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  • Springer  (62,697)
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  • 1970-1974
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  • 1992  (62,697)
  • 1
    Electronic Resource
    Electronic Resource
    Composting of explosives and propellant contaminated soils under thermophilic and mesophilic conditions (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 137-144 
    Details
    ISSN: 1476-5535
    Keywords: Composting ; Explosives ; Propellants ; Thermophilic ; Mesophilic ; Bioremediation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Composting was investigated as a bioremediation technology for clean-up of sediments contaminated with explosives and propellants. Two field demonstrations were conducted, the first using 2,4,6-trinitrotoluene (TNT), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine (HMX), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and N-methyl-N,2,4,6-tetranitroaniline (tetryl) contaminated sediment, and the second using nitrocellulose (NC) contaminated soil. Tests were conducted in thermophilic and mesophilic aerated static piles. Extractable TNT was reduced from 11840 mg/kg to 3 mg/kg, and NC from 13090 mg/kg to 16 mg/kg under thermophilic conditions. Under mesophilic conditions, TNT was reduced from 11 190 mg/kg to 50 mg/kg. The thermophilic and mesophilic half-lives were 11.9 and 21.9 days for TNT, 17.3 and 30.1 days for RDX, and 22.8 and 42.0 days for HMX, respectively. Known nitroaromatic transformation products increased in concentration over the first several weeks of the test period, but decreased to low concentrations thereafter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569746
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  • 2
    Electronic Resource
    Electronic Resource
    Purification and properties of extracellularβ-fructofuranosidases fromAureobasidium sp. ATCC 20524 (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 145-147 
    Details
    ISSN: 1476-5535
    Keywords: Fructo-oligosaccharide ; 1-Kestose ; Glycoprotein ; Fructosyl-transferring activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Two extracellular β-fructofuranosidases (E-1 andE-2) fromAureobasidium sp. ATCC 20524, producing 1-kestose (1F-β-fructofuranosyl-sucrose) from sucrose, were purified to homogeneity. Molecular weights of the enzymes were estimated to be about 304000 (E-1) and 315000 (E-2) Da by gel filtration. The enzymes contained 33% (w/w) (E-1) and 27% (w/w) (E-2) carbohydrate. TheK m values for sucrose ofE-1 andE-2 andE-2 were 0.34 and 0.28 M, respectively. were 0.34 and 0.28 M, respectively. The enzymatic profiles of these enzymes were almost identical to intracellular enzymesP-1 andP-2 except for the differences in carbohydrate content andK m values ofE-2 andP-2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569747
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  • 3
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    Insect fungal symbionts: A promising source of detoxifying enzymes (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 149-161 
    Details
    ISSN: 1476-5535
    Keywords: Toxin ; Secondary plant metabolite ; Allelochemical ; Insecticide ; Mycotoxin ; Endocytobiont
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Many species of insects cultivate, inoculate, or contain symbiotic fungi. Insects feed on plant materials that contain plant-produced defensive toxins, or are exposed to insecticides or other pesticides when they become economically important pests. Therefore, it is likely that the symbiotic fungi are also exposed to these toxins and may actually contribute to detoxification of these compounds. Fungi associated with bark beetles, ambrosia beetles, termites, leaf-cutting ants, long-horned beetles, wood wasps, and drug store beetles can variously metabolize/detoxify tannins, lignins, terpenes, esters, chlorinated hydrocarbons, and other toxins. The fungi (Attamyces) cultivated by the ants and the yeast (Symbiotaphrina) contained in the cigarette beetle gut appear to have broad-spectrum detoxifying abilities. The present limiting factor for using many of these fungi for large scale detoxification of, for example, contaminated soils or agricultural commodities is their slow growth rate, but conventional strain selection techniques or biotechnological approaches should overcome this problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569619
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  • 4
    Electronic Resource
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    Biosensors for process monitoring (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 163-172 
    Details
    ISSN: 1476-5535
    Keywords: Biosensors ; Process control ; Enzyme thermistor ; Immunoassay ; Bio-field effect transistor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A short review about the biosensor research activities for bioprocess monitoring in the F.R.G. after its reunification is given. The principles of biosensor applications are presented. In situ sensors and sensors based on the principles of flow injection analysis are studied. Some applications of a four-channel enzyme thermistor, bio-field effect transistors, and immunoanalysis systems for real process monitoring are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569620
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  • 5
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    Ecology ofVibrio vulnificus in Galveston Bay oysters, suspended particulate matter, sediment and seawater: Detection by monoclonal antibody — immunoassay — most probable number procedures (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 219-223 
    Details
    ISSN: 1476-5535
    Keywords: Vibrio vulnificus ; Oyster ; Monoclonal antibody ; Most probable number ; Enzyme immunoassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Oysters, suspended particulate matter (SPM), sediment and seawater samples were collected from West Galveston Bay, Texas over a 16-month period and analyzed for the presence ofVibrio vulnificus, a naturally-occurring human marine pathogen. Detection and enumeration ofV. vulnificus was performed using a species-specific monoclonal antibody (mAb FRBT37) in an enzyme immunoassay (EIA)-most probable number (MPN) procedure capable of detecting as few as 2000 target organisms.V. vulnificus was not detected in seawater, oyster or SPM samples during the cold weather months, but was detected at low levels in several sediment samples during this time period. Increased levels of the organism were first observed in early spring in the sediment, and then in SPM and oysters. The major increase inV. vulnificus occurred only after the seawater temperature had increased above 20°C and the winter-spring rainfall had lowered the salinity below 16‰. The highestV. vulnificus levels at each site were associated with suspended particulate matter. These results are consistent with the hypothesis that (1)V. vulnificus over-winters in a floc zone present at the sediment-water interface, (2) is resuspended into the water column in early spring following changes in climatic conditions, (3) colonizes the surfaces of zooplankton which are also blooming during early spring and (4) are ingested by oysters during their normal feeding process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569626
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  • 6
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    Conversion of sodium cyanide to carbon dioxide and ammonia by immobilized cells ofPseudomonas putida (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 235-238 
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    ISSN: 1476-5535
    Keywords: Biodegradation ; Pseudomonas putida ; Immobilization ; Sodium cyanide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Pseudomonas putida, isolated from contaminated industrial wastewaters and soil sites, was found to utilize sodium cyanide (NaCN) as a sole source of carbon and nitrogen. Cells, immobilized in calcium alginate beads (1–2 mm diameter) were aerated in air-uplift-type fluidized batch bioreactor containing 100–400 ppm of NaCN. Degradation of NaCN was monitored for 168 h by analyzing gaseous and dissolved ammonia (NH3), CO2, pH and optical density. The results indicated that the alginate-immobilized cells ofP. putida were able to degrade NaCN into NH3 and CO2 in a time-dependent manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569629
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  • 7
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    Changes in protein composition ofSaccharomyces brewing strains in response to heat shock and ethanol stress (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 229-234 
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    ISSN: 1476-5535
    Keywords: Heat shock protein (HSP) ; Yeast ; Saccharomyces ; Viability ; Thermotolerance ; Ethanol tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Heat shock and ethanol stress of brewing yeast strains resulted in the induction of a set of proteins referred to as heat shock proteins (HSPs). At least six strongly induced HSPs were identified in a lager brewing strain and four HSPs in an ale brewing strain. Four of these HSPs with molecular masses of approximately 70, 38, 26 and 23 kDa were also identified in two laboratory strains ofSaccharomyces cerevisiae. The appearance of HSPs correlated with increased survival of strains at elevated temperatures and high concentrations of ethanol. These results suggest that HSPs may play a role in the ethanol and thermotolerance of yeasts. The properties of these proteins and membrane fatty acids in relation to heat and ethanol shock are being investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569628
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  • 8
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    Isolation and characterization of a novel polysaccharide fromBacillus licheniformis NCIB 11634 (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 239-245 
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    ISSN: 1476-5535
    Keywords: Novel polysaccharide ; Bacillus licheniformis ; Raffia venifera ; d-Glucose ; d-Mannose ; d-Xylose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A polysaccharide producing strain ofBacillus licheniformis was isolated from exudate of raffia palm,Raffia vinifera. The optimum conditions for growth and polysaccharide production have been investigated and established. No appreciable polysaccharide was formed on glucose. It grew best in Czapek-Dox media with sucrose as the carbon source. The polysaccharide has been characterized as a heteropolymer containingd-glucose,d-mannose andd-xylose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569630
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  • 9
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    Announcement from the publisher (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 269-269 
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    ISSN: 1476-5535
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    URL: http://dx.doi.org/10.1007/BF01569634
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  • 10
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    Effect of deglycosylation on the properties of β-fructofuranosidaseP-1 fromAureobasidium sp. ATCC 20524 (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 251-255 
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    ISSN: 1476-5535
    Keywords: β-Fructofuranosidase ; Deglycosylation ; Aureobasidium ; Enzymatic stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Most of the carbohydrate moiety of β-fructofuranosidaseP-1 fromAureobasidium sp. ATCC 20524 was removed by endo-β-N-acetylglucosaminidase F. A subunit of 94000 Da was observed in SDS-PAGE after deglycosylation. TheK m value for sucrose was not changed by deglycosylation but the stability at pH 4–5 and 50°C was decreased. The deglycosylated enzyme was more sensitive to proteases such as pronase E and subtilisin than the native enzyme. It is considered that the carbohydrate moiety of β-fructofuranosidaseP-1 contributes to the stability of the enzyme but is not essential in its catalytic function.
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    URL: http://dx.doi.org/10.1007/BF01569632
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  • 11
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    Modularity and reliability in the organization of organisms (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 1-20 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract An organism persists only if it satisfies internal and external constraints. Within the organism networks of processes meet the constraints. In such networks a principle of matching often obtains: the pattern of coupling among processes matches the correlation among constraints. That is, a module—a cluster of coupled processes—meets a constraint. Dissociable modules meet dissociàble constraints. A hierarchy of modules meets a hierarchy of constraints. We have inquired whether such matching is predicted by an optimality criterion in a simple example. We find that in an ensemble of networks with unreliable processes, the networks that meet the constraints with highest reliability obey the principle of matching. The difference in reliability between modular and nonmodular networks that meet the same constraints is a function of the probability of success per process. Our results suggest that this difference is maximal at a probability of success that increases monotonically with the number of processes in the network.
