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  • 1
    ISSN: 1572-9729
    Keywords: fire ; climate change ; boreal forest ; stream ; sulfate ; acidity ; watershed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a boreal forest catchment in the Experimental Lakes Area in northwestern Ontario, wildfire caused an increase in the concentrations of strong acid anions and base cations of the stream. In the naturally base-poor Northwest (NW) Subbasin, a 1980 wildfire caused exports of strong acid anions to increase more than export of base cations, causing a 2.5 fold increase in the acidity of the stream. Mean annual stream pH declined from 5.15 prior to fire to 4.76 two years after fire. Acid-neutralizing capacity (ANC), calculated as the difference between total base cations and strong acid anions, decreased to 20% of pre-fire values. Sulfate and chloride were the strong acid anions responsible for the decline in ANC, increasing four-fold. While nitrate increased eleven-fold, concentrations were too low to significantly affect ANC. There was a significant correlation between weekly sulfate concentration and base cation concentration (r 2 = 0.83) in the two years after fire. Recovery of ANC was caused by the more rapid decline in concentration of sulfate than by changes in base cations. Drought produced a similar but weaker response than fire, with increased sulfate concentrations and decreased stream pH. Climatic warming that increases drought and fire frequency would have effects that mimic the impacts of acidic precipitation (i.e. higher sulfate concentrations and acidic stream waters). Areas which have higher concentrations of stored S from past acid precipitation or have large areas of peatlands in the watershed may have aggravated losses of S and H+ after drought and fire.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 24 (1989), S. 2177-2182 
    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 α-phase of the Al−Mn−Si ternary system has been precipitated from four liquid solutions (2.8 wt% Mn−3.7 wt% Si, 4.5 wt% Mn−7 wt% Si, 7.7 wt% Mn−10 wt% Si and 8.7 wt% Mn−12.6 wt% Si) and equilibrated slightly over the melting point of the (secondary) solid solution. Quenching into water enabled the precipitates to be separated from the solid solution and the co-nodal tie-lines for the α-phase and liquid to be determined. The silicon content varied from 9.8 to 11.8 wt%, while the manganese content, 29.6±0.6 wt%, did not vary significantly. The lattice parameter of the cubic unit cell decreased from 1.267 6(2) nm to 1.265 10(4) nm with increasing silicon. Neutron powder diffraction showed silicon to constitute approximately 50% of atoms on the icosahedral aluminium sublattices and 70% of a six-fold aluminium site in the interstices between the almost spherical, 54-atom clusters. This decrease in unit cell volume is interpreted as evidence for substitution of the silicon atoms on the six-fold sublattice.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 25 (1990), S. 2100-2106 
    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 Strontium-modified aluminium alloys containing 14 to 15 wt% silicon were cast with fully eutectic structures by using heated moulds and high-purity materials. In alloys containing the additional elements magnesium, copper or nickel, a distinct eutectic colony structure was evident outlined by intermetallic compounds. At the edges of the castings the eutectic colony structures and the aluminium grains (revealed by anodizing) were of a similar scale. Further from the mould walls the eutectic colonies contained several aluminium grains. This is believed to result from the blocking of growth of the aluminium phase by the silicon phase.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 71 (1985), S. 518-526 
    ISSN: 1432-2242
    Keywords: Wheat ; Vernalisation genes ; Agronomic characters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chromosome 5A of bread wheat, Triticum aestivum carries the major gene, Vrnl, which is one of the main determinants of the winter/spring growth habit polymorphism in this species. Genetical analysis of this chromosome has been carried out using single-chromosome recombinant lines to establish the pleiotropic effects of this locus and two other major genes, q determining ear morphology and bl determining the presence of awns, on important agronomic characters. The three major genes were located on the long arm of chromosome 5A with a gene order of: centromere -bl-q-Vrnl. Analysis of quantitative characters from a winter sowing revealed pleiotropic effects of Vrnl or the effects of closely linked loci on the characters plant height, tiller number and spikelet number. However effects on ear emergence time were not associated with Vrnl but with q as were effects on spikelet number and ear length. In addition a locus determining yield/plant was located between Vrnl and q. Independant loci determining height and ear length were apparent on the short arm of chromosome 5A. From a spring sowing, however, there was a large pleiotropic effect of Vrnl on ear emergence time, as well as the effects previously detected. In addition, associated with q were effects on plant height and grain size which were not expressed from the winter sowing.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 85 (1992), S. 197-204 
    ISSN: 1432-2242
    Keywords: Wheat ; Chromosome 5BL ; Major genes ; Quantitative trait loci
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chromosome 5B of bread wheat is known to carry two major genes giving rise to genetic disorders, Ne1 for hybrid necrosis and Vg for winter variegation. Additionally, in many european winter wheat varieties this chromosome is represented in a translocated form, with 5BL-7BL, 5BL-7BS chromosomes rather than the normal 5B and 7B forms of the standard variety Chinese Spring. Genetic analysis has been carried out to map these genes and the translocation break point, and to investigate their pleiotropic effects or those of linked quantitative trait loci (qtl) for economically important characters. This was facilitated by the development of single chromosome recombinant lines between a normal and translocated karyotype, and growing these in field experiments over two seasons. There was differential segregation in favour of the translocated karyotype in the population of recombinant lines. Linkage analysis revealed that the two morphological markers and the isozyme locus Ibf-B1 were located on the long arm of 5B with a gene order of: breakpoint — Ne1 — Vg — Ibf-B1. Analysis of quantitative characters using these genes as landmarks showed pleiotropic effects of Ne1 or effects of tightly linked qtl on most of the quantitative characters related to grain yield. An additional qtl determining spikelet and grain number/ear appeared to be linked to the centromere. Effects on ear emergence time were associated with both Ne1 and Vg, and these interacted with environments. Similarly, effects on plant height were associated with Ne1 and Vg. In addition, there was a further unlocated locus (loci) for height acting independently of the markers.
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  • 6
    ISSN: 1432-2242
    Keywords: Gametoclonal variation ; Barley doubled haploids ; Wheat doubled haploids ; Hordeum bulbosum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To investigate whether the Hordeum bulbosum system of doubled haploid production generates gametoclonal variation, populations of second generation doubled haploid lines were developed from first generation doubled haploid lines of two barley varieties and three wheat genotypes. In barley, no variation between doubled haploids from doubled haploids was detected for a range of quantitative characters, suggesting the absence of any gametoclonal effects. However, the original selfed-seed stocks were shown to contain cryptic allelic variation for some of the characters investigated. In wheat, gametoclonal variation was detected for ear emergence time, plant height and yield, and its components for two out of the three genotypes investigated. The type and range of variation was similar to that reported from studies of somaclonal variation from immature embryos and gametoclonal variation from anther culture. Generally, the effects appeared to reduce the yield performance of individual lines. The difference in response between the two species and the consequences for the use of the doubled haploid system in breeding programmes are discussed.
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  • 7
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of natural factors (drought and forest fire), and experimental perturbations (fertilization and acidification) on dissolved organic carbon (DOC) concentrations and ratios to other nutrients in lakes of the Experimental Lakes Area are examined using data obtained over a period of 20 years. DOC concentration, and the ratio of dissolved iron to DOC in lakes of the area were strongly correlated with the relative size of the catchment to the lake. DOC in many lakes of the area declined over 20 years, due to increased water residence times caused by increasing average temperature and decreasing precipitation. Inexplicably, Lake 382 was an exception to this general observation. Acidification of Lake 302S to below pH 5.0 also caused DOC to decrease. The lesser acidification of Lake 223 (min. pH 5.0) did not significantly affect DOC. Experimental acidification of a small peatland also caused a temporary decline in DOC concentrations in bog pools. Changes in DOC appear to affect the availability of mercury for methylation. Addition of aluminum to a small acidic lake caused a two-fold decline in DOC. Fertilization of Lake 227 caused a considerable increase in DOC, and in ratios of DOC to other carbon fractions. New stable ratios did not occur for a decade after fertilization began. Lake 226N, fertilized at a lower rate, showed similar but less pronounced increases in DOC, but the experiment was terminated after only eight years. Phosphorus fertilization caused a dramatic increase in the lability of the DOC pool in Lake 226N, where the autochthonous carbon pool was labelled with DI14C. A large increase in autochthonous production of DOC and increased microbial utilization of allochthonous DOC appear to have occurred. DOC concentrations in streams were higher after drought, but concentrations were unrelated to flow volume during wet periods. Due to lower streamflows in drought years, annual yields of DOC from streams were unaffected by drought. Mesocosm experiments showed that DOC's primary effect on iron is to inhibit sedimentation, possibly by suppressing flocculation reactions that are known to control the cycles of many metals. The changes in DOC in lakes brought about by changes in water renewal, acidification, or other perturbations can have major effects on the cycles of metals, lake transparency, and phytoplankton production and standing crop.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 7 (1988), S. 88-90 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied climatology 48 (1994), S. 187-194 
    ISSN: 1434-4483
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The structure and variability of the inter-tropical convergence zone (ITCZ) in the SW Indian Ocean in the austral summer is investigated. The ITCZ is identified by satellite microwave (SSMI) precipitable water (PW) values 〉 5 g cm−2, minimum outgoing longwave radiation (OLR) values 〈 220 W m−2 and the pattern of convergence in the low level (850 hPa) winds. According to OLR climatology, the ITCZ lies over 15°S latitude to the west of Madagascar (40–50°E), but near 10°S to the east of 60°E. Inter-annual and intra-seasonal variability is induced by the interaction of the convective NW monsoon and subsident easterly trades. Symptoms of the structure and variability are presented using tropical cyclone (TC) tracks, axes of PW exceedences and OLR, 850hPa wind and PW fields in the period 1988–1990. The shape and intensity of the ITCZ is modulated by the strength of the NW monsoon off east Africa and by standing vortices in the SW Indian Ocean. The topography of Madagascar imparts a distinctive break in convective characteristics, and distinguishes the SE African ITCZ from its maritime counterpart.
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  • 10
    ISSN: 1573-8248
    Keywords: Insecta ; gypsy moth ; parasitism ; low-level host populations ; Compsilura concinnata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Résumé Une étude a été menée pendant 2 ans sur la distribution des parasitoïdes deLymantria dispar (L.) dans une forêt du Vermont, dans la zone mésique, dans la zone de transition adjacente d'altitude plus élevée et dans la zone xérique. Dans chaque habitat, le parasitisme varie de 12 à 18% au cours des 2 années. Quand l'analyse est faite en fonction du stade de développement auquel l'hôte est récolté, les taux de parasitisme de plus de 40% sont observés sur les stades les plus âgés.Parasetigena silvestris (Robineau-Desvoidy) etPhobocampe disparis (Viereck) sont obtenus plus fréquemment dans l'habitat mésique alors queCotesia melanoscelus (Ratzeburg) etBlepharipa pratensis (= Sturmia scutellata) (Meigen) sont mieux représentés dans les récoltes provenant des zones xériques. Le parasitisme parCompsilura concinnata (Meigen) atteint des niveaux similaires dans les 3 habitats, cette espèce étant responsable des plus forts taux de parasitisme, qui s'élevait jusqu'à 40% dans les derniers stades en 1985. Le taux de parasitisme dû àC. concinnata a augmenté 3 à 4 fois de 1984 à 1985, alors que le parasitisme par les autres espèces diminuait.
    Notes: Abstract A 2-year study was conducted on the distribution of parasitoids of gypsy moth,Lymantria dispar (L.) (Lep.: Lymantriidae), in mesic and adjacent higher elevation transition and xeric forest habitats in Vermont (U.S.A.). In both years, overall parasitism ranged from 12–18% in each habitat. When analyzed according to the life stage at which the host was collected, parasitism rates of greater than 40% were obtained among the late instars.Parasetigena silvestris (Robineau-Desvoidy) andPhobocampe disparis (Viereck) were recovered most commonly from the mesic habitat, andCotesia melanoscelus (Ratzeburg) andBlepharipa pratensis (= Sturmia scutellata) (Meigen) were most common in collections from the xeric area. Parasitism byCompsilura concinnata (Meigen) occurred at similar levels in all three habitats, and this species was responsible for the highest parasitism rates on the site, reaching 40% among the late instars in 1985. Percent parasitism byC. concinnata increased three-four-fold from 1984 to 1985, while parasitism by other species declined.
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