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  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The arrangement of the chemical elements in the periodic table highlights resemblances in chemical properties, which reflect the elements’ electronic structure. For the heaviest elements, however, deviations in the periodicity of chemical properties are expected: electrons in ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Polluted air masses are characterized by high concentrations of oxidized nitrogen compounds which are involved in photochemical smog and ozone formation. The OH radical is a key species in these oxidation processes. The photolysis of nitrous acid (HNO2), in the morning, leads to the ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 52 (1904), S. 116-139 
    ISSN: 1432-1912
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 174 (1994), S. 145-155 
    ISSN: 1432-1351
    Keywords: Sleep ; Djungarian hamster ; Sleep regulation ; Photoperiod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The Djungarian hamster (Phodopus sungorus) is a markedly photoperiodic rodent which exhibits daily torpor under short photoperiod. Normative data were obtained on vigilance states, electroencephalogram (EEG) power spectra (0.25–25.0 Hz), and cortical temperature (TCRT) under a 16∶8 h light-dark schedule, in 7 Djungarian hamsters for 2 baseline days, 4 h sleep deprivation (SD) and 20 h recovery. During the baseline days total sleep time amounted to 59% of recording time, 67% in the light period and 43% in the dark period. The 4 h SD induced a small increase in the amount of non-rapid eye movement (NREM) sleep and a marked increase in EEG slow-wave activity (SWA; mean power density 0.75–4.0 Hz) within NREM sleep in the first hours of recovery. TCRT was lower in the light period than in the dark period. It decreased at transitions from either waking or rapid eye movement (REM) sleep to NREM sleep, and increased at the transition from NREM sleep to waking or REM sleep. After SD, TCRT was lower in all vigilance states. In conclusion, the sleep-wake pattern, EEG spectrum, and time course of TCRT in the Djungarian hamster are similar to other nocturnal rodents. Also in the Djungarian hamster the time course of SWA seems to reflect a homeostatically regulated process as was formulated in the two-process model of sleep regulation.
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  • 5
    ISSN: 1432-2285
    Keywords: Picea abies ; Seasonal variation ; Correlations ; Elemental concentrations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The concentration of 20 elements (including eight nutritional elements) in spruce needles was monitored by taking samples at nine different dates in a single year. On each date the youngest and the 1-year-old needles were collected at four different sites. The needles were washed with an organic solvent to remove surface contamination before analysis by instrumental neutron activation. Although the sites showed widely different concentrations for the same element, they could be treated as a uniform population using normalized concentration values. Taking the time dependence of the concentration and the ratio of the concentrations in new and old needles as criteria, the following three groups of elements could be distinguished: 9 group I —Ca, Sr, Ba, and Mn; group II — Al, Br, Co, Fe, Hg, La, Sc, Sb, and Zn; group III — K, Rb, Cs, P, and Cl. Mg and Na did not fit into any of these groups. Within group I and III elements the strongest variations occur during the growing season (late spring and early summer) and the weakest during the dormant season; the variation is greater in the younger needles. Group II elements show an approximately linear increase throughout the year in both the younger and older needles. The concentrations of elements of groups I and II increase with time, while those of group III decrease. Na is unique insofar as its concentration is influenced by foliar uptake of road de-icing salt. The concentration of elements belonging to the same group shows strong inter-element correlations. The grouping of elements deduced here shows similarities with the chemical nature of the elements and with their transportability within the plant.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2285
    Keywords: Picea abies ; Seasonal variation ; Correlations ; Elemental concentrations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The concentration of 20 elements (including eight nutritional elements) in spruce needles was monitored by taking samples at nine different dates in a single year. On each date the youngest and the 1-year-old needles were collected at four different sites. The needles were washed with an organic solvent to remove surface contamination before analysis by instrumental neutron activation. Although the sites showed widely different concentrations for the same element, they could be treated as a uniform population using normalized concentration values. Taking the time dependence of the concentration and the ratio of the concentrations in new and old needles as criteria, the following three groups of elements could be distinguished: 9 group I —Ca, Sr, Ba, and Mn; group II — Al, Br, Co, Fe, Hg, La, Sc, Sb, and Zn; group III — K, Rb, Cs, P, and Cl. Mg and Na did not fit into any of these groups. Within group I and III elements the strongest variations occur during the growing season (late spring and early summer) and the weakest during the dormant season; the variation is greater in the younger needles. Group II elements show an approximately linear increase throughout the year in both the younger and older needles. The concentrations of elements of groups I and II increase with time, while those of group III decrease. Na is unique insofar as its concentration is influenced by foliar uptake of road de-icing salt. The concentration of elements belonging to the same group shows strong inter-element correlations. The grouping of elements deduced here shows similarities with the chemical nature of the elements and with their transportability within the plant.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0931-1890
    Keywords: Key words Heavy metals ; Picea abies needles ; Biodynamic curves ; Retranslocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The concentrations of Fe, Zn and Co were determined in up to five successive needle age classes in 54 individual Norway spruce trees from eight different sites (soil pH 3.1–7.7). Fe concentrations (12–25 µg in needles from the current year) were lower than most published values, due to the removal of surface contamination prior to analysis. Fe showed a significant positive correlation with Al. Successive needle age classes either had constant values or showed an increase for Fe concentrations; individual trees on a given site were rather uniform in their behaviour. Zn concentrations were 19–40 µg/g. On acid sites, they showed a positive correlation with total soil concentrations. The majority of trees showed decreasing Zn concentrations in successive needle age classes, but constant or increasing concentrations were also found; site homogeneity was less than with Fe. Co concentrations differed between trees on a neutral soil (12 ng/g) and on acid soils (41–174 ng/g). They showed a significant positive correlation with Mn needle concentrations. The changes of Co with needle age in most, but not all, trees were similar to those of Zn. The different changes of Fe, Zn and Co with needle age may be due to a different retranslocation. A modest retranslocation of Fe as opposed to a high retranslocation of Zn and Co (in most trees) is consistent with the observed behaviour.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 366 (2000), S. 171-173 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Size fractionated aerosols were collected with low pressure Berner impactors on a radio/TV tower 110 m above ground on a hill 10 km east of Bern at a total elevation of 1060 m asl. Two different wind sectors were chosen with the goal of assessing any differences in lead concentration and the 3 radiogenic lead isotopes (206,207,208) for east and west wind, respectively. A leaching technique was used to extract the lead quantitatively from the surface of the impaction foils. This method has been proven to be better suited for airborne particles than complete microwave digestion because it is less time consuming and contamination risk is smaller. Blank considerations played a major role in choosing all the chemicals, tubes, beakers and selecting the analytical method. Lead concentrations were determined with GF-AAS and lead isotopes with two different ICP-MS systems, one being a multicollector system. Precision of the simultaneous multicollector system was found to be at least a factor of 3 better than that of the sequentially operating ICP-MS. The small variations in isotope ratios from the two wind sectors can be distinctly seen with this enhanced precision. The observed relative difference in isotope ratios between east- and westwind was ∼0.6% for 207Pb/206Pb and ∼0.5% for 208Pb/206Pb.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 62 (1910), S. 431-463 
    ISSN: 1432-1912
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 5 (1913), S. 85-93 
    ISSN: 1432-1076
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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