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  • Springer  (221)
  • Oxford University Press  (79)
  • American Chemical Society (ACS)  (35)
  • American Physical Society (APS)  (30)
  • Nature Publishing Group (NPG)
  • 2010-2014  (265)
  • 1990-1994  (112)
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  • 1
    Electronic Resource
    Electronic Resource
    The aggregation states of spinach phosphoribulokinase (1990)
    Springer
    Planta 181 (1990), S. 349-357 
    Details
    ISSN: 1432-2048
    Keywords: Light/dark regulation ; Phosphoribulokinase ; Protein aggregation ; Spinacia (phosphoribulokinase)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phosphoribulokinase (PRK; EC 2.1.7.19) is active in illuminated chloroplasts and inactive in darkened chloroplasts. This regulatory mechanism is mediated by thioredoxin-dependent reduction of a kinase disulfide in vivo. Extracts of spinach (Spinacia oleracea L.) leaves in the presence of 10 mM dithiothreitol contain a single 80-kDa form of PRK as judged by gel filtration. Gel filtration of thiol-free extracts of light-harvested tissue shows the presence of two inactive forms of PRK, the 80-kDa form and an aggregate (〉 550 kDa) form, but treatment of both forms with dithiothreitol restores kinase activity. Gel filtration following extraction of dark-harvested tissue in the absence of dithiotreitol demonstrates the presence of only the heavier form. Inclusion of 400 mM (NH4)2SO4 in the homogenization buffer during extraction of light-harvested tissue suppresses the formation of the high-M r form of PRK, but does not eliminate the aggregate form observed in extracts of dark-harvested leaves. However, prolonged treatment of extracts from dark-harvested tissue with 400 mM (NH4)2SO4 results in conversion of the high-M r form of phosphoribulokinase to the low-M r form. The data are consistent with the heavier form of phosphoribulokinase being the normal in-vivo aggregation state in the dark, while the lighter form is the normal aggregation state in the light. This research was sponsored jointly by the science and education administration of the U.S. Department of Agriculture under Grant No. 88-37130-3722 from the Competitive Research Grants Office and by the Office of Health and Environmental Research, U.S. Department of Energy under Contract DE-AC05-84OR21400 with Martin Marietta Energy Systems Inc., Oak Ridge, Tenn., USA. The author is Postdoctoral Investigator supported by the U.S. Department of Agriculture through Subcontract No. 88-37130-3722 from the Biology Division of Oak Ridge National Laboratory to the University of Tennessee.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195887
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  • 2
    Electronic Resource
    Electronic Resource
    A numerical study of supersonic turbulence (1992)
    Springer
    Theoretical and computational fluid dynamics 4 (1992), S. 13-49 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We report on simulations of nonstationary supersonic isotropic turbulent flow using the Piecewise-Parabolic Method on uniform grids of 20482 in two dimensions and 2563 in three dimensions. Intersecting shock waves initiate the transfer of energy from long to short wavelengths. Weak shocks survive for many acoustic times τac. In two dimensions eddies merge over many τac. In three dimensions vortex sheets break-up into short vortex filaments within two τac. Entropy fluctuations, produced by strong shocks, are stretched into filaments over several τac. These filaments persist and are mirrored in the density. We observe three temporal phases: onset, with the initial formation of shocks; quasi-supersonic, with strong density contrasts; and post-supersonic, with a slowly decaying root mean square Mach number. Compressive modes quickly establish a k −2 velocity power spectrum. In three dimensions solenoidal modes build-up during the supersonic phase delineating through time a Kolmogorov k −5/3 envelope and leaving a self-similarly decaying ∼k −0.9 spectrum at lower wave numbers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417962
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  • 3
    Electronic Resource
    Electronic Resource
    Relationship between phototrophy and phagotrophy in the mixotrophic chrysophytePoterioochromonas malhamensis (1990)
    Springer
