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  • Springer  (25)
  • American Physical Society
  • 1990-1994  (25)
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  • 1
    Electronic Resource
    Electronic Resource
    Appinitic intrusions in the English Lake District (1994)
    Springer
    Mineralogy and petrology 51 (1994), S. 355-375 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Die Skiddaw-Gruppe im Liegenden des mittelordovizischen Vulkanbogens des englischen Lake District enthält kleinere Intrusionen von kalkalkalischen, HornblendeAugit-reichen, dioritischen bis pikritischen Magmen, die an das Appinit-Vorkommen in den schottischen Kaledoniden erinnern. Für diese Intrusionen ist der Scawgill Bridge-Mikrodiorit repräsentativ. Er stellt einen variablen, Hornblende-reichen Körper mit Einschlüssen von Augit-porphyrischem Meladiorit und Pyroxenit dar; zu den anderen gehören die “pikritischen” (Augit-Meladiorit oder Cortlandit) Stöcke bei Dash und Barkbeth. Sie unterscheiden sich von tholeiitischen Intrusionen gleichen Alters, die durch den Embleton-Diorit vertreten sind, und auch von den spätsilurischen Biotit-Lamprophyren. Trotz Alteration werden primäre Korrelationen, die durch immobile Spurenelemente angezeigt werden, auch von Hauptelementen einschließlich Mg, Fe und Ca nachgezeichnet. Die Differentiation bei Scawgill Bridge wird als eine Fraktionierung von Olivin, Augit, Hornblende und Chromit modelliert, und ein ähnlicher Prozeß wird für die Meladiorit-Intrusion angenommen. Daraus wird geschlossen, daß diese Körper primitive, kalkalkalische Magmen repräsentieren, die zur Unteren Borrowdale Volcanic Group gehören und die unter hohem PH2O fraktionierten. Im Gegensatz dazu wird die Untere Borrowdale Volcanic Group selbst von plagiophyrischen Gesteinen dominiert, die durch Fraktionierung unter niedrigem P(inH2O) entstanden sind.
    Notes: Summary Within the Skiddaw Group, which underlies the mid-Ordovician volcanic arc of the English Lake District, are minor intrusions of calc-alkaline, hornblende-augite rich, dioritic to picritic bodies reminiscent of the appinite suite of the Scottish Caledonides. Representative of these is the Scawgill Bridge microdiorite, a variable, hornblendic body which includes augite-phyric meladiorite and pyroxenite; others include the ‘picrtte’ (augite-meladiorite or cortlandtite) plugs at Dash and Barkbeth. They are distinct from tholeiitic intrusions of similar age represented by the Embleton Diorite, and also from late Silurian biotite-lamprophyres. Despite alteration, primary variation trends indicated by immobile trace elements are also expressed by major elements including Mg, Fe and Ca. Differentiation at Scawgill Bridge is modelled as fractionation of olivine, augite, hornblende and chromite, and a similar process is inferred for the meladiorite intrusions. It is concluded these bodies represent primitive, calc-alkaline magmas related to the Lower Borrowdale Volcanic Group, which fractionated under confined conditions of high P(inH2o). In contrast, the Lower Borrowdale Volcanic Group itself is dominated by plagiophyric rocks which resulted from fractionation at lower P(inH2O).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01159737
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  • 2
    Electronic Resource
    Electronic Resource
    A synthesis of post-glacial diatom records from Lake Baikal (1994)
    Springer
    Journal of paleolimnology 10 (1994), S. 213-252 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; paleolimnology ; palynology ; Holocene ; climate change ; Lake Baikal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake. Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub — steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence. On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During glacial periods, the deep basin sediments of Lake Baikal are dominated by rapidly deposited clastics entering from large rivers with possibly glaciated headwaters. On the sublacustrine Academician Ridge (depth = 300 m), however, detailed analysis of the diatom biostratigraphy indicates that diastems (hiatuses of minor duration) and (or) highly variable rates of accumulation complicate paleolimnologic and paleoclimatic reconstructions from these records.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00684034
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  • 3
    Electronic Resource
    Electronic Resource
    Holocene paleoclimatic evidence and sedimentation rates from a core in southwestern Lake Michigan (1990)
    Springer
    Journal of paleolimnology 4 (1990), S. 269-284 
    Details
    ISSN: 1573-0417