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    URL: http://dx.doi.org/10.1007/BF02458617
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  • 12
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    Maximum-likelihood estimation of the statistical distribution of Smith-Waterman local sequence similarity scores (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 59-75 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A method is described for estimating the distribution and hence testing the statistical significance of sequence similarity scores obtained during a data-bank search. Maximum-likelihood is used to fit a model to the scores, avoiding any costly simulation of random sequences. The method is applied in detail to the Smith-Waterman algorithm when gaps are allowed, and is shown to give results very similar to those obtained by simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02458620
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  • 13
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    A general theory for host seeking decisions in mosquitoes (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 401-412 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We develop a theory for host seeking decisions in mosquitoes that explicitly considers the tradeoffs mosquitoes face in allocation to somatic and gametic function. Specifically, we consider conditions under which mosquitoes should seek out nectar and blood hosts upon encountering host odours. Results from development of a dynamic model that considers free and crop energy states suggest that mosquitoes should seek out blood hosts under a wide variety of conditions but that decisions to seek nectar depends upon crop volume, concentration and free energy. This pattern arises because mosquitoes carrying large crop loads are constrained in their ability to obtain large blood meals due to space limitations in the abdomen. The predicted patterns of behaviour are supported by published observations of mosquito behaviour.
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    URL: http://dx.doi.org/10.1007/BF02464840
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  • 14
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    Rate maximizing and state variable theories of diet selection (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 413-422 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In behavioral ecology, diet selection is often predicted by using a theory in which it is assumed that behaviors have evolved to maximize the rate of intake of energy. In this theory, it is assumed that fitness is a monotonic function of energy intake. An alternative is to deal directly with fitness, measured in terms of expected reproduction, and thus connect short term behavior with reproduction. Following the usual assumptions of the theory of diet choice, fitness satisfies a partial differential-difference equation. Conditions under which rate maximizing and state variable theories of diet selection yield identical predictions are identified. When predation, as well as starvation, is a source of mortality, the identification is not as complete.
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    URL: http://dx.doi.org/10.1007/BF02464841
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  • 15
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    Components of uncertainty in clutch-size optimization (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 445-464 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Environmental uncertainty can be both a cause and consequence of chance variation in many of the phenotypic factors associated with the control of clutch size in birds. When such uncertainty inflates or otherwise influences the variance associated with expected reproductive success for any genotype, it will also influence the resulting phenotypic optima. Random variation that affects the evolution of clutch size optima explicitly may occur both within (intra-) and across (inter-) generations. Examples of intra-generational uncertainty could include chance variation in: (1) the quality and quantity of offspring, (2) parental quality, and (3) temporal resources like food. Inter-generational uncertainty would include chance variation in demographic and population characters. With respect to clutch (or litter) size, almost all forms of uncertainty tend to favor an optimum (genetic) strategy with a clutch that is smaller than the clutch associated with the apparent or actual maximal fitness of an individual parent. The overall effect of all the components of uncertainty can be evaluated through the integration of all this phenotypic variation: however each step of the integration is a conditional expectation of each component. Therefore, a single factor analysis may indicate a false optimum, and an integrated analysis of all components is necessary to evaluate the importance of their individual and joint effects on the adaptive evolution of clutch size.
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    URL: http://dx.doi.org/10.1007/BF02464843
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  • 16
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    Intra-specific competition and density dependent juvenile growth (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 503-519 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A difference equation model for the dynamics of a semelparous size-structured species consisting of juvenile and adult individuals is derived and studied. The adult population consists of two size classes, a smaller class and a larger more fertile class. Negative feedback occurs through slowed juvenile growth due to increased total population levels during the developmental period and consequently a smaller adult size at maturation. Intra-specific competition coefficients are size dependent and measure the strength of intra-specific competition between juveniles and adults. It is shown that equilibrium states in which adults and juveniles occur together at all times are in general destabilized by significantly increased juvenilevs adults competition with the result that stable periodic cycles appear, in which the generations alternate in time and hence avoid competition. This result supports the tenet that intra-specific competition between juveniles and adults is destabilizing. Exceptions to this destabilization principle are found, however, in which populations exhibiting non-equilibrium, aperiodic dynamics can be equilibrated by increase competition between juveniles and adults. This occurs, for example, when adult fertility and competition coefficients are significantly size class dependent.
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    URL: http://dx.doi.org/10.1007/BF02459632
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  • 17
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    Analysis of volume regulation in an epithelial cell model (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 537-561 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract An epithelial cell is modeled as a single compartment, bounded by apical and basolateral cell membranes, and containing two nonelectrolyte solute species, nominally NaCl and KCl. Membrane transport of these species may be metabolically driven, or it may follow the transmembrane concentration gradients, either singly (a channel) or jointly (a cotransporter). To represent the effect of stretch-activated channels or shrinkage-activated cotransporters, the membrane permeabilities and cotransport coefficients are permitted to be functions of cell volume. When this epithelium is considered as a dynamical system, conditions are indicated which guarantee the uniqueness and stability of equilibria. Experimentally, many epithelial cells can regulate their volume, and such volume regulatory capability is defined for this model. It is clearly distinct from dynamical stability of the equilibrium and requires more stringent conditions on the volume-dependent permeabilities and cotransporters. For a previously developed model of the toad urinary bladder (Strieteret al., 1990,J. gen. Physiol. 96, 319–344) the uniqueness and stability of its equilibria are indicated. The analysis also demonstrates that under some conditions a second stable equilibrium may appear, along with a saddle-node bifurcation. This is illustrated numerically in a modified model of the epithelium of the thick ascending limb of Henle.
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    URL: http://dx.doi.org/10.1007/BF02459634
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  • 18
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    Book reviews (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 687-694 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
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    URL: http://dx.doi.org/10.1007/BF02459640
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  • 19
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    Modeling immune reactivity in secondary lymphoid organs (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 649-672 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Models of the dynamical interactions important in generating immune reactivity have generally assumed that the immune system is a single well-stirred compartment. Here we explicitly take into account the compartmentalized nature of the immune system and show that qualitative conclusions, such as the stability of the immune steady state, depend on architectural details. We examine a simple model idiotypic network involving only two types of B cells and antibody molecules. We show, for model parameters used by De Boeret al. (1990,Chem. Eng. Sci. 45, 2375–2382), that the immune steady state is unstable in a one compartmental model but stable in a two compartment model that contains both a lymphoid organ, such as the spleen, and the circulatory system.
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    URL: http://dx.doi.org/10.1007/BF02459638
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  • 20
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    On the kinetics and optimal specificity of cytotoxic reactions mediated by T-lymphocyte clones (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 839-873 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Using the chromium release assay and the single cell assay in agarose, we study the cytotoxic reaction of the MHC-restricted T lymphocyte clones P89:15 and P1:3, which recognize distinct but specific tumour antigens on the surface of syngeneic P815 mastocytoma cells. We propose a mathematical model which describes these experiments, accounts for the strongly non-Michaelian behaviour of the reaction and permits us to estimate the kinetic parameters characterizing effector-target conjugation and lethal hit delivery. The results show that the binding and lytic activity of effector cells is modulated by the number of targets bound to them. The binding of a second target by an effector having already a target bound is facilitated; on the other hand, an effector having bound two targets delivers a lethal hit more slowly than one with a single target bound. We investigate the role of these kinetic properties in the competition between the process of tumour progression due to cancer cell replication and the process of tumour regression due to T lymphocyte cytotoxic activity. For both clones, we estimate the effector-target ratio beyond which rejection prevails. This ratio is nine times larger for P1:3 than for P89:15. Furthermore, our analysis suggests that there exists an optimal specificity minimizing this ratio. Deviations from this optimum, be it in the sense of an increase or decrease of specificity, tendsto stabilize the tumoural state: a situation which in the broader context of the immune response evolution and regulation can be viewed as animmune response dilemma.
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    URL: http://dx.doi.org/10.1007/BF02459933
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  • 21
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    Compartmental models with Erlang distributed residence times and random rate coefficients (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 929-938 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In this paper a stochastic model for a two-compartment system which incorporates Erlang residence time distributions (i.e. the residence times have the gamma distribution where the shape parameters assume integer values only) into each compartment is generalized to include random rate coefficients. Analytical forms of the model are derived for the case where the rate coefficients have gamma densities. A relationship is established between the new models and existing models that are in current practical usage.
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    URL: http://dx.doi.org/10.1007/BF02460659
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  • 22
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    Nonlinear phenomena and chaos in a Monte Carlo simulated microbial ecosystem (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 939-955 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Oscillations and chaos can be modelled and observed in a realistic simulation model of interacting prey-predator populations based on Monte Carlo simulation methods. These nonlinear phenomena are linked with some biological and physical bifurcation parameters and mathematical tools from dynamical systems theory may be used in order to characterize this behaviour. Chaotic dynamics are therefore, in our simulation, more the rule than the exception, and are related to delays associated with spatial degrees of freedom.
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    URL: http://dx.doi.org/10.1007/BF02460660
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  • 23
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    A mathematical model of the P-glycoprotein pump as a mediator of multidrug resistance (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 1023-1038 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Cells displaying the classic multidrug resistant (MDR) phenotype possess a transmembrane protein (p170 or P-glycoprotein) which can actively extrude cytotoxic agents from the cytoplasm. A mathematical model of this drug efflux pump has been developed. Outward transport is modeled as a facilitated diffusion process. Since energy-dependent efflux of cytotoxic agents requires that ATP also bind to p170, the model includes a dynamic calculation for efflux rate which considers Michaelis-Menten kinetics for both the substrate agent and ATP. The final system consists of one partial differential equation (PDE) for the facilitated diffusion of substrate agents out of the cell a 2×2 ordinary differential equation (ODE) system for the dynamic calculation of the ATP-ADP pool, and a dynamic algebraic calculation of the efflux rate given substrate levels at the interior cell membrane interface and ATP levels in the cell. A stability analysis of the ATP-ADP pool distribution and a simplistic closed form solution of the linearized PDE are included. Numerical simulations are also provided.
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    URL: http://dx.doi.org/10.1007/BF02460664
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  • 24
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    Initiation and stability of reentry in two coupled excitable fibers (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 1039-1056 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Reentry in the heart is the repeated excitation of the same tissue by a single excitation wave; it is responsible for several types of cardiac arrhythmia. The simplest model which permits the phenomenon of reentry is two laterally coupled excitable fibers; in this paper we examine such a model in order to establish a basis for the understanding of the fundamental physical processes underlying the process of reentry. Two versions of the FitzHugh-Nagumo equations are used to develop complementary numerical and analytical results for the coupled fiber model. On the basis of numerical studies, regions of qualitatively different behaviour are mapped in the parameter space of excitation threshold and coupling strength between the fibers, and the effect of the rate of recovery is explored. Some of these regions are also obtained analytically, in good agreement with the numerical results. Finally, the results are discussed in the light of recent work on the role of the anisotropy of cardiac tissue in the initiation of reentrant activity in the heart.
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    Use of a flexible logistic function to describe axial growth of plants (1992)
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    Bulletin of mathematical biology 54 (1992), S. 1069-1081 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A sigmoid curve with three fitting parameters is proposed as a descriptive model for the spatial velocity field in one-dimensional growth of plant organs. Analytic expressions are derived for the relative elemental growth (REG) rate, the position and value of the REG rate maximum, the length of the growth zone, the inverse of the growth trajectory and cell length in the “elongation only” zone. The expressions are fit to published data to characterize the effects of environmental variation on growth of monocotyledonous roots. The simple expressions for growth may prove useful in mechanistic models. The fitted curves summarize more than a decade of observations and thus provide a challenge to theorists.
