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  • METEOROLOGY AND CLIMATOLOGY  (223)
  • Analytical Chemistry and Spectroscopy  (214)
  • 1990-1994  (206)
  • 1980-1984  (231)
  • 1994  (206)
  • 1984  (231)
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  • 1990-1994  (206)
  • 1980-1984  (231)
Year
  • 1
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of protonation and hydrogen bonding in linear Schiff bases obtained from n-butylamine with butyraldehyde, crotonaldehyde, sorbaldehyde and all-trans-retinal were studied by means of 15N and 13C NMR. The protonation-induced chemical shifts (Δδ) are an order of magnitude larger for 15N than for 13C. For 15N, this effect was found to increase with the extent of conjugation, culminating in the retinylideneimine (Δδ = -146 ppm), which constitutes a model for the study of the structure of the Schiff base linkage in visual pigments and related systems. Theoretical calculations of protonation-induced Δδ values based on MINDO/ 3 are in agreement with experimental results.
    Additional Material: 4 Ill.
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  • 2
    Publication Date: 2019-07-13
    Description: Snow feedbacks produced by 14 atmospheric general circulation models have been analyzed through idealized numerical experiments. Included in the analysis is an investigation of the surface energy budgets of the models. Negative or weak positive snow feedbacks occurred in some of the models, while others produced strong positive snow feedbacks. These feedbacks are due not only to melting snow, but also to increases in boundary temperature, changes in air temperature, changes in water vapor, and changes in cloudiness. As a result, the net response of each model is quite complex. We analyze in detail the responses of one model with a strong positive snow feedback and another with a weak negative snow feedback. Some of the models include a temperature dependence of the snow albedo, and this has significantly affected the results.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; D10; p. 20,757-20,771
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  • 3
    Publication Date: 2019-08-27
    Description: Acetone (CH3COCH3) was found to be the dominant nonmethane organic species present in the atmosphere sampled primarily over eastern Canada (0-6 km, 35 deg-65 deg N) during ABLE3B (July to August 1990). A concentration range of 357 to 2310 ppt (= 10(exp -12) v/v) with a mean value of 1140 +/- 413 ppt was measured. Under extremely clean conditions, generally involving Arctic flows, lowest (background) mixing ratios of 550 +/- 100 ppt were present in much of the troposphere studied. Correlations between atmospheric mixing ratios of acetone and select species such as C2H2, CO, C3H8, C2Cl4 and isoprene provided important clues to its possible sources and to the causes of its atmospheric variability. Biomass burning as a source of acetone has been identified for the first time. By using atmospheric data and three-dimensional photochemical models, a global acetone source of 40-60 Tg (= 10(exp 12) g)/yr is estimated to be present. Secondary formation from the atmospheric oxidation of precursor hydrocarbons (principally propane, isobutane, and isobutene) provides the single largest source (51%). The remainder is attributable to biomass burning (26%), direct biogenic emissions (21%), and primary anthropogenic emissions (3%). Atmospheric removal of acetone is estimated to be due to photolysis (64%), reaction with OH radicals (24%), and deposition (12%). Model calculations also suggest that acetone photolysis contributed significantly to PAN formation (100-200 ppt) in the middle and upper troposphere of the sampled region and may be important globally. While the source-sink equation appears to be roughly balanced, much more atmospheric and source data, especially from the southern hemisphere, are needed to reliably quantify the atmospheric budget of acetone.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; D1; p. 1805-1819
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  • 4
    Publication Date: 2019-08-28
    Description: Aircraft measurements of key reactive nitrogen species (NO, NO2, HNO3, PAN, PPN, NO3(-), NO(y)), C1 to C6 hydrocarbons, acetone, O3, chemical tracers (C2Cl4, CO), and important meteorological parameters were performed over eastern Canada during July to August 1990 at altitudes between 0 and 6 km as part of an Arctic Boundary Layer Expedition (ABLE3B). In the free troposphere, PAN was found to be the single most abundant reactive nitrogen species constituting a major fraction of NO(y) and was significantly more abundant than NO(x) and HNO3. PAN and O3 were well correlated both in their fine and gross structures. Compared to data previously collected in the Arctic/subarctic atmosphere over Alaska (ABLE3A), the lower troposphere (0-4 km) over eastern Canada was found to contain larger reactive nitrogen and anthropogenic tracer concentrations. At higher altitudes (4-6 km) the atmospheric composition was in many ways similar to what was seen over Alaska and supports the view that a large-scale reservoir of PAN (and NO(y)) is present in the upper troposphere over the entire Arctic/subarctic region. The reactive nitrogen budget based on missions conducted from the North Bay site (missions 2-10) showed a small shortfall, whereas the budget for data collected from the Goose Bay operation (missions 11-19) showed essential balance. It is calculated that 15-20 ppt of the observed NO(x) may find its source from the available PAN reservoir. Meteorological considerations as well as relationships between reactive nitrogen and tracer species suggest that the atmosphere over eastern Canada during summer is greatly influenced by forest fires and transported industrial pollution.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; D1; p. 1821-1835
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  • 5
    Publication Date: 2013-08-31