    Microbial ecology 19 (1990), S. 97-109 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The time scales involved in the transition between phototrophic and phagotrophic modes of nutrition were examined in the mixotrophic chrysophytePoterioochromonas malhamensis. Phagotrophy began almost immediately when bacteria were added to phototrophically growing cultures of the alga, and chlorophylla concentration per cell in these cultures decreased over a 24-hour period. Chlorophyll concentrations per cell began to increase when bacteria were grazed to a density of approximately 106 ml−1, but after more than 24 hours they had not returned to the higher chlorophyll concentrations observed in the phototrophically grown cultures. Bacterivory was the dominant mode of nutrition in all cultures containing heat-killed bacteria. Photosynthesis did not contribute more than ≈7% of the total carbon budget of the alga when in the presence of abundant heat-killed bacteria. Bacterial density was the primary factor influencing the ability ofP. malhamensis to feed phagotrophically, while light intensity, pH, and the presence of dissolved organic matter had no effect on phagotrophy. We conclude thatP. malhamensis is capable of phagotrophy at all times. In contrast, phototrophy is inducible in the light during starvation and is a long-term survival strategy for this mixotrophic alga (i.e., it operates on time scales greater than a diel cycle).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02015056
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  • 4
    Electronic Resource
    Electronic Resource
    Broadband ultrasound attenuation and dual energy X-ray absorptiometry in patients with hip fractures: Which technique discriminates fracture risk (1994)
    Springer
    Calcified tissue international 54 (1994), S. 466-469 
    Details
    ISSN: 1432-0827
    Keywords: Osteoporosis ; Ultrasound ; Hip fractures ; Bone density ; DXA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract There is considerable interest in predicting risk of hip fracture in order to allow targeting of preventive care. This study aimed to determine which of two methods best discriminates a hip fracture population from controls. Fifty women with fractured neck of femur, and 50 control subjects were scanned using dual energy X-ray absorptiometry (DXA) of the spine and hip and broadband ultrasound attenuation (BUA) of the os calcis. Significant differences between the two populations could be found for both DXA and BUA, with BUA showing the largest percentage difference (27%). The mean z-scores showed that BUA had the lowest, with the exception of DXA trochanter. However, no significant difference between BUA and DXA trochanter Z-scores was found. A receiver operator characteristic (ROC) analysis showed that BUA has a superior sensitivity and specificity compared with DXA measurements, with DXA of the hip being better than the spine. This retrospective study shows that BUA is a better discriminator of hip fracture than DXA lumbar spine of DXA hip, which may have important implications for predicting those at risk of future hip fracture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334324
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  • 5
    Electronic Resource
    Electronic Resource
    Reproduction by virgin queen fire ants in queenless colonies: Comparative study of three taxa (Solenopsis richteri, hybridS. invicta/richteri, S. geminata) (Hymenoptera: Formicidae) (1993)
    Springer
    Insectes sociaux 40 (1993), S. 283-293 
    Details
    ISSN: 1420-9098
    Keywords: Fire ants ; virgin queens ; reproduction ; execution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the fire ant,Solenopsis invicta, some winged virgin queens are known to shed their wings (dealate) upon removal of the mated mother queen. These virgin queens then develop their ovaries and begin to lay eggs, thereby foregoing the option of leaving on mating flights and attempting to found their own colonies. Such a response of virgin queens to queenlessness has not been reported for other ants. In order to determine if virgin queens of some other fire ants (subgenusSolenopsis) would respond in the same way, experiments were conducted onS. richteri, hybridS. invicta/richteri andS. geminata, a member of a species complex different from that of the other taxa. Just as inS. invicta, virgin queens ofS. richteri and the hybrid dealated and began to lay eggs within days of the removal of the queen. In addition, workers executed many of the reproductively active virgin queens, a phenomenon also found inS. invicta. In contrast, virgin queens ofS. geminata did not dealate or quickly begin to lay eggs upon separation from the queen. Reasons for the variability in the response of virgin queens of the different species may be 1) higher probability of reproductive success for unmated dealated queens compared to normal claustral founding inS. invicta andS. richteri linked to relatively frequent loss of the mother queen; or 2) phylogenetic constraint.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01242364
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  • 6
    Electronic Resource
    Electronic Resource
    Recovery of the coral Montastrea annularis in the Florida Keys after the 1987 Caribbean “bleaching event” (1993)
    Springer
    Coral reefs 12 (1993), S. 57-64 
    Details
    ISSN: 1432-0975
