Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    Electronic Resource
    Electronic Resource
    Minimal Presentations and Efficiency of Semigroups (2000)
    Springer
    Semigroup forum 60 (2000), S. 231-242 
    Details
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: S is said to be efficient if it can be defined by a presentation (A | R) with |R| -|A|=rank(H 2(S)). In this paper we demonstrate certain infinite classes of both efficient and inefficient semigroups. Thus, finite abelian groups, dihedral groups D 2 n with n even, and finite rectangular bands are efficient semigroups. By way of contrast we show that finite zero semigroups and free semilattices are never efficient. These results are compared with some well-known results on the efficiency of groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002339910016
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Thermal and optical studies on some monomer and polymer diacetylenes (1990)
    Springer
    Journal of thermal analysis and calorimetry 36 (1990), S. 1669-1674 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden thermische und optische Studien einiger Diacethylene beschrieben, die zwecks der Senkung der Temperatur für das Auftreten von Mesophasen eigens gestaltet wurden. Ursprüngliche Untersuchungen an symmetrischen Molekülen wurden erweitert, um auch typische Flüssigkeitskristallmoleküle mit Diacethylenen mit Polymerhauptketten und unsymmetrisch substituierte Diacethylene wie Schiff-Basen mit langen Alkylketten einzubeziehen.
    Notes: Abstract We describe the thermal and optical studies of some diacetylene molecules which were specially designed in an attempt to reduce the temperature at which the mesophase appears. Original studies were on symmetrical molecules and these were extended to include typical liquid crystal molecules with diacetylenes providing a polymeric backbone and unsymmetrically substituted diacetylenes including Schiffs bases with long alkyl chains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01913413
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Sex attractant pheromone of damson-hop aphid Phorodon humuli (Homoptera, aphididae) (1990)
    Springer
    Journal of chemical ecology 16 (1990), S. 3455-3465 
    Details
    ISSN: 1573-1561
    Keywords: Pheromone ; sex ; attractant ; aphid ; Phorodon humuli ; Homoptera ; Aphididae ; nepetalactol ; monoterpenoid ; electrophysiology ; single cell recording ; mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Behavioral studies using an olfactometer demonstrated that sexual females (oviparae) of the damson-hop aphid,Phorodon humuli, release a pheromone to which males respond. Volatiles produced by the oviparae were analyzed by coupled gas chromatography-single cell recording from the secondary rhinaria on the male antenna and showed the presence of one peak with major activity. Coupled gas chrornatography-mass spectrometry suggested a nepetalactol, which was shown to have the 4aR, 7S, 7aS stereochemistry by synthesis from the corresponding nepetalactone isolated from the labiate plantNepeta mussinii. Although the stereochemistry at carbon-1 is not yet established, a synthetic sample comprising ca. 70% 1S and 30% 1R attracted highly significant numbers of males to water traps placed within and adjacent to a hop garden. Initial studies also indicated attraction of males in both the olfactometer and in the field by volatiles from the primary host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00982110
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Microbial Biomass and Community Structure in a Sequence of Soils with Increasing Fertility and Changing Land Use (2000)
    Springer
    Microbial ecology 40 (2000), S. 223-237 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The microbial biomass and community structure of eight Chinese red soils with different fertility and land use history was investigated. Two community based microbiological measurements, namely, community level physiological profiling (CLPP) using Biolog sole C source utilization tests and phospholipid fatty acid (PLFA) profiles, were used to investigate the microbial ecology of these soils and to determine how land use alters microbial community structure. Microbial biomass-C and total PLFAs were closely correlated to organic carbon and total nitrogen, indicating that these soil microbial measures are potentially good indices of soil fertility in these highly weathered soils. Metabolic quotients and C source utilization were not correlated with organic carbon or microbial biomass. Multivariate analysis of sole carbon source utilization patterns and PLFAs demonstrated that land use history and plant cover type had a significant impact on microbial community structure. PLFAs showed these differences more than CLPP methods. Consequently, PLFA analysis was a better method for assessing broad-spectrum community differences and at the same time attempting to correlate changes with soil fertility. Soils from tea orchards were particularly distinctive in their CLPP. A modified CLPP method, using absorbance readings at 405 nm and different culture media at pH values of 4.7 and 7.0, showed that the discrimination obtained can be influenced by the culture conditions. This method was used to show that the distinctive microbial community structure in tea orchard soils was not, however, due to differences in pH alone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002480000053
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Comparison of techniques for extracting volatile compounds from conifer needles (1990)
    Springer
    Journal of chemical ecology 16 (1990), S. 2713-2722 
    Details
    ISSN: 1573-1561
    Keywords: Monoterpenes ; Abies grandis ; Picea pungens ; steam distillation ; extraction ; secondary chemicals ; grand fir ; blue spruce ; coefficient of variation ; MANOVA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Five extraction techniques were used to obtain quantitative measurements of monoterpenes from blue spruce and grand fir needles. Multivariate analysis of variance indicated that there was a significant difference in the amount of each monoterpene extracted by using different techniques. For both species, an 8-hr steam distillation of 10 g of material yielded the greatest amount of each monoterpene. This technique was also the most reproducible in that the coefficients of variation were lowest. A rapid steam distillation was relatively effective for grand fir, but not for blue spruce. A CO2 extraction was unreliable for both species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00988080
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...