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  • American Chemical Society  (2,084,048)
  • American Institute of Physics (AIP)  (241,959)
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  • 1
    Journal cover
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    American Crystallographic Association (ACA) | American Institute of Physics (AIP)
    Online: 1(1).2014 –
    Publisher: American Crystallographic Association (ACA) , American Institute of Physics (AIP)
    Electronic ISSN: 2329-7778
    Topics: Physics
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  • 2
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    American Institute of Physics (AIP)
    Online: 1.1994 –
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
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  • 3
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    American Institute of Physics (AIP)
    Online: 1(1).1989 – 5(12).1993
    Online: 1(1).1989 – 5(12).1993
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0899-8221
    Topics: Physics
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  • 4
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    American Institute of Physics (AIP)
    Online: 1(1).1989 – 5(12).1993
    Online: 1(1).1989 – 5(12).1993
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0899-8213
    Topics: Physics
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  • 5
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    American Institute of Physics (AIP)
    Online: 1.1969 – 34.2002
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0002-7537
    Topics: Physics
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  • 6
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    American Institute of Physics (AIP)
    Online: 1.1991 –
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 1054-1500
    Electronic ISSN: 1089-7682
    Topics: Physics
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  • 7
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    American Institute of Physics (AIP) | IEEE Computer Society | Institute of Electrical and Electronics Engineers (IEEE)
    Online: 1.1999 –
    Publisher: American Institute of Physics (AIP) , IEEE Computer Society , Institute of Electrical and Electronics Engineers (IEEE)
    Print ISSN: 1521-9615
    Electronic ISSN: 1558-366X
    Topics: Computer Science , Natural Sciences in General , Technology
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  • 8
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    American Institute of Physics (AIP)
    Online: 36.2004 –
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0148-5857
    Topics: Physics
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  • 9
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    American Institute of Physics (AIP)
    Online: 1.1933 –
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
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  • 10
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    American Institute of Physics (AIP)
    Online: 1.1960 –
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0022-2488
    Electronic ISSN: 1089-7658
    Topics: Mathematics , Physics
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  • 11
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    Laser Institute of America (LIA) | American Institute of Physics (AIP)
    Online: 1(1).1988 –
    Publisher: Laser Institute of America (LIA) , American Institute of Physics (AIP)
    Print ISSN: 1042-346X
    Electronic ISSN: 1938-1387
    Topics: Physics
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  • 12
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    American Institute of Physics (AIP)
    Online: 1.1931 –
    Formerly as: Physics  (1931–1936)
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Acronym: JAP
    Abbreviation: J Appl Phys
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  • 13
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    American Institute of Physics (AIP)
    Online: 1.2009 –
    Publisher: American Institute of Physics (AIP)
    Electronic ISSN: 1941-7012
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 14
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    Society of Rheology (SoR) | American Institute of Physics (AIP)
    Online: 1(1).1929 –
    Formerly as: Transactions of the Society of Rheology  (1957–1977)
    Publisher: Society of Rheology (SoR) , American Institute of Physics (AIP)
    Print ISSN: 0038-0032 , 0097-0360 , 0148-6055
    Electronic ISSN: 1520-8516
    Topics: Physics
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  • 15
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    American Institute of Physics (AIP)
    Online: 52.1999 –
    Print: 39(7).1986 – 45.1992 (Location: A17, Kompaktmagazin, 58/6-7)
    Print: 44.1991 – 63.2010 (Location: A43, Archiv)
    Print: 46.1993 – 71.2018 (Location: A17, Kompaktmagazin, 58/6-7)
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0031-9228
    Electronic ISSN: 1945-0699
    Topics: Physics
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  • 16
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    American Institute of Physics (AIP)
    Online: 1.1958 –
    Formerly as: Physics of Fluids A: Fluid Dynamics ; Physics of Fluids B: Plasma Physics  (1989–1993)
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0031-9171 , 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
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  • 17
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    American Institute of Physics (AIP)
    Online: 1.1930 –
    Print: 28.1957 – 41.1970 (Location: A18, ---)
    Formerly as: Review of Scientific Instruments with Physics News and Views  (1933–1938)
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 18
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    American Institute of Physics (AIP) | American Crystallographic Association (ACA)
    Online: 1.2011 –
    Publisher: American Institute of Physics (AIP) , American Crystallographic Association (ACA)
    Electronic ISSN: 2158-3226
    Topics: Physics
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  • 19
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    American Institute of Physics (AIP)
    Online: 1.2013 –
    Publisher: American Institute of Physics (AIP)
    Electronic ISSN: 2166-532X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Keywords: Werkstoffkunde
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  • 20
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    American Institute of Physics (AIP)
    Online: 1(1).2016 –
    Publisher: American Institute of Physics (AIP)
    Electronic ISSN: 2378-0967
    Topics: Physics
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  • 21
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    American Institute of Physics (AIP)
    Online: 1.1962 – 123.2023
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 22
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    American Institute of Physics (AIP)
    Online: 1(1).1970 –
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0094-243X
    Electronic ISSN: 1551-7616
    Topics: Physics
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  • 23
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    American Institute of Physics (AIP)
    Online: 1(1).2014 –
    Publisher: American Institute of Physics (AIP)
    Electronic ISSN: 1931-9401
    Topics: Physics
    Keywords: Allgemeine Physik
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  • 24
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    American Institute of Physics (AIP)
    Online: 1.1975 – 29.2003
    Formerly as: Soviet Astronomy / Letters. A translation of the Astronomical journal of the Soviet Academy of Sciences of the USSR  (1975–1992)
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 0360-0327 , 1063-7737
    Topics: Physics
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  • 25
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    American Chemical Society | ACS Publications
    Online: 1.1879 –
    Publisher: American Chemical Society , ACS Publications
    Print ISSN: 0002-7863
    Electronic ISSN: 1520-5126
    Topics: Chemistry and Pharmacology
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  • 26
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    American Institute of Physics (AIP)
    Online: 23.1997 –
    Publisher: American Institute of Physics (AIP)
    Print ISSN: 1063-777X
    Electronic ISSN: 1090-6517
    Topics: Physics
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  • 27
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    American Chemical Society | ACS Publications
    Online: 1(1).2021 –
    Publisher: American Chemical Society , ACS Publications
    Electronic ISSN: 2691-3704
    Topics: Chemistry and Pharmacology
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  • 28
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    American Institute of Physics (AIP) | früher: Elsevier
    Online: 1(1).2016 –
    Publisher: American Institute of Physics (AIP) , früher: Elsevier
    Print ISSN: 2468-2047
    Electronic ISSN: 2468-080X
    Topics: Physics
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  • 29
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    American Chemical Society
    In:  EPIC3Environmental Science and Technology, American Chemical Society, 48, pp. 13451-13458, ISSN: 0013-936X
    Publication Date: 2014-11-21
    Description: Plastic pollution is an emerging global threat for marine wildlife. Many species of birds, reptiles and fishes are directly impaired by plastics as they can get entangled in ropes and drown or they can ingest plastic fragments which, in turn, may clog their stomachs and guts. Microplastics of less than 1 mm can be ingested by small invertebrates but their fate in the digestive organs and their effects on the animals are yet not well understood. We embedded fluorescent microplastics in artificial agarose-based food and offered the food to marine isopods, Idotea emarginata. The isopods did not distinguish between food with and food without microplastics. Upon ingestion, the microplastics were present in the stomach and in the gut but not in the tubules of the midgut gland which is the principal organ of enzyme-secretion and nutrient resorption. The feces contained the same concentration of micro-plastics as the food which indicates that no accumulation of microplastics happens during the gut passage. Long-term bioassays of six weeks showed no distinct effects of continu¬ous micro-plastic consumption on mortality, growth, and intermolt duration. I. emarginata are able to prevent intrusion of particles even smaller than 1 µm into the midgut gland which is facilitated by the complex structure of the stomach including a fine filter system. It separates the midgut gland tubules from the stomach and allows only the passage of fluids and chyme. Our results indicate that micro¬plastics, as administered in the experi¬ments, do not clog the digestive organs of isopods and do not have adverse effects on their life history parameters.
    Repository Name: EPIC Alfred Wegener Institut
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  • 30
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    American Chemical Society
    In:  EPIC3Environmental Science & Technology, American Chemical Society, 52(22), pp. 13279-13288
    Publication Date: 2019-03-13
    Repository Name: EPIC Alfred Wegener Institut
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  • 31
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    American Chemical Society
    In:  EPIC3Environmental Science & Technology, American Chemical Society, 54(24), pp. 15893-15903, ISSN: 0013-936X
    Publication Date: 2021-04-08
    Repository Name: EPIC Alfred Wegener Institut
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  • 32
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    American Chemical Society
    In:  EPIC3Environmental Science & Technology, American Chemical Society, 53, pp. 8747-8756, ISSN: 1520-5851
    Publication Date: 2020-06-04
    Description: Recent studies pointed to a high ice nucleating activity (INA) in the Arctic sea surface microlayer (SML). However, related chemical information is still sparse. In the present study, INA and free glucose concentrations were quantified in Arctic SML and bulk water samples from the marginal ice zone, the ice-free ocean, melt ponds, and open waters within the ice pack. T50 (defining INA) ranged from −17.4 to −26.8 °C. Glucose concentrations varied from 0.6 to 51 μg/L with highest values in the SML from the marginal ice zone and melt ponds (median 16.3 and 13.5 μg/L) and lower values in the SML from the ice pack and the ice-free ocean (median 3.9 and 4.0 μg/L). Enrichment factors between the SML and the bulk ranged from 0.4 to 17. A positive correlation was observed between free glucose concentration and INA in Arctic water samples (T50(°C) = (−25.6 ± 0.6) + (0.15 ± 0.04)·Glucose(μg/L), RP = 0.66, n = 74). Clustering water samples based on phytoplankton pigment composition resulted in robust but different correlations within the four clusters (RP between 0.67 and 0.96), indicating a strong link to phytoplankton-related processes. Since glucose did not show significant INA itself, free glucose may serve as a potential tracer for INA in Arctic water samples.
    Repository Name: EPIC Alfred Wegener Institut
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  • 33
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    American Chemical Society
    In:  EPIC3Environmental Science and Technology, American Chemical Society, 50(13), pp. 7066-7073, ISSN: 0013936X
    Publication Date: 2016-10-12
    Description: Atmospheric nuclear weapons testing (NWT) resulted in the injection of plutonium (Pu) into the atmosphere and subsequent global deposition. We present a new method for continuous semiquantitative measurement of 239Pu in ice cores, which was used to develop annual records of fallout from NWT in ten ice cores from Greenland and Antarctica. The 239Pu was measured directly using an inductively coupled plasma-sector field mass spectrometer, thereby reducing analysis time and increasing depth-resolution with respect to previous methods. To validate this method, we compared our one year averaged results to published 239Pu records and other records of NWT. The 239Pu profiles from the Arctic ice cores reflected global trends in NWT and were in agreement with discrete Pu profiles from lower latitude ice cores. The 239Pu measurements in the Antarctic ice cores tracked low latitude NWT, consistent with previously published discrete records from Antarctica. Advantages of the continuous 239Pu measurement method are (1) reduced sample preparation and analysis time; (2) no requirement for additional ice samples for NWT fallout determinations; (3) measurements are exactly coregistered with all other chemical, elemental, isotopic, and gas measurements from the continuous analytical system; and (4) the long half-life means the 239Pu record is stable through time.
