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  • 1
    Publication Date: 1999-05-01
    Print ISSN: 1434-6001
    Electronic ISSN: 1434-601X
    Topics: Physics
    Published by Springer
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  • 2
    Publication Date: 1967-09-01
    Print ISSN: 0026-3672
    Electronic ISSN: 1436-5073
    Topics: Chemistry and Pharmacology
    Published by Springer
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  • 3
    Publication Date: 1967-09-01
    Print ISSN: 0026-3672
    Electronic ISSN: 1436-5073
    Topics: Chemistry and Pharmacology
    Published by Springer
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  • 4
    ISSN: 1570-7458
    Keywords: Sitobion avenae ; Sitobion fragariae ; RAPD ; PCR ; microsatellites ; mtDNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A set of molecular markers to differentiate the aphid (Hemiptera: Aphidoidea) species Sitobion avenae (Fabricius) from Sitobion fragariae (Walker), is presented. These markers correspond to (1) a region of the mitochondrial DNA, (2) five species-specific RAPD banding patterns and (3) four microsatellite loci. Each of the markers was able to clearly distinguish between the species. The utility of each molecular marker is discussed. Mitochondrial DNA is best applicable to species determination and relative abundance, RAPDs to the evaluation of genetic diversity, and microsatellites to the assessment of the population genetic structure; the combined use of mtDNA with the other techniques can be of importance when the presence of hybrids is suspected, and RAPDs with microsatellites are best used together in population genetics and host preference studies.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1570-7458
    Keywords: sieve element ; salivation ; aphid ; plant resistance ; wheat ; Sitobion fragariae ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Extended sieve element salivation (E1 waveform in the electrical penetration graph) is a characteristic activity during early sieve element punctures, particularly in resistant plants. In order to explore a chemically-mediated mechanism of resistance associated with sieve element salivation, we compared the pattern of feeding behaviour of the aphid, Sitobion fragariae (Walker), on two cultivars of the wheat Triticum aestivum L., with different concentrations of hydroxamic acids (Hx). During 24 h of electronic monitoring, aphids dedicated over 50% of the total time to phloem ingestion from the sieve elements. Total time allocated to E1 in the experiment, time to first E1 within the experiment, time allocated to E1 before a sustained phloem ingestion (E2) and the contribution of sieve element salivation to the phloem phase (E1/[E1+E2]) were significantly higher in the high-Hx cultivar. The increased salivation in plants with higher contents of Hx suggests the existence, at least in this system, of a chemically-mediated sieve element constraint.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 55 (1967), S. 872-884 
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary A volumetric procedure has been described for determining the hydrogen content of organic compounds in the form of sulfuric acid. The combustions were conducted in the presence of sulfur, sulfur dioxide, or carbon disulfide in an oxygen atmosphere. Sulfur dioxide is oxidized to sulfur trioxide on a platinum catalyst in the combustion tube, and the water resulting from the combustion combines with the sulfur trioxide formed to yield concentrated sulfuric acid. This condenses in an absorption vessel attached to the combustion tube. Any excess sulfur trioxide is expelled from the oleum during the purging period by warming. After the absorber has been swept out, the sulfuric acid equivalent to the hydrogen content of the samples is titrated acidimetrically.
    Abstract: Résumé On présente une méthode volumétrique pour déterminer la teneur en hydrogène de composés organiques, sous forme d'acide sulfurique. Les combustions s'effectuent en présence de soufre, d'anhydride sulfureux ou de sulfure de carbone en atmosphère d'oxygène. L'anhydride sulfureux est oxydé en anhydride sulfurique sur catalyseur au platine placé dans le tube à combustion. Il se forme ensuite de l'acide sulfurique concentré au contact de l'eau produite par la combustion. Celle-ci se condense dans un récipient pour absorption relié au tube à combustion. On chasse l'anhydride sulfurique en excès de l'oléum pendant la période de balayage, par échauffement. Après balayage de l'absorbeur on titre par acidimétrie l'acide sulfurique équivalent à la teneur en hydrogène de l'échantillon.
    Notes: Zusammenfassung Eine volumetrische Methode zur Bestimmung des Wasserstoffgehaltes organischer Verbindungen in Form von Schwefelsäure wird dargelegt. Die Verbrennungen werden in Gegenwart von Schwefel, Schwefeldioxid oder Schwefelkohlenstoff in Sauerstoffatmosphäre durchgeführt. Das Schwefeldioxid wird an dem im Verbrennungsrohr untergebrachten Platinkatalysator zu Schwefeltrioxid oxydiert, das mit dem bei der Verbrennung entstandenen Wasser konz. Schwefelsäure bildet. Diese kondensiert in einem dem Verbrennungsrohr angeschlossenen Absorptionsgefäß. Das überschüssige Schwefeltrioxid vertreibt man aus dem Oleum im Laufe der Spülungsperiode durch Erwärmen. Nach der Ausspülung des Absorbers wird die dem Wasserstoffgehalt der Proben äquivalente Schwefelsäure acidimetrisch titriert.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 55 (1967), S. 920-928 
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary A new method for the iodometric determination of the hydrogen content of organic materials has been described. The sample is mixed with powdered sulfur and decomposed at 1200° C in a stream of nitrogen over quartz wool or a platinum-quartz wool catalyst. The sulfur-bearing pyrolysis products yield hydrogen sulfide that is then, absorbed in a zinc sulfate-sodium acetate solution and titrated iodometrically. The optimal reaction conditions were thoroughly studied and also explained from the theoretical standpoint.
