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  • 1
    Electronic Resource
    Electronic Resource
    Coherent anti-Stokes Raman spectroscopy of shock-compressed liquid carbon monoxide–oxygen and nitrogen–oxygen mixtures (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 325-336 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A two-stage light gas gun and single-pulse multiplex coherent anti-Stokes Raman scattering (CARS) have been used to obtain carbon monoxide, nitrogen, and oxygen vibrational spectra for several high-pressure/high-temperature, dense fluid, carbon monoxide–oxygen, and nitrogen–oxygen mixtures. The experimental spectra were compared to synthetic spectra calculated with a semiclassical model for CARS intensities and using best fit vibrational frequencies, peak Raman susceptibilities, and Raman linewidths for each mixture component. Up to a maximum shock pressure of 6.75 GPa for carbon monoxide–oxygen mixtures, the CO and O2 vibrational frequencies were found to increase monotonically with pressure and depended on the carbon monoxide–oxygen mixture ratio. For the nitrogen–oxygen mixtures, the N2 vibrational frequency increased monotonically with pressure to a maximum experimental pressure of 12.9 GPa, however the O2 vibrational frequency increased with pressure to about 11 GPa and then appeared to decrease slightly as the pressure increased to the experiment maximum of 12.9 GPa. Empirical fits of the measured Raman frequencies incorporating previously published neat nitrogen, carbon monoxide, and oxygen data and using a functional form dependent on pressure, temperature, and mixture ratio, accurately describe the N2 , CO, and O2 vibrational frequency shifts for both the carbon monoxide–oxygen and the nitrogen–oxygen mixtures. The transition intensity and linewidth data suggest that thermal equilibrium of the vibrational levels is attained in less than 10 ns at these shock pressures. The vibrational temperatures obtained for the nitrogen–oxygen mixtures were used to improve the oxygen potential function used to calculate equation-of-state pressures and temperatures. The measured linewidths for CO, N2 , and O2 were different for the different mixtures and did not appear to depended significantly on mixture ratios. The broadening of all spectral lines suggested that the vibrational dephasing time for each species decreased to a few ps at the highest pressure shock states. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474393
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  • 2
    Electronic Resource
    Electronic Resource
    15N natural abundance of vascular rainforest epiphytes: implications for nitrogen source and acquisition (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The foliar natural abundance of 15N was analysed to compare the potential nitrogen sources of vascular rainforest epiphytes and associated soil-rooted trees. Leaves of epiphytes collected from six rainforest communities in Brazil, Australia and the Solomon Islands were depleted in 15N relative to the trees at each site. Epiphyte δ15N was as low as -6.4%o, while trees were generally enriched in 15N (0.7 to 3.5%o). These results indicate either that epiphytes use nitrogen sources depleted in 15N or that discrimination against 15N is an intrinsic function of epiphyte physiology. At three sites, epiphytes could be grouped into those having both low δ15N and low leaf-nitrogen content and those possessing both high δ15N and high leaf-nitrogen content. The second group had δ15N values in the range sometimes attributable to N2 fixation (-2 to 0%o). There was no correlation between growth form and δ15N. It is concluded that epiphytes may utilize 15N-depleted nitrogen from atmospheric deposition and N2 fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00547.x
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  • 3
    Electronic Resource
    Electronic Resource
    Water availability – a physiological constraint on nitrate utilization in plants of Australian semi-arid muiga woodlands (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Nitrate was found to be the predominant form of available nitrogen in mulga soils. Nitrate reductase activities on a fresh mass basis of a range of plants from eastern (Queensland) mulga ecosystems 2 weeks after partial relief from drought were uniformly low for both herbaceous species (165 ± 25 pkat g−1) and woody perennials (77 ± 14 pkat g−1). Supply of nitrate for 24 h to cut transpiring shoots of woody species or application of nitrate solution to the rooting zone of herbaceous species promoted little further increase in mean shoot nitrate reductase activities. Most species exhibited high tissue nitrate concentrations during water stress and soluble organic N profiles were in many cases dominated by the osmoprotective compounds, proline or glycine betaine. Species with low levels of proline or glycine betaine showed high foliar concentrations of other compatible osmotica such as polyols or sugars. Effects of relieving water stress on nitrate reductase activity, proline, glycine betaine and nitrate levels were followed over, 3d of irrigation. Available soil nitrate rose 10-fold immediately and, following rapid restoration of leaf water status of the eight study species, a 4-fold increase occurred in mean nitrate reductase activity together with progressive decreases in mean tissue concentrations of nitrate, proline and glycine betaine over the 3 d period. Similar changes in soil nitrate, nitrate reductase activity, proline and tissue nitrate were observed in the same ecosystem following a natural rainfall event and in western (S.W. Australia) mulga following irrigation. It is concluded that, although nitrate nitrogen is present at high concentrations and is the predominant inorganic nitrogen source in soils of the mulga biogeographic region, its assimilation by perennial and ephemeral vegetation is limited primarily by water availability. A scheme is presented depicting interrelated physiological and biochemical events in typical mulga species following a rain event and subsequent drying out of the habitat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00430.x
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  • 4
    Electronic Resource
    Electronic Resource
    Waterlogging and fire impacts on nitrogen availability and utilization in a subtropical wet heathland (wallum) (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Protein, amino acids and ammonium were the main forms of soluble soil nitrogen in the soil solution of a subtropical heathland (wallum). After fire, soil ammonium and nitrate increased 90- and 60-fold, respectively. Despite this increase in nitrate availability after fire, wallum species exhibited uniformly low nitrate reductase activities and low leaf and xylem nitrate. During waterlogging soil amino acids increased, particularly γ-aminobutyric acid (GABA) which accounted for over 50% of amino nitrogen. Non-mycorrhizal wallum species were significantly (P 〈 0.05) 15N-enriched (0.3–4.3‰) compared to species with mycorrhizal associations (ericoid-type, ecto-, va-mycorrhizal) which were strongly depleted in 15N (-6.3 to -1.8‰). Lignotubers and roots had δ15N signatures similar to that of the leaves of respective species. The exceptions were fine roots of ecto-, ecto/va-, and ericoid type mycorrhizal species which were enriched in 15N (0.1–2.4‰). The 515N signatures of δ15Ntotal soil N and δ15Nsoil NH4+ were in the range 3.7–4.5‰, whereas δ15Nsoil NO3− was significantly (P 〈 0.05) more enriched in 15N (9.2–9.8‰). It is proposed that there is discrimination against 15N during transfer of nitrogen from fungal to plant partner. Roots of selected species incorporated nitrogen sources in the order of preference: ammonium 〉 glycine 〉 nitrate. The exception were proteoid roots of Hakea (Proteaceae) which incorporated equal amounts of glycine and ammonium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1997.d01-20.x
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  • 5
    Electronic Resource
    Electronic Resource
    Catabolism of 2,7-dichloro- and 2,4,8-trichlorodibenzofuran by Sphingomonas sp strain RW1 (1999)
    Springer
    Journal of industrial microbiology and biotechnology 23 (1999), S. 359-363 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: biotransformation; Sphingomonas; 2,7-dichlorodibenzofuran; 2,4,8-trichlorodibenzofuran; 6-chloro-2-methyl-4H-chromen-4-one; 7-chloro-2-methyl-4H-chromen-4-one; 6,8-dichloro-2-methyl-4H-chromen-4-one
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Due to their physicochemical and toxicological properties, polychlorinated dibenzofurans are regarded as a class of compounds providing reason for serious environmental concern. While the nonhalogenated basic structure dibenzofuran is effectively mineralized by appropriate bacterial strains, its polychlorinated derivatives are not. To elucidate the ability of the strain Sphingomonas sp RW1 to metabolize some of these chlorinated derivatives, we performed turnover experiments using 2,7-dichloro- and 2,4,8-trichlorodibenzofuran. As indicated by the oxygen-uptake rates determined for these two chlorinated dibenzofurans, Sphingomonassp RW1 can catabolize these chlorinated dibenzofurans yielding small quantities of oxidation products, which we isolated and subsequently characterized employing GC/MS and 1H- as well as 13C-NMR spectroscopy. In the case of 2,7-dichlorodibenzofuran, two metabolites accumulated, which we identified as 6-chloro- and 7-chloro-2-methyl-4H-chromen-4-one. The single metabolite isolated from the turnover experiments performed with 2,4,8-trichlorodibenzofuran was unequivocally identified as 6,8-dichloro-2-methyl-4H-chromen-4-one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.2900739
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  • 6
    Electronic Resource
    Electronic Resource
    Colonization of contaminated soil by an introduced bacterium: effects of initial pentachlorophenol levels on the survival of Sphingomonas chlorophenolica strain RA2 (1999)
    Springer
    Journal of industrial microbiology and biotechnology 23 (1999), S. 326-331 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: Sphingomonas; pentachlorophenol; bioaugmentation; microbial survival
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The survival of a Sphingomonas species that was introduced into pentachlorophenol (PCP)-contaminated soil was monitored with two complementary methods, a respiration-based assay and a most probable number (MPN) technique. Sphingomonas chlorophenolicastrain RA2 is a PCP-mineralizing bacterium that was introduced into soil contaminated with a range of PCP concentrations (0–300 μg PCP g−1 soil). The population of introduced microorganisms was followed for 170 days using a substrate-induced growth-response method and a MPN assay that specifically targets PCP-mineralizing bacteria. Varying the initial PCP concentration resulted in the emergence of three distinct patterns of survival. In soil contaminated with 300 μg PCP g−1 the population of S. chlorophenolica strain RA2 immediately declined following introduction, increased by 200-fold and leveled off by the end of the 170-day incubation. In contrast, populations of S. chlorophenolica strain RA2 declined to levels below detection limits in uncontaminated soil by the end of the experiment. Intermediate PCP concentrations (10–100 μg PCP g−1 soil) resulted in the establishment of S. chlorophenolica strain RA2 that slowly declined in numbers. These results indicate that Sphingomonas chlorophenolica strain RA2 is an effective colonizer of PCP-contaminated soil but will not persist in the absence of PCP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.2900718
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  • 7
    Electronic Resource
    Electronic Resource
    The phosphonate-phosphate and phosphate-phosphonate rearrangement and their applications V. On the reaction ofs-butyllithium/TMEDA with symmetrical trialkyl phosphates (1997)
    Springer
    Monatshefte für Chemie 128 (1997), S. 1173-1180 
    Details
    ISSN: 1434-4475
    Keywords: α-Hydroxyphosphonates ; Phosphates ; Phosphate-phosphonate rearrangement ; s-BuLi/TMEDA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung 1-(Tributylstanny)hexanol ((±)-8) wird phosphoryliert und liefert Phosphat (±)-9, das transmetalliert wird. Das lithiumorganische Zwischenprodukt (±)-10 isomerisiert zum α-Hydroxyphosphonat (±)-12. Ähnliche Intermediate werden auch bei der direkten Deprotonierung von Triethyl-, Tri-n-propyl- und Tri-n-butylphosphat gebildet, die anschließend zu den α-Hydroxy-phosphonaten (±)-14a–c umlagern.
    Notes: Summary 1-(Tributylstannyl)hexanol ((±)-8 is phosphorylated to give phosphate (±)-9 which is then transmetallated. The organolithium intermediate (±)-10 isomerizes to α-hydroxyphosphonate (±)-12. Similar intermediates are also formed upon direct deprotonation of triethyl, tri-n-propyl, and tri-n-butyl phosphate, which subsequently rearrange to α-hydroxyphosphonates (±)-14a–c.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807567
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  • 8
    Electronic Resource
    Electronic Resource
    Hydrogen depth profiling using18O ions (1995)
    Springer
    The European physical journal 351 (1995), S. 453-465 
    Details
    ISSN: 1434-601X
    Keywords: 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Nuclear resonant reaction analysis techniques for hydrogen depth profiling in solid materials typically have used15N ion beams at 6.40 MeV and19F ion beams at 6.42 MeV, which require a tandem accelerator. We report a new technique using an18O ion beam at a resonance energy of 2.70 MeV, which requires only a single stage accelerator. Improved values of the nuclear parameters for the 2.70 MeV (18O) and 6.40 MeV (15N) resonances are reported. The beam energy spread was investigated for different ions and ion charge states and found to scale with the charge state. Data obtained using atomic and molecular gas targets reveal the research potential of Doppler spectroscopy. Examples of hydrogen depth profiling in solid materials using15N and18O ion beams are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01291151
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  • 9
    Electronic Resource
    Electronic Resource
    Virtual pitch formation in the ultrasonic range (1995)
    Springer
    Naturwissenschaften 82 (1995), S. 45-47 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01167873
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  • 10
    Electronic Resource
    Electronic Resource
    Virtual Pitch Formation in the Ultrasonic Range (1995)
    Springer
    Naturwissenschaften 82 (1995), S. 45-47 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01167873
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