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  • 1
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    Seismic source summary for all U.S. below-surface nuclear explosions (2002)
    In:  Bull. Seism. Soc. Am., Berlin, 120 pp., Akademie-Verlag, vol. 92, no. 5, pp. 1806-1840, pp. 1051, (ISSN: 1340-4202)
    Details
    Publication Date: 2002
    Keywords: Seismology ; Nuclear explosion ; Earthquake catalog ; Source parameters ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    HOx budgets during HOxComp: A case study of HOx chemistry under NOx-limited conditions (2012)
    Wiley
    Details
    Publication Date: 2012-02-10
    Description: Recent studies have shown that measured OH under NOx-limited, high-isoprene conditions are many times higher than modeled OH. In this study, a detailed analysis of the HOx radical budgets under low-NOx, rural conditions was performed employing a box model based on the Master Chemical Mechanism (MCMv3.2). The model results were compared with HOx radical measurements performed during the international HOxComp campaign carried out in Jülich, Germany, during summer 2005. Two different air masses influenced the measurement site denoted as high-NOx (NO, 1–3 ppbv) and low-NOx (NO, 〈 1 ppbv) periods. Both modeled OH and HO2 diurnal profiles lay within the measurement range of all HOx measurement techniques, with correlation slopes between measured and modeled OH and HO2 around unity. Recently discovered interference in HO2 measurements caused by RO2 cross sensitivity was found to cause a 30% increase in measured HO2 during daytime on average. After correction of the measured HO2 data, the model HO2 is still in good agreement with the observations at high NOx but overpredicts HO2 by a factor of 1.3 to 1.8 at low NOx. In addition, for two different set of measurements, a missing OH source of 3.6 ± 1.6 and 4.9 ± 2.2 ppb h−1 was estimated from the experimental OH budget during the low-NOx period using the corrected HO2 data. The measured diurnal profile of the HO2/OH ratio, calculated using the corrected HO2, is well reproduced by the MCM at high NOx but is significantly overestimated at low NOx. Thus, the cycling between OH and HO2 is better described by the model at high NOx than at low NOx. Therefore, similar comprehensive field measurements accompanied by model studies are urgently needed to investigate HOx recycling under low-NOx conditions.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Experimental evidence for efficient hydroxyl radical regeneration in isoprene oxidation (2013)
    Springer Nature
    Details
    Publication Date: 2013-11-29
    Description: Nature Geoscience 6, 1023 (2013). doi:10.1038/ngeo1964 Authors: H. Fuchs, A. Hofzumahaus, F. Rohrer, B. Bohn, T. Brauers, H-P. Dorn, R. Häseler, F. Holland, M. Kaminski, X. Li, K. Lu, S. Nehr, R. Tillmann, R. Wegener & A. Wahner Most pollutants in the Earth’s atmosphere are removed by oxidation with highly reactive hydroxyl radicals. Field measurements have revealed much higher concentrations of hydroxyl radicals than expected in regions with high loads of the biogenic volatile organic compound isoprene. Different isoprene degradation mechanisms have been proposed to explain the high levels of hydroxyl radicals observed. Whether one or more of these mechanisms actually operates in the natural environment, and the potential impact on climate and air quality, has remained uncertain. Here, we present a complete set of measurements of hydroxyl and peroxy radicals collected during isoprene-oxidation experiments carried out in an atmospheric simulation chamber, under controlled atmospheric conditions. We detected significantly higher concentrations of hydroxyl radicals than expected based on model calculations, providing direct evidence for a strong hydroxyl radical enhancement due to the additional recycling of radicals in the presence of isoprene. Specifically, our findings are consistent with the unimolecular reactions of isoprene-derived peroxy radicals postulated by quantum chemical calculations. Our experiments suggest that more than half of the hydroxyl radicals consumed in isoprene-rich regions, such as forests, are recycled by these unimolecular reactions with isoprene. Although such recycling is not sufficient to explain the high concentrations of hydroxyl radicals observed in the field, we conclude that it contributes significantly to the oxidizing capacity of the atmosphere in isoprene-rich regions.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 4
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    Amplified trace gas removal in the troposphere (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2009-06-06