    Keywords: Lake Michigan ; paleolimnology ; radiocarbon ; stable isotopes ; ostracodes ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Preliminary results of a multidisciplinary study of cores in southwestern Lake Michigan suggest that the materials in these cores can be interpreted in terms of both isostatically and climatically induced changes in lake level. Ostracodes and mollusks are well preserved in the Holocene sediments, and they provide paleolimnologic and paleoclimatic data, as well as biogenic carbonate for stable-isotope studies and radiocarbon dating. Pollen and diatom preservation in the cores is poor, which prevents comparison with regional vegetation records. New accelerator-mass spectrometer 14C ages, from both carbon and carbonate fractions, provide basin-wide correlations and appear to resolve the longstanding problem of anomalously old ages that result from detrital organic matter in Great Lakes sediments. Several cores contain a distinct unconformity associated with the abrupt fall in lake level that occurred about 10.3 ka when the isostatically depressed North Bay outlet was uncovered by the retreating Laurentide Ice Sheet. Below the unconformity, ostracode assemblages imply deep, cold water with very low total dissolved solids (TDS), and bivalves have δ 18O (PDB) values as light as — 10 per mil. Samples from just above the unconformity contain littoral to sublittoral ostracode species that imply warmer, higher-TDS (though still dilute) water than that inferred below the unconformity. Above this zone, another interval with δ 18O values more negative than — 10 occurs. The isotopic data suggest that two influxes of cold, isotopically light meltwater from Laurentide ice entered the lake, one shortly before 10.3 ka and the other about 9 ka. These influxes were separated by a period during which the lake was warmer, shallower, but still very low in dissolved solids. One or both of the meltwater influxes may be related to discharge from Lake Agassiz into the Great Lakes. Sedimentation rates appear to have been constant from about 10 ka to 5 ka. Bivalve shells formed between about 8 and 5 ka have δ 18O values that range from-2.3 to-3.3 per mil and appear to decrease toward the end of the interval. The ostracode assemblages and the stable isotopes suggest changes that are climatically controlled, including fluctuating water levels and increasing dissolved solids, although the water remained relatively dilute (TDS 〈 300 mg/l). A dramatic decrease in sedimentation rates occurred at about 5 ka, about the time of the peak of the Nippissing high lake stage. This decrease in sedimentation rate may be associated with a large increase in effective wave base as the lake approached its present size and fetch. A dramatic reduction in ostracode and mollusk abundances during the late Holocene is probably due to this decrease in sedimentation rates, which would result in increased carbonate dissolution. Ostracode productivity may also have declined due to a reduction in bottom-water oxygen caused by increased epilimnion algal productivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239699
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  • 4
    Electronic Resource
    Electronic Resource
    Annual mean meridional energy transport modelled by a general circulation model for present and 2 × CO2 equilibrium climates (1994)
    Springer
    Climate dynamics 10 (1994), S. 221-229 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The meridional energy flux modelled by the Bureau of Meteorology Research Centre general circulation model is examined. It is divided into atmospheric and oceanic components, and the resolved atmospheric components in turn into mean and eddy circulations. Comparison with observations shows the modelled total planetary meridional energy transport to be low, but shows better agreement for the resolved atmospheric component alone. The overall patterns of the individual circulation and energy components of the model also agree well, although strengths and locations do show some discrepancies. The doubled CO2 climate change is analyzed in terms of the changes in each of the circulation and energy components. It is found that the changes are the relatively small residual of larger, and generally opposing changes in sensible heat and potential energy fluxes. Despite the general decrease in poleward energy flux, the poleward latent heat flux is found to increase. The reduction in poleward transport is found to be dominated by changes in the mean meridional circulation at low southern latitudes, and changes in both mean circulations and eddy fluxes elsewhere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208989
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  • 5
    Electronic Resource
    Electronic Resource
    Active uptake of CO2 during photosynthesis in the green alga Eremosphaera viridis is mediated by a CO2-ATPase (1992)
    Springer