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Many reef-building corals and other cnidarians lost photosynthetic pigments and symbiotic algae (zooxanthellae) during the coral bleaching event in the Caribbean in 1987. The Florida Reef Tract included some of the first documented cases, with widespread bleaching of the massive coral Montastrea annularis beginning in late August. Phototransects at Carysfort Reef showed discoloration of 〉90% of colonies of this species in March 1988 compared to 0% in July 1986; however no mortality was observed between 1986 and 1988. Samples of corals collected in February and June 1988 had zooxanthellae densities ranging from 0.1 in the most lightly colored corals, to 1.6x106 cells/cm2 in the darker corals. Minimum densities increased to 0.5x106 cells/cm2 by August 1989. Chlorophyll-a content of zooxanthellae and zooxanthellar mitotic indices were significantly higher in corals with lower densities of zooxanthellae, suggesting that zooxanthellar at low densities may be more nutrientsufficient than those in unbleached corals. Ash-free dry weight of coral tissue was positively correlated with zooxanthellae density at all sample times and was significantly lower in June 1988 compared to August 1989. Proteins and lipids per cm2 were significantly higher in August 1989 than in February or June, 1988. Although recovery of zooxanthellae density and coral pigmentation to normal levels may occur in less than one year, regrowth of tissue biomass and energy stores lost during the period of low symbiont densities may take significantly longer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00302102
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  • 7
    Electronic Resource
    Electronic Resource
    Social organization in deer: Implications for localized management (1991)
    Springer
    Environmental management 15 (1991), S. 809-814 
    Details
    ISSN: 1432-1009
    Keywords: White-tailed deer ; Odocoileus virginianus ; Behavior ; Philopatry ; Population management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Populations of white-tailed deer (Odocoileus virginianus) inhabiting many state and national parks and suburban areas have grown to the point that they conflict with human activities. Conflicts range from destruction of vegetation through browsing to public perception that diseases carried by deer pose threats to human health. Traditional modes of hunting to control populations are inappropriate in many of these areas because of intense human development and activity. This article explores an alternative approach for population reduction based on deer social organization. Female white-tailed deer are highly philopatric and female offspring remain near their dams for life. This suggests that a population expands slowly as a series of overlapping home ranges in a form analogous to the petals on a rose. Incorporating the rose petal concept into a model of population growth shows that removal of deer by family unit can potentially alleviate conflicts in localized areas for as many as 10–15 yr.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02394818
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  • 8
    Electronic Resource
    Electronic Resource
    Absorption of theophylline from a new theophylline controlled-release capsule (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 319-320 
    Details
    ISSN: 1432-1041
    Keywords: Theophylline ; controlled-release formulation ; absorption ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315219
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  • 9
    Electronic Resource
    Electronic Resource
    An experimental examination into the design of decentralized methods to solve the assignment problem with and without money (1994)
    Springer
    Economic theory 4 (1994), S. 11-40 
    Details
    ISSN: 1432-0479
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Summary An experimental examination of the assignment problem, matching individuals to positions or slots, is conducted in which various assignment mechanisms are analyzed. Generalized versions of both the Vickrey and English auctions are designed to solve the assignment problem along with oridinal ranking mechanisms (serial dictator and “funny” money system). The generalized auctions result in efficient allocations. In contrast, the ordinal ranking mechanisms, which require no monetary transfers, are significantly less efficient in their assignments. However, the efficient allocations obtained from the competitive bidding processes are at the expense of consumers' surplus since demanders retain significantly larger profits with the ordinal ranking mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01211117
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  • 10
    Electronic Resource
    Electronic Resource
    Recent progress on higher order moment neural arrays (1993)
    Springer
    Circuits, systems and signal processing 12 (1993), S. 309-329 
    Details
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Higher order moment computations are generally necessary wherever the recognition task exceeds the confines of linearity. This paper provides an overview of recent progress on a specific neural network design, which explicitly uses higher order moment information. Attention is focused on the training algorithms used in the design and on network performance in prototype applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01189879
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