    Description: An international comparison of Dobson ozone spectrophotometers, organized and partially funded by the World Meteorological Organization (WMO), was held at the Lichtklimatisches Observatorium (LKO) in Arosa, Switzerland, July-August 1990. Countries participating with a total of 18 Dobson instruments were Belgium, Czechoslovakia, Denmark, Germany, Greece, Hungary, Iceland, Norway, Poland, Portugal, Rumania, Spain, Switzerland, the United Kingdom, the United States, and the United Soviet Socialist Republics. The reference standard instrument for the comparison was U.S.A. Secondary Standard Dobson Spectrophotometer 65 maintained by the NOAA Climate and Monitoring and Diagnostics Laboratory, Boulder, Colorado. The mean difference in ozone obtained with the Dobson instruments relative to Dobson instrument 65, calculated from ADDSGQP observations in the air mass range 1.15-3.2, was minus 1.0 plus or minus 1.2 (1 sigma) percent. The WMO Standard Brewer Spectrometer 39 also participated. In the mean, the Brewer instrument measured 0.6 plus or minus 0.2 (1 sigma) percent more ozone than did Dobson instrument 65. Results are presented, also, of ozone vertical profile measurements made with the Dobson instruments, two Brewer spectrometers, a LIDAR, a balloon ozonesonde flown from Hohenpeissenberg, Germany, and balloon ozonesondes flown from Payerne, Switzerland.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA. Goddard Space Flight Center, Ozone in the Troposphere and Stratosphere, Part 1; p 266-270
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  • 6
    Publication Date: 2013-08-31
    Description: Ozone trends for 1979-1991, determined from Dobson spectrophotometer observations made at eight stations in the United States, are augmented with trend data from four foreign cooperative stations operated by NOAA/CMDL. Results are based on provisional data archived routinely throughout the years at the World Ozone Data Center in Toronto, Canada, with calibration corrections applied to some of the data. Trends through 1990 exhibit values of minus 0.3 percent to minus 0.5 percent yr(exp -1) at mid-to-high latitudes in the northern hemisphere. With the addition of 1991 data, however, the trends become less negative, indicating that ozone increased in many parts of the world during 1991. Stations located within the plus or minus 20 deg N-S latitude band exhibit no ozone trends. Early 1992 data show decreased ozone values at some of the stations. At South Pole, Antarctica, October ozone values have remained low during the past 3 years.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA. Goddard Space Flight Center, Ozone in the Troposphere and Stratosphere, Part 1; p 195-198
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 7 (1984), S. 196-202 
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; LC/MS ; Mass spectrometry ; Field desorption ; Chemical ionization ; Gossypol ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conditions are reported for the reverse-phase HPLC analysis of gossypol and of some of its derivatives, including anhydrogossypol, gossypolone, gossypol hexaacetate, and Schiff's base derivatives. It is shown that field desorption (FD) and chemical ionization (CI) mass spectrometry have advantages over electron impact (EI) mass spectrometry for the characterization of these compounds and that combined high-performance liquid chromatography/mass spectrometry (LC/MS), especially when used in the CI mode, is particularly effective.
    Additional Material: 12 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 403-406 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Massive-cluster impact is demonstrated to be an effective ionization technique for the mass analysis of proteins as large as 17 kDa. The design of the cluster source permits coupling to both magnetic-sector and quadrupole mass spectrometers. Mass spectra are characterized by the almost total absence of chemical background and a predominance of multiply charged ions formed from 100% glycerol matrix. The number of charge states produced by the technique is observed to range from +3 to +9 for chicken egg lysozyme (14 310 Da). The lower m/z values provided by higher charge states increase the effective mass range of analyses performed with conventional ionization by fast-atom bombardment or liquid secondary ion mass spectrometry.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 996-1000 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Massive-cluster impact (MCI) ionization was found to be capable of producing high secondary-ion yields from biological samples without the use of a liquid matrix. Dry samples of molecules as large as cytochrome c were observed to be efficiently desorbed without significant fragmentation by the MCI beam of glycerol clusters. In addition, signals from protonated molecules retained a significant proportion of their initial intensity even after several minutes exposure to the primary beam. It was determined that these remarkable phenomena are not the result of the build-up of a layer of glycerol caused by the cluster bombardment.
    Additional Material: 4 Ill.
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  • 10
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Unknown, specific mutations in the sequence of an enzyme variant (a Bacillus subtilisin protease) produced by protein engineering were identified using High-performance Liquid Chromatographic/Fast Atom Bombardment Mass Spectrometric (HPLC/FAB MS) techniques. The variant and the highly homologous wild-type enzyme were treated with CNBr followed by tryptic digestion. The resulting peptides were analysed using HPLC/frit FAB MS. The peptides with molecular masses beyond the range of the HPLC/MS system under the chosen scanning conditions were collected using HPLC and subsequently analysed ‘off-line’ using static FAB MS. This procedure allowed the complete amino acid sequence determination of the variant protease using the known amino acid sequence of the wild-type enzyme as reference.
    Additional Material: 5 Ill.
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