    Planta 188 (1992), S. 539-545 
    Details
    ISSN: 1432-2048
    Keywords: ATPase ; Bicarbonate transport ; Carbon dioxide ; Carbonic anhydrase ; Eremosphaera ; Inor ganic carbon (dissolved)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mass spectrometry was used to investigate the uptake of CO2 in Eremosphaera viridis DeBary. Upon illumination, cells preincubated at pH 7.5 with 100 μM dissolved inorganic carbon (DIC) rapidly depleted almost all the free CO2 from the medium. Rapid equilibrium between HCO 3 - and CO2 occurred upon addition of bovine carbonic anhydrase (CA) to the medium, showing that CO2 depletion resulted from a selective uptake of CO2 rather than an uptake of all inorganic carbon species. Glycolaldehyde (10 mM) completely inhibited CO2 fixation but had little effect on CO2 transport. Transfer of glycolaldehyde-treated cells to the dark caused a rapid efflux of CO2 from the unfixed intracellular DIC pool which was found to be at least threeto sixfold higher in concentration than that of the external medium. These results indicate that E. viridis actively transports CO2 against a concentration gradient. No external CA was detected in these cells either by potentiometric or mass-spectrometric assay. In the absence of external CA, the rate of photosynthetic O2 evolution in the pH range 7.5 to 8.0 did not exceed the calculated rate of CO2 supply, indicating a limited capacity for HCO2 uptake in these cells. Electrophysiological measurements indicate that CO2 uptake is electrically silent and thus is not a consequence of H+-CO2 symport activity. Microsomal membranes isolated from Eremosphaera showed ATPase activity which was enhanced by CO2. These results indicate that active CO2 uptake is mediated by an ATPase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197046
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  • 6
    Electronic Resource
    Electronic Resource
    Snow and cloud feedbacks modelled by an atmospheric general circulation model (1994)
    Springer
    Climate dynamics 9 (1994), S. 253-265 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract. One of the most important parametrizations in general circulation models used for climate change experiments is that of the surface albedo. The results of an albedo feedback experiment carried out under the auspices of the US Department of Energy are presented. An analysis of long and short wave components of the model response shows that short wave response dominates changes in fixed to variable albedo experiments, but that long wave response dominates in clear to cloudy sky changes. Cloud distribution changes are also discussed and are related to changes in global sensitivity. At the surface, the heat balance change for perturbed sea surface temperatures is dominated by changes in latent heat flux and downward long wave radiation. If albedo is freed up however, the major contrast lies in the change in surface reflected short wave radiation, amplified by changes in downward short wave radiation caused by cloud amount changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050024
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  • 7
    Electronic Resource
    Electronic Resource
    Snow and cloud feedbacks modelled by an atmospheric general circulation model (1994)
    Springer
    Climate dynamics 9 (1994), S. 253-265 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract One of the most important parametrizations in general circulation models used for climate change experiments is that of the surface albedo. The results of an albedo feedback experiment carried out under the auspices of the US Department of Energy are presented. An analysis of long and short wave components of the model response shows that short wave response dominates changes in fixed to variable albedo experiments, but that long wave response dominates in clear to cloudy sky changes. Cloud distribution changes are also discussed and are related to changes in global sensitivity. At the surface, the heat balance change for perturbed sea surface temperatures is dominated by changes in latent heat flux and downward long wave radiation. If albedo is freed up however, the major contrast lies in the change in surface reflected short wave radiation, amplified by changes in downward short wave radiation caused by cloud amount changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208257
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  • 8
    Electronic Resource
    Electronic Resource
    Characterization of a malate dehydrogenase in the cyanobacterium Coccochloris peniocystis (1991)
    Springer
