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Sample records for means halogen oxidant

  1. ASCORBIC ACID TREATMENT TO REDUCE RESIDUAL HALOGEN-BASED OXIDANTS PRIOR TO THE DETERMINATION OF HALOGENATED DISINFECTION BYPRODUCTS IN POTABLE WATER

    Science.gov (United States)

    Treatment of potable water samples with ascorbic acid has been investigated as a means for reducing residual halogen-based oxidants (disinfectants)i.e., HOCl, Cl2, Brw and BrCl, prior to determination of EPA Method 551.1A and 551.1B analytes. These disinfection byproducts include...

  2. Global impacts of tropospheric halogens (Cl, Br, I) on oxidants and composition in GEOS-Chem

    Science.gov (United States)

    Sherwen, Tomás; Schmidt, Johan A.; Evans, Mat J.; Carpenter, Lucy J.; Großmann, Katja; Eastham, Sebastian D.; Jacob, Daniel J.; Dix, Barbara; Koenig, Theodore K.; Sinreich, Roman; Ortega, Ivan; Volkamer, Rainer; Saiz-Lopez, Alfonso; Prados-Roman, Cristina; Mahajan, Anoop S.; Ordóñez, Carlos

    2016-09-01

    We present a simulation of the global present-day composition of the troposphere which includes the chemistry of halogens (Cl, Br, I). Building on previous work within the GEOS-Chem model we include emissions of inorganic iodine from the oceans, anthropogenic and biogenic sources of halogenated gases, gas phase chemistry, and a parameterised approach to heterogeneous halogen chemistry. Consistent with Schmidt et al. (2016) we do not include sea-salt debromination. Observations of halogen radicals (BrO, IO) are sparse but the model has some skill in reproducing these. Modelled IO shows both high and low biases when compared to different datasets, but BrO concentrations appear to be modelled low. Comparisons to the very sparse observations dataset of reactive Cl species suggest the model represents a lower limit of the impacts of these species, likely due to underestimates in emissions and therefore burdens. Inclusion of Cl, Br, and I results in a general improvement in simulation of ozone (O3) concentrations, except in polar regions where the model now underestimates O3 concentrations. Halogen chemistry reduces the global tropospheric O3 burden by 18.6 %, with the O3 lifetime reducing from 26 to 22 days. Global mean OH concentrations of 1.28 × 106 molecules cm-3 are 8.2 % lower than in a simulation without halogens, leading to an increase in the CH4 lifetime (10.8 %) due to OH oxidation from 7.47 to 8.28 years. Oxidation of CH4 by Cl is small (˜ 2 %) but Cl oxidation of other VOCs (ethane, acetone, and propane) can be significant (˜ 15-27 %). Oxidation of VOCs by Br is smaller, representing 3.9 % of the loss of acetaldehyde and 0.9 % of the loss of formaldehyde.

  3. Laboratory Studies of Halogen Oxides Important to Stratospheric Ozone Depletion

    Science.gov (United States)

    Wilmouth, D. M.; Klobas, J. E.; Anderson, J. G.

    2016-12-01

    Inorganic chlorine and bromine molecules are primarily responsible for stratospheric ozone destruction, with BrO, ClO, and ClOOCl comprising the two reaction cycles that cause most polar ozone losses. Despite comprehensive international treaties regulating CFCs and halons, seasonal polar ozone depletion will likely continue for decades to come. Accurate spectroscopic and kinetic measurements of inorganic bromine and chlorine molecules obtained in the laboratory are essential for reducing uncertainty in atmospheric models, better interpreting atmospheric field measurements, and forming trusted projections of future ozone changes. Here we present results from recent work in our laboratory using absorption spectroscopy and atomic resonance fluorescence detection to determine rate constants of halogen reactions, the equilibrium constant of ClO/ClOOCl, and absorption cross sections of several halogen oxides using a new cold trap-thermal desorption approach.

  4. Complete reaction mechanisms of mercury oxidation on halogenated activated carbon.

    Science.gov (United States)

    Rungnim, Chompoonut; Promarak, Vinich; Hannongbua, Supa; Kungwan, Nawee; Namuangruk, Supawadee

    2016-06-05

    The reaction mechanisms of mercury (Hg) adsorption and oxidation on halogenated activated carbon (AC) have been completely studied for the first time using density functional theory (DFT) method. Two different halogenated AC models, namely X-AC and X-AC-X (X=Cl, Br, I), were adopted. The results revealed that HgX is found to be stable-state on the AC edge since its further desorption from the AC as HgX, or further oxidation to HgX2, are energetically unfavorable. Remarkably, the halide type does not significantly affect the Hg adsorption energy but it strongly affects the activation energy barrier of HgX formation, which obviously increases in the order HgIBr-AC>Cl-AC. Thus, the study of the complete reaction mechanism is essential because the adsorption energy can not be used as a guideline for the rational material design in the halide impregnated AC systems. The activation energy is an important descriptor for the predictions of sorbent reactivity to the Hg oxidation process.

  5. Highly Regioselective Halogenation of Pyridine N-Oxide: Practical Access to 2-Halo-Substituted Pyridines.

    Science.gov (United States)

    Chen, Ying; Huang, Jinkun; Hwang, Tsang-Lin; Chen, Maosheng J; Tedrow, Jason S; Farrell, Robert P; Bio, Matthew M; Cui, Sheng

    2015-06-19

    A highly efficient and regioselective halogenation reaction of unsymmetrical pyridine N-oxide under mild conditions is described. The methodology provides a practical access to various 2-halo-substituted pyridines, which are pharmaceutically important intermediates.

  6. Destruction of halogen-containing pesticides by means of detonation combustion.

    Science.gov (United States)

    Biegańska, Jolanta

    2013-02-01

    Pesticides that contain a halogen functional group have been destructed by means of detonative combustion. The following compounds were examined: (1) atrazine-2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine-herbicide; (2) bromophos-O,4-bromo-2,5-dichlorophenyl O,O-dimethyl phosphorothioate-insecticide; (3) chloridazon-5-amino-4-chloro-2-phenylopyridazin-3(2H)-one-herbicide; (4) linuron-3-(3,4-dichlorophenyl)-1-metoxy-1-methylurea-herbicide; (5) metoxychlor-1,1,1-trichloro-2,2-bis(4-metoxyphenyl)ethane-insecticide and acaricide; and (6) trichlorfon-dimethyl 2,2,2-trichloro-1-hydroxyethylphosphonate-insecticide. Explosive material has been produced on the basis of ammonium nitrate, which served as an oxidizer while the pesticides were used as fuels. Composition of the explosive was adjusted in such a way as to respect thermodynamic parameters. Detonative decomposition of the mixtures has been carried out in shot-holes pre-drilled in soil. Efficiency of the pesticide decomposition has been examined with gas chromatography in order to determine pesticides residues in the environment. It was found that for some, the amount of pesticides in some compounds in the analyzed samples after decomposition was below the determination threshold of the applied method.

  7. Spatial Gradients in Halogen Oxides Across the North Slope of Alaska Indicate That Halogen Activated Airmasses are Spatially Large

    Science.gov (United States)

    Simpson, W. R.; Hoenninger, G. S.; Platt, U.

    2005-12-01

    Reactive halogens are important oxidizers in the polar atmosphere during springtime. They deplete tropospheric ozone, oxidize hydrocarbons, and oxidize gas-phase mercury, causing it to deposit to the snow pack. We want to understand the mechanism by which halides in on snow/ice crystals and/or in aerosol particles are converted to reactive halogen species. This understanding can assist in prediction of mercury deposition and how that deposition depends on environmental variables like sea-ice extent and temperature. This mechanistic knowledge is particularly important in the context of a changing Arctic system. To study halogen activation, we are working in the Studies of the Northern Alaskan Coastal System (SNACS) project and here show results from 2005 including the LEADX experiment. A number of studies have implicated leads (cracks in the sea ice) as a source of halogen activation, but it is unclear if halogens are directly activated on ice surfaces at the lead (e.g. frost flowers) or if the lead is less directly involved. To address the role of leads in halogen activation, we measured bromine monoxide (BrO) using Multiple Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) at Barrow and Atqasuk, Alaska over a four-month period. The locations of these sites, either on the coast near a recurring lead in the case of Barrow, or 100km inland in the case of Atqasuk provides an ability to measure spatial gradients on the 100km length scale. In addition, the Barrow instrument was the first implementation of fully automated two dimensional MAX-DOAS where both elevation and azimuth were scanned. Because the MAX-DOAS method typically detects path-averaged BrO amounts between the instrument and a range of approximately 10km, differences in BrO between viewing azimuths allows us to determine short-length scale BrO gradients. From the 2-D MAX-DOAS observations at Barrow, we find that there are very small if any spatial gradients on the 10km length scale. From the

  8. Influence of Halogen Substituents on the Catalytic Oxidation of 2,4,6-Halogenated Phenols by Fe(III-Tetrakis(p-hydroxyphenyl porphyrins and Potassium Monopersulfate

    Directory of Open Access Journals (Sweden)

    Seiya Nagao

    2011-12-01

    Full Text Available The influence of halogen substituents on the catalytic oxidation of 2,4,6-trihalogenated phenols (TrXPs by iron(III-porphyrin/KHSO5 catalytic systems was investigated. Iron(III-5,10,15,20-tetrakis(p-hydroxyphenylporphyrin (FeTHP and its supported variants were employed, where the supported catalysts were synthesized by introducing FeTHP into hydroquinone-derived humic acids via formaldehyde poly-condensation. F (TrFP, Cl (TrCP, Br (TrBP and I (TrIP were examined as halogen substituents for TrXPs. Although the supported catalysts significantly enhanced the degradation and dehalogenation of TrFP and TrCP, the oxidation of TrBP and TrIP was not enhanced, compared to the FeTHP catalytic system. These results indicate that the degree of oxidation of TrXPs is strongly dependent on the types of halogen substituent. The order of dehalogenation levels for halogen substituents in TrXPs was F > Cl > Br > I, consistent with their order of electronegativity. The electronegativity of a halogen substituent affects the nucleophilicity of the carbon to which it is attached. The levels of oxidation products in the reaction mixtures were analyzed by GC/MS after extraction with n-hexane. The most abundant dimer product from TrFP via 2,6-difluoroquinone is consistent with a scenario where TrXP, with a more electronegative halogen substituent, is readily oxidized, while less electronegative halogen substituents are oxidized less readily by iron(III-porphyrin/KHSO5 catalytic systems.

  9. Destruction of halogen-containing pesticides by means of detonation combustion

    OpenAIRE

    Biegańska, Jolanta

    2012-01-01

    Pesticides that contain a halogen functional group have been destructed by means of detonative combustion. The following compounds were examined: (1) atrazine—2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine—herbicide; (2) bromophos—O,4-bromo-2,5-dichlorophenyl O,O-dimethyl phosphorothioate—insecticide; (3) chloridazon—5-amino-4-chloro-2-phenylopyridazin-3(2H)-one—herbicide; (4) linuron—3-(3,4-dichlorophenyl)-1-metoxy-1-methylurea—herbicide; (5) metoxychlor—1,1,1-trichloro-2,2-bis(4-meto...

  10. Model study of multiphase DMS oxidation with a focus on halogens

    Directory of Open Access Journals (Sweden)

    R. von Glasow

    2004-01-01

    Full Text Available We studied the oxidation of dimethylsulfide (DMS in the marine boundary layer (MBL with a one-dimensional numerical model and focused on the influence of halogens. Our model runs show that there is still significant uncertainty about the end products of the DMS addition pathway, which is especially caused by uncertainty in the product yield of the reaction of the intermediate product methyl sulfinic acid (MSIA with OH. BrO strongly increases the importance of the addition branch in the oxidation of DMS even when present at mixing ratios smaller than 0.5pmol mol-1. The inclusion of halogen chemistry leads to higher DMS oxidation rates and smaller DMS to SO2 conversion efficiencies. The DMS to SO2 conversion efficiency is also drastically reduced under cloudy conditions. In cloud-free model runs between 5 and 15% of the oxidized DMS reacts further to particulate sulfur, in cloudy runs this fraction is almost 100%. Sulfate production by HOClaq and HOBraq is important in cloud droplets even for small Br- deficits and related small gas phase halogen concentrations. In general, more particulate sulfur is formed when halogen chemistry is included. A possible enrichment of HCO3- in fresh sea salt aerosol would increase pH values enough to make the reaction of S(IV* (=SO2,aq+HSO3-+SO32- with O3 dominant for sulfate production. It leads to a shift from methyl sulfonic acid (MSA to non-sea salt sulfate (nss-SO42- production but increases the total nss-SO42- only somewhat because almost all available sulfur is already oxidized to particulate sulfur in the base scenario. We discuss how realistic this is for the MBL. We found the reaction MSAaq+OH to contribute about 10% to the production of nss-SO42- in clouds. It is unimportant for cloud-free model runs. Overall we find that the presence of halogens leads to processes that decrease the albedo of stratiform clouds in the MBL.

  11. Measurements of reactive halogen species as oxidants of mercury over the Gulf of Mexico

    Science.gov (United States)

    Volkamer, R.; Coburn, S.; Dix, B. K.; Sinreich, R.; Terschure, A. F.; Edgerton, E. S.; Wu, Y.; Nair, U. S.

    2011-12-01

    The gas-phase reaction of bromine and chlorine radicals with gaseous elemental mercury (GEM) is a source for gaseous oxidized mercury (GOM). It has been established that oxidation by bromine is relevant at high latitudes, and can also occur in mid-latitude regions (Peleg et al. 2007), or in the free troposphere. A subject of ongoing debate concerns the role of free tropospheric bromine vs boundary layer bromine in oxidizing mercury. Here we present measurements of reactive halogen species bromine oxide (BrO) and iodine oxide (IO) along with gaseous oxidized mercury (GOM), gaseous elemental mercury (GEM), and particulate mercury (Hgp) at a coastal location in Gulf Breeze, Fl. The University of Colorado has deployed a research grade Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument to measure BrO, IO, as well as formaldehyde (HCHO), glyoxal (CHOCHO), nitrogen dioxide (NO2) and oxygen dimers (O4). Here we present the compilation of the data collected by this instrument over the time period from May 2009 to January 2011, which include the first measurements of BrO, IO, and CHOCHO over the Gulf of Mexico. We also present several case studies for days where significant amounts of reactive halogens were measured, explore the sources and back trajectories of the air masses carrying these compounds, and relate our observations to mercury data collected at a nearby SEARCH network site.

  12. Ozone variability and halogen oxidation within the Arctic and sub-Arctic springtime boundary layer

    Directory of Open Access Journals (Sweden)

    J. B. Gilman

    2010-11-01

    Full Text Available The influence of halogen oxidation on the variabilities of ozone (O3 and volatile organic compounds (VOCs within the Arctic and sub-Arctic atmospheric boundary layer was investigated using field measurements from multiple campaigns conducted in March and April 2008 as part of the POLARCAT project. For the ship-based measurements, a high degree of correlation (r = 0.98 for 544 data points collected north of 68° N was observed between the acetylene to benzene ratio, used as a marker for chlorine and bromine oxidation, and O3 signifying the vast influence of halogen oxidation throughout the ice-free regions of the North Atlantic. Concurrent airborne and ground-based measurements in the Alaskan Arctic substantiated this correlation and were used to demonstrate that halogen oxidation influenced O3 variability throughout the Arctic boundary layer during these springtime studies. Measurements aboard the R/V Knorr in the North Atlantic and Arctic Oceans provided a unique view of the transport of O3-poor air masses from the Arctic Basin to latitudes as far south as 52° N. FLEXPART, a Lagrangian transport model, was used to quantitatively determine the exposure of air masses encountered by the ship to first-year ice (FYI, multi-year ice (MYI, and total ICE (FYI+MYI. O3 anti-correlated with the modeled total ICE tracer (r = −0.86 indicating that up to 73% of the O3 variability measured in the Arctic marine boundary layer could be related to sea ice exposure.

  13. Halogen poisoning effect of Pt-TiO{sub 2} for formaldehyde catalytic oxidation performance at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaofeng; Cheng, Bei [State Key Laboratory of Advanced Technology for Material Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122#, Wuhan 430070 (China); Yu, Jiaguo, E-mail: jiaguoyu@yahoo.com [State Key Laboratory of Advanced Technology for Material Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122#, Wuhan 430070 (China); Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Ho, Wingkei, E-mail: keithho@ied.edu.hk [Department of Science and Environmental Studies and Centre for Education in Environmental Sustainability, The Hong Kong Institute of Education, Tai Po, N.T. Hong Kong (China)

    2016-02-28

    Graphical abstract: - Highlights: • The Pt-TiO{sub 2} catalyst is deactivated by adsorption of halogen ions. • The halogen poison is mainly attributed to the active site blocking of the Pt surface. • Halogen ions and Pt form Pt−X coordination bonds. • Large halogen diameter exhibits severe poisoning effect. - Abstract: Catalytic decomposition of formaldehyde (HCHO) at room temperature is an important method for HCHO removal. Pt-based catalysts are the optimal catalyst for HCHO decomposition at room temperature. However, the stability of this catalyst remains unexplored. In this study, Pt-TiO{sub 2} (Pt-P25) catalysts with and without adsorbed halogen ions (including F{sup −}, Cl{sup −}, Br{sup −}, and I{sup −}) were prepared through impregnation and ion modification. Pt-TiO{sub 2} samples with adsorbed halogen ions exhibited reduced catalytic activity for formaldehyde decomposition at room temperature compared with the Pt-TiO{sub 2} sample; the catalytic activity followed the order of F-Pt-P25, Cl-Pt-P25, Br-Pt-P25, and I-Pt-P25. Characterization results (including XRD, TEM, HRTEM, BET, XPS, and metal dispersion) showed that the adsorbed halogen ions can poison Pt nanoparticles (NPs), thereby reducing the HCHO oxidation activity of Pt-TiO{sub 2}. The poison mechanism is due to the strong adsorption of halogen ions on the surface of Pt NPs. The adsorbed ions form coordination bonds with surface Pt atoms by transferring surplus electrons into the unoccupied 5d orbit of the Pt atom, thereby inhibiting oxygen adsorption and activation of the Pt NP surface. Moreover, deactivation rate increases with increasing diameter of halogen ions. This study provides new insights into the fabrication of high-performance Pt-based catalysts for indoor air purification.

  14. Oxidative dechlorination of halogenated phenols catalyzed by two distinct enzymes: Horseradish peroxidase and dehaloperoxidase.

    Science.gov (United States)

    Szatkowski, Lukasz; Thompson, Matthew K; Kaminski, Rafal; Franzen, Stefan; Dybala-Defratyka, Agnieszka

    2011-01-01

    The mechanism of the dehalogenation step catalyzed by dehaloperoxidase (DHP) from Amphitrite ornata, an unusual heme-containing protein with a globin fold and peroxidase activity, has remarkable similarity with that of the classical heme peroxidase, horseradish peroxidase (HRP). Based on quantum mechanical/molecular mechanical (QM/MM) modeling and experimentally determined chlorine kinetic isotope effects, we have concluded that two sequential one electron oxidations of the halogenated phenol substrate leads to a cationic intermediate that strongly resembles a Meisenheimer intermediate - a commonly formed reactive complex during nucleophilic aromatic substitution reactions especially in the case of arenes carrying electron withdrawing groups.

  15. Ground-based observations of Halogen Oxides in the Antarctic Boundary Layer

    Science.gov (United States)

    Prados-Roman, Cristina; Gómez, Laura; Puentedura, Olga; Navarro-Comas, Mónica; Ochoa, Héctor; Yela, Margarita

    2017-04-01

    Being involved in ozone destruction cycles, the halogen oxides (containing Br, Cl or I) are relevant reactants not only in the stratosphere but also in the troposphere. In order to characterize the presence of halogen oxides in the Antarctic boundary layer (BL), two MAX-DOAS instruments developed by INTA were installed at two different Antarctic sites: Marambio (64° S) and Belgrano (78° S). Note that, although both stations sit on pristine and remote locations, the surroundings of each station is unique and so is the atmospheric chemistry. Here we present the results of the measurements of BrO and IO performed in the sunlit atmosphere of both stations during 2015. We will focus on the activation of reactive bromine, its sources and sinks and its vertical distribution in the troposphere. We will also address the differences found regarding the bromine content of the BL in the two Antarctic sites. Moreover, we will investigate the presence of IO in the Antarctic BL.

  16. Performance of the wet oxidation unit of the HPLC isotope ratio mass spectrometry system for halogenated compounds.

    Science.gov (United States)

    Gilevska, Tetyana; Gehre, Matthias; Richnow, Hans Hermann

    2014-08-05

    The performance of liquid chromatography-isotope ratio mass spectrometry (LC-IRMS) for polar halogenated compounds was evaluated. Oxidation capacity of the system was tested with halogenated acetic acids and halogenated aromatic compounds. Acetic acid (AA) was selected as a reference compound for complete oxidation and compared on the molar basis to the oxidation of other analytes. The isotope values were proofed with calibrated δ(13)C values obtained with an elemental analyzer (EA). Correct isotope values were obtained for mono- and dichlorinated, fluorinated, and tribrominated acetic acids and also for aniline, phenol, benzene, bromobenzene, chlorobenzene, 1,2-dichlorobenzene, 2,4,6-trichlorophenol, pentafluorophenol, and nitrobenzene. Incomplete oxidation of trichloroacetic acid (TCA) and trifluoroacetic acid (TFA) resulted in lower recovery compared to AA (37% and 24%, respectively) and in isotopic shift compared to values obtained with EA (TCA Δδ(13)C(EA/LC-IRMS) = 8.8‰, TFA Δδ(13)C(EA/LC-IRMS) = 6.0‰). Improvement of oxidation by longer reaction time in the reactor and increase in the concentration of sulfate radicals did not lead to complete combustion of TCA and TFA needed for δ(13)C analysis. To the best of our knowledge, this is the first time such highly chlorinated compounds were studied with the LC-IRMS system. This work provides information for method development of LC-IRMS methods for halogenated contaminants that are known as potential threats to public health and the environment.

  17. Halogen poisoning effect of Pt-TiO2 for formaldehyde catalytic oxidation performance at room temperature

    Science.gov (United States)

    Zhu, Xiaofeng; Cheng, Bei; Yu, Jiaguo; Ho, Wingkei

    2016-02-01

    Catalytic decomposition of formaldehyde (HCHO) at room temperature is an important method for HCHO removal. Pt-based catalysts are the optimal catalyst for HCHO decomposition at room temperature. However, the stability of this catalyst remains unexplored. In this study, Pt-TiO2 (Pt-P25) catalysts with and without adsorbed halogen ions (including F-, Cl-, Br-, and I-) were prepared through impregnation and ion modification. Pt-TiO2 samples with adsorbed halogen ions exhibited reduced catalytic activity for formaldehyde decomposition at room temperature compared with the Pt-TiO2 sample; the catalytic activity followed the order of F-Pt-P25, Cl-Pt-P25, Br-Pt-P25, and I-Pt-P25. Characterization results (including XRD, TEM, HRTEM, BET, XPS, and metal dispersion) showed that the adsorbed halogen ions can poison Pt nanoparticles (NPs), thereby reducing the HCHO oxidation activity of Pt-TiO2. The poison mechanism is due to the strong adsorption of halogen ions on the surface of Pt NPs. The adsorbed ions form coordination bonds with surface Pt atoms by transferring surplus electrons into the unoccupied 5d orbit of the Pt atom, thereby inhibiting oxygen adsorption and activation of the Pt NP surface. Moreover, deactivation rate increases with increasing diameter of halogen ions. This study provides new insights into the fabrication of high-performance Pt-based catalysts for indoor air purification.

  18. Oxidation of carbon tetrachloride, bromotrichloromethane, and carbon tetrabromide by rat liver microsomes to electrophilic halogens

    Energy Technology Data Exchange (ETDEWEB)

    Mico, B.A. (National Inst. of General Medical Sciences, Bethesda, MD); Branchflower, R.V.; Pohl, L.R.; Pudzianowski, A.T.; Loew, G.H.

    1982-01-11

    In order to determine whether CCl/sub 4/, CBrCl/sub 3/, CBr/sub 4/ or CHCl/sub 3/ undergo oxidative metabolism to electrophilic halogens by liver microsomes, they were incubated with liver microsomes from phenobarbital pretreated rats in the presence of NADPH and 2,6-dimethylphenol. The analysis of the reaction mixtures by capillary gas chromatography mass spectrometry revealed that 4-chloro-2,6-dimethylphenol was a metabolite of CCl/sub 4/ and CBrCl/sub 3/ whereas 4-bromo-2,6-dimethylphenol was a metabolite of CBr/sub 4/. The formation of the metabolites was significantly decreased when the reactions were conducted with heat denatured microsomes, in the absence of NADPH or under an atmosphere of N/sub 2/. These results indicate that the chlorines of CBrCl/sub 3/ and CCl/sub 4/ and the bromines of CBr/sub 4/ are oxidatively metabolized by rat liver microsomes to electrophilic and potentially toxic metabolites.

  19. Potent Methyl Oxidation of 5-Methyl-2′-deoxycytidine by Halogenated Quinoid Carcinogens and Hydrogen Peroxide via a Metal-independent Mechanism

    OpenAIRE

    Shao, Jie; Huang, Chun-Hua; Kalyanaraman, Balaraman; Zhu, Ben-Zhan

    2013-01-01

    Halogenated quinones are a class of carcinogenic intermediates and newly identified chlorination disinfection byproducts in drinking water. We found recently that the highly reactive and biologically important hydroxyl radical (•OH) can be produced by halogenated quinones and H2O2 independent of transition metal ions. However, it is not clear whether these quinoid carcinogens and H2O2 can oxidize the nucleoside 5-methyl-2′-deoxycytidine (5mdC) to its methyl oxidation prod...

  20. Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes

    KAUST Repository

    Baron, Marco

    2016-06-14

    Gold(I) dicarbene complexes [Au2(MeIm-Y-ImMe)2](PF6)2(Y=CH2(1), (CH2)2(2), (CH2)4(4), MeIm=1-methylimidazol-2-ylidene) react with iodine to give the mixed-valence complex [Au(MeIm-CH2-ImMe)2AuI2](PF6)2(1 aI) and the gold(III) complexes [Au2I4(MeIm-Y-ImMe)2](PF6)2(2 cIand 4 cI). Reaction of complexes 1 and 2 with an excess of ICl allows the isolation of the tetrachloro gold(III) complexes [Au2Cl4(MeIm-CH2-ImMe)2](PF6)2(1 cCl) and [Au2Cl4(MeIm-(CH2)2-ImMe)2](Cl)2(2 cCl-Cl) (as main product); remarkably in the case of complex 2, the X-ray molecular structure of the crystals also shows the presence of I-Au-Cl mixed-sphere coordination. The same type of coordination has been observed in the main product of the reaction of complexes 3 or 4 with ICl. The study of the reactivity towards the oxidative addition of halogens to a large series of dinuclear bis(dicarbene) gold(I) complexes has been extended and reviewed. The complexes react with Cl2, Br2and I2to give the successive formation of the mixed-valence gold(I)/gold(III) n aXand gold(III) n cX(excluding compound 1 cI) complexes. However, complex 3 affords with Cl2and Br2the gold(II) complex 3 bX[Au2X2(MeIm-(CH2)3-ImMe)2](PF6)2(X=Cl, Br), which is the predominant species over compound 3 cXeven in the presence of free halogen. The observed different relative stabilities of the oxidised complexes of compounds 1 and 3 have also been confirmed by DFT calculations. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Impacts of halogen additions on mercury oxidation, in a slipstream selective catalyst reduction (SCR), reactor when burning sub-bituminous coal.

    Science.gov (United States)

    Cao, Yan; Gao, Zhengyang; Zhu, Jiashun; Wang, Quanhai; Huang, Yaji; Chiu, Chengchung; Parker, Bruce; Chu, Paul; Pant, Wei-Ping

    2008-01-01

    This paper presents a comparison of impacts of halogen species on the elemental mercury (Hg(0)) oxidation in a real coal-derived flue gas atmosphere. It is reported there is a higher percentage of Hg(0) in the flue gas when burning sub-bituminous coal (herein Powder River Basin (PRB) coal) and lignite, even with the use of selective catalytic reduction (SCR). The higher Hg(0)concentration in the flue gas makes it difficult to use the wet-FGD process for the mercury emission control in coal-fired utility boilers. Investigation of enhanced Hg(0) oxidation by addition of hydrogen halogens (HF, HCl, HBr, and HI) was conducted in a slipstream reactor with and without SCR catalysts when burning PRB coal. Two commercial SCR catalysts were evaluated. SCR catalyst no. 1 showed higher efficiencies of both NO reduction and Hg(0) oxidation than those of SCR catalyst no. 2. NH3 addition seemed to inhibit the Hg(0) oxidation, which indicated competitive processes between NH3 reduction and Hg(0) oxidation on the surface of SCR catalysts. The hydrogen halogens, in the order of impact on Hg(0) oxidation, were HBr, HI, and HCl or HF. Addition of HBr at approximately 3 ppm could achieve 80% Hg(0) oxidation. Addition of HI at approximately 5 ppm could achieve 40% Hg(0) oxidation. In comparison to the empty reactor, 40% Hg(0) oxidation could be achieved when HCl addition was up to 300 ppm. The enhanced Hg(0) oxidation by addition of HBr and HI seemed not to be correlated to the catalytic effects by both evaluated SCR catalysts. The effectiveness of conversion of hydrogen halogens to halogen molecules or interhalogens seemed to be attributed to their impacts on Hg(0) oxidation.

  2. The halogen effect for Ni-base alloys - A new method for increasing the oxidation protection at high temperatures

    Science.gov (United States)

    Zschau, Hans-Eberhard; Renusch, Daniel; Masset, Patrick J.; Schütze, Michael

    2009-05-01

    A new method for oxidation protection of Ni-base alloys is presented. The method is based on the halogen effect. Thermodynamic calculations show the preferred formation of gaseous Al-halogenides within a certain region of fluorine partial pressures. Ion implantation has been chosen for fluorine treatment. The implantation parameters are defined by using the T-DYN simulation software. Based on these results fluorine implantations of the Ni-base alloy IN 738 are performed to meet the required fluorine content near the surface. The fluorine depth profiles are analyzed by using the PIGE-technique. After oxidation at 1050 °C a dense protecting external alumina scale is formed on the surface.

  3. Oxidative addition of halogens to homoleptic perfluoromethyl or perfluorophenyl derivatives of platinum(II): a comparative study.

    Science.gov (United States)

    Menjón, Babil; Martínez-Salvador, Sonia; Gómez-Saso, Miguel A; Forniés, Juan; Falvello, Larry R; Martín, Antonio; Tsipis, Athanassios

    2009-06-22

    Chlorocarbon solvents (solv=CH(2)Cl(2), CHCl(3)) are suggested to play an active role in the oxidative addition of halogens, X(2) (X=Cl, Br, I), to homoleptic d(8) perfluoromethyl and -phenyl platinum(II) species [Pt(R(F))(4)](2-) (R(F)=CF(3), C(6)F(5)). The perfluoromethyl group, CF(3), has been found to be considerably less prone to undergo reductive elimination processes, and is, therefore, more suitable for stabilizing organoplatinum(IV) derivatives (see scheme).The equilibrium geometries of the homoleptic perfluorinated organoplatinate(II) anions [Pt(CF(3))(4)](2-) and [Pt(C(6)F(5))(4)](2-) have been computed at the B3P86/LANL2DZ level of theory. Remarkably good agreement with the experimentally determined structures has been obtained by X-ray diffraction methods. The reactivity of [NBu(4)](2)[Pt(CF(3))(4)] (1) towards halogens (Cl(2), Br(2), and I(2)) has been investigated by using a combined experimental and theoretical approach. The perfluoromethyl derivative 1 has been found to undergo clean oxidative addition of the three halogens under investigation, giving rise to [NBu(4)](2)[trans-Pt(CF(3))(4)X(2)] (X=Cl (7), Br (10), I (13)) in a quantitative and stereoselective way. In the low-temperature reaction of the perfluorophenyl derivative [NBu(4)](2)[Pt(C(6)F(5))(4)] (3) with Cl(2) or Br(2), the corresponding oxidative-addition products [NBu(4)](2)[trans-Pt(C(6)F(5))(4)X(2)] (X=Cl (14), Br (15)) can also be obtained. In the case in which X=Br and working in CHCl(3) at -55 degrees C, it has been possible to detect the formation of an intermediate species to which we assign the formula [trans-Pt(C(6)F(5))(4)Br(ClCHCl(2))](-) (16). The solvento complex 16 is thermally unstable and prone to undergo reductive elimination of C(6)F(5)--C(6)F(5). In the presence of PhCN, complex [NBu(4)][trans-Pt(C(6)F(5))(4)Br(NCPh)] (17) was isolated and structurally characterized. The reaction of 3 with I(2) gave no organoplatinum(IV) compound. Our comparative study reveals that

  4. OH and HO2 chemistry during NAMBLEX: roles of oxygenates, halogen oxides and heterogeneous uptake

    Directory of Open Access Journals (Sweden)

    R. Sommariva

    2006-01-01

    Full Text Available Several zero-dimensional box-models with different levels of chemical complexity, based on the Master Chemical Mechanism (MCM, have been used to study the chemistry of OH and HO2 in a coastal environment in the Northern Hemisphere. The models were constrained to and compared with measurements made during the NAMBLEX campaign (Mace Head, Ireland in summer 2002. The base models, which were constrained to measured CO, CH4 and NMHCs, were able to reproduce [OH] within 25%, but overestimated [HO2] by about a factor of 2. Agreement was improved when the models were constrained to oxygenated compounds (acetaldehyde, methanol and acetone, highlighting their importance for the radical budget. When the models were constrained to measured halogen monoxides (IO, BrO and used a more detailed, measurements-based, treatment to describe the heterogeneous uptake, modelled [OH] increased by up to 15% and [HO2] decreased by up to 30%. The actual impact of halogen monoxides on the modelled concentrations of HOx was dependant on the uptake coefficients used for HOI, HOBr and HO2. Better agreement, within the combined uncertainties of the measurements and of the model, was achieved when using high uptake coefficients for HO2 and HOI (γHO2=1, γHOI=0.6. A rate of production and destruction analysis of the models allowed a detailed study of OH and HO2 chemistry under the conditions encountered during NAMBLEX, showing the importance of oxygenates and of XO (where X=I, Br as co-reactants for OH and HO2 and of HOX photolysis as a source for OH.

  5. Potent methyl oxidation of 5-methyl-2'-deoxycytidine by halogenated quinoid carcinogens and hydrogen peroxide via a metal-independent mechanism.

    Science.gov (United States)

    Shao, Jie; Huang, Chun-Hua; Kalyanaraman, Balaraman; Zhu, Ben-Zhan

    2013-07-01

    Halogenated quinones are a class of carcinogenic intermediates and are newly identified chlorination disinfection by-products in drinking water. We found recently that the highly reactive and biologically important hydroxyl radical ((•)OH) can be produced by halogenated quinones and H2O2 independent of transition metal ions. However, it is not clear whether these quinoid carcinogens and H2O2 can oxidize the nucleoside 5-methyl-2'-deoxycytidine (5mdC) to its methyl oxidation products and, if so, what the underlying molecular mechanism is. Here we show that three methyl oxidation products, 5-(hydroperoxymethyl)-, 5-(hydroxymethyl)-, and 5-formyl-2'-deoxycytidine, could be produced when 5mdC was treated with tetrachloro-1,4-benzoquinone (TCBQ) and H2O2. The formation of the oxidation products was markedly inhibited by typical (•)OH scavengers and under anaerobic conditions. Analogous effects were observed with other halogenated quinones and the classic Fenton system. Based on these data, we propose that the oxidation of 5mdC by TCBQ/H2O2 might be through the following mechanism: (•)OH produced by TCBQ/H2O2 may first abstract hydrogen from the methyl group of 5mdC, leading to the formation of 5-(2'-deoxycytidylyl)methyl radical, which may combine with O2 to form the peroxyl radical. The unstable peroxyl radical transforms into the corresponding hydroperoxide 5-(hydroperoxymethyl)-2'-deoxycytidine, which reacts with TCBQ and results in the formation of 5-(hydroxymethyl)-2'-deoxycytidine and 5-formyl-2'-deoxycytidine. This is the first report that halogenated quinoid carcinogens and H2O2 can induce potent methyl oxidation of 5mdC via a metal-independent mechanism, which may partly explain their potential carcinogenicity. Copyright © 2013 Elsevier Inc. All rights reserved.

  6. Halogenation of cobalt dicarbollide

    Science.gov (United States)

    Hurlburt, Paul K.; Abney, Kent D.; Kinkead, Scott A.

    1997-01-01

    A method for selectively adding chlorine, bromine, or iodine to cobalt dicarbollide anions by means of electrophilic substitution reactions. Halogens are added only to the B10 and B10' positions of the anion. The process involves use of hypohalous acid or N-halosuccinimide or gaseous chlorine in the presence of iron.

  7. Cytotoxicity of halogenated graphenes

    Science.gov (United States)

    Teo, Wei Zhe; Khim Chng, Elaine Lay; Sofer, Zdeněk; Pumera, Martin

    2013-12-01

    Graphene and its family of derivatives possess unique and remarkable physicochemical properties which make them valuable materials for applications in many areas like electronics, energy storage and biomedicine. In response to the possibility of its large-scale manufacturing as commercial products in the future, an investigation was conducted to determine the cytotoxicity of one particular family of graphene derivatives, the halogenated graphenes, for the first time. Halogenated graphenes were prepared through thermal exfoliation of graphite oxide in gaseous chlorine, bromine or iodine atmospheres to yield chlorine- (TRGO-Cl), bromine- (TRGO-Br) and iodine-doped graphene (TRGO-I) respectively. 24 h exposure of human lung carcinoma epithelial cells (A549) to the three halogenated graphenes and subsequent cell viability assessments using methylthiazolyldiphenyl-tetrazolium bromide (MTT) and water-soluble tetrazolium salt (WST-8) assays revealed that all the halogenated graphenes examined are rather cytotoxic at the concentrations tested (3.125 μg mL-1 to 200 μg mL-1) and the effects are dose-dependent, with TRGO-Cl reducing the cell viability to as low as 25.7% at the maximum concentration of 200 μg mL-1. Their levels of cytotoxicity can be arranged in the order of TRGO-Cl > TRGO-Br > TRGO-I, and it is suggested that the amount of halogen present in the graphene material is the determining factor for the observed trend. Control experiments were carried out to test for possible nanomaterial-induced interference as a consequence of reaction between the halogenated graphenes and the viability markers (MTT/WST-8 reagent) or binding of the formazan products under cell-free conditions. The data obtained eliminate the probability of significant influence by these interferents as the change in the normalized percentage of formazan formed is relatively small and thorough washings were performed prior to the viability assessments to reduce the amount of halogenated

  8. Selective hydrogenation of halogenated arenes using porous manganese oxide (OMS-2) and platinum supported OMS-2 catalysts.

    Science.gov (United States)

    McManus, Iain J; Daly, Helen; Manyar, Haresh G; Taylor, S F Rebecca; Thompson, Jillian M; Hardacre, Christopher

    2016-07-04

    Porous manganese oxide (OMS-2) and platinum supported on OMS-2 catalysts have been shown to facilitate the hydrogenation of the nitro group in chloronitrobenzene to give chloroaniline with no dehalogenation. Complete conversion was obtained within 2 h at 25 °C and, although the rate of reaction increased with increasing temperature up to 100 °C, the selectivity to chloroaniline remained at 99.0%. Use of Pd/OMS-2 or Pt/Al2O3 resulted in significant dechlorination even at 25 °C and 2 bar hydrogen pressure giving a selectivity to chloroaniline of 34.5% and 77.8%, respectively, at complete conversion. This demonstrates the potential of using platinum group metal free catalysts for the selective hydrogenation of halogenated aromatics. Two pathways were observed for the analogous nitrobenzene hydrogenation depending on the catalyst used. The hydrogenation of nitrobenzene was found to follow a direct pathway to aniline and nitrosobenzene over Pd/OMS-2 in contrast to the OMS and Pt/OMS-2 catalysts which resulted in formation of nitrosobenzene, azoxybenzene and azobenzene/hydrazobenzene intermediates before complete conversion to aniline. These results indicate that for Pt/OMS-2 the hydrogenation proceeds predominantly over the support with the metal acting to dissociate hydrogen. In the case of Pd/OMS-2 both the hydrogenation and hydrogen adsorption occur on the metal sites.

  9. A single-source precursor route to anisotropic halogen-doped zinc oxide particles as a promising candidate for new transparent conducting oxide materials

    Directory of Open Access Journals (Sweden)

    Daniela Lehr

    2015-11-01

    Full Text Available Numerous applications in optoelectronics require electrically conducting materials with high optical transparency over the entire visible light range. A solid solution of indium oxide and substantial amounts of tin oxide for electronic doping (ITO is currently the most prominent example for the class of so-called TCOs (transparent conducting oxides. Due to the limited, natural occurrence of indium and its steadily increasing price, it is highly desired to identify materials alternatives containing highly abundant chemical elements. The doping of other metal oxides (e.g., zinc oxide, ZnO is a promising approach, but two problems can be identified. Phase separation might occur at the required high concentration of the doping element, and for successful electronic modification it is mandatory that the introduced heteroelement occupies a defined position in the lattice of the host material. In the case of ZnO, most attention has been attributed so far to n-doping via substitution of Zn2+ by other metals (e.g., Al3+. Here, we present first steps towards n-doped ZnO-based TCO materials via substitution in the anion lattice (O2− versus halogenides. A special approach is presented, using novel single-source precursors containing a potential excerpt of the target lattice 'HalZn·Zn3O3' preorganized on the molecular scale (Hal = I, Br, Cl. We report about the synthesis of the precursors, their transformation into halogene-containing ZnO materials, and finally structural, optical and electronic properties are investigated using a combination of techniques including FT-Raman, low-T photoluminescence, impedance and THz spectroscopies.

  10. 气相光催化氧化降解卤代烃的研究%Gas-Phase Photocatalytic Oxidation of Halogenated Hydrocarbons

    Institute of Scientific and Technical Information of China (English)

    李功虎; 安纬珠

    2000-01-01

      本文介绍了气相光催化作用的基本原理,从光催化剂的改性技术、反应动力学和反应机理三个方面综述了近年来气相光催化氧化降解卤代烃的研究。%  This paper introduced the photocatalyzing principle of semiconductor in gas phase,and summarized the recent studies on the gas-phase photocatalytic oxidation of halogenated hydrocarbons,including modification of semiconductor,reaction kinetics and the degradation mechanism of TCE.

  11. Inorganic Halogen Oxidizer Research

    Science.gov (United States)

    1981-04-21

    et ad .1J. Torg . Nucl Chem., Suppiement (1976) U.S. PATENT DOCUMENTS Primary Examtner-Edvxard A. Miller 3,213,6i,) i0/1965 Gr.gger ct u...1.2- r -1,6F 12 -2.0 0.5 0.6 0.7 0.8 0.9 1.0 F2 3 RI/RD81-140 .1-19 /J-20 APPENDIX KC Das Kraftfeld von SF, The Force Field of SF4 Wolfgang Sawodny

  12. Inorganic Halogen Oxidizer Research

    Science.gov (United States)

    1979-02-16

    CIO042C12, BrCF2CF2CF2BT, and CF3CFBrCF2CIO4. 5301 1-57-7. CFSCFBrCF2CIO4. 38126-26-0: i-C3FII(C104)2. Fromthee vrios Rrr-C20istuies thepaternemeged 53078...of fluorine favoring [il J. F. LixtimAN, J Chem. Educ . 48, 189 (1971). highly polar bonds and by tho striot validity of [12] A. RAY, J. Indian Chem

  13. Inorganic Halogen Oxidizer Research.

    Science.gov (United States)

    1980-03-17

    0 4.. *~~ 0 0 4 S a, 0 .- F_ I . 0 - n V t o C N 0 .0 C; 0 . 𔃺~~ V Oh Ix ca . VW W i-si I. 0 (0 UU Clo~~~*N 0 ( l 00 *Lf) 0 j ,) Z, U__ - (00 C6 0...Solubility products fora metathesis in iii [41: CS NiF + 2NF SbF F 2 CsShF 4 +(N i 2 6 𔃾 6 _ 780 6 (N 4)2 ; 6 R ( R8-1 3 H-owever, in cases where the

  14. Inorganic Halogen Oxidizer Research

    Science.gov (United States)

    1975-02-26

    Fessenden and R. H. Schüler, J. Chem. Phys., 43, 2704 (1965). (II) J. Maruani, J.A.R. Coope, and C A. McDowell, Mol. Phys., 18, 105 (1970). (12) J...14) W. E. Tolberg, private eommuncation. (15) R. W. Fessenden , J. Chem. Phys., 37, 747 (1902). (l’\\) J.A.R. Coope, Chem. Phys. Letts., 3, 589...W. Fessenden and 11. II. Schüler, J. Chem. Phys., 45, 1845 (i960). (20) F. G. Herring, J. II. Hwang and W. C. Lin, J. Phys. Chem.» 71, 2080 (1907

  15. Mercury and halogens in coal: Chapter 2

    Science.gov (United States)

    Kolker, Allan; Quick, Jeffrey C.; Granite, Evan J.; Pennline, Henry W.; Senior, Constance L.

    2014-01-01

    Apart from mercury itself, coal rank and halogen content are among the most important factors inherent in coal that determine the proportion of mercury captured by conventional controls during coal combustion. This chapter reviews how mercury in coal occurs, gives available concentration data for mercury in U.S. and international commercial coals, and provides an overview of the natural variation in halogens that influence mercury capture. Three databases, the U.S. Geological Survey coal quality (USGS COALQUAL) database for in-ground coals, and the 1999 and 2010 U.S. Environmental Protection Agency (EPA) Information Collection Request (ICR) databases for coals delivered to power stations, provide extensive results for mercury and other parameters that are compared in this chapter. In addition to the United States, detailed characterization of mercury is available on a nationwide basis for China, whose mean values in recent compilations are very similar to the United States in-ground mean of 0.17 ppm mercury. Available data for the next five largest producers (India, Australia, South Africa, the Russian Federation, and Indonesia) are more limited and with the possible exceptions of Australia and the Russian Federation, do not allow nationwide means for mercury in coal to be calculated. Chlorine in coal varies as a function of rank and correspondingly, depth of burial. As discussed elsewhere in this volume, on a proportional basis, bromine is more effective than chlorine in promoting mercury oxidation in flue gas and capture by conventional controls. The ratio of bromine to chlorine in coal is indicative of the proportion of halogens present in formation waters within a coal basin. This ratio is relatively constant except in coals that have interacted with deep-basin brines that have reached halite saturation, enriching residual fluids in bromine. Results presented here help optimize mercury capture by conventional controls and provide a starting point for

  16. Halogenation of microcapsule walls

    Science.gov (United States)

    Davis, T. R.; Schaab, C. K.; Scott, J. C.

    1972-01-01

    Procedure for halogenation of confining walls of both gelatin and gelatin-phenolic resin capsules is similar to that used for microencapsulation. Ten percent halogen content renders capsule wall nonburning; any higher content enhances flame-retardant properties of selected internal phase material. Halogenation decreases permeability of wall material to encapsulated materials.

  17. Fabrication and in vitro release behavior of a novel antibacterial coating containing halogenated furanone-loaded poly(L-lactic acid nanoparticles on microarc-oxidized titanium

    Directory of Open Access Journals (Sweden)

    Cheng YC

    2012-11-01

    Full Text Available Yicheng Cheng,1 Jiang Wu,1 Bo Gao,1 Xianghui Zhao,2 Junyan Yao,3 Shenglin Mei,1 Liang Zhang,4 Huifang Ren1 1Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, 2Institute of Neuroscience, School of Basic Medicine, Fourth Military Medical University, 3Department of Applied Chemistry, School of Science, Northwestern Polytechnical University, 4Department of Orthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, ChinaYicheng Cheng and Jiang Wu contributed equally to this workBackground: Dental implants have become increasingly common for the management of missing teeth. However, peri-implant infection remains a problem, is usually difficult to treat, and may lead eventually to dental implant failure. The aim of this study was to fabricate a novel antibacterial coating containing a halogenated furanone compound, ie, (Z--4-bromo-5-(bromomethylene-2(5H-furanone (BBF-loaded poly(L-lactic acid (PLLA nanoparticles on microarc-oxidized titanium and to evaluate its release behavior in vitro.Methods: BBF-loaded PLLA nanoparticles were prepared using the emulsion solvent-evaporation method, and the antibacterial coating was fabricated by cross-linking BBF-loaded PLLA nanoparticles with gelatin on microarc-oxidized titanium.Results: The BBF-loaded PLLA nanoparticles had a small particle size (408 ± 14 nm, a low polydispersity index (0.140 ± 0.008, a high encapsulation efficiency (72.44% ± 1.27%, and a fine spherical shape with a smooth surface. The morphology of the fabricated antibacterial coating showed that the BBF-loaded PLLA nanoparticles were well distributed in the pores of the microarc oxidation coating, and were cross-linked with each other and the wall pores by gelatin. The release study indicated that the antibacterial coating could achieve sustained release of BBF for 60 days, with a slight initial burst release during the first 4 hours.Conclusion: The novel antibacterial coating

  18. Halogen Chemistry on Catalytic Surfaces.

    Science.gov (United States)

    Moser, Maximilian; Pérez-Ramírez, Javier

    2016-01-01

    Halogens are key building blocks for the manufacture of high-value products such as chemicals, plastics, and pharmaceuticals. The catalytic oxidation of HCl and HBr is an attractive route to recover chlorine and bromine in order to ensure the sustainability of the production processes. Very few materials withstand the high corrosiveness and the strong exothermicity of the reactions and among them RuO2 and CeO2-based catalysts have been successfully applied in HCl oxidation. The search for efficient systems for HBr oxidation was initiated by extrapolating the results of HCl oxidation based on the chemical similarity of these reactions. Interestingly, despite its inactivity in HCl oxidation, TiO2 was found to be an outstanding HBr oxidation catalyst, which highlighted that the latter reaction is more complex than previously assumed. Herein, we discuss the results of recent comparative studies of HCl and HBr oxidation on both rutile-type (RuO2, IrO2, and TiO2) and ceria-based catalysts using a combination of advanced experimental and theoretical methods to provide deeper molecular-level understanding of the reactions. This knowledge aids the design of the next-generation catalysts for halogen recycling.

  19. [Use of coulometric titration for elucidating the mechanism of the oxidation of 6-APA alkaline breakdown products by halogens].

    Science.gov (United States)

    Kharlamov, V T; Inkin, A A; Ermolina, G E

    1975-02-01

    Penaldinic acid and penicillamine were formed on alkali decomposition (1 N NaOH) of 6-APA for 20 minutes at room temperature, penicillamine being completely oxidized to disulphide by the air oxygen. Coulometric titration of the alkali decomposition products showed that generated chlorine in 0.5 N HCl solution or bromine in a week acid solution of KBr oxidized them with participation of 7 electrones. Generated iodine did not practically oxidize the 6-APA decomposition products during the coulometric titration.

  20. Measurement and meaning of oxidatively modified DNA lesions in urine

    DEFF Research Database (Denmark)

    Cooke, Marcus S; Olinski, Ryszard; Loft, Steffen

    2008-01-01

    . METHODS: We have reviewed the literature to establish the status quo with regard to the methods and meaning of measuring DNA oxidation products in urine. RESULTS: Most of the literature focus upon 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), and whereas a large number of these reports concern clinical......G levels and is not sufficiently specific for accurate quantification. With increasing numbers of lesions being studied, it is vital that these fundamental issues are addressed. We report the formation of the European Standards Committee on Urinary (DNA) Lesion Analysis whose primary goal is to achieve...

  1. Organic halogens in spruce forest throughfall

    DEFF Research Database (Denmark)

    Öberg, G.; Johansen, C.; Grøn, C.

    1998-01-01

    . No relationship between the position of the collectors and the forest edge or dominating wind-direction was found, suggesting that dry deposition was not a major source. The concentration of organic halogens was related to that of organic carbon and decreased from the tree-trunk and outwards. In addition......Deposition of dissolved organic halogens by throughfall was determined in a small spruce forest site in Denmark (56 degrees 28'N, 8 degrees 24'E). The mean annual deposition of dissolved organic halogens was 377 g ha(-1)yr(-1), and larger than the general deposition by precipitation......, the concentrations were higher during the growing season than during the dormant season. This indicates that the major part of the organic carbon and organic halogens in spruce forest throughfall originates from canopy leachates or other internal sources. (C) 1998 Elsevier Science Ltd....

  2. The Halogen Occultation Experiment

    Science.gov (United States)

    Russell, James M., III; Gordley, Larry L.; Park, Jae H.; Drayson, S. R.; Hesketh, W. D.; Cicerone, Ralph J.; Tuck, Adrian F.; Frederick, John E.; Harries, John E.; Crutzen, Paul J.

    1993-01-01

    The Halogen Occultation Experiment (HALOE) uses solar occultation to measure vertical profiles of O3, HCl, HF, CH4, H2O, NO, NO2, aerosol extinction, and temperature versus pressure with an instantaneous vertical field of view of 1.6 km at the earth limb. Latitudinal coverage is from 80 deg S to 80 deg N over the course of 1 year and includes extensive observations of the Antarctic region during spring. The altitude range of the measurements extends from about 15 km to about 60-130 km, depending on channel. Experiment operations have been essentially flawless, and all performance criteria either meet or exceed specifications. Internal data consistency checks, comparisons with correlative measurements, and qualitative comparisons with 1985 atmospheric trace molecule spectroscopy (ATMOS) results are in good agreement. Examples of pressure versus latitude cross sections and a global orthographic projection for the September 21 to October 15, 1992, period show the utility of CH4, HF, and H2O as tracers, the occurrence of dehydration in the Antarctic lower stratosphere, the presence of the water vapor hygropause in the tropics, evidence of Antarctic air in the tropics, the influence of Hadley tropical upwelling, and the first global distribution of HCl, HF, and NO throughout the stratosphere. Nitric oxide measurements extend through the lower thermosphere.

  3. Nitric oxide production inhibition and anti-mycobacterial activity of extracts and halogenated sesquiterpenes from the Brazilian red alga laurencia dendroidea J. Agardh

    Directory of Open Access Journals (Sweden)

    Thatiana Lopes Biá Ventura

    2015-01-01

    Full Text Available Background: Red algae of the genus Laurencia J. V. Lamouroux are a rich source of secondary metabolites with important pharmacological activities such as anti-tumoral, anti-inflammatory, anti-fungal, anti-viral, anti-leishmanial, anti-helminthic, anti-malarial, anti-trypanosomal, anti-microbial as well as anti-bacterial against Mycobacterium tuberculosis. Objective: In the present study, we evaluated the inhibition of nitric oxide (NO and tumor necrosis factor-a production and the anti-mycobacterial activity of crude extracts from the red Alga Laurencia dendroidea (from the South-Eastern coast of Brazil. Halogenated sesquiterpenes elatol (1, obtusol (2 and cartilagineol (3, previously isolated from this Alga by our group, were also studied. Materials and Methods: The lipopolysaccharide-activated macrophage cells (RAW 264.7 were used as inflammation model. Cytotoxic effect was determined using a commercial  lactate dehydrogenase (LDH kit and 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide assay. The growing Mycobacterium inhibition was verified against Mycobacterium bovis Bacillus Calmette-Guιrin and M. tuberculosis H 37 Rv strains. Results: The crude extract from Alga collected at Angra dos Reis, RJ, Brazil, was the most active inhibitor of both mycobacterial growth (half maximal inhibitory concentration [IC 50 ] 8.7 ± 1.4 mg/mL and NO production by activated macrophages (IC 50 5.3 ± 1.3 mg/mL. The assays with isolated compounds revealed the anti-mycobacterial activity of obtusol (2, whereas (--elatol (1 inhibited the release of inflammatory mediators, especially NO. To our knowledge, this is the first report describing an anti-mycobacterial effect of L. dendroidea extract and demonstrating the association of this activity with obtusol (2. Conclusion: The described effects of active compounds from L. dendroidea are promising for the control of inflammation in infectious diseases and specifically, against mycobacterial

  4. Halogenated fatty acids

    DEFF Research Database (Denmark)

    Mu, Huiling; Sundin, Peter; Wesén, Clas

    1997-01-01

    Halogenated fatty acids are the major contributors to organohalogen compounds in lipids of marine mammals, fish, and bivalves. For the initial characterization of these recently noticed compounds, a determination of the halogen concentration has usually been combined with some lipid isolation...... and separation method. This review covers separation by solid phase chromatography, gel permeation chromatography, and liquid-liquid extraction, followed by halogen determination. All studies performed according to this outline have indicated that the major organohalogen compounds are chlorinated fatty acids...... bound in different lipids. For the detection and identification of individual, halogenated fatty acid methyl esters (FAMEs) liberated from the lipids, gas chromatography (GC) has been employed together with detection methods such as electron capture detection, electrolytic conductivity detection (ELCD...

  5. Halogens in the atmosphere

    Science.gov (United States)

    Cicerone, R. J.

    1981-01-01

    Atmospheric halogen measurement data are presented for: (1) inorganic and organic gaseous compounds of chlorine, fluorine, bromine and iodine; and (2) chloride, fluoride, bromide and iodine in particulate form and in precipitation. The roles that these data and other, unavailable data play in the determination of the global cycles of the halogens are discussed. It is found that the speciation of the halogen gases in the troposphere is uncertain, with the only inorganic species detected by species-specific methods being HC1 and SF6. It is shown that heterogeneous reactions, both gas-to-particle and particle-to-gas processes, precipitation removal, and sea-salt aerosol generation and fractionation processes, need quantitative investigation to allow progress in estimating halogen sources and sinks. Where practical, quantitative comparisons are made between measured and predicted concentrations.

  6. Halogens in the atmosphere

    Science.gov (United States)

    Cicerone, R. J.

    1981-01-01

    Atmospheric halogen measurement data are presented for: (1) inorganic and organic gaseous compounds of chlorine, fluorine, bromine and iodine; and (2) chloride, fluoride, bromide and iodine in particulate form and in precipitation. The roles that these data and other, unavailable data play in the determination of the global cycles of the halogens are discussed. It is found that the speciation of the halogen gases in the troposphere is uncertain, with the only inorganic species detected by species-specific methods being HC1 and SF6. It is shown that heterogeneous reactions, both gas-to-particle and particle-to-gas processes, precipitation removal, and sea-salt aerosol generation and fractionation processes, need quantitative investigation to allow progress in estimating halogen sources and sinks. Where practical, quantitative comparisons are made between measured and predicted concentrations.

  7. Halogens in the troposphere.

    Science.gov (United States)

    Finlayson-Pitts, Barbara J

    2010-02-01

    Although inorganic halogen gases are believed to play key roles in the chemistry of the lower atmosphere, many of them have not yet been detected or measured in ambient air. This article describes some of the current techniques and future needs for inorganic halogens in air. (To listen to a podcast about this feature, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html.).

  8. Metal and H2O2 free aerobic oxidative aromatic halogenation with [RNH3(+)] [NO3(-)]/HX and [BMIM(SO3H)][NO3)x(X)y] (X = Br, Cl) as multifunctional ionic liquids.

    Science.gov (United States)

    Prebil, Rok; Laali, Kenneth K; Stavber, Stojan

    2013-05-03

    Novel multifunctional ionic liquids (ILs) are generated by addition of HBr or HCl to alkylammonium nitrates ([RNH3(+)] [NO3(-)]) and to 3-methyl-1-(butyl-4-sulfonyl)imidazolium nitrate ([BMIM(SO3H)][NO3]). The resulting [RNH3(+)] [NO3(-)]/HX and mono (3-methyl-1-(butyl-4-sulfonyl)imidazolium) monohalogenide mononitrate ([BMIM(SO3H)][NO3)x(X)y] (X = Br, Cl)) systems act as solvent and promoter for aerobic oxidative halogenation of arenes under mild conditions in high yields that can be repeated over several cycles.

  9. Occurrence of halogenated alkaloids.

    Science.gov (United States)

    Gribble, Gordon W

    2012-01-01

    Once considered to be isolation artifacts or chemical "mistakes" of nature, the number of naturally occurring organohalogen compounds has grown from a dozen in 1954 to >5000 today. Of these, at least 25% are halogenated alkaloids. This is not surprising since nitrogen-containing pyrroles, indoles, carbolines, tryptamines, tyrosines, and tyramines are excellent platforms for biohalogenation, particularly in the marine environment where both chloride and bromide are plentiful for biooxidation and subsequent incorporation into these electron-rich substrates. This review presents the occurrence of all halogenated alkaloids, with the exception of marine bromotyrosines where coverage begins where it left off in volume 61 of The Alkaloids. Whereas the biological activity of these extraordinary compounds is briefly cited for some examples, a future volume of The Alkaloids will present full coverage of this topic and will also include selected syntheses of halogenated alkaloids. Natural organohalogens of all types, especially marine and terrestrial halogenated alkaloids, comprise a rapidly expanding class of natural products, in many cases expressing powerful biological activity. This enormous proliferation has several origins: (1) a revitalization of natural product research in a search for new drugs, (2) improved compound characterization methods (multidimensional NMR, high-resolution mass spectrometry), (3) specific enzyme-based and other biological assays, (4) sophisticated collection methods (SCUBA and remote submersibles for deep ocean marine collections), (5) new separation and purification techniques (HPLC and countercurrent separation), (6) a greater appreciation of traditional folk medicine and ethobotany, and (7) marine bacteria and fungi as novel sources of natural products. Halogenated alkaloids are truly omnipresent in the environment. Indeed, one compound, Q1 (234), is ubiquitous in the marine food web and is found in the Inuit from their diet of whale

  10. A MCM modeling study of the effects of nitryl chloride on oxidant budgets, ozone production, VOC lifetimes, and halogen recycling in polluted regions

    Science.gov (United States)

    Riedel, T. P.; Thornton, J. A.; Wolfe, G. M.; Gilman, J. B.; Kuster, W. C.; De Gouw, J. A.; Bon, D.; Vlasenko, A. L.; Li, S.; Williams, E. J.; Lerner, B. M.; Veres, P. R.; Roberts, J. M.

    2012-12-01

    Nitryl chloride (ClNO2) is produced at night by reactions of dinitrogen pentoxide (N2O5) on chloride containing particles. Nitryl chloride is photolyzed during the day to liberate highly reactive chlorine atoms. This chemistry takes place primarily in urban environments where the concentrations of N2O5 precursors (NOx and ozone) are high, though it can likely occur in remote regions at lower intensity. Recent field measurements have illustrated the potential importance of ClNO2 as a chlorine atom source and a NOx reservoir. However, the fate of these chlorine atoms and the overall impact of ClNO2 remain unclear. To this end we have incorporated ClNO2 production, photolysis, and subsequent Cl-atom reactions into an existing Master Chemical Mechanism (MCM version 3.2) based model framework. Cl-atom reactions with alkenes and alcohols not presently part of the MCM have also been added. Using observational constraints from the CalNex 2010 field study, we assess the dominant reactive sinks and sources of chlorine atoms over the course of a model day. Relative to model runs excluding ClNO2 formation, the presence of ClNO2 produces marked changes on a variety of species important to tropospheric chemistry and air quality (e.g. O3, RO2, OH, HO2, ClOx). For example a 50% yield of ClNO2 (max ClNO2 of 1.5 ppb) from nighttime N2O5 reactions leads to a ~10% enhancement in integrated ozone production. VOC and NOx lifetimes are shorter due primarily to enhanced OH from propagation of RO2 produced by Cl-atom chemistry under high NOx. The impact of ClNO2 on daytime halogen atom recycling is substantial, with order of magnitude higher daytime Cl2 production predicted with ClNO2 chemistry than without. In fact, incorporation of ClNO2 could help explain daytime levels of Cl2 observed in polluted coastal regions. Additionally, we highlight a set of chlorinated VOC oxidation products that are predicted to form at small, but potentially detectable levels in regions with similar VOC

  11. Halogenated solvent remediation

    Science.gov (United States)

    Sorenson, Kent S.

    2004-08-31

    Methods for enhancing bioremediation of ground water contaminated with nonaqueous halogenated solvents are disclosed. A preferred method includes adding a composition to the ground water wherein the composition is an electron donor for microbe-mediated reductive dehalogenation of the halogenated solvents and enhances mass transfer of the halogenated solvents from residual source areas into the aqueous phase of the ground water. Illustrative compositions effective in these methods include surfactants such as C.sub.2 -C.sub.4 carboxylic acids and hydroxy acids, salts thereof, esters of C.sub.2 -C.sub.4 carboxylic acids and hydroxy acids, and mixtures thereof. Especially preferred compositions for use in these methods include lactic acid, salts of lactic acid, such as sodium lactate, lactate esters, and mixtures thereof. The microbes are either indigenous to the ground water, or such microbes can be added to the ground water in addition to the composition.

  12. A theoretical model on the formation mechanism and kinetics of highly toxic air pollutants from halogenated formaldehydes reacted with halogen atoms

    Science.gov (United States)

    Ji, Y. M.; Wang, H. H.; Gao, Y. P.; Li, G. Y.; An, T. C.

    2013-11-01

    The atmospheric reactions of halogenated formaldehydes with halogen atoms were investigated by high-accuracy molecular orbital calculation. Our studies showed that compared to X-addition pathway, the H-abstraction pathway was demonstrated to be more preferred to form halogenated formyl radicals and hydrogen halides (HX). In specific areas with abundant halogen atoms, such as the marine boundary layer (MBL), halogenated formyl radical was reacted easily with halogen atoms and finally transformed into HX and CO2 in the presence of water; otherwise, this radical was degraded to CO2, halogen gas, and halogenated oxide in the presence of O2 and halogen atoms. By using the canonical variational transition state theory, the kinetics calculations were performed within a wide atmospheric temperature range of 200-368 K, and theoretical values agreed well with the available experimental data. Under atmospheric conditions, rate constants decreased as altitude increased, and especially the rate constants of halogen atoms reacted with FCHO quickly reduced. The kinetic results showed that although the reactions of halogenated formaldehydes with F atoms occurred more easily than did those with Cl and Br atoms, the two latter reactions were still important atmospheric degradation process, especially in the MBL. The modified Arrhenius equations of rate constants within the atmospheric temperature range were fitted, which helped to understand the established atmospheric model and estimated the contribution of title reactions to atmospheric chemistry pollution.

  13. Resistance to oxidation of white wines assessed by voltammetric means.

    Science.gov (United States)

    Rodrigues, Astride; Silva Ferreira, A C; Guedes de Pinho, Paula; Bento, Fátima; Geraldo, Dulce

    2007-12-26

    This work concerns the development of a methodology suited to measure the resistance to oxidation of white wines by cyclic voltammetry. The voltammetric responses of several white wines of different origin and age were analyzed in the oxidation potential range (0.2-1.2 V vs SCE). Currents measured at fixed potentials were correlated to the concentration of ascorbic acid, SO2, and total phenolics. A forced degradation study was monitored by cyclic voltammetry; from plots of current versus time, the consumption rates of oxidizable species in wine were estimated.

  14. Degradation of metoprolol by means of advanced oxidation processes

    OpenAIRE

    Romero Olarte, Rossmary Violette

    2015-01-01

    For this study the emerging contaminant ß-blocker Metoprolol (MET) has been selected due that it is a highly prescribed pharmaceutical and it has been detected in waste water treatment plants influents, thus, in natural waters. Several studies, focused on the toxicological potential of Metoprolol, indicate its potential environmental relevance and its recalcitrant nature. To remove MET from water, different Advanced Oxidation Processes (AOPs) were used. MET removal was studied, in diffe...

  15. Retention of Halogens in Waste Glass

    Energy Technology Data Exchange (ETDEWEB)

    Hrma, Pavel R.

    2010-05-01

    In spite of their potential roles as melting rate accelerators and foam breakers, halogens are generally viewed as troublesome components for glass processing. Of five halogens, F, Cl, Br, I, and At, all but At may occur in nuclear waste. A nuclear waste feed may contain up to 10 g of F, 4 g of Cl, and ≤100 mg of Br and I per kg of glass. The main concern is halogen volatility, producing hazardous fumes and particulates, and the radioactive iodine 129 isotope of 1.7x10^7-year half life. Because F and Cl are soluble in oxide glasses and tend to precipitate on cooling, they can be retained in the waste glass in the form of dissolved constituents or as dispersed crystalline inclusions. This report compiles known halogen-retention data in both high-level waste (HLW) and low-activity waste (LAW) glasses. Because of its radioactivity, the main focus is on I. Available data on F and Cl were compiled for comparison. Though Br is present in nuclear wastes, it is usually ignored; no data on Br retention were found.

  16. Retention of Halogens in Waste Glass

    Energy Technology Data Exchange (ETDEWEB)

    Hrma, Pavel R.

    2010-05-01

    In spite of their potential roles as melting rate accelerators and foam breakers, halogens are generally viewed as troublesome components for glass processing. Of five halogens, F, Cl, Br, I, and At, all but At may occur in nuclear waste. A nuclear waste feed may contain up to 10 g of F, 4 g of Cl, and ≤100 mg of Br and I per kg of glass. The main concern is halogen volatility, producing hazardous fumes and particulates, and the radioactive iodine 129 isotope of 1.7x10^7-year half life. Because F and Cl are soluble in oxide glasses and tend to precipitate on cooling, they can be retained in the waste glass in the form of dissolved constituents or as dispersed crystalline inclusions. This report compiles known halogen-retention data in both high-level waste (HLW) and low-activity waste (LAW) glasses. Because of its radioactivity, the main focus is on I. Available data on F and Cl were compiled for comparison. Though Br is present in nuclear wastes, it is usually ignored; no data on Br retention were found.

  17. Nitric Oxide Production Inhibition and Anti-Mycobacterial Activity of Extracts and Halogenated Sesquiterpenes from the Brazilian Red Alga Laurencia Dendroidea J. Agardh.

    Science.gov (United States)

    Biá Ventura, Thatiana Lopes; da Silva Machado, Fernanda Lacerda; de Araujo, Marlon Heggdorne; de Souza Gestinari, Lísia Mônica; Kaiser, Carlos Roland; de Assis Esteves, Francisco; Lasunskaia, Elena B; Soares, Angélica Ribeiro; Muzitano, Michelle Frazão

    2015-10-01

    Red algae of the genus Laurencia J. V. Lamouroux are a rich source of secondary metabolites with important pharmacological activities such as anti-tumoral, anti-inflammatory, anti-fungal, anti-viral, anti-leishmanial, anti-helminthic, anti-malarial, anti-trypanosomal, anti-microbial as well as anti-bacterial against Mycobacterium tuberculosis. In the present study, we evaluated the inhibition of nitric oxide (NO) and tumor necrosis factor-α production and the anti-mycobacterial activity of crude extracts from the red Alga Laurencia dendroidea (from the South-Eastern coast of Brazil). Halogenated sesquiterpenes elatol (1), obtusol (2) and cartilagineol (3), previously isolated from this Alga by our group, were also studied. The lipopolysaccharide-activated macrophage cells (RAW 264.7) were used as inflammation model. Cytotoxic effect was determined using a commercial lactate dehydrogenase (LDH) kit and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The growing Mycobacterium inhibition was verified against Mycobacterium bovis Bacillus Calmette-Guérin and M. tuberculosis H37 Rv strains. The crude extract from Alga collected at Angra dos Reis, RJ, Brazil, was the most active inhibitor of both mycobacterial growth (half maximal inhibitory concentration [IC50] 8.7 ± 1.4 μg/mL) and NO production by activated macrophages (IC50 5.3 ± 1.3 μg/mL). The assays with isolated compounds revealed the anti-mycobacterial activity of obtusol (2), whereas (-)-elatol (1) inhibited the release of inflammatory mediators, especially NO. To our knowledge, this is the first report describing an anti-mycobacterial effect of L. dendroidea extract and demonstrating the association of this activity with obtusol (2). The described effects of active compounds from L. dendroidea are promising for the control of inflammation in infectious diseases and specifically, against mycobacterial infections associated with exacerbated inflammation. Inflammation is strongly involved

  18. Halogenated fatty acids

    DEFF Research Database (Denmark)

    Mu, Huiling; Wesén, Clas; Sundin, Peter

    1997-01-01

    Chlorinated fatty acids have been found to be major contributors to organohalogen compounds in fish, bivalves, jellyfish, and lobster, and they have been indicated to contribute considerably to organohalogens in marine mammals. Brominated fatty acids have been found in marine sponges. Also......, chlorinated lipids have been found in meat exposed to hypochlorite disinfected water, and in chlorine-treated flour and in products made from such flour. Following exposure to chlorine bleached pulp mill effluents, aquatic organisms may have elevated concentrations of chlorinated fatty acids in their lipids....... However, a natural production of halogenated fatty acids is also possible. In this paper we summarize the present knowledge of the occurrence of halogenated fatty acids in lipids and suggested ways of their formation. In Part II (Trends Anal. Chem. 16 (1997) 274) we deal with methods...

  19. Weak acidity of vinyl CH bonds enhanced by halogen substitution.

    Science.gov (United States)

    Craig, Norman C; Matlin, Albert R

    2014-02-21

    As shown by the rates of proton-deuteron exchange in ethylenes with halogen substituents, the weak acidity of vinyl CH bonds is enhanced by halogen substitution. Relative rates of exchange in basic deuterium oxide reflect the relative acidities. Substitution in the α position has the strongest effect. Less electronegative halogens such as bromine increase the acidity more than does fluorine. The vinyl CH acid strengths correlate closely with the energies of deprotonation of isolated molecules into isolated anions, as computed with the MP2/cc-pVQZ model. The smaller deprotonation energies are associated with the stronger acids. Atomic charges from a natural bond order analysis done with the MP2/aug-cc-pVQZ model show that the negative charge becomes more dispersed in the anions of the stronger acids. Results are given for 13 haloethylenes and for 6 halogen-substituted butadienes, cyclopropenes, and a cyclobutene.

  20. Halogen Bonding Promotes Higher Dye-Sensitized Solar Cell Photovoltages.

    Science.gov (United States)

    Simon, Sarah J C; Parlane, Fraser G L; Swords, Wesley B; Kellett, Cameron W; Du, Chuan; Lam, Brian; Dean, Rebecca K; Hu, Ke; Meyer, Gerald J; Berlinguette, Curtis P

    2016-08-24

    We report here an enhancement in photovoltage for dye-sensitized solar cells (DSSCs) where halogen-bonding interactions exist between a nucleophilic electrolyte species (I(-)) and a photo-oxidized dye immobilized on a TiO2 surface. The triarylamine-based dyes under investigation showed larger rate constants for dye regeneration (kreg) by the nucleophilic electrolyte species when heavier halogen substituents were positioned on the dye. The open-circuit voltages (VOC) tracked these kreg values. This analysis of a homologous series of dyes that differ only in the identity of two halogen substituents provides compelling evidence that the DSSC photovoltage is sensitive to kreg. This study also provides the first direct evidence that halogen-bonding interactions between the dye and the electrolyte can bolster DSSC performance.

  1. Halogen Chemistry in the CMAQ Model

    Science.gov (United States)

    Halogens (iodine and bromine) emitted from oceans alter atmospheric chemistry and influence atmospheric ozone mixing ratio. We previously incorporated a representation of detailed halogen chemistry and emissions of organic and inorganic halogen species into the hemispheric Commun...

  2. Radical and Atom Transfer Halogenation (RATH): A Facile Route for Chemical and Polymer Functionalization.

    Science.gov (United States)

    Han, Yi-Jen; Lin, Chia-Yu; Liang, Mong; Liu, Ying-Ling

    2016-05-01

    This work demonstrates a new halogenation reaction through sequential radical and halogen transfer reactions, named as "radical and atom transfer halogenation" (RATH). Both benzoxazine compounds and poly(2,6-dimethyl-1,4-phenylene oxide) have been demonstrated as active species for RATH. Consequently, the halogenated compound becomes an active initiator of atom transfer radical polymerization. Combination of RATH and sequential ATRP provides an convenient and effective approach to prepare reactive and crosslinkable polymers. The RATH reaction opens a new window both to chemical synthesis and molecular design and preparation of polymeric materials.

  3. Purification of carbon nanotubes from cathode deposit by means of different oxidation rates

    Energy Technology Data Exchange (ETDEWEB)

    Ikazaki, Fumikazu; Uchida, Kunio; Ohshima, Satoshi; Kuriki, Yasunori [National Inst. of Materials and Chemical Research, Ibaraki (Japan)] [and others

    1996-10-01

    Two purification methods of nanotubes from a cathode deposit by an arc plasma were conducted by means of different oxidation rates of various graphites. One was chemical and the other physical method. Both could purify nanotubes at their optimum conditions. In the former, the catalytic oxidation was used of graphitic materials by copper. Copper supported graphite was prepared by the intercalation of copper chloride and by the reduction to metal copper. The catalytic oxidation decomposed the graphite at 773 K. The temperature was 200 K lower than the oxidation temperature of graphite, which enabled purification. In the latter, dispersion, comminution and filtration of a cathode deposit in ethanol were used to separate coarse graphite. The rate of weight loss by oxidation increased with the decrease of size of the graphite. Nanotubes were more slowly oxidized from the edges than the graphite of the same size. This could purify nanotubes.