    Repository Name: EPIC Alfred Wegener Institut
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  • 34
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    American Chemical Society
    In:  EPIC3Crystal Growth & Design, American Chemical Society, 18, pp. 2563-2571
    Publication Date: 2018-04-23
    Description: The morphology and growth kinetics of ice single crystals in aqueous solutions of type III antifreeze protein (AFP-III) have been studied in detail over a range of AFP-III concentrations and supercoolings. In pure water, the shape of ice crystals changes from the circular disklike to planar dendritic with increasing supercooling. In AFP-III solutions, ice crystals in the form of faceted plates, irregular dendrites with polygonized tips, and needles appear with increasing supercooling and AFP-III concentration. The growth rate of ice crystals in the crystallographic a direction is 2 orders of magnitude higher than that in the c direction. AFP-III molecules cause the stoppage of the growth of the prismatic and basal faces at low supercoolings. When supercooling exceeds the critical value, AFP-III favors the acceleration of the growth in both a and c directions. The observed behavior of AFP-III is explained in terms of the Cabrera-Vermilyea pinning model and the specificity of the dissipation of latent heat from the growing crystals with different shapes.
    Repository Name: EPIC Alfred Wegener Institut
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  • 35
    Publication Date: 2017-04-04
    Description: Red Pompeian paintings, very famous for their deep intensity, are currently suffering from darkening. The origins of this darkening degradation are not clearly identified yet and remain a major issue for curators. In the specific case of cinnabar (HgS)-based red pigment, a photoinduced conversion into black metacinnabar is usually suspected. This work is focused on the blackening of red cinnabar paintings coated on a sparry calcite mortar. Different samples exhibiting different levels of degradation were selected upon visual observations and analyzed by synchrotron-based microanalytical techniques. Atomic and molecular compositions of the different debased regions revealed two possible degradation mechanisms. On one hand, micro X-ray fluorescence elemental maps show peculiar distributions of chlorine and sulfur. On the other hand, X-ray absorption spectroscopy performed at both Cl and S K-edges confirms the presence of characteristic degradation products: (i) Hg- Cl compounds (e.g., corderoite, calomel, and terlinguaite), which may result from the reaction with exogenous NaCl, in gray areas; (ii) gypsum, produced by the calcite sulfation, in black coatings. Metacinnabar is never detected. Finally, a cross section was analyzed to map the in-depth alteration gradient. Reduced and oxidized sulfur distributions reveal that the sulfated black coating consists of a 5-ím-thick layer covering intact cinnabar.
    Description: Published
    Description: 7484-7492
    Description: reserved
    Keywords: Microspectroscopy Analysis ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 36
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    American Chemical Society
    In:  EPIC3Environ. Sci. Technol., American Chemical Society, 46, pp. 11327-11335
    Publication Date: 2019-07-17
    Description: In this study, we investigated if industrial high-density polyethylene (HDPE) particles, a model microplastic free of additives, ranging 〉 0− 80 μm are ingested and taken up into the cells and tissue of the blue mussel Mytilus edulis L. The effects of exposure (up to 96 h) and plastic ingestion were observed at the cellular and subcellular level. Microplastic uptake into the gills and digestive gland was analyzed by a new method using polarized light microscopy. Mussel health status was investigated incorporating histological assessment and cytochemical biomarkers of toxic effects and early warning. In addition to being drawn into the gills, HDPE particles were taken up into the stomach and transported into the digestive gland where they accumulated in the lysosomal system after 3 h of exposure. Our results show notable histological changes upon uptake and a strong inflammatory response demonstrated by the formation of granulocytomas after 6 h and lysosomal membrane destabilization, which significantly increased with longer exposure times. We provide proof of principle that microplastics are taken up into cells and cause significant effects on the tissue and cellular level, which can be assessed with standard cytochemical biomarkers and polarized light microscopy for microplastic tracking in tissue.
    Repository Name: EPIC Alfred Wegener Institut
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  • 37
    Publication Date: 2022-05-25
    Description: © American Chemical Society, 2015. This article is posted here by permission of American Chemical Society; copying and redistribution for non-commercial research and education purposes only. The definitive version was published in ACS Nano 10 (2016): 6-37, doi:10.1021/acsnano.5b07826.
    Description: The microbiome presents great opportunities for understanding and improving the world around us and elucidating the interactions that compose it. The microbiome also poses tremendous challenges for mapping and manipulating the entangled networks of interactions among myriad diverse organisms. Here, we describe the opportunities, technical needs, and potential approaches to address these challenges, based on recent and upcoming advances in measurement and control at the nanoscale and beyond. These technical needs will provide the basis for advancing the largely descriptive studies of the microbiome to the theoretical and mechanistic understandings that will underpin the discipline of microbiome engineering. We anticipate that the new tools and methods developed will also be more broadly useful in environmental monitoring, medicine, forensics, and other areas.
    Description: This research was supported by the Office of Naval Research Grant #N000141410051 (P.S.W., G.C.L.W., and T.Y.), the Genomic Science Program of the U.S. DOE-OBER,
    Repository Name: Woods Hole Open Access Server
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  • 38
    Publication Date: 2022-05-25
    Description: Author Posting. © American Chemical Society, 2018. This is an open access article published under an ACS AuthorChoice License. The definitive version was published in Environmental Science and Technology Letters 5 (2018): 226–231, doi:10.1021/acs.estlett.8b00084.
    Description: Chemical dispersants are one of many tools used to mitigate the overall environmental impact of oil spills. In principle, dispersants break up floating oil into small droplets that disperse into the water column where they are subject to multiple fate and transport processes. The effectiveness of dispersants typically decreases as oil weathers in the environment. This decrease in effectiveness is often attributed to evaporation and emulsification, with the contribution of photochemical weathering assumed to be negligible. Here, we aim to test this assumption using Macondo well oil released during the Deepwater Horizon spill as a case study. Our results indicate that the effects of photochemical weathering on Deepwater Horizon oil properties and dispersant effectiveness can greatly outweigh the effects of evaporative weathering. The decrease in dispersant effectiveness after light exposure was principally driven by the decreased solubility of photo-oxidized crude oil residues in the solvent system that comprises COREXIT EC9500A. Kinetic modeling combined with geospatial analysis demonstrated that a considerable fraction of aerial applications targeting Deepwater Horizon surface oil had low dispersant effectiveness. Collectively, the results of this study challenge the paradigm that photochemical weathering has a negligible impact on the effectiveness of oil spill response and provide critical insights into the “window of opportunity” to apply chemical dispersants in response to oil spills in sunlit waters.
    Description: This work was supported, in part, by National Science Foundation Grant OCE-1333148, Gulf of Mexico Research Initiative Grants 015, SA 16-30, the DEEP-C consortium, and the Clark Family Foundation, Inc. EPA funding was provided to R.N.C. from the Oil Spill Liability Trust Fund.
    Repository Name: Woods Hole Open Access Server
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  • 39
    Publication Date: 2019-07-17
    Description: The low temperatures of polar regions and high-altitude environments, especially icy habitats, present challenges for many microorganisms. Their ability to live under subfreezing conditions implies the production of compounds conferring cryotolerance. Colwellia psychrerythraea 34H, a γ-proteobacterium isolated from subzero Arctic marine sediments, provides a model for the study of life in cold environments. We report here the identification and detailed molecular primary and secondary structures of capsular polysaccharide from C. psychrerythraea 34H cells. The polymer was isolated in the water layer when cells were extracted by phenol/water and characterized by one- and two-dimensional NMR spectroscopy together with chemical analysis. Molecular mechanics and dynamics calculations were also performed. The polysaccharide consists of a tetrasaccharidic repeating unit containing two amino sugars and two uronic acids bearing threonine as substituent. The structural features of this unique polysaccharide resemble those present in antifreeze proteins and glycoproteins. These results suggest a possible correlation between the capsule structure and the ability of C. psychrerythraea to colonize subfreezing marine environments.
    Repository Name: EPIC Alfred Wegener Institut
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  • 40
    Publication Date: 2022-01-07
    Description: Microplastic (MP) pollution has been found in the Southern Ocean surrounding Antarctica, but many local regions within this vast area remain uninvestigated. The remote Weddell Sea contributes to the global thermohaline circulation, and one of the two Antarctic gyres is located in that region. In the present study, we evaluate MP (〉300 μm) concentration and composition in surface (n = 34) and subsurface water samples (n = 79, ∼11.2 m depth) of the Weddell Sea. All putative MP were analyzed by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. MP was found in 65% of surface and 11.4% of subsurface samples, with mean (±standard deviation (SD)) concentrations of 0.01 (±0.01 SD) MP m–3 and 0.04 (±0.1 SD) MP m–3, respectively, being within the range of previously reported values for regions south of the Polar Front. Additionally, we aimed to determine whether identified paint fragments (n = 394) derive from the research vessel. Environmentally sampled fragments (n = 101) with similar ATR-FTIR spectra to reference paints from the research vessel and fresh paint references generated in the laboratory were further subjected to micro-X-ray fluorescence spectroscopy (μXRF) to compare their elemental composition. This revealed that 45.5% of all recovered MP derived from vessel-induced contamination. However, 11% of the measured fragments could be distinguished from the reference paints via their elemental composition. This study demonstrates that differentiation based purely on visual characteristics and FTIR spectroscopy might not be sufficient for accurately determining sample contamination sources.
    Repository Name: EPIC Alfred Wegener Institut
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  • 41
    Publication Date: 2022-05-26
    Description: Author Posting. © American Chemical Society, 2014. This article is posted here by permission of American Chemical Society for personal use, not for redistribution. The definitive version was published in Environmental Science and Technology 38 (2014): 4732–4738, doi:10.1021/es4053076.
    Description: We present an extensive survey of floating plastic debris in the eastern North and South Pacific Oceans from more than 2500 plankton net tows conducted between 2001 and 2012. From these data we defined an accumulation zone (25 to 41°N, 130 to 180°W) in the North Pacific subtropical gyre that closely corresponds to centers of accumulation resulting from the convergence of ocean surface currents predicted by several oceanographic numerical models. Maximum plastic concentrations from individual surface net tows exceeded 106 pieces km–2, with concentrations decreasing with increasing distance from the predicted center of accumulation. Outside the North Pacific subtropical gyre the median plastic concentration was 0 pieces km–2. We were unable to detect a robust temporal trend in the data set, perhaps because of confounded spatial and temporal variability. Large spatiotemporal variability in plastic concentration causes order of magnitude differences in summary statistics calculated over short time periods or in limited geographic areas. Utilizing all available plankton net data collected in the eastern Pacific Ocean (17.4°S to 61.0°N; 85.0 to 180.0°W) since 1999, we estimated a minimum of 21 290 t of floating microplastic.
    Description: This work was supported by Sea Education Association, NFWF-NOAA Marine Debris Program (Nos. 2009-0062-002, NA10OAR4320148, Amend. 71), and NSF (Nos. OCE-0087528, OCE-1155379, OCE-1260403, OCE-1352422).
    Repository Name: Woods Hole Open Access Server
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  • 42
    Publication Date: 2022-05-26
    Description: © The American Chemical Society, 2016. This is an open access article published under an ACS AuthorChoice License. The definitive version was published in Analytical Chemistry 88 (2016): 7154–7162, doi:10.1021/acs.analchem.6b01260.