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    URL: http://dx.doi.org/10.1007/BF02460667
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    Analysis of weighted median filters based on inequalities relating the weights (1992)
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    Circuits, systems and signal processing 11 (1992), S. 115-136 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract By considering all orderings of the input samples, which are discrete-time continuous-valued, it is shown here that a weighted median (WM) filter of spanN can be specified unambiguously by 2N−1 consistent linear inequalities relating the weights. This specification is identical to that of a self-dual threshold function with the same weights. It is also shown that WM filters with symmetric weights can be specified by ternary threshold functions. Based on these inequalities, properties of WM filters which can be used to check equivalence of some WM filters are derived.
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    URL: http://dx.doi.org/10.1007/BF01189223
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    Signal and image processing using three-dimensional binary ranking transforms (1992)
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    Circuits, systems and signal processing 11 (1992), S. 137-151 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Because binary mathematical morphology permits fast local neighborhood operations by flash conversion, it is used extensively in high-speed pattern-recognition computer systems. Further, since anyN-dimensional integer function may be represented by an (N + 1)-dimensional binary (bilevel) function, ordinary two-dimensional graylevel images become three-dimensional binary images. Thus these images may be processed by high-speed flash-conversion computers assuming that a sufficiently compact three-dimensional kernel can be devised. The tetradekahedron of the face-centered-cubic tessellation forms a perfect kernel in three-dimensions. Its neighborhood is compact. It has total symmetry with all 12 neighbors equidistant from the central element. Using this kernel a variety of useful three-dimensional morphological operations may be performed for target track detection, shaded graphics, data clustering, automated focusing, and spatial filtering.
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    URL: http://dx.doi.org/10.1007/BF01189224
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    On the performance of stack filters and vector detection in image restoration (1992)
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    Circuits, systems and signal processing 11 (1992), S. 153-169 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Two techniques for image restoration are compared in this paper. One is a technique based on the theory of optimal adaptive stack filtering; the other is a recently developed vector detection approach to image restoration. The primary difference between these two techniques is that the optimal detection technique exploits multilevela priori information, while the stack filter uses only single level zero crossing information. The design constraints for stack filters and vector detection are similar. Both approaches rely on the existence of a training sequence for the image source in order to obtain optimal processing. Adaptive stack filters do, however, require a training set of the noise while the optimal detection approach only needs a multivariate parametric representation. The image-restoration performance of these two methods is compared in a signal dependent noise environment characterizing imaging systems with speckle, film-grain, and Poisson shot noise. Comparisons are made using the mean absolute error measure as well as a subjective measure.
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    Losslessness and stability of LDI ladders and filters (1992)
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    Circuits, systems and signal processing 11 (1992), S. 325-352 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The stability of digital ladder filters close in form, via the lossless discrete integrator (LDI) transformation, to doubly terminatedLC Cauer ladder low-pass filters is studied. The LDI transformation does not necessarily map stable analogue into stable digital filters. Necessary and sufficient conditions for these digital filter to be lossless and for a corresponding doubly terminated filter to be stable are given. LDIs are often used in the design of switched capacitor (SC) filters. For this case we provide a threshold sampling rate above which the SC LDI filter retains the stability of the analogue filter. In spite of the stability problem with the LDI mapping, it has been observed that when applied to simulate analogue filters the resulting filter is stable. It can now be argued that, in these cases, other factors in the determination of the sampling rate leads typically to a choice that is also sufficiently above the threshold rate for stability. The theory described is also useful to derive more general digital filters and to perform the design of stable LDI filters exclusively in the Z-plane without reference to analogue prototypes.
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    URL: http://dx.doi.org/10.1007/BF01293679
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    On construction of coprime factorizations for nonlinear feedback control systems (1992)
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    Circuits, systems and signal processing 11 (1992), S. 285-307 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper we describe a family of operators for constructing nontrivial left and right coprime factorizations under rather weak conditions for a large class of nonlinear feedback control systems that has a stabilizable or unstabilizable plant, using a common criterion of input-output stability. The proposed sufficiency and construction method are based on a generalization of the nonlinear Lipschitz operator theory formulated by us for such systems. This class of generalized nonlinear Lipschitz operators constitutes a very large family (an infinite-dimensional Banach space) of bounded nonlinear operators that describe (part of) the underlying systems. One of the main difficulties in constructing coprine factorizations for nonlinear feedback systems has been in taking care of the nonlinear composite and inverse operators that appear in the closed-loop configuration such that the overall feedback system is well defined in the sense of stability, causality, and uniqueness of the internal signals and such that the coprime factorizations can be achieved. In this paper we show how these difficult issues can be handled nicely under our framework of generalized nonlinear Lipschitz operator theory, at least for a very large class of nonlinear control systems. We give a simple illustrative example to show how these coprime factorizations can actually be characterized and constructed to yield explicit closed-form solutions.
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    URL: http://dx.doi.org/10.1007/BF01293677
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    Improved neural networks for analog-to-digital conversion (1992)
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    Circuits, systems and signal processing 11 (1992), S. 387-398 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper we study the problem of designing a neural network that gives the correct binary representation of a given real number. Previously this problem has been studied by Tank and Hopfield. The network proposed by them exhibits “hysteresis” in the sense that the current vector of the network sometimes converges towards a binary vector that isnot the correct binary representation of the input current. The reason for this is that the network proposed by them has multiple asymptotically stable equilibria. In the present paper, we propose another neural network which has the property that it hasa single, globally attractive equilibrium for almost all values of the input current. Hence, irrespective of the initial conditions of the network, the current vector converges towards the correct binary representation of the input current.
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    URL: http://dx.doi.org/10.1007/BF01190983
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    On observability of singular systems (1992)
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    Circuits, systems and signal processing 11 (1992), S. 421-430 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Concepts of observability and strong observability for singular systems are introduced and characterized geometrically in terms of the system matrices without using the Weierstrass decomposition. Duality relations between observability and controllability and that between reachability and strong observability are established. A canonical form for the action of the output injection group on the set of observable systems is presented.
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    Rotationally invariant pecstrum: A rotationally invariant object descriptor based on mathematical morphology (1992)
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    Circuits, systems and signal processing 11 (1992), S. 455-492 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Mathematical morphology is becoming increasingly important in industrial vision applications for object recognition and defect inspection. In this paper we define a new function based on mathematical morphology, which we named the Rotationally Invariant Pecstrum (RIP). The RIP is proven to be invariant under rotation regardless of the shape of the structuring element. This paper also discusses how to use the RIP as an object descriptor and studies the effect of using different structuring elements on recognizing objects of different shapes.
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    Close-form coefficient expressions of typical two-dimensional band-select linear-phase FIR filters (1992)
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    Circuits, systems and signal processing 11 (1992), S. 493-508 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This work presents close-form formulas for typical two-dimensional bandselect linear-phase FIR filters (e.g., band-pass, high-pass, and band-stop filters) optimal in the least-squares sense. Cases of both circular and elliptical symmetry are considered. The formulas refer to the coefficients of the frequency sampling form of the frequency response. Therefore they can either be directly used for filter implementation, if the frequency sampling structure is adopted, or used to obtain the impulse response coefficients via an inverse FFT.
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    Beneficial changes in random variables under multiple sources of risk and their comparative statics (1992)
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    The Geneva risk and insurance review 17 (1992), S. 7-191 
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    ISSN: 1554-9658
    Keywords: Risk ; Insurance Demand ; Deterministic Transformations ; Stochastic Dominance ; Expected Utility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract The consequences of a change in a random parameter are determined for a decision model with more than one source of randomness. The two cases of independent and stochastically dependent sources of risk are discussed. Four comparative static theorems are given. These state the effect of first degree stochastically dominant shifts or risk decreases for one random variable while the other random variable is held fixed. Deterministic transformations are used to represent random parameter changes. The results are presented in the context of the coinsurance demand model with a risky insurable asset and background risk.
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    URL: http://dx.doi.org/10.1007/BF00941954
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    Comparative statics under multiple sources of risk with applications to insurance demand (1992)
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    The Geneva risk and insurance review 17 (1992), S. 21-33 
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    ISSN: 1554-9658
    Keywords: Insurance Demand ; Multiple Sources of Risk ; Comparative Statics ; Increases in Risk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract In this paper we propose an answer to the following problem of comparative statics in models with multiple sources of risk: How a risk averse agent will change his coinsurance demand when the distribution of the insurable loss is shifted? To answer the question, we first comment on Jack Meyer's results and then we show how an alternate approach leads to more definitive comparative statics.
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    Pricing insurance and warranties: Ambiguity and correlated risks (1992)
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    The Geneva risk and insurance review 17 (1992), S. 35-60 
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    ISSN: 1554-9658
    Keywords: Ambiguity ; Pricing ; Actuaries ; Decision Processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper reports on the results of a questionnaire study of pricing decisions made by professional actuaries when the probabilities of a loss are either ambiguous or nonambiguous. Theoretical hypotheses derived from the expected utility model were compared with the implications of procedures described by practicing actuaries. Actuaries were asked to act as consultants to a computer manufacturer concerning the price of a warranty. The suggested prices were considerably higher when probabilities were ambiguous than when they were well-specified. These pricing decisions were consistent with the procedures described by actuaries but inconsistent with predictions from expected utility theory when the risks are perfectly correlated. Further insight into the actual decision process is provided by interviews with actuaries and an analysis of comments written on the questionnaire forms.
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    Saving under uncertainty: A bivariate non-expected utility approach (1992)
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    The Geneva risk and insurance review 17 (1992), S. 61-75 
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    ISSN: 1554-9658
    Keywords: Saving ; Borrowing ; Increases in Risk Aversion ; Increases in Risk ; Multivariate NonExpected Utility Model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract We adopt the multivariate non-expected utility approach proposed by Yaari [1986] to provide a characterization of the comparative statics effects of greater risk aversion and of mean-preserving increases in risk on saving and borrowing in the presence of income and interest rate risk. We show that in Yaari's model, it is possible to extend the applicability of the Diamond and Stiglitz [1974] and Kihlstrom and Mirman [1974] (DSKM) single-crossing property to establish a relationship between greater risk aversion and saving (or borrowing) on the basis of the individual's ordinal preferences as long as the two risks are independent. We also demonstrate that the comparative statics effects of a joint mean-preserving increase in random income and interest rate on saving and borrowing can be determined by an extension of the DSKM single-crossing property.
