Science.gov

Sample records for adjacent aromatic rings

  1. Entropy versus aromaticity in the conformational dynamics of aromatic rings.

    PubMed

    Shishkin, Oleg V; Dopieralski, Przemyslaw; Omelchenko, Irina V; Gorb, Leonid; Latajka, Zdzislaw; Leszczynski, Jerzy

    2013-10-01

    Comparison of the results of Car-Parrinello molecular dynamics simulations of isolated benzene, pyrimidine and 1,2,4-triazine molecules reveals that the unusually low population of planar geometry of the benzene ring is caused by entropy effects despite its high aromaticity. The decrease in symmetry of the molecule results in smaller changes in entropy and Gibbs free energy due to out-of-plane deformations of the ring, leading to an increase in the population of planar geometry of the ring. This leads to differences in the topology of potential energy and Gibbs free energy surfaces.

  2. Praziquantel derivatives with antischistosomal activity: aromatic ring modification.

    PubMed

    Wang, Zhi-xia; Chen, Jing-lei; Qiao, Chunhua

    2013-08-01

    A series of aromatic ring-modified praziquantel derivatives were prepared and evaluated against juvenile and adult stage of Schistosoma japonicumin. Several analogs comparable in activity to the drug praziquantel have been identified based on in vitro and in vivo japonuicum schistosomes worm viability assay. Structure and activity relationship of these praziquantel aromatic ring-modified compounds was revealed. Specifically, a compound in which a bromine has been introduced in the aromatic ring of praziquantel demonstrated close antischistosomal activity to praziquantel in vivo.

  3. 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.

  4. Experimental measurement of noncovalent interactions between halogens and aromatic rings.

    PubMed

    Adams, Harry; Cockroft, Scott L; Guardigli, Claudio; Hunter, Christopher A; Lawson, Kevin R; Perkins, Julie; Spey, Sharon E; Urch, Christopher J; Ford, Rhonan

    2004-05-03

    Chemical double mutant cycles have been used to quantify the interactions of halogens with the faces of aromatic rings in chloroform. The halogens are forced over the face of an aromatic ring by an array of hydrogen-bonding interactions that lock the complexes in a single, well-defined conformation. These interactions can also be engineered into the crystal structures of simpler model compounds, but experiments in solution show that the halogen-aromatic interactions observed in the solid state are all unfavourable, regardless of whether the aromatic rings contain electron-withdrawing or electron-donating substituents. The halogen-aromatic interactions are repulsive by 1-3 kJ mol(-1). The interactions with fluorine are slightly less favourable than with chlorine and bromine.

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

    DOEpatents

    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.

  6. Aromatic and antiaromatic ring currents in a molecular nanoring

    NASA Astrophysics Data System (ADS)

    Peeks, Martin D.; Claridge, Timothy D. W.; Anderson, Harry L.

    2016-12-01

    Aromatic and antiaromatic molecules—which have delocalized circuits of [4n + 2] or [4n] electrons, respectively—exhibit ring currents around their perimeters. The direction of the ring current in an aromatic molecule is such as to generate a magnetic field that opposes the external field inside the ring (a ‘diatropic’ current), while the ring current in an antiaromatic molecule flows in the reverse direction (‘paratropic’). Similar persistent currents occur in metal or semiconductor rings, when the phase coherence of the electronic wavefunction is preserved around the ring. Persistent currents in non-molecular rings switch direction as a function of the magnetic flux passing through the ring, so that they can be changed from diatropic (‘aromatic’) to paratropic (‘antiaromatic’) simply by changing the external magnetic field. As in molecular systems, the direction of the persistent current also depends on the number of electrons. The relationship between ring currents in molecular and non-molecular rings is poorly understood, partly because they are studied in different size regimes: the largest aromatic molecules have diameters of about one nanometre, whereas persistent currents are observed in microfabricated rings with diameters of 20-1,000 nanometres. Understanding the connection between aromaticity and quantum-coherence effects in mesoscopic rings provides a motivation for investigating ring currents in molecules of an intermediate size. Here we show, using nuclear magnetic resonance spectroscopy and density functional theory, that a six-porphyrin nanoring template complex, with a diameter of 2.4 nanometres, is antiaromatic in its 4+ oxidation state (80 π electrons) and aromatic in its 6+ oxidation state (78 π electrons). The antiaromatic state has a huge paramagnetic susceptibility, despite having no unpaired electrons. This work demonstrates that a global ring current can be promoted in a macrocycle by adjusting its oxidation state

  7. Improved synthesis of 3-aryl isoxazoles containing fused aromatic rings

    PubMed Central

    Mirzaei, Yousef R.; Weaver, Matthew J.; Steiger, Scott A.; Kearns, Alison K.; Gajewski, Mariusz P.; Rider, Kevin C.; Beall, Howard D.; Natale, N.R.

    2012-01-01

    A critical comparison of methods to prepare sterically hindered 3-aryl isoxazoles containing fused aromatic rings using the nitrile oxide cycloaddition (NOC) reveal that modification of the method of Bode, Hachisu, Matsuura, and Suzuki (BHMS), utilizing either triethylamine as base or sodium enolates of the diketone, ketoester, and ketoamide dipolarophiles, respectively, was the method of choice for this transformation. PMID:23526841

  8. Assessment of polycyclic aromatic hydrocarbon input to urban wetlands in relation to adjacent land use.

    PubMed

    Kimbrough, K L; Dickhut, R M

    2006-11-01

    The relationship between polycyclic aromatic hydrocarbons (PAHs) in wetland surface sediments and adjacent land use was assessed in the Elizabeth River, VA, an urbanized sub-estuary of the Chesapeake Bay. Significant differences (p<0.05) in surface sediment PAH concentration between sites indicated adjacent land use had a substantial influence on PAH concentration in wetland sediments. Wetlands adjacent to parking lots and petroleum industrial sites exhibited the highest PAH concentrations of all wetlands examined. Overall, commercial land uses had the highest PAH concentrations and automotive sources dominated (52-69%) PAH input to wetland surface sediments irrespective of adjacent land use.

  9. Gas-particle partitioning of polycyclic aromatic hydrocarbons in urban, adjacent coastal, and continental background sites of western Greece.

    PubMed

    Terzi, Eleni; Samara, Constantini

    2004-10-01

    Particle- and gas-phase polycyclic aromatic hydrocarbons (PAHs) were collected from an urban, an adjacent coastal, and a continental background site located in Eordea basin, western Greece, to investigate their gas/ particle distributions. Thirteen two- to six-ring PAHs, included in the U.S. EPA priority pollutant list, were determined in 24-h integrated glass fiber filters and polyurethane foam samples. At the prevailing ambient temperature levels, the three-ringed species (phenanthrene, anthracene) and the four-ringed fluoranthene and pyrene were primarily found in the gas phase. Conversely, the five- and six-ring PAHs were mainly associated with the particle phase. Gas/particle partitioning coefficients, Kp, were calculated, and their relationship with the subcooled liquid vapor pressure p degrees L of individual PAHs was investigated. Despite the large variability among samples, a good linear relationship between log Kp and log p degrees L was obtained for all sampling sites following the equation log Kp = m(r) log p degrees L + b(r). In the majority of sampling events, particularly in the adjacent coastal and the continental background sites, slopes (m(r)) were found to be shallower than the value of -1, which has been suggested as reflecting equilibrium partitioning. The deviations from predicted aerosol behavior observed in the present study may be attributed to several reasons, such as the presence of nonexchangeable PAH fraction, nonequilibrium as well as different particle characteristics.

  10. 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.

  11. 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.

  12. Understanding substituent effects in noncovalent interactions involving aromatic rings.

    PubMed

    Wheeler, Steven E

    2013-04-16

    Noncovalent interactions involving aromatic rings such as π-stacking, cation/π, and anion/π interactions are central to many areas of modern chemistry. Decades of experimental studies have provided key insights into the impact of substituents on these interactions, leading to the development of simple intuitive models. However, gas-phase computational studies have raised some doubts about the physical underpinnings of these widespread models. In this Account we review our recent efforts to unravel the origin of substituent effects in π-stacking and ion/π interactions through computational studies of model noncovalent dimers. First, however, we dispel the notion that so-called aromatic interactions depend on the aromaticity of the interacting rings by studying model π-stacked dimers in which the aromaticity of one of the monomers can be "switched off". Somewhat surprisingly, the results show that not only is aromaticity unnecessary for π-stacking interactions, but it actually hinders these interactions to some extent. Consequently, when thinking about π-stacking interactions, researchers should consider broader classes of planar molecules, not just aromatic systems. Conventional models maintain that substituent effects in π-stacking interactions result from changes in the aryl π-system. This view suggests that π-stacking interactions are maximized when one ring is substituted with electron-withdrawing groups and the other with electron donors. In contrast to these prevailing models, we have shown that substituent effects in π-stacking interactions can be described in terms of direct, local interactions between the substituents and the nearby vertex of the other arene. As a result, in polysubstituted π-stacked dimers the substituents operate independently unless they are in each other's local environment. This means that in π-stacked dimers in which one arene is substituted with electron donors and the other with electron acceptors the interactions will

  13. The metabolism of aromatic compounds by Rhodopseudomonas palustris. A new, reductive, method of aromatic ring metabolism

    PubMed Central

    Dutton, P. L.; Evans, W. C.

    1969-01-01

    1. Rhodopseudomonas palustris grows both aerobically and photosynthetically on aromatic acids. p-Hydroxybenzoate and protocatechuate are able to support aerobic growth; these compounds are metabolized by the protocatechuate 4,5-oxygenase pathway. 2. The photoassimilation of benzoate and hydroxybenzoates and the effects of air and darkness on the photoassimilation of benzoate are described. 3. Evidence in conflict with the pathway previously proposed for the photometabolism of benzoate is discussed. 4. The photometabolism of benzoate is accomplished by a novel reductive pathway involving its reduction to cyclohex-1-ene-1-carboxylate, followed by hydration to 2-hydroxycyclohexanecarboxylate and after dehydrogenation to 2-oxocyclohexanecarboxylate further hydration results in ring-fission and the production of pimelate. 5. Attempts were made to prepare cell-free extracts capable of dissimilating benzoate. PMID:5807211

  14. 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…

  15. 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)

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Influence of chemical structure on skin reactions induced by antiepileptic drugs--the role of the aromatic ring.

    PubMed

    Wang, Xiang-Qing; Shi, Xiao-Bing; Au, Ran; Chen, Fu-Shun; Wang, Fang; Lang, Sen-Yang

    2011-05-01

    Here we assessed whether the presence of an aromatic ring as a commonality in chemical structures of AEDs can explain skin reaction. We found that 164 cases of skin reactions associated with the use of AEDs were reported. Aromatic AEDs were suspected in 88.41% (145/164) of patients with skin reactions versus 59.80% (2316/3873) of patients without skin reactions. The presence of an aromatic ring in the chemical structure was associated with a significant increased risk of skin reactions (adjusted ROR 3.50; 95% CI 2.29, 5.35). Among the aromatic AEDs, skin reactions were significantly associated with carbamazepine, lamotrigine, and oxarbazepine. These results confirm that the presence of an aromatic ring as a common feature in chemical structures of AEDs partly explains AED-skin reactions. Skin reactions were reported triple as frequently with aromatic AEDs than with non-aromatic AEDs.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

  2. Methanogenic biodegradation of two-ringed polycyclic aromatic hydrocarbons.

    PubMed

    Berdugo-Clavijo, Carolina; Dong, Xiaoli; Soh, Jung; Sensen, Christoph W; Gieg, Lisa M

    2012-07-01

    Polycyclic aromatic hydrocarbons (PAH) are widespread in methane-rich subsurface environments, such as oil reservoirs and fuel-contaminated aquifers; however, little is known about the biodegradation of these compounds under methanogenic conditions. To assess the metabolism of PAH in the absence of electron acceptors, a crude oil-degrading methanogenic enrichment culture was tested for the ability to biodegrade naphthalene, 1-methylnaphthalene (1-MN), 2-methylnaphthalene (2-MN), and 2, 6-dimethylnaphthalene (2, 6-diMN). When methane was measured as an indicator of metabolism, nearly 400 μmol of methane was produced in the 2-MN- and 2, 6-diMN-amended cultures relative to substrate-unamended controls, which is close to the amount of methane stoichiometrically predicted based on the amount of substrate added (51-56 μmol). In contrast, no substantial methane was produced in the naphthalene- and 1-MN-amended enrichments. In time course experiments, metabolite analysis of enrichments containing 2-MN and 2, 6-diMN revealed the formation of 2-naphthoic acid and 6-methyl-2-naphthoic acid, respectively. Microbial community analysis by 454 pyrosequencing revealed that these PAH-utilizing enrichments were dominated by archaeal members most closely affiliated with Methanosaeta and Methanoculleus species and bacterial members most closely related to the Clostridiaceae, suggesting that these organisms play an important role in the methanogenic metabolism of the substituted naphthalenes in these cultures.

  3. Synthesis and antifungal activity of C-21 steroids with an aromatic D ring.

    PubMed

    Sonego, Juan M; Cirigliano, Adriana M; Cabrera, Gabriela M; Burton, Gerardo; Veleiro, Adriana S

    2013-07-01

    Six analogues of salpichrolides with a simplified side chain (6-11) were synthesized using a new methodology to obtain steroids with an aromatic D-ring. The key step was the elimination of HBr in a vicinal dibromo D-homosteroid by treatment with 1,4-diazabicyclo[2.2.2]octane (DABCO). All new compounds were completely characterized by 2D NMR techniques and tested on two fungal pathogenic species, Fusarium virguliforme and Fusarium solani.

  4. Aromaticity of rings-in-molecules (RIMs) from electron localization-delocalization matrices (LDMs)

    NASA Astrophysics Data System (ADS)

    Sumar, Ismat; Cook, Ronald; Ayers, Paul W.; Matta, Chérif F.

    2016-01-01

    A new and powerful molecular descriptor termed the LDM (localization-delocalization matrix) has recently been proposed as a molecular fingerprinting tool and has been shown to yield robust quantitative-structure-to-activity/property-relationships (QSAR/QSPR). An LDM lists the average number of electrons localized within an atom in a molecule along its diagonal while the off-diagonal elements are the pair-wise average number of electrons shared between every pair of atoms in the molecule, bonded or not. Hence, the LDM is a representation of a fuzzy molecular graph that accounts for the whereabouts of all electron(s) in the molecule and can be expected to encode for several facets of its chemistry at once. We show that the LDM captures the aromatic character of a ring-in-a-molecule by comparing the aromaticity ranking based on the LDMs and their eigenvalues of 6-membered carbon rings within (polycyclic) benzenoid hydrocarbons with the ranking based on four well-established local aromaticity measures (harmonic oscillator model of aromaticity, acromatic fluctuation index, para delocalization index, and nucleus independent chemical shift(0)). This paper is dedicated to the memory of Professor Paul von Ragué Schleyer (1930-2014).

  5. 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.

  6. Aliphatic and polycyclic aromatic hydrocarbons in sediments of Kaohsiung Harbour and Adjacent Coast, Taiwan.

    PubMed

    Lee, Chon-Lin; Hsieh, Ming-Tsuen; Fang, Meng-Der

    2005-01-01

    Surficial sediment samples collected from Kaohsiung Harbour and its nearby coast were analyzed for aliphatic hydrocarbons and parent polycyclic aromatic hydrocarbons (PAHs). According to our results, the average total concentrations of n-alkanes (n-C12 to C35) and aromatics (15 PAHs) were 4.33 microg g(-1) dry weight (ranged 0.46-22.60) and 0.59 microg g(-1) dry weight (ranged 0.09-1.75), respectively. The highest concentrations of aliphatic and aromatic hydrocarbons were recorded in stations near the estuaries of Qianzhen River and Love River, respectively. Aliphatic hydrocarbons in the samples indicate that there has been significant non-petrogenic, possibly terrestrial, contribution in the sediment of the open coast of Kaohsiung Harbour and that there has been dominant contribution from petrogenic sources in the sediment of the inner harbour. PAHs, detected in the samples, however, indicated a higher pyrolytic contribution in open-coast samples and a higher petrogenic contribution in the inner harbour. Overall, sediment concentrations of total alkanes in this study were comparable to those found in Victoria Harbour, Hong Kong and are higher than those found in Xiamen Harbour, China. Concentrations of total PAHs in inner Kaohsiung Harbour sediments were relatively lower than those found in Victoria Harbour, Hong Kong and Xiamen Harbour, China, but comparable to those found in Hsin-ta Harbour, Taiwan and Incheon Harbour, Korea. In comparison with several effect-based sediment quality guidelines, most PAH concentrations found in samples taken from inner harbour stations exceeded the Threshold Effect Level of Florida indicating a slight possibility of adverse effects.

  7. 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.

  8. 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.

  9. Determination of Aromatic Ring Number Using Multi-Channel Deep UV Native Fluorescence

    NASA Technical Reports Server (NTRS)

    Bhartia, R.; McDonald, G. D.; Salas, E.; Conrad, P.

    2004-01-01

    The in situ detection of organic material on an extraterrestrial surface requires both effective means of searching a relatively large surface area or volume for possible organic carbon, and a more specific means of identifying and quantifying compounds in indicated samples. Fluorescence spectroscopy fits the first requirement well, as it can be carried out rapidly, with minimal or no physical contact with the sample, and with sensitivity unmatched by any other organic analytical technique. Aromatic organic compounds with know fluorescence signatures have been identified in several extraterrestrial samples, including carbonaceous chondrites, interplanetary dust particles, and Martian meteorites. The compound distributions vary among these sources, however, with clear differences in relative abundances by number of aromatic rings and by degree of alkylation. This relative abundance information, therefore, can be used to infer the source of organic material detected on a planetary surface.

  10. Single-molecule nanosized polycyclic aromatics with alternant five- and six-membered rings: synthesis and optical properties.

    PubMed

    Zhang, Wei; Cao, Xiao-Yu; Zi, Hong; Pei, Jian

    2005-03-17

    [structure: see text] A synthetic protocol for a novel family of symmetric polycyclic aromatics with a benzene or cyclooctatetraene (COT) ring as the core and alternant fused benzene and cyclopentadiene rings as branches has been developed. The TiCl(4)-promoted cyclizations construct both planar trimers and tubelike tetramers via the "in situ" generation of the benzene or COT skeleton. The structures of 6b, 7a, 7b, and 10 have been characterized by (1)H and (13)C NMR spectra and MALDI-TOF mass spectroscopy. These polycyclic aromatics also exhibit interesting optical properties.

  11. Structure-activity relationships for vitamin D3-based aromatic a-ring analogues as hedgehog pathway inhibitors.

    PubMed

    Deberardinis, Albert M; Madden, Daniel J; Banerjee, Upasana; Sail, Vibhavari; Raccuia, Daniel S; De Carlo, Daniel; Lemieux, Steven M; Meares, Adam; Hadden, M Kyle

    2014-05-08

    A structure-activity relationship study for a series of vitamin D3-based (VD3) analogues that incorporate aromatic A-ring mimics with varying functionality has provided key insight into scaffold features that result in potent, selective Hedgehog (Hh) pathway inhibition. Three analogue subclasses containing (1) a single substitution at the ortho or para position of the aromatic A-ring, (2) a heteroaryl or biaryl moiety, or (3) multiple substituents on the aromatic A-ring were prepared and evaluated. Aromatic A-ring mimics incorporating either single or multiple hydrophilic moieties on a six-membered ring inhibited the Hh pathway in both Hh-dependent mouse embryonic fibroblasts and cultured cancer cells (IC50 values 0.74-10 μM). Preliminary studies were conducted to probe the cellular mechanisms through which VD3 and 5, the most active analogue, inhibit Hh signaling. These studies suggested that the anti-Hh activity of VD3 is primarily attributed to the vitamin D receptor, whereas 5 affects Hh inhibition through a separate mechanism.

  12. 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.

  13. Highly regioselective hydrogenolysis of bis(alpha-methylbenzyl)amine derivatives affected by the trifluoromethyl substituent on the aromatic ring.

    PubMed

    Kanai, Masatomi; Yasumoto, Manabu; Kuriyama, Yokusu; Inomiya, Kenjin; Katsuhara, Yutaka; Higashiyama, Kimio; Ishii, Akihiro

    2003-04-03

    [reaction: see text] The highly regioselective hydrogenolysis of bis(alpha-methylbenzyl)amine derivatives proceeded with influence not from the electronic effect but from the steric effect of the trifluoromethyl substituent on the aromatic ring to provide a practical asymmetric synthesis of trifluoromethyl-substituted alpha-phenylethylamines.

  14. Direct Functionalization of Poly(spirophosphazene)s via the Regioselective Lithiation of the Aromatic Rings Using a Cooperative Superbase.

    PubMed

    de la Campa, Raquel; García, Diego; Rodríguez, Sandra; Carriedo, Gabino A; Presa Soto, Alejandro

    2017-03-27

    The direct chemical functionalization of poly(spirophosphazene) [NP(O2 C12 H8 )]n (1) can be performed by the lithiation of the aromatic rings at low temperature using Schlosser's base (Li(t) Bu/KO(t) Bu or "superbase"), and the subsequent reaction with various electrophiles such as ClSiMe3 , ClPPh2 , or MeOB(O2 C6 H12 ) (MeOBpin). The functionalized polymers, isolated in very high yields (>90%) and without degradation of the polymeric chains, have an average degree of substitution per repeat unit ranging from 0.3 (random copolymers) to a maximum of 1.0, which corresponds to the homopolymers [NP(O2 C12 H7 FG)]n (FG (functional group) =SiMe3 , PPh2 , and Bpin). NMR studies, including bidimensional high temperature experiments on silylated and deuterated polymers, show that the substitution is regioselectively occurring at the C3 carbon of the aromatic rings due to the coordination of the lithium cations to the nitrogen of the polyphosphazene chain. The introduction of functional groups on the aromatic rings leads to significant changes in the solubility (silylated polymers), Tg , and electronic properties of the material, showing how the change of substituents in the aromatic rings can lead to polyphosphazenes with properties markedly different from those of the precursor polymer.

  15. 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.

  16. Aromatic Metamorphosis of Dibenzofurans into Triphenylenes Starting with Nickel-Catalyzed Ring-Opening C-O Arylation.

    PubMed

    Kurata, Yuto; Otsuka, Shinya; Fukui, Norihito; Nogi, Keisuke; Yorimitsu, Hideki; Osuka, Atsuhiro

    2017-02-28

    A new class of aromatic metamorphosis has been developed in which dibenzofurans were converted into triphenylenes. This transformation is composed of three successive operations: (1) nickel-catalyzed ring-opening C-O bond arylation with arylmagnesium bromides, (2) trifluoromethanesulfonylation (triflation) of the resulting hydroxy moiety with Tf2O, and (3) palladium-catalyzed or photoinduced ring closure. In the last ring-closing step, the photoinduced process has proven to be more productive than the palladium-catalyzed one. By employing π-extended dinaphthofuran as the substrate, dorsally benzo-fused [5]helicene was obtained in a satisfactory yield.

  17. Biodegradation of three- and four-ring polycyclic aromatic hydrocarbons under aerobic and denitrifying conditions

    SciTech Connect

    McNally, D.L.; Mihelcic, J.R.; Lueking, D.R.

    1998-09-01

    PAHs are thought to be particularly persistent in environments where anaerobic conditions exist. This study presents evidence for the biodegradation of three- and four-ringed PAHs (anthracene, phenanthrene, and pyrene) under strict anaerobic, denitrifying conditions. Three pseudomonad strains, isolated from contrasting environments, were used in this study. All three strains were known PAH degraders and denitrifiers. Degradation proceeded to nondetectable levels in 12--80 h for anthracene, 12--44 h for phenanthrene, and 24--72 h for pyrene. The rates of anaerobic degradation were typically slower than under aerobic conditions in almost all cases, except for strain SAG-R which had similar removal rates for all three and four-ring PAHs. Denitrification activity was verified by monitoring nitrate utilization and nitrous oxide production. Although none of the pseudomonads were adapted to the denitrifying conditions, only the pseudomonad isolated from a noncontaminated site consistently exhibited an adaptation period which approximated 12 h. This study supports growing evidence that the degradation of aromatic hydrocarbons coupled to denitrification may be an important factor affecting the fate of these compounds in natural and engineered systems.

  18. Unprecedented π···π interaction between an aromatic ring and a pseudo-aromatic ring formed through intramolecular H-bonding in a bidentate Schiff base ligand: crystal structure and DFT calculations.

    PubMed

    Dutta, Arpan; Jana, Atish Dipankar; Gangopadhyay, Sumana; Das, Kalyan Kumar; Marek, Jaromir; Marek, Radek; Brus, Jiri; Ali, Mahammad

    2011-09-21

    A combination of a single crystal X-ray diffraction study and density functional theory calculations has been applied to a bidentate Schiff base compound to elucidate different cooperative non-covalent interactions involved in the stabilization of the keto form over the enol one in the solid state. The single crystal X-ray structure reveals a remarkable supramolecular assembly of the keto form through a cyclic hydrogen bonded dimeric motif. The most interesting feature in the supramolecular assembly is the formation of a 'dimer of dimer' motif by π···π, CH···π and N···O/O···O interactions in which the π···π interaction involving the aromatic phenyl ring and the intramolecularly hydrogen bonded pseudo-aromatic ring of the keto form lying just above or below the phenyl ring of the other dimer seems to be unprecedented. The optimized geometry of the hydrogen bonded dimeric motif of the keto form of the organic molecule has been obtained by DFT calculations and agrees very well with that found within the crystalline state. The X-ray crystallographic geometry of the 'dimer of dimer' has also been computed, which shows that in the HOMO, the π electrons are localized in the phenyl rings away from each other, while in the LUMO, there is a strong π-π interaction between the phenyl ring of one dimer with the pseudo-aromatic ring of another dimer with an energy estimated to be 7.95 kJ mol(-1). Therefore, on HOMO → LUMO excitation there is localization of π electrons in the central part of the complex moiety which plays a stabilizing role of the dimer of dimer motif in the solid state.

  19. 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

  20. Desorption of polycyclic aromatic hydrocarbons from a soot surface: three- to five-ring PAHs.

    PubMed

    Guilloteau, Angélique; Bedjanian, Yuri; Nguyen, Mai Lan; Tomas, Alexandre

    2010-01-21

    The kinetics of the thermal desorption of a set of three- to five-ring polycyclic aromatic hydrocarbons (PAHs) from a laboratory-generated kerosene soot surface was studied over the temperature range 250-355 K in a low-pressure flow reactor combined with an electron-impact mass spectrometer. Two methods were used to measure the desorption rate constants: monitoring of the surface-bound PAH decays due to desorption using off-line HPLC measurements of their concentrations in soot samples and monitoring of the desorbed molecules (anthracene and phenanthtrene) in the gas phase using in situ mass spectrometric detection. The Arrhenius parameters (A factors and activation energies) for the desorption rate constants of 10 soot-bound PAHs were determined. The PAH-soot binding energies were found to be similar for PAHs with the same number of carbon atoms and to increase with increasing number of PAH carbon atoms. The experimental data are discussed in the frame of the existing theoretical gas to particle partitioning model.

  1. 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

  2. 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.

  3. 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.

  4. Potassium ion surrounded by aromatic rings: molecular dynamics of the first solvation shell

    NASA Astrophysics Data System (ADS)

    Albertí, Margarita; Aguilar, Antonio; Marques, Jorge M. C.

    2014-12-01

    We study the potassium ion in non-polar environments due to the interaction with aromatic rings, which is relevant to get insight on the selectivity of several biochemical processes. In concrete, we performed molecular dynamics simulations of the first solvation shell of K+ surrounded by either benzene (Bz) or hexafluorobenzene (HFBz) molecules. The global intermolecular interaction for these clusters has been decomposed in Bz-Bz (or HFBz-HFBz) and in K+-Bz (or K+-HFBz) contributions, using a potential model based on different decompositions of the molecular polarizability of the solvent molecule (Bz or HFBz). For the molecular dynamics simulations, we used as starting geometries the low-energy structures of the K+-(Bz) n ( n = 3,4) and K+-(HFBz) n ( n = 8,9) clusters that were obtained in our previous global optimization studies [J.M.C. Marques, J.L. Llanio-Trujillo, M. Albertí, A. Aguilar, F. Pirani, J. Phys. Chem. A 116, 4947 (2012); J.M.C. Marques, J.L. Llanio-Trujillo, M. Albertí, A. Aguilar, F. Pirani, J. Phys. Chem. A 117, 8043 (2013)]; a total of 11 starting geometries were employed (including the 4 global minima): 4 (4) for K+-(Bz)3 (K+-(Bz)4) and 2 (1) for K+-(HFBz)8 (K+-(HFBz)9). We have found that all the K+-(Bz)3 local minimum structures isomerise to form the lowest-energy aggregate at T< 20 K. As for K+-(Bz)4, such kind of isomerisation is only observed at T> 90 K for two of the local minima; the highest-energy minimum, that corresponds to a K+-(Bz)4 structure with a Bz molecule placed in the second solvation shell, tends to dissociate before it can isomerise. In the case of K+-(HFBz)8 (or K+-(HFBz)9), the dissociation only occurs at higher temperatures, i.e., T = 260 K (or T = 210 K). By lowering the temperature of the simulation after the dissociation of K+-(HFBz)9, one observes the formation of the global minimum structure of K+-(HFBz)8.

  5. Sources and distribution of polycyclic aromatic hydrocarbons in a an urbanized tropical estuary and adjacent shelf, Northeast of Brazil.

    PubMed

    Maciel, Daniele Claudino; de Souza, José Roberto Botelho; Taniguchi, Satie; Bícego, Márcia Caruso; Zanardi-Lamardo, Eliete

    2015-12-15

    Located in Northeastern Brazil, the Capibaribe Estuarine System is an important ecosystem that supplies food and protection for nursery of several species with ecological and economic importance. It is located inside an urbanized area, receives untreated domestic and industrial effluents, and houses some marinas and the Harbor of Recife, which are very important to national and international communities. The distribution and sources of PAHs were investigated in sediments from CES and adjacent shelf. Total PAH concentrations ranged from non-detectable to 497.6 μg g(-1). Pyrolytic sources predominated in most of sites, but petrogenic PAHs were also recorded. The concentration decrease of PAHs toward adjacent shelf suggests that the main source of these compounds is in the upper portion of estuary, where there is an intense discharge of sewage, but atmospheric input also seems to be relevant to the area. The results reinforce the important role of an estuary in contaminant retention.

  6. Sequential aza-Baylis-Hillman/ring closing metathesis/aromatization as a novel route for the synthesis of substituted pyrroles.

    PubMed

    Declerck, Valérie; Ribière, Patrice; Martinez, Jean; Lamaty, Frédéric

    2004-11-26

    A new route to diverse 2-substituted-3-methoxycarbonyl pyrroles has been developed. Diverse SES protected alpha-methylene beta-aminoesters were obtained by a 3-component aza-Baylis-Hillman reaction. Diversity arose from the aryl aldehydes which can be used in this reaction. N-Alkylation with allyl bromide under mild conditions provided the corresponding dienes. These substituted dienes were cyclized by ring closing metathesis at room temperature or under microwave-activation with Grubbs-type II catalyst to yield SES-protected pyrroline intermediates. The final pyrroles were obtained by base-promoted dehydrodesulfinylation/aromatization. The scope of each of these reactions was explored.

  7. Surface chemistry of five-membered aromatic ring molecules containing two different heteroatoms on Si(111)-7 x 7.

    PubMed

    Tao, Feng; Bernasek, Steven L

    2007-04-18

    The surface chemistry of three representative aromatic molecules containing two different heteroatoms isoxazole, oxazole, and thiazole on Si(111)-7 x 7 was studied. These molecules exhibit different competition and selectivity for multiple reaction channels with this surface, determined by a combination of molecular electronic and structural factors. Isoxazole is chemically attached to Si(111)-7 x 7 through both dative-bond addition and [4 + 2]-like cycloaddition. Oxazole chemisorbs on Si(111)-7 x 7 through both dative-bond addition and [2 + 2]-like cycloaddition. The kinetically favored [2 + 2]-like cycloadduct at low temperature is thermally converted into the thermodynamically preferred [4 + 2]-like cycloadduct at a temperature higher than 300 K. Thiazole is chemically bound to this surface only through formation of a Si...N dative bond at low temperature. This dative-bonded molecule is thermally converted into a [4 + 2]-like cycloadduct. The reaction channels of the three five-membered aromatic molecules containing two different heteroatoms (isoxazole, oxazole, and thiazole) and of the aromatic molecules containing only one heteroatom (pyridine, pyrrole, furan, and thiophene) are compared and analyzed for a thorough understanding of the reaction mechanisms of various heterocyclic aromatic molecules on this surface. The intrinsic connection between surface reaction mechanism and molecular electronic structure is demonstrated. This includes the distribution of electron density on the molecular ring determined by the geometric arrangement of the heteroatoms, the electronegativity of the heteroatoms, and the electronic contribution of the heteroatoms to formation of aromatic pi conjugation, as well as the molecular polarity.

  8. 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

  9. Identification and quantification of seven fused aromatic rings C26H14 peri-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 C26H14 peri-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.

  10. Theoretical study of the formation of naphthalene from the radical/π-bond addition between single-ring aromatic hydrocarbons.

    PubMed

    Comandini, Andrea; Brezinsky, Kenneth

    2011-06-09

    The experimental investigations performed in the 1960s on the o-benzyne + benzene reaction as well as the more recent studies on reactions involving π-electrons highlight the importance of π-bonding for different combustion processes related to PAH's and soot formation. In the present investigation radical/π-bond addition reactions between single-ring aromatic compounds have been proposed and computationally investigated as possible pathways for the formation of two-ring fused compounds, such as naphthalene, which serve as precursors to soot formation. The computationally generated optimized structures for the stationary points were obtained with uB3LYP/6-311+G(d,p) calculations, while the energies of the optimized complexes were refined using the uCCSD(T) method and the cc-pVDZ basis set. The computations have addressed the relevance of a number of radical/π-bond addition reactions including the singlet benzene + o-benzyne reaction, which leads to formation of naphthalene and acetylene through fragmentation of the benzobicyclo[2,2,2]octatriene intermediate. For this reaction, the high-pressure limit rate constants for the individual elementary reactions involved in the overall process were evaluated using transition state theory analysis. Other radical/π-bond addition reactions studied were between benzene and triplet o-benzyne, between benzene and phenyl radical, and between phenyl radicals, for all of which potential energy surfaces were produced. On the basis of the results of these reaction studies, it was found necessary to propose and subsequently confirm additional, alternative pathways for the formation of the types of PAH compounds found in combustion systems. The potential energy surface for one reaction in particular, the phenyl + phenyl addition, is shown to contain a low-energy channel leading to formation of naphthalene that is energetically comparable to the other examined conventional pathways leading to formation of biphenyl compounds. This

  11. Regiospecific incorporation of no-carrier-added radiobromine and radioiodine into aromatic rings via halodegermylation

    SciTech Connect

    Moerlein, S.M.

    1984-01-01

    In view of the low energy and high polarity of aromatic carbon-germanium bonds, the utility of trimethylarylgermanium compounds as precursors for regiospecific no-carrier-added (NCA) electrophilic aromatic halogenation was investigated. Para-substituted trimethylarylgermanium compounds (p-X-C/sub 6/H/sub 4/-Ge(CH/sub 3/)/sub 3/; X = NO/sub 2/, CF/sub 3/, Br, F, H, CH/sub 3/) were synthesized in 45-95% yield, purified by fractionation, and chemically characterized. Radiohalogenation reactions were carried out at 25/sup 0/C in sealed reaction vessels containing a homogeneous mixture of NCA /sup 77/Br/sup -/ or /sup 131/I/sup -/, dichloramine-T (DCT) oxidizing agent, organogermanium compound, and solvent. Product analyses were done using radio-HPLC and radio-GC. The choice of solvent affected the kinetics of NCA halodegermylation as well as the radiochemical yields attained. For polar solvents (MeOH, EtOH, CH/sub 2/Cl/sub 2/, CHCl/sub 3/), high radiochemical yields were achieved within 10 minutes using DCT concentrations as low as 10/sup -3/ M. Regiospecific displacement of the trimethylgermyl group by radiohalogen occurred in both activated and deactivated aromatic systems, and competitive halodeprotonation yields were negligible. Although electron-withdrawing substituents decreased the radiochemical yield even in such heavily-deactivated systems as benzotrifluoride (X = CF/sub 3/), aromatic substitution yields exceeded 30%. For electron-donating groups, yields were greater than 75%. The high radiochemical yields, short reaction times, and low concentration of oxidizing agent required for this regiospecific n.c.a. halogenation reaction make halodegermylation a useful technique for radiopharmaceutical production.

  12. Stereocontrolled ring-opening of a hindered sulfamidate with nitrogen-containing aromatic heterocycles: synthesis of chiral quaternary imidazole derivatives.

    PubMed

    Mata, Lara; Jiménez-Osés, Gonzalo; Avenoza, Alberto; Busto, Jesús H; Peregrina, Jesús M

    2011-05-20

    This paper explores the role of a hindered cyclic sulfamidate derived from α-methylisoserine as an electrophile in a nucleophilic displacement reaction with nitrogen-containing aromatic heterocycles. Several imidazoles and pyrazole were tested as nucleophiles in the absence of an additional base to give the corresponding ring-opening compounds. We show that the process takes place by inversion of the configuration of the quaternary electrophilic center, retaining the enantiomeric excess of the starting sulfamidate. This reaction opens the way to obtain important quaternary imidazole derivatives such as an innovative type of bis-amino acid related to histidinoalanine and a novel α,α-disubstituted β-amino acid (β(2,2)-amino acid).