    Description: Discovery and identification of molecular biomarkers in large LC/MS data sets requires significant automation without loss of accuracy in the compound screening and annotation process. Here, we describe a lipidomics workflow and open-source software package for high-throughput annotation and putative identification of lipid, oxidized lipid, and oxylipin biomarkers in high-mass-accuracy HPLC-MS data. Lipid and oxylipin biomarker screening through adduct hierarchy sequences, or LOBSTAHS, uses orthogonal screening criteria based on adduct ion formation patterns and other properties to identify thousands of compounds while providing the user with a confidence score for each assignment. Assignments are made from one of two customizable databases; the default databases contain 14 068 unique entries. To demonstrate the software’s functionality, we screened more than 340 000 mass spectral features from an experiment in which hydrogen peroxide was used to induce oxidative stress in the marine diatom Phaeodactylum tricornutum. LOBSTAHS putatively identified 1969 unique parent compounds in 21 869 features that survived the multistage screening process. While P. tricornutum maintained more than 92% of its core lipidome under oxidative stress, patterns in biomarker distribution and abundance indicated remodeling was both subtle and pervasive. Treatment with 150 μM H2O2 promoted statistically significant carbon-chain elongation across lipid classes, with the strongest elongation accompanying oxidation in moieties of monogalactosyldiacylglycerol, a lipid typically localized to the chloroplast. Oxidative stress also induced a pronounced reallocation of lipidome peak area to triacylglycerols. LOBSTAHS can be used with environmental or experimental data from a variety of systems and is freely available at https://github.com/vanmooylipidomics/LOBSTAHS.
    Description: This research was supported by the Gordon and Betty Moore Foundation through Grant GBMF3301 to B.A.S.V.M. This research was also funded in part by a grant to B.A.S.V.M. from the Simons Foundation and is a contribution of the Simons Collaboration on Ocean Processes and Ecology (SCOPE). J.R.C. acknowledges support from a U.S. Environmental Protection Agency (EPA) STAR Graduate Fellowship (Fellowship Assistance Agreement No. FP-91744301-0).
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  • 43
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Walsh, A. N., Reddy, C. M., Niles, S. F., McKenna, A. M., Hansel, C. M., & Ward, C. P. Plastic formulation is an emerging control of its photochemical fate in the ocean. Environmental Science & Technology, 55(18), (2021): 12383–12392, https://doi.org/10.1021/acs.est.1c02272.
    Description: Sunlight exposure is a control of long-term plastic fate in the environment that converts plastic into oxygenated products spanning the polymer, dissolved, and gas phases. However, our understanding of how plastic formulation influences the amount and composition of these photoproducts remains incomplete. Here, we characterized the initial formulations and resulting dissolved photoproducts of four single-use consumer polyethylene (PE) bags from major retailers and one pure PE film. Consumer PE bags contained 15–36% inorganic additives, primarily calcium carbonate (13–34%) and titanium dioxide (TiO2; 1–2%). Sunlight exposure consistently increased production of dissolved organic carbon (DOC) relative to leaching in the dark (3- to 80-fold). All consumer PE bags produced more DOC during sunlight exposure than the pure PE (1.2- to 2.0-fold). The DOC leached after sunlight exposure increasingly reflected the 13C and 14C isotopic composition of the plastic. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry revealed that sunlight exposure substantially increased the number of DOC formulas detected (1.1- to 50-fold). TiO2-containing bags photochemically degraded into the most compositionally similar DOC, with 68–94% of photoproduced formulas in common with at least one other TiO2-containing bag. Conversely, only 28% of photoproduced formulas from the pure PE were detected in photoproduced DOC from the consumer PE. Overall, these findings suggest that plastic formulation, especially TiO2, plays a determining role in the amount and composition of DOC generated by sunlight. Consequently, studies on pure, unweathered polymers may not accurately represent the fates and impacts of the plastics entering the ocean.
    Description: Funding was provided by the Seaver Institute, the Gerstner Family Foundation, Woods Hole Oceanographic Institution, and the National Science Foundation Graduate Research Fellowship Program (A.N.W.). The Ion Cyclotron Resonance user facility at the National High Magnetic Field Laboratory is supported by the National Science Foundation Division of Chemistry and Division of Materials Research through DMR-1644779 and the State of Florida.
    Keywords: Plastic pollution ; Marine debris ; Additives ; Dissolved organic carbon ; Photochemical oxidation ; FT-ICR-MS ; Titanium dioxide
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  • 44
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gosselin, K. M., Nelson, R. K., Spivak, A. C., Sylva, S. P., Van Mooy, B. A. S., Aeppli, C., Sharpless, C. M., O’Neil, G. W., Arrington, E. C., Reddy, C. M., & Valentine, D. L. Production of two highly abundant 2-methyl-branched fatty acids by blooms of the globally significant marine cyanobacteria Trichodesmium erythraeum. ACS Omega, 6(35), (2021): 22803–22810, https://doi.org/10.1021/acsomega.1c03196.
    Description: The bloom-forming cyanobacteria Trichodesmium contribute up to 30% to the total fixed nitrogen in the global oceans and thereby drive substantial productivity. On an expedition in the Gulf of Mexico, we observed and sampled surface slicks, some of which included dense blooms of Trichodesmium erythraeum. These bloom samples contained abundant and atypical free fatty acids, identified here as 2-methyldecanoic acid and 2-methyldodecanoic acid. The high abundance and unusual branching pattern of these compounds suggest that they may play a specific role in this globally important organism.
    Description: This work was funded with grants from the National Science Foundation grants OCE-1333148, OCE-1333162, and OCE-1756254 and the Woods Hole Oceanographic Institution (IR&D). GCxGC analysis made possible by WHOI’s Investment in Science Fund.
    Keywords: Lipids ; Alkyls ; Bacteria ; Genetics ; Chromatography
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  • 45
    Publication Date: 2022-05-27
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Mazzotta, M. G., Reddy, C. M., & Ward, C. P. Rapid degradation of cellulose diacetate by marine microbes. Environmental Science & Technology Letters, 9(1), (2022): 37-41. https://doi.org/10.1021/acs.estlett.1c00843.
    Description: The persistence of cellulose diacetate (CDA), a biobased plastic used in textiles and single-use consumer products, in the ocean is currently unknown. Here, we probe the disintegration and degradation of CDA-based materials (25 μm films, 510 μm foam, and 97 g/m2 fabric) by marine microbes in a continuous flow seawater mesocosm. Photographic evidence and mass loss measurements demonstrate that CDA-based materials disintegrate in months. Disintegration is marked by the increasing esterase and cellulase activity of the biofilm community, suggesting that marine microbes degrade CDA. The natural abundance stable (13C) and radiocarbon (14C) isotopic signature of carbon dioxide respired during short-term bottle incubations confirms the rapid degradation of both acetyl and cellulosic components of CDA by seawater microbial communities. These findings challenge the paradigm set by governmental agencies and advocacy groups that CDA-based materials persist in the ocean for decades, and represent a positive step toward identifying high-utility, biobased plastics with low environmental persistence.
    Description: M.G.M., C.M.R., and C.P.W. thank Eastman Chemical Co. and Woods Hole Oceanographic Institution (WHOI) for scientific and financial support.
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  • 46
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Xie, L., Liu, X., Caratenuto, A., Tian, Y., Chen, F., DeGiorgis, J. A., Wan, Y., & Zheng, Y. Environmentally friendly and efficient hornet nest envelope-based photothermal absorbers. Acs Omega, 6(50), (2021): 34555–34562, https://doi.org/10.1021/acsomega.1c04851.
    Description: Water shortage is a critical global issue that threatens human health, environmental sustainability, and the preservation of Earth’s climate. Desalination from seawater and sewage is a promising avenue for alleviating this stress. In this work, we use the hornet nest envelope material to fabricate a biomass-based photothermal absorber as part of a desalination isolation system. This system realizes an evaporation rate of 3.98 kg m–2 h–1 under one-sun illumination, with prolonged evaporation rates all above 4 kg m–2 h–1. This system demonstrates a strong performance of 3.86 kg m–2 h–1 in 3.5 wt % saltwater, illustrating its effectiveness in evaporation seawater. Thus, with its excellent evaporation rate, great salt rejection ability, and easy fabrication approach, the hornet nest envelope constitutes a promising natural material for solar water treatment applications.
    Description: The authors acknowledge the support from the National Science Foundation, USA, through grant number CBET-1941743 and the National Science Foundation under EPSCoR Cooperation Agreement OIA-1655221.
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  • 47
    Publication Date: 2022-05-26
    Description: Author Posting. © American Chemical Society, 2019. This article is posted here by permission of American Chemical Society for personal use, not for redistribution. The definitive version was published in Kivenson, V., Lemkau, K. L., Pizarro, O., Yoerger, D. R., Kaiser, C., Nelson, R. K., Carmichael, C., Paul, B. G., Reddy, C. M., & Valentine, D. L. (2019). Ocean Dumping of Containerized DDT Waste Was a Sloppy Process. Environmental Science and Technology (2019), doi:10.1021/acs.est.8b05859.
    Description: Industrial-scale dumping of organic waste to the deep ocean was once common practice, leaving a legacy of chemical pollution for which a paucity of information exists. Using a nested approach with autonomous and remotely operated underwater vehicles, a dumpsite offshore California was surveyed and sampled. Discarded waste containers littered the site and structured the suboxic benthic environment. Dichlorodiphenyltrichloroethane (DDT) was reportedly dumped in the area, and sediment analysis revealed substantial variability in concentrations of p,p-DDT and its analogs, with a peak concentration of 257 μg g–1, ∼40 times greater than the highest level of surface sediment contamination at the nearby DDT Superfund site. The occurrence of a conspicuous hydrocarbon mixture suggests that multiple petroleum distillates, potentially used in DDT manufacture, contributed to the waste stream. Application of a two end-member mixing model with DDTs and polychlorinated biphenyls enabled source differentiation between shelf discharge versus containerized waste. Ocean dumping was found to be the major source of DDT to more than 3000 km2 of the region’s deep seafloor. These results reveal that ocean dumping of containerized DDT waste was inherently sloppy, with the contents readily breaching containment and leading to regional scale contamination of the deep benthos.
    Description: This material is based upon work supported by the National Science Foundation Graduate Research Fellowship for V.K. under Grant No. 1650114. Expeditions AT-18-11 and AT-26-06 were funded by the NSF (OCE-0961725 and OCE-1046144). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. We thank the captain and crew of the RV Atlantis, the pilots and crew of the ROV Jason, the crew of the AUV Sentry, the scientific party of the AT-18-11 and AT-26-06 expeditions, Justin Tran for assistance with the preparation of multibeam data, M. Indira Venkatesan for a helpful discussion of the NOAA datasets, and Nathan Dodder for advice on the procedure for compound identification.
    Repository Name: Woods Hole Open Access Server
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  • 48
    Publication Date: 2022-05-26
    Description: Author Posting. © American Chemical Society, 2011. This article is posted here by permission of American Chemical Society for personal use, not for redistribution. The definitive version was published in Environmental Science and Technology 45 (2011): 9931–9935, doi:10.1021/es202816c.
