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  • 1
    Electronic Resource
    Electronic Resource
    Determination of the width of a narrow molecular weight distribution by gel-permeation chromatography (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 411-415 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A recycle gel-permeation chromatography (GPC) method for extrapolating to infinite resolution is proposed. From the GPC calibration curve, the extrapolated elution peak width volume can be converted into peak width in decades of molecular weight. For an essentially Gaussian distribution, the weight-average/number-average molecular weight ratio can be determined from a calculated conversion table.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160080307
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  • 2
    Electronic Resource
    Electronic Resource
    Study of (π-C5H5)2Ti(CH3)Cl and (π-C5H5)2Ti(C6H5)Cl in soluble Ziegler catalysts (1972)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 10 (1972), S. 1827-1837 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Soluble ethylene polymerization catalysts derived from (π-C5H5)2Ti(R)Cl and R ′AlCl2, where R = methyl or phenyl and R ′ = methyl or ethyl, were studied both by polymerization kinetics at 0°C and by diagnostic experiments. It was found that the first insertion of ethylene into the Ti—R bond is difficult when R = methyl or phenyl, and for this reason these catalysts show a different overall behavior than when R = ethyl or higher alkyl.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1972.150100620
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  • 3
    Electronic Resource
    Electronic Resource
    Study of (π-C5H5)2Ti(C2H5)Cl and its higher homologs in soluble Ziegler catalysts (1972)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 10 (1972), S. 895-907 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Soluble ethylene polymerization catalysts derived from (π-C5H5)2Ti(R)Cl and R′AlCl2 where R is ethyl or higher alkyl and R′ may be methyl or ethyl, were studied both by polymerization kinetics at 0°C and by diagnostic experiments. An early acceleration in rate occurred at this temperature in toluene solvent which was due to a solvent dependent increase in catalyst activity, not to a gradual formation of catalyst. No such solvent effect was found in nonaromatic solvents. The subsequent decay in rate, at least at low temperatures, did not depend upon valence reduction. The effect of Al/Ti ratio was studied, and certain discrepancies in the literature were shown to be due to the method of making kinetic measurements. Oxygen, which has previously been reported to affect the polymerization rate with these catalysts, was also found to eliminate the acceleration period in toluene when present in the amount of 1% of the catalyst. These catalysts gave polymers at low temperature for which the active site had long life and which did not undergo chain transfer. Therefore, they approximate many of the characteristics of living polymers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1972.150100324
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  • 4
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    The Carbon Monoxide Tape Recorder (2006)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Using Aura MLS data we have identified the stratospheric tape recorder in carbon monoxide (CO). Unlike the water vapor tape recorder, which is controlled by upper troposphere processes, the CO tape recorder is linked to seasonal biomass burning. Since CO has a lifetime of only a few months, the CO tape recorder barely extends above 20 km. The tape head for CO appears to be close to 360K near the same location as the water vapor tape head [Read et al, 20041. Both tape heads are below the equatorial cold point tropopause but above the base of the tropical tropopause layer. The tape recorder signal becomes more distinct from 360K to 380K suggesting that convective detrainment of plays a decreasingly important role with altitude. The Global Modeling Initiative chemical transport model forced by the climatology of biomass burning reproduces the CO tape recorder.
    Keywords: Environment Pollution
    Format: application/pdf
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  • 5
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    UARS MLS Observations of Lower Stratospheric ClO in the 1992-93 and 1993-94 Arctic Winter Vortices (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: UARS (Upper Atmosphere Research Satellite) MLS (Microwave Limb Sounder) measurements of lower stratospheric ClO during the 1992-93 and 1993-94 Arctic winters are presented. Enhanced ClO in the 1992-93 winter was first observed in early December, and extensively during February when temperatures were continually low enough for PSCs. Sporadic episodes of enhanced ClO were observed for most of the 1993-94 winter as minimum temperatures hovered near the PSC threshold, with largest ClO amounts occurring in early March after a sudden deep cooling in late February.
    Keywords: Environment Pollution
    Type: Paper-94GL00083 , Geophysical Research Letters (ISSN 0094-8534); 22; 7; 823-826
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  • 6
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    Evidence for Arctic Ozone Depletion in Late February and early March 1994 (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Significant chemical ozone (O3 ) loss in the 1993-94 Arctic winter occurred mainly during an unusually late cold spell of approximately 10 days in late Feb/early Mar. Over the 30 d period studied (including the cold spell), observed vortex-averaged O3 at 465 K (approximately 40 hPa) decreased by approximately 10%. New three-dimensional, diabatic trajectory calculations show that this observed decrease represents only about half of the net chemical loss (approximately 20%) during the 30 day period. The resupply of lower stratospheric O3 by transport in Feb 1994 was considerably greater than in 1993, when transport masked only about a quarter of the chemical loss in Feb/Mar. The net estimated chemical loss over 30 days in 1994 was comparable to that over the same 30 days in 1993, but mainly occurred at a faster rate during the brief cold spell. These results highlight the impact of Arctic interannual variability on the relative roles of chemistry and dynamics in O3 evolution during recent Arctic winters.