  4. Purification of carbon nanotubes from cathode deposit by means of different oxidation rates

    Energy Technology Data Exchange (ETDEWEB)

    Ikazaki, F.; Uchida, K.; Ohshima, S. [National Institute of Materials and Chemical Research, Tsukuba, Ibaraki (Japan)] [and others

    1996-12-31

    Two purification methods of nanotubes from a cathode deposit by an arc plasma were conducted by means of different oxidation rates of various graphites. One was chemical and the other physical method. Both could purify nanotubes at their optimum conditions. In the former, the catalytic oxidation was used of graphite materials by copper. Copper supported graphite was prepared by the intercalation of copper chloride and by the reduction to metal copper. The catalytic oxidation decomposed the graphite at 773 K and less. The temperature was significantly lower than the oxidation temperature former reported of graphite, which enabled purification. In the latter, dispersion, comminution and filtration of a cathode deposit in ethanol were used to separate coarse graphite. The rate of weight loss by oxidation increased with the decrease of size of the graphite. Nanotubes were more slowly oxidized from the edges than the graphite of the same size. This could purify nanotubes.

  5. Coating of tips for electrochemical scanning tunneling microscopy by means of silicon, magnesium, and tungsten oxides.

    Science.gov (United States)

    Salerno, Marco

    2010-09-01

    Different combinations of metal tips and oxide coatings have been tested for possible operation in electrochemical scanning tunneling microscopy. Silicon and magnesium oxides have been thermally evaporated onto gold and platinum-iridium tips, respectively. Two different thickness values have been explored for both materials, namely, 40 and 120 nm for silicon oxide and 20 and 60 nm for magnesium oxide. Alternatively, tungsten oxide has been grown on tungsten tips via electrochemical anodization. In the latter case, to seek optimal results we have varied the pH of the anodizing electrolyte between one and four. The oxide coated tips have been first inspected by means of scanning electron microscopy equipped with microanalysis to determine the morphological results of the coating. Second, the coated tips have been electrically characterized ex situ for stability in time by means of cyclic voltammetry in 1 M aqueous KCl supporting electrolyte, both bare and supplemented with K(3)[Fe(CN)(6)] complex at 10 mM concentration in milliQ water as an analyte. Only the tungsten oxide coated tungsten tips have shown stable electrical behavior in the electrolyte. For these tips, the uncoated metal area has been estimated from the electrical current levels, and they have been successfully tested by imaging a gold grating in situ, which provided stable results for several hours. The successful tungsten oxide coating obtained at pH=4 has been assigned to the WO(3) form.

  6. Halogens and their role in polar boundary-layer ozone depletion

    Directory of Open Access Journals (Sweden)

    W. R. Simpson

    2007-03-01

    Full Text Available During springtime in the polar regions, unique photochemistry converts inert halide salts ions (e.g. Br into reactive halogen species (e.g. Br atoms and BrO that deplete ozone in the boundary layer to near zero levels. Since their discovery in the late 1980s, research on ozone depletion events (ODEs has made great advances; however many key processes remain poorly understood. In this article we review the history, chemistry, dependence on environmental conditions, and impacts of ODEs. This research has shown the central role of bromine photochemistry, but how salts are transported from the ocean and are oxidized to become reactive halogen species in the air is still not fully understood. Halogens other than bromine (chlorine and iodine are also activated through incompletely understood mechanisms that are probably coupled to bromine chemistry. The main consequence of halogen activation is chemical destruction of ozone, which removes the primary precursor of atmospheric oxidation, and generation of reactive halogen atoms/oxides that become the primary oxidizing species. The different reactivity of halogens as compared to OH and ozone has broad impacts on atmospheric chemistry, including near complete removal and deposition of mercury, alteration of oxidation fates for organic gases, and export of bromine into the free troposphere. Recent changes in the climate of the Arctic and state of the Arctic sea ice cover are likely to have strong effects on halogen activation and ODEs; however, more research is needed to make meaningful predictions of these changes.

  7. Halogen Bonding: An AIM Analysis of the Weak Interactions

    Institute of Scientific and Technical Information of China (English)

    ZOU, Jian-Wei; LU, Yun-Xiang; YU, Qing-Sen; ZHANG, Hua-Xin; JIANG, Yong-Jun

    2006-01-01

    A series of complexes formed between halogen-containing molecules and ammonia have been investigated by means of the atoms in molecules (AIM) approach to gain a deeper insight into halogen bonding. The existence of the halogen bond critical points (XBCP) and the values of the electron density (ρb) and Laplacian of electron density (▽2pb) at the XBCP reveal the closed-shell interactions in these complexes. Integrated atomic properties such as charge, energy, polarization moment, volume of the halogen bond donor atoms, and the corresponding changes (△) upon complexation have been calculated. The present calculations have demonstrated that the halogen bond represents different AIM properties as compared to the well-documented hydrogen bond. Both the electron density and the Laplacian of electron density at the XBCP have been shown to correlate well with the interaction energy, which indicates that the topological parameters at the XBCP can be treated as a good measure of the halogen bond strength.In addition, an excellent linear relationship between the interatomic distance d(X…N) and the logarithm of ρb has been established.

  8. Halogen chemistry reduces tropospheric O3 radiative forcing

    Science.gov (United States)

    Sherwen, Tomás; Evans, Mat J.; Carpenter, Lucy J.; Schmidt, Johan A.; Mickley, Loretta J.

    2017-01-01

    Tropospheric ozone (O3) is a global warming gas, but the lack of a firm observational record since the preindustrial period means that estimates of its radiative forcing (RFTO3) rely on model calculations. Recent observational evidence shows that halogens are pervasive in the troposphere and need to be represented in chemistry-transport models for an accurate simulation of present-day O3. Using the GEOS-Chem model we show that tropospheric halogen chemistry is likely more active in the present day than in the preindustrial. This is due to increased oceanic iodine emissions driven by increased surface O3, higher anthropogenic emissions of bromo-carbons, and an increased flux of bromine from the stratosphere. We calculate preindustrial to present-day increases in the tropospheric O3 burden of 113 Tg without halogens but only 90 Tg with, leading to a reduction in RFTO3 from 0.43 to 0.35 Wm-2. We attribute ˜ 50 % of this reduction to increased bromine flux from the stratosphere, ˜ 35 % to the ocean-atmosphere iodine feedback, and ˜ 15 % to increased tropospheric sources of anthropogenic halogens. This reduction of tropospheric O3 radiative forcing due to halogens (0.087 Wm-2) is greater than that from the radiative forcing of stratospheric O3 (˜ 0.05 Wm-2). Estimates of RFTO3 that fail to consider halogen chemistry are likely overestimates (˜ 25 %).

  9. Structural perspective on enzymatic halogenation.

    Science.gov (United States)

    Blasiak, Leah C; Drennan, Catherine L

    2009-01-20

    Simple halogen substituents frequently afford key structural features that account for the potency and selectivity of natural products, including antibiotics and hormones. For example, when a single chlorine atom on the antibiotic vancomycin is replaced by hydrogen, the resulting antibacterial activity decreases by up to 70% ( Harris , C. M. ; Kannan , R. ; Kopecka , H. ; Harris , T. M. J. Am. Chem. Soc. 1985 , 107 , 6652 - 6658 ). This Account analyzes how structure underlies mechanism in halogenases, the molecular machines designed by nature to incorporate halogens into diverse substrates. Traditional synthetic methods of integrating halogens into complex molecules are often complicated by a lack of specificity and regioselectivity. Nature, however, has developed a variety of elegant mechanisms for halogenating specific substrates with both regio- and stereoselectivity. An improved understanding of the biological routes toward halogenation could lead to the development of novel synthetic methods for the creation of new compounds with enhanced functions. Already, researchers have co-opted a fluorinase from the microorganism Streptomyces cattleya to produce (18)F-labeled molecules for use in positron emission tomography (PET) ( Deng , H. ; Cobb , S. L. ; Gee , A. D. ; Lockhart , A. ; Martarello , L. ; McGlinchey , R. P. ; O'Hagan , D. ; Onega , M. Chem. Commun. 2006 , 652 - 654 ). Therefore, the discovery and characterization of naturally occurring enzymatic halogenation mechanisms has become an active area of research. The catalogue of known halogenating enzymes has expanded from the familiar haloperoxidases to include oxygen-dependent enzymes and fluorinases. Recently, the discovery of a nucleophilic halogenase that catalyzes chlorinations has expanded the repertoire of biological halogenation chemistry ( Dong , C. ; Huang , F. ; Deng , H. ; Schaffrath , C. ; Spencer , J. B. ; O'Hagan , D. ; Naismith , J. H. Nature 2004 , 427 , 561 - 565 ). Structural

  10. Halogenated compounds from marine algae.

    Science.gov (United States)

    Cabrita, Maria Teresa; Vale, Carlos; Rauter, Amélia Pilar

    2010-08-09

    Marine algae produce a cocktail of halogenated metabolites with potential commercial value. Structures exhibited by these compounds go from acyclic entities with a linear chain to complex polycyclic molecules. Their medical and pharmaceutical application has been investigated for a few decades, however other properties, such as antifouling, are not to be discarded. Many compounds were discovered in the last years, although the need for new drugs keeps this field open as many algal species are poorly screened. The ecological role of marine algal halogenated metabolites has somehow been overlooked. This new research field will provide valuable and novel insight into the marine ecosystem dynamics as well as a new approach to comprehending biodiversity. Furthermore, understanding interactions between halogenated compound production by algae and the environment, including anthropogenic or global climate changes, is a challenging target for the coming years. Research of halogenated metabolites has been more focused on macroalgae than on phytoplankton. However, phytoplankton could be a very promising material since it is the base of the marine food chain with quick adaptation to environmental changes, which undoubtedly has consequences on secondary metabolism. This paper reviews recent progress on this field and presents trends on the role of marine algae as producers of halogenated compounds.

  11. The influence of ocean halogen and sulfur emissions in the air quality of a coastal megacity: The case of Los Angeles.

    Science.gov (United States)

    Muñiz-Unamunzaga, Maria; Borge, Rafael; Sarwar, Golam; Gantt, Brett; de la Paz, David; Cuevas, Carlos A; Saiz-Lopez, Alfonso

    2017-06-27

    The oceans are the main source of natural halogen and sulfur compounds, which have a significant influence on the oxidizing capacity of the marine atmosphere; however, their impact on the air quality of coastal cities is currently unknown. We explore the effect of marine halogens (Cl, Br and I) and dimethyl sulfide (DMS) on the air quality of a large coastal city through a set of high-resolution (4-km) air quality simulations for the urban area of Los Angeles, US, using the Community Multiscale Air Quality (CMAQ model). The results indicate that marine halogen emissions decrease ozone and nitrogen dioxide levels up to 5ppbv and 2.5ppbv, respectively, in the city of Los Angeles. Previous studies suggested that the inclusion of chlorine in air quality models leads to the generation of ozone in urban areas through photolysis of nitryl chloride (ClNO2). However, we find that when considering the chemistry of Cl, Br and I together the net effect is a reduction of surface ozone concentrations. Furthermore, combined ocean emissions of halogens and DMS cause substantial changes in the levels of key urban atmospheric oxidants such as OH, HO2 and NO3, and in the composition and mass of fine particles. Although the levels of ozone, NO3 and HOx are reduced, we find a 10% increase in secondary organic aerosol (SOA) mean concentration, attributed to the increase in aerosol acidity and sulfate aerosol formation when combining DMS and bromine. Therefore, this new pathway for enhanced SOA formation may potentially help with current model under predictions of urban SOA. Although further observations and research are needed to establish these preliminary conclusions, this first city-scale investigation suggests that the inclusion of oceanic halogens and DMS in air quality models may improve regional air quality predictions over coastal cities around the world. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Halogen radicals contribute to photooxidation in coastal and estuarine waters

    Science.gov (United States)

    Parker, Kimberly M.; Mitch, William A.

    2016-05-01

    Although halogen radicals are recognized to form as products of hydroxyl radical (•OH) scavenging by halides, their contribution to the phototransformation of marine organic compounds has received little attention. We demonstrate that, relative to freshwater conditions, seawater halides can increase photodegradation rates of domoic acid, a marine algal toxin, and dimethyl sulfide, a volatile precursor to cloud condensation nuclei, up to fivefold. Using synthetic seawater solutions, we show that the increased photodegradation is specific to dissolved organic matter (DOM) and halides, rather than other seawater salt constituents (e.g., carbonates) or photoactive species (e.g., iron and nitrate). Experiments in synthetic and natural coastal and estuarine water samples demonstrate that the halide-specific increase in photodegradation could be attributed to photochemically generated halogen radicals rather than other photoproduced reactive intermediates [e.g., excited-state triplet DOM (3DOM*), reactive oxygen species]. Computational kinetic modeling indicates that seawater halogen radical concentrations are two to three orders of magnitude greater than freshwater •OH concentrations and sufficient to account for the observed halide-specific increase in photodegradation. Dark •OH generation by gamma radiolysis demonstrates that halogen radical production via •OH scavenging by halides is insufficient to explain the observed effect. Using sensitizer models for DOM chromophores, we show that halogen radicals are formed predominantly by direct oxidation of Cl- and Br- by 3DOM*, an •OH-independent pathway. Our results indicate that halogen radicals significantly contribute to the phototransformation of algal products in coastal or estuarine surface waters.

  13. 40 CFR 721.8675 - Halogenated pyridines.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated pyridines. 721.8675... Substances § 721.8675 Halogenated pyridines. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as halogenated pyridine (PMN P-83-1163)...

  14. Simulation of 3D mesoscale structure formation in concentrated aqueous solution of the triblock polymer surfactants (ethylene oxide)(13)(propylene oxide)(30)(ethylene oxide)(13) and (propylene oxide)(19)(ethylene oxide)(33)(propylene oxide)(19). Application of dynamic mean-field density functional theory

    NARCIS (Netherlands)

    van Vlimmeren, BAC; Maurits, NM; Zvelindovsky, AV; Sevink, GJA; Fraaije, JGEM

    1999-01-01

    We simulate the microphase separation dynamics of aqueous solutions of the triblock polymer surfactants (ethylene oxide)(13)(propylene oxide)(30)(ethylene oxide)(13) and (propylene oxide)(19)(ethylene oxide)(33)(propylene oxide)(19) by a dynamic variant of mean-field density functional theory for

  15. Simulation of 3D mesoscale structure formation in concentrated aqueous solution of the triblock polymer surfactants (ethylene oxide)(13)(propylene oxide)(30)(ethylene oxide)(13) and (propylene oxide)(19)(ethylene oxide)(33)(propylene oxide)(19). Application of dynamic mean-field density functional theory

    NARCIS (Netherlands)

    van Vlimmeren, BAC; Maurits, NM; Zvelindovsky, AV; Sevink, GJA; Fraaije, JGEM

    1999-01-01

    We simulate the microphase separation dynamics of aqueous solutions of the triblock polymer surfactants (ethylene oxide)(13)(propylene oxide)(30)(ethylene oxide)(13) and (propylene oxide)(19)(ethylene oxide)(33)(propylene oxide)(19) by a dynamic variant of mean-field density functional theory for Ga

  16. Halogen and Cl isotopic systematics in Martian phosphates: Implications for the Cl cycle and surface halogen reservoirs on Mars

    Science.gov (United States)

    Bellucci, J. J.; Whitehouse, M. J.; John, T.; Nemchin, A. A.; Snape, J. F.; Bland, P. A.; Benedix, G. K.

    2017-01-01

    The Cl isotopic compositions and halogen (Cl, F, Br, and I) abundances in phosphates from eight Martian meteorites, spanning most rock types and ages currently available, have been measured in situ by Secondary Ion Mass Spectrometry (SIMS). Likewise, the distribution of halogens has been documented by x-ray mapping. Halogen concentrations range over several orders of magnitude up to some of the largest concentrations yet measured in Martian samples or on the Martian surface, and the inter-element ratios are highly variable. Similarly, Cl isotope compositions exhibit a larger range than all pristine terrestrial igneous rocks. Phosphates in ancient (>4 Ga) meteorites (orthopyroxenite ALH 84001 and breccia NWA 7533) have positive δ37Cl anomalies (+1.1 to + 2.5 ‰). These samples also exhibit explicit whole rock and grain scale evidence for hydrothermal or aqueous activity. In contrast, the phosphates in the younger basaltic Shergottite meteorites (<600 Ma) have negative δ37Cl anomalies (-0.2 to - 5.6 ‰). Phosphates with the largest negative δ37Cl anomalies display zonation in which the rims of the grains are enriched in all halogens and have significantly more negative δ37Cl anomalies suggestive of interaction with the surface of Mars during the latest stages of basalt crystallization. The phosphates with no textural, major element, or halogen enrichment evidence for mixing with this surface reservoir have an average δ37Cl of - 0.6 ‰, supporting a similar initial Cl isotope composition for Mars, the Earth, and the Moon. Oxidation and reduction of chlorine are the only processes known to strongly fractionate Cl isotopes, both positively and negatively, and perchlorate has been detected in weight percent concentrations on the Martian surface. The age range and obvious mixing history of the phosphates studied here suggest perchlorate formation and halogen cycling via brines, which have been documented on the Martian surface, has been active throughout Martian

  17. Halogen Bonding in Organic Synthesis and Organocatalysis.

    Science.gov (United States)

    Bulfield, David; Huber, Stefan M

    2016-10-01

    Halogen bonding is a noncovalent interaction similar to hydrogen bonding, which is based on electrophilic halogen substituents. Hydrogen-bonding-based organocatalysis is a well-established strategy which has found numerous applications in recent years. In light of this, halogen bonding has recently been introduced as a key interaction for the design of activators or organocatalysts that is complementary to hydrogen bonding. This Concept features a discussion on the history and electronic origin of halogen bonding, summarizes all relevant examples of its application in organocatalysis, and provides an overview on the use of cationic or polyfluorinated halogen-bond donors in halide abstraction reactions or in the activation of neutral organic substrates.

  18. Magnetic filtration of an iron oxide aerosol by means of magnetizable grates

    Institute of Scientific and Technical Information of China (English)

    A. Alvaro; J.M. Rodríguez; Paulo A. Augusto; A.M. Estévez

    2007-01-01

    The cleaning of gases with low concentrations of small ferromagnetic or paramagnetic particles is a difficult task for conventional filtration. A new alternative procedure, magnetic filtration, is used in this work.Iron oxide aerosol was generated by elutriation of iron oxide particles from a fluidized bed consisting of a mixture of Geldart-C iron oxide powder and large spherical Geldart-B sand particles. The aerosol was filtered by means of a magnetic filter which consisted of one, two or three iron grates staggered to each other. The experimental installation contained also an isokinetic sampling system and a Microtrac SRA 150 Particle Analyser.A theoretical expression for filtration efficiency was deduced from a previous model taking into account the different forces acting on the iron oxide particles. Experimental filtration efficiency matches quite well calculated theoretical efficiency. It was found that an increase in particle size,in the number of grates or in the applied magnetic field produced higher filtration efficiencies up to 100% in some cases. In all filtration experiments pressure drop through the magnetic filter was very small.

  19. High Energy Halogen Chemistry.

    Science.gov (United States)

    1978-01-01

    diphenylsilanes , displacement of halo- gen to give the nitro compound, oxidative nitration and fluorination to give — the fluorodinitro compound, and...V - - - - Simple oxetanes arc gen ~rally obtained by cycl iz ing :~onotosy lates of 1,3-diols with...d initro - tropropy lltr imethyls ilane . using the theor etica l amount of and fluorodinitrosi lanes and polysiloxanes by the step wise base, gave

  20. How do halogen bonds (S-O⋯I, N-O⋯I and C-O⋯I) and halogen-halogen contacts (C-I⋯I-C, C-F⋯F-C) subsist in crystal structures? A quantum chemical insight.

    Science.gov (United States)

    Pandiyan, B Vijaya; Deepa, P; Kolandaivel, P

    2017-01-01

    Thirteen X-ray crystal structures containing various non-covalent interactions such as halogen bonds, halogen-halogen contacts and hydrogen bonds (I⋯N, I⋯F, I⋯I, F⋯F, I⋯H and F⋯H) were considered and investigated using the DFT-D3 method (B97D/def2-QZVP). The interaction energies were calculated at MO62X/def2-QZVP and MP2/aug-cc-pvDZ level of theories. The higher interaction and dispersion energies (2nd crystal) of -9.58 kcal mol(-1) and -7.10 kcal mol(-1) observed for 1,4-di-iodotetrafluorobenzene bis [bis (2-phenylethyl) sulfoxide] structure indicates the most stable geometrical arrangement in the crystal packing. The electrostatic potential values calculated for all crystal structures have a positive σ-hole, which aids understanding of the nature of σ-hole bonds. The significance of the existence of halogen bonds in crystal packing environments was authenticated by replacing iodine atoms by bromine and chlorine atoms. Nucleus independent chemical shift analysis reported on the resonance contribution to the interaction energies of halogen bonds and halogen-halogen contacts. Hirshfeld surface analysis and topological analysis (atoms in molecules) were carried out to analyze the occurrence and strength of all non-covalent interactions. These analyses revealed that halogen bond interactions were more dominant than hydrogen bonding interactions in these crystal structures. Graphical Abstract Molecluar structure of 1,4-Di-iodotetrafluorobenzene bis(thianthrene 5-oxide) moelcule and its corresponding molecular electrostatic potential map for the view of σ-hole.

  1. Measurements of vertical distributions of bromine oxide, iodine oxide, oxygenated hydrocarbons and ozone over the Eastern Tropical Pacific Ocean

    Science.gov (United States)

    Volkamer, R. M.; Baidar, S.; Dix, B. K.; Apel, E. C.; Hornbrook, R. S.; Pierce, B.; Gao, R.

    2012-12-01

    As part of the Tropical Ocean tRoposphere Exchange of Reactive halogen species and Oxygenated VOC (TORERO) field experiment 17 research flights were conducted with the NSF/NCAR GV aircraft equipped with a combination of chemical in-situ sensors, and remote sensing instruments to characterize air-sea exchange of reactive halogen species, oxygenated hydrocarbons, and aerosols, and their transport into the free troposphere, over different ocean environments of the Humboldt current in the Eastern Tropical Pacific Ocean (42S to 14N Lat.; 70W to 105W Long.). This presentation presents measurements of the spatial distributions of halogen oxide radicals, oxygenated hydrocarbons, and discusses their impact on ozone destruction rates, and the oxidation of atmospheric mercury. Air mass history is assessed by means of the Real-time Air Quality Modeling System (RAQMS), a global meteorological, chemical and aerosol assimilation/forecasting system that assimilates real-time stratospheric ozone retrievals from the Microwave Limb Sounder (MLS), total column ozone from the Ozone Monitoring Instrument (OMI), and aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS). Reactive halogen species and organic carbon are important in the atmosphere, because they modify HOx radical abundances, influence the reactive chemistry and lifetime of climate active gases (e.g., ozone, methane, dimethyl sulfide), modify aerosol-cloud interactions; halogen radicals can further oxidize atmospheric mercury.

  2. Easy oxidative addition of the carbon-halogen bond by dimethylplatinum(II) complexes containing a related series of diimine ligands: Synthesis, spectral characterization and crystal structure

    Science.gov (United States)

    Momeni, Badri Z.; Fathi, Nastaran; Mohagheghi, Arezoo

    2015-01-01

    Dimethylplatinum(II) complexes [PtMe2(NN)] {NN = 4,4‧-Me2bpy (4,4‧-dimethyl-2,2‧-bipyridine); 5,5‧-Me2bpy (5,5‧-dimethyl-2,2‧-bipyridine)} were reacted with alkyl halides (RX = EtI, EtBr) to yield the organoplatinum(IV) complexes [PtMe2RX(NN)]. On the basis of NMR data, the platinum(IV) product of each reaction contains almost exclusively the trans isomer but small traces of the cis isomers are also observed. On the other hand, the reaction of [PtMe2(NN)] {NN = bu2bpy (4,4‧-di-tert-butyl-2,2‧-bipyridine); 4,4‧-Me2bpy; 5,5‧-Me2bpy} with CH2Br2 gave a mixture of cis and trans-[PtMe2(CH2Br)Br(NN)] formed by the oxidative addition of one of the C-Br bonds. The formation of the cis isomer increases in the order of 5,5‧-Me2bpy > bu2bpy > 4,4‧-Me2bpy. The reaction of [PtMe2(NN)] {NN = bpy (2,2‧-bipyridine), phen (1,10-phenanthroline)} with 1,8-dibromooctane or 1,9-dibromononane afforded the mononuclear complexes [PtMe2{(CH2)nBr}Br(NN)] (n = 8-9). The products were fully characterized by elemental analysis, 1H, 13C, HH COSY, HMQC, DEPT and DEPTQ-135 NMR spectroscopy. The crystal structure of [PtMe2EtI(4,4‧-Me2bpy)] reveals that Pt(IV) atom is six-coordinated in a slightly distorted octahedral geometry with the ethyl group trans to iodide.

  3. Competition of hydrogen bonds and halogen bonds in complexes of hypohalous acids with nitrogenated bases.

    Science.gov (United States)

    Alkorta, Ibon; Blanco, Fernando; Solimannejad, Mohammad; Elguero, Jose

    2008-10-30

    A theoretical study of the complexes formed by hypohalous acids (HOX, X = F, Cl, Br, I, and At) with three nitrogenated bases (NH 3, N 2, and NCH) has been carried out by means of ab initio methods, up to MP2/aug-cc-pVTZ computational method. In general, two minima complexes are found, one with an OH...N hydrogen bond and the other one with a X...N halogen bond. While the first one is more stable for the smallest halogen derivatives, the two complexes present similar stabilities for the iodine case and the halogen-bonded structure is the most stable one for the hypoastatous acid complexes.

  4. [Halogenated natural products from the marine-derived actinobacteria and their halogenation mechanism].

    Science.gov (United States)

    Tan, Yi; Zhou, Hong-xia; Wang, Yi-guang; Gan, Mao-luo; Yang, Zhao-yong

    2013-09-01

    In the last decade, along with the development of taxonomy research in marine-derived actinobacteria, more and more halogenated natural products were discovered from marine actinobacteria. Most of them showed good biological activity and unique structure compared to those from land. The special halogenation mechanism in some compounds' biosynthesis has drawn great attention. So in this review, we focus on the halogenated natural products from marine actinobacteria and their halogenation mechanisms.

  5. Iron Coordination and Halogen-Bonding Assisted Iodosylbenzene Activation

    DEFF Research Database (Denmark)

    Wegeberg, Christina; Poulsen de Sousa, David; McKenzie, Christine

    catalytic mixtures using soluble terminal oxygen transfer agents. Isolation of a reactive iron-terminal oxidant adduct, an unique Fe(III)-OIPh complex, is facilitated by strong stabilizing supramolecular halogen-bonding. L3-edge XANES suggests +1.6 for the average oxidation state for the iodine atom3...... in the iron(III)-coordinated PhIO. This represents a reduction of iodine relative to the original “hypervalent” (+3) PhIO. The equivalent of electron density must be removed from the {(tpena)Fe(III)O} moiety, however Mössbauer spectroscopy shows that the iron atom is not high valent....

  6. Relationship between Glycosylated Hemoglobin, Serum Nitric Oxide and Mean Arterial Blood Pressure.

    Science.gov (United States)

    Manju, M; Mishra, Sasmita; Toora, B D; Vijayakumar; Vinod, R

    2014-12-01

    Hypertension is about twice as frequent in individuals with diabetes as in those without diabetes. Formation of glycosylated conjugates like HbA1c is implicated to have many effects on the vascular endothelium which leads to the development of hypertension in diabetes. Nitric oxide (NO)-dependent vasodilatation has been shown to be an important factor in the maintenance and regulation of peripheral vascular tone. Studies correlating these parameters give conflicting results. Hence the present study was designed to correlate HbA1c, Serum NO & mean arterial blood pressure. To study the relationship between glycosylated hemoglobin, serum nitric oxide & mean arterial blood pressure. It is a case control study with 28 type 2 diabetic hypertensives, 32 type 2 diabetic normotensives and 51 controls (non diabetic normotensives). The study subjects included 28 type 2 diabetic hypertensives, 32 type 2 diabetic normotensives and 51 controls (non diabetic normotensives) [ADA 2010 and JNC7]. FBS, PPBS, PCV, Hb, HbA1c & serum NO estimation and BP recording was done in all the study subjects. Normalised mean arterial blood pressure (MAPn) and calculated glycosylated hemoglobin (cHbA1c) were calculated from mean arterial BP (MAP) and HbA1c respectively. was done using R commander software. The difference in the distribution of cHbA1c, MAPn & NO levels between all 3 groups was measured using ANOVA and Kruskal-Wallis test. Correlation between the parameters was measured by Correlation coefficient and logistic regression (Spearman linear regression) analysis (univariate and multivariate). There was a significant difference in the distribution of cHbA1c, MAPn & NO levels (p<0.001) between all 3 groups, whether measured by ANOVA or Kruskal-Wallis test. On univariate analysis, there was a positive correlation between cHbA1c & MAPn (ρ= +0.26), a negative correlation between NO & MAPn (ρ = -0.54) and cHbA1c & NO (ρ= -0.66) .On multivariate analysis, not only NO, but contrary to

  7. Spectrographic determination of traces of halogens; Dosage de traces d'halogenes par la methode spectrographique

    Energy Technology Data Exchange (ETDEWEB)

    Melamed, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    Hollow cathode source is employed for determining traces of halogens (fluorine - chlorine) in the uranium oxide U{sub 3}O{sub 8} qualitatively, detection of at least 40 ppm of fluorine, as alkali fluoride and 125 ppm of chlorine, is possible. (author) [French] Un tube a decharge a cathode creuse a ete utilise pour la determination spectrographique des halogenes (fluor - chlore) presentes a l'etat de traces dans un oxyde d'uranium U{sub 3}O{sub 8}. On a pu deceler qualitativement des teneurs de 40 ppm de fluor sous forme de fluorures alcalins. En ce qui concerne le chlore, la plus faible teneur decelee a ete de 125 ppm. (auteur)

  8. Volatile halogenated hydrocarbons in foods

    Energy Technology Data Exchange (ETDEWEB)

    Miyahara, Makoto; Toyoda, Masatake; Saito, Yukio [National Institute of Health Services, Tokyo (Japan)] [and others

    1995-02-01

    Volatile halogenated organic compounds were determined in foods. Statistical treatment of the data for 13 sampled from 20 families living in suburban Tokyo (Saitama prefecture) indicated that the foods were contaminated by water pollution and/or substances introduced by the process of food production. Butter and margarine were contaminated by chlorinated ethylene, ethane, and related compounds released by dry cleaning and other operations. Soybean sprouts and tofu (soybean curd) contained chloroform and related trihalomethanes absorbed during the production process. 27 refs., 6 figs., 5 tabs.

  9. Stereoselective Halogenation in Natural Product Synthesis.

    Science.gov (United States)

    Chung, Won-jin; Vanderwal, Christopher D

    2016-03-24

    At last count, nearly 5000 halogenated natural products have been discovered. In approximately half of these compounds, the carbon atom to which the halogen is bound is sp(3) -hybridized; therefore, there are an enormous number of natural products for which stereocontrolled halogenation must be a critical component of any synthesis strategy. In this Review, we critically discuss the methods and strategies used for stereoselective introduction of halogen atoms in the context of natural product synthesis. Using the successes of the past, we also attempt to identify gaps in our synthesis technology that would aid the synthesis of halogenated natural products, as well as existing methods that have not yet seen application in complex molecule synthesis. The chemistry described herein demonstrates yet again how natural products continue to provide the inspiration for critical advances in chemical synthesis.

  10. Structural studies of epitaxial ultrathin oxide films and nanoclusters by means of angle-scanned photoelectron diffraction (XPD)

    Energy Technology Data Exchange (ETDEWEB)

    Granozzi, Gaetano [Dipartimento di Chimica Inorganica, Metallorganica ed Analitica e Unita INFM, Universita di Padova, Padova (Italy)]. E-mail: granozzi@unipd.it; Rizzi, G. Andrea; Sambi, Mauro [Dipartimento di Chimica Inorganica, Metallorganica ed Analitica e Unita INFM, Universita di Padova, Padova (Italy)

    2002-04-29

    Selected examples of the application of angle-scanned x-ray photoelectron diffraction (XPD) to structural studies of epitaxial oxide ultrathin films and nanoclusters deposited either on metal or on oxide single-crystalline substrates are briefly reviewed. A short introduction discusses the preparative strategies adopted in order to grow the desired oxide systems, as well as the basic features of the XPD technique which are relevant to the field of oxide epitaxy. Synthesis routes include both e-beam metal evaporation and oxidation and a modification of metal-organic chemical vapour deposition to suit ultra-high-vacuum conditions. These introductory remarks are followed by an overview of some systems that have been investigated in our laboratory. The discussion is particularly aimed at highlighting the peculiar capabilities and strengths of photoelectron diffraction applied to - even short-range-ordered - oxide epitaxial systems. Oxide overlayers obtained by means of reactive deposition or post-oxidation comprise various vanadium oxide phases grown on rutile TiO{sub 2}(110), while metalcarbonyl precursor decomposition in an oxygen atmosphere as a source of oxide ultrathin films is illustrated through the cases of RuO{sub 2}/TiO{sub 2}(110) from Ru{sub 3}(CO){sub 12} and MnO/Pt(111) from Mn{sub 2}(CO){sub 10}. Finally, some remarks are made on recent developments and future perspectives in the field of synchrotron-radiation-based implementations of photoelectron diffraction and holography. (author)

  11. Halogen versus halide electronic structure

    Institute of Scientific and Technical Information of China (English)

    Willem-Jan; van; Zeist; F.Matthias; Bickelhaupt

    2010-01-01

    Halide anions X-are known to show a decreasing proton affinity(PA),as X descends in the periodic table along series F,Cl,Br and I.But it is also well-known that,along this series,the halogen atom X becomes less electronegative(or more electropositive).This corresponds to an increasing energy of the valence np atomic orbital(AO) which,somewhat contradictorily,suggests that the electron donor capability and thus the PA of the halides should increase along the series F,Cl,Br,I.To reconcile these contradictory observations,we have carried out a detailed theoretical analysis of the electronic structure and bonding capability of the halide anions X-as well as the halogen radicals X-,using the molecular orbital(MO) models contained in Kohn-Sham density functional theory(DFT,at SAOP/TZ2P as well as OLYP/TZ2P levels) and ab initio theory(at the HF/TZ2P level).We also resolve an apparent intrinsic contradiction in Hartree-Fock theory between orbital-energy and PA trends.The results of our analyses are of direct relevance for understanding elementary organic reactions such as nucleophilic substitution(SN2) and base-induced elimination(E2) reactions.

  12. Transepidermal water loss during halogen spotlight phototherapy in preterm infants.

    Science.gov (United States)

    Grünhagen, Dirk J; de Boer, Mark G J; de Beaufort, Arnout Jan; Walther, Frans J

    2002-03-01

    Among preterm infants there is a relationship between skin blood flow and transepidermal water loss (TEWL). The aim of this study was to assess whether halogen spotlight phototherapy without significant heat stress increases TEWL and affects maintenance fluid requirements in preterm infants. TEWL was measured noninvasively before the start and after 1 h of halogen spotlight phototherapy in a group of preterm infants, nursed in double-walled incubators with moderately high relative humidity. Relative humidity and ambient temperature in the incubator were tightly controlled. Mean +/- SD birth weight of the 18 infants was 1412 +/- 256 g, gestational age 30.6 +/- 1.6 wk, and age at measurement 5 +/- 3 d. Nine infants received ventilatory assistance. Relative humidity was 40-80% (mean 52%). Average TEWL increased from 13.6 to 16.5 g/m(2)/h during phototherapy. These data show that TEWL increases by approximately 20% during phototherapy despite constant skin temperature and relative humidity. Maintenance fluids of preterm infants should be increased by 0.35 mL/kg/h during exposure to halogen spotlight phototherapy.

  13. Halogens in pore water of peat bogs – the role of peat decomposition and dissolved organic matter

    Directory of Open Access Journals (Sweden)

    H. Biester

    2006-01-01

    Full Text Available Halogens are strongly enriched in peat and peatlands and such they are one of their largest active terrestrial reservoir. The enrichment of halogens in peat is mainly attributed to the formation of organohalogens and climatically controlled humification processes. However, little is known about release of halogens from the peat substrate and the distribution of halogens in the peat pore water. In this study we have investigated the distribution of chlorine, bromine and iodine in pore water of three pristine peat bogs located in the Magellanic Moorlands, southern Chile. Peat pore waters were collected using a sipping technique, which allows in situ sampling down to a depth greater than 6m. Halogens and halogen species in pore water were determined by ion-chromatography (IC (chlorine and IC-ICP-MS (bromine and iodine. Results show that halogen concentrations in pore water are 15–30 times higher than in rainwater. Mean concentrations of chlorine, bromine and iodine in pore water were 7–15 mg l−1, 56–123 μg l−1, and 10–20 μg l−1, which correspond to mean proportions of 10–15%, 1–2.3% and 0.5–2.2% of total concentrations in peat, respectively. Organobromine and organoiodine were the predominant species in pore waters, whereas chlorine in pore water was mostly chloride. Advection and diffusion of halogens were found to be generally low and halogen concentrations appear to reflect release from the peat substrate. Release of bromine and iodine from peat depend on the degree of peat degradation, whereas this relationship is weak for chlorine. Relatively higher release of bromine and iodine was observed in less degraded peat sections, where the release of dissolved organic carbon (DOC was also the most intensive. It has been concluded that the release of halogenated dissolved organic matter (DOM is the predominant mechanism of iodine and bromine release from peat.

  14. Halogen Bonding in Hypervalent Iodine Compounds.

    Science.gov (United States)

    Catalano, Luca; Cavallo, Gabriella; Metrangolo, Pierangelo; Resnati, Giuseppe; Terraneo, Giancarlo

    Halogen bonds occur when electrophilic halogens (Lewis acids) attractively interact with donors of electron density (Lewis bases). This term is commonly used for interactions undertaken by monovalent halogen derivatives. The aim of this chapter is to show that the geometric features of the bonding pattern around iodine in its hypervalent derivatives justify the understanding of some of the longer bonds as halogen bonds. We suggest that interactions directionality in ionic and neutral λ(3)-iodane derivatives is evidence that the electron density distribution around iodine atoms is anisotropic, a region of most positive electrostatic potential exists on the extensions of the covalent bonds formed by iodine, and these positive caps affect, or even determine, the crystal packing of these derivatives. For instance, the short cation-anion contacts in ionic λ(3)-iodane and λ(5)-iodane derivatives fully match the halogen bond definition and geometrical prerequisites. The same holds for the short contacts the cation of ionic λ(3)-iodanes forms with lone-pair donors or the short contacts given by neutral λ(3)-iodanes with incoming nucleophiles. The longer and weaker bonds formed by iodine in hypervalent compounds are usually called secondary bondings and we propose that the term halogen bond can also be used. Compared to the term secondary bond, halogen bond may possibly be more descriptive of some bonding features, e.g., its directionality and the relationships between structure of interacting groups and interaction strength.

  15. Does fluorine participate in halogen bonding?

    Science.gov (United States)

    Eskandari, Kiamars; Lesani, Mina

    2015-03-16

    When R is sufficiently electron withdrawing, the fluorine in the R-F molecules could interact with electron donors (e.g., ammonia) and form a noncovalent bond (F⋅⋅⋅N). Although these interactions are usually categorized as halogen bonding, our studies show that there are fundamental differences between these interactions and halogen bonds. Although the anisotropic distribution of electronic charge around a halogen is responsible for halogen bond formations, the electronic charge around the fluorine in these molecules is spherical. According to source function analysis, F is the sink of electron density at the F⋅⋅⋅N BCP, whereas other halogens are the source. In contrast to halogen bonds, the F⋅⋅⋅N interactions cannot be regarded as lump-hole interactions; there is no hole in the valence shell charge concentration (VSCC) of fluorine. Although the quadruple moment of Cl and Br is mainly responsible for the existence of σ-holes, it is negligibly small in the fluorine. Here, the atomic dipole moment of F plays a stabilizing role in the formation of F⋅⋅⋅N bonds. Interacting quantum atoms (IQA) analysis indicates that the interaction between halogen and nitrogen in the halogen bonds is attractive, whereas it is repulsive in the F⋅⋅⋅N interactions. Virial-based atomic energies show that the fluorine, in contrast to Cl and Br, stabilize upon complex formation. According to these differences, it seems that the F⋅⋅⋅N interactions should be referred to as "fluorine bond" instead of halogen bond.

  16. Halogen bond: a long overlooked interaction.

    Science.gov (United States)

    Cavallo, Gabriella; Metrangolo, Pierangelo; Pilati, Tullio; Resnati, Giuseppe; Terraneo, Giancarlo

    2015-01-01

    Because of their high electronegativity, halogen atoms are typically considered, in most of their derivatives, as sites of high electron density and it is commonly accepted that they can form attractive interactions by functioning as the electron donor site (nucleophilic site). This is the case when they work as hydrogen bond acceptor sites. However, the electron density in covalently bound halogens is anisotropically distributed. There is a region of higher electron density, accounting for the ability of halogens to function as electron donor sites in attractive interactions, and a region of lower electron density where the electrostatic potential is frequently positive (mainly in the heavier halogens). This latter region is responsible for the ability of halogen atoms to function as the electron-acceptor site (electrophilic site) in attractive interactions formed with a variety of lone pair-possessing atoms, anions, and π-systems. This ability is quite general and is shown by a wide diversity of halogenated compounds (e.g., organohalogen derivatives and dihalogens). According to the definition proposed by the International Union of Pure and Applied Chemistry, any attractive interactions wherein the halogen atom is the electrophile is named halogen bond (XB). In this chapter, it is discussed how the practice and the concept of XB developed and a brief history of the interaction is presented. Papers (either from the primary or secondary literature) which have reported major experimental findings in the field or which have given important theoretical contributions for the development of the concept are recollected in order to trace how a unifying and comprehensive categorization emerged encompassing all interactions wherein halogen atoms function as the electrophilic site.

  17. The effect of plasma electrolytic oxidation on the mean stress sensitivity of the fatigue life of the 6082 aluminum alloy

    Science.gov (United States)

    Winter, L.; Morgenstern, R.; Hockauf, K.; Lampke, T.

    2016-03-01

    In this work the mean stress influence on the high cycle fatigue behavior of the plasma electrolytic oxidized (PEO) 6082 aluminum alloy (AlSi1MgMn) is investigated. The present study is focused on the fatigue life time and the susceptibility of fatigue-induced cracking of the oxide coating and their dependence on the applied mean stress. Systematic work is done comparing conditions with and without PEO treatment, which have been tested using three different load ratios. For the uncoated substrate the cycles to failure show a significant dependence on the mean stress, which is typical for aluminum alloys. With increased load ratio and therefore increased mean stress, the fatigue strength decreases. The investigation confirms the well-known effect of PEO treatment on the fatigue life: The fatigue strength is significantly reduced by the PEO process, compared to the uncoated substrate. However, also the mean stress sensitivity of the fatigue performance is reduced. The fatigue limit is not influenced by an increasing mean stress for the PEO treated conditions. This effect is firstly shown in these findings and no explanation for this effect can be found in literature. Supposedly the internal compressive stresses and the micro-cracks in the oxide film have a direct influence on the crack initiation and growth from the oxide film through the interface and in the substrate. Contrary to these findings, the susceptibility of fatigue-induced cracking of the oxide coating is influenced by the load ratio. At tension-tension loading a large number of cracks, which grow partially just in the aluminum substrate, are present. With decreasing load ratio to alternating tension-compression stresses, the crack number and length increases and shattering of the oxide film is more pronounced due to the additional effective compressive part of the load cycle.

  18. Inhibiting the photosensitized oxidation of anthracene and tryptophan by means of natural antioxidants

    Science.gov (United States)

    Aksenova, N. A.; Vyzhlova, E. N.; Malinovskaya, V. V.; Parfenov, V. V.; Solov'eva, A. B.; Timashev, P. S.

    2013-08-01

    It is shown that model reactions of photosensitized oxidation of anthracene and tryptophan can be used for evaluation and comparison of antioxidant activity of various classes of compounds. Inhibition of the oxidation of substrates in the presence of the familiar antioxidants tocopherol (vitamin E), ascorbic acid (vitamin C), and mixtures of these vitamins with methionine, and in the presence of reputed antioxidants dihydroquercetin and taurine, are considered. It is concluded that all of the above compounds except for taurine have antioxidant properties; i.e., they reduce the rate constants of the photosensitized oxidation of anthracene and tryptophan. It is found that the inhibition of oxidation is associated with the interaction between antioxidants and singlet oxygen. Analysis of the kinetic dependences of the photosensitized oxidation of substrates in the presence of antioxidants reveals that a mixture of vitamins inhibits the process most efficiently, and inhibition occurs at the initial stages due to more active interaction between singlet oxygen and vitamin C

  19. Investigations of the tropospheric halogen chemistry around Ross Island, Antarctica, during austral spring 2012

    Science.gov (United States)

    Zielcke, Johannes; Pöhler, Denis; Frieß, Udo; Hay, Tim; Kreher, Karin; Kalnajs, Lars; Platt, Ulrich

    2013-04-01

    A unique feature of the polar troposphere is the strong impact of halogen photochemistry, in which reactive halogen species (RHS) are responsible for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide. The source, however, as well as release and recycling mechanisms of these halogen species are far from being completely understood, especially the role of chlorine and iodine compounds. Reactive chlorine, bromine and iodine compounds are thought to be released from sea salt particles or produced by the photolysis of halocarbons and I2 emitted by the ocean. Here we present observations of halogen oxides, ozone and nitrogen dioxide conducted for three months during austral spring 2012 on Ross Island, Antarctica. Measurements were performed with a suite of remote sensing instruments. An active long-path differential optical absorption spectroscopy (LP-DOAS) system was set up, measuring several species (BrO, O3, NO2, OBrO, IO, OIO, I2, ClO, OClO, CHOCHO, HCHO, HONO) continuously for the whole period, with two light paths over first year sea ice. In addition, a passive MAX-DOAS as well as a new Cavity-Enhanced (CE)-DOAS system were used for mobile halogen oxide measurements on a variety of locations around Ross Island (sea ice, shelf ice, snow, coastal, etc.), with top surface layer pH measurements performed at the different measurement sites. First results show highly variable ozone concentrations including partial Ozone Depletion Events (ODEs), as well as concentrations of BrO up to 16ppt and NO2 up to 15ppb. Suprisingly, a high variation of ozone was observed without significant amounts of BrO, indicating already depleted air masses transported to the measurement site and/or NOx chemistry inhibiting halogen radical reactions.

  20. Informative document halogenated hydrocarbon-containing waste

    NARCIS (Netherlands)

    Verhagen H

    1992-01-01

    This "Informative document halogenated hydrocarbon-containing waste" forms part of a series of "Informative documents waste materials". These documents are conducted by RIVM on the instructions of the Directorate General for the Environment, Waste Materials Directorate, in behal

  1. Cross-reactivity of Halogenated Platinum Salts

    Science.gov (United States)

    Halogenated platinum (Pt) salts are well-known respiratory sensitizers associated with the development of asthma. People may be exposed to a variety of platinum compounds in different contexts (e.g. occupationally, automobile exhaust). Published reports suggest that sensitizati...

  2. Removal of PCBs in contaminated soils by means of chemical reduction and advanced oxidation processes.

    Science.gov (United States)

    Rybnikova, V; Usman, M; Hanna, K

    2016-09-01

    Although the chemical reduction and advanced oxidation processes have been widely used individually, very few studies have assessed the combined reduction/oxidation approach for soil remediation. In the present study, experiments were performed in spiked sand and historically contaminated soil by using four synthetic nanoparticles (Fe(0), Fe/Ni, Fe3O4, Fe3 - x Ni x O4). These nanoparticles were tested firstly for reductive transformation of polychlorinated biphenyls (PCBs) and then employed as catalysts to promote chemical oxidation reactions (H2O2 or persulfate). Obtained results indicated that bimetallic nanoparticles Fe/Ni showed the highest efficiency in reduction of PCB28 and PCB118 in spiked sand (97 and 79 %, respectively), whereas magnetite (Fe3O4) exhibited a high catalytic stability during the combined reduction/oxidation approach. In chemical oxidation, persulfate showed higher PCB degradation extent than hydrogen peroxide. As expected, the degradation efficiency was found to be limited in historically contaminated soil, where only Fe(0) and Fe/Ni particles exhibited reductive capability towards PCBs (13 and 18 %). In oxidation step, the highest degradation extents were obtained in presence of Fe(0) and Fe/Ni (18-19 %). The increase in particle and oxidant doses improved the efficiency of treatment, but overall degradation extents did not exceed 30 %, suggesting that only a small part of PCBs in soil was available for reaction with catalyst and/or oxidant. The use of organic solvent or cyclodextrin to improve the PCB availability in soil did not enhance degradation efficiency, underscoring the strong impact of soil matrix. Moreover, a better PCB degradation was observed in sand spiked with extractable organic matter separated from contaminated soil. In contrast to fractions with higher particle size (250-500 and oxidation reactions in soils and understand the impact of soil properties on remediation performance.

  3. Halogens, Barium and Uranium in Mantle Fluid Inclusions

    Science.gov (United States)

    Villa, I. M.; Peverelli, V.; Oglialoro, E.; Pettke, D. T.; Frezzotti, M. L.

    2016-12-01

    Halogens are an underexplored geochemical marker. A way to measure halogens at ng/g levels is measuring Ar, Kr and Xe in irradiated samples [1,2]. We derive absolute halogen amounts from rare gas amounts via scapolite monitor SY [2]. Kr-Xe systematics also yield Ba and U concentrations. We combined irradiation with stepheating on carbonate-sulfate-rich fluid inclusions (FI)-bearing xe­no­liths from El Hierro, Canarias: spinel harzburgite XML-7 and spinel dunite XML-1 [3]. Three components are recognized in the rare gas release. (1) Atmospheric surface contamination occurs up to 1000 °C. (2) FI decrepitation by laboratory heating occurs above 1200 °C [4], corresponding to the release of 80,82Kr and 128Xe in the 1200 and 1400 °C steps. Br whole-rock concentrations are 3-8 ng/g; the molar Br/Cl and I/Cl ratios in the harzburgite FI, 9 E-4 resp. 2 E-4, are identical to those in the dunite FI. This sets the halogens in our FI apart from MORB [2]. Halogen-derived rare gases are closely associated to artificial 131Xe from Ba; Ba has a high affinity of for CO2-rich fluids. Daughter minerals in multiphase FI were identified by Raman micro­spectroscopy [4]. The calculated Ba concentrations are 2-6 µg/g. (3) The third component is U-derived 134,136Xe and 86Kr released in a spike at 1000 °C, decoupled from FI. This requires a different carrier than FI, e.g. Ti oxides. As U concentrations are 10-20 pg/g, the U-bearing phase needs to be below a ppm, invisible by petro­graphy. The 136Xe/134Xe ratio > 1 suggests retention of radio­genic Xe. However, analysis of an unirradiated sample detected no radiogenic Xe. It is likely that Xe-U produced in the core of the McMaster reactor (thermal, epithermal and fast neutrons) has a different isotopic composition from that in textbooks, as proposed by [2].[1] Jeffery & Reynolds (1961) J.Geophys. Res. 66, 3582 [2] Kendrick (2012) Chem. Geol. 292, 116 [3] Oglialoro et al (2015) AGU Fall Meeting abstract V21C-3046 [4] Roedder (1965

  4. FIELD SCREENING FOR HALOGENATED VOLATILE ORGANIC COMPOUNDS

    Energy Technology Data Exchange (ETDEWEB)

    John F. Schabron; Joseph F. Rovani Jr.; Theresa M. Bomstad

    2002-06-01

    Western Research Institute (WRI) initiated exploratory work towards the development of new field screening methodology and a test kit to measure halogenated volatile organic compounds (VOCs) in the field. Heated diode and corona discharge sensors are commonly used to detect leaks of refrigerants from air conditioners, freezers, and refrigerators. They are both selective to the presence of carbon-halogen bonds. Commercially available heated diode and corona discharge leak detectors were procured and evaluated for halogenated VOC response. The units were modified to provide a digital readout of signal related to VOC concentration. Sensor response was evaluated with carbon tetrachloride and tetrachloroethylene (perchloroethylene, PCE), which represent halogenated VOCs with and without double bonds. The response characteristics were determined for the VOCs directly in headspace in Tedlar bag containers. Quantitation limits in air were estimated. Potential interferences from volatile hydrocarbons, such as toluene and heptane, were evaluated. The effect of humidity was studied also. The performance of the new devices was evaluated in the laboratory by spiking soil samples and monitoring headspace for halogenated VOCs. A draft concept of the steps for a new analytical method was outlined. The results of the first year effort show that both devices show potential utility for future analytical method development work towards the goal of developing a portable test kit for screening halogenated VOCs in the field.

  5. Latest generation of halogen-containing pesticides.

    Science.gov (United States)

    Jeschke, Peter

    2017-02-01

    Agriculture is confronted with enormous challenges, from production of enough high-quality food to water use, environmental impacts and issues combined with a continually growing world population. Modern agricultural chemistry has to support farmers by providing innovative agrichemicals, used in applied agriculture. In this context, the introduction of halogen atoms into an active ingredient is still an important tool to modulate the properties of new crop protection compounds. Since 2010, around 96% of the launched products (herbicides, fungicides, insecticides/acaricides and nematicides) contain halogen atoms. The launched nematicides contain the largest number of halogen atoms, followed by insecticides/acaricides, herbicides and fungicides. In this context, fungicides and herbicides contain in most cases fluorine atoms, whereas nematicides and insecticides contain in most cases 'mixed' halogen atoms, for example chlorine and fluorine. This review gives an overview of the latest generation of halogen-containing pesticides launched over the past 6 years and describes current halogen-containing development candidates. © 2017 Society of Chemical Industry.

  6. Halogens, OVOC and H2O Distributions over the Eastern Pacific Ocean during TORERO

    Science.gov (United States)

    Dix, B. K.; Apel, E. C.; Baidar, S.; Zondlo, M. A.; Volkamer, R.

    2013-12-01

    As part of the Tropical Ocean tRoposphere Exchange of Reactive halogen species and Oxygenated VOC (TORERO) field project 17 research flights were conducted with the NSF/NCAR GV aircraft over the Eastern Tropical Pacific Ocean (42S to 14N Lat.; 70W to 105W Long). Equipped with a combination of chemical in-situ sensors and remote sensing instruments, a broad spectrum of reactive halogen species, oxygenated hydrocarbons, and aerosols were measured over different ocean environments. Using optical remote sensing (airborne Multi Axis DOAS), we measured iodine monoxide (IO), bromine monoxide (BrO), glyoxal (CHOCHO) and water vapor among others. A newly developed parameterization method allowed us to directly convert the measured slant column densities into mixing ratios along the whole flight track. Atmospheric reactive halogen species and organic carbon are important, because they modify HOx radical abundances, influence the reactive chemistry and lifetime of climate active gases (e.g., ozone, methane, dimethyl sulfide), modify aerosol-cloud interactions and halogen radicals can also oxidize atmospheric mercury. Here we summarize and evaluate the spatial distribution of IO, BrO and glyoxal over the TORERO study area. For select case studies we present comparisons to halogen precursors and OVOCs measured in-situ by on-line mass spectrometry (trace organic gas analyzer). The correlation of remotely observed water vapor to in-situ measurements further allows us to conclude on the homogeneity of spatial scales covered by both remote and in-situ sensors.

  7. Iron oxide-based nanoparticles with different mean sizes obtained by the laser pyrolysis: structural and magnetic properties.

    Science.gov (United States)

    Morjan, I; Alexandrescu, R; Dumitrache, F; Birjega, R; Fleaca, C; Soare, I; Luculescu, C R; Filoti, G; Kuncer, V; Vekas, L; Popa, N C; Prodan, G; Ciupina, V

    2010-02-01

    Nano-sized iron oxide-based particles have been directly synthesized by the laser induced pyrolysis of a mixture containing iron pentacarbonyl/air (as oxidizer)/ethylene (as sensitizer). In this paper we further demonstrate the possibility to vary the chemical composition and the nanoparticle dimensions of the iron oxide-based materials by handling the oxidation procedure in the frame of the laser pyrolysis process. Thus, nanoparticles with major maghemite/magnetite content may change composition into mixtures with variable amounts of three components: major gamma-Fe2O3/Fe3O4 iron oxide, metallic Fe and cementite Fe3C. By X-ray diffraction (XRD) it is found that the relative proportion of these phases differs in function of the reaction temperature (laser power). As revealed by transmission electron microscopy (TEM), mean particle sizes between about 4 nm and 6 nm and between about 9 and 11 nm may be prepared by varying the oxidation procedure and the laser power, respectively. By the controlled heating of samples (maximum temperature 185 degrees C), increased crystallinity for the gamma-Fe2O3/Fe3O4 oxide phase was found as well as an increase of the mean particle diameters. The examination of the magnetization curves for samples obtained for different laser powers indicates notable differences in the magnetic behavior and parameters. The temperature dependent Mossbauer measurements confirm the formation of larger particles at higher laser power densities as well as the presence of inter-particle magnetic interactions. On this basis, the estimation of phase composition for the different representative samples is given.

  8. Study of silicon/oxides interfaces by means of Si2p resonant photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Tallarida, Massimo [BTU-Cottbus, Konrad-Wachsmann-Allee 17, 03046, Cottbus (Germany)], E-mail: tallamas@tu-cottbus.de; Schmeisser, Dieter [BTU-Cottbus, Konrad-Wachsmann-Allee 17, 03046, Cottbus (Germany)

    2008-11-03

    In this paper we show results from resonant photoemission experiments where energy dispersive curves (EDC) were collected at various photon energies around the Si2p absorption edge. From the complete collection we have extracted the spectrum measured at the photon energy of 125 eV and studied the Auger feature included in the EDC. From the comparison of the Auger line of the bulk SiO{sub 2} with the expected transitions we demonstrate the occurrence of inter-atomic transitions in the bulk oxide. Comparing the Auger line from the bulk oxide with that from a native oxide we may observe the occurrence of inter-atomic transitions localized at the interface. We propose an interpretation of this result by considering the geometry at the interface.

  9. Treatment System for Removing Halogenated Compounds from Contaminated Sources

    Science.gov (United States)

    Quinn, Jacqueline W. (Inventor); Clausen, Christian A. (Inventor); Yestrebsky, Cherie L. (Inventor)

    2015-01-01

    A treatment system and a method for removal of at least one halogenated compound, such as PCBs, found in contaminated systems are provided. The treatment system includes a polymer blanket for receiving at least one non-polar solvent. The halogenated compound permeates into or through a wall of the polymer blanket where it is solubilized with at least one non-polar solvent received by said polymer blanket forming a halogenated solvent mixture. This treatment system and method provides for the in situ removal of halogenated compounds from the contaminated system. In one embodiment, the halogenated solvent mixture is subjected to subsequent processes which destroy and/or degrade the halogenated compound.

  10. Stability of mutagenic tautomers of uracil and its halogen derivatives: the results of quantum-mechanical investigation

    OpenAIRE

    Hovorun D. M.; Brovarets’ O. O.

    2010-01-01

    Aim. To investigate using the quantum-mechanical methods uracil (Ura) intramolecular tautomerisation and the effect of the thymine (Thy) methyl (Me) group substitution by the halogen on that process. Methods. Non-empirical quantum mechanic, analysis of the electron density by means of Bader’s atom in molecules (AIM) theory and physicochemical kinetics were used. Results. For the first time it has been established that the substitution of thymine Me-group for the halogen (Br, F, Cl) has practi...

  11. A QTAIM exploration of the competition between hydrogen and halogen bonding in halogenated 1-methyluracil: Water systems

    Science.gov (United States)

    Huan, Guo; Xu, Tianlv; Momen, Roya; Wang, Lingling; Ping, Yang; Kirk, Steven R.; Jenkins, Samantha; van Mourik, Tanja

    2016-10-01

    Using QTAIM we show that the hydrogen bonding complexes of 5-halogenated-1-methyluracil (XmU; X = F, Cl, Br, I or At) with a water molecule were always stronger than the corresponding halogen bonds. The strength of the hydrogen bond decreased with increasing halogen size. The hydrogen bonds displayed an admixture of covalent character but all the halogen bonds were purely electrostatic in nature. An F---O halogen bond was found and was facilitated by an intermediate F---H bonding interaction. The metallicity ξ(rb) of the C = O bonds neighboring the hydrogen bonds and of the C-X bonds contiguous with the halogen bonds was explored.

  12. Halogen-bonding-triggered supramolecular gel formation.

    Science.gov (United States)

    Meazza, Lorenzo; Foster, Jonathan A; Fucke, Katharina; Metrangolo, Pierangelo; Resnati, Giuseppe; Steed, Jonathan W

    2013-01-01

    Supramolecular gels are topical soft materials involving the reversible formation of fibrous aggregates using non-covalent interactions. There is significant interest in controlling the properties of such materials by the formation of multicomponent systems, which exhibit non-additive properties emerging from interaction of the components. The use of hydrogen bonding to assemble supramolecular gels in organic solvents is well established. In contrast, the use of halogen bonding to trigger supramolecular gel formation in a two-component gel ('co-gel') is essentially unexplored, and forms the basis for this study. Here, we show that halogen bonding between a pyridyl substituent in a bis(pyridyl urea) and 1,4-diiodotetrafluorobenzene brings about gelation, even in polar media such as aqueous methanol and aqueous dimethylsulfoxide. This demonstrates that halogen bonding is sufficiently strong to interfere with competing gel-inhibitory interactions and create a 'tipping point' in gel assembly. Using this concept, we have prepared a halogen bond donor bis(urea) gelator that forms co-gels with halogen bond acceptors.

  13. Removal mechanisms for endocrine disrupting compounds (EDCs) in wastewater treatment - physical means, biodegradation, and chemical advanced oxidation: a review.

    Science.gov (United States)

    Liu, Ze-Hua; Kanjo, Yoshinori; Mizutani, Satoshi

    2009-01-01

    Endocrine disrupting compounds (EDCs) are pollutants with estrogenic or androgenic activity at very low concentrations and are emerging as a major concern for water quality. Within the past few decades, more and more target chemicals were monitored as the source of estrogenic or androgenic activity in wastewater, and great endeavors have been done on the removal of EDCs in wastewater. This article reviewed removal of EDCs from three aspects, that is, physical means, biodegradation, and chemical advanced oxidation (CAO).

  14. Halogen degassing during ascent and eruption of water-poor basaltic magma

    Science.gov (United States)

    Edmonds, M.; Gerlach, T.M.; Herd, Richard A.

    2009-01-01

    A study of volcanic gas composition and matrix glass volatile concentrations has allowed a model for halogen degassing to be formulated for K??lauea Volcano, Hawai'i. Volcanic gases emitted during 2004-2005 were characterised by a molar SO2/HCl of 10-64, with a mean of 33; and a molar HF/HCl of 0-5, with a mean of 1.0 (from approximately 2500 measurements). The HF/HCl ratio was more variable than the SO2/HCl ratio, and the two correlate weakly. Variations in ratio took place over rapid timescales (seconds). Matrix glasses of Pele's tears erupted in 2006 have a mean S, Cl and F content of 67, 85 and 173??ppm respectively, but are associated with a large range in S/F. A model is developed that describes the open system degassing of halogens from parental magmas, using the glass data from this study, previously published results and parameterisation of sulphur degassing from previous work. The results illustrate that halogen degassing takes place at pressures of pressure, virtually at the top of the magma column. This model reproduces the volcanic gas data and other observations of volcanic activity well and is consistent with other studies of halogen degassing from basaltic magmas. The model suggests that variation in volcanic gas halogen ratios is caused by exsolution and gas-melt separation at low pressures in the conduit. There is no evidence that either diffusive fractionation or near-vent chemical reactions involving halogens is important in the system, although these processes cannot be ruled out. The fluxes of HCl and HF from K??lauea during 2004-5 were ~ 25 and 12??t/d respectively. ?? 2008 Elsevier B.V.

  15. Treatment of surfactant stabilized oil-in-water emulsions by means of chemical oxidation and coagulation.

    Science.gov (United States)

    Kulik, N; Trapido, M; Veressinina, Y; Munter, R

    2007-12-01

    The model wastewater samples investigated in the current study represented oil-in-water (O/W) emulsions with small oil (diesel/black oil) and high surfactant (Anrol/Decon90) concentrations generated during washing of oil tankers or tank-wagons. Coagulation with aluminium sulphate, ferric chloride and lime milk, and chemical oxidation by hydrogen peroxide catalyzed ferrous ions were applied as traditional and advanced treatment processes, respectively. Coagulation proved more feasible for oil content removal than for COD reduction. Both COD and oil content removal, were higher if Anrol was used as a surface active agent. The comparison of wastewater samples with different oil products but the same detergent showed more effective black oil removal. Coagulation was found ineffective as a pre-treatment technology for biodegradability improvement and toxicity reduction in surfactant stabilized O/W emulsion wastewater samples. The application of Fenton chemistry showed significant COD, UV absorbance and BOD removal, but no improvement in wastewater samples biodegradability. The maximum COD reduction and oil content removal from wastewater samples was above 90%. The oxidation of wastewater containing Decon90 required higher dosages of the Fenton reagent than wastewater with Anrol. Both Anrol and Decon90 contaminated wastewater samples were found to be detoxified even after moderate hydrogen peroxide dosages had been applied in the oxidation step.

  16. Study of molybdenum oxide by means of Perturbed Angular Correlations (PAC) and Mössbauer spectroscopy

    CERN Multimedia

    Among transition-metal oxides, the molybdenum oxide compounds are particularly attractive due to the structural (2D) anisotropy and to the ability of the molybdenum ion to change its oxidation state. These properties make it suitable for applications on, e.g., chemical sensors, solar cells, catalytic and optoelectronic devices. At ISOLDE we aim studying the incorporation of selected dopants by ion implantation, using the nuclear techniques of Perturbed Angular Correlations (PAC) and Mössbauer spectroscopy (MS). Both techniques make use of highly diluted radioactive probe nuclei, which interact – as atomic-sized tips – with the host atoms and defects. The objectives of this project are to study at the atomic scale the probe’s local environment, its electronic configuration and polarization, the probe’s lattice sites, point defects and its recombination dynamics. In the case of e-$\\gamma$ PAC, the electron mobility on the host can be further studied, e.g., as a function of temperature.

  17. Low-Cost Synthesis of Smart Biocompatible Graphene Oxide Reduced Species by Means of GFP.

    Science.gov (United States)

    Masullo, Tiziana; Armata, Nerina; Pendolino, Flavio; Colombo, Paolo; Lo Celso, Fabrizio; Mazzola, Salvatore; Cuttitta, Angela

    2016-02-01

    The aim of this work is focused on the engineering of biocompatible complex systems composed of an inorganic and bio part. Graphene oxide (GO) and/or graphite oxide (GtO) were taken into account as potential substrates to the linkage of the protein such as Anemonia sulcata recombinant green fluorescent protein (rAsGFP). The complex system is obtained through a reduction process between GO/GtO and rAsGFP archiving an environmentally friendly biosynthesis. Spectroscopic measurements support the formation of reduced species. In particular, photoluminescence shows a change in the activity of the protein when a bond is formed, highlighted by a loss of the maximum emission signal of rAsGFP and a redshift of the maximum absorption peak of the GO/GtO species. Moreover, the hemolysis assay reveals a lower value in the presence of less oxidized graphene species providing evidence for a biocompatible material. This singular aspect can be approached as a promising method for circulating pharmaceutical preparations via intravenous administration in the field of drug delivery.

  18. Retention efficiencies of halogenated and non-halogenated hydrocarbons in selected wetland ecosystem in Lake Victoria Basin

    Directory of Open Access Journals (Sweden)

    Shadrack Mule

    2015-06-01

    Full Text Available The determination of retention efficiencies of halogenated and non-halogenated hydrocarbon in selected wetland ecosystems in Lake Victoria basin was carried out. Qualitative and quantitative determination of the presence of residual hydrocarbons in Kigwal/Kimondi, Nyando and Nzoia wetland ecosystems using Gas Chromatography - Mass Spectrometer (GC-MS instrument indicated the presence of residual organochlorines, organophosphorus, carbamates and synthetic pyrethroid hydrocarbons in water, sediment and plant materials. In order to compare the retention efficiencies of the wetlands, the wetland ecosystems were divided into three different sections, namely: inlet, mid and outlet. Calculations of mass balances of residual halogenated and non-halogenated hydrocarbons at the respective sections was done taking into account the partition of the studied compounds in samples of water, sediments and papyrus reed plant materials and analyzed using validated Gas Chromatography - Mass Spectrometer (GC-MS method. From the analysis, several residual hydrocarbons namely: bendiocarb, benzene hexachloride (BHC, carbaryl, cypermethrin, decis, deltamethrin, diazinon, dieldrin, DDT, DDD, DDE, malathion, propoxur, sumithion, 5-phenylrhodanine, 1,3,5-trichlorobenzene, 1-(2-phenoxybenzylhydrazine were detected and quantified. The levels of the selected residual hydrocarbons in water samples were used to calculate the retention efficiencies of a specific hydrocarbon and the values recorded. Generally, River Nyando wetland recorded mean percentage retention efficiencies of 76 and 94% for dry and rainy seasons respectively; Kigwal/Kimondi wetland had seasonal mean percentage retention efficiencies of 63 to 78%. River Nzoia also had calculated seasonal mean percentage retention efficiencies of between 56 to 88%. Dry season had lower mean percentages retention efficiencies as compared to rainy season in the three wetlands of interest during the period of study. The study

  19. Evaluation of Halogenated Coumarins for Antimosquito Properties

    Directory of Open Access Journals (Sweden)

    Venugopala K. Narayanaswamy

    2014-01-01

    Full Text Available Mosquitoes are the major vectors of parasites and pathogens affecting humans and domestic animals. The widespread development of insecticide resistance and negative environmental effects of most synthetic compounds support an interest in finding and developing alternative products against mosquitoes. Natural coumarins and synthetic coumarin analogues are known for their several pharmacological properties, including being insecticidal. In the present study halogenated coumarins (3-mono/dibromo acetyl, 6-halogenated coumarin analogues were screened for larvicidal, adulticidal, and repellent properties against Anopheles arabiensis, a zoophilic mosquito that is one of the dominant vectors of malaria in Africa. Five compounds exerted 100% larval mortality within 24 h of exposure. All coumarins and halogenated coumarins reversibly knocked down adult mosquitoes but did not kill them after 24 h of exposure. Repellent properties could not be evidenced. Five compounds were considered potential larvicidal agents for further research and development, while adulticidal activity was considered only mild to moderate.

  20. Tropospheric Chemistry and Climate Impacts of VSL Halogens: Pre-Industrial to Present day

    Science.gov (United States)

    Kinnison, Douglas; Saiz-Lopez, Alfonso; Lamarque, Jean-Francois; Ordoñez, Carlos; Fernandez, Rafael; Tilmes, Simone

    2013-04-01

    Ozone in the troposphere is one of the most important short-lived gases contributing to greenhouse radiative forcing (IPCC, 2007) and is of central importance to the chemistry of this region of the atmosphere. Tropospheric ozone is produced by photochemical oxidation of carbon monoxide, methane and non-methane volatile organic compounds in the presence of nitrogen oxide. A large fraction of the tropospheric ozone loss occurs within the tropical marine boundary layer via photolysis to excited oxygen atoms followed by reaction with water vapor, reactions with odd hydrogen radical, and surface deposition. In addition, inorganic halogens (i.e., chlorine, bromine, and iodine species) are known to destroy ozone through efficient catalytic reaction cycles. In this study, we use the NCAR 3D chemistry climate model (CAM-CHEM). The model has a full representation of tropospheric and stratospheric chemistry. Its scope has been extended to include halogen sources, reactive halogen chemistry, and related atmospheric processes (Ordonez et al. 2012; Saiz-Lopez et al. 2012). The purpose of this work is to contrast the pre-industrial importance of tropospheric halogen driven ozone loss to present day conditions; specifically the importance of iodine chemistry.

  1. Chemistry of Very Short Lived Halogens in the Troposphere: Pre-Industrial to Present day

    Science.gov (United States)

    Kinnison, Douglas; Saiz-Lopez, Alfonso; Fernandez, Rafael; Lamarque, Jean-Francois; Tilmes, Simone

    2014-05-01

    Ozone in the troposphere is one of the most important short-lived gases contributing to greenhouse radiative forcing (IPCC, 2007) and is of central importance to the chemistry of this region of the atmosphere. Tropospheric ozone is produced by photochemical oxidation of carbon monoxide, methane and other non-methane volatile organic compounds in the presence of nitrogen oxide. A large fraction of the tropospheric ozone loss occurs within the tropical marine boundary layer via photolysis to excited oxygen atoms followed by reaction with water vapor, reactions with odd hydrogen radical, and surface deposition. In addition, inorganic halogens (i.e., chlorine, bromine, and iodine species) are known to destroy ozone through efficient catalytic reaction cycles. In this study, we use the NCAR 3D chemistry climate model (CAM-Chem), including a detailed representation of tropospheric and stratospheric chemistry. Its scope has been extended to include halogen sources, reactive halogen chemistry, and related atmospheric processes (Ordonez et al., ACP, 2012; Saiz-Lopez et al., ACP,. 2012). The purpose of this work is to contrast the pre-industrial importance of tropospheric halogen driven ozone loss to present day conditions, specifically the importance of iodine and bromine chemistry. The sensitivity to inorganic nitrogen abundance will be shown. The model results compared to the pre-industrial surface ozone measurements at Montsouris (Volz and Kley, 1988) will also be discussed.

  2. Halogen Chemistry in Volcanic Plumes (Invited)

    Science.gov (United States)

    Roberts, Tjarda

    2017-04-01

    Volcanoes release vast amounts of gases and particles in the atmosphere. Volcanic halogens (HF, HCl, HBr, HI) are co-emitted alongside SO2, and observations show rapid formation of BrO and OClO in the plume as it disperses into the troposphere. The development of 1D and Box models (e.g. PlumeChem) that simulate volcanic plume halogen chemistry aims to characterise how volcanic reactive halogens form and quantify their atmospheric impacts. Following recent advances, these models can broadly reproduce the observed downwind BrO/SO2 ratios using "bromine-explosion" chemistry schemes, provided they use a "high-temperature initialisation" to inject radicals (OH, Cl, Br and possibly NOx) which "kick-start" the low-temperature chemistry cycles that convert HBr into reactive bromine (initially as Br2). The modelled rise in BrO/SO2 and subsequent plateau/decline as the plume disperses downwind reflects cycling between reactive bromine, particularly Br-BrO, and BrO-HOBr-BrONO2. BrCl is produced when aerosol becomes HBr-depleted. Recent model simulations suggest this mechanism for reactive chlorine formation can broadly account for OClO/SO2 reported at Mt Etna. Predicted impacts of volcanic reactive halogen chemistry include the formation of HNO3 from NOx and depletion of ozone. This concurs with HNO3 widely reported in volcanic plumes (although the source of NOx remains under question), as well as observations of ozone depletion reported in plumes from several volcanoes (Mt Redoubt, Mt Etna, Eyjafjallajokull). The plume chemistry can transform mercury into more easily deposited and potentially toxic forms, for which observations are limited. Recent incorporation of volcanic halogen chemistry in a 3D regional model of degassing from Ambrym (Vanuatu) also predicts how halogen chemistry causes depletion of OH to lengthen the SO2 lifetime, and highlights the potential for halogen transport from the troposphere to the stratosphere. However, the model parameter-space is vast and

  3. 40 CFR 721.329 - Halogenated benzyl ester acrylate (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated benzyl ester acrylate... Specific Chemical Substances § 721.329 Halogenated benzyl ester acrylate (generic). (a) Chemical substance... halogenated benzyl ester acrylate (PMN P-90-1527) is subject to reporting under this section for...

  4. 40 CFR 721.535 - Halogenated alkane (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated alkane (generic). 721.535... Substances § 721.535 Halogenated alkane (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halogenated alkane (PMN P-01-433) is...

  5. 40 CFR 721.536 - Halogenated phenyl alkane.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated phenyl alkane. 721.536... Substances § 721.536 Halogenated phenyl alkane. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as halogenated phenyl alkane (PMN P-89-867)...

  6. 40 CFR 721.8700 - Halogenated alkyl pyridine.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated alkyl pyridine. 721.8700... Substances § 721.8700 Halogenated alkyl pyridine. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as halogenated alkyl pyridine (PMN P-83-237)...

  7. Halogen chemistry reduces tropospheric O3 radiative forcing

    DEFF Research Database (Denmark)

    Sherwen, Tomás; Evans, Mat J.; Carpenter, Lucy J.

    2017-01-01

    Tropospheric ozone (O3) is a global warming gas, but the lack of a firm observational record since the preindustrial period means that estimates of its radiative forcing (RFTO3) rely on model calculations. Recent observational evidence shows that halogens are pervasive in the troposphere and need...

  8. Reduction of tritium permeation through Inconel 718 and Incoloy 800 HT by means of natural oxides

    Science.gov (United States)

    Aiello, A.; Utili, M.; Ciampichetti, A.

    2011-10-01

    Chronical releases of tritium from the helium primary coolant into the water secondary coolant is a fundamental safety issue in the design of a fusion reactor steam generator. It is well known that the steam/water circuit of a fusion reactor would be considered not relevant from a radiological point of view, while if a strong permeation of tritium will be present it will be released together with incondensable gases in the condenser. The permeation of hydrogen isotopes through candidate steam generator materials in different conditions was studied in the past. Further experiments demonstrated that nickel alloys of nuclear interest are always covered by a thin and adherent oxide layer able to reduce permeation of orders of magnitude. The major objective of this work is the evaluation of the permeated flux through nickel alloys, when exposed to pure hydrogen and to an oxidant gas stream, to verify the real permeability of these materials in conditions close to those foreseen in the helium side of the steam generator.

  9. Efficiently exploiting the waste heat in solid oxide fuel cell by means of thermophotovoltaic cell

    Science.gov (United States)

    Liao, Tianjun; Cai, Ling; Zhao, Yingru; Chen, Jincan

    2016-02-01

    Through the combination of the current models of solid oxide fuel cells (SOFCs) and thermophotovoltaic cells (TPVCs), a new model of the hybrid device composed of an SOFC, a regenerator, and a TPVC with integrated back surface reflector (BSR) is proposed. Analytical expressions for the power output and efficiency of two subsystems and hybrid device are derived. The relations between the performance of the TPVC and the operating current density of the SOFC in the hybrid device are revealed. The performance characteristics of the hybrid device are discussed in detail. The maximum power output density is calculated. The optimally operating region of the hybrid device is determined, compared with the performance of the SOFC in the hybrid device. The choice criteria of some key parameters are given. Moreover, it is proved that the proposed model can exploit the waste heat produced in SOFCs more efficiently than other SOFC-based hybrid systems.

  10. Solid oxide electrolysis cell analysis by means of electrochemical impedance spectroscopy: A review

    Science.gov (United States)

    Nechache, A.; Cassir, M.; Ringuedé, A.

    2014-07-01

    High temperature water electrolysis based on Solid Oxide Electrolysis Cell (SOEC) is a very promising solution to produce directly pure hydrogen. However, degradation issues occurring during operation still represent a scientific and technological barrier in view of its development at an industrial scale. Electrochemical Impedance Spectroscopy (EIS) is a powerful in-situ fundamental tool adapted to the study of SOEC systems. Hence, after a quick presentation of EIS principle and data analysis methods, this review demonstrates how EIS can be used: (i) to characterize the performance and mechanisms of SOEC electrodes; (ii) as a complementary tool to study SOEC degradation processes for different cell configurations, in addition to post-test tools such as scanning electron microscopy (SEM) or X-ray diffraction (XRD). The use of EIS to establish a systematic SOEC analysis is introduced as well.

  11. Analysis of Halogen-Mercury Reactions in Flue Gas

    Energy Technology Data Exchange (ETDEWEB)

    Paula Buitrago; Geoffrey Silcox; Constance Senior; Brydger Van Otten

    2010-01-01

    Oxidized mercury species may be formed in combustion systems through gas-phase reactions between elemental mercury and halogens, such as chorine or bromine. This study examines how bromine species affect mercury oxidation in the gas phase and examines the effects of mixtures of bromine and chlorine on extents of oxidation. Experiments were conducted in a bench-scale, laminar flow, methane-fired (300 W), quartz-lined reactor in which gas composition (HCl, HBr, NO{sub x}, SO{sub 2}) and temperature profile were varied. In the experiments, the post-combustion gases were quenched from flame temperatures to about 350 C, and then speciated mercury was measured using a wet conditioning system and continuous emissions monitor (CEM). Supporting kinetic calculations were performed and compared with measured levels of oxidation. A significant portion of this report is devoted to sample conditioning as part of the mercury analysis system. In combustion systems with significant amounts of Br{sub 2} in the flue gas, the impinger solutions used to speciate mercury may be biased and care must be taken in interpreting mercury oxidation results. The stannous chloride solution used in the CEM conditioning system to convert all mercury to total mercury did not provide complete conversion of oxidized mercury to elemental, when bromine was added to the combustion system, resulting in a low bias for the total mercury measurement. The use of a hydroxylamine hydrochloride and sodium hydroxide solution instead of stannous chloride showed a significant improvement in the measurement of total mercury. Bromine was shown to be much more effective in the post-flame, homogeneous oxidation of mercury than chlorine, on an equivalent molar basis. Addition of NO to the flame (up to 400 ppmv) had no impact on mercury oxidation by chlorine or bromine. Addition of SO{sub 2} had no effect on mercury oxidation by chlorine at SO{sub 2} concentrations below about 400 ppmv; some increase in mercury oxidation

  12. On the directionality of halogen bonding.

    Science.gov (United States)

    Huber, Stefan M; Scanlon, Joseph D; Jimenez-Izal, Elisa; Ugalde, Jesus M; Infante, Ivan

    2013-07-07

    The origin of the high directionality of halogen bonding was investigated quantum chemically by a detailed comparison of typical adducts in two different orientations: linear (most stable) and perpendicular. Energy decomposition analyses revealed that the synergy between charge-transfer interactions and Pauli repulsion are the driving forces for the directionality, while electrostatic contributions are more favourable in the less-stable, perpendicular orientation.

  13. Halogen Bonding in (Z-2-Iodocinnamaldehyde

    Directory of Open Access Journals (Sweden)

    Miriam Rossi

    2013-07-01

    Full Text Available Based on the bulkiness of the iodine atom, a non-planar conformation was expected for the title compound. Instead, its molecular structure is planar, as experimentally determined using single crystal X-ray diffraction, and confirmed theoretically by DFT calculations on the single molecule and the halogen pair paired molecules, therefore ruling out crystal packing forces as a principal factor leading to planarity. Indeed, planarity is ascribed to the carbonyl double bond, as when this bond is saturated on forming the related alcohol derivative, the molecule loses planarity. The X-ray molecular structure shows an intermolecular separation between the iodine and the oxygen of the carbonyl shorter than the corresponding van der Waals distance suggesting a weak halogen bond interaction. DFT minimization of this 2-molecule arrangement shows the iodine--oxygen distance much shorter than that observed in the crystal interaction and confirming its stronger halogen bond nature. A trend between increasing I•••O(carbonyl separation and decreasing C-I•••O(carbonyl angle is demonstrated, further confirming the existence of a halogen bond.

  14. Skin Sensitizing Potency of Halogenated Platinum Salts.

    Science.gov (United States)

    The relationship between occupational exposure to halogenated platinum (Pt) salts and Pt-specific allergic sensitization is well-established. Although human case reports and clinical studies demonstrate that Pt salts are potent skin sensitizers, no studies have been published tha...

  15. Syntheses of very dense halogenated liquids.

    Science.gov (United States)

    Ye, Chengfeng; Shreeve, Jean'ne M

    2004-09-17

    A family of halogenated liquids with densities ranging from 1.95 to 2.80 g cm(-3) was readily synthesized by a one-pot procedure. These liquids exhibit characteristics of ionic liquids with melting/transition points lower than room temperature, long liquid ranges, and marked hydrolytic and thermal stabilities.

  16. The Brenner Moor - A saline bog as a source for halogenated and non-halogenated volatile compounds

    Science.gov (United States)

    Krause, T.; Studenroth, S.; Furchner, M.; Hoffman, A.; Lippe, S.; Kotte, K.; Schöler, H. F.

    2012-04-01

    The Brenner Moor is a small bog in the catchment area of the river Trave located in Schleswig-Holstein, North Germany, between Baltic and North Sea. The bog is fed by several saline springs with chloride concentrations up to 15 g/L. The high chloride concentrations and the high organic content of the peat make the Brenner Moor an ideal source for the abiotic formation of volatile organic halogenated compounds (VOX). VOX play an important role in the photochemical processes of the lower atmosphere and information on the atmospheric input from saline soils like the Brenner Moor will help to understand the global fluxes of VOX. Soil samples were taken in spring 2011 from several locations and depths in the vicinity of the Brenner Moor. The samples were freeze-dried, ground and incubated in water emphasising an abiotic character for the formation of volatile organic compounds. 1,2-dichloroethane and trichloromethane are the main halogenated compounds emitted from soils of the Brenner Moor. The abiotic formation of trichloromethane as well as other trihalomethanes has been part of intensive studies. A well known source is the decarboxylation of trichloroacetic acid and trichloroacetyl-containing compounds to trichloromethane [1]. Huber et al. discovered another pathway in which catechol, as a model compound for organic substances, is oxidised under Fenton-like conditions with iron(III), hydrogen peroxide and halides to form trihalomethanes [2]. Besides the halogenated compounds, the formation of sulphur compounds such as dimethyl sulfide and dimethyl disulfide and several furan derivatives could be detected which also have an impact on atmospheric chemistry, especially particle formation of clouds. Furan, methylfuran and dimethylfuran are compounds that can be obtained under Fenton-like oxidation from catechol, methyl- and dimethylcatechol and are known to be produced in natural soils [3]. A novel class of furan derivatives that are formed under abiotic conditions from

  17. The mechanism of cysteine detection in biological media by means of vanadium oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Bezerra, A. G. [Universidade Tecnologica Federal do Parana, Departamento Academico de Fisica (Brazil); Barison, A. [Universidade Federal do Parana, Departamento de Quimica (Brazil); Oliveira, V. S. [Universidade Federal do Parana, Departamento de Fisica (Brazil); Foti, L.; Krieger, M. A. [Fundacao Oswaldo Cruz, Instituto de Biologia Molecular do Parana (Brazil); Dhalia, R.; Viana, I. F. T. [Fundacao Oswaldo Cruz, Centro de Pesquisas Aggeu Magalhaes (Brazil); Schreiner, W. H., E-mail: wido@fisica.ufpr.br [Universidade Federal do Parana, Departamento de Fisica (Brazil)

    2012-09-15

    We report on the interaction of vanadate nanoparticles, produced using the laser ablation in liquids synthesis, with cysteine in biological molecules. Cysteine is a very important amino acid present in most proteins, but also because cysteine and the tripeptide glutathione are the main antioxidant molecules in our body system. Detailed UV-Vis absorption spectra and dynamic light scattering measurements were done to investigate the detection of cysteine in large biological molecules. The intervalence band of the optical absorption spectra shows capability for quantitative cysteine sensing in the {mu}M range in biological macromolecules. Tests included cytoplasmic repetitive antigen and flagellar repetitive antigen proteins of the Trypanosoma cruzi protozoa, as well as the capsid p24 proteins from Human Immunodeficiency Virus type 1 and type 2. Detailed NMR measurements for hydrogen, carbon, and vanadium nuclei show that cysteine in contact with the vanadate looses hydrogen of the sulphydryl side chain, while the vanadate is reduced. The subsequent detachment of two deprotonated molecules to form cystine and the slow return to the vanadate complete the oxidation-reduction cycle. Therefore, the vanadate acts as a charge exchanging catalyst on cysteine to form cystine. The NMR results also indicate that the nanoparticles are not formed by the common orthorhombic V{sub 2}O{sub 5} form.

  18. Repowering of an Existing Power Plant by Means of Gas Turbine and Solid Oxide Fuel Cell

    DEFF Research Database (Denmark)

    Rokni, Masoud

    2014-01-01

    Repowering is a process consisting in a transformation of an old power plant in order to have a greater nameplate capacity or more efficiency, which result in a net increase of power generated. As a consequence of the higher efficiency, the repow ered plant is characterized by higher power output...... for topping an existing steam cycle, instead of gas turbine on the top. This is also the target of this study, r epowering of an existing power plant with SOFC as well as gas turbines. The plant used here for repowering is the Kyndby power station is an emergency and peak load facility for Zealand in Denmark....... This means the facilities at the station can be started up within minutes if operational irregularities occur in the high voltage electricity grid or problems arise at other power stations. Nowadays this station is repowered with two gas turbines but the current study is about the original steam plant before...

  19. Macrophagic enhancement in optical coherence tomography imaging by means of superparamagnetic iron oxide nanoparticles.

    Science.gov (United States)

    Gutiérrez-Chico, Juan Luis; Jaguszewski, Milosz; Comesaña-Hermo, Miguel; Correa-Duarte, Miguel Ángel; Mariñas-Pardo, Luis; Hermida-Prieto, Manuel

    2017-05-12

    The ability of optical coherence tomography (OCT) to visualise macrophages in vivo in coronary arteries is still controversial. We hypothesise that imaging of macrophages in OCT could be enhanced by means of superparamagnetic nanoparticles. We compared the optical backscattering and attenuation of cell pellets containing RAW 264.7 macrophages with those of macrophagic cell pellets labelled with very small superparamagnetic oxydised nanoparticles (VSOP) by means of light intensity analysis in OCT. The labelled macrophages were incubated with VSOP at a concentration of 1 mM Fe, corresponding to intracellular iron concentrations of 8.8 pg/cell. To study the effect of intracellular accumulation on the backscattering, VSOP dilutions without cells were also compared. OCT pullbacks of the PCR tubes containing the cell pellets were obtained and light intensity analysis was performed on raw OCT images in polar view, after normalisation by the backscattering of the PCR tube. The backscattering was estimated by the peak normalised intensity, whilst the attenuation was estimated by the number of pixels between the peak and the normalised intensity 1 (peak-to-one). VSOP-loaded macrophages have higher backscattering than the corresponding unlabelled macrophages (peak normalised intensity 6.30 vs. 3.15) with also slightly higher attenuation (peak-to-one 61 vs. 66 pixels). The backscattering of the nanoparticles in suspension was negligible in the light intensity analysis. VSOP increase significantly the optical backscattering of macrophages in the near-infrared region, with minimal increase in signal attenuation. This finding enables the enhancement of macrophages in conventional OCT imaging with an easily implementable methodology.

  20. Rapid and reliable determination of the halogenating peroxidase activity in blood samples.

    Science.gov (United States)

    Flemmig, Jörg; Schwarz, Pauline; Bäcker, Ingo; Leichsenring, Anna; Lange, Franziska; Arnhold, Jürgen

    2014-12-15

    By combining easy and fast leukocyte enrichment with aminophenyl-fluorescein (APF) staining we developed a method to quickly and specifically address the halogenating activity of the immunological relevant blood heme peroxidases myeloperoxidase and eosinophil peroxidase, respectively. For leukocyte enrichment a two-fold hypotonic lysis procedure of the blood with Millipore water was chosen which represents a cheap, fast and reliable method to diminish the amount of erythrocytes in the samples. This procedure is shown to be suitable both to human and murine blood micro-samples, making it also applicable to small animal experiments with recurring blood sampling. As all types of leukocytes are kept in the sample during the preparation, they can be analysed separately after discrimination during the flow cytometry analysis. This also holds for all heme peroxidase-containing cells, namely neutrophils, eosinophils and monocytes. Moreover additional parameters (e.g. antibody staining) can be combined with the heme peroxidase activity determination to gain additional information about the different immune cell types. Based on previous results we applied APF for specifically addressing the halogenating activity of leukocyte peroxidases in blood samples. This dye is selectively oxidized by the MPO and EPO halogenation products hypochlorous and hypobromous acid. This approach may provide a suitable tool to gain more insights into the immune-physiological role of the halogenating activity of heme peroxidases.

  1. Fumigant Activity of the Psidium guajava Var. Pomifera (Myrtaceae Essential Oil in Drosophila melanogaster by Means of Oxidative Stress

    Directory of Open Access Journals (Sweden)

    Antonio Ivanildo Pinho

    2014-01-01

    Full Text Available The guava fruit, Psidium guajava var. pomifera (Myrtaceae family, is a native plant from South America. Its leaves and fruits are widely used in popular medicine in tropical and subtropical countries. Drosophila melanogaster has been used as one of the main model organisms in genetic studies since the 1900s. The extensive knowledge about this species makes it one of the most suitable organisms to study many aspects of toxic compound effects. Due to the lack of studies on the effects of the bioactive compounds present in the P. guajava var. pomifera essential oil, we performed a phytochemical characterization by CG-MS and evaluated the toxicity induced by the essential oil in the D. melanogaster insect model. In order to understand the biochemical mechanisms of toxicity, changes on the Nrf2 signaling as well as hallmarks of oxidative stress response were followed in the exposed flies. Our results showed that exposure of insects to the P. guajava oil increased mortality and locomotor deficits in parallel with an oxidative stress response signaling. Therefore, it suggested a bioinsecticidal activity for P. guajava volatile compounds by means of oxidative stress. Further studies are ongoing to identify which oil compounds are responsible for such effect.

  2. Fumigant activity of the Psidium guajava var. pomifera (Myrtaceae) essential oil in Drosophila melanogaster by means of oxidative stress.

    Science.gov (United States)

    Pinho, Antonio Ivanildo; Wallau, Gabriel Luz; Nunes, Mauro Eugenio Medina; Leite, Nadghia Figueiredo; Tintino, Saulo Relison; da Cruz, Litiele Cezar; da Cunha, Francisco Assis Bezerra; da Costa, José Galberto Martins; Douglas Melo Coutinho, Henrique; Posser, Thais; Franco, Jeferson Luis

    2014-01-01

    The guava fruit, Psidium guajava var. pomifera (Myrtaceae family), is a native plant from South America. Its leaves and fruits are widely used in popular medicine in tropical and subtropical countries. Drosophila melanogaster has been used as one of the main model organisms in genetic studies since the 1900s. The extensive knowledge about this species makes it one of the most suitable organisms to study many aspects of toxic compound effects. Due to the lack of studies on the effects of the bioactive compounds present in the P. guajava var. pomifera essential oil, we performed a phytochemical characterization by CG-MS and evaluated the toxicity induced by the essential oil in the D. melanogaster insect model. In order to understand the biochemical mechanisms of toxicity, changes on the Nrf2 signaling as well as hallmarks of oxidative stress response were followed in the exposed flies. Our results showed that exposure of insects to the P. guajava oil increased mortality and locomotor deficits in parallel with an oxidative stress response signaling. Therefore, it suggested a bioinsecticidal activity for P. guajava volatile compounds by means of oxidative stress. Further studies are ongoing to identify which oil compounds are responsible for such effect.

  3. Halogen bonding origin properties and applications

    Energy Technology Data Exchange (ETDEWEB)

    Hobza, Pavel [Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Prague (Czech Republic); Regional Center of Advanced Technologies and Materials, Department of Physical Chemistry, Palacky University, 77146 Olomouc (Czech Republic)

    2015-12-31

    σ-hole bonding represents an unusual and novel type of noncovalent interactions in which atom with σ- hole interacts with Lewis base such as an electronegative atom (oxygen, nitrogen, …) or aromatic systems. This bonding is of electrostatic nature since the σ-hole bears a positive charge. Dispersion energy forms equally important energy term what is due to the fact that two heavy atoms (e.g. halogen and oxygen) having high polarizability lie close together (the respective distance is typically shorter than the sum of van der Waals radii). Among different types of σ-hole bondings the halogen bonding is by far the most known but chalcogen and pnictogen bondings are important as well.

  4. Computational Tools To Model Halogen Bonds in Medicinal Chemistry.

    Science.gov (United States)

    Ford, Melissa Coates; Ho, P Shing

    2016-03-10

    The use of halogens in therapeutics dates back to the earliest days of medicine when seaweed was used as a source of iodine to treat goiters. The incorporation of halogens to improve the potency of drugs is now fairly standard in medicinal chemistry. In the past decade, halogens have been recognized as direct participants in defining the affinity of inhibitors through a noncovalent interaction called the halogen bond or X-bond. Incorporating X-bonding into structure-based drug design requires computational models for the anisotropic distribution of charge and the nonspherical shape of halogens, which lead to their highly directional geometries and stabilizing energies. We review here current successes and challenges in developing computational methods to introduce X-bonding into lead compound discovery and optimization during drug development. This fast-growing field will push further development of more accurate and efficient computational tools to accelerate the exploitation of halogens in medicinal chemistry.

  5. Soil nitrogen cycling and availability are linked to ammonia oxidizer abundance across a tropical mean annual temperature gradient

    Science.gov (United States)

    Pierre, S.; Litton, C. M.; Giardina, C. P.; Sparks, J. P.; Groffman, P.; Hewson, I.; Fahey, T.

    2016-12-01

    Interactions among environmental variables can obfuscate the primary drivers linking soil microbial community function to ecosystem biogeochemistry. These connections are important to understand in order to predict ecosystem responses to global climate change. In particular, the role of mean annual temperature (MAT) in regulating carbon (C) and nitrogen (N) cycling via microbial communities remains unclear. To study these dynamics in situ, we used a a natural elevation gradient of tropical wet montane forest on Mauna Kea, Hawai'i with established permanent plots. Across the gradient, environmental variables besides MAT remain constant. We studied the abundance and activity of the amoA gene, which regulates the rate-limiting step of nitrification, in ammonia oxidizing archaea (AOA) and bacteria (AOB) with relation to N availability and cycling across increasing MAT. Our results show that the abundance of amoA is positively correlated with MAT (pcDNA/DNA) is not correlated with MAT or potential net nitrification rate. Our results indicate the direct role of MAT in ammonia oxidizer community structure and demonstrate feedbacks to nutrient availability in forest systems. These findings suggest that forest primary production and carbon cycling may be affected by AOA and AOB responses to rising MAT.

  6. Halogens behaviours in Magma Degassing: Insights into Eruptive Dynamics, Hydrothermal Systems and Atmospheric Impact of Andesitic Volcanism

    Science.gov (United States)

    Villemant, B.; Balcone, H.; Mouatt, J.; Michel, A.; Komorowski, J.; Boudon, G.

    2007-12-01

    Shallow degassing of H2O in andesitic magmas determines the eruptive styles of volcanic eruptions and contributes to the hydrothermal systems developed around active volcanoes. Halogens behaviour during magma degassing primarily depends on their incompatible behaviour in the melts and on water solubility. Thus, residual contents of halogens in volcanic juvenile vitric clasts may be used as tracers of H2O degassing processes during explosive and effusive eruptions. Because of the large range of water-melt partition coefficients of halogens and their relatively low diffusion coefficients, a comparison of F, Cl, Br and I contents in volcanic clasts in function of their vesicularity and micro-cristallinity allows to precisely model the main degassing processes and to establish constraints on pre-eruptive conditions. Halogens acids (HCl, HBr and HI) extracted in the vapour phase have much more complex behaviours because of their high solubility in low temperature thermal waters, their variable condensation temperatures and their very high reactivity when mixed with low temperature and oxidizing atmospheric gases. A comparison of model compositions of high temperature gases with the composition of thermal waters, and gases from fumaroles or plumes of active volcanoes allows to characterise the shallow volcanic system and its evolutionary states. Variable halogen behaviours are discussed for a variety of eruption types (plinian, vulcanian and dome-forming) and active volcanic systems from the Lesser Antilles (Montagne Pelee, Soufrière of Guadeloupe, Soufriere Hills of Montserrat).

  7. Effects of Halogen Ions on Phase Equilibrium of Methane Hydrate in Porous Media

    Science.gov (United States)

    Yang, Mingjun; Song, Yongchen; Liu, Yu; Lam, Wei-Haur; Li, Qingping; Yu, Xichong

    2012-05-01

    The influences of halogen ions extracted from sodium fluoride, sodium chloride, sodium bromide, and sodium iodide and their concentrations on methane hydrate phase equilibrium conditions in porous media were investigated experimentally using an orthogonal test method at a pressure of 8 MPa. The experimental results showed that the equilibrium temperature of methane hydrate decreased when halogen ions were added. The equilibrium temperature decreased with the increase of halogen ion concentrations. The influence of the sources of the halogens ion to the methane hydrate equilibrium temperature were insensitive according to variance analysis, which could be explained by about the same mean ionic activity coefficient (a dimensionless coefficient relates the activity to a measured concentration) of sodium fluoride, sodium chloride, sodium bromide, and sodium iodide. The experimental measurements were also in close agreement with the thermodynamic model of Song et al. (J. Nat. Gas Chem. 19, 241 (2010)), in which the mechanical equilibrium of force between the interfaces in a hydrate-liquid-vapor system was considered.

  8. Methane oxidation and degradation of organic compounds in landfill soil covers

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Kjeldsen, Peter

    2002-01-01

    High rates of methane oxidation and degradation of the lowed halogenated methanes (TCM and DCM) and HCFCs (HCFC-21 and HCFC-22) were found in an investigation of the oxidation of methane and halogenated organic compunds (HOCs) in landfill gas affected soil. The degradation followed zero-order kin......High rates of methane oxidation and degradation of the lowed halogenated methanes (TCM and DCM) and HCFCs (HCFC-21 and HCFC-22) were found in an investigation of the oxidation of methane and halogenated organic compunds (HOCs) in landfill gas affected soil. The degradation followed zero...

  9. Manganese Catalyzed C-H Halogenation.

    Science.gov (United States)

    Liu, Wei; Groves, John T

    2015-06-16

    The remarkable aliphatic C-H hydroxylations catalyzed by the heme-containing enzyme, cytochrome P450, have attracted sustained attention for more than four decades. The effectiveness of P450 enzymes as highly selective biocatalysts for a wide range of oxygenation reactions of complex substrates has driven chemists to develop synthetic metalloporphyrin model compounds that mimic P450 reactivity. Among various known metalloporphyrins, manganese derivatives have received considerable attention since they have been shown to be versatile and powerful mediators for alkane hydroxylation and olefin epoxidation. Mechanistic studies have shown that the key intermediates of the manganese porphyrin-catalyzed oxygenation reactions include oxo- and dioxomanganese(V) species that transfer an oxygen atom to the substrate through a hydrogen abstraction/oxygen recombination pathway known as the oxygen rebound mechanism. Application of manganese porphyrins has been largely restricted to catalysis of oxygenation reactions until recently, however, due to ultrafast oxygen transfer rates. In this Account, we discuss recently developed carbon-halogen bond formation, including fluorination reactions catalyzed by manganese porphyrins and related salen species. We found that biphasic sodium hypochlorite/manganese porphyrin systems can efficiently and selectively convert even unactivated aliphatic C-H bonds to C-Cl bonds. An understanding of this novel reactivity derived from results obtained for the oxidation of the mechanistically diagnostic substrate and radical clock, norcarane. Significantly, the oxygen rebound rate in Mn-mediated hydroxylation is highly correlated with the nature of the trans-axial ligands bound to the manganese center (L-Mn(V)═O). Based on the ability of fluoride ion to decelerate the oxygen rebound step, we envisaged that a relatively long-lived substrate radical could be trapped by a Mn-F fluorine source, effecting carbon-fluorine bond formation. Indeed, this idea

  10. The Halogenated Metabolism of Brown Algae (Phaeophyta, Its Biological Importance and Its Environmental Significance

    Directory of Open Access Journals (Sweden)

    Stéphane La Barre

    2010-03-01

    Full Text Available Brown algae represent a major component of littoral and sublittoral zones in temperate and subtropical ecosystems. An essential adaptive feature of this independent eukaryotic lineage is the ability to couple oxidative reactions resulting from exposure to sunlight and air with the halogenations of various substrates, thereby addressing various biotic and abiotic stresses i.e., defense against predators, tissue repair, holdfast adhesion, and protection against reactive species generated by oxidative processes. Whereas marine organisms mainly make use of bromine to increase the biological activity of secondary metabolites, some orders of brown algae such as Laminariales have also developed a striking capability to accumulate and to use iodine in physiological adaptations to stress. We review selected aspects of the halogenated metabolism of macrophytic brown algae in the light of the most recent results, which point toward novel functions for iodide accumulation in kelps and the importance of bromination in cell wall modifications and adhesion properties of brown algal propagules. The importance of halogen speciation processes ranges from microbiology to biogeochemistry, through enzymology, cellular biology and ecotoxicology.

  11. Importance of reactive halogens in the tropical marine atmosphere using WRF-chem

    Science.gov (United States)

    Badia, Alba; Reeves, Claire E.; Baker, Alex; Volkamer, Rainer; Apel, Eric; Saiz-Lopez, Alfonso; von Glasow, Roland

    2017-04-01

    Halogen species (chlorine, bromine and iodine) are known to play an important role in the chemistry and oxidizing capacity of the troposphere, particularly in the marine boundary layer (MBL). Reactive halogens participate in catalytic reaction cycles that efficiently destroy O3, change the HOX and NOX partitioning, affect the oxidation of volatile organic compounds (VOCs) and mercury, reduce the lifetime of methane, and take part in new particle formation. Numerical models predicted that reactive halogen compounds account for 30% of O3 destruction in the MBL and 5-20% globally. Up to 34% of O3 loss in the tropical East Pacific is due to I and Br combined. Recent studies have highlighted the key role that heterogeneous chemistry plays in explaining observations of BrO and IO abundances in the tropical troposphere. The main objective of this study is to investigate the atmospheric chemistry in the tropical East Pacific with a focus on reactive halogens using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and field data from the TORERO campaign. Our reaction mechanism in WRF-Chem is based on the MOZART mechanism and has been extended to include bromine, chlorine and iodine chemistry. Heterogeneous recycling reactions involving sea-salt aerosol and other particles have been included into the model, along with oceanic emissions of important OVOCs and halocarbons. Sea surface emissions of inorganic iodine are calculated using the parameterisation of Carpenter et al., 2013. Focusing on TORERO observations from the ships and a selected number of flights we present the tropospheric impacts of halogens (BrO, IO) in the tropospheric chemistry of relevant species (O3, OH and OVOCS). Sensitivity runs are made in order to study the impact of heterogeneous chemistry in the iodine and bromine species partitioning. A comparison between the online calculation of Very Short Lived Halocarbons (VSLH) oceanic emissions with prescribed oceanic emissions is

  12. Monitoring of oxidative and metabolic stress during cardiac surgery by means of breath biomarkers: an observational study

    Directory of Open Access Journals (Sweden)

    Kischkel Sabine

    2007-09-01

    Full Text Available Abstract Background Volatile breath biomarkers provide a non-invasive window to observe physiological and pathological processes in the body. This study was intended to assess the impact of heart surgery with extracorporeal circulation (ECC onto breath biomarker profiles. Special attention was attributed to oxidative or metabolic stress during surgery and extracorporeal circulation, which can cause organ damage and poor outcome. Methods 24 patients undergoing cardiac surgery with extracorporeal circulation were enrolled into this observational study. Alveolar breath samples (10 mL were taken after induction of anesthesia, after sternotomy, 5 min after end of ECC, and 30, 60, 90, 120 and 150 min after end of surgery. Alveolar gas samples were withdrawn from the circuit under visual control of expired CO2. Inspiratory samples were taken near the ventilator inlet. Volatile substances in breath were preconcentrated by means of solid phase micro extraction, separated by gas chromatography, detected and identified by mass spectrometry. Results Mean exhaled concentrations of acetone, pentane and isoprene determined in this study were in accordance with results from the literature. Exhaled substance concentrations showed considerable inter-individual variation, and inspired pentane concentrations sometimes had the same order of magnitude than expired values. This is the reason why, concentrations were normalized by the values measured 120 min after surgery. Exhaled acetone concentrations increased slightly after sternotomy and markedly after end of ECC. Exhaled acetone concentrations exhibited positive correlation to serum C-reactive protein concentrations and to serum troponine-T concentrations. Exhaled pentane concentrations increased markedly after sternotomy and dropped below initial values after ECC. Breath pentane concentrations showed correlations with serum creatinine (CK levels. Patients with an elevated CK-MB (myocardial&brain/CK ratio had

  13. Halogen-induced organic aerosol (XOA) formation and decarboxylation of carboxylic acids by reactive halogen species - a time-resolved aerosol flow-reactor study

    Science.gov (United States)

    Ofner, Johannes; Zetzsch, Cornelius

    2013-04-01

    Reactive halogen species (RHS) are released to the atmosphere from various sources like photo-activated sea-salt aerosol and salt lakes. Recent studies (Cai et al., 2006 and 2008, Ofner et al., 2012) indicate that RHS are able to interact with SOA precursors similarly to common atmospheric oxidizing gases like OH radicals and ozone. The reaction of RHS with SOA precursors like terpenes forms so-called halogen-induced organic aerosol (XOA). On the other hand, RHS are also able to change the composition of functional groups, e.g. to initiate the decarboxylation of carboxylic acids (Ofner et al., 2012). The present study uses a 50 cm aerosol flow-reactor, equipped with a solar simulator to investigate the time-resolved evolution and transformation of vibrational features in the mid-infrared region. The aerosol flow-reactor is coupled to a home-made multi-reflection cell (Ofner et al., 2010), integrated into a Bruker IFS 113v FTIR spectrometer. The reactor is operated with an inlet feed (organic compound) and a surrounding feed (reactive halogen species). The moveable inlet of the flow reactor allows us to vary reaction times between a few seconds and up to about 3 minutes. Saturated vapours of different SOA precursors and carboxylic acids were fed into the flow reactor using the moveable inlet. The surrounding feed inside the flow reactor was a mixture of zero air with molecular chlorine as the precursor for the formation of reactive halogen species. Using this setup, the formation of halogen-induced organic aerosol could be monitored with a high time resolution using FTIR spectroscopy. XOA formation is characterized by hydrogen-atom abstraction, carbon-chlorine bond formation and later, even formation of carboxylic acids. Several changes of the entire structure of the organic precursor, caused by the reaction of RHS, are visible. While XOA formation is a very fast process, the decarboxylation of carboxylic acids, induced by RHS is rather slow. However, XOA formation

  14. Spectroscopical Determination of ground-level concentrations of Reactive Halogen Species (RHS) above salt lakes, salt pans and other areas with high halogen emissions

    Science.gov (United States)

    Holla, Robert; Landwehr, Sebastian; Platt, Ulrich; Kotte, Karsten; Lisitsyna, Linda V.; Mulder, Ines; Emmerich, Maren; Huber, Stefan; Heidak, Markus

    2010-05-01

    Reactive Halogen Species (RHS), especially BrO and IO, are crucial for the photo chemistry of ozone, the oxidation capacity of the troposphere and have an impact on the equilibria of many atmospheric reaction cycles. This also induces a potential influence on the earth's climate. Beside polar regions, volcanoes and the marine boundary layer salt lakes are an important source for reactive halogen species. At the Dead Sea BrO mixing ratios of up to 176 ppt were measured in summer 2001 [Matveev et al., 2001] and IO was identified with maximal mixing ratios of more than 10 ppt by [Zingler and Platt, 2005]. The Salar de Uyuni in Bolivia showed the presence of up to 20 ppt BrO [Hönninger et al., 2004]. Salt pans and salt deserts may be important halogen sources as well. Saline soils cover 2.5% of the land surface of the earth and might increase in the near future due to desertification as one aspect of the global climate change. Within the scope of the DFG research group HALOPROC a measurement campaign in Southern Russia was performed in August 2009. The ground-level concentrations of BrO, IO, Ozone and other trace gases above the salt lakes El'Ton, Baskuntschak and other local areas were measured using the Multi-AXis-DOAS technique. A further campaign was performed in Mauritania in November/December 2009 in cooperation with the BMBF project SOPRAN. In addition to the above-mentioned measurements the Long-Path DOAS technique was used in order to measure the ground-level concentrations at two different sites: 1. the salt pan Sebkha N'Dramcha and 2. close to a sea weed field at Poste Iwik in a coastal area. We present results from both campaigns concerning the concentrations of bromine oxide (BrO), iodine oxide (IO), ozone (O3)and formaldehyde (HCHO) and give an outlook on possible further campaigns in the future.

  15. Halogen bonds in crystal engineering: like hydrogen bonds yet different.

    Science.gov (United States)

    Mukherjee, Arijit; Tothadi, Srinu; Desiraju, Gautam R

    2014-08-19

    The halogen bond is an attractive interaction in which an electrophilic halogen atom approaches a negatively polarized species. Short halogen atom contacts in crystals have been known for around 50 years. Such contacts are found in two varieties: type I, which is symmetrical, and type II, which is bent. Both are influenced by geometric and chemical considerations. Our research group has been using halogen atom interactions as design elements in crystal engineering, for nearly 30 years. These interactions include halogen···halogen interactions (X···X) and halogen···heteroatom interactions (X···B). Many X···X and almost all X···B contacts can be classified as halogen bonds. In this Account, we illustrate examples of crystal engineering where one can build up from previous knowledge with a focus that is provided by the modern definition of the halogen bond. We also comment on the similarities and differences between halogen bonds and hydrogen bonds. These interactions are similar because the protagonist atoms-halogen and hydrogen-are both electrophilic in nature. The interactions are distinctive because the size of a halogen atom is of consequence when compared with the atomic sizes of, for example, C, N, and O, unlike that of a hydrogen atom. Conclusions may be drawn pertaining to the nature of X···X interactions from the Cambridge Structural Database (CSD). There is a clear geometric and chemical distinction between type I and type II, with only type II being halogen bonds. Cl/Br isostructurality is explained based on a geometric model. In parallel, experimental studies on 3,4-dichlorophenol and its congeners shed light on the nature of halogen···halogen interactions and reveal the chemical difference between Cl and Br. Variable temperature studies also show differences between type I and type II contacts. In terms of crystal design, halogen bonds offer a unique opportunity in the strength, atom size and interaction gradation; this may be

  16. Phases quantification in titanium oxides by means of X-ray diffraction; Cuantificacion de fases en oxidos de titanio por medio de difraccion de rayos x

    Energy Technology Data Exchange (ETDEWEB)

    Macias B, L.R. [Instituto Nacional de Investigaciones Nucleares, A.P: 18-1027, 11801 Mexico D.F. (Mexico); Garcia C, R.M. [Secretaria de Hacienda y Credito Publico (Mexico); Ita T, A. de [UAM (Mexico); Chavez R, A. [Aerobal S.A. (Mexico)

    2001-07-01

    In this work two phases of titanium oxides are quantified which belong to the same crystalline system and by means of a computer program named Quanto created by the first author, contains the information for calculating the absorption coefficients, it can be quantified phases having one of the pure phases and the problem samples. In order to perform this work different mixtures of different titanium oxides were prepared measuring by means of the X-ray diffraction technique in the Siemens X-ray diffractometer of ININ which were processed with the Peakfit package and also they were evaluated by means of the computer program with the necessary information finding acceptable results. (Author)

  17. Active and Widespread Halogen Chemistry in the Tropical and Subtropical Free Troposphere

    Science.gov (United States)

    Wang, Siyuan; Schmidt, Johan A.; Baidar, Sunil; Coburn, Sean; Dix, Barbara; Koenig, Theodore K.; Apel, Eric; Bowdalo, Dene; Campos, Teresa; Eloranta, Ed; Evans, Mathew J.; Digangi, Joshua P.; Zondlo, Mark A.; Gao, Ru-shan; Haggerty, Julie A.; Hall, Samuel R.; Hornbrook, Rebecca S.; Jacob, Daniel; Morley, Bruce; Pierce, Bradley; Reeves, Mike; Romashkin, Pavel; Ter Schure, Arnout; Volkamer, Rainer

    2015-01-01

    Halogens in the troposphere are increasingly recognized as playing an important role for atmospheric chemistry, and possibly climate. Bromine and iodine react catalytically to destroy ozone (O3), oxidize mercury, and modify oxidative capacity that is relevant for the lifetime of greenhouse gases. Most of the tropospheric O3 and methane (CH4) loss occurs at tropical latitudes. Here we report simultaneous measurements of vertical profiles of bromine oxide (BrO) and iodine oxide (IO) in the tropical and subtropical free troposphere (10degN to 40degS), and show that these halogens are responsible for 34% of the column-integrated loss of tropospheric O3. The observed BrO concentrations increase strongly with altitude (approx.3.4 pptv at 13.5 km), and are 2-4 times higher than predicted in the tropical free troposphere. BrO resembles model predictions more closely in stratospheric air. The largest model low bias is observed in the lower tropical transition layer (TTL) over the tropical eastern Pacific Ocean, and may reflect a missing inorganic bromine source supplying an additional 2.5-6.4 pptv total inorganic bromine (Bry), or model overestimated Bry wet scavenging. Our results highlight the importance of heterogeneous chemistry on ice clouds, and imply an additional Bry source from the debromination of sea salt residue in the lower TTL. The observed levels of bromine oxidize mercury up to 3.5 times faster than models predict, possibly increasing mercury deposition to the ocean. The halogen-catalyzed loss of tropospheric O3 needs to be considered when estimating past and future ozone radiative effects.

  18. Interactions between volatile organic compounds and reactive halogen in the tropical marine atmosphere using WRF-Chem

    Science.gov (United States)

    Badia, Alba; Reeves, Claire E.; Baker, Alex; Volkamer, Rainer; von Glasow, Roland

    2016-04-01

    Halogen species (chlorine, bromine and iodine) are known to play an important role in the chemistry and oxidizing capacity of the troposphere, particularly in the marine boundary layer (MBL). Reactive halogens cause ozone (O3) destruction, change the HOx and NOX partitioning, affect the oxidation of volatile organic compounds (VOCs) and mercury, reduce the lifetime of methane, and take part in new particle formation. Numerical models predicted that reactive halogen compounds account for 30% of O3 destruction in the MBL and 5-20% globally. There are indications that the chemistry of reactive halogens and oxygenated VOCs (OVOCs) in the tropics are inter-related. Moreover, the presence of aldehydes, such as glyoxal (CHOCHO), has a potential impact on radical cycling and secondary organic aerosol (SOA) formation in the MBL and free troposphere (FT). Model calculations suggest aldehydes to be an important sink for bromine atoms and hence competition for their reaction with O3 forming BrO and so illustrating a link between the cycles of halogens and OVOCs in the marine atmosphere. The main objective of this contribution is to investigate the atmospheric chemistry in the tropical East Pacific with a focus on reactive halogens and OVOCs and their links using the latest version of the Weather Research and Forecasting (WRF) model coupled with Chemistry (WRF-Chem) and field data from the TORERO campaign. WRF-Chem is a highly flexible community model for atmospheric research where aerosol-radiation-cloud feedback processes are taken into account. Our current reaction mechanism in WRF-Chem is based on the MOZART mechanism and has been extended to include bromine, chlorine and iodine chemistry. The MOZART mechanism includes detailed gas-phase chemistry of CHOCHO formation as well as state-of-the-science pathways to form SOA. Oceanic emissions of aldehydes, including CHOCHO, and of organic halogens based on measurements from the TORERO campaign have been added into the model. Sea

  19. FIELD SCREENING FOR HALOGENATED VOLATILE ORGANIC COMPOUNDS

    Energy Technology Data Exchange (ETDEWEB)

    John F. Schabron; Joseph F. Rovani, Jr.; Theresa M. Bomstad

    2003-07-01

    Western Research Institute (WRI) is continuing work toward the development of new screening methodology and a test kit to measure halogenated volatile organic compounds (VOCs) in the field. Heated diode and corona discharge sensors are commonly used to detect leaks of refrigerants from air conditioners, freezers, and refrigerators. They are both selective to the presence of halogens. In prior work, the devices were tested for response to carbon tetrachloride, heptane, toluene, and water vapors. In the current work, sensor response was evaluated with sixteen halogenated VOCs relative to carbon tetrachloride. The results show that the response of the various chlorinated VOCs is within an order of magnitude of the response to carbon tetrachloride for each of the sensors. Thus, for field screening a single response factor can be used. Both types of leak detectors are being further modified to provide an on-board LCD signal readout, which is related to VOC concentration. The units will be fully portable and will operate with 115-V line or battery power. Signal background, noise level, and response data on the Bacharach heated diode detector and the TIF corona discharge detector show that when the response curves are plotted against the log of concentration, the plot is linear to the upper limit for the particular unit, with some curvature at lower levels. When response is plotted directly against concentration, the response is linear at the low end and is curved at the high end. The dynamic ranges for carbon tetrachloride of the two devices from the lower detection limit (S/N=2) to signal saturation are 4-850 vapor parts per million (vppm) for the corona discharge unit and 0.01-70 vppm for the heated diode unit. Additional circuit modifications are being made to lower the detection limit and increase the dynamic response range of the corona discharge unit. The results indicate that both devices show potential utility for future analytical method development work toward

  20. Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants

    Science.gov (United States)

    Yoshida, Suguru; Fujita, Yasunobu

    The current state of knowledge on heat transfer to boiling refrigerants (halogenated hydrocarbons) in a pool and flowing inside a horizontal tube is reviewed with an emphasis on information relevant to the design of refrigerant evaporators, and some recommendations are made for future research. The review covers two-phase flow pattern, heat transfer characteristics, correlation of heat transfer coefficient, influence of oil, heat transfer augmentation, boiling from tube-bundle, influence of return bend, burnout heat flux, film boiling, dryout and post-dryout heat transfer.

  1. Review of Rate Constants and Exploration of Correlations of the Halogen Transfer Reaction of Tri-substituted Carbon-centered Radicals with Molecular Halogens

    Energy Technology Data Exchange (ETDEWEB)

    Poutsma, Marvin L [ORNL

    2012-01-01

    Rate constants for the reaction (R 3C + X2 R 3CX + X ; X = F, Cl, Br, and I) are reviewed. Because of curved Arrhenius plots and negative EX values, empirical structure-reactivity correlations are sought for log kX,298 rather than EX. The well-known poor correlation with measures of reaction enthalpy is demonstrated. The best quantitative predictor for R 3C is p, the sum of the Hammett p constants for the three substituents, R . Electronegative substituents with lone pairs, such as halogen or oxygen, thus appear to destabilize the formation of a polarized pre-reaction complex and/or TS ( +R---X---X -) by -inductive/field electron withdrawal while simultaneously stabilizing them by -resonance electron donation. The best quantitative predictor of the reactivity order of the halogens, I2 > Br2 >> Cl2 F2, is the polarizability of the halogen, (X-X). For the data set of 60 rate constants which span 6.5 orders of magnitude, a modestly successful correlation of log kX,298 is achieved with only two parameters, p and (X-X), with a mean unsigned deviation of 0.59 log units. How much of this residual variance is the result of inaccuracies in the data compared with over-simplification of the correlation approach remains to be seen.

  2. Halogenation processes of secondary organic aerosol and implications on halogen release mechanisms

    Directory of Open Access Journals (Sweden)

    J. Ofner

    2012-07-01

    Full Text Available Reactive halogen species (RHS, such as X·, X2 and HOX containing X = chlorine and/or bromine, are released by various sources like photo-activated sea-salt aerosol or from salt pans, and salt lakes. Despite many studies of RHS reactions, the potential of RHS reacting with secondary organic aerosol (SOA and organic aerosol derived from biomass-burning (BBOA has been neglected. Such reactions can constitute sources of gaseous organohalogen compounds or halogenated organic matter in the tropospheric boundary layer and can influence physicochemical properties of atmospheric aerosols.

    Model SOA from α-pinene, catechol, and guaiacol was used to study heterogeneous interactions with RHS. Particles were exposed to molecular chlorine and bromine in an aerosol smog-chamber in the presence of UV/VIS irradiation and to RHS, released from simulated natural halogen sources like salt pans. Subsequently, the aerosol was characterized in detail using a variety of physicochemical and spectroscopic methods. Fundamental features were correlated with heterogeneous halogenation, which results in new functional groups (FTIR spectroscopy, changes UV/VIS absorption, chemical composition (ultrahigh resolution mass spectroscopy (ICR-FT/MS, or aerosol size distribution. However, the halogen release mechanisms were also found to be affected by the presence of organic aerosol. Those interaction processes, changing chemical and physical properties of the aerosol are likely to influence e.g. the ability of the aerosol to act as cloud condensation nuclei, its potential to adsorb other gases with low-volatility, or its contribution to radiative forcing and ultimately the Earth's radiation balance.

  3. Photoresponsive liquid crystals based on halogen bonding of azopyridines.

    Science.gov (United States)

    Chen, Yinjie; Yu, Haifeng; Zhang, Lanying; Yang, Huai; Lu, Yunfeng

    2014-09-04

    A series of photoresponsive halogen-bonded liquid crystals (LCs) were successfully constructed using molecular halogen and azopyridine compounds, which show interesting properties of photoinduced phase transition upon UV irradiation. In addition, bromine-bonded LCs were first obtained with high mesophase stability.

  4. Scientific conferences: A big hello to halogen bonding

    Science.gov (United States)

    Erdelyi, Mate

    2014-09-01

    Halogen bonding connects a wide range of subjects -- from materials science to structural biology, from computation to crystal engineering, and from synthesis to spectroscopy. The 1st International Symposium on Halogen Bonding explored the state of the art in this fast-growing field of research.

  5. 40 CFR 721.8900 - Substituted halogenated pyridinol, alkali salt.

    Science.gov (United States)

    2010-07-01

    ..., alkali salt. 721.8900 Section 721.8900 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.8900 Substituted halogenated pyridinol, alkali salt. (a) Chemical... as substituted halogenated pyridinols, alkali salts (PMNs P-88-1271 and P-88-1272) are subject to...

  6. 40 CFR 721.8750 - Halogenated substituted pyridine.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated substituted pyridine. 721... Substances § 721.8750 Halogenated substituted pyridine. (a) Chemical substances and significant new uses... pyridine (PMN P-86-838) is subject to reporting under this section for the significant new uses...

  7. Synthesis and characterization of zinc oxide nanocrystals and histologic evaluation of their biocompatibility by means of intraosseous implants.

    Science.gov (United States)

    Sousa, C J A; Pereira, M C; Almeida, R J; Loyola, A M; Silva, A C A; Dantas, N O

    2014-05-01

    To synthesize and characterize zinc oxide (ZnO) nanocrystals and assess their biological properties for applications in dentistry, particularly in endodontics, by means of intraosseous implants. ZnO nanocrystals were synthesized and characterized by micro-Raman spectroscopy and X-ray Diffraction. Ten guinea pigs were divided into two groups representing experimental periods of 4 and 12 weeks and received implants on both sides of the mandible in the region of the symphysis. The connective tissue response along the lateral wall outside the cup served as the negative control. The animals were euthanized at the end of each observation period and prepared for routine histological examinations which evaluated inflammatory response and material biocompatibility. ZnO nanocrystals were highly pure, crystalline, and averaged 21 nm in size. After 12 weeks, tissue analysis revealed the presence of a thin layer of connective tissue with some giant cells between the implanted material and underlying bone tissue. While signs of mild inflammation could be seen, bone resorption and remodeling were not apparent. ZnO nanocrystals were biocompatible, well tolerated and allowed new bone formation and bone remodelling. © 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  8. Unexpected autumnal halogen activity in the lower troposphere at Neumayer III/Antarctica

    Science.gov (United States)

    Nasse, Jan-Marcus; Frieß, Udo; Pöhler, Denis; Schmitt, Stefan; Weller, Rolf; Schaefer, Thomas; Platt, Ulrich

    2017-04-01

    The influence of Reactive Halogen Species (RHS, like IO, BrO, ClO, etc.) on the lower polar troposphere has been subject of intense research for several decades. Ozone Depletion Events (ODEs) caused by the catalytic reaction of tropospheric ozone with inorganic halogen species or the oxidation of gaseous elemental mercury are well observed phenomena that occur during the respective springtime in both Arctic and Antarctica. Chlorine atoms also react more efficiently with hydrocarbons than e.g. OH radicals and all reactive halogen species can furthermore influence the atmospheric sulphur or nitrate cycles. While an autocatalytic release mechanism from salty surfaces, the so called bromine explosion, has been identified to rapidly increase inorganic bromine mixing ratios many aspects of atmospheric halogen chemistry in polar regions remains unclear. Since January 2016, we are operating an active Long Path DOAS instrument at Neumayer III on the Antarctic Ekström shelf ice designed for autonomous measurements. This instrument is able to detect a wide range of trace gases absorbing in the UV/Vis including ClO, BrO, OClO, IO, I2, OIO, ozone, NO2, H2O, O4, and SO2 at a temporal resolution of 5-30 minutes. The analysis of the first year of observations shows several surprising findings which give new insights into polar halogen chemistry. E.g. we observe surprisingly strong bromine activity in late summer and autumn (in addition to well-known springtime events) with mixing ratios often higher than 20 pptv. We could even observe peak mixing ratios of 110 pptv. The observed BrO levels could be the result of local/regional chemistry rather than long-range transport and modulated by the stability of the boundary layer. Also, there are hints for NOx - driven halogen activation. Furthermore, chlorine monoxide (ClO) and OClO mixing ratios of several ten pptv could be detected on a number of days, however the source mechanism for reactive chlorine remains unclear. We will give an

  9. Hydrogen bond and halogen bond inside the carbon nanotube

    Science.gov (United States)

    Wang, Weizhou; Wang, Donglai; Zhang, Yu; Ji, Baoming; Tian, Anmin

    2011-02-01

    The hydrogen bond and halogen bond inside the open-ended single-walled carbon nanotubes have been investigated theoretically employing the newly developed density functional M06 with the suitable basis set and the natural bond orbital analysis. Comparing with the hydrogen or halogen bond in the gas phase, we find that the strength of the hydrogen or halogen bond inside the carbon nanotube will become weaker if there is a larger intramolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom donor to the antibonding orbital of the X-H or X-Hal bond involved in the formation of the hydrogen or halogen bond and will become stronger if there is a larger intermolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom acceptor to the antibonding orbital of the X-H or X-Hal bond. According to the analysis of the molecular electrostatic potential of the carbon nanotube, the driving force for the electron-density transfer is found to be the negative electric field formed in the carbon nanotube inner phase. Our results also show that the X-H bond involved in the formation of the hydrogen bond and the X-Hal bond involved in the formation of the halogen bond are all elongated when encapsulating the hydrogen bond and halogen bond within the carbon nanotube, so the carbon nanotube confinement may change the blue-shifting hydrogen bond and the blue-shifting halogen bond into the red-shifting hydrogen bond and the red-shifting halogen bond. The possibility to replace the all electron nanotube-confined calculation by the simple polarizable continuum model is also evaluated.

  10. Halogen control in integrated hot gas cleaning: final report

    Energy Technology Data Exchange (ETDEWEB)

    Nieminen, M.; Kangasmaa, K.; Laatikainen-Luntama, J.; Kurkela, E. [VTT Energy (Finland)

    1998-12-31

    A simple and cost effective dry-scrubbing halogen control method for hot gasification gas cleaning applications was developed. The work aimed to develop a dry scrubbing method for integration into a hot gas cleaning system including particulate removal by cyclones, filtration and possibly a desulphurisation system. Work started by determining the behaviour of halogen compounds in a reducing gasification atmosphere to evaluate the fate of halogens on downstream components, to understand the role of halogens as precursors for environmental emissions, and to give background information for developing halogen control methods. New halogen sampling and analysis methods for pressurised gasification gas conditions were also developed. Mass balances were determined for several gasification conditions, with and without calcium-based bed additives. Several potential dry scrubbing sorbent candidates were evaluated. Chemical, technical, economical and environmental aspects were used as selection criteria, calcium-based sorbents being chosen for development of the halogen removal system. The process concept was based on sorbent feeding into the product gas prior to the hot gas filter unit, where the final step of halogen capture takes place and both sorbent and particulates are removed from the gas. Preliminary screening of calcium-based sorbents and preoptimisation of process conditions was performed in a laboratory scale dry scrubbing test rig. Finally, the performance of the developed dry scrubbing halogen removal system was verified in a PDU scale pressurised fluidised bed gasification and gas cleaning test rig. Preliminary verification showed that, in favourable conditions, the system developed formed a potential halogen control system that could be easily integrated into the other hot gas cleaning systems. 2 refs., 9 figs., 2 tabs.

  11. [Near infrared light irradiator using halogen lamp].

    Science.gov (United States)

    Ide, Yasuo

    2012-07-01

    The practical electric light bulb was invented by Thomas Alva Edison in 1879. Halogen lamp is the toughest and brightest electric light bulb. With light filter, it is used as a source of near infrared light. Super Lizer and Alphabeam are made as near infrared light irradiator using halogen lamp. The light emmited by Super Lizer is linear polarized near infrared light. The wave length is from 600 to 1,600 nm and strongest at about 1,000 nm. Concerning Super Lizer, there is evidence of analgesic effects and normalization of the sympathetic nervous system. Super Lizer has four types of probes. SG type is used for stellate ganglion irradiation. B type is used for narrow area irradiation. C and D types are for broad area irradiation. The output of Alphabeam is not polarized. The wave length is from 700 to 1,600 nm and the strongest length is about 1,000nm. Standard attachment is used for spot irradiation. Small attachment is used for stellate ganglion irradiation. Wide attachment is used for broad area irradiation. The effects of Alphabeam are thought to be similar to that of Super Lizer.

  12. Experimental and theoretical studies on a novel helical architecture driven by hydrogen and halogen bonding interactions

    Indian Academy of Sciences (India)

    QING ZHU LIU; SHAN SHAN WANG; TENG FEI WANG; JIAN GUO LIN; XUE HAI JU; LING QIU

    2016-12-01

    A novel two-dimensional (2D), layered, helical supramolecular architecture constructed via cooperative hydrogen bond and halogen bonds was synthesized and characterized: [(BMBA)₂(TPB)]n (1) [BMBA= 3-bromo-2-methylbenzoic acid, TPB = 1,2,3,4-tetra-(4-pyridyl)-butane]. Density functional theory (DFT) calculations were carried out to investigate the nature of intermolecular interactions between BMBA and TPB. The cooperation between hydrogen bond and halogen bond in building up the open organic architecture was demonstrated elaborately. Complex 1 exhibits strong photoluminescence and high thermal stability. The nature of electronic transitions in the photoluminescent process was investigated by means of time-dependent DFT (TDDFT) calculations and molecular orbital analyses, revealing that the luminescent property of the helical supramolecular architecture of 1 was ligand-based. Periodic DFT calculations show that 1 is an electrical insulator with a band gap of 3.29 eV.

  13. Nitrous oxide emissions from intensive agricultural systems: Variations between crops and seasons, key driving variables, and mean emission factors

    Science.gov (United States)

    Dobbie, K. E.; McTaggart, I. P.; Smith, K. A.

    1999-11-01

    Emissions of nitrous oxide from intensively managed agricultural fields were measured over 3 years. Exponential increases in flux occurred with increasing soil water- filled pore space (WFPS) and temperature; increases in soil mineral N content due to fertilizer application also stimulated emissions. Fluxes were low when any of these variables was below a critical value. The largest fluxes occurred when WFPS values were very high (70-90%), indicating that denitrification was the major process responsible. The relationships with the driving variables showed strong similarities to those reported for very different environments: irrigated sugar cane crops, pastures, and forest in the tropics. Annual emissions varied widely (0.3-18.4 kg N2O-N ha-1). These variations were principally due to the degree of coincidence of fertilizer application and major rainfall events. It is concluded therefore that several years' data are required from any agricultural ecosystem in a variable climate to obtain a robust estimate of mean N2O fluxes. The emissions from small-grain cereals (winter wheat and spring barley) were consistently lower (0.2-0.7 kg N2O-N per 100 kg N applied) than from cut grassland (0.3-5.8 kg N2O- N per 100 kg N). Crops such as broccoli and potatoes gave emissions of the same order as those from the grassland. Although these differences between crop types are not apparent in general data comparisons, there may well be distinct regional differences in the relative and absolute emissions from different crops, due to local factors relating to soil type, weather patterns, and agricultural management practices. This will only be determined by more detailed comparative studies.

  14. Environmental Factors Influencing Arctic Halogen Chemistry During Late Spring

    Science.gov (United States)

    Burd, J.; Nghiem, S. V.; Simpson, W. R.

    2015-12-01

    Reactive halogen radicals (e.g. Br, Cl atoms and their oxides, BrO, ClO) are important oxidizers in the troposphere that decrease atmospheric pollutants and deplete tropospheric ozone, affecting the abundance of other oxidizers such as the hydroxyl radical. During Arctic springtime, the heterogeneous chemical cycles (often called the "bromine explosion") produce high levels of bromine monoxide (BrO), through reactions on saline snow, ice, and/or aerosol surfaces. Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) measured BrO at Barrow, AK, from 2008-2009 and 2012-2015, as well at various locations above the frozen Arctic Ocean with O-Buoys in 2008 and 2011-2015. Observed BrO levels drop suddenly during late spring (May-June) and generally do not recover, which indicates the bromine explosion cycle can no longer produce significant amounts of BrO. We have established, through an objective algorithm, the local day of year of this drop in BrO as the "seasonal end." Additionally, in about half of the years, "recurrence" events were observed where BrO levels recover for at least a day. This study investigates the environmental factors influencing seasonal end and recurrence events including: temperature, relative humidity, precipitation and snowmelt. Analysis of BrO and air temperature revealed the temperature reaches 0°C within five days of the seasonal end event; however, temperatures drop below freezing during a recurrence event. In addition, there are periods where the temperature remains below freezing, but no recurrence event is observed. This BrO and temperature analysis indicates above-freezing air temperature prevents reactive bromine release; however, it is not the only environmental factor influencing this heterogeneous recycling. Further analysis of additional environmental influences on the bromine explosion cycle could help to better understand and model bromine chemistry in the Arctic.

  15. Effects of halogenated aromatics/aliphatics and nitrogen(N)-heterocyclic aromatics on estimating the persistence of future pharmaceutical compounds using a modified QSAR model.

    Science.gov (United States)

    Lim, Seung Joo; Fox, Peter

    2014-02-01

    The effects of halogenated aromatics/aliphatics and nitrogen(N)-heterocyclic aromatics on estimating the persistence of future pharmaceutical compounds were investigated using a modified half life equation. The potential future pharmaceutical compounds investigated were approximately 2000 pharmaceutical drugs currently undergoing the United States Food and Drug Administration (US FDA) testing. EPI Suite (BIOWIN) model estimates the fates of compounds based on the biodegradability under aerobic conditions. While BIOWIN considered the biodegradability of a compound only, the half life equation used in this study was modified by biodegradability, sorption and cometabolic oxidation. It was possible that the potential future pharmaceutical compounds were more accurately estimated using the modified half life equation. The modified half life equation considered sorption and cometabolic oxidation of halogenated aromatic/aliphatics and nitrogen(N)-heterocyclic aromatics in the sub-surface, while EPI Suite (BIOWIN) did not. Halogenated aliphatics in chemicals were more persistent than halogenated aromatics in the sub-surface. In addition, in the sub-surface environment, the fates of organic chemicals were much more affected by halogenation in chemicals than by nitrogen(N)-heterocyclic aromatics.

  16. Adsorption of halogenated aliphatic contaminants by graphene nanomaterials.

    Science.gov (United States)

    Zhou, Yang; Apul, Onur Guven; Karanfil, Tanju

    2015-08-01

    In this study, adsorption of ten environmentally halogenated aliphatic synthetic organic compounds (SOCs) by a pristine graphene nanosheet (GNS) and a reduced graphene oxide (rGO) was examined, and their adsorption behaviors were compared with those of a single-walled carbon nanotube (SWCNT) and a granular activated carbon (GAC). In addition, the impacts of background water components (i.e., natural organic matter (NOM), ionic strength (IS) and pH) on the SOC adsorption behavior were investigated. The results indicated HD3000 and SWCNT with higher microporous volumes exhibited higher adsorption capacities for the selected aliphatic SOCs than graphenes, demonstrating microporosity of carbonaceous adsorbents played an important role in the adsorption. Analysis of adsorption isotherms demonstrated that hydrophobic interactions were the dominant contributor to the adsorption of aliphatic SOCs by graphenes. However, π-π electron donor-acceptor and van der Waals interactions are likely the additional mechanisms contributing to the adsorption of aliphatic SOCs on graphenes. Among the three background solution components examined, NOM showed the most influential effect on adsorption of the selected aliphatic SOCs, while pH and ionic strength had a negligible effects. The NOM competition on aliphatic adsorption was less pronounced on graphenes than SWCNT. Overall, in terms of adsorption capacities, graphenes tested in this study did not exhibit a major advantage over SWCNT and GAC for the adsorption of aliphatic SOCs. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Nucleophilic reactivity and electrocatalytic reduction of halogenated organic compounds by nickel o-phenylenedioxamidate complexes.

    Science.gov (United States)

    Das, Siva Prasad; Ganguly, Rakesh; Li, Yongxin; Soo, Han Sen

    2016-09-14

    A growing number of halogenated organic compounds have been identified as hazardous pollutants. Although numerous advanced oxidative processes have been developed to degrade organohalide compounds, reductive and nucleophilic molecular approaches to dehalogenate organic compounds have rarely been reported. In this manuscript, we employ nickel(ii)-ate complexes bearing the o-phenylenebis(N-methyloxamide) (Me2opba) tetraanionic ligand as nucleophilic reagents that can react with alkyl halides (methyl up to the bulky isobutyl) by O-alkylation to give their respective imidate products. Four new nickel(ii) complexes have been characterized by X-ray crystallography, and the salient structural parameters and FT-IR vibrational bands (∼1655 cm(-1)) concur with their assignment as the imidate tautomeric form. To the best of our knowledge, this is the first report on the nucleophilic reactivity of Ni(II)(Me2opba) with halogenated organic compounds. The parent nickel(ii) Me2opba complex exhibits reversible electrochemical oxidation and reduction behavior. As a proof of concept, Ni(II)(Me2opba) and its alkylated congeners were utilized for the electrocatalytic reduction of chloroform, as a representative, simple polyhalogenated organic molecule that could arise from the oxidative treatment of organic compounds by chlorination. Modest turnover numbers of up to 6 were recorded, with dichloromethane identified as one of the possible products. Future efforts are directed towards bulkier -ate complexes that possess metal-centered instead of ligand-centered nucleophilic activity to create more effective electrocatalysts for the reduction of halogenated organic compounds.

  18. Halogenated coumarin derivatives as novel seed protectants.

    Science.gov (United States)

    Brooker, N; Windorski, J; Bluml, E

    2008-01-01

    Development of new and improved antifungal compounds that are target-specific is backed by a strong Federal, public and commercial mandate. Many plant-derived chemicals have proven fungicidal properties, including the coumarins (1,2-Benzopyrone) found in a variety of plants such as clover, sweet woodruff and grasses. Preliminary research has shown the coumarins to be a highly active group of molecules with a wide range of antimicrobial activity against both fungi and bacteria. It is believed that these cyclic compounds behave as natural pesticidal defence molecules for plants and they represent a starting point for the exploration of new derivative compounds possessing a range of improved antifungal activity. Within this study, derivatives of coumarin that were modified with halogenated side groups were screened for their antifungal activity against a range of soil-borne plant pathogenic fungi. Fungi included in this in vitro screen included Macrophomina phaseolina (charcoal rot), Phytophthora spp. (damping off and seedling rot), Rhizoctonia spp. (damping off and root rot) and Pythium spp. (seedling blight), four phylogenetically diverse and economically important plant pathogens. Studies indicate that these halogenated coumarin derivatives work very effectively in vitro to inhibit fungal growth and some coumarin derivatives have higher antifungal activity and stability as compared to the original coumarin compound alone. The highly active coumarin derivatives are brominated, iodinated and chlorinated compounds and results suggest that besides being highly active, very small amounts can be used to achieve LD100 rates. In addition to the in vitro fungal inhibition assays, results of polymer seed coating compatibility and phytotoxicity testing using these compounds as seed treatments will also be reported. These results support additional research in this area of natural pesticide development.

  19. Phase identification and internal stress analysis of steamside oxides on superheater tubes by means of X-ray diffraction

    DEFF Research Database (Denmark)

    Pantleon, Karen; Montgomery, Melanie

    Steamside oxides formed on plant exposed superheated tubes were investigated using X-ray diffraction. Phase identification and stress analysis revealed that on ferritic X20CrMoV12-1 pure Hematite and pure Magnetite formed and both phases are under tensile stress. IN contrast, on austenitic TP347H...... Mn-, Cr- and/or Ni-containing oxides are observed, instead of pure Magnetite, underneath a pure Hematite surface layer. Oxides on the austenitic steel are under compressive stress or even stress-free....

  20. Dynamic behavior of protium and deuterium implanted into an oxide ceramic studied by means of ERD techniques

    Energy Technology Data Exchange (ETDEWEB)

    Iizuka, Emi; Horikawa, Tomoaki; Tsuchiya, Bun; Soda, Kazuo; Morita, Kenji; Iwahara; Hiroyasu [Nagoya Univ. (Japan)

    1998-03-01

    We have investigated exchange of deuterium (or protium) implanted into an oxide ceramic, SrCe{sub 0.95}Yb{sub 0.05}O{sub 3-{delta}}, for protium (or deuterium) due to exposure to H{sub 2}O (or D{sub 2}O) vapor at room temperature by means of the elastic recoil detection (ERD) technique. It is found that D is completely exchanged for H by expose to H{sub 2}O vapor, while H is hardly exchanged for D by expose to D{sub 2}O vapor, namely there exists a great isotope difference between the exchange of D for H and that of H for D. This result suggests that the exchanges do not take place on a conventional model of following subsequent reactions; dissociative absorption at the surface, diffusion (H), replacement of D by H, diffusion (D), and release due to surface recombination, but on a new model of following reactions; dissociative absorption at the surface, diffusion and release through bulk recombination due to mixed molecule formation. In order to clarify the reaction leading to the great isotope difference, the experiments on the retention of H and D by simultaneous H{sup +}, D{sup +} implantation and the release of 5 keV D{sub 2}{sup +} implants by 0.5 keV H{sub 2}{sup +} irradiation and 5 keV H{sub 2}{sup +} implants by 0.5 keV D{sub 2}{sup +} irradiation have been done. The retention experiment shows that the D/H ratio of the saturation implantation concentration is 1.3. Competition among H-H, H-D and D-D bulk recombination prefers to enrich D, which is opposite to the isotope difference observed. The release experiment shows that the slow and continuous decay of 5 keV D{sub 2}{sup +} implants is induced by 0.5 keV H{sub 2}{sup +} irradiation for long term, while that of 5 keV H{sub 2}{sup +} implants is hardly induced by 0.5 keV D{sub 2}{sup +} irradiation for long term. The latter result suggests that the diffusion may play a major rule in the great isotope difference. (author)

  1. UARS Halogen Occultation Experiment (HALOE) Level 2 V001

    Data.gov (United States)

    National Aeronautics and Space Administration — The HALOE home page on the WWW is http://haloe.gats-inc.com/home/index.php The Halogen Occultation Experiment (HALOE) on NASA's Upper Atmosphere Research Satellite...

  2. Halogenated naphthyl methoxy piperidines for mapping serotonin transporter sites

    Science.gov (United States)

    Goodman, M.M.; Faraj, B.

    1999-07-06

    Halogenated naphthyl methoxy piperidines having a strong affinity for the serotonin transporter are disclosed. Those compounds can be labeled with positron-emitting and/or gamma emitting halogen isotopes by a late step synthesis that maximizes the useable lifeterm of the label. The labeled compounds are useful for localizing serotonin transporter sites by positron emission tomography and/or single photon emission computed tomography.

  3. Characterization of oxidation protection coatings for high temperature applications by means of nanoindentation and scanning electron microscopy methods; Charakterisierung von Oxidationsschutzschichten fuer Hochtemperaturanwendungen mittels Nanoindentierung und rasterelektronenmikroskopischen Methoden

    Energy Technology Data Exchange (ETDEWEB)

    Webler, R.; Neumeier, S.; Goeken, M. [Erlangen-Nuernberg Univ., Erlangen (Germany). Lehrstuhl fuer Allgemeine Werkstoffeigenschaften

    2014-10-01

    Oxidation protection coatings are required for thermally highly stressed components such as turbine blades in aircraft engines. Cyclic oxidation experiments were performed on a NiCoCrAlY protective coating of a nickel-based superalloy and hardness and modulus of elasticity (mechanical properties) were determined by nanoindentation before and after the experiments. Microstructure and chemical composition were characterized by means of scanning electron microscopy. Here, the focus is on the phase identification by combining electron backscatter diffraction and energy dispersive X-ray spectroscopy. Findings indicate that the chemical composition strongly influences the mechanical properties.

  4. Assessment of the oxidative stability of conventional and high-oleic sunflower oil by means of solid-phase microextraction-gas chromatography.

    Science.gov (United States)

    Petersen, Katharina Domitila; Kleeberg, Kim Karen; Jahreis, Gerhard; Fritsche, Jan

    2012-03-01

    Headspace-solid-phase microextraction-gas chromatography (HS-SPME-GC) was used to identify in total 74 volatile lipid oxidation compounds altogether in thermally stressed conventional and high-oleic sunflower (HOSF) oil samples (in accelerated storage conditions for 14 days at 80°C). Out of the volatile compounds identified, six volatile compounds were selected as marker compounds for the assessment of lipid oxidation of sunflower (SF) and HOSF oils due to their low odour threshold values and fatty-rancid odour impression. Additionally, other oxidation parameters such as fatty acid composition, peroxide value (PV), anisidine value and tocopherol and tocotrienol composition were determined. Multivariate statistical methods (principal component analysis and agglomerative hierarchical cluster analysis) were applied to identify sensitive oxidation marker compounds. Preliminary results revealed that hexanal, E-2-heptenal, E-2-decenal and E,E-2,4-nonadienal were the most suitable in differentiating HOSF and SF oil varieties from each other and SF samples with differing oxidative properties. Differentiation of SF samples according to their volatile compound composition was done in accordance with the results from the well-known oil quality parameters (e.g. PV or fatty acid composition). In conclusion, the combination of volatile compound analysis with HS-SPME-GC and multivariate statistical methods provides a sensitive tool in differentiating conventional SF and HOSF oils by means of volatile lipid oxidation marker compounds.

  5. Perchlorate and Halogen-Free High Energy Dense Oxidizers (HEDO)

    Science.gov (United States)

    2011-06-01

    hexamethylenetetramine would afford bis(2,2,2-trinitroethyl) amine we were not successful using this strategy or confirm it. Potassium nitroformate (0.8849 g, 4.47...mmol) was suspended in water (1 mL) and hydrochloric acid was added (1 M) until the pH value of one was achieved. Hexamethylenetetramine (0.1026 g

  6. A box model study on photochemical interactions between VOCs and reactive halogen species in the marine boundary layer

    Directory of Open Access Journals (Sweden)

    K. Toyota

    2004-01-01

    Full Text Available A new chemical scheme is developed for the multiphase photochemical box model SEAMAC (size-SEgregated Aerosol model for Marine Air Chemistry to investigate photochemical interactions between volatile organic compounds (VOCs and reactive halogen species in the marine boundary layer (MBL. Based primarily on critically evaluated kinetic and photochemical rate parameters as well as a protocol for chemical mechanism development, the new scheme has achieved a near-explicit description of oxidative degradation of up to C3-hydrocarbons (CH4, C2H6, C3H8, C2H4, C3H6, and C2H2 initiated by reactions with OH radicals, Cl- and Br-atoms, and O3. Rate constants and product yields for reactions involving halogen species are taken from the literature where available, but the majority of them need to be estimated. In particular, addition reactions of halogen atoms with alkenes will result in forming halogenated organic intermediates, whose photochemical loss rates are carefully evaluated in the present work. Model calculations with the new chemical scheme reveal that the oceanic emissions of acetaldehyde (CH3CHO and alkenes (especially C3H6 are important factors for regulating reactive halogen chemistry in the MBL by promoting the conversion of Br atoms into HBr or more stable brominated intermediates in the organic form. The latter include brominated hydroperoxides, bromoacetaldehyde, and bromoacetone, which sequester bromine from a reactive inorganic pool. The total mixing ratio of brominated organic species thus produced is likely to reach 10-20% or more of that of inorganic gaseous bromine species over wide regions over the ocean. The reaction between Br atoms and C2H2 is shown to be unimportant for determining the degree of bromine activation in the remote MBL. These results imply that reactive halogen chemistry can mediate a link between the oceanic emissions of VOCs and the behaviors of compounds that are sensitive to halogen chemistry such as dimethyl

  7. Synthesis and mechanistic study of in situ halogen/nitrogen dual-doping in graphene tailored by stepwise pyrolysis of ionic liquids

    Science.gov (United States)

    Park, Ok-Kyung; Kim, Hyun Joo; Hwang, Jun Yeon; Lee, Dong Su; Koo, Jahyun; Lee, Hoonkyung; Yu, Jong-Sung; Ku, Bon-Cheol; Lee, Jae Kwan

    2015-03-01

    New halogen/nitrogen dual-doped graphenes (X/N-G) with thermally tunable doping levels are synthesized via the thermal reduction of graphite oxide (GO) with stepwise-pyrolyzed ionic liquids. The doping process of halogen and nitrogen into the graphene lattice proceeds via substitutional or covalent bonding through the physisorption or chemisorption of in situ pyrolyzed dopant precursors. The doping process is performed by heating to 300-400 °C of ionic liquid, and the chemically assisted reduction of GO is facilitated by ionic iodine, resulting in I/N-G materials possessing about three and two orders of magnitude higher conductivity (˜22 200 S m-1) and charge carrier density (˜1021 cm-3), compared to those of thermally reduced GO. The thermally tunable doping levels of halogen in X/N-G significantly increase the conductivity of doped graphene to ˜27 800 S m-1.