    Description: The impacts on the ocean of releases of radionuclides from the Fukushima Dai-ichi nuclear power plants remain unclear. However, information has been made public regarding the concentrations of radioactive isotopes of iodine and cesium in ocean water near the discharge point. These data allow us to draw some basic conclusions about the relative levels of radionuclides released which can be compared to prior ocean studies and be used to address dose consequences as discussed by Garnier-Laplace et al. in this journal.(1) The data show peak ocean discharges in early April, one month after the earthquake and a factor of 1000 decrease in the month following. Interestingly, the concentrations through the end of July remain higher than expected implying continued releases from the reactors or other contaminated sources, such as groundwater or coastal sediments. By July, levels of 137Cs are still more than 10 000 times higher than levels measured in 2010 in the coastal waters off Japan. Although some radionuclides are significantly elevated, dose calculations suggest minimal impact on marine biota or humans due to direct exposure in surrounding ocean waters, though considerations for biological uptake and consumption of seafood are discussed and further study is warranted.
    Description: Funding for this work to KOB is from the Gordon and Betty Moore Foundation as well as the Chemical Oceanography Program of the US National Science Foundation.
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  • 49
    Publication Date: 2022-05-26
    Description: Author Posting. © American Chemical Society, 2019. This is an open access article published under an ACS AuthorChoice License. The definitive version was published in Environmental Science and Technology 53(16), (2019): 9398-9406, doi:10.1021/acs.est.9b02395.
    Description: Geochemical data from 40 water wells were used to examine the occurrence and sources of radium (Ra) in groundwater associated with three oil fields in California (Fruitvale, Lost Hills, South Belridge). 226Ra+228Ra activities (range = 0.010–0.51 Bq/L) exceeded the 0.185 Bq/L drinking-water standard in 18% of the wells (not drinking-water wells). Radium activities were correlated with TDS concentrations (p 〈 0.001, ρ = 0.90, range = 145–15,900 mg/L), Mn + Fe concentrations (p 〈 0.001, ρ = 0.82, range = 〈0.005–18.5 mg/L), and pH (p 〈 0.001, ρ = −0.67, range = 6.2–9.2), indicating Ra in groundwater was influenced by salinity, redox, and pH. Ra-rich groundwater was mixed with up to 45% oil-field water at some locations, primarily infiltrating through unlined disposal ponds, based on Cl, Li, noble-gas, and other data. Yet 228Ra/226Ra ratios in pond-impacted groundwater (median = 3.1) differed from those in oil-field water (median = 0.51). PHREEQC mixing calculations and spatial geochemical variations suggest that the Ra in the oil-field water was removed by coprecipitation with secondary barite and adsorption on Mn–Fe precipitates in the near-pond environment. The saline, organic-rich oil-field water subsequently mobilized Ra from downgradient aquifer sediments via Ra-desorption and Mn/Fe-reduction processes. This study demonstrates that infiltration of oil-field water may leach Ra into groundwater by changing salinity and redox conditions in the subsurface rather than by mixing with a high-Ra source.
    Description: This article was improved by the reviews of John Izbicki and anonymous reviewers for the journal. This work was funded by the California State Water Resources Control Board’s Regional Groundwater Monitoring in Areas of Oil and Gas Production Program and the USGS Cooperative Water Program. A.V., A.J.K., and Z.W were supported by USDA-NIFA grant (#2017-68007-26308). Any use of trade, firm, or product names is for description purposes only and does not imply endorsement by the U.S. Government.
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  • 50
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McLean, C., & Kujawinski, E. B. AutoTuner: high fidelity and robust parameter selection for metabolomics data processing. Analytical Chemistry, 92(8), (2020): 5724-5732, doi:10.1021/acs.analchem.9b04804.
    Description: Untargeted metabolomics experiments provide a snapshot of cellular metabolism but remain challenging to interpret due to the computational complexity involved in data processing and analysis. Prior to any interpretation, raw data must be processed to remove noise and to align mass-spectral peaks across samples. This step requires selection of dataset-specific parameters, as erroneous parameters can result in noise inflation. While several algorithms exist to automate parameter selection, each depends on gradient descent optimization functions. In contrast, our new parameter optimization algorithm, AutoTuner, obtains parameter estimates from raw data in a single step as opposed to many iterations. Here, we tested the accuracy and the run-time of AutoTuner in comparison to isotopologue parameter optimization (IPO), the most commonly used parameter selection tool, and compared the resulting parameters’ influence on the properties of feature tables after processing. We performed a Monte Carlo experiment to test the robustness of AutoTuner parameter selection and found that AutoTuner generated similar parameter estimates from random subsets of samples. We conclude that AutoTuner is a desirable alternative to existing tools, because it is scalable, highly robust, and very fast (∼100–1000× speed improvement from other algorithms going from days to minutes). AutoTuner is freely available as an R package through BioConductor.
    Description: We thank Titus Brown and Ben Temperton for advice on the algorithm validation, Arthur Eschenlauer for constructive feedback on the software design, Krista Longnecker for continuous support and discussions, Gabriel Leventhal for mathematics advice, the users of AutoTuner for debugging help through Github, and David Angeles-Albores and two anonymous reviewers for critical feedback on the manuscript. Funding support included the National GEM Consortium and NSF graduate research program fellowships (C.M.) and grants from the MIT Microbiome Center (Award 6936800, E.B.K.) and the Simons Foundation (Award ID #509034, E.B.K.).
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  • 51
    Publication Date: 2022-05-26
    Description: Author Posting. © American Chemical Society, 2020. This is an open access article published under an ACS AuthorChoice License. The definitive version was published in Chemical Research in Toxicology, 33(4), (2020): 860-879, doi:10.1021/acs.chemrestox.9b00476.
    Description: The Ah receptor (AHR) has been studied for almost five decades. Yet, we still have many important questions about its role in normal physiology and development. Moreover, we still do not fully understand how this protein mediates the adverse effects of a variety of environmental pollutants, such as the polycyclic aromatic hydrocarbons (PAHs), the chlorinated dibenzo-p-dioxins (“dioxins”), and many polyhalogenated biphenyls. To provide a platform for future research, we provide the historical underpinnings of our current state of knowledge about AHR signal transduction, identify a few areas of needed research, and then develop concepts such as adaptive metabolism, ligand structural diversity, and the importance of proligands in receptor activation. We finish with a discussion of the cognate physiological role of the AHR, our perspective on why this receptor is so highly conserved, and how we might think about its cognate ligands in the future.
    Description: This review is dedicated in memory of the career of Alan Poland, one of the truly great minds in pharmacology and toxicology. This work was supported by the National Institutes of Health Grants R35-ES028377, T32-ES007015, P30-CA014520, P42-ES007381, and U01-ES1026127, The UW SciMed GRS Program, and The Morgridge Foundation. The authors would like to thank Catherine Stanley of UW Media Solutions for her artwork.
    Repository Name: Woods Hole Open Access Server
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  • 52
    Publication Date: 2022-12-07
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in James, B., de Vos, A., Aluwihare, L., Youngs, S., Ward, C., Nelson, R., Michel, A., Hahn, M., & Reddy, C. Divergent forms of pyroplastic: lessons learned from the M/V X-Press Pearl ship fire. ACS Environmental Au, 2(5), (2022): 467–479, https://doi.org/10.1021/acsenvironau.2c00020.
    Description: In late May 2021, the M/V X-Press Pearl container ship caught fire while anchored 18 km off the coast of Colombo, Sri Lanka and spilled upward of 70 billion pieces of plastic or “nurdles” (∼1680 tons), littering the country’s coastline. Exposure to combustion, heat, chemicals, and petroleum products led to an apparent continuum of changes from no obvious effects to pieces consistent with previous reports of melted and burned plastic (pyroplastic) found on beaches. At the middle of this continuum, nurdles were discolored but appeared to retain their prefire morphology, resembling nurdles that had been weathered in the environment. We performed a detailed investigation of the physical and surface properties of discolored nurdles collected on a beach 5 days after the ship caught fire and within 24 h of their arrival onshore. The color was the most striking trait of the plastic: white for nurdles with minimal alteration from the accident, orange for nurdles containing antioxidant degradation products formed by exposure to heat, and gray for partially combusted nurdles. Our color analyses indicate that this fraction of the plastic released from the ship was not a continuum but instead diverged into distinct groups. Fire left the gray nurdles scorched, with entrained particles and pools of melted plastic, and covered in soot, representing partial pyroplastics, a new subtype of pyroplastic. Cross sections showed that the heat- and fire-induced changes were superficial, leaving the surfaces more hydrophilic but the interior relatively untouched. These results provide timely and actionable information to responders to reevaluate cleanup end points, monitor the recurrence of these spilled nurdles, gauge short- and long-term effects of the spilled nurdles to the local ecosystem, and manage the recovery of the spill. These findings underscore partially combusted plastic (pyroplastic) as a type of plastic pollution that has yet to be fully explored despite the frequency at which plastic is burned globally.
    Description: This work was supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution (WHOI), with funding provided by the Weston Howland Jr. Postdoctoral Scholarship. Additional support was provided by the WHOI Marine Microplastics Catalyst Program, the WHOI Marine Microplastics Innovation Accelerator Program, the WHOI Investment in Science Fund, the March Marine Initiative (a program of March Limited, Bermuda), The Seaver Institute, Gerstner Philanthropies, the Wallace Research Foundation, the Richard Saltonstall Charitable Foundation, the Harrison Foundation, Hollis and Ermine Lovell Charitable Foundation, and the Richard Grand Foundation. AdV was supported by funding from the Schmidt Foundation.
    Keywords: Microplastic ; Resin pellets ; Pollution ; Additives ; Open burning ; Weathering ; Maritime accident
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  • 53
    Publication Date: 2022-05-26
    Description: Author Posting. © American Chemical Society, 2019. This is an open access article published under an ACS AuthorChoice License. The definitive version was published in Environmental Science and Technology 53(14), (2019):8244-8251, doi:10.1021/acs.est.9b02344.
    Description: Perylene is a frequently abundant, and sometimes the only polycyclic aromatic hydrocarbon (PAH) in aquatic sediments, but its origin has been subject of a longstanding debate in geochemical research and pollutant forensics because its historical record differs markedly from typical anthropogenic PAHs. Here we investigate whether perylene serves as a source-specific molecular marker of fungal activity in forest soils. We use a well-characterized sedimentary record (1735 to 1999) from the anoxic-bottom waters of the Pettaquamscutt River basin, RI, USA to examine mass accumulation rates and isotope records of perylene, and compare them with total organic carbon and the anthropogenic PAH fluoranthene. We support our arguments with radiocarbon (14C) data of higher plant leaf-wax n-alkanoic acids. Isotope-mass balance calculations of perylene and n-alkanoic acids indicate that ~40 % of sedimentary organic matter is of terrestrial origin. Further, both terrestrial markers are pre-aged on millennial time-scales prior to burial in sediments and insensitive to elevated 14C concentrations following nuclear weapons testing in the mid-20th Century. Instead, changes coincide with enhanced erosional flux during urban sprawl. These findings suggest that perylene is definitely a product of soil derived fungi, and a powerful chemical tracer to study spatial and temporal connectivity between terrestrial and aquatic environments.
    Description: We thank John King, Sean Sylva, Brad Hubeny, Peter Sauer, and Jim Broda for their help in sampling; Carl Johnson and Daniel Montluçon for their incessant help with analyses; as well as Mark Yunker for critical discussion on the perils of perylene. Professor Phil Meyers and two anonymous reviewers provided comments that improved the quality of the manuscript. U.M.H. acknowledges the Swiss National Science Foundation for his postdoctoral fellowship and T.I.E. and K.A.H. acknowledges the NSF for research grants CHE-0089172 and OCE-9708478.