    Keywords: Environment Pollution
    Type: Paper-95GL02229 , Geophysical Research Letters (ISSN 0094-8534); 32; 21; 2941-2944
    Format: text
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  • 7
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    MLS Observations of Arctic Ozone Loss in 1996-1997 (1997)
    In:  Other Sources
    Details
    Publication Date: 2019-08-16
    Description: The Microwave Limb Sounder (MLS) observed ozone (O3) loss in the Arctic vortex beginning in January 1997 at 585 K (approximately 25 hPa) and in February 1997 at 465 K (approximately 50 hPa). Minimum vortex-averaged O3 mixing ratios observed in 1997 were higher than those in 1996, which were the lowest ever recorded by MLS. The vertical extent of O3 loss and maximum local O3 decreases were larger, but the decrease filled the vortex less completely, in 1997 than in 1996. Unusually low high-latitude column O3 above 100 hPa in April 1997 resulted mainly from dynamical effects of the unusually persistent lower stratospheric vortex and winter-like temperature patterns. Column O3 above 100 hPa averaged in comparable regions of the vortex showed a stronger decreasing trend in 1996-97 than in 1995-96, consistent with the larger vertical extent and maximum local values of lower stratospheric O3 loss. Chemical O3 loss resulted in an approximately 10% observed decrease in column O3 between late January and early April 1997.
    Keywords: Environment Pollution
    Type: Paper 97GL52827 , Geophysical Research Letters (ISSN 0094-8534); 24; 22; Paper 97GL52827; 2697-2700
    Format: text
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  • 8
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    Validation of UARS Microwave Limb Sounder ClO Measurements (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Validation of stratospheric ClO measurements by the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS) is described. Credibility of the measurements is established by (1) the consistency of the measured ClO spectral emission line with the retrieved ClO profiles and (2) comparisons of ClO from MLS with that from correlative measurements by balloon-based, ground-based, and aircraft-based instruments. Values of "noise" (random), "scaling" (multiplicative), and "bias" (additive) uncertainties are determined for the Version 3 data, in the first version public release of the known artifacts in these data are identified. Comparisons with correlative measurements indicate agreement to within the combined uncertainties expected for MLS and the other measurements being compared. It is concluded that MLS Version 3 ClO data, with proper consideration of the uncertainties and "quality" parameters produced with these data, can be used for scientific analyses at retrieval surfaces between 46 and 1 hPa (approximately 20-50 km in height). Future work is planned to correct known problems in the data and improve their quality.
    Keywords: Environment Pollution
    Type: Paper-95JD03351 , Journal of Geophysical Research (ISSN 0148-0227); 101; D6; 10,091-10,127
    Format: text
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  • 9
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    Validation of UARS Microwave Limb Sounder Ozone Measurements (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-08-16
    Description: This paper describes the validation of ozone data from the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS). The MLS ozone retrievals are obtained from the calibrated microwave radiances (emission spectra) in two separate bands, at frequencies near 205 and 183 GHz. Analyses described here focus on the MLS Version 3 data (the first set of files made publicly available). We describe results of simulations performed to assess the quality of the retrieval algorithms, in terms of both mixing ratio and radiance closure. From actual MLS observations, the 205-GHz ozone retrievals give better closure (smaller radiance residuals) than that from the 183-GHz measurements and should be considered more accurate from the calibration aspects. However, the 183-GHz data are less noise limited in the mesosphere and can provide the most useful scientific results in that region. We compare the retrieved 205-GHz ozone profiles in the middle-to lower stratosphere to ozonesonde measurements at a wide range of latitudes and seasons. Ground-based lidar data from Table Mountain, California, provide a good reference for comparisons at higher altitudes. Based on these analyses, comparisons with balloon-borne measurements and others, as well as a detailed budget of estimated uncertainties, MLS results appear to be generally of high quality, with some biases worth mentioning. Results for the lowermost stratosphere (approx. 50 to 100 bPa) are still in need of improvement. A set of estimated precision and accuracy values is derived for the MLS ozone data sets. We also comment on recent updates in the retrieval algorithms and their impact on ozone values.
    Keywords: Environment Pollution
    Type: Paper-95JD02325 , Journal of Geophysical Research (ISSN 0148-0227); 101; D6; 10,017-10,060
    Format: text
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