  8. Synthesis of Soluble Halogenated Polyphenylenes. Mechanism for the Coupling Halogenated Lithiobenzenes

    Science.gov (United States)

    1993-11-22

    the halogen content in these polymers was lowered using larger amounts of tert- butyllithium. TGA analysis (N2 , 20C/rmin) of I1 showed a 10% weight...iodide for every three aryl rings. DSC analysis (N2 , 20°C/min) for 1 8 showed no transitions on either the first or second heating scans to 230"C. TGA ... analysis (N2. 20C/rmin) showed a 10% weight loss at 3220C and char yields of 46% at 900"C. Visual analysis of the charred material did indicate that

  9. Negative Halogen Ions for Fusion Applications

    Energy Technology Data Exchange (ETDEWEB)

    Grisham, L.R.; Kwan, J.W.; Hahto, S.K.; Hahto, S.T.; Leung, K.N.; Westenskow, G.

    2006-01-01

    Over the past quarter century, advances in hydrogen negative ion sources have extended the usable range of hydrogen isotope neutral beams to energies suitable for large magnetically confined fusion devices. Recently, drawing upon this experience, negative halogen ions have been proposed as an alternative to positive ions for heavy ion fusion drivers in inertial confinement fusion, because electron accumulation would be prevented in negative ion beams, and if desired, the beams could be photo-detached to neutrals. This paper reports the results of an experiment comparing the current density and beam emittance of Cl+ and Cl- extracted from substantially ion-ion plasmas with that of Ar+ extracted from an ordinary electron-ion plasma, all using the same source, extractor, and emittance scanner. At similar discharge conditions, the Cl- current was typically 85 – 90% of the positive chlorine current, with an e-/ Cl- ratio as low as seven without grid magnets. The Cl- was as much as 76% of the Ar+ current from a discharge with the same RF drive. The minimum normalized beam emittance and inferred ion temperatures of Cl+, Cl-, and Ar+ were all similar, so the current density and optical quality of Cl- appear as suitable for heavy ion fusion driver applications as a positive noble gas ion of similar mass. Since F, I, and Br should all behave similarly in an ion source, they should also be suitable as driver beams.

  10. Catalytic mechanisms, basic roles, and biotechnological and environmental significance of halogenating enzymes

    Institute of Scientific and Technical Information of China (English)

    Xianping Chen; Karl-Heinz van Pée

    2008-01-01

    The understanding of enzymatic incorporation of halogen atoms into organic molecules has increased during the last few years. Two novel types of halogenating enzymes, flavindependent halogenases and α-ketoglutarate-dependent halogenases, are now known to play a significant role in enzyme-catalyzed halogenation. The recent advances on the halogenating enzymes RebH, SyrB2, and CytC3 have suggested some new mechanisms for enzymatic halogenations. This review concentrates on the occurrence, catalytic mechanisms, and biotechnological applications of the halogenating enzymes that are currently known.

  11. 40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

    Science.gov (United States)

    2010-07-01

    ... alcohol, halogenated alkane, substituted epoxide, and amino compound (generic). 721.10145 Section 721... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane,...

  12. Brønsted Acidic Ionic Liquid Accelerated Halogenation of Organic Compounds with N-Halosuccinimides (NXS)

    National Research Council Canada - National Science Library

    Stojan Stavber; Kenneth K. Laali; Dejan Vražič; Marjan Jereb

    2012-01-01

    ...;-halogenated ketone and ring-halogenated ketones were obtained. Activated aromatics were regioselectively ring halogenated to give mono- and dihalo-substituted products. The [BMIM(SO3H)][OTf] ionic liquid (IL...

  13. Brønsted acidic ionic liquid accelerated halogenation of organic compounds with N-Halosuccinimides (NXS)

    National Research Council Canada - National Science Library

    Vražič, Dejan; Jereb, Marjan; Laali, Kenneth K; Stavber, Stojan

    2012-01-01

    ...-halogenated ketone and ring-halogenated ketones were obtained. Activated aromatics were regioselectively ring halogenated to give mono- and dihalo-substituted products. The [BMIM(SO(3)H)][OTf] ionic liquid (IL...

  14. Kinetic method for assaying the halogenating activity of myeloperoxidase based on reaction of celestine blue B with taurine halogenamines.

    Science.gov (United States)

    Sokolov, A V; Kostevich, V A; Kozlov, S O; Donskyi, I S; Vlasova, I I; Rudenko, A O; Zakharova, E T; Vasilyev, V B; Panasenko, O M

    2015-06-01

    Myeloperoxidase (MPO) is a challenging molecular target which, if put under control, may allow regulating the development of inflammatory reactions associated with oxidative/halogenative stress. In this paper, a new kinetic method for assaying the halogenating activity of MPO is described. The method is based on measuring the rate of iodide-catalyzed oxidation of celestine blue B (CB) by oxygen and taurine N-chloramine (bromamine). The latter is produced in a reaction of taurine with HOCl (HOBr). CB is not a substrate for the peroxidase activity of MPO and does not react with hydrogen peroxide and superoxide anion radical. Taurine N-chloramine (bromamine) reacts with CB in molar ratio of 1:2. Using the new method, we studied the dependence of MPO activity on concentration of substrates and inhibitors. The specificity of MPO inhibition by non-proteolyzed ceruloplasmin is characterized. The inhibition of taurine N-chloramine production by neutrophils and HL-60 cells in the presence of MPO-affecting substances is demonstrated. The new method allows determining the kinetic parameters of MPO halogenating activity and studying its inhibition by various substances, as well as screening for potential inhibitors of the enzyme.

  15. Reducing nitrogen oxides in exhaust gases by means of urea. Final report; Reduzierung von Stickoxiden in Abgasen mittels Harnstoff. Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, M.; Elsener, M.; Marti, T. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1994-11-01

    Ammonia has been used for about twenty years as a selective reducing agent for reducing NO{sub x} in lean exhaust gases containing excess oxygen. Although urea has distinct advantages compared with ammonia (solid substance, cheap, practically nontoxic, not explosive) it has hardly been considered for this purpose. In the present work the possibilities of using aqueous urea solutions for the DeNOx processes based on selective catalytic reduction (SCR) and selective non catalytic reduction (SNCR) are explored. SCR: Urea-SCR poses little problems: If the process equipment is properly designed, no appreciable emissions of flue gas components related to urea are found, e.g. isocyanic acid, hydrogen cyanide, nitrous oxide, urea, biuret, cyanuric acid and melamine. On the other hand, like ammonia, use of urea leads to an emission of ammonia which limits the maximum attainable degree of NO{sub x} reduction. With industrial bulk catalysts based on TiO{sub 2}-WO{sub 3}-V{sub 2}O{sub 5} and gas hourly space velocities of 10`000 h{sup -1}, NO{sub x} reductions of over 98% at an ``ammonia slip`` below 10 ppm may be attained. SNCR: The use of urea instead of ammonia shifts the optimum temperature window upwards by about 50 K. Besides an ``ammonia slip``, some isocyanic acid is found, and the emissions of carbon monoxide and nitrous oxide are definitely higher. As nitrous oxide is considered to be a greenhouse gas and a scavenger of stratospheric ozone, the use of urea is no longer recommended in future SNCR installations. If the advantages of storage convenience of urea to be combined optimally with the advantages of ammonia as selective reducing agent, the hydropyrolysis of urea in an external reactor is a possible solution. (author) 38 figs., 5 tabs., 36 refs.

  16. Investigating Planetary Volatile Accretion Mechanisms Using the Halogens

    Science.gov (United States)

    Ballentine, C. J.; Clay, P. L.; Burgess, R.; Busemann, H.; Ruzié, L.; Joachim, B.; Day, J. M.

    2014-12-01

    Depletion of the volatile elements in the Earth relative to the CI chondrites is roughly correlated with volatility, or decreasing condensation temperature. For the heavy halogen group elements (Cl, Br and I), volatility alone does not account for their apparent depletion, which early data has suggested is far greater than predicted [1-2]. Such depletion has been used to argue for the preferential loss of halogens by, amongst other processes, impact-driven erosive loss from Earth's surface [2]. Little consensus exists as to why the halogens should exhibit such preferential behavior during accretionary processes. Early efforts to constrain halogen abundance and understand their behavior in both Earth and planetary materials [3-6] have been hampered by their typically low abundance (ppb level) in most geologic materials. We present the results of halogen analysis of 23 chondrite samples, selected to represent diverse groups and petrologic type. Halogen abundances were measured by neutron irradiation noble gas mass spectrometry (NI-NGMS). Significant concentration heterogeneity is observed within some samples. However, a single Br/Cl and I/Cl ratio of 1.9 ± 0.2 (x 10-3) and 335 ± 10 (x 10-6) can be defined for carbonaceous chondrites with a good correlation between Br and Cl (R2 = 0.97) and between I and Cl (R2 = 0.84). Ratios of I/Cl overlap with terrestrial estimates of Bulk Silicate Earth and Mid Ocean Ridge Basalts. Similarly, good correlations are derived for enstatite (E) chondrites and a sulfide- and halogen- rich subset of E-chondrites. Chlorine abundances of CI (Orgueil) in this study are lower by factor of ~ 3 than the value of ~ 700 ppm Cl (compilation in [1]). Our results are similar to early discarded low values for Ivuna and Orgueil from [5,6] and agree more closely with values for CM chondrites. Halogens may not be as depleted in Earth as previously suggested, or a high degree of heterogeneity in the abundance of these volatile elements in

  17. Redox activity of melanin from the ink sac of Sepia officinalis by means of colorimetric oxidative assay.

    Science.gov (United States)

    Srisuk, Pathomthat; Correlo, Vitor M; Leonor, Isabel B; Palladino, Pasquale; Reis, Rui L

    2016-01-01

    The redox properties of natural extract from cuttlefish ink sac (Sepia officinalis) and synthetic melanin used as a biomimetic in melanin structural investigation were determined by comparison of this phenol-based heterogeneous pigment with gallic acid used as a standard in Folin-Ciocalteu colorimetric assay widely employed for characterisation of oxidative properties of biomaterials. Reactivity of sepia melanin reported here is much higher than previously indicated and this protocol should allow the redox characterisation of all melanins irrespective of their origin and composition.

  18. Thermochemical properties and phase behavior of halogenated polycyclic aromatic hydrocarbons.

    Science.gov (United States)

    Fu, Jinxia; Suuberg, Eric M

    2012-03-01

    Knowledge of vapor pressure of organic pollutants is essential in predicting their fate and transport in the environment. In the present study, the vapor pressures of 12 halogenated polycyclic aromatic compounds (PACs), 9-chlorofluorene, 2,7-dichlorofluorene, 2-bromofluorene, 9-bromofluorene, 2,7-dibromofluorene, 2-bromoanthracene, 9-chlorophenanthrene, 9-bromophenanthrene, 9,10-dibromophenanthrene, 1-chloropyrene, 7-bromobenz[a]anthracene, and 6,12-dibromochrysene, were measured using the Knudsen effusion method over the temperature range of 301 to 464 K. Enthalpies and entropies of sublimation of these compounds were determined via application of the Clausius-Clapeyron equation. The data were also compared with earlier published literature values to study the influence of halogen substitution on vapor pressure of PACs. As expected, the halogen substitution decreases vapor pressure compared with parent compounds but does not necessarily increase the enthalpy of sublimation. Furthermore, the decrease of vapor pressure also depends on the substitution position and the substituted halogen, and the di-substitution of chlorine and/or bromine decreases the vapor pressure compared with single halogen-substituted polycyclic aromatic hydrocarbons. In addition, the enthalpy of fusion and melting temperature of these 12 PACs were determined using differential scanning calorimetry and melting point analysis.

  19. The mechanism of halogen liberation in the polar troposphere

    Directory of Open Access Journals (Sweden)

    E. Lehrer

    2004-06-01

    Full Text Available Sudden depletions of tropospheric ozone during spring were reported from the Arctic and also from Antarctic coastal sites. Field studies showed that those depletion events are caused by reactive halogen species, especially bromine compounds. However the source and seasonal variation of reactive halogen species is still not completely understood. There are several indications that the halogen mobilisation from the sea ice surface of the polar oceans may be the most important source for the necessary halogens. Here we present a 1-D model study aimed at determining the primary source of reactive halogens. The model includes gas phase and heterogeneous bromine and chlorine chemistry as well as vertical transport between the surface and the top of the boundary layer. The autocatalytic Br release by photochemical processes (bromine explosion and subsequent rapid bromine catalysed ozone depletion is well reproduced in the model and the major source of reactive bromine appears to be the sea ice surface. The sea salt aerosol alone is not sufficient to yield the high levels of reactive bromine in the gas phase necessary for fast ozone depletion. However, the aerosol efficiently 'recycles' less reactive bromine species (e.g. HBr and feeds them back into the ozone destruction cycle. Isolation of the boundary layer air from the free troposphere by a strong temperature inversion was found to be critical for boundary layer ozone depletion to happen. The combination of strong surface inversions and presence of sunlight occurs only during polar spring.

  20. Chain architecture and micellization: A mean-field coarse-grained model for poly(ethylene oxide) alkyl ether surfactants

    Energy Technology Data Exchange (ETDEWEB)

    García Daza, Fabián A.; Mackie, Allan D., E-mail: allan.mackie@urv.cat [Department d’Enginyeria Química, ETSEQ, Universitat Rovira i Virgili, Avinguda dels Països Catalans 26, 43007 Tarragona (Spain); Colville, Alexander J. [Department of Chemical Engineering, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115-5000 (United States)

    2015-03-21

    Microscopic modeling of surfactant systems is expected to be an important tool to describe, understand, and take full advantage of the micellization process for different molecular architectures. Here, we implement a single chain mean field theory to study the relevant equilibrium properties such as the critical micelle concentration (CMC) and aggregation number for three sets of surfactants with different geometries maintaining constant the number of hydrophobic and hydrophilic monomers. The results demonstrate the direct effect of the block organization for the surfactants under study by means of an analysis of the excess energy and entropy which can be accurately determined from the mean-field scheme. Our analysis reveals that the CMC values are sensitive to branching in the hydrophilic head part of the surfactant and can be observed in the entropy-enthalpy balance, while aggregation numbers are also affected by splitting the hydrophobic tail of the surfactant and are manifested by slight changes in the packing entropy.

  1. Investigation of acid red 88 oxidation in water by means of electro-Fenton method for water purification.

    Science.gov (United States)

    Özcan, Ali; Gençten, Metin

    2016-03-01

    In this study, electro-Fenton method was applied to acid red 88 (AR88) containing aqueous solutions for the removal of it from water. The mineralization of AR88 has been achieved by oxidation with hydroxyl radicals. These radicals were produced simultaneously by the electro-Fenton method using an electrochemical cell including a carbon felt cathode and a platinum anode. Applied current and concentrations of catalyst and supporting electrolyte were optimized to obtain the best effective parameters of 500 mA, 0.1 mM and 75 mM, respectively. The absolute rate constant for the oxidation reaction of AR88 with hydroxyl radical was determined as (1.57 ± 0.06) x 10(10) M(-1) s(-1). Total organic carbon (TOC) analysis was performed to determine whether the organics were converted to carbon dioxide or not. A two-hour electrolysis at 500 mA is enough to remove 87% of initial TOC values of 0.25 mM AR88 solution. Electro-Fenton treatment of AR88 led to the formation of five aromatic intermediates, five short-chain carboxylic acids and three inorganic ions. Identified intermediates and complete mineralization of AR88 allowed us to propose a mineralization pathway for first time in the literature.

  2. Fabrication of hybrid graphene oxide/polyelectrolyte capsules by means of layer-by-layer assembly on erythrocyte cell templates.

    Science.gov (United States)

    Irigoyen, Joseba; Politakos, Nikolaos; Diamanti, Eleftheria; Rojas, Elena; Marradi, Marco; Ledezma, Raquel; Arizmendi, Layza; Rodríguez, J Alberto; Ziolo, Ronald F; Moya, Sergio E

    2015-01-01

    A novel and facile method was developed to produce hybrid graphene oxide (GO)-polyelectrolyte (PE) capsules using erythrocyte cells as templates. The capsules are easily produced through the layer-by-layer technique using alternating polyelectrolyte layers and GO sheets. The amount of GO and therefore its coverage in the resulting capsules can be tuned by adjusting the concentration of the GO dispersion during the assembly. The capsules retain the approximate shape and size of the erythrocyte template after the latter is totally removed by oxidation with NaOCl in water. The PE/GO capsules maintain their integrity and can be placed or located on other surfaces such as in a device. When the capsules are dried in air, they collapse to form a film that is approximately twice the thickness of the capsule membrane. AFM images in the present study suggest a film thickness of approx. 30 nm for the capsules in the collapsed state implying a thickness of approx. 15 nm for the layers in the collapsed capsule membrane. The polyelectrolytes used in the present study were polyallylamine hydrochloride (PAH) and polystyrenesulfonate sodium salt (PSS). Capsules where characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS) and Raman microscopy, the constituent layers by zeta potential and GO by TEM, XRD, and Raman and FTIR spectroscopies.

  3. Fabrication of hybrid graphene oxide/polyelectrolyte capsules by means of layer-by-layer assembly on erythrocyte cell templates

    Directory of Open Access Journals (Sweden)

    Joseba Irigoyen

    2015-12-01

    Full Text Available A novel and facile method was developed to produce hybrid graphene oxide (GO–polyelectrolyte (PE capsules using erythrocyte cells as templates. The capsules are easily produced through the layer-by-layer technique using alternating polyelectrolyte layers and GO sheets. The amount of GO and therefore its coverage in the resulting capsules can be tuned by adjusting the concentration of the GO dispersion during the assembly. The capsules retain the approximate shape and size of the erythrocyte template after the latter is totally removed by oxidation with NaOCl in water. The PE/GO capsules maintain their integrity and can be placed or located on other surfaces such as in a device. When the capsules are dried in air, they collapse to form a film that is approximately twice the thickness of the capsule membrane. AFM images in the present study suggest a film thickness of approx. 30 nm for the capsules in the collapsed state implying a thickness of approx. 15 nm for the layers in the collapsed capsule membrane. The polyelectrolytes used in the present study were polyallylamine hydrochloride (PAH and polystyrenesulfonate sodium salt (PSS. Capsules where characterized by transmission electron microscopy (TEM, atomic force microscopy (AFM, dynamic light scattering (DLS and Raman microscopy, the constituent layers by zeta potential and GO by TEM, XRD, and Raman and FTIR spectroscopies.

  4. On the interactions of human bone cells with Ti6Al4V thermally oxidized by means of laser shock processing.

    Science.gov (United States)

    Crespo, Lara; Hierro-Oliva, Margarita; Barriuso, Sandra; Vadillo-Rodríguez, Virginia; Montealegre, M Ángeles; Saldaña, Laura; Gomez-Barrena, Enrique; González-Carrasco, José Luis; González-Martín, María Luisa; Vilaboa, Nuria

    2016-02-02

    We investigated a Ti6Al4V alloy modified by means of laser peening in the absence of sacrificial coatings. As a consequence of the temperature rise during laser focusing, melting and ablation generated an undulated surface that exhibits an important increase in the content of titanium oxides and OH- ions. Human mesenchymal stem cells and osteoblasts cultured on the oxidized alloy develop noticeable filopodia and lamellipodia. Their paxillin-stained focal adhesions are smaller than in cells attached to the untreated alloy and exhibit a marked loss of colocalization with the ends of actin stress fibers. An important imbalance of phosphorylation and/or dephosphorylation of the focal adhesion kinase is detected in cells grown on the oxidized alloy. Although these mechanisms of adhesion are deeply altered, the surface treatment does not affect cell attachment or proliferation rates on the alloy. Human mesenchymal stem cells cultured on the treated alloy in media containing osteogenic inducers differentiate towards the osteoblastic phenotype to a higher extent than those on the untreated surface. Also, the specific functions of human osteoblasts cultured on these media are enhanced on the treated alloy. In summary, laser peening tailors the Ti6Al4V surface to yield an oxidized layer with increased roughness that allows the colonization and activities of bone-lineage cells.

  5. Monitoring and risk assessment by means of alkyl groups in hemoglobin in persons occupationally exposed to ethylene oxide.

    Science.gov (United States)

    Calleman, C J; Ehrenberg, L; Jansson, B; Osterman-Golkar, S; Segerbäck, D; Svensson, K; Wachtmeister, C A

    1978-01-01

    In persons occupationally exposed to ethylene oxide, i.e. under the conditions described by Dunkelberg and Hartmetz (1977), the degree of alkylation in histidine of hemoglobin was determined. Quantitative determination of N-3-(2-hydroxyethyl)histidine by mass fragmentography and by ion-exchange amino-acid analysis gave consistent results. Data are in agreement with the fast elimination from tissues (lambda = 4.6 hr-1, i.e. biological half-life about 9 min) found in the mouse. At the respiration rate of light work, and exposure dose of 1 ppm/hr results in a tissue dose that is estimated to involve a risk amounting to 1.101 mrad-equivalents of stochastic effects with a genetic mechanism.

  6. Formation of grafted surface layers on silicon dioxide particles and their investigation by means of thermoprogrammed oxidation

    Science.gov (United States)

    Aleksandrova, E. O.; Novichkov, R. V.; Olenin, A. Yu.; Zuev, B. K.

    2017-03-01

    Silica nanoparticles are obtained according to the Stober-Fink-Bohn method, and their surfaces are chemically modified with 1H,1H,2H,2H-perfluorodecyltriethoxysilane. It is estimated that sols of porous silica nanoparticles (average sizes, 50-200 nm) form during primary chemical process; the average size of the particles can be increased to 400-500 nm by consecutive growth. Oxythermography (thermoprogrammed oxidation) measurements reveal a stepped dependence between the content of organic substance of nanoparticles and the duration of chemical modification reaction exists. It is concluded that this could be due to the formation of dense shell (or shells) as a result of sols aging between the cycles of growth; such shells impose diffusive restrictions when molecules penetrate into the pores of the internal volume of the particles.

  7. Biodegradation of Trihalomethanes and Other Halogenated Aliphatic Compounds

    Science.gov (United States)

    Smith, G. B.

    1996-01-01

    The biological dehalogenation of common water pollutants such as trichloromethane (chloroform) and other halogenated aliphatic compounds was the subject of this project. Samples from diverse water environments such as from groundwater contaminated with halogenated compounds and wastewaters from regional treatment plants were studied to identify conditions that favor certain dehalogenation reactions over others. Gene probe analyses of DNA extracted from the dichlormethane-degrading wastewater indicated the presence of the gene coding for dichloromethane dehalogenase, indicating the genetic basis for the dechlorination activity observed. These studies indicate that methanogenic bacteria are the organisms responsible for the chloroform dechlorination. Dechlorination of a common chlorofluorocarbon (CFC-11) was identified in samples taken from a regional aquifer contaminated with halogenated aliphatic compounds.

  8. Thief carbon catalyst for oxidation of mercury in effluent stream

    Science.gov (United States)

    Granite, Evan J.; Pennline, Henry W.

    2011-12-06

    A catalyst for the oxidation of heavy metal contaminants, especially mercury (Hg), in an effluent stream is presented. The catalyst facilitates removal of mercury through the oxidation of elemental Hg into mercury (II) moieties. The active component of the catalyst is partially combusted coal, or "Thief" carbon, which can be pre-treated with a halogen. An untreated Thief carbon catalyst can be self-promoting in the presence of an effluent gas streams entrained with a halogen.

  9. Behavior of halogens during the degassing of felsic magmas

    Science.gov (United States)

    Balcone-Boissard, H.; Villemant, B.; Boudon, G.

    2010-09-01

    Residual concentrations of halogens (F, Cl, Br, I) and H2O in glass (matrix glass and melt inclusions) have been determined in a series of volcanic clasts (pumice and lava-dome fragments) of plinian, vulcanian and lava dome-forming eruptions. Felsic magmas from calc-alkaline, trachytic and phonolitic systems have been investigated: Montagne Pelée and Soufrière Hills of Montserrat (Lesser Antilles), Santa Maria-Santiaguito (Guatemala), Fogo (Azores) and Vesuvius (Italy). The behavior of halogens during shallow H2O degassing primarily depends on their incompatible character and their partitioning between melt and exsolved H2O vapor. However, variations in pre-eruptive conditions, degassing kinetics, and syn-eruptive melt crystallization induce large variations in the efficiency of halogen extraction. In all systems studied, Cl, Br and I are not fractionated from each other by differentiation or by degassing processes. Cl/Br/I ratios in melt remain almost constant from the magma reservoir to the surface. The ratios measured in erupted clasts are thus characteristic of pre-eruptive magma compositions and may be used to trace deep magmatic processes. F behaves as an incompatible element and, unlike the other halogens, is never significantly extracted by degassing. Cl, Br and I are efficiently extracted from melts at high pressure by H2O-rich fluids exsolved from magmas or during slow effusive magma degassing, but not during rapid explosive degassing. Because H2O and halogen mobility depends on their speciation, which strongly varies with pressure in both silicate melts and exsolved fluids, we suggest that the rapid pressure decrease during highly explosive eruptions prevents complete equilibrium between the diverse species of the volatiles and consequently limits their degassing. Conversely, degassing in effusive eruptions is an equilibrium process and leads to significant halogen output in volcanic plumes.

  10. Fine tuning of graphene properties by modification with aryl halogens

    Science.gov (United States)

    Bouša, D.; Pumera, M.; Sedmidubský, D.; Šturala, J.; Luxa, J.; Mazánek, V.; Sofer, Z.

    2016-01-01

    Graphene and its derivatives belong to one of the most intensively studied materials. The radical reaction using halogen derivatives of arene-diazonium salts can be used for effective control of graphene's electronic properties. In our work we investigated the influence of halogen atoms (fluorine, chlorine, bromine and iodine) as well as their position on the benzene ring towards the electronic and electrochemical properties of modified graphenes. The electronegativity as well as the position of the halogen atoms on the benzene ring has crucial influence on graphene's properties due to the inductive and mesomeric effects. The results of resistivity measurement are in good agreement with the theoretical calculations of electron density within chemically modified graphene sheets. Such simple chemical modifications of graphene can be used for controllable and scalable synthesis of graphene with tunable transport properties.Graphene and its derivatives belong to one of the most intensively studied materials. The radical reaction using halogen derivatives of arene-diazonium salts can be used for effective control of graphene's electronic properties. In our work we investigated the influence of halogen atoms (fluorine, chlorine, bromine and iodine) as well as their position on the benzene ring towards the electronic and electrochemical properties of modified graphenes. The electronegativity as well as the position of the halogen atoms on the benzene ring has crucial influence on graphene's properties due to the inductive and mesomeric effects. The results of resistivity measurement are in good agreement with the theoretical calculations of electron density within chemically modified graphene sheets. Such simple chemical modifications of graphene can be used for controllable and scalable synthesis of graphene with tunable transport properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06295k

  11. Symmetric and asymmetric halogen-containing metallocarboranylporphyrins and uses thereof

    Energy Technology Data Exchange (ETDEWEB)

    Miura, Michiko; Wu, Haitao

    2013-05-21

    The present invention is directed to low toxicity boronated compounds and methods for their use in the treatment, visualization, and diagnosis of tumors. More specifically, the present invention is directed to low toxicity halogenated, carborane-containing 5,10,15,20-tetraphenylporphyrin compounds and methods for their use particularly in boron neutron capture therapy (BNCT) and photodynamic therapy (PDT) for the treatment of tumors of the brain, head and neck, and surrounding tissue. The invention is also directed to using these halogenated, carborane-containing tetraphenylporphyrin compounds in methods of tumor imaging and/or diagnosis such as MRI, SPECT, or PET.

  12. Supramolecular self-assembly of graphene oxide and metal nanoparticles into stacked multilayers by means of a multitasking protein ring

    Science.gov (United States)

    Ardini, Matteo; Golia, Giordana; Passaretti, Paolo; Cimini, Annamaria; Pitari, Giuseppina; Giansanti, Francesco; Leandro, Luana Di; Ottaviano, Luca; Perrozzi, Francesco; Santucci, Sandro; Morandi, Vittorio; Ortolani, Luca; Christian, Meganne; Treossi, Emanuele; Palermo, Vincenzo; Angelucci, Francesco; Ippoliti, Rodolfo

    2016-03-01

    Graphene oxide (GO) is rapidly emerging worldwide as a breakthrough precursor material for next-generation devices. However, this requires the transition of its two-dimensional layered structure into more accessible three-dimensional (3D) arrays. Peroxiredoxins (Prx) are a family of multitasking redox enzymes, self-assembling into ring-like architectures. Taking advantage of both their symmetric structure and function, 3D reduced GO-based composites are hereby built up. Results reveal that the ``double-faced'' Prx rings can adhere flat on single GO layers and partially reduce them by their sulfur-containing amino acids, driving their stacking into 3D multi-layer reduced GO-Prx composites. This process occurs in aqueous solution at a very low GO concentration, i.e. 0.2 mg ml-1. Further, protein engineering allows the Prx ring to be enriched with metal binding sites inside its lumen. This feature is exploited to both capture presynthesized gold nanoparticles and grow in situ palladium nanoparticles paving the way to straightforward and ``green'' routes to 3D reduced GO-metal composite materials.Graphene oxide (GO) is rapidly emerging worldwide as a breakthrough precursor material for next-generation devices. However, this requires the transition of its two-dimensional layered structure into more accessible three-dimensional (3D) arrays. Peroxiredoxins (Prx) are a family of multitasking redox enzymes, self-assembling into ring-like architectures. Taking advantage of both their symmetric structure and function, 3D reduced GO-based composites are hereby built up. Results reveal that the ``double-faced'' Prx rings can adhere flat on single GO layers and partially reduce them by their sulfur-containing amino acids, driving their stacking into 3D multi-layer reduced GO-Prx composites. This process occurs in aqueous solution at a very low GO concentration, i.e. 0.2 mg ml-1. Further, protein engineering allows the Prx ring to be enriched with metal binding sites inside its

  13. 40 CFR 721.785 - Halogenated alkane aromatic compound (generic name).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated alkane aromatic compound... Specific Chemical Substances § 721.785 Halogenated alkane aromatic compound (generic name). (a) Chemical... as a halogenated alkane aromatic compound (PMN P-94-1747) is subject to reporting under this...

  14. Overcoming the Gas-Liquid Mass Transfer of O₂ by Means of Photosynthetic Water Oxidation Coupled with Biocatalytic Oxyfunctionalization.

    Science.gov (United States)

    Hoschek, Anna; Bühler, Bruno; Schmid, Andreas

    2017-09-25

    Gas-liquid mass transfer of gaseous reactants is a major limitation for high space-time yields, especially for O₂-dependent (bio)catalytic reactions in aqueous solutions. Oxygenic photosynthesis was used for homogeneous O₂-supply via in situ generation in the liquid phase to overcome gas-liquid mass transfer limitations. The phototrophic cyanobacterium Synechocystis sp. PCC6803 was engineered to synthesize alkane monooxygenase AlkBGT, originating from Pseudomonas putida GPo1. With light, but without external addition of O₂, the chemo- and regioselective hydroxylation of nonanoic acid methyl ester to ω-hydroxynonanoic acid methyl ester was driven by O₂ generated via photosynthetic water oxidation. Photosynthesis also delivered the necessary reduction equivalents regenerating Fe2+ in AlkB for oxygen transfer to the terminal methyl group. The in situ coupling of oxygenic photosynthesis to O₂-transferring enzymes now allows the design of fast hydrocarbon oxyfunctionalization reactions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Solution phase synthesis of halogenated graphene and the electrocatalytic activity for oxygen reduction reaction

    Institute of Scientific and Technical Information of China (English)

    Kuang-Hsu Wu; Da-Wei Wang; Qingcong Zeng; Yang Li; Ian R. Gentle

    2014-01-01

    Metal-free carbon electrocatalyts for the oxygen reduction reaction (ORR) are attractive for their high activity and economic advantages. However, the origin of the activity has never been clearly elucidated in a systematic manner. Halogen group elements are good candidates for elucidating the effect, although it has been a difficult task due to safety issues. In this report, we demonstrate the synthesis of Cl-, Br-and I-doped reduced graphene oxide through two solution phase syntheses. We have evaluated the effectiveness of doping and performed electrochemical measurements of the ORR activity on these halogenated graphene materials. Our results suggest that the high electroneg-ativity of the dopant is not the key factor for high ORR activity;both Br-and I-doped graphene pro-moted ORR more efficiently than Cl-doped graphene. Furthermore, an unexpected sulfur-doping in acidic conditions suggests that a high level of sulfide can degrade the ORR activity of the graphene material.

  16. Investigation of zinc oxide particles in cosmetic products by means of centrifugal and asymmetrical flow field-flow fractionation.

    Science.gov (United States)

    Sogne, Vanessa; Meier, Florian; Klein, Thorsten; Contado, Catia

    2017-09-15

    The dimensional characterization of insoluble, inorganic particles, such as zinc oxide ZnO, dispersed in cosmetic or pharmaceutical formulations, is of great interest considering the current need of declaring the possible presence of nanomaterials on the label of commercial products. This work compares the separation abilities of Centrifugal- and Asymmetrical Flow Field-Flow Fractionation techniques (CF3 and AF4, respectively), equipped with UV-vis, MALS and DLS detectors, in size sorting ZnO particles, both as pristine powders and after their extraction from cosmetic matrices. ZnO particles, bare and superficially modified with triethoxycaprylyl silane, were used as test materials. To identify the most suitable procedure necessary to isolate the ZnO particles from the cosmetic matrix, two O/W and two W/O emulsions were formulated on purpose. The suspensions, containing the extracted particles ZnO, were separated by both Field-Flow Fractionation (FFF) techniques to establish a common analysis protocol, applicable for the analysis of ZnO particles extracted from three commercial products, sold in Europe for the baby skin care. Key aspects of this study were the selection of an appropriate dispersing agent enabling the particles to stay in stable suspensions (>24h)and the use of multiple detectors (UV-vis, MALS and DLS) coupled on-line with the FFF channels, to determine the particle dimensions without using the retention parameters. Between the two FFF techniques, CF3 revealed to be the most robust one, able to sort all suspensions created in this work. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Development and application of a sampling method for the determination of reactive halogen species in volcanic gas emissions

    Science.gov (United States)

    Rüdiger, Julian; Bobrowski, Nicole; Liotta, Marcello; Hoffmann, Thorsten

    2017-04-01

    Volcanoes are a potential large source of several reactive atmospheric trace gases including sulfur and halogen containing species. Besides the importance for atmospheric chemistry, the detailed knowledge of halogen chemistry in volcanic plumes can help to get insights into subsurface processes. In this study a gas diffusion denuder sampling method, using a 1,3,5-trimethoxybenzene (1,3,5-TMB) coating for the derivatization of reactive halogen species (RHS), was characterized by dilution chamber experiments. The coating proved to be suitable to collect selectively gaseous bromine species with oxidation states (OS) of +1 or 0 (such as Br2, BrCl, BrO(H) and BrONO2), while being ignorant to HBr (OS -1). The reaction of 1,3,5-TMB with reactive bromine species gives 1-bromo-2,4,6-trimethoxybenzene (1-bromo-2,4,6-TMB) - other halogens give corresponding products. Solvent elution of the derivatized analytes and subsequent analysis with gas chromatography mass spectrometry gives detection limits of 10 ng or less for Br2, Cl2, and I2. In 2015 the method was applied on volcanic gas plumes at Mt. Etna (Italy) giving reactive bromine mixing ratios from 0.8 ppbv to 7.0 ppbv. Total bromine mixing ratios of 4.7 ppbv to 27.5 ppbv were obtained by simultaneous alkaline trap sampling (by a Raschig-tube) followed by analysis with ion chromatography and inductively coupled plasma mass spectrometry. This leads to the first results of in-situ measured reactive bromine to total bromine ratios, spanning a range between 12±1 % and 36±2 %. Our finding is in an agreement with previous model studies, which imply values < 44 % for plume ages < 1 minute, which is consistent with the assumed plume age at the sampling sites.

  18. From charge transfer to electron transfer in halogen-bonded complexes of electrophilic bromocarbons with halide anions.

    Science.gov (United States)

    Rosokha, Sergiy V; Traversa, Alfredo

    2015-02-21

    Experimental and computational studies of the halogen-bonded complexes, [R-Br, X(-)], of bromosubstituted electrophiles, R-Br, and halide anions, X(-), revealed that decrease of a gap between the frontier orbitals of interacting species led to reduction of the energy of the optical charge-transfer transition and to increase in the ground-state charge transfer (X(-) → R-Br) in their associates. These variations were accompanied by weakening of the intramolecular, C-Br, and strengthening of the intermolecular, BrX(-), bonds. In the limit of the strongest electron donor-acceptor pairs, formation of the halogen-bonded complexes was followed by the oxidation of iodide to triiodide, which took place despite the fact that the I(-) → R-Br electron-transfer step was highly endergonic and the calculated outer-sphere rate constant was negligibly small. However, the calculated barrier for the inner-sphere electron transfer accompanied by the halogen transfer, R-BrI(-) → R˙Br-I(-)˙, was nearly 24 kcal mol(-1) lower as compared to that calculated for the outer-sphere process and the rate constant of such reaction was consistent with the experimental kinetics. A dramatic decrease of the electron-transfer barriers (leading to 18-orders of magnitude increase of the rate constant) was related to the strong electronic coupling of the donor and acceptor within the halogen-bonded precursor complex, as well as to the lower solvent reorganization energy and the successor-complex stabilization.

  19. Alkali and Halogen Chemistry in Volcanic Gases on Io

    CERN Document Server

    Schaefer, L

    2004-01-01

    We use chemical equilibrium calculations to model the speciation of alkalis and halogens in volcanic gases emitted on Io. The calculations cover wide temperature (500-2000 K) and pressure (10^-6 to 10^+1 bars) ranges, which overlap the nominal conditions at Pele (T = 1760 K, P = 0.01 bars). About 230 compounds of 11 elements (O, S, Li, Na, K, Rb, Cs, F, Cl, Br, I) are considered. We predict the major alkali and halogen species in a Pele-like volcanic gas and the major alklai and halogen condensates. We also model disequilibrium chemistry of the alkalis and halogens in the volcanic plume. Based on this work and our prior modeling for Na, K, and Cl in a volcanic plume, we predict the major loss processes for the alkali halide gases are photolysis and/or condensation onto grains. On the basis of elemental abundances and photochemical lifetimes, we recommend searching for gaseous KCl, NaF, LiF, LiCl, RbF, RbCl, CsF, and CsCl around volcanic vents during eruptions. Based on abundance considerations and observation...

  20. First negative halogen beams produced at PSBooster-ISOLDE

    CERN Document Server

    Stora, T; Bouquerel, E; Catherall, R; Eller, M; Lettry, J; Menna, M

    Chemically pure radioactive halogen beams have interesting potentials for solid state and nuclear physics, for instance for implantation studies or in precise -decay measurements. They can be produced as positive ions by the ISOL approach, with possible isobaric contaminations, or as pure negative ion beams, with a LaB6 negative surface ion source...

  1. Influence of saponins on the biodegradation of halogenated phenols.

    Science.gov (United States)

    Kaczorek, Ewa; Smułek, Wojciech; Zdarta, Agata; Sawczuk, Agata; Zgoła-Grześkowiak, Agnieszka

    2016-09-01

    Biotransformation of aromatic compounds is a challenge due to their low aqueous solubility and sorptive losses. The main obstacle in this process is binding of organic pollutants to the microbial cell surface. To overcome these, we applied saponins from plant extract to the microbial culture, to increase pollutants solubility and enhance diffusive massive transfer. This study investigated the efficiency of Quillaja saponaria and Sapindus mukorossi saponins-rich extracts on biodegradation of halogenated phenols by Raoultella planticola WS2 and Pseudomonas sp. OS2, as an effect of cell surface modification of tested strains. Both strains display changes in inner membrane permeability and cell surface hydrophobicity in the presence of saponins during the process of halogenated phenols biotransformation. This allows them to more efficient pollutants removal from the environment. However, only in case of the Pseudomonas sp. OS2 the addition of surfactants to the culture improved effectiveness of bromo-, chloro- and fluorophenols biodegradation. Also introduction of surfactant allowed higher biodegradability of halogenated phenols and can shorten the process. Therefore this suggests that usage of plant saponins can indicate more successful halogenated phenols biodegradation for selected strains.

  2. Ruthenium-catalyzed intramolecular selective halogenation of O-methylbenzohydroximoyl halides: a new route to halogenated aromatic nitriles.

    Science.gov (United States)

    Chinnagolla, Ravi Kiran; Pimparkar, Sandeep; Jeganmohan, Masilamani

    2013-04-18

    The intramolecular halogenation of O-methylbenzohydroximoyl halides in the presence of a Ru catalyst and the ligand diphenylacetylene afforded halo substituted aromatic nitriles in a highly regioselective manner. Further, substituted nitriles were converted into substituted tetrazole derivatives in the presence of NaN3 and I2.

  3. Apatite trace element and halogen compositions as petrogenetic-metallogenic indicators: Examples from four granite plutons in the Sanjiang region, SW China

    Science.gov (United States)

    Pan, Li-Chuan; Hu, Rui-Zhong; Wang, Xin-Song; Bi, Xian-Wu; Zhu, Jing-Jing; Li, Chusi

    2016-06-01

    The abundances of trace elements including Sr, Ga and rare earth elements (REE) and halogens in apatite crystals from four intermediate-felsic plutons in the Zhongdian terrane in the Sanjiang region have been determined using electron microprobe and laser ablation inductively coupled plasma mass spectrometry to evaluate the potential of apatite as a petrogenic-metallogenic indicator. The selected plutons include one that is not mineralized (the Triassic Xiuwacu pluton, or the TXWC pluton), one that hosts a porphyry-type Cu deposit (the Pulang pluton, or the PL pluton), one that hosts a porphyry-type Mo deposit (the Tongchanggou pluton, or the TCG pluton), and one that hosts a vein-type Mo deposit (the Cretaceous Xiuwacu pluton, or the CXWC pluton). Except for the CXWC pluton, the other three plutons have adakite-like trace element signatures in whole rocks. The results from this study show that REE, Sr and halogens in apatite can be used to track magma compositions, oxidation states and crystallization history. Apatite crystals from the adakite-like plutons are characterized by much higher Sr/Y and δEu than the non-adakite-type pluton. This means that apatite, which is not susceptible to alteration, is a useful tool for identifying the adakite-like plutons that no longer preserve the initial Sr/Y ratios in whole rocks due to weathering and hydrothermal alteration. Based on apatite Ga contents and δEu values, it is inferred that the parental magmas for the two adakite-like plutons containing porphyry-type Cu and Mo mineralization are more oxidized than that for the non-adakite-type pluton containing vein-type Mo mineralization. Apatite crystals from the vein-type Mo deposit have much lower Cl/F ratios than those from the porphyry-type Cu and Mo deposits. Apatite crystals from the adakite-like pluton without Cu or Mo mineralization is characterized by much lower Cl/F ratios than those from the adakite-like plutons that host the porphyry-type Cu and Mo deposits. The

  4. Synthesis and characterization of lead-free tin silver nanosolders and their application to halogen free nanosolder pastes

    Science.gov (United States)

    Wernicki, Evan

    Solder paste is a key material used in attaching electronic components to printed circuit boards (PCBs). Commonly used lead-based solders, such as eutectic Sn/37Pb, are currently being replaced by lead-free alloy materials due to health and environmental concerns associated with lead. Many solder pastes, both lead-containing and lead-free, contain halogens which act as activators to remove surface oxide and enhance surface wetting, posing further environmental concern from the halogen species. Difficulties in obtaining reliable joints can occur since lead-free solder material candidates have higher melting temperatures (30-50 °C) than that of lead-based solders. Differences in material properties between the numerous materials used in assembly and packaging processes can lead to component damage during manufacturing. Furthermore, designs that include more electrical interconnects in smaller areas give rise for the need for new materials to allow this trend to continue. A surfactant-assisted chemical reduction method was used to synthesize Sn/Ag alloy nanoparticles with a target composition range of 3.5-5 wt% Ag that served as the lead-free solder material within a nanosolder paste. Structure and size characterization via SEM and TEM showed Sn-Ag nanosolders size average approximately 19 nm. Differential scanning calorimetry (DSC) measurements of the nanosolder samples containing 4.5 wt% Ag showed an endothermic peak at 222.5 °C and an onset of 219.2 °C, indicating up to 17.5 °C melting temperature depression when compared to the bulk liquidus value of 240 °C. Composition of the nanosolder material was confirmed using energy dispersive x-ray spectroscopy (EDS) and structures formed were analyzed via x-ray diffraction (XRD). Both halogen-free and halogen-containing flux materials were combined with the nanosolder material, respectively, with varying preparation parameters to form a design of experiments (DoE) for nanosolder paste preparation. Solder pastes

  5. Effect of halogen light in fetal stimulation for fetal well-being assessment.

    Science.gov (United States)

    Thanaboonyawat, Isarin; Wataganara, Tuangsit; Boriboonhiransarn, Dittakarn; Viboonchart, Sommai; Tontisirin, Pornpen

    2006-09-01

    To evaluate the shortening of the time of nonstress test (NST) by using transabdominal fetal stimulation with halogen light. Experimental research. The authors enrolled 176 pregnant women between 32 and 42 weeks of gestation indicated for NST at the Division of Maternal Fetal Medicine, Siriraj Hospital, Mahidol University. They were randomly assigned to receive either NST (control) or halogen light stimulation test (LST). The stimulation was performed at the beginning of the test and repeated every 10 minutes until reassuring fetal heart rate (FHR) acceleration was achieved, or up to 3 times. All tracings were interpreted blindly by one investigator at the end of the tests. The mean (+/- SD) duration from starting the test to the first FHR acceleration was not significantly different between the control group and the LST group (5.6 +/- 7.2 and 5.4 +/- 5.2 minutes, respectively). The average testing time (+/- SD) to achieved reactivity was 10.5 +/- 8.8 minutes in the controls and 9.6 +/- 6.7 minutes in the LST group. This was not statistically different. The incidence of nonreactive tests was not significantly different between the LST and the controls (15.9% and 11.4%, respectively). Among the LST subjects, term fetuses and women with BMI stimulation did not shorten the duration of NST in the presented population. However, the presented data suggests that the fetus at term could respond to visual stimulation, especially when the gestational age is more advanced.

  6. Halogen species record Antarctic sea ice extent over glacial–interglacial periods

    Directory of Open Access Journals (Sweden)

    A. Spolaor

    2013-07-01

    Full Text Available Sea ice is an integral part of the earth's climate system because it affects planetary albedo, sea-surface salinity, and the atmosphere–ocean exchange of reactive gases and aerosols. Bromine and iodine chemistry is active at polar sea ice margins with the occurrence of bromine explosions and the biological production of organoiodine from sea ice algae. Satellite measurements demonstrate that concentrations of bromine oxide (BrO and iodine oxide (IO decrease over sea ice toward the Antarctic interior. Here we present speciation measurements of bromine and iodine in the TALDICE (TALos Dome Ice CorE ice core (159°11' E, 72°49' S; 2315 m a.s.l. spanning the last 215 ky. The Talos Dome ice core is located 250 km inland and is sensitive to marine air masses intruding onto the Antarctic Plateau. Talos Dome bromide (Br− is positively correlated with temperature and negatively correlated with sodium (Na. Based on the Br−/Na seawater ratio, bromide is depleted in the ice during glacial periods and enriched during interglacial periods. Total iodine, consisting of iodide (I− and iodate (IO3−, peaks during glacials with lower values during interglacial periods. Although IO3− is considered the most stable iodine species in the atmosphere it was only observed in the TALDICE record during glacial maxima. Sea ice dynamics are arguably the primary driver of halogen fluxes over glacial–interglacial timescales, by altering the distance between the sea ice edge and the Antarctic plateau and by altering the surface area of sea ice available to algal colonization. Based on our results we propose the use of both halogens for examining Antarctic variability of past sea ice extent.

  7. Modeling the reactive halogen plume from Ambrym volcano and its impact on the troposphere with the CCATT-BRAMS mesoscale model

    OpenAIRE

    Jourdain, L.; T. J. Roberts; M. Pirre; Josse, B.

    2015-01-01

    Ambrym volcano (Vanuatu, Southwest Pacific) is one of the largest sources of continuous volcanic emissions worldwide. As well as releasing SO2 that is oxidized to sulfate, volcanic plumes in the troposphere are shown to undergo reactive halogen chemistry whose atmospheric impacts have been little explored to date. Here, two-way nested simulations were performed with the regional scale model CCATT-BRAMS to test our understanding of the volcano plume chemical...

  8. N-Nitrosamines and halogenated disinfection byproducts in U.S. Full Advanced Treatment trains for potable reuse.

    Science.gov (United States)

    Zeng, Teng; Plewa, Michael J; Mitch, William A

    2016-09-15

    Water utilities are increasingly considering indirect and direct potable reuse of municipal wastewater effluents. Disinfection byproducts (DBPs), particularly N-nitrosamines, are key contaminants of potential health concern for potable reuse. This study quantified the concentrations of N-nitrosamines and a suite of regulated and unregulated halogenated DBPs across five U.S. potable reuse Full Advanced Treatment trains incorporating microfiltration, reverse osmosis, and UV-based advanced oxidation. Low μg/L concentrations of trihalomethanes, haloacetic acids, dichloroacetonitrile, and dichloroacetamide were detected in the secondary or tertiary wastewater effluents serving as influents to potable reuse treatment trains, while the concentrations of N-nitrosamines were more variable (e.g., trains. Reverse osmosis rejected DBPs to varying degrees, ranging from low for some (e.g., N-nitrosamines, trihalomethanes, and haloacetonitriles) to high for other DBPs. UV-based advanced oxidation eliminated N-nitrosamines, but only partially removed halogenated DBPs. Chloramination of the treatment train product waters under simulated distribution system conditions formed additional DBPs, with concentrations often equaling or exceeding those in the treatment train influents. Overall, the concentration profiles of DBPs were fairly consistent within individual treatment trains for sampling campaigns separated by months and across different treatment trains for the same sampling time window. Weighting DBP concentrations by their toxic potencies highlighted the potential significance of haloacetonitriles, which were not effectively removed by reverse osmosis and advanced oxidation, to the DBP-associated toxicity in potable reuse waters.

  9. Stability of mutagenic tautomers of uracil and its halogen derivatives: the results of quantum-mechanical investigation

    Directory of Open Access Journals (Sweden)

    Hovorun D.M.

    2010-07-01

    Full Text Available Aim. To investigate using the quantum-mechanical methods uracil (Ura intramolecular tautomerisation and the effect of the thymine (Thy methyl (Me group substitution by the halogen on that process. Methods. Non-empirical quantum mechanic, analysis of the electron density by means of Bader’s atom in molecules (AIM theory and physicochemical kinetics were used. Results. For the first time it has been established that the substitution of thymine Me-group for the halogen (Br, F, Cl has practically no effect on the main physico-chemical characteristics of intramolecular tautomerisation. At the same time, the energy of Ura tautomerisation increases for 3,08 kcal/mol in comparison with corresponding value for Thy under standard conditions. Conclusions. So, Thy, unlike Ura, is obviously able, as a canonical DNA nucleotide base, to provide together with Ade, Gua and Cyt an acceptable mutability degree of the genome from the point of view of its adaptation reserve. Mutagenic action of the Ura halogen derivatives is not directly associated with their tautomerisation.

  10. Quadrupole coupling constants and isomeric Moessbauer shifts for halogen-containing gold, platinum, niobium, tantalum and antimony compounds

    Energy Technology Data Exchange (ETDEWEB)

    Poleshchuk, O. K., E-mail: poleshch@tspu.edu.ru [Tomsk State Pedagogical University (Russian Federation); Branchadell, V. [Universitat Autonoma de Barcelona, Departament de Quimica (Spain); Ritter, R. A.; Fateev, A. V. [Tomsk State Pedagogical University (Russian Federation)

    2008-01-15

    We have analyzed by means of Density functional theory calculations the nuclear quadrupole coupling constants of a range of gold, antimony, platinum, niobium and tantalum compounds. The geometrical parameters and halogen nuclear quadrupole coupling constants obtained by these calculations substantially corresponded to the data of microwave and nuclear quadrupole resonance spectroscopy. An analysis of the quality of the calculations that employ pseudo-potentials and all-electron basis sets for the halogen compounds was carried out. The zero order regular approximation (ZORA) method is shown to be a viable alternative for the calculation of halogen coupling constants in molecules. In addition, the ZORA model, in contrast to the pseudo-potential model, leads to realistic values of all metal nuclear quadrupole coupling constants. From Klopman's approach, it follows that the relationship between the electrostatic bonding and covalent depends on the nature of the central atom. The results on Moessbauer chemical shifts are also in a good agreement with the coordination number of the central atom.

  11. Detection of the adsorption of water monolayers through the ion oscillation frequency in the magnesium oxide lattice by means of low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Guevara-Bertsch, M.; Avendaño, E. [Escuela de Física, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Ramírez-Hidalgo, G. [Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Sección de Física Teórica, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Chavarría-Sibaja, A.; Araya-Pochet, J. A. [Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Herrera-Sancho, O. A., E-mail: oscar-andrey.herrera@uibk.ac.at [Escuela de Física, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstr. 21a, 6020 Innsbruck (Austria)

    2016-03-15

    We investigate the variation of the oscillation frequency of the Mg{sup 2+} and O{sup 2−} ions in the magnesium oxide lattice due to the interactions of the surface with water monolayers by means of Low Energy Electron Diffraction. Our key result is a new technique to determine the adsorbate vibrations produced by the water monolayers on the surface lattice as a consequence of their change in the surface Debye temperature and its chemical shift. The latter was systematically investigated for different annealing times and for a constant external thermal perturbation in the range of 110–300 K in order to accomplish adsorption or desorption of water monolayers in the surface lattice.

  12. Detection of the adsorption of water monolayers through the ion oscillation frequency in the magnesium oxide lattice by means of low energy electron diffraction

    Directory of Open Access Journals (Sweden)

    M. Guevara-Bertsch

    2016-03-01

    Full Text Available We investigate the variation of the oscillation frequency of the Mg2+ and O2− ions in the magnesium oxide lattice due to the interactions of the surface with water monolayers by means of Low Energy Electron Diffraction. Our key result is a new technique to determine the adsorbate vibrations produced by the water monolayers on the surface lattice as a consequence of their change in the surface Debye temperature and its chemical shift. The latter was systematically investigated for different annealing times and for a constant external thermal perturbation in the range of 110–300 K in order to accomplish adsorption or desorption of water monolayers in the surface lattice.

  13. All-metal clusters that mimic the chemistry of halogens.

    Science.gov (United States)

    Zhao, Tianshan; Li, Yawei; Wang, Qian; Jena, Puru

    2013-10-07

    Owing to their s(2)p(5) electronic configuration, halogen atoms are highly electronegative and constitute the anionic components of salts. Whereas clusters that contain no halogen atoms, such as AlH(4), mimic the chemistry of halogens and readily form salts (e.g., Na(+)(AlH(4))(-)), clusters that are solely composed of metal atoms and yet behave in the same manner as a halogen are rare. Because coinage-metal atoms (Cu, Ag, and Au) only have one valence electron in their outermost electronic shell, as in H, we examined the possibility that, on interacting with Al, in particular as AlX(4) (X=Cu, Ag, Au), these metal atoms may exhibit halogen-like properties. By using density functional theory, we show that AlAu(4) not only mimics the chemistry of halogens, but also, with a vertical detachment energy (VDE) of 3.98 eV in its anionic form, is a superhalogen. Similarly, analogous to XHX superhalogens (X=F, Cl, Br), XAuX species with VDEs of 4.65, 4.50, and 4.34 eV in their anionic form, respectively, also form superhalogens. In addition, Au can also form hyperhalogens, a recently discovered species that show electron affinities (EAs) that are even higher than those of their corresponding superhalogen building blocks. For example, the VDEs of M(AlAu(4))(2)(-) (M=Na and K) and anionic (FAuF)Au(FAuF) range from 4.06 to 5.70 eV. Au-based superhalogen anions, such as AlAu(4)(-) and AuF(2)(-), have the additional advantage that they exhibit wider optical absorption ranges than their H-based analogues, AlH(4)(-) and HF(2)(-). Because of the catalytic properties and the biocompatibility of Au, Au-based superhalogens may be multifunctional. However, similar studies that were carried out for Cu and Ag atoms have shown that, unlike AlAu(4), AlX(4) (X=Cu, Ag) clusters are not superhalogens, a property that can be attributed to the large EA of the Au atom. Copyright © 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Radiochemical photon activation analysis of Halogens in meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Oura, Yasuji; Latif, S.A.; Setoguchi, Mina; Nakamoto, Tomoshi; Ebihara, Mitsuru; Nakahara, Hiromichi [Tokyo Metropolitan Univ. (Japan). Faculty of Science; Ohtsuki, Tsutomu

    1999-12-01

    Halogens (F, Cl, Br and I) in meteorites and rocks are determined by a radiochemical photon activation analysis (RPAA) and compared with that of NPAA. We tried to determine all halogen elements at one time by one irradiation with 20 or 30 MeV maximum energy (E{sub 0}) by controlling irradiation for 2 or 6 hours with cooling. Average current is about 110 {mu}A. After irradiation, the sample was separated by radiochemical analysis. Allende meteorite, JR-I and d-41-7 were analyzed. The value of F, Cl and Br showed good reproducibility and agreed with the value in the reference. However, I showed small value. It may indicate volatilizing of I. (S.Y.)

  15. Polarographic behaviour of pesticides with carbon-halogen bonds

    Energy Technology Data Exchange (ETDEWEB)

    Jehring, H.; La Chevallerie-Haaf, U. de; Meyer, A.; Henze, G.

    1989-01-01

    The dp-polarographic behaviour of different pesticides with carbon-halogen bonds was investigated in dimethylsulfoxide and methanol-water as solvents; the peak-potentials are demonstrated graphically. From peak-height the pesticides are detectable up to 100 ng.ml/sup -1/. The investigations are of interest for the development of multistage-combined procedures by h.p.l.c. with amperometric detection.

  16. Reactive halogen species in the troposphere - Are there general principles?

    Science.gov (United States)

    Platt, Ulrich

    2017-04-01

    Reactive halogen species (RHS, e.g. BrO, IO, HOBr) are abundant in many parts of the troposphere (as well as in the stratosphere), these 'halogen compartments' include polar regions, coastal areas, vicinity of salt pans, parts of the free troposphere, and volcanic plumes. These RHS have been shown to have a profound impact on tropospheric chemistry. During the recent years much progress has been made with respect to elucidating the spatial and temporal distribution of RHS, their origin, and their chemical interactions in these compartments as well as in the theoretical understanding of these processes. However many unanswered questions remain, for instance: Why is there an Antarctic - Arctic asymmetry of reactive iodine species? Does the bromine explosion only occur during polar springtime? What is the influence of the shrinking Sea Ice area? What drives the autocatalytic bromine release from halogenides (the bromine explosion)? What is the effect of coupling cycles involving different halogens? How wide-spread are RHS in the free troposphere? We give an overview of ground- aircraft- and satellite- based observations and recent advances modeling illustrating the above questions. It is attempted to identify common features of the RHS-related processes in the different compartments and thus to derive answers to some of the questions.

  17. Pop-like halogenated natural products in antarctic sponges

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, W. [Hohenheim Univ., Stuttgart (Germany); Janussen, D. [Senckenbergische Naturforschende Gesellschaft (Natur-Museum und Forschungs-Institut), Frankfurt am Main (Germany)

    2004-09-15

    Persistent organic pollutants (POPs) are major contaminants of our days. This group of chemicals comprises a number of halogenated compounds used as pesticides (DDT, lindane, chlordane, toxaphene and others) as well as industrial chemicals (PCBs, PCNs, CPs, and brominated flameretardants). Although the list of known POPs including isomers and metabolites is long, there are frequent reports on the detection of unknown organohalogen compounds in the literature. Recent work demonstrated that some of these unknown peaks in gas chromatograms originate from halogenated natural products (HNPs). Sometimes, HNPs have been found at remarkably high concentrations in marine birds, mammals and fish. Due to the structural similarities with anthropogenic POPs, these substances may possess a potential risk for wildlife and man. HNPs are known to be produced with an overwhelming variety by marine organisms such as algae, sponges, microorganisms and others. In this study we have screened different species of Antarctic sponges on the occurrence of halogenated compounds which may be of environmental concern. Thus, we were only interested in lipophilic and persistent HNPs. Following that, we applied our standard sample clean-up procedure for the analysis of nonpolar POPs. Two steps on deactivated and activated silica yielded compounds with similar polarity as PCBs, chloropesticides and brominated analogues in the sample extracts. Additionally, all samples were treated with concentrated sulphuric acid in order to eliminate labile (non-presistent) HNPs.

  18. Non-conventional halide oxidation pathways : oxidation by imidazole triplet and surface specific oxidation by ozone

    Science.gov (United States)

    Ammann, Markus; Corral-Arroyo, Pablo; Aellig, Raphael; Orlando, Fabrizio; Lee, Ming-Tao; Artiglia, Luca

    2016-04-01

    Oxidation of halide ions (chloride, bromide, iodide) are the starting point of halogen release mechanisms out of sea water, marine aerosol or other halide containing continental aerosols. Slow oxidation of chloride and bromide by ozone in the bulk aqueous phase is of limited relevance. Faster surface specific oxidation has been suggested based on heterogeneous kinetics experiments. We provide first insight into very efficient bromide oxidation by ozone at the aqueous solution - air interface by surface sensitive X-ray photoelectron spectroscopy indicating significant build-up of an oxidized intermediate at the surface within millisecond time scales. The second source of oxidants in the condensed we have considered is the absorption of light by triplet forming photosensitizers at wavelengths longer than needed for direct photolysis and radical formation. We have performed coated wall flow tube experiments with mixtures of citric acid (CA) and imidazole-2-carboxaldehyde (IC) to represent secondary organic material rich marine aerosol. The halide ions bromide and iodide have been observed to act as efficient electron donors leading to their oxidation, HO2 formation and finally release of molecular halogen compounds. The photosensitization of imidazole-2-carboxaldehyde (IC) involves a well-known mechanism where the triplet excited state of IC is reduced by citric acid to a reduced ketyl radical that reacts with halide ions. A competition kinetics approach has been used to evaluate the rate limiting steps and to assess the significance of this source of halogens to the gas phase.

  19. Screening of organic halogens and identification of chlorinated benzoic acids in carbonaceous meteorites.

    Science.gov (United States)

    Schöler, Heinz F; Nkusi, Gerard; Niedan, Volker W; Müller, German; Spitthoff, Bianca

    2005-09-01

    The occurrence of halogenated organic compounds measured as a sum parameter and the evidence of chlorinated benzoic acids in four carbonaceous meteorites (Cold Bokkeveld, Murray, Murchison and Orgueil) from four independent fall events is reported. After AOX (Adsorbable organic halogen) and EOX (Extractable organic halogen) screening to quantify organically bound halogens, chlorinated organic compounds were analyzed by gas chromatography. AOX concentrations varying from 124 to 209 microg Cl/g d.w. were observed in carbonaceous meteorites. Ion chromatographic analysis of the distribution of organically bound halogens performed on the Cold Bokkeveld meteorite revealed that chlorinated and brominated organic compounds were extractable, up to 70%, whereas only trace amounts of organofluorines could be extracted. Chlorinated benzoic acids have been identified in carbonaceous meteorite extracts. Their presence and concentrations raise the question concerning the origin of halogenated, especially chlorinated, organic compounds in primitive planetary matter.

  20. Behaviour of antimony during thermal treatment of Sb-rich halogenated waste

    Energy Technology Data Exchange (ETDEWEB)

    Klein, J. [Laboratoire Gestion des Risques et Environnement, 25 rue de Chemnitz, 68200 Mulhouse (France); Dorge, S., E-mail: sophie.dorge@uha.fr [Laboratoire Gestion des Risques et Environnement, 25 rue de Chemnitz, 68200 Mulhouse (France); Trouve, G. [Laboratoire Gestion des Risques et Environnement, 25 rue de Chemnitz, 68200 Mulhouse (France); Venditti, D.; Durecu, S. [TREDI Departement de Recherche, Technopole de Nancy-Brabois, 9 avenue de la Foret de Haye, BP 184, 54505 Vandoeuvre-les-Nancy (France)

    2009-07-30

    Antimony compounds have a wide range of industrial applications, particularly as additives in flame retardants. To ensure environmentally friendly waste incineration of Sb-rich wastes, it is essential to strengthen the knowledge about the fate of antimony and the potential formation of harmful species. Investigations should be conducted particularly in relation with the main operational parameters controlling the process, chiefly temperature, residence time and air supply in the oven and in the post-combustion zone, prior final adapted cleaning of the flue-gas stream. Experimental studies focusing on antimony behaviour were undertaken through laboratory-scale thermal treatment at 850 deg. C and 1100 deg. C of a Sb-rich halogenated waste, originating from the sector of flame retardants formulation. The configuration of our laboratory experimental device allowed to achieve only low oxidative conditions in the waste bed, but high oxidative strength coupled with high temperature and sufficient gas residence time in the post-combustion zone, as prescribed during the incineration of hazardous wastes. Atomic absorption spectroscopy was used to assess the partition of antimony in the different compartments of the process. The oxidation degree of antimony in the gas-phase was determined by the use of electrochemical techniques, namely polarography coupled with anodic stripping voltamperometry. The partition of antimony between the residual ash and the gas-phase under moderate oxidative conditions in the waste bed was constant, whatever the temperature: the volatilization rate for antimony was {approx}64%, while a {approx}36% fraction remained in the residual bottom ashes. But interestingly, while at 850 {sup o}C, antimony was mainly present in the gas-phase at a +III oxidation degree, an increase in temperature of 250 {sup o}C favoured the presence of antimony to its highest oxidation degree +V in the flue-gas stream, a valence known to be involved in less toxic species.

  1. Identification of methyl triclosan and halogenated analogues in male common carp (Cyprinus carpio) from Las Vegas Bay and semipermeable membrane devices from Las Vegas Wash, Nevada.

    Science.gov (United States)

    Leiker, Thomas J; Abney, Sonja R; Goodbred, Steven L; Rosen, Michael R

    2009-03-01

    Methyl triclosan and four halogenated analogues have been identified in extracts of individual whole-body male carp (Cyprinus carpio) tissue that were collected from Las Vegas Bay, Nevada, and Semipermeable Membrane Devices (SPMD) that were deployed in Las Vegas Wash, Nevada. Methyl triclosan is believed to be the microbially methylated product of the antibacterial agent triclosan (2, 4, 4'-trichloro-4-hydroxydiphenyl ether, Chemical Abstract Service Registry Number 3380-34-5, Irgasan DP300). The presence of methyl triclosan and four halogenated analogues was confirmed in SPMD extracts by comparing low- and high-resolution mass spectral data and Kovats retention indices of methyl triclosan with commercially obtained triclosan that was derivatized to the methyl ether with ethereal diazomethane. The four halogenated analogues of methyl triclosan detected in both whole-body tissue and SPMD extracts were tentatively identified by high resolution mass spectrometry. Methyl triclosan was detected in all 29 male common carp from Las Vegas Bay with a mean concentration of 596 microg kg(-1) wet weight (ww) which is more than an order of magnitude higher than previously reported concentrations in the literature. The halogenated analogs were detected less frequently (21%-76%) and at much lower concentrations (<51 microg kg(-1) ww). None of these compounds were detected in common carp from a Lake Mead reference site in Overton Arm, Nevada.

  2. Identification of methyl triclosan and halogenated analogues in male common carp (Cyprinus carpio) from Las Vegas Bay and semipermeable membrane devices from Las Vegas Wash, Nevada

    Science.gov (United States)

    Leiker, T.J.; Abney, S.R.; Goodbred, S.L.; Rosen, Michael R.

    2009-01-01

    Methyl triclosan and four halogenated analogues have been identified in extracts of individual whole-body male carp (Cyprinus carpio) tissue that were collected from Las Vegas Bay, Nevada, and Semipermeable Membrane Devices (SPMD) that were deployed in Las Vegas Wash, Nevada. Methyl triclosan is believed to be the microbially methylated product of the antibacterial agent triclosan (2, 4, 4'-trichloro-4-hydroxydiphenyl ether, Chemical Abstract Service Registry Number 3380-34-5, Irgasan DP300). The presence of methyl triclosan and four halogenated analogues was confirmed in SPMD extracts by comparing low- and high-resolution mass spectral data and Kovats retention indices of methyl triclosan with commercially obtained triclosan that was derivatized to the methyl ether with ethereal diazomethane. The four halogenated analogues of methyl triclosan detected in both whole-body tissue and SPMD extracts were tentatively identified by high resolution mass spectrometry. Methyl triclosan was detected in all 29 male common carp from Las Vegas Bay with a mean concentration of 596????g kg- 1 wet weight (ww) which is more than an order of magnitude higher than previously reported concentrations in the literature. The halogenated analogs were detected less frequently (21%-76%) and at much lower concentrations (< 51????g kg- 1 ww). None of these compounds were detected in common carp from a Lake Mead reference site in Overton Arm, Nevada.

  3. Converting a conventional wired-halogen illuminated indirect ophthalmoscope to a wireless-light emitting diode illuminated indirect ophthalmoscope in less than 1000/- rupees

    Directory of Open Access Journals (Sweden)

    Mihir Kothari

    2015-01-01

    Full Text Available Aim: To report the "do it yourself" method of converting an existing wired-halogen indirect ophthalmoscope (IO to a wireless-light emitting diode (LED IO and report the preferences of the patients and the ophthalmologists. Subjects and Methods: In this prospective observational study, a conventional IO was converted to wireless-LED IO using easily available, affordable electrical components. Conventional and the converted IO were then used to perform photo-stress test and take the feedback of subjects and the ophthalmologists regarding its handling and illumination characteristics. Results: The cost of conversion to wireless-LED was 815/- rupees. Twenty-nine subjects, mean age 34.3 ΁ 10 years with normal eyes were recruited in the study. Between the two illumination systems, there was no statistical difference in the magnitude of the visual acuity loss and the time to recovery of acuity and the bleached vision on photo-stress test, although the visual recovery was clinically faster with LED illumination. The heat sensation was more with halogen illumination than the LED (P = 0.009. The ophthalmologists rated wireless-LED IO higher than wired-halogen IO on the handling, examination comfort, patient′s visual comfort and quality of the image. Twenty-two (81% ophthalmologists wanted to change over to wireless-LED IO. Conclusions: Converting to wireless-LED IO is easy, cost-effective and preferred over a wired-halogen indirect ophthalmoscope.

  4. Halogen content in Lesser Antilles arc volcanic rocks : exploring subduction recycling

    Science.gov (United States)

    Thierry, Pauline; Villemant, Benoit; Caron, Benoit

    2016-04-01

    Halogens (F, Cl, Br and I) are strongly reactive volatile elements which can be used as tracers of igneous processes, through mantle melting, magma differentiation and degassing or crustal material recycling into mantle at subduction zones. Cl, Br and I are higly incompatible during partial melting or fractional cristallization and strongly depleted in melts by H2O degassing, which means that no Cl-Br-I fractionation is expected through magmatic differenciation [current thesis]. Thus, Cl/Br/I ratios in lavas reflect the halogen content of their mantle sources. Whereas these ratios seemed quite constant (e.g. Cl/Br =300 as seawater), recent works suggest significant variations in arc volcanism [1,2]. In this work we provide high-precision halogen measurements in volcanic rocks from the recent activity of the Lesser Antilles arc (Montserrat, Martinique, Guadeloupe, Dominique). Halogen contents of powdered samples were determined through extraction in solution by pyrohydrolysis and analysed by Ion Chromatography for F and Cl and high performance ICP-MS (Agilent 8800 Tripe Quad) for Cl, Br and I [3,4]. We show that lavas - and mantle sources - display significant vraiations in Cl/Br/I ratios along the Lesser Antilles arc. These variations are compared with Pb, Nd and Sr isotopes and fluid-mobile elements (Ba, U, Sr, Pb etc.) compositions which vary along the arc from a nothern ordinary arc compositions to a southern 'crustal-like' composition [5,6]. These characteristics are attributed to subducted sediments recycling into the mantle wedge, whose contribution vary along the arc from north to south [7,8]. The proportion of added sediments is also related to the distance to the trench as sediment melting and slab dehydration may occur depending on the slab depth [9]. Further Cl-Br-I in situ measurements by LA-ICP-MS in Lesser Antilles arc lavas melt inclusions will be performed, in order to provide better constraints on the deep halogen recycling cycle from crust to

  5. Non-conventional gas phase remediation of volatile halogenated compounds by dehydrated bacteria

    OpenAIRE

    Erable, Benjamin; Goubet, Isabelle; Seltana, Amira; Maugard, Thierry

    2009-01-01

    Traditional biological removal processes are limited by the low solubility of halogenated compounds in aqueous media. A new technology appears very suitable for the remediation of these volatile organic compounds (VOCs). Solid/gas bio-catalysis applied in VOC remediation can transform halogenated compounds directly in the gas phase using dehydrated cells as a bio-catalyst. The hydrolysis of volatile halogenated substrates into the corresponding alcohol was studied in a solid/gas bio...

  6. The pharmacology of halogenated salicylanilides and their anthelmintic use in animals

    National Research Council Canada - National Science Library

    Swan, G E

    1999-01-01

    .... Several halogenated salicylanilides with potent antiparasitic activity have been synthesised of which only closantel, niclosamide, oxyclozanide, rafoxanide and resorantel are commercially available...

  7. The pharmacology of halogenated salicylanilides and their anthelmintic use in animals : review article

    National Research Council Canada - National Science Library

    G.E. Swan

    1999-01-01

    .... Several halogenated salicylanilides with potent antiparasitic activity have been synthesised of which only closantel, niclosamide, oxyclozanide, rafoxanide and resorantel are commercially available...

  8. New halogenated additives to propylene carbonate-based electrolytes for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Naji, A.; Ghanbaja, J.; Billaud, D. [Universite Henri Poincare, Vandoeuvre les Nancy (France). LCSM; Willmann, P. [CNES, Toulouse (France)

    2000-07-01

    Lithium cannot be electrointercalated into graphite in an electrolyte containing propylene carbonate (PC) as the only solvent species. In order to improve the cyclability of graphite electrodes in the presence of PC two methods were used: use of solvent mixtures containing PC and halogen-substituted solvent molecules ({alpha}-bromo-{gamma}-butyrolactone and methyl chloroformate); impregnation of the graphite electrode by halogenated solvents prior to cycling in PC-based electrolytes. It appears that the reversible capacity is increased by {approx}10% when such halogenated solvent molecules are used. Moreover, the cyclability is dependent on the nature of lithium salt, the concentration of halogen solvent and the specific current.

  9. The physiological and ecological roles of volatile halogen production by marine diatoms

    Science.gov (United States)

    Hughes, Claire; Sun, Shuo

    2015-04-01

    Sea-to-air halogen flux is known to have a major impact on catalytic ozone cycling and aerosol formation in the troposphere. The biological production of volatile organic (e.g. bromoform, diiodomethane) and reactive inorganic halogens (e.g. molecular iodine) is believed to play an important role in mediating halogen emissions from the marine environment. Marine diatoms in particular are known to produce the organic and inorganic volatile halogens at high rates in pelagic waters and sea-ice systems. The climate-induced changes in diatom communities that have already been observed and are expected to occur throughout the world's oceans as warming progresses are likely to alter sea-to-air halogen flux. However, we currently have insufficient understanding of the physiological and ecological functions of volatile halogen production to develop modelling tools that can predict the nature and magnitude of the impact. The results of a series of laboratory studies aimed at establishing the physiological and ecological role of volatile halogen production in two marine polar diatoms (Thalassiosira antarctica and Porosira glacialis) will be described in this presentation. We will focus on our work investigating how the activity of the haloperoxidases, a group of enzymes known to be involved in halogenation reactions in marine organisms, is altered by environmental conditions. This will involve exploring the antioxidative defence role proposed for marine haloperoxidases by showing specifically how halogenating activity varies with photosynthetic rate and changes in the ambient light conditions in the two model marine diatoms. We will also present results from our experiments designed to investigate how volatile halogen production is impacted by and influences diatom-bacterial interactions. We will discuss how improved mechanistic understanding like this could pave the way for future volatile halogen-ecosystem model development.

  10. The 2009-2010 eruption of Gaua volcano (Vanuatu archipelago): Eruptive dynamics and unsuspected strong halogens source

    Science.gov (United States)

    Bani, Philipson; Boudon, Georges; Balcone-Boissard, Hélène; Delmelle, Pierre; Quiniou, Thomas; Lefèvre, Jérôme; Bule, Esline Garaebiti; Hiroshi, Shinohara; Lardy, Michel

    2016-08-01

    Gaua, a little known volcano in the northern part of Vanuatu archipelago, went through a long term eruptive activity between September 2009 and July 2010. The eruption started by a phreatic to phreatomagmatic activity which progressively shifted into a magmatic discharge. The first eruptive phase involved the hydrothermal system in place. The latter was likely influenced by seawater seepage, leading to the formation of anhydrite. Magma involved hereafter this opening phase is of basaltic andesite and basaltic trachyandesite composition (high K calc-alkaline series), typical of the northern part of the Vanuatu archipelago. The 2009-2010 activity discharged at least 184 kt of SO2 and a significant amount of halogens (72 kt Cl and 217 kt F). Such halogen releases indicate that Gaua is a strong source of halogens into the atmosphere. High and sustained amount of F discharges are known to induce health issues and should not be ignored on Gaua island. During this eruption the quiescent and voluminous Lake Letas was slightly affected by the eruption. Nevertheless the hydrothermal discharge point into the lake, situated on the southeastern part of Mt. Garet appeared to be relatively active. At this particular location rock forming elements, leached out from volcanic rock by acid fluids released by the new intrusion of magma, were discharged along with anions into Lake Letas. This release has triggered localized chemistry changes in the lake. We speculate that this discharge has also disturbed the bottom water in a limited perimeter, remobilizing reduced Fe to the surface and subsequently triggering the change in the water color by Fe oxidation.