    Description: 2020-06-19
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  • 54
    Publication Date: 2022-05-26
    Description: © American Chemical Society, 2016. This article is distributed under the terms of the AuthorsChoice License. The definitive version was published in Environmental Science & Technology 50 (2016): 7397–7408, doi:10.1021/acs.est.5b04617.
    Description: With the expansion of offshore petroleum extraction, validated models are needed to simulate the behaviors of petroleum compounds released in deep (〉100 m) waters. We present a thermodynamic model of the densities, viscosities, and gas–liquid−water partitioning of petroleum mixtures with varying pressure, temperature, and composition based on the Peng–Robinson equation-of-state and the modified Henry’s law (Krychevsky−Kasarnovsky equation). The model is applied to Macondo reservoir fluid released during the Deepwater Horizon disaster, represented with 279–280 pseudocomponents, including 131–132 individual compounds. We define 〉n-C8 pseudocomponents based on comprehensive two-dimensional gas chromatography (GC × GC) measurements, which enable the modeling of aqueous partitioning for n-C8 to n-C26 fractions not quantified individually. Thermodynamic model predictions are tested against available laboratory data on petroleum liquid densities, gas/liquid volume fractions, and liquid viscosities. We find that the emitted petroleum mixture was ∼29–44% gas and ∼56–71% liquid, after cooling to local conditions near the broken Macondo riser stub (∼153 atm and 4.3 °C). High pressure conditions dramatically favor the aqueous dissolution of C1−C4 hydrocarbons and also influence the buoyancies of bubbles and droplets. Additionally, the simulated densities of emitted petroleum fluids affect previous estimates of the volumetric flow rate of dead oil from the emission source.
    Description: This research was made possible by grants from the NSF (OCE- 0960841, OCE-1043976, and EAR-0950600) and the Gulf of Mexico Research Initiative (GoMRI) to the C-IMAGE and DEEP-C consortia.
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  • 55
    Publication Date: 2022-05-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Widner, B., Kido Soule, M. C., Ferrer-González, F. X., Moran, M. A., & Kujawinski, E. B. Quantification of amine- and alcohol-containing metabolites in saline samples using pre-extraction benzoyl chloride derivatization and ultrahigh performance liquid chromatography tandem mass spectrometry (UHPLC MS/MS). Analytical Chemistry, 93(11), (2021): 4809-4817, https://doi.org/10.1021/acs.analchem.0c03769.
    Description: Dissolved metabolites serve as nutrition, energy, and chemical signals for microbial systems. However, the full scope and magnitude of these processes in marine systems are unknown, largely due to insufficient methods, including poor extraction of small, polar compounds using common solid-phase extraction resins. Here, we utilized pre-extraction derivatization and ultrahigh performance liquid chromatography electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) to detect and quantify targeted dissolved metabolites in seawater and saline culture media. Metabolites were derivatized with benzoyl chloride by their primary and secondary amine and alcohol functionalities and quantified using stable isotope-labeled internal standards (SIL-ISs) produced from 13C6-labeled benzoyl chloride. We optimized derivatization, extraction, and sample preparation for field and culture samples and evaluated matrix-derived biases. We have optimized this quantitative method for 73 common metabolites, of which 50 cannot be quantified without derivatization due to low extraction efficiencies. Of the 73 metabolites, 66 were identified in either culture media or seawater and 45 of those were quantified. This derivatization method is sensitive (detection limits = pM to nM), rapid (∼5 min per sample), and high throughput.
    Description: Funding included the Gordon and Betty Moore Foundation (Award GBMF5503 to M.A.M. and E.B.K.), Simons Foundation International (Award 409923 to E.B.K.), and the National Science Foundation (Award 1656311 to M.A.M.).
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  • 56
    Publication Date: 2023-03-13
    Description: Goniodomin A (GDA, 1) is a phycotoxin produced by at least four species of Alexandrium dinoflagellates that are found globally in brackish estuaries and lagoons. It is a linear polyketide with six oxygen heterocyclic rings that is cyclized into a macrocyclic structure via lactone formation. Two of the oxygen heterocycles in 1 comprise a spiro-bis-pyran, whereas goniodomin B (GDB) contains a 2,7-dioxabicyclo[3.3.1]nonane ring system fused to a pyran. When H2O is present, 1 undergoes facile conversion to isomer GDB and to an α,β-unsaturated ketone, goniodomin C (GDC, 7). GDB and GDC can be formed from GDA by cleavage of the spiro-bis-pyran ring system. GDA, but not GDB or GDC, forms a crown ether-type complex with K+. Equilibration of GDA with GDB and GDC is observed in the presence of H+ and of Na+, but the equilibrated mixtures revert to GDA upon addition of K+. Structural differences have been found between the K+ and Na+ complexes. The association of GDA with K+ is strong, while that with Na+ is weak. The K+ complex has a compact, well-defined structure, whereas Na+ complexes are an ill-defined mixture of species. Analyses of in vitro A. monilatum and A. hiranoi cultures indicate that only GDA is present in the cells; GDB and GDC appear to be postharvest transformation products.
    Repository Name: EPIC Alfred Wegener Institut
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  • 57
    Publication Date: 2022-10-21
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Colson, B. C., & Michel, A. P. M. Flow-through quantification of microplastics using impedance spectroscopy. ACS Sensors, 6(1), (2021): 238–244, doi:10.1021/acssensors.0c02223.
    Description: Understanding the sources, impacts, and fate of microplastics in the environment is critical for assessing the potential risks of these anthropogenic particles. However, our ability to quantify and identify microplastics in aquatic ecosystems is limited by the lack of rapid techniques that do not require visual sorting or preprocessing. Here, we demonstrate the use of impedance spectroscopy for high-throughput flow-through microplastic quantification, with the goal of rapid measurement of microplastic concentration and size. Impedance spectroscopy characterizes the electrical properties of individual particles directly in the flow of water, allowing for simultaneous sizing and material identification. To demonstrate the technique, spike and recovery experiments were conducted in tap water with 212–1000 μm polyethylene beads in six size ranges and a variety of similarly sized biological materials. Microplastics were reliably detected, sized, and differentiated from biological materials via their electrical properties at an average flow rate of 103 ± 8 mL/min. The recovery rate was ≥90% for microplastics in the 300–1000 μm size range, and the false positive rate for the misidentification of the biological material as plastic was 1%. Impedance spectroscopy allowed for the identification of microplastics directly in water without visual sorting or filtration, demonstrating its use for flow-through sensing.
    Description: The authors thank the Richard Saltonstall Charitable Foundation and the National Academies Keck Futures Initiative (NAKFI DBS13) for their funding support.
    Keywords: Microplastics ; Plastics ; Impedance spectroscopy ; Dielectric properties ; Instrumentation ; Particle detection ; Flow-through ; Environmental sensing
    Repository Name: Woods Hole Open Access Server
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  • 58
    Publication Date: 2023-01-16
    Description: The uptake ability toward arsenic(V), chromium(VI), and boron(III) ions of ad hoc functionalized magnetic nanostructured devices has been investigated. To this purpose, ligands based on meglumine have been synthesized and used to coat magnetite nanoparticles (Fe3O4) obtained by the co-precipitation methodology. The as-prepared hybrid material was characterized by infrared spectroscopy (IR), X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy combined with energy-dispersive X-ray analysis. Moreover, its magnetic hysteresis properties were measured to evaluate its magnetic properties, and the adsorption kinetics and isothermal models were applied to discern between the different adsorption phenomena. Specifically, the better fitting was observed by the Langmuir isotherm model for all metal ions tested, highlighting a higher uptake in arsenic (28.2 mg/g), chromium (12.3 mg/g), and boron (23.7 mg/g) sorption values if compared with other magnetic nanostructured materials. After adsorption, an external magnetic stimulus can be used to efficiently remove nanomaterials from the water. Finally the nanomaterial can be reused up to five cycles and regenerated for another three cycles.
    Description: Published
    Description: 10775–10788
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 59
    facet.materialart.
    Unknown
    American Chemical Society
    In:  EPIC3Environmental Science & Technology Letters, American Chemical Society
    Publication Date: 2024-01-24
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 60
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    The Journal of Chemical Physics 113 (2000), S. 7621-7626 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: When placed into an external magnetic field inhomogeneous porous structures, like rocks, cement gels, ceramics, etc., exhibit strong local magnetic field gradients (LMFG), which are inherently related with the size, shape, and distribution of their pores. In this paper, we present a method of measuring LMFG in a liquid-filled porous media, provided that the fast exchange model sufficiently describes water motion in the pores, which is based solely on the measurement of the water 1H NMR spin lattice relaxation rates and the knowledge of the unrestricted diffusion coefficient. The method is applied to two hydrating white cement samples with different hydration kinetics, and the results are correlated with the time evolution of the pore structure. It is shown that the measured LMFG have extremely high values, which qualitatively reflect the sharp needlelike morphology of the internal cement gel surface. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7627-7634 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: By use of optical steady state and time resolved spectroscopy, we studied the evolution of the triplet excited state in a series of six ethynylenic polymers of the structure [-Pt(PBu3n)2-C(Triple Bond)C-R-C(Triple Bond)C-]n where the spacer unit R is systematically varied to give optical gaps from 1.7–3.0 eV. The inclusion of platinum in the polymer backbone induces a strong spin-orbit coupling such that triplet state emission (phosphorescence) associated with the conjugated system can be detected. Throughout the series we find the S1-T1 (singlet-triplet) energy splitting to be independent of the spacer R, such that the T1 state is always 0.7±0.1 eV below the S1 state. With decreasing optical gap, the intensity and lifetime of the triplet state emission were seen to reduce in accordance with the energy gap law. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7511-7518 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A modified conductorlike screening continuum solvation model, implemented in the quantum chemistry program GAMESS, has been extended to second order perturbation theory (MP2). Two possible schemes have been considered: (a) the calculation of the MP2 energy using the solvated Hartree–Fock (HF) orbitals, and (b) the implementation of a double-iterative procedure where the HF density is updated with respect to the MP2 surface charges. The influence of the self-consistency of the surface charge distribution with respect to the MP2 density has been analyzed for a small dataset of 21 neutral molecules and 13 ions. In addition, the details of the distribution of surface charge density (σ profiles) and the effects of electron correlation on the accuracy of such distributions is analyzed in terms of the overall concept of deviation of continuum models from dielectric theory, leading to insights into higher order models. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7519-7529 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The conductorlike continuum solvation model, modified for ab initio in the quantum chemistry program GAMESS, implemented at the Møller–Plesset Order 2 (MP2) level of theory has been applied to a group of push–pull pyrrole systems to illustrate the effects of donor/acceptor and solvation on the stability and energetics of such systems. The most accurate theoretical gas and solution phase data to date has been presented for the parent furan-2-carbaldehyde (furfural) system, and predictions made for three additional analogues, thiophene-2-carbaldehyde, pyrrole2-carbaldehyde, and, cyclopentadiene-1-carbaldehyde. Solvent effects on internal rotational barriers in all systems were evaluated over six different values of dielectric, using the new method. Calculated electrostatic energies are shown to be highly sensitive to level of theory incorporated. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7554-7563 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Exploiting an electrostatic analogy, we show that the elastic forces between a set of rigid particles embedded in a phantom polymer network can be represented by a simple bead-and-spring model. The beads represent the particles and the springs the rubber matrix. The model is validated by Monte Carlo simulation of rubbers filled with hard spherical particles, at volume fractions between 0.1 and 0.3. We derive both the moduli and the full stress–strain curves, under uniaxial elongation. The model reproduces and extends previous theoretical results on the so-called hydrodynamic reinforcement effect. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7571-7577 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The temperature dependence of electron transmission through various organized organic thin films (OOTFs) was investigated. For most systems a strong dependence of the transmission efficiency on temperature was observed, even for a relatively small temperature range. The well defined structure of the OOTFs and the monitoring of the angular dependence of both the initial and the final velocities of photoelectrons were used to reveal the mechanism behind the temperature effect and further elucidate the transmission mechanism. A simple model, which assumes that the electron transmission yield is much higher along the organic chains than in any other direction, was able to reproduce the experimental observations. We find that the photoelectron transmission yield through OOTFs is extremely sensitive to the structural order in the film. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7546-7553 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Femtosecond vibrational wave-packet dynamics in a cyanine molecule is observed to be strongly dependent on the chirp direction of the excitation pulse. The slow-decay component associated with an oscillatory structure, which corresponds to the excited-state lifetime and a vibrational mode of 160±10 cm−1, respectively, is measured by the femtosecond time-resolved transmission spectroscopy. The excited-state population is substantially decreased and enhanced in the cases of negatively chirped (NC) and positively chirped (PC) excitations, respectively. A quantum mechanical calculation by means of the split operator scheme is performed to reproduce the wave-packet propagation after the chirped pulse excitation. The calculation shows that the spatial distribution of the wave packet for the NC case is narrower than that for the PC case during the excitation, and that the overlap integral between the excited- and ground-state wave packets determines the efficiency of the population dumping. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7564-7570 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy are used in this study to investigate low-defect and defective MgO(100) thin films. Unlike low-defect films, defective films exhibit a new spectroscopic feature located ∼2 eV above the top of valence band. Exposing the defective film to oxygen quenches the emission of electrons from F centers created on the surface and in the subsurface regions. Extended defects, unseen in the MIES spectra of the clean surface, are detectable using NO titration. MIES and thermal programmed desorption indicate that at ∼100 K NO adsorbs dissociatively on defects, forming N2O. Only a small fraction of the MgO surface becomes covered with N2O at ∼100 K for the low-defect MgO film indicating that N2O molecules preferentially adsorb on the extended defects. The saturation coverage of N2O increases appreciably for the defective sample. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7530-7545 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: The Yang–Yang relation expresses the heat capacity at constant volume, CV(T,ρ), of a fluid linearly in terms of the second temperature derivatives of the pressure and the chemical potential, p″(T,ρ) and μ″(T,ρ). At a gas–liquid critical point CV diverges so, on approaching Tc from below, either pσ″(T), or μσ″(T), or both must diverge, where the subscript σ denotes the evaluation of p and μ on the phase boundary or vapor-pressure curve. However, previous theoretical and experimental studies have suggested that μσ″(T) always remains finite. To test these inferences, we present an analysis of extensive two-phase heat capacity data for propane recently published by Abdulagatov and co-workers. By careful interpolation in temperature and subsequently making linear, isothermal fits vs specific volume and vs density, we establish that the divergence is shared almost equally between the derivatives pσ″(T) and μσ″(T). A re-examination of the analysis of Gaddy and White for carbon dioxide leads to similar conclusions although the singular contribution from μσ″(T) is found to be of opposite sign and probably somewhat smaller than in propane. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7578-7581 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: Circular-difference effects in second-harmonic generation have been used to study chiral, anisotropic thin films of a helicene derivative. For such samples, these effects arise both from the chirality of the film and from its anisotropy. We show theoretically and experimentally that there is a fundamental difference between a circular-difference effect originating from chirality and anisotropy. A method is described that distinguishes the two contributions. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7588-7592 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: Recent molecular dynamics data on the diffusion of linear diatomic and triatomic molecules in the zeolite silicalite are analyzed in terms of a new correlated model [F. Jousse, S. M. Auerbach, and D. P. Vercauteren, J. Chem. Phys. 112, 1531 (2000)] capable to account for both first- and higher-order correlation effects. This "N-step" model reproduces very well our calculated mean square displacements and diffusion coefficients of the molecules considered. The improvements with respect to the results obtained with our previous "two-step" model [P. Demontis, J. Kärger, G. B. Suffritti, and A. Tilocca, Phys. Chem. Chem. Phys. 2, 1455 (2000)] are remarkable for all molecules except chlorine, showing that only in this case the effect of (negative) correlations spanning more than two jumps between channel intersections (∼20 Å) can be neglected. The basic trajectory analysis in terms of single- and two-step models, besides being an useful reference, provides all the input data needed for the application of the N-step model. Indeed, in its silicalite formulation, the N-step model is strongly linked to the two-step one because it calculates the probability of a sequence of jumps in the same channel by means of the correlations between any two consecutive jumps. Finally, the possibility to obtain qualitative insight into the diffusive mechanism through various kind of correlation coefficients is discussed. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7598-7605 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: A model is developed that describes bimolecular recombination of photogenerated carriers in two dimensional systems. Carriers are free to diffuse in two dimensions and undergo bimolecular recombination, while drifting under the influence of an electric field in the third dimension. The model describes a competition between carrier loss due to transiting and loss due to bimolecular recombination. This model of recombination quenching is then used to obtain information on microscopic parameters associated with photogeneration efficiency and charge transport in organic quantum wells formed from Langmuir Blodgett films of conjugated molecules. The ratio of the intralayer to interlayer tunneling rates is found along with the quantum efficiency for photocarrier generation for two bis-phthalocyanine amphiphilic molecules. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7593-7597 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: Films of pure polyaniline and polyaniline-tetracyanoquinodinodimethane have been prepared. The optical absorption spectra of both the samples in the emeraldine base forms are explained in light of the three-dimensional exciton model. A temperature dependence study of the electrical conductivity of the samples shows an interesting crossover phenomenon (Tc=143 K) which may be considered as competition of the two opposingly directed factors, namely, charge transfer interaction and the disorderness parameter (r). While charge transfer interaction is evident from optical absorption spectroscopy, the extent of disorderness is reflected by the results of CHN microanalysis and temperature dependent electrical conductivity measurement. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7582-7587 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: In this investigation we use B3LYP density functional theory (DFT) to investigate the CVD growth mechanism of (100) diamond. Our results are consistent with the Garrison mechanism in which the dimer-opening step involves simultaneous formation of a surface olefin and dissociation of the dimer. We calculate this step to have a barrier of 9.6 kcal/mol. The olefin is then attacked by a surface radical to form a six-membered ring. We find this reaction to be the rate-limiting step with an activation energy of 13.6 kcal/mol. This is in excellent agreement with the experimental value of 15 kcal/mol obtained by the selective growth method and XPS. The direct ring-opening and ring-closing reaction from adsorbed CH2 radical has an activation energy of 49.4 kcal/mol and does not contribute significantly to the growth rate. The barrier on larger clusters that include the effects of neighboring adsorbed hydrogen increases to 15.6 kcal/mol. Additionally, our calculated vibrational frequencies agree within 2% of experimental IR and HREELS spectra. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7606-7612 
    ISSN: 1089-7690
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    Topics: Physics , Chemistry and Pharmacology
    Notes: The tunneling rate of photocreated charge carriers between layers in Langmuir–Blodgett multilayer structures is measured indirectly using the novel technique of bimolecular recombination quenching. The tunneling rate is demonstrated to be dependent upon the applied electrostatic potential difference between the layers. This dependence is explored in light of the Marcus theory of charge transfer. That theory was developed to describe redox reactions where the driving force is supplied by a chemical potential difference between two chemically different parts of a more complex system. In the current work the electrostatic potential replaces the chemical potential as the driving potential. The field dependence of the exciton dissociation probability is also determined. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 7613-7620 
    ISSN: 1089-7690
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    Topics: Physics , Chemistry and Pharmacology
    Notes: The tunneling rate of photocreated charge carriers between layers in Langmuir–Blodgett multilayer structures is measured indirectly using the novel technique of bimolecular recombination quenching. The tunneling rate is measured as a function of the applied electrostatic potential difference between the layers as the temperature is varied between 300 and 4 K. This dependence is examined in light of the Marcus theory of charge transfer where the electrostatic potential replaces the chemical potential as the driving potential. The expectations of the Marcus theory are not met and the rate is effectively temperature independent, contrary to expectation. Other mechanisms are explored that may explain the lack of temperature dependence including the role of high frequency vibrations and the role of the zero point energy of those vibrations. The temperature dependence of the exciton dissociation probability is also examined. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6652-6659 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: The equilibrium constants for water oligomers ranging from dimers to cyclic hexamers are determined using Wertheim's theory of associating systems. In the present model for water, the pair potential has a spherical hard core, and tetrahedral hydrogen bonds which are represented by an energy parameter and an interaction volume. On the basis of the present theory, one predicts that in earth's troposphere, water dimers and perhaps trimers may contribute to the absorption of solar radiation, but concentrations of higher oligomers are too low to influence the optical properties of the earth's atmosphere. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6673-6676 
    ISSN: 1089-7690
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    Topics: Physics , Chemistry and Pharmacology
    Notes: Steric effect in the Penning ionization reaction of Ar*(3P2,0)+CHCl3→Ar+CHCl2++Cl+e− was directly observed at an average collision energy of 0.13 eV using the oriented CHCl3 molecular beam. The product CHCl2+ ions are measured for the H-end, the CCl3-end, and sideways orientations. The obtained steric opacity function reveals that the CCl3-end orientation is more favorable than the H-end orientation, and the sideways approach is found to be more favorable than the collinear approaches from both ends of the molecule. Furthermore, we confirm the good correlation between Penning ionization anisotropy and the electron density distribution of the 2a2 HOMO orbital of the CHCl3 molecule, whose electron cloud is mostly localized around the sideways. These results substantiate the electron exchange mechanism which is commonly accepted for the Penning ionization reaction, where the overlap of projectile atomic and target molecular orbital plays a key role in Penning ionization efficiency. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6677-6686 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: The potential-energy curves for the X 1Σg+, a 1Πg, a′ 1Σu−, w 1Δu, c3 1Πu, and b 1Πu states of N2 have been investigated in full configuration interaction (FCI) and coupled-cluster response calculations. The equilibrium bond lengths, adiabatic excitation energies, and harmonic frequencies have been obtained with the coupled-cluster singles model (CCS), an approximate coupled-cluster singles and doubles model (CC2), the coupled-cluster singles and doubles model (CCSD), and an approximate coupled-cluster singles, doubles, and triples model (CC3), and subsequently compared to FCI results. The weak and strong features of the coupled-cluster models are discussed and illustrated. Overall, improvements towards FCI are obtained in the hierarchy CCS–CC2–CCSD–CC3. CC3 is always consistently better than CCSD, and for all the considered spectroscopic constants CC3 provides excellent results. Examples where the CC3 model fails are also given. The noniterative triples model, CCSDR(3), is compared to the iterative triples models CC3 and FCI. CCSDR(3) recovers the major part of the CC3 correlation contribution and is thus a cheap alternative to the CC3 model. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6660-6672 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: Photodissociation and recombination of an F2 molecule embedded in an Ar cluster is investigated. The electronic states involved are described by the valence bond approach for the F(2P)+F(2P) interaction, with spin–orbit coupling included and the anisotropic interactions between F and Ar atoms described by the diatomics-in-molecules (DIM) approach. The potential energy surfaces for 36 electronic states and the nonadiabatic couplings between them are constructed in this basis. The surface hopping method is used for dynamical simulations. The main results are: (i) Spin nonconserving transitions play a crucial role both in the dissociation and in the recombination dynamics. (ii) The ratio between the population of the triplet states and the population of the singlet states reaches the statistical equilibrium value of 3:1 60 fs after the photoexcitation, but the population of specific singlet and triplet states remains nonstatistical for at least 1.5 ps. (iii) Recombination on the only bound excited state (3Πu) becomes significant within 100 fs and builds up to 40% of the trajectories within 1 ps after excitation of the cluster with 4.6 eV. This is in accord with recent experiments on ClF/Ar solid, where strong emission from this state was found. (iv) 3% of recombination on the ground 1Σg state is found as well. (v) For excitation energy of 4.6 eV, the dissociation can be direct or delayed. In delayed dissociation the F photofragments hit the Ar cage more than once before escaping the cage. (vi) For excitation energy of 6.53 eV the yield of dissociation was found to be 100%, and the dissociation is direct only. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6687-6701 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: A new ab initio pair potential for water was generated by fitting 2510 interaction energies computed by the use of symmetry-adapted perturbation theory (SAPT). The new site–site functional form, named SAPT-5s, is simple enough to be applied in molecular simulations of condensed phases and at the same time reproduces the computed points with accuracy exceeding that of the elaborate SAPT-pp functional form used earlier [J. Chem. Phys. 107, 4207 (1997)]. SAPT-5s has been shown to quantitatively predict the water dimer spectra, see the following paper (paper II). It also gives the second virial coefficient in excellent agreement with experiment. Features of the water dimer potential energy surface have been analyzed using SAPT-5s. Average values of powers of the intermolecular separation—obtained from the ground-state rovibrational wave function computed in the SAPT-5s potential—have been combined with measured values to obtain a new empirical estimate of the equilibrium O–O separation equal to 5.50±0.01 bohr, significantly shorter than the previously accepted value. The residual errors in the SAPT-5s potential have been estimated by comparison to recent large-scale extrapolated ab initio calculations for water dimer. This estimate—together with the dissociation energy D0 computed from SAPT-5s—leads to a new prediction of the limit value of D0 equal to 1165±54 cm−1, close to but significantly more accurate than the best empirical value. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6702-6715 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: Nearly exact six-dimensional quantum calculations of the vibration–rotation–tunneling (VRT) levels of the water dimer for values of the rotational quantum numbers J and K ≤2 show that the SAPT-5s water pair potential presented in the preceding paper (paper I) gives a good representation of the experimental high-resolution far-infrared spectrum of the water dimer. After analyzing the sensitivity of the transition frequencies with respect to the linear parameters in the potential we could further improve this potential by using only one of the experimentally determined tunneling splittings of the ground state in (H2O)2. The accuracy of the resulting water pair potential, SAPT-5st, is established by comparison with the spectroscopic data of both (H2O)2 and (D2O)2: ground and excited state tunneling splittings and rotational constants, as well as the frequencies of the intermolecular vibrations. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6716-6723 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: The group of three lowest singlet C 1s-excited states of formaldehyde H2CO is studied theoretically. The equilibrium geometries are determined at the restricted open-shell Hartree–Fock (ROHF) level and refined total energies are obtained using the multireference configuration interaction (MRCI) approach. In agreement with an earlier prediction [Chem. Phys. 122, 9 (1988)] the second lowest singlet state, 1B2, is characterized by a doubly excited, "two particle–two hole" (2p–2h), configuration C 1s,n→π*2. Our calculations predict that H2CO in the 1B2(2p–2h) state has a stable pyramidal equilibrium structure with a barrier to inversion of 0.28 eV, the valence angle being close to 107°. The calculated length of the CO bond is 1.390 Å. The 1B2(2p–2h) state is shown to be also bound with respect to all possible dissociation and rearrangement processes. The lowest predicted dissociation energy for the 1B2 state (H2CO*→H2+CO* reaction) is 0.29 eV (6.69 kcal/mol). The rationalization of the great stability of the 1B2(2p–2h) state is the similarity of its electronic structure to that of the first singly-excited state 2A″(n) of nitroxyl radical H2NO⋅. The neighboring states 1B1(C 1s→π*) and 1A1(C 1s→3s) are characterized within the same framework. Spectroscopic implications and possibilities for the experimental identification of the 1B2(2p–2h) state are discussed. © 2000 American Institute of Physics.
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  • 83
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    Notes: A general nonorthogonal coupled electron pair approach for the evaluation of electron correlation contribution is presented in details. The self-consistent field for molecular interactions wave function is used as reference state for a multistructure valence bond (VB) calculation. The central idea of the method is the optimization of the virtual space of the VB wave function by means of a procedure very close to the independent electron pair approach (IEPA) scheme. All the orbitals employed are expanded in the basis set of their fragment so as to exclude the basis set superposition error (BSSE) in a priori fashion. As an example, the application to the study of the van der Waals complex He–CH4 is reported. The equilibrium geometry of the system occurs at a He–C distance of 3.6 Å , with the He atom pointing to the center of one of the faces of the CH4 molecule, with a well depth of 19 cm−1. The potential energy surface of the He–CH4 complex is used to determine the parameters of a potential model which is employed in close-coupling calculations of integral state-to-state cross sections for rotationally inelastic scattering of methane molecules with helium atoms. The predicted values are compared with the available experimental data. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6736-6747 
    ISSN: 1089-7690
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    Topics: Physics , Chemistry and Pharmacology
    Notes: An ab initio study of the ground potential energy surface (PES) of the O(1D)+H2O system has been performed, employing Møller–Plesset methods. From the stationary and additional points calculated, the ground PES has been modeled as a triatomic system, with an OH group of the H2O molecule treated as a single atom of 17.0 amu. The rate constant of reaction (1), O(1D)+H2O→2OH (main reaction channel), estimated from the quasiclassical trajectory (QCT) calculations is reasonably close to the recommended experimental value. For the relative translational energies explored (ET=0.234, 0.303, and 0.443 eV) and H2O at T=300 K, the QCT OH vibrational populations are in good agreement with the experimental values reported for the new OH fragment, but the QCT OH average rotational energies are in general quite larger than the experimental ones. Regarding the stereodynamics, for ET=0.234 eV there is not a clear tendency to a particular rotational alignment of the OH product with respect to the initial relative velocity vector, in agreement with experiments. The QCT results also show that nearly all reactive trajectories leading to reaction (1) take place through an insertion microscopic mechanism, which, even at the highest ET value considered (0.443 eV), is mainly (70%) a nondirect one. The collision complex has an average lifetime of about three rotational periods and a geometry around that of the HO(OH) hydrogen peroxide molecule. The QCT results concerning the microscopic mechanism of reaction (1) are in agreement with the suggested ones by the experimentalists to interpret their results. The present study should be considered as a starting point in the study of reaction (1) from which different aspects on the dynamics may be learned. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6782-6787 
    ISSN: 1089-7690
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    Topics: Physics , Chemistry and Pharmacology
    Notes: A molecular dynamics simulation of molten ZnCl2 with a realistic interionic potential is used to evaluate the contribution of interaction-induced dipoles to the dielectric response, or equivalently, to the conductivity. The induced dipoles are included self-consistently in the interionic potential. The contribution is found to be significant across the accessible range of frequencies, modifying various features of the spectrum ordinarily attributed to elementary translations of the ionic charges, and markedly improving agreement with experimental spectra. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6774-6781 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: Homogeneous nucleation rates of n-pentanol in nitrogen are presented. They are obtained from a piston-expansion tube (pex-tube) involving the nucleation pulse method which generates a limited number of nuclei that grow into droplets. The detection of the droplets is achieved by a new counting method developed on the basis of a CCD camera in combination with a laser light sheet. Nucleation rates between 104 and 109 cm−3 s−1 are covered for three nucleation temperatures 250, 260, and 270 K. The rates are plotted as isotherms vs supersaturation. Influence of the initial expansion temperature and the nucleation pressure on the nucleation rate is identified. Comparison with results available in literature and classical nucleation theory (CNT) is provided. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6748-6759 
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    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A previously reported potential energy surface (PES) and a new barrierless PES (both based on ab initio data and describing the CH3 group as a pseudoatom) were used to study the O(1D)+CH4→OH+CH3 reaction with the quasiclassical trajectory (QCT) method. The new PES accurately reproduces the experimental rate constant values, in contrast to the previous PES. The QCT study was mainly performed at the relative translational energy (ET) resulting from the photodissociation of N2O at 193 nm (〈ET〉=0.403 eV), although the collision energy obtained from the photodissociation of O3 at 248 nm (〈ET〉=0.212 eV) was also considered. Good agreement between theory and experiment was obtained for the OH vibrational populations and for the OH rotational populations for the v′≥2 vibrational levels, while the rotational distributions for v′=0–1 are more excited than in the experiment. The QCT results at ET=0.403 eV satisfactorily reproduce the experimental kk′ angular distribution of the state-specific channel OH(v′=4, N′=8) and the corresponding ET′ distribution. For OH(v′=0, N′=5) the reproduction of these properties is poorer, especially for the ET′ distribution. At 0.403 eV the contribution of the abstraction mechanism to the reaction mode is negligible and two insertion like mechanisms (with fast or slow elimination) are found to be predominant, as suggested experimentally. The discrepancies observed between the QCT and experimental results can be explained on the basis of the defective description of the insertion/slow elimination mechanism provided by the model. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6760-6773 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: Resonance Raman spectra are presented for the nitrate anion, NO3−, in water, ethylene glycol, methanol, and acetonitrile solution at six excitation wavelengths from 246 to 204 nm, on resonance with the lowest π→π* excitation. Absolute Raman cross sections for the CH stretches of ethylene glycol and methanol at these wavelengths are also reported. The nitrate spectra in all four solvents are dominated by fundamentals, overtones, and combination bands of the totally symmetric NO stretch (ν1) near 1043 cm−1 and the out-of-phase NO stretches (ν3) at 1340–1400 cm−1, consistent with substantial changes in NO bond length upon π-electron excitation. The intensity in ν3 and the (approximate)60 cm−1 splitting of this nominally degenerate vibration are indicative of pronounced breaking of the isolated molecules D3h symmetry by the local solvent environment. Intensity in the overtone of the out-of-plane mode (ν2) near 830 cm−1 suggests a change in the equilibrium geometry from planar to pyramidal upon electronic excitation. The absorption spectra and absolute Raman cross sections are simulated with a model that considers resonance with two orthogonally polarized electronic states whose degeneracy is broken by the locally asymmetric environment. Both solvent reorganization and geometry changes along the nitrate molecular vibrations make major contributions to the breadth of the absorption band. No differences between resonant and nonresonant linewidths are observed for the ν1 band. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6788-6794 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: High resolution neutron powder diffraction experiments on NaDS and KDS were carried out as a function of temperature between T=4 K and T=470 K at ROTAX (ISIS, UK). The probability density function (pdf) of the atoms was studied in detail, in particular that of deuterium. Several forms of temperature dependent reorientational disorder of the anions are the reason for structural polymorphism of these compounds. A monoclinic low (LTM), a rhombohedral middle (MTM), and a cubic high temperature (HTM) modification are the polymorphs. For the structures of the different modifications the parameters were refined by the use of split-atom models, Fourier synthesis, and/or cubic harmonics. As a main result of this study the anisotropy of the pdf of deuterium in NaDS and KDS was evaluated. It is due to large amplitudes of librations of the anions. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6815-6821 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: The self-consistent integral equation method is applied to calculate the structure and the thermodynamic properties of supercritical argon considered in a recent neutron-scattering experiment by Pfleiderer et al. [J. Chem. Phys. 111, 2641 (1999)]. Two kinds of potentials, different in nature, are used for the calculations. One is an empirical standard potential and the other is founded upon ab initio quantum chemical calculations. The small discrepancies between the two approaches are discussed, and the results are compared to the recent measurements for structure and experimental thermodynamic properties as well. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6795-6802 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: We describe a new type of solid effect for dynamic nuclear polarization (DNP) that is based on simultaneous, near resonant microwave (mw) and radio frequency (rf) irradiation of a coupled electron nuclear spin system. The interaction of the electron spin with the mw field is treated as an electron spin dressed state. In contrast to the customary laboratory frame solid effect, it is possible to obtain nuclear polarization with the dressed state solid effect (DSSE) even in the absence of nonsecular hyperfine coupling. Efficient, selective excitation of dressed state transitions generates nuclear polarization in the nuclear laboratory frame on a time scale of tens of μs, depending on the strength of the electron–nuclear coupling, the mw and rf offset and field strength. The experiment employs both pulsed mw and rf irradiation at a repetition rate comparable to T1e−1, where T1e is the electronic spin lattice relaxation time. The DSSE is demonstrated on a perdeuterated BDPA radical in a protonated matrix of polystyrene. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6803-6814 
