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  • 11
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 335 (1988), S. 21-22 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] DURING the nineteenth century, the discovery and study of 'lost civilizations' gave great impetus to the development of archaeology. The surviving traces of such civilizations - whether in the Mycenaean and Minoan palaces of the Aegean, the frontier defences of the Roman Empire, the pyramids of the ...
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The reaction64Ni(36S,34Si)66Zn atE=198 MeV has been used to measure the mass excess of34Si; a value of −19.971 −0.044 +0.037 MeV was obtained. This result which is in agreement with the previous value (−19.85±0.30 MeV) is in excellent agreement with recent shell-model mass predictions. The result is discussed within the context of the proposed region of deformation aroundZ=11,N=20.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1432-2048
    Keywords: Acer ; Daucus ; Cell culture ; Freeze-fracture (rapid freezing) ; Membrane recycling ; Plasma membrane ; Secretion (vesicle-mediated)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Freeze-fracture electron microscopy of propane-jet-frozen samples has been employed to investigate vesicle-mediated secretion and membrane recycling events in carrot (Daucus carota L.) and sycamore maple (Acer pseudoplatanus L.) suspension-culture cells. Stabilization of the cells by means of ultrarapid freezing has enabled us to preserve the cells in a turgid state and to visualize new intermediate membrane configurations related to these events. Indeed, many of the observed membrane configurations, such as flattened membrane vesicles with slit-shaped membrane fusion sites and horseshoe-shaped membrane infoldings, appear to result from the action of turgor forces on the plasma membrane. Individual cells exhibited great variations in numbers and types of membrane configurations postulated to be related to secretion and membrane-recycling events. In the majority of cells, the different membrane profiles displayed a patchy distribution, and within each patch the membrane configurations tended to be of the same stage. This result indicates that secretory events are triggered in domains measuring from 0.1 to about 10 μm in diameter. Based on an extensive analysis of the different membrane configurations seen in our samples, we have formulated the following model of vesicle-mediated secretion in plant cells: Fusion of a secretory vesicle with the plasma membrane leads to the formation of a single, narrow-necked pore that increases in diameter up to about 60 nm. During discharge, the vesicle is flattened, forming a disc-shaped structure perpendicular to the plane of the plasma membrane. As the vesicle is flattened, the pore is converted to a slit, the maximum length of which coincides with the diameter of the flattened vesicle. The flattened vesicle then tips over and concomitantly the plasma-membrane slit becomes curved into a horseshoe-shaped configuration as it extends along the outer margins of the tipped-over vesicle. Some coated pits are present interspersed between the above-mentioned structures, but their numbers appear insufficient to account for an exclusively endocytotic mechanism of membrane recycling. Instead, our micrographs are more consistent with a mixed mode of recycling of membrane components to the cortical endoplamic reticulum and to Golgi cisternae that involves both internalization of membrane by endocytosis and of individual lippid molecules by unknown mechanisms (lipid exchange proteins?). To this end, overall flattening out of the horseshoe-shaped membrane infoldings is accompanied by a retraction and reduction in size of their central, tongue-like structure.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 328 (1987), S. 379-380 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two-dimensional γ-ray energy correlations have been measured at high spins in1800s with the TESSA2 spectrometer. The Eγ − Eγcorrelation matrix displays ridges characteristic of rotational bands with different energy separations of 96± and 72± keV for the energy regions of 660 to 840 keV and 975 to 1170 keV, respectively. The separation of these ridges remains constant in both energy regions. The dynamical moments of inertia are θ(2) =83±3 and 111±5 ħ2/MeV, respectively. The latter value suggests superdeformation in1800s with an axis ratio c/a=1.76 (β2 ≅0.64) at high spins.
    Type of Medium: Electronic Resource
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  • 15
    ISSN: 1434-601X
    Keywords: 21.10.Dr ; 25.70.Cd ; 27.30.+t
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The ground-state masses of35Si and34Si have been measured using the reactions64Ni(36S,35,34Si)65,66Zn at a36S beam energy of 198 MeV.34,35Si14+ ions were analysed and identified in a QMG/2 magnetic spectrometer and gas-filled focal-plane detector. The experimental mass excess of35Si was determined to be −14.58± 0.12 0.07 MeV while that of34Si was measured as −19.961±0.034 MeV. A comparison is made with the results of mass model predictions.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Experimental and applied acarology 4 (1988), S. 265-276 
    ISSN: 1572-9702
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Factors inducing outbreaks of spider mites (Acari: Tetranychidae) following use of pyrethroid insecticides are reviewed. Differentials in direct toxicity between spider mites and phytoseiid (Acari: Phytoseiidae) predators provide one explanation. Wide variation exists between pyrethroids in their direct toxicity toTetranychus urticae. The acaricidal action of pyrethroids is largely controlled by the amount of irritancy or repellency induced by the respective chemicals. Laboratory assays for repellency reflect field results. Repellent activity induces spider-mite dispersal to either recolonise plants free of residues or leave the treated habitat. Pyrethroids may also affect reproduction and development rates. Residual activity is likely to vary, so limiting any general theory of spider-mite responses to pyrethroids. Variable responses to pyrethroids, strain variation and development of behavioural resistance also add complications to understanding outbreaks. Future research needs are identified.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 37 (1985), S. 306-306 
    ISSN: 1570-7458
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 14 (1988), S. 561-579 
    ISSN: 1573-1561
    Keywords: Creosote bush ; Larrea ; nordihydroguaiaretic acid ; grasshoppers ; monophagy ; Bootettix ; Ligurotettix ; Cibolacris ; Orthoptera ; Acrididae ; host selection ; feeding deterrence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The host-selection behavior of three species of grasshopper feeding on creosote bush,Larrea tridentata, in southern California was investigated. The species wereBootettix argentatus, which is monophagous;Ligurotettix coquilletti, oligophagous; andCibolacris parviceps, polyphagous. The monophagous species is stimulated to bite by nordihydroguaiaretic acid (NDGA), a compound that is characteristic of the host plant and that may comprise up to 10% of the dry weight of the leaf. Host specificity ofB. argentatus is enhanced by deterrent responses to compounds present in the surface waxes of all non-host-plant species. Both the oligophagous and polyphagous species are deterred by NDGA at naturally occurring concentrations. Their association withLarrea is probably based on tolerance of the plant chemicals rather than on dependence on specific chemicals. Factors other than the chemistry of the plant probably also contribute to the specificity ofB. argentatus andL. coquilletti.
    Type of Medium: Electronic Resource
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  • 19
    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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