000 Jefferson Drive, between Ninth & Twelfth Streets, Southwest, Washington, District of Columbia, DC

  9. View of viaduct, looking SE from roof of adjacent parking ...

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

    View of viaduct, looking SE from roof of adjacent parking garage. - Mulberry Street Viaduct, Spanning Paxton Creek & Cameron Street (State Route 230) at Mulberry Street (State Route 3012), Harrisburg, Dauphin County, PA

  10. Cement Leakage into Adjacent Vertebral Body Following Percutaneous Vertebroplasty

    PubMed Central

    Park, Jae Hoo; Kim, Hyeun Sung

    2016-01-01

    Percutaneous vertebroplasty (PV) is a minimally invasive procedure for osteoporotic vertebral compression fractures that fail to respond to conventional conservative treatment. It significantly improves intolerable back pain within hours, and has a low complication rate. Although rare, PV is not free of complications, most of which are directly related to cement leakage. Because of its association with new adjacent fracture, the importance of cement leakage into the adjacent disc space is paramount. Here, we report an interesting case of cement leakage into the adjacent upper vertebral body as well as disc space following PV. To the best of our knowledge, there has been no report of cement leakage into the adjacent vertebral body following PV. This rare case is presented along with a review of the literature. PMID:27437018

  11. 1. HEBRONVILLE MILL COMPLEX ADJACENT TO NORTHEAST CORRIDOR. HEBRONVILLE, BRISTOL ...

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

    1. HEBRONVILLE MILL COMPLEX ADJACENT TO NORTHEAST CORRIDOR. HEBRONVILLE, BRISTOL CO., MA. Sec. 4116, MP 193.75. - Northeast Railroad Corridor, Amtrak Route between RI/MA State Line & South Station, Boston, Suffolk County, MA

  12. 3. DODGEVILLE MILL COMPLEX ADJACENT TO NORTHEAST CORRIDOR DODGEVILLE, BRISTOL ...

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

    3. DODGEVILLE MILL COMPLEX ADJACENT TO NORTHEAST CORRIDOR DODGEVILLE, BRISTOL CO., MA. Sec. 4116, MP 195.55. - Northeast Railroad Corridor, Amtrak Route between RI/MA State Line & South Station, Boston, Suffolk County, MA

  13. 33. HISTORIC PLAQUE MARKING WHERE JOHNSTON DIED, ADJACENT TO PATHWAY ...

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

    33. HISTORIC PLAQUE MARKING WHERE JOHNSTON DIED, ADJACENT TO PATHWAY WITH CONCRETE CULVERT LEADING NORTH OUT OF RAVINE TOWARD JOHNSTON MEMORIAL SITE. VIEW NW. - Shiloh National Military Park Tour Roads, Shiloh, Hardin County, TN

  14. Lock 4 View east of lock wall and adjacent ...

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

    Lock 4 - View east of lock wall and adjacent roadway built atop tow path. The gate pocket can be seen at center. - Savannah & Ogeechee Barge Canal, Between Ogeechee & Savannah Rivers, Savannah, Chatham County, GA

  15. 1. Ninth Street (west) facade. Adjacent on the north is ...

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

    1. Ninth Street (west) facade. Adjacent on the north is the 9th Street facade of 816 E Street. Both buildings were originally one property. - Riley Building, Rendezvous Adult Magazines & Films, 437 Ninth Street, Northwest, Washington, District of Columbia, DC

  16. 2. THREEQUARTER VIEW FROM ADJACENT ACCESS ROAD SHOWING THREE SPANS ...

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

    2. THREE-QUARTER VIEW FROM ADJACENT ACCESS ROAD SHOWING THREE SPANS AND NORTHWEST APPROACH SPANS, LOOKING SOUTHEAST - Red River Bridge, Spanning Red River at U.S. Highway 82, Garland, Miller County, AR

  17. 1. VIEW FROM ROOFTOP OF BUILDING (MOTEL) ADJACENT TO TECHWOOD ...

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

    1. VIEW FROM ROOFTOP OF BUILDING (MOTEL) ADJACENT TO TECHWOOD HOMES, LOOKING SOUTH. GARAGE TO EXTREME LEFT, BUILDING 1 TO EXTREME RIGHT. - Techwood Homes (Public Housing), Bounded by North Avenue, Parker Street, William Street & Lovejoy Street, Atlanta, Fulton County, GA

  18. 3. View of north side of house facing from adjacent ...

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

    3. View of north side of house facing from adjacent vacant property. Original wood lap siding and trim is covered by aluminum siding. Recessed side porch is in middle. - 645 South Eighteenth Street (House), Louisville, Jefferson County, KY

  19. 1. A BRICK AND CONCRETE FAN HOUSING ADJACENT TO ONE ...

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

    1. A BRICK AND CONCRETE FAN HOUSING ADJACENT TO ONE OF THE ADIT OPENINGS (VIEW TO THE NORTH). - Foster Gulch Mine, Fan Housing, Bear Creek 1 mile Southwest of Town of Bear Creek, Red Lodge, Carbon County, MT

  20. 7. August, 1970 9 ORANGE STREET, ADJACENT TO UNITARIAN CHURCH ...

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

    7. August, 1970 9 ORANGE STREET, ADJACENT TO UNITARIAN CHURCH (NOT IN STUDY AREA) - Orange & Union Streets Neighborhood Study, 8-31 Orange Street, 9-21 Union Street & Stone Alley, Nantucket, Nantucket County, MA