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1

Digitale Medien

Mandibular Gland Secretion in Different Castes of the Leaf-Cutter Ant Atta laevigata (1999)

Hernández, José V. ; Cabrera, Aivlé ; Jaffe, Klaus

Springer

Journal of chemical ecology 25 (1999), S. 2433-2444

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ISSN: 1573-1561

Schlagwort(e): 4-Methyl-3-heptanone ; 4-methyl-3-hexanone ; 4-methyl-3-heptanol ; castes ; Atta laevigata ; Formicidae ; Attini ; leaf-cutting ant ; mandibular gland ; behavior

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie

Notizen: 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.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1020813905989

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2

Digitale Medien

Effect of x-rays on extended chain crystals of polyoxymethylene (1968)

Jaffe, M. ; Wunderlich, B.

New York : Wiley-Blackwell

Journal of Polymer Science Part A-2: Polymer Physics 6 (1968), S. 825-831

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ISSN: 0449-2978

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Extended chain crystals of polyoxymethylene were irradiated with x-rays of about 105 r./min. An immediate decrease in superheating on melting was noted. After 90 min. of irradiation the melting point level, refractive indices, and density also decreased. After 480 min. the DTA melting peak at a heating rate of 20°C./min. had decreased 25°C., the melting point decreased about 18°C., and the density calculated from refractive indices decreased 0.031 g./cm.-3. These effects are interpreted as indication of chain scission and formation of amorphous defects.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1968.160060503

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3

Digitale Medien

Les polyélectrolytes à l'interface liquide-liquide (1966)

Jaffe, J. ; Ruysschaert, J.-M. ; Bricman, G.

New York : Wiley-Blackwell

Journal of Polymer Science Part A-2: Polymer Physics 4 (1966), S. 765-775

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ISSN: 0449-2978

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: The behavior of films of polyelectrolytes at the water-organic liquid interface depends on the nature of the interface and the pH of the substratum. The present paper investigates the influence of these two factors on the cohesive forces between monomer units. Two polyelectrolytes were studied: poly(methacrylic acid) (APM) and poly-2-vinylpyridine (2-PVP). In the case of uncharged films, the collapse pressure decreases when the polarity of the organic phase becomes more important, whereas the term ω/kT, which appears in the theory of Motomura and Matuura, increases. A quantitative relation between the parameter ω/kT and the collapse pressure may be deduced. The behavior of the ionized surface film at different pH values is modified by the choice of the interface. However, there exists a competition between two phenomena: the dissolution of ionized residues in the substratum and the electrostatic repulsion between charges in the surface plane. Depending upon whether the first or the second parameter is more important, we observed that the surface pressure decreased or increased with the degree of ionization.

Zusätzliches Material: 6 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1966.160040508

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4

Digitale Medien

Effect of thermal annealing on the gas permeability of HIQ-40 films (1996)

Park, J. Y. ; Paul, D. R. ; Haider, I. ; [weitere]

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 1741-1745

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ISSN: 0887-6266

Schlagwort(e): Liquid crystalline polymer ; permeability ; crystallinity ; annealing ; gases ; Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: 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.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

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5

Digitale Medien

Experimental and theoretical estimations of surface tensions for commercial liquid crystalline polymers, Vectra™ A-950, B-950 and Xydar™ SRT-900 (1998)

Chung, Tai-Shung ; Ma, Kui Xiang ; Jaffe, Mike

Weinheim : Wiley-Blackwell

Macromolecular Chemistry and Physics 199 (1998), S. 1013-1017

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ISSN: 1022-1352

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: 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.

Zusätzliches Material: 5 Tab.

Materialart: Digitale Medien

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6

Digitale Medien

Evaluation du degre d'hydrolyse du polymethacrylate de methyle par la methode bidimensionnelle (1967)

Jaffé, J. ; Bricman, G. ; Berliner, C.

New York : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Letters 5 (1967), S. 153-155

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ISSN: 0449-2986

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1967.110050205

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7

Digitale Medien

Contribution à l'étude de l'ionisation des polyelectrolytes à l'interface air-eau (1965)

Jaffe, J. ; Ruysschaert, J.-M.

New York : Wiley-Blackwell

Journal of Polymer Science Part A: General Papers 3 (1965), S. 4047-4064

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ISSN: 0449-2951

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Monolayers of poly-2-vinylpyridine (2-PVP), of poly(methacrylic acid) (PMA), as well as of a polyampholyte containing definite proportions of 2-vinylpyridine and acrylic acid were investigated at the air-water interface. We studied particularly the ionization of the film. The variation of surface pressure with respect to the nature of the ionic subsolution was analyzed. At constant degree of ionization, two factors determine the surface pressure: the valence and the dimension of the counterion. The polyampholyte may be considered alternatively as a polycation or a polyanion depending on the pH value of the support. The small concentration of dipolar ions permits the presence in the same macromolecule of the properties of the poly-2-vinylpyridine and of the poly(methacrylic acid). Qualitatively, the influence of the counterions is reproduced for the three polyelectrolytes. With monovalent ions, a quantitative approach is possible. The surface pressure is analyzed in terms of current theories of the ionic double layer. The application of the Gouy-Chapman model gives satisfactory results at different polymer and ionic concentrations. The theory has been extended with success to completely and incompletely ionized monolayers. However, there is evidence that the Gouy-Chapman theory is obeyed only at high areas. For denser films, the discrepancy between the calculated and experimental pressure is often quite large. The inclusion of a “fluctuation potential” contribution to the surface pressure permits a good agreement between the theory and the experiments.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1965.100031204

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8

Digitale Medien

Applications of limiting conversion free-radical polymerizations. II. Azobisisobutyronitrile-initiated polymerization of methyl methacrylate in benzene (1967)

Indictor, N. ; Mogolesko, P. ; Jaffe, H.

New York : Wiley-Blackwell

Journal of Polymer Science Part A-1: Polymer Chemistry 5 (1967), S. 1107-1111

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ISSN: 0449-296X

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Data for the azobisisobutyronitrile-initiated polymerization of methyl methacrylate in dilute benzene solution is presented at 80, 100, and 126°C. in terms of Tobolsky's limiting conversion kinetics. Number-average molecular weights were obtained viscometrically. Attempts to evaluate the relative amounts of combination and disproportionation in the chain-terminating reaction were foiled by the discovery that under the conditions reported the initiator efficiency is temperature-dependent decreasing markedly with increasing temperature.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1967.150050515

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9

Digitale Medien

Les polymeres à l'interface eau-air (1964)

Jaffe, J. ; Loutz, J.-M.

New York : Wiley-Blackwell

Journal of Polymer Science Part A: General Papers 2 (1964), S. 1669-1685

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ISSN: 0449-2951

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: 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.

Zusätzliches Material: 11 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1964.100020412

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