  13. Water flow in carbon-based nanoporous membranes impacted by interactions between hydrated ions and aromatic rings

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Shi, Guosheng; Fang, Haiping

    2017-02-01

    Carbon-based nanoporous membranes, such as carbon nanotubes (CNTs), graphene/graphene oxide and graphyne, have shown great potential in water desalination and purification, gas and ion separation, biosensors, and lithium-based batteries, etc. A deep understanding of the interaction between hydrated ions in an aqueous solution and the graphitic surface in systems composed of water, ions and a graphitic surface is essential for applications with carbon-based nanoporous membrane platforms. In this review, we describe the recent progress of the interaction between hydrated ions and aromatic ring structures on the carbon-based surface and its applications in the water flow in a carbon nanotube. We expect that these works can be extended to the understanding of water flow in other nanoporous membranes, such as nanoporous graphene, graphyne and stacked sheets of graphene oxide.

  14. Water flow in carbon-based nanoporous membranes impacted by interactions between hydrated ions and aromatic rings.

    PubMed

    Liu, Jian; Shi, Guosheng; Fang, Haiping

    2017-02-24

    Carbon-based nanoporous membranes, such as carbon nanotubes (CNTs), graphene/graphene oxide and graphyne, have shown great potential in water desalination and purification, gas and ion separation, biosensors, and lithium-based batteries, etc. A deep understanding of the interaction between hydrated ions in an aqueous solution and the graphitic surface in systems composed of water, ions and a graphitic surface is essential for applications with carbon-based nanoporous membrane platforms. In this review, we describe the recent progress of the interaction between hydrated ions and aromatic ring structures on the carbon-based surface and its applications in the water flow in a carbon nanotube. We expect that these works can be extended to the understanding of water flow in other nanoporous membranes, such as nanoporous graphene, graphyne and stacked sheets of graphene oxide.

  15. Polycyclic aromatic hydrocarbons and metals in transplanted lichen (Pseudovernia furfuracea) at sites adjacent to a solid-waste landfill in central Italy.

    PubMed

    Protano, C; Guidotti, M; Owczarek, M; Fantozzi, L; Blasi, G; Vitali, M

    2014-05-01

    The aim of the study was to evaluate the airborne contamination by polycyclic aromatic hydrocarbons (PAHs) and some heavy metals (arsenic [As], cadmium [Cd], chromium [Cr], copper [Cu], nickel [Ni], lead [Pb], and zinc [Zn]) of different pollution scenarios around a solid-waste landfill in central Italy using the lichen Pseudovernia furfuracea as a monitoring tool. For this purpose, eight stations around a landfill characterized by different air pollution sources (industrial, agricultural, residential areas, and roads with different traffic intensities), together with three stations far from the landfill (control areas), were monitored using a set of 22 lichen samples (11 samples analysed for PAHs and metals after 4 months, and 11 samples analysed for metals after 8 months). After 4 months of exposure, the lichen content of all of the analysed elements was greater than that in the pre-exposed lichens. In addition, the Cu and Pb concentration after 8 months was greater than the level after 4 months. The order of metal concentration was Zn > Pb > Cu (or Cu > Pb) > Cr > Ni > As > Cd in all cases. The range of ∑11PAHs concentration was 634-1,371 ng/g dw (three to seven times greater than the amount in the pre-exposed lichens). The ∑11PAHs were dominated (>70 %) by compounds with three aromatic rings. The comparison of the levels of air pollutants among the monitored stations shows nonrelevant spatial patterns between the landfill stations and the control areas; the levels of PAHs and metals found in the lichen samples around the landfill seemed to be more related to the general diffusion of these pollutants in that area.

  16. 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.

  17. Distribution and source recognition of polycyclic aromatic hydrocarbons in the sediments of Hsin-ta Harbour and adjacent coastal areas, Taiwan.

    PubMed

    Fang, Meng-Der; Lee, Chon-Lin; Yu, Chia-Shun

    2003-08-01

    Thirty-three sediment samples from Hsin-ta Harbour and neighboring coastal areas were analyzed by GC-MS for polycyclic aromatic hydrocarbons (PAHs). Total concentrations of 30 analyzed parental and alkylated PAHs ( summation operator PAH) varied from 98.1 to 3382 ng/g dry weight. MP/P (methylphenanthrenes/phenanthrene) values larger than 2 coincided with very low P/A (phenanthrene/anthracene) values at inner harbour stations, revealing that a significant portion of low molecular weight PAHs are probably from petrogenic pollution sources, specifically, illegal disposal of used motor oil. The 4,6-dimethyldibenzothiophene/3,6-dimethylphenanthrene (4,6-C(2)D/3,6-C(2)P) ratio is found to be more useful than the MP/P ratio in tracing petrogenic PAHs from the inner harbour area to the adjacent coastal environment. In addition, according to hierarchical cluster analysis, collected sediments cluster in three major groups, Off-shore Group, Near-shore Group and Inner Harbour Group. Three diagnostic ratios, 4,6-C(2)D/3,6-C(2)P, PER/ summation operator PAH (perylene to summation operator PAH) and BaA/CHR (benzo(a)anthracene/chrysene), representing petrogenic, biogenic and pyrogenic origins, are found to be effective in differentiating and characterizing sediments among the groups in this study. Enrichment of pyrogenic and petrogenic PAHs in sediments collected exhibits mixing or dilution, spatially, by biogenic (or natural) PAHs.

  18. Investigations of the origins of estrogenic A-ring aromatic steroids in UK sewage treatment works effluents.

    PubMed

    Niven, S J; Snape, J; Hetheridge, M; Evans, M; McEvoy, J; Sutton, P G; Rowland, S J

    2001-03-01

    The present preliminary study describes an investigation of a putative aromatisation pathway in sewage from cholesterol through the corresponding A-ring aromatic steroid, norcholest-1,3,5(10)-trienol (NCT) to estrone. The synthesis and analytical characterisation of NCT and of the trimethyl silyl ether by gas chromatography-mass spectrometry, is described. The analytical properties of synthetic NCT were used to direct a search for the compound over several months in 1998 in the effluents of two sewage treatment works (STW; Deephams and Harpenden, north London). The study was prompted by the earlier findings that increased vitellogenin concentrations in the plasma of caged male rainbow trout held in the STW effluents (so-called fish 'feminisation') could be attributed to the presence of A-ring steroids such as estrone. Until now it has been assumed that these steroids originate from the STW influents and it is not clear to what extent, if at all, aromatisation of steroids might occur during STW operation. NCT was only detected in the solid particles associated with the effluents on one occasion in 8 months. This suggests that the hypothesised pathway is not a major one. Confirmation of previous reports of estrone and 17 beta-estradiol was also obtained using a published analytical method and by a simple modification of the method these reports were extended to include a regular occurrence of the weaker estrogen, 16 alpha-estriol in the case of Harpenden STW effluents in 1998.

  19. Reversal of Orbital Symmetry Control in Electrocyclic Ring Closures through Craig-Möbius Aromaticity.

    PubMed

    Mauksch, Michael; Tsogoeva, Svetlana B

    2016-04-04

    Experimentalists are challenged to find the organometallic thermal electrocyclizations that are computationally predicted to proceed with opposite stereoselectivity compared to their metal-free parent 4n and 4n+2 π-electron systems. While ring closure of, for example, s-cis-butadiene proceeds conrotatory, an iron alkyl complex formed by replacement of a (CH) unit by an [FeH] metal fragment results in a disrotatory electrocyclization.

  20. 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

  1. Mechanism of aromatic ring cleavage of a. beta. -biphenylyl ether dimer catalyzed by lignin peroxidase of Phanerochaete chrysosporium

    SciTech Connect

    Miki, K.; Kondo, R.; Renganathan, V.; Mayfield, M.B.; Gold, M.H.

    1988-06-28

    Homogeneous lignin peroxidase (LiP) oxidized 1-(4-methoxyphenyl)-2-)2,6-dimethoxy-4-phenylphenoxy)-1,3-propanediol (I) to yield 1-(4-methoxyphenyl)-1,2,3-propanetriol (II), ..cap alpha..-(4-methoxy-phenyl)-2-oxo-1,3-dioxolane-4-methanol (III), 5-(4-methoxyphenyl)-2-oxo-1,3-dioxolane-4-methanol (IV), 4-oxo-3-phenyl-2-butenoic acid methyl ester (V), 5-hydroxy-4-phenyl-2(5H)-furanone (VI), 4-oxo-3-phenyl-2-pentenedioic acid dimethyl ester (VII), and 5-carbomethoxy-5-hydroxy-4-phenyl-2(5H)-furanone (VIII). Products II-VIII are all derived from the opening of the B aromatic ring of the substrate. Oxidation of I in H/sub 2/ /sup 18/O resulted in 87% and 65% incorporation of /sup 18/O into the carbonyl oxygen of III and IV, respectively. Oxidation of I under /sup 18/O/sub 2/ resulted in the incorporation of two atoms of oxygen into the aldehyde (V). Oxidation of I under either /sup 18/O/sub 2/ or H/sub 2//sup 18/O resulted in the incorporation of three atoms of oxygen into the lactol VI. Finally, oxidation of I under either /sup 18/O/sub 2/ or H/sub 2//sup 18/O indicated that four atoms of oxygen were incorporated into the lactol VIII. These results are explained by a mechanism involving the one-electron oxidation of the B ring of the substrate to an aryl cation radical by the H/sub 2/O/sub 2/ oxidized enzyme. In these oxidative pathways, only the formation of the aryl cation radical is enzyme-catalyzed. Subsequent reactions appear to be nonenzymatic, accounting for the variety of ring-opened products formed.

  2. Coupling of complex aromatic ring vibrations to solvent through hydrogen bonds: effect of varied on-ring and off-ring hydrogen-bonding substitutions.

    PubMed

    Nucci, Nathaniel V; Scott, J Nathan; Vanderkooi, Jane M

    2008-04-03

    In this study, we examine the coupling of a complex ring vibration to solvent through hydrogen-bonding interactions. We compare phenylalanine, tyrosine, l-dopa, dopamine, norepinephrine, epinephrine, and hydroxyl-dl-dopa, a group of physiologically important small molecules that vary by single differences in H-bonding substitution. By examination of the temperature dependence of infrared absorptions of these molecules, we show that complex, many-atom vibrations can be coupled to solvent through hydrogen bonds and that the extent of that coupling is dependent on the degree of both on- and off-ring H-bonding substitution. The coupling is seen as a temperature-dependent frequency shift in infrared spectra, but the determination of the physical origin of that shift is based on additional data from temperature-dependent optical experiments and ab initio calculations. The optical experiments show that these small molecules are most sensitive to their immediate H-bonding environment rather than to bulk solvent properties. Ab initio calculations demonstrate H-bond-mediated vibrational coupling for the system of interest and also show that the overall small molecule solvent dependence is determined by a complex interplay of specific interactions and bulk solvation characteristics. Our findings indicate that a full understanding of biomolecule vibrational properties must include consideration of explicit hydrogen-bonding interactions with the surrounding microenvironment.

  3. Identification and Functional Analysis of Two Aromatic-Ring-Hydroxylating Dioxygenases from a Sphingomonas Strain That Degrades Various Polycyclic Aromatic Hydrocarbons

    PubMed Central

    Demanèche, Sandrine; Meyer, Christine; Micoud, Julien; Louwagie, Mathilde; Willison, John C.; Jouanneau, Yves

    2004-01-01

    In this study, the enzymes involved in polycyclic aromatic hydrocarbon (PAH) degradation in the chrysene-degrading organism Sphingomonas sp. strain CHY-1 were investigated. [14C]chrysene mineralization experiments showed that PAH-grown bacteria produced high levels of chrysene-catabolic activity. One PAH-induced protein displayed similarity with a ring-hydroxylating dioxygenase beta subunit, and a second PAH-induced protein displayed similarity with an extradiol dioxygenase. The genes encoding these proteins were cloned, and sequence analysis revealed two distinct loci containing clustered catabolic genes with strong similarities to corresponding genes found in Novosphingobium aromaticivorans F199. In the first locus, two genes potentially encoding a terminal dioxygenase component, designated PhnI, were followed by a gene coding for an aryl alcohol dehydrogenase (phnB). The second locus contained five genes encoding an extradiol dioxygenase (phnC), a ferredoxin (phnA3), another oxygenase component (PhnII), and an isomerase (phnD). PhnI was found to be capable of converting several PAHs, including chrysene, to the corresponding dihydrodiols. The activity of PhnI was greatly enhanced upon coexpression of genes encoding a ferredoxin (phnA3) and a reductase (phnA4). Disruption of the phnA1a gene encoding the PhnI alpha subunit resulted in a mutant strain that had lost the ability to grow on PAHs. The recombinant PhnII enzyme overproduced in Escherichia coli functioned as a salicylate 1-hydroxylase. PhnII also used methylsalicylates and anthranilate as substrates. Our results indicated that a single enzyme (PhnI) was responsible for the initial attack of a range of PAHs, including chrysene, in strain CHY-1. Furthermore, the conversion of salicylate to catechol was catalyzed by a three-component oxygenase unrelated to known salicylate hydroxylases. PMID:15528538

  4. Neuroleptics related to butaclamol. An investigation of the effects of chlorine substituents on the aromatic rings.

    PubMed

    Humber, L G; Sideridis, N; Asselin, A A; Bruderlein, F T; Voith, K

    1978-12-01

    The synthesis of analogues of the antipsychotic drug butaclamol bearing chloro substituents on the benzene rings is described. On the basis of a perceived topographical similarity of a putative chlorophenylethylamine pharmacophore present in these analogues and in VUFB-10032 and doclothepin, agents related to octoclothepin which do not induce catalepsy, they have been tested for "noncataleptic" neuroleptic activity. None of the butaclamol analogues exhibit this type of activity. Depending on the position of the chlorine, the analogues either retained butaclamol-like activity or were inactive.

  5. 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.

  6. 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

  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. AgOTf-catalyzed reactions of naphthols/substituted phenols with 2-hydroxychalcones: facile synthesis of di-aromatic ring-fused [3.3.1]bicyclic compounds.

    PubMed

    Rao, Yin; Yin, Guodong

    2013-09-28

    A simple and efficient method for the synthesis of functionalized di-aromatic ring-fused 2,8-dioxabicyclo[3.3.1]nonane derivatives catalyzed by silver triflate from easily available 2-hydroxychalcones and naphthols/substituted phenols is described. Two six-membered cycles were formed in a one-pot operation. This reaction was probably achieved via a Friedel-Crafts alkylation/bicyclization domino process.

  10. Structure-activity study on the spatial arrangement of the third aromatic ring of endomorphins 1 and 2 using an atypical constrained C terminus.

    PubMed

    Yu, Ye; Shao, Xuan; Cui, Yun; Liu, Hong-mei; Wang, Chang-ling; Fan, Ying-zhe; Liu, Jing; Dong, Shou-liang; Cui, Yu-xing; Wang, Rui

    2007-03-01

    The discovery of endomorphins (EMs) has opened the possibility of searching for new analgesics. However, the design of peptide analgesics has proven to be very difficult as a result of their conformational flexibility and a lack of clarity in structure-activity relationships (SAR). In EMs, the amino acid side chains exhibit considerable conformational flexibility, especially in the third aromatic ring, which is free to adopt a bioactive conformation. To resolve these problems, a series of C terminus EM analogues, [Xaa(4)-R]EMs, modified through the substitution of Phe(4) with nonaromatic residues and termination with benzyl groups, were designed to generate conformational constrains of the third aromatic ring by amide bond and torsion angles (phi(4) and psi(4)) of Xaa(4). Introduction of (S)-alpha-methyl or (S)/(R)-alpha-carboxamide on the methylene unit of the benzyl group was designed to produce an atypical topographical constraint (phi(5)) of the third aromatic ring rotation. Interestingly, some EM derivatives, with elimination of the C-terminal carboxamide group and significant changes in the address sequence (Phe(4)-NH(2)), still exhibited higher mu-opioid receptor (MOR) affinity than unmodified EMs. In contrast, some analogues with incorrectly constrained C termini displayed very low affinity and pharmacological activities. Thus, our results indicate that these EM analogues, with atypical constrained C termini, provide model compounds with potent MOR agonism. They also give evidence that the proper spatial orientation and conformational restriction of the third aromatic ring are crucial for the interaction of EMs with MOR.

  11. Copper Causes Regiospecific Formation of C4 F8 -Containing Six-Membered Rings and their Defluorination/Aromatization to C4 F4 -Containing Rings in Triphenylene/1,4-C4 F8 I2 Reactions.

    PubMed

    Rippy, Kerry C; Bukovsky, Eric V; Clikeman, Tyler T; Chen, Yu-Sheng; Hou, Gao-Lei; Wang, Xue-Bin; Popov, Alexey A; Boltalina, Olga V; Strauss, Steven H

    2016-01-18

    The presence of Cu in reactions of triphenylene (TRPH) and 1,4-C4 F8 I2 at 360 °C led to regiospecific substitution of TRPH ortho C(β) atoms to form C4 F8 -containing rings, completely suppressing substitution on C(α) atoms. In addition, Cu caused selective reductive-defluorination/aromatization (RD/A) to form C4 F4 -containing aromatic rings. Without Cu, the reactions of TRPH and 1,4-C4 F8 I2 were not regiospecific and no RD/A was observed. These results, supported by DFT calculations, are the first examples of Cu-promoted 1) regiospecific perfluoroannulation, 2) preparative C-F activation, and 3) RD/A. HPLC-purified products were characterized by X-ray diffraction, low-temperature PES, and (1) H/(19) F NMR.

  12. Copper Causes Regiospecific Formation of C4F8-Containing Six-Membered Rings and their Defluorination/Aromatization to C4F4-Containing Rings in Triphenylene/1,4-C4F8I2 Reactions

    SciTech Connect

    Rippy, Kerry C.; Bukovsky, Eric V.; Clikeman, Tyler T.; Chen, Yu-Sheng; Hou, Gao-Lei; Wang, Xue B.; Popov, Alexey; Boltalina, Olga V.; Strauss, Steven H.

    2016-01-18

    The presence of Cu in reactions of triphenylene (TRPH) and 1,4-C4F8I2 at 360 °C led to regiospecific substitution of TRPH ortho C(β) atoms to form C4F8-containing rings, completely suppressing substitution on C(α) atoms. In addition, Cu caused selective reductive-defluorination/aromatization (RD/A) to form C4F4- containing aromatic rings. Without Cu, the reactions of TRPH and 1,4- C4F8I2 were not regiospecific and no RD/A was observed. These results, supported by DFT calculations, are the first examples of Cupromoted (i) regiospecific perfluoroannulation, (ii) preparative C–F activation, and (iii) RD/A. HPLC-purified products were characterized by X-ray diffraction, low-temperature PES, and 1H/19F NMR.

  13. Analysis of polycyclic aromatic hydrocarbons in tree-rings of Masson pine (Pinus massoniana L.) from two industrial sites in the Pearl River Delta, south China.

    PubMed

    Kuang, Yuan-wen; Zhou, Guo-yi; Wen, Da-zhi; Li, Jiong; Sun, Fang-fang

    2011-09-01

    Concentrations of polycyclic aromatic hydrocarbons (PAHs) were examined and potential sources of PAHs were identified from the dated tree-rings of Masson pine (Pinus massoniana L.) near two industrial sites (Danshuikeng, DSK and Xiqiaoshan, XQS) in the Pearl River Delta of south China. Total concentrations of PAHs (∑PAHs) were revealed with similar patterns of temporal trends in the tree-rings at both sites, suggesting tree-rings recorded the historical variation in atmospheric PAHs. The differences of individual PAHs and of ∑PAHs detected in the tree-rings between the two sites reflected the historical differences of airborne PAHs. Regional changes in industrial activities might contribute to the site-specific and period-specific patterns of the tree-ring PAHs. The diagnostic PAH ratios of Ant/(Ant + PA), FL/(FL + Pyr), and BaA/(BaA + Chr)) revealed that PAHs in the tree-rings at both sites mainly stemmed from the combustion process (pyrogenic sources). Principal component analysis further confirmed that wood burning, coal combustion, diesel, and gasoline-powered vehicular emissions were the dominant contributors of PAHs sources at DSK, while diesel combustion, gasoline and natural gas combustion, and incomplete coal combustion were responsible for the main origins of PAHs at XQS. Tree-ring analysis of PAHs was indicative of PAHs from a mixture of sources of combustion, thus minimizing the bias of short-term active air sampling.

  14. 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.

  15. Theoretical Study on the Dual Behavior of XeO3 and XeF4 toward Aromatic Rings: Lone Pair-π versus Aerogen-π Interactions.

    PubMed

    Bauzá, Antonio; Frontera, Antonio

    2015-12-01

    In this study, several lone pair-π and aerogen-π complexes between XeO3 and XeF4 and aromatic rings with different electronic natures (benzene, trifluorobenzene, and hexafluorobenzene) are optimized at the RI-MP2/aug-cc-pVTZ level of theory. All complexes are characterized as true minima by frequency analysis calculations. The donor/acceptor role of the ring in the complexes is analyzed using the natural bond orbital computational tool, showing a remarkable contribution of orbital interactions to the global stabilization of the aerogen-π complexes. Finally, Bader's AIM analysis of several complexes is performed to further characterize the lone pair-π and aerogen-π interactions.

  16. One-pot hydrogen peroxide and hydrohalic acid induced ring closure and selective aromatic halogenation to give new ring-fused benzimidazoles.

    PubMed

    Gurry, Michael; Sweeney, Martin; McArdle, Patrick; Aldabbagh, Fawaz

    2015-06-05

    A new series of selectively dichlorinated and dibrominated five- to eight-membered-ring [1,2-a]-fused benzimidazoles and [1,4]oxazino[4,3-a]benzimidazoles are synthesized in mostly high yields of >80% using the reaction of hydrogen peroxide and hydrohalic acid with commercially available o-cyclic amine substituted anilines. Domestic bleach with HCl can also be used for a one-pot ring closure and chlorination.

  17. 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.

  18. Effects of Lewis acid catalysts on the hydrogenation and cracking of two-ring aromatic and hydroaromatic structures related to coal

    SciTech Connect

    Salim, Sadie S.; Bell, Alexis T.

    1982-08-01

    Little is known about the hydrogenation of fused aromatic nuclei during the liquefaction of coal under the influence of Lewis acid catalysts. For this paper, this study was conducted to establish the effects of catalyst acidity on the activity and selectivity of Lewis acid catalysts, the sources of hydrogen involved in hydrogenation and cracking, and the relations between reactant structure and reactivity. Two-ring aromatic and hydroaromatic compounds were used to simulate some of the structural units present in coal. The catalysts examined were ZnCl2 and AlCl3. ZnCl2 is less active than AlCl3 for both hydrogenation and cracking but it does not promote the formation of tars via Scholl condensation: Methyl or hydroxyl substitution of the reactants greatly enhances their reactivity towards hydrogenation and cracking. The source of hydrogen consumed during hydrogenation depends on the choice of catalyst. In the presence of AlCl3, Scholl condensation of aromatic nuclei serves as the principal source of hydrogen. Molecular hydrogen is used exclusively, though, when hydrogenation is catalysed by ZnCl2. The formation of reaction products and the trends in reactant reactivity can be interpreted on the basis of carbonium ion mechanisms. Finally, the results of this study provide a basis for assessing the extent of hydrogenation occurring during the liquefaction of coal using ZnCl2 or AlCl3.

  19. A highly sensitive monoclonal antibody based biosensor for quantifying 3-5 ring polycyclic aromatic hydrocarbons (PAHs) in aqueous environmental samples

    PubMed Central

    Li, Xin; Kaattari, Stephen L.; Vogelbein, Mary A.; Vadas, George G.; Unger, Michael A.

    2016-01-01

    Immunoassays based on monoclonal antibodies (mAbs) are highly sensitive for the detection of polycyclic aromatic hydrocarbons (PAHs) and can be employed to determine concentrations in near real-time. A sensitive generic mAb against PAHs, named as 2G8, was developed by a three-step screening procedure. It exhibited nearly uniformly high sensitivity against 3-ring to 5-ring unsubstituted PAHs and their common environmental methylated PAHs, with IC50 values between 1.68–31 μg/L (ppb). 2G8 has been successfully applied on the KinExA Inline Biosensor system for quantifying 3-5 ring PAHs in aqueous environmental samples. PAHs were detected at a concentration as low as 0.2 μg/L. Furthermore, the analyses only required 10 min for each sample. To evaluate the accuracy of the 2G8-based biosensor, the total PAH concentrations in a series of environmental samples analyzed by biosensor and GC-MS were compared. In most cases, the results yielded a good correlation between methods. This indicates that generic antibody 2G8 based biosensor possesses significant promise for a low cost, rapid method for PAH determination in aqueous samples. PMID:26925369

  20. Liquid chromatography-atmospheric pressure laser ionization-mass spectrometry (LC-APLI-MS) analysis of polycyclic aromatic hydrocarbons with 6-8 rings in the environment.

    PubMed

    Thiäner, Jan B; Achten, Christine

    2017-03-01

    A method has been developed for the sensitive and rapid analysis of polycyclic aromatic hydrocarbons (PAHs) in environmental samples using liquid chromatography time-of-flight mass spectrometry as well as the selective atmospheric pressure laser ionization (APLI) process (LC-APLI-MS). Upon analyzing 34 PAHs, the limits of detection of this method were found to range from 0.008 to 1.824 pg (0.024 pg for benzo[a]pyrene). The method therefore provides 30-fold to 5,400-fold increased sensitivity compared with the established GC-MS technique. This LC-APLI-MS method was optimized for higher molecular weight PAHs (C24-C30 PAHs with 6-8 rings), which are difficult to detect or cannot be detected by GC-MS. Using the LC-APLI-MS method, various 6- to 8-ring PAHs were detected in environmental samples for the first time. After developing the method, it was successfully validated in ruggedness tests. The concentrations determined by the LC-APLI-MS method were in good accord with the certified concentrations in three certified reference materials (contaminated soils and sediments). Upon applying the method to environmental samples, it was found that (1) the presence of dibenzo[a,i]pyrene and dibenzo[a,h]pyrene in urban soil samples could only be detected using LC-APLI-MS (i.e., not GC-MS) due to its high sensitivity, (2) a bituminous coal sample yielded 211 tentative peaks from aromatic compounds in the C24-C30 range, and (3) eleven of those compounds occurred in different environmental samples in similar patterns. Hence, 6- to 8-ring PAHs occur in solid environmental samples in which other 6-ring PAHs such as indeno[1,2,3-cd]pyrene or benzo[ghi]perylene may also be present. Some of these numerous higher molecular weight PAH compounds could have very high carcinogenic potential, which will need to be elucidated to ensure the reliability of PAH risk assessments.

  1. Pleiotropic and epistatic behavior of a ring-hydroxylating oxygenase system in the polycyclic aromatic hydrocarbon metabolic network from Mycobacterium vanbaalenii PYR-1.

    PubMed

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

    2014-10-01

    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.

  2. 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

  3. 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.

  4. 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)

  5. 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

    2016-06-07

    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.

  6. A new type of excited-state intramolecular proton transfer: proton transfer from phenol OH to a carbon atom of an aromatic ring observed for 2-phenylphenol.

    PubMed

    Lukeman, Matthew; Wan, Peter

    2002-08-14

    The photochemical deuterium incorporation at the 2'- and 4'-positions of 2-phenylphenol (4) and equivalent positions of related compounds has been studied in D(2)O (CH(3)OD)-CH(3)CN solutions with varying D(2)O (CH(3)OD) content. Predominant exchange was observed at the 2'-position with an efficiency that is independent of D(2)O (MeOD) content. Exchange at the 2'-position (but not at the 4'-position) was also observed when crystalline samples of 4-OD were irradiated. Data are presented consistent with a mechanism of exchange that involves excited-state intramolecular proton transfer (ESIPT) from the phenol to the 2'-carbon position of the benzene ring not containing the phenol, to generate the corresponding keto tautomer (an o-quinone methide). This is the first explicit example of a new class of ESIPT in which an acidic phenolic proton is transferred to an sp(2)-hybridized carbon of an aromatic ring. The complete lack of exchange observed for related substrates 6-9 and for planar 4-hydroxyfluorene (10) is consistent with a mechanism of ESIPT that requires an initial hydrogen bonding interaction between the phenol proton and the benzene pi-system. Similar exchange was observed for 2,2'-biphenol (5), suggesting that this new type of ESIPT is a general reaction for unconstrained 2'-aryl-substituted phenols and other related hydroxyarenes.

  7. Aromaticity-controlled thermal stability of photochromic systems based on a six-membered ring as ethene bridges: photochemical and kinetic studies.

    PubMed

    Yang, Yuheng; Xie, Yongshu; Zhang, Qiong; Nakatani, Keitaro; Tian, He; Zhu, Weihong

    2012-09-10

    Three photochromic compounds--2-butyl-5,6-bis[5-(4-methoxyphenyl)-2-methylthiophen-3-yl]-1 H-benzo[de]isoquinoline-1,3(2 H)-dione (BTE-NA), 4,5-bis[5-(4-methoxyphenyl)-2-methylthiophen-3-yl]benzo[c][1,2,5]thiadiazole (BTA), and BTTA, which contain naphthalimide, benzothiadiazole, and benzobisthiadiazole as six-membered ethene bridges with different aromaticities--were systematically studied in solution, sol-gel, and single-crystal states. They exhibit typical photochromic performance with considerably high cyclization quantum yields. BTE-NA, BTA, and BTTA form a typical donor-π-acceptor (D-π-A) system with significant intramolecular charge transfer (ICT) between HOMO and LUMO upon excitation, thus realizing the fluorescence modulation by both photochromism and solvatochromism. The three ethene bridges with different degrees of aromaticity can provide a systematic comparison of the thermal stability evolution for their corresponding closed forms (c-BTE-NA, c-BTA, and c-BTTA). c-BTE-NA shows first-order decay in various solvents from cyclohexane to acetonitrile. c-BTA only shows first-order decay in polar solvents such as chloroform, whereas it is stable in nonpolar solvents like toluene. In contrast, the less aromatic property of BTTA gives rise to its unprecedented thermal stability in various solvents even at elevated temperatures in toluene (328 K). Moreover, the small energy barrier between the parallel and antiparallel conformers allows the full conversion from BTTA to c-BTTA. In well-ordered crystal states, all three compounds adopt a parallel conformation. Interestingly, BTTA forms a twin crystal of asymmetric nature with interactions between the electron-rich oxygen atom of the methoxy group and the carbon atom of the electron-deficient benzobisthiadiazole moiety. This work contributes to the understanding of aromaticity-controlled thermal stability of photochromic systems based on a six-membered ring as an ethene bridge, and a broadening of the

  8. 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.

  9. Mechanism of alkoxy groups substitution by Grignard reagents on aromatic rings and experimental verification of theoretical predictions of anomalous reactions.

    PubMed

    Jiménez-Osés, Gonzalo; Brockway, Anthony J; Shaw, Jared T; Houk, K N

    2013-05-01

    The mechanism of direct displacement of alkoxy groups in vinylogous and aromatic esters by Grignard reagents, a reaction that is not observed with expectedly better tosyloxy leaving groups, is elucidated computationally. The mechanism of this reaction has been determined to proceed through the inner-sphere attack of nucleophilic alkyl groups from magnesium to the reacting carbons via a metalaoxetane transition state. The formation of a strong magnesium chelate with the reacting alkoxy and carbonyl groups dictates the observed reactivity and selectivity. The influence of ester, ketone, and aldehyde substituents was investigated. In some cases, the calculations predicted the formation of products different than those previously reported; these predictions were then verified experimentally. The importance of studying the actual system, and not simplified models as computational systems, is demonstrated.

  10. Nucleophilic substitution by amide nitrogen in the aromatic rings of [zn - H]˙⁺ ions; the structures of the [b₂ - H - 17]˙⁺ and [c1 - 17]⁺ ions.

    PubMed

    Mu, Xiaoyan; Lau, Justin Kai-Chi; Lai, Cheuk-Kuen; Siu, K W Michael; Hopkinson, Alan C; Chu, Ivan K

    2016-04-28

    Peptide radical cations that contain an aromatic amino acid residue cleave to give [zn - H]˙⁺ ions with [b2 - H - 17]˙⁺ and [c1 - 17](+) ions, the dominant products in the dissociation of [zn - H]˙⁺, also present in lower abundance in the CID spectra. Isotopic labeling in the aromatic ring of [Yπ˙GG](+) establishes that in the formation of [b2 - H - 17]˙⁺ ions a hydrogen from the δ-position of the Y residue is lost, indicating that nucleophilic substitution on the aromatic ring has occurred. A preliminary DFT investigation of nine plausible structures for the [c1 - 17](+) ion derived from [Y(π)˙GG](+) shows that two structures resulting from attack on the aromatic ring by oxygen and nitrogen atoms from the peptide backbone have significantly better energies than other isomers. A detailed study of [Y(π)˙GG](+) using two density functionals, B3LYP and M06-2X, with a 6-31++G(d,p) basis set gives a higher barrier for attack on the aromatic ring of the [zn - H]˙⁺ ion by nitrogen than by the carbonyl oxygen. However, subsequent rearrangements involving proton transfers are much higher in energy for the oxygen-substituted isomer leading to the conclusion that the [c1 - 17](+) ions are the products of nucleophilic attack by nitrogen, protonated 2,7-dihydroxyquinoline ions. The [b2 - H - 17]˙⁺ ions are formed by loss of glycine from the same intermediates involved in the formation of the [c1 - 17](+) ions.

  11. In vitro and in vivo characterization of opioid activities of endomorphins analogs with novel constrained C-terminus: evidence for the important role of proper spatial disposition of the third aromatic ring.

    PubMed

    Yu, Ye; Shao, Xuan; Wang, Chang-Lin; Liu, Hong-Mei; Cui, Yun; Fan, Ying-Zhe; Liu, Jing; Wang, Rui

    2007-04-01

    In the present study, the C-terminus of endomorphin (Tyr(1)-Pro(2)-Trp/Phe(3)-Phe(4)-NH(2), EMs) analogs [Xaa(4)-R]EMs, modified by substitution of a non-aromatic residue for Phe(4) and ending up with -NH-benzyl, were designed to generate an atypical conformationally constrained peptide set. We investigated the effects of these analogs on the opioid receptors affinity, guinea pig ileum (GPI) and mouse vas deferens (MVD) activity, system arterial pressure (SAP), heart rate (HR), antinociception and colonic motility. Analogs 5 ([D-V(4)-Bzl]EM1) and 10 ([D-V(4)-Bzl]EM2), which exhibit appropriate spatial orientations of the third aromatic ring, were about 3-4 times more potent than their parents both in vivo and in vitro. However, a drastic loss of activity was found in analogs 2 ([A(4)-Bzl]EM1) and 7 ([A(4)-Bzl]EM2), which possess improper spatial orientations of the third aromatic ring. Interestingly, analog 7 or 3 ([G(4)-Bzl]EM1), when injected intravenously (i.v.), produced significantly different changes in SAP from their parents. Surprisingly, analog 4 displayed relatively higher vasodepressor activity but significantly less potent colonic contractile activity than analog 5. This may be elicited by the differences in the spatial disposition of the third aromatic ring, which were verified by molecular modeling. Our results indicate that the proper spatial disposition of the third aromatic ring plays an important role in the regulation of pharmacological activities of EMs.

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

    PubMed

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

    2011-12-01

    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 (40μM) produced AHR2-dependent bradycardia, pericardial edema, and myocardial CYP1A immunofluorescence. By contrast, BkF exposure (4-40μM) 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 (40μM) 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.

  13. Desorption of polycyclic aromatic hydrocarbons from soot surface: five- and six-ring (C22, C24) PAHs.

    PubMed

    Bedjanian, Yuri; Nguyen, Mai Lan; Guilloteau, Angélique

    2010-03-18

    The kinetics of thermal desorption of five soot-bound nonvolatile (C(22), C(24)) polycyclic aromatic hydrocarbons (benzo(ghi)perylene (BghiP), indeno(1,2,3-cd)pyrene (IdP), anthanthrene (Antha), dibenz(ah)anthracene (DBahA), dibenzo(ae)pyrene (DBaeP)) identified in laboratory-generated kerosene soot were studied over the temperature range 335-370 K in a low pressure flow reactor. The PAH desorption rate constants were measured using off-line HPLC monitoring of their concentrations in soot samples as a function of desorption time. The following Arrhenius expressions were determined for the desorption rate constants of the soot-bound PAHs studied: k(des) = 8.4 x 10(15) exp[-(129.7 +/- 4.4)/RT], 1.0 x 10(16) exp[-(130.6 +/- 6.1)/RT], 1.1 x 10(16) exp[-(131.6 +/- 3.2)/RT], 1.0 x 10(16) exp[-(128.0 +/- 3.9)/RT], and 1.4 x 10(16) exp[-(134.2 +/- 10.7)/RT] (k(des) are in s(-1) and activation energies in kJ mol(-1)) for BghiP, IdP, Antha, DBahA, and DBaeP, respectively. Analysis of the present and previous experimental data showed that PAH-soot binding energies linearly correlate with the number of PAH carbon atoms. The present data and those from previous studies are discussed in the frame of the existing theoretical gas-to-particle partitioning model.

  14. Metal-Organic Framework with Aromatic Rings Tentacles: High Sulfur Storage in Li-S Batteries and Efficient Benzene Homologues Distinction.

    PubMed

    Li, Meng-Ting; Sun, Yu; Zhao, Kai-Sen; Wang, Zhao; Wang, Xin-Long; Su, Zhong-Min; Xie, Hai-Ming

    2016-12-07

    We designed and fabricated a fluorophore-containing tetradentate carboxylate ligand-based metal-organic framework (MOF) material with open and semiopen channels, which acted as the host for sulfur trapped in Li-S batteries and sensor of benzene homologues. These channels efficiently provide a π-π* conjugated matrix for the charge transfer and guest molecule trapping. The open channel ensured a much higher loading quantitative of sulfur (S content-active material, 72 wt %; electrode, 50.4 wt %) than most of the MOF/sulfur composites, while the semiopen channel possessing aromatic rings tentacles guaranteed an outstanding specific discharge capacity (1092 mA h g(-1) at 0.1 C) accompanied by good cycling stability. To our surprise, benefiting from special π-π* conjugated conditions, compound 1 could be a chemical sensor for benzene homologues, especially for 1,2,4-trimethylbenzene (1,2,4-TMB). This is the first example of MOFs materials serving as a sensor of 1,2,4-TMB among benzene homologues. Our works may be worthy of use for references in other porous materials systems to manufacture more long-acting Li-S batteries and sensitive chemical sensors.

