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  • 1
    Electronic Resource
    Electronic Resource
    Feeding ecology and interannual variations in diet of larval jack mackerel, Trachurus declivis (Pisces: Carangidae), from coastal waters of eastern Tasmania (1992)
    Springer
    Marine biology 113 (1992), S. 11-20 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Crustacean microzooplankton were the main prey of larval Trachurus declivis collected in the summers of 1988, 1989 and 1990 from coastal waters of eastern Tasmania. The diet was dominated by harpacticoids (Microsetella rosea), cyclopoids (mainly Oithona spp.), calanoids and the calyptopis stage of the euphausiid Nyctiphanes australis. Bivalve veligers were occasionally eaten. Diets of larvae were affected by interannual variations in plankton composition, particularly in 1989 when intrusions of low-nutrient subtropical water exclused large zooplankters (e.g. N. australis) from the study area. Larvae≤6 mm selected for copepod nauplii; all larvae selected for M. rosea, cyclopoids, and the calyptopis stage of N. australis. Even though calanoids were a major prey taxon, there were proportionally fewer eaten than were present in the environment. In all, 78% of larvae taken during the daytime had food in their stomachs, as opposed to 38% of the larvae from night samples. Feedmid-morning and late afternoon. A gut evacuation rate of ∼4 to 6 h was estimated. We calculated that the larvae ate between 9 and 13% of their body weight in food per day. The larvae of T. declivis in this study were not sufficiently abundant to have an impact on their prey.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367633
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  • 2
    Electronic Resource
    Electronic Resource
    Estimates of bacterial productivity in marine sediments and water from a temperate saltmarsh lagoon (1992)
    Springer
    Microbial ecology 23 (1992), S. 195-209 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tritiated thymidine incorporation (TTI) into DNA was used to estimate bacterial productivity in sediment and water samples from two sites in Langebaan Lagoon, South Africa. Routine analysis of isotope dilution showed seasonal variations of approximately threefold in the thymidine precursor pool sizes for bacterial assemblages from each site. Dual label incorporation of [3H]-thymidine and 14C-leucine into DNA and protein, respectively, showed that pelagic but not sediment assemblages were in a balanced state of growth during TTI. This is the first report of dual label measurements of bacterial production in sediments. Sediments supported bacterial productivities that exceeded those in the water column by factors from five- to 950-fold, whereas bacterial abundance supported by sediments exceeded that in the water column by more than 3 orders of magnitude. Estimates of bacterial productivities in sediments were coincident with levels of organic content in sediments, but not with bacterial abundance. Measurements of TTI activity for 5 different benthic microhabitats at one lagoon site showed highest activity associated with seagrass beds (2.11 ± 0.84 nmol thymidine hours−1 g-1 dry weight), whereas activities decreased with depth (0.46 ± 0.21 nmol thymidine hours−1 g−I dry weight) below sediment surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164096
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  • 3
    Electronic Resource
    Electronic Resource
    Action potential refractory period in axonal demyelination: a computer simulation (1992)
    Springer
    Biological cybernetics 67 (1992), S. 545-552 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Axonal demyelination leads to an increase in the refractory period for propagation of the action potential. Computer simulations were used to investigate the mechanism by which changes in the passive properties of the internodal membrane increase the refractory period. The properties of the voltage dependent ion channels can be altered to restore conduction in demyeliated nerve fibers. The ability of these alterations to decrease the refractory period of demyelinated model nerve fibers was compared. The model nerve fiber contained six nodes. The action potential was stimulated at node one and propagated to node six. The internode between nodes three and four was demyelinated in a graded manner. The absolute refractory period for propagation of the action potential through the demyelinated internode increased as the number of myelin wraps was reduced to less than 25% of the normal value. The increase in refractory period was found to be due to a reduction in the rate or repolarization of the action potential at node three. The delay in repolarization reduced the rate of recovery of inactivated Na channels and slowed the closing of K channels. The rate of repolarization of node three was reduced by the conduction delay for the depolarization of node four caused by demyelination of the preceeding internode. In these simulations the increase in refractory period due to demyelination was eliminated by slowing the onset of Na channel inactivation. A small reduction of the K conductance also decreased the refractory period. However, larger reductions eliminated this effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198761
