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  • Articles  (52)
  • Springer  (52)
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  • Articles  (52)
Journal
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 46 (1990), S. 737-739 
    ISSN: 1420-9071
    Keywords: Heat shock protein ; stress ; in vitro translation ; gene regulation ; Apis mellifera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We employed in vitro translation of mRNA and product separation using SDS-PAGE to examine the heat-shock response of the worker honey bee. Increases in the levels of 6 translatable RNA populations were observed following heat stress. The greatest response was observed among bees aged 9 days. Slight levels of induction of 70 and 82 kDa heat shock proteins were evident among bees taken directly from the colony.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 99 (1994), S. 16-20 
    ISSN: 1432-1939
    Keywords: Barnacles ; Marine macro-algae Nutritional interaction ; Nitrogen limitation ; Ammonium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen is the major growth-limiting nutrient for marine algae. One potential source of nitrogen for marine algae is ammonium released by invertebrates. Many mid-intertidal reefs in northeastern New Zealand are dominated by a close association between the honeycomb barnacle Chamaesipho columna and an encusting brown alga Pseudolithoderma sp. Growth of Pseudolithoderma was enhanced in the presence of live C. columna, which released ammonium at a greater rate than the maximum rate of ammonium uptake by Pseudolithoderma. Algal tissue on barnacle tests had a lower C:N ratio than tissue located more than 2 cm from the nearest barnacle, suggesting the barnacle is an important source of nitrogen for the alga. The role of nutrient exchange in determining ecological patterns of species in marine communities is discussed.
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  • 3
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relative contribution of dissolved nitrogen (ammonium and dissolved free amino acids DFAAs) to the nitrogen budget of the reef-building coral Pocillopora damicornis was assessed for colonies growing on control and ammonium-enriched reefs at One Tree Island (southern Great Barrier Reef) during the ENCORE (Enrichment of Nutrient on Coral Reef; 1993 to 1996) project. P. damicornis acquired ammonium at rates of between 5.1 and 91.8 nmol N cm−2 h−1 which were not affected by nutrient treatment except in the case of one morph. In this case, uptake rates decreased from 80.5 to 42.8 nmol cm−2 h−1 (P 〈 0.05) on exposure to elevated ammonium over 12 mo. The presence or absence of light during measurement did not influence the uptake of ammonium ions. Nitrogen budgets revealed that the uptake of ammonium from concentrations of 0.11 to 0.13 μM could completely satisfy the demand of growing P. damicornis for new nitrogen. P. damicornis also took up DFAAs at rates ranging from 4.9 to 9.8 nmol N cm−2 h−1. These rates were higher in the dark than in the light (9.0 vs 5.1 nmol m−2 h−1, P 〈 0.001). Uptake rates were highest for the amino acids serine, arginine and alanine, and lowest for tyrosine. DFAA concentrations within the ENCORE microatolls that received ammonium were undetectable, whereas they ranged up to 100 nM within the control microatolls. The contribution of DFAAs to the nitrogen budget of P. damicornis constituted only a small fraction of the nitrogen potentially contributed by ammonium under field conditions. Even at the highest field concentrations measured during this study, DFAAs could contribute only ≃11.3% of the nitrogen demand of P.␣damicornis. This contribution, however, may be an important source of nitrogen when other sources such as ammonium are scarce or during periods when high concentrations of DFAAs become sporadically available (e.g. cell breakage during fish-grazing).
