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  • 1990-1994  (10)
  • Analytical Chemistry and Spectroscopy  (7)
  • predation  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Evolutionary ecology 6 (1992), S. 449-457 
    ISSN: 1573-8477
    Keywords: optimal foraging ; predation ; predator-prey interactions ; mathematical models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three mechanisms by which increasing predation can increase prey population density are discussed: (1) Additional predation on species which have negative effects on the prey; (2) Predation on consumer species whose relationship with their own prey is characterized by a unimodal prey isocline; (3) Predation on species which adaptively balance predation risk and food intake while foraging. Possible reasons are discussed for the rarity of positive effects in previous predator-manipulation studies; these include the short-term nature of experiments, the large magnitudes of predator density manipulation, and various sources of bias in choice of system and interpretation of results.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Evolutionary ecology 4 (1990), S. 93-102 
    ISSN: 1573-8477
    Keywords: character displacement ; competition ; consumer-resource system ; frequency dependence ; functional response ; predation ; resource
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary How should a consumer of two resource types adapt to changes in their abundances? This paper shows that many different biological circumstances produce mixed responses; i.e. increasing availability of one resource increases the consumer's efforts to obtain it, while increasing availability of the other resource decreases the consumer's efforts at exploitation. This implies that competition from a second consumer species may cause convergent or divergent character displacement of the first species. The signs and magnitudes of the second derivative of the fitness function are important in determining which outcome occurs. The degree of resource limitation of the consumer species also influences the nature of adaptive shifts in resource use.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Evolutionary ecology 8 (1994), S. 36-52 
    ISSN: 1573-8477
    Keywords: foraging ; daily routine ; digestion ; starvation ; predation ; reserves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Birds show a typical daily pattern of heavy morning and secondary afternoon feeding. We investigate the pattern of foraging by a bird that results in the lowest long-term rate of mortality. We assume the following: mortality is the sum of starvation and predation. The bird is characterized by two state variables, its energy reserves and the amount of food in its stomach. Starvation occurs during the day if the bird's reserves fall to zero. The bird starves during the night if the total energy stored in reserves and the stomach is less than a critical amount. The probability that the bird is killed by a predator is higher if the bird is foraging than if it is resting. Furthermore, the predation risk while foraging increases with the bird's mass. From these assumptions, we use dynamic programming techniques to find the daily foraging routine that minimizes mortality. The principal results are (1) Variability in food finding leads to routines with feeding concentrated early in the day, (2) digestive constraints cause feeding to be spread more evenly through the day, (3) even under fairly severe digestive constraints, the stomach is generally not full and (4) optimal fat reserve levels are higher in more variable environments and under digestive constraints. This model suggests that the characteristic daily feeding pattern of small birds is not due to digestive constraints but is greatly influenced by environmental variability.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 543-550 
    ISSN: 0886-9383
    Keywords: Fragment occurrence data ; Molecular similarity ; Similarity searching ; Standardization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substructural fragment occurrence data are widely used as the basis for measures of inter-molecular structural similarity. This paper investigates the effect of standardization on the effectiveness of such measures using eight data sets for which both structural and biological activity data are available. Eight different standardization methods are studied and it is shown that there is no significant difference in the effectivenesses of the various methods; accordingly, any of them can be used for the calculation of intermolecular structural similarity.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0935-6304
    Keywords: GC-AED ; Sulfur ; FCC gasoline ; Compound-independent calibration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The identification and quantification of sulfur-containing compounds in gasoline has become an area of interest because of impending legislation regulating total sulfur levels in these fuels. To study the effects of catalyst type and catalytic conditions on gasoline sulfur distribution, a method has been developed employing both the compound-independent and element-specific response of the atomic emission detector (AED). Calibration and quantification can be accomplished even where standards are not available, owing to the nature of the AED response.Compounds were separated on a thick film polydimethylsiloxane column. An external calibration curve was applied to the area responses of individual sulfur components in the sulfur chromatogram, and the concentrations of each were calculated. Summation of these sulfur concentrations over the gasoline range yields the total sulfur content of the gasoline.The method is applicable to the determination of these compounds in raw crude oils, finished gasolines, fluid cracking catalyst (FCC) unit gasolines, and fluid catalytic cracking “model” compound studies. A prefractionating column was employed to remove heavy (〉C13) materials; prefractionation is not, however, necessary for distilled or commercial gasoline samples. Detection limits, linearity, detector stability, and accuracy are discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 23 (1994), S. 169-172 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Geometrical effects occur when primary x-rays irradiate a mineral inclusion which lies close to the boundary between it and a surrounding mineral having a different chemical composition. An investigation of two types of near-edge effects was performed in the case when x-ray microfluorescence is applied for analysis. For zinc sulfide in calcium carbonate and for arsenopyrite in serpentine, the increase in measured characteristic x-ray intensity near the boundary is 15-25%. Analytical mathematical expressions were developed to correct for such effects and the calculated results are in good agreement with measured values.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 23 (1994), S. 242-242 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 74-80 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 252Cf plasma desorption mass Spectrometry was applied to some series of ionic coordination compounds and was demonstrated to yield better results than fast atom bombardment mass Spectrometry. Intra-ligand fragmentadon was observed regularly, and evidence was also obtained for a fission fragment-induced methylene transfer reaction.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 23 (1994), S. 286-287 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 377-381 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: In characteristic x-ray intensity calculations, the total L spectrum can be represented by separate spectra from L1, L2 and L3 subshell transitions. The expressions presented here take into account the ionization not only of the L1, L2 and L3 subshells but also of the K shell. The approximating polynomials for the calculation of the radiative transition probability and the Koster-Kroning transition probability are derived. Examples are presented of intensity calculations in multi-component systems using the TEREN program.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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