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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 73 (1994), S. 255-264 
    ISSN: 1570-7458
    Keywords: grasshopper ; monophagy ; polyphagy ; Simmondsia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The feeding behavior of different populations of the grasshopper,Schistocerca shoshone, was investigated in the southwestern United States. Insects from three riparian populations, with a broad spectrum of plants available to them, tended to eat plants roughly in relation to their availability except that broad-leaved herbaceous plants were avoided. Insects from a desert population in a plantation ofSimmondsia fed exclusively on that plant, as did those from another population in the Tucson mountains, despite the availability of a range of other plants. Insects from a third desert population, near Portal, fed mainly onProsopis, the dominant woody plant. In detailed behavioral experiments in the laboratory, insects from Tucson mountains readily acceptedSimmondsia, and less readily acceptedProsopis. Three other common woody plants from the habitat were generally rejected without feeding. Insects from Portal acceptedProsopis andSimmondsia with approximately equal readiness. Breeding experiments suggested that the differences between the plantation insects and those from Portal was genetic and not induced by experience. The insects from both populations were potentially polyphagous and ate a wide range of plants in the laboratory if given no alternative.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8889
    Keywords: development ; food aversion learning ; grasshopper ; habituation ; plant acceptability ; polyphagy ; survival
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The feeding behavior of final-instar nymphs ofSchistocerca americana was observed when they first encountered plants that ranged in acceptability from being eaten in large amounts to not being eaten at all. Growth and survival on the same plants through the last stadium were also studied and the results combined as a suitability index to facilitate comparison with the behavior. Although the plants that were eaten most gave the highest suitability index and those that were not eaten permitted no survival, there was no simple relationship between the amounts eaten and the suitability for growth and survival. The possibility that the insects might become habituated to plants that were initially unacceptable was investigated, but no habituation was found over a 3-day period. It is suggested that food intake is largely determined by the presence of deterrent compounds in the less acceptable foods and that nutritional differences between the plants are likely to have been of minor importance. The behavior on some foods suggests that food aversion learning may be involved. It is concluded that the variability of the insects' behavior makes it impossible to predict the suitability of a plant from their immediate behavioral responses. In the field, insects may sometimes reject foods that would be suitable for survival and development, and feed on plants that are nutritionally deficient or even toxic.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 7 (1969), S. 527-537 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dilatometric measurements were made to determine the change in apparent specific volume ϕ of DNA resulting from thermal denaturation in neutral solution, ϕ increased continuously with temperature in the range 10-85°C. No deviations from a monotonically rising curve were observed in the ϕ versus temperature profile in the region of the melting temperature. The results are interpreted in terms of a partial loss of the preferentially bound DNA hydration shell. The nature of the well known buoyant density difference between native and denatured DNA was investigated by evaluating the densities in a series of cesium salt gradients at constant temperature. Extrapolation of the results to zero water activity indicates that the partial specific volumes of anhydrous native and denatured DNA are equal. The density difference at nonzero water activities is attributed to decreased hydration in the denatured state. The absence of a related change in ϕ accompanying the denaturation in the dilatometric experiments suggests that the probable volume change associated with loss of bound water during denaturation is accompanied by other compensatory volume effects. The possible nature of these volume effects is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 445-457 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The change in apparent molal volume φ of DNA on thermal denaturation in carbonate buffer at pH 11.0 has been determined by the dilatometric method. It was found that φ increases sigmoidally during the helix-coil transition. Several methods, including a colorimetric technique that closely simulates the conditions used in the dilatometric experiments, were employed to estimate the protons lost by the DNA during the transition. These measurements indicated that the extent of the proton loss depends on the counterion present, increasing in the order Li+ 〈 Na+ 〈 K+ 〈 Cs+. The major part of the volume changes observed during the denaturation is due to the volume changes expected to accompany the transfer of protons from the bases guanine and thym ne to carbonate ions. As has been previously reported for the denaturation of DNA at neutral pH, the volume change directly due to the change in shape of the polymer molecules is so small as to be experimentally undetectable.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The appearance of a significant deuterium isotope effect during the combustion of the solid HMX compound verifies that the chemical reaction kinetics is a major contributor in determining the experimentally observed or global burn rate. Burn rate comparison of HMX and its deuterium labeled HMX-d8 analogue reveals a primary kinetic deuterium isotope effect (1° KDIE) at 500 psig (3.55 MPa) and l000 psig (6.99 MPa) pressures and selectively identifies covalent carbon-hydrogen bond rupture as the mechanistic step which ultimately controls the HMX bum rate under the static combustion conditions of this experiment. The 1° KDIE value further suggests the rate-limiting C—H bond rupture occurs during the solid state HMX decomposition/deflagration portion of the overall combustion event and is supported by other independently published studies. A possible anomalous KDIE result at 1500 psig (10.4 MPa) is addressed. This condensed phase KDIE approach illustrates a direct link between lower temperature/pressure thermal decomposition and deflagration processes and their potential applicability to the combustion regime. Most importantly, a new general method is demonstrated for mechanistic combustion investigations which selectively permits an in-situ identification of the compound's burn rate-controlling step.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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