  11. Abiotic and biotic reductive dehalogenation of halogenated methanes

    Energy Technology Data Exchange (ETDEWEB)

    Matheson, L.J.

    1994-01-01

    Reductive dehalogenation is an important reaction that generally leads to detoxification of many halogenated methanes. Halogenated methanes are widely used in industrial and commercial applications and the inadvertent or deliberate release of these chemicals has caused contamination of the atmosphere, soil and groundwater. The research presented here details the study of several systems for reductive dehalogenation of chlorinated methanes. The first system described in this dissertation involves reductive dechlorination of chlorinated methanes by laboratory cultures of methanogens. A vessel was constructed that allowed maintenance of anaerobic conditions and minimized losses of the volatile chlorocarbons. Methylene chloride was not dechlorinated in the presence of pure cultures of methanogens. Similarly, dechlorination did not occur in enrichments made with samples from several different anaerobic digesters. Abiotic dehalogenation studies showed that cobalamins, cobalt-centered macrocyclic compounds, catalyzed the reductive dechlorination of several halomethanes in anaerobic, closed batch systems. These studies focused on immobilization of cobalamins to several types of supports for use in pollution remediation strategies. Cyanocobalamin bound to Epoxy-Activated Sepharose 6B and talc catalyzed the rapid reduction of carbon tetrachloride and methylene chloride to sequentially reduced products. Corroding iron metal was also studied as a reductant for halogenated methanes. Several chlorinated methanes were reductively dechlorinated in closed, anaerobic, laboratory-scale model systems containing granular iron. Carbon tetrachloride was sequentially dehalogenated, via chloroform, to methylene chloride. The initial rate of each reaction was pseudo-first order in substrate and declined substantially with each dehalogenation step. Trichloroethene was also dechlorinated by iron, although more slowly than carbon tetrachloride.

  12. Halogen-Bonding-Assisted Iodosylbenzene Activation by a Homogenous Iron Catalyst

    DEFF Research Database (Denmark)

    de Sousa, David P.; Wegeberg, Christina; Vad, Mads Sørensen;

    2016-01-01

    The iron(III) complex of hexadentate N,N,N′-tris(2-pyridylmethyl)ethylendiamine-N′-acetate (tpena−) is a more effective homogenous catalyst for selective sulfoxidation and epoxidation with insoluble iodosylbenzene, [PhIO]n, compared with soluble methyl-morpholine-N-oxide (NMO). We propose that two...... molecules of [Fe(tpena)]2+ cooperate to solubilize PhIO, extracting two equivalents to form the halogen-bonded dimeric {[Fe(tpena)OIPh]2}4+. The closest intradimeric I⋅⋅⋅O distance, 2.56 Å, is nearly 1 Å less than the sum of the van de Waals radii of these atoms. A correlation of the rates of the reaction...... of {[Fe(tpena)OIPh]2}4+ with para-substituted thioanisoles indicate that this species is a direct metal-based oxidant rather than a derived ferryl or perferryl complex. A study of gas-phase reactions indicate that an ion at m/z=231.06100 originates from solution-state {[Fe(tpena)OIPh]2}4+ and is ascribed...

  13. Theoretical and Experimental Study of the Friction Behavior of Halogen-Free Ionic Liquids in Elastohydrodynamic Regime

    National Research Council Canada - National Science Library

    Janardhanan, Karthik; Iglesias, Patricia

    2016-01-01

    .... Halogen-free ionic liquids have recently been considered as more environmentally stable than their halogenated counterparts, which tend to form highly toxic and corrosive acids when exposed to moisture...

  14. Preliminary assessment of halogenated alkanes as vapor-phase tracers

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Michael C.; Moore, Joseph N.; Hirtz, Paul

    1991-01-01

    New tracers are needed to evaluate the efficiency of injection strategies in vapor-dominated environments. One group of compounds that seems to meet the requirements for vapor-phase tracing are the halogenated alkanes (HCFCs). HCFCs are generally nontoxic, and extrapolation of tabulated thermodynamic data indicate that they will be thermally stable and nonreactive in a geothermal environment. The solubilities and stabilities of these compounds, which form several homologous series, vary according to the substituent ratios of fluorine, chlorine, and hydrogen. Laboratory and field tests that will further define the suitability of HCFCs as vapor-phase tracers are under way.

  15. New halogenated agents: should I change my practice?

    Science.gov (United States)

    Feiss, P

    2000-05-01

    Sevoflurane and Desflurane are relatively new halogenated agents which make induction and control of depth of anaesthesia easier, recovery rapid and of good quality and they have less side-effects and toxicity. In children sevoflurane could replace halothane because it provides smooth and rapid induction with less cardiovascular depression and arrhythmias. Desflurane is not used because of its pungent odour. In adults sevoflurane could be preferred to desflurane because it allows rapid induction and laryngeal mask insertion or tracheal intubation without myorelaxants, a similar time of recovery, no clinical evidence for renal and hepatic toxicity, no more costs for anaesthesia for a lower MAC.

  16. Molecular dynamics of halogenated graphene - hexagonal boron nitride nanoribbons

    Science.gov (United States)

    Nemnes, G. A.; Visan, Camelia; Anghel, D. V.; Manolescu, A.

    2016-08-01

    The hybrid graphene - hexagonal boron nitride (G-hBN) systems offer new routes in the design of nanoscale electronic devices. Using ab initio density functional theory calculations we investigate the dynamics of zig-zag nanoribbons a few interatomic distances wide. Several structures are analyzed, namely pristine graphene, hBN and G-hBN systems. By passivating the nanoribbon edges with hydrogen and different halogen atoms, one may tune the electronic and mechanical properties, like the band gap energies and the natural frequencies of vibration.

  17. Halogen free benzoxazine based curable compositions for high T.sub.g applications

    Energy Technology Data Exchange (ETDEWEB)

    Tietze, Roger; Nguyen, Yen-Loan

    2016-08-16

    A method for forming a halogen-free curable composition containing a benzoxazine monomer, at least one epoxy resin, a catalyst, a toughening agent and a solvent. The halogen-free curable composition is especially suited for use in automobile and aerospace applications since the composition, upon curing, produces a composite having a high glass transition temperature.

  18. Toxicity of gaseous halogenated organic compounds. (Latest citations from the NTIS bibliographic database). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-02-01

    The bibliography contains citations concerning the toxicology of halogenated hydrocarbons and their health effects. Topics cover halogenated gases used as industrial chemicals, fire extinguishers, anesthetics, solvents, pesticides, and aerosol propellants. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  19. A 19F NMR study of C-I....pi- halogen bonding

    DEFF Research Database (Denmark)

    Hauchecorne, Dieter; vand er Veken, Benjamin J.; Herrebout, Wouter A.

    2011-01-01

    The formation of halogen bonded complexes between toluene-d8 and the perfluoroiodopropanes 1-C3F7I and 2-C3F7I has been investigated using 19F NMR spectroscopy. For both Lewis acids, evidence was found for the formation of a C–I⋯π halogen bonded complex. The complex formed is a 1:1 type. Using...

  20. Investigation of non-halogenated solvent mixtures for high throughput fabrication of polymerfullerene solar cells

    NARCIS (Netherlands)

    Schmidt-Hansberg, B.; Sanyal, M.; Grossiord, N.; Galagan, Y.O.; Baunach, M.; Klein, M.F.G.; Colsmann, A.; Scharfer, P.; Lemmer, U.; Dosch, H.; Michels, J.J; Barrena, E.; Schabel, W.

    2012-01-01

    The rapidly increasing power conversion efficiencies of organic solar cells are an important prerequisite towards low cost photovoltaic fabricated in high throughput. In this work we suggest indane as a non-halogenated replacement for the commonly used halogenated solvent o-dichlorobenzene. Indane w

  1. Anaerobic microbial transformation of halogenated aromatics and fate prediction using electron density modeling.

    Science.gov (United States)

    Cooper, Myriel; Wagner, Anke; Wondrousch, Dominik; Sonntag, Frank; Sonnabend, Andrei; Brehm, Martin; Schüürmann, Gerrit; Adrian, Lorenz

    2015-05-19

    Halogenated homo- and heterocyclic aromatics including disinfectants, pesticides and pharmaceuticals raise concern as persistent and toxic contaminants with often unknown fate. Remediation strategies and natural attenuation in anaerobic environments often build on microbial reductive dehalogenation. Here we describe the transformation of halogenated anilines, benzonitriles, phenols, methoxylated, or hydroxylated benzoic acids, pyridines, thiophenes, furoic acids, and benzenes by Dehalococcoides mccartyi strain CBDB1 and environmental fate modeling of the dehalogenation pathways. The compounds were chosen based on structural considerations to investigate the influence of functional groups present in a multitude of commercially used halogenated aromatics. Experimentally obtained growth yields were 0.1 to 5 × 10(14) cells mol(-1) of halogen released (corresponding to 0.3-15.3 g protein mol(-1) halogen), and specific enzyme activities ranged from 4.5 to 87.4 nkat mg(-1) protein. Chlorinated electron-poor pyridines were not dechlorinated in contrast to electron-rich thiophenes. Three different partial charge models demonstrated that the regioselective removal of halogens is governed by the least negative partial charge of the halogen. Microbial reaction pathways combined with computational chemistry and pertinent literature findings on Co(I) chemistry suggest that halide expulsion during reductive dehalogenation is initiated through single electron transfer from B12Co(I) to the apical halogen site.

  2. Investigation of non-halogenated solvent mixtures for high throughput fabrication of polymerfullerene solar cells

    NARCIS (Netherlands)

    Schmidt-Hansberg, B.; Sanyal, M.; Grossiord, N.; Galagan, Y.O.; Baunach, M.; Klein, M.F.G.; Colsmann, A.; Scharfer, P.; Lemmer, U.; Dosch, H.; Michels, J.J; Barrena, E.; Schabel, W.

    2012-01-01

    The rapidly increasing power conversion efficiencies of organic solar cells are an important prerequisite towards low cost photovoltaic fabricated in high throughput. In this work we suggest indane as a non-halogenated replacement for the commonly used halogenated solvent o-dichlorobenzene. Indane w

  3. Principles and applications of halogen bonding in medicinal chemistry and chemical biology.

    Science.gov (United States)

    Wilcken, Rainer; Zimmermann, Markus O; Lange, Andreas; Joerger, Andreas C; Boeckler, Frank M

    2013-02-28

    Halogen bonding has been known in material science for decades, but until recently, halogen bonds in protein-ligand interactions were largely the result of serendipitous discovery rather than rational design. In this Perspective, we provide insights into the phenomenon of halogen bonding, with special focus on its role in drug discovery. We summarize the theoretical background defining its strength and directionality, provide a systematic analysis of its occurrence and interaction geometries in protein-ligand complexes, and give recent examples where halogen bonding has been successfully harnessed for lead identification and optimization. In light of these data, we discuss the potential and limitations of exploiting halogen bonds for molecular recognition and rational drug design.

  4. 40 CFR Appendix III to Part 268 - List of Halogenated Organic Compounds Regulated Under § 268.32

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 26 2010-07-01 2010-07-01 false List of Halogenated Organic Compounds... Part 268—List of Halogenated Organic Compounds Regulated Under § 268.32 In determining the... defined the HOCs that must be included in a calculation as any compounds having a carbon-halogen...

  5. Novel Halogenated Pyrazine-Based Chalcones as Potential Antimicrobial Drugs

    Directory of Open Access Journals (Sweden)

    Marta Kucerova-Chlupacova

    2016-10-01

    Full Text Available Chalcones, i.e., compounds with the chemical pattern of 1,3-diphenylprop-2-en-1-ones, exert a wide range of bio-activities, e.g., antioxidant, anti-inflammatory, anticancer, anti-infective etc. Our research group has been focused on pyrazine analogues of chalcones; several series have been synthesized and tested in vitro on antifungal and antimycobacterial activity. The highest potency was exhibited by derivatives with electron withdrawing groups (EWG in positions 2 and 4 of the ring B. As halogens also have electron withdrawing properties, novel halogenated derivatives were prepared by Claisen-Schmidt condensation. All compounds were submitted for evaluation of their antifungal and antibacterial activity, including their antimycobacterial effect. In the antifungal assay against eight strains of selected fungi, growth inhibition of Candida glabrata and Trichophyton interdigitale (formerly T. mentagrophytes was shown by non-alkylated derivatives with 2-bromo or 2-chloro substitution. In the panel of selected bacteria, 2-chloro derivatives showed the highest inhibitory effect on Staphylococcus sp. In addition, all products were also screened for their antimycobacterial activity against Mycobacterium tuberculosis H37RV My 331/88, M. kansasii My 235/80, M. avium 152/80 and M. smegmatis CCM 4622. Some of the examined compounds, inhibited growth of M. kansasii and M. smegmatis with minimum inhibitory concentrations (MICs comparable with those of isoniazid.

  6. Toward hydrogen detection at room temperature with printed ZnO nanoceramics films activated with halogen lighting

    Science.gov (United States)

    Nguyen, Van Son; Jubera, Véronique; Garcia, Alain; Debéda, Hélène

    2015-12-01

    Though semiconducting properties of ZnO have been extensively investigated under hazardous gases, research is still necessary for low-cost sensors working at room temperature. Study of printed ZnO nanopowders-based sensors has been undertaken for hydrogen detection. A ZnO paste made with commercial nanopowders is deposited onto interdigitated Pt electrodes and sintered at 400 °C. The ZnO layer structure and morphology are first examined by XRD, SEM, AFM and emission/excitation spectra prior to the study of the effect of UV-light on the electrical conduction of the semiconductor oxide. The response to hydrogen exposure is subsequently examined, showing that low UV-light provided by halogen lighting enhances the gas response and allows detection at room temperature with gas responses similar to those obtained in dark conditions at 150 °C. A gas response of 44% (relative change in current) under 300 ppm is obtained at room temperature. Moreover, it is demonstrated that very low UV-light power (15 μW/mm2) provided by the halogen lamp is sufficient to give sensitivities as high as those for much higher powers obtained with a UV LED (7.7 mW/mm2). These results are comparable to those obtained by others for 1D or 2D ZnO nanostructures working at room temperature or at temperatures up to 250 °C.

  7. Nitrated metalloporphyrins as catalysts for alkane oxidation

    Science.gov (United States)

    Ellis, Jr., Paul E.; Lyons, James E.

    1992-01-01

    Alkanes are oxidized by contact with oxygen-containing gas in the presence as catalyst of a metalloporphyrin in which hydrogen atoms in the porphyrin ring have been replaced with one or more nitro groups. Hydrogen atoms in the porphyrin ring may also be substituted with halogen atoms.

  8. Ion-Pair Halogen Bonds in 2-Halo-Functionalized Imidazolium Chloride Receptors: Substituent and Solvent Effects.

    Science.gov (United States)

    Nunes, Rafael; Costa, Paulo J

    2017-01-03

    The interaction of 2-halo-functionalized imidazolium derivatives (n-X(+) ; X=Cl, Br, I) with a chloride anion through ion-pair halogen bonds (n-X⋅Cl) was studied by means of DFT and ab initio calculations. A method benchmark was performed on 2-bromo-1H-imidazol-3-ium in association with chloride (1-Br⋅Cl); MP2 yielded the best results when compared with CCSD(T) calculations. The interaction energies (ΔE) in the gas phase are high and, although the electrostatic interaction is strong owing to the ion-pair nature of the system, large X⋅⋅⋅Cl(-) Wiberg bond orders and contributions from charge transfer (nCl- →σ*C-X) are obtained. These values drop considerably in chloroform and water; this shows that solvent plays a role in modulating the interaction and that gas-phase calculations are particularly unrealistic for experimental applications. The introduction of electron-withdrawing groups in the 4,5-positions of the imidazolium (e.g., -NO2 , -F) increases the halogen-bond strength in both the gas phase and solvent, including water. The effect of the substituents on the 1,3-positions (N-H groups) also depends on the solvent. The variation of ΔE can be predicted through a two-parameter linear regression that optimizes the weights of charge-transfer and electrostatic interactions, which are different in vacuum and in solvent (chloroform and water). These results could be used in the rational design of efficient chloride receptors based on halogen bonds that work in solution, in particular, in an aqueous environment.

  9. Interplay between halogen and chalcogen bonding in the XCl∙∙∙OCS∙∙∙NH₃ (X = F, OH, NC, CN, and FCC) complex.

    Science.gov (United States)

    Zhao, Qiang

    2014-10-01

    The interplay between halogen and chalcogen bonding in the XCl∙∙∙OCS and XCl∙∙∙OCS∙∙∙NH3 (X = F, OH, NC, CN, and FCC) complex was studied at the MP2/6-311++G(d,p) computational level. Cooperative effect is observed when halogen and chalcogen bonding coexist in the same complex. The effect is studied by means of binding distance, interaction energy, and cooperative energy. Molecular electrostatic potential calculation reveals the electrostatic nature of the interactions. Cooperative effect is explained by the difference of the electron density. Second-order stabilization energy was calculated to study the orbital interaction in the complex. Atoms in molecules analysis was performed to analyze the enhancement of the electron density in the bond critical point.

  10. The application of differential scanning calorimetry as a mean to determine the oxidative stability of vegetable oils and its comparison with Rancimat

    Directory of Open Access Journals (Sweden)

    Yousef Ramezan

    2015-09-01

    Full Text Available Differential scanning calorimetry (DSC and Rancimat apparatus have been used to evaluate the oxidative stability of eight different edible vegetable oils. Rancimat apparatus was operated at 110 ⁰C with an air flow of 18-20 L/hand measures the induction period (IP of the selected samples. The DSC technique involved the oxidation of the samples in an oxygen flow DSC cell when the cell temperature was set at isothermal temperatures of 100, 110, 120 and 130 ⁰C. Oxidative induction time (T0 determined by the time, where a rapid exothermic reaction were occurred between oil and oxygen. The results showed that unsaturated edible oils are more susceptible to oxidation in short time, than saturated one. Furthermore, the results indicated that there is a good correlation (p<0.0001 between DSC T0 and the Rancimat values.

  11. Evaluation of blood levels of nitric oxide as a means of differentiation between neonatal hepatitis and extrahepatic biliary atresia: A pilot study

    Science.gov (United States)

    Goel, Prabudh; Bhatnagar, Veereshwar; Das, Nibhriti; Kalaivani, Mani

    2015-01-01

    Aim: The differentiation between neonatal hepatitis (NH) and extrahepatic biliary atresia (EHBA) is not always possible despite all the currently available diagnostic modalities. In this study, an attempt has been made to evaluate the role of nitric oxide (NO) levels in the peripheral blood to differentiate between the two conditions, one requiring early surgical intervention (EHBA) and the other amenable to conservative medical management (NH). Patients and Methods: Twenty patients who presented to the pediatric surgical service, over a 2 years period, with features of neonatal cholestasis were enrolled in the study. The diagnostic workup included documentation of history and clinical examination, biochemical liver function tests, ultrasonography, hepatobiliary scintigraphy (HS), and magnetic resonance cholangio-pancreaticography (MRCP). These patients did not show excretion on HS and intrahepatic ducts on MRCP. Hence, they were subjected to mini-laparotomy and operative cholangiography (OC). The EHBA patients were treated with the Kasai's portoenterostomy procedure, and the extrahepatic ducts were flushed with normal saline in NH patients. All patients were evaluated preoperatively for levels of NO in the peripheral blood by the Greiss reaction spectrophotometrically at 540 nm. Normal values were determined from a cohort of controls. The median (range) levels of NO in patients with EHBA and NH were compared, and the statistical significance of the difference was calculated by applying the Wilcox Rank Sum test. A P = 0.05 was considered as significant. Results: Of the 20 patients enrolled in the study, 17 patients were treated for EHBA (Group I) and the remaining 3 patients had patent ducts on OC and were thus diagnosed as NH (Group II). The mean age of the patients in Groups I and II was comparable: 2.79 ± 0.75 and 2.67 ± 0.58 months, respectively (P = 0.866). The median NO levels were significantly elevated in each of the two groups as compared to the controls

  12. A metagenomic-based survey of microbial (de)halogenation potential in a German forest soil.

    Science.gov (United States)

    Weigold, Pascal; El-Hadidi, Mohamed; Ruecker, Alexander; Huson, Daniel H; Scholten, Thomas; Jochmann, Maik; Kappler, Andreas; Behrens, Sebastian

    2016-06-29

    In soils halogens (fluorine, chlorine, bromine, iodine) are cycled through the transformation of inorganic halides into organohalogen compounds and vice versa. There is evidence that these reactions are microbially driven but the key enzymes and groups of microorganisms involved are largely unknown. Our aim was to uncover the diversity, abundance and distribution of genes encoding for halogenating and dehalogenating enzymes in a German forest soil by shotgun metagenomic sequencing. Metagenomic libraries of three soil horizons revealed the presence of genera known to be involved in halogenation and dehalogenation processes such as Bradyrhizobium or Pseudomonas. We detected a so far unknown diversity of genes encoding for (de)halogenating enzymes in the soil metagenome including specific and unspecific halogenases as well as metabolic and cometabolic dehalogenases. Genes for non-heme, no-metal chloroperoxidases and haloalkane dehalogenases were the most abundant halogenase and dehalogenase genes, respectively. The high diversity and abundance of (de)halogenating enzymes suggests a strong microbial contribution to natural halogen cycling. This was also confirmed in microcosm experiments in which we quantified the biotic formation of chloroform and bromoform. Knowledge on microorganisms and genes that catalyze (de)halogenation reactions is critical because they are highly relevant to industrial biotechnologies and bioremediation applications.

  13. Modeling the reactive halogen plume from Ambrym volcano and its impact on the troposphere with the CCATT-BRAMS mesoscale model

    Directory of Open Access Journals (Sweden)

    L. Jourdain

    2015-12-01

    Full Text Available Ambrym volcano (Vanuatu, Southwest Pacific is one of the largest sources of continuous volcanic emissions worldwide. As well as releasing SO2 that is oxidized to sulfate, volcanic plumes in the troposphere are shown to undergo reactive halogen chemistry whose atmospheric impacts have been little explored to date. Here, two-way nested simulations were performed with the regional scale model CCATT-BRAMS to test our understanding of the volcano plume chemical processing and to assess the impact of Ambrym on atmospheric chemistry at local and regional scales. We focus on an episode of extreme passive degassing that occurred in early 2005 and for which airborne DOAS measurements of SO2 and BrO columns, in the near downwind plume, have been reported. The model was developed to include reactive halogen chemistry and a volcanic emission source specific to this extreme degassing event. SO2 simulated columns show very good quantitative agreement with the DOAS observations as well as with OMI data, suggesting that the plume direction as well as its dilution are well represented. Simulations are presented with and without a high-temperature initialization that includes radicals formed by high temperature partial oxidation of magmatic gases by ambient air. When included high-temperature chemistry initialization, the model is able to capture the observed BrO/SO2 trend with distance from the vent in the near downwind plume. However, the maximum of BrO columns enhancement is still underestimated by a factor 3. The model identifies total in-plume depletion of ozone (15 ppbv as a limiting factor to the partitioning of reactive bromine into BrO, of particular importance in this very strong plume at low background ozone conditions. Impacts of Ambrym in the Southwest Pacific region were also evaluated. As the plume disperses regionally, reactive halogen chemistry continues on sulfate aerosols produced by SO2 oxidation and promotes BrCl formation. Ozone depletion is

  14. Evaluating the potential for halogen bonding in ketosteroid isomerase’s oxyanion hole using unnatural amino acid mutagenesis

    Science.gov (United States)

    Kraut, Daniel A; Churchil, Michael J; Dawson, Phillip E

    2009-01-01

    There has recently been an increasing interest in controlling macromolecular conformations and interactions through halogen bonding. Halogen bonds are favorable electrostatic interactions between polarized, electropositive chlorine, bromine or iodine atoms and electronegative atoms such as oxygen or nitrogen. These interactions have been likened to hydrogen bonds both in terms of their favored acceptor molecules, their geometries, and their energetics. We asked whether a halogen bond could replace a hydrogen bond in the oxyanion hole of ketosteroid isomerase, using semi-synthetic enzyme containing para-halogenated phenylalanine derivatives to replace the tyrosine hydrogen bond donor. Formation of a halogen bond to the oxyanion in the transition state would be expected to rescue the effects of mutation to phenylalanine, but all of the halogenated enzymes were comparable in activity to the phenylalanine mutant. We conclude that, at least in this active site, a halogen bond cannot functionally replace a hydrogen bond. PMID:19260691

  15. Halogenation generates effective modulators of amyloid-Beta aggregation and neurotoxicity.

    Directory of Open Access Journals (Sweden)

    H Edward Wong

    Full Text Available Halogenation of organic compounds plays diverse roles in biochemistry, including selective chemical modification of proteins and improved oral absorption/blood-brain barrier permeability of drug candidates. Moreover, halogenation of aromatic molecules greatly affects aromatic interaction-mediated self-assembly processes, including amyloid fibril formation. Perturbation of the aromatic interaction caused by halogenation of peptide building blocks is known to affect the morphology and other physical properties of the fibrillar structure. Consequently, in this article, we investigated the ability of halogenated ligands to modulate the self-assembly of amyloidogenic peptide/protein. As a model system, we chose amyloid-beta peptide (Aβ, which is implicated in Alzheimer's disease, and a novel modulator of Aβ aggregation, erythrosine B (ERB. Considering that four halogen atoms are attached to the xanthene benzoate group in ERB, we hypothesized that halogenation of the xanthene benzoate plays a critical role in modulating Aβ aggregation and cytotoxicity. Therefore, we evaluated the modulating capacities of four ERB analogs containing different types and numbers of halogen atoms as well as fluorescein as a negative control. We found that fluorescein is not an effective modulator of Aβ aggregation and cytotoxicity. However, halogenation of either the xanthenes or benzoate ring of fluorescein substantially enhanced the inhibitory capacity on Aβ aggregation. Such Aβ aggregation inhibition by ERB analogs except rose bengal correlated well to the inhibition of Aβ cytotoxicity. To our knowledge, this is the first report demonstrating that halogenation of aromatic rings substantially enhance inhibitory capacities of small molecules on Aβ-associated neurotoxicity via Aβ aggregation modulation.

  16. Transformation of halogen-, alkyl-, and alkoxy-substituted anilines by a lactase of Trametes versicolor

    Energy Technology Data Exchange (ETDEWEB)

    Hoff, T.; Liu, S.Y.; Bollag, J.M.

    1985-05-01

    The lactase of the fungus Trametes versicolor was able to polymerize various halogen-, alkyl-, and alkoxy-substituted anilines, showing substrate specificity similar to that of horseradish peroxidase, whereas the lactase of Rhizoctonia praticola was active only with p-methoxyaniline. The substrate specificities of the enzymes were determined by using gas chromatography to measure the decrease in substrate concentration during incubation. With p-chloroaniline as the substrate, the peroxidase and the Trametes lactase showed maximum activity near pH 4.2. The transformation of this substrate gave rise to a number of oligomers, ranging from dimers to pentamers, as determined by mass spectrometry. The product profiles obtained by high-pressure liquid chromatography were similar for the two enzymes. A chemical reaction was observed between p-chloroaniline and an enzymatically formed dimer, resulting in the formation of a trimer. All three enzymes oxidized p-methoxyaniline to 2-amino-5-p-anisidinobenzoquinone di-p-methoxyphenylimine, but only the T. versicolor lactase and the peroxidase caused the formation of a pentamer (2,5-di-p-anisidinobenzoquinone di-p-methoxyphenylimine). These results demonstrate that in addition to horseradish peroxidase, a T. versicolor lactase can also polymerize aniline derivatives.

  17. Etching of organosilicate glass low-k dielectric films in halogen plasmas

    CERN Document Server

    Vitale, S A

    2002-01-01

    The chemistry and kinetics of alternative etching chemistries for low-k dielectric materials are explored to improve the anisotropy of the etching process and to reduce the problems associated with postetch clean-up. Etching rates, selectivities, and etching yields of Black Diamond and Coral organosilicate glasses (OSGs) have been measured. Black Diamond and Coral are etched rapidly in F sub 2 , Cl sub 2 , and HBr high density plasmas, and Cl sub 2 +HBr plasmas have been identified as a viable process chemistry with several advantages over traditional fluorocarbon plasmas. The OSG films are not spontaneously etched by F sub 2 , Cl sub 2 , HBr molecules, Cl, or Br atoms, however, F atoms etch the OSGs spontaneously. F, Cl, and H atoms extract a substantial amount of carbon from the films, but Cl and H do not attack the OSG oxide matrix. The Coral films are more strongly depleted of carbon after halogen plasma etching than the Black Diamond. In addition, oxygen atoms extract nearly all of the carbon and nitroge...

  18. A comparative evaluation of the shear bond strength of five different orthodontic bonding agents polymerized using halogen and light-emitting diode curing lights: An in vitro investigation

    Directory of Open Access Journals (Sweden)

    Sujoy Banerjee

    2011-01-01

    Full Text Available Purpose: With the introduction of photosensitive (light-activated restorative materials in orthodontics, various methods have been suggested to enhance the polymerization of the materials used, including use of more powerful light curing devices. Bond strength is an important property and determines the amount of force delivered and the treatment duration. Many light-cured bonding materials have become popular but it is the need of the hour to determine the bonding agent that is the most efficient and has the desired bond strength. Aim: To evaluate and compare the shear bond strengths of five different orthodontic light cure bonding materials cured with traditional halogen light and low-intensity light-emitting diode (LED light curing unit. Materials and Methods: 100 human maxillary premolar teeth, extracted for orthodontic purpose, were used to prepare the samples. 100 maxillary stainless steel bicuspid brackets of 0.018 slot of Roth prescription, manufactured by D-tech Company, were bonded to the prepared tooth surfaces of the mounted samples using five different orthodontic bracket bonding light-cured materials, namely, Enlight, Fuji Ortho LC (resin-modified glass ionomer cement, Orthobond LC, Relybond, and Transbond XT. The bond strength was tested on an Instron Universal testing machine (model no. 5582. Results: In Group 1 (halogen group, Enlight showed the highest shear bond strength (16.4 MPa and Fuji Ortho LC showed the least bond strength (6.59 MPa (P value 0.000. In Group 2 (LED group, Transbond showed the highest mean shear bond strength (14.6 MPa and Orthobond LC showed the least mean shear bond strength (6.27 MPa (P value 0.000. There was no statistically significant difference in the shear bond strength values of all samples cured using either halogen (mean 11.49 MPa or LED (mean 11.20 MPa, as the P value was 0.713. Conclusion: Polymerization with both halogen and LED resulted in shear bond strength values which were above the

  19. Vertical ionization energies of halogen anions in solution

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Based on the constrained equilibrium state theory,the nonequilibrium solvation energy is derived in the framework of the continuum model.The formula for spectral shift and vertical ionization energy are deduced for a single sphere cavity with the point charge assumption.The new model is adopted to investigate the vertical ionization for halogen atomic and molecular anions X(X = Cl,Br,I,Cl2,Br2,I2) in aqueous solution.According to the calculation using the CCSD-t/aug-cc-pVQZ method in vacuum,our final estimated vertical ionization energies in solution are very close to the experimental observations,while the traditional nonequilibrium solvation theory overestimates these vertical ionization energies.

  20. Retention of Halogenated Solutes on Stationary Phases Containing Heavy Atoms

    Directory of Open Access Journals (Sweden)

    Toshio Miwa

    2013-05-01

    Full Text Available To examine the effects of weak intermolecular interactions on solid-phase extraction (SPE and chromatographic separation, we synthesized some novel stationary phases with a heavy atom effect layer by immobilizing halogenated aromatic rings and hydroxyl groups onto the surface of a hydrophilic base polymer. Using SPE cartridges packed with the functionalized materials, we found that the heavy atom stationary phases could selectively retain halophenols in organic solvents, such as 1-propanol which blocks the hydrogen bonding, or acetonitrile which blocks the p-p interaction. The extraction efficiency of the materials toward the halophenols depended on the dipole moments of phenoxy groups present as functional groups. On the other hand, the extraction efficiency of solutes toward the functional group depended on their molar refractions, i.e., induced dipole moments. The retention of the solutes to the stationary phase ultimately depended on not only strong intermolecular interactions, but also the effects of weak interactions such as the dispersion force.

  1. Fluorescence cell imaging and manipulation using conventional halogen lamp microscopy.

    Directory of Open Access Journals (Sweden)

    Kazuo Yamagata

    Full Text Available Technologies for vitally labeling cells with fluorescent dyes have advanced remarkably. However, to excite fluorescent dyes currently requires powerful illumination, which can cause phototoxic damage to the cells and increases the cost of microscopy. We have developed a filter system to excite fluorescent dyes using a conventional transmission microscope equipped with a halogen lamp. This method allows us to observe previously invisible cell organelles, such as the metaphase spindle of oocytes, without causing phototoxicity. Cells remain healthy even after intensive manipulation under fluorescence observation, such as during bovine, porcine and mouse somatic cell cloning using nuclear transfer. This method does not require expensive epifluorescence equipment and so could help to reduce the science gap between developed and developing countries.

  2. Improving the Solubility of Halogenated 1-Ammonio-closo-dodecaborate Anions.

    Science.gov (United States)

    Bertocco, Philipp; Derendorf, Janis; Jenne, Carsten; Kirsch, Christoph

    2017-03-20

    The partly halogenated and N-alkylated closo-dodecaborates [B12Cl6H5N(propyl)3](-) and [B12Br6H5NR3](-) (R = ethyl-pentyl) were prepared by alkylation of [B12H11NH3](-) and subsequent halogenation with elemental chlorine or N-bromosuccinimide. Simple metathesis reactions yielded the [HNMe3](+), [C6mim](+), [NBu4](+), and Na(+) salts, which were characterized by heteronuclear NMR and IR spectroscopy as well as electrospray ionization mass spectrometry. The crystal structures of the salts [HNMe3][B12Br6H5N(ethyl)3]·CH3CN, [HNMe3][B12Br6H5N(propyl)3], Na[B12Br6H5N(butyl)3], and [HNMe3][B12Cl7H4N(propyl)3]·CH3CN were determined by single-crystal X-ray diffraction. The [C6mim](+) salts are thermally stable to temperatures higher than 300 °C. The melting points are between 57 and 80 °C, which classify the [C6mim](+) salts of [B12Cl6H5N(propyl)3](-) and [B12Br6H5NR3](-) (R = propyl-pentyl) as ionic liquids. The anions are oxidized only at potentials higher than 2 V versus Fc(0/+) as determined by cyclic voltammetry. The solubility of the sodium salts in CH2Cl2 solution was determined by NMR spectroscopy. With the increasing length of the alkyl chain attached to the ammonio group the solubility is significantly enhanced. A solubility up to 125 mmol/L for Na[B12Br6H5N(pentyl)3] in dichloromethane was determined. In addition, the trialkylation of the perchlorinated anion [B12Cl11NH3](-) was investigated in detail. A Hofmann elimination was observed to occur at higher temperatures, when alkyl groups with β-hydrogen atoms were introduced. Organic substituents without β-hydrogen atoms gave more stable compounds; however, trialkylation proved to be difficult presumably due to steric hindrance. The crystal structure of the byproduct [PPh4]2[B12Cl11N(propargyl)2] was determined.

  3. Determination of heavy metals and halogens in plastics from electric and electronic waste.

    Science.gov (United States)

    Dimitrakakis, Emmanouil; Janz, Alexander; Bilitewski, Bernd; Gidarakos, Evangelos

    2009-10-01

    The presence of hazardous substances and preparations in small waste electrical and electronic equipment (sWEEE) found in the residual household waste stream of the city of Dresden, Germany has been investigated. The content of sWEEE plastics in heavy metals and halogens is determined using handheld X-ray fluorescence analysis (HXRF), elemental analysis by means of atomic absorption spectrometry (AAS) and ion exchange chromatography (IEC). Mean value of results for heavy metals in samples (n=51) by AAS are 17.4 mg/kg for Pb, 5.7 mg/kg for Cd, 8.4 mg/kg for Cr. The mass fraction of an additive as shown by HXRF (n=161) can vary over a wide range. Precise deductions as regards sWEEE plastics content in hazardous substances and preparations cannot be made. Additional research would be expedient regarding the influence of hazardous substances to recycling processes, in particular regarding the contamination of clean fractions in the exit streams of a WEEE treatment plant. Suitable standards for calibrating HXRF for use on EEE plastics or complex electr(on)ic components do not exist and should be developed.

  4. Fundamental insight in soot oxidation over a Ag/Co3O4 catalyst by means of Environmental TEM

    DEFF Research Database (Denmark)

    Gardini, Diego; Christiansen, J. M.; Jensen, Anker Degn

    to minimize the filter regeneration temperature – ideally down to the normal temperature of the exhaust gas - a new catalyst for soot oxidation consisting of Ag nanoparticles supported on Co3O4 has been synthesized using flame spray pyrolysis and characterized using electron microscopy and X-Ray diffraction...... locally and globally. Removal of these particles from the exhaust gas is normally carried out by filtration through a ceramic filter. A major disadvantage of this technique is the need for periodic regenerations involving temperature increases in order to oxidize the collected soot. In an effort...... in an Environmental TEM (ETEM) at different temperatures and gas compositions....

  5. Construction of Tungsten Halogen, Pulsed LED, and Combined Tungsten Halogen-LED Solar Simulators for Solar Cell I-V Characterization and Electrical Parameters Determination

    Directory of Open Access Journals (Sweden)

    Anon Namin

    2012-01-01

    Full Text Available I-V characterization of solar cells is generally done under natural sunlight or solar simulators operating in either a continuous mode or a pulse mode. Simulators are classified on three features of irradiance, namely, spectral match with respect to air mass 1.5, spatial uniformity, and temporal stability. Commercial solar simulators use Xenon lamps and halogen lamps, whereas LED-based solar simulators are being developed. In this work, we build and test seven simulators for solar cell characterization, namely, one tungsten halogen simulator, four monochromatic (red, green, blue, and white LED simulators, one multicolor LED simulator, and one tungsten halogen-blue LED simulator. The seven simulators provide testing at nonstandard test condition. High irradiance from simulators is obtained by employing elevated supply voltage to tungsten halogen lamps and high pulsing voltages to LEDs. This new approach leads to higher irradiance not previously obtained from tungsten halogen lamps and LEDs. From I-V curves, electrical parameters of solar cell are made and corrected based on methods recommended in the IEC 60891 Standards. Corrected values obtained from non-STC measurements are in good agreement with those obtained from Class AAA solar simulator.

  6. Fundamental insight in soot oxidation over a Ag/Co3O4 catalyst by means of Environmental TEM

    DEFF Research Database (Denmark)

    Gardini, Diego; Christiansen, J. M.; Jensen, Anker Degn

    locally and globally. Removal of these particles from the exhaust gas is normally carried out by filtration through a ceramic filter. A major disadvantage of this technique is the need for periodic regenerations involving temperature increases in order to oxidize the collected soot. In an effort...

  7. Ultraviolet radiation and blue-light emissions from spotlights incorporating tungsten halogen lamps

    CERN Document Server

    MacKinlay, Alistair F; Whillock, M J

    1989-01-01

    This report summarises measurements of the ultraviolet radiation and blue-light emissions from eleven 'desk-top' tungsten halogen (quartz) lamps and one 'floor-standing' tungsten halogen (quartz) lamp available in the UK. Values of occupational hazard weighted and erythemally weighted ultraviolet radiation irradiance and measurements and relevant calculations of blue-light hazards are presented. It is concluded that the safety design of some desk-top tungsten halogen lamps is inadequate to prevent unnecessary exposure of the skin to potentially harmful ultraviolet radiation. It is recommended that all tungsten halogen lamps should have sufficient filtration to reduce their ultraviolet emissions to an acceptably low level. As long as the comfort aversion responses of the eye are respected, direct viewing of the lamps examined should not constitute a retinal hazard.

  8. Development of Non-Halogen Flame Retardant Optical Fiber and Optical Fiber Cord

    Institute of Scientific and Technical Information of China (English)

    Kazunori; Tanaka; Kaoru; Okuno; Tomoyuki; Hattori; Kiyoaki; Moriuchi; Hiroshi; Hayami; Wataru; Katsurashima; Yoshikyo; Tamekuni

    2003-01-01

    A non-halogen highly flame-retardant 0.9mm optical fiber and 2.0mm simplex optical cord, which are harmonized with the ecosystem, have been developed. The characteristics of them are presented in this paper.

  9. Mechanisms of halogen-based covalent self-assembly on metal surfaces.

    Science.gov (United States)

    Björk, Jonas; Hanke, Felix; Stafström, Sven

    2013-04-17

    We computationally study the reaction mechanisms of halogen-based covalent self-assembly, a major route for synthesizing molecular nanostructures and nanographenes on surfaces. Focusing on biphenyl as a small model system, we describe the dehalogenation, recombination, and diffusion processes. The kinetics of the different processes are also investigated, in particular how diffusion and coupling barriers affect recombination rates. Trends across the periodic table are derived from three commonly used close-packed (111) surfaces (Cu, Ag, and Au) and two halogens (Br and I). We show that the halogen atoms can poison the surface, thus hindering long-range ordering of the self-assembled structures. Finally, we present core-level shifts of the relevant carbon and halogen atoms, to provide reference data for reliably detecting self-assembly without the need for atomic-resolution scanning tunneling microscopy.

  10. Halogen behaviours during andesitic magma degassing: from magma chamber to volcanic plume

    Science.gov (United States)

    Balcone-Boissard, H.; Villemant, B.; Boudon, G.; Michel, A.

    2009-04-01

    Halogen (F, Cl, Br and I) behaviours during degassing of H2O-rich silicic magmas are investigated using volatile content analysis in glass (matrix glass and melt inclusions) of volcanic clasts (pumice and lava-dome fragments) in a series of plinian, vulcanian and lava dome-forming eruptions. Examples are taken from andesitic systems in subduction zones: Montagne Pelée and Soufrière Hills of Montserrat (Lesser Antilles) and Santa Maria-Santiaguito (Guatemala). Halogens behaviour during shallow degassing primarily depends on their incompatible character in melts and on H2O solubility. But variations in pre-eruptive conditions, degassing kinetics and syn-eruptive melt crystallisation, induce large variations in halogen extraction efficiency during H2O degassing, up to prevent halogen loss. In all studied systems, Cl, Br and I are not fractionated neither by differentiation nor by degassing processes: thus Cl/Br/I ratios remain well preserved in melts from reservoirs to eruption. These ratios measured in erupted clasts are characteristic of pre-eruptive magma compositions and may be used to trace deep magmatic processes. Moreover, during plinian eruptions, Cl, Br and I are extracted by H2O degassing but less efficiently than predicted by available experimental fluid-melt partition coefficients, by a factor as high as 5. F behaves as an incompatible element and, contrary to other halogens, is never significantly extracted by degassing. Degassing during lava dome-forming eruptions of andesitic magmas occurs mainly at equilibrium and is more efficient at extracting halogens and H2O than explosive degassing. The mobility of H2O and halogens depends on their speciation in both silicate melts and exsolved fluids which strongly varies with pressure. We suggest that the rapid pressure decrease during highly explosive eruptions prevents complete volatile speciation at equilibrium and consequently strongly limits halogen degassing.

  11. A 19F NMR study of C-I....pi- halogen bonding

    DEFF Research Database (Denmark)

    Hauchecorne, Dieter; vand er Veken, Benjamin J.; Herrebout, Wouter A.;

    2011-01-01

    The formation of halogen bonded complexes between toluene-d8 and the perfluoroiodopropanes 1-C3F7I and 2-C3F7I has been investigated using 19F NMR spectroscopy. For both Lewis acids, evidence was found for the formation of a C–I⋯π halogen bonded complex. The complex formed is a 1:1 type. Using sp...

  12. Advances in Metal-Catalyzed Cross-Coupling Reactions of Halogenated Quinazolinones and Their Quinazoline Derivatives

    Directory of Open Access Journals (Sweden)

    Malose Jack Mphahlele

    2014-10-01

    Full Text Available Halogenated quinazolinones and quinazolines are versatile synthetic intermediates for the metal-catalyzed carbon–carbon bond formation reactions such as the Kumada, Stille, Negishi, Sonogashira, Suzuki-Miyaura and Heck cross-coupling reactions or carbon-heteroatom bond formation via the Buchwald-Hartwig cross-coupling to yield novel polysubstituted derivatives. This review presents an overview of the application of these methods on halogenated quinazolin-4-ones and their quinazolines to generate novel polysubstituted derivatives.

  13. Halogenated cytisine derivatives as agonists at human neuronal nicotinic acetylcholine receptor subtypes.

    Science.gov (United States)

    Slater, Y E; Houlihan, L M; Maskell, P D; Exley, R; Bermúdez, I; Lukas, R J; Valdivia, A C; Cassels, B K

    2003-03-01

    Cytisine (cy) is a potent and competitive partial agonist at alpha4 subunit-containing nicotinic acetylcholine (nACh) receptors while at homomeric alpha7-nACh receptors it behaves as a full agonist with a relatively lower potency. In the present study, we assessed the effects of bromination or iodination of the pyridone ring of cy and N-methylcytisine (N-Me-cy) on the effects of these compounds on recombinant human (h) alpha7, halpha4beta2 and halpha4beta4 nACh receptors expressed in clonal cell lines and Xenopus oocytes. Halogenation at C(3) of cy or N-Me-cy usually brings about a marked increase in both affinity and efficacy at halpha7, halpha4beta2 and halpha4beta4 nACh, the extent of which depends on whether the halogen is bromine or iodine, and upon receptor subtype. The effects of halogenation at C(5) are strongly influenced by the specific halogen substituent so that bromination causes a decrease in both affinity and efficacy while iodination decreases affinity but its effects on efficacy range from a decrease (halpha7, halpha4beta4 nACh receptors) to a marked increase (halpha4beta2 nACh receptors). Based on these findings, which differ from those showing that neither the affinity nor efficacy of nicotine, 3-(2-azetidinylmethoxy)-pyridine or epibatidine are greatly affected by halogenation, dehalogenation or halogen exchange at equivalent positions, we suggest that cy, N-Me-cy and their halo-isosteres bind to neuronal nACh receptors in a different orientation allowing the halogen atom to interact with a hydrophobic halogen-accepting region within the predominantly hydrophobic agonist-binding pocket of the receptors.

  14. 卤键弱作用浅谈%Brief discussion on halogen bonding weak interaction

    Institute of Scientific and Technical Information of China (English)

    王亚琴; 邵群

    2015-01-01

    Halogen bonding, a noncovalent, int ermolecular weak interaction analogues to hydrogen bonding, exists between σ antibonding orbital of halogen atoms and atoms with lone-pair electron and πelectron system, which exerts unique effect in the field of desigh of functional materials and biomedicine. In this paper, the interaction essence of halogen bonding was simply introduced, the developing history of halogen bonding was elaborated and the basic character of halogen bonding was depicted, looking forward to much more comprehension toward halogen bonding.%卤键是与氢键相似的一种分子间非共价作用,存在于卤原子的σ反键轨道与具有孤电子对的原子或π电子体系之间,在功能材料与生物药物设计方面发挥了独特作用。介绍卤键的作用本质,阐述卤键发展简史,并描述卤键的基本特征。

  15. QSARS for Acute Toxicity of Halogenated Benzenes to Bacteria in Natural Waters

    Institute of Scientific and Technical Information of China (English)

    GUAN-GHUA LU; CHAO WANG; YU-MEI LI

    2006-01-01

    Objective To measure the acute toxicity of halogenated benzenes to bacteria in natural waters and to study quantitative relationships between the structure and activity of chemicals. Methods The concentration values causing 50% inhibition of bacteria growth (24h-IC50) were determined according to the bacterial growth inhibition test method. The energy of the lowest unoccupied molecular orbital and the net charge of carbon atom of 20 halogenated benzenes were calculated by the quantum chemical MOPAC program. Results The log1/IC50 values ranged from 4.79 for 2,4-dinitrochlorobenzene to 3.65 for chlorobenzene. A quantitative structure-activity relationship model was derived from the toxicity and structural parameters: log1/IC50 =-0.531(ELUMO)+1.693(Qc)+0.163(logP)+3.375. This equation was found to fit well (r2=0.860, s=0.106), and the average percentage error was only 1.98%. Conclusion Halogenated benzenes and alkyl halogenated benzenes are non-polar narcotics, and have hydrophobicity-dependent toxicity. The halogenated phenols and anilines exhibit a higher toxic potency than their hydrophobicity, whereas 2,4-dinitrochlorobenzene is electrophile with the halogen acting as the leaving group.

  16. Benchmarking DFT methods with small basis sets for the calculation of halogen-bond strengths.

    Science.gov (United States)

    Siiskonen, Antti; Priimagi, Arri

    2017-02-01

    In recent years, halogen bonding has become an important design tool in crystal engineering, supramolecular chemistry and biosciences. The fundamentals of halogen bonding have been studied extensively with high-accuracy computational methods. Due to its non-covalency, the use of triple-zeta (or larger) basis sets is often recommended when studying halogen bonding. However, in the large systems often encountered in supramolecular chemistry and biosciences, large basis sets can make the calculations far too slow. Therefore, small basis sets, which would combine high computational speed and high accuracy, are in great demand. This study focuses on comparing how well density functional theory (DFT) methods employing small, double-zeta basis sets can estimate halogen-bond strengths. Several methods with triple-zeta basis sets are included for comparison. Altogether, 46 DFT methods were tested using two data sets of 18 and 33 halogen-bonded complexes for which the complexation energies have been previously calculated with the high-accuracy CCSD(T)/CBS method. The DGDZVP basis set performed far better than other double-zeta basis sets, and it even outperformed the triple-zeta basis sets. Due to its small size, it is well-suited to studying halogen bonding in large systems.

  17. Persistence, bioaccumulation, and toxicity of halogen-free flame retardants.

    Science.gov (United States)

    Waaijers, Susanne L; Kong, Deguo; Hendriks, Hester S; de Wit, Cynthia A; Cousins, Ian T; Westerink, Remco H S; Leonards, Pim E G; Kraak, Michiel H S; Admiraal, Wim; de Voogt, Pim; Parsons, John R

    2013-01-01

    Polymers are synthetic organic materials having a high carbon and hydrogen content, which make them readily combustible. Polymers have many indoor uses and their flammability makes them a fire hazard. Therefore, flame retardants (FRs) are incorporated into these materials as a safety measure. Brominated flame retardants (BFRs), which accounted for about 21% of the total world market of FRs, have several unintended negative effects on the environment and human health. Hence, there is growing interest in finding appropriate alternative halogen-free flame retardants (HFFRs). Many of these HFFRs are marketed already, although their environ- mental behavior and toxicological properties are often only known to a limited extent, and their potential impact on the environment cannot yet be properly assessed. Therefore, we undertook this review to make an inventory of the available data that exists (up to September 2011) on the physical-chemical properties, pro- duction volumes, persistence, bioaccumulation, and toxicity (PBT) of a selection of HFFRs that are potential replacements for BFRs in polymers. Large data gaps were identified for the physical-chemical and the PBT properties of the reviewed HFFRs. Because these HFFRs are currently on the market, there is an urgent need to fill these data gaps. Enhanced transparency of methodology and data are needed to reevaluate certain test results that appear contradictory, and, if this does not provide new insights, further research should be performed. TPP has been studied quite extensively and it is clearly persistent, bioaccumulative, and toxic. So far, RDP and BDP have demonstrated low to high ecotoxicity and persistence. The compounds ATH and ZB exerted high toxicity to some species and ALPI appeared to be persistent and has low to moderate reported ecotoxicity. DOPO and MPP may be persistent, but this view is based merely on one or two studies, clearly indicating a lack of information. Many degradation studies have been

  18. Halogen bonds in some dihalogenated phenols: applications to crystal engineering.

    Science.gov (United States)

    Mukherjee, Arijit; Desiraju, Gautam R

    2014-01-01

    3,4-Dichlorophenol (1) crystallizes in the tetragonal space group I41/a with a short axis of 3.7926 (9) Å. The structure is unique in that both type I and type II Cl⋯Cl interactions are present, these contact types being distinguished by the angle ranges of the respective C-Cl⋯Cl angles. The present study shows that these two types of contacts are utterly different. The crystal structures of 4-bromo-3-chlorophenol (2) and 3-bromo-4-chlorophenol (3) have been determined. The crystal structure of (2) is isomorphous to that of (1) with the Br atom in the 4-position participating in a type II interaction. However, the monoclinic P21/c packing of compound (3) is different; while the structure still has O-H⋯O hydrogen bonds, the tetramer O-H⋯O synthon seen in (1) and (2) is not seen. Rather than a type I Br⋯Br interaction which would have been mandated if (3) were isomorphous to (1) and (2), Br forms a Br⋯O contact wherein its electrophilic character is clearly evident. Crystal structures of the related compounds 4-chloro-3-iodophenol (4) and 3,5-dibromophenol (5) were also determined. A computational survey of the structural landscape was undertaken for (1), (2) and (3), using a crystal structure prediction protocol in space groups P21/c and I41/a with the COMPASS26 force field. While both tetragonal and monoclinic structures are energetically reasonable for all compounds, the fact that (3) takes the latter structure indicates that Br prefers type II over type I contacts. In order to differentiate further between type I and type II halogen contacts, which being chemically distinct are expected to have different distance fall-off properties, a variable-temperature crystallography study was performed on compounds (1), (2) and (4). Length variations with temperature are greater for type II contacts compared with type I. The type II Br⋯Br interaction in (2) is stronger than the corresponding type II Cl⋯Cl interaction in (1), leading to elastic bending

  19. Halogen bonds in some dihalogenated phenols: applications to crystal engineering

    Directory of Open Access Journals (Sweden)

    Arijit Mukherjee

    2014-01-01

    Full Text Available 3,4-Dichlorophenol (1 crystallizes in the tetragonal space group I41/a with a short axis of 3.7926 (9 Å. The structure is unique in that both type I and type II Cl...Cl interactions are present, these contact types being distinguished by the angle ranges of the respective C—Cl...Cl angles. The present study shows that these two types of contacts are utterly different. The crystal structures of 4-bromo-3-chlorophenol (2 and 3-bromo-4-chlorophenol (3 have been determined. The crystal structure of (2 is isomorphous to that of (1 with the Br atom in the 4-position participating in a type II interaction. However, the monoclinic P21/c packing of compound (3 is different; while the structure still has O—H...O hydrogen bonds, the tetramer O—H...O synthon seen in (1 and (2 is not seen. Rather than a type I Br...Br interaction which would have been mandated if (3 were isomorphous to (1 and (2, Br forms a Br...O contact wherein its electrophilic character is clearly evident. Crystal structures of the related compounds 4-chloro-3-iodophenol (4 and 3,5-dibromophenol (5 were also determined. A computational survey of the structural landscape was undertaken for (1, (2 and (3, using a crystal structure prediction protocol in space groups P21/c and I41/a with the COMPASS26 force field. While both tetragonal and monoclinic structures are energetically reasonable for all compounds, the fact that (3 takes the latter structure indicates that Br prefers type II over type I contacts. In order to differentiate further between type I and type II halogen contacts, which being chemically distinct are expected to have different distance fall-off properties, a variable-temperature crystallography study was performed on compounds (1, (2 and (4. Length variations with temperature are greater for type II contacts compared with type I. The type II Br...Br interaction in (2 is stronger than the corresponding type II Cl...Cl interaction in (1, leading to elastic

  20. Formation of halogenated acetones in the lower troposphere

    Science.gov (United States)

    Sattler, Tobias; Wittmer, Julian; Krause, Torsten; Schöler, Heinz Friedrich; Kamilli, Katharina; Held, Andreas; Zetzsch, Cornelius; Ofner, Johannes; Atlas, Elliot

    2015-04-01

    Western Australia is a semi-/arid region that is heavily influenced by climate change and agricultural land use. The area is known for its saline lakes with a wide range of hydrogeochemical parameters and consists of ephemeral saline and saline groundwater fed lakes with a pH range from 2.5 to 7.1. In 2012 a novel PTFE-chamber was setup directly on the lakes. The 1.5 m³ cubic chamber was made of UV transparent PTFE foil to permit photochemistry while preventing dilution of the air due to lateral wind transport. This experimental setup allows linking measured data directly to the chemistry of and above the salt lakes. Air samples were taken using stainless steel canisters and measured by GC-MS/ECD. Sediment, crust and water samples were taken for investigation of potential VOC and VOX emissions in the laboratory using GC-MS. Several lakes were investigated and canister samples were taken over the day to see diurnal variations. The first samples were collected at 6 a.m. and from this time every 2 hours a canister was filled with chamber air. Concentrations of chloroacetone up to 15 ppb and of bromoacetone up to 40 ppb in the air samples were detected. The concentrations vary over the day and display their highest values around noon. Soil and water samples showed a variety of highly volatile and semi-volatile VOC/VOX but no halogenated acetones. An abiotic formation of these VOC/VOX seems conclusive due to iron-catalysed reactions below the salt crust [1]. The salt crust is the interface through which VOC/VOX pass from soil/groundwater to the atmosphere where they were photochemically altered. This explains the finding of halo acetones only in the air samples and not in water and soil samples measured in the laboratory. The main forming pathway for these haloacetones is the direct halogenation due to atomic chlorine and bromine above the salt lakes [2]. A minor pathway is the atmospheric degradation of chloropropane and bromopropane [3]. These halopropanes were found

  1. Assessing developmental toxicity and estrogenic activity of halogenated bisphenol A on zebrafish (Danio rerio).

    Science.gov (United States)

    Song, Maoyong; Liang, Dong; Liang, Yong; Chen, Minjie; Wang, Fengbang; Wang, Hailin; Jiang, Guibin

    2014-10-01

    Halogenated bisphenol A (H-BPAs), widely used in industrial production, have been identified in various environmental matrices and detected in human serum and breast milk. The persistence and prevalence of H-BPAs in the environment underscore the need to in-depth understand their adverse effects to humans and other organisms. In the present study, zebrafish embryos/larvae were used as models to investigate the developmental toxicities of three H-BPAs, namely tetrabromobisphenol A (TBBPA), tetrachlorobisphenol A (TCBPA), and bisphenol AF (BPAF). The half lethal concentration (LC50) values indicated that the rank order of toxicities of the chemicals were TCBPA>TBBPA>BPAF. Three H-BPAs exposure resulted in a variety of developmental lesions in the embryos/larvae, such as a delay in time to hatch, edema, and hemorrhage. The estrogenic activities of H-BPAs were determined by means of in vivo vitellogenin (vtg) assay and in vitro MVLN assay. Here only BPAF specifically shows a stronger estrogenic activity than BPA both in in vivo and in vitro. These data suggest that TCBPA, TBBPA, and BPAF are more potent toxicants than BPA, and indicate that further research of the mechanisms on their toxicities is required.

  2. What Does the Mean Mean?

    Science.gov (United States)

    Watier, Nicholas N.; Lamontagne, Claude; Chartier, Sylvain

    2011-01-01

    The arithmetic mean is a fundamental statistical concept. Unfortunately, social science students rarely develop an intuitive understanding of the mean and rely on the formula to describe or define it. According to constructivist pedagogy, educators that have access to a variety of conceptualizations of a particular concept are better equipped to…

  3. Default Meanings

    Institute of Scientific and Technical Information of China (English)

    K. M. Jaszczolt

    2006-01-01

    In this paper I present some aspects of the controversy surrounding the semantics/pragmatics boundary and offer a possible solution in the form of Default Semantics. First, I present a brief introduction to Paul Grice's approach to meaning as intentional communication. Next, I address the problem of the unit of which truth conditions should be predicated, assuming after Grice that the most successful approach to meaning has to make use of truth conditions.Further, I extend the discussion to some aspects of neo-Gricean pragmatics, most notably the issue of pragmatic processing that contributes to the truth-conditional representation and the proposed shortcuts through this processing in the form of default meanings. In the main part, I present the theory of Default Semantics ( Jaszczolt 2005a) , assess some arguments in favour of such an interactive theory of meaning that combines information from various sources, and address the issue of compositionality of meaning so conceived. In the final part, I apply the theory of Default Semantics to expressions with future-time reference in English in order to demonstrate the advantages of a framework that combines various types of information about utterance meaning in one, merged semantic representation. The main advantage turns out to be, in this domain, the unified treatment of all expressions with future-time reference.

  4. Intonational meaning.

    Science.gov (United States)

    Prieto, Pilar

    2015-01-01

    Traditionally, prosodic studies have focused on the study of intonational form and the study of intonational meaning has been relatively neglected. Similarly, the fields of semantics and pragmatics have paid little attention to the pragmatic uses of intonation. As a result, there is no firm agreement within the linguistic community on how to integrate the analysis of intonational meaning across languages into a unified prosodic, semantic, and pragmatic approach. This article provides an overview of the literature on intonational meaning, describing the recent advances made in the fields of prosody, semantics/pragmatics, and syntax. Several theoretical approaches to explaining the semantics and pragmatics of intonation are presented. A common feature to most frameworks is that intonation (1) should be regarded as an integral part of linguistic grammar; and (2) typically encodes meanings related to the modal aspect of propositions. However, features such as compositionality, duality of structure, and context-dependency are still hotly debated issues. These features will be discussed from different theoretical perspectives, and we will identify potential advances related to the full integration of intonational meaning into dynamic and multidimensional models of meaning.

  5. View of the bacterial strains of Escherichia coli M-17 and its interaction with the nanoparticles of zinc oxide by means of atomic force microscopy

    Science.gov (United States)

    Sagitova, A.; Yaminsky, I.; Meshkov, G.

    2016-08-01

    Visualization of the structure of biological objects plays a key role in medicine, biotechnology, nanotechnology and IT-technology. Atomic force microscopy (AFM) is a promising method of studying of objects’ morphology and structure. In this work, AFM was used to determine the size and shape of the bacterial strains of Escherichia coli M-17 and visualization its interaction with the nanoparticles of zinc oxide. The suspension of E.coli bacteria was applied to natural mica and studied by contact mode using the FemtoScan multifunctional scanning probe microscope.

  6. Microbial methane oxidation as a means of treating residual emissions during passive landfill venting; Mikrobielle Methanoxidation zur Behandlung von Rest-Emissionen bei der passiven Deponieentgasung

    Energy Technology Data Exchange (ETDEWEB)

    Gebert, J.; Groengroeft, A. [Hamburg Univ. (Germany). Inst. fuer Bodenkunde

    2005-07-01

    Microbial oxidation of methane in biofilters provides a way of treating residual or lean gas emissions from landfills whose methane content and quantities no longer meet the minimum requirements for gas utilisation or flaring. In this process methane is oxidised by methanotropic bacteria in the presence of atmospheric oxygen. This yields carbon dioxide, which is less hazardous on account of its nonflammability and lower global warming potential. This contribution describes the methane degradation performance and performance governing factors of a biofilter which was exposed to a passive gas flow and observed over a period of two years.

  7. Biomimetic Sulfide Oxidation by the Means of Immobilized Fe(III-5,10,15,20-tetrakis(pentafluorophenylporphin under Mild Experimental Conditions

    Directory of Open Access Journals (Sweden)

    Paolo Zucca

    2013-01-01

    Full Text Available This paper describes the oxidation of inorganic sulfide to sulfate, minimizing the formation of elemental sulfur. The described catalytic reaction uses dilute hydrogen peroxide at nearly neutral pH values in the presence of a bioinspired, heterogenized, and commercial ferriporphin. A substantial increase of the percentage of sulfide converted to sulfate is obtained in comparison with the yields obtained when working with hydrogen peroxide alone. The biomimetic catalyst also proved to be a much more efficient catalyst than horseradish peroxidase. Accordingly, it could be suitable for large-scale applications. Further studies are in progress to drive sulfate yields up to nearly quantitative.

  8. Halogen bonding: A new retention mechanism for the solid phase extraction of perfluorinated iodoalkanes

    Energy Technology Data Exchange (ETDEWEB)

    Yan Xiaoqing; Shen Qianjin; Zhao Xiaoran; Gao Haiyue; Pang Xue [College of Chemistry, Beijing Normal University, Beijing 100875 (China); Jin Weijun, E-mail: wjjin@bnu.edu.cn [College of Chemistry, Beijing Normal University, Beijing 100875 (China)

    2012-11-13

    Highlights: Black-Right-Pointing-Pointer Halogen bonding (XB) is firstly utilised in solid phase extraction. Black-Right-Pointing-Pointer The perfluorinated iodine alkanes can be extracted by C-I Midline-Horizontal-Ellipsis Cl{sup -} halogen bonding. Black-Right-Pointing-Pointer The C-I Midline-Horizontal-Ellipsis Cl{sup -} halogen bond is well characterised by spectroscopy methods. Black-Right-Pointing-Pointer The analytes with strong halogen-bonding abilities can be selectively extracted. - Abstract: For the first time, halogen-bonding interaction is utilised in the solid phase extraction of perfluorinated iodoalkane (PFI). Nine PFIs, as model analytes, were tested, and analyses by UV, {sup 19}F NMR and Raman spectroscopies demonstrate that the PFIs are extracted by a strong anion exchange (SAX) sorbent from n-hexane due to the C-I Midline-Horizontal-Ellipsis Cl{sup -} halogen-bonding interactions. The results also show that the adsorptivities of SAX for the diiodoperfluoro-alkanes (diiodo-PFIs) were much stronger than those for the perfluoroalkyl iodides (monoiodo-PFIs). Specifically, the recoveries for 1,6-diiodoperfluorohexane and 1,8-diiodoperfluorooctane were higher than 80% when 100 mL of sample spiked with a 5 ng mL{sup -1} analyte mixture was extracted. Interestingly, SAX had no adsorption for hexafluorobenzene at all, which is known to be unable to form a halogen bond with Cl{sup -}. The analytical performance of the halogen bond-based SPE-GC-MS method for the diiodo-PFIs was also examined in soil samples. The sorbent SAX enabled the selective extraction of four diiodo-PFIs successfully from soil samples. The recoveries of the diiodo-PFIs extracted from 5 g soil sample at the 100 ng g{sup -1} spike level were in the range of 73.2-93.8% except 26.8% for 1,2-diiodoperfluoroethane. The limit of detection varied from 0.02 to 0.04 ng g{sup -1} in soil samples. Overall, this work reveals the great application potential of halogen bonding in the field of solid

  9. Contextual Meaning and Word Meaning

    Institute of Scientific and Technical Information of China (English)

    Istvan Kecskes

    2006-01-01

    The paper has three goals: 1 ) Explain the role of context and word in meaning construction and comprehension. 2) Present a model that can explain meaning generated by both monolingual and multilingual meaning construction systems. 3) Discuss how the model can be applied to explain major issues in pragmatics.Pragmatics is understood here in a narrow sense as defined by Sperber & Noveck: "...pragmatics is the study of how linguistic properties and contextual factors interact in the interpretation of utterances" ( Sperber & Noveck 2004:1 ). It is argued that world knowledge is available to interlocutors in two forms: as encapsulated in lexical items based on prior encounters and experience (conventionalized cognitive context), and as provided by the actual situational context framed by the situation in which the interaction takes place. Meaning formally expressed in the linguistic interactional context is created on-the-spot, and is the result of the interaction of the two sides of world knowledge and the actual situational context.The paper makes three claims: First, supremacy of context is not unconditional in language processing. Second,salient meaning rather than literal meaning of lexical units plays a central role in comprehension. Third, intercultural communication differs from intracultural communication in the conceptual content of conventionalized cognitive contexts rather than in communicative means.

  10. Gas chromatography mass spectrometry computer analysis of volatile halogenated hydrocarbons in man and his environment--A multimedia environmental study.

    Science.gov (United States)

    Barkley, J; Bunch, J; Bursey, J T; Castillo, N; Cooper, S D; Davis, J M; Erickson, M D; Harris, B S; Kirkpatrick, M; Michael, L C; Parks, S P; Pellizzari, E D; Ray, M; Smith, D; Tomer, K B; Wagner, R; Zweidinger, R A

    1980-04-01

    As part of a study to make a comparative analysis of selected halogenated compounds in man and the environmental media, a quantitative gas chromatography mass spectrometric analysis of the levels of the halogenated compounds found in the breath, blood and urine of an exposed population (Old Love Canal area, Niagara, New York) and their immediate environment (air and water) was undertaken. In addition, levels of halogenated hydrocarbons in air samples taken in the general Buffalo, Niagara Falls area were determined.

  11. Sea ice dynamics influence halogen deposition to Svalbard

    Directory of Open Access Journals (Sweden)

    A. Spolaor

    2013-10-01

    Full Text Available Sea ice is an important parameter in the climate system and its changes impact upon the polar albedo and atmospheric and oceanic circulation. Iodine (I and bromine (Br have been measured in a shallow firn core drilled at the summit of the Holtedahlfonna glacier (Northwest Spitsbergen, Svalbard. Changing I concentrations can be linked to the March–May maximum sea ice extension. Bromine enrichment, indexed to the Br / Na sea water mass ratio, appears to be influenced by changes in the seasonal sea ice area. I is emitted from marine biota and so the retreat of March–May sea ice coincides with enlargement of the open-ocean surface which enhances marine primary production and consequent I emission. The observed Br enrichment could be explained by greater Br emissions during the Br explosions that have been observed to occur mainly above first year sea ice during the early springtime. In this work we present the first comparison between halogens in surface snow and Arctic sea ice extension. Although further investigation is required to characterize potential depositional and post-depositional processes, these preliminary findings suggest that I and Br can be linked to variability in the spring maximum sea ice extension and seasonal sea ice surface area.

  12. Deciphering Halogen Competition in Organometallic Halide Perovskite Growth.

    Science.gov (United States)

    Yang, Bin; Keum, Jong; Ovchinnikova, Olga S; Belianinov, Alex; Chen, Shiyou; Du, Mao-Hua; Ivanov, Ilia N; Rouleau, Christopher M; Geohegan, David B; Xiao, Kai

    2016-04-20

    Organometallic halide perovskites (OHPs) hold great promise for next-generation, low-cost optoelectronic devices. During the chemical synthesis and crystallization of OHP thin films, a major unresolved question is the competition between multiple halide species (e.g., I(-), Cl(-), Br(-)) in the formation of the mixed-halide perovskite crystals. Whether Cl(-) ions are successfully incorporated into the perovskite crystal structure or, alternatively, where they are located is not yet fully understood. Here, in situ X-ray diffraction measurements of crystallization dynamics are combined with ex situ TOF-SIMS chemical analysis to reveal that Br(-) or Cl(-) ions can promote crystal growth, yet reactive I(-) ions prevent them from incorporating into the lattice of the final perovskite crystal structure. The Cl(-) ions are located in the grain boundaries of the perovskite films. These findings significantly advance our understanding of the role of halogens during synthesis of hybrid perovskites and provide an insightful guidance to the engineering of high-quality perovskite films, essential for exploring superior-performing and cost-effective optoelectronic devices.

  13. Identification and quantification of the halogenated natural product BC-3

    Energy Technology Data Exchange (ETDEWEB)

    Melcher, J.; Olbrich, D.; Vetter, W. [Hohenheim Univ., Stuttgart (Germany). Inst. fuer Lebensmittelchemie; Marsh, G. [Stockholm Univ. (Sweden). Dept. of Environmental Chemistry; Gaus, C.; Mueller, J.F. [National Research Centre for Environmental Toxicology, Coopers Plains (Australia)

    2004-09-15

    Halogenated natural products (HNPs) of marine origin are increasingly recognized as critical residues in foodstuff (e. g. fish) and environmental samples (e. g. marine mammals and birds). Some of these HNPs (Q1, MHC-1, BC-2, and HDBPs including BC-10) were detected in diverse fish and marine mammal samples at concentrations sometimes exceeding those of PCBs, DDT, and other anthropogenic pollutants. Recent studies with marine mammal samples from Australia led to the detection of six abundant HNPs (Q1, BC-1, BC-2, BC-3, BC-10, and BC-11). In the meantime, Q1 was identified as heptachloro-1{sup '}-methyl-1,2{sup '}-bipyrrole, BC-2 as 4,6-dibromo-2-(2{sup '},4{sup '}-dibromo)phenoxyanisole, BC- 10 as 1,1{sup '}-dimethyl-3,3{sup '},4,4{sup '}-tetrabromo-5,5{sup '}-dichloro-2,2{sup '}-bipyrrole, and BC-11 as 3,5-dibromo- 2-(3{sup '},5{sup '}-dibromo,2{sup '}-methoxy)phenoxyanisole. However the identity of BC-1 and BC-3 remained unclear. The goal of the present study was the identification of BC-3. The tetrabromo compound BC-3 has previously been detected in marine mammals from four continents. Furthermore, we attempted establishing quantitative concentrations in diverse marine biota samples.

  14. Hydroxyl radical substitution in halogenated carbonyls: oxalic acid formation.

    Science.gov (United States)

    Christiansen, Carrie J; Dalal, Shakeel S; Francisco, Joseph S; Mebel, Alexander M; Gaffney, Jeffrey S

    2010-03-04

    An ab initio study of OH radical substitution reactions in halogenated carbonyls is conducted. Hydroxyl radical substitution into oxalyl dichloride [ClC(O)C(O)Cl] and oxalyl dibromide [BrC(O)C(O)Br], resulting in the formation of oxalic acid, is presented. Analogous substitution reactions in formyl chloride [ClCH(O)], acetyl chloride [ClC(O)CH(3)], formyl bromide [BrCH(O)], and acetyl bromide [BrC(O)CH(3)] are considered. Energetics of competing hydrogen abstraction reactions for all applicable species are computed for comparison. Geometry optimizations and frequency computations are performed using the second-order Møller-Plesset perturbation theory (MP2) and the 6-31G(d) basis set for all minimum species and transition states. Single point energy computations are performed using fourth-order Møller-Plesset perturbation theory (MP4) and coupled cluster theory [CCSD(T)]. Potential energy surfaces, including activation energies and enthalpies, are determined from the computations. These potential energy surfaces show that OH substitution into ClC(O)C(O)Cl and BrC(O)C(O)Br, resulting in the formation of oxalic acid and other minor products, is energetically favorable. Energetics of analogous reactions with ClCH(O), BrCH(O), ClC(O)CH(3), and BrC(O)CH(3) are also computed.

  15. Designer Metallic Acceptor-Containing Halogen Bonding: General Strategies.

    Science.gov (United States)

    Zhang, Xinxing; Bowen, Kit H

    2017-03-13

    Being electrostatic interactions in nature, hydrogen bonding (HB) and halogen bonding (XB) are considered to be two parallel worlds. In principle, all the applications that HB has could also be applied to XB. However, there has been no report on a metallic XB acceptor but metal anions have been observed to be good HB acceptors. This missing mosaic piece of XB is because common metal anions are reactive for XB donors. In view of this, we propose two strategies for designing metallic acceptor-containing XB using ab initio calculations. The first one is to utilize a metal cluster anion with a high electron detachment energy, such as the superatom, Al13- as the XB acceptor. The second strategy is to design a ligand passivated/protected metal core while it still can maintain the negative charge; several exotic clusters, such as PtH5-, PtZnH5- and PtMgH5-, are utilized as examples. Based on these two strategies, we anticipate that more metallic acceptor-containing XB will be discovered.

  16. Sea ice dynamics influence halogen deposition to Svalbard

    Directory of Open Access Journals (Sweden)

    A. Spolaor

    2013-03-01

    Full Text Available Sea ice is an important parameter in the climate system and its changes impact upon the polar albedo and the atmospheric and oceanic circulation. Iodine (I and bromine (Br have been measured in a shallow ice core drilled at the summit of the Holtedahlfonna glacier (Northwest Spitsbergen, Svalbard. Changing I concentrations can be linked to the spring maximum sea ice extension. Bromine enrichment, indexed to the Br/Na sea water mass ratio, appears to be influenced by changes in the seasonal sea ice area. I is emitted from marine biota and so the retreat of spring sea ice coincides with enlargement of the open ocean surface which enhances marine primary production and consequent I emission. The observed Br enrichment can be explained by greater Br emissions during the Br explosion that have been observed to occur above first year sea ice during the early springtime. In this work we present the first comparison between halogens in surface snow and Arctic sea ice extension. Although further investigation is required to characterize potential depositional and post-depositional processes, these preliminary findings suggest that I and Br can be linked to variability in the spring maximum sea ice extension and seasonal sea ice surface area.