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    Plasmid incidence and linear alkylbenzene sulfonate biodegradation in wastewater and pristine pond ecosystems (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 37-43 
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    ISSN: 1476-5535
    Keywords: Linear alkylbenzene sulfonate ; Biodegradation ; Plasmid ; Detergent ; Gene probe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Linear alkylbenzene sulfonate (LAS) is a widely used anionic surfactant. Although approximately 1 million metric tons of LAS are produced annually, relatively little is known about the bacteria or the genetic factors that control LAS degradation in the environment. The objectives of this research were to: i) compare bacterial populations in wastewater and pristine pond systems; ii) determine the frequency of plasmids in bacteria from these sites; and iii) compare the frequency of DNA sequences coding for aromatic catabolism in isolates from these two sites. Plate counts indicated that exposure to wastewater resulted in higher levels of both heterotrophic bacteria and bacteria capable of growing on LAS containing medium (LAS/YEPG). In addition to higher numbers, a higher proportion of heterotrophs from the wastewater system were capable of growth on LAS/YEPG medium. Thus, the high levels of LAS in the wastewater system apparently selected fro organisms that were able to tolerate and/or degrade, it. Mineralization of14C-ring labelled LAS in any habitat related to the presence of organisms that grew on LAS/YEPG. Although may of these isolates could carry out primary degradation, no isolate, could mineralize14C-ring LAS in pure culture. A higher incidence of plasmids was found in bacteria from the wastewater pond and among bacteria that grew on LAS containing medium. However, the presence of plasmid, DNA did not necessarily confer the ability to degrade LAS nor was the ability to degrade LAS dependent on the presence of a plasmid. The incidence of selected genotypes for aromatic catabolism was similar among isolates on LAS/YEPG at both sites, suggesting that LAS ring degradation may be present in other populations or encoded by alternative sequences. In conclusion, LAS mineralization is mediated by a consortium and the evidence that initial attack of LAS is plasmid mediated is inconclusive.
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    10-Hydroxy-8(Z)-octadecenoic acid, an intermediate in the bioconversion of oleic acid to 7,10-dihydroxy-8(E)-octadecenoic acid (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 103-107 
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    ISSN: 1476-5535
    Keywords: Fatty acid bioconversion ; hydroxy octadecenoic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Previously, we reported the discovery of a new compound, 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) which was produced from oleic acid by a new bacterial isolate PR3 [6,7]. The reaction is unique in that it involves a hydroxylation at two positions and a rearrangement of the double bond of the substrate molecule. Now, we have isolated another compound from the reaction mixture determined by GC/MS to be 10-hydroxy-8-octadecenoic acid (HOD). NMR and IR data indicate that the unsaturation is probablycis. The optimum pH and temperature for the production of HOD by strain PR3 were 6.5 and 30°C, about the same as those for DOD. However, the amount of HOD detected remained small throughout an 48-h reaction period during which the amount of DOD increased sharply. At 48 h of reaction, the ratio between HOD∶DOD was 1∶10. HOD may be an intermediate in the biosynthesis of DOD from oleic acid.
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    Cultivation ofCandida blankii in simulated bagasse hemicellulose hydrolysate (1992)
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    Journal of industrial microbiology and biotechnology 9 (1992), S. 109-113 
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    ISSN: 1476-5535
    Keywords: Candida blankii ; Biomass ; d-Xylose ; l-Arabinose ; Acetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary All fourCandida blankii isolates evaluated for growth in simulated bagasse hemicellulose hydrolysate utilized the sugars and acetic acid completely. The utilization ofd-xylose,l-arabinose and acetic acid were delayed by the presence ofd-glucose, but after glucose depletion the other carbon sources were utilized simultaneously. The maximum specific growth rate of 0.36 h−1 and cell yield of 0.47 g cells/g carbon source assimilate compared with published results obtained withC. utilis. C. blankii appeared superior toC. utilis for biomass production from hemicellulose hydrolysate in that it utilizedl-arabinose and was capable of growth at higher temperatures.
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    Laboratory-scale biosynthesis ofTrichoderma mycolytic enzymes for protoplast release fromCochliobolus lunatus (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 115-119 
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    ISSN: 1476-5535
    Keywords: Mycolytic enzymes ; Trichoderma viride ; Protoplasts ; Cochliobolus lunatus ; Fermentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Microorganism useful for the induction of enzymes lytic towards walls of filamentous fungusCochliobolus lunatus were studies. Production of specificTrichoderma viride mycolytic enzymes was studied in a laboratory fermentor. The product with high chitinase and relatively low protease activity gave better yields ofC. lunatus protoplasts than commercial Novozym 234.
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    Optimized protocol for the pilot-scale preparation of fungal cellulase (1992)
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    Journal of industrial microbiology and biotechnology 9 (1992), S. 121-125 
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    ISSN: 1476-5535
    Keywords: Trichoderma viride ; Cellulase production ; Optimized production medium and parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A 25-l scale protocol is devised for the optimal secretion and recovery of fungal cellulase. Using a selected higher yieldingTrichoderma viride SMC strain, a protocol consisted of: a) an optimized production medium rich in microcrystalline cellulose (MCC), fortified with 1% (w/v) ammonium sulphate, 0.5% (w/v) soybean flour, 0.1% (v/v) Tween-80 and other trace nutrients; b) optimized physical parameters of production, such as an inoculum containing a homogeneous suspension of 6×107 conidia per 1,28±1°C, pH 4.0±0.5, 300±20 rpm, 11000±1000 l/h aeration, and 170–220 h duration; c) optimal recovery through a filter press (450 l/h rate of filtration) followed by precipitation with 2.5–3.0 volumes of acetone (15°C and basket centrifugation (27°C, 1700 rpm)); and d) vacuum drying (35°C, 4–6 h). This afforded 70% recovery of cellulase in the form of white fluffy powder containing 20000±2000 carboxy methyl cellulase and 1000±50 units filter paperase per g activities, with raw material cost of US$ 8–10 per million carboxy methyl cellulase units. During storage for 18 months at 4°C, ambient temperature and 37°C, the cellulase preparation was found to retain 100, 75 and 60% of its initial activity, respectively.
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    Production ofLactococcus lactis biomass by immobilized cell technology (1992)
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    Journal of industrial microbiology and biotechnology 9 (1992), S. 131-135 
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    ISSN: 1476-5535
    Keywords: Cheese ; Starters ; Production ; Alignate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Calcium alginate beads containingLactococcus lactis cells were used for three batch fermentations of milk or a commercially available growth medium (Gold Complete, Nordica) with the aim of producing concentrated cultures. Repeated fermentations did not significantly increase bead CFU counts which were between 3.3–7.8×1010 CFU/g. During the second and third fermentations, which lasted 6 h each, the bead populations decreased if the incubation was extended over 2 h. There was cell release from the beads. Fermentation media and fermentation time all had an effect on free cell counts, but none of these factors statistically interacted. Free cell counts were higher at the end of fermentations 2 and 3 than in the first fermentation and approximately 50% of the population was in the free state. Free cell counts were higher when the beads were incubated in Gold complete than in milk. Although the total bacterial population of a standard free cell fermentation was always higher than those having immobilized cells, immobilized cell technology did enable the production of dense cultures.
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    Immobilization ofβ-fructofuranosidase fromAureobasidium sp. ATCC 20524 on porous silica (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 247-250 
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    ISSN: 1476-5535
    Keywords: Fructosyl-transferring enzyme ; 1-Kestose ; Fructo-oligosaccharide ; Continuous production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary β-Fructofuranosidase P-1 fromAureobasidium sp. ATCC 20524, which produces a fructo-oligosaccharide (1-kestose) from sucrose, was immobilized covalently onto alkylamine porous silica with glutaraldehyde at high efficiency (44.4%). Optimum pore diameter of porous silica for immobilization of the enzyme was 91.7 nm. The enzymatic profiles of immobilized enzyme were almost identical to the native one except its stabilities to temperature and metal ions were improved. 1-Kestose was produced continuously and selectively from 40% (w/v) sucrose at fast flow rates by a column packed with the immobilized enzyme for up to 26 days, and the effluent concentration of 1-kestose remained in the range 113–135 mg ml−1.
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    Production of microbial levan from sucrose, sugarcane juice and beet molasses (1992)
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    Journal of industrial microbiology and biotechnology 9 (1992), S. 257-260 
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    ISSN: 1476-5535
    Keywords: Polysaccharide ; Fructan ; Gum ; Fermentation ; Bacillus polymyxa ; Sweetener
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Bacillus polymyxa (NRRL-18475) produced a levan-type fructan (B, 2→6 fructofuranoside) when grown on sucrose, sugarcane juice, and sugarbeet molasses. The organism converted about 46% of the fructose moiety of sucrose to levan when grown on sucrose medium, however, the yields of levan from sugarcane juice and beet molasses were much less than sucrose solution. Such sugarcane juice and beet molasses can be made a good substrate for levan production by various modifications. Adding peptone to sugarcane juice or passing beet molasses through a column of gel filtration media improved levan yield to a level almost comparable to that obtained from sucrose.
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    Editorial (1992)
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    Circuits, systems and signal processing 11 (1992), S. 3-4 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
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    Preface (1992)
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    Circuits, systems and signal processing 11 (1992), S. 5-6 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
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    URL: http://dx.doi.org/10.1007/BF01189219
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    Design of universal, variable frequency range FIR digital differentiators (1992)
    Springer
    Circuits, systems and signal processing 11 (1992), S. 431-439 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract An efficient design of digital differentiators (DD), with a variable frequency range of operation at low and midband frequencies, has been proposed. Implemented as a Taylor structure, a DD designed for orderN can be made to function as a universal configuration giving optimal transfer functions for all possible ordersN, without changing the coefficients.
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    Optimisation of culture conditions for production of eicosapentaenoic acid byMortierella elongate NRRL 5513 (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 11-17 
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    ISSN: 1476-5535
    Keywords: Eicosapentaenoic acid ; Mortierella elongata ; Omega-3 fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary WhenMortierella elongata NRRL 5513 was cultured in shake flasks at 25°C, mycelial growth reached a stationary phase at 48 h but maximum eicosapentaenoic acid (EPA) production was observed at 6 days. When incubated at 11°C, EPA production also continued to rise during the stationary phase of growth, reaching a maximum after 10 days. An initial culture pH of 6.1 was found to be optimum for EPA production. The effect of temperature on EPA production was dependent on medium constituents. In glucose and linseed oil supplemented media, optimum temperature for EPA production was 11 and 15°C respectively. A maximum EPA yield of 0.61 g/l was obtained in linseed oil (2%), yeast extract (0.5%) supplemented basal medium. Maximum EPA content as a percentage of lipids (15.12%) was observed when the latter medium was supplemented with 0.25% urea.
