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  • 1
    Electronic Resource
    Electronic Resource
    PHYTOREMEDIATION (1998)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 49 (1998), S. 643-668 
    Details
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Contaminated soils and waters pose a major environmental and human health problem, which may be partially solved by the emerging phytoremediation technology. This cost-effective plant-based approach to remediation takes advantage of the remarkable ability of plants to concentrate elements and compounds from the environment and to metabolize various molecules in their tissues. Toxic heavy metals and organic pollutants are the major targets for phytoremediation. In recent years, knowledge of the physiological and molecular mechanisms of phytoremediation began to emerge together with biological and engineering strategies designed to optimize and improve phytoremediation. In addition, several field trials confirmed the feasibility of using plants for environmental cleanup. This review concentrates on the most developed subsets of phytoremediation technology and on the biological mechanisms that make phytoremediation work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.arplant.49.1.643
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Generation of voluminous silicic magmas and formation of mid-Cenozoic crust beneath north-central Mexico: evidence from ignimbrites, associated lavas, deep crustal granulites, and mantle pyroxenites (1996)
    Springer
    Contributions to mineralogy and petrology 123 (1996), S. 375-389 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Isotopic and trace element data from mantle and granulite xenoliths are used to estimate the relative contributions of mantle and crustal components to a large ignimbrite, referred to as the upper ignimbrite, that is representative of the voluminous mid-Cenozoic rhyolites of northwestern Mexico. The study also uses data from the volcanic rocks to identify deep crustal xenoliths that are samples of new crust created by the Tertiary magmatism. The isotopic composition of the mantle component is defined by mantle-derived pyroxenites that are interpreted to have precipitated from mid-Cenozoic basaltic magmas. This component has ɛNd≈+1.5, 87Sr/86Sr≈0.7043 and 206Pb/204Pb≈18.6. Within the upper ignimbrite and associated andesitic and dacitic lavas, initial 87Sr/86Sr is positively correlated with SiO2, reaching 0.7164 in the ignimbrite. Initial 206Pb/204Pb ratios also show a positive correlation with silica, whereas ɛNd values have a crude negative correlation, reaching values as low as −2. Of the four isotopically distinct crustal components identified from studies of granulite xenoliths, only the sedimentary protolith of the paragneiss xenoliths can be responsible for the high initial 87Sr/86Sr of the upper ignimbrite. The Nd, Sr, and Pb isotopic compositions of the upper ignimbrite can be modeled with relatively modest assimilation (≤20%) of the sedimentary component ± Proterozoic granulite. Gabbroic composition granulite xenoliths have distinctive Nd, Sr, and Pb isotope ratios that cluster closely within the range of compositions found in the andesitic and dacitic lavas. These mafic granulites are cumulates, and their protoliths are interpreted to have precipitated from the intermediate to silicic magmas at 32–31 Ma. These mafic cumulate rocks are probably representative of much of the deep crust that formed during mid-Cenozoic magmatism in Mexico. Worldwide xenolith studies suggest that the relatively great depth (≤20 km) at which assimilation-fractional crystallization took place in the intermediate to silicic magma systems of the La Olivina region is the rule rather than the exception. Oligocene ignimbrites of the southwestern United States (SWUS) have substantially lower ɛNd values (e.g. 〈−6) than the upper ignimbrite and other rhyolites from Mexico. This difference appears to reflect a greater crustal contribution to ignimbrites of the SWUS, perhaps due to a higher temperature of the lower crust prior to the emplacement of the Oligocene basaltic magmas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050163
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  • 3
    Electronic Resource
    Electronic Resource
    The effects of changing intracellular pH on calcium and potassium currents in smooth muscle cells from the guinea-pig ureter (1998)
    Springer
    Pflügers Archiv 435 (1998), S. 518-522 
    Details
    ISSN: 1432-2013
    Keywords: Key words Calcium ; Contraction ; Electrophysiology ; Guinea-pig ; pH ; Potassium ; Ureter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Guinea-pig ureteric smooth muscle is unusual in that intracellular acidification increases and alkalinization decreases force production. To help elucidate the mechanism underlying these effects on force we have investigated the effects of changing intracellular pH on both calcium and potassium currents in single cells isolated from the guinea-pig ureter to determine their possible role in force development. Depolarization to +40 mV resulted in a fast transient outward current which was inhibited by 4-aminopyridine but not tetraethylammonium. Intracellular alkalinization (20 mM trimethylamine) increased this current to 179 ± 24% of the control and resulted in the development of a slowly activating large outward current which was inhibited by tetraethylammonium and washout. Acidification (40 mM sodium butyrