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  • 1
    Electronic Resource
    Electronic Resource
    The role of upstream ULF waves in the generation of quasi-periodic ELF-VLF emissions (1995)
    Springer
    Annales geophysicae 13 (1995), S. 1127-1133 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Recent work suggests that the quasi-periodic (QP) modulation \sim10-50 s of naturally occurring ELF-VLF radio emissions (\sim0.5-5 kHz) is produced by the compressional action of Pc3 magnetic pulsations on the source of the emissions. Whilst it is generally accepted that these magnetic pulsations have an exogenic source, it is not clear what the mechanism of their generation is. A study of QP emissions observed during 1988 at Halley, Antarctica, in conjunction with IMP-8 satellite solar wind data, shows that the occurrence and modulation frequency of the emissions are strongly dependent upon the direction and strength of the IMF, respectively. The observed relationships are very similar to those previously reported for Pc3 pulsations associated with upstream ion-cyclotron resonance, involving proton beams reflected at the bowshock. In comparing the observed QP modulation frequencies with upstream wave theory, agreement was found by considering wave excitation exclusively associated with a proton beam reflected from a position on the bowshock at which the shock normal is parallel to the ambient IMF direction. Other geometries were found to be either impropitious or uncertain. The work indicates the useful diagnostic role QP emissions could play in the study of compressional ULF waves in the upstream solar wind and in monitoring the IMF conditions responsible for their generation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-995-1127-3
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  • 2
    Electronic Resource
    Electronic Resource
    Polymorphisms in the glutamate transporter gene EAAT2 in European ALS patients (1999)
    Springer
    Journal of neurology 246 (1999), S. 1140-1144 
    Details
    ISSN: 1432-1459
    Keywords: Key words Amyotrophic lateral sclerosis ; Genetics ; Glutamate transporter gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Amyotrophic lateral sclerosis (ALS) is a progressive neurological disorder characterised by degeneration of upper and lower motor neurons. Whilst the primary pathogenic trigger is unknown in most cases, evidence is mounting to implicate a role for glutamate-mediated neurotoxicity in the disorder. Recent studies have shown reduced levels of the mainly astroglial glutamate transporter EAAT2 in ALS motor cortex and spinal cord and multiple abnormal EAAT2 mRNA species in ALS brain tissue. One cause of the low EAAT2 levels may be that point mutations in the EAAT2 gene, EAAT2, result in an abnormal unstable protein. To test this hypothesis we analysed EAAT2 in 128 sporadic and 23 familial European ALS cases. No variants within the coding sequence of EAAT2 to affect the protein sequence nor in the consensus splice sites of the flanking intronic sequences were found in any cases, similar to findings in other reports. Frequent polymorphisms within the flanking intronic sequences of both exons 2 and 4 were seen but at similar frequencies in controls. Mechanisms other than mutations within the coding region of EAAT2 must therefore be responsible for the low levels of EAAT2 seen in most cases of ALS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050532
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  • 3
    Electronic Resource
    Electronic Resource
    Methylmercury production in the anoxic hypolimnion of a Dimictic Seepage Lake (1995)
    Springer
    Water, air & soil pollution 80 (1995), S. 735-745 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Experimental results and field data indicated that methyl-Hg was produced within a layer of bacterioplankton near the top of the anoxic hypolimnion of Pallette Lake. In situ incubations at ambient Hg concentrations indicated that the net flux of methyl-Hg from the layer was between 50 and 100 pmol/m2*d. This input was sufficient to account for the summer accumulation of methyl-Hg in the entire hypolimnion and it exceeded atmospheric inputs by 2 orders of magnitude. Maximum rates of net methylation occurred in the same region of the water column where we observed maximum rates of sulfate reduction. The measured rates were: 100 fmol rriethyl-Hg/L*d and 90 nmol SO4/L*d. Sulfate reducing enrichment cultures isolated from the hypolimnion were also able to methylate Hg in the laboratory. Sulfate reduction did not occur in anoxic profundal sediments during summer and we infer from ancillary data that methylation in profundal sediments was also low. Whole-lake rates of sulfate reduction in the hypolimnetic layer and shallow sediments were roughly equivalent, but we cannot yet compare methylation rates at these sites due to large uncertainties in the littoral flux of methyl-Hg. We propose that zones of Hg methylation and SO4 reduction follow the oxic/anoxic boundary in both the watercolumn and sediments. The relative importance of watercolumn and sediment processes will depend on the physical and chemical structure of a given lake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01189725
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  • 4
    Electronic Resource
    Electronic Resource
    Fluxes of mercury through biota in the LG-2 reservoir after flooding (1995)
    Springer
    Water, air & soil pollution 80 (1995), S. 573-576 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The purpose of this study was to estimate the temporal fluxes of mercury (Hg) among the diverse biotic components of the aquatic ecosystem of the LG-2 reservoir before and shortly after flooding, and to compare the relative magnitudes of these fluxes. Flooding took place from autumn 1978 to autumn 1979. The basic food chain considered was: Phytoplankton ⇒ Zooplankton ⇒ Prey Fish ⇒ Predatory Fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01189707
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  • 5
    Electronic Resource
    Electronic Resource
    Changes in mercury levels in lake whitefish (Coregonus clupeaformis) and northern pike (Esox lucius) in the LG-2 reservoir since flooding (1995)
    Springer
    Water, air & soil pollution 80 (1995), S. 819-828 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract After flooding of the LG-2 reservoir in 1978–1979, it was noticed that Hg levels in fish rose dramatically. In this study the Hg data have been examined on the basis of fish age for lake whitefish (Coregonus clupeaformis) and northern pike (Esox lucius), representing two different trophic levels. Data were fit to Von Bertalanffy functions using non-linear regression analyses. Reductions in error sums of squares indicated that differences among years were the major sources of variation, but that there were differences among stations within years. For age profiles both species showed changes after flooding, whitefish increasing immediately and remaining similar until 8 years after flooding, with decreases afterward, while pike continued to increase until 8 years after flooding, remaining somewhat stable afterwards. For whitefish, cohorts (year classes) from before flooding had similar concentrations, with maxima reached by around 1982, concentrations afterward remaining stable. Subsequent cohorts reached plateaus at around 2–4 years of age, each successive cohort having a lower plateau. For pike, Hg kept increasing in an almost linear fashion, cohorts from before flooding having similar concentrations. Analyses indicated the very gradual return of whitefish to conditions present before flooding, while pike were remaining at much higher levels. Inputs to older pike were therefore not decreasing, but younger pike may have been improving.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01189733
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  • 6
    Electronic Resource
    Electronic Resource
    Chemical correlates of Hg and methyl-Hg in northern Wisconsin lake waters under ice-cover (1995)
    Springer
    Water, air & soil pollution 84 (1995), S. 253-267 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Total and dissolved concentrations of Hg and methyl-Hg (MeHg) were determined in the surface waters of 19 northern Wisconsin lakes under ice-cover when differences due to temperature, hydrology, productivity, and atmospheric exchange were minimal. Measured concentrations ranged from 0.3 to 5.3 ng/L for HgT and from 0.01 to 2.8 ng/L for MeHgT. Dissolved species comprised 30% to 95% of the HgT and MeHgT. MeHg was strongly correlated with Hg for both total and dissolved fractions. Thirteen ancillary constituents were measured in conjunction with the Hg determinations (pH, DOC, DIC, DO2, conductivity, suspended particulate matter (SPM), Ca, Mg, Mn, Fe, Na, SO4, Cl). Simple linear regressions indicated that DOC explained 87% of the variability in HgT and 79% of the variability in MeHgT. Of the other measured variables, pH, DO2, Fe and Mn showed weak but significant simple correlations with Hg and MeHg (@ p 〈 0.05). Multiple regression models containing two independent variables, (DOC and pH), explained 92% of the variability in HgT and 83% of the variability in MeHgT. Models containing DOC alone fit the dissolved Hg data well. We conclude that organic carbon concentrations have a strong effect on the concentrations of Hg and MeHg in these lakewaters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00475343
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  • 7
    Electronic Resource
    Electronic Resource
    Satellite Experiments Simultaneous with Antarctic Measurements (SESAME) (1995)
    Springer
    Space science reviews 71 (1995), S. 705-742 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Satellite Experiments Simultaneous with Antarctic Measurements (SESAME) is one of the four ground-based programmes within the NASA/ISAS Global Geospace Science (GGS) mission, itself part of the International Solar-Terrestrial Physics (ISTP) programme. The scientific objectives of SESAME are carefully selected to make an invaluable contribution to the GGS mission by capitalising on the unique geophysical advantages of Antarctica for geospace research. These arise mainly from the large displacement of the geographic and geomagnetic poles. Specifically, SESAME is designed to study the ionospheric effects of merging at the magnetopause, reconnection in the geomagnetic tail and its relationship to substorms, mapping of significant geospace boundaries to ionospheric altitudes, plasma wave generation and propagation at high latitudes, and ionosphere-thermosphere interactions. The experimental programme is centred at Halley (76° S, 27° W) but also utilises automatic geophysical observatories located poleward of Halley. The suite of instruments provides an excellent image of the inner boundary of geospace and thus is complementary to the GGS spacecraft measurements. The data products that will be supplied askey parameters to the GGS experimenters on a routine basis are described. A brief review of previous results is presented, and some of the significant scientific questions to be addressed using the combination of ground-based and space-based observations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00751348
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    The identification of novel sequences expressed in the mouse notochord (1997)
    Springer
    Mammalian genome 8 (1997), S. 42 -44 
    Details
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003359900344
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