  17. Metal hydrides form halogen bonds: measurement of energetics of binding.

    Science.gov (United States)

    Smith, Dan A; Brammer, Lee; Hunter, Christopher A; Perutz, Robin N

    2014-01-29

    The formation of halogen bonds from iodopentafluorobenzene and 1-iodoperfluorohexane to a series of bis(η(5)-cyclopentadienyl)metal hydrides (Cp2TaH3, 1; Cp2MH2, M = Mo, 2, M = W, 3; Cp2ReH, 4; Cp2Ta(H)CO, 5; Cp = η(5)-cyclopentadienyl) is demonstrated by (1)H NMR spectroscopy. Interaction enthalpies and entropies for complex 1 with C6F5I and C6F13I are reported (ΔH° = -10.9 ± 0.4 and -11.8 ± 0.3 kJ/mol; ΔS° = -38 ± 2 and -34 ± 2 J/(mol·K), respectively) and found to be stronger than those for 1 with the hydrogen-bond donor indole (ΔH° = -7.3 ± 0.1 kJ/mol, ΔS° = -24 ± 1 J/(mol·K)). For the more reactive complexes 2-5, measurements are limited to determination of their low-temperature (212 K) association constants with C6F5I as 2.9 ± 0.2, 2.5 ± 0.1, <1.5, and 12.5 ± 0.3 M(-1), respectively.

  18. Boiling of simulated tap water: effect on polar brominated disinfection byproducts, halogen speciation, and cytotoxicity.

    Science.gov (United States)

    Pan, Yang; Zhang, Xiangru; Wagner, Elizabeth D; Osiol, Jennifer; Plewa, Michael J

    2014-01-01

    Tap water typically contains numerous halogenated disinfection byproducts (DBPs) as a result of disinfection, especially of chlorination. Among halogenated DBPs, brominated ones are generally significantly more toxic than their chlorinated analogues. In this study, with the aid of ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry by setting precursor ion scans of m/z 79/81, whole spectra of polar brominated DBPs in simulated tap water samples without and with boiling were revealed. Most polar brominated DBPs were thermally unstable and their levels were substantially reduced after boiling via decarboxylation or hydrolysis; the levels of a few aromatic brominated DBPs increased after boiling through decarboxylation of their precursors. A novel adsorption unit for volatile total organic halogen was designed, which enabled the evaluation of halogen speciation and mass balances in the simulated tap water samples during boiling. After boiling for 5 min, the overall level of brominated DBPs was reduced by 62.8%, of which 39.8% was volatilized and 23.0% was converted to bromide; the overall level of chlorinated DBPs was reduced by 61.1%, of which 44.4% was volatilized and 16.7% was converted to chloride; the overall level of halogenated DBPs was reduced by 62.3%. The simulated tap water sample without boiling was cytotoxic in a chronic (72 h) exposure to mammalian cells; this cytotoxicity was reduced by 76.9% after boiling for 5 min. The reduction in cytotoxicity corresponded with the reduction in overall halogenated DBPs. Thus, boiling of tap water can be regarded as a "detoxification" process and may reduce human exposure to halogenated DBPs through tap water ingestion.

  19. Optimal nano-descriptors as translators of eclectic data into prediction of the cell membrane damage by means of nano metal-oxides.

    Science.gov (United States)

    Toropova, Alla P; Toropov, Andrey A; Benfenati, Emilio; Korenstein, Rafi; Leszczynska, Danuta; Leszczynski, Jerzy

    2015-01-01

    Systematization of knowledge on nanomaterials has become a necessity with the fast growth of applications of these species. Building up predictive models that describe properties (both beneficial and hazardous) of nanomaterials is vital for computational sciences. Classic quantitative structure-property/activity relationships (QSPR/QSAR) are not suitable for investigating nanomaterials because of the complexity of their molecular architecture. However, some characteristics such as size, concentration, and exposure time can influence endpoints (beneficial or hazardous) related to nanoparticles and they can therefore be involved in building a model. Application of the optimal descriptors calculated with the so-called correlation weights of various concentrations and different exposure times are suggested in order to build up a predictive model for cell membrane damage caused by a series of nano metal-oxides. The numerical data on correlation weights are calculated by the Monte Carlo method. The obtained results are in good agreement with the experimental data.

  20. Chloramination of nitrogenous contaminants (pharmaceuticals and pesticides): NDMA and halogenated DBPs formation.

    Science.gov (United States)

    Le Roux, Julien; Gallard, Hervé; Croué, Jean-Philippe

    2011-05-01

    Disinfection with chloramines is often used to reduce the production of regulated disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). However, chloramination can lead to the formation of N-nitrosamines, including N-nitrosodimethylamine (NDMA), a probable human carcinogen. Previous research used dimethylamine (DMA) as a model precursor of NDMA, but certain widely used tertiary dimethylamines (e.g. the pharmaceutical ranitidine) show much higher conversion rates to NDMA than DMA. This study investigates the NDMA formation potential of several tertiary amines including pharmaceuticals and herbicides. The reactivity of these molecules with monochloramine (NH(2)Cl) is studied through the formation of NDMA, and other halogenated DBPs such as haloacetonitriles (HANs) and AOX (Adsorbable Organic Halides). Several compounds investigated formed NDMA in greater amounts than DMA, revealing the importance of structural characteristics of tertiary amines for NDMA formation. Among these compounds, the pharmaceutical ranitidine showed the highest molar conversion to NDMA. The pH and dissolved oxygen content of the solution were found to play a major role for the formation of NDMA from ranitidine. NDMA was formed in higher amounts at pH around pH 8 and a lower concentration of dissolved oxygen dramatically decreased NDMA yields. These findings seem to indicate that dichloramine (NHCl(2)) is not the major oxidant involved in the formation of NDMA from ranitidine, results in contradiction with the reaction mechanisms proposed in the literature. Dissolved oxygen was also found to influence the formation of other oxygen-containing DBPs (i.e. trichloronitromethane and haloketones). The results of this study identify several anthropogenic precursors of NDMA, indicating that chloramination of waters impacted by these tertiary amines could lead to the formation of significant amounts of NDMA and other non-regulated DBPs of potential health concern (e

  1. Chloramination of nitrogenous contaminants (pharmaceuticals and pesticides): NDMA and halogenated DBPs formation

    KAUST Repository

    Le Roux, Julien

    2011-05-01

    Disinfection with chloramines is often used to reduce the production of regulated disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). However, chloramination can lead to the formation of N-nitrosamines, including N-nitrosodimethylamine (NDMA), a probable human carcinogen. Previous research used dimethylamine (DMA) as a model precursor of NDMA, but certain widely used tertiary dimethylamines (e.g. the pharmaceutical ranitidine) show much higher conversion rates to NDMA than DMA. This study investigates the NDMA formation potential of several tertiary amines including pharmaceuticals and herbicides. The reactivity of these molecules with monochloramine (NH2Cl) is studied through the formation of NDMA, and other halogenated DBPs such as haloacetonitriles (HANs) and AOX (Adsorbable Organic Halides). Several compounds investigated formed NDMA in greater amounts than DMA, revealing the importance of structural characteristics of tertiary amines for NDMA formation. Among these compounds, the pharmaceutical ranitidine showed the highest molar conversion to NDMA. The pH and dissolved oxygen content of the solution were found to play a major role for the formation of NDMA from ranitidine. NDMA was formed in higher amounts at pH around pH 8 and a lower concentration of dissolved oxygen dramatically decreased NDMA yields. These findings seem to indicate that dichloramine (NHCl2) is not the major oxidant involved in the formation of NDMA from ranitidine, results in contradiction with the reaction mechanisms proposed in the literature. Dissolved oxygen was also found to influence the formation of other oxygen-containing DBPs (i.e. trichloronitromethane and haloketones). The results of this study identify several anthropogenic precursors of NDMA, indicating that chloramination of waters impacted by these tertiary amines could lead to the formation of significant amounts of NDMA and other non-regulated DBPs of potential health concern (e

  2. Cyano- and polycyanometalloporphyrins as catalysts for alkane oxidation

    Science.gov (United States)

    Ellis, Jr., Paul E.; Lyons, James E.

    1992-01-01

    Alkanes are oxidized by contact with oxygen-containing gas in the presence as catalyst of a metalloporphyrin in which hydrogen atoms in the porphyrin ring have been substituted with one or more cyano groups. Hydrogen atoms in the porphyrin ring may also be substituted with halogen atoms.

  3. Removal of antibiotic cloxacillin by means of electrochemical oxidation, TiO2 photocatalysis, and photo-Fenton processes: analysis of degradation pathways and effect of the water matrix on the elimination of antimicrobial activity.

    Science.gov (United States)

    Serna-Galvis, Efraim A; Giraldo-Aguirre, Ana L; Silva-Agredo, Javier; Flórez-Acosta, Oscar A; Torres-Palma, Ricardo A

    2017-03-01

    This study evaluates the treatment of the antibiotic cloxacillin (CLX) in water by means of electrochemical oxidation, TiO2 photocatalysis, and the photo-Fenton system. The three treatments completely removed cloxacillin and eliminated the residual antimicrobial activity from synthetic pharmaceutical wastewater containing the antibiotic, commercial excipients, and inorganic ions. However, significant differences in the degradation routes were found. In the photo-Fenton process, the hydroxyl radical was involved in the antibiotic removal, while in the TiO2 photocatalysis process, the action of both the holes and the adsorbed hydroxyl radicals degraded the pollutant. In the electrochemical treatment (using a Ti/IrO2 anode in sodium chloride as supporting electrolyte), oxidation via HClO played the main role in the removal of CLX. The analysis of initial by-products showed five different mechanistic pathways: oxidation of the thioether group, opening of the central β-lactam ring, breakdown of the secondary amide, hydroxylation of the aromatic ring, and decarboxylation. All the oxidation processes exhibited the three first pathways. Moreover, the aromatic ring hydroxylation was found in both photochemical treatments, while the decarboxylation of the pollutant was only observed in the TiO2 photocatalysis process. As a consequence of the degradation routes and mechanistic pathways, the elimination of organic carbon was different. After 480 and 240 min, the TiO2 photocatalysis and photo-Fenton processes achieved ∼45 and ∼15 % of mineralization, respectively. During the electrochemical treatment, 100 % of the organic carbon remained even after the antibiotic was treated four times the time needed to degrade it. In contrast, in all processes, a natural matrix (mineral water) did not considerably inhibit pollutant elimination. However, the presence of glucose in the water significantly affected the degradation of CLX by means of TiO2 photocatalysis.

  4. Correlation of Boiling Points with Molecular Structure for Halogenated Propanes%卤代丙烷的沸点与分子结构的关联及预测

    Institute of Scientific and Technical Information of China (English)

    王克强; 孙献忠

    2000-01-01

    探讨了卤代丙烷沸点的变化规律,发展了一种直接根据分子结构信息计算和预测卤代丙烷沸点的方法.对53种卤代丙烷的计算结果表明,沸点计算值与实验值的一致性令人满意,平均误差1.18%.本文方法的提出,不仅在一定程度上揭示了卤代丙烷沸点与分子结构之间的定量关系,而且为工程上提供了一种预测卤代丙烷沸点的有效方法.%A correlation was investigated between the boiling points and molecular structure of halogenated propanes,and a method which can be used to calculate and predict the boiling points of halogenated propanes was developed.The results showed that the calculated boiling points are in good agreement with the experimental data,and the mean relative deviation was 1.18% for 53 halogenated propanes.The boiling points of 6 halogenated propanes were predicted for reference and testing in the future.Not only can the method be used to predict haloenated propance,but can help to understand the quantitative relation between boiling point and molecular structure of halogenated propanes as well.

  5. Variation of crystallinity and stoichiometry in films of gallium oxide, gallium nitride and barium zirconate prepared by means of PLD; Variation von Kristallinitaet und Stoechiometrie in mittels PLD hergestellten Schichten aus Galliumoxid, Galliumnitrid und Bariumzirkonat

    Energy Technology Data Exchange (ETDEWEB)

    Brendt, Jochen

    2011-08-05

    Pulsed Laser Deposition (PLD) is an ablation technique for thin film preparation of many materials. The film properties can be well controlled by the process parameters. Therefore, in many cases a given material can be deposited with different properties by changing one or more process parameters. In this thesis thin films of gallium oxide, gallium nitride and barium zirconate were deposited with a large variation in structure and stoichiometry by means of Pulsed Laser Deposition. The characterization of the film crystallinity, phase purity and short range structural order was completed by means of X-ray diffraction and X-ray absorption spectroscopy. The stoichiometry was investigated using electron probe microanalysis. For analyzing the correlation between the structure and stoichiometry with the optical and electrical properties, optical absorption and electrical conductivity measurements were carried out. The investigation of all three material systems showed that very unique properties can be realized when combining an amorphous structure and a non-stoichiometric composition. For example, in amorphous and oxygen deficient gallium oxide an insulator-metal-transition can be induced by partial crystallization of the as prepared phase accomplished by annealing at about 400 C in argon atmosphere (as shown in literature). Furthermore, amorphous and highly non-stoichiometric barium zirconate has the ability to split water molecules to hydrogen and oxygen at room temperature. A detailed analysis of both phenomena has been performed by means of photoemission and transmission electron microscopy in the case of gallium oxide and via X-ray absorption spectroscopy and gas chromatography in the case of barium zirconate.

  6. A QSRR Study on the Relative Retention Time of Halogenated Methyl-phenyl Ethers

    Institute of Scientific and Technical Information of China (English)

    XU Hui-Ying; YU Qing-Sen; ZOU Jian-Wei; WANG Yan-Hua; WANG Hong-Qing; CHEN Xue-Song

    2006-01-01

    Halogenated methyl-phenyl ethers (anisoles) are ubiquitous organic compounds in the environment. In the present study, geometrical optimization and electrostatic potential calculations have been performed for 42 halogenated anisoles at the HF/6-31 G* level. A number of statistically based parameters have been obtained. By multiple regression method, linear relationships between the gas-chromatographic relative retention time (RRT) and structural descriptors have been established for the training set of 32 halogenated anisoles. The result showed that the parameters derived from electrostatic potentials (ESPs) together with the molecular volume (Vmc) could be well used to express the quantitative structure-RRT relationships of halogenated anisoles. The best two-variable regression model gives a correlation coefficient of 0.980 and a standard deviation of 0.07, and the leave-one-out cross-validated correlation coefficient is 0.975. The goodness of the model has been further validated through exploring the predictive power for the testing set of 10 halogenated anisoles.

  7. Quantifying the effects of halogen bonding by haloaromatic donors on the acceptor pyrimidine.

    Science.gov (United States)

    Ellington, Thomas L; Reves, Peyton L; Simms, Briana L; Wilson, Jamey L; Watkins, Davita L; Tschumper, Gregory S; Hammer, Nathan I

    2017-02-28

    The effects of intermolecular interactions by a series of haloaromatic halogen bond donors on the normal modes and chemical shifts of the acceptor pyrimidine are investigated by Raman and NMR spectroscopies and electronic structure computations. Halogen bond interactions with pyrimidine's nitrogen atoms shift normal modes to higher energy and shift 1H and 13C NMR peaks upfield in adjacent nuclei. This perturbation of vibrational normal modes is reminiscent of the effects of hydrogen bonded networks of water, methanol, or silver on pyrimidine. The unexpected observation of vibrational red shifts and downfield 13C NMR shifts in some complexes suggests that other intermolecular forces such as pi-interactions are competing with halogen bonding. Natural bond orbital analyses indicate a wide range of charge transfer from pyrimidine to different haloaromatic donors is possible and computed halogen bond binding energies can be larger than a typical hydrogen bond. These results emphasize the importance in strategic selection of substituents and electron withdrawing groups in developing supramolecular structures based on halogen bonding.

  8. Seaonal Sea Ice as a source of organo-halogens during Polar night

    Science.gov (United States)

    Abrahamsson, Katarina; Granfors, Anna; Ahnoff, Martin

    2016-04-01

    The release of bromine from snow and sea ice surfaces has mainly been attributed to the reaction of hypobromous acid with bromide at acidic conditions to form Br2. Little attention has been given to the role of volatile halogenated organic compounds (organo-halogens) in the formation of reactive halogen species in the atmosphere during bromine explosion events. The load of organo-halogens was studied during a winter expedition to the Weddell Sea in June to August 2013. These compounds are emitted from the different compartments of the cryosphere to the atmosphere where they are photolysed to BrO and IO, which are involved in the degradation of ozone. We will present results that show the importance of organo-halogens formed during polar winter. In newly formed ice, in contrast to summer sea ice, the concentration of organo-bromine was found at levels as high as nM. These high concentrations were reflected both in frost flowers and in the sea-snow interface. Moreover, air measurements revealed high loads of organo-bromine over the sea ice. The situation was similar for iodinated compounds. Interestingly, the precursers of IO, mainly diiodomethane, could be measured in sea ice and snow, most probably due to the low light levels.

  9. Non-conventional gas phase remediation of volatile halogenated compounds by dehydrated bacteria.

    Science.gov (United States)

    Erable, Benjamin; Goubet, Isabelle; Seltana, Amira; Maugard, Thierry

    2009-06-01

    Traditional biological removal processes are limited by the low solubility of halogenated compounds in aqueous media. A new technology appears very suitable for the remediation of these volatile organic compounds (VOCs). Solid/gas bio-catalysis applied in VOC remediation can transform halogenated compounds directly in the gas phase using dehydrated cells as a bio-catalyst. The hydrolysis of volatile halogenated substrates into the corresponding alcohol was studied in a solid/gas biofilter where lyophilised bacterial cultures were used as the catalyst. Four strains containing dehalogenase enzymes were tested for the hydrolysis of 1-chlorobutane. The highest removal yield was obtained using the dhaA-containing strains, the maximal reaction rate of 0.8 micromol min(-1)g(-1) being observed with Escherichia coli BL21(DE3)(dhaA). Various treatments such as cell disruption by lysozyme or alkaline gas addition in the bio-filter could stabilise the dehalogenase activity of the bacteria. A pre-treatment of the dehydrated bacterial cells by ammonia vapour improved the stability of the catalyst and a removal activity of 0.9 micromol min(-1)g(-1) was then obtained for 60h. Finally, the process was extended to a range of halogenated substrates including bromo- and chloro-substrates. It was shown that the removal capacity for long halogenated compounds (C(5)-C(6)) was greatly increased relative to traditional biological processes.

  10. Oceanic contributions from tropical upwelling systems to atmospheric halogens

    Science.gov (United States)

    Ziska, Franziska; Hepach, Helmke; Stemmler, Irene; Quack, Birgit; Atlas, Elliot; Fuhlbrügge, Steffen; Bracher, Astrid; Tegtmeier, Susann; Krüger, Kirstin

    2014-05-01

    Short lived halogenated substances (halocarbons) from the oceans contribute to atmospheric halogens, where they are involved in ozone depletion and aerosol formation. Oceanic regions that are characterized by high biological activity are often associated with increased halocarbon abundance of e.g. bromoform (CHBr3) and dibromomethane (CH2Br2), representing the main contributors to atmospheric organic bromine. Apart from biological production, photochemical pathways play an important role in the formation of methyl iodide (CH3I), the most abundant organoiodine in the marine atmosphere. Recently, the contribution of biogenic diiodomethane (CH2I2) and chloroiodomethane (CH2ClI) to atmospheric organic iodine has been estimated to be similarly significant as CH3I. In the tropics, rapid uplift of surface air can transport these short-lived compounds into the upper troposphere and into the stratosphere. Oceanic upwelling systems off Mauritania, Peru and in the equatorial Atlantic might therefore potentially contribute large amounts of halocarbons to the stratosphere. Concentrations and emissions of iodo- and bromocarbons from several SOPRAN campaigns in different tropical upwelling systems, the Mauritanian and the equatorial upwelling in the Atlantic, as well as the Peruvian upwelling in the Pacific, will be presented. Processes contributing to halocarbon occurrence in the water column, as well as biological and physical factors influencing their emission into the atmosphere are investigated (Fuhlbrügge, et al. 2013; Hepach et al., 2013). We will present the relative contribution of the upwelling systems to global air-sea fluxes from different modelling studies. The data based bottom-up emissions from Ziska et al. (2013) will be compared to model simulated halocarbons. The model is a global three-dimensional ocean general circulation model with an ecosystem model and halocarbon module embedded (MPIOM/HAMOCC). It resolves CH3I and CHBr3 production, degradation, and

  11. A DFT study of halogen atoms adsorbed on graphene layers

    Energy Technology Data Exchange (ETDEWEB)

    Medeiros, Paulo V C; De Brito Mota, F; De Castilho, Caio M C [Grupo de Fisica de Superfcies e Materiais, Instituto de Fisica, Universidade Federal da Bahia, Campus Universitario da Federacao/Ondina, 40170-115 Salvador, Bahia (Brazil); Mascarenhas, Artur J S, E-mail: caio@ufba.br [Instituto Nacional de Ciencia e Tecnologia em Energia e Ambiente-INCT-E and A, Universidade Federal da Bahia, 40170-280 Salvador, Bahia (Brazil)

    2010-12-03

    In this work, ab initio density functional theory calculations were performed in order to study the structural and electronic properties of halogens (X = fluorine, chlorine, bromine or iodine) that were deposited on both sides of graphene single layers (X-graphene). The adsorption of these atoms on only one side of the layer with hydrogen atoms adsorbed on the other was also considered (H,X-graphene). The results indicate that the F-C bond in the F-graphene system causes an sp{sup 2} to sp{sup 3} transition of the carbon orbitals, and similar effects seem to occur in the H,X-graphene systems. For the other cases, two configurations are found: bonded (B) and non-bonded (NB). For the B configuration, the structural arrangement of the atoms was similar to F-graphene and H-graphene (graphane), although the electronic structures present some differences. In the NB configuration, the interaction between the adsorbed atoms and the graphene layer seems to be essentially of the van der Waals type. In these cases, the original shape of the graphene layer presents only small deviations from the pristine form and the adsorbed atoms reach equilibrium far from the sheet. The F-graphene structure has a direct bandgap of approximately 3.16 eV at the {Gamma} point, which is a value that is close to the value of 3.50 eV that was found for graphane. The Cl-graphene (B configuration), H,F-graphene and H,Cl-graphene systems have smaller bandgap values. All of the other systems present metallic behaviours. Energy calculations indicate the possible stability of these X-graphene layers, although some considerations about the possibility of spontaneous formation have to be taken into account.

  12. Global distribution of halogenated dimethyl bipyrroles in marine mammal blubber.

    Science.gov (United States)

    Tittlemier, S; Borrell, A; Duffe, J; Duignan, P J; Fair, P; Hall, A; Hoekstra, P; Kovacs, K M; Krahn, M M; Lebeuf, M; Lydersen, C; Muir, D; O'Hara, T; Olsson, M; Pranschke, J; Ross, P; Siebert, U; Stern, G; Tanabe, S; Norstrom, R

    2002-08-01

    Four halogenated dimethyl bipyrroles (HDBPs), hypothesized to be naturally produced, were quantitated in marine mammal blubber from a number of species obtained from various locations worldwide. HDBPs were found in samples from all locations studied. Concentrations of total HDBPs (SigmaHDBPs) ranged from 0.4 ng/g lipid weight in ringed seals (Phoca hispida) from the White Sea to 2,540 ng/g lipid weight in Dall's porpoise (Phocoenoides dalli) from the northwestern North Pacific Ocean. At their highest levels, SigmaHDBPs made up 11% of the total quantitated organohalogen body burden of adult male Dall's porpoises. In two beluga (Delphinapterus leucas) data subsets, it was found that males contained significantly higher concentrations of SigmaHDBPs than females. No significant effects of age or sex on SigmaHDBPs were observed in harbor seal (Phoca vitulina) and bowhead whale (Balaena mysticetus) data subsets. The geographical distribution of concentrations did not resemble that of the ubiquitous anthropogenic organohalogen, polychlorinated biphenyl congener CB-153. Higher concentrations of HDBPs and different patterns of congeners were observed in samples from Pacific as opposed to non-Pacific Ocean influenced environments. Concentrations of HDBPs in beluga from the Arctic and St. Lawrence River were similar. Their high abundance in north Pacific Ocean biota and widespread occurrence suggest that HDBPs undergo extensive transport from a source located primarily in the Pacific Ocean. Evidence from HDBP congener patterns indicates that both ocean currents and atmospheric transport likely play a role in the movement of HDBPs. These results imply that HDBPs and anthropogenic organohalogens have different sources and support the natural production hypothesis.

  13. Halogen-bonded network of trinuclear copper(II 4-iodopyrazolate complexes formed by mutual breakdown of chloroform and nanojars

    Directory of Open Access Journals (Sweden)

    Stuart A. Surmann

    2016-11-01

    Full Text Available Crystals of bis(tetrabutylammonium di-μ3-chlorido-tris(μ2-4-iodopyrazolato-κ2N:N′tris[chloridocuprate(II] 1,4-dioxane hemisolvate, (C16H36N2[Cu3(C3H2IN23Cl5]·0.5C4H8O or (Bu4N2[CuII3(μ3-Cl2(μ-4-I-pz3Cl3]·0.5C4H8O, were obtained by evaporating a solution of (Bu4N2[{CuII(μ-OH(μ-4-I-pz}nCO3] (n = 27–31 nanojars in chloroform/1,4-dioxane. The decomposition of chloroform in the presence of oxygen and moisture provides HCl, which leads to the breakdown of nanojars to the title trinuclear copper(II pyrazolate complex, and possibly CuII ions and free 4-iodopyrazole. CuII ions, in turn, act as catalyst for the accelerated decomposition of chloroform, ultimately leading to the complete breakdown of nanojars. The crystal structure presented here provides the first structural description of a trinuclear copper(II pyrazolate complex with iodine-substituted pyrazoles. In contrast to related trinuclear complexes based on differently substituted 4-R-pyrazoles (R = H, Cl, Br, Me, the [Cu3(μ-4-I-pz3Cl3] core in the title complex is nearly planar. This difference is likely a result of the presence of the iodine substituent, which provides a unique, novel feature in copper pyrazolate chemistry. Thus, the iodine atoms form halogen bonds with the terminal chlorido ligands of the surrounding complexes [mean length of I...Cl contacts = 3.48 (1 Å], leading to an extended two-dimensional, halogen-bonded network along (-110. The cavities within this framework are filled by centrosymmetric 1,4-dioxane solvent molecules, which create further bridges via C—H...Cl hydrogen bonds with terminal chlorido ligands of the trinuclear complex not involved in halogen bonding.

  14. Methane oxidation and degradation of organic compounds in landfill soil covers

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Kjeldsen, Peter

    2002-01-01

    High rates of methane oxidation and degradation of the lowed halogenated methanes (TCM and DCM) and HCFCs (HCFC-21 and HCFC-22) were found in an investigation of the oxidation of methane and halogenated organic compunds (HOCs) in landfill gas affected soil. The degradation followed zero-order kin......High rates of methane oxidation and degradation of the lowed halogenated methanes (TCM and DCM) and HCFCs (HCFC-21 and HCFC-22) were found in an investigation of the oxidation of methane and halogenated organic compunds (HOCs) in landfill gas affected soil. The degradation followed zero......-order kinetics and occurred in parallel with the oxidation of methane. TeCM, CFC-11, and CFC-12 were not degradable in presence of oxygen and degradation of these compounds in the oxidative zone in landfill top covers is therefore expected to be limited. However these compounds were found degradable...... in the anaerobic zone in the lower part of soil columns permeated with artificial landfill gas. The lesser-chlorinated compounds were degraded in the upper oxic zone with overlapping gradients of methane and oxygen. Methane oxidation and degradation of HOCs in the top-soils may play a very important role...

  15. Correlating Precisely Defined Primary Structure with Crystalline Properties in Halogen Containing Polyolefins

    Science.gov (United States)

    Boz, Emine; Alamo, Rufina G.; Wagener, Kenneth B.

    Polyethylene (PE) and poly(vinyl chloride) (PVC) are among the most important polymers produced in industry, although other halogen-containing derivatives of PE, such as poly(tetrafluorethylene) (PTFE) have also found wides pread use. A related class of polymers is the ethylene-co-vinyl-halide family. Such copolymers are expected to show distinct properties relative to their better known industrial analogues. For example, much interest has focused on ethylene vinyl chloride (EVC) polymers based on their potential for improved thermal stability relative to PVC. Various techniques have been used to synthesize these ethylene vinyl halide (EVH) copolymers and the simplest approach is halogenation of PE, which results in an irregular distribution of halogens along the polymer backbone and poorly defined materials.

  16. Induction of bacterial antibiotic resistance by mutagenic halogenated nitrogenous disinfection byproducts.

    Science.gov (United States)

    Lv, Lu; Yu, Xin; Xu, Qian; Ye, Chengsong

    2015-10-01

    Halogenated nitrogenous disinfection byproducts (N-DBPs) raise concerns regarding their mutagenicity and carcinogenicity threatening public health. However, environmental consequence of their mutagenicity has received less attention. In this study, the effect of halogenated N-DBPs on bacterial antibiotic resistance (BAR) was investigated. After exposure to bromoacetamide (BAcAm), trichloroacetonitrile (TCAN) or tribromonitromethane (TBNM), the resistance of Pseudomonas aeruginosa PAO1 to both individual and multiple antibiotics (ciprofloxacin, gentamicin, polymyxin B, rifampin, tetracycline, ciprofloxacin + gentamicin and ciprofloxacin + tetracycline) was increased, which was predominantly ascribed to the overexpression of efflux pumps. The mechanism of this effect was demonstrated to be mutagenesis through sequencing and analyzing antibiotic resistance genes. The same induction phenomena also appeared in Escherichia coli, suggesting this effect may be universal to waterborne pathogens. Therefore, more attention should be given to halogenated N-DBPs, as they could increase not only genotoxicological risks but also epidemiological risks of drinking water.

  17. Halogen- and hydrogen-bonding catenanes for halide-anion recognition.

    Science.gov (United States)

    Gilday, Lydia C; Beer, Paul D

    2014-07-01

    Halogen-bonding (XB) interactions were exploited in the solution-phase assembly of anion-templated pseudorotaxanes between an isophthalamide-containing macrocycle and bromo- or iodo-functionalised pyridinium threading components. (1)H NMR spectroscopic titration investigations demonstrated that such XB interpenetrated assemblies are more stable than analogous hydrogen bonding (HB) pseudorotaxanes. The stability of the anion-templated halogen-bonded pseudorotaxane architectures was exploited in the preparation of new halogen-bonding interlocked catenane species through a Grubbs' ring-closing metathesis (RCM) clipping methodology. The catenanes' anion recognition properties in the competitive CDCl(3)/CD(3) OD 1:1 solvent mixture revealed selectivity for the heavier halides iodide and bromide over chloride and acetate.

  18. Detection of halogenated flame retardants in polyurethane foam by particle induced X-ray emission

    Energy Technology Data Exchange (ETDEWEB)

    Maley, Adam M.; Falk, Kyle A.; Hoover, Luke; Earlywine, Elly B.; Seymour, Michael D. [Department of Chemistry, Hope College, 35 E. 12th Street, Holland, MI 49423 (United States); DeYoung, Paul A. [Department of Physics, Hope College, 27 Graves Place, Holland, MI 49423 (United States); Blum, Arlene [Green Science Policy Institute, Box 5455, Berkeley, CA 94705 (United States); Stapleton, Heather M. [Nicholas School of the Environment, Duke University, LSRC Box 90328, Durham, NC 27708 (United States); Peaslee, Graham F., E-mail: peaslee@hope.edu [Department of Chemistry, Hope College, 35 E. 12th Street, Holland, MI 49423 (United States)

    2015-09-01

    A novel application of particle-induced X-ray emission (PIXE) has been developed to detect the presence of chlorinated and brominated flame retardant chemicals in polyurethane foams. Traditional Gas Chromatography–Mass Spectrometry (GC–MS) methods for the detection and identification of halogenated flame retardants in foams require extensive sample preparation and data acquisition time. The elemental analysis of the halogens in polyurethane foam performed by PIXE offers the opportunity to identify the presence of halogenated flame retardants in a fraction of the time and sample preparation cost. Through comparative GC–MS and PIXE analysis of 215 foam samples, excellent agreement between the two methods was obtained. These results suggest that PIXE could be an ideal rapid screening method for the presence of chlorinated and brominated flame retardants in polyurethane foams.

  19. SYNTHESIS AND STUDY OF HALOGENATED BENZYLAMIDES OF SOME ISOCYCLIC AND HETEROCYCLIC ACIDS AS POTENTIAL ANTICONVULSANTS.

    Science.gov (United States)

    Strupińska, Marzanna; Rostafińska-Suchar, Grażyna; Pirianowicz-Chaber, Elżbieta; Grabczuk, Mateusz; Józwenko, Magdalena; Kowalczyk, Hubert; Szuba, Joanna; Wójcicka, Monika; Chen, Tracy; Mazurek, Aleksander P

    2015-01-01

    A series of potential anticonvulsants have been synthesized. There are eight fluorobenzylamides and three chlorobenzylamides of isocyclic or heterocyclic acids. Two not halogenated benzylamides were also synthesized to compare the effect of halogenation. The aim of the research performed was to evaluate whether halogenation of the mother structure is able to improve its anticonvulsant activity. The compounds were tested in Anticonvulsant Screening Project (ASP) of Antiepileptic Drug Development Program (ADDP) of NIH. Compound 1 showed MES ED50 = 80.32 mg/kg, PI = 3.16. Compound 7 showed CKM ED50 = 56.72 mg/kg. Compound 8 showed MES ED50 = 34.23 mg/kg and scPTZ ED50 > 300 mg/kg, PI = 8.53.Compound 13 showed 6Hz ED50 = 78.96, PI = 3.37. The results indicate that fluorination does not improve activity, whereas chlorination in our experiment even reduces it.

  20. Halogen bond preferences of thiocyanate ligand coordinated to Ru(II) via sulphur atom

    Science.gov (United States)

    Ding, Xin; Tuikka, Matti; Hirva, Pipsa; Haukka, Matti

    2017-09-01

    Halogen bonding between [Ru(bpy)(CO)2(S-SCN)2] (bpy = 2,2'-bipyridine), I2 was studied by co-crystallising the metal compound and diiodine from dichloromethane. The only observed crystalline product was found to be [Ru(bpy)(CO)2(S-SCN)2]ṡI2 with only one NCSṡṡṡI2 halogen bond between I2 and the metal coordinated S atom of one of the thiocyanate ligand. The dangling nitrogen atoms were not involved in halogen bonding. However, computational analysis suggests that there are no major energetic differences between the NCSṡṡṡI2 and SCNṡṡṡI2 bonding modes. The reason for the observed NCSṡṡṡI2 mode lies most probably in the more favourable packing effects rather than energetic preferences between NCSṡṡṡI2 and SCNṡṡṡI2 contacts.

  1. Halogenated and isosteric cytisine derivatives with increased affinity and functional activity at nicotinic acetylcholine receptors.

    Science.gov (United States)

    Fitch, Richard W; Kaneko, Yumika; Klaperski, Paul; Daly, John W; Seitz, Gunther; Gündisch, Daniela

    2005-02-15

    A series of pyridone ring-modified derivatives of (7R,9S)-(-)-cytisine were evaluated for affinity and functional activity at neuromuscular alpha1beta1gammadelta, ganglionic alpha3beta4, and central neuronal alpha4beta2 subtypes of nicotinic receptors. Halogenation at the 3-position improved affinity and functional activity, while substitution at the 5-position led to modest decreases in both, and disubstitution led to near abolition of functional activities and could be correlated with the electron-withdrawing ability of the halogen. Subtype selectivities of the halogenated derivatives were altered relative to cytisine in a substitution-dependent manner. Caulophylline methiodide was less potent than cytisine, but retained significant activity. Thiocytisine was relatively weak in potency and efficacy, but was significantly selective for the alpha4beta2 subtype.

  2. AutoDock VinaXB: implementation of XBSF, new empirical halogen bond scoring function, into AutoDock Vina.

    Science.gov (United States)

    Koebel, Mathew R; Schmadeke, Grant; Posner, Richard G; Sirimulla, Suman

    2016-01-01

    Halogen bonding has recently come to play as a target for lead optimization in rational drug design. However, most docking program don't account for halogen bonding in their scoring functions and are not able to utilize this new approach. In this study a new and improved halogen bonding scoring function (XBSF) is presented along with its implementation in the AutoDock Vina molecular docking software. This new improved program is termed as AutoDock VinaXB, where XB stands for the halogen bonding parameters that were added. XBSF scoring function is derived based on the X···A distance and C-X···A angle of interacting atoms. The distance term was further corrected to account for the polar flattening effect of halogens. A total of 106 protein-halogenated ligand complexes were tested and compared in terms of binding affinity and docking poses using Vina and VinaXB. VinaXB performed superior to Vina in the majority of instances. VinaXB was closer to native pose both above and below 2 Å deviation categories almost twice as frequently as Vina. Implementation of XBSF into AutoDock Vina has been shown to improve the accuracy of the docking result with regards to halogenated ligands. AutoDock VinaXB addresses the issues of halogen bonds that were previously being scored unfavorably due to repulsion factors, thus effectively lowering the output RMSD values.

  3. Stability and Characteristics of the Halogen Bonding Interaction in an Anion-Anion Complex: A Computational Chemistry Study.

    Science.gov (United States)

    Wang, Guimin; Chen, Zhaoqiang; Xu, Zhijian; Wang, Jinan; Yang, Yang; Cai, Tingting; Shi, Jiye; Zhu, Weiliang

    2016-02-04

    Halogen bonding is the noncovalent interaction between the positively charged σ-hole of organohalogens and nucleophiles. In reality, both the organohalogen and nucleophile could be deprotonated to form anions, which may lead to the vanishing of the σ-hole and possible repulsion between the two anions. However, our database survey in this study revealed that there are halogen bonding-like interactions between two anions. Quantum mechanics calculations with small model complexes composed of halobenzoates and propiolate indicated that the anion-anion halogen bonding is unstable in vacuum but attractive in solvents. Impressively, the QM optimized halogen bonding distance between the two anions is shorter than that in a neutral system, indicating a possibly stronger halogen bonding interaction, which is verified by the calculated binding energies. Furthermore, natural bond orbital and quantum theory of atoms in molecule analyses also suggested stronger anion-anion halogen bonding than that of the neutral one. Energy decomposition by symmetry adapted perturbation theory revealed that the strong binding might be attributed to large induction energy. The calculations on 4 protein-ligand complexes from PDB by the QM/MM method demonstrated that the anion-anion halogen bonding could contribute to the ligands' binding affinity up to ∼3 kcal/mol. Therefore, anion-anion halogen bonding is stable and applicable in reality.

  4. Unstable, metastable, or stable halogen bonding interaction involving negatively charged donors? A statistical and computational chemistry study.

    Science.gov (United States)

    Yang, Zhuo; Xu, Zhijian; Liu, Yingtao; Wang, Jinan; Shi, Jiye; Chen, Kaixian; Zhu, Weiliang

    2014-12-11

    The noncovalent halogen bonding could be attributed to the attraction between the positively charged σ-hole and a nucleophile. Quantum mechanics (QM) calculation indicated that the negatively charged organohalogens have no positively charged σ-hole on their molecular surface, leading to a postulation of repulsion between negatively charged organohalogens and nucleophiles in vacuum. However, PDB survey revealed that 24% of the ligands with halogen bonding geometry could be negatively charged. Moreover, 36% of ionizable drugs in CMC (Comprehensive Medicinal Chemistry) are possibly negatively charged at pH 7.0. QM energy scan showed that the negatively charged halogen bonding is probably metastable in vacuum. However, the QM calculated bonding energy turned negative in various solvents, suggesting that halogen bonding with negatively charged donors should be stable in reality. Indeed, QM/MM calculation on three crystal structures with negatively charged ligands revealed that the negatively charged halogen bonding was stable. Hence, we concluded that halogen bonding with negatively charged donors is unstable or metastable in vacuum but stable in protein environment, and possesses similar geometric and energetic characteristics as conventional halogen bonding. Therefore, negatively charged organohalogens are still effective halogen bonding donors for medicinal chemistry and other applications.

  5. Efficiency of light-emitting diode and halogen units in reducing residual monomers

    Science.gov (United States)

    de Assis Ribeiro Carvalho, Felipe; Almeida, Rhita C.; Almeida, Marco Antonio; Cevidanes, Lucia H. S.; Leite, Marcia C. Amorim M.

    2011-01-01

    Introduction In this in-vitro study, we aimed to compare the residual monomers in composites beneath brackets bonded to enamel, using a light-emitting diode (LED) or a halogen unit, and to compare the residual monomers in the central to the peripheral areas of the composite. Methods Twenty bovine teeth preserved in 0.1% thymol were used in this study. Ten teeth were used to standardize the thickness of the composite film, since different thicknesses would cause different absorbance of light. Brackets were bonded to 10 bovine incisors, with the halogen light (n = 5) and the LED (n = 5). The brackets were debonded, and the remaining composite on the enamel surface was sectioned in 2 regions: peripheral (0.8 mm) and central, resulting in 2 subgroups per group: central halogen (n = 5), peripheral halogen (n = 5), central LED (n = 5), and peripheral LED (n = 5). The spectrometric analysis in the infrared region was used to measure the free monomers with the attenuated total reflectance method. Results Normal distribution was tested by using the Kolmogorov-Smirnov test. Data were compared by 2-way analysis of variance (ANOVA) at P <0.05. The LED group showed fewer residual monomers than did the halogen group (P = 0.014). No differences were found among the regions (P = 0.354), and there were no interactions between light type and region (P = 0.368). Conclusions LED leaves less residual monomer than does the halogen light, even with half of the irradiation time; there were no differences between the central and peripheral regions, and no interaction between light type and region. PMID:21055603

  6. Thermodynamics parameters for binding of halogenated benzotriazole inhibitors of human protein kinase CK2α.

    Science.gov (United States)

    Winiewska, Maria; Kucińska, Katarzyna; Makowska, Małgorzata; Poznański, Jarosław; Shugar, David

    2015-10-01

    The interaction of human CK2α (hCK2α) with nine halogenated benzotriazoles, TBBt and its analogues representing all possible patterns of halogenation on the benzene ring of benzotriazole, was studied by biophysical methods. Thermal stability of protein-ligand complexes, monitored by calorimetric (DSC) and optical (DSF) methods, showed that the increase in the mid-point temperature for unfolding of protein-ligand complexes (i.e. potency of ligand binding to hCK2α) follow the inhibitory activities determined by biochemical assays. The dissociation constant for the ATP-hCK2α complex was estimated with the aid of microscale thermophoresis (MST) as 4.3±1.8 μM, and MST-derived dissociation constants determined for halogenated benzotriazoles, when converted according to known ATP concentrations, perfectly reconstruct IC50 values determined by the biochemical assays. Ligand-dependent quenching of tyrosine fluorescence, together with molecular modeling and DSC-derived heats of unfolding, support the hypothesis that halogenated benzotriazoles bind in at least two alternative orientations, and those that are efficient hCK2α inhibitors bind in the orientation which TBBt adopts in its complex with maize CK2α. DSC-derived apparent heat for ligand binding (ΔΔHbind) is driven by intermolecular electrostatic interactions between Lys68 and the triazole ring of the ligand, as indicated by a good correlation between ΔΔHbind and ligand pKa. Overall results, additionally supported by molecular modeling, confirm that a balance of hydrophobic and electrostatic interactions contribute predominantly (~40 kJ/mol), relative to possible intermolecular halogen/hydrogen bonding (less than 10 kJ/mol), in binding of halogenated benzotriazoles to the ATP-binding site of hCK2α. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases.

  7. Rational design of organic semiconductors for texture control and self-patterning on halogenated surfaces

    KAUST Repository

    Ward, Jeremy W.

    2014-05-15

    Understanding the interactions at interfaces between the materials constituting consecutive layers within organic thin-film transistors (OTFTs) is vital for optimizing charge injection and transport, tuning thin-film microstructure, and designing new materials. Here, the influence of the interactions at the interface between a halogenated organic semiconductor (OSC) thin film and a halogenated self-assembled monolayer on the formation of the crystalline texture directly affecting the performance of OTFTs is explored. By correlating the results from microbeam grazing incidence wide angle X-ray scattering (μGIWAXS) measurements of structure and texture with OTFT characteristics, two or more interaction paths between the terminating atoms of the semiconductor and the halogenated surface are found to be vital to templating a highly ordered morphology in the first layer. These interactions are effective when the separating distance is lower than 2.5 dw, where dw represents the van der Waals distance. The ability to modulate charge carrier transport by several orders of magnitude by promoting "edge-on" versus "face-on" molecular orientation and crystallographic textures in OSCs is demonstrated. It is found that the "edge-on" self-assembly of molecules forms uniform, (001) lamellar-textured crystallites which promote high charge carrier mobility, and that charge transport suffers as the fraction of the "face-on" oriented crystallites increases. The role of interfacial halogenation in mediating texture formation and the self-patterning of organic semiconductor films, as well as the resulting effects on charge transport in organic thin-film transistors, are explored. The presence of two or more anchoring sites between a halogenated semiconductor and a halogenated self-assembled monolayer, closer than about twice the corresponding van der Waals distance, alter the microstructure and improve electrical properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Screen-printed (La,Sr)CrO3 coatings on ferritic stainless steel interconnects for solid oxide fuel cells using nanopowders prepared by means of ultrasonic spray pyrolysis

    Science.gov (United States)

    Brylewski, Tomasz; Dabek, Jaroslaw; Przybylski, Kazimierz; Morgiel, Jerzy; Rekas, Mieczyslaw

    2012-06-01

    In order to protect the cathode from chromium poisoning and improve electrical resistance, a perovskite (La,Sr)CrO3 coating was deposited on the surface of a DIN 50049 ferritic stainless steel by means of the screen-printing method, using a paste composed of an ultra-fine powder prepared via ultrasonic spray pyrolysis. Investigations of the oxidation process of the coated steel in air and the Ar-H2-H2O gas mixture at 1073 K for times up to 820 h showed high compactness of the protective film, good adhesion to the metal substrate, as well as area specific resistance (ASR) at a level acceptable for metallic SOFC interconnect materials. The microstructure, nanostructure, phase composition of the thick film, and in particular the film/substrate interface, were examined via chemical analyses by means of SEM-EDS and TEM-SAD. It was shown that the (La,Sr)CrO3 coating interacts with the steel during long-term thermal oxidation in the afore-mentioned conditions and intermediate, chromia-rich and/or spinel multilayer interfacial zones are formed. Cr-vaporization tests showed that the (La,Sr)CrO3 coating may play the role of barriers that decrease the volatilization rate of chromia species.

  9. Estimation of mean-glandular dose from monitoring breast entrance skin air kerma using a high sensitivity metal oxide semiconductor field effect transistor (MOSFET) dosimeter system in mammography.

    Science.gov (United States)

    Dong, S L; Chu, T C; Lee, J S; Lan, G Y; Wu, T H; Yeh, Y H; Hwang, J J

    2002-12-01

    Estimation of mean-glandular dose (MGD) has been investigated in recent years due to the potential risks of radiation-induced carcinogenesis associated with the mammographic examination for diagnostic radiology. In this study, a new technique for immediate readout of breast entrance skin air kerma (BESAK) using high sensitivity MOSFET dosimeter after mammographic projection was introduced and a formula for the prediction of tube output with exposure records was developed. A series of appropriate conversion factors was applied to the MGD determination from the BESAK. The study results showed that signal response of the high sensitivity MOSFET exhibited excellent linearity within mammographic dose ranges, and that the energy dependence was less than 3% for each anode/filter combination at the tube potentials 25-30 kV. Good agreement was observed between the BESAK and the tube exposure output measurement for breasts thicker than 30 mm. In addition, the air kerma estimated from our prediction formula provided sufficient accuracy for thinner breasts. The average MGD from 120 Asian females was 1.5 mGy, comparable to other studies. Our results suggest that the high sensitivity MOSFET dosimeter system is a good candidate for immediately readout of BESAK after mammographic procedures.

  10. Superfluorinated Ionic Liquid Crystals Based on Supramolecular, Halogen-Bonded Anions.

    Science.gov (United States)

    Cavallo, Gabriella; Terraneo, Giancarlo; Monfredini, Alessandro; Saccone, Marco; Priimagi, Arri; Pilati, Tullio; Resnati, Giuseppe; Metrangolo, Pierangelo; Bruce, Duncan W

    2016-05-17

    Unconventional ionic liquid crystals in which the liquid crystallinity is enabled by halogen-bonded supramolecular anions [Cn F2 n+1 -I⋅⋅⋅I⋅⋅⋅I-Cn F2 n+1 ](-) are reported. The material system is unique in many ways, demonstrating for the first time 1) ionic, halogen-bonded liquid crystals, and 2) imidazolium-based ionic liquid crystals in which the occurrence of liquid crystallinity is not driven by the alkyl chains of the cation.

  11. New Insecticidal Agents from Halogenation/Acylation of the Furyl-Ring of Fraxinellone

    Science.gov (United States)

    Guo, Yong; Yang, Ruige; Xu, Hui

    2016-10-01

    Introduction of the halogen atom or the acyl group at the C-ring of fraxinellone was investigated. Some unexpected halogenation products were obtained with the different chlorination/bromination reagents, and their possible reaction mechanisms were also proposed. Seven key steric structures of 2a’, 2b, 2b’, 2c’, 3a, 3b, and one isomer (5’α-Cl) of 2a were further confirmed by single-crystal X-ray diffraction. Especially compounds 2a, 2a’, 3a and 3c exhibited more potent insecticidal activity than toosendanin. Some structure-activity relationships of tested compounds were also described.

  12. Chlorine dioxide as phenol and H2S scavenger - formation of halogenated phenols and subsequent environmental risk

    Energy Technology Data Exchange (ETDEWEB)

    Melbye, Alf G.; Faksness, Liv-Guri; Knudsen, Boerre Leif

    2006-03-15

    Formation of halogenated phenols as side products from treatment of produced water with aqueous chlorine dioxide has been investigated. The literature describes formation of halogenated hydrocarbons in effluent treatment using chlorine, hypochlorite and chlorine dioxide. A new chlorine dioxide product, originally intended as a H2S scavenger in the oil and gas industry, has been tested both as a phenol scavenger and H2S-scavenger for produced water applications. The concern about the possible formation of halogenated by-products initiated laboratory testing of chlorine dioxide as phenol and H2S scavenger for produced water applications. The tests also included synthetic matrixes containing phenols, and the tests show that halogenated phenols, mainly brominated species, are found in produced water after treatment with chlorine dioxide. Due to potential environmental risk from halogenated organic contaminants, the use of chlorine dioxide as phenol and H2S scavenger is not recommended. (Author)

  13. 40 CFR 721.2140 - Carbo-poly-cycli-col azo-alkyl-aminoalkyl-carbo-mono-cyclic ester, halogen acid salt.

    Science.gov (United States)

    2010-07-01

    ...-aminoalkyl-carbo-mono-cyclic ester, halogen acid salt. 721.2140 Section 721.2140 Protection of Environment...-aminoalkyl-carbo-mono-cyclic ester, halogen acid salt. (a) Chemical substance and significant new uses...-mino-al-kyl-car-bo-mon-o-cyc-lic ester, halogen acid salt (PMN P-88-1682) is subject to reporting...

  14. Halogenated organic species over the tropical South American rainforest

    Directory of Open Access Journals (Sweden)

    S. Gebhardt

    2008-06-01

    Full Text Available Airborne measurements of the halogenated trace gases methyl chloride, methyl bromide and chloroform were conducted over the Atlantic Ocean and about 1000 km of pristine tropical rainforest in Suriname and French Guyana (3–6° N, 51–59° W in October 2005. In the boundary layer (0–1.4 km, maritime air masses, advected over the forest by southeasterly trade winds, were measured at various distances from the coast. Since the organohalogens presented here have relatively long atmospheric lifetimes (0.4–1.0 years in comparison to the advection times from the coast (1–2 days, emissions will accumulate in air traversing the rainforest. The distributions of methyl chloride, methyl bromide and chloroform were analyzed as a function of time the air spent over land and the respective relationship used to determine net fluxes from the rainforest for one week within the long dry season.

    Net fluxes from the rainforest ecosystem have been calculated for methyl chloride and chloroform as 9.5 (±3.8 2σ and 0.35 (±0.15 2σμg m-2 h−1, respectively. No significant flux was observed for methyl bromide within the limits of these measurements.

    The global budget of methyl chloride contains large uncertainties, in particular with regard to a possible source from tropical vegetation. Our measurements are used in a large-scale approach to determine the net flux from a tropical ecosystem to the planetary boundary layer. The obtained global net flux of 1.5 (±0.6 2σ Tg yr-1 for methyl chloride is at the lower end of current estimates for tropical vegetation sources, which helps to constrain the range of tropical sources and sinks (0.82 to 8.2 Tg yr-1 from tropical plants, 0.03 to 2.5 Tg yr-1 from senescent/dead leaves and a sink of 0.1 to 1.6 Tg yr-1 by soil uptake. Nevertheless, these results show that the contribution of the rainforest ecosystem is the major source in the

  15. Field Emission Electron Microprobe Analysis of Halogens in Apatite

    Science.gov (United States)

    Tacker, R. C.

    2011-12-01

    counts increase as expected from 10 to 20 kV, but the loss of chlorine is more strongly controlled by crystal orientation. With electron beam parallel to the c-axis, chlorine counts are very low, pointing to the chlorine loss during analysis. Hence fluorine and chlorine are fractionated during analysis as a complicated function of beam energies and crystal orientation. Routine analyses of halogens in apatite are unlikely to yield a quantitative analysis, and OH calculated by the difference in a normalized analysis is less likely to be meaningful. Further, the use of 15-20 kV secondary electron or backscatter electron imaging prior to analysis should be reconsidered. Stormer et al., 1993, Am. Min., 78, 641. Fialin and Chopin, 2006, Am. Min. 91, 503.

  16. Construction of Tungsten Halogen, Pulsed LED, and Combined Tungsten Halogen-LED Solar Simulators for Solar Cell I-V Characterization and Electrical Parameters Determination

    OpenAIRE

    Anon Namin; Chaya Jivacate; Dhirayut Chenvidhya; Krissanapong Kirtikara; Jutturit Thongpron

    2012-01-01

    I-V characterization of solar cells is generally done under natural sunlight or solar simulators operating in either a continuous mode or a pulse mode. Simulators are classified on three features of irradiance, namely, spectral match with respect to air mass 1.5, spatial uniformity, and temporal stability. Commercial solar simulators use Xenon lamps and halogen lamps, whereas LED-based solar simulators are being developed. In this work, we build and test seven simulators for solar cell charac...

  17. Are superhalogens without halogen ligand capable of transcending traditional halogen-based superhalogens? Ab initio case study of binuclear anions based on pseudohalogen ligand

    Science.gov (United States)

    Li, Jin-Feng; Sun, Yin-Yin; Bai, Hongcun; Li, Miao-Miao; Li, Jian-Li; Yin, Bing

    2015-06-01

    The superhalogen properties of polynuclear structures without halogen ligand are theoretically explored here for several [M2(CN)5]-1 (M = Ca, Be) clusters. At CCSD(T) level, these clusters have been confirmed to be superhalogens due to their high vertical electron detachment energies (VDE). The largest one is 9.70 eV for [Ca2(CN)5]-1 which is even higher than those of corresponding traditional structures based on fluorine or chlorine ligands. Therefore the superhalogens stronger than the traditional halogen-based structures could be realized by ligands other than halogen atoms. Compared with CCSD(T), outer valence Green's function (OVGF) method either overestimates or underestimates the VDEs for different structures while MP2 results are generally consistent in the aspect of relative values. The extra electrons of the highest VDE anions here aggregate on the bridging CN units with non-negligible distribution occurring on other CN units too. These two features lower both the potential and kinetic energies of the extra electron respectively and thus lead to high VDE. Besides superhalogen properties, the structures, relative stabilities and thermodynamic stabilities with respect to the detachment of cyanide ligand were also investigated. The sum of these results identifies the potential of polynuclear structures with pseudohalogen ligand as suitable candidates with enhanced superhalogens properties.

  18. Are superhalogens without halogen ligand capable of transcending traditional halogen-based superhalogens? Ab initio case study of binuclear anions based on pseudohalogen ligand

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jin-Feng; Sun, Yin-Yin; Li, Miao-Miao; Li, Jian-Li; Yin, Bing, E-mail: rayinyin@nwu.edu.cn [MOE Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry and Materials Science, Northwest University, Xi’an 710069 (China); Bai, Hongcun [Key Laboratory of Energy Source and Chemical Engineering, Ningxia University, Yinchuan, Ningxia 750021 (China)

    2015-06-15

    The superhalogen properties of polynuclear structures without halogen ligand are theoretically explored here for several [M{sub 2}(CN){sub 5}]{sup −1} (M =  Ca, Be) clusters. At CCSD(T) level, these clusters have been confirmed to be superhalogens due to their high vertical electron detachment energies (VDE). The largest one is 9.70 eV for [Ca{sub 2}(CN){sub 5}]{sup −1} which is even higher than those of corresponding traditional structures based on fluorine or chlorine ligands. Therefore the superhalogens stronger than the traditional halogen-based structures could be realized by ligands other than halogen atoms. Compared with CCSD(T), outer valence Green’s function (OVGF) method either overestimates or underestimates the VDEs for different structures while MP2 results are generally consistent in the aspect of relative values. The extra electrons of the highest VDE anions here aggregate on the bridging CN units with non-negligible distribution occurring on other CN units too. These two features lower both the potential and kinetic energies of the extra electron respectively and thus lead to high VDE. Besides superhalogen properties, the structures, relative stabilities and thermodynamic stabilities with respect to the detachment of cyanide ligand were also investigated. The sum of these results identifies the potential of polynuclear structures with pseudohalogen ligand as suitable candidates with enhanced superhalogens properties.

  19. Are superhalogens without halogen ligand capable of transcending traditional halogen-based superhalogens? Ab initio case study of binuclear anions based on pseudohalogen ligand

    Directory of Open Access Journals (Sweden)

    Jin-Feng Li

    2015-06-01

    Full Text Available The superhalogen properties of polynuclear structures without halogen ligand are theoretically explored here for several [M2(CN5]−1 (M =  Ca, Be clusters. At CCSD(T level, these clusters have been confirmed to be superhalogens due to their high vertical electron detachment energies (VDE. The largest one is 9.70 eV for [Ca2(CN5]−1 which is even higher than those of corresponding traditional structures based on fluorine or chlorine ligands. Therefore the superhalogens stronger than the traditional halogen-based structures could be realized by ligands other than halogen atoms. Compared with CCSD(T, outer valence Green’s function (OVGF method either overestimates or underestimates the VDEs for different structures while MP2 results are generally consistent in the aspect of relative values. The extra electrons of the highest VDE anions here aggregate on the bridging CN units with non-negligible distribution occurring on other CN units too. These two features lower both the potential and kinetic energies of the extra electron respectively and thus lead to high VDE. Besides superhalogen properties, the structures, relative stabilities and thermodynamic stabilities with respect to the detachment of cyanide ligand were also investigated. The sum of these results identifies the potential of polynuclear structures with pseudohalogen ligand as suitable candidates with enhanced superhalogens properties.

  20. Modified Toepler pump for small-scale halogen-deuterium exchange reactions

    Energy Technology Data Exchange (ETDEWEB)

    Bindal, R.D.

    1987-04-06

    A modified version of the Toepler pump/microhydrogenator apparatus for the preparation of tritium labelled oestrogenic compounds using deuterium gas for halogen-tritium exchange, is described. The modifications allow the transferred gas to maintain atmospheric pressure during the course of the reaction and it allows small volumes of gas uptake to be followed. (U.K.).

  1. Preparation of an Ester-Containing Grignard Reagent by Halogen-Metal Exchange

    Science.gov (United States)

    Snider, Barry B.

    2015-01-01

    In this experiment, students carry out a halogen-metal exchange reaction of methyl 2-iodobenzoate with isopropylmagnesium chloride in THF at 0°C to afford 2-carbomethoxyphenylmagnesium chloride, which is treated with "p"-methoxybenzaldehyde to give a lactone (phthalide) product. This reaction introduces students to the modern method of…

  2. Stability, defect and electronic properties of graphane-like carbon-halogen compounds

    Institute of Scientific and Technical Information of China (English)

    Lu Di; Yang Yu-Rong; Xiao Yang; Zhang Xiao-Yu

    2011-01-01

    We perform first-principles total energy calculations to investigate the stabilities and the electronic structures of graphane-like structures of carbon-halogen compounds,where the hydrogen atoms in the graphane are substituted by halogen atoms.Three halogen elements,fluorine (F),chlorine (Cl) and bromine (Br),are considered,and the graphanelike structures are named as CF,CCl and CBr,respectively.It is found that for the single-atom adsorption,only the F adatom can be chemically adsorbed on the graphene.However,the stable graphane-like structures of CF,CCl and CBr can form due to the interaction between the halogen atoms.The carbon atoms in the stable CF,CCl and CBr compounds are in the sp3 hybridization,forming a hexagonal network similar to the graphane.The electronic band calculations show that CF and CCl are semiconductors with band gaps of 3.28 eV and 1.66 eV,respectively,while CBr is a metal.Moreover,the molecular dynamics simulation is employed to clarify the stabilities of CF and CCl.Those two compounds are stable at room temperature.A high temperature (≥ 1200 K) is needed to damage CF,while CCl is destroyed at 700 K.Furthermore,the effects of a vacancy on the structure and the electronic property of CF are discussed.

  3. New Route to Synthesize Surface Organometallic Complexes (SOMC): An Approach by Alkylating Halogenated Surface Organometallic Fragments

    KAUST Repository

    Hamieh, Ali Imad

    2017-02-01

    The aim of this thesis is to explore new simpler and efficient routes for the preparation of surface organometallic complexes (SOMC) for the transformation of small organic molecules to valuable products. The key element in this new route relies on surface alkylation of various halogenated surface coordination complexes or organometallic fragments (SOMF).

  4. Synthesis and photophysical properties of halogenated derivatives of (dibenzoylmethanato)boron difluoride

    Science.gov (United States)

    Kononevich, Yuriy N.; Surin, Nikolay M.; Sazhnikov, Viacheslav A.; Svidchenko, Evgeniya A.; Aristarkhov, Vladimir M.; Safonov, Andrei A.; Bagaturyants, Alexander A.; Alfimov, Mikhail V.; Muzafarov, Aziz M.

    2017-03-01

    A series of (dibenzoylmethanato)boron difluoride (BF2DBM) derivatives with a halogen atom in one of the phenyl rings at the para-position were synthesized and used to elucidate the effects of changing the attached halogen atom on the photophysical properties of BF2DBM. The room-temperature absorption and fluorescence maxima of fluoro-, chloro-, bromo- and iodo-substituted derivatives of BF2DBM in THF are red-shifted by about 2-10 nm relative to the corresponding peaks of the parent BF2DBM. The fluorescence quantum yields of the halogenated BF2DBMs (except the iodinated derivative) are larger than that of the unsubstituted BF2DBM. All the synthesized compounds are able to form fluorescent exciplexes with benzene and toluene (emission maxima at λem = 433 and 445 nm, respectively). The conformational structure and electronic spectral properties of halogenated BF2DBMs have been modeled by DFT/TDDFT calculations at the PBE0/SVP level of theory. The structure and fluorescence spectra of exciplexes were calculated using the CIS method with empirical dispersion correction.

  5. The pharmacology of halogenated salicylanilides and their anthelmintic use in animals : review article

    Directory of Open Access Journals (Sweden)

    G.E. Swan

    1999-07-01

    Full Text Available The halogenated salicylanilides are a large group of compounds developed mainly for their antiparasitic activity in animals. Several halogenated salicylanilides with potent antiparasitic activity have been synthesised of which only closantel, niclosamide, oxyclozanide, rafoxanide and resorantel are commercially available. Closantel and rafoxanide, which represent the most important drugs in the group, are used extensively for the control of Haemonchus spp. and Fasciola spp. infestations in sheep and cattle and Oestrus ovis in sheep in many parts of the world. Niclosamide is used extensively for its anticestodal activity in a wide range of animals. Antiparasitic activity of the halogenated salicylanilides has also been demonstrated against a large number of other internal parasites, in particular haematophagous helminths, and external parasites including ticks and mites, in a variety of animal species. Several cases of toxicity and mortality have been reported for closantel and rafoxanide in sheep and goats. Their unique pharmacokinetic behaviour appears to play an important role in the efficacy and safety of these compounds. The chemical and physical characteristics, mode of action, pharmacokinetics, antiparasitic activity and toxicity of the halogenated salicylanilides in animals are reviewed.

  6. [Degradation of halogenated compounds by haloalkane dehalogenase DadA from Alcanivorax dieselolei B-5 ].

    Science.gov (United States)

    Li, Anzhang; Shao, Zongze

    2014-09-04

    [OBJECTIVE] Alcanivorax dieselolei B-5 is an important oil-degrading bacterium. We studied its substrate range and degradation of halogenated compounds. [METHODS] Growth capability of B-5 was examined with different halogenated substrates as sole carbon source. A putative haloalkane dehalogenase (HLD) gene named dadA was found from the genome of strain B-5 and analyzed by sequence alignment, phylogenetic analysis and homologous modeling. After heterologous expression in Escherichia coli and purification, the activity of DadA towards 46 substrates was determined. [RESULTS] Strain B-5 was capable of utilizing various halogenated compounds (C3-C,8) as the sole carbon source. DadA had typical catalytic pentad residues of HLD-II subfamily, but it was independent from other members of this subfamily according to phylogenetic analysis. Activity assay showed that DadA has higher specificity and narrower substrate range than other characterized HLDs and it only showed activity toward 1,2,3-tribromopropane, 1,2-dibromo-3-chloropropane and 2,3-dichloroprop-1-ene among 46 tested substrates. [CONCLUSIONS] Strain B-5 and its HLD DadA can degrade halogenated aliphatic pollutants although.

  7. Polydiphenylamine/Zeolite Y composites and electrical conductivity responses toward halogenated hydrocarbons

    Directory of Open Access Journals (Sweden)

    Tharaporn Permpool

    2013-01-01

    Full Text Available Composites of polydiphenylamine (D-PDPA and zeolite Y with H+ as the cation (Y_H+ have been fabricated to be used as a sensing material towards non-halogenated and halogenated solvents (hexane, dichloromethane, 1, 2-dichloroethane, chloroform. These composites are toxic towards human and environment and are widely used as solvents in various industries. Polydiphenylamine, zeolite Y, and their composites are characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, particle size analysis, surface area, and pore size analysis. The effects of the Si/Al ratio, zeolite content, and vapor concentrations are investigated. The electrical conductivity sensitivity of the composites towards the solvents is higher than the pristine D-PDPA by ~1 order of magnitude. The composites can discriminate a non-halogenated solvent from halogenated solvents. They possess maximum electrical conductivity sensitivity values towards dichloromethane, but the composites do not respond to hexane. Generally, the sensitivity of the composites increases with increasing zeolite content and vapor concentration. The interactions between the composites and the vapors are investigated by FT-IR spectroscopy and UV-Vis spectroscopy. A mechanism for the interaction between the composites and the solvents is proposed.

  8. 21 CFR 700.15 - Use of certain halogenated salicylanilides as ingredients in cosmetic products.

    Science.gov (United States)

    2010-04-01

    ... ingredients in cosmetic products. 700.15 Section 700.15 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.15 Use of certain halogenated salicylanilides as ingredients in cosmetic products....

  9. Inhibition of quorum sensing in Pseudomonas aeruginosa biofilm bacteria by a halogenated furanone compound

    DEFF Research Database (Denmark)

    Hentzer, Morten; Riedel, K.; Rasmussen, Thomas Bovbjerg

    2002-01-01

    ). Gfp-based reporter technology has been applied for non-destructive, single-cell-level detection of quorum sensing in laboratory-based P. aeruginosa biofilms. It is reported that a synthetic halogenated furanone compound, which is a derivative of the secondary metabolites produced by the Australian...

  10. Protecting-group-free amination of halogenated nitrobenzaldehyde with palladium catalyst

    Institute of Scientific and Technical Information of China (English)

    Jing Cao; Jun Xiang Feng; Yong Xiang Wu; Ya Ya Tuo

    2010-01-01

    One-step method for the synthesis of secondary aliphatic amine substituted nitrobenzaldehyde was developed.In the presence of Pd catalyst,halogenated nitrobenzaldehyde could be smoothly coupled with secondary aliphatic amine to give the target product in hexamethylphosphamide (HMPT) media without the protection of aldehyde groups.

  11. Request for Correction 11001 Toxicological Review of Halogenated Platinum Salts and Platinum Compounds

    Science.gov (United States)

    Request for Correction by the International Platinum Group Metals Association seeking the correction of information disseminated in the draft EPA document Toxicological Review of Halogenated Platinum Salts and Platinum Compounds: In Support of Summary Information on the Integrated Risk Information System (IRIS).

  12. Tumour radiosensitization with the halogenated pyrimidines 5'-bromo-and 5'-iododeoxyuridine

    Energy Technology Data Exchange (ETDEWEB)

    Epstein, A.H.; Cook, J.A.; Goffman, T. (National Cancer Inst., Bethesda, MD (United States)); Glatstein, E. (Texas Univ., Dallas, TX (United States). Southwestern Medical Center)

    1993-02-01

    The authors review studies of the use of iododeoxyuridine (IdUrd) and bromodeoxyuridine as radiosensitizers and attempt to correlate the clinical outcome for patients treated with radiation and IdUrd with the extent of halogenated pyrimidine cellular uptake and incorporation. (U.K.).

  13. Free Radical Halogenation, Selectivity, and Thermodynamics: The Polanyi Principle and Hammond's Postulate

    Science.gov (United States)

    Scala, Alfred A.

    2004-01-01

    The underlying ideas of the Polanyi principle and Hammond's postulate in relation to the simple free halogenation reactions and their selectivity and thermodynamics is presented. The results indicate that the chlorine atom exhibits a slightly less selectivity in the liquid phase as compared to in the gas phase.

  14. Halogen-free ionic liquids and their utilization as cellulose solvents

    Science.gov (United States)

    Gräsvik, John; Eliasson, Bertil; Mikkola, Jyri-Pekka

    2012-11-01

    This work demonstrates a novel synthesis route to halogen-free ionic liquids. A one-pot synthetic reaction route avoiding the use of toxic and high-energetic alkyl halides was developed to reduce the environmental impact of the synthesis process of ionic liquids. However, the elimination of halogens and alkyl halides in the preparation of ionic liquids is not just an environmental issue: the aforementioned species are also among the most common and persistent contaminants in today's Ionic Liquids (ILs). Thus, this paper introduces a range of quaternized nitrogen based ionic liquids, including both aromatic and non-aromatic components, all prepared without alkyl halides in any step of the process. Moreover, bio-renewable precursors such as (bio-)alcohols and carboxylic acids were employed as anion sources and alkylation media, thus avoiding halogen contamination or halogen-containing anions. The IL's prepared were designed to dissolve cellulose, some of which was included in a cellulose dissolution study using a sulphite cellulose from the company Domsjö.

  15. Mean ozone and water vapour height profiles for Southern hemisphere region using radiosonde or ozonesonde and haloe satelite data

    CSIR Research Space (South Africa)

    Sivakumar, V

    2009-01-01

    Full Text Available The aim of this work is to construct a model (mean) profile for ozone and water vapor in Southern hemisphere latitude using 14 years (1993-2006) of Halogen Occultation Experiment (HALOE) satellite data and about 10 years (1998-2007) of the Southern...

  16. Extending Halogen-based Medicinal Chemistry to Proteins: IODO-INSULIN AS A CASE STUDY.

    Science.gov (United States)

    El Hage, Krystel; Pandyarajan, Vijay; Phillips, Nelson B; Smith, Brian J; Menting, John G; Whittaker, Jonathan; Lawrence, Michael C; Meuwly, Markus; Weiss, Michael A

    2016-12-30

    Insulin, a protein critical for metabolic homeostasis, provides a classical model for protein design with application to human health. Recent efforts to improve its pharmaceutical formulation demonstrated that iodination of a conserved tyrosine (Tyr(B26)) enhances key properties of a rapid-acting clinical analog. Moreover, the broad utility of halogens in medicinal chemistry has motivated the use of hybrid quantum- and molecular-mechanical methods to study proteins. Here, we (i) undertook quantitative atomistic simulations of 3-[iodo-Tyr(B26)]insulin to predict its structural features, and (ii) tested these predictions by X-ray crystallography. Using an electrostatic model of the modified aromatic ring based on quantum chemistry, the calculations suggested that the analog, as a dimer and hexamer, exhibits subtle differences in aromatic-aromatic interactions at the dimer interface. Aromatic rings (Tyr(B16), Phe(B24), Phe(B25), 3-I-Tyr(B26), and their symmetry-related mates) at this interface adjust to enable packing of the hydrophobic iodine atoms within the core of each monomer. Strikingly, these features were observed in the crystal structure of a 3-[iodo-Tyr(B26)]insulin analog (determined as an R6 zinc hexamer). Given that residues B24-B30 detach from the core on receptor binding, the environment of 3-I-Tyr(B26) in a receptor complex must differ from that in the free hormone. Based on the recent structure of a "micro-receptor" complex, we predict that 3-I-Tyr(B26) engages the receptor via directional halogen bonding and halogen-directed hydrogen bonding as follows: favorable electrostatic interactions exploiting, respectively, the halogen's electron-deficient σ-hole and electronegative equatorial band. Inspired by quantum chemistry and molecular dynamics, such "halogen engineering" promises to extend principles of medicinal chemistry to proteins.

  17. Comparison of halogen light and vibroacoustic stimulation on nonreactive fetal heart rate pattern.

    Science.gov (United States)

    Rahimikian, Fatemeh; Rahiminia, Tahereh; Modarres, Maryam; Mehran, Abbas

    2013-03-01

    One of the first-line assessment tools for fetal surveillance is nonstress test (NST), although it is limited by a high rate of false-nonreactive results. This study was performed to investigate if external stimulation from vibroacoustic and halogen light could help in provoking fetal responsiveness and altering NST results. This is a clinical trial. Sampling was done from April to July 2010. One hundred pregnant women with nonreactive NST for 20 min were allocated in two groups: Vibroacoustic stimulated NST (VNST, n = 50) who received vibration from a standard fetal vibratory stimulator and halogen light stimulated NST (LNST, n = 50) who received a halogen light source for 3 and 10 sec, respectively. Results were compared together and then compared to biophysical profile (BPP) scores as a backup test. We used Mann-Whitney U test, Chi-square test, and Fisher's exact test to compare the variables in the two groups through SPSS version 14. P stimulations, 68% nonreactive subjects in halogen light stimulation group and 62% in vibroacoustic stimulation group changed to reactive patterns. Time to onset of the first acceleration (VNST: 2.17 min; LNST: 2.27 min) and the test duration (VNST: 4.91 min; LNST: 5.26 min) were the same in the two groups. In VNST 89.5% and in LNST 87.5% of nonreactivity followed by score 8 in BPP. There was no significant relation between stimulus NSTs and BPPs. Vibroacoustic and light stimulation offer benefits by decreasing the incidence of nonreactive results and reducing the test time. Both halogen light stimulation and vibroacoustic stimulation are safe and efficient in fetal well-being assessment services.

  18. Theoretical study on O$\\cdots$Br and O$\\cdots$Cl halogen bonds in some small model molecular systems

    Indian Academy of Sciences (India)

    Damanjit Kaur; Rajinder Kaur

    2014-11-01

    Halogen bonding interactions of type X$\\cdots$O=C are important in various fields including biological systems. In this work, theoretical calculations were carried out using B3LYP/6-31++G∗∗, MP2/6-31++G∗∗ and MP2/aug-cc-pVDZ methods on a series of O$\\cdots$X halogen bonds between CH2O andCH3CHO as halogen bond acceptor with X-Y (X = Cl, Br; Y = CF3, CF2 H, CFH2, CN, CCH, CCCN) as halogen bond donors. The strength of interaction energy for O$\\cdots$Br halogen-bonded complexes varies from −2.16 to −5.26 kcal/mol while for O$\\cdots$Cl complexes, it is between −1.65 to −3.67 kcal/mol, which indicate the O$\\cdots$Br bond to be stronger in comparison to O$\\cdots$Cl bond. SAPT analysis suggests that the strength of halogen bonding arises from the electrostatic and induction forces while dispersion is playing a comparatively smaller role. The halogen-bonded interaction energies were found to correlate well with positive electrostatic potential VS,max, halogen bonded distances, and the change in s-character of C-X bond. The halogen-bonded interaction energies were also evaluated for O$\\cdots$I bonded complexes and thus these complexes were found to be stronger than O$\\cdots$Br and O$\\cdots$Cl bonded complexes.

  19. Monomer conversion of composite dental resins photoactivated by a halogen lamp and a LED: a FT-Raman spectroscopy study

    Directory of Open Access Journals (Sweden)

    Luís Eduardo Silva Soares

    2005-03-01

    Full Text Available Eighteen circular blocks of resins cured either by a LED or a halogen lamp (20, 40 and 60 s, had their top (T and bottom (B surfaces studied using a FT-Raman spectrometer. Systematic changes in the intensity of the methacrylate C=C stretching mode at 1638 cm-1 as a function of exposure duration were observed. The calculated degree of conversion (DC ranged from 45.0% (B to 52.0% (T and from 49.0% (B to 55.0% (T for the LED and halogen lamp, respectively. LED and halogen light produced similar DC values with 40 and 60 s of irradiation.

