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  • PAN  (3)
  • Polymer and Materials Science  (3)
  • 4-Methyl-3-heptanone
  • 1995-1999  (6)
  • 1960-1964  (1)
  • 1915-1919
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 25 (1999), S. 2433-2444 
    ISSN: 1573-1561
    Keywords: 4-Methyl-3-heptanone ; 4-methyl-3-hexanone ; 4-methyl-3-heptanol ; castes ; Atta laevigata ; Formicidae ; Attini ; leaf-cutting ant ; mandibular gland ; behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Gas chromatography analyses and behavioral assays showed that Atta laevigata, a highly polymorphic ant species, has a mandibular gland secretion that varies with castes. All castes contain 4-methyl-3-heptanone as the main component and its concentration is proportional to head size. Small workers and soldiers, but not medium size workers, also contain 4-methyl-3-heptanol. Queens show variations in their chemical composition after mating, as virgin males contain a secretion dominated by 4-methyl-3-heptanol, and, in a lesser proportion, 4-methyl-3-heptanone. In mated males these proportions are inverted. The compounds 4-methyl-6-hepten-3-one, 4-methyl-4-hepten-3-one, 6-methyl-tetradecene, and 2,6-dimethyl-2-dodecene are found only in queens. The behavioral response elicited by the secretion is mainly alarm, which is elicited more strongly by glands of larger workers. The results suggest that chemical castes, behavioral castes, and morphological castes overlap in this species.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-0662
    Keywords: PAN ; ozone ; troposphere ; photochemistry ; Alaska
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Springtime measurements of NOx, ozone, PAN,J(NO2), and other compounds were made near Ny-Ålesund,Svalbard (78°54′N, 11°53′E), in 1994 and Poker Flat,Alaska (65°08′N, 147°29′W), in 1995. At Svalbard medianmixing ratios for PAN and NOx of 237 and 23.7 pptv,respectively, were observed. The median mixing ratios at Poker Flat for PANand NOx were 79.5 and 85.9 pptv, respectively. These data areused to estimate thermal PAN decomposition using several differentapproaches. At Svalbard PAN decomposition was very small, while at PokerFlat up to 30 pptv/h PAN decomposed. At both sites the NOx/PANratio increased with temperature between –10 and 20°C implyingthat PAN decomposition is an important NOx source. In-situozone production was calculated from the measured NO, NO2,O3, J(NO2), and temperature data, using thesteady state assumption Median ozone production was 605 pptv/h at PokerFlat, and one order of magnitude smaller at Svalbard during the daytime.Only at Poker Flat could a direct influence on the diurnal ozone cycle beobserved from in-situ production. These results imply that PAN decompositionis a major source of NOx in the high latitude troposphere, andthat this contributes to the observed spring maximum in surface ozone.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-0662
    Keywords: PAN ; ozone ; troposphere ; photochemistry ; Alaska
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A seven-year record of surface ozone measurements from Denali NationalPark, Alaska shows a persistent spring maximum. These data, combined withmeasurements of NOx, hydrocarbons, O3, and PANfrom a continental site in Alaska during the spring of 1995 are used as thebasis for a sensitivity study to explore tropospheric photochemistry in thisregion. Because of the relatively high concentrations of NOx(mean of 116, median of 91 pptv), the net tendency was for photochemicalozone production. The range of net O3 production for averageconditions measured at this site during spring is between 0.96–3.9ppbv/day depending on the assumptions used; in any case, this productionmust contribute to the observed springtime maximum in O3.Model calculations showed that of the anthropogenic ozone precursors, onlyNOx had a strong effect on the rate of ozone production; themeasured concentrations of anthropogenic hydrocarbons did not significantlyaffect the ozone budget. Naturally produced biogenic hydrocarbons, such asisoprene, may also have a significant effect on ozone production, even atconcentrations of a few 10's of pptv. An observed temperature-isoprenerelationship from a boreal site in Canada indicates that isoprene may bepresent during the Alaskan spring. Measurements of isoprene taken duringthe spring of 1996 suggest that reactive biogenic hydrocarbon emissionsbegin before the emergence of leaves on deciduous trees and that theconcentrations were sufficient to accelerate ozone production.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-0662
    Keywords: PAN ; NOy ; Arctic measurements ; nitrogen oxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Simultaneousindependent measurements of NOy and NOx(NOx= NO + NO2) by high-sensitivitychemiluminescence systems and of PAN (peroxyacetylnitrate) and PPN (peroxypropionyl nitrate) by GC-ECDwere made at Spitsbergen in the Norwegian Arcticduring the first half year of 1994. The average mixingratio of the sum of PAN and PPN (denoted PANs)increased from around 150 pptv in early winter to amaximum of around 500 pptv in late March, whereasepisodic peak values reached 800 pptv. This occurredsimultaneously with a maximum in ozone which increasedto 45–50 ppbv in March–April. The average NOxmixing ratio was 27 pptv and did not show any cyclethrough the period. The NOy mixing ratio showeda maximum in late March, while the difference betweenNOy and PAN decreased during spring. This is anindication of the dominance of PAN in the NOybudget in the Arctic, but possible changes in theefficiency of the NOy converter could alsocontribute to this. Although most PAN in theArctic is believed to be due to long range transport,the observations indicate local loss and formationrates of up to 1–2 pptv h-1 in April–May.Measurements of carbonyl compounds suggest thatacetaldehyde was the dominant, local precursor ofPAN.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 1741-1745 
    ISSN: 0887-6266
    Keywords: Liquid crystalline polymer ; permeability ; crystallinity ; annealing ; gases ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The copolyester formed from 40 mol% p-hydroxybenzoic acid (H), 30 mol% isophthalic acid (I), and 30 mol% hydroquinone (Q), designated as HIQ-40, forms isotropic, amorphous films when appropriately cast from a solvent. Thermal annealing leads to a mesogenic texture and some level of crystallinity. It is shown that these ordering processes lead to dramatic reductions in gas permeability; the magnitude of the decrease increases with the size of the penetrant. The current results are consistent with previously reported sorption data for acetone in HIQ-40. © 1996 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1013-1017 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By using the Lifshitz-Van der Waals-Acid-Base theory, we have determined the surface tensions (γs) of three commercially available liquid crystalline polymers (LCPs) from the measurement of contact angles on thin films. The values obtained are 43.1, 41.1 and 41.5 mJ/m2 (dyn/cm) for Vectra™ A-950, Vectra™ B-950 and Xydar™ SRT-900, respectively. Experimental data suggest that all the three LCPs are monopolar. The strength of Lewis base (tendency to donate a pair of electrons for the formation of a covalent bond) for these three LCPs is as follows: Vectra™ B-950 〉 Xydar™ SRT-900 〉 Vectra™ A-950. We also theoretically estimated γs from both parachor (Ps) and cohesive energy (Ecoh) utilizing the concept of molecular group contribution. It was found that γs's calculated from Hoftyzer & Van Krevelen and Hayes' Ecoh values are close to our experimental results obtained from contact angle measurements. This is especially true for Xydar™ SRT-900 LCP, where γs obtained from contact angle measurements is 41.5 mJ/m2, while from Hoftyzer and Van Krevelen, and Hayes it is 42.4 and 41.8 mJ/m2, respectively. However, more adequate group contributions for naphthalene and amide groups are urgently needed.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 2 (1964), S. 1669-1685 
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Even at high superficial dilution (π 〈 40 mdyne/cm.-1) it is impossible to determine the molecular weight of a flexible polymer. Using statistical equations containing an adjustable parameter it can be accounted for the compression isotherms. This parameter corresponds not to an experimental relation, and is without any physical significance. The polymeric layers can be described by Singer's equation, if one attributes to the term x the significance of an experimental parameter.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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