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  • 4
    Electronic Resource
    Electronic Resource
    Ability of vertebral dimensions from a single radiograph to identify fractures (1992)
    Springer
    Calcified tissue international 51 (1992), S. 95-99 
    Details
    ISSN: 1432-0827
    Keywords: Epidemiology ; Vertebral fractures ; Morphology ; Prospective studies ; Fracture prevalence, incidence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary It has been proposed that vertebral dimensions be used to objectively identify vertebral fractures, permitting standardization of methodology for comparisons between studies. In this report, we evaluate the ability of various vertebral dimensions and ratios to identify “abnormal” vertebrae. As no “gold standard” exists for prevalent vertebral fractures, we examined the ability of cross-sectional dimensions (at a single point in time) to detect fractured vertebrae that had been identified from changes in dimensions compared with previous radiographs. Theoretically, a cutoff of 3 SD below the mean will rarely misclassify normal vertebrae as fractured (specificity=99.9%). However, we found that this cutoff correctly identified only about 70% of the incident fractures. A less stringent criterion (2 SD below the mean; theoretical specificity=97.7%) identified about 85–90% of true fractures. Dividing by stature or other vertebral heights sometimes yielded marginal improvements in the ability of the anterior or posterior height dimensions to diagnose fractures. The results suggest that the true fracture prevalence may sometimes be substantially higher than suggested by cross-sectional vertebral measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298495
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  • 5
    Electronic Resource
    Electronic Resource
    A biodegradable composite artificial tendon (1992)
    Springer
    Journal of materials science 3 (1992), S. 359-364 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The development of a completely biodegradable composite artificial tendon prosthesis that mimics the structure and stress-strain response of natural tendon is presented. The artificial tendon is a composite of water-swollen poly(2-hydroxyethylmethacrylate)/poly(caprolactone) blend hydrogel matrix reinforced with poly(lactic acid) fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705368
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  • 6
    Electronic Resource
    Electronic Resource
    Extracellular recordings from the motor nervous system of the nematode, Ascaris suum (1992)
    Springer
    Journal of comparative physiology 171 (1992), S. 17-28 
    Details
    ISSN: 1432-1351
    Keywords: Ascaris suum ; Nematode ; Motor nervous ; system ; Extracellular recording ; Extracellular spike
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The close association of muscle and neurons in Ascaris suum makes it difficult to determine whether spikes recorded from nerve cords originate in muscle or neurons. We have developed criteria that distinguish muscle and neuronal activity. There are two categories of extracellular spikes. 2. The first category consists of spikes with a wide range of amplitudes, marked by large spikes. These spikes, which can be recorded over lateral muscle and over the dorsal and ventral nerve cords, are abolished when muscle is disrupted or removed, or when curare is applied. Large spikes are relatively infrequent, are correlated with intracellularly recorded muscle events, and respond to polarizations of motor neurons, implying that they originate in muscle. 3. The second spike category, small amplitude spikes, is exclusive to the ventral nerve cord, occurs more frequently than large spikes and displays patterned firing. Small spikes are not affected by muscle removal or by curare, and are correlated with motor neuronal postsynaptic potentials, but not with intracellularly recorded muscle events. We infer that they originate in neurons. 4. Low level activity recorded extracellularly over nerve cords may represent muscle activity due to tonic motor neuronal synaptic transmission. It responds to motor neuronal polarization and is suppressed by curare or muscle removal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195957