  20. Halonium ion mediated synthesis of 2-halomethylene-3-oxoketoxime derivatives from isoxazoline N-oxides.

    Science.gov (United States)

    Raihan, Mustafa J; Rajawinslin, R R; Kavala, Veerababurao; Kuo, Chun-Wei; Kuo, Ting-Shen; He, Chiu-Hui; Huang, Hsiu-Ni; Yao, Ching-Fa

    2013-09-06

    A protocol for the N-bromosuccinimide (NBS)- and trichloroisocyanuric acid (TCCA)-mediated synthesis of novel 2-halomethylene-3-oxoketoximes via one-pot halogenation/oxidation of isoxazoline N-oxide derivatives is described here. The keto functionality of 3-ketoximes was selectively reduced by lithiumaluminum hydride to synthesize an unprecedented type of Baylis-Hillman oxime, which underwent N-O coupling to produce new isoxazoline N-oxide derivative.

  1. The detection of some halogenated phenols and nitrophenols in thin-layer chromatography by means of bromine

    NARCIS (Netherlands)

    Tadema, G.; Batelaan, P.H.

    1968-01-01

    A method is described for the detection of halogeno- and nitro-phenols in sub-microgram quantities. Theses compounds are made visible by exposure of the developed thin layer plates to bromine vapour and subsequent spraying with an aqueous solution of potassium iodide or an ethanolic solution of fluo

  2. The detection of some halogenated phenols and nitrophenols in thin-layer chromatography by means of bromine

    NARCIS (Netherlands)

    Tadema, G.; Batelaan, P.H.

    1968-01-01

    A method is described for the detection of halogeno- and nitro-phenols in sub-microgram quantities. Theses compounds are made visible by exposure of the developed thin layer plates to bromine vapour and subsequent spraying with an aqueous solution of potassium iodide or an ethanolic solution of

  3. Effect of catalysts in the quality of syngas and by-products obtained by co-gasification of coal and wastes. 2: Heavy metals, sulphur and halogen compounds abatement

    Energy Technology Data Exchange (ETDEWEB)

    Filomena Pinto; Helena Lopes; Rui Neto Andre; I. Gulyurtlu; I. Cabrita [INETI-DEECA, Lisbon (Portugal)

    2008-06-15

    This paper analyses the formation of sulphur and halogens compounds during co-gasification of low grade coals with different types of wastes that include: pine, petcoke and polyethylene (PE) with the aim of taking profit of waste energy value with the smallest possible impact on the environment. The influence of different types of catalysts or sorbents was studied: calcined dolomite, dolomite enriched with nickel, olivine, nickel and magnesium oxides, zinc oxide and cobalt and molybdenum oxides. The presence of dolomite led to the lowest HCl, HF and H{sub 2}S concentrations in the syngas produced. ZnO also gave rise to significant decrease in H{sub 2}S concentration, though higher concentrations were obtained than those with dolomite. It was found that when catalysts or sorbents were used, a significant fraction of sulphur, halogens and heavy metals were trapped in the solid residue left behind in the bed and cyclone. Higher temperatures increased the volatility of some metals and sulphur. Leachability assays of solids showed that small quantities of SO{sub 4}{sup 2-} and Cl{sup -} could be released and most metals were not leachable, although the use of dolomite slightly increased metals leachability, because of the higher alkaline nature of residual solids produced. 27 refs., 10 figs., 5 tabs.

  4. Organic halogenated contaminants in mother-fetus pairs of harbor seals (Phoca vitulina richardii) from Alaska, 2000-2002

    Science.gov (United States)

    Environmental stressors may interfere with foraging, survival and reproduction of marine mammals resulting in marine mammal population decline. In this study, organic halogenated pollutants [OHs, including organochlorine pesticides, polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCN...

  5. Investigations into the nature of halogen- and hydrogen-bonding interactions of some heteroaromatic rings with dichlorine monoxide.

    Science.gov (United States)

    Wu, Junyong

    2014-09-01

    We have studied the structures, properties, and nature of halogen- and hydrogen-bonding interactions between some heteroaromatic rings (C(5)H(5)N, C(4)H(4)O, and C(4)H(4)S) with Cl(2)O at the MP2/aug-cc-pVTZ level. We also considered the solvent effect on the halogen bonds and hydrogen bonds in the C(5)H(5)N-Cl(2)O complexes and found that the solvent has a weakening effect on the π-type halogen bond and hydrogen bond but a prominent enhancing effect on σ-type halogen bond. The complexes have also been analyzed with symmetry adapted perturbation theory method (SAPT).

  6. Degradation of 5-FU by means of advanced (photo)oxidation processes: UV/H2O2, UV/Fe2+/H2O2 and UV/TiO2--Comparison of transformation products, ready biodegradability and toxicity.

    Science.gov (United States)

    Lutterbeck, Carlos Alexandre; Wilde, Marcelo Luís; Baginska, Ewelina; Leder, Christoph; Machado, Ênio Leandro; Kümmerer, Klaus

    2015-09-15

    The present study investigates the degradation of the antimetabolite 5-fluorouracil (5-FU) by three different advanced photo oxidation processes: UV/H2O2, UV/Fe(2+)/H2O2 and UV/TiO2. Prescreening experiments varying the H2O2 and TiO2 concentrations were performed in order to set the best catalyst concentrations in the UV/H2O2 and UV/TiO2 experiments, whereas the UV/Fe(2+)/H2O2 process was optimized varying the pH, Fe(2+) and H2O2 concentrations by means of the Box-Behnken design (BBD). 5-FU was quickly removed in all the irradiation experiments. The UV/Fe(2+)/H2O2 and UV/TiO2 processes achieved the highest degree of mineralization, whereas the lowest one resulted from the UV/H2O2 treatment. Six transformation products were formed during the advanced (photo)oxidation processes and identified using low and high resolution mass spectrometry. Most of them were formed and further eliminated during the reactions. The parent compound of 5-FU was not biodegraded, whereas the photolytic mixture formed in the UV/H2O2 treatment after 256 min showed a noticeable improvement of the biodegradability in the closed bottle test (CBT) and was nontoxic towards Vibrio fischeri. In silico predictions showed positive alerts for mutagenic and genotoxic effects of 5-FU. In contrast, several of the transformation products (TPs) generated along the processes did not provide indications for mutagenic or genotoxic activity. One exception was TP with m/z 146 with positive alerts in several models of bacterial mutagenicity which could demand further experimental testing. Results demonstrate that advanced treatment can eliminate parent compounds and its toxicity. However, transformation products formed can still be toxic. Therefore toxicity screening after advanced treatment is recommendable.

  7. Syntheses of halogen derivatives of L-tryptophan, L-tyrosine and L-phenylalanine labeled with hydrogen isotopes.

    Science.gov (United States)

    Pająk, Małgorzata; Pałka, Katarzyna; Winnicka, Elżbieta; Kańska, Marianna

    2016-01-01

    Halogenated, labeled with tritium and doubly with deuterium and tritium, derivatives of L-tryptophan, i.e. 5'-bromo-[2-(3)H]-, 5'-bromo-[2-(2)H/(3)H]-, 5'-fluoro-[2-(3)H]-5'-fluoro-[2-(2)H/(3)H]-, 6'-fluoro-[2-(3)H]-, 6'-fluoro-[2-(2)H/(3)H]-L-tryptophan, as well as, L-tyrosine, i.e. 3'-fluoro-[2-(3)H]-, 3'-fluoro-[2-(2)H/(3)H]-, 3'-chloro-[2-(3)H]-, and 3'-chloro-[2-(2)H/(3)H]-L-tyrosine, and also L-phenylalanine, i.e. 2'-fluoro-[(3S)-(3)H]-, 2'-fluoro-[(3S)-(2)H/(3) H]-, 2'-chloro-[(3S)-(3)H]-, 2'-chloro-[(3S)-(2)H/(3)H]-, 4'-chloro-[(3S)-(3)H]-, and 4'-chloro-[(3S)-(2)H/(3)H]-L-phenylalanine were synthesized using enzymatic methods. Isotopomers of L-tryptophan were synthesized by coupling of halogenated indoles with S-methyl-L-cysteine carried out in deuteriated or tritiated incubation media. Labeled halogenated derivatives of L-tyrosine were obtained by the enzymatically supported exchange between halogenated L-tyrosine and isotopic water. Labeled halogenated isotopologues of L-Phe were synthesized by the enzymatic addition of ammonia to halogenated cinnamic acid. As a source of hydrogen tritiated water (HTO) and heavy water (D2O) with addition of HTO were used.

  8. Brønsted Acidic Ionic Liquid Accelerated Halogenation of Organic Compounds with N-Halosuccinimides (NXS

    Directory of Open Access Journals (Sweden)

    Stojan Stavber

    2012-12-01

    Full Text Available The Brønsted-acidic ionic liquid 1-methyl-3-(4-sulfobutylimidazolium triflate [BMIM(SO3H][OTf] was demonstrated to act efficiently as solvent and catalyst for the halogenation of activated organic compounds with N-halosuccinimides (NXS under mild conditions with short reaction times. Methyl aryl ketones were converted into α-halo and α,α-dihaloketones, depending on the quantity of NXS used. Ketones with activated aromatic rings were selectively halogenated, however in some cases mixtures of α-halogenated ketone and ring-halogenated ketones were obtained. Activated aromatics were regioselectively ring halogenated to give mono- and dihalo-substituted products. The [BMIM(SO3H][OTf] ionic liquid (IL-A was successfully reused eight times in a representative monohalogenation reaction with no noticeable decrease in efficiency. An effective halogenation scale-up in this IL is also presented. The reactivity trend and the observed chemo- and regioselectiivities point to an ET process in these IL-promoted halofunctionalization reactions.

  9. Brønsted acidic ionic liquid accelerated halogenation of organic compounds with N-Halosuccinimides (NXS).

    Science.gov (United States)

    Vražič, Dejan; Jereb, Marjan; Laali, Kenneth K; Stavber, Stojan

    2012-12-21

    The Brønsted-acidic ionic liquid 1-methyl-3-(4-sulfobutyl)imidazolium triflate [BMIM(SO(3)H)][OTf] was demonstrated to act efficiently as solvent and catalyst for the halogenation of activated organic compounds with N-halosuccinimides (NXS) under mild conditions with short reaction times. Methyl aryl ketones were converted into α-halo and α,α-dihaloketones, depending on the quantity of NXS used. Ketones with activated aromatic rings were selectively halogenated, however in some cases mixtures of α-halogenated ketone and ring-halogenated ketones were obtained. Activated aromatics were regioselectively ring halogenated to give mono- and dihalo-substituted products. The [BMIM(SO(3)H)][OTf] ionic liquid (IL-A) was successfully reused eight times in a representative monohalogenation reaction with no noticeable decrease in efficiency. An effective halogenation scale-up in this IL is also presented. The reactivity trend and the observed chemo- and regioselectiivities point to an ET process in these IL-promoted halofunctionalization reactions.

  10. Impact of wastewater infrastructure upgrades on the urban water cycle: Reduction in halogenated reaction byproducts following conversion from chlorine gas to ultraviolet light disinfection

    Energy Technology Data Exchange (ETDEWEB)

    Barber, Larry B. [U.S. Geological Survey, 3215 Marine St., Boulder, CO 80303 (United States); Hladik, Michelle L. [U.S. Geological Survey, 6000 J Street Placer Hall, Sacramento, CA 95819 (United States); Vajda, Alan M. [University of Colorado, Department of Integrative Biology, CB 171, Denver, CO 80217 (United States); Fitzgerald, Kevin C. [U.S. Geological Survey, 3215 Marine St., Boulder, CO 80303 (United States); AECOM, 500 West Jefferson St., Ste. 1600, Louisville, KY 40202 (United States); Douville, Chris [City of Boulder, 4049 75th Street, Boulder, CO 80301 (United States)

    2015-10-01

    The municipal wastewater treatment facility (WWTF) infrastructure of the United States is being upgraded to expand capacity and improve treatment, which provides opportunities to assess the impact of full-scale operational changes on water quality. Many WWTFs disinfect their effluent prior to discharge using chlorine gas, which reacts with natural and synthetic organic matter to form halogenated disinfection byproducts (HDBPs). Because HDBPs are ubiquitous in chlorine-disinfected drinking water and have adverse human health implications, their concentrations are regulated in potable water supplies. Less is known about the formation and occurrence of HDBPs in disinfected WWTF effluents that are discharged to surface waters and become part of the de facto wastewater reuse cycle. This study investigated HDBPs in the urban water cycle from the stream source of the chlorinated municipal tap water that comprises the WWTF inflow, to the final WWTF effluent disinfection process before discharge back to the stream. The impact of conversion from chlorine-gas to low-pressure ultraviolet light (UV) disinfection at a full-scale (68,000 m{sup 3} d{sup −1} design flow) WWTF on HDBP concentrations in the final effluent was assessed, as was transport and attenuation in the receiving stream. Nutrients and trace elements (boron, copper, and uranium) were used to characterize the different urban source waters, and indicated that the pre-upgrade and post-upgrade water chemistry was similar and insensitive to the disinfection process. Chlorinated tap water during the pre-upgrade and post-upgrade samplings contained 11 (mean total concentration = 2.7 μg L{sup −1}; n = 5) and 10 HDBPs (mean total concentration = 4.5 μg L{sup −1}), respectively. Under chlorine-gas disinfection conditions 13 HDBPs (mean total concentration = 1.4 μg L{sup −1}) were detected in the WWTF effluent, whereas under UV disinfection conditions, only one HDBP was detected. The chlorinated WWTF effluent had

  11. Survey of reproductive hazards among oil, chemical, and atomic workers exposed to halogenated hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Savitz, D.A.; Harley, B.; Krekel, S.; Marshall, J.; Bondy, J.; Orleans, M.

    1984-01-01

    Several halogenated hydrocarbons are suspected of causing adverse reproductive effects. Because of such concerns, the Oil, Chemical, and Atomic Workers International Union surveyed the reproductive histories of two groups of workers. One group worked at plants engaged in the production or use of halogenated hydrocarbons (exposed) whereas the others had no such opportunity for exposure (nonexposed). Although a low response rate precludes firm conclusions, the 1,280 completed questionnaires provide useful data for generating hypotheses in this developing field of interest. A history of diagnosed cancer was reported more frequently among exposed workers. The infant mortality rate was also significantly elevated among the offspring of exposed workers. No risk gradient was observed for episodes of infertility, fetal loss, congenital defects, or low-birthweight offspring. Concerns with nonresponse, exposure characterization, possible confounding factors, and limited statistical power are addressed. The results provide further suggestions which help to direct studies of occupational reproductive risks.

  12. Effect of phenol and halogenated phenols on energy transfer reactions of rat liver mitochondria.

    Directory of Open Access Journals (Sweden)

    Izushi,Fumio

    1988-02-01

    Full Text Available The in vitro effects of phenol and p-halogenated phenols on mitochondrial energy transfer reactions were examined using isolated rat liver mitochondria. The relationship between physiochemical properties of phenolic compounds and their effects on mitochondria were studied. Phenol and p-halogenated phenols induced the release of K+ ions from mitochondria, suggesting a change in permeability to K+ ions. A decrease in the respiratory control index, an increase in K+ release and stimulation of latent ATPase activity were observed with these compounds in the descending order of p-iodophenol, p-bromophenol, p-chlorophenol, p-fluorophenol and phenol. The concentrations of the phenolic compounds resulting in fifty percent inhibition of the respiratory control index and those resulting in fifty percent release of K+ ions significantly correlated with Hammett's substituent constant (sigma and the hydrophobic binding constant (pi of the compounds.

  13. Halogenated furanones inhibit quorum sensing through accelerated LuxR turnover

    DEFF Research Database (Denmark)

    Manefield, Michael; Rasmussen, Thomas Bovbjerg; Henzter, Morten

    2002-01-01

    N-acyl-L-homoserine lactones (AHLs) are co-regulatory ligands required for control of the expression of genes encoding virulence traits in many Gram-negative bacterial species. Recent studies have indicated that AHLs modulate the cellular concentrations of LuxR-type regulatory proteins by binding...... and fortifying these proteins against proteolytic degradation (Zhu & Winans, 2001 ). Halogenated furanones produced by the macroalga Delisea pulchra inhibit AHL-dependent gene expression. This study assayed for an in vivo interaction between a tritiated halogenated furanone and the LuxR protein of Vibrio...... furanones modulate LuxR activity but act to destabilize, rather than protect, the AHL-dependent transcriptional activator. The furanone-dependent reduction in the cellular concentration of the LuxR protein was associated with a reduction in expression of a plasmid encoded P(luxI)-gfp(ASV) fusion suggesting...

  14. Halogenated furanones inhibit quorum sensing through accelerated LuxR turnover

    DEFF Research Database (Denmark)

    Manefield, M.; Rasmussen, Thomas Bovbjerg; Henzter, M.

    2002-01-01

    N-acyl-L-homoserine lactones (AHLs) are co-regulatory ligands required for control of the expression of genes encoding virulence traits in many Gram-negative bacterial species. Recent studies have indicated that AHLs modulate the cellular concentrations of LuxR-type regulatory proteins by binding...... and fortifying these proteins against proteolytic degradation (Zhu & Winans, 2001). Halogenated furanones produced by the macroallga Delisea pulchra inhibit AHL-dependent gene expression. This study assayed for an in vivo interaction between a tritiated halogenated furanone and the LuxR protein of Vibrio...... furanones modulate LuxR activity but act to destabilize, rather than protect, the AHL-dependent transcriptional activator. The furanone-dependent reduction in the cellular concentration of the LuxR protein was associated with a reduction in expression of a plasmid encoded P-luxl-gfp(ASV) fusion suggesting...

  15. Harnessing the Potential of Halogenated Natural Product Biosynthesis by Mangrove-Derived Actinomycetes

    Directory of Open Access Journals (Sweden)

    Xiang Xiao

    2013-10-01

    Full Text Available Mangrove-derived actinomycetes are promising sources of bioactive natural products. In this study, using homologous screening of the biosynthetic genes and anti-microorganism/tumor assaying, 163 strains of actinomycetes isolated from mangrove sediments were investigated for their potential to produce halogenated metabolites. The FADH2-dependent halogenase genes, identified in PCR-screening, were clustered in distinct clades in the phylogenetic analysis. The coexistence of either polyketide synthase (PKS or nonribosomal peptide synthetase (NRPS as the backbone synthetases in the strains harboring the halogenase indicated that these strains had the potential to produce structurally diversified antibiotics. As a validation, a new enduracidin producer, Streptomyces atrovirens MGR140, was identified and confirmed by gene disruption and HPLC analysis. Moreover, a putative ansamycin biosynthesis gene cluster was detected in Streptomyces albogriseolus MGR072. Our results highlight that combined genome mining is an efficient technique to tap promising sources of halogenated natural products synthesized by mangrove-derived actinomycetes.

  16. Comparative computational study of model halogen-bonded complexes of FKrCl.

    Science.gov (United States)

    Joseph, Jerelle A; McDowell, Sean A C

    2015-03-19

    Quantum chemical calculations for the FKrCl molecule at various levels of theory were performed and suggest that this molecule is metastable and may be amenable to experimental synthesis under cryogenic conditions. The FKrCl molecule forms weak halogen-bonded complexes FKrCl···Y with small molecules like FH and H2O and its computed properties were compared with those for analogous complexes of its precursor, FCl, and its rare gas hydride counterpart, FKrH. The cooperative effect of additional noncovalent interactions introduced at the F atom in the FKrCl···Y dimer (to give Z···FKrCl···Y trimers) showed a general strengthening of the intermolecular interactions in the order halogen bond < hydrogen bond < beryllium bond < lithium bond.

  17. Structure-activity relationship of dopaminergic halogenated 1-benzyl-tetrahydroisoquinoline derivatives.

    Science.gov (United States)

    El Aouad, Noureddine; Berenguer, Inmaculada; Romero, Vanessa; Marín, Paloma; Serrano, Angel; Andujar, Sebastián; Suvire, Fernando; Bermejo, Almudena; Ivorra, M Dolores; Enriz, Ricardo D; Cabedo, Nuria; Cortes, Diego

    2009-11-01

    Two series of halogenated 1-benzyl-7-chloro-6-hydroxy-tetrahydroisoquinolines were prepared to explore the influence of each series on the affinity for dopamine receptors. All the compounds displayed a high affinity for D(1)-like and/or D(2)-like dopamine receptors in striatal membranes, although they were unable to inhibit [(3)H]-dopamine uptake in striatal synaptosomes. The halogen placed on the benzylic ring in 1-benzyl-THIQs, compounds of the series 1, 2'-bromobenzyl derivatives with K(i) values into the nanomolar range, and the series 2, 2',4'-dichlorobenzyl-THIQ homologues, proves to be an important factor to modulate affinity at dopamine receptor.

  18. A 19F NMR study of C-I....pi- halogen bonding

    DEFF Research Database (Denmark)

    Hauchecorne, Dieter; vand er Veken, Benjamin J.; Herrebout, Wouter A.

    2011-01-01

    The formation of halogen bonded complexes between toluene-d8 and the perfluoroiodopropanes 1-C3F7I and 2-C3F7I has been investigated using 19F NMR spectroscopy. For both Lewis acids, evidence was found for the formation of a C–I⋯π halogen bonded complex. The complex formed is a 1:1 type. Using...... spectra recorded at different temperatures, the complexation enthalpies and entropies for the complexes were determined to be −2.9(1) kJ mol−1 and −19.1(2) J K−1 mol−1 for the 2-C3F7I⋅toluene-d8 complex and −2.7(1) kJ mol−1 and −16.0(4) K−1 mol−1 for the 1-C3F7I⋅toluene-d8 complex. The experimental...

  19. Conformational equilibrium of phenylacetic acid and its halogenated analogues through theoretical studies, NMR and IR spectroscopy

    Science.gov (United States)

    Levandowski, Mariana N.; Rozada, Thiago C.; Melo, Ulisses Z.; Basso, Ernani A.; Fiorin, Barbara C.

    2017-03-01

    This paper presents a study on the conformational preferences of phenylacetic acid (PA) and its halogenated analogues (FPA, CPA, BPA). To clarify the effects that rule these molecules' behaviour, theoretical calculations were used, for both the isolated phase and solution, combined with nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. Most conformations of phenylacetic acid and its halogenated derivatives are stabilized through the hyperconjugative effect, which rules the conformational preference. NMR analyses showed that even with the variation in medium polarity, there was no significant change in the conformation population. Infrared spectroscopy showed similar results for all compounds under study. In most spectra, two bands were found through the carbonyl deconvolution, which is in accordance with the theoretical data. It was possible to prove that variation in the nature of the substituent in the ortho position had no significant influence on the conformational equilibrium.

  20. Volatile organic compound ratios as probes of halogen atom chemistry in the Arctic

    Directory of Open Access Journals (Sweden)

    P. B. Shepson

    2008-03-01

    Full Text Available Volatile organic compound concentration ratios can be used as indicators of halogen chemistry that occurs during ozone depletion events in the Arctic during spring. Here we use a combination of modeling and measurements of [acetone]/[propanal] as an indicator of bromine chemistry, and [isobutane]/[n-butane] and [methyl ethyl ketone]/[n-butane] are used to study the extent of chlorine chemistry during four ozone depletion events during the Polar Sunrise Experiment of 1995. Using a 0-D photochemistry model in which the input of halogen atoms is controlled and varied, the approximate ratio of [Br]/[Cl] can be estimated for each ozone depletion event. It is concluded that there must be an additional source of propanal (likely from the snowpack to correctly simulate the VOC chemistry of the Arctic, and further evidence that the ratio of Br atoms to Cl atoms can vary greatly during ozone depletion events is presented.

  1. Volatile organic compound ratios as probes of halogen atom chemistry in the Arctic

    Directory of Open Access Journals (Sweden)

    A. E. Cavender

    2007-08-01

    Full Text Available Volatile organic compound concentration ratios can be used as indicators of halogen chemistry that occurs during ozone depletion events in the Arctic during spring. Here we use a combination of modeling and measurements of [acetone]/[propanal] as an indicator of bromine chemistry, and [isobutane]/[n-butane] and [methyl ethyl ketone]/[n-butane] are used to study the extent of chlorine chemistry during four ozone depletion events during the Polar Sunrise Experiment of 1995. Using a 0-D photochemistry model in which the input of halogen atoms is controlled and varied, the approximate ratio of [Br]/[Cl] can be estimated for each ozone depletion event. It is concluded that there must be an additional source of propanal (likely from the snowpack to correctly simulate the VOC chemistry of the Arctic, and that the ratio of Br atoms to Cl atoms can vary greatly during ozone depletion events.

  2. The chemistry of halogens on diamond: effects on growth and electron emission

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, W.L.; Pan, L.S.; Brown, L.A. [Sandia National Labs., Livermore, CA (United States)] [and others

    1997-02-01

    Diamond growth using halogenated precursors was studied in several diamond growth reactors. In a conventionao plasma reactor, diamond growth using the following gas mixtures was studied: CF{sub 4}/H{sub 2}, CH{sub 4}/H{sub 2}, CH{sub 3}F/H{sub 2}, and CH{sub 3}CL/H{sub 2}. Both the diamond growth measurements demonstrated ineffective transport of halogen radicals to the diamond surface during the growth process. In order to transport radical halogen species to the diamond surface during growth, a flow-tube reactor was constructed which minimized gas phase reactions. Also, the flow-tube reactor enabled pulsed gs transport to the diamond surface by fast-acting valves. Molecular beam mass spectroscopy was used to find condition which resulted in atomic hydrogen and/or atomic fluorine transport to the growing diamond surface. Although such conditions were found, they required very low pressures (0.5 Torr and below); these low pressures produce radical fluxes which are too low to sustain a reasonable diamond growth rate. The sequential reactor at Stanford was modified to add a halogen-growth step to the conventinoal atomic hydrogen/atomic carbon diamond growth cycle. Since the atomic fluorine, hydrogen and carbon environments are independent in the sequential reactor, the effect of fluorine on diamond growth could be studied independently of gas phase reactions. Although the diamond growth rate was increased by the use of fluorine, the film quality was seen to deteriorate as well as the substrate surface. Moreover, materials incompatibilities with fluorine significantly limited the use of fluorine in this reactor. A diamond growth model incorporating both gas phase and surface reactions was developed for the halocarbon system concurrent with the film growth efforts. In this report, we review the results of the growth experiments, the modeling, and additional experiments done to understand fluorine with diamond surfaces.

  3. Halogen bonded supramolecular capsules: a challenging test case for quantum chemical methods.

    Science.gov (United States)

    Sure, Rebecca; Grimme, Stefan

    2016-08-02

    Recently, Diederich et al. synthesized the first supramolecular capsule with a well-defined four-point halogen bonding interaction [Angew. Chem., Int. Ed., 2015, 54, 12339]. This interesting system comprising about 400 atoms represents a challenging test case for accurate quantum chemical methods. We investigate it with our new density functional based composite method for structures and noncovalent interactions (PBEh-3c) as well as our standard protocol for supramolecular thermochemistry and give predictions for chemical modifications to improve the binding strength.

  4. Determination of absolute configuration using heavy atom based co-crystallization method: Halogen atom effects

    Science.gov (United States)

    Wang, Jian-Rong; Fan, Xiaowu; Ding, Qiaoce; Mei, Xuefeng

    2016-09-01

    Heavy atom (chloride, bromide, and iodide) based co-crystals for determination of absolute configuration (AC) for chiral molecules were synthesized and evaluated. Co-crystals of cholestanol and L-ascorbic acid were analysed and the effects and potential benefits of varying the heavy atom are discussed. Changing the halogen atoms (chloride, bromide, or iodide) affects the co-crystal formation, X-ray absorption, and anomalous dispersion, and hence the ability to determine AC.

  5. Cascade anionotropy of the halogen in 3-acetoxy-4-bromo(chloro)-2-methyl-1-butanes

    Energy Technology Data Exchange (ETDEWEB)

    Gevorkyan, A.A.; Kazaryan, P.I.; Avakyan, S.V.

    1987-10-20

    The authors determined that the title compounds, which contain the halogen at the homoallylic position, undergo anionotropy without skeletal isomerization when heated or under the influence of acidic catalysts. Temperature ranges for the bromine and chlorine variants of the compounds were established. Gas-liquid chromatography was used along with IR and NMR spectroscopy to identify the compounds. Chemical shifts and spin-spin coupling constants were analyzed.

  6. Changes in patterns of persistent halogenated compounds through a pelagic food web in the Baltic Sea

    DEFF Research Database (Denmark)

    Stephansen, Diana Agnete; Svendsen, Tore Christian; Vorkamp, Katrin

    2012-01-01

    The concentrations and patterns of persistent halogenated compounds (PHCs), including polychlorinated biphenyls (PCBs), DDT, hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB) and polybrominated diphenyl ethers (PBDEs) were examined in a pelagic food web from the southern Baltic Sea consisting......-normalized concentrations were found in brown trout. Salmon and brown trout were similar in their PHC pattern suggesting similar food sources. Variation in PHC patterns among trophic levels was not smaller than that among geographically distinct locations, confirming the importance of comparable trophic levels...

  7. Preparation of functionalized cyclic enol phosphates by halogen-magnesium exchange and directed deprotonation reactions.

    Science.gov (United States)

    Piller, Fabian M; Bresser, Tomke; Fischer, Markus K R; Knochel, Paul

    2010-07-02

    Cyclic enol phosphates were magnesiated by a halogen/magnesium exchange reaction or deprotonation using TMP-derived magnesium amide bases. The resulting magnesium reagents react readily with a wide range of electrophiles like allyl bromides and acid chlorides or can be used in Pd-catalyzed cross-coupling reactions. Several optically pure enol phosphates were prepared starting from readily available d-(+)-camphor derivatives.

  8. Evaluated kinetic and photochemical data for atmospheric chemistry: Volume III ? gas phase reactions of inorganic halogens

    OpenAIRE

    Atkinson, R.; Baulch, D. L.; Cox, R A; J. N. Crowley; Hampson, R. F.; Hynes, R. G.; Jenkin, M. E.; M. J. Rossi; Troe, J.

    2007-01-01

    International audience; This article, the third in the series, presents kinetic and photochemical data evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of inorganic halogen species, which were last published in J. Phys. Chem. Ref. Data, in 2000 (Atkinson et al., 2000), were updated on the IUPAC website in 2003 and are updated again in the present evaluation. The article consists of a summary sheet...

  9. Halogenation of a capsaicin analogue leads to novel vanilloid TRPV1 receptor antagonists

    Science.gov (United States)

    Appendino, Giovanni; Harrison, Selena; De Petrocellis, Luciano; Daddario, Nives; Bianchi, Federica; Schiano Moriello, Aniello; Trevisani, Marcello; Benvenuti, Francesca; Geppetti, Pierangelo; Di Marzo, Vincenzo

    2003-01-01

    The C-5 halogenation of the vanillyl moiety of resiniferatoxin, an ultrapotent agonist of vanilloid TRPV1 receptors, results in a potent antagonist for these receptors. Here, we have synthesized a series of halogenated derivatives of ‘synthetic capsaicin' (nonanoyl vanillamide=nordihydrocapsaicin) differing for the nature (iodine, bromine–chlorine) and the regiochemistry (C-5, C-6) of the halogenation.The activity of these compounds was investigated on recombinant human TRPV1 receptors overexpressed in HEK-293 cells. None of the six compounds exerted any significant agonist activity, as assessed by measuring their effect on TRPV1-mediated calcium mobilization. Instead, all compounds antagonized, to various extents, the effect of capsaicin in this assay.All 6-halo-nordihydrocapsaicins behaved as competitive antagonists against human TRPV1 according to the corresponding Schild's plots, and were more potent than the corresponding 5-halogenated analogues. The iodo-derivatives were more potent than the bromo- and chloro-derivatives.Using human recombinant TRPV1, 6-iodo-nordihydrocapsaicin (IC50=10 nM against 100 nM capsaicin) was about four times more potent than the prototypical TRPV1 antagonist, capsazepine, and was tested against capsaicin also on native TRPV1 in: (i) rat dorsal root ganglion neurons in culture; (ii) guinea-pig urinary bladder; and (iii) guinea-pig bronchi. In all cases, except for the guinea-pig bronchi, the compound was significantly more potent than capsazepine as a TRPV1 antagonist.In conclusion, 6-iodo-nordihydrocapsaicin, a stable and easily prepared compound, is a potent TRPV1 antagonist and a convenient replacement for capsazepine in most of the in vitro preparations currently used to assess the activity of putative vanilloid receptor agonists. PMID:12922928

  10. Enthalpy-entropy compensation in biomolecular halogen bonds measured in DNA junctions.

    Science.gov (United States)

    Carter, Megan; Voth, Andrea Regier; Scholfield, Matthew R; Rummel, Brittany; Sowers, Lawrence C; Ho, P Shing

    2013-07-23

    Interest in noncovalent interactions involving halogens, particularly halogen bonds (X-bonds), has grown dramatically in the past decade, propelled by the use of X-bonding in molecular engineering and drug design. However, it is clear that a complete analysis of the structure-energy relationship must be established in biological systems to fully exploit X-bonds for biomolecular engineering. We present here the first comprehensive experimental study to correlate geometries with their stabilizing potentials for fluorine (F), chlorine (Cl), bromine (Br), or iodine (I) X-bonds in a biological context. For these studies, we determine the single-crystal structures of DNA Holliday junctions containing halogenated uracil bases that compete X-bonds against classic hydrogen bonds (H-bonds), estimate the enthalpic energies of the competing interactions in the crystal system through crystallographic titrations, and compare the enthalpic and entropic energies of bromine and iodine X-bonds in solution by differential scanning calorimetry. The culmination of these studies demonstrates that enthalpic stabilization of X-bonds increases with increasing polarizability from F to Cl to Br to I, which is consistent with the σ-hole theory of X-bonding. Furthermore, an increase in the X-bonding potential is seen to direct the interaction toward a more ideal geometry. However, the entropic contributions to the total free energies must also be considered to determine how each halogen potentially contributes to the overall stability of the interaction. We find that bromine has the optimal balance between enthalpic and entropic energy components, resulting in the lowest free energy for X-bonding in this DNA system. The X-bond formed by iodine is more enthalpically stable, but this comes with an entropic cost, which we attribute to crowding effects. Thus, the overall free energy of an X-bonding interaction balances the stabilizing electrostatic effects of the σ-hole against the competing

  11. Directional emission of nonthermal halogen atoms by electron bombardment of alkali halides

    Energy Technology Data Exchange (ETDEWEB)

    Postawa, Z.; Szymonski, M.

    1989-06-15

    We present the first experimental results on angle-resolved kinetic-energydistributions of halogen atoms desorbed from single crystals of alkali halidesbecause of electron bombardment. We found that the ejection of nonthermal Bratoms from the (100) surface of KBr is strongly forward peaked along thenormal. We suggest that this effect is caused by a thin damaged layer on thesurface due to a strong nonstoichiometry of the erosion process itself.

  12. Engaging the Terminal: Promoting Halogen Bonding Interactions with Uranyl Oxo Atoms.

    Science.gov (United States)

    Carter, Korey P; Kalaj, Mark; Surbella, Robert G; Ducati, Lucas C; Autschbach, Jochen; Cahill, Christopher L

    2017-07-13

    Engaging the nominally terminal oxo atoms of the linear uranyl (UO2(2+) ) cation in non-covalent interactions represents both a significant challenge and opportunity within the field of actinide hybrid materials. An approach has been developed for promoting oxo atom participation in a range of non-covalent interactions, through judicious choice of electron donating equatorial ligands and appropriately polarizable halogen-donor atoms. As such, a family of uranyl hybrid materials was generated based on a combination of 2,5-dihalobenzoic acid and aromatic, chelating N-donor ligands. Delineation of criteria for oxo participation in halogen bonding interactions has been achieved by preparing materials containing 2,5-dichloro- (25diClBA) and 2,5-dibromobenzoic acid (25diBrBA) coupled with 2,2'-bipyridine (bipy) (1 and 2), 1,10-phenanthroline (phen) (3-5), 2,2':6',2''-terpyridine (terpy) (6-8), or 4'-chloro-2,2':6',2''-terpyridine (Cl-terpy) (9-10), which have been characterized through single crystal X-ray diffraction, Raman, Infrared (IR), and luminescence spectroscopy, as well as through density functional calculations of electrostatic potentials. Looking comprehensively, these results are compared with recently published analogues featuring 2,5-diiodobenzoic acid which indicate that although inclusion of a capping ligand in the uranyl first coordination sphere is important, it is the polarizability of the selected halogen atom that ultimately drives halogen bonding interactions with the uranyl oxo atoms. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. "Textbook" adsorption at "nontextbook" adsorption sites: Halogen atoms on alkali halide surfaces

    OpenAIRE

    Li, B.; Michaelides, A.; Scheffler, M.

    2006-01-01

    Density-functional theory (DFT) and second order Møller-Plesset perturbation theory calculations indicate that halogen atoms bond preferentially to halide substrate atoms on a series of alkali halide surfaces, rather than to the alkali atoms as might be anticipated. An analysis of the electronic structures in each system reveals that this novel adsorption mode is stabilized by the formation of textbook two-center three-electron covalent bonds. The implications of these findings to, for exampl...

  14. Biodehalogenation: The kinetics and rates of the microbial cleavage of carbon-halogen bonds

    Energy Technology Data Exchange (ETDEWEB)

    Castro, C.E. (Univ. of California, Riverside, CA (United States). Nematology Dept.)

    1993-09-01

    Specific rate constants associated with defined molecular paths of carbon-halogen bond cleavage from a variety of alkyl halide substrates by six soil organisms are presented. Five aerobes (three pseudomonads, one methylotroph, and one flavobacterium) and one anaerobe (a methanogen) are compared. The rate constants were obtained with resting cells in phosphate buffer at pH 7.4 in the absence of nutrients or other substances. The observed general rate law is d(X[sup [minus

  15. Synthesis, Characterization, and Multimillion-Atom Simulation of Halogen-Based Energetic Materials for Agent Defeat

    Science.gov (United States)

    2013-04-01

    Kolesnikov NIST: Liu New Discoveries, Inventions, or Patent Disclosures K. O. Christe and G. Drake, “Energetic Ionic Liquids ,” US Patent 7,771,549, Aug...DTRA-TR-13-23 Synthesis, Characterization, and Multimillion-Atom Simulation of Halogen -Based Energetic Materials for Agent Defeat Approved for...second foot foot-pound-force gallon (U.S. liquid ) inch jerk joule/kilogram (J/kg) radiation dose absorbed kilotons kip (1000 lbf) kip/inch 2

  16. Synthesis of 4-Halogenated 3-Fluoro-6-methoxyquinolines: Key Building Blocks for the Synthesis of Antibiotics

    DEFF Research Database (Denmark)

    Flagstad, Thomas; Petersen, Mette Terp; Hinnerfeldt, Daniel Michael

    2014-01-01

    A practical and scalable 4-step route is presented for the synthesis of 4-bromo-3-fluoro-6-methoxyoquinoline and 3-fluoro-4-iodo-6-methoxyoquinoline from readily available 2,4-dichloro-3-fluoroquinoline with an overall yield of 81-85%. Halogenated quinoline building blocks have found much use in ...... in antimicrobial drug discovery, and the method reported here would be useful for the synthesis of these compounds. © Georg Thieme Verlag....

  17. Determination of the Halogenated Skeleton Constituents of the Marine Demosponge Ianthella basta.

    Science.gov (United States)

    Ueberlein, Susanne; Machill, Susanne; Schupp, Peter J; Brunner, Eike

    2017-02-10

    Demosponges of the order Verongida such as Ianthella basta exhibit skeletons containing spongin, a collagenous protein, and chitin. Moreover, Verongida sponges are well known to produce bioactive brominated tyrosine derivatives. We recently demonstrated that brominated compounds do not only occur in the cellular matrix but also in the skeletons of the marine sponges Aplysina cavernicola and I. basta. Further investigations revealed the amino acid composition of the skeletons of A. cavernicola including the presence of several halogenated amino acids. In the present work, we investigated the skeletal amino acid composition of the demosponge I. basta, which belongs to the Ianthellidae family, and compared it with that of A. cavernicola from the Aplysinidae family. Seventeen proteinogenic and five non-proteinogenic amino acids were detected in I. basta. Abundantly occurring amino acids like glycine and hydroxyproline show the similarity of I. basta and A. cavernicola and confirm the collagenous nature of their sponging fibers. We also detected nine halogenated tyrosines as an integral part of I. basta skeletons. Since both sponges contain a broad variety of halogenated amino acids, this seems to be characteristic for Verongida sponges. The observed differences of the amino acid composition confirm that spongin exhibits a certain degree of variability even among the members of the order Verongida.

  18. Prediction of Infinite Dilution Activity Coefficients of Halogenated Hydrocarbons in Water

    Institute of Scientific and Technical Information of China (English)

    XU Hui-Ying; MIN Jian-Qing

    2008-01-01

    Geometrical optimization and electrostatic potential calculations have been performed for a series of halogenated hydrocarbons at the HF/Gen-6d level. A number of electrostatic potentials and the statistically based structural descriptors derived from these electrostatic potentials have been obtained. Multiple linear regression analysis and artificial neural network are employed simultaneously in this paper. The result shows that the parameters derived from electrostatic potentials σ2tot, Vs and ΣVs+, together with the molecular volume (Vmc) can be used to express the quantitative structure-infinite dilution activity coefficients (γ∞) relationship of halogenated hydrocarbons in water. The result also demonstrates that the model obtained by using BFGS quasi-Newton neural network method has much better predictive capability than that from multiple linear regression. The goodness of the model has been validated through exploring the predictive power for the external test set. The model obtained via neural network may be applied to predict γ∞ of other halogenated hydrocarbons not present in the data set.

  19. Molecular Engineering of Non-Halogenated Solution-Processable Bithiazole based Electron Transport Polymeric Semiconductors

    KAUST Repository

    Fu, Boyi

    2015-04-01

    The electron deficiency and trans planar conformation of bithiazole is potentially beneficial for the electron transport performance of organic semiconductors. However, the incorporation of bithiazole into polymers through a facile synthetic strategy remains a challenge. Herein, 2,2’-bithiazole was synthesized in one step and copolymerized with dithienyldiketopyrrolopyrrole to afford poly(dithienyldiketopyrrolopyrrole-bithiazole), PDBTz. PDBTz exhibited electron mobility reaching 0.3 cm2V-1s-1 in organic field-effect transistor (OFET) configuration; this contrasts with a recently discussed isoelectronic conjugated polymer comprising an electron rich bithiophene and dithienyldiketopyrrolopyrrole, which displays merely hole transport characteristics. This inversion of charge carrier transport characteristics confirms the significant potential for bithiazole in the development of electron transport semiconducting materials. Branched 5-decylheptacyl side chains were incorporated into PDBTz to enhance polymer solubility, particularly in non-halogenated, more environmentally compatible solvents. PDBTz cast from a range of non-halogenated solvents exhibited film morphologies and field-effect electron mobility similar to those cast from halogenated solvents.

  20. Evaluation of wear rate of dental composites polymerized by halogen or LED light curing units

    Directory of Open Access Journals (Sweden)

    Alaghehmand H.

    2006-08-01

    Full Text Available Background and Aim: Sufficient polymerization is a critical factor to obtain optimum physical properties and clinical efficacy of resin restorations. The aim of this study was to evaluate wear rates of composite resins polymerized by two different systems Light Emitting Diodes (LED to and Halogen lamps. Materials and Methods: In this laboratory study, 20 specimens of A3 Tetric Ceram composite were placed in brass molds of 2*10*10 mm dimensions and cured for 40 seconds with 1 mm distance from surface. 10 specimens were cured with LED and the other 10 were cured with Halogen unit. A device with the ability to apply force was developed in order to test the wear of composites. After storage in distilled water for 10 days, the specimens were placed in the wear testing machine. A chrome cobalt stylus with 1.12 mm diameter was applied against the specimens surfaces with a load of 2 kg. The weight of each samples before and after 5000, 10000, 20000, 40000, 80000 and 120000 cycles was measured using an electronic balance with precision of 10-4 grams. Data were analyzed using t test and paired t test. P0.05. Conclusion: Based on the results of this study, LED and halogen light curing units resulted in a similar wear rate in composite resin restorations.

  1. Estimating the climate significance of halogen-driven ozone loss in the tropical marine troposphere

    Directory of Open Access Journals (Sweden)

    A. Saiz-Lopez

    2012-05-01

    Full Text Available We have integrated observations of tropospheric ozone, very short-lived (VSL halocarbons and reactive iodine and bromine species from a wide variety of tropical data sources with the global CAM-Chem chemistry-climate model and offline radiative transfer calculations to compute the contribution of halogen chemistry to ozone loss and associated radiative impact in the tropical marine troposphere. The inclusion of tropospheric halogen chemistry in CAM-Chem leads to an annually averaged depletion of around 10% (~2.5 Dobson units of the tropical tropospheric ozone column, with largest effects in the middle to upper troposphere. This depletion contributes approximately −0.10 W m−2 to the radiative flux at the tropical tropopause. This negative flux is of similar magnitude to the ~0.33 W m−2 contribution of tropospheric ozone to present-day radiative balance as recently estimated from satellite observations. We find that the implementation of oceanic halogen sources and chemistry in climate models is an important component of the natural background ozone budget and we suggest that it needs to be considered when estimating both preindustrial ozone baseline levels and long term changes in tropospheric ozone.

  2. Synthesis of deuterium-labelled halogen derivatives of L-tryptophan catalysed by tryptophanase.

    Science.gov (United States)

    Winnicka, Elżbieta; Szymańska, Jolanta; Kańska, Marianna

    2016-06-01

    The isotopomers of halogen derivatives of l-tryptophan (l-Trp) (4'-F-, 7'-F-, 5'-Cl- and 7'-Br-l-Trp), specifically labelled with deuterium in α-position of the side chain, were obtained by enzymatic coupling of the corresponding halogenated derivatives of indole with S-methyl-l-cysteine in (2)H2O, catalysed by enzyme tryptophanase (EC 4.1.99.1). The positional deuterium enrichment of the resulting tryptophan derivatives was controlled using (1)H NMR. In accordance with the mechanism of the lyase reaction, a 100% deuterium labelling was observed in the α-position; the chemical yields were between 23 and 51%. Furthermore, β-F-l-alanine, synthesized from β-F-pyruvic acid by the l-alanine dehydrogenase reaction, has been tested as a coupling agent to obtain the halogenated deuterium-labelled derivatives of l-Trp. The chemical yield (∼30%) corresponded to that as observed with S-methyl-l-cysteine but the deuterium label was only 63%, probably due to the use of a not completely deuterated incubation medium.

  3. Dansylglycine, a fluorescent probe for specific determination of halogenating activity of myeloperoxidase and eosinophil peroxidase.

    Science.gov (United States)

    Bertozo, Luiza de Carvalho; Zeraik, Maria Luiza; Ximenes, Valdecir Farias

    2017-09-01

    Myeloperoxidase (MPO) and eosinophil peroxidase (EPO) are enzymes present in neutrophil and eosinophil leukocytes, respectively. Here, we present the development of a sensitive and specific assay for determination of the halogenating enzymatic activity of MPO and EPO based on the electrophilic attack of HOCl and HOBr on aromatic ring of dansylglycine (DG). We found that the intrinsic fluorescence of DG was promptly depleted by the action of these acids. In the presence of the enzymes, the fluorescence bleaching was dependent of chloride (Cl(-)) and bromide (Br(-)), which makes the assay able to distinguish the halogenating from the peroxidase activity. A linear correlation was obtained between the hydrogen peroxide (H2O2) concentration and the fluorescent decay. Similarly, the enzyme activity was measured by keeping constant H2O2. The method was applied for studding MPO/EPO specific inhibitors as 5-fluortryptamine (reversible inhibitor) and 4-hydroxybenzhydrazide (irreversible inhibitor). Differently of the taurine chloramine/3,3',5,5'-tetramethylbenzidine assay, which is among the most used technique, the dansylglycine assay was able to differentiate these inhibitors based on their kinetic behavior. In conclusion, this assay can differentiate the peroxidase and halogenating activity of MPO and EPO. Moreover, the method is adequate for real-time measurement of the production of HOCl and HOBr. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Determination of halogens and sulfur in high-purity polyimide by IC after digestion by MIC.

    Science.gov (United States)

    Krzyzaniak, Sindy R; Santos, Rafael F; Dalla Nora, Flavia M; Cruz, Sandra M; Flores, Erico M M; Mello, Paola A

    2016-09-01

    In this work, a method for sample preparation of high-purity polyimide was proposed for halogens and sulfur determination by ion chromatography (IC) with conductivity detection and, alternatively, by inductively coupled plasma mass spectrometry (ICP-MS). A relatively high polyimide mass (600mg) was completely digested by microwave-induced combustion (MIC) using 20bar of O2 and 50mmolL(-1) NH4OH as absorbing solution. These conditions allowed final solutions with low carbon content (IC and ICP-MS. The accuracy was evaluated using a certified reference material of polymer for Cl, Br and S and spike recovery experiments for all analytes. No statistical difference (t-test, 95% of confidence level) was observed between the results obtained for Cl, Br and S by IC after MIC and the certified values. In addition, spike recoveries obtained for F, Cl, Br, I and S ranged from 94% to 101%. The proposed method was suitable for polyimide decomposition for further determination of halogens and sulfur by IC and by ICP-MS (Br and I only). Taking into account the lack of methods and the difficulty of bringing this material into solution, MIC can be considered as a suitable alternative for the decomposition of polyimide for routine quality control of halogens and sulfur using IC or ICP-MS.

  5. C3-halogenation of cytisine generates potent and efficacious nicotinic receptor agonists.

    Science.gov (United States)

    Abin-Carriquiry, J Andrés; Voutilainen, Merja H; Barik, Jacques; Cassels, Bruce K; Iturriaga-Vásquez, Patricio; Bermudez, Isabel; Durand, Claudia; Dajas, Federico; Wonnacott, Susan

    2006-04-24

    Neuronal nicotinic acetylcholine receptors subserve predominantly modulatory roles in the brain, making them attractive therapeutic targets. Natural products provide key leads in the quest for nicotinic receptor subtype-selective compounds. Cytisine, found in Leguminosae spp., binds with high affinity to alpha4beta2* nicotinic receptors. We have compared the effect of C3 and C5 halogenation of cytisine and methylcytisine (MCy) on their interaction with native rat nicotinic receptors. 3-Bromocytisine (3-BrCy) and 3-iodocytisine (3-ICy) exhibited increased binding affinity (especially at alpha7 nicotinic receptors; Ki approximately 0.1 microM) and functional potency, whereas C5-halogenation was detrimental. 3-BrCy and 3-ICy were more potent than cytisine at evoking [3H]dopamine release from striatal slices (EC50 approximately 11 nM), [3H]noradrenaline release from hippocampal slices (EC50 approximately 250 nM), increases in intracellular Ca2+ in PC12 cells and inward currents in Xenopus oocytes expressing human alpha3beta4 nicotinic receptor (EC50 approximately 2 microM). These compounds were also more efficacious than cytisine. C3-halogenation of cytisine is proposed to stabilize the open conformation of the nicotinic receptor but does not enhance subtype selectivity.

  6. Halogen-directed drug design for Alzheimer's disease: a combined density functional and molecular docking study.

    Science.gov (United States)

    Rahman, Adhip; Ali, Mohammad Tuhin; Shawan, Mohammad Mahfuz Ali Khan; Sarwar, Mohammed Golam; Khan, Mohammad A K; Halim, Mohammad A

    2016-01-01

    A series of halogen-directed donepezil drugs has been designed to inhibit acetyl cholinesterase (AChE). Density Functional theory (DFT) has been employed to optimize the chair as well as boat conformers of the parent drug and modified ligands at B3LYP/MidiX and B3LYP/6-311G + (d,p) level of theories. Charge distribution, dipole moment, enthalpy, free energy and molecular orbitals of these ligands are also investigated to understand how the halogen-directed modifications impact the ligand structure and govern the non-bonding interactions with the receptors. Molecular docking calculation has been performed to understand the similarities and differences between the binding modes of unmodified and halogenated chair-formed ligands. Molecular docking indicated donepezil and modified ligands had non-covalent interactions with hydrophobic gorges and anionic subsites of AChE. The -CF3-directed ligand possessed the most negative binding affinity. Non-covalent interactions within the ligand-receptor systems were found to be mostly hydrophobic and π- stacking type. F, Cl and -CF3 containing ligands emerge as effective and selective AChE inhibitors, which can strongly interact with the two active sites of AChE. In addition, we have also investigated selected pharmacokinetic parameters of the parent and modified ligands.

  7. Self-assembly of iodine in superfluid helium droplets. Halogen bonds and nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    He, Yunteng; Zhang, Jie; Lei, Lei; Kong, Wei [Department of Chemistry, Oregon State University, Corvallis, OR (United States)

    2017-03-20

    We present evidence of halogen bond in iodine clusters formed in superfluid helium droplets based on results from electron diffraction. Iodine crystals are known to form layered structures with intralayer halogen bonds, with interatomic distances shorter than the sum of the van der Waals radii of the two neighboring atoms. The diffraction profile of dimer dominated clusters embedded in helium droplets reveals an interatomic distance of 3.65 Aa, much closer to the value of 3.5 Aa in iodine crystals than to the van der Waals distance of 4.3 Aa. The profile from larger iodine clusters deviates from a single layer structure; instead, a bi-layer structure qualitatively fits the experimental data. This work highlights the possibility of small halogen bonded iodine clusters, albeit in a perhaps limited environment of superfluid helium droplets. The role of superfluid helium in guiding the trapped molecules into local potential minima awaits further investigation. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Electrostatically enhanced FF interactions through hydrogen bonding, halogen bonding and metal coordination: an ab initio study.

    Science.gov (United States)

    Bauzá, Antonio; Frontera, Antonio

    2016-07-27

    In this manuscript the ability of hydrogen and halogen bonding interactions, as well as metal coordination to enhance FF interactions involving fluorine substituted aromatic rings has been studied at the RI-MP2/def2-TZVPD level of theory. We have used 4-fluoropyridine, 4-fluorobenzonitrile, 3-(4-fluorophenyl)propiolonitrile and their respective meta derivatives as aromatic compounds. In addition, we have used HF and IF as hydrogen and halogen bond donors, respectively, and Ag(i) as the coordination metal. Furthermore, we have also used HF as an electron rich fluorine donor entity, thus establishing FF interactions with the above mentioned aromatic systems. Moreover, a CSD (Cambridge Structural Database) search has been carried out and some interesting examples have been found, highlighting the impact of FF interactions involving aromatic fluorine atoms in solid state chemistry. Finally, cooperativity effects between FF interactions and both hydrogen and halogen bonding interactions have been analyzed and compared. We have also used Bader's theory of "atoms in molecules" to further describe the cooperative effects.

  9. Development of an enzymatic fiber-optic biosensor for detection of halogenated hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Bidmanova, Sarka; Chaloupkova, Radka; Damborsky, Jiri; Prokop, Zbynek [Masaryk University, Loschmidt Laboratories, Department of Experimental Biology and Research Centre for Toxic Compounds in the Environment, Faculty of Science, Brno (Czech Republic)

    2010-11-15

    An enzyme-based biosensor was developed by co-immobilization of purified enzyme haloalkane dehalogenase (EC 3.8.1.5) and a fluorescence pH indicator on the tip of an optical fiber. Haloalkane dehalogenase catalyzes hydrolytic dehalogenation of halogenated aliphatic hydrocarbons, which is accompanied by a pH change influencing the fluorescence of the indicator. The pH sensitivity of several fluorescent dyes was evaluated. The selected indicator 5(6)-carboxyfluorescein was conjugated with bovine serum albumin and its reaction was tested under different immobilization conditions. The biosensor was prepared by cross-linking of the conjugate in tandem with haloalkane dehalogenase using glutaraldehyde vapor. The biosensor, stored for 24 h in 50 mM phosphate buffer (pH 7.5) prior to measurement, was used after 15 min of equilibration, the halogenated compound was added, and the response was monitored for 30 min. Calibration of the biosensor with 1,2-dibromoethane and 3-chloro-2-(chloromethyl)-1-propene showed an excellent linear dependence, with detection limits of 0.133 and 0.014 mM, respectively. This biosensor provides a new tool for continuous in situ monitoring of halogenated environmental pollutants. (orig.)

  10. Determination of the Halogenated Skeleton Constituents of the Marine Demosponge Ianthella basta

    Directory of Open Access Journals (Sweden)

    Susanne Ueberlein

    2017-02-01

    Full Text Available Demosponges of the order Verongida such as Ianthella basta exhibit skeletons containing spongin, a collagenous protein, and chitin. Moreover, Verongida sponges are well known to produce bioactive brominated tyrosine derivatives. We recently demonstrated that brominated compounds do not only occur in the cellular matrix but also in the skeletons of the marine sponges Aplysina cavernicola and I. basta. Further investigations revealed the amino acid composition of the skeletons of A. cavernicola including the presence of several halogenated amino acids. In the present work, we investigated the skeletal amino acid composition of the demosponge I. basta, which belongs to the Ianthellidae family, and compared it with that of A. cavernicola from the Aplysinidae family. Seventeen proteinogenic and five non-proteinogenic amino acids were detected in I. basta. Abundantly occurring amino acids like glycine and hydroxyproline show the similarity of I. basta and A. cavernicola and confirm the collagenous nature of their sponging fibers. We also detected nine halogenated tyrosines as an integral part of I. basta skeletons. Since both sponges contain a broad variety of halogenated amino acids, this seems to be characteristic for Verongida sponges. The observed differences of the amino acid composition confirm that spongin exhibits a certain degree of variability even among the members of the order Verongida.

  11. Photofragmentation spectra of halogenated methanes in the VUV photon energy range.

    Science.gov (United States)

    Cartoni, Antonella; Bolognesi, Paola; Fainelli, Ettore; Avaldi, Lorenzo

    2014-05-14

    In this paper an investigation of the photofragmentation of dihalomethanes CH2X2 (X = F, Cl, Br, I) and chlorinated methanes (CH(n)Cl(4-n) with n = 0-3) with VUV helium, neon, and argon discharge lamps is reported and the role played by the different halogen atoms is discussed. Halogenated methanes are a class of molecules used in several fields of chemistry and the study of their physical and chemical proprieties is of fundamental interest. In particular their photodissociation and photoionization are of great importance since the decomposition of these compounds in the atmosphere strongly affects the environment. The results of the present work show that the halogen-loss is the predominant fragmentation channel for these molecules in the VUV photon energy range and confirm their role as reservoir of chlorine, bromine, and iodine atoms in the atmosphere. Moreover, the results highlight the peculiar feature of CH2F2 as a source of both fluorine and hydrogen atoms and the characteristic formation of I2(+) and CH2(+) ions from the photofragmentation of the CH2I2 molecule.

  12. Photofragmentation spectra of halogenated methanes in the VUV photon energy range

    Energy Technology Data Exchange (ETDEWEB)

    Cartoni, Antonella, E-mail: antonella.cartoni@uniroma1.it [Dipartimento di Chimica e Tecnologie del Farmaco, Sapienza Università di Roma, P.le Aldo Moro 5, Roma 00185 (Italy); Bolognesi, Paola; Fainelli, Ettore; Avaldi, Lorenzo [CNR-IMIP, Area della Ricerca di Roma 1, Monterotondo Scalo (Rm) 00015 (Italy)

    2014-05-14

    In this paper an investigation of the photofragmentation of dihalomethanes CH{sub 2}X{sub 2} (X = F, Cl, Br, I) and chlorinated methanes (CH{sub n}Cl{sub 4−n} with n = 0–3) with VUV helium, neon, and argon discharge lamps is reported and the role played by the different halogen atoms is discussed. Halogenated methanes are a class of molecules used in several fields of chemistry and the study of their physical and chemical proprieties is of fundamental interest. In particular their photodissociation and photoionization are of great importance since the decomposition of these compounds in the atmosphere strongly affects the environment. The results of the present work show that the halogen-loss is the predominant fragmentation channel for these molecules in the VUV photon energy range and confirm their role as reservoir of chlorine, bromine, and iodine atoms in the atmosphere. Moreover, the results highlight the peculiar feature of CH{sub 2}F{sub 2} as a source of both fluorine and hydrogen atoms and the characteristic formation of I{sub 2}{sup +} and CH{sub 2}{sup +} ions from the photofragmentation of the CH{sub 2}I{sub 2} molecule.

  13. Halogen-abstraction reactions from chloromethane and bromomethane molecules by alkaline-earth monocations.

    Science.gov (United States)

    Redondo, Pilar; Largo, Antonio; Rayón, Víctor Manuel; Molpeceres, Germán; Sordo, José Ángel; Barrientos, Carmen

    2014-08-14

    The reactions, in the gas phase, between alkali-earth monocations (Mg(+), Ca(+), Sr(+), Ba(+)) and CH3X (X = Cl, Br) have been theoretically studied. The stationary points on the potential energy surfaces were characterized at the Density Functional Theory level on the framework of the mPW1K functional with the QZVPP Ahlrichs's basis sets. A complementary kinetics study has also been performed using conventional/variational microcanonical transition state theory. In the reactions of Mg(+) with either chloro- or bromomethane the transition structure lies in energy clearly above the reactants rendering thermal activation of CH3Cl or CH3Br extremely improbable. The remaining reactions are exothermic and barrierless processes; thus carbon-halogen bonds in chloro- or bromomethane can be activated by calcium, strontium or barium monocations to obtain the metal halogen cation and the methyl radical. The Mulliken population analysis for the stationary points of the potential energy surfaces supports a "harpoon"-like mechanism for the halogen-atom abstraction processes. An analysis of the bonding situation for the stationary points on the potential energy surface has also been performed in the framework of the quantum theory of atoms in molecules.

  14. Superior anticancer activity of halogenated chalcones and flavonols over the natural flavonol quercetin.

    Science.gov (United States)

    Dias, Tatiana A; Duarte, Cecília L; Lima, Cristovao F; Proença, M Fernanda; Pereira-Wilson, Cristina

    2013-07-01

    A series of chalcone and flavonol derivatives were synthesized in good yield by an eco-friendly approach. A pharmacological evaluation was performed with the human colorectal carcinoma cell line HCT116 and revealed that the anticancer activity of flavonols was higher when compared with that of the respective chalcone precursors. The antiproliferative activity of halogenated derivatives increases as the substituent in the 3- or 4-positon of the B-ring goes from F to Cl and to Br. In addition, halogens in position 3 enhance anticancer activity in chalcones whereas for flavonol derivatives the best performance was registered for the 4-substituted derivatives. Flow cytometry analysis showed that compounds 3p and 4o induced cell cycle arrest and apoptosis as demonstrated by increased S, G2/M and sub-G1 phases. These data were corroborated by western blot and fluorescence microscopy analysis. In summary, halogenated chalcones and flavonols were successfully prepared and presented high anticancer activity as shown by their cell growth and cell cycle inhibitory potential against HCT116 cells, superior to that of quercetin, used as a positive control.

  15. Dietary exposure to a group of naturally produced organohalogens (halogenated dimethyl bipyrroles) via consumption of fish and seafood.

    Science.gov (United States)

    Tittlemier, Sheryl A

    2004-04-07

    Concentrations of four naturally produced halogenated dimethyl bipyrroles (HDBPs) were quantitated in marine fish (n = 10), freshwater fish (n = 10), canned fish (n = 10), and shrimp composites (n = 10) collected from 1992 to 2002 for the Canadian Total Diet Study. Canned fish composites composed of epipelagic higher trophic level species contained the highest concentration of HDBPs (SigmaHDBP geometric mean +/- standard error = 880 +/- 690 pg/g of wet weight, n = 10), which was significantly higher than that found in the other three composites. There were no significant temporal trends of HDBP concentrations observed for any of the four composites. The estimated daily intake of HDBPs via consumption of fish and seafood was determined to be 53 pg/kg of body mass/day and 0.10 pg of TEQ/kg of body mass/day when transformed to 2,3,7,8-tetrachlorodibenzodioxin equivalents (TEQs). In the canned fish and shrimp composites collected in 1998, HDBPs accounted for approximately 98 and 19%, respectively, of the total quantitated TEQ (which included polychlorinated biphenyls, dioxins, and furans). The results of this study provide the first estimate of human exposure to naturally produced bioaccumulating organohalogens.

  16. Halogen Bonding or Hydrogen Bonding between 2,2,6,6-Tetramethyl-piperidine-noxyl Radical and Trihalomethanes CHX3 (X=Cl, Br, I)

    Institute of Scientific and Technical Information of China (English)

    Xiao-ran Zhao; Xue Pang; Xiao-qing Yan; Wei-jun Jin

    2013-01-01

    The halogen and hydrogen bonding complexes between 2,2,6,6-tetramethylpiperidine-noxyl and trihalomethanes (CHX3,X=Cl,Br,I) are simulated by computational quantum chemistry.The molecular electrostatic potentials,geometrical parameters and interaction energy of halogen and hydrogen bonding complexes combined with natural bond orbital analysis are obtained.The results indicate that both halogen and hydrogen bonding interactions obey the order Cl<Br<I,and hydrogen bonding is stronger than the corresponding halogen bond ing.So,hydrogen bonding complexes should be dominant in trihalomethanes.However,it is possible that halogen bonding complex is competitive,even preponderant,in triiodomethane due to the similar interaction energy.This work might provide useful information on specific solvent effects as well as for understanding the mechanism of nitroxide radicals as a bioprobe to interact with the halogenated compounds in biological and biochemical fields.

  17. On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for O3, HOx, NOx and the Hg lifetime

    Directory of Open Access Journals (Sweden)

    W. J. Bloss

    2007-07-01

    Full Text Available A one-dimensional chemical transport model has been developed to investigate the vertical gradients of bromine and iodine compounds in the Antarctic coastal boundary layer. The model has been applied to interpret recent year-round observations of iodine and bromine monoxides (IO and BrO at Halley Station, Antarctica. The model requires an equivalent I atom flux of ~109 molecule cm−2 s−1 from the snowpack in order to account for the measured IO levels, which are up to 20 ppt during spring. Using the current knowledge of gas-phase iodine chemistry, the model predicts significant gradients in the vertical distribution of iodine species. However, recent ground-based and satellite observations of IO imply that the radical is well-mixed in the boundary layer, indicating a longer than expected atmospheric lifetime for the radical. This can be modelled by including photolysis of the higher iodine oxides (I2O2, I2O3, I2O4 and I2O5, and rapid recycling of HOI and INO3 through sea-salt aerosol. The model also predicts significant concentrations (up to 25 ppt of I2O5 in the lowest 10 m of the boundary layer, which could lead to the formation of ultrafine iodine oxide aerosols. Heterogeneous chemistry involving sea-salt aerosol is also necessary to account for the vertical profile of BrO. Iodine chemistry causes a large increase (typically more than 3-fold in the rate of O3 depletion in the BL, compared with bromine chemistry alone. Rapid entrainment of O3 from the free troposphere is required to account for the observation that on occasion there is little O3 depletion at the surface in the presence of high concentrations of IO and BrO. The halogens also cause significant changes to the vertical profiles of HO and HO2 and the NO2/NO ratio. The average Hg0 lifetime against oxidation is also predicted to be about 10 h during springtime. Overall, our results show that halogens profoundly influence the oxidizing capacity of the Antarctic troposphere.

  18. Technology for radiation efficiency measurement of high-power halogen tungsten lamp used in calibration of high-energy laser energy meter.

    Science.gov (United States)

    Wei, Ji Feng; Hu, Xiao Yang; Sun, Li Qun; Zhang, Kai; Chang, Yan

    2015-03-20

    The calibration method using a high-power halogen tungsten lamp as a calibration source has many advantages such as strong equivalence and high power, so it is very fit for the calibration of high-energy laser energy meters. However, high-power halogen tungsten lamps after power-off still reserve much residual energy and continually radiate energy, which is difficult to be measured. Two measuring systems were found to solve the problems. One system is composed of an integrating sphere and two optical spectrometers, which can accurately characterize the radiative spectra and power-time variation of the halogen tungsten lamp. This measuring system was then calibrated using a normal halogen tungsten lamp made of the same material as the high-power halogen tungsten lamp. In this way, the radiation efficiency of the halogen tungsten lamp after power-off can be quantitatively measured. In the other measuring system, a wide-spectrum power meter was installed far away from the halogen tungsten lamp; thus, the lamp can be regarded as a point light source. The radiation efficiency of residual energy from the halogen tungsten lamp was computed on the basis of geometrical relations. The results show that the halogen tungsten lamp's radiation efficiency was improved with power-on time but did not change under constant power-on time/energy. All the tested halogen tungsten lamps reached 89.3% of radiation efficiency at 50 s after power-on. After power-off, the residual energy in the halogen tungsten lamp gradually dropped to less than 10% of the initial radiation power, and the radiation efficiency changed with time. The final total radiation energy was decided by the halogen tungsten lamp's radiation efficiency, the radiation efficiency of residual energy, and the total power consumption. The measuring uncertainty of total radiation energy was 2.4% (here, the confidence factor is two).

  19. Nonlinear lattice relaxation of photogenerated charge-transfer excitation in halogen-bridged mixed-valence metal complexes. II. Polaron channel

    Science.gov (United States)

    Mishima, A.; Nasu, K.

    1989-03-01

    The one-dimensional extended Peierls-Hubbard model with half-filled-band electrons is studied in order to clarify the lattice relaxation path of the photogenerated charge-transfer excitation in halogen-bridged mixed-valence metal complexes. The ground and excited states are calculated within mean-field theory for electrons and the adiabatic approximation for phonons. It is concluded that the main origin of the photoinduced absorption is a distant pair of the hole-polaron and the electron-polaron. This distant pair is created not from the ground state of the self-trapped exciton (STE), but from the excited states of the STE through their autodissociation. This is consistent with the experiment on the excitation energy dependence of the photoinduced absorption yield.

  20. Estudio in vivo de la oxidación mitocondrial en pacientes obesos tratados mediante restricción calórica In vivo study of mitochondrial oxidation in obese patients treated by means of calorie restriction

    Directory of Open Access Journals (Sweden)

    M.ª D. Parra

    2004-10-01

    2-keto[1-13C]isocaproate breath test was performed by ingestion of 1 mg/kg tracer and 20 mg/kg L-leucine, dissolved in 200 ml orange juice. Breath samples were recovered at baseline and at 10 min intervals for 2 h after ingestion. The 13C-enrichment in breath was measured by isotope ratio mass spectrometry and the percentage of mitochondrial oxidation of tracer (%13C was calculated. The percentage of oxidized tracer marginally tended to be lower in obese than in controls (25.1 ± 5.5%, vs 27.5 ± 4.0%, p = 0.175. After the intervention, the mean of weight loss was -7.8% ± 3% p < 0.001, and the mitocondrial oxidation of the tracer statistically increased (25.1 ± 5.5% vs 34.3 ± 5.2%, p < 0.001. In fact, the body weight and the percentage of oxidized 2-ceto[1-13C]isocaproate were inversely related (r = -0.34, p = 0.018. Thus, the 2-keto[1-13C]isocaproate in vivoshowed the mitochondrial adaptation of obese volunteers treated by caloric-restriction intake and provided new information about the weight loss process induced by an hypocaloric diet.

  1. Slab-derived halogens and noble gases illuminate closed system processes controlling volatile element transport into the mantle wedge

    Science.gov (United States)

    Kobayashi, Masahiro; Sumino, Hirochika; Nagao, Keisuke; Ishimaru, Satoko; Arai, Shoji; Yoshikawa, Masako; Kawamoto, Tatsuhiko; Kumagai, Yoshitaka; Kobayashi, Tetsuo; Burgess, Ray; Ballentine, Chris J.

    2017-01-01

    Halogen and noble gas systematics are powerful tracers of volatile recycling in subduction zones. We present halogen and noble gas compositions of mantle peridotites containing H2O-rich fluid inclusions collected at volcanic fronts from two contrasting subduction zones (the Avacha volcano of Kamchatka arc and the Pinatubo volcano of Luzon arcs) and orogenic peridotites from a peridotite massif (the Horoman massif, Hokkaido, Japan) which represents an exhumed portion of the mantle wedge. The aims are to determine how volatiles are carried into the mantle wedge and how the subducted fluids modify halogen and noble gas compositions in the mantle. The halogen and noble gas signatures in the H2O-rich fluids are similar to those of marine sedimentary pore fluids and forearc and seafloor serpentinites. This suggests that marine pore fluids in deep-sea sediments are carried by serpentine and supplied to the mantle wedge, preserving their original halogen and noble gas compositions. We suggest that the sedimentary pore fluid-derived water is incorporated into serpentine through hydration in a closed system along faults at the outer rise of the oceanic, preserving Cl/H2O and 36Ar/H2O values of sedimentary pore fluids. Dehydration-hydration process within the oceanic lithospheric mantle maintains the closed system until the final stage of serpentine dehydration. The sedimentary pore fluid-like halogen and noble gas signatures in fluids released at the final stage of serpentine dehydration are preserved due to highly channelized flow, whereas the original Cl/H2O and 36Ar/H2O ratios are fractionated by the higher incompatibility of halogens and noble gases in hydrous minerals.

  2. Characterization of halogenated DBPs and identification of new DBPs trihalomethanols in chlorine dioxide treated drinking water with multiple extractions.

    Science.gov (United States)

    Han, Jiarui; Zhang, Xiangru; Liu, Jiaqi; Zhu, Xiaohu; Gong, Tingting

    2017-08-01

    Chlorine dioxide (ClO2) is a widely used alternative disinfectant due to its high biocidal efficiency and low-level formation of trihalomethanes and haloacetic acids. A major portion of total organic halogen (TOX), a collective parameter for all halogenated DBPs, formed in ClO2-treated drinking water is still unknown. A commonly used pretreatment method for analyzing halogenated DBPs in drinking water is one-time liquid-liquid extraction (LLE), which may lead to a substantial loss of DBPs prior to analysis. In this study, characterization and identification of polar halogenated DBPs in a ClO2-treated drinking water sample were conducted by pretreating the sample with multiple extractions. Compared to one-time LLE, the combined four-time LLEs improved the recovery of TOX by 2.3 times. The developmental toxicity of the drinking water sample pretreated with the combined four-time LLEs was 1.67 times higher than that pretreated with one-time LLE. With the aid of ultra-performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry, a new group of polar halogenated DBPs, trihalomethanols, were detected in the drinking water sample pretreated with multiple extractions; two of them, trichloromethanol and bromodichloromethanol, were identified with synthesized standard compounds. Moreover, these trihalomethanols were found to be the transformation products of trihalomethanes formed during ClO2 disinfection. The results indicate that multiple LLEs can significantly improve extraction efficiencies of polar halogenated DBPs and is a better pretreatment method for characterizing and identifying new polar halogenated DBPs in drinking water. Copyright © 2017. Published by Elsevier B.V.

  3. Dimethylselenide as a probe for reactions of halogenated alkoxyl radicals in aqueous solution. Degradation of dichloro- and dibromomethane.

    Science.gov (United States)

    Makogon, Oksana; Flyunt, Roman; Tobien, Thomas; Naumov, Sergej; Bonifacić, Marija

    2008-07-03

    Using pulse radiolysis and steady-state gamma-radiolysis techniques, it has been established that, in air-saturated aqueous solutions, peroxyl radicals CH 2HalOO (*) (Hal = halogen) derived from CH 2Cl 2 and CH 2Br 2 react with dimethyl selenide (Me 2Se), with k on the order of 7 x 10 (7) M (-1) s (-1), to form HCO 2H, CH 2O, CO 2, and CO as final products. An overall two-electron oxidation process leads directly to dimethyl selenoxide (Me 2SeO), along with oxyl radical CH 2HalO (*). The latter subsequently oxidizes another Me 2Se molecule by a much faster one-electron transfer mechanism, leading to the formation of equal yields of CH 2O and the dimer radical cation (Me 2Se) 2 (*+). In absolute terms, these yields amount to 18% and 28% of the CH 2ClO (*) and CH 2BrO (*) yields, respectively, at 1 mM Me 2Se. In competition, CH 2HalO (*) rearranges into (*)CH(OH)Hal. These C-centered radicals react further via two pathways: (a) Addition of an oxygen molecule leads to the corresponding peroxyl radicals, that is, species prone to decomposition into H (+)/O 2 (*-) and formylhalide, HC(O)Hal, which further degrades mostly to H (+)/Hal (-) and CO. (b) Elimination of HHal yields the formyl radical H-C(*)=O with a rate constant of about 6 x 10 (5) s (-1) for Hal = Cl. In an air-saturated solution, the predominant reaction pathway of the H-C(*)=O radical is addition of oxygen. The formylperoxyl radical HC(O)OO (*) thus formed reacts with Me 2Se via an overall two-electron transfer mechanism, giving additional Me 2SeO and formyloxyl radicals HC(O)O(*). The latter rearrange via a 1,2 H-atom shift into (*)C(O)OH, which reacts with O2 to give CO2 and O2(*)(-). The minor fraction of H-C(*)=O undergoes hydration, with an estimated rate constant of k approximately 2 x 10(5) s(-1). The resulting HC(*)(OH)2 radical, upon reaction with O2, yields HCO 2H and H (+)/O2(*-). Some of the conclusions about the reactions of halogenated alkoxyl radicals are supported by quantum chemical

  4. Hydrothermal origin of halogens at Home Plate, Gusev Crater

    Science.gov (United States)

    Schmidt, M.E.; Ruff, S.W.; McCoy, T.J.; Farrand, W. H.; Johnson, J. R.; Gellert, Ralf; Ming, D. W.; Morris, R.V.; Cabrol, N.; Lewis, K.W.; Schroeder, C.