    Description: The degradation of trace gases and pollutants in the troposphere is dominated by their reaction with hydroxyl radicals (OH). The importance of OH rests on its high reactivity, its ubiquitous photochemical production in the sunlit atmosphere, and most importantly on its regeneration in the oxidation chain of the trace gases. In the current understanding, the recycling of OH proceeds through HO2 reacting with NO, thereby forming ozone. A recent field campaign in the Pearl River Delta, China, quantified tropospheric OH and HO2 concentrations and turnover rates by direct measurements. We report that concentrations of OH were three to five times greater than expected, and we propose the existence of a pathway for the regeneration of OH independent of NO, which amplifies the degradation of pollutants without producing ozone.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hofzumahaus, Andreas -- Rohrer, Franz -- Lu, Keding -- Bohn, Birger -- Brauers, Theo -- Chang, Chih-Chung -- Fuchs, Hendrik -- Holland, Frank -- Kita, Kazuyuki -- Kondo, Yutaka -- Li, Xin -- Lou, Shengrong -- Shao, Min -- Zeng, Limin -- Wahner, Andreas -- Zhang, Yuanhang -- New York, N.Y. -- Science. 2009 Jun 26;324(5935):1702-4. doi: 10.1126/science.1164566. Epub 2009 Jun 4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Forschungszentrum Julich, Institut fur Chemie und Dynamik der Geosphare-2: Troposphare, 52425 Julich, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19498111" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Missing gas-phase source of HONO inferred from Zeppelin measurements in the troposphere (2014)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2014-04-20
    Description: Gaseous nitrous acid (HONO) is an important precursor of tropospheric hydroxyl radicals (OH). OH is responsible for atmospheric self-cleansing and controls the concentrations of greenhouse gases like methane and ozone. Due to lack of measurements, vertical distributions of HONO and its sources in the troposphere remain unclear. Here, we present a set of observations of HONO and its budget made onboard a Zeppelin airship. In a sunlit layer separated from Earth's surface processes by temperature inversion, we found high HONO concentrations providing evidence for a strong gas-phase source of HONO consuming nitrogen oxides and potentially hydrogen oxide radicals. The observed properties of this production process suggest that the generally assumed impact of HONO on the abundance of OH in the troposphere is substantially overestimated.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, Xin -- Rohrer, Franz -- Hofzumahaus, Andreas -- Brauers, Theo -- Haseler, Rolf -- Bohn, Birger -- Broch, Sebastian -- Fuchs, Hendrik -- Gomm, Sebastian -- Holland, Frank -- Jager, Julia -- Kaiser, Jennifer -- Keutsch, Frank N -- Lohse, Insa -- Lu, Keding -- Tillmann, Ralf -- Wegener, Robert -- Wolfe, Glenn M -- Mentel, Thomas F -- Kiendler-Scharr, Astrid -- Wahner, Andreas -- New York, N.Y. -- Science. 2014 Apr 18;344(6181):292-6. doi: 10.1126/science.1248999.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut fur Energie-und Klimaforschung: Troposphare (IEK-8), Forschungszentrum Julich, Julich, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24744373" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    ATMOSPHERIC SCIENCE. Response to Comment on "Missing gas-phase source of HONO inferred from Zeppelin measurements in the troposphere" (2015)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2015-06-20
    Description: Ye et al. have determined a maximum nitrous acid (HONO) yield of 3% for the reaction HO2.H2O + NO2, which is much lower than the yield used in our work. This finding, however, does not affect our main result that HONO in the investigated Po Valley region is mainly from a gas-phase source that consumes nitrogen oxides.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, Xin -- Rohrer, Franz -- Hofzumahaus, Andreas -- Brauers, Theo -- Haseler, Rolf -- Bohn, Birger -- Broch, Sebastian -- Fuchs, Hendrik -- Gomm, Sebastian -- Holland, Frank -- Jager, Julia -- Kaiser, Jennifer -- Keutsch, Frank N -- Lohse, Insa -- Lu, Keding -- Tillmann, Ralf -- Wegener, Robert -- Wolfe, Glenn M -- Mentel, Thomas F -- Kiendler-Scharr, Astrid -- Wahner, Andreas -- New York, N.Y. -- Science. 2015 Jun 19;348(6241):1326. doi: 10.1126/science.aaa3777.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut fur Energie und Klimaforschung, Troposphare (IEK-8), Forschungszentrum Julich, Julich, Germany. f.rohrer@fz-juelich.de x.li@fz-juelich.de. ; Institut fur Energie und Klimaforschung, Troposphare (IEK-8), Forschungszentrum Julich, Julich, Germany. ; Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26089508" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Seasonal measurements of OH, NOx, and J(O1D) at mace head, Ireland (2013)
    Wiley
    Details
    Publication Date: 2013-03-15
    Description: [1]  Measurements of atmospheric OH concentrations were conducted between August 2010 and July 2011 at Mace Head showing maximum daytime values of 0.21 (±0.25) x 10 6  cm -3 in winter and 2.26 (±1.37) x 10 6  cm -3 in summer. Plots of OH vs. ozone photolysis frequency, J (O 1 D), exhibited strong linear correlations with slopes of 1.06 (± 0.05) x 10 11  cm -3  s (R = 0.75) in clean marine air and 1.31 (± 0.04) x 10 11  cm -3  s (R = 0.79) in mixed marine/continental air. Surprisingly, no significant difference in the former correlation was found between low and high tide periods. NO and NO 2 levels in air from the marine sector (190-300°) were typically below the detection limit (30 pptv) and 〈200 pptv, respectively. In the land sector, NO mixing ratios 〈50 pptv dominated most of the time suggesting that the atmospheric oxidation efficiency in this region is predominantly characterized by primary OH sources in a low NOx environment.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
    Electronic Resource
    Electronic Resource
    The 193 (and 248) nm photolysis of HN3: Formation and internal energy distributions of the NH (a 1Δ, b 1∑+, A 3Π, and c 1Π) states (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4788-4799 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The UV photolysis of HN3 at 193 nm was investigated in detail in the bulk phase at 300 K. NH radicals in the X, a, b, A, and c states were found to be formed with quantum yields ≤0.0019, 0.4, 0.017, 0.000 15, and 0.000 61, respectively. Relative rotational and vibrational populations were measured for all states except for NH(X). Average translational energies were estimated for NH(a,v=0 and 1) and NH(b,v=0). The 248 nm photolysis of HN3 was reinvestigated with respect to processes forming NH radicals other than NH(a). The observed energy distributions differ for both laser wavelengths and for high and low lying NH states. The distribution can be better described by a simple impulsive than by a statistical model. Some conclusions are drawn concerning the upper HN3 potential surfaces involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454691
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  • 9
    Electronic Resource
    Electronic Resource
    Generation of NH(a 1Δ) in the 193 nm photolysis of ammonia (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2036-2043 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the observation of NH(a 1Δ) formation in a one-photon process during the ArF laser (193 nm) photolysis of ammonia. We have used laser-induced fluorescence to detect NH(a) and ND(a) and report the rotational and vibrational populations generated. We have also reinvestigated the generation of NH(a) in the 248 nm photolysis of HN3 and find substantial vibrational excitation in contrast to the results of previous workers. We give estimates for the quantum yields for NH(a) and ND(a) in the photolysis of ammonia based on comparison with the yield in 248 nm photolysis of HN3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452153
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  • 10
    Electronic Resource
    Electronic Resource
    Collision-induced intersystem crossing NH(c 1Π)→NH(A 3Π) (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 226-233 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The kinetics and the specific products of the collision-induced intersystem crossing NH(c 1Π,v=0)+M→NH(A 3Π,v)+M were investigated in the ArF laser photolysis of HN3 for various M. The efficiency of the intersystem crossing process was monitored time and spectrally resolved by the enhancement of the NH(A→X) emission. The efficiencies for M=O2, NO, Xe, and N2O are 0.95±0.05, 0.95±0.05, ≤0.15, 〈0.10, respectively. For M=O2, various vibrational NH(A,v=0, 1, and 2) states are formed with the detailed efficiencies of 0.64, 0.12, and 0.24. We propose that these vibrational states are generated together with O2(a 1Δ,v=4, 2, and 0), respectively. The rotational temperatures for the NH(A,v) products are much colder for M=O2 than for M=NO. For M=Xe, the enhancement of NH(A,v=0) is much larger than that predicted for an efficiency of one and, in the presence of Ar, it is markedly reduced. This large enhancement might be due to a second intersystem crossing process such as NH(b 1Σ+,v≥3)+Xe→NH(A,v=0,1)+Xe. A similar quenchable, but much weaker, additional triplet emission was observed for M=N2O. Absolute rate constants for the quenching of NH(c,v=0) by M=O2, NO, Xe, and N2O were determined at room temperature. Similarly, a value was measured for NH(A,v=2)+O2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452613
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