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  • 7
    Electronic Resource
    Electronic Resource
    Neodymium isotopic evidence for the tectonic assembly of Late Archean crust in the Slave Province, northwest Canada (1992)
    Springer
    Contributions to mineralogy and petrology 111 (1992), S. 493-504 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The ca. 2.7–2.5 Ga Slave Province is a “granitegreenstone” terrane comprising deformed sedimentary and subordinate volcanic belts extensively intruded by granitoid rocks. The Nd isotopic data are reported for 58 samples of supracrustal and granitoid rocks exposed along a 400 km, east-west, transect at 65°N across the structural grain of the province. Initial ɛ Nd values reveal distinctly different crustal sources in the eastern compared to the western parts of the province, as expected from tectonic assembly of the province through accretion of juvenile crust to older continental crust. Supracrustal sequences (ca. 2.71–2.65 Ga) from the central and eastern parts of the province have positive ɛ Nd(1) values (+0.3 to +3.6), consistent with juvenile sources and formation remote from significantly older crust. Syn to late-deformation (ca. 2.63–2.60 Ga), mantle-derived diorites and related tonalites (type I) from the central and eastern parts of the province have similar initial ɛ Nd values (-0.1 to +2.7). In contrast, samples from the westernmost plutons, which intrude exposed pre-3.1 Ga crust, have much lower ɛ Nd(1) values (-1.0 to4.6) suggesting contamination of these magmas by older crust. The ɛ Nd(1) values of post-deformation granites (s.s.) (type II) also vary systematically across the province: values for granites west of longitude 110°30′W range from-0.2 to -5.3; those to the east range from +0.6 to +3.7. These data suggest mixed crustal sources dominated by Mid to Early Archean material (ɛ Nd-2.6 to- 17 at 2.6 Ga) for the western granitoid rocks and juvenile sources for the eastern granites. The Nd isotopic data are consistent with the geology of the province in that exposures of Mid to Early Archean crustal rocks, predating the principal 2.7–2.5 Ga orogenic event are restricted to the western part of the province. The asymmetric pattern defined by the Nd isotopic data indicates the presence of distinct crustal rocks beneath the Slave Province. Similar isotopic variations observed across Phanerozoic collisional orogens have been interpreted to reflect tectonic assembly of crust by accretion of juvenile crustal terranes to an older continental margin. This process may also have been an important mechanism in the cratonization of the Slave Province.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320904
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  • 8
    Electronic Resource
    Electronic Resource
    Mississippi-Alabama outer continental shelf topographic features formed during the late Pleistocene-Holocene transgression (1992)
    Springer
    Geo-marine letters 12 (1992), S. 41-48 
    Details
    ISSN: 1432-1157
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A geophysical survey of the outer Missisippi-Alabama continental shelf revealed three types of topographic features: 1) reef-like mounds (RLM), 2) isobath-parallel ridges, and 3) shallow depressions. RLM appear to be bioherms. Their bases cluster in two isobath bands, 105 to 120 m and 74 to 82 m, implying the late Pleistocene-Holocene transgression was nonuniform. The deeper RLM probably formed during a slow sea level rise at the beginning of the deglaciation. An 11 ka BP C14 age was obtained from the summit of one, at a depth of 90 m. Depth relationships suggest the shallower RLM and most ridges formed about the time of the mid-deglacial Younger Dryas cooling episode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02092107
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  • 9
    Electronic Resource
    Electronic Resource
    Almost difference sets and reversible divisible difference sets (1992)
    Springer
    Archiv der Mathematik 59 (1992), S. 595-602 
    Details
    ISSN: 1420-8938
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01194853
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  • 10
    Electronic Resource
    Electronic Resource
    The end of cold dark matter? (1992)
    [s.l.] : Nature Publishing Group
    Nature 356 (1992), S. 489-494 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The successful cold dark matter (CDM) theory for the formation of structure in the Universe has suffered recent setbacks from observational evidence suggesting that there is more large-scale structure than it can explain. This may force a fundamental revision or even abandonment of the theory, or ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/356489a0
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