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    Effect of the levels of dissolved oxygen on the expression of recombinant proteins in four recombinantEscherichia coli strains (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 1-9 
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    ISSN: 1476-5535
    Keywords: Recombinant culture ; Dissolved oxygen ; Biomass ; Plasmid content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Four recombinant strains ofEscherichia coli were examined for the effects of the dissolved oxygen level on the level of biomass, the plasmid content, and the level of recombinant protein at the stationary phase of batch growth. Strains JM101/pYEJ001, and TB-1/pYEJ001 (encoding chloramphenicol acetyltransferase), and strain TB-1/p1034, and TB-1/pUC19 (encoding β-galactosidase) were grown at the constant dissolved oxygen levels of 0, 50, and 100% air saturation, as well as in the absence of dissolved, oxygen control. The biomass of all strains under constant aerobic conditions was 12–36 times higher than that under anaerobic conditions, but was the same as or slightly higher than that without dissolved oxygen control. The plasmid content in all strains under anaerobic conditions was 2.9–11.7 times higher than that under aerobic conditions. The optimal dissolved oxygen concentration for the specific activity of recombinant proteins was dependent upon the strain. In no strain were constant aerobic conditions optimal. However, because of the effect on biomass, controlled aerobic conditions were optimal for the volumetric activity of recombinant protein in all but one strain.
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    Enhanced glucan formation of filamentous fungi by effective mixing, oxygen limitation and fed-batch processing (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 19-25 
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    ISSN: 1476-5535
    Keywords: Schizophyllum commune ; Sclerotium glucanicum ; Branched β-1,3-glucan ; Fan-impeller ; Oxygen limitation ; Process design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Glucan formation ofSchizophyllum commune andSclerotium glucanicum were investigated. Process data obtained during batch cultivation are presented. Glucan release can be improved by oxygen limitation. Thus, growth and glucan release are influenced by oxygen in opposite ways. Possible pathways of this oxygen-dependent regulation are discussed. A draft-tube/propeller system, rushtonturbine-, fan- and helicon-ribbon-impeller as well as a fundaspi and intermig agitator were tested. The 4-bladed fan impeller withd *=0.64 yielded the best results, since effective bulk mixing is much more important than bubble break up (micromixing) with regard to this system. Fed-batch cultivation always resulted in higher rates of glucan formation than the batch process.
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    Fate in water of a recombinantEscherichia coli K-12 strain used in the commercial production of bovine somatotropin (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 27-36 
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    ISSN: 1476-5535
    Keywords: Genetically engineered microorganisms ; Bovine somatotropin ; Survival ; River
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The fate in water ofEscherichia coli K-12 strain LBB269, both plasmid-free and carrying the recombinant plasmid pBGH1, was studied.E. coli K-12 strain LBB269 (pBGH1) is a nalidixic acid resistant derivative of W3110G (pBGH1), the microorganism used by Monsanto Company for the commercial production of bovine somatotropin. Water samples were obtained from the Missouri River and from the Monsanto Life Sciences Research Center aqueous waste basin. Strains LBB269 and LBB269 (pBGH1) were grown in fermentation vessel under bovine somatotropin (BST) production conditions, and inoculated into the water samples. The inoculated water samples were incubated, at 26°C, and the number of viableE. coli cells was determined as a function of time. In sterile water from both sources, the two strains remained, at a constant level for at least 28 days; LBB269 (pBGH1) remained at a constant level in sterile water for at least 300 days. In non-sterile water from both sources, the two strains declined from an initial concentration of about 3.0×106 cells per ml to less than 10 cells per ml in 147 h. The study conditions did not adversely affect the populations of indigenous microorganisms. The selective loss of strains LBB269 and LBB269 (pBGH1) demonstrates that theseE. coli strains do not survive in environmental sources of water. In addition, it was observed that the presence of pBGH1 had essentially no effect on the disappearance of strain LBB269 from either source of water.
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    Rapid identification of teleocidins in fermentation broth using HPLC photodiode array and LC/MS methodology (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 45-52 
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    ISSN: 1476-5535
    Keywords: Protein kinase C (PKC) ; Phorbol ester ; Methylpendolmycin ; Pendolmycin ; Actinomycete
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary During the course of screening for inhibitors of phorbol ester binding to protein kinase C, several actinomycete cultures were discovered that produce active metabolites. HPLC coupled to photodiode array and LC/MS techniques were applied to broth extracts to identify the presence of indolactams belonging to the teleocidin family. Various members of this family were rapidly identified from crude broth extracts using a combination of these spectroanalytical procedures. An analytical HPLC system was developed to optimize separation of teleocidin, A and B analogues directly from ethyl acetate extracts of whole broth cultures. This technique allowed us to identify a novel homologue of pendolmycin and demonstrated the utility of photodiode array HPLC coupled with LC/MS as an intial analytical tool in the analyses of these secondary metabolites produced by soil microorganisms.
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    Detoxification of polycyclic aromatic hydrocarbons by fungi (1992)
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    Journal of industrial microbiology and biotechnology 9 (1992), S. 53-61 
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    ISSN: 1476-5535
    Keywords: Bioremediation ; Biotransformation ; Cytochrome P-450 ; Metabolism ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The polycyclic aromatic hydrocarbons (PAHs) are a group of hazardous environmental pollutants, many of which are acutely toxic, mutagenic, or carcinogenic. A diverse group of fungi, includingAspergillus ochraceus, Cunninghamella elegans, Phanerochaete chrysosporium, Saccharomyces cerevisiae, andSyncephalastrum racemosum, have the ability to oxidize PAHs. The PAHs anthracene, benz[a]anthracene, benzo[a]pyrene, fluoranthene, fluorene, naphthalene, phenanthrene, and pyrene, as well as several methyl-, nitro-, and fluoro-substituted PAHs, are metabolized by one or more of these fungi. Unsubstituted PAHs are oxidized initially to arene oxides,trans-dihydrodiols, phenols, quinones, and tetralones. Phenols andtrans-dihydrodiols may be further metabolized, and thus detoxified, by conjugation with sulfate, glucuronic acid, glucose, or xylose. Although dihydrodiol epoxides and other mutagenic and carcinogenic compounds have been detected as minor fungal metabolites of a few PAHs, most transformations performed by fungi reduce the mutagenicity and thus detoxify the PAHs.
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    Chemical modification of the α-amylase ofBacillus caldovelox with diethyl pyrocarbonate: Evidence for an essential histidine at the active site (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 63-68 
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    ISSN: 1476-5535
    Keywords: α-Amylase ; Histidine ; Chemical modification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The α-amylase ofBacillus caldovelox is inactivated by diethyl pyrocarbonate at pH 6.6 and 20°C by a monomolecular reaction with a second-order rate constant of 41.7 M−1·min−1. The rate of inactivation increases with decreasing pH, suggesting participation of an amino acid residue with a pK a of 6.6. The increase in absorbance at 240 nm, unchanged absorbance at 280 nm and reactivation in the presence of hydroxylamine suggest the participation of a histidine residue. Statistical analyses of inactivation suggest that only one histidine residue is essential for activity. Substrate afforded complete protection against inactivation, indicating the involvement of the histidine residue at the active site of the enzyme.
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    Some factors influencing the proportion of periplasmic hepatitisB virus pre-S2 antigen in the recombinant yeastHansenula polymorpha (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 69-72 
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    ISSN: 1476-5535
    Keywords: Secretion ; Periplasmic pre-S2 antigen ; Recombinant protein ; Experimental design ; Methylotrophic yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A central composite design (CCD) was used to evaluate, for the purpose of future process optimization, the influence of pH, yeast extract and ammonium chloride concentrations on the proportion of periplasmic hepatitisB pre-S2 antigen in the recombinant yeastHansenula polymorpha. Each factor was tested at five levels, and a second order polynomial model for the proportion of periplasmic antigen was fitted to the treatment combinations. pH showed the greatest effect: the proportion of periplasmic antigen was greatly increased at the higher pH levels. At the higher pH levels used, the proportion of periplasmic antigen was enhanced by a high concentration of ammonium chloride. Additional experiments have confirmed both the validity of the selected model and the optimal conditions found. A significant correlation was found between the proportion of periplasmic antigen and the total yield of antigen. These results indicated that is should be possible to modulate the distribution of the pre-S2 antigen between the periplasm and the cytoplasm of the yeast.
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    Antimicrobial activities of 2-arylthio-N-alkylmaleimides (1992)
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    Journal of industrial microbiology and biotechnology 9 (1992), S. 91-96 
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    ISSN: 1476-5535
    Keywords: Antimicrobial activity ; 2-Arylthio-N-alkylmaleimide ; Antibacterial activity ; Antifungal activity ; Minimum inhibitory concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A variety of 2-arylthio-N-alkylmaleimides were prepared, and their antimicrobial activities were examined. Almost all of these compounds exhibited antibacterial activity against Gram-positive bacteria such asBacillus subtilis andStaphylococcus aureus. Some compounds such as 2-(halogeno-phenyl)-thio-N-methylmaleimides (4, 5, 6, 8 and 10) and 2-(2-carbamoylphenyl)thio-N-methylmaleimide(35) exhibited antibacterial activity againstEscherichia coli. All compounds tested were inactive againstPseudomonas aeruginosa except 2-(2-carbamoylphenyl)thio-N-methylmaleimide(35) which was marginally active. Activities against Gram-positive bacteria were not due to the effect of the substituent on the benzene ring, except in the instances 2-carboxy, 2-carbomethoxy, 2-amino groups and alkyl chains, however, activities against Gram-negative bacteria were due to phenylthio and the alkyl substituents. Some of 2-arylthio-N-alkylmaleimides were examined for their antifungal activities using eight strains of fungi, and they showed activity against these.
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    Clusters of genes for the biosynthesis of antibiotics: Regulatory genes and overproduction of pharmaceuticals (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 73-90 
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    ISSN: 1476-5535
    Keywords: β-Lactam antibiotics ; Penicillin ; Cephalosporin ; Cephamycin ; Biosynthetic gene clusters ; Control of expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary In the last decade numerous genes involved in the biosynthesis of antibiotics, pigments, herbicides and other secondary metabolites have been cloned. The genes involved in the biosynthesis of penicillin, cephalosporin and cephamycins are organized in clusters as occurs also with the biosynthetic genes of other antibiotics and secondary metabolites (see review by Martín and Liras [65]). We have cloned genes involved in the biosynthesis of β-lactam antibiotics from five different β-lactam producing organisms both eucaryotic (Penicillium chrysogenum, Cephalosporium acremonium (syn.Acremonium chrysogenum) Aspergillus nidulans) and procaryotic (Nocardia lactamdurans, Streptomyces clavuligerus). InP. chrysogenum andA. nidulans the organization of thepcbAB,pcbC andpenDE genes for ACV synthetase, IPN synthase and IPN acyltransferase showed a similar arrangement. InA. chrysogenum two different clusters of genes have been cloned. The cluster of early genes encodes ACV synthetase and IPN synthase, whereas the cluster of late genes encodes deacetoxycephalosporin C synthetase/hydroxylase and deacetylcephalosporin C acetyltransferase. InN. lactamdurans andS. clavuligerus a cluster of early cephamycin genes has been fully characterized. It includes thelat (for lysine-6-aminotransferase),pcbAB (for ACV synthase) andpcbC (for IPN synthase) genes. Pathway-specific regulatory genes which act in a positive (or negative) form are associated with clusters of genes involved in antibiotic biosynthesis. In addition, widely acting positive regulatory elements exert a pleiotropic control on secondary metabolism and differentiation of antibiotic producing microorganisms. The application of recombinant DNA techniques will contribute significantly to the improvement of fermentation organisms.