    2008-01-01

    In the Inner Basin of the Columbia Hills, Gusev Crater is Home Plate, an 80 m platform of layered elastic rocks of the Barnhill class with microscopic and macroscopic textures, including a bomb sag, suggestive of a phreatomagmatic origin. We present data acquired by the Spirit Mars Exploration Rover by Alpha Particle X-Ray Spectrometer (APXS), Mo??ssbauer Spectrometer, Miniature Thermal Emission Spectrometer (Mini-TES), and Panoramic Camera (Pancam) for the Barnhill class rocks and nearby vesicular Irvine class basalts. In major element concentrations (e.g., SiO2, Al2O3, MgO, and FeO*), the two rock classes are similar, suggesting that they are derived from a similar magmatic source. The Barnhill class, however, has higher abundances of Cl, Br, Zn, and Ge with comparable SO3 to the Irvine basalts. Nanophase ferric oxide (np ox) and volcanic glass were detected in the Barnhill class rocks by Mo??ssbauer and Mini-TES, respectively, and imply greater alteration and cooling rates in the Barnhill than in the Irvine class rocks. The high volatile elements in the Barnhill class agree with volcanic textures that imply interaction with a briny groundwater during eruption and (or) by later alteration. Differences in composition between the Barnhill and Irvine classes allow the fingerprinting of a Na-Mg-Zn-Ge-Cl-Br (??Fe ?? Ca ?? CO2) brine with low S. Nearby sulfate salt soils of fumarolic origin may reflect fractionation of an acidic S-rich vapor during boiling of a hydrothermal brine at depth. Persistent groundwater was likely present during and after the formation of Home Plate. Copyright 2008 by the American Geophysical Union.

  5. Monitoring of nitrogen dioxide, ozone and halogens radicals in Antarctica

    Science.gov (United States)

    Bortoli, Daniele; Ravegnani, Fabrizio; Costa, Maria J.; Genco, Silvia; Kulkarni, Pavan K.; Mendes, Rui; Domingues, Ana Filipa; Anton, Manuel; Giovanelli, Giorgio; Silva, Ana Maria

    2013-10-01

    Monitoring of atmospheric compounds at high latitudes is a key factor for a better understanding of the processes driving the chemical cycles of ozone and related chemical species. In this frame, the GASCOD (Gas Analizer Spectrometer Correlating Optical Differences) equipment is installed at the Mario Zucchelli Station (MZS - 74.69S, 164.12E) since December 1995, carrying out observations of nitrogen dioxide (NO2) and ozone (O3). The recent advances in sensor technologies and processor capabilities, suggested the setup of a new equipment, based on the same optical layout of the 'old' GASCOD , with enhanced performances and improved capabilities for the measurements of solar radiation in the UV-visible spectral range (300-700nm). The efforts accomplished, allowed for the increase of the investigated tracers. Actually, mainly due to the enlargement of the covered spectral range and to the adoption of a CCD sensor, in addition to the NO2 and O3 compounds, others species can be monitored with the new instrumental setup such as bromine, chlorine and iodine oxides (BrO, OClO and IO). The innovative equipment called GASCODNG (GASCOD New Generation) was installed at MZS during the 2012/2013 Italian Antarctic expedition, in the framework of the research projects SAMOA (Automatic Station Monitoring Antarctic Ozonosphere) and MATAGRO (Monitoring Atmospheric Tracers in Antarctica with Ground Based Observations) funded by the Italian and Portuguese Antarctic programs respectively. In this paper a brief description of the new equipment is provided, highlighting the main improvements with regard to the 'old' one. Furthermore the full dataset (1996 - 2012) of NO2 total columns, obtained with the GASCOD installed at MZS, is compared with the data obtained with satellite borne equipments (GOME, SCIAMACHY, OMI and GOME2) and the main statistical parameters are analyzed and discussed in detail.

  6. The structures of heterocyclic complexes ruled by hydrogen bonds and halogen interactions: interaction strength and IR modes.

    Science.gov (United States)

    Oliveira, Boaz G

    2014-04-24

    In this work, the existence of multiple interactions in heterocyclic complexes of C2H4O⋯nHCCl3 and C2H4S⋯nHCCl3 with n=2 and 3 was unveiled at the B3LYP/6-311++G(d,p) level of theory. The forward analyses of the vibrational spectra revealed the appearing of red-shifts in the H-C bond. In agreement with this and through the optimized geometries of these systems, an increase in the H-C bond length was also observed. Besides O⋯H and S⋯H, other hydrogen bonds formed between chlorine⋯hydrogen and mainly the halogen interactions formed by chlorine⋯chlorine were identified. Thereby, the vibration spectra of the heterocyclic complexes were reanalyzed with the purpose to locate new red-shifts, although only those characterized in H-C have been detected up to then. In addition to the correlation between the frequencies shifted to downward values followed by increases in the bond lengths, the interpretation of the red-shifts was conducted by means of the Bent rule of the hybridization theory. The interaction strength was examined in several viewpoints, and one of them was the relationship between the H-bond energies and the intermolecular electronic density computed by means of the Quantum Theory of Atoms in Molecules (QTAIM). Moreover, the prediction of the interaction strength was also made through the combination between vibration modes (red-shifts) and variation of topological parameters, such as the electronic density and Laplacian of the proton donor bond (C-H).

  7. Dramatic effects of halogen substitution and solvent on the rates and mechanisms of nucleophilic substitution reactions of aziridines.

    Science.gov (United States)

    Banks, Harold D

    2008-04-04

    In a previous study we reported that fluorine substitution at the carbon positions of aziridine results in profound enhancements of the rate of reaction with ammonia, a typical nucleophile, in the gas phase. In this study the investigation is extended to include chloro- and bromoaziridines. Because syntheses are largely performed in the condensed phase, the present computational investigation [(MP2(Full)/6-311++G(d,p)//MP2(Full)/6-31+G(d) level] was conducted with three typical solvents that cover a wide range of polarity: THF, CH3CN, and H2O. Nucleophiles can react with haloaziridines 1 by displacing a substituted amide ion by means of an SN2 mechanism (pathway a), producing 1,2-diaminohaloethanes (from the initially formed dipolar species 2). Alternatively, a rearrangement mechanism involving rate-determining departure of a halide ion (pathway b) to form an imidoyl halide, 3, is possible. Transition-state theory was used to compute relative reaction rates of these mechanistic possibilities and to assess the role of the halogen substituents and the reaction solvent. Gas-phase results provided the basis of mechanistic insights that were more apparent in the absence of intermolecular interactions. Fluoroaziridines were found to react at accelerated rates relative to aziridine exclusively by means of the a Menshutkin-type mechanism (SN2) in each solvent tested, while the reactions of the chloro- and bromoaziridines could be directed toward 2 in the highly nonpolar solvent, cyclohexane, or toward 3 in the more polar solvents. An assessment is made of the feasibility of using this chemistry of the haloazirdines in the synthetic laboratory.

  8. Crystal structures of four δ-keto esters and a Cambridge Structural Database analysis of cyano-halogen interactions.

    Science.gov (United States)

    Kamal, Kulsoom; Maurya, Hardesh K; Gupta, Atul; Vasudev, Prema G

    2015-10-01

    The revived interest in halogen bonding as a tool in pharmaceutical cocrystals and drug design has indicated that cyano-halogen interactions could play an important role. The crystal structures of four closely related δ-keto esters, which differ only in the substitution at a single C atom (by H, OMe, Cl and Br), are compared, namely ethyl 2-cyano-5-oxo-5-phenyl-3-(piperidin-1-yl)pent-2-enoate, C19H22N2O3, (1), ethyl 2-cyano-5-(4-methoxyphenyl)-5-oxo-3-(piperidin-1-yl)pent-2-enoate, C20H24N2O4, (2), ethyl 5-(4-chlorophenyl)-2-cyano-5-oxo-3-(piperidin-1-yl)pent-2-enoate, C19H21ClN2O3, (3), and the previously published ethyl 5-(4-bromophenyl)-2-cyano-5-oxo-3-(piperidin-1-yl)pent-2-enoate, C19H21BrN2O3, (4) [Maurya, Vasudev & Gupta (2013). RSC Adv. 3, 12955-12962]. The molecular conformations are very similar, while there are differences in the molecular assemblies. Intermolecular C-H...O hydrogen bonds are found to be the primary interactions in the crystal packing and are present in all four structures. The halogenated derivatives have additional aromatic-aromatic interactions and cyano-halogen interactions, further stabilizing the molecular packing. A database analysis of cyano-halogen interactions using the Cambridge Structural Database [CSD; Groom & Allen (2014). Angew. Chem. Int. Ed. 53, 662-671] revealed that about 13% of the organic molecular crystals containing both cyano and halogen groups have cyano-halogen interactions in their packing. Three geometric parameters for the C-X...N[triple-bond]C interaction (X = F, Cl, Br or I), viz. the N...X distance and the C-X...N and C-N...X angles, were analysed. The results indicate that all the short cyano-halogen contacts in the CSD can be classified as halogen bonds, which are directional noncovalent interactions.

  9. On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for O3, HOx, NOx and the Hg lifetime

    Directory of Open Access Journals (Sweden)

    W. J. Bloss

    2008-02-01

    Full Text Available A one-dimensional chemical transport model has been developed to investigate the vertical gradients of bromine and iodine compounds in the Antarctic coastal boundary layer (BL. The model has been applied to interpret recent year-round observations of iodine and bromine monoxides (IO and BrO at Halley Station, Antarctica. The model requires an equivalent I atom flux of ~1010 molecule cm−2 s−1 from the snowpack in order to account for the measured IO levels, which are up to 20 ppt during spring. Using the current knowledge of gas-phase iodine chemistry, the model predicts significant gradients in the vertical distribution of iodine species. However, recent ground-based and satellite observations of IO imply that the radical is well-mixed in the Antarctic boundary layer, indicating a longer than expected atmospheric lifetime for the radical. This can be modelled by including photolysis of the higher iodine oxides (I2O2, I2O3, I2O4 and I2O5, and rapid recycling of HOI and INO3 through sea-salt aerosol. The model also predicts significant concentrations (up to 25 ppt of I2O5 in the lowest 10 m of the boundary layer. Heterogeneous chemistry involving sea-salt aerosol is also necessary to account for the vertical profile of BrO. Iodine chemistry causes a large increase (typically more than 3-fold in the rate of O3 depletion in the BL, compared with bromine chemistry alone. Rapid entrainment of O3 from the free troposphere appears to be required to account for the observation that on occasion there is little O3 depletion at the surface in the presence of high concentrations of IO and BrO. The halogens also cause significant changes to the vertical profiles of OH and HO2 and the NO2/NO ratio. The average Hg0 lifetime against oxidation is also predicted to be about 10 h during springtime. An important result from the model is that very large fluxes of iodine precursors into the boundary layer are required to account for the observed levels of IO. The

  10. Protection of halogenated DNA from strand breakage and sister-chromatid exchange induced by the topoisomerase I inhibitor camptothecin

    Energy Technology Data Exchange (ETDEWEB)

    Orta, Manuel Luis; Mateos, Santiago; Cantero, Gloria [Department of Cell Biology, Faculty of Biology, University of Seville (Spain); Wolff, Lisa J. [Sweet Briar College, VA (United States); Cortes, Felipe [Department of Cell Biology, Faculty of Biology, University of Seville (Spain)], E-mail: cortes@us.es

    2008-01-01

    The fundamental nuclear enzyme DNA topoisomerase I (topo I), cleaves the double-stranded DNA molecule at preferred sequences within its recognition/binding sites. We have recently reported that when cells incorporate halogenated nucleosides analogues of thymidine into DNA, it interferes with normal chromosome segregation, as shown by an extraordinarily high yield of endoreduplication, and results in a protection against DNA breakage induced by the topo II poison m-AMSA [F. Cortes, N. Pastor, S. Mateos, I. Dominguez, The nature of DNA plays a role in chromosome segregation: endoreduplication in halogen-substituted chromosomes, DNA Repair 2 (2003) 719-726; G. Cantero, S. Mateos, N. Pastor; F. Cortes, Halogen substitution of DNA protects from poisoning of topoisomerase II that results in DNA double-strand breaks (DSBs), DNA Repair 5 (2006) 667-674]. In the present investigation, we have assessed whether the presence of halogenated nucleosides in DNA diminishes the frequency of interaction of topo I with DNA and thus the frequency with which the stabilisation of cleavage complexes by the topo I poison camptothecin (CPT) takes place, in such a way that it protects from chromosome breakage and sister-chromatid exchange. This protective effect is shown to parallel a loss in halogen-substituted cells of the otherwise CPT-increased catalytic activity bound to DNA.

  11. Determination of gaseous semi-and low-volatile organic halogen compounds by barrier-discharge atomic emission spectrometry

    Institute of Scientific and Technical Information of China (English)

    Yifei Sun; Nobuhisa Watanabe; Wei Wang; Tianle Zhu

    2013-01-01

    A group parameter approach using "total organic halogen" is effective for monitoring gaseous organic halogen compounds,including fluorine,chlorine,and bromine compounds,generated from combustion.We described the use of barrier-discharge radiofrequencyhelium-plasma/atomic emission spectrometry,for the detection of semi-and low-volatile organic halogen compounds (SLVOXs),which can be collected by CarbotrapTM adsorbents and analyzed using thermal desorption.The optimal carrier gas flow rates at the injection and desorption lines were established to be 100 mL/min.The detection range for SLVOXs in the gaseous samples was from 10 ng to tens of micrograms.Measuring F was more diflicult than measuring Cl or Br,because the wavelength ofF is dose to that of air.The barrierdischarge radiofrequency-helium-plasma/atomic emission spectrometry measured from 85% to 103% of the SLVOXs in the gas sample.It has been found that Carbotrap B is appropriate for high-boiling-point compounds,and Carbotrap C is suitable for the determination of organic halogen compounds with lower boiling points,in the range 200-230℃.Under optimal analysis conditions,a chlorinecontaining plastic was destroyed using different oxygen concentrations.Lower oxygen concentrations resulted in the production of lower amounts of organic halogen compounds.

  12. A one dimensional model study of the mechanism of halogen liberation and vertical transport in the polar troposphere

    Directory of Open Access Journals (Sweden)

    E. Lehrer

    2004-01-01

    Full Text Available Sudden depletions of tropospheric ozone during spring were reported from the Arctic and also from Antarctic coastal sites. Field studies showed that those depletion events are caused by reactive halogen species, especially bromine compounds. However the source and seasonal variation of reactive halogen species is still not completely understood. There are several indications that the halogen mobilisation from the sea ice surface of the polar oceans may be the most important source for the necessary halogens. Here we present a one dimensional model study aimed at determining the primary source of reactive halogens. The model includes gas phase and heterogeneous bromine and chlorine chemistry as well as vertical transport between the surface and the top of the boundary layer. The autocatalytic Br release by photochemical processes (bromine explosion and subsequent rapid bromine catalysed ozone depletion is well reproduced in the model and the major source of reactive bromine appears to be the sea ice surface. The sea salt aerosol alone is not sufficient to yield the high levels of reactive bromine in the gas phase necessary for fast ozone depletion. However, the aerosol efficiently 'recycles' less reactive bromine species (e.g. HBr and feeds them back into the ozone destruction cycle. Isolation of the boundary layer air from the free troposphere by a strong temperature inversion was found to be critical for boundary layer ozone depletion to happen. The combination of strong surface inversions and presence of sunlight occurs only during polar spring.

  13. On the ultrafast charge migration and subsequent charge directed reactivity in Cl⋯N halogen-bonded clusters following vertical ionization

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Sankhabrata; Bhattacharya, Atanu, E-mail: atanub@ipc.iisc.ernet.in [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore (India); Periyasamy, Ganga [Department of Chemistry, Central College Campus, Bangalore University, Bangalore (India)

    2015-06-28

    In this article, we have presented ultrafast charge transfer dynamics through halogen bonds following vertical ionization of representative halogen bonded clusters. Subsequent hole directed reactivity of the radical cations of halogen bonded clusters is also discussed. Furthermore, we have examined effect of the halogen bond strength on the electron-electron correlation- and relaxation-driven charge migration in halogen bonded complexes. For this study, we have selected A-Cl (A represents F, OH, CN, NH{sub 2}, CF{sub 3}, and COOH substituents) molecules paired with NH{sub 3} (referred as ACl:NH{sub 3} complex): these complexes exhibit halogen bonds. To the best of our knowledge, this is the first report on purely electron correlation- and relaxation-driven ultrafast (attosecond) charge migration dynamics through halogen bonds. Both density functional theory and complete active space self-consistent field theory with 6-31 + G(d, p) basis set are employed for this work. Upon vertical ionization of NCCl⋯NH{sub 3} complex, the hole is predicted to migrate from the NH{sub 3}-end to the ClCN-end of the NCCl⋯NH{sub 3} complex in approximately 0.5 fs on the D{sub 0} cationic surface. This hole migration leads to structural rearrangement of the halogen bonded complex, yielding hydrogen bonding interaction stronger than the halogen bonding interaction on the same cationic surface. Other halogen bonded complexes, such as H{sub 2}NCl:NH{sub 3}, F{sub 3}CCl:NH{sub 3}, and HOOCCl:NH{sub 3}, exhibit similar charge migration following vertical ionization. On the contrary, FCl:NH{sub 3} and HOCl:NH{sub 3} complexes do not exhibit any charge migration following vertical ionization to the D{sub 0} cation state, pointing to interesting halogen bond strength-dependent charge migration.

  14. Fast and Specific Assessment of the Halogenating Peroxidase Activity in Leukocyte-enriched Blood Samples.

    Science.gov (United States)

    Flemmig, Jörg; Schwarz, Pauline; Bäcker, Ingo; Leichsenring, Anna; Lange, Franziska; Arnhold, Jürgen

    2016-07-28

    In this paper a protocol for the quick and standardized enrichment of leukocytes from small whole blood samples is described. This procedure is based on the hypotonic lysis of erythrocytes and can be applied to human samples as well as to blood of non-human origin. The small initial sample volume of about 50 to 100 µl makes this method applicable to recurrent blood sampling from small laboratory animals. Moreover, leukocyte enrichment is achieved within minutes and with low material efforts regarding chemicals and instrumentation, making this method applicable in multiple laboratory environments. Standardized purification of leukocytes is combined with a highly selective staining method to evaluate halogenating peroxidase activity of the heme peroxidases, myeloperoxidase (MPO) and eosinophil peroxidase (EPO), i.e., the formation of hypochlorous and hypobromous acid (HOCl and HOBr). While MPO is strongly expressed in neutrophils, the most abundant immune cell type in human blood as well as in monocytes, the related enzyme EPO is exclusively expressed in eosinophils. The halogenating activity of these enzymes is addressed by using the almost HOCl- and HOBr-specific dye aminophenyl fluorescein (APF) and the primary peroxidase substrate hydrogen peroxide. Upon subsequent flow cytometry analysis all peroxidase-positive cells (neutrophils, monocytes, eosinophils) are distinguishable and their halogenating peroxidase activity can be quantified. Since APF staining may be combined with the application of cell surface markers, this protocol can be extended to specifically address leukocyte sub-fractions. The method is applicable to detect HOCl and HOBr production both in human and in rodent leukocytes. Given the widely and diversely discussed immunological role of these enzymatic products in chronic inflammatory diseases, this protocol may contribute to a better understanding of the immunological relevance of leukocyte-derived heme peroxidases.

  15. Side-polished multimode fiber biosensor based on surface plasmon resonance with halogen light

    Science.gov (United States)

    Lin, Hong-Yu; Tsai, Woo-Hu; Tsao, Yu-Chia; Sheu, Bor-Chiou

    2007-02-01

    A side-polished multimode fiber sensor based on surface plasmon resonance (SPR) as the transducing element with a halogen light source is proposed. The SPR fiber sensor is side polished until half the core is closed and coated with a 37 nm gold thin film by dc sputtering. The SPR curve on the optical spectrum is described by an optical spectrum analyzer and can sense a range of widths in wavelengths of SPR effects. The measurement system using the halogen light source is constructed for several real-time detections that are carried out for the measurement of the index liquid detections for the sensitivity analysis. The sensing fiber is demonstrated with a series of refractive index (RI) liquids and set for several experiments, including the stability, repeatability, and resolution calibration. The results for the halogen light source with the resolution of the measurement based on wavelength interrogation were 3×10-6 refractive index units (RIUs). The SPR dip shifted in wavelength is used as a measure of the RI change at a surface, and this RI change varies directly with the number of biomolecules at the surface. The SPR dip shift in wavelength, which was hybridized at 0.1 μM of the target DNA to the probe DNA, was 8.66 nm. The all-fiber multimode SPR sensor, which has the advantages of being low cost, being disposable, having high stability and linearity, being free of labeling, and having potential for real-time detection, permit the sensor and system to be used in biochemical sensing and environmental monitoring.

  16. Noncovalent Halogen Bonding as a Mechanism for Gas-Phase Clustering

    Science.gov (United States)

    Wegeberg, Christina; Donald, William A.; McKenzie, Christine J.

    2017-10-01

    Gas-phase clustering of nonionizable iodylbenzene (PhIO2) is attributed to supramolecular halogen bonding. Electrospray ionization results in the formation of ions of proton-charged and preferably sodium-charged clusters assignable to [H(PhIO2) n ]+, n = 1-7; [Na(PhIO2) n ]+, n = 1-6; [Na2(PhIO2) n ]2+, n = 7-20; [HNa(PhIO2) n ]2+, n = 6-19; [HNa2(PhIO2) n ]3+, n = 15-30; and [Na3(PhIO2) n ]3+, n = 14-30. The largest cluster detected has a supramolecular mass of 7147 Da. Electronic structure calculations using the M06-2X functional with the 6-311++G(d,p) basis set for C, H, and O, and LANL2DZ basis set for I and Na predict 298 K binding enthalpies for the protonated and sodiated iodylbenzene dimers and trimers are greater than 180 kJ/mol. This is exceptionally high in comparison with other protonated and sodiated clusters with well-established binding enthalpies. Strongly halogen-bonded motifs found in the crystalline phases of PhIO2 and its derivatives serve as models for the structures of larger gas-phase clusters, and calculations on simple model gas-phase dimer and trimer clusters result in similar motifs. This is the first account of halogen bonding playing an extensive role in gas-phase associations. [Figure not available: see fulltext.

  17. Influence of the Halogen Activation on the Ozone Layer in XXIst Century

    Science.gov (United States)

    Larin, Igor; Aloyan, Artash; Yermakov, Alexandr

    2016-04-01

    The aim of the work is to evaluate a possible effect of heterophase chemical reactions (HCR) with participation of reservoir gases (ClONO2, HCl) and sulfate particles of the Junge layer on the ozone layer at mid-latitudes in the XXI century, which could be relevant for more accurate predicting a recovery of the ozone layer, taking into account that just these processes were the main cause of the ozone depletion at the end of XXth century. Required for calculating the dynamics of GHR data on the specific volume/surface of the sulfate aerosols in the lower stratosphere were taken from the data of field experiments. Their physico-chemical properties (chemical composition, density, water activity and free protons activity et al.) have been obtained with help of thermodynamic calculations (Atmospheric Inorganic Model, AIM). Altitude concentration profiles of individual gas components, as well as temperature and relative humidity (RH) at a given geographic location and season have been calculated using a two-dimensional model SOCRATES. The calculations have been made for the conditions of June 1995, 2040 and 2080 at 15 km altitude and 50° N latitude. It has been shown that the rate of ozone depletion as a result of processes involving halogen activation for the given conditions in 2040, 2080 is about 35% lower than a corresponding value in 1995 (a year of maximum effect of halogen activation). From this we can conclude that in the XXI century, despite the natural decline of ozone-depleting chlorofluorocarbons. processes of halogen activation of the ozone depletion with participation of sulfate aerosols should be taken into account in the calculations of the recovery of the ozone layer at mid-latitudes.

  18. 阻挡放电联合金属氧化物催化降解H2S的研究%On the decomposition of hydrogen sulfide by means of dielectric barrier discharge and metal oxide catalysis

    Institute of Scientific and Technical Information of China (English)

    党小庆; 黄家玉; 康露; 吴涛; 张青

    2012-01-01

    The paper takes as its research focus the study of the decomposition of hydrogen sulfide by means of dielectric harrier discharge and metal oxide catalysis. In order to promote our intended study, we have done experiments with the dielectric barrier discharge (DBD) plasma combined with metal oxide catalysis to remove the gaseous H2S. We have also investigated the effects of metal oxide catalyst type, i.e. single-component and complex-component, along with the relation between the catalyst and non-thermal plasma(NTP) on the simultaneous removal of H2S and O3. It is on the basis of the work done above, we have brought about a model for proper interpretation of the catalytic decomposition mechanism of H2S. The experimental results we have gained show that under the condition of the same active component loading and at the same voltage applied in the NTP reactor, the catalytic activities of the Mn-cumplex catalyst prove to be higher than that of the single-component catalyst at the voltage applied below 22 kV. In terms of H2S removal efficiency, the metal oxide catalysts are expected to be ranked as follows: Ag + Mn > Cu + Mn > Fe + Mn > Mn. which is also in accord with the sequence of O3 decomposition ability. At 18 kV, compared to Mn catalyst (single-component) , H2S removal efficiency with Ag-Mn catalyst, Cu-Mn catalyst and Fe-Mn catalyst prove to be increased hy 10% , 6% and 4% respectively, whereas at the voltage of 18 kV, the removing efficiency of the Ag-Mn catalyst can be expected to reach 92% , The highest H2S removal efficiency we have achieved through experiments by using Mn-complex catalysts. The catalysts placed in the downstream of NTP also display a high catalytic activity for H2S. As to the H2S removal efficiency, Mn-catalyst in the post plasma zone turned to be lower than that in plasma area. But Mn-eatalyst in the post-plasma zone tends to be able to decompose O3 effectively both in air and H2S feeding environment. In the case of H2S feeding, ozone

  19. In vitro and in vivo studies of the effects of halogenated histidine analogs on Plasmodium falciparum.

    OpenAIRE

    Panton, L J; Rossan, R N; Escajadillo, A; Matsumoto, Y; Lee, A.T.; Labroo, V M; Kirk, K L; Cohen, L. A.; Aikawa, M.; Howard, R J

    1988-01-01

    The effects of four halogenated analogs of histidine on in vitro growth of Plasmodium falciparum malaria parasites were monitored by measurement of the incorporation of 3H-labeled amino acids into parasite proteins and by light and electron microscopy. The uptake of [3H]isoleucine was reduced to 50% of the control value by addition of 70 microM 2-fluoro-L-histidine (2-F-HIS) or 420 microM 2-iodo-L-histidine (2-I-HIS). [3H]histidine uptake into acid-insoluble material was affected equally by t...

  20. Protein ligand interactions 7 halogenated pyridinium salts as inhibitors of acetylcholinesterase from Electrophorus electricus.

    Science.gov (United States)

    Whiteley, C G; Ngwenya, D S

    1995-08-01

    The interaction of halo-quaternary pyridinium hydrochloride salts on acetylcholinesterase (AChE, E.C.3.1.1.7) has been investigated. Kinetic analysis has shown that they reflect a non-competitive inhibition with Ki values in the range 8-13 microM and 5-34 microM for chloro- and bromo-substituted salts respectively. Spectrophotometry was used to study the binding of the ligands with the enzyme and Scatchard analysis used to calculate the respective dissociation constants (Kd) and the number of binding sites. The substitution position of the halogen on the pyridine ring also influenced the binding capacity and the Ki values.

  1. Halogen bonded two-dimensional supramolecul arassemblies studied by high resolution scanning tunneling microscopy

    Institute of Scientific and Technical Information of China (English)

    YANG XunYu; WANG Fang; CHEN QiuXia; WANG LiYan; WANG ZhiQiang

    2007-01-01

    We described the formation of self-organized two-dimensional (2D) assemblies of N-(2,3,5,6-tetrafluoro- 4-iodophenyl)hexadecylamine and 1-dodecyl-imidazole at the liquid/HOPG interface. The two-dimen- sional assemblies showed a fishbone-like pattern structure as revealed by high-resolution scanning tunneling microscopy. Although different interactions can drive the formation of 2D assemblies,as far as we know,this is the first report on halogen bond-driven 2D assemblies.

  2. Did the Siberian Traps eruptions emit enough halogens to have an impact on ozone geochemistry?

    Science.gov (United States)

    Sibik, Svetlana; Edmonds, Marie; Villemant, Benoit; Thierry, Pauline; Polozov, Alexander

    2015-04-01

    The Siberian Traps Large Igneous Province is thought to have formed over 1 Ma at the end of the Permian, synchronous with the largest mass extinction in Earth's history. There remains much controversy as to the exact mechanism of the mass extinction, but all hypotheses revolve around the emission of volatiles in various forms. The research to date has tended to focus on sulfur and carbon rather than halogen degassing, despite this being probably critical in terms of environmental impact as they might have been played a crucial role in ozone layer depletion and therefore promote mass extinction. Current study aims to look at the behaviour of chlorine, bromine, iodine and fluorine to evaluate the halogen budget contribution from heterogeneous mantle source and from evaporates, which dominate in the south (Cambrian evaporites) and north (Devonian evaporites) of Siberian platform. For this study we use basaltic sills and lava flows emplaced in the area with no volatile-rich sediments south-east from Norilsk (Dyupkin lake and Lower Tunguska river regions) and a sill intruded into evaporates in Nepa location in the south of the platform, originally aimed at prospecting for potassium salts. Borehole samples of basalts intruded into evaporites might have been penetrated by salts and anhydrite. In order to eliminate this effect and ensure that we analyse halogen contents in pure basalts prior to any further analysis the samples were specifically treated so that penetrated material was removed as leachates. Whole rock fine powders of basalts were analysed for halogens, major and trace elements. The solutions obtained by basalt pyrohydrolysis extraction, leachates of basaltic powders and dissolved evaporites were analysed by ion chromatography for chlorine and fluorine and by ICP-MS for bromine and iodine. Basalts intruded into evaporites demonstrate predicted pronounced chlorine, bromine and iodine enrichments associated with salt assimilation. The results show that bromine

  3. Theoretical Study of the Iodine-catalyzed Nucleophilic Addition by Halogen Bond

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The iodine-catalyzed nucleophilic addition of pyrrole to acetone has been studied by density functional theory at the level of Lanl2DZ*. It has been shown that the first iodine molecule appears to have a remarkable catalytic effect on this reaction by halogen bond between carbonyl oxygen and iodine molecule, but the second one does not improve the reaction largely. In general, the nucleophilic addition at the C(2) site of pyrrole is more favorable than that at the C(3)site;however, this trend is not prominent or even changed in acetronitrile solvent for the indole system, which is consistent with the experimental result by Bandgar.

  4. Application of the Langley plot for calibration of sun sensors for the Halogen Occultation Experiment (HALOE)

    Science.gov (United States)

    Moore, Alvah S., Jr.; Mauldin, L. ED, III; Stump, Charles W.; Reagan, John A.; Fabert, Milton G.

    1989-01-01

    The calibration of the Halogen Occultation Experiment (HALOE) sun sensor is described. This system consists of two energy-balancing silicon detectors which provide coarse azimuth and elevation control signals and a silicon photodiode array which provides top and bottom solar edge data for fine elevation control. All three detectors were calibrated on a mountaintop near Tucson, Ariz., using the Langley plot technique. The conventional Langley plot technique was modified to allow calibration of the two coarse detectors, which operate wideband. A brief description of the test setup is given. The HALOE instrument is a gas correlation radiometer that is now being developed for the Upper Atmospheric Research Satellite.

  5. A New Halogenated Biindole and A New Apo-carotenone from Green Alga Chaetomorpha basiretorsa Setchell

    Institute of Scientific and Technical Information of China (English)

    Da Yong SHI; Li Jun HAN; Jie SUN; Shuai LI; Su Juan WANG; Yong Chun YANG; Xiao FAN; Jian Gong SHI

    2005-01-01

    A new halogenated biindole and a new apo-carotenone have been isolated from the ethanolic extract of the green alga Chaetomorpha basiretorsa Sethcell. On the basis of chemical and spectroscopic methods including 2D NMR technique, their structures have been elucidated as 4,4′-dichloro-5,5′-dibromo-7,7′-dimethoxy-2,2′-bi- 1H-indole and l ′S*,4′R*-8-(4′-hydroxy-2′,6′,6′-trimethylcyclohex-2-enyl)-6-methyloct-3E,5E,7E-trien-2-one, respectively.

  6. Inhibition of quorum sensing in Pseudomonas aeruginosa biofilm bacteria by a halogenated furanone compound

    DEFF Research Database (Denmark)

    Hentzer, Morten; Riedel, K.; Rasmussen, Thomas Bovbjerg

    2002-01-01

    Novel molecular tools have been constructed which allow for in situ detection of N-acyl homoserine lactone (AHL)-mediated quorum sensing in Pseudomonas aeruginosa biofilms. The reporter responds to AHL activation of LasR lay expression of an unstable version of the green-fluorescent protein (Gfp......). Gfp-based reporter technology has been applied for non-destructive, single-cell-level detection of quorum sensing in laboratory-based P. aeruginosa biofilms. It is reported that a synthetic halogenated furanone compound, which is a derivative of the secondary metabolites produced by the Australian...

  7. "Textbook" adsorption at "nontextbook" adsorption sites: halogen atoms on alkali halide surfaces.

    Science.gov (United States)

    Li, Bo; Michaelides, Angelos; Scheffler, Matthias

    2006-07-28

    Density-functional theory and second order Møller-Plesset perturbation theory calculations indicate that halogen atoms bond preferentially to halide substrate atoms on a series of alkali halide surfaces, rather than to the alkali atoms as might be anticipated. An analysis of the electronic structures in each system reveals that this novel adsorption mode is stabilized by the formation of textbook two-center three-electron covalent bonds. The implications of these findings to, for example, nanostructure crystal growth, are briefly discussed.

  8. Atomic forces between noble gas atoms, alkali ions, and halogen ions for surface interactions

    Science.gov (United States)

    Wilson, J. W.; Outlaw, R. A.; Heinbockel, J. H.

    1988-01-01

    The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base developed from analysis of the two-body potential data, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas surfaces and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

  9. Assembling supramolecular networks by halogen bonding in coordination polymers driven by 5-bromonicotinic acid

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Jin-Zhong, E-mail: gujzh@lzu.edu.cn [State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Wu, Jiang [State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Kirillov, Alexander M. [Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, The University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Lv, Dong-Yu; Tang, Yu; Wu, Jin-Cai [State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China)

    2014-05-01

    A series of six coordination compounds ([Zn(5-Brnic){sub 2}]·1.5H{sub 2}O){sub n} (1), [Cd(5-Brnic){sub 2}]{sub n} (2), [Co(5-Brnic){sub 2}(H{sub 2}O){sub 2}]{sub n} (3), [Zn(5-Brnic){sub 2}(H{sub 2}biim)]{sub n} (4), ([Cd(5-Brnic){sub 2}(phen)]·H{sub 2}O){sub n} (5), and [Pb(5-Brnic){sub 2}(phen)] (6) have been generated by the hydrothermal method from the metal(II) nitrates, 5-bromonicotinic acid (5-BrnicH), and an optional ancillary 1,10-phenanthroline (phen) or 2,2′-biimidazole (H{sub 2}biim) ligand. All the products 1–6 have been characterized by IR spectroscopy, elemental, thermal, powder and single-crystal X-ray diffraction analyses. Their 5-bromonicotinate-driven structures vary from the 3D metal-organic framework with the seh-3,5-P21/c topology (in 2) and the 2D interdigitated layers with the sql topology (in 1 and 3), to the 1D chains (in 4 and 5) and the 0D discrete monomers (in 6). The 5-bromonicotinate moiety acts as a versatile building block and its tethered bromine atom plays a key role in reinforcing and extending the structures into diverse 3D supramolecular networks via the various halogen bonding Br⋯O, Br⋯Br, and Br⋯π interactions, as well as the N–H⋯O and C–H⋯O hydrogen bonds. The obtained results demonstrate a useful guideline toward engineering the supramolecular architectures in the coordination network assembly under the influence of various halogen bonding interactions. The luminescent (for 1, 2, 4, 5, and 6) and magnetic (for 3) properties have also been studied and discussed in detail. - Graphical abstract: Six coordination compounds driven by 5-bromonicotinic acid have been generated and structurally characterized, revealing diverse metal-organic networks that are further reinforced and extended via various halogen bonding interactions. - Highlights: • 5-Bromonicotinic acid is a versatile ligand for Zn, Cd, Co and Pb derivatives. • Careful selection of co-ligands and metals resulted in different network

  10. Strong and Selective Halide Anion Binding by Neutral Halogen-Bonding [2]Rotaxanes in Wet Organic Solvents.

    Science.gov (United States)

    Lim, Jason Y C; Bunchuay, Thanthapatra; Beer, Paul D

    2017-04-03

    The design and construction of neutral interlocked host molecules for anion recognition are rare. Using an active-metal template approach, the preparation of a family of neutral halogen bonding (XB) rotaxanes containing two, three and four iodotriazole groups integrated into the macrocycle and axle components is achieved. In spite of the interlocked hosts' neutrality, such rotaxane systems are capable of binding halide anions strongly and selectively in wet organic solvent mixtures. Importantly, halide-binding strength and selectivity can be modulated by varying the number and position of the halogen bond donor iodotriazole groups within the interlocked cavity; the rotaxane containing the largest number of halogen bond donor groups exhibits the highest halide anion-binding affinities. By varying the percentage of water content in the solvent, neutral XB donor-mediated anion-binding strength is also demonstrated to be highly sensitive to solvent polarity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Process for simultaneously processing of used metal and/or metal scrap and scrap containing halogenated hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Dapper, G.; Kirchner, W.; Sloterdijk, W.; Verbraak, C.A.

    1982-03-02

    A process is presened for reducing environmental pollution resulting from disposal of waste containing halogenated hydrocarbons by simultaneous treatment with used metal and/or metal scrap at elevated temperatures. The halogenated hydrocarbons are pyrolyzed and the resulting hydrogen halide containing gas is brought into contact with the used metal and/or metal scrap at elevated temperatures so as to form metal halogenides that are volatile under the conditions applied. The volatile metal halogenides are largely separated from the gaseous mixture formed, and at least part of the remaining gaseous mixture and/or hydrocarbon residue is used as fuel to maintain the required temperature. The waste feed compositions and process conditions can be chosen to effect separation between various metals by selective halogenation and condensation, and substantially all of the hydrogen halide can be tied up and recovered as metal halogenides.

  12. Determination of small halogenated carboxylic acid residues in drug substances by high performance liquid chromatography-diode array detection following derivatization with nitro-substituted phenylhydrazines.

    Science.gov (United States)

    Hou, Desheng; Fan, Jingjing; Han, Lingfei; Ruan, Xiaoling; Feng, Feng; Liu, Wenyuan; Zheng, Feng

    2016-03-18

    A method for the determination of small halogenated carboxylic acid (HCA) residues in drug substances is urgently needed because of the potential of HCAs for genotoxicity and carcinogenicity in humans. We have now developed a simple method, involving derivatization followed by high performance liquid chromatography-diode array detection (HPLC-DAD), for the determination of six likely residual HCAs (monochloroacetic acid, monobromoacetic acid, dichloroacetic acid, 2-chloropropionic acid, 2-bromopropionic acid and 3-chloropropionic acid) in drug substances. Different nitro-substituted phenylhydrazines (NPHs) derivatization reagents were systematically compared and evaluated. 2-Nitrophenylhydrazine hydrochloride (2-NPH·HCl) was selected as the most suitable choice since its derivatives absorb strongly at 392 nm, a region of the spectrum where most drug substances and impurities absorb very weakly. During the derivatization process, the commonly used catalyst, pyridine, caused rapid dechlorination or chlorine substitution of α-halogenated derivatives. To avoid these unwanted side reactions, a reliable derivatization method that did not use pyridine was developed. Reaction with 2-NPH·HCl using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride as coupling agent in acetonitrile-water (70:30) at room temperature for 2h gave complete reaction and avoided degradation products. The derivatives were analyzed, without any pretreatment, using gradient HPLC with detection in the near visible region. Organic acids commonly found in drug substances and other impurities did not interfere with the analysis. Good linearity (r>0.999) and low limits of quantitation (0.05-0.12 μg mL(-1)) were obtained. The mean recoveries were in the range of 80-115% with RSD <5.81% except for 3-CPA in ibuprofen which was 78.5%. The intra- and inter-day precisions were expressed as RSD <1.98% and <4.39%, respectively. Finally, the proposed method was successfully used for the residue

  13. Composes inter-halogenes sous pression: etude des transformations structurales dans le monobromure d'iode sous forme dense

    Science.gov (United States)

    Bouchard, Alexandre

    La famille des composes halogenes et inter-halogenes representent des solides moleculaires adoptant des phases denses communes avec des solides moleculaires diatomiques comme l'azote et l'hydrogene. Parmi les transformations structurales et electroniques induites sous haute pression et observees dans ces solides, on note, entre autres, la dissociation moleculaire et la metallisation. De plus, l'etude des phases denses de l'iode a permis recemment l'observation d'une structure cristalline possedant une modulation dite incommensurable, c'est-a-dire une modulation possedant une periodicite differente de celle de la structure cristalline, jetant ainsi une lumiere nouvelle sur le processus de dissociation moleculaire dans les solides halogenes. Dans ce memoire, on propose d'etudier les changements structuraux dans monobromure d'iode (IBr), un compose inter-halogene possedant des proprietes structurales semblables a celles de deux composes halogenes, soit l'iode (I 2) et le brome (Br2) sous leur forme solide. Des experiences de diffraction des rayons X de poudres en utilisant un rayonnement synchrotron ont ete realisees a temperature ambiante sur l'IBr en variant la pression jusqu'aux environs de 60 GPa. La nature chimique particuliere du compose IBr a necessite la mise au point de techniques de chargement d'echantillon destinees a preserver l'integrite chimique de la substance utilisee. On rapporte egalement l'observation d'une phase de l'IBr presentant une modulation incommensurable. Les phases observees dans l'IBr permettent d'etablir des paralleles avec les phases denses rapportees dans I2 et Br2 par le biais d'un modele phenomenologique decrivant la sequence structurale des solides halogenes sous forme condensee.

  14. Fabrication and thermal stability studies of polyamide 66 containing triaryl phosphine oxide

    Indian Academy of Sciences (India)

    Xiaofeng Yang; Qiaoling Li; Zhiping Chen; Hongli Han

    2009-08-01

    An intrinsically halogen-free flame retardant polyamide 66 (FR-PA66) was fabricated successfully by two-step polymerization reaction with adipic acid hexamethylene salt (AH salt) and bis(4-carboxyphenyl) phenyl phosphine oxide (BCPPO) as raw materials. The structure, combustion properties and thermal stability were characterized by means of intrinsic viscosity, Fourier transform infrared spectroscopy (FTIR), combustion testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and scanning electron microscope (SEM). Experiments show that BCPPO have excellent copolymerization properties with AH salt. And incorporation of triaryl phosphine oxide (TPO) did not transform the crystal phase structure of PA66. During fabrication of FR-PA66, melt polymerization time exhibits more surprising influence on intrinsic viscosity than aqueous solution polymerization time. The LOI value of FR-PA66 with 9 wt% TPO reaches 27.2, and corresponding UL94 rating reaches V-0. Improved thermo-stability of FR-PA66 can be attributed to both forming of compact char protective layer and further consolidation effect of / synergistic system.

  15. Products and mechanisms of the oxidation of organic compounds in atmospheric air plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Marotta, Ester; Schiorlin, Milko; Paradisi, Cristina [Department of Chemical Sciences, Universita di Padova, Via Marzolo 1, 35131 Padova (Italy); Rea, Massimo, E-mail: cristina.paradisi@unipd.i [Department of Electrical Engineering, Universita di Padova, 35131 Padova (Italy)

    2010-03-31

    Atmospheric plasma-based technologies are developing as a powerful means for air purification, specifically for the oxidation of organic pollutants. To achieve a better control on the emissions produced by such treatments mechanistic insight is needed in the complex reactions of volatile organic compounds (VOCs) within the plasma. An account is given here of our comparative studies of the behaviour of model VOCs in response to different corona regimes (+dc, -dc and +pulsed) implemented within the same flow reactor. Model VOCs considered include two alkanes (n-hexane and i-octane), one aromatic hydrocarbon (toluene) and two halogenated methanes, dibromomethane (CH{sub 2}Br{sub 2}) and dibromodifluoromethane (CF{sub 2}Br{sub 2}, halon 1202). Efficiency and product data are reported and discussed as well as various possible initiation reactions. A powerful diagnostic tool is ion analysis, performed by atmospheric pressure chemical ionization-mass spectrometry: it provides a map of major ions and ion-molecule reactions and a rationale for interpreting current/voltage characteristics of dc coronas. It is shown that, depending on the specific VOC and corona regime adopted, different initiation steps prevail in the VOC-oxidation process and that the presence of a VOC, albeit in small amounts (500 ppm), can greatly affect some important plasma properties (ion population, current/voltage profile, post-discharge products).

  16. The dance of meaning

    DEFF Research Database (Denmark)

    Rasmussen, Ole Elstrup

    2005-01-01

    competence, qualifications, sense making, reasoning, meaning, intentionality, interpersonal relationship......competence, qualifications, sense making, reasoning, meaning, intentionality, interpersonal relationship...

  17. Halogen-Bond Effects on the Thermo- and Photochromic Behaviour of Anil-Based Molecular Co-crystals.

    Science.gov (United States)

    Carletta, Andrea; Spinelli, Floriana; d'Agostino, Simone; Ventura, Barbara; Chierotti, Michele R; Gobetto, Roberto; Wouters, Johan; Grepioni, Fabrizia

    2017-02-27

    N-Salicilideneanilines are among the most studied thermo- and photochromic systems in the solid state. Although thermochromism is a general property of crystalline N-salicilideneanilines, photochromism is known in a limited number of cases. As a method for the construction of thermo- and photo-responsive molecular architectures, the co-crystallisation of 1,2,4,5-tetrafluoro-3,6-diiodobenzene (I2F4) with three selected imines of o-vanillin, named 1, 2 and 3, obtained through a condensation reaction with 3-aminopyridine, 4-bromoaniline and 4-iodoaniline, respectively, is reported herein. All crystals and co-crystals have been characterised by means of solid-state complementary techniques (X-ray diffraction, solid-state NMR spectroscopy, absorption and emission spectroscopy). The role of halogen bonding and crystal packing in the optical and chromic properties of all solid materials is discussed. All solids exhibit thermochromic behaviour, and three of them (2, 22 ⋅I2F4 and 32 ⋅I2F4) are also photochromic. Imine derivative 3 crystallises in two different polymorphic forms (3 A and 3 B) and a solvate (3Solv ). The bromo and iodo derivatives, 2 and 3 B, are isomorphous and form isomorphous co-crystals with I2F4, but behave differently when exposed to UV light because only crystalline 2 is photochromic. Interestingly, the replacement of bromine with iodine seems to turn off the photochromism because crystalline 3 A and 3Solv , and even the 20.7 30.3 solid solution, do not manifest photochromic behaviour.

  18. Catalytic wet-oxidation of a mixed liquid waste: COD and AOX abatement.

    Science.gov (United States)

    Goi, D; de Leitenburg, C; Trovarelli, A; Dolcetti, G

    2004-12-01

    A series of catalytic wet oxidation (CWO) reactions, at temperatures of 430-500 K and in a batch bench-top pressure vessel were carried out utilizing a strong wastewater composed of landfill leachate and heavily organic halogen polluted industrial wastewater. A CeO2-SiO2 mixed oxide catalyst with large surface area to assure optimal oxidation performance was prepared. The catalytic process was examined during batch reactions controlling Chemical Oxygen Demand (COD) and Adsorbable Organic Halogen (AOX) parameters, resulting AOX abatement to achieve better effect. Color and pH were also controlled during batch tests. A simple first order-two stage reaction behavior was supposed and verified with the considered parameters. Finally an OUR test was carried out to evaluate biodegradability changes of wastewater as a result of the catalytic reaction.

  19. Synthesis and improved photochromic properties of pyrazolones in the solid state by incorporation of halogen

    Science.gov (United States)

    Guo, Jixi; Yuan, Hui; Jia, Dianzeng; Guo, Mingxi; Li, Yinhua

    2017-01-01

    Four novel photochromic pyrazolones have been prepared by introducing halogen atoms as substituents on the benzene ring. All as-synthesized compounds exhibited excellent reversible photochromic performances in the solid state. Upon UV light irradiation, the as-synthesized compounds can change their structures from E-form to K-form with yellow coloration. Further processed by heating, they rapidly reverted to their initial states at 120 °С. Their photo-response and thermal bleaching kinetics were detailed investigated by UV absorption spectra. The results showed that the time constants were higher than that of our previously reported compounds at least one order of magnitude and the rate constants of the as-synthesized compounds were significantly influenced by the size and electronegativity of different halogen atoms. The fluorescence emission were modulated in a high degree via photoisomerization of pyrazolones, which might be due to the efficient energy transfer from E-form to K-form isomers for their partly overlaps between their E-form absorption spectra and K-form fluorescence spectra.

  20. Synthesis and cytotoxic properties of halogen and aryl-/heteroarylpiperazinyl derivatives of benzofurans.

    Science.gov (United States)

    Krawiecka, Mariola; Kuran, Bozena; Kossakowski, Jerzy; Cieslak, Marcin; Kazmierczak-Baranska, Julia; Krolewska, Karolina; Nawrot, Barbara

    2015-01-01

    A series of seven derivatives of 1,1'-(5,6-dimethoxy-3-methyl-1-benzofuran-2,7-diyl)diethanone was synthesized and characterized by (1)HNMR and ESI MS spectra and elemental analyses. The obtained new compounds and three halogen derivatives of benzofuran, reported in our earlier work, were tested for their cytotoxic properties in human chronic (K562) and acute (HL60) leukemia cells, human cervical cancer (HeLa), and normal endothelial cells (HUVEC). Four compounds (2, 3, 4, 5), which contain halogens in their structure showed significant anticancer activity. The most promising was 1,1'-[3- (bromomethyl)-5,6-dimethoxy-1-benzofuran-2,7-diyl]diethanone (2), which was highly and selectively toxic for K562 cells (IC50 of 5µM) and HL60 cells (IC50 of 0.1µM), which showed no cytotoxicity toward HeLa and HUVEC cells. Moreover, the observed remarkable cytotoxicity of this compound toward K562 cells resulted from cells apoptosis.

  1. Halogenation effects on electron collisions with CF3Cl, CF2Cl2, and CFCl3

    Science.gov (United States)

    Freitas, T. C.; Lopes, A. R.; Azeredo, A. D.; Bettega, M. H. F.

    2016-04-01

    We report differential and integral elastic cross sections for low-energy electron collisions with CF3Cl, CF2Cl2, and CFCl3 molecules for energies ranging from 0.1 eV to 30 eV. The calculations were performed using the Schwinger multichannel method with pseudopotentials in the static-exchange and static-exchange plus polarization approximations. The influence of the permanent electric dipole moment on the cross sections was included using the Born closure scheme. A very good agreement between our calculations and the experimental results of Jones [J. Chem. Phys. 84, 813 (1986)], Mann and Linder [J. Phys. B 25, 1621 (1992); 25, 1633 (1992)] and Hoshino et al. [J. Chem. Phys. 138, 214305 (2013)] was found. We also compare our results with the calculations of Beyer et al. [Chem. Phys. 255, 1 (2000)] using the R-matrix method, where we find good agreement with respect to the location of the resonances, and with the calculations of Hoshino et al. using the independent atom method with screening corrected additivity rule, where we find qualitative agreement at energies above 20 eV. Additional electronic structure calculations were carried out in order to help in the interpretation of the scattering results. The stabilization the lowest σ∗ resonance due to the exchange of fluorine by chlorine atoms (halogenation effect) follows a simple linear relation with the energy of the lowest unoccupied molecular orbitals and can be considered as a signature of the halogenation effect.

  2. NanoSIMS50 - a powerful tool to elucidate cellular localization of halogenated organic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Gutleb, Arno C.; Hoffmann, Lucien [Centre de Recherche Public - Gabriel Lippmann, Department Environment and Agro-biotechnologies (EVA), Belvaux (Luxembourg); Freitas, Jaime [Wageningen University, Toxicology Section, Wageningen (Netherlands); Murk, Albertinka J. [Wageningen University, Toxicology Section, Wageningen (Netherlands); Wageningen IMARES, P.O. Box 68, IJmuiden (Netherlands); Verhaegen, Steven; Ropstad, Erik [Norwegian School of Veterinary Science, Oslo (Norway); Udelhoven, Thomas [Centre de Recherche Public - Gabriel Lippmann, Department Environment and Agro-biotechnologies (EVA), Belvaux (Luxembourg); Trier University, Remote Sensing and Geoinformatics Department, Trier (Germany); Audinot, Jean-Nicolas [Centre de Recherche Public - Gabriel Lippmann, Departement Science et Analyse des Materiaux (SAM), Belvaux (Luxembourg)

    2012-11-15

    Persistent organic pollutants are widely distributed in the environment and lots of toxicological data are available. However, little is known on the intracellular fate of such compounds. Here a method applying secondary ion mass spectrometry is described that can be used to visualize cellular localization of halogenated compounds and to semi-quantitatively calculate concentrations of such compounds. Of the model compounds tested, TBBPA was homogenously distributed in the cell membrane of the H295R cells while PFOS accumulated in very distinct locations in the cell membrane. Relative intracellular concentrations of 4-OH-BDE69 and 4-OH-BDE121 in GH3.TRE were 61 % and 18 %, respectively, compared to the parent compounds. These differences may partly explain that observed effect concentrations for 4-OH-BDEs in in vitro experiments are usually lower than what would be expected based on receptor binding studies. NanoSIMS50 proved to be a powerful tool to describe the cellular distribution of halogenated compounds. The semi-quantitative data that can be obtained may help to further explain results from in vitro or in vivo experiments. (orig.)

  3. Identifying bioaccumulative halogenated organic compounds using a nontargeted analytical approach: seabirds as sentinels.

    Directory of Open Access Journals (Sweden)

    Christopher J Millow

    Full Text Available Persistent organic pollutants (POPs are typically monitored via targeted mass spectrometry, which potentially identifies only a fraction of the contaminants actually present in environmental samples. With new anthropogenic compounds continuously introduced to the environment, novel and proactive approaches that provide a comprehensive alternative to targeted methods are needed in order to more completely characterize the diversity of known and unknown compounds likely to cause adverse effects. Nontargeted mass spectrometry attempts to extensively screen for compounds, providing a feasible approach for identifying contaminants that warrant future monitoring. We employed a nontargeted analytical method using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS to characterize halogenated organic compounds (HOCs in California Black skimmer (Rynchops niger eggs. Our study identified 111 HOCs; 84 of these compounds were regularly detected via targeted approaches, while 27 were classified as typically unmonitored or unknown. Typically unmonitored compounds of note in bird eggs included tris(4-chlorophenylmethane (TCPM, tris(4-chlorophenylmethanol (TCPMOH, triclosan, permethrin, heptachloro-1'-methyl-1,2'-bipyrrole (MBP, as well as four halogenated unknown compounds that could not be identified through database searching or the literature. The presence of these compounds in Black skimmer eggs suggests they are persistent, bioaccumulative, potentially biomagnifying, and maternally transferring. Our results highlight the utility and importance of employing nontargeted analytical tools to assess true contaminant burdens in organisms, as well as to demonstrate the value in using environmental sentinels to proactively identify novel contaminants.

  4. The photodynamic therapy on Streptococcus mutans biofilms using erythrosine and dental halogen curing unit.

    Science.gov (United States)

    Lee, Young-Ho; Park, Ho-Won; Lee, Ju-Hyun; Seo, Hyun-Woo; Lee, Si-Young

    2012-12-01

    The purpose of our study was to evaluate the effect of photodynamic therapy (PDT), using erythrosine as a photosensitizing agent and a dental halogen curing unit as a light source, on Streptococcus mutans in a biofilm phase. The S. mutans biofilms were formed in a 24-well cell culture cluster. Test groups consisted of biofilms divided into four groups: group 1: no photosensitizer or light irradiation treatment (control group); group 2: photosensitizer treatment alone; group 3: light irradiation alone; group 4: photosensitizer treatment and light irradiation. After treatments, the numbers of colony-forming unit (CFU) were counted and samples were examined by confocal laser scanning fluorescence microscopy (CLSM). Only group 4 (combined treatment) resulted in significant increases in cell death, with rates of 75% and 55% after 8 h of incubation, and 74% and 42% at 12 h, for biofilms formed in brain-heart infusion (BHI) broth supplemented with 0% or 0.1% sucrose, respectively. Therefore, PDT of S. mutans biofilms using a combination of erythrosine and a dental halogen curing unit, both widely used in dental clinics, resulted in a significant increase in cell death. The PDT effects are decreased in biofilms that form in the presence of sucrose.

  5. Conformation stability, halogen and solvent effects on CO stretching of 4-chloro-3-halogenobenzaldehydes.

    Science.gov (United States)

    Tursun, Mahir; Parlak, Cemal

    2015-04-15

    The effects of halogen and solvent on the conformation and carbonyl stretching of 4-chloro-3-halogenobenzaldehydes [C7H4ClXO; X=F (CFB), Cl (CCB) or Br (CBB)] were investigated using the density functional theory (DFT) method. The B3LYP functional was used by the 6-311+G(3df,p) basis set in combination with the polarizable continuum model (PCM). Computations were focused on the cis and trans isomers of the compounds in 18 different polar or non-polar organic solvents. The theoretical frequencies of the solvent-induced CO stretching vibrations were correlated with the empirical solvent parameters such as the Kirkwood-Bauer-Magat (KBM) equation, the solvent acceptor number (AN), Swain parameters and the linear solvation energy relationships (LSER). The present work explores the effect of both the halogen and medium on the conformational preference and CO vibrational frequency. The findings of this work can be useful to those systems involving changes in the conformations analogous to the compounds studied.

  6. Isomorphous Crystals from Diynes and Bromodiynes Involved in Hydrogen and Halogen Bonds

    Directory of Open Access Journals (Sweden)

    Pierre Baillargeon

    2016-04-01

    Full Text Available Isomorphous crystals of two diacetylene derivatives with carbamate functionality (BocNH-CH2-diyne-X, where X = H or Br have been obtained. The main feature of these structures is the original 2D arrangement (as supramolecular sheets or walls in which the H bond and halogen bond have a prominent effect on the whole architecture. The two diacetylene compounds harbor neighboring carbamate (Boc protected amine and conjugated alkyne functionalities. They differ only by the nature of the atom located at the penultimate position of the diyne moiety, either a hydrogen atom or a bromine atom. Both of them adopt very similar 2D wall organizations with antiparallel carbamates (as in antiparallel beta pleated sheets. Additional weak interactions inside the same walls between molecular bricks are H bond interactions (diyne-H···O=C or halogen bond interactions (diyne-Br···O=C, respectively. Based on crystallographic atom coordinates, DFT (B3LYP/6-31++G(d,p and DFT (M06-2X/6-31++G(d,p calculations were performed on these isostructural crystals to gain insight into the intermolecular interactions.

  7. Alkoxy substituted halogenated closo-dodecaborates as anions for ionic liquids.

    Science.gov (United States)

    Jenne, Carsten; Kirsch, Christoph

    2015-08-07

    Halogenated and alkoxylated closo-dodecaborates [B12X11OR](2-) (X = Cl, Br; R = propyl, octyl, dodecyl) have been synthesized by halogenation of the known [B12H11OH](2-) anion followed by alkylation in the superbasic medium DMSO/KOH. The obtained sodium salts were transformed by simple metathesis reactions in aqueous solution to the tetrabutylammonium ([NBu4](+)) and 1-hexyl-3-methylimidazolium ([C6mim](+)) salts. All compounds were fully characterized by heteronuclear NMR, IR and Raman spectroscopy, ESI mass spectrometry, and thermal analytical measurements. Selected anions were also structurally characterized as their [Ph4P](+) salts by single crystal X-ray diffraction. The [C6mim](+) salts are thermally stable up to more than 300 °C and show clear melting points. Surprisingly, the compound [C6mim]2[B12Cl11O-propyl] having the short propyl group bound to the boron cluster shows the lowest melting point (96 °C) of all the investigated compounds. Thus this compound is a rare member of the class of ionic liquids consisting of dianions.

  8. New halogenated disinfection byproducts in swimming pool water and their permeability across skin.

    Science.gov (United States)

    Xiao, Feng; Zhang, Xiangru; Zhai, Hongyan; Lo, Irene M C; Tipoe, George L; Yang, Mengting; Pan, Yang; Chen, Guanghao

    2012-07-01

    Chlorine is widely used for disinfecting public swimming pool water. The disinfectant chlorine, protecting swimmers from pathogenic infection in swimming, may be responsible for some adverse effects on swimmers' skin and health. In this study, numerous new halogenated disinfection byproducts (DBPs) in chlorinated pool water were detected with a powerful precursor ion scan method using electrospray ionization triple quadrupole mass spectrometry, with or without preseparation with ultra performance liquid chromatography. These new pool DBPs were demonstrated to be mainly halo(nitro)phenols, resulting from chlorination of human body substances (such as urine) in the presence of bromide. Among these new DBPs, 2,4-dibromophenol, 2,4-dichlorophenol, 2-bromophenol, 2,6-dibromo-4-nitrophenol, 2-bromo-6-chloro-4-nitrophenol, and 2,6-dichloro-4-nitrophenol were fully identified or confirmed. For 2,4-dibromophenol, 2,4-dichlorophenol and 2-bromophenol with pure standard compounds available, their permeability values across human skin were measured to be 0.031, 0.021, and 0.023 cm/h, respectively. The effects of chlorine on human skin were also investigated. The interaction of chlorine with epidermis was found to generate many new halogenated DBPs as well as common DBPs; the corneous layer was observed to become rough and even form larger pores after chlorine interaction. It is recommended that swimmers should avoid urinating in pools, and avoid prolonged swimming to reduce chlorine contact and prevent accelerated permeation of DBPs across skin.

  9. Role of intermolecular interaction in crystal packing: A competition between halogen bond and electrostatic interaction

    Science.gov (United States)

    Chen, Peng-Yuan; Zhang, Lin; Zhu, Shun-Guan; Cheng, Guang-Bin

    2017-03-01

    To investigate the competition between halogen bond and electrostatic interaction and their influence on the crystal packing, four novel solvates of 1,3,5-trichloro-2,4,6-trinitrobenzene (TCTNB) and 1,3,5-tribromo-2,4,6-trinitrobenzene (TBTNB) were synthesized while the intermolecular forces and the contribution of each interaction were analyzed quantitatively. The electrostatic interaction is the main link between TCTNB, TBTNB and 1,4-dioxane respectively, while π-π interaction dominates in these two solvates of TCTNB/1,4-dimethylbenzene (PX) and TCTNB/mesitylene. The solvate interaction changes and varieties were illuminated by Hirshfeld surface analysis, and the group contributions were illustrated respectively. Molecular electrostatic potential surface (MEPs) with density functional theory (DFT) calculation was performed to compare the relative strength of electrostatic interaction and halogen bond. The result shows that MEPs can be used as a descriptor for determining the most possible intermolecular interaction under certain circumstances. The study presented here may provide the guidance for the design and synthesis of the complex with desired properties.

  10. Molecular, vibrational and electronic structure of 4-bromo-2-halogenobenzaldehydes: Halogen and solvent effects

    Science.gov (United States)

    Fernández, David; Parlak, Cemal; Bilge, Metin; Kaya, Mehmet Fatih; Tursun, Mahir; Keşan, Gürkan; Rhyman, Lydia; Ramasami, Ponnadurai; Şenyel, Mustafa

    2017-09-01

    The halogen and solvent effects on the structure of 4-bromo-2-halogenobenzaldehydes [C7H4BrXO; X = F (BFB), Cl (BCB) or Br (BBB)] were investigated by the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The B3LYP functional and HF and MP2 levels of theory were used with the 6-311+G(3df,p) or aug-cc-pVDZ basis sets. Computations were focused on the cis and trans conformers of the investigated compounds in the gas phase and solutions of 18 different polar or non-polar organic solvents. The computed frequencies of the C=O stretching vibration of the compounds were correlated with some empirical solvent parameters such as the Kirkwood-Bauer-Magat (KBM) equation, solvent acceptor number (AN), Swain parameters and linear solvation energy relationships (LSERs). The electronic properties of the compounds were also examined. The present work explores the effects of the medium and halogen on the conformation, geometrical parameters, dipole moment, ν(C=O) vibration, UV data, frontier orbitals and density-of-states diagram of the compounds. The findings of this research can be useful for studies on benzaldehydes.

  11. Reactive Halogens in the Marine Boundary Layer (RHaMBLe: the tropical North Atlantic experiments

    Directory of Open Access Journals (Sweden)

    J. D. Lee

    2009-10-01

    Full Text Available The NERC UK SOLAS-funded Reactive Halogens in the Marine Boundary Layer (RHaMBLe programme comprised three field experiments. This manuscript presents an overview of the measurements made within the two simultaneous remote experiments conducted in the tropical North Atlantic in May and June 2007. Measurements were made from two mobile and one ground-based platforms. The heavily instrumented cruise D319 on the RRS Discovery from Lisbon, Portugal to São Vicente, Cape Verde and back to Falmouth, UK was used to characterise the spatial distribution of boundary layer components likely to play a role in reactive halogen chemistry. Measurements onboard the ARSF Dornier aircraft were used to allow the observations to be interpreted in the context of their vertical distribution and to confirm the interpretation of atmospheric structure in the vicinity of the Cape Verde islands. Long-term ground-based measurements at the Cape Verde Atmospheric Observatory (CVAO on São Vicente were supplemented by long-term measurements of reactive halogen species and characterisation of additional trace gas and aerosol species during the intensive experimental period.

    This paper presents a summary of the measurements made within the RHaMBLe remote experiments and discusses them in their meteorological and chemical context as determined from these three platforms and from additional meteorological analyses. Air always arrived at the CVAO from the North East with a range of air mass origins (European, Atlantic and North American continental. Trace gases were present at stable and fairly low concentrations with the exception of a slight increase in some anthropogenic components in air of North American origin, though NOx mixing ratios during this period remained below 20 pptv. Consistency with these air mass classifications is observed in the time series of soluble gas and aerosol composition measurements, with additional identification of periods of

  12. Reactive Halogens in the Marine Boundary Layer (RHaMBLe): the tropical North Atlantic experiments

    Science.gov (United States)

    Lee, J. D.; McFiggans, G.; Allan, J. D.; Baker, A. R.; Ball, S. M.; Benton, A. K.; Carpenter, L. J.; Commane, R.; Finley, B. D.; Evans, M.; Fuentes, E.; Furneaux, K.; Goddard, A.; Good, N.; Hamilton, J. F.; Heard, D. E.; Herrmann, H.; Hollingsworth, A.; Hopkins, J. R.; Ingham, T.; Irwin, M.; Jones, C. E.; Jones, R. L.; Keene, W. C.; Lawler, M. J.; Lehmann, S.; Lewis, A. C.; Long, M. S.; Mahajan, A.; Methven, J.; Moller, S. J.; Müller, K.; Müller, T.; Niedermeier, N.; O'Doherty, S.; Oetjen, H.; Plane, J. M. C.; Pszenny, A. A. P.; Read, K. A.; Saiz-Lopez, A.; Saltzman, E. S.; Sander, R.; von Glasow, R.; Whalley, L.; Wiedensohler, A.; Young, D.

    2010-02-01

    The NERC UK SOLAS-funded Reactive Halogens in the Marine Boundary Layer (RHaMBLe) programme comprised three field experiments. This manuscript presents an overview of the measurements made within the two simultaneous remote experiments conducted in the tropical North Atlantic in May and June 2007. Measurements were made from two mobile and one ground-based platforms. The heavily instrumented cruise D319 on the RRS Discovery from Lisbon, Portugal to São Vicente, Cape Verde and back to Falmouth, UK was used to characterise the spatial distribution of boundary layer components likely to play a role in reactive halogen chemistry. Measurements onboard the ARSF Dornier aircraft were used to allow the observations to be interpreted in the context of their vertical distribution and to confirm the interpretation of atmospheric structure in the vicinity of the Cape Verde islands. Long-term ground-based measurements at the Cape Verde Atmospheric Observatory (CVAO) on São Vicente were supplemented by long-term measurements of reactive halogen species and characterisation of additional trace gas and aerosol species during the intensive experimental period. This paper presents a summary of the measurements made within the RHaMBLe remote experiments and discusses them in their meteorological and chemical context as determined from these three platforms and from additional meteorological analyses. Air always arrived at the CVAO from the North East with a range of air mass origins (European, Atlantic and North American continental). Trace gases were present at stable and fairly low concentrations with the exception of a slight increase in some anthropogenic components in air of North American origin, though NOx mixing ratios during this period remained below 20 pptv (note the non-IUPAC adoption in this manuscript of pptv and ppbv, equivalent to pmol mol-1 and nmol mol-1 to reflect common practice). Consistency with these air mass classifications is observed in the time series of

  13. Kinetic and product studies of Criegee intermediate reactions with halogenated and non-halogenated carboxylic acids and their implications in the troposphere

    Science.gov (United States)

    Chhantyal-Pun, Rabi; Rotavera, Brandon; Eskola, Arkke; Taatjes, Craig; Percival, Carl; Shallcross, Dudley; Orr-Ewing, Andrew

    2016-04-01

    Criegee intermediates are important species formed during the ozonolysis of alkenes. Direct measurement and modelling studies have shown that reactions of stabilized Criegee intermediates with species like SO2 and NO2 may have a significant effect in tropospheric chemistry.[1, 2] Reaction rates of Criegee intermediates with simple carboxylic acids like HCOOH and CH3COOH have been shown to be near the collision limit and may be a significant sink for these otherwise stable species in the atmosphere.[3, 4] Results obtained from our time-resolved Cavity Ring-Down Spectroscopy (CRDS) apparatus[5] for reactions of the Criegee intermediates, CH2OO and (CH3)2COO with various halogenated (CF3COOH, CF3CF2COOH, CClF2COOH and CHCl2COOH) and non-halogenated (HCOOH and CH3COOH) carboxylic acids will be presented, together with Structure Activity Relationship (SAR) based on these observations. Structure characterization of the products from these reactions using the Multiplexed PhotoIonization Mass Spectrometry (MPIMS) apparatus[1,3] as well as implications for Secondary Organic Aerosol (SOA) formation, assessed using the global atmospheric model STOCHEM, will also be discussed. Bibliography 1. O. Welz, J. D. Savee, D. L. Osborn, S. S. Vasu, C. J. Percival, D. E. Shallcross and C. A. Taatjes, Science, 2012, 335, 204-207. 2. C. J. Percival, O. Welz, A. J. Eskola, J. D. Savee, D. L. Osborn, D. O. Topping, D. Lowe, S. R. Utembe, A. Bacak, G. McFiggans, M. C. Cooke, P. Xiao, A. T. Archibald, M. E. Jenkin, R. G. Derwent, I. Riipinen, D. W. K. Mok, E. P. F. Lee, J. M. Dyke, C. A. Taatjes and D. E. Shallcross, Faraday Discuss., 2013, 165, 45-73. 3. O. Welz, A. J. Eskola, L. Sheps, B. Rotavera, J. D. Savee, A. M. Scheer, D. L. Osborn, D. Lowe, A. M. Booth, P. Xiao, M. A. H. Khan, C. J. Percival, D. E. Shallcross and C. A. Taatjes, Angew. Chem. Int. Ed., 2014, 53, 4547-4550. 4. M. D. Hurley, M. P. S. Andersen, T. J. Wallington, D. A. Ellis, J. W. Martin and S. A. Mabury, J. Phys. Chem. A

  14. Photochemical oxidation of halocarbons in the troposphere

    Energy Technology Data Exchange (ETDEWEB)

    Cox, R.A. (Atomic Energy Research Establishment, Harwell, Eng.); Derwent, R.G.; Eggleton, A.E.J.; Lovelock, J.E.

    1976-01-01

    Measurements of the reactivity of hydroxyl radicals with some simple halocarbons are reported, together with some new measurements of the air concentration of halocarbons in the N and S hemispheres. The OH reactivities are used to derive life-times of the halocarbons with respect to photo-oxidation in the troposphere. It is found that the chlorohydrocarbons containing H atoms are moderately reactive with lifetimes of 1 y or less but the fully halogenated compounds carbon tetrachloride and Freons 11 and 12 are essentially inert towards photo-oxidation. The air concentration and reactivity data are combined to provide an estimate of the magnitude of the tropospheric sink for the halocarbons due to oxidation by OH radicals. For some of the more reactive halocarbons this sink exceeds the estimated anthropogenic emissions and an additional, possibly natural, source is indicated.

  15. Rotational spectrum of the tetrafluoromethane-ethylene oxide

    Science.gov (United States)

    Gou, Qian; Feng, Gang; Evangelisti, Luca; Caminati, Walther

    2017-05-01

    The rotational spectrum of one conformer of the CF4-ethylene oxide complex has been measured by using a pulsed jet Fourier-transform microwave spectrometer. The observed conformer is stabilized by a CF3⋯O halogen bond, with a distance rC⋯O of ∼3.341 Å. No experimental evidence of the internal rotation of CF4 with respect to ethylene oxide has been observed, but it is expected to be almost free (V3 ∼ 14 cm-1 from ab initio calculations).

  16. Pilot-scale laboratory waste treatment by supercritical water oxidation.

    Science.gov (United States)

    Oshima, Yoshito; Hayashi, Rumiko; Yamamoto, Kazuo

    2006-01-01

    Supercritical water oxidation (SCWO) is a reaction in which organics in an aqueous solution can be oxidized by O2 to CO2 and H2O at a very high reaction rate. In 2003, The University of Tokyo constructed a facility for the SCWO process, the capacity of which is approximately 20 kl/year, for the purpose of treating organic laboratory waste. Through the operation of this facility, we have demonstrated that most of the organics in laboratory waste including halogenated organic compounds can be successfully treated without the formation of dioxines, suggesting that SCWO is useful as an alternative technology to the conventional incineration process.

  17. Headspace GC-MS Analysis of Halogenated Volatile Organic Compounds in Aqueous Samples: An Experiment for General Chemistry Laboratory

    Science.gov (United States)

    Keller, John W.; Fabbri, Cindy E.

    2012-01-01

    Analysis of halogenated volatile organic compounds (HVOCs) by GC-MS demonstrates the use of instrumentation in the environmental analysis of pollutant molecules and enhances student understanding of stable isotopes in nature. In this experiment, students separated and identified several HVOCs that have been implicated as industrial groundwater…

  18. A new halogen-free chemical oscillator: the reaction between permanganate ion and ninhydrin in a continuously stirred tank reactor

    Science.gov (United States)

    Treindl, Ľudovít; Nagy, Arpád

    1987-07-01

    The reaction between permanganate ion and ninhydrin in the presence of phosphoric acid in aqueous solution shows sustained oscillations in a continuously stirred tank reactor (CSTR). It exhibits a kinetic bistability between an oscillatory and a stationary state. Our new oscillating system seems to be a second permanganate chemical oscillator, thus broadening the small group of non-halogen-based chemical oscillators.

  19. A study of the hydration of deoxydinucleoside monophosphates containing thymine, uracil and its 5-halogen derivatives: Monte Carlo simulation.

    Science.gov (United States)

    Alderfer, J L; Danilov, V I; Poltev, V I; Slyusarchuk, O N

    1999-04-01

    An extensive Monte Carlo simulation of hydration of various conformations of the dinucleoside monophosphates (DNP), containing thymine, uracil and its 5-halogen derivatives has been performed. An anti-anti conformation is the most energetically stable one for each of the DNPs. In the majority of cases the energy preference is determined by water-water interaction. For other dimers conformational energy is the most important factor, or both the factors are of nearly equal importance. The introduction of the methyl group into the 5-position of uracil ring most noticeably influences the conformational energy and leads to the decrease of its stabilizing contribution to the total interaction energy. The introduction of halogen atoms increases the relative content of anti-syn and syn-anti conformations of DNPs as compared to the parent ones due to the formation of an energetically more favorable water structure around these conformations. A correlation is observed between the Monte Carlo results for the halogenated DNPs and their experimental photoproduct distribution. The data obtained demonstrates a sequence dependence in the photochemistry of the halogenated dinucleoside monophosphates.

  20. Large area inkjet printing for organic photovoltaics and organic light emitting diodes using non-halogenated ink formulations

    NARCIS (Netherlands)

    Eggenhuisen, T.M.; Coenen, M.J.J.; Slaats, M.W.L.; Groen, W.A.

    2014-01-01

    The transfer of laboratory scale solution processing of organic electronics to large area roll-to-roll production requires the use of up-scalable deposition techniques. Furthermore, industrial production demands the omission of halogenated and other harmful solvents. Here, the authors discuss large