    ISSN: 1089-7690
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    Topics: Physics , Chemistry and Pharmacology
    Notes: The aqueous solutions of CsCl were studied at room temperature by infrared (IR) spectroscopy in the entire solubility range, 0–1200 g/L, using attenuated total reflection (ATR) sampling. The influence of anomalous dispersion on the IR–ATR spectra was evaluated by calculating the imaginary refractive index, k(ν), of each sample. Factor analysis (FA) was used to determine the number and abundance of species in the solutions. FA applied to both k(ν) spectra and IR-ATR spectra produced two principal spectra with a similar abundance of species. This result indicates that, even at high salt concentration, the optical effects do not influence the chemical analysis of IR–ATR spectra. The spectral modifications related to the salt concentrations are mainly first order. Second order effects were observed, but being weak, were not investigated. The two principal spectra are related to the two species present in the solution: pure water and CsCl–solvated water. From the latter, 2.8±0.4 water molecules were calculated to be associated with each close-bound Cs+/Cl− ion pair. In the case of KCl and NaCl aqueous solutions, both of which showed the same number of species, the number of water molecules associated to an ion pair was 5.0±0.4. That the latter number is different from that of CsCl indicates that the interaction between water molecules and ion pairs is different when cation Na or K in the chloride salt is replaced by Cs. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6822-6830 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: We consider a nucleating center consisting of both an insoluble core and soluble species and develop the thermodynamics of isothermal formation of a droplet on such a nucleus in a multicomponent vapor mixture. Two different approaches to the derivation of the free energy of droplet formation within the framework of the capillarity approximation are considered. If condensation is not barrierless, the free energy of formation describes a multidimensional free-energy surface having a "well" point and a "saddle" point. It is shown that in a strict theory, taking account of surface enrichment effects, the compositions of droplets corresponding to these two points are equal and can be found without knowing the surface tension of the droplet. For the case of no surfactants in the droplet, we extend the Kuni method of investigating the behavior of the free energy of droplet formation to the case of heterogeneous multicomponent condensation on mixed nuclei, which makes it possible to find out all the main features of the free-energy surface without explicitly knowing the free-energy itself. The theoretical results are illustrated by numerical calculations for the water–methanol condensation on mixed nuclei. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6851-6863 
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    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A classical molecular dynamics simulation of liquid benzene is performed, using a potential model which allows for full molecular flexibility. The short range intermolecular radial distribution function is on average reminiscent of the crystalline structure, although practically no preferential orientation can be found for the molecules in the first coordination shell. The average cage lifetime and its vibrational dynamics are obtained from appropriate time correlation functions. The intramolecular vibrations are investigated by calculating the vibrational density of states and the infrared and Raman spectra, achieving an excellent agreement with the experimental data. Finally, the dephasing of the ν1(A1g) ring breathing mode and of the ν6(E2g) in-plane bending mode is analyzed on the basis of the Kubo dephasing function. For ν1 mode the Kubo correlation time of 516 fs agrees with the experimental value, and is consistent with a relaxation mechanism involving the cage reorganization. In contrast, ν6 has a practically pure Lorentzian line shape, with a width of 7.16 cm−1 in perfect agreement with the experimental value of 7.2 cm−1. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6831-6850 
    ISSN: 1089-7690
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    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a microscopic model of carbon monoxide (CO) binding to myoglobin which reproduces the experimentally observed Arrhenius pre-exponential factor of 109 s−1 and activation enthalpy distribution centered at 12 kJ/mol. The model is based on extensive ab initio calculations of CO interacting with a model heme-imidazole group which we performed using a fully quantum mechanical Hartree–Fock/density functional theory (HF/DFT) hybrid method. We fit the HF/DFT calculated energies, obtained for over 1000 heme-CO structures with varied CO and iron positions and orientations for both high (S=2) and low (S=0) spin states, to a model potential function which includes a bonding interaction in both of the spin states, electrostatic, and anisotropic Lennard-Jones-type interactions. By combining the x-ray determined protein structure with this potential and protein-CO interactions and internal heme interaction potentials obtained from established molecular dynamics literature, we calculate the energy required for the CO to reach the spin crossing from the heme pocket. We find that the transition between the two spin states occurs when CO and iron have activation enthalpies of 8 kJ/mol and 3 kJ/mol, respectively, which are necessary to move CO towards the iron and the iron atom relative to the heme plane Npyr. At the same time we find that 1 kJ/mol is needed to move Nε of His-64 and Cγ of Val-68 relative to the heme group. The requirement that these motions be synchronized reduces the Arrhenius pre-exponential by a factor of 150 from the 1012 s−1 obtained from CO motion across the heme pocket, leaving a factor of ∼ 6 to account for CO orientation and nonadiabaticity of the electronic spin change. The observed width of the enthalpy distribution is reproduced by assuming a Gaussian distribution of the heme positions with a standard deviation of 0.2 Å. We characterize the conformational relaxation by calculating an enthalpy barrier using x-ray structures of myoglobin in both the MbCO photoproduct and deoxy conformations, and we find a small difference, ∼ 5 kJ/mol, between the two conformations. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6864-6874 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: The oxidation of carbon monoxide on a Pt(111) electrode surface is studied under transient and stationary reaction conditions in a 0.1 M HClO4 aqueous solution as a function of the applied electrode potential. The optical response is investigated by optical second harmonic generation (SHG) at 280 nm and infrared absorption spectroscopy (IRAS) starting at low potentials where the electrode is not reactive [e.g., 0.1 V vs the reversible hydrogen electrode (RHE)] towards more positive potentials where CO oxidation is initiated. For transient reaction conditions, in the absence of CO dissolved in solution, the oxidation starts at about 0.5 V vs. RHE and consists of a fast oxidation of about 10% of the adlayer and of a second reaction with slower kinetics involving the removal of the complete CO layer (overlayer stripping). Under steady-state conditions in CO-saturated solution the CO adlayer is stable up to 0.9 V vs RHE. At 0.63 V an overlayer phase transition is indicated by a 20% increase of the isotropic component of the second harmonic (SH) intensity (pp-polarization). The same potential region for this phase transition in the adlayer structure is derived from IRAS spectra after correcting for the effect of the thin layer electrolyte in IRAS measurements. The disappearance of hollow sites, the appearance of bridge sites, as well as an increased occupation of on-top sites at 0.63 V is interpreted as corresponding to the adlayer phase transition. The observations are consistent with a transition from the c(2×2) to the ((square root of)19×(square root of)19) adlayer structure of CO. The high sensitivity of SHG with regard to structural phase transitions of the CO adlayer is explained by distinct charge transfer contributions to the second-order surface susceptibility at different coordination sites. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 6875-6881 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: Transport diffusion of argon in the unidirectional channels of the molecular sieve AlPO4-5 has been studied using molecular dynamics simulations. Using the Green–Kubo formalism, this nonequilibrium property is, for the first time, extracted from just one equilibrium simulation. Apart from the computational advantages above nonequilibrium simulations, the new method also provides a way to check the validity of the assumption of linear response, which is at the basis of both methods. The transport diffusion coefficient for argon at 87 K and half the maximum loading is found to be equal to Dt=(1.4±0.1)×10−5 cm2/s, of which approximately 20% can be attributed to correlated, collective motion. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 5138-5140 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: The energies of six stationary points on the OH+CO→HOCO→H+CO2 potential energy surface have been calculated using the G3 and CBS-QB3 methods. An analysis combining ab initio and experimental enthalpies yielded ΔHf298 K (trans-HOCO)=−42.9±1.5 kcal mol−1 (−43.8±1.4 kcal mol−1) at the G3(CBS-QB3) level of theory. These results confirm the revised HOCO heat of formation derived from photoionization spectroscopy and suggest that the HOCO potential well is 8.8 kcal mol−1 shallower than previously thought. We discuss the implications of these results for accurate Rice–Ramsperger–Kassel–Marcus modeling or quantum mechanical scattering calculations of the OH+CO reaction. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 5141-5144 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: We characterize the low-temperature dynamics of CO intercalated in C60 using NMR spectroscopy. CO in C60 is found to be dynamically inhomogeneous below 30 K: The 13CO line shapes reflect a dynamic disorder to static disorder transition, with only quantum tunneling among equivalent orientations in a local S6 symmetry potential remaining. The increased hindrance of the CO motion cannot be reconciled with common expectations of a homogeneous, thermally activated jumplike reorientation process, but is well accounted for in a model of orientational pinning due to asymmetric distortions of the cage potential. © 2000 American Institute of Physics.
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    The Journal of Chemical Physics 113 (2000), S. 5145-5153 
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    Topics: Physics , Chemistry and Pharmacology
    Notes: A new formula, EL−E∝(L+3/4)−3, to extrapolate energies, EL (that arise when the basis set is truncated at a finite angular momentum quantum number, L) to the limit, E, is derived and applied to the computation of the pair potential of He. Large basis sets up to d-aug-cc-pV5Z and -6Z are used, and in addition, a new cc-pV7Z set is presented. The full-CI is approximated using the "multireference averaged coupled-pair functional" (MR-ACPF) with 121 references. The calculated molecular constants of He2 are in excellent agreement with those recently obtained with r12-MR-ACPF [R. J. Gdanitz, Mol. Phys. 96, 1423 (1999)], but they agree only fairly with the complete-CI estimate of van Mourik and Dunning [J. Chem. Phys. 111, 9248 (1999)]. The potential of Komasa [J. Chem. Phys. 110, 7909 (1999)] which has been calculated with the "exponentially correlated Gaussians" method does not give a bound state. The sensitivity of the molecular constants 〈R〉 and D0 to errors of the interaction potential at different distances is estimated by perturbing the potential by Gaussian functions. The region of 5(approximately-less-than)R/a0(approximately-less-than)9 is found to be most sensitive. From this analysis, doubts arise that recent calculations (including the present one) are accurate enough to allow the molecular constants to be determined to better than (approximate)10%. © 2000 American Institute of Physics.
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