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    Preparation of (S)-2,3-dichloro-1-propanol byPseudomonas sp. and its use in the synthesis of (R)-epichlorohydrin (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 97-101 
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    ISSN: 1476-5535
    Keywords: Stereospecific degradation of 2,3-dichloro-1-propanol ; Pseudomonas sp. ; Microbial resolution ; (S)-2,3-Dichloro-1-propanol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Pseudomonas sp. OS-K-29 assimilated (R)-2,3-dichloro-1-propanol preferentially as the sole source of carbon. Isolation of optically pure (S)-2,3-dichloro-1-propanol with 100% enantiomer excess (e.e.) from the racemate was done based on this bacterial assimilation using immobilized-cells of OS-K-29 with calcium-alginate. The overall examination of the reactor involved 19 batches for 50 days without loss of its activity. Highly pure (R)-epichlorohydrin with 99.5% e.e. was prepared from the (S)-2,3-dichloro-1-propanol with treatment of aqueous NaOH. This new method is simple and useful for manufacturing optically active (S)-2,3-dichloro-1-propanol and (R)-epichlorohydrin.
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    Regulation of glucose and maltose transport in strains ofSaccharomyces (1992)
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    Journal of industrial microbiology and biotechnology 9 (1992), S. 127-130 
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    ISSN: 1476-5535
    Keywords: Repression ; Derepression ; Transport ; Saccharomyces ; Glucose ; Maltose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Growth of yeast cells on glucose resulted in complete inactivation of maltose transport and repression of the high affinity glucose transport system. When the cells were grown on maltose or subjected to substrate starvation, an increase in glucose and maltose transport was observed in both brewing and non-brewing yeast strains. The concentration of glucose employed in the growth medium was also observed to affect sugar transport activity. The higher the glucose concentration, the more pronounced the repressive effect. In addition, the time of growth of yeast on glucose or maltose also intermining the rate of sugar transport. These results are consistent with the repressive effect of glucose on the high affinity glucose and maltose transport systems.
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    Formation of water-solubleMonascus red pigments by biological and semi-synthetic processes (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 173-179 
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    ISSN: 1476-5535
    Keywords: Monascus ; Water-soluble pigments ; Semi-synthesis ; Amino acids ; Natural food color
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary New water-soluble red pigments were produced byMonascus sp. in a chemically defined fermentation medium containing glutamate as nitrogen source. They were isolated and characterized as glutamate derivatives of the well-known orangeMonascus pigments (monascorubrin and rubropunctatin). The new pigments have several advantages over the known redMonascus pigments (rubropunctamine and monascorubramine) including very high water-solubility, higher absorption coefficient, and greater resistance to decoloration by light. Adding glutamate, glycine or leucine to a resting-cell system led to the formation of specific water-soluble red pigments corresponding to the exogenous amino acid. The water-soluble red pigments produced by resting-cells have retention times identical to those of the corresponding red derivatives made chemically from the orange pigments in methanol-phosphate buffer at pH 7. The hydrophobicities of the amino acid sources correspond to the HPLC retention times of the red pigments derived from them.
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    Microbial biomass and community structure of a phase-separated methanogenic reactor determined by lipid analysis (1992)
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    Journal of industrial microbiology and biotechnology 9 (1992), S. 193-199 
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    ISSN: 1476-5535
    Keywords: Acetogenesis ; Biomarkers ; Cluster analysis ; Fermentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary An anaerobic phase-separation biomass reactor was established on cellulose with the hydrolysis and fermentation steps occurring in the first stage, and acetogenesis and methanogenesis in the second stage. Based upon lipid biomarker analysis, eubacterial and eukaryotic cells accounted for approximately 6% of the volatile solids of the first stage and 17% of the second, while methanogens were approximately 1% of the volatile solids in the first stage and 9% of the second. Clustering the polar lipid fatty acids into groups based upon their distributions between the two stages of the reactor clarified the differences in community structure caused by phase-separated operation. Although inoculated from the same source, the two stages maintained very different microbial communities. Signature fatty acids known as indicators of unbalanced growth in eubacteria were significantly higher in the first stage of the reactor.
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    Detoxification of sesquiterpene phytoalexins byGibberella pulicaris (Fusarium sambucinum) and its importance for virulence on potato tubers (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 201-211 
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    ISSN: 1476-5535
    Keywords: Solanum tuberosum ; Dry-rot ; Rishitin ; Lubimin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Gibberella pulicaris (Fusarium sambucinum) is a major cause of dry-rot of stored potatoes (Solanum tuberosum) worldwide. The ability of field strains ofG. pulicaris to cause dry-rot is correlated with their ability to detoxify sesquiterpene phytoalexins produced by potato. All highly virulent field strains can detoxify the sesquiterpenes rishitin and lubimin. Meiotic recombinational analysis indicates that rishitin detoxification can be controlled at two or more loci. High virulence has been associated with one of these loci, designatedRiml. Detoxification of rishitin and lubimin comprises a complex pattern of reactions involving epoxidation, dehydrogenation, and cyclization. To date, seven lubimin metabolites and one rishitin metabolite have been characterized. Genes for rishitin and lubimin detoxification are being cloned fromG. pulicaris in order to more rigorously analyze the role and regulation of sesquiterpene metabolism in potato dry-rot. Our results indirectly support a role for sesquiterpene phytoalexins in resistance of potato tubers to dry-rot and may enhance research on alternative control strategies for this economically important potato disease.
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    Use of lignin-degrading fungi in the disposal of pentachlorophenol-treated wood (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 181-191 
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    ISSN: 1476-5535
    Keywords: Pentachlorophenol ; Lignin-degrading fungi ; White-rot fungi ; Phanerochaete chrysosporium ; Phanerochaete sordida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The lignin-degrading fungiPhanerochaete chrysosporium, P. sordida, Trametes hirsuta, andCeriporiopsis subvermispora were evaluated for their ability to decrease the concentration of pentachlorophenol (PCP) and to cause dry weight loss in PCP-treated wood. Hardwood and softwood materials from PCP-treated ammunition boxes that were chipped to pass a 3.8-cm screen were used. All four fungi caused significant weight losses and decreases in the PCP concentration. The largest PCP decrease (84% in 4 weeks) was caused byT. hirsuta, and the smallest decrease was caused byC. subvermispora (37% in 4 weeks). After 4 weeks, the fate of spiked14C[PCP] in softwood chips inoculated withT. hirsuta was as follows: 27% was mineralized, 42.5% was non-extractable and bound to the chips, 23.5% was associated with fungal hyphae, and 6% was organic-extractable. Decreases of PCP byP. chrysosporium andP. sordida averaged 59% and 57%, respectively. PCP decreases caused byPhanerochaete spp. were not significantly affected by wood type or sterilization and were primarily due to methylation of PCP that resulted in accumulation of pentachloroanisole. Softwood weight losses caused byT. hirsuta, P. chrysosporium andC. subvermispora were respectively, 24, 6.5, and 17%, after 4 weeks. These weight losses are comparable to reported weight losses by these organisms in non-treated softwood. Nutrient supplementation significantly increased weight loss but not percentage decrease of PCP. The results of this research demonstrate the potential for using lignin-degrading fungi to destroy PCP-treated wood.
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    Copper removal from an industrial waste by bioleaching (1992)
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    Journal of industrial microbiology and biotechnology 9 (1992), S. 213-218 
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    ISSN: 1476-5535
    Keywords: Industrial waste ; Copper removal ; Bioleaching ; Fe medium ; Thiobacillus ferrooxidans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Copper contained in a solid industrial waste produced in a silicone manufacturing process was leached with spent iron medium from aThiobacillus ferrooxidans culture. Most effective leaching was observed in a continuously fed, dual reactor system. Spent iron medium was generated by growingT. ferrooxidans in 0.9 K iron medium at pH 1.5 in the first reactor, and was transferred to a second reactor in which it leached the copper from the waste. Leaching was effective at a pulp density of the waste material as high as 20%. In experiments run at a pulp density of 2.5%, the spent iron medium was most efficient in leaching copper when it was first diluted 100-fold with a mineral salts solution at pH 1.5. Removal of the copper from the waste appeared to involve its displacement by acid, dissolved mineral salts, and ferric iron. Potentials for practical application of this process are discussed.
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    A simple method to study microbial coal solubilization using Pluronic F-127-amended media (1992)
    Springer
    Journal of industrial microbiology and biotechnology 9 (1992), S. 225-227 
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    ISSN: 1476-5535
    Keywords: Pluronic F-127 ; Coal solubilization ; Polyol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Microbial coal solubilization and the extraction of solubilized coal products were carried out in media amended with polyol (Pluronic F-127), an agent which gels above 18°C but reverts to a liquid state at low temperature (4°C). The solubilized coal products, the unsolubilized coal particles and the mycelial mat were separated effectively by centrifugation at 4°C. The amount of coal solubilization was 30–50% higher in polyol-amended media than in agar media regardless of the microorganism. On the other hand, the amount of coal solubilization in polyol-amended control media was less compared to agar-amended control media.
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    Monod's bacterial growth model revisited (1992)
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    Bulletin of mathematical biology 54 (1992), S. 117-122 
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    Notes: Abstract An attempt to justify Monod's bacterial growth model is presented. The justification is based on a mechanistic approach to growth which leads to a differential equation with delay and then to Monod's model. An unexpected increase of parameterK s with μm is predicted by the theory. A survey of literature shows that this effect is present in a large majority of published data.
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    Optimal sex ratio as a function of EGG incubation temperature in the crocodilians (1992)
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    Bulletin of mathematical biology 54 (1992), S. 123-148 
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    Notes: Abstract Recently, there has been a growing consensus as to the adaptive significance of temperature-dependent sex determination in the Crocodilia. The observationally and experimentally motivated hypotheses are that male fitness depends more strongly on quality of incubation environment than female fitness, and that there is a strong correlation between a female's egg incubation temperature choice and her own egg incubation temperature. A population genetics model based on these hypotheses is derived. A method for finding the optimal sex ratio as a function of temperature, which is an evolutionary stable strategy (ESS), is stated and applied under various assumptions. This extends ESS theory to thefunctional case. Cases where there is no ESS and the population sex ratio oscillates in evolutionary time are discovered. Numerical computation is needed to solve the full problem and the resulting optimal sex ratio is compared to laboratory sex ratio data. The general pattern of TSD in crocodilians (female-male-female with female biased overall sex ratio) agrees well with the theory, but details of the pattern are problematic.