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 20 (1985), S. 4045-4049 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A two-stage heat treatment of an aluminosilicate glass containing both TiO2 and Nb2O5 may be used to precipitate a fine dispersion of doped TiO2 crystals within a glassy matrix. The resulting partially crystalline product exhibits the properties of a semiconducting material with activation energies for conduction ranging from 0.2 to 0.35 eV. The d.c. conductivity of the specimens has been shown to be related to the size of the TiO2 crystals. With prolonged crystallization treatment a second non-conducting crystalline phase, anorthite, reduces the conductivity of the glass-ceramics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biochemical genetics 17 (1979), S. 867-879 
    ISSN: 1573-4927
    Keywords: malic enzyme ; development ; NADP enzymes ; Drosophila ; nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract NADP-malic enzyme (NADP-ME) (E.C. 1.1.1.40) is situated in the cytosol of Drosophila melanogaster. Both the tissue activity and CRM level of NADP-ME parallel changes in the dosage of a gene, Men +, located in region 87C2-3 to 87D1-2 of the third chromosome. The tissue activity of NADP-ME is very high in early third instar larvae, providing about 33% of the NADPH at this life stage. The tissue activity declines during pupal development but increases as the adult ages. The concentration of NADP-ME CRM and tissue activity are coordinately increased in third instar larvae by dietary carbohydrate and decreased by dietary lipid.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 16 (1981), S. 1264-1272 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Several studies have been made of the mechanism of the reaction between zirconia and silica using plasma dissociated zircon (DZ) as the source of zirconia and of the silica. The suggestions have been made that the formation of a ceramic body from milled DZ proceeds at significantly lower temperatures than it does with the mixed oxides for reasons largely connected with the intrinsically near-perfect mixing, and that the implications could have some commercial importance. The re-association and dissociation reactions are very complex in nature and the completion, or otherwise, and the reassociation to zircon is not necessarily reflected in the mechanical properties of the ceramic body; purely textural considerations may be more relevant.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied charging effects in a lateral split-gate quantum dot defined by metal gates in the two dimensional electron gas (2 DEG) of a GaAs/AlGaAs heterostructure. The gate structure allows an independent control of the conductances of the two tunnel barriers separating the quantum dot from the two 2 DEG leads, and enables us to vary the number of electrons that are localized in the dot. We have measured Coulomb oscillations in the conductance and the Coulomb staircase in current-voltage characteristics and studied their dependence on the conductances of the tunnel barriers. We show experimentally that at zero magnetic field charging effects start to affect the transport properties when both barrier conductances are smaller than the first quantized conductance value of a point contact at 2e 2/h. The experiments are described by a simple model in terms of electrochemical potentials, which includes both the discreteness of the electron charge and the quantum energy states due to confinement.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The surface topographic development by sputter erosion of a solid resulting from spatially non-uniform projectile bombardment is considered theoretically. It is shown that whilst formal prediction of time-dependent surface geometry is possible, analytic solution of the defining equations is generally unachievable, although an approximate treatment may be made for the case of a Gaussian flux distribution profile and an initially plane surface. It is shown that profile perturbations resulting from erosion rate-projectile incidence angle variations can assume importance when erosion crater depths become of similar order to projectile beam width. This behaviour is also revealed by computer simulation of the erosion process and a sand blasting experimental analogue study.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 15 (1980), S. 670-676 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The diffusion coefficients of Sn(IV) in an aluminosilicate glass and a commercial glaze have been measured from 809 to 1505° C. Two experimental techniques have been used. In one method, single crystals of SnO2 were embedded in either the powdered glass or sealed into a bar of the glass. After the diffusion anneal, the Sn(IV) concentration profile was determined by EPMA. In the other method, radioactive 113Sn was used as a tracer and the profile determined by measuring the X-ray emission. The results gave a good agreement between the two methods. The diffusion coefficients in the glaze ranged from 7×10−20 m2 sec−1 at 809° C to 1.9×10−14 m2 sec−1 at 1250° C and in the glass, from 5.6×10−15 m2 sec−1 at 1307° C to 1.6×10−11 m2 sec−1 at 1505° C.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 15 (1980), S. 2325-2330 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The foam texture developed in plasma-dissociated zircon consists of plane surfaced interlocking grains which contain crystallites of dendritic zirconia embedded in amorphous silica. In the interstices of these grains silica has been segregated. This segregation appears to have come about mainly as the result of supercooling and liquid immiscibility. This accounts for the development of the almost pure silica phase and the formation of a zirconia-rich phase which crystallized to yield dendrites consisting of monoclinic zirconia at ambient temperature. Clear envelopes on the grains were found to consist of amorphous silica-rich material containing zirconia spherulites whose density of development is proportional to the zirconia content of the envelopes.
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