    Notes: Zusammenfassung Eine neue Methode zur jodometrischen Bestimmung des Wasserstoffgehaltes organischer Verbindungen wird beschrieben. Die Probe wird mit Schwefelpulver vermischt und bei 1200° C im Stickstoff strom über Quarzwolle oder einem Platin- Quarzwollekatalysator zersetzt. Aus den schwefelhaltigen Pyrolyseprodukten bildet sich Schwefelwasserstoff, der in einer Zinksulfat-Natriumacetatlösung absorbiert und jodometrisch titriert wird. Die optimalen Reaktionsbedingungen wurden eingehend untersucht und auch in theoretischer Hinsicht erklärt.
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  • 8
    ISSN: 1423-0445
    Keywords: Key words. defense allocation — hydroxamic acids — leaf age — optimal defense theory — rye —Secale cereale— Poaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary. The among-leaves allocation of DIBOA, a hydroxamic acid associated with plant resistance, in the shoot of rye (Secale cereale) was evaluated over the vegetative development of the plant. The appropriateness of using the concentration of secondary metabolites, DIBOA in this case, as the parameter to evaluate defense allocation in plants is discussed. Both biological and statistical arguments are put forward to suggest that allocation of chemical defenses should refer to absolute content and not to concentration. Results showed that leaf age was significantly linked to leaf concentration of DIBOA, young leaves having higher concentrations. In contrast, leaf content of DIBOA, our proposed currency of allocation, was not significantly higher in younger leaves. Furthermore, a regression analysis showed that the DIBOA content of leaves was better explained by the leaf relative biomass (proportion of shoot biomass) than by leaf biomass itself. It is suggested that, rather than leaf age, leaf relative biomass is the major factor determining DIBOA allocation in rye shoots. It is proposed that studies addressing within-plant defense allocation should use chemical defense content as the currency, emphasizing the major factors driving this process and its underlying mechanisms. Likewise, it is proposed that studies aiming at characterizing optimal patterns of plant defense should use chemical defense concentration as the currency, and be accompanied by evaluations of the actual resistance against herbivores of the plant parts analyzed, together with the effect on plant fitness.
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  • 9
    ISSN: 1573-1561
    Keywords: Aphids ; Sitobion avenae ; feeding deterrents ; antibiotics ; DIMBOA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A total of 25 compounds including benzoxazinones, benzoxazolinones, and N-glyoxylamide derivatives were tested as antifeedants and antibiotics towards the aphid Sitobion avenae in diet bioassays. The antifeedant and mortality indexes increased with the presence of electron-donating groups in the 7 position of the benzoxazinone moiety, the replacement of the oxygen atom by sulfur in the heterocyclic ring, the presence of a hemiacetal instead of an acetal at C-2 of the benzoxazine moiety (and hence the possibility of ring opening), and the presence of a hydroxyl group at C-4 of the benzoxazine moiety (hydroxamic acid) instead of a hydrogen atom (lactam). The results support earlier hypotheses on the chemical bases for the mode of action of these compounds.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 25 (1999), S. 1799-1811 
    ISSN: 1573-1561
    Keywords: Liolaemus lizards ; conspecific chemical recognition ; tongue-flick
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Experimental tests were conducted to determine whether females and males of the tree-dwelling lizard Liolaemus tenuis (Tropiduridae) show intraspecific chemical recognition during breeding and postreproductive seasons. Animals were individually maintained in plastic enclosures for one week. Thereafter, the number of tongue-flicks that a lizard performed in the enclosure of a male, a female, its own home enclosure, and a control (unused) enclosure were recorded. In both seasons, males and females made fewer tongue-flicks in their home enclosures than in any other one, indicating a recognition of a familiar place, probably a chemical self-recognition. Conspecific chemical recognition was season dependent. During the post-reproductive season, lizards tongue-flicked at similar rates in conspecific and control enclosures, while during the breeding season enclosures of females elicited more tongue-flicks by both sexes, and the overall tongue-flick rates were higher than in the postreproductive season. Results are discussed within the context of the social system of the species.
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