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    License values in restricted access fisheries (1992)
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    Bulletin of mathematical biology 54 (1992), S. 209-218 
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    Spatial pattern in catch rates: A test of economic theory (1992)
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    Bulletin of mathematical biology 54 (1992), S. 263-273 
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    Notes: Abstract Gordon (1953,J. Fish. Res. Bd Can.10, 442–457) used economic theory to predict how catch rates, price and fishing costs should balance in a multi-area, open-access fishery. We use the data from the Tasmanian rock lobster fishery to test this theory. We find that, as prediced by theory, areas with higher monetary and non-monetary costs have consistently higher catch rates than areas with lower costs. We show that this theory also predicts that an increase in price would result in an overall increase in catch rate, and suggest that in fisheries with spatial variation in costs, catch rates may be determined as much by economic factors as biological ones.
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    Review of proposed mechanisms for sockeye salmon population cycles in the fraser river (1992)
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    Bulletin of mathematical biology 54 (1992), S. 241-261 
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    Notes: Abstract Prominent and persistent cyclic fluctuations in the abundance of consecutive year-classes occur in some sockeye salmon populations throughout the species' range. We review and test a number of explanations for the existence of these cycles using qualitative biological arguments, including a consideration of the synchrony of cycles among populations. Most of the hypotheses involve mechanisms that would reinforce synchronous population fluctuations within watersheds. However, the 4-year cycles characteristic of many Fraser River sockeye populations are sometimes out of phase with each other, both among populations which migrate together as mixed stocks while vulnerable to commerical fisheries, and among populations whose juveniles share the same nursery lake habitat (Shuswap Lake). Such asynchrony suggests that the mechanism(s) causing population cycles can operate independently within reproductively isolated populations. Of the mechanisms reviewed here, only those involving genetic effects on age at maturation, or on resistance to disease or parasites, or those involving depensatory predation soon after fry emergence, appear to offer satisfactory explanations.
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    Territorial bequeathal by red squirrel mothers: A dynamic model (1992)
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    Bulletin of mathematical biology 54 (1992), S. 335-354 
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    Notes: Abstract Female red squirrels (Tamiasciurus hudsonicus) sometimes bequeath their territory to their offspring. Late-breeding females are more likely to leave than are early-breeding females. Early-breeding females tend to lose weight during reproduction while late-breeding females do not. Early-born juveniles are more successful at winning territories than are those born late. I use dynamic programming to investigate the trade-offs involved in territorial bequeathal from the female's perspective as a function of breeding date, litter size and female body condition. The model predicts that two classes of females are more likely to bequeath: those in good condition early in the season, and those in poor condition at the season's end. Only versions of the model incorporating a function improving the female's ability to win a territory over the season mimicked the pattern of bequeathal observed in the field. A seasonal effect is likely an important factor in driving the pattern of strategies observed.
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    Sex ratio genetics and the competitiveness of parasitic wasps (1992)
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    Bulletin of mathematical biology 54 (1992), S. 295-311 
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    Notes: Abstract In the first part of the paper we analyse dynamics of the genetic mechanisms responsible for maintaining biased sex ratios in host-parasitoid interactions. We begin by reviewing recent results relating to the maintenance of sibmating in haplo-diploid populations. We then investigate the evolutionary stable sex ratio in populations in which all or some of the females mate with their brothers. In particular, we derive a diallelic one-locus model for studying evolutionary stable sex ratios in partially sibmating haplo-diploid populations. In the second part of the paper we review the impact of sex ratio on host-parasitoid populations. We then analyse how the sex ratio strategy of one parasitoid species may affect its interaction with another parasitoid species competing for the same host. In particular we show that, although a female biased sex ratio may enhance the inherent competitiveness of one species, it may also destabilize the ecological interaction of the three species so that all become extinct.
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    Determination of time-constants in cables of finite length (1992)
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    Bulletin of mathematical biology 54 (1992), S. 673-686 
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    Notes: Abstract Current flow in cylindrical nerve and muscle fibre has been analysed in terms of a mathematical model leading to a linear partial differential equation for the voltage as a function of both position and time. In the case of a one-dimensional cable subject to a step input of current, the solution will consist of a steady-state behaviour preceded by an initial transient. The electrical properties of the fibre or cable itself determine a length-constant, λ, which can be determined experimentally from the steady-state response, and a time-constant, τ, which must be found from the initial transient. When the cable is infinite and when there is a single input electrode, an exact solution can be produced which enables ready determination of the time-constant τ. Two complications arise in experimental practice, however. In the first place, the fibre has finite length, and in the second, two spatially separated stimulation electrodes are often required. We thus analyse a more complicated and more general situation. The linearity of the membrane properties, however, allows the solution to the more general case to be built up by superposition of solutions from the simpler case (equivalent to the classical method of images). We also approximate the Hodgkin and Rushton solution by asymptotic formulae in order to allow more tractable expressions for the exact solution. We are thus able to give a method for the ready evaluation of the time constant τ under more general conditions.
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    Ising model forB-Z transition in supercoiled DNA (1992)
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    Bulletin of mathematical biology 54 (1992), S. 727-732 
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    Notes: Abstract The possible existence of nucleic acids in right-handed and left-handed helical forms is considered. A statistical mechanical model is developed to obtain an expression for a change in twist during helical transformation in terms of corresponding free energies and linking for a supercoiled DNA. The theoretically predicted values are compared with those determined experimentally. The physico-chemical significance of the parameters is discussed.
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    Tree asymmetry—A sensitive and practical measure for binary topological trees (1992)
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    Bulletin of mathematical biology 54 (1992), S. 759-784 
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    Notes: Abstract The topological structure of a binary tree is characterized by a measure called tree asymmetry, defined as the mean value of the asymmetry of its partitions. The statistical properties of this tree-asymmetry measure have been studied using a growth model for binary trees. The tree-asymmetry measure appears to be sensitive for topological differences and the tree-asymmetry expectation for the growth model that we used appears to be almost independent of the size of the trees. These properties and the simple definition make the measure suitable for practical use, for instance for characterizing, comparing and interpreting sets of branching patterns. Examples are given of the analysis of three sets of neuronal branching patterns. It is shown that the variance in tree-asymmetry values for these observed branching patterns corresponds perfectly with the variance predicted by the used growth model.
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    Poisson, compound poisson and process approximations for testing statistical significance in sequence comparisons (1992)
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    Bulletin of mathematical biology 54 (1992), S. 785-812 
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    Notes: Abstract DNA and protein sequence comparisons are performed by a number of computational algorithms. Most of these algorithms search for the alignment of two sequences that optimizes some alignment score. It is an important problem to assess the statistical significance of a given score. In this paper we use newly developed methods for Poisson approximation to derive estimates of the statistical significance ofk-word matches on a diagonal of a sequence comparison. We require at leastq of thek letters of the words to match where 0〈q≤k. The distribution of the number of matches on a diagonal is approximated as well as the distribution of the order statistics of the sizes of clumps of matches on the diagonal. These methods provide an easily computed approximation of the distribution of the longest exact matching word between sequences. The methods are validated using comparisons of vertebrate andE. coli protein sequences. In addition, we compare two HLA class II transplantation antigens by this method and contrast the results with a dynamic programming approach. Several open problems are outlined in the last section.
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    Book reviews (1992)
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    Bulletin of mathematical biology 54 (1992), S. 895-901 
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    Modelling the fast fluorescence rise of photosynthesis (1992)
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    Bulletin of mathematical biology 54 (1992), S. 999-1021 
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    Notes: Abstract We construct an ODE model for the fast fluorescence rise of photosynthesis by combining the current reaction scheme of the PS II two-electron-gate with a quasi steady-state description of the fast processes of excitation energy transfer and primary charge separation. The model is fitted to measured induction curves with a multiple shooting algorithm, and remarkably good approximations of the data are obtained. Model refinements are discussed focusing on PS II heterogeneity, and on PS I.
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    Window automata analysis of population dynamics in the immune system (1992)
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    Bulletin of mathematical biology 54 (1992), S. 21-44 
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    Notes: Abstract A formalism based on window automata is proposed as a method to analyse complex population dynamics. The method is applied to a model of the immune network (Weisbuch, G.et al., 1990.J. theor. Biol. 146, 483–499), and used to predict which attractor the system reaches after antigenic stimulation, as a function of the parameters. The attractors of the dynamics are interpreted in terms of immune conditions such as vaccination or tolerance. Scaling laws that define the regimes in the parameter space corresponding to the specific attractor reached under antigenic stimulation are derived.
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    A maximum likelihood approach to correlation dimension and entropy estimation (1992)
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    Bulletin of mathematical biology 54 (1992), S. 45-58 
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    Notes: Abstract To obtain the correlation dimension and entropy from an experimental time series we derive estimators for these quantities together with expressions for their variances using a maximum likelihood approach. The validity of these expressions is supported by Monte Carlo simulations. We illustrate the use of the estimators with a local recording of atrial fibrillation obtained from a conscious dog.
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    Analysis of propagating pattern in a chemotaxis system (1992)
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    Bulletin of mathematical biology 54 (1992), S. 77-94 
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    Notes: Abstract We consider a cell-chemotaxis model which can generate spatially heterogeneous patterns in cell density and chemoattractant. A local perturbation about the uniform steady state propagates across the domain leaving behind a steady state pattern of standing peaks and troughs. We investigate this patterning process analytically and obtain estimates for the pattern wavelength and speed of spread. We compare the analytical results with numerical simulation of the full model systems.
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    Bulletin of mathematical biology 54 (1992), S. 149-161 
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    Model of calcium-induced calcium release mechanism in cardiac cells (1992)
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    Bulletin of mathematical biology 54 (1992), S. 95-116 
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    Notes: Abstract A model with which to elucidate the mechanism of Ca2+ release from, and Ca2+ loading in the sarcoplasmic reticulum (SR) by Ca2+ current (I Ca) in cardiac cells is proposed. The SR is assumed to be comprised of three functional subcompartments: (1) the main calcium store (MCS), which contains most of the calcium (both free and bound); (2) the releasable terminal (RT), which contains the calcium readily available for release; and (3) the longitudinal network of the SR (LSR), which sequesters and the transfers the sarcoplasmic calcium to the RT. A rapid increase of the Ca2+ concentration at the outer surface of the SR (Cae) due to the fast component ofI Ca activates and inactivates this surface, inducing the release of Ca2+ from the RT to the sarcoplasmic space. The RT in turn is further activated and inactivated by a increase in the concentration of sarcoplasmic Ca2+. The Ca2+ in the sarcoplasmic space is then sequestered by the LSR, leading to the reactivation of the RT. Further increase of Cae due to the slow component ofI Ca enhances the entry of Ca2+ into the MCS to be bound by the binding substance. The free Ca2+ released from the Ca-binding substance complex is transferred to the RT for subsequent release. The activation, inactivation and reactivation are Ca2+-mediated and time-dependent. The proposed model yields simulation of the many events qualitatively similar to those observed experimentally in skinned cardiac cells.