    Archives of microbiology 156 (1991), S. 28-33 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Coccochloris peniocystis ; Malate dehydrogenase ; Glyoxylate cycle ; TCA cycle ; Carbon metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A malate dehydrogenase (MDH) was characterized from the cyanobacterium Coccochloris peniocystis. The enzyme was purified approximately 180-fold and had a molecular weight of about 90000. The enzyme had a pH optimum of pH 6.7 to 7.5; a Km (malate) of 5.6 mM and Kms for NAD and NADP of 24 μM and 178 μM, respectively, although similar Vmax were obtained with either pyridine nucleotide. Enzyme activity was inhibited by ATP, citrate, oxalacetate, acetyl CoA and CoA. Enzyme assays with uniformly 14C-labelled malate caused no 14CO2 release, indicating this MDH is not a malic enzyme. Electrophoresis and S-200 gel filtration of the partially purified enzyme indicated a single MDH was present in this preparation. A second, less abundant, MDH was present in crude extracts. The presence of MDH in this organism is consistent with the operation of a glyoxylate cycle which, in the absence of a TCA cycle, would provide organic acids required in secondary carbon metabolism. ATP inhibition of MDH may allow for light regulation of MDH activity since, in the light, oxaloacetic acid is generated by phosphoenolpyruvate carboxylase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418183
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  • 9
    Electronic Resource
    Electronic Resource
    Formation and metabolism of glycolate in the cyanobacterium Coccochloris peniocystis (1992)
    Springer
    Archives of microbiology 157 (1992), S. 375-380 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Coccochloris peniocystis ; Glycolate metabolism ; Photosynthesis ; Glyoxylate cycle ; Photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The formation and metabolism of glycolate in the cyanobacterium Coccochloris peniocystis was investigated and the activities of enzymes of glycolate metabolism assayed. Photosynthetic 14CO2 incorporation was O2 insensitive and no labelled glycolate could be detected in cells incubated at 2 and 21% O2. Under conditions of 100% O2 glycolate comprised less than 1% of the acid-stable products indicating ribulose 1,5 bisphosphate (RuBP) oxidation only occurs under conditions of extreme O2 stress. Metabolism of [1-14C] glycolate indicated that as much as 62% of 14C metabolized was released as 14CO2 in the dark. Metabolism of labelled glycolate, particularly incorporation of 14C into glycine, was inhibited by the amino-transferase inhibitor amino-oxyacetate. Metabolism of [2-14C] glycine was not inhibited by the serine hydroxymethyltransferase inhibitor isonicotinic acid hydrazide and little or no labelled serine was detected as a result of 14C-glycolate metabolism. These findings indicate that a significant amount of metabolized glycolate is totally oxidized to CO2 via formate. The remainder is converted to glycine or metabolized via a glyoxylate cycle. The conversion of glycine to serine contributes little to glycolate metabolism and the absence of hydroxypyruvate reductase confirms that the glycolate pathway is incomplete in this cyanobacterium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248684
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  • 10
    Electronic Resource
    Electronic Resource
    Exclusion of two candidate pigment loci, c and b, part of chromosome 11p, and 33 random polymorphic markers as the locus for tyrosinase-positive oculocutaneous albinism (1993)
    Springer
    Human genetics 〈Berlin〉 90 (1993), S. 556-560 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The locus for Tyrosinase-Positive Oculocutaneous Albinism (ty-pos OCA) has not yet been localised. The search for the ty-pos OCA locus has included a search for linkage to candidate pigment loci and a candidate chromosomal region, as well as a random search using highly polymorphic markers in 42 families, including 271 individuals of whom 79 are affected. The lod scores for the tyrosinase (TYR) locus (11q14–q21), homologous to the albino locus, c, in the mouse and the CAS2/TRP1 locus (9p22-pter), homologous to the brown locus, b, in the mouse were -5.89 and -7.22, respectively, at a recombination fraction of θ=0.01, thus excluding them from being the ty-pos OCA locus. In the candidate chromosomal region, 11p, four loci (probes) were tested, SAA (pSAA82), CALC (pHC36), HBB (Gamma-globin haplotype) and an AC repeat polymorphism at the Wilm's Tumour locus (WT1). A portion of 11p was excluded with the following lod scores: pSAA82 lod=-2.05 at θ=0.10; pHC36 lod=-3.87 at θ=0.05; gamma-globin haplotype lod=-2.80 at θ=0.10; and WT1 lod=-2.34 at θ=0.10. Thirty-three polymorphic markers randomly distributed on 13 different chromosomes were all excluded from close linkage to ty-pos OCA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217458
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