  15. Development of highly potent phosphodiesterase 4 inhibitors with anti-neuroinflammation potential: Design, synthesis, and structure-activity relationship study of catecholamides bearing aromatic rings.

    PubMed

    Zhou, Zhong-Zhen; Ge, Bing-Chen; Zhong, Qiu-Ping; Huang, Chang; Cheng, Yu-Fang; Yang, Xue-Mei; Wang, Hai-Tao; Xu, Jiang-Ping

    2016-11-29

    In this study, catecholamides (7a-l) bearing different aromatic rings (such as pyridine-2-yl, pyridine-3-yl, phenyl, and 2-chlorophenyl groups) were synthesized as potent phosphodiesterase (PDE) 4 inhibitors. The inhibitory activities of these compounds were evaluated against the core catalytic domains of human PDE4 (PDE4CAT), full-length PDE4A4, PDE4B1, PDE4C1, and PDE4D7 enzymes, and other PDE family members. Eight of the synthesized compounds were identified as having submicromolar IC50 values in the mid-to low-nanomolar range. Careful analysis on the structure-activity relationship of compounds 7a-l revealed that the replacement of the 4-methoxy group with the difluoromethoxy group improved inhibitory activities. More interesting, 4-difluoromethoxybenzamides 7i and 7j exhibited preference for PDE4 with higher selectivities of about 3333 and 1111-fold over other PDEs, respectively. In addition, compound 7j with wonderful PDE4D7 inhibitory activities inhibited LPS-induced TNF-α production in microglia.

  16. 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.

  17. 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

  18. 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

    2016-06-06

    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.

  19. Substrate specificity and structural characteristics of the novel Rieske nonheme iron aromatic ring-hydroxylating oxygenases NidAB and NidA3B3 from Mycobacterium vanbaalenii PYR-1.

    PubMed

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

    2010-06-15

    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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. Insights into Thiol-Aromatic Interactions: A Stereoelectronic Basis for S-H/π Interactions.

    PubMed

    Forbes, Christina R; Sinha, Sudipta K; Ganguly, Himal K; Bai, Shi; Yap, Glenn P A; Patel, Sandeep; Zondlo, Neal J

    2017-02-08

    Thiols can engage favorably with aromatic rings in S-H/π interactions, within abiological systems and within proteins. However, the underlying bases for S-H/π interactions are not well understood. The crystal structure of Boc-l-4-thiolphenylalanine tert-butyl ester revealed crystal organization centered on the interaction of the thiol S-H with the aromatic ring of an adjacent molecule, with a through-space Hthiol···Caromatic distance of 2.71 Å, below the 2.90 Å sum of the van der Waals radii of H and C. The nature of this interaction was further examined by DFT calculations, IR spectroscopy, solid-state NMR spectroscopy, and analysis of the Cambridge Structural Database. The S-H/π interaction was found to be driven significantly by favorable molecular orbital interactions, between an aromatic π donor orbital and the S-H σ* acceptor orbital (a π → σ* interaction). For comparison, a structural analysis of O-H/π interactions and of cation/π interactions of alkali metal cations with aromatic rings was conducted. Na(+) and K(+) exhibit a significant preference for the centroid of the aromatic ring and distances near the sum of the van der Waals and ionic radii, as expected for predominantly electrostatic interactions. Li(+) deviates substantially from Na(+) and K(+). The S-H/π interaction differs from classical cation/π interactions by the preferential alignment of the S-H σ* toward the ring carbons and an aromatic π orbital rather than toward the aromatic centroid. These results describe a potentially broadly applicable approach to understanding the interactions of weakly polar bonds with π systems.

  5. Dimethandrolone (7alpha,11beta-dimethyl-19-nortestosterone) and 11beta-methyl-19-nortestosterone are not converted to aromatic A-ring products in the presence of recombinant human aromatase.

    PubMed

    Attardi, Barbara J; Pham, Trung C; Radler, Lisa C; Burgenson, Janet; Hild, Sheri A; Reel, Jerry R

    2008-06-01

    Dimethandrolone undecanoate (DMAU: 7alpha,11beta-dimethyl-19-nortestosterone 17beta-undecanoate) is a potent orally active androgen in development for hormonal therapy in men. Cleavage of the 17beta-ester bond by esterases in vivo leads to liberation of the biologically active androgen, dimethandrolone (DMA), a 19-norandrogen. For hormone replacement in men, administration of C19 androgens such as testosterone (T) may lead to elevations in circulating levels of estrogens due to aromatization. As several reports have suggested that certain 19-norandrogens may serve as substrates for the aromatase enzyme and are converted to the corresponding aromatic A-ring products, it was important to investigate whether DMA, the related compound, 11beta-methyl-19-nortestosterone (11beta-MNT), also being tested for hormonal therapy in men, and other 19-norandrogens can be converted to aromatic A-ring products by human aromatase. The hypothetical aromatic A-ring product corresponding to each substrate was obtained by chemical synthesis. These estrogens bound with high affinity to purified recombinant human estrogen receptors (ER) alpha and beta in competitive binding assays (IC50's: 5-12 x 10(-9) M) and stimulated transcription of 3XERE-luciferase in T47Dco human breast cancer cells with a potency equal to or greater than that of estradiol (E2) (EC50's: 10(-12) to 10(-11) M). C19 androgens (T, 17alpha-methyltestosterone (17alpha-MT), androstenedione (AD), and 16alpha-hydroxyandrostenedione (16alpha-OHAD)), 19-norandrogens (DMA, 11beta-MNT, 19-nortestosterone (19-NT), and 7alpha-methyl-19-nortestosterone (MENT)) or the structurally similar 19-norprogestin, norethindrone (NET) were incubated at 50 microM with recombinant human aromatase for 10-180 min at 37 degrees C. The reactions were terminated by extraction with acetonitrile and centrifugation, and substrate and potential product were separated by HPLC. Retention times were monitored by UV absorption, and UV peaks were quantified

  6. C-H and N-H bond dissociation energies of small aromatic hydrocarbons

    SciTech Connect

    Barckholtz, C.; Barckholtz, T.A.; Hadad, C.M.

    1999-01-27

    A survey of computational methods was undertaken to calculate the homolytic bond dissociation energies (BDEs) of the C-H and N-H bonds in monocyclic aromatic molecules that are representative of the functionalities present in coal. These include six-membered rings (benzene, pyridine, pyridazine, pyrimidine, pyrazine) and five-membered rings (furan, thiophene, pyrrole, oxazole). By comparison of the calculated C-H BDEs with the available experimental values for these aromatic molecules, the B3LYP/6-31G(d) level of theory was selected to calculate the BDEs of polycyclic aromatic hydrocarbons (PAHs), including carbonaceous PAHs (naphthalene, anthracene, pyrene, coronene) and heteroatomic PAHs (benzofuran, benzothiophene, indole, benzoxazole, quinoline, isoquinoline, dibenzofuran, carbazole). The cleavage of a C-H or a N-H bond generates a {sigma} radical that is, in general, localized at the site from which the hydrogen atom was removed. However, delocalization of the unpaired electron results in {approximately} 7 kcal {center{underscore}dot} mol{sup {minus}1} stabilization of the radical with respect to the formation of phenyl when the C-H bond is adjacent to a nitrogen atom in the azabenzenes. Radicals from five-membered rings are {approximately} 6 kcal {center{underscore}dot} mol{sup {minus}1} less stable than those formed from six-membered rings due to both localization of the spin density and geometric factors. The location of the heteroatoms in the aromatic ring affects the C-H bond strengths more significantly than does the size of the aromatic network. Therefore, in general, the monocyclic aromatic molecules can be used to predict the C-H BDE of the large PAHs within 1 kcal {center{underscore}dot} mol{sup {minus}1}.

  7. Insights into Hydrocarbon Chain and Aromatic Ring Formation in the Interstellar Medium: Computational Study of the Isomers of C4H3+ C6H3+ and C6H5+ and Their Formation Pathways

    NASA Astrophysics Data System (ADS)

    Peverati, Roberto; Bera, Partha P.; Lee, Timothy J.; Head-Gordon, Martin

    2016-10-01

    Small hydrocarbons such as acetylene is present in circumstellar envelopes of carbon-rich stars, but the processes that yield larger molecules, and eventually polycyclic aromatic hydrocarbons (PAHs), remain poorly understood. To gain additional insight into the early steps of such processes, electronic structure calculations were performed on the potential energy surfaces of {{{C}}}4{{{{H}}}3}+, {{{C}}}6{{{{H}}}3}+ and {{{C}}}6{{{{H}}}5}+. The results establish reactive pathways from acetylene and its ion to formation of the first aromatic ring. We characterize the stable isomers, their spectroscopic properties, and many of the transition structures that represent barriers to isomerization. The pathways to stabilized {{{C}}}4{{{{H}}}3}+ and {{{C}}}6{{{{H}}}3}+ are most likely to arise from unimolecular decomposition of hot {{{C}}}4{{{{H}}}4}+ and {{{C}}}6{{{{H}}}4}+ by H atom elimination. By contrast, we found an ion-molecule pathway to {{{C}}}6{{{{H}}}5}+ to be very stable to fragmentation and elimination reactions even without collisional stabilization. This aromatic species is a good nucleation center for the growth of larger PAHs in interstellar conditions.

  8. 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.

  9. 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.

  10. Metallic Ca-Rh/C-methanol, a high-performing system for the hydrodechlorination/ring reduction of mono- and poly chlorinated aromatic substrates.

    PubMed

    Mitoma, Yoshiharu; Kakeda, Mitsunori; Simion, Alina Marieta; Egashira, Naoyoshi; Simion, Cristian

    2009-08-01

    We investigated the reduction of some substituted mono- and poly chlorobenzenes bearing functional groups such as methyl, methoxy, hydroxyl, and amino, under mild conditions (80 degrees C and magnetic stirring, for 2 h) using a system consisting of metallic calcium and methanol (as hydrogen donor system) and 5% wt. Rh/C (as hydrodechlorination/ring reduction catalyst). Hydrodechlorination easily took place for methoxy- and alkyl-chlorobenzenes, yielding the corresponding hydrodechlorinated compounds (57-76%) and affording as secondary reaction products the ring-reduced compounds (16-43%). Treatment of hydroxy- and amino-chlorobenzenes under the same conditions, respectively, gave corresponding hydrodechlorinated compounds (over 60%) along with the ring-reduced compounds. Results show that the reaction of substituted polychlorinated benzenes needs a longer reaction time (6 h), the transformation being nevertheless complete.

  11. Research on Aromatic Poly

    NASA Astrophysics Data System (ADS)

    Kiebooms, Rafael Hugo Ludo

    1995-11-01

    A detailed analysis of the literature indicated that substituents can only be used at the level of improving properties during processing, that end groups are only important for those polymers where the energy difference between the aromatic and quinoid structure is very small, and that stability of pi delocalisation is the most important tool for the design of low bandgap polymers. From our research it appeared that, based on a detailed NMR and FT-Raman analysis of oligomers and model compounds, the low band gap of PITN could be associated with the quinoid structure. However, a theoretical analysis of the UV-vis data of a series of aromatic isothianaphthene oligomers indicates that a substantial lowering of the band gap can be obtained in planar aromatic isothianaphthene systems. A parallel investigation of PTFITN, a soluble isothianaphthene analogue, gave some indications that this polymer should possess an aromatic structure. The aromatic structure makes it possible that the fluorines probably induce non planarity such that inter ring pi -conjugation is lowered to a considerable extent. This could explain the increased band gap of 2.1eV observed by Swann et al.^{[1] }. Analysis of a series of aza-analogues of PITN revealed that in these materials it should be possible to combine a planar aromatic geometry with enhanced processability. The 4,5-diaza and 4,7-diaza isothianaphthene polymers can therefore be considered as very promising low band gap materials. Finally, we showed that it is possible to combine the aromatic isothianaphthene ring system with another heterocycle such as thiophene in a formal copolymer. Through the development of a highly specific and efficient synthesis route to 1,3-dithienylisothianaphthene (DTI, 4), we established the basis for the further synthesis and study of formal copolymers with tailor-made electronic properties. ftn ^{[1]}M. J. Swann, G. Brooke, D. Bloor. Synth.Met., 55-57, 281-286, (1993).

  12. 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

  13. 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

  14. High aromatic ring-cleavage diversity in birch rhizosphere: PAH treatment-specific changes of I.E.3 group extradiol dioxygenases and 16S rRNA bacterial communities in soil.

    PubMed

    Sipilä, Timo P; Keskinen, Anna-Kaisa; Akerman, Marja-Leena; Fortelius, Carola; Haahtela, Kielo; Yrjälä, Kim

    2008-09-01

    Genes encoding key enzymes of catabolic pathways can be targeted by DNA fingerprinting to explore genetic degradation potential in pristine and polluted soils. We performed a greenhouse microcosm experiment to elucidate structural and functional bacterial diversity in polyaromatic hydrocarbon (PAH)-polluted soil and to test the suitability of birch (Betula pendula) for remediation. Degradation of PAHs was analysed by high-performance liquid chromatography, DNA isolated from soil amplified and fingerprinted by restriction fragment length polymorphism (RFLP) and terminal restriction fragment length polymorphism (T-RFLP). Bacterial 16S rRNA T-RFLP fingerprinting revealed a high structural bacterial diversity in soil where PAH amendment altered the general community structure as well as the rhizosphere community. Birch augmented extradiol dioxygenase diversity in rhizosphere showing a rhizosphere effect, and further pyrene was more efficiently degraded in planted pots. Degraders of aromatic compounds upon PAH amendment were shown by the changed extradiol ring-cleavage community structure in soil. The RFLP analysis grouped extradiol dioxygenase marker genes into 17 distinct operational taxonomic units displaying novel phylogenetic clusters of ring-cleavage dioxygenases representing putative catabolic pathways, and the peptide sequences contained conserved amino-acid signatures of extradiol dioxygenases. A branch of major environmental TS cluster was identified as being related to Parvibaculum lavantivorans ring-cleavage dioxygenase. The described structural and functional diversity demonstrated a complex interplay of bacteria in PAH pollution. The findings improve our understanding of rhizoremediation and unveil the extent of uncharacterized enzymes and may benefit bioremediation research by facilitating the development of molecular tools to detect and monitor populations involved in degradative processes.

  15. Superconductivity in aromatic hydrocarbons

    NASA Astrophysics Data System (ADS)

    Kubozono, Yoshihiro; Goto, Hidenori; Jabuchi, Taihei; Yokoya, Takayoshi; Kambe, Takashi; Sakai, Yusuke; Izumi, Masanari; Zheng, Lu; Hamao, Shino; Nguyen, Huyen L. T.; Sakata, Masafumi; Kagayama, Tomoko; Shimizu, Katsuya

    2015-07-01

    'Aromatic hydrocarbon' implies an organic molecule that satisfies the (4n + 2) π-electron rule and consists of benzene rings. Doping solid aromatic hydrocarbons with metals provides the superconductivity. The first discovery of such superconductivity was made for K-doped picene (Kxpicene, five benzene rings). Its superconducting transition temperatures (Tc's) were 7 and 18 K. Recently, we found a new superconducting Kxpicene phase with a Tc as high as 14 K, so we now know that Kxpicene possesses multiple superconducting phases. Besides Kxpicene, we discovered new superconductors such as Rbxpicene and Caxpicene. A most serious problem is that the shielding fraction is ⩽15% for Kxpicene and Rbxpicene, and it is often ∼1% for other superconductors. Such low shielding fractions have made it difficult to determine the crystal structures of superconducting phases. Nevertheless, many research groups have expended a great deal of effort to make high quality hydrocarbon superconductors in the five years since the discovery of hydrocarbon superconductivity. At the present stage, superconductivity is observed in certain metal-doped aromatic hydrocarbons (picene, phenanthrene and dibenzopentacene), but the shielding fraction remains stubbornly low. The highest priority research area is to prepare aromatic superconductors with a high superconducting volume-fraction. Despite these difficulties, aromatic superconductivity is still a core research target and presents interesting and potentially breakthrough challenges, such as the positive pressure dependence of Tc that is clearly observed in some phases of aromatic hydrocarbon superconductors, suggesting behavior not explained by the standard BCS picture of superconductivity. In this article, we describe the present status of this research field, and discuss its future prospects.

  16. Aromatic-Aromatic Interactions in Biological System: Structure Activity Relationships

    SciTech Connect

    Rajagopal, Appavu; Deepa, Mohan; Govindaraju, Munisamy

    2016-02-26

    While, intramolecular hydrogen bonds have attracted the greatest attention in studies of peptide conformations, the recognition that several other weakly polar interactions may be important determinants of folded structure has been growing. Burley and Petsko provided a comprehensive overview of the importance of weakly polar interactions, in shaping protein structures. The interactions between aromatic rings, which are spatially approximate, have attracted special attention. A survey of the proximal aromatic residue pairs in proteins, allowed Burley and Petsko to suggest that, “phenyl ring centroids are separated by a preferential distance of between 4.5 and 7 Å, and dihedral angles approximately 90° are most common”.

  17. Double Ring Expansion from an Aromatic [18]Porphyrin(1.1.1.1) to an Antiaromatic [20]Porphyrin(2.1.2.1).

    PubMed

    Umetani, Masataka; Tanaka, Takayuki; Kim, Taeyeon; Kim, Dongho; Osuka, Atsuhiro

    2016-07-04

    Double ring expansion from a 5,15-diarylporphyrin to a 5,16-diaryl-10,11,21,22-tetradehydro[20]porphyrin(2.1.2.1) occurred through a reaction sequence consisting of oxidation with PbO2 to 5,15-dioxoporphodimethene, a Corey-Fuchs reaction with tetrabromomethane in the presence of triphenylphosphine, and Fritsch-Buttenberg-Wiechell rearrangement triggered by tert-butyllithium. The obtained tetradehydro[20]porphyrin(2.1.2.1) and its mono- and dihydrogenated congeners exhibited 20 π antiaromatic character, whereas overhydrogenated congeners bearing a saturated bridge were nonaromatic owing to disrupted π conjugation.

  18. The aromatic ene reaction

    PubMed Central

    Niu, Dawen; Hoye, Thomas R.

    2014-01-01

    The ene reaction is a pericyclic process in which an alkene having an allylic hydrogen atom (the ene donor) reacts with a second unsaturated species (the enophile) to form a new product with a transposed π-bond. The aromatic ene reaction, in which the alkene component is embedded in an aromatic ring, has only been reported in a few (four) instances and has proceeded in low yield (≤6%). Here we show efficient aromatic ene reactions in which a thermally generated aryne engages a pendant m-alkylarene substituent to produce a dearomatized isotoluene, itself another versatile but rare reactive intermediate. Our experiments were guided by computational studies that revealed structural features conducive to the aromatic ene process. We proceeded to identify a cascade comprising three reactions: (i) hexadehydro-Diels-Alder (for aryne generation), (ii) intramolecular aromatic ene, and (iii) bimolecular Alder ene. The power of this cascade is evident from the structural complexity of the final products, the considerable scope, and the overall efficiency of these multi-stage, reagent- and byproduct-free, single-pot transformations. PMID:24345944

  19. Reactivity of Tp(Me2) -supported yttrium alkyl complexes toward aromatic N-heterocycles: ring-opening or C-C bond formation directed by C-H activation.

    PubMed

    Yi, Weiyin; Zhang, Jie; Huang, Shujian; Weng, Linhong; Zhou, Xigeng

    2014-01-13

    Unusual chemical transformations such as three-component combination and ring-opening of N-heterocycles or formation of a carbon-carbon double bond through multiple C-H activation were observed in the reactions of Tp(Me2) -supported yttrium alkyl complexes with aromatic N-heterocycles. The scorpionate-anchored yttrium dialkyl complex [Tp(Me2) Y(CH2 Ph)2 (THF)] reacted with 1-methylimidazole in 1:2 molar ratio to give a rare hexanuclear 24-membered rare-earth metallomacrocyclic compound [Tp(Me2) Y(μ-N,C-Im)(η(2) -N,C-Im)]6 (1; Im=1-methylimidazolyl) through two kinds of C-H activations at the C2- and C5-positions of the imidazole ring. However, [Tp(Me2) Y(CH2 Ph)2 (THF)] reacted with two equivalents of 1-methylbenzimidazole to afford a C-C coupling/ring-opening/C-C coupling product [Tp(Me2) Y{η(3) -(N,N,N)-N(CH3 )C6 H4 NHCHC(Ph)CN(CH3 )C6 H4 NH}] (2). Further investigations indicated that [Tp(Me2) Y(CH2 Ph)2 (THF)] reacted with benzothiazole in 1:1 or 1:2 molar ratio to produce a C-C coupling/ring-opening product {(Tp(Me2) )Y[μ-η(2) :η(1) -SC6 H4 N(CHCHPh)](THF)}2 (3). Moreover, the mixed Tp(Me2) /Cp yttrium monoalkyl complex [(Tp(Me2) )CpYCH2 Ph(THF)] reacted with two equivalents of 1-methylimidazole in THF at room temperature to afford a trinuclear yttrium complex [Tp(Me2) CpY(μ-N,C-Im)]3 (5), whereas when the above reaction was carried out at 55 °C for two days, two structurally characterized metal complexes [Tp(Me2) Y(Im-Tp(Me2) )] (7; Im-Tp(Me2) =1-methyl-imidazolyl-Tp(Me2) ) and [Cp3 Y(HIm)] (8; HIm=1-methylimidazole) were obtained in 26 and 17 % isolated yields, respectively, accompanied by some unidentified materials. The formation of 7 reveals an uncommon example of construction of a CC bond through multiple C-H activations.

  20. Introduction of aromatic ring-containing substituents in cyclic nucleotides is associated with inhibition of toxin uptake by the hepatocyte transporters OATP 1B1 and 1B3.

    PubMed

    Herfindal, Lars; Krakstad, Camilla; Myhren, Lene; Hagland, Hanne; Kopperud, Reidun; Teigen, Knut; Schwede, Frank; Kleppe, Rune; Døskeland, Stein Ove

    2014-01-01

    Analogs of the cyclic nucleotides cAMP and cGMP have been extensively used to mimic or modulate cellular events mediated by protein kinase A (PKA), Exchange protein directly activated by cAMP (Epac), or protein kinase G (PKG). We report here that some of the most commonly used cyclic nucleotide analogs inhibit transmembrane transport mediated by the liver specific organic anion transporter peptides OATP1B1 and OATP1B3, unrelated to actions on Epac, PKA or PKG. Several cAMP analogs, particularly with 8-pCPT-substitution, inhibited nodularin (Nod) induced primary rat hepatocyte apoptosis. Inhibition was not mediated by PKA or Epac, since increased endogenous cAMP, and some strong PKA- or Epac-activating analogs failed to protect cells against Nod induced apoptosis. The cAMP analogs inhibiting Nod induced hepatocyte apoptosis also reduced accumulation of radiolabeled Nod or cholic acid in primary rat hepatocytes. They also inhibited Nod induced apoptosis in HEK293 cells with enforced expression of OATP1B1 or 1B3, responsible for Nod transport into cells. Similar results were found with adenosine analogs, disconnecting the inhibitory effect of certain cAMP analogs from PKA or Epac. The most potent inhibitors were 8-pCPT-6-Phe-cAMP and 8-pCPT-2'-O-Me-cAMP, whereas analogs like 6-MB-cAMP or 8-Br-cAMP did not inhibit Nod uptake. This suggests that the addition of aromatic ring-containing substituents like the chloro-phenyl-thio group to the purines of cyclic nucleotides increases their ability to inhibit the OATP-mediated transport. Taken together, our data show that aromatic ring substituents can add unwanted effects to cyclic nucleotides, and that such nucleotide analogs must be used with care, particularly when working with cells expressing OATP1B1/1B3, like hepatocytes, or intact animals where hepatic metabolism can be an issue, as well as certain cancer cells. On the other hand, cAMP analogs with substituents like bromo, monobutyryl were non-inhibitory, and could be

  1. The role of cytochrome P4501A activity inhibition in three- to five-ringed polycyclic aromatic hydrocarbons embryotoxicity of marine medaka (Oryzias melastigma).

    PubMed

    Mu, Jing-li; Wang, Xin-hong; Jin, Fei; Wang, Ju-ying; Hong, Hua-sheng

    2012-07-01

    The mode of action of PAHs that causes fish developmental malformations is unclear. The embryotoxicity of marine medaka (Oryzias melastigma) was investigated after individual exposure to three- to five-ring PAHs Phe, Py, and BaP or co-exposure with α-ANF for 18 days. We found that the relationships between EROD induction and developmental deformities of embryos showed a various pattern under different exposure scenarios of Phe, Py, and BaP, which suggested possibly different modes of action in determining the developmental toxicities. As for co-exposure scenarios of each PAH combined with ANF, it showed potentially synergistic effects. The inhibited CYP1A mediated enzyme activity by ANF after co-exposure did not effectively alleviate developmental toxicity of embryo. It showed potentially synergistic effects after co-exposure of marine fish embryos to CYP1A inhibitors and PAH-type CYP1A inducers. Heart deformities in the early life stages of marine medaka were recommended as a biomarker for indicating the extent of PAH pollution.

  2. Structural characterization of 2,6-dichloro-p-hydroquinone 1,2-dioxygenase (PcpA) from Sphingobium chlorophenolicum, a new type of aromatic ring-cleavage enzyme

    PubMed Central

    Hayes, Robert P.; Green, Abigail R.; Nissen, Mark S.; Lewis, Kevin M.; Xun, Luying; Kang, ChulHee

    2014-01-01

    Summary PcpA (2,6-dichloro-p-hydroquinone 1,2-dioxygenase) from Sphingobium chlorophenolicum, a non-haem Fe(II) dioxygenase capable of cleaving the aromatic ring of p-hydroquinone and its substituted variants, is a member of the recently discovered p-hydroquinone 1,2-dioxygenases. Here we report the 2.6 Å structure of PcpA, which consists of four βαβββ motifs, a hallmark of the vicinal oxygen chelate superfamily. The secondary co-ordination sphere of the Fe(II) centre forms an extensive hydrogen-bonding network with three solvent exposed residues, linking the catalytic Fe(II) to solvent. A tight hydrophobic pocket provides p-hydroquinones access to the Fe(II) centre. The p-hydroxyl group is essential for the substrate-binding, thus phenols and catechols, lacking a p-hydroxyl group, do not bind to PcpA. Site-directed mutagenesis and kinetic analysis confirm the critical catalytic role played by the highly conserved His10, Thr13, His226 and Arg259. Based on these results, we propose a general reaction mechanism for p-hydroquinone 1,2-dioxygenases. PMID:23489289

  3. 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.

  4. "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

  5. 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

  6. 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.

  7. 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.

  8. Dianthra[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DATT): synthesis, characterization, and FET characteristics of new π-extended heteroarene with eight fused aromatic rings.

    PubMed

    Niimi, Kazuki; Shinamura, Shoji; Osaka, Itaru; Miyazaki, Eigo; Takimiya, Kazuo

    2011-06-08

    A novel highly π-extended heteroarene with eight fused aromatic rings, dianthra[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DATT), was selectively synthesized via a newly developed synthetic strategy, fully characterized by means of single crystal X-ray structural analysis, and examined as an organic semiconductor in thin film transistors. Even with its highly extended acene-like π-system, DATT is a fairly air-stable compound with IP of 5.1 eV. Single crystal X-ray structural analysis revealed its planar molecular structure and the lamella-like layered structure with typical herringbone packing. Theoretical calculations of the solid state electronic structure based on the bulk single crystal structure suggest that DATT affords almost comparable intermolecular orbital couplings between HOMOs (t(HOMO)) with those of dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT), implying its good potential as an organic semiconductor for organic field-effect transistors. In fact, field-effect mobilities as high as 3.0 cm(2) V(-1) s(-1) were achieved with vapor-processed DATT-based devices, which is comparable with that of DNTT-based devices. The molecular ordering of DATT in the thin film state, however, turned out to be not completely uniform; as elucidated by in-plane and out-of-plane XRD measurements, the face-on molecular orientation was contaminated in the edge-on orientation, the former of which is not optimal for efficient carrier transport and thus could limit the mobility.

  9. From Dibismuthenes to Three- and Two-Coordinated Bismuthinidenes by Fine Ligand Tuning: Evidence for Aromatic BiC3N Rings through a Combined Experimental and Theoretical Study.

    PubMed

    Vránová, Iva; Alonso, Mercedes; Lo, Rabindranath; Sedlák, Robert; Jambor, Roman; Růžička, Aleš; De Proft, Frank; Hobza, Pavel; Dostál, Libor

    2015-11-16

    The reduction of N,C,N-chelated bismuth chlorides [C6H3-2,6-(CH=NR)2]BiCl2 [where R = tBu (1), 2',6'-Me2C6H3 (2), or 4'-Me2NC6H4 (3)] or N,C-chelated analogues [C6H2-2-(CH=N-2',6'-iPr2C6H3)-4,6-(tBu)2]BiCl2 (4) and [C6H2-2-(CH2NEt2)-4,6-(tBu)2]BiCl2 (5) is reported. Reduction of compounds 1-3 gave monomeric N,C,N-chelated bismuthinidenes [C6H3-2,6-(CH=NR)2]Bi [where R = tBu (6), 2',6'-Me2C6H3 (7) or 4'-Me2NC6H4 (8)]. Similarly, the reduction of 4 led to the isolation of the compound [C6H2-2-(CH=N-2',6'-iPr2C6H3)-4,6-(tBu)2]Bi (9) as an unprecedented two-coordinated bismuthinidene that has been structurally characterized. In contrast, the dibismuthene {[C6H2-2-(CH2NEt2)-4,6-(tBu)2]Bi}2 (10) was obtained by the reduction of 5. Compounds 6-10 were characterized by using (1)H and (13)C NMR spectroscopy and their structures, except for 7, were determined with the help of single-crystal X-ray diffraction analysis. It is clear that the structure of the reduced products (bismuthinidene versus dibismuthene) is ligand-dependent and particularly influenced by the strength of the N→Bi intramolecular interaction(s). Therefore, a theoretical survey describing the bonding situation in the studied compounds and related bismuth(I) systems is included. Importantly, we found that the C3NBi chelating ring in the two-coordinated bismuthinidene 9 exhibits significant aromatic character by delocalization of the bismuth lone pair.

  10. Nature of the attractive interaction between proton acceptors and organic ring systems.

    PubMed

    Arras, Emmanuel; Seitsonen, Ari Paavo; Klappenberger, Florian; Barth, Johannes V

    2012-12-14

    Systematic ab initio calculations are combined with a deconvolution of electrostatic contributions to analyze the interplay between potential hydrogen bond acceptors and organic rings with C(sp(2))-H groups (benzene, pyridine and cyclopentadiene). A distinct anisotropic interaction between the ring systems and the electron lone pairs of cyanide, water and other acceptor species is revealed that favors the in-plane orientation of the proton acceptor group. In the attractive regime this interaction carries a pronounced electrostatic signature. By decomposing the electrostatic contribution into parts attributed to different subunits of the ring systems we demonstrate that a major proportion of the interaction energy gain is originating from the non-adjacent moieties, that are not in close contact with. This behavior holds equally for homocyclic, heterocyclic and non-aromatic rings but contrasts that of the ethyne molecule, taken as reference for a weak hydrogen bond donor clearly exhibiting the expected localized character. The ring interaction requires the presence of π-electron clouds and typically results in an interaction energy gain of 40 to 80 meV. Our findings suggest the proton acceptor-ring interaction as a new category of intermolecular non-covalent interactions.

  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. 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.

  13. Ring laser gyroscope anode

    SciTech Connect

    Ljung, B.H.

    1981-03-17

    An anode for a ring laser gyroscope which provides improved current stability in the glow discharge path is disclosed. The anode of this invention permits operation at lower currents thereby allowing a reduction of heat dissipation in the ring laser gyroscope. The anode of one embodiment of this invention is characterized by a thumbtack appearance with a spherical end where the normal sharp end of the thumbtack would be located. The stem of the anode extends from the outside of the gyroscope structure to the interior of the structure such that the spherical end is substantially adjacent to the laser beam.

  14. Aromatic catabolic pathway selection for optimal production of pyruvate and lactate from lignin.

    PubMed

    Johnson, Christopher W; Beckham, Gregg T

    2015-03-01

    Lignin represents an untapped feedstock for the production of fuels and chemicals, but its intrinsic heterogeneity makes lignin valorization a significant challenge. In nature, many aerobic organisms degrade lignin-derived aromatic molecules through conserved central intermediates including catechol and protocatechuate. Harnessing this microbial approach offers potential for lignin upgrading in modern biorefineries, but significant technical development is needed to achieve this end. Catechol and protocatechuate are subjected to aromatic ring cleavage by dioxygenase enzymes that, depending on the position, ortho or meta relative to adjacent hydroxyl groups, result in different products that are metabolized through parallel pathways for entry into the TCA cycle. These degradation pathways differ in the combination of succinate, acetyl-CoA, and pyruvate produced, the reducing equivalents regenerated, and the amount of carbon emitted as CO2-factors that will ultimately impact the yield of the targeted product. As shown here, the ring-cleavage pathways can be interchanged with one another, and such substitutions have a predictable and substantial impact on product yield. We demonstrate that replacement of the catechol ortho degradation pathway endogenous to Pseudomonas putida KT2440 with an exogenous meta-cleavage pathway from P. putida mt-2 increases yields of pyruvate produced from aromatic molecules in engineered strains. Even more dramatically, replacing the endogenous protocatechuate ortho pathway with a meta-cleavage pathway from Sphingobium sp. SYK-6 results in a nearly five-fold increase in pyruvate production. We further demonstrate the aerobic conversion of pyruvate to l-lactate with a yield of 41.1 ± 2.6% (wt/wt). Overall, this study illustrates how aromatic degradation pathways can be tuned to optimize the yield of a desired product in biological lignin upgrading.

  15. 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 ...

  16. 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

  17. 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.

  18. 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.

  19. Reaction of disubstituted aromatic compounds with styrene

    SciTech Connect

    Grushin, A.I.; Grigor'ev, V.V.; Prokof'ev, K.V.; Kozlova, N.M.

    1988-03-20

    Hydrocarbons of the 1,1-diphenylethane type were obtained by the reaction of styrene with various disubstituted derivatives of benzene in the presence of titanium tetrachloride. It was found that the yield of the desired compound depends on the strength of the electron-donating substituents and on steric factors in the aromatic ring.

  20. Inhibitory effects of polycyclic aromatic hydrocarbons (PAHs) on photosynthetic performance are not related to their aromaticity.

    PubMed

    Jajoo, Anjana; Mekala, Nageswara Rao; Tomar, Rupal Singh; Grieco, Michele; Tikkanen, Mikko; Aro, Eva-Mari

    2014-08-01

    Polycyclic aromatic hydrocarbons (PAHs) are very toxic and highly persistent environmental pollutants which accumulate in soil and affect growth of the plants adversely. This study aims to investigate inhibitory effects of 3 major PAH particularly on photosynthetic processes in Arabidopsis thaliana grown in soil treated with PAH. The 3 PAH chosen differ from each other in aromaticity (number of rings) comprising their structure (2 rings: naphthalene, 3 rings: anthracene and 4 rings: pyrene). Several growth parameters and Chlorophyll a fluorescence was monitored in PAH treated plants. BN-PAGe analysis was done in order to get information about change in the protein conformation. PAH treatment led to increased value of Fo which collaborated with increase in the amount of free LHC as seen through BN-Page analysis. Thus PAH were found to inhibit PS II photochemistry and caused distinct change in pigment composition. However the results led us to infer that 3-ring anthracence is more inhibitory as compared to 2-ring naphthalene and 4-ring pyrene. This indicates that aromaticity of PAH is unrelated to their response on photosynthetic processes.

  1. The fundamental chemical equation of aromaticity.

    PubMed

    Chauvin, Remi; Lepetit, Christine

    2013-03-21

    In the search for the chemical measure of molecular aromaticity, namely the energetic gain of a cyclic delocalized structure for just being cyclic, the numerous definitions of generic aromatic stabilisation energies proposed hitherto stand as approximates of the conceptual limit devised within the framework of spectral graph theory, i.e. the topological resonance energy (TRE). After a 36 year challenge, the TRE acyclic reference of any π-cyclic molecule, originally merely defined by an abstract matching polynomial, is now given a real chemical structure: the Möbius-twisted head-to-tail metathesis cyclo-dimer of the parent ring. The original treatment at the Hückel molecular orbital level of theory can now be extended to DFT or ab initio levels. The corresponding ring opening-closing-twisting chemical transformation provides the observable basis for the measure of aromaticity under either vertical or adiabatic conditions.

  2. The origin of global and macrocyclic aromaticity in porphyrinoids.

    PubMed

    Nakagami, Yuto; Sekine, Rika; Aihara, Jun-ichi

    2012-07-21

    The global and macrocyclic aromaticity of porphyrinoids was characterized using our graph theory of aromaticity. The sequential line plots of topological resonance energy (TRE) against the number of π-electrons (N(π)) for different porphyrinoids are similar with four major extrema to those for five-membered heterocycles. This supports the view that five-membered rings are the main origin of global aromaticity in porphyrinoids. Macrocyclic circuits contribute significantly to macrocyclic π-circulation but modestly to global aromaticity. Macrocyclic aromaticity/antiaromaticity in oligopyrrolic macrocycles can be predicted by formally applying Hückel's [4n + 2] rule to an annulene-like main macrocyclic conjugation pathway (MMCP). This bridged annulene model can be justified by examining the contribution of individual macrocyclic circuits to macrocyclic aromaticity. A Hückel-like rule of macrocyclic aromaticity was found for porphyrinoid species.

  3. 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 ...

  4. 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.

  5. Ring currents in azulene

    NASA Astrophysics Data System (ADS)

    Paxton, A. T.; Todorov, T. N.; Elena, A. M.

    2009-11-01

    We propose a self consistent polarisable ion tight binding theory for the study of push-pull processes in aromatic molecules. We find that the method quantitatively reproduces ab initio calculations of dipole moments and polarisability. We apply the scheme in a simulation which solves the time dependent Schrödinger equation to follow the relaxation of azulene from the second excited to the ground states. We observe rather spectacular oscillating ring currents which we explain in terms of interference between the HOMO and LUMO states.

  6. Nucleophilic fluorination of aromatic compounds

    SciTech Connect

    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.

  7. Aromatic Polyamide Reverse-Osmosis Membrane: An Atomistic Molecular Dynamics Simulation.

    PubMed

    Wei, Tao; Zhang, Lin; Zhao, Haiyang; Ma, Heng; Sajib, Md Symon Jahan; Jiang, Hua; Murad, Sohail

    2016-10-06

    Polyamide (PA) membrane-based reverse-osmosis (RO) serves as one of the most important techniques for water desalination and purification. Fundamental understanding of PA RO membranes at the atomistic level is critical to enhance their separation capabilities, leading to significant societal and commercial benefits. In this paper, a fully atomistic molecular dynamics simulation was performed to investigate PA membrane. Our simulated cross-linked membrane exhibits structural properties similar to those reported in experiments. Our results also reveal the presence of small local two-layer slip structures in PA membrane with 70% cross-linking, primarily due to short-range anisotropic interactions among aromatic benzene rings. Inside the inhomogeneous polymeric structure of the membrane, water molecules show heterogeneous diffusivities and converge adjacent to polar groups. Increased diffusion of water molecules is observed through the less cross-linked pathways. The existence of the fast pathways for water permeation has no effect on membrane's salt rejections.

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

    DOEpatents

    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.

  9. Hydrotreatment of Irati shale oil; Behavior of the aromatic fraction

    SciTech Connect

    Afonso, J.C.; Schmal, M. ); Cardoso, J.N. ); Frety, R. )

    1991-09-01

    This paper presents the chemical transformations that occur in the aromatic fraction of Irati shale oil under rather drastic hydrotreating conditions, at 400{degrees} C and 125 atm, using a commercial Ni-Mo/Al{sub 2}O{sub 3} catalyst in sulfided form. The aromatic fraction was analyzed before and after reaction by gas chromatography/ mass spectrometry. Several compounds were identified by using this method. The main reactions are the partial hydrogenation of the aromatic rings forming hydroaromatic compounds and the cracking of the lateral alkyl chains. Hydrotreatment leads to a more complex aromatic fraction due to the formation of new compounds.

  10. Vortex rings

    NASA Technical Reports Server (NTRS)

    Shariff, Karim; Leonard, Anthony

    1992-01-01

    The vortex-ring problem in fluid mechanics is examined generally in terms of formation, the steady state, the duration of the rings, and vortex interactions. The formation is studied by examining the generation of laminar and turbulent vortex rings and their resulting structures with attention given to the three stages of laminar ring development. Inviscid dynamics is addressed to show how core dynamics affects overall ring motion, and laminar vortex structures are described in two dimensions. Viscous and inviscid structures are related in terms of 'leapfrogging', head-on collisions, and collisions with a no-slip wall. Linear instability theory is shown to successfully describe observational data, although late stages in the breakdown are not completely understood. This study of vortex rings has important implications for key aerodynamic issues including sound generation, transport and mixing, and vortex interactions.

  11. 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

  12. Degradation of diphenyl ether in Sphingobium phenoxybenzoativorans SC_3 is initiated by a novel ring-cleavage dioxygenase.

    PubMed

    Cai, Shu; Chen, Li-Wei; Ai, Yu-Chun; Qiu, Ji-Guo; Wang, Cheng-Hong; Shi, Chao; He, Jian; Cai, Tian-Ming

    2017-03-10

    Sphingobium phenoxybenzoativorans SC_3 degrades and utilizes diphenyl ether (DE) and 2-carboxy DE as its sole carbon and energy source. In this study, we report the degradation of DE and 2-carboxy DE initiated by a novel ring-cleavage angular dioxygenase (Dpe) in the strain. Dpe functions at the angular carbon and its adjacent carbon (C1a, C2) of a benzene ring in DE (or the 2-carboxy benzene ring in 2-carboxy DE) and cleaves the C1a-C2 bond (decarboxylation is simultaneously happened for 2-carboxy DE), yielding 2,4-hexadienal phenyl ester, which is subsequently hydrolyzed to muconic acid semialdehyde and phenol. Dpe is a type IV Rieske non-heme iron oxygenase (RHO) and consists of three components: a hetero-oligomer oxygenase, a [2Fe-2S]-type ferredoxin and a GR (glutathione reductase)-type reductase. Genetic analyses revealed that dpeA1A2 plays an essential role in degradation and utilization of DE and 2-carboxy DE in S. phenoxybenzoativorans SC_3. Enzymatic study showed that transformation of one molecule of DE needs two molecules of oxygen and two molecules of NADH, supporting the assumption that the cleavage of DE catalyzed by Dpe is a continuous two-step dioxygenation process: DE is dioxygenated at C1a, C2 to form an hemiacetal-like intermediates, which is further dioxygenated resulting the cleavage of the C1a-C2 bond to form one molecule of 2,4-hexadienal phenyl ester and two molecules of H2O. This study extends our knowledge of the mode and mechanism of ring-cleavage of aromatic compounds.IMPORTANCE Benzene ring-cleavage, catalyzed by dioxygenase, is the key and speed limiting step in the aerobic degradation of aromatic compounds. Previously reported ring-cleavage of DEs, the benzene ring needs to be firstly dihydroxylated at lateral position, and subsequently dehydrogenated and opened through extradiol cleavage. This process requires three enzymes (two dioxygenases and one dehydrogenase). In this study, we identified a novel angular dioxygenase (Dpe) in S

  13. Facile Formation of Redox-Active Totally Organic Nanoparticles in Water by In Situ Reduction of Organic Precursors Stabilized through Aromatic-Aromatic Interactions by Aromatic Polyelectrolytes.

    PubMed

    Flores, Mario E; Garcés-Jerez, Pablo; Fernández, Daniel; Aros-Perez, Gustavo; González-Cabrera, Diego; Álvarez, Eduardo; Cañas, Ignacio; Oyarzun-Ampuero, Felipe; Moreno-Villoslada, Ignacio

    2016-11-01

    The formation of redox-active, totally organic nanoparticles in water is achieved following a strategy similar to that used to form metal nanoparticles. It is based on two fundamental concepts: i) complexation through aromatic-aromatic interactions of a water-soluble precursor aromatic molecule with polyelectrolytes bearing complementary charged aromatic rings, and ii) reduction of the precursor molecule to achieve stabilized nanoparticles. Thus, formazan nanoparticles are synthesized by reduction of a tetrazolium salt with ascorbic acid using polyelectrolytes bearing benzene sulfonate residues of high linear aromatic density, but cannot be formed in the presence of nonaromatic polyelectrolytes. The red colored nanoparticles are efficiently encapsulated in calcium alginate beads, showing macroscopic homogeneity. Bleaching kinetics with chlorine show linear rates on the order of tenths of milli-meters per minute. A linear behavior of the dependence of the rate of bleaching on the chlorine concentration is found, showing the potential of the nanoparticles for chlorine sensing.

  14. [Classification and Contribution Analysis of Aromatic Clusters in Protein-Ligand Complexes].

    PubMed

    Yamasaki, Hiroyuki; Koseki, Jun; Nishibata, Yoshihiko; Hirono, Shuichi

    2016-01-01

      Intermolecular interactions are key features in the stabilization or destabilization of complexes. In particular, interactions involving aromatic rings have been extensively studied both theoretically and experimentally. Studies have shown that aromatic-aromatic interactions can be categorized by ring-ring orientation into a variety of different types, such as stacking interactions and T-shaped interactions. Because these different orientations affect stabilization, analyses of such interactions, for example ab initio molecular orbital calculations, are applied to pairs of aromatic rings, both in model systems and real systems. An important series of aromatic-aromatic interactions include those between pairs of aromatic residues in proteins. These residues have been studied computationally using both a theoretical chemistry approach and a knowledge-based analys. Protein 3D structural information is essential for knowledge-based studies of aromatic-aromatic interactions in protein-ligand complexes. Some databases filter entries from the Protein Data Bank (PDB) using criteria that make them suitable for computational approaches involving specific research targets. Lanzarotti et al. have shown that aromatic clusters in which three or more aromatic residues are in close proximity to each other are found in many protein structures, expanding pairwise aromatic-aromatic interactions. Moreover, these clusters are thought to be important in terms of protein function, structural stability and ligand recognition. Here, we show that aromatic clusters, as well as individual proteins, are found in a variety of protein-ligand complexes. As such, we anticipate that these clusters might have a significant role in ligand binding and could help in efficient ligand design.

  15. High temperature chemistry of aromatic hydrocarbons

    SciTech Connect

    Scott, L.T.

    1991-12-31

    We have not only gained new insight into the mechanism and generality of Polycyclic Aromatic Hydrocarbon (PAH) thermal automerization reactions, we have also uncovered several new high temperature reactions and added a third dimension to our program by applying high temperature chemistry to problems in organic synthesis. Our synthesis of corannulene has attracted much recent attention; however, we believe that the uncatalyzed ``cyclodehydrogenation reactions`` which form 5-membered rings and 6-membered rings at high temperatures may prove to be of greater general importance in the long term. This bias is reflected in the accompanying proposal.

  16. High temperature chemistry of aromatic hydrocarbons

    SciTech Connect

    Scott, L.T.

    1991-01-01

    We have not only gained new insight into the mechanism and generality of Polycyclic Aromatic Hydrocarbon (PAH) thermal automerization reactions, we have also uncovered several new high temperature reactions and added a third dimension to our program by applying high temperature chemistry to problems in organic synthesis. Our synthesis of corannulene has attracted much recent attention; however, we believe that the uncatalyzed cyclodehydrogenation reactions'' which form 5-membered rings and 6-membered rings at high temperatures may prove to be of greater general importance in the long term. This bias is reflected in the accompanying proposal.

  17. 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.

  18. Argentivorous molecules with two kinds of aromatic side-arms: intramolecular competition between side-arms.

    PubMed

    Habata, Yoichi; Oyama, Yosuke; Ikeda, Mari; Kuwahara, Shunsuke

    2013-06-21

    Three tetra-armed cyclens with two kinds of side-arms, 3',5'-difluorobenzyl/4'-methylbenzyl, 3',5'-difluorobenzyl/1'-naphthylmethyl, and 3',5'-difluorobenzyl/9'-anthrylmethyl groups, were prepared by reductive amination of 1,7-bis(3',5'-difluorobenzyl)-1,4,7,10-tetraazacyclododecane and the corresponding aromatic aldehydes in the presence of NaBH(OAc)3. The X-ray structures of the Ag(+) complexes and Ag(+)-ion-induced (1)H NMR spectral changes suggest that (i) the chemical shift changes of the protons at the 2'- and 6'-positions in the 3',5'-difluorobenzyl/4'-methylbenzyl side-arms are dependent on the electron density on the adjacent substituted benzenes, and (ii) in the tetra-armed cyclens with 3',5'-difluorobenzyl/1'-naphthylmethyl and 3',5'-difluorobenzyl/9'-anthrylmethyl groups as side-arms, electron-rich aromatic rings preferentially cover the Ag(+) ions incorporated into the ligand cavities, and 3',5'-difluorobenzyl groups do not participate in the Ag(+) interactions. The log K values were estimated using Ag(+)-ion-induced UV-vis spectral changes.

  19. Distribution and mass inventory of polycyclic aromatic hydrocarbons in the sediments of the south Bohai Sea, China.

    PubMed

    Qin, Yanwen; Zheng, Binghui; Lei, Kun; Lin, Tian; Hu, Limin; Guo, Zhigang

    2011-02-01

    Recent occurrence, distribution and mass inventories of 16 priority polycyclic aromatic hydrocarbons (PAHs) proposed by USEPA in the south Bohai Sea (BS) were studied based on the analytical data of 71 surface sediment samples. The concentrations of 16 PAHs varied from 37 to 537 ngg⁻¹ (dry weight). A clear difference was observed between the coastal Bohai Bay (CBB) and its adjacent BS (ABS) in the distribution and compositions of PAHs. The petrogenic source of phenanthrene in CBB was attributable to the industrial wastewater, fugitive fuel leakages from ships and offshore oil production. Four to six ring PAHs were predominantly from the coal and wood combustions in the whole area. The estimated PAH input to the south BS (43,000 km², 56% of BS in area) was 36.6 ton yr⁻¹, indicating that the study area was one of the important reservoirs of PAHs in world.

  20. Aromaticity of closed-shell charged polybenzenoid hydrocarbons.

    PubMed

    Ramos-Berdullas, Nicolás; Radenković, Slavko; Bultinck, Patrick; Mandado, Marcos

    2013-06-06

    The aromatic stabilization of closed-shell charged polybenzenoid hydrocarbons (PBHs) has been scrutinized by means of energetic and magnetic aromaticity criteria and by direct measures of electron delocalization. Thus, topological resonance energies and their circuit contributions, ring current maps, and multicenter delocalization indices have been calculated for a series of 18 polybenzenoid cations containing from 3 to 10 benzene rings. All calculations indicate that the closed-shell cations have a similar degree of aromaticity compared to that of the corresponding closed-shell neutral PBHs. All cations investigated display a large degree of electronic delocalization in the ring, accompanied by significant aromatic stabilization and a strong diatropic peripheral electron current. Graph theoretical models describe perfectly the aromatic features of these hydrocarbon fragments, showing how they can be understood as a superposition of specific neutral PBHs. The large aromatic character of these systems suggests they may be relatively stable upon formation at combustion conditions, like those given in the interstellar medium. It has been postulated that closed-shell fragments of PBHs may play an important role in the photoluminescent phenomenon known as extended red emission.

  1. Ghostly Ring

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Click on image for poster version

    This image shows a ghostly ring extending seven light-years across around the corpse of a massive star. The collapsed star, called a magnetar, is located at the exact center of this image. NASA's Spitzer Space Telescope imaged the mysterious ring around magnetar SGR 1900+14 in infrared light. The magnetar itself is not visible in this image, as it has not been detected at infrared wavelengths (it has been seen in X-ray light).

    Magnetars are formed when a massive giant star ends its life in a supernova explosion, leaving behind a super dense neutron star with an incredibly strong magnetic field. The ring seen by Spitzer could not have formed during the original explosion, as any material as close to the star as the ring would have been disrupted by the supernova shock wave. Scientists suspect that the ring my actually be the edges of a bubble that was hollowed out by an explosive burst from the magnetar in 1998. The very bright region near the center of the image is a cluster of young stars, which may be illuminating the inner edge of the bubble, making it look like a ring in projection.

    This composite image was taken using all three of Spitzer's science instruments. The blue color represents 8-micron infrared light taken by the infrared array camera, green is 16-micron light from the infrared spectograph, and red is 24-micron radiation from the multiband imaging photometer.

  2. Luminescent Rings

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This view shows the unlit face of Saturn's rings, visible via scattered and transmitted light. In these views, dark regions represent gaps and areas of higher particle densities, while brighter regions are filled with less dense concentrations of ring particles.

    The dim right side of the image contains nearly the entire C ring. The brighter region in the middle is the inner B ring, while the darkest part represents the dense outer B Ring. The Cassini Division and the innermost part of the A ring are at the upper-left.

    Saturn's shadow carves a dark triangle out of the lower right corner of this image.

    The image was taken in visible light with the Cassini spacecraft wide-angle camera on June 8, 2005, at a distance of approximately 433,000 kilometers (269,000 miles) from Saturn. The image scale is 22 kilometers (14 miles) per pixel.

    The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

    For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

  3. Cave Rings

    DTIC Science & Technology

    2010-10-13

    hypothesis, that cave rings are formed in the same manner as coffee rings[3], that is, due to the enhanced deposition at the edges of sessile drops ...Literature The ‘splash ring’ conjecture is described in [5]. It is claimed that 45◦ is the most probable angle for secondary drops to be ejected at, and that...ring’ is the deposit formed when a sessile drop of a solution containing dissolved particles, such as coffee or salt, dries. This was investigated by

  4. Flux of aliphatic and polycyclic aromatic hydrocarbons to Central Puget Sound from Seattle (Westpoint) primary sewage effluent

    SciTech Connect

    Barrick, R.C.

    1982-10-01

    Concentrations and mass emission rates are reported for hydrocarbons in a 20-month evaluation of primary municipal waste water discharging to marine waters of Puget Sound from Seattle, WA. On the average, METRO (Westpoint) discharges 475 metric tons/year of aliphatic hydrocarbons and approximately 1 metric ton/year of 3-7 ring polynuclear aromatic hydrocarbons (PAH), corresponding to discharges of 2.6 and 0.005 g/(capita day), respectively. Effluent PAH containing greater than or equal to 4 rings apparently derive principally from storm-water contributions. A comparison of METRO's yearly average discharge of different hydrocarbon components with observed hydrocarbon fluxes in adjacent Puget Sound surface sediments suggests negligible accumulations of the resolvable alkanes (derived from the effluent), partial accumulations of an unresolved complex mixture and phenanthrene, and substantial accumulations of the greater than or equal to4-ring PAH. The discharge accounts for a major portion of the sedimentary aliphatic fossil hydrocarbon flux and is one of several important PAH contributors. 45 references, 2 figures, 5 tables.

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

    PubMed Central

    2016-01-01

    The stereospecific cross-coupling of secondary boronic esters with sp2 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(sp2)–C(sp3) 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

  6. 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

    2016-08-03

    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.

  7. 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.

  8. Formation of six-membered rings via alkyne insertion into four-membered rings

    NASA Astrophysics Data System (ADS)

    Matsuda, Takanori; Miura, Norio; Matsumoto, Takeshi

    2017-01-01

    Alkyne insertion into four-membered carbocyclic rings was achieved through rhodium(I)-catalyzed C-C bond cleavage. The reaction of (2-pyridylmethylene)cyclobutenes proceeded via C-C oxidative addition, and that of cyclobutenols involved β-carbon elimination. In both the cases, multiply substituted benzenes were obtained through the aromatization of the initially formed 1,4-cyclohexadienes.

  9. First approach to nitrogen-containing fused aromatic hydrocarbons as targets for organoelectronics utilizing a new transformation of O-protected diaryl methanols.

    PubMed

    Bałczewski, Piotr; Bodzioch, Agnieszka; Rózycka-Sokołowska, Ewa; Marciniak, Bernard; Uznański, Paweł

    2010-02-22

    A new concise approach for the construction of heteroatom analogues of polycyclic aromatic benzo[g]quinoline, benzo[b]carbazole, and pyrido[b]carbazole systems via diaryl methanols is described. This transformation involves formation of a central benzene ring fused to two aromatic 5- or 6-membered rings of pyrrole and/or pyridine by using a combination of two aromatic aldehydes, of which at least one contains a ring nitrogen. Analysis of the UV and fluorescent properties, Stokes shifts, quantum yields in solution, and pi-stacking interactions in the crystal structures of the new materials was performed. These polycyclic aromatic compounds show potential as small-molecule organoelectronic materials.

  10. Unexpectedly Enhanced Solubility of Aromatic Amino Acids and Peptides in an Aqueous Solution of Divalent Transition-Metal Cations

    NASA Astrophysics Data System (ADS)

    Shi, Guosheng; Dang, Yaru; Pan, Tingting; Liu, Xing; Liu, Hui; Li, Shaoxian; Zhang, Lijuan; Zhao, Hongwei; Li, Shaoping; Han, Jiaguang; Tai, Renzhong; Zhu, Yiming; Li, Jichen; Ji, Qing; Mole, R. A.; Yu, Dehong; Fang, Haiping

    2016-12-01

    We experimentally observed considerable solubility of tryptophan (Trp) in a CuCl2 aqueous solution, which could reach 2-5 times the solubility of Trp in pure water. Theoretical studies show that the strong cation-π interaction between Cu2 + and the aromatic ring in Trp modifies the electronic distribution of the aromatic ring to enhance significantly the water affinity of Trp. Similar solubility enhancement has also been observed for other divalent transition-metal cations (e.g., Zn2 + and Ni2 + ), another aromatic amino acid (phenylalanine), and three aromatic peptides (Trp-Phe, Phe-Phe, and Trp-Ala-Phe).

  11. Kayser-Fleischer Rings

    MedlinePlus

    ... to know about Wilson Disease Kayser-Fleischer Rings Definition Kayser-Fleischer Ring: Clinical sign. Brownish-yellow ring ... Diet & Nutrition Kayser-Fleischer Rings Wilson Disease FAQs Definitions Transplantation For Patients & Families Resources Membership Events Centers ...

  12. 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.

  13. Xenoestrogenic gene expression: structural features of active polycyclic aromatic hydrocarbons.

    PubMed

    Schultz, T Wayne; Sinks, Glendon D

    2002-04-01

    Estrogenicity was assessed using the Saccharomyces cerevisiae-based Lac-Z reporter assay and was reported as the logarithm of the inverse of the 50% molar beta-galactosidase activity (log[EC50(-1)]). In an effort to quantify the relationship between molecular structure of polycyclic aromatic hydrocarbons (PAHs) and estrogenic gene expression, a series of PAHs were evaluated. With noted exceptions, the results of these studies indicate that the initial two-dimensional structural warning for estrogenicity, the superpositioning of a hydroxylated aromatic system on the phenolic A-ring of 17-beta-estradiol, can be extended to the PAHs. This two-dimensional-alignment criterion correctly identified estrogenicity of 22 of the 29 PAHs evaluated. Moreover, the estrogenic potency of these compounds was directly related to the size of the hydrophobic backbone. The seven compounds classified incorrectly by this structural feature were either dihydroxylated naphthalenes or aromatic nitrogen-heterocyclic compounds; all such compounds were false positives. Results with dihydroxylated naphthalenes reveal derivatives that were nonestrogenic when superimposed on the phenolic A-ring of 17-beta-estradiol had the second hydroxyl group in the position of the C-ring or were catechol-like in structure. Structural alerts for nitrogen-heterocyclic compounds must take into account the position of the hydroxyl group and the in-ring nitrogen atom; compounds with the hydroxyl group and nitrogen atom involved with the same ring were observed to be nonactive.

  14. 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.

  15. Nonlinearity of cationic aromatic amine sorption to aluminosilicates and soils: role of intermolecular cation-π interactions.

    PubMed

    Vasudevan, Dharni; Arey, Teresa A; Dickstein, Daniel R; Newman, Mark H; Zhang, Tina Y; Kinnear, Heather M; Bader, Mohammad M

    2013-12-17

    Through the study of substituted anilines and benzylamines, we demonstrated that cooperative cation-π, π-π, and van der Waals interactions can increase aromatic cationic amine sorption to Na/Ca-montmorillonite well beyond the extent expected by cation exchange alone. Cationic amines exhibiting cooperative interactions displayed nonlinear S-shaped isotherms and increased affinity for the sorbent at low surface coverage; parallel cation exchange and cooperative interactions were noted above a sorption threshold of 0.3-2.3% of exchange sites occupied. Our experiments revealed the predominance of intermolecular cation-π interactions, which occurred between the π system of a compound retained on the surface via cation exchange and the cationic amine group of an adjacent molecule. Compounds with greater amine charge/area and electron-donating substituents that allowed for greater electron density at the center of the aromatic ring showed a greater potential for cation-π interactions on montmorillonite surfaces. However, benzylamine sorption to nine soils, at charge loadings comparable to the experiments with montmorillonite, revealed no significant cooperative interactions. It appears that cation-π interactions may be likely in soils with exceptionally high cation exchange capacities (>0.7 mol charge/kg) and low organic matter contents, abundant in montmorillonite and other expanding clay minerals.

  16. 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)

  17. 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.

  18. 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.

  19. 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.

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. Transformations of aromatic compounds by nitrosomonas europaea

    SciTech Connect

    Keener, W.K.; Arp, D.J.

    1994-06-01

    The soil bacterium Nitrosomonas europaea is an obligate autotroph which uses O2 as an electron acceptor and ammonia as its sole natural energy source. The ubiquity of nitrifying bacteria may facilitate their use in bioremediation applications, but such applications will require a thorough knowledge of the substrate range of Ammonia monooxygenase (AMO) (catalyzing the oxidation of ammonia). This study extends the know substrate range of N. europaea to include alkylbenzenes, halobenzenes, and various N- and O-containing aromatics. Evidence is also presented that oxidation of p-cresol and ring-substituted benzylic alcohols to corresponding aldehydes joccures even in the absence of AMO activity. 33 refs., 7 figs.

  5. 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.

  6. 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.

  7. 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

  8. Overview of Polycyclic Aromatic Compounds (PAC).

    PubMed

    Achten, Christine; Andersson, Jan T

    2015-03-15

    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.

  9. 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

  10. 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.

  11. Identification of dinuclear aromatics in the gas oil fraction of Kuwait petroleum

    SciTech Connect

    Ijam, M.J.; Qatami, S.Y.A.; Arif, S.F.

    1988-08-01

    For several decades removal of aromatics from crude oil fractions (e.g. kerosene and lubricating oils) has been practiced in oil refining to produce fuels and lubricants of lower aromatic content and hence of improved quality. These aromatics are suitable raw materials for the manufacture of aromatic solvents, aromatic process oils, high octane gasoline, and as basic materials for making detergents, perfumes and dyes. Detailed study of molecular structure and substituent effects on the retention characteristics of aromatic hydrocarbons have been reported on alumina, silica and various chemically bonded silicas containing -C/sub 18/, -NH/sub 2/, -R(NH)/sub 2//sub 2/, -CN, RCN, RON and phenyl-mercuric acetate for the compound class (ring-numbered) high performance liquid chromatography (2, 3, 8, 12, 24, 28). Previous work in this laboratory has demonstrated that individual normal and branched aliphatic hydrocarbons from kerosene and light gas oil were isolated and identified. This paper describes the extension of this work to cover the separation and identification of aromatic ring classes (mono-, di-, and tri-aromatics) in the gas oil fraction of Kuwait petroleum. Characterization and identification of the major components in the dinuclear aromatics is our primary objective in this study.

  12. Kinetics of ring formation

    NASA Astrophysics Data System (ADS)

    Ben-Naim, E.; Krapivsky, P. L.

    2011-06-01

    We study reversible polymerization of rings. In this stochastic process, two monomers bond and, as a consequence, two disjoint rings may merge into a compound ring or a single ring may split into two fragment rings. This aggregation-fragmentation process exhibits a percolation transition with a finite-ring phase in which all rings have microscopic length and a giant-ring phase where macroscopic rings account for a finite fraction of the entire mass. Interestingly, while the total mass of the giant rings is a deterministic quantity, their total number and their sizes are stochastic quantities. The size distribution of the macroscopic rings is universal, although the span of this distribution increases with time. Moreover, the average number of giant rings scales logarithmically with system size. We introduce a card-shuffling algorithm for efficient simulation of the ring formation process and we present numerical verification of the theoretical predictions.

  13. 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.

  14. Distribution and sources of polycyclic aromatic hydrocarbons in intertidal flat surface sediments from the Yangtze estuary, China

    NASA Astrophysics Data System (ADS)

    Liu, M.; Hou, L. J.; Yang, Y.; Zou, H.; Lu, J.; Wang, X.

    2001-11-01

    Polycyclic aromatic hydrocarbons (PAHs) in surface sediments taken from intertidal flats in the Yangtze estuary and adjacent coastal areas were determined by GC-MS. The results have shown that total PAH concentration ranged from 0.263-6.372 mg/kg in tidal flat surface sediments from the study area. Mean concentration level is 1.662 mg/kg. The concentration levels of total PAHs varied dramatically with in the region. They are characteristically at maximum near sewage discharge points. Petroleum-derived contamination may be a dominant source in the study area based on the distributions of Flu/Pyr and two and three-ringed and four-ringed congeners in surface sediments. A pyrolytic origin was responsible for higher PAH concentration levels at three sampling sites. The degree of sediment contamination by PAHs in the study area is low to moderate in comparison with other estuarine and tidal flat surface sediments elsewhere. However, anthracene and fluorene exceed the effects of low range (ER-L) values, showing a primary potential impact for the Yangtze estuarine tidal flat ecosystem.

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

    PubMed Central

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

    2015-01-01

    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

  16. 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.

  17. Thermodiffusion of polycyclic aromatic hydrocarbons in binary mixtures

    NASA Astrophysics Data System (ADS)

    Hashmi, Sara M.; Senthilnathan, Sid; Firoozabadi, Abbas

    2016-11-01

    Thermodiffusion in liquid mixtures may explain some counter-intuitive but naturally occurring phenomena such as hydrocarbon reservoirs with heavier component(s) stratified on top of lighter ones. However, beyond benchmark systems, systematic measurements of thermodiffusion in binary organic mixtures are lacking. We use an optical beam deflection apparatus to simultaneously probe Fickian and thermal diffusion in binary solution mixtures of polycyclic aromatic hydrocarbons dissolved in alkanes, and measure both Fickian diffusion D and the Soret coefficient ST, and then obtain the thermodiffusion coefficient DT. In a series of nine binary mixtures, we vary both the size of the aromatic compound from two to four rings, as well as the length of the alkane chain from 6 to 16 carbons. To probe the effect of increasing ring size, we include a 6-ringed aromatic compound, coronene, and toluene as a solvent, due to the insolubility of coronene in alkanes. Our results suggest that Fickian diffusion increases with the inverse of solvent viscosity and also with decreasing molecular weight of the solute. While both of these trends match our intuition, the behavior of ST and DT is more complicated. We find that ST and DT increase with the solute molecular weight when the solvent is held fixed and that the impact of solute ring size is higher in shorter chain alkane solvents.

  18. Dimerization of polycyclic aromatic hydrocarbons in soot nucleation.

    PubMed

    Zhang, Hong-Bo; You, Xiaoqing; Wang, Hongmiao; Law, Chung K

    2014-02-27

    A possible pathway of soot nucleation, in which localized π electrons play an important role in binding the polycyclic aromatic hydrocarbon (PAH) molecules having multiradical characteristics to form stable polymer molecules through covalent bonds, is studied using density functional and semiempirical methods. Results show that the number of covalent bonds formed in the dimerization of two identical PAHs is determined by the radical character, and the sites to form bonds are related to the aromaticity of individual six-membered ring structure. It is further shown that the binding energy of dimerization increases linearly with the diradical character in the range relevant to soot nucleation.

  19. Microbial remediation of nitro-aromatic compounds: an overview.

    PubMed

    Kulkarni, Meenal; Chaudhari, Ambalal

    2007-10-01

    Nitro-aromatic compounds are produced by incomplete combustion of fossil fuel or nitration reactions and are used as chemical feedstock for synthesis of explosives, pesticides, herbicides, dyes, pharmaceuticals, etc. The indiscriminate use of nitro-aromatics in the past due to wide applications has resulted in inexorable environmental pollution. Hence, nitro-aromatics are recognized as recalcitrant and given Hazardous Rating-3. Although several conventional pump and treat clean up methods are currently in use for the removal of nitro-aromatics, none has proved to be sustainable. Recently, remediation by biological systems has attracted worldwide attention to decontaminate nitro-aromatics polluted sources. The incredible versatility inherited in microbes has rendered these compounds as a part of the biogeochemical cycle. Several microbes catalyze mineralization and/or non-specific transformation of nitro-aromatics either by aerobic or anaerobic processes. Aerobic degradation of nitro-aromatics applies mainly to mono-, dinitro-derivatives and to some extent to poly-nitro-aromatics through oxygenation by: (i) monooxygenase, (ii) dioxygenase catalyzed reactions, (iii) Meisenheimer complex formation, and (iv) partial reduction of aromatic ring. Under anaerobic conditions, nitro-aromatics are reduced to amino-aromatics to facilitate complete mineralization. The nitro-aromatic explosives from contaminated sediments are effectively degraded at field scale using in situ bioremediation strategies, while ex situ techniques using whole cell/enzyme(s) immobilized on a suitable matrix/support are gaining acceptance for decontamination of nitrophenolic pesticides from soils at high chemical loading rates. Presently, the qualitative and quantitative performance of biological approaches of remediation is undergoing improvement due to: (i) knowledge of catabolic pathways of degradation, (ii) optimization of various parameters for accelerated degradation, and (iii) design of microbe

  20. Singly N-fused Möbius aromatic [28]hexaphyrins(1.1.1.1.1.1).

    PubMed

    Higashino, Tomohiro; Inoue, Mitsunori; Osuka, Atsuhiro

    2010-11-19

    A singly N-fused [28]hexaphyrin was isolated and metalated with Pd(OAc)2 to give a conformationally twisted Pd(II) complex that displays distinct Möbius aromatic properties such as a strong ring current and an absorption spectrum characteristic of an aromatic porphyrinoid.

  1. Ringing phenomenon of the fiber ring resonator.

    PubMed

    Ying, Diqing; Ma, Huilian; Jin, Zhonghe

    2007-08-01

    A resonator fiber-optic gyro (R-FOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A fiber ring resonator is the core sensing element in the R-FOG. When the frequency of the fiber ring resonator input laser is swept linearly with time, ringing of the output resonance curve is observed. The output field of the fiber ring resonator is derived from the superposition of the light transmitted through the directional coupler directly and the multiple light components circulated in the fiber ring resonator when the frequency of the laser is swept. The amplitude and phase of the output field are analyzed, and it is found that the difference in time for different light components in the fiber ring resonator to reach a point of destructive interference causes the ringing phenomenon. Finally the ringing phenomenon is observed in experiments, and the experimental results agree with the theoretical analysis well.

  2. Contribution of methyl group to secondary organic aerosol formation from aromatic hydrocarbon photooxidation

    NASA Astrophysics Data System (ADS)

    Li, Lijie; Qi, Li; Cocker, David R.

    2017-02-01

    The complete atmospheric oxidation pathways leading to secondary organic aerosol remain elusive for aromatic compounds including the role of methyl substitutes on oxidation. This study investigates the contribution of methyl group to Secondary Organic Aerosol (SOA) formation during the photooxidation of aromatic hydrocarbons under low NOx condition by applying methyl carbon labeled aromatic hydrocarbons ((13C2) m-xylene and (13C2) p-xylene). Particle and gas phase oxidation products are analyzed by a series of mass spectrometers (HR-TOF-AMS, PTR-MS and SIFT-MS). The methyl group carbon containing oxidation products partition to the particle-phase at a lower rate than the carbons originating from the aromatic ring as a result of ring opening reactions. Further, the methyl carbon in the original aromatic structure is at least 7 times less likely to be oxidized when forming products that partition to SOA than the aromatic ring carbon. Therefore, oxidation of the methyl group in xylenes exerts little impact on SOA formation in current study. This study provides supporting evidence for a recent finding - a similarity in the SOA formation and composition from aromatic hydrocarbons regardless of the alkyl substitutes.

  3. Free energy profiles of base flipping in intercalative polycyclic aromatic hydrocarbon-damaged DNA duplexes: Energetic and structural relationships to nucleotide excision repair susceptibility

    PubMed Central

    Cai, Yuqin; Zheng, Han; Ding, Shuang; Kropachev, Konstantin; Schwaid, Adam G.; Tang, Yijin; Mu, Hong; Wang, Shenglong; Geacintov, Nicholas E.; Zhang, Yingkai; Broyde, Suse

    2013-01-01

    The crystal structure of Rad4/Rad23, the yeast homolog of the human nucleotide excision repair (NER) lesion recognition factor XPC-RAD23B (Min and Pavletich, (2007) Nature 449:570–575) reveals that the lesion-partner base is flipped out of the helix and binds the protein. This suggests the hypothesis that flipping of this partner base must overcome a free energy barrier, which constitutes one element contributing to changes in the thermodynamic properties induced by the DNA damage and sensed by the recognition protein. We explored this hypothesis by computing complete flipping free energy profiles for two lesions derived from the procarcinogenic polycyclic aromatic hydrocarbons (PAHs), dibenzo[a,l]pyrene (DB[a,l]P) and benzo[a]pyrene (B[a]P), R-trans-anti-DB[a,l]P-N6-dA (R-DB[a,l]P-dA) and R-trans-anti-B[a]P-N6-dA (R-B[a]P-dA), and the corresponding unmodified duplex. The DB[a,l]P and B[a]P adducts differ in number and organization of their aromatic rings. We integrate these results with prior profiles for the R-trans-anti-DB[a,l]P-dG adduct (Zheng et al., (2010) Chem. Res. Toxicol. 23:1868–1870). All adopt conformational themes involving intercalation of the PAH aromatic ring system into the DNA duplex; however, R-DB[a,l]P-dA and R-B[a]P-dA intercalate from the major groove, while R-DB[a,l]P-dG intercalates from the minor groove. These structural differences produce different computed van der Waals stacking interaction energies between the flipping partner base with the lesion aromatic ring system and adjacent bases; we find that the better the stacking, the higher the relative flipping free energy barrier and hence lower flipping probability. The better relative NER susceptibilities correlate with greater ease of flipping in these three differently intercalated lesions. In addition to partner base-flipping, the Rad4/Rad23 crystal structure shows that a protein-β-hairpin, BHD3, intrudes from the major groove side between the DNA strands at the lesion site. We

  4. Cyclophanes containing large polycyclic aromatic hydrocarbons.

    PubMed

    Ghasemabadi, Parisa Ghods; Yao, Tieguang; Bodwell, Graham J

    2015-09-21

    Cyclophanes have been firmly entrenched as a distinct class of compounds for well over half a century. The two main factors that have kept this field of chemistry going so strongly for such a long time are tremendous structural diversity and the interesting behaviour that is often observed. Although a very large number cyclophanes has been reported, only a very small proportion of them contain polycyclic aromatic systems that can be thought of as "large", i.e. with ≥4 rings. This Review puts the spotlight on such cyclophanes, illuminating both the chemistry that was used to synthesize them and what was learned from studying them. Context for the main body is provided by the careful consideration of the anatomy of a cyclophane and the classification of general synthetic approaches. The subsequent sections cover eleven different PAHs and are organized primarily according to increasing size of the aromatic system, starting with pyrene (C16, the only large polycyclic aromatic system to have been incorporated into numerous cyclophanes) and ending with hexabenzo[bc,ef,hi,kl,no,qr]coronene (C42).

  5. Mechanical seal having a double-tier mating ring

    SciTech Connect

    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.

  6. 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.

  7. The Effect of n vs. iso Isomerization on the Thermophysical Properties of Aromatic and Non-aromatic Ionic Liquids.

    PubMed

    Rodrigues, Ana S M C; Almeida, Hugo F D; Freire, Mara G; Lopes-da-Silva, José A; Coutinho, João A P; Santos, Luís M N B F

    2016-09-15

    This work explores the n vs. iso isomerization effects on the physicochemical properties of different families of ionic liquids (ILs) with variable aromaticity and ring size. This study comprises the experimental measurements, in a wide temperature range, of the ILs' thermal behavior, heat capacities, densities, refractive indices, surface tensions, and viscosities. The results here reported show that the presence of the iso-alkyl group leads to an increase of the temperature of the glass transition, Tg. The iso-pyrrolidinium (5 atoms ring cation core) and iso-piperidinium (6 atoms ring cation core) ILs present a strong differentiation in the enthalpy and entropy of melting. Non-aromatic ILs have higher molar heat capacities due to the increase of the atomic contribution, whereas it was not found any significant differentiation between the n and iso-alkyl isomers. A small increase of the surface tension was observed for the non-aromatic ILs, which could be related to their higher cohesive energy of the bulk, while the lower surface entropy observed for the iso isomers indicates a structural resemblance between the IL bulk and surface. The significant differentiation between ILs with a 5 and 6 atoms ring cation in the n-alkyl series (where 5 atoms ring cations have higher surface entropy) is an indication of a more efficient arrangement of the non-polar region at the surface in ILs with smaller cation cores. The ILs constituted by non-aromatic piperidinium cation, and iso-alkyl isomers were found to be the most viscous among the studied ILs due to their higher energy barriers for shear stress.

  8. The Effect of n vs. iso Isomerization on the Thermophysical Properties of Aromatic and Non-aromatic Ionic Liquids

    PubMed Central

    Rodrigues, Ana S.M.C.; Almeida, Hugo F. D.; Freire, Mara G.; Lopes-da-Silva, José A.; Coutinho, João A. P.; Santos, Luís M. N. B. F.

    2016-01-01

    This work explores the n vs. iso isomerization effects on the physicochemical properties of different families of ionic liquids (ILs) with variable aromaticity and ring size. This study comprises the experimental measurements, in a wide temperature range, of the ILs’ thermal behavior, heat capacities, densities, refractive indices, surface tensions, and viscosities. The results here reported show that the presence of the iso-alkyl group leads to an increase of the temperature of the glass transition, Tg. The iso-pyrrolidinium (5 atoms ring cation core) and iso-piperidinium (6 atoms ring cation core) ILs present a strong differentiation in the enthalpy and entropy of melting. Non-aromatic ILs have higher molar heat capacities due to the increase of the atomic contribution, whereas it was not found any significant differentiation between the n and iso-alkyl isomers. A small increase of the surface tension was observed for the non-aromatic ILs, which could be related to their higher cohesive energy of the bulk, while the lower surface entropy observed for the iso isomers indicates a structural resemblance between the IL bulk and surface. The significant differentiation between ILs with a 5 and 6 atoms ring cation in the n-alkyl series (where 5 atoms ring cations have higher surface entropy) is an indication of a more efficient arrangement of the non-polar region at the surface in ILs with smaller cation cores. The ILs constituted by non-aromatic piperidinium cation, and iso-alkyl isomers were found to be the most viscous among the studied ILs due to their higher energy barriers for shear stress. PMID:27682333

  9. Bio-Based Aromatic Epoxy Monomers for Thermoset Materials.

    PubMed

    Ng, Feifei; Couture, Guillaume; Philippe, Coralie; Boutevin, Bernard; Caillol, Sylvain

    2017-01-18

    The synthesis of polymers from renewable resources is a burning issue that is actively investigated. Polyepoxide networks constitute a major class of thermosetting polymers and are extensively used as coatings, electronic materials, adhesives. Owing to their outstanding mechanical and electrical properties, chemical resistance, adhesion, and minimal shrinkage after curing, they are used in structural applications as well. Most of these thermosets are industrially manufactured from bisphenol A (BPA), a substance that was initially synthesized as a chemical estrogen. The awareness on BPA toxicity combined with the limited availability and volatile cost of fossil resources and the non-recyclability of thermosets implies necessary changes in the field of epoxy networks. Thus, substitution of BPA has witnessed an increasing number of studies both from the academic and industrial sides. This review proposes to give an overview of the reported aromatic multifunctional epoxide building blocks synthesized from biomass or from molecules that could be obtained from transformed biomass. After a reminder of the main glycidylation routes and mechanisms and the recent knowledge on BPA toxicity and legal issues, this review will provide a brief description of the main natural sources of aromatic molecules. The different epoxy prepolymers will then be organized from simple, mono-aromatic di-epoxy, to mono-aromatic poly-epoxy, to di-aromatic di-epoxy compounds, and finally to derivatives possessing numerous aromatic rings and epoxy groups.

  10. 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.

  11. Biotechnological production of aromatic compounds of the extended shikimate pathway from renewable biomass.

    PubMed

    Lee, Jin-Ho; Wendisch, Volker F

    2016-11-18

    Aromatic chemicals that contain an unsaturated ring with alternating double and single bonds find numerous applications in a wide range of industries, e.g. paper and dye manufacture, as fuel additives, electrical insulation, resins, pharmaceuticals, agrochemicals, in food, feed and cosmetics. Their chemical production is based on petroleum (BTX; benzene, toluene, and xylene), but they can also be obtained from plants by extraction. Due to petroleum depletion, health compliance, or environmental issues such as global warming, the biotechnological production of aromatics from renewable biomass came more and more into focus. Lignin, a complex polymeric aromatic molecule itself, is a natural source of aromatic compounds. Many microorganisms are able to catabolize a plethora of aromatic compounds and interception of these pathways may lead to the biotechnological production of value-added aromatic compounds which will be discussed for Corynebacterium glutamicum. Biosynthesis of aromatic amino acids not only gives rise to l-tryptophan, L-tyrosine and l-phenylalanine, but also to aromatic intermediates such as dehydroshikimate or chorismate from which value-added aromatic compounds can be derived. In this review, we will summarize recent strategies for the biotechnological production of aromatic and related compounds from renewable biomass by Escherichia coli, Pseudomonas putida, C. glutamicum and Saccharomyces cerevisiae. In particular, we will focus on metabolic engineering of the extended shikimate pathway.

  12. 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.

  13. 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.

  14. 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

  15. Metabolic Pathways for Degradation of Aromatic Hydrocarbons by Bacteria.

    PubMed

    Ladino-Orjuela, Guillermo; Gomes, Eleni; da Silva, Roberto; Salt, Christopher; Parsons, John R

    2016-01-01

    The aim of this review was to build an updated collection of information focused on the mechanisms and elements involved in metabolic pathways of aromatic hydrocarbons by bacteria. Enzymes as an expression of the genetic load and the type of electron acceptor available, as an environmental factor, were highlighted. In general, the review showed that both aerobic routes and anaerobic routes for the degradation of aromatic hydrocarbons are divided into two pathways. The first, named the upper pathways, entails the route from the original compound to central intermediate compounds still containing the aromatic ring but with the benzene nucleus chemically destabilized. The second, named the lower pathway, begins with ring de-aromatization and subsequent cleavage, resulting in metabolites that can be used by bacteria in the production of biomass. Under anaerobic conditions the five mechanisms of activation of the benzene ring described show the diversity of chemical reactions that can take place. Obtaining carbon and energy from an aromatic hydrocarbon molecule is a process that exhibits the high complexity level of the metabolic apparatus of anaerobic microorganisms. The ability of these bacteria to express enzymes that catalyze reactions, known only in non-biological conditions, using final electron acceptors with a low redox potential, is a most interesting topic. The discovery of phylogenetic and functional characteristics of cultivable and noncultivable hydrocarbon degrading bacteria has been made possible by improvements in molecular research techniques such as SIP (stable isotope probing) tracing the incorporation of (13)C, (15)N and (18)O into nucleic acids and proteins. Since many metabolic pathways in which enzyme and metabolite participants are still unknown, much new research is required. Therefore, it will surely allow enhancing the known and future applications in practice.

  16. 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 OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of...

  17. 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 OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of...

  18. 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 OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of...

  19. 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...

  20. 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...

  1. 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.

  2. Birth Control Ring

    MedlinePlus

    ... Loss Surgery? A Week of Healthy Breakfasts Shyness Birth Control Ring KidsHealth > For Teens > Birth Control Ring Print A A A What's in this ... español Anillo vaginal anticonceptivo What Is It? The birth control ring is a soft, flexible, doughnut-shaped ring ...

  3. Integrated reforming/aromatization process

    SciTech Connect

    Harandi, M.N.; Owen, H.

    1990-06-26

    This patent describes an integrated process for increasing the gasoline yield from a catalytic reforming process. It comprises: charging a naphtha boiling range feedstream to a catalytic reforming reaction zone under reforming conversion conditions; withdrawing a reactor effluent stream from the reforming reaction zone; separating the reactor effluent stream into a hydrogen-rich gas stream and an unstabilized reformate stream; further separating the unstabilized reformate in a fractionator into an overhead stream containing C{sub 4} - components and a bottom stream containing C{sub 6} + components; charging the fractionator overhead stream to a catalytic aromatization zone under aromatization conversion conditions; withdrawing an aromatization zone effluent stream from the aromatization zone; cooling the aromatization zone effluent stream; separating the cooled aromatization zone effluent steam into a C{sub 4} - stream and a C{sub 5} + stream; and refluxing the C{sub 5} + aromatic gasoline stream to the fractionation zone.

  4. 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.

  5. 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.

  6. Evidence of Accretion in Saturn's F Ring (Invited)

    NASA Astrophysics Data System (ADS)

    Agnor, C. B.; Buerle, K.; Murray, C. D.; Evans, M. W.; Cooper, N. J.; Williams, G. W.

    2010-12-01

    Lying slightly outside the classical Roche radius and being strongly perturbed by the adjacent moons Prometheus and Pandora, Saturn's F ring represents a unique astrophysical laboratory for examining the processes of mass accretion and moonlet formation. Recent images from the Cassini spacecraft reveal optically thick clumps, capable of casting shadows, and associated structures in regions of the F ring following close passage by Prometheus. Here we examine the accretion environment of the F ring and Prometheus' role in moonlet formation and evolution. Using the observed structures adjacent to these clumps and dynamical arguments we estimate the masses of these clumps and find them comparable to that of ~10-20-km contiguous moonlets. Further, we show that Prometheus' perturbations on the F ring create regions of enhanced density and low relative velocity that may accelerate the accretion of clumps and moonlets.

  7. 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.

  8. A Description of Vibrational Modes in Hexaphyrins: Understanding the Aromaticity Reversal in the Lowest Triplet State.

    PubMed

    Sung, Young Mo; Oh, Juwon; Naoda, Koji; Lee, Taegon; Kim, Woojae; Lim, Manho; Osuka, Atsuhiro; Kim, Dongho

    2016-09-19

    Aromaticity reversal in the lowest triplet state, or Baird's rule, has been postulated for the past few decades. Despite numerous theoretical works on aromaticity reversal, experimental study is still at a rudimentary stage. Herein, we investigate the aromaticity reversal in the lowest excited triplet state using a comparable set of [26]- and [28]hexaphyrins by femtosecond time-resolved infrared (IR) spectroscopy. Compared to the relatively simple IR spectra of [26]bis(rhodium) hexaphyrin (R26H), those of [28]bis(rhodium) hexaphyrin (R28H) show complex IR spectra the region for the stretching modes of conjugated rings. Whereas time-resolved IR spectra of R26H in the excited triplet state are dominated by excited state IR absorption peaks, while those of R28H largely show ground state IR bleaching peaks, reflecting the aromaticity reversal in the lowest triplet state. These contrasting IR spectral features serve as new experimental aromaticity indices for Baird's rule.

  9. Dispersion of boron nitride nanotubes in aqueous solution by simple aromatic molecules.

    PubMed

    Kim, Dukeun; Sawada, Toshiki; Zhi, Chunyi; Bando, Yoshio; Golberg, Dmitri; Serizawa, Takeshi

    2014-04-01

    We report that the simple aromatic molecules successfully disentangle and disperse multi-walled boron nitride nanotubes (BNNTs) in aqueous solutions through pi-pi stacking interactions. Aromatic molecules such as derivatives of naphthalene, anthracene, and pyrene were used as dispersants and components for construction of nanohybrids. Spectroscopic analyses of water-dispersed BNNTs revealed that not only numbers of aromatic rings but also substituted functional groups were essential for dispersion capabilities. It was suggested that greater numbers of aromatic rings and a carboxylic acid as the substituted group showed higher dispersion capabilities among the molecules used in this study. Detailed microscopic analyses using atomic force microscopy and transmission electron microscopy showed certain isolation capabilities of the aromatic molecules for BNNTs in aqueous solution. Moreover, fluorescence spectra indicated that BNNTs and the aromatic molecules have different electronic states after hybrid formation. Our results using the simple aromatic molecules will be utilized as a basic data for dispersion of BNNTs and construction of disentangled BNNT nanohybrids effectively.

  10. 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

  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. 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

  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. Genes coding for the benzoyl-CoA pathway of anaerobic aromatic metabolism in the bacterium Thauera aromatica.

    PubMed

    Breese, K; Boll, M; Alt-Mörbe, J; Schägger, H; Fuchs, G

    1998-08-15

    Many aromatic compounds are anaerobically oxidized to CO2 via benzoyl-CoA as the common aromatic intermediate. In Thauera aromatica, the central benzoyl-CoA pathway comprises the ATP-driven two-electron reduction of the benzene ring; this reaction uses a ferredoxin as electron donor and is catalyzed by benzoyl-CoA reductase. The first intermediate, cyclohex-1,5-diene-1-carboxyl-CoA, is subsequently hydrated by dienoyl-CoA hydratase to 6-hydroxycyclohex-1-ene-1-carboxyl-CoA. Formation of the main product produced by cell extracts, 3-hydroxypimelyl-CoA, requires at least two further steps; the oxidation of a hydroxyl group and the hydrolytic carbon ring cleavage of a CoA-activated beta-oxoacid. In addition, enoyl-CoA hydratase may come into play. A cluster of eight adjacent genes, which are transcribed in the same direction and may form an operon, was found in this bacterium. The cluster codes for proven and postulated enzymes of the benzoyl-CoA pathway. The genes for the enzymes code for ferredoxin, four subunits of benzoyl-CoA reductase, dienoyl-CoA hydratase, 6-hydroxycyclohex-1-ene-1-carboxyl-CoA dehydrogenase (NAD+), and the ring hydrolyzing enzyme. The deduced amino acid sequences of these proteins were 35-86% similar to the corresponding sequences found in Rhodopseudomonas palustris. Benzoyl-CoA reductase subunits exhibit distinct similarities with 2-hydroxyglutaryl-CoA dehydratase and its ATP-hydrolysing activase protein of Acidaminococcus fermentans as well as with open reading frames of unknown function in other bacteria. Conversion of benzoyl-CoA to 3-hydroxypimelyl-CoA can be explained by a minimal model of the benzoyl-CoA pathway assuming the four enzymes whose genes were characterized and an additional enoyl-CoA hydratase. In R. palustris the dienoyl-CoA hydratase gene is lacking suggesting the operation of a modified benzoyl-CoA pathway with cyclohex-1-ene-1-carboxyl-CoA as intermediate.

  16. 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.

  17. 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

    2006-04-07

    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.

  18. 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.

  19. 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

  20. On certain Hecke rings

    PubMed Central

    Evens, Sam; Bressler, Paul

    1987-01-01

    We examine rings that embed into the smash product of the group algebra of the Weyl group with the field of meromorphic functions on the Cartan subalgebra and are generated by elements that satisfy braid relations. We prove that every such ring is isomorphic to either the Hecke algebra, the nil Hecke ring, or the group algebra of the Weyl group. PMID:16593804

  1. 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…

  2. 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)

  3. Soft normed rings.

    PubMed

    Uluçay, Vakkas; Şahin, Mehmet; Olgun, Necati

    2016-01-01

    Molodtsov introduced the concept of soft sets, which can be seen as a new mathematical tool for dealing with uncertainty. In this paper, we initiate the study of soft normed rings by soft set theory. The notions of soft normed rings, soft normed ideals, soft complete normed rings are introduced and also several related properties and examples are given.

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. On the solar dust ring(s)

    NASA Astrophysics Data System (ADS)

    Mukai, T.

    Based on a mechanism to form the solar dust ring, it is proved that the observed peak in infrared F-corona cannot be explained by silicate type grains alone. Preliminary analysis on the recent infrared data of the F-corona by Maihara et al. (1984) has suggested that the ring particles have different physical properties compared with the dust grains, which produce the background F-corona.

  9. Mechanistic Studies of TiO2 Photocatalysis and Fenton Degradation of Hydrophobic Aromatic Pollutants in Water.

    PubMed

    Gong, Yuanzheng; Yang, Chun; Ji, Hongwei; Chen, Chuncheng; Ma, Wanhong; Zhao, Jincai

    2016-12-19

    HO-adduct radicals have been investigated and confirmed as the common initial intermediates in TiO2 photocatalysis and Fenton degradations of water-insoluble aromatics. However, the evolution of HO-adduct radicals to phenols has not been completely clarified. When 4-d-toluene and p-xylene were degraded by TiO2 photocatalysis and Fenton reactions, respectively, a portion of the 4-deuterium or 4-CH3 group (18-100 %) at the attacked ipso position shifted to the adjacent position of the ring in the formed phenols (NIH shift; NIH is short for the National Institutes of Health, to honor the place where this phenomenon was first discovered). The results, combined with the observation of a key dienyl cationic intermediate by in situ attenuated total reflectance FTIR spectroscopy, indicate that, for the evolution of HO-adduct radicals, a mixed mechanism of both the carbocation intermediate pathway and O2 -capturing pathway occurs in both aqueous TiO2 photocatalysis and aqueous Fenton reactions.

  10. Bioactive Secondary Metabolites with Unique Aromatic and Heterocyclic Structures Obtained from Terrestrial Actinomycetes Species.

    PubMed

    Abdelfattah, Mohamed S; Arai, Midori A; Ishibashi, Masami

    2016-07-01

    Natural products from actinomycetes are important and valuable sources for drug discovery and the development of biological tools. The present review describes our recent study on the isolation of new natural products mainly possessing heterocyclic and aromatic ring structures with biological effects on cancer-related cellular pathways such as tumor necrosis factor-α-related apoptosis-inducing ligand (TRAIL) and Wnt signaling.

  11. 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

  12. 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

  13. Measurement procedures of polycyclic aromatic hydrocarbons in undiluted diesel exhaust gases

    SciTech Connect

    Wajsman, J.; Champoussin, J.C.; Dessalces, G.; Claus, G.

    1996-09-01

    Procedures for the measurement of aromatic hydrocarbons in undiluted Diesel exhaust gases were developed and compared. In the first one, hydrocarbons are trapped on sorbents, then analyzed by thermal desorption coupled to GC/FID. Eight monoaromatic hydrocarbons and eleven PAHs from two to four aromatic rings have been detected. The second procedure uses three media: a filter, a condenser and a resin cartridge. After extraction, samples are purified and analyzed by GC/FID or by HPLC/Fluorescence. Fourteen PAHs of two to six aromatic rings have been thus quantified. The two procedures are in agreement for the common species measured. The procedure using the analysis by HPLC/Fluorescence is both more selective and more sensitive. It allows an estimate to be made of the influence of load and speed on PAH emissions.

  14. Dependency of the regio- and stereoselectivity of intramolecular, ring-closing glycosylations upon the ring size

    PubMed Central

    Claude, Patrick; Lehmann, Christian

    2011-01-01

    Summary Phenyl 3,4,6-tri-O-benzyl-2-O-(3-carboxypropionyl)-1-thio-β-D-galactopyranoside (1) was condensed via its pentafluorophenyl ester 2 with 5-aminopentyl (4a), 4-aminobutyl (4b), 3-aminopropyl (4c) and 2-aminoethyl 4,6-O-benzylidene-β-D-glucopyranoside (4d), prepared from the corresponding N-Cbz protected glucosides 3a–d, to give the corresponding 2-[3-(alkylcarbamoyl)propionyl] tethered saccharides 5a–d. Intramolecular, ring closing glycosylation of the saccharides with NIS and TMSOTf afforded the tethered β(1→3) linked disaccharides 6a–c, the α(1→3) linked disaccharides 7a–d and the α(1→2) linked disaccharide 8d in ratios depending upon the ring size formed during glycosylation. No β(1→2) linked disaccharides were formed. Molecular modeling of saccharides 6–8 revealed that a strong aromatic stacking interaction between the aromatic parts of the benzyl and benzylidene protecting groups in the galactosyl and glucosyl moieties was mainly responsible for the observed regioselectivity and anomeric selectivity of the ring-closing glycosylation step. PMID:22238538

  15. Pyrene degradation by a Mycobacterium sp.: identification of ring oxidation and ring fission products.

    PubMed Central

    Heitkamp, M A; Freeman, J P; Miller, D W; Cerniglia, C E

    1988-01-01

    The degradation of pyrene, a polycyclic aromatic hydrocarbon containing four aromatic rings, by pure cultures of a Mycobacterium sp. was studied. Over 60% of [14C]pyrene was mineralized to CO2 after 96 h of incubation at 24 degrees C. High-pressure liquid chromatography analyses showed the presence of one major and at least six other metabolites that accounted for 95% of the total organic-extractable 14C-labeled residues. Analyses by UV, infrared, mass, and nuclear magnetic resonance spectrometry and gas chromatography identified both pyrene cis- and trans-4,5-dihydrodiols and pyrenol as initial microbial ring-oxidation products of pyrene. The major metabolite, 4-phenanthroic acid, and 4-hydroxyperinaphthenone and cinnamic and phthalic acids were identified as ring fission products. 18O2 studies showed that the formation of cis- and trans-4,5-dihydrodiols were catalyzed by dioxygenase and monooxygenase enzymes, respectively. This is the first report of the chemical pathway for the microbial catabolism of pyrene. PMID:3202634

  16. Colorless, Transparent, Aromatic Polyimide Films

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; St. Clair, T. L.; Ezzell, K. S.; Ely, R. M.

    1986-01-01

    New process yields aromatic condensation polyimide films essentially colorless. Films between 90- and 100-percent transparent at visible wavelength of 500 nm. Optically transparent polyimide films made from variety of aromatic condensation polyimides. Range from very pale in color to colorless, compared to bright yellow color of conventional/ commercial aromatic polyimide film. Increased transparency achieved at no sacrifice in thermal stability, flexibility, toughness, or mechanical properties. These features extremely attractive as films or coating materials for aerospace applications or for any other applications where high optical transparency or thermal stability is required.

  17. 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.

  18. Retardation effect of nitrogen compounds and condensed aromatics on shale oil catalytic cracking processing and their characterization.

    PubMed

    Li, Nan; Chen, Chen; Wang, Bin; Li, Shaojie; Yang, Chaohe; Chen, Xiaobo

    Untreated shale oil, shale oil treated with HCl aqueous solution and shale oil treated with HCl and furfural were used to do comparative experiments in fixed bed reactors. Nitrogen compounds and condensed aromatics extracted by HCl and furfural were characterized by electrospray ionization Fourier transform cyclotron resonance mass spectrometry and gas chromatography and mass spectrometry, respectively. Compared with untreated shale oil, the conversion and yield of liquid products increased considerably after removing basic nitrogen compounds by HCl extraction. Furthermore, after removing nitrogen compounds and condensed aromatics by both HCl and furfural, the conversion and yield of liquid products further increased. In addition, N1 class species are predominant in both basic and non-basic nitrogen compounds, and they are probably indole, carbazole, cycloalkyl-carbazole, pyridine and cycloalkyl-pyridine. As for the condensed aromatics, most of them possess aromatic rings with two to three rings and zero to four carbon atom.

  19. Sources of polycyclic aromatic hydrocarbons in sediments of the Bharalu River, a tributary of the River Brahmaputra in Guwahati, India.

    PubMed

    Hussain, Karishma; Balachandran, S; Rafiqul Hoque, Raza

    2015-12-01

    Analysis of riverine sediments offers important information regarding anthropogenic activities in the adjacent watershed. In this study, we provide polycyclic aromatic hydrocarbon (PAH) levels, their possible sources and potential hazards in the Bharalu tributary of the Brahmaputra River flowing through Guwahati city in India. The USEPA's 16 priority PAHs were determined in river bank sediments during two distinct seasons viz. pre- and post-monsoon. The ∑PAHs concentrations varied between 338 and 23,100 ng g(-1) during post-monsoon and between 609 and 8620 ng g(-1) during pre-monsoon. Mean benzo(a)pyrene (BaP) levels were between 17.8 ± 12 and 21.9 ± 27 ng g(-1) during post- and pre-monsoon seasons respectively. Spatial variations were observed. Interestingly, bank sediment samples from the sites near the confluence of the Bharalu River with the Brahmaputra River were found to have maximum concentrations of PAHs during post-monsoon season. The profile of the PAHs was dominated by 3-, 4- and 6-ring compounds. We estimated hazards of PAHs as RQ∑PAHs, which showed seasonal variation: 3 times higher during post-monsoon than pre-monsoon. 3-and 4-ring PAHs were the major PAHs of concern. The Bharalu River sediment was found to pose medium to high hazards to ecosystem. The individual PAHs including Acy, Phen and Pyr were observed with RQ(MPCs) value >1 indicating severe hazards during post-monsoon and pre-monsoon season. A very high percentage of coefficient of variation (CV) for PAHs during post-monsoon also revealed great variation in hazards and sources in this season. The diagnostic ratios indicated both petrogenic and pyrogenic origin of the PAHs. The pyrogenic contributions were mainly attributed to emissions from diesel, gasoline and wood combustion which are mainly from anthropogenic sources.

  20. 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

  1. Slowing of Vortex Rings

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell; Bolster, Diogo; Hershberger, Robert

    2008-11-01

    We have investigated the slowing of vortex rings in water which are created with very thin cores. We find that these rings propagate with no measurable change in diameter or core size. The drag appears to be the result of viscous forces on the core. A simple model for this drag describes experimental data in terms of a drag coefficient, which depends only on Reynolds number. Barenghi's group at Newcastle found that the translational velocity of a ring in an inviscid fluid perturbed by Kelvin waves decreases with increasing amplitude of Kelvin waves. This suggests that the velocity of vortex rings in a viscous fluid may well depend on the amplitude of Kelvin waves at the time of formation. Rings with substantial amplitude of Kelvin waves will be expected to move more slowly than rings with little or no Kelvin wave amplitude. We present experimental data confirming this suggestion.

  2. Nuclear Magnetic Shieldings of Stacked Aromatic and Antiaromatic Molecules.

    PubMed

    Sundholm, Dage; Rauhalahti, Markus; Özcan, Nergiz; Mera-Adasme, Raúl; Kussmann, Jörg; Luenser, Arne; Ochsenfeld, Christian

    2017-04-04

    Nuclear magnetic shieldings have been calculated at the density functional theory (DFT) level for stacks of benzene, hexadehydro[12]annulene, dodecadehydro[18]annulene, and hexabenzocoronene. The magnetic shieldings due to the ring currents in the adjacent molecules have been estimated by calculating nucleus independent molecular shieldings for the monomer in the atomic positions of neighbor molecules. The calculations show that the independent shielding model works reasonably well for the (1)H NMR shieldings of benzene and hexadehydro[12]annulene, whereas for the larger molecules and for the (13)C NMR shieldings the interaction between the molecules leads to shielding effects that are at least of the same size as the ring current contributions from the adjacent molecules. A better agreement is obtained when the nearest neighbors are also considered at full quantum mechanical (QM) level. The calculations suggest that the nearest solvent molecules must be included in the quantum mechanical system, at least when estimating solvent shifts at the molecular mechanics (MM) level. Current density calculations show that the stacking does not significantly affect the ring current strengths of the individual molecules, whereas the shape of the ring current for a single molecule differs from that of the stacked molecules.

  3. Revisiting Aromaticity and Chemical Bonding of Fluorinated Benzene Derivatives

    PubMed Central

    Torres-Vega, Juan J; Vásquez-Espinal, Alejandro; Ruiz, Lina; Fernández-Herrera, María A; Alvarez-Thon, Luis; Merino, Gabriel; Tiznado, William

    2015-01-01

    The electron delocalization of benzene (C6H6) and hexafluorobenzene (C6F6) was analyzed in terms of the induced magnetic field, nucleus-independent chemical shift (NICS), and ring current strength (RCS). The computed out-of-plane component of the induced magnetic field at a distance (r) greater than or equal to 1.0 Å above the ring center correlates well (R2>0.99) with the RCS value. According to these criteria, fluorination has two effects on the C6 skeleton; concomitantly, the resonant effects diminish the π electron delocalization and the inductive effects decrease the charge density at the ring center and therefore reduce the magnitude of the paratropic current generated in this region. The equilibrium between both effects decreases aromaticity in the fluorinated benzene derivatives. These results can be extrapolated to determine the aromaticity of any derivative within the series of fluorinated benzene derivatives (C6H(6−n)Fn, where n=1–5). PMID:26246992

  4. 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.

  5. Saturn's E ring revisited

    NASA Astrophysics Data System (ADS)

    Feibelman, W. A.; Klinglesmith, D. A.

    1980-07-01

    Images of the E ring of Saturn obtained by the image processing of photographs of the 1966 edge-on presentation of the planet's ring plane are presented. Two methods of image enhancement were used: scanning with an image quantizer operated in the derivative mode to enhance contrast and computerized subtraction of a circularly symmetric image of the overexposed Saturn disk. Further photographic and CCD observation confirming the existence of the ring extending to twice the diameter of the A ring, which was not detected by the Pioneer 11 imaging photopolarimeter, is indicated.

  6. 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

  7. Phylogenetic comparison of two polycyclic aromatic hydrocarbon-degrading mycobacteria.

    PubMed Central

    Govindaswami, M; Feldhake, D J; Kinkle, B K; Mindell, D P; Loper, J C

    1995-01-01

    Two mycobacterial strains previously isolated from fossil-fuel-contaminated environments and shown to degrade four- and/or five-ring polycyclic aromatic hydrocarbons were further characterized. The two strains, PYR-I and RJGII-135, had similar growth characteristics, colony morphologies, and scotochromogenic pigmentations. DNA amplification fingerprints obtained with total genomic DNA indicated some strain similarities but with several distinctly different bands. Moreover, phylogenetic analysis based upon essentially full-length 16S rRNA gene sequences separates the two strains as distinct species within the fast-growing group of mycobacteria. Although both strains are thermosensitive, strain PYR-I has the bulged U between positions 184 and 193 characteristic of thermotolerant mycobacteria. Both strains are of potential use for reintroduction into and bioremediation of polycyclic aromatic hydrocarbon-contaminated soils. PMID:7574631

  8. Phylogenetic comparison of two polycyclic aromatic hydrogen-degrading mycobacteria

    SciTech Connect

    Govindaswami, M.; Loper, J.C.; Feldhake, D.J.

    1995-09-01

    Two mycobacterial strains previously isolated from fossil-fuel-contaminated environments and shown to degrade four- and/or five-ring polycyclic aromatic hydrocarbons were further characterized. The two strains, PYR-I and RJGII-135, had similar growth characteristics, colony morphologies, and scotochromogenic pigmentations. DNA amplification fringerprints obtained with total genomic DNA indicated some strain similarities but with several distinctly different bands. Moreover, phylogenetic analysis based upon essentially full-length 16S rRNA gene sequences separates the two strains as distinct species within the fast-growing group of mycobacteria. Although both strains are thermosensitive, strain PYR-I has the bulged U between positions 184 and 193 characteristic of thermotolerant mycobacteria. Both strains are of potential use for reintroduction into and bioremediation of polycyclic aromatic hydrocarbon-contaminated soils. 26 refs., 4 figs., 1 tab.

  9. Bond cleavage of lignin model compounds into aromatic monomers using supported metal catalysts in supercritical water

    PubMed Central

    Yamaguchi, Aritomo; Mimura, Naoki; Shirai, Masayuki; Sato, Osamu

    2017-01-01

    More efficient use of lignin carbon is necessary for carbon-efficient utilization of lignocellulosic biomass. Conversion of lignin into valuable aromatic compounds requires the cleavage of C–O ether bonds and C–C bonds between lignin monomer units. The catalytic cleavage of C–O bonds is still challenging, and cleavage of C–C bonds is even more difficult. Here, we report cleavage of the aromatic C–O bonds in lignin model compounds using supported metal catalysts in supercritical water without adding hydrogen gas and without causing hydrogenation of the aromatic rings. The cleavage of the C–C bond in bibenzyl was also achieved with Rh/C as a catalyst. Use of this technique may greatly facilitate the conversion of lignin into valuable aromatic compounds. PMID:28387304

  10. 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.

  11. 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.

  12. Three-dimensional aromatic networks.

    PubMed

    Toyota, Shinji; Iwanaga, Tetsuo

    2014-01-01

    Three-dimensional (3D) networks consisting of aromatic units and linkers are reviewed from various aspects. To understand principles for the construction of such compounds, we generalize the roles of building units, the synthetic approaches, and the classification of networks. As fundamental compounds, cyclophanes with large aromatic units and aromatic macrocycles with linear acetylene linkers are highlighted in terms of transannular interactions between aromatic units, conformational preference, and resolution of chiral derivatives. Polycyclic cage compounds are constructed from building units by linkages via covalent bonds, metal-coordination bonds, or hydrogen bonds. Large cage networks often include a wide range of guest species in their cavity to afford novel inclusion compounds. Topological isomers consisting of two or more macrocycles are formed by cyclization of preorganized species. Some complicated topological networks are constructed by self-assembly of simple building units.

  13. Modified spiral wound retaining ring

    NASA Technical Reports Server (NTRS)

    Lawson, A. G. (Inventor)

    1980-01-01

    A spiral wound retaining ring with angled ends is described. The ring is crimped at the same angle as the ring ends to maintain a constant thickness dimension. The angling of the ends of the ring and crimp allow the ends to be positioned closer together while maintaining enough clearance to enable insertion and removal of the ring. By reducing the separation distance between the ends a stronger ring results since the double layer area of the ring is maximized.

  14. 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.

  15. Polyphenylquinoxalines via aromatic nucleophilic displacement

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    Polyphenylquinoxalines are prepared by the nucleophilic displacement reaction of di(hydroxyphenyl)quinoxaline monomers with activated aromatic dihalides or dinitro compounds. The reactions are carried out in polar aprotic solvents using alkali metal bases at elevated temperatures under nitrogen. The di(hydroxyphenyl)quinoxaline monomers are prepared either by reacting stoichiometric quantities of aromatic bis(o-diamines) with a hydroxybenzil or by reacting o-phenylenediamine with a dihydroxybenzil or bis(hydroxyphenylglyoxylyl)benzene.

  16. Polyphenylquinoxalines via aromatic nucleophilic displacement

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    Polyphenylquinoxalines are prepared by the nucleophilic displacement reaction of di(hydroxyphenyl)quinoxaline monomers with activated aromatic dihalides or dinitro compounds. The reactions are carried out in polar aprotic solvents during alkali metal bases at elevated temperatures under nitrogen. The di(hydroxyphenyl)quinoxaline monomers are prepared either by reacting stoichiometric quantities of aromatic bis(o-diamines) with a hydroxybenzil or by reacting o-phenylenediamine with a dihydroxybenzil or bis(hydroxyphenylglyoxylyl)benzene.

  17. 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.

  18. 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.

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

    DOE PAGES

    Pandini, Alessandro; Kleinjung, Jens; Taylor, Willie R.; ...

    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

  20. Understanding of assembly phenomena by aromatic-aromatic interactions: benzene dimer and the substituted systems.

    PubMed

    Lee, Eun Cheol; Kim, Dongwook; Jurecka, Petr; Tarakeshwar, P; Hobza, Pavel; Kim, Kwang S

    2007-05-10

    Interactions involving aromatic rings are important in molecular/biomolecular assembly and engineering. As a consequence, there have been a number of investigations on dimers involving benzene or other substituted pi systems. In this Feature Article, we examine the relevance of the magnitudes of their attractive and repulsive interaction energy components in governing the geometries of several pi-pi systems. The geometries and the associated binding energies were evaluated at the complete basis set (CBS) limit of coupled cluster theory with singles, doubles, and perturbative triples excitations [CCSD(T)] using a least biased scheme for the given data set. The results for the benzene dimer indicate that the floppy T-shaped structure (center-to-center distance: 4.96 A, with an axial benzene off-centered above the facial benzene) is isoenergetic in zero-point-energy (ZPE) corrected binding energy (D0) to the displaced-stacked structure (vertical interplanar distance: 3.54 A). However, the T-shaped structure is likely to be slightly more stable (D0 approximately equal to 2.4-2.5 kcal/mol) if quadruple excitations are included in the coupled cluster calculations. The presence of substituents on the aromatic ring, irrespective of their electron withdrawing or donating nature, leads to an increase in the binding energy, and the displaced-stacked conformations are more stabilized than the T-shaped conformers. This explains the wide prevalence of displaced stacked structures in organic crystals. Despite that the dispersion energy is dominating, the substituent as well as the conformational effects are correlated to the electrostatic interaction. This electrostatic origin implies that the substituent effect would be reduced in polar solution, but important in apolar media, in particular, for assembling processes.

  1. 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.

  2. 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.

  3. Birth Control Ring

    MedlinePlus

    ... It? The birth control ring is a soft, flexible, doughnut-shaped ring about 2 inches (5 centimeters) in diameter. It is inserted into the vagina, where it slowly releases hormones — the chemicals the body makes to control organ function — through the vaginal wall into the ...

  4. Steroidal contraceptive vaginal rings.

    PubMed

    Sarkar, N N

    2003-06-01

    The development of steroid-releasing vaginal rings over the past three decades is reviewed to illustrate the role of this device as an effective hormonal contraceptive for women. Vaginal rings are made of polysiloxane rubber or ethylene-vinyl-acetate copolymer with an outer diameter of 54-60 mm and a cross-sectional diameter of 4-9.5 mm and contain progestogen only or a combination of progestogen and oestrogen. The soft flexible combined ring is inserted in the vagina for three weeks and removed for seven days to allow withdrawal bleeding. Progesterone/progestogen-only rings are kept in for varying periods and replaced without a ring-free period. Rings are in various stages of research and development but a few, such as NuvaRing, have reached the market in some countries. Women find this method easy to use, effective, well tolerated and acceptable with no serious side-effects. Though the contraceptive efficacy of these vaginal rings is high, acceptability is yet to be established.

  5. Smoke Ring Physics

    NASA Astrophysics Data System (ADS)

    Huggins, Elisha

    2011-11-01

    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 Ampère's law in an introductory physics course. We discuss these common features.

  6. 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.

  7. 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.)

  8. 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)

  9. 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.

  10. 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

  11. Capricious selectivity in electrophilic deuteration of methylenedioxy substituted aromatic compounds.

    PubMed

    Pohjoispää, Monika; Mera-Adasme, Raúl; Sundholm, Dage; Heikkinen, Sami; Hase, Tapio; Wähälä, Kristiina

    2014-11-07

    Ring deuteration via the SEAr mechanism, which is usually problem-free, is found to be troublesome with methylenedioxy substituent aromatics. We report a case where the deuteration not only partially fails at one of the ortho positions but also is completely prevented by a conformation dependent effect at the other o-position. Such selectivity discrepancies are important due to the widespread occurrence of methylenedioxy substituted natural products. Density functional theory calculations were used to elucidate the exchange reaction mechanism in 1,2-dialkoxybenzenes.

  12. Halogen substituents on the aromatic moiety of the tetracaine scaffold improve potency of cyclic nucleotide-gated channel block.

    PubMed

    Kirk, Sarah R; Andrade, Adriana L; Melich, Kenneth; Jackson, Evan P; Cuellar, Elysia; Karpen, Jeffrey W

    2011-11-01

    A series of new tetracaine derivatives with substituents on the aromatic ring was prepared and evaluated for block of retinal rod cyclic nucleotide-gated (CNG) channels. Aromatic substitutions had little effect starting with the basic tetracaine scaffold, but electron-withdrawing substituents significantly improved the blocking potency of an octyl-tail derivative of tetracaine. In particular, halogen substitutions at either the 2- or 3-position on the ring resulted in compounds that were up to eight-fold more potent than the parent octyl-tail derivative and up to 50-fold more potent than tetracaine.

  13. Halogen substituents on the aromatic moiety of the tetracaine scaffold improve potency of cyclic nucleotide-gated channel block

    PubMed Central

    Kirk, Sarah R.; Andrade, Adriana L.; Melich, Kenneth; Jackson, Evan P.; Cuellar, Elysia; Karpen, Jeffrey W.

    2011-01-01

    A series of new tetracaine derivatives with substituents on the aromatic ring was prepared and evaluated for block of retinal rod cyclic nucleotide-gated (CNG) channels. Aromatic substitutions had little effect starting with the basic tetracaine scaffold, but electron-withdrawing substituents significantly improved the blocking potency of an octyl-tail derivative of tetracaine. In particular, halogen substitutions at either the 2- or 3-position on the ring resulted in compounds that were up to 8-fold more potent than the parent octyl-tail derivative and up to 50-fold more potent than tetracaine. PMID:21944857

  14. 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

  15. Ring chromosome 4.

    PubMed Central

    McDermott, A; Voyce, M A; Romain, D

    1977-01-01

    A mentally and physically retarded boy with a 46,XY,ring (4) (p16q35) chromosome complement is described. Chromosome banding showed that the amount of chromosome material deleted from the ring chromosome 4 was minimal, apparently no more than the telomeres. Chromosomal aberrations appear to be restricted to the production of double-sized dicentric rings, and aneuploidy. The mosiacism resulting from the behavioural peculiarities of ring chromosomes is described as dynamic mosaicism. It is suggested that the clinical features associated with this ring chromosome are more likely to be the result of the effects of a diploid/monosomy 4/polysomy 4 mosaicism than to the deficiency of the telomeric regions of the chromosome. Images PMID:881718

  16. 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.

  17. 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.

  18. A quantitative scale for the degree of aromaticity and antiaromaticity: a comparison of theoretical and experimental enthalpies of hydrogenation.

    PubMed

    Mucsi, Zoltán; Viskolcz, Béla; Csizmadia, Imre G

    2007-02-15

    Chemical structures and transition states are often influenced by aromatic stabilization or antiaromatic destabilizing effects, which are not easy to characterize theoretically. The exact description and precise quantification of the aromatic characteristics of ring structures is difficult and requires special theoretical investigation. The present paper suggests a novel, yet simple, method to quantify both aromatic and antiaromatic qualities on the same linear scale, by using the experimentally measured or theoretically computed enthalpy of hydrogenation reaction of the compound examined [DeltaHH2(examined)]. A reference hydrogenation reaction is also considered on a corresponding nonaromatic reference compound [DeltaHH2(reference)] to cancel all secondary structure destabilization factors, such as ring strain or double bond strain. From these data the relative enthalpy of hydrogenation may easily be calculated: DeltaDeltaHH2=DeltaHH2(examined)-DeltaHH2(reference). In the present work concept, the DeltaDeltaHH2 value of benzene defines the completely aromatic character (+100%), and the closed shell of the singlet cyclobutadiene represents maximum antiaromaticity (-100%). The component DeltaHH2 values were computed at different levels of theory offering a computational "method-independent" measure for aromaticity. A total of 28 well-known aromatic, antiaromatic and nonaromatic, neutral and charged compounds were examined to demonstrate the efficiency of this methodology. Finally, a correlation was made between the calculated aromaticity percentage of the compound examined and their popular Schleyers NICS values.

  19. 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.

  20. 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

  1. Perimeter ring currents in benzenoids from Pauling bond orders.

    PubMed

    Fowler, Patrick W; Myrvold, Wendy; Jenkinson, Daniel; Bird, William H

    2016-04-28

    It is shown that the ring currents in perimeter hexagonal rings of Kekulean benzenoids, as estimated within the Randić conjugated-circuit model, can be calculated directly without tedious pairwise comparison of Kekulé structures or Kekulé counting for cycle-deleted subgraphs. Required are only the Pauling bond orders of perimeter bonds and the number of Kekulé structures of the benzenoid, both readily available from the adjacency matrix of the carbon skeleton. This approach provides easy calculation of complete current maps for benzenoids in which every face has at least one bond on the perimeter (as in the example of cata-condensed benzenoids), and allows qualitative evaluation of the main ring-current contributions to (1)H chemical shifts in general benzenoids. A combined Randić-Pauling model for correlation of ring current and bond length through bond order is derived and shown to be consistent with resilience of current under bond alternation.

  2. 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

  3. Bacterial degradation of monocyclic aromatic amines.

    PubMed

    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.

  4. 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

  5. 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.

  6. 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.

  7. Effect of ZSM-5 Acidity on Aromatic Product Selectivity during Upgrading of Pine Pyrolysis Vapors

    SciTech Connect

    Engtrakul, Chaiwat; Mukarakate, Calvin; Starace, Anne K.; Magrini, Kimberly A.; Rogers, Allyson K.; Yung, Matthew M.

    2016-07-01

    The impact of catalyst acidity on the selectivity of upgraded biomass pyrolysis products was studied by passing pine pyrolysis vapors over five ZSM-5 catalysts of varying acidity at 500 degrees C. The SiO2-to-Al2O3 ratio (SAR) of the ZSM-5 zeolite was varied from 23 to 280 to control the acidity of the catalyst and the composition of upgraded products. The upgraded product stream was analyzed by GCMS. Additionally, catalysts were characterized using temperature programmed desorption, diffuse-reflectance FTIR spectroscopy, N2 physisorption, and X-ray diffraction. The results showed that the biomass pyrolysis vapors were highly deoxygenated to form a slate of aromatic hydrocarbons over all of the tested ZSM-5 catalysts. As the overall acidity of the ZSM-5 increased the selectivity toward alkylated (substituted) aromatics (e.g., xylene, dimethyl-naphthalene, and methyl-anthracene) decreased while the selectivity toward unsubstituted aromatics (e.g., benzene, naphthalene, and anthracene) increased. Additionally, the selectivity toward polycyclic aromatic compounds (2-ring and 3-ring) increased as catalyst acidity increased, corresponding to a decrease in acid site spacing. The increased selectivity toward less substituted polycyclic aromatic compounds with increasing acidity is related to the relative rates of cyclization and alkylation reactions within the zeolite structure. As the acid site concentration increases and sites become closer to each other, the formation of additional cyclization products occurs at a greater rate than alkylated products. The ability to adjust product selectivity within 1-, 2-, and 3-ring aromatic families, as well as the degree of substitution, by varying ZSM-5 acidity could have significant benefits in terms creating a slate of upgraded biomass pyrolysis products to meet specific target market demands.

  8. Effect of ZSM-5 acidity on aromatic product selectivity during upgrading of pine pyrolysis vapors

    DOE PAGES

    Engtrakul, Chaiwat; Mukarakate, Calvin; Starace, Anne K.; ...

    2015-11-14

    The impact of catalyst acidity on the selectivity of upgraded biomass pyrolysis products was studied by passing pine pyrolysis vapors over five ZSM-5 catalysts of varying acidity at 500 degrees C. The SiO2-to-Al2O3 ratio (SAR) of the ZSM-5 zeolite was varied from 23 to 280 to control the acidity of the catalyst and the composition of upgraded products. The upgraded product stream was analyzed by GCMS. Additionally, catalysts were characterized using temperature programmed desorption, diffuse-reflectance FTIR spectroscopy, N2 physisorption, and X-ray diffraction. The results showed that the biomass pyrolysis vapors were highly deoxygenated to form a slate of aromatic hydrocarbonsmore » over all of the tested ZSM-5 catalysts. As the overall acidity of the ZSM-5 increased the selectivity toward alkylated (substituted) aromatics (e.g., xylene, dimethyl-naphthalene, and methyl-anthracene) decreased while the selectivity toward unsubstituted aromatics (e.g., benzene, naphthalene, and anthracene) increased. Additionally, the selectivity toward polycyclic aromatic compounds (2-ring and 3-ring) increased as catalyst acidity increased, corresponding to a decrease in acid site spacing. The increased selectivity toward less substituted polycyclic aromatic compounds with increasing acidity is related to the relative rates of cyclization and alkylation reactions within the zeolite structure. As the acid site concentration increases and sites become closer to each other, the formation of additional cyclization products occurs at a greater rate than alkylated products. The ability to adjust product selectivity within 1-, 2-, and 3-ring aromatic families, as well as the degree of substitution, by varying ZSM-5 acidity could have significant benefits in terms creating a slate of upgraded biomass pyrolysis products to meet specific target market demands.« less

  9. Effect of ZSM-5 acidity on aromatic product selectivity during upgrading of pine pyrolysis vapors

    SciTech Connect

    Engtrakul, Chaiwat; Mukarakate, Calvin; Starace, Anne K.; Magrini, Kimberly A.; Rogers, Allyson K.; Yung, Matthew M.

    2015-11-14

    The impact of catalyst acidity on the selectivity of upgraded biomass pyrolysis products was studied by passing pine pyrolysis vapors over five ZSM-5 catalysts of varying acidity at 500 degrees C. The SiO2-to-Al2O3 ratio (SAR) of the ZSM-5 zeolite was varied from 23 to 280 to control the acidity of the catalyst and the composition of upgraded products. The upgraded product stream was analyzed by GCMS. Additionally, catalysts were characterized using temperature programmed desorption, diffuse-reflectance FTIR spectroscopy, N2 physisorption, and X-ray diffraction. The results showed that the biomass pyrolysis vapors were highly deoxygenated to form a slate of aromatic hydrocarbons over all of the tested ZSM-5 catalysts. As the overall acidity of the ZSM-5 increased the selectivity toward alkylated (substituted) aromatics (e.g., xylene, dimethyl-naphthalene, and methyl-anthracene) decreased while the selectivity toward unsubstituted aromatics (e.g., benzene, naphthalene, and anthracene) increased. Additionally, the selectivity toward polycyclic aromatic compounds (2-ring and 3-ring) increased as catalyst acidity increased, corresponding to a decrease in acid site spacing. The increased selectivity toward less substituted polycyclic aromatic compounds with increasing acidity is related to the relative rates of cyclization and alkylation reactions within the zeolite structure. As the acid site concentration increases and sites become closer to each other, the formation of additional cyclization products occurs at a greater rate than alkylated products. The ability to adjust product selectivity within 1-, 2-, and 3-ring aromatic families, as well as the degree of substitution, by varying ZSM-5 acidity could have significant benefits in terms creating a slate of upgraded biomass pyrolysis products to meet specific target market demands.

  10. Heavy ion storage rings

    SciTech Connect

    Schuch, R.

    1987-01-01

    A brief overview of synchrotron storage rings for heavy ions, which are presently under construction in different accelerator laboratories is given. Ions ranging from protons up to uranium ions at MeV/nucleon energies will be injected into these rings using multiturn injection from the accelerators available or being built in these laboratories. After injection, it is planned to cool the phase space distribution of the ions by merging them with cold electron beams or laser beams, or by using stochastic cooling. Some atomic physics experiments planned for these rings are presented.

  11. 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.

  12. Supernumerary small ring chromosome.

    PubMed Central

    Kaffe, S; Kim, H J; Hsu, L Y; Brill, C B; Hirschhorn, K

    1977-01-01

    A supernumerary small ring chromosome was found in 30% of cultured peripheral leucocytes and 50% of skin fibroblasts in a 6-year-old boy with mild mental retardation and midline cleft palate. The extra chromosome appeared to carry a densely staining region on Giemsa banding. The banding patterns of the remaining 46 chromosomes were normal. C banding indicated that the ring chromosome contained mainly centromeric constitutive heterochromatin. Chromosome analysis of both parents showed normal karyotypes by both conventional and banding techniques; thus the origin of the ring chromosome could not be determined. Images PMID:604496

  13. 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.

  14. Aromatic Cations from Oxidative Carbon–Hydrogen Bond Cleavage in Bimolecular Carbon–Carbon Bond Forming Reactions

    PubMed Central

    Clausen, Dane J.

    2012-01-01

    Chromenes and isochromenes react quickly with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to form persistent aromatic oxocarbenium ions through oxidative carbon–hydrogen cleavage. This process is tolerant of electron-donating and electron-withdrawing groups on the benzene ring and additional substitution on the pyran ring. A variety of nucleophiles can be added to these cations to generate a diverse set of structures. PMID:22780559

  15. Adjacent-level arthroplasty following cervical fusion.

    PubMed

    Rajakumar, Deshpande V; Hari, Akshay; Krishna, Murali; Konar, Subhas; Sharma, Ankit

    2017-02-01

    OBJECTIVE Adjacent-level disc degeneration following cervical fusion has been well reported. This condition poses a major treatment dilemma when it becomes symptomatic. The potential application of cervical arthroplasty to preserve motion in the affected segment is not well documented, with few studies in the literature. The authors present their initial experience of analyzing clinical and radiological results in such patients who were treated with arthroplasty for new or persistent arm and/or neck symptoms related to neural compression due to adjacent-segment disease after anterior cervical discectomy and fusion (ACDF). METHODS During a 5-year period, 11 patients who had undergone ACDF anterior cervical discectomy and fusion (ACDF) and subsequently developed recurrent neck or arm pain related to adjacent-level cervical disc disease were treated with cervical arthroplasty at the authors' institution. A total of 15 devices were implanted (range of treated levels per patient: 1-3). Clinical evaluation was performed both before and after surgery, using a visual analog scale (VAS) for pain and the Neck Disability Index (NDI). Radiological outcomes were analyzed using pre- and postoperative flexion/extension lateral radiographs measuring Cobb angle (overall C2-7 sagittal alignment), functional spinal unit (FSU) angle, and range of motion (ROM). RESULTS There were no major perioperative complications or device-related failures. Statistically significant results, obtained in all cases, were reflected by an improvement in VAS scores for neck/arm pain and NDI scores for neck pain. Radiologically, statistically significant increases in the overall lordosis (as measured by Cobb angle) and ROM at the treated disc level were observed. Three patients were lost to follow-up within the first year after arthroplasty. In the remaining 8 cases, the duration of follow-up ranged from 1 to 3 years. None of these 8 patients required surgery for the same vertebral level during the follow

  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. Stochastic atomistic simulation of polycyclic aromatic hydrocarbon growth in combustion.

    PubMed

    Lai, Jason Y W; Elvati, Paolo; Violi, Angela

    2014-05-07

    Nanoparticles formed in gas phase environments, such as combustion, have an important impact on society both as engineering components and hazardous pollutants. A new software package, the Stochastic Nanoparticle Simulator (SNAPS) was developed, applying a stochastic chemical kinetics methodology, to computationally investigate the growth of nanoparticle precursors through trajectories of chemical reactions. SNAPS was applied to characterize the growth of polycyclic aromatic hydrocarbons (PAHs), important precursors of carbonaceous nanoparticles and soot, in a premixed laminar benzene flame, using a concurrently developed PAH growth chemical reaction mechanism, as well as an existing benzene oxidation mechanism. Simulations of PAH ensembles successfully predicted existing experimentally measured data and provided novel insight into chemical composition and reaction pathways. The most commonly observed PAH isomers in simulations showed the importance of 5-membered rings, which contrasts with traditionally assumed compositions involving primarily pericondensed 6-membered rings. In addition, the chemical growth of PAHs involved complex sequences of highly reversible reactions, rather than relatively direct routes of additions and ring closures. Furthermore, the most common reactions involved 5-membered rings, suggesting their importance to PAH growth. The framework developed in this work will facilitate future investigation of particle inception and soot formation and will benefit engineering of novel combustion technologies to mitigate harmful emissions.

  18. 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.

  19. 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.

  20. 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.

  1. Aromatizing olefin metathesis by ligand isolation inside a metal-organic framework.

    PubMed

    Vermeulen, Nicolaas A; Karagiaridi, Olga; Sarjeant, Amy A; Stern, Charlotte L; Hupp, Joseph T; Farha, Omar K; Stoddart, J Fraser

    2013-10-09

    The aromatizing ring-closing metathesis has been shown to take place inside an extended porous framework. Employing a combination of solvent-assisted linker exchange and postsynthesis modification using olefin metathesis, the noninterpenetrated SALEM-14 was formed and converted catalytically into PAH-MOF-1 with polycyclic aromatic hydrocarbon (PAH) pillars. The metal-organic framework in SALEM-14 prevents "intermolecular" olefin metathesis from occurring between the pillars in the presence of the first generation Hoveyda-Grubbs catalyst, while favoring the production of a PAH, which can be released from the framework under acidic conditions in dimethylsulfoxide.

  2. 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.

  3. 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.

  4. 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.

  5. Ultrasonic Newton's rings

    SciTech Connect

    Hsu, D.K. ); Dayal, V. )

    1992-03-09

    Interference fringes due to bondline thickness variation were observed in ultrasonic scans of the reflected echo amplitude from the bondline of adhesively joined aluminum skins. To demonstrate that full-field interference patterns are observable in point-by-point ultrasonic scans, an optical setup for Newton's rings was scanned ultrasonically in a water immersion tank. The ultrasonic scan showed distinct Newton's rings whose radii were in excellent agreement with the prediction.

  6. Polyphenylquinoxalines via Aromatic Nucleophilic Displacement

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M.; Connell, John W.

    1988-01-01

    Polyphenylquinoxalines are produced by an aromatic nucleophilic displacement reaction involving an activated aromatic dihalide with an appropriate quinoxaline monomer. Polyphenylquinoxalines are high temperature thermoplastics used as adhesives, coatings, films and composite matrices. The novelty of this invention is threefold: (1) some of the quinoxaline monomers are new compositions of matter; (2) the phenylquinoxaline polymers which are the end products of the invention are new compositions of matter; and (3) the method of forming the polymers is novel, replacing a more costly prior art process, which is also limited in the kinds of products prepared therefrom.

  7. Bending the Rings

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Saturn's rings appear strangely warped in this view of the rings seen through the upper Saturn atmosphere.

    The atmosphere acts like a lens in refracting (bending) the light reflected from the rings. As the rings pass behind the overexposed limb (edge) of Saturn as seen from Cassini, the ring structure appears to curve downward due to the bending of the light as it passes through the upper atmosphere.

    This image was obtained using a near-infrared filter. The filter samples a wavelength where methane gas does not absorb light, thus making the far-off rings visible through the upper atmosphere.

    By comparing this image to similar ones taken using filters where methane gas does absorb, scientists can estimate the vertical profile of haze and the abundance of methane in Saturn's high atmosphere.

    The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 14, 2005, through a filter sensitive to wavelengths of infrared light centered at 938 nanometers and at a distance of approximately 197,000 kilometers (123,000 miles) from Saturn. The image scale is 820 meters (2,680 feet) per pixel.

  8. Influence of thermal vibrations on aromaticity of benzene.

    PubMed

    Cysewski, Piotr

    2011-07-28

    The values of twenty-eight aromaticity indices were estimated for distorted benzene geometries coming from normal modes of thermal vibrations at room temperature. The applied Principal Component Analysis (PCA) revealed that four orthogonal principal components are sufficient for the description of 80% of the population variance. The importance of different aromaticity criteria was confirmed by values of variable loadings. The first principal component has a quite complex composition. Although the highest contribution to PC1 comes from ATI the roles of magnetic susceptibility, REC, EN and A(j) are also non-negligible. The second orthogonal set of variables constituting PC2 comprises PDI and to a lesser extent REC. The importance of θ and EN is emphasized by contributions to PC3. The fourth PC is defined mostly by ΔE. This suggests that geometry alterations encountered during thermal vibrations are associated with changes in electron delocalization and chemical shift. Additionally, electron density changes along normal vibration modes affect also the resonance energy of the ring. Although thermal vibrations of benzene at room temperature do not exceed ±25% and most of analyzed parameters fluctuate within ±10%, the very different molecular properties must be taken into account for proper description of consequences of molecular vibrations on π-electron delocalization in a benzene ring.

  9. NMR analysis of cross strand aromatic interactions in an 8 residue hairpin and a 14 residue three stranded β-sheet peptide.

    PubMed

    Sonti, Rajesh; Rai, Rajkishor; Ragothama, Srinivasarao; Balaram, Padmanabhan

    2012-12-13

    Cross strand aromatic interactions between a facing pair of phenylalanine residues in antiparallel β-sheet structures have been probed using two structurally defined model peptides. The octapeptide Boc-LFV(D)P(L)PLFV-OMe (peptide 1) favors the β-hairpin conformation nucleated by the type II' β-turn formed by the (D)Pro-(L)Pro segment, placing Phe2 and Phe7 side chains in proximity. Two centrally positioned (D)Pro-(L)Pro segments facilitate the three stranded β-sheet formation in the 14 residue peptide Boc-LFV(D)P(L)PLFVA(D)P(L)PLFV-OMe (peptide 2) in which the Phe2/Phe7 orientations are similar to that in the octapeptide. The anticipated folded conformations of peptides 1 and 2 are established by the delineation of intramolecularly hydrogen bonded NH groups and by the observation of specific cross strand NOEs. The observation of ring current shifted aromatic protons is a diagnostic of close approach of the Phe2 and Phe7 side chains. Specific assignment of aromatic proton resonances using HSQC and HSQC-TOCSY methods allow an analysis of interproton NOEs between the spatially proximate aromatic rings. This approach facilitates specific assignments in systems containing multiple aromatic rings in spectra at natural abundance. Evidence is presented for a dynamic process which invokes a correlated conformational change about the C(α)-C(β)(χ(1)) bond for the pair of interacting Phe residues. NMR results suggest that aromatic ring orientations observed in crystals are maintained in solution. Anomalous temperature dependence of ring current induced proton chemical shifts suggests that solvophobic effects may facilitate aromatic ring clustering in apolar solvents.

  10. 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

  11. 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...

  12. 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.

  13. Single base substitution causing the fragrant phenotype and development of a type-specific marker in aromatic coconut (Cocos nucifera).

    PubMed

    Vongvanrungruang, A; Mongkolsiriwatana, C; Boonkaew, T; Sawatdichaikul, O; Srikulnath, K; Peyachoknagul, S

    2016-09-19

    The fragrance gene, betaine aldehyde dehydrogenase 2 (Badh2), has been well studied in many plant species. The objectives of this study were to clone Badh2 and compare the sequences between aromatic and non-aromatic coconuts. The complete coding region was cloned from cDNA of both aromatic and non-aromatic coconuts. The nucleotide sequences were highly homologous to Badh2 genes of other plants. Badh2 consisted of a 1512-bp open reading frame encoding 503 amino acids. A single nucleotide difference between aromatic and non-aromatic coconuts resulted in the conversion of alanine (non-aromatic) to proline (aromatic) at position 442, which was the substrate binding site of BADH2. The ring side chain of proline could destabilize the structure leading to a non-functional enzyme. Badh2 genomic DNA was cloned from exon 1 to 4, and from exon 5 to 15 from the two coconut types, except for intron 4 that was very long. The intron sequences of the two coconut groups were highly homologous. No differences in Badh2 expression were found among the tissues of aromatic coconut or between aromatic and non-aromatic coconuts. The amino acid sequences of BADH2 from coconut and other plants were compared and the genetic relationship was analyzed using MEGA 7.0. The phylogenetic tree reconstructed by the Bayesian information criterion consisted of two distinct groups of monocots and dicots. Among the monocots, coconut (Cocos nucifera) and oil palm (Elaeis guineensis) were the most closely related species. A marker for coconut differentiation was developed from one-base substitution site and could be successfully used.

  14. 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.

  15. Binuclear Phthalocyanines with Aromatic Bridges

    DTIC Science & Technology

    1989-03-01

    successful. (Scheme 2) Synthesis of Binuclear Phthalocyanines Covalently Bridged by Anthracene The coupling reaction of aromatic halides using elemental...available (16), it Is not active enough to undergo the desired cross coupling reaction . Less electropositive arylzinc derivatives can tolerate various electro...philic functional groups such as nitriles and esters (17). These organo- metallic reagents readily undergo cross coupling reaction with aryl halides

  16. Risk factors and management for pyloric stenosis occurred after endoscopic submucosal dissection adjacent to pylorus

    PubMed Central

    Lee, Jae Un; Park, Moon Sik; Yun, So Hee; Yang, Min A.; Han, Shang Hoon; Lee, Young Jae; Jung, Gum Mo; Kim, Ji Woong; Cho, Yong Keun; Cho, Jin Woong

    2016-01-01

    Abstract Endoscopic submucosal dissection (ESD) has been widely accepted as a curative treatment for gastric neoplasm. Pyloric stenosis is a chronic complication that can be caused by ESD. The aim of this study is to clarify the risk factors and management for pyloric stenosis. From January 2004 to January 2014, a total of 126 patients who underwent ESD adjacent to pylorus were reviewed retrospectively. Pyloric mucosal defect was defined as when any resection margin of ESD was involved in the pyloric ring. Pyloric stenosis was defined as when a conventional endoscope could not be passed to the duodenum. Among the 126 patients, pyloric stenosis was identified in 9. In a univariate analysis, pyloric stenosis was more common in older patients (P < 0.05) and in lesions with resections over 75% of the pyloric ring circumference (P < 0.001). In a multivariate analysis, the factor that was associated with pyloric stenosis was the extent of the pyloric ring dissection (P < 0.001). Four of the 9 patients with pyloric stenosis had mild dyspepsia, and the others had gastric outlet obstruction symptoms. The 5 symptomatic patients underwent endoscopic balloon dilation (EBD), and the frequency of EBD was 1 to 8 times. The asymptomatic patients were treated conservatively. The incidence of pyloric stenosis was higher in lesions with resections over 75% of the pyloric ring circumference. Although EBD was an effective treatment for pyloric stenosis, conservative management was also helpful in patients who had mild symptoms. PMID:27977608

  17. 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....

  18. 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....

  19. 49 CFR 236.404 - Signals at adjacent control points.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ..., INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Traffic Control Systems Standards § 236.404 Signals at adjacent control points. Signals at adjacent controlled... 49 Transportation 4 2011-10-01 2011-10-01 false Signals at adjacent control points....

  20. 49 CFR 236.404 - Signals at adjacent control points.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ..., INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Traffic Control Systems Standards § 236.404 Signals at adjacent control points. Signals at adjacent controlled... 49 Transportation 4 2010-10-01 2010-10-01 false Signals at adjacent control points....

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. The Aromaticity of Pericyclic Reaction Transition States

    ERIC Educational Resources Information Center

    Rzepa, Henry S.

    2007-01-01

    An approach is presented that starts from two fundamental concepts in organic chemistry, chirality and aromaticity, and combines them into a simple rule for stating selection rules for pericyclic reactions in terms of achiral Huckel-aromatic and chiral Mobius-aromatic transition states. This is illustrated using an example that leads to apparent…

  7. 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.

  8. Ring correlations in random networks

    NASA Astrophysics Data System (ADS)

    Sadjadi, Mahdi; Thorpe, M. F.

    2016-12-01

    We examine the correlations between rings in random network glasses in two dimensions as a function of their separation. Initially, we use the topological separation (measured by the number of intervening rings), but this leads to pseudo-long-range correlations due to a lack of topological charge neutrality in the shells surrounding a central ring. This effect is associated with the noncircular nature of the shells. It is, therefore, necessary to use the geometrical distance between ring centers. Hence we find a generalization of the Aboav-Weaire law out to larger distances, with the correlations between rings decaying away when two rings are more than about three rings apart.

  9. 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.

  10. Ring-Opening 1,3-Halochalcogenation of Cyclopropane Dicarboxylates

    PubMed Central

    2016-01-01

    Donor–acceptor cyclopropanes with two geminal carboxylic esters are reacted with chalcogenyl chlorides and bromides to afford ring-opened products bearing the halogen atoms in the 1-position, adjacent to the donor, and the chalcogenyl residue in the 3-position next to the two acceptor groups. A variety of different donors (e.g., aryl, N, and O) are used. The stereospecificity of the reaction is demonstrated by using a chiral starting material. PMID:27966993

  11. Propellers in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Sremcevic, M.; Stewart, G. R.; Albers, N.; Esposito, L. W.

    2013-12-01

    Theoretical studies and simulations have demonstrated the effects caused by objects embedded in planetary rings. 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 (~<500m in size) have been indirectly identified in Saturn's A ring through their propeller signature in the images. Furthermore, recent Cassini observations indicate the possible existence of objects embedded even in Saturn's B and C ring. In this paper we present evidence for the existence of propellers in Saturn's B ring by combining data from Cassini Ultraviolet Imaging Spectrograph (UVIS) and Imaging Science Subsystem (ISS) experiments. We show evidence that B ring seems to harbor two distinct populations of propellers: "big" propellers covering tens of degrees in azimuth situated in the densest part of B ring, and "small" propellers in less dense inner B ring that are similar in size and shape to known A ring propellers. The population of "big" propellers is exemplified with a single object which is observed for 5 years of Cassini data. The object is seen as a very elongated bright stripe (40 degrees wide) in unlit Cassini images, and dark stripe in lit geometries. In total we report observing the feature in images at 18 different epochs between 2005 and 2010. In UVIS occultations we observe this feature as an optical depth depletion in 14 out of 93 occultation cuts at corrotating longitudes compatible with imaging data. Combining the available Cassini data we infer that the object is a partial gap located at r=112,921km embedded in the high optical depth region of the B

  12. 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.

  13. Functional soil metagenomics: Elucidation of polycyclic aromatic hydrocarbon degradation potential following 12 years of in situ bioremediation.

    PubMed

    Duarte, Márcia; Nielsen, Agnes; Camarinha-Silva, Amélia; Vilchez-Vargas, Ramiro; Bruls, Thomas; Wos-Oxley, Melissa L; Jauregui, Ruy; Pieper, Dietmar H

    2017-04-12

    A culture-independent function-based screening approach was used to assess the microbial aerobic catabolome for polycyclic aromatic hydrocarbons degradation of a soil subjected to 12 years of in situ bioremediation. A total of 422,750 fosmid clones were screened for key aromatic ring-cleavage activities using 2,3-dihydroxybiphenyl as substrate. Most of the genes encoding ring-cleavage enzymes on the 768 retrieved positive fosmids could not be identified using primer-based approaches and, thus, 205 fosmid inserts were sequenced. Nearly two hundred extradiol dioxygenase encoding genes of three different superfamilies could be identified. Additional key genes of aromatic metabolic pathways were identified, including a high abundance of Rieske non-heme iron oxygenases that provided detailed information on enzymes activating aromatic compounds and enzymes involved in activation of the side chain of methylsubstituted aromatics. The gained insights indicated a complex microbial network acting at the site under study, which comprises organisms similar to recently identified Immundisolibacter cernigliae TR3.2 and Rugosibacter aromaticivorans Ca6 and underlined the great potential of an approach that combines an activity-screening, a cost-effective high-throughput sequencing of fosmid clones and a phylogenomic-routed and manually curated database to carefully identify key proteins dedicated to aerobic degradation of aromatic compounds. This article is protected by copyright. All rights reserved.

  14. 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.

  15. 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.

  16. 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)

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. [Analysis of group components in oils and aromatics in fuel oils].

    PubMed

    Guan, Yafeng; Zhao, Jinghong; Liu, Wenmin; Wang, Hanwen

    2004-09-01

    On-line coupling of capillary liquid chromatography-capillary gas chromatography (CGC) technique for detailed group component analysis of aviation kerosene, diesel fuels, lubricating oils, extraction oils, and residuum, is described. Aromatics in fuel oils were separated according to their ring number and structures. Different eluents were stored in loops on interface, and introduced sequentially onto the CGC for detailed separation and quantitative anal- pre-column and the components of interest (aromatics plus heavier compounds) eluting from an analytical column were all directed to the same flame ionization detector, which performed quantitative analysis of aromatic hydrocarbons in oils by correction factor normalization method. Real oil samples were analyzed and the results showed that the reproducibility, accuracy and reliability of the method can fulfill the requirements of practical application.

  3. 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)

  4. 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.

  5. 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.

  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. Synthesis, electronic properties and WOLED devices of planar phosphorus-containing polycyclic aromatic hydrocarbons.

    PubMed

    Riobé, François; Szűcs, Rózsa; Bouit, Pierre-Antoine; Tondelier, Denis; Geffroy, Bernard; Aparicio, Fátima; Buendía, Julia; Sánchez, Luis; Réau, Régis; Nyulászi, László; Hissler, Muriel

    2015-04-20

    We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P-containing PAHs exhibit properties expected for an emitter in white organic light-emitting diodes (WOLEDs).

  8. Transition-Metal Planar Boron Clusters: a New Class of Aromatic Compounds with High Coordination

    NASA Astrophysics Data System (ADS)

    Wang, Lai-Sheng

    2012-06-01

    Photoelectron spectroscopy in combination with computational studies over the past decade has shown that boron clusters possess planar or quasi-planar structures, in contrast to that of bulk boron, which is dominated by three-dimensional cage-like building blocks. All planar or quasi-planar boron clusters are observed to consist of a monocyclic circumference with one or more interior atoms. The propensity for planarity has been found to be due to both σ and π electron delocalization throughout the molecular plane, giving rise to concepts of σ and π double aromaticity. We have found further that the central boron atoms can be substituted by transition metal atoms to form a new class of aromatic compounds, which consist of a central metal atom and a monocyclic boron ring (M B_n). Eight-, nine-, and ten-membered rings of boron have been observed, giving rise to octa-, ennea-, and deca-coordinated aromatic transition metal compounds [1-3]. References: [1] ``Aromatic Metal-Centered Monocyclic Boron Rings: Co B_9^- and Ru B_9^-" (Constantin Romanescu, Timur R. Galeev, Wei-Li Li, A. I. Boldyrev, and L. S. Wang), Angew. Chem. Int. Ed. {50}, 9334-9337 (2011). [2] ``Transition-Metal-Centered Nine-Membered Boron Rings: M B_9 and M B_9^- (M = Rh, Ir)" (Wei-Li Li, Constantin Romanescu, Timur R. Galeev, Zachary Piazza, A. I. Boldyrev, and L. S. Wang), J. Am. Chem. Soc. {134}, 165-168 (2012). [3] ``Observation of the Highest Coordination Number in Planar Species: Decacoordinated Ta B10^- and Nb B_9^- Anions" (Timur R. Galeev, Constantin Romanescu, Wei-Li Li, L. S. Wang, and A. I. Boldyrev), Angew. Chem. Int. Ed. {51}, 2101-2105 (2012).

  9. Gadolinium-Catalyzed Regio-, and Enantioselective Aminolysis of Aromatic trans-2,3-Epoxy Sulfonamides

    PubMed Central

    Wang, Chuan

    2015-01-01

    The first enantioselective aminolysis of aromatic trans-2,3-epoxy sulfonamides has been accomplished, which was efficiently catalyzed by a Gd-N,N′-dioxide complex. Under the directing effect of the sulfonamide-moiety the ring-opening reaction proceeded selectively at the C-3 position in highly enantioselective manner furnishing various Ts- and SES-protected 3-amino-3-phenylpropan-2-olamines as products. PMID:26058560

  10. Gadolinium-Catalyzed Regio- and Enantioselective Aminolysis of Aromatic trans-2,3-Epoxy Sulfonamides.

    PubMed

    Wang, Chuan; Yamamoto, Hisashi

    2015-07-20

    The first enantioselective aminolysis of aromatic trans-2,3-epoxy sulfonamides has been accomplished, which was efficiently catalyzed by a Gd-N,N'-dioxide complex. Under the directing effect of the sulfonamide moiety the ring-opening reaction proceeded selectively at the C-3 position in a highly enantioselective manner furnishing various Ts- and SES-protected 3-amino-3-phenylpropan-2-olamines as products.

  11. Ultrasound assisted Bradsher reaction in aqueous and non-aqueous media: First use of ultrasounds in electrophilic aromatic cyclisation leading to polyacenes.

    PubMed

    Kowalska, Emilia; Bałczewski, Piotr

    2017-01-01

    The present work describes the first use of ultrasounds in the Bradsher cyclisation of activated and non-activated ortho-formyl diarylmethanes. This reaction is also the first example of electrophilic, aromatic cyclisation assisted by ultrasounds which leads to pure polycyclic, fused aromatic hydrocarbons containing 3 and 4 fused rings in excellent yields. The reaction proceeds not only in aqueous but also in non-aqueous media at milder conditions (room temperature) and in much shorter reaction times than in conventional protocols.

  12. Self-assembled electrical materials from contorted aromatics

    NASA Astrophysics Data System (ADS)

    Xiao, Shengxiong

    This thesis describes the design, synthesis, self-assembly and electrical properties of new types of contorted polycyclic aromatic hydrocarbons. These topologically interesting contorted aromatics show promising transistor characteristics as new building blocks for organic field-effect transistors (OFETs) at different length scales. In chapter 2, a class of pentacenes that are substituted along their long edges with aromatic rings were synthesized. Their solid-state assemblies were studied by X-ray crystallography. Their performance as thin film transistors (TFTs) and single crystal field effect transistors (SCFETs) were systematically evaluated. A structure-property relationship between these highly phenylated pentacenes was found. Chapter 3 explores the new concept of whether a non-planar aromatic core could yield efficacious electronic materials, as the ultimate success in the organic electronics will require a holistic approach to creating new building blocks. Synthesis, functionalization and assembly of a new type of contorted hexabenzocoronene (HBC) whose aromatic core is heavily distorted away from planarity due to the steric congestion around its proximal carbons were discussed. Structural studies by X-ray crystallography showed that these HBC molecules stack into columnar structures in the solid state, which are ideal for conduction. Chapter 4 describes that microscale liquid crystalline thin film OFETs of tetradodecyloxy HBC showed the best transistor properties of all discotic columnar materials. Chapter 5 details the fabrication and characterization of nanoscale single crystalline fiber OFETs of octadodecyloxyl HBC. In Chapter 6 we show that a molecular scale monolayer of HBC acid chlorides could be self-assembled on SiO2 insulating layer and could be organized laterally between the ends of 2 nm carbon nanotube gaps to form high quality FETs that act as environmental and chemical sensors. Chapter 7 details the enforced one-dimensional photoconductivity

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Closed-orbit correction of the NSLS VUV ring

    SciTech Connect

    Bozoki, E.; Bittner, J.; Blumberg, L.; Dickinson, T.; Galayda, J.

    1983-01-01

    We describe the results obtained from the orbit correction system in the NSLS VUV storage ring which consists of 24 PUE stations and 16 horizontal and vertical correction dipoles. The data were obtained by the PUEREAL module of the RING control program which provides automatic switching of the signal from individual electrodes of the PUE stations and provides a readout at harmonic of the rf frequency. The closed orbit is then calculated and corrected by measured displacements of the PUE's from the adjacent quadrupoles. The ORBIT module of the RING program was used to minimize the RMS orbit deviations choosing the most effective correctors and calculating their strengths. For the horizontal case, the correction was accomplished using 3 correctors in two iterations starting with RMS values X = 2.9 mm to X = 0.9 mm. Vertically three iterations and 6 correctors were required to correct the RMS value from Z = 6.8 nm to Z = 0.8 mm.

  20. Ring Flame Stabilizer

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Ring Flame Stabilizer has been developed in conjunction with Lewis Research Center. This device can lower pollutant emissions (which contribute to smog and air pollution) from natural-gas appliances such as furnaces and water heaters by 90 percent while improving energy efficiency by 2 percent.

  1. 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).

  2. 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.

  3. 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.

  4. 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…

  5. 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…

  6. Hybrid Ionosilica containing aromatic groups

    NASA Astrophysics Data System (ADS)

    Thach, U. D.; Prelot, B.; Hesemann, P.

    2015-07-01

    Ionosilicas are defined as mesostructured silica based materials bearing covalently bound ionic groups. These materials, situated at the interface of ionic liquids and structured silica mesophases, are usually synthesized following template directed hydrolysis-polycondensation procedures starting from silylated ionic compounds. Here, we report new ammonium type hybrid ionosilicas containing aromatic groups which can serve as a new platform for the design of functional materials, for applications in the areas of ion exchange reactions, drug delivery or wastewater treatment.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. Characterization of aromaticity in analogues of titan's atmospheric aerosols with two-step laser desorption ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Mahjoub, Ahmed; Schwell, Martin; Carrasco, Nathalie; Benilan, Yves; Cernogora, Guy; Szopa, Cyril; Gazeau, Marie-Claire

    2016-10-01

    The role of polycyclic aromatic hydrocarbons (PAH) and Nitrogen containing PAH (PANH) as intermediates of aerosol production in the atmosphere of Titan has been a subject of controversy for a long time. An analysis of the atmospheric emission band observed by the Visible and Infrared Mapping Spectrometer (VIMS) at 3.28 μm suggests the presence of neutral polycyclic aromatic species in the upper atmosphere of Titan. These molecules are seen as the counter part of negative and positive aromatics ions suspected by the Plasma Spectrometer onboard the Cassini spacecraft, but the low resolution of the instrument hinders any molecular speciation. In this work we investigate the specific aromatic content of Titan's atmospheric aerosols through laboratory simulations. We report here the selective detection of aromatic compounds in tholins, Titan's aerosol analogs, produced with a capacitively coupled plasma in a N2:CH4 95:5 gas mixture. For this purpose, Two-Step Laser Desorption Ionization Time-of-Flight Mass Spectrometry (L2DI-TOF-MS) technique is used to analyze the so produced analogs. This analytical technique is based on the ionization of molecules by Resonance Enhanced Multi-Photon Ionization (REMPI) using a λ=248 nm wavelength laser which is selective for aromatic species. This allows for the selective identification of compounds having at least one aromatic ring. Our experiments show that tholins contain a trace amount of small PAHs with one to three aromatic rings. Nitrogen containing PAHs (PANHs) are also detected as constituents of tholins. Molecules relevant to astrobiology are detected as is the case of the substituted DNA base adenine.

  12. Aromatic interactions as control elements in stereoselective organic reactions.

    PubMed

    Krenske, Elizabeth H; Houk, K N

    2013-04-16

    This Account describes how attractive interactions of aromatic rings with other groups can influence and control the stereoselectivity of many reactions. Recent developments in theory have improved the 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, including asymmetric dihydroxylations, transfer hydrogenations, hetero-Diels-Alder reactions, acyl transfers, and Claisen rearrangements. Our recent studies have also 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 oxyallyl intermediates that contain a chiral oxazolidinone auxiliary. Originally, it was thought that these cycloadditions relied on differential steric crowding of the two faces of a planar intermediate. Computations reveal a different picture and show that cycloaddition with furan takes place preferentially through the more crowded transition state: the furan adds on the same side as the Ph substituent of the oxazolidinone. The crowded transition state is stabilized by a CH-π interaction between furan and Ph worth approximately 2 kcal/mol. Attractive interactions with aromatic rings also control the stereoselectivity in a second class of (4+3) cycloadditions involving chiral alkoxy siloxyallyl cations. Alkoxy groups derived from chiral α-methylbenzyl alcohols favor crowded transition states, where a stabilizing CH-π interaction is present between the furan and the Ar group. The cationic cycloadditions are stepwise, while the Hsung cycloadditions

  13. 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

  14. 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.

  15. Protection by uridine diphosphoglucuronic acid and DT-diaphorase against the cytotoxicity of polycyclic aromatic hydrocarbons isolated from a complex coal gasification condensate.

    PubMed

    Swanson, M S; Haugen, D A; Reilly, C A; Stamoudis, V C

    1986-06-30

    The cytotoxicities of polycyclic aromatic hydrocarbon (PAH) subclasses isolated from a complex organic mixture (coal gasification condensate) were studied in vitro in Chinese hamster ovary cells, in the presence of rat liver microsomes from animals pretreated with Aroclor. Toxicity was enhanced by microsomal metabolism and was inversely related to aromatic ring number. Rat liver cytosol, semipurified DT-diaphorase, and uridine diphosphoglucuronic acid decreased the cytotoxicity of a variety of PAH mixtures and representative PAH, as well as individual PAH metabolites. The results indicate that the in vitro toxicity of complex PAH mixtures is caused primarily by hydroxy-PAH and quinone metabolites of the predominant, nonmutagenic two- and three-ring PAHs.

  16. 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.

  17. Polycyclic aromatic hydrocarbon emissions from motorcycles

    NASA Astrophysics Data System (ADS)

    Yang, Hsi-Hsien; Hsieh, Lien-Te; Liu, Hsu-Chung; Mi, Hsiao-Hsuan

    Emissions of polycyclic aromatic hydrocarbons (PAHs, 2-7 ring) and regulated air pollutants (CO, HC, NO x, PM) from 2-stroke carburetor (2-Stk/Cb), 4-stroke carburetor (4-Stk/Cb) and 4-stroke fuel injection (4-Stk/FI) motorcycles were investigated by testing these vehicles on a chassis dynamometer. Exhaust samplings were carried out on diluted exhausts in a dilution tunnel connected to a constant volume sampling system. Measurements were performed on a standard driving cycle. The results reveal that low molecular weight PAHs (especially naphthalene) dominated in the exhaust gas. The averages of soluble organic fractions were 86.4%, 46.3% and 48.9% for the 2-Stk/Cb, 4-Stk/Cb and 4-Stk/FI motorcycles, respectively. PAH emissions are greater from cold-start driving than those from hot-start driving cycle for all these three kinds of motorcycles. Total PAH emission factors were 8320, 5990 and 3390 μg km -1 for the in-used 2-Stk/Cb, 4-Stk/Cb and 4-Stk/FI motorcycles, respectively. PAH emission factors were the largest for the 2-Stk/Cb motorcycles. Besides, the 2-Stk/Cb motorcycle had the largest total BaP equivalent emission factor of 10.8 μg km -1, indicating that the emission exhaust from the 2-Stk/Cb motorcycle was most carcinogenic. HC, PM and PAH emissions were the lowest for the 4-Stk/FI motorcycles. The correlation coefficient between CO and total PAH emissions for all the test motorcycles was 0.51, indicating that CO and PAH emissions are not highly correlated.

  18. 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.

  19. 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.

  20. 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%.

  1. RINGED ACCRETION DISKS: EQUILIBRIUM CONFIGURATIONS

    SciTech Connect

    Pugliese, D.; Stuchlík, Z. E-mail: zdenek.stuchlik@physics.cz

    2015-12-15

    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.

  2. Ring closure in actin polymers

    NASA Astrophysics Data System (ADS)

    Sinha, Supurna; Chattopadhyay, Sebanti

    2017-03-01

    We present an analysis for the ring closure probability of semiflexible polymers within the pure bend Worm Like Chain (WLC) model. The ring closure probability predicted from our analysis can be tested against fluorescent actin cyclization experiments. We also discuss the effect of ring closure on bend angle fluctuations in actin polymers.

  3. 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…

  4. Uranus: the rings are black.

    PubMed

    Sinton, W M

    1977-11-04

    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.

  5. 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.

  6. 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.

  7. 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

  8. Strained Ring Energetic Binders

    DTIC Science & Technology

    1993-08-27

    polyhomobenzvalene ( PHBV ). PHBV was not found to have the mechanical instability problems of PBV, but was still thermally unstable (Tonset - 660C, Tmax - 1090C...DISCUSSION 4 Polybenzvalene (PBV) 4 Polyhomobenzvalene ( PHBV ) 6 Chain-Transfer Studies 11 CONCLUSIONS 15 EXPERIMENTAL PROCEDURES 16 .F 4E 19 APPENDICES A...strained ring polymers similar to PBV are known. The investigation of one of these polymers, polyhomobenzvalene ( PHBV ), is also described in this report

  9. Which Ringed Planet...!?

    NASA Astrophysics Data System (ADS)

    2002-12-01

    Don't worry - you are not the only one who thought this was a nice amateur photo of planet Saturn, Lord of the Rings in our Solar System! But then the relative brightness and positions of the moons may appear somewhat unfamiliar... and the ring system does look unusually bright when compared to the planetary disk...?? Well, it is not Saturn, but Uranus , the next giant planet further out, located at a distance of about 3,000 million km, or 20 times the distance between the Sun and the Earth. The photo shows Uranus surrounded by its rings and some of the moons, as they appear on a near-infrared image that was obtained in the K s -band (at wavelength 2.2 µm) with the ISAAC multi-mode instrument on the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory (Chile) . The exposure was made on November 19, 2002 (03:00 hrs UT) during a planetary research programme. The observing conditions were excellent (seeing 0.5 arcsec) and the exposure lasted 5 min. The angular diameter of Uranus is about 3.5 arcsec. The observers at ISAAC were Emmanuel Lellouch and Thérése Encrenaz of the Observatoire de Paris (France) and Jean-Gabriel Cuby and Andreas Jaunsen (both ESO-Chile). The rings The rings of Uranus were discovered in 1977, from observations during a stellar occultation event by astronomer teams at the Kuiper Airborne Observatory (KAO) and the Perth Observatory (Australia). Just before and after the planet moved in front of the (occulted) star, the surrounding rings caused the starlight to dim for short intervals of time. Photos obtained from the Voyager-2 spacecraft in 1986 showed a multitude of very tenuous rings. These rings are almost undetectable from the Earth in visible light. However, on the present VLT near-infrared picture, the contrast between the rings and the planet is strongly enhanced. At the particular wavelength at which this observation was made, the infalling sunlight is almost completely absorbed by gaseous methane present in the planetary atmosphere

  10. Precooler Ring Vacuum System

    SciTech Connect

    Moenich, J.

    1980-10-02

    The precooler vacuum system, as proposed by FNAL, is based on a suitable modification of the existing Electron Cooling Ring System. Because of the magnetic cycle of the bending magnets, distributed ion pumping, as exists in the Electron Cooling Ring, is not applicable. Instead, the proposed pumping will be done with commercial appendage ion pumps mounted approximately every two meters around the circumference of the ring. The loss of effective pumping speed and non-uniformity of system pressure with appendage pumps may not be major considerations but the large number required does effect experimental and analytical equipment placement considerations. There is a distributed pumping technique available which: (1) is not affected by the magnetic cycle of the bending magnets; (2) will provide a minimum of four times the hydrogen pumping speed of the proposed appendage ion pumps; (3) will require no power during pumping after the strip is activated; (4) will provide the heat source for bakeout; (5) is easily replaceable; and (6) can be purchased, installed, and operated at a generous economic advantage over the presently proposed ion pumped system. The pumping technique referred to is non-evaporable gettering with ST101 Zr/Al pumping strip. A technical description of this pumping strip is given on Data Sheet 1 and 2 attached to this report.

  11. Saturn's ``Gossamer'' Ring: The F Ring's Inner Sheet

    NASA Astrophysics Data System (ADS)

    Showalter, M. R.; Burns, J. A.; Hamilton, D. P.

    1998-09-01

    Recent Galileo and Earth-based images have revealed for the first time that Jupiter's ``gossamer'' ring is actually composed of two rings, one bounded at the outer edge by Amalthea and the other bounded by Thebe. Dynamical models suggest that these rings are composed of dust grains ejected off the surfaces of the two moons, which then evolve inward under Poynting-Robertson drag. A very faint sheet of material filling the region between Saturn's A and F Rings reported by Burns et al. (BAAS 15, 1013--1014, 1983) may be a dynamically analogous system, in which dust escapes from the F Ring and evolves inward to the A Ring. Unlike Jupiter's gossamer rings, however, the inner sheet of Saturn's F Ring has been well observed from a large range of phase angles and visual wavelengths by Voyager. Voyager images reveal that this faint ring shows a tenfold increase in brightness between phase angles of 125(deg) and 165(deg) , indicating that it is composed of fine dust microns in size. Preliminary estimates of the normal optical depth fall in the range 1--2*E(-4) , depending on the dust size distribution assumed. Initial spectrophotometry reveals that the ring is neutral in color. The ring is uniform in brightness over the entire region between the two rings, with no evidence for internal structure associated with Prometheus and Atlas, suggesting that neither of these embedded moons acts as either a source or a sink. We will refine the aforementioned measurements and develop photometric models to better constrain the properties of the dust in this ring. This will enable us to relate the dust population to that in the F Ring proper, and to better explore the dynamical processes at work.

  12. 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

  13. Transmission performance of one waveguide and double micro-ring resonator using 3×3 optical fiber coupler

    NASA Astrophysics Data System (ADS)

    Zhao, Chao Ying; Tan, Wei Han

    2016-09-01

    This paper investigates theoretically the transmission characteristics of one waveguide and double micro-ring resonator using 3 × 3 optical fibre coupler. Our analytical solution of transmittance is suitable for either linearly distributed coupler or circularly symmetric distributed coupler. The all-optical analogue to electromagnetic inducted transparency spectrum of one waveguide and double micro-ring resonators can be controlled by changing the coupling strength between waveguide and micro-rings, the absorption coefficient around micro-rings, as well as the asymmetric coupling coefficients between non-adjacent waveguides. The curves show that the transitions of transmission spectra sensitively depend on asymmetric coupling coefficients.

  14. Biodegradation for polynuclear aromatic hydrocarbons in the environment

    SciTech Connect

    Prince, R.C.; Brake, E.N.; Rothenburger, S.J.

    1996-10-01

    Bioremediation promises to be a cost-effective remediation option for hydrocarbon contaminated soils and sediments, but much remains to be determined about the molecular fate of specific molecules in spilled oil and refined products. We have examined the biodegradation of polynuclear aromatic hydrocarbons with two to five rings, in aqueous flask systems, and in soils where the hydrocarbons have been present for many years. We have used consortia of indigenous organisms, and have attempted to use optimal nutrient strategies to stimulate microbial growth. We find that all the alkylated forms of naphthalene with 0-4 methyl groups, and of phenanthrene and dibenzothiophene with 0-3 methyl groups are biodegradable, and that parent compounds such as naphthalene, phenanthrene, anthracene, dibenzothiophene, benz[a]anthracene, pyrene, chrysene and benz[a]anthracene are all degradable under conditions that mimic field application of nutrient-assisted bioremediation.

  15. 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.

  16. 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.

  17. Helmet latching and attaching ring

    NASA Technical Reports Server (NTRS)

    Chase, E. W.; Viikinsalo, S. J. (Inventor)

    1970-01-01

    A neck ring releasably secured to a pressurized garment carries an open-ended ring normally in the engagement position fitted into an annular groove and adapted to fit into a complementary annular groove formed in a helmet. Camming means formed on the inner surface at the end of the helmet engages the open-ended ring to retract the same and allow for one motion donning even when the garment is pressurized. A projection on the end of the split ring is engageable to physically retract the split ring.

  18. 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.

  19. Mass of Saturn's A ring

    NASA Technical Reports Server (NTRS)

    Horn, L. J.; Russell, C. T.

    1993-01-01

    The mass of Saturn's A ring is reestimated using the behavior of spiral density waves embedded in the ring. The Voyager photopolarimeter (PPS) observed the star delta-Scorpii as it was occulted by Saturn's rings during the Voyager 2 flyby of Saturn in 1981 producing a radial profile of the rings. We examined forty spiral density waves in the Voyager PPS data of the A ring including 10 weaker waves that have not been previously analyzed by means of an autoregressive power spectral technique called Burg. The strengths of this new method for ring studies are that weaker, less extended waves are easily detected and characterized. This method is also the first one which does not require precise knowledge of the resonance location and phase of the wave in order to calculate the surface mass density. Uncertainties of up to 3 km are present in the currently available radial scales for Saturn's rings.

  20. A season in Saturn's rings: Cycling, recycling and ring history

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.; Meinke, B. K.; Albers, N.; Sremcevic, M.

    2012-04-01

    Cassini experiments have watched Saturn's ring system evolve before our eyes. Images and occultations show changes and transient events. The rings are a dynamic and complex geophysical system, incompletely modeled as a single-phase fluid. Key Cassini observations: High resolution images show straw, propellers, embedded moonlets, and F ring objects. Multiple UVIS, RSS and VIMS occutlations indicate multimodal ringlet and edge structure, including free and forced modes along with stochastic perturbations that are most likely caused by nearby mass concentrations. Vertical excursions are evident at ring edges and in other perturbed regions. The rings are occasionally hit by meteorites that leave a signature that may last centuries; meteoritic dust pollutes the rings. Temperature, reflectance and transmission spectra are influenced by the dynamical state of the ring particles. Saturn's Equinox 2009: Oblique lighting exposed vertical structure and embedded objects. The rings were the coldest ever. Images inspired new occultation and spectral analysis that show abundant structure in the perturbed regions. The rings are more variable and complex than we had expected prior to this seasonal viewing geometry. Sub-kilometer structure in power spectral analysis: Wavelet analysis shows features in the strongest density waves and at the shepherded outer edge of the B ring. Edges are variable as shown by multiple occultations and occultations of double stars. F ring kittens: 25 features seen in the first 102 occultations show a weak correlation with Prometheus location. We interpret these features as temporary aggregations. Simulation results indicate that accretion must be enhanced to match the kittens' size distribution. Images show that Prometheus triggers the formation of transient objects. Propellers and ghosts: Occulations and images provide evidence for small moonlets in the A, B and C rings. These indicate accretion occurs inside the classical Roche limit. Implications

  1. 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

  2. Comparison of polycyclic aromatic hydrocarbon pollution in Chinese and Japanese residential air.

    PubMed

    Lu, Hao; Amagai, Takashi; Ohura, Takeshi

    2011-01-01

    Comparative studies on polycyclic aromatic hydrocarbon (PAH) pollution in residential air of Hangzhou (China) and Shizuoka (Japan) were conducted in summer (August, 2006) and winter (January, 2007). Total concentrations of 8 PAHs ranged from 7.1 to 320 ng/m3 and 0.15 to 35 ng/m3 in residential air of Hangzhou and Shizuoka, respectively. Air PAH concentrations in smoking houses were higher than that in nonsmoking houses. In nonsmoking houses, mothball emission and cooking practice were the emission sources of 2- and 3-ring PAHs in Hangzhou, respectively. The 2- and 3-ring PAHs were from use of insect repellent, kerosene heating and outdoor environment in nonsmoking houses in Shizuoka. The 5- and 6-ring PAHs in residential air were mainly from outdoor environment in both cities. Toxicity potencies of PAHs in residential air of Hangzhou were much higher than that in Shizuoka.

  3. 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…

  4. 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

  5. A Study of the Pronunciation of Words Containing Adjacent Vowels.

    ERIC Educational Resources Information Center

    Greif, Ivo P.

    To determine the usefulness of the commonly taught phonics rule, "only pronounce the first vowel in words that contain adjacent vowels" (the VV rule, with the first "v" pronounced with the long vowel sound), two new studies applied it to words with adjacent vowels in several lists and dictionaries. The first study analyzed words containing…

  6. 47 CFR 90.221 - Adjacent channel power limits.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Adjacent channel power limits. 90.221 Section 90.221 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES General Technical Standards § 90.221 Adjacent channel...

  7. 47 CFR 90.221 - Adjacent channel power limits.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Adjacent channel power limits. 90.221 Section 90.221 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES General Technical Standards § 90.221 Adjacent channel...

  8. 30 CFR 57.14109 - Unguarded conveyors with adjacent travelways.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Unguarded conveyors with adjacent travelways... conveyors with adjacent travelways. Unguarded conveyors next to travelways shall be equipped with— (a) Emergency stop devices which are located so that a person falling on or against the conveyor can...

  9. 30 CFR 56.14109 - Unguarded conveyors with adjacent travelways.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Unguarded conveyors with adjacent travelways... MINES Machinery and Equipment Safety Devices and Maintenance Requirements § 56.14109 Unguarded conveyors with adjacent travelways. Unguarded conveyors next to the travelways shall be equipped with—...

  10. 30 CFR 56.14109 - Unguarded conveyors with adjacent travelways.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Unguarded conveyors with adjacent travelways... MINES Machinery and Equipment Safety Devices and Maintenance Requirements § 56.14109 Unguarded conveyors with adjacent travelways. Unguarded conveyors next to the travelways shall be equipped with—...

  11. 30 CFR 57.14109 - Unguarded conveyors with adjacent travelways.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Unguarded conveyors with adjacent travelways... conveyors with adjacent travelways. Unguarded conveyors next to travelways shall be equipped with— (a) Emergency stop devices which are located so that a person falling on or against the conveyor can...

  12. 30 CFR 56.14109 - Unguarded conveyors with adjacent travelways.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Unguarded conveyors with adjacent travelways... MINES Machinery and Equipment Safety Devices and Maintenance Requirements § 56.14109 Unguarded conveyors with adjacent travelways. Unguarded conveyors next to the travelways shall be equipped with—...

  13. 30 CFR 57.14109 - Unguarded conveyors with adjacent travelways.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Unguarded conveyors with adjacent travelways... conveyors with adjacent travelways. Unguarded conveyors next to travelways shall be equipped with— (a) Emergency stop devices which are located so that a person falling on or against the conveyor can...

  14. 30 CFR 56.14109 - Unguarded conveyors with adjacent travelways.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Unguarded conveyors with adjacent travelways... MINES Machinery and Equipment Safety Devices and Maintenance Requirements § 56.14109 Unguarded conveyors with adjacent travelways. Unguarded conveyors next to the travelways shall be equipped with—...

  15. 30 CFR 56.14109 - Unguarded conveyors with adjacent travelways.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Unguarded conveyors with adjacent travelways... MINES Machinery and Equipment Safety Devices and Maintenance Requirements § 56.14109 Unguarded conveyors with adjacent travelways. Unguarded conveyors next to the travelways shall be equipped with—...

  16. 30 CFR 57.14109 - Unguarded conveyors with adjacent travelways.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Unguarded conveyors with adjacent travelways... conveyors with adjacent travelways. Unguarded conveyors next to travelways shall be equipped with— (a) Emergency stop devices which are located so that a person falling on or against the conveyor can...

  17. 30 CFR 57.14109 - Unguarded conveyors with adjacent travelways.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Unguarded conveyors with adjacent travelways... conveyors with adjacent travelways. Unguarded conveyors next to travelways shall be equipped with— (a) Emergency stop devices which are located so that a person falling on or against the conveyor can...

  18. Ring cleavage of sulfur heterocycles: how does it happen?

    PubMed

    Bressler, D C; Norman, J A; Fedorak, P M

    Sulfur heterocycles are common constituents of petroleum and liquids derived from coal, and they are found in some secondary metabolites of microorganisms and plants. They exist primarily as saturated rings and thiophenes. There are two major objectives driving investigations of the microbial metabolism of organosulfur compounds. One is the quest to develop a process for biodesulfurization of fossil fuels, and the other is to understand the fates of organosulfur compounds in petroleum- or creosote-contaminated environments which is important in assessing bioremediation processes. For these processes to be successful, cleavage of different types of sulfur heterocyclic rings is paramount. This paper reviews the evidence for microbial ring cleavage of a variety of organosulfur compounds and discusses the few well-studied cases which have shown that the C-S bond is most susceptible to breakage leading to disruption of the ring. In most cases, the introduction of one or more oxygen atom(s) onto the adjacent C atom and/or onto the S atom weakens the C-S bond, facilitating its cleavage. Although much is known about the thiophene ring cleavage in dibenzothiophene, there is still a great deal to be learned about the cleavage of other sulfur heterocycles.

  19. 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.

  20. 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.

  1. 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.

  2. New Views of Jupiter's Rings

    NASA Astrophysics Data System (ADS)

    Burns, J. A.

    1998-09-01

    Jupiter's rings are the archetype of ethereal planetary rings (very-low optical-depth bands containing micron-sized "dust"). As a result of much improved observations by Galileo (Ockert-Bell* -- most citations are et al. and Icarus in press* or this meeting) and Keck (de Pater*), we now understand the nature of such rings. The ring has three components: a 104 km-thick toroidal halo (1.4-1.7 RJ; normal optical depth t = 10-6), a thin main ring (1.7-1.8 RJ; t = 10-6), and a pair of exterior gossamer rings (1.8-3.5RJ; t = 10-7). The main ring has patchy ( 20-30 percent) brightness. The ring is reddish and its particles satisfy a -2.5 differential power-law size distribution. Because particle lifetimes are brief, the rings must be continually regenerated, by collisions into parent bodies, which may be unseen or may be the known small ring-moons (Thomas*, Simonelli). The gossamer ring seems to be collisional ejecta derived from the ring-moons Amalthea and Thebe, and evolving inward by Poynting-Robertson drag (Burns). The particles drift through many electromagnetic resonances, clustering around synchronous orbit, which produce jumps in the particles' inclinations (Hamilton). The main ring is probably debris from Adrastea and Metis, which orbit in the equatorial plane. The halo particles are driven vertically by electromagnetic forces, which may be resonant (Schaffer & Burns) or not (Horanyi & Cravens). When halo orbits become highly distorted, particles are lost into Jupiter. Similar faint rings may be attendant to all small, close-in satellites (Showalter).

  3. Fate of polycyclic aromatic hydrocarbons during composting of oily sludge.

    PubMed

    Kriipsalu, M; Marques, M; Hogland, W; Nammari, D R

    2008-01-01

    In order to assess the effectiveness of aerobic degradation with emphasis on the 16 U.S. EPA priority polycyclic aromatic hydrocarbons (PAH), oily sludge generated by a dissolved air flotation flocculation unit of a wastewater treatment plant in a petroleum refinery was amended with remediated oil-contaminated soil and non-mature garden waste compost 40:40:20 (wet weight) respectively. About 21 t of the mixture with a top-layer formed by 30 cm of remediated soil was treated in a 28 m3 air-forced reactor. The PAH concentration was monitored for 370 days. In the top-layer, a reduction of 88 % of the total extractable PAH was measured at day 62 and a final reduction of 93% at day 370. In the mixture, a reduction of 72% in total PAH was measured at day 62, followed by fluctuation in concentration with a final measured reduction of 53% at day 370. The analysis of individual PAH in the mixture suggested that volatilization and biodegradation are the main mechanisms responsible for the reduction of 2 ring PAH and 3-4 ring PAH, respectively. Fluctuation of 5-6 ring PAH concentrations with increase observed at the end of the period might result from a combination of the following: (i) sequestration of large PAH in the organic matrix (reducing bioavailability, biodegradability and eventually, extractability) and desorption as composting progresses; (ii) heterogeneous distribution of the stable large PAH in the mixture, thus affecting sampling. It was concluded that one-time composting in static-aerated biopiles with organic amendments as the sole strategy to treat oily sludge is very effective in reducing the content of 2-4 ring PAH, but it is not effective in reducing the content of 5-6 ring PAHs, even after a relatively long time span (370 d). The concentrations measured in the remediated soil that formed the top layer after 62 days of composting suggests that further relevant reduction of residual PAH (89% of total PAH and 69% of 5-6 ring PAH) can be obtained if the

  4. Tree Rings: Timekeepers of the Past.

    ERIC Educational Resources Information Center

    Phipps, R. L.; McGowan, J.

    One of a series of general interest publications on science issues, this booklet describes the uses of tree rings in historical and biological recordkeeping. Separate sections cover the following topics: dating of tree rings, dating with tree rings, tree ring formation, tree ring identification, sample collections, tree ring cross dating, tree…

  5. Wave structure in planetary rings

    NASA Astrophysics Data System (ADS)

    Horn, Linda Joyce

    1992-01-01

    Planetary rings contain a wealth of wavelike structure that is driven by gravitational resonance interactions with nearby satellites. Wave behavior is a powerful tool for estimating physical ring parameters that are key to our understanding of ring origin and evolution. A new technique, utilizing the Burg autoregressive power spectral algorithm, was developed for probing the physical characteristics of rings and for detecting waves that are not otherwise visible. Data from the Voyager photopolarimeter (PPS) stellar occultations by the rings of Saturn, Uranus, and Neptune and the Voyager radio science (RSS) occultation by Saturn's rings were used. Local surface mass density estimates are obtained from the dispersion of 40 spiral density waves in Saturn's A ring, including 10 weaker waves not previously analyzed. Surface mass densities vary from 20 to 60 gm sq cm. Increasing optical depth is not correlated with increasing surface mass density, especially after the Keeler gap, suggesting that ring particle size and composition are not uniform throughout the A ring. Saturn's A ring mass is reestimated using the surface mass densities and is 5.2 +/- 1.3 x 1021 gm. The wakes of Saturn's satellite Pan are not short timescale phenomena because the effects of Pan's gravitational perturbations persist for more than one Pan encounter. Four additional Pan wakes were discovered at longitudes greater than 360 deg. Collective effects such as collisions modify the wake dispersion more extensively at greater longitudes. Pan is the dominant mass in the Encke gap. A spiral density wave was detected inside the Uranian delta ring. Upper and lower bounds were estimated for the surface mass density of the delta ring 5 less than or equal to sigma less than or equal to 10 gm/sq cm, the viscosity 10 less than or equal to nu less than or equal to 40 sq cm/sec, and the local ring height 7 less than or equal to h less than or equal to 20 m. These values are comparable to the corresponding

  6. Spiral and Rotor Patterns Produced by Fairy Ring Fungi

    NASA Astrophysics Data System (ADS)

    Karst, N.; Dralle, D.; Thompson, S. E.

    2015-12-01

    Soil fungi fill many essential ecological and biogeochemical roles, e.g. decomposing litter, redistributing nutrients, and promoting biodiversity. Fairy ring fungi offer a rare glimpse into the otherwise opaque spatiotemporal dynamics of soil fungal growth, because subsurface mycelial patterns can be inferred from observations at the soil's surface. These observations can be made directly when the fungi send up fruiting bodies (e.g., mushrooms and toadstools), or indirectly via the effect the fungi have on neighboring organisms. Grasses in particular often temporarily thrive on the nutrients liberated by the fungus, creating bands of rich, dark green turf at the edge of the fungal mat. To date, only annular (the "ring" in fairy ring) and arc patterns have been described in the literature. We report observations of novel spiral and rotor pattern formation in fairy ring fungi, as seen in publically available high-resolution aerial imagery of 22 sites across the continental United States. To explain these new behaviors, we first demonstrate that a well-known model describing fairy ring formation is equivalent to the Gray-Scott reaction-diffusion model, which is known to support a wide range of dynamical behaviors, including annular traveling waves, rotors, spirals, and stable spatial patterns including spots and stripes. Bifurcation analysis and numerical simulation are then used to define the region of parameter space that supports spiral and rotor formation. We find that this region is adjacent to one within which typical fairy rings develop. Model results suggest simple experimental procedures that could potentially induce traditional ring structures to exhibit rotor or spiral dynamics. Intriguingly, the Gray-Scott model predicts that these same procedures could be used to solicit even richer patterns, including spots and stripes, which have not yet been identified in the field.

  7. Spiral and Rotor Patterns Produced by Fairy Ring Fungi

    NASA Astrophysics Data System (ADS)

    Karst, N.; Dralle, D.; Thompson, S. E.

    2014-12-01

    Soil fungi fill many essential ecological and biogeochemical roles, e.g. decomposing litter, redistributing nutrients, and promoting biodiversity. Fairy ring fungi offer a rare glimpse into the otherwise opaque spatiotemporal dynamics of soil fungal growth, because subsurface mycelial patterns can be inferred from observations at the soil's surface. These observations can be made directly when the fungi send up fruiting bodies (e.g., mushrooms and toadstools), or indirectly via the effect the fungi have on neighboring organisms. Grasses in particular often temporarily thrive on the nutrients liberated by the fungus, creating bands of rich, dark green turf at the edge of the fungal mat. To date, only annular (the "ring" in fairy ring) and arc patterns have been described in the literature. We report observations of novel spiral and rotor pattern formation in fairy ring fungi, as seen in publically available high-resolution aerial imagery of 22 sites across the continental United States. To explain these new behaviors, we first demonstrate that a well-known model describing fairy ring formation is equivalent to the Gray-Scott reaction-diffusion model, which is known to support a wide range of dynamical behaviors, including annular traveling waves, rotors, spirals, and stable spatial patterns including spots and stripes. Bifurcation analysis and numerical simulation are then used to define the region of parameter space that supports spiral and rotor formation. We find that this region is adjacent to one within which typical fairy rings develop. Model results suggest simple experimental procedures that could potentially induce traditional ring structures to exhibit rotor or spiral dynamics. Intriguingly, the Gray-Scott model predicts that these same procedures could be used to solicit even richer patterns, including spots and stripes, which have not yet been identified in the field.

  8. Aromatic Polyimides With Group VI Linkages

    NASA Technical Reports Server (NTRS)

    St. Clair, T. L.; Burks, H. D.; Ely, R. M.

    1983-01-01

    New polymer system combines thermal and solvent resistant properties of aromatic polyimides with processability of PPX polymers. PPX polymers include polyphenylene oxide, polyphenylene sulfide, and polyphenylene sulfone classes. Generally more processable by hot melt or thermoplastic techniques than aromatic polyimides. PPX systems more susceptible to attack by solvents and have lower glass transition temperatures than PI group.

  9. Heterogeneous photocatalytic reactions of sulfur aromatic compounds.

    PubMed

    Samokhvalov, Alexander

    2011-11-18

    Sulfur aromatic compounds, such as mono-, di-, tri-, and tetraalkyl-substituted thiophene, benzothiophenes, dibenzothiophenes, are the molecular components of many fossils (petroleum, oil shale, tar sands, bitumen). Structural units of natural, cross-linked heteroaromatic polymers present in brown coals, turf, and soil are similar to those of sulfur aromatic compounds. Many sulfur aromatic compounds are found in the streams of petroleum refining and upgrading (naphthas, gas oils) and in the consumer products (gasoline, diesel, jet fuels, heating fuels). Besides fossils, the structural fragments of sulfur aromatic compounds are present in molecules of certain organic semiconductors, pesticides, small molecule drugs, and in certain biomolecules present in human body (pheomelanin pigments). Photocatalysis is the frontier area of physical chemistry that studies chemical reactions initiated by absorption of photons by photocatalysts, that is, upon electronic rather than thermal activation, under "green" ambient conditions. This review provides systematization and critical review of the fundamental chemical and physicochemical information on heterogeneous photocatalysis of sulfur aromatic compounds accumulated in the last 20-30 years. Specifically, the following topics are covered: physicochemical properties of sulfur aromatic compounds, major classes of heterogeneous photocatalysts, mechanisms and reactive intermediates of photocatalytic reactions of sulfur aromatic compounds, and the selectivity of these reactions. Quantum chemical calculations of properties and structures of sulfur aromatic compounds, their reactive intermediates, and the structure of adsorption complexes formed on the surface of the photocatalysts are also discussed.

  10. On Organic Material in E Ring Ice Grains

    NASA Astrophysics Data System (ADS)

    Postberg, F.; Khawaja, N.; Reviol, R.; Nölle, L.; Klenner, F.; Hsu, H. W.; Horanyi, M.

    2015-12-01

    Pure water ice dominates the composition of the micron and sub-micron sized dust particles in Saturn's E-ring, a ring constantly replenished by active ice jets of the moon Enceladus [1]. Details about the composition of this tenuous, optically thin ring can only be constrained by in situ measurements. The Cosmic Dust Analyzer (CDA) onboard Cassini investigates the composition of these grains by cationic time-of-flight mass spectra of individual ice grains hitting the instruments target surface. From these spectra three compositional types of E ring ice grains have been identified previously [2,3]: Type-1: Almost pure water, Type-2: Enriched in organics, and Type-3: Enriched in salt. Unlike Type-1 and 3, organic-enriched Type-2 spectra have not yet been investigated in depth. Here we report the first detailed compositional analysis of this type. The spectra analysis is supported by a large-scale laboratory ground campaign yielding a library of analogue spectra for organic material embedded in a water ice matrix. In contrast to Type 1 and 3, Type-2 spectra display a great compositional diversity, which indicates varying contributions of several organic species. So far we have identified characteristic fragment patterns of at least three classes of organic compounds: aromatic species, amines, and carbonyl group species. Work is in progress to quantify concentrations of the identified species and to assign yet un-specified organic mass lines in Type 2 spectra. Due to the dynamical evolution of the orbital elements of E ring grains a large fraction collides with the icy moons embedded in the E ring. Therefore, the organic components identified by CDA can accumulate on the surfaces of these bodies over time. Ref: :[1]Kempf et al., Icarus-206, 2010. [2]Postberg et al., Nature-459, 2009. [3]Postberg et al., Icarus-193, 2008.

  11. The Charging of Planetary Rings

    NASA Astrophysics Data System (ADS)

    Graps, Amara L.; Horanyi, M.; Havnes, O.; Gruen, E.

    2008-09-01

    Planetary rings have an undeniable aesthetic appeal, resulting in media icons of ringed planets as descriptive of the planetary sciences field as a whole. Such far-reaching symbolism might not be misplaced, however, because planetary rings represent a fundamental class of planetary structure that invites interdisciplinary investigations from specialists in dust, gravitational, plasma, collisional, and radiative transfer physics, due to: its sub-micron to meters-sized particles, its immersion in the planet's magnetic field, its embedded moonlets and its close proximity to the ringed planet's ionosphere and innermost moons. As such, planetary rings are a metaphoric bridge through a wide range of planetary physical processes. Processes to charge ring particles have different relative dynamical effects, dependent upon the rings' particle sizes, and the ring's plasma, magnetic and gravitational environments. This presentation will review what is known about the charging parameters and processes of planetary rings, in particular the sum of the individual currents from the time-varying charge dQ/dt, of the planetary ring particle. The individual currents depend on the environmental plasma conditions: number density, flow speed, temperature, and mass for the currents: electron and ion capture from the plasma, ion currents to a moving grain, photoelectron emission, secondary electron emission, thermionic effects, with stochastic charging influencing all of the above. Since rings are an ensemble of particles, ("cloud" Ring), we will define an ensemble, and consider the above currents, including those for the smallest ring particles, the dust particles, to arrive at a table giving charge potential and other relevant parameters.

  12. Heterocyclic replacements for benzene: Maximising ADME benefits by considering individual ring isomers.

    PubMed

    Ritchie, Timothy J; Macdonald, Simon J F

    2016-11-29

    The impact of replacing a mono-substituted benzene (phenyl) ring with thirty three aromatic and nine aliphatic heterocycles on nine ADME-related screens (solubility, lipophilicity, permeability, protein binding CYP450 inhibition and metabolic clearance) was assessed using matched molecular pair analysis. The results indicate that the influence on the ADME profile can differ significantly depending on the ring identity and importantly on the individual regioisomers that are possible for some rings. This information enables the medicinal chemist to make an informed choice about which rings and regioisomers to employ as mono-substituted benzene replacements, based upon the knowledge of how such replacements are likely to influence ADME-related parameters, for example to target higher solubility whilst avoiding CYP450 liabilities.

  13. Metabolism of roxatidine acetate hydrochloride. Liberation of deuterium from the piperidine ring during hydroxylation

    SciTech Connect

    Honma, S.; Iwamura, S.; Kobayashi, R.; Kawabe, Y.; Shibata, K.

    1987-07-01

    The metabolism of roxatidine acetate hydrochloride (RA), a new histamine-2 receptor antagonist, was studied by GC/MS in rats and dogs in vivo. The co-administration of /sup 14/C-RA and RA-d10 labeled with deuterium in the piperidine ring expedited the isolation and identification of 15 urinary metabolites. The major metabolites in both animals were M-1, M-8, M-10, and M-11; M-4 could be found only in the rat. The aromatic and piperidine ring-hydroxylated metabolites were found in small amounts in both species. Following the administration of RA-d10 to rats and dogs, oxygenated metabolites on the piperidine ring, such as M-3 and M-4, were isolated and their analysis indicated the unexpected loss of three or four deuterium atoms from the ring. Also, first and second isotope effects were observed on the conversion rate in vivo and retention time in HPLC, respectively.

  14. Process for producing high purity aromatic compounds

    SciTech Connect

    Mayes, W.W.

    1980-05-20

    High-purity C7 and/or C8 aromatic hydrocarbons are produced by reforming a C7 or C8 full boiling carbon number naphtha feed fraction or combinations thereof under reforming conditions of sufficient severity to convert essentially all of the nonaromatic portion of the naphtha feed boiling in the C7 to C8 aromatic boiling range to C7 and/or C8 aromatics, and then separating the reformate by fractional distillation into highpurity fractions of C7 and/or C8 aromatic hydrocarbons. Preferably, the C7 and/or C8 full boiling carbon number naphtha feed fraction is reformed in a plurality of reformer reaction stages with increasingly more severe conditions in order to maximize the yield of the C7 and C8 aromatics.

  15. Buoyant Norbury's vortex rings

    NASA Astrophysics Data System (ADS)

    Blyth, Mark; Rodriguez-Rodriguez, Javier; Salman, Hayder

    2014-11-01

    Norbury's vortices are a one-parameter family of axisymmetric vortex rings that are exact solutions to the Euler equations. Due to their relative simplicity, they are extensively used to model the behavior of real vortex rings found in experiments and in Nature. In this work, we extend the original formulation of the problem to include buoyancy effects for the case where the fluid that lies within the vortex has a different density to that of the ambient. In this modified formulation, buoyancy effects enter the problem through the baroclinic term of the vorticity equation. This permits an efficient numerical solution of the governing equation of motion in terms of a vortex contour method that tracks the evolution of the boundary of the vortex. Finally, we compare our numerical results with the theoretical analysis of the short-time evolution of a buoyant vortex. Funded by the Spanish Ministry of Economy and Competitiveness through grant DPI2011-28356-C03-02 and by the London Mathematical Society.

  16. Storage ring injection

    SciTech Connect

    Burke, R.J.

    1980-01-01

    Some basic issues involved in injecting the beam into storage rings with the principal parameters of those studied at the workshop have been considered. The main conclusion is that straightforward adjustments of the storage ring parameters makes injection easy. The largest number of injected turns is fourteen, and the phase space dilution allowance seems adequate to ensure very small beam loss during injection. The adjustments also result in lower bending magnet fields, and high field superconducting magnets (e.g., 5 Tesla) are not necessary. The design changes do not necessarily affect the Keil-Schnell criterion for stability of the longitudinal microwave instability, although that criterion appears to be irrelevant. Because the beams are expected to be unstable, but with slow growth rates, the vacuum chamber impedances required to give equal risetimes for the various designs are compared for systems posing various degrees of difficulty for injection. Finally, the impact of the parameters on cost is noted, and a system is considered that cuts the length of the linac in half by using doubly charged ions.

  17. Ring Image Analyzer

    NASA Technical Reports Server (NTRS)

    Strekalov, Dmitry V.

    2012-01-01

    Ring Image Analyzer software analyzes images to recognize elliptical patterns. It determines the ellipse parameters (axes ratio, centroid coordinate, tilt angle). The program attempts to recognize elliptical fringes (e.g., Newton Rings) on a photograph and determine their centroid position, the short-to-long-axis ratio, and the angle of rotation of the long axis relative to the horizontal direction on the photograph. These capabilities are important in interferometric imaging and control of surfaces. In particular, this program has been developed and applied for determining the rim shape of precision-machined optical whispering gallery mode resonators. The program relies on a unique image recognition algorithm aimed at recognizing elliptical shapes, but can be easily adapted to other geometric shapes. It is robust against non-elliptical details of the image and against noise. Interferometric analysis of precision-machined surfaces remains an important technological instrument in hardware development and quality analysis. This software automates and increases the accuracy of this technique. The software has been developed for the needs of an R&TD-funded project and has become an important asset for the future research proposal to NASA as well as other agencies.

  18. Atmospheric photochemistry of aromatic hydrocarbons: Analysis of OH budgets during SAPHIR chamber experiments and evaluation of MCMv3.2

    NASA Astrophysics Data System (ADS)

    Nehr, S.; Bohn, B.; Brauers, T.; Dorn, H.; Fuchs, H.; Häseler, R.; Hofzumahaus, A.; Li, X.; Lu, K.; Rohrer, F.; Tillmann, R.; Wahner, A.

    2012-12-01

    Aromatic hydrocarbons, almost exclusively originating from anthropogenic sources, comprise a significant fraction of volatile organic compounds observed in urban air. The photo-oxidation of aromatics results in the formation of secondary pollutants and impacts air quality in cities, industrialized areas, and districts of dense traffic. Up-to-date photochemical oxidation schemes of the Master Chemical Mechanism (MCMv3.2) exhibit moderate performance in simulating aromatic compound degradation observed during previous environmental chamber studies. To obtain a better understanding of aromatic photo-oxidation mechanisms, we performed experiments with a number of aromatic hydrocarbons in the outdoor atmosphere simulation chamber SAPHIR located in Jülich, Germany. These chamber studies were designed to derive OH turnover rates exclusively based on experimental data. Simultaneous measurements of NOx (= NO + NO2), HOx (= OH + HO2), and the total OH loss rate constant k(OH) facilitate a detailed analysis of the OH budgets during photo-oxidation experiments. The OH budget analysis was complemented by numerical model simulations using MCMv3.2. Despite MCM's tendency to overestimate k(OH) and to underpredict radical concentrations, the OH budgets are reasonably balanced for all investigated aromatics. However, the results leave some scope for OH producing pathways that are not considered in the current MCMv3.2. An improved reaction mechanism, derived from MCMv3.2 sensitivity studies, is presented. The model performance is basically improved by changes of the mechanistic representation of ring fragmentation channels.

  19. 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.

  20. Ring current and radiation belts

    NASA Technical Reports Server (NTRS)

    Williams, D. J.

    1987-01-01

    Studies performed during 1983-1986 on the ring current, the injection boundary model, and the radiation belts are discussed. The results of these studies yielded the first observations on the composition and charge state of the ring current throughout the ring-current energy range, and strong observational support for an injection-boundary model accounting for the origins of radiation-belt particles, the ring current, and substorm particles observed at R less than about 7 earth radii. In addition, the results have demonstrated that the detection of energetic neutral atoms generated by charge-exchange interactions between the ring current and the hydrogen geocorona can provide global images of the earth's ring current and its spatial and temporal evolution.

  1. Reversible Rings with Involutions and Some Minimalities

    PubMed Central

    Fakieh, W. M.; Nauman, S. K.

    2013-01-01

    In continuation of the recent developments on extended reversibilities on rings, we initiate here a study on reversible rings with involutions, or, in short, ∗-reversible rings. These rings are symmetric, reversible, reflexive, and semicommutative. In this note we will study some properties and examples of ∗-reversible rings. It is proved here that the polynomial rings of ∗-reversible rings may not be ∗-reversible. A criterion for rings which cannot adhere to any involution is developed and it is observed that a minimal noninvolutary ring is of order 4 and that a minimal noncommutative ∗-reversible ring is of order 16. PMID:24489510

  2. Polycyclic aromatic hydrocarbons in rock oysters: a baseline study.

    PubMed

    Kagi, R; Alexander, R; Cumbers, M

    1985-01-01

    Coral-rock oysters were collected in September 1982 from six locations in the area of Mermaid Sound in North-Western Australia. Analysis was carried out by digestion of the samples, followed by solvent extraction and analysis of the extracts using HPLC-UVF and GC-MS. The levels of two- and three-ring aromatics ranged from very low for the site outside Mermaid Sound and for one site within the Sound, to low for the four other sites within the Sound. The PAH values at the latter four sites are attributed to occasional petroleum release episodes related to small boat activities and large-scale salt and iron ore shipping and general cargo activities of the Port of Dampier. The levels of PAHs with four or more rings were found to be low or very low at all sites; in fact, in most cases values measured for specific PAHs were below the limits of detection of even the very sensitive methods used in this study. Samples from sites within Mermaid Sound closest to the town and port of Dampier showed noticeably higher levels than those from outside; the present study does not allow the source of the PAHs to be determined. It is interesting to note, however, that the parent PAHs appear to form a greater proportion of the total PAH assemblage in these cases, indicating contributions from material which has been subjected to high temperature processing prior to release into the Sound.

  3. Polycyclic aromatic hydrocarbon (PAH) ecotoxicology in marine ecosystems.

    PubMed

    Hylland, Ketil

    2006-01-08

    Low levels of oil and hence polycyclic aromatic hydrocarbons (PAHs) are naturally present in the marine environment, although levels have increased significantly following human extraction and use of oil and gas. Other major anthropogenic sources of PAHs include smelters, the use of fossil fuels in general, and various methods of waste disposal, especially incineration. There are two major sources for PAHs to marine ecosystems in Norway: the inshore smelter industry, and offshore oil and gas production activities. A distinction is generally made between petrogenic (oil-derived) and pyrogenic (combustion-derived) PAHs. Although petrogenic PAHs appear to be bioavailable to a large extent, pyrogenic PAHs are often associated with soot particles and less available for uptake into organisms. There is extensive evidence linking sediment-associated PAHs to induction of phase-I enzymes, development of DNA adducts, and eventually neoplastic lesions in fish. Most studies have focused on high-molecular-weight, carcinogenic PAHs such as benzo[a]pyrene. It is less clear how two- and three-ring PAHs affect fish, and there is even experimental evidence to indicate that these chemicals may inhibit some components of the phase I system rather than produce induction. There is a need for increased research efforts to clarify biological effects of two- and three-ring PAHs, PAH mixtures, and adaptation processes in marine ecosystems.

  4. PIXE analysis of elements in gastric cancer and adjacent mucosa

    NASA Astrophysics Data System (ADS)

    Liu, Qixin; Zhong, Ming; Zhang, Xiaofeng; Yan, Lingnuo; Xu, Yongling; Ye, Simao

    1990-04-01

    The elemental regional distributions in 20 resected human stomach tissues were obtained using PIXE analysis. The samples were pathologically divided into four types: normal, adjacent mucosa A, adjacent mucosa B and cancer. The targets for PIXE analysis were prepared by wet digestion with a pressure bomb system. P, K, Fe, Cu, Zn and Se were measured and statistically analysed. We found significantly higher concentrations of P, K, Cu, Zn and a higher ratio of Cu compared to Zn in cancer tissue as compared with normal tissue, but statistically no significant difference between adjacent mucosa and cancer tissue was found.

  5. 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.

  6. 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.

  7. Polycyclic aromatic hydrocarbons in carcinogenesis.

    PubMed Central

    Warshawsky, D

    1999-01-01

    A symposium on "Polycyclic Aromatic Hydrocarbons (PAHs) in Carcinogenesis" was presented at the third International Congress of Pathophysiology held in Lathi, Finland, 28 June-3 July 1998. The congress was also sponsored by the International Union of Biological Sciences and the International Society of Free Radical Research. Institutional support for the symposium included the Electric Power Research Institute, National Center for Toxicological Research, and EPA/National Health and Environmental Effects Research Laboratory and the Office of Solid Waste and Emergency Response. The symposium focused on the sources, carcinogenicity, genotoxicity, and risk assessment of individual and mixtures of PAHs that are found in solid wastes, Superfund sites, and other hazardous waste sites. Based on the occurrence of PAHs at numerous Superfund sites and the significant data gaps on the toxic potential of certain PAHs, the information developed during this symposium would be of value in assessing health risks of these chemicals at Superfund and other hazardous waste sites. PMID:10090712

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. Polycyclic aromatic hydrocarbon (PAH) formation from benzyl radicals: a reaction kinetics study.

    PubMed

    Sinha, Sourab; Raj, Abhijeet

    2016-03-21

    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.

  14. On the aliphatic versus aromatic content of the carriers of the `unidentified' infrared emission features

    NASA Astrophysics Data System (ADS)

    Yang, X. J.; Glaser, R.; Li, Aigen; Zhong, J. X.

    2016-10-01

    Although it is generally accepted that the unidentified infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm are characteristic of the stretching and bending vibrations of aromatic hydrocarbon materials, the exact nature of their carriers remains unknown: whether they are free-flying, predominantly aromatic gas-phase molecules, or amorphous solids with a mixed aromatic/aliphatic composition are being debated. Recently, the 3.3 and 3.4 μm features which are commonly respectively attributed to aromatic and aliphatic C-H stretches have been used to place an upper limit of ˜2 per cent on the aliphatic fraction of the UIE carriers (i.e. the number of C atoms in aliphatic chains to that in aromatic rings). Here we further explore the aliphatic versus aromatic content of the UIE carriers by examining the ratio of the observed intensity of the 6.2 μm aromatic C-C feature (I6.2) to that of the 6.85 μm aliphatic C-H deformation feature (I6.85). To derive the intrinsic oscillator strengths of the 6.2 μm stretch (A6.2) and the 6.85 μm deformation (A6.85), we employ density functional theory to compute the vibrational spectra of seven methylated polycyclic aromatic hydrocarbon molecules and their cations. By comparing I6.85/I6.2 with A6.85/A6.2, we derive the fraction of C atoms in methyl(ene) aliphatic form to be at most ˜10 per cent, confirming the earlier finding that the UIE emitters are predominantly aromatic. We have also computed the intrinsic strength of the 7.25 μm feature (A7.25), another aliphatic C-H deformation band. We find that A6.85 appreciably exceeds A7.25. This explains why the 6.85 μm feature is more frequently detected in space than the 7.25 μm feature.

  15. Emission of polycyclic aromatic hydrocarbons from coal and sewage sludge co-combustion in a drop tube furnace.

    PubMed

    Han, Jun; Qin, Linbo; Ye, Wei; Li, Yuqi; Liu, Long; Wang, Hao; Yao, Hong

    2012-09-01

    The emission characteristics of polycyclic aromatic hydrocarbons (PAHs) during coal and sewage sludge co-combustion were investigated in a laboratory-scale drop tube furnace. The experimental results demonstrated that coal and sewage sludge co-combustion was beneficial in reducing PAH emissions and PAH toxic equivalent (TEQ) concentrations. Meanwhile, the five-ring PAHs were the main contributor in reducing the concentration of PAHs and TEQ. Moreover, the two- and five-ring PAH concentrations decreased as the mass fraction of sewage sludge in the mixture increased from 0% to 100%. It was also found that PAHs from coal mono-combustion was dominated by the four- and five-ring PAHs. As for the sewage sludge mono-combustion, the three- and four-ring PAHs were the principal components.

  16. The formation and evolution of moonlets in Saturn's F ring

    NASA Astrophysics Data System (ADS)

    Murray, C. D.; Williams, G. A.; Evans, M. W.; Cooper, N. J.; Agnor, C. B.

    2010-05-01

    Images of Saturn's F ring from the Cassini spacecraft, including several obtained near the time of the 2009 equinox, have revealed bright clumps capable of casting shadows on nearby ring material. In the vicinity of the inner shepherding satellite, Prometheus, the clumps are clearly associated with the edges of the channel structures (Murray et al., Nature 437, 1326 (2005)) created by the gravitational perturbations from the satellite. Furthermore, the detection of "fan"-like structures (Murray et al., Nature 453, 739 (2008)) in adjacent ring material is consistent with the effect of an embedded object on an orbit with an eccentricity different to that of the F ring; these structures are also associated with the channel edges. Bright clumps have been detected throughout the ring and not just in those regions that have just encountered Prometheus, although the regularity of their spacing is most obvious at these locations. Cassini images of the F ring obtained over several months show that the clumps drift with respect to the core of the F ring implying semi-major axes that differ from that of the core. Numerical simulations of the interaction between Prometheus and test particles in the F ring show that the effect of the satellite's passage is to create regions of enhanced mass density and low relative velocity at the channel edges. These are suitable conditions for instabilities in the ring leading to collapse into gravitationally bound objects or moonlets. The initial perturbation leads to changes of ~10% in the particles' eccentricities as well as changes in their semi-major axes of up to +/-20 km. The former could account for the observed "fans" while the latter could account for the observed drift of the bright clumps over time. The same mechanism causes the channels to widen with time and this effect is seen in the Cassini images. Loosely bound objects or moonlets formed in this way could be disrupted by subsequent Prometheus passages or could survive and

  17. Formation of lunar basin rings

    USGS Publications Warehouse

    Hodges, C.A.; Wilhelms, D.E.

    1978-01-01

    The origin of the multiple concentric rings that characterize lunar impact basins, and the probable depth and diameter of the transient crater have been widely debated. As an alternative to prevailing "megaterrace" hypotheses, we propose that the outer scarps or mountain rings that delineate the topographic rims of basins-the Cordilleran at Orientale, the Apennine at Imbrium, and the Altai at Nectaris-define the transient cavities, enlarged relatively little by slumping, and thus are analogous to the rim crests of craters like Copernicus; inner rings are uplifted rims of craters nested within the transient cavity. The magnitude of slumping that occurs on all scarps is insufficient to produce major inner rings from the outer. These conclusions are based largely on the observed gradational sequence in lunar central uplifts:. from simple peaks through somewhat annular clusters of peaks, peak and ring combinations and double ring basins, culminating in multiring structures that may also include peaks. In contrast, belts of slump terraces are not gradational with inner rings. Terrestrial analogs suggest two possible mechanisms for producing rings. In some cases, peaks may expand into rings as material is ejected from their cores, as apparently occurred at Gosses Bluff, Australia. A second process, differential excavation of lithologically diverse layers, has produced nested experimental craters and is, we suspect, instrumental in the formation of terrestrial ringed impact craters. Peak expansion could produce double-ring structures in homogeneous materials, but differential excavation is probably required to produce multiring and peak-in-ring configurations in large lunar impact structures. Our interpretation of the representative lunar multiring basin Orientale is consistent with formation of three rings in three layers detected seismically in part of the Moon-the Cordillera (basin-bounding) ring in the upper crust, the composite Montes Rook ring in the underlying

  18. Fingering inside the coffee ring

    NASA Astrophysics Data System (ADS)

    Weon, Byung Mook; Je, Jung Ho

    2013-01-01

    Colloidal droplets including micro- and nanoparticles generally leave a ringlike stain, called the “coffee ring,” after evaporation. We show that fingering emerges during evaporation inside the coffee ring, resulting from a bidispersed colloidal mixture of micro- and nanoparticles. Microscopic observations suggest that finger formation is driven by competition between the coffee-ring and Marangoni effects, especially when the inward Marangoni flow is overwhelmed by the outward coffee-ring flow. This finding could help to understand the variety of the final deposition patterns of colloidal droplets.

  19. Split ring containment attachment device

    DOEpatents

    Sammel, Alfred G.

    1996-01-01

    A containment attachment device 10 for operatively connecting a glovebag 200 to plastic sheeting 100 covering hazardous material. The device 10 includes an inner split ring member 20 connected on one end 22 to a middle ring member 30 wherein the free end 21 of the split ring member 20 is inserted through a slit 101 in the plastic sheeting 100 to captively engage a generally circular portion of the plastic sheeting 100. A collar potion 41 having an outer ring portion 42 is provided with fastening means 51 for securing the device 10 together wherein the glovebag 200 is operatively connected to the collar portion 41.

  20. Ground Movement in SSRL Ring

    SciTech Connect

    Sunikumar, Nikita; /UCLA /SLAC

    2011-08-25

    Users of the Stanford Synchrotron Radiation Lightsource (SSRL) are being affected by diurnal motion of the synchrotron's storage ring, which undergoes structural changes due to outdoor temperature fluctuations. In order to minimize the effects of diurnal temperature fluctuations, especially on the vertical motion of the ring floor, scientists at SSRL tried three approaches: painting the storage ring white, covering the asphalt in the middle of the ring with highly reflective Mylar and installing Mylar on a portion of the ring roof and walls. Vertical motion in the storage ring is measured by a Hydrostatic Leveling System (HLS), which calculates the relative height of water in a pipe that extends around the ring. The 24-hr amplitude of the floor motion was determined using spectral analysis of HLS data, and the ratio of this amplitude before and after each experiment was used to quantitatively determine the efficacy of each approach. The results of this analysis showed that the Mylar did not have any significant effect on floor motion, although the whitewash project did yield a reduction in overall HLS variation of 15 percent. However, further analysis showed that the reduction can largely be attributed to a few local changes rather than an overall reduction in floor motion around the ring. Future work will consist of identifying and selectively insulating these local regions in order to find the driving force behind diurnal floor motion in the storage ring.

  1. Saturn's Rings Edge-on

    NASA Technical Reports Server (NTRS)

    1995-01-01

    In one of nature's most dramatic examples of 'now-you see-them, now-you-don't', NASA's Hubble Space Telescope captured Saturn on May 22, 1995 as the planet's magnificent ring system turned edge-on. This ring-plane crossing occurs approximately every 15 years when the Earth passes through Saturn's ring plane.

    For comparison, the top picture was taken by Hubble on December 1, 1994 and shows the rings in a more familiar configuration for Earth observers.

    The bottom picture was taken shortly before the ring plane crossing. The rings do not disappear completely because the edge of the rings reflects sunlight. The dark band across the middle of Saturn is the shadow of the rings cast on the planet (the Sun is almost 3 degrees above the ring plane.) The bright stripe directly above the ring shadow is caused by sunlight reflected off the rings onto Saturn's atmosphere. Two of Saturn's icy moons are visible as tiny starlike objects in or near the ring plane. They are, from left to right, Tethys (slightly above the ring plane) and Dione.

    This observation will be used to determine the time of ring-plane crossing and the thickness of the main rings and to search for as yet undiscovered satellites. Knowledge of the exact time of ring-plane crossing will lead to an improved determination of the rate at which Saturn 'wobbles' about its axis (polar precession).

    Both pictures were taken with Hubble's Wide Field Planetary Camera 2. The top image was taken in visible light. Saturn's disk appears different in the bottom image because a narrowband filter (which only lets through light that is not absorbed by methane gas in Saturn's atmosphere) was used to reduce the bright glare of the planet. Though Saturn is approximately 900 million miles away, Hubble can see details as small as 450 miles across.

    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

  2. Molecular rotors as simple models to study amide NH-aromatic interactions and their role in the folding of peptide-like structures.

    PubMed

    Alfonso, Ignacio; Burguete, M Isabel; Galindo, Francisco; Luis, Santiago V; Vigara, Laura

    2007-10-12

    The conformational behavior of designed macrocyclic naphthalenophanes (1a,b and 2a,b) derived from amino acids (Phe and Val) has been used for studying NH...pi interactions. The cycles having 16- and 17-membered rings showed a dynamic process within the NMR time scale, produced by the flipping of the aromatic naphthalene moiety with respect to the macrocyclic main plane. We used the temperature dependence of 1H NMR to obtain activation parameters of the energetic barrier for the process (variable temperature NMR and line shape analysis). The rate of the movement clearly depends on the macrocyclic ring size and, more interestingly, on the nature of the peptidomimetic side chain, the energetic barrier being higher for the compounds bearing aromatic side chains. A largely negative entropic contribution to the free energy of activation was observed, with clear differences due to the side chain nature. Molecular modeling studies suggest that the aromatic rings interact with intramolecularly H-bonded amide NH groups, protecting them from solvation and thus leading to a larger unfavorable activation entropy. This NH...pi interaction has been exploited for the preparation of new systems (1c and meso-1b) with designed conformational preferences, in which aromatic rings tend to fold over amide NH groups. Thus, these minimalistic molecular rotors have served us as simple model systems for the study of NH...pi interactions and their implication in the folding of peptide-like molecules.

  3. 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

  4. [Distribution of polycyclic aromatic hydrocarbons in soil profiles in southeast suburb of Beijing wastewater irrigation area].

    PubMed

    He, Jiang-Tao; Jin, Ai-Fang; Chen, Su-Nuan; Wei, Yong-Xia

    2009-05-15

    3 borehole profiles samples were collected using Eijkelkamp soil sampler from the wastewater irrigation area of Beijing Southeast suburb. The soil samples were collected from surface to 5.5 m underground every 0.5 m. Physical-chemical properties of the samples such as clay content, total amount of clay minerals, cation exchange capacity (CEC), total organic compounds (TOC), etc. were analyzed. 16 polycyclic aromatic hydrocarbons (PAHs) defined by the U.S. EPA were also analyzed with gas chromatography-mass spectrometry (GC-MS). Results show that 14 PAHs were detected in the surface soil samples. The concentrations of PAHs range from 4 microg/kg to 428 microg/kg. Under the surface,both species and concentrations of PAHs in soil samples drop very fast. Only 2 rings and 3 rings PAHs were detected, which were naphthalene,phenanthrene, fluorene, acenaphthylene, acenaphthene, and fluoranthene. Clay content, total amount of clay minerals, CEC and TOC have significant correlations at 0.05 level between each other. Under the surface, clay contents also have a relationship with low-rings PAHs concentration. Where the layers have higher clay contents,the PAHs have higher concentrations. The contents of PAHs changing along the profiles also show that, low-rings PAHs are easier to migrate than high-rings PAHs. The sequence of the migration capabilities of low-ring PAHs is acenaphthene > fluorene > naphthalene > phenanthrene > acenaphthylene > fluoranthene. However, high-ring PAHs were only detected in surface soil samples. That means low-rings PAHs can reach the deep layers of the vertical profiles under long-term wastewater irrigation. Therefore, the shallow groundwater has the possibility to be contaminated.

  5. Role of Kekulé and Non-Kekulé Structures in the Radical Character of Alternant Polycyclic Aromatic Hydrocarbons: A TAO-DFT Study

    PubMed Central

    Yeh, Chia-Nan; Chai, Jeng-Da

    2016-01-01

    We investigate the role of Kekulé and non-Kekulé structures in the radical character of alternant polycyclic aromatic hydrocarbons (PAHs) using thermally-assisted-occupation density functional theory (TAO-DFT), an efficient electronic structure method for the study of large ground-state systems with strong static correlation effects. Our results reveal that the studies of Kekulé and non-Kekulé structures qualitatively describe the radical character of alternant PAHs, which could be useful when electronic structure calculations are infeasible due to the expensive computational cost. In addition, our results support previous findings on the increase in radical character with increasing system size. For alternant PAHs with the same number of aromatic rings, the geometrical arrangements of aromatic rings are responsible for their radical character. PMID:27457289

  6. Role of Kekulé and Non-Kekulé Structures in the Radical Character of Alternant Polycyclic Aromatic Hydrocarbons: A TAO-DFT Study.

    PubMed

    Yeh, Chia-Nan; Chai, Jeng-Da

    2016-07-26

    We investigate the role of Kekulé and non-Kekulé structures in the radical character of alternant polycyclic aromatic hydrocarbons (PAHs) using thermally-assisted-occupation density functional theory (TAO-DFT), an efficient electronic structure method for the study of large ground-state systems with strong static correlation effects. Our results reveal that the studies of Kekulé and non-Kekulé structures qualitatively describe the radical character of alternant PAHs, which could be useful when electronic structure calculations are infeasible due to the expensive computational cost. In addition, our results support previous findings on the increase in radical character with increasing system size. For alternant PAHs with the same number of aromatic rings, the geometrical arrangements of aromatic rings are responsible for their radical character.

  7. Overall view of tower and adjacent aircraft shelters on flight ...

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

    Overall view of tower and adjacent aircraft shelters on flight line. View to east. - Plattsburgh Air Force Base, Security Guard Tower, Florida Street at Aircraft Shelters Area, Plattsburgh, Clinton County, NY

  8. Interior building details of Building A, dungeon cell adjacent to ...

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

    Interior building details of Building A, dungeon cell adjacent to northwest cell: granite and brick threshold, poured concrete floors, plastered finished walls, vaulted veiling; northwesterly view - San Quentin State Prison, Building 22, Point San Quentin, San Quentin, Marin County, CA

  9. 10. View north from the adjacent B & O railroad ...

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

    10. View north from the adjacent B & O railroad bridge of portion of the Main truss span over the reservoir of the Augustine Paper Mills, National Register Site. - Augustine Bridge, Brandywine River,Augustine Cutoff, Wilmington, New Castle County, DE

  10. 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

  11. 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

  12. 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

  13. VIEW FROM ROOFTOP OF BUILDING (MOTEL) ADJACENT TO TECHWOOD HOMES, ...

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

    VIEW FROM ROOFTOP OF BUILDING (MOTEL) ADJACENT TO TECHWOOD HOMES, LOOKING SOUTH. GARAGE TO EXTREME LEFT, BUILDING 1 TO EXTREME RIGHT. - Techwood Homes, Building No. 16, 488-514 Techwood Drive, Atlanta, Fulton County, GA

  14. View from water showing south facade and adjacent boat slips ...

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

    View from water showing south facade and adjacent boat slips (Facility Nos. S375 & S376) - U.S. Naval Base, Pearl Harbor, Boat House, Hornet Avenue at Independence Street, Pearl City, Honolulu County, HI

  15. Cement Leakage into Adjacent Vertebral Body Following Percutaneous Vertebroplasty.

    PubMed

    Park, Jae Hoo; Kim, Hyeun Sung; Kim, Seok Won

    2016-06-01

    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.

  16. 15. View north from the adjacent B & O railroad ...

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

    15. View north from the adjacent B & O railroad bridge of Pier No. 5 and portion of the deck and super-structure. - Augustine Bridge, Brandywine River,Augustine Cutoff, Wilmington, New Castle County, DE

  17. 7. View north from the adjacent B & O railroad ...

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

    7. View north from the adjacent B & O railroad bridge of Pier No. 1 and portions of the deck and super-structure. - Augustine Bridge, Brandywine River,Augustine Cutoff, Wilmington, New Castle County, DE

  18. 8. View north from the adjacent B & O railroad ...

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

    8. View north from the adjacent B & O railroad bridge of Pier No. 2 and portions of the deck and super-structure. - Augustine Bridge, Brandywine River,Augustine Cutoff, Wilmington, New Castle County, DE

  19. VIEW OF NORTHERN AND EASTERN SIDES FROM PARKING LOT ADJACENT ...

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

    VIEW OF NORTHERN AND EASTERN SIDES FROM PARKING LOT ADJACENT TO BUILDING 199 (POLICE STATION) - U.S. Naval Base, Pearl Harbor, Post Office, Avenue A near Eleventh Avenue, Pearl City, Honolulu County, HI

  20. Basement, room 23, looking southwest into two adjacent offices with ...

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

    Basement, room 23, looking southwest into two adjacent offices with soundproof walls and pedestal flooring - March Air Force Base, Strategic Air Command, Combat Operations Center, 5220 Riverside Drive, Moreno Valley, Riverside County, CA