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    Mathematical bioeconomics and the evolution of modern fisheries economics (1992)
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    Bulletin of mathematical biology 54 (1992), S. 163-184 
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    The conservation and exploitation of vulnerable resources (1992)
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    Bulletin of mathematical biology 54 (1992), S. 185-207 
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    Notes: Abstract The maximum principle of deterministic optimal control, which has proved to be a very useful tool in theoretical bioeconomics, is extended in this article to cover the optimal exploitation of a biological resource vulnerable to catastrophic collapse, the probability of which may depend in general on the state of the resource, the current control and time. A general formulation of the maximum principle for such stochastic problems is presented and a number of applications are outlined. These include: optimal harvesting of a fishery vulnerable to catastrophic collapse; optimal thinning of a forest vulnerable to fire; optimal expenditure and investment in forest fire protection and optimal consumption-pollution tradeoffs in an ecosystem vulnerable to pollution-related collapse. In addition an application of the method to a highly stylized behavioral ecology model is given.
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    A bioeconomic model of the pacific whiting (1992)
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    Bulletin of mathematical biology 54 (1992), S. 219-239 
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    Notes: Abstract The Pacific whiting (Merluccius productus) is a highly migratory fish occupying the continental shelf and slope off the west coast of North America. The species spawns in January off southern California and northern Mexico. During spring and summer the older and larger fish will migrate as far north as central Vancouver Island. Recruitment is highlys variable, with strong year classes often supporting the commercial fishery during several years of low recruitment. The level of recruitment appears to be independent of the size of the spawning population. A simple bioeconomic model of the Pacific whiting is constructed with independent recruitment. Fishery production functions are estimated from data on U.S. catch, average annual biomass and the number of vessels in the U.S. fleet. A stochastic optimization problem, seeking to maximize the expected value of industry profit, is formulated. Its solution would require a joint distribution on future recruiment and other bioeconomic parameters. Such a distribution is problematic. As an alternative, the certainty-equivalent problem is solved yielding solution values for the stochastic equilibrium and an approximately-optimal rule that sets allowable catch based on an estimate of current-year biomass. Adaptive management can result in large changes in fleet size and allowable catch from year to year. The whiting fishery might be characterized as an opportunistic fishery, requiring a generalist fleet to expand or contract as bioeconomic conditions warrant. It is possible that longrun conditions would not support a profitable fishery, but that short-run fishing is profitable based on previous years of strong recruitment. The situation is not dissimilar to that facing the owner of a marginal gold mine that opens or closes depending on the price of gold. In the case of the whiting fishery, the optimal level of short-run fishing will depend not only on price, but on current biomass, the annual cost of fishing, the discount rate and vessel productivity. A simple interactive program is provided for would-be managers.
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    Further analysis of Clark's delayed recruitment model (1992)
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    Bulletin of mathematical biology 54 (1992), S. 275-293 
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    Notes: Abstract I explore the nonlinear behavior of a model in which the number of adults in each year is the sum of recruitment (which depends nonlinearly on adult abundanceT years in the past) and a constant fraction (survival) of adults in the previous year. Adding even a small amount of age structure to the semelparous version of this model (by increasing adult survival from zero) is stabilizing in that: (1) it shifts the value of slope at which the linearized model becomes unstable about the equilibrium to a lower value; and (2) it stretches the pattern of period doubling bifurcations so that bifurcations occur at much lower values of the slope. For the iteroparous case with a maturation and survival pattern reasonably typical of long-lived organisms, the period of cycles or quasi-cycles produced increases continuously as the slope of the stock-recruitment function decreases. The possibility of arbitrarily long cycles is not predicted by the linear theory, and has important practical implictions for analyses of cyclic populations. Both truncation of the age structure and an upper limit on recruitment seem to remove this gradual increase in period. However, the former can give rise to doubling of the period. Although the nonlinear behavior is not analysed in detail, a qualitative interpretation of the behavior of this model in terms of population inertia seems to explain the behavior observed in these numerical simulations.
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    Risk-sensitive foraging: A review of the theory (1992)
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    Bulletin of mathematical biology 54 (1992), S. 355-378 
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    Environmental variability and the persistence of multiple emergence strategies (1992)
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    Bulletin of mathematical biology 54 (1992), S. 313-334 
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    Notes: Abstract Studies of plant and animal populations have demonstrated the occurrence of multiple and mixed life history strategies such as polymodal timing of germination and emergence from dormancy. We present the results of a simulation model used to test whether between-year variance in mortality can lead to the persistence of multiple hatching strategies considered over an ecological time scale (50 years). The model is based on the general life history characteristics of a population of planktonic copepods (Diaptomus sanguineus) in Bullhead Pond, Rhode Island. Our model results demonstrate that, given a range of between-year variance in mortality, multiple strategies for timing of emergence can persist in a common environment for ecologically relevant periods of time. A qualitative test of the model comparing field estimates of mean and variance of mortality in Bullhead Pond with the region of persistence indicates that the model results are in approximate agreement with field estimates. The results suggest that variability in year-to-year selection pressures, such as predation or harsh winters, may play an important role in determining the evolution of life histories.
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    Hungry chicks and mortal parents: A state-variable approach to the breeding seasons of birds (1992)
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    Bulletin of mathematical biology 54 (1992), S. 379-400 
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    Notes: Abstract We here report the results of a dynamic programming model of the breeding season of a bird, patterned after the Black-capped Chickadee (Parus atricapillus) nesting near Ithaca, New York. Optimal breeding seasons fall largely before the peak in food distribution, and this shift appears to be because peak metabolic demands of the brood are coordinated with the peak in food density and because the risk of adult mortality selects for earlier breeding than would otherwise be favored. This latter effect, first proposed by Fisher, may explain the nearly universal observation that early breeding appears to be favored in birds from a wide range of habitats and phylogenies.
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    On the iterated prisoner's dilemma in a finite population (1992)
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    Bulletin of mathematical biology 54 (1992), S. 423-443 
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    Notes: Abstract Two standard assumptions in analytical work on the iterated prisoner's dilemma are that the population is infinite, and that opponents—though randomly selected—are fixed for the duration of the game. This paper explores the consequences of relaxing both assumptions. It is shown in particular that if opponents are drawn at random throughout the game, then stable cooperation via reciprocity requires both that the probability of a further interaction be sufficiently high—higher than when opponents are fixed—and that the population not exceed a certain critical size, which depends on the probability of further interaction.
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    The effect of variability on host feeding and reproductive success in parasitoids (1992)
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    Bulletin of mathematical biology 54 (1992), S. 465-476 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We model the behaviour of a solitary parasitoid that can either eat a host or lay an egg on it. When the parasitoid does not die as a result of starvation, it should always lay an egg on a host. We compute the parasitoid's lifetime reproductive success in this case, and illustrate the effects of the mean time to find hosts and the variance in this time. We then develop a state-dependent model in which the decision to eat the host or lay an egg on it depend on the parasitoid's state. This model is used to explore the effects of variability in the time to find hosts on the parasitoid's lifetime reproductive success. It is shown that there can be a non-monotonic relationship between reproductive success and variability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02464844
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  • 95
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    Quantitative PCR: Procedures and precisions (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 477-502 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We develop a multitype branching-process model for the Polymerase Chain Reaction (PCR). We apply the model to a comparison of three methods for estimating the initial number of molecules of target present in a PCR. These three methods are: one which uses a coamplified, internal control; one which uses an external control series; and one which uses simple extrapolation of log outputvs time (no control). We identify assumptions for each method which permit mathematical analysis of bias and precision. All three methods perform well if: (1) replication efficiencies are stable among reactions; (2) other method-specific conditions on efficiencies are met; and (3) product accumulates exponentially throughout the range where it is observed. When replication efficiencies vary among reactions but other optimal conditions for each method hold, the no-control and external-control methods lose precision relative to the internal control method, but they may still perform satisfactorily for many applications. The internal control method continues to perform well even if accumulation of product plateaus. This method depends, however, on a condition we call equivalence of replication efficiencies, the attainability of which in practice remains to be proven.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02459631
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  • 96
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    A local algorithm for DNA sequence alignment with inversions (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 521-536 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A dynamic programming algorithm to find all optimal alignments of DNA subsequences is described. The alignments use not only substitutions, insertions and deletions of nucleotides but also inversions (reversed complements) of substrings of the sequences. The inversion alignments themselves contain substitutions, insertions and deletions of nucleotides. We study the problem of alignment with non-intersecting inversions. To provide a computationally efficient algorithm we restrict candidate inversions to theK highest scoring inversions. An algorithm to find theJ best non-intersecting alignments with inversions is also described. The new algorithm is applied to the regions of mitochondrial DNA ofDrosophila yakuba and mouse coding for URF6 and cytochrome b and the inversion of the URF6 gene is found. The open problem of intersecting inversions is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02459633
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  • 97
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    AnO(N 2 logN) restriction map comparison and search algorithm (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 599-618 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We present anO(R logP) time,O(M+P 2 ) space algorithm for searching a restriction map withM sites for the best matches to a shorter map withP sites, whereR, the number of matching site pairs, is bounded byMP. As first proposed by Watermanet al. (1984,Nucl. Acids Res. 12, 237–242) the objective function used to score matches is additive in the number of unaligned sites and the discrepancies in the distances between adjacent aligned sites. Our algorithm is basically a sparse dynamic programming computation in which “candidate lists” are used to model the future contribution of all previously computed entries to those yet to be computed. A simple modification to the algorithm computes the distance between two restriction maps withM andN sites, respectively, inO(MN(logM+logN)) time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02459636
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  • 98
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    A survey of multiple sequence comparison methods (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 563-598 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Multiple sequence comparison refers to the search for similarity in three or more sequences. This article presents a survey of the exhaustive (optimal) and heuristic (possibly sub-optimal) methods developed for the comparison of multiple macromolecular sequences. Emphasis is given to the different approaches of the heuristic methods. Four distance measures derived from information engineering and genetic studies are introduced for the comparison between two alignments of sequences. The use ofentropy, which plays a central role in information theory as measures of information, choice and uncertainty, is proposed as a simple measure for the evaluation of the optimality of an alignment in the absence of anya priori knowledge about the structures of the sequences being compared. This article also gives two examples of comparison between alternative alignments of the same set of 5SRNAs as obtained by several different heuristic methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02459635
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  • 99
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    Complex dynamics in a model microbial system (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 619-648 
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    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The forced double-Monod model (for a chemostat with a predator, a prey and periodically forced inflowing substrate) displays quasiperiodicity, phase locking, period doubling and chaotic dynamics. Stroboscopic sections reveal circle maps for the quasiperiodic regimes and noninvertible maps of the interval for the chaotic regimes. Criticality in the circle maps sets the stage for chaos in the model. This criticality may arise with an increase in the period or amplitude of forcing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02459637
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  • 100
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    Population studies: animal ecology and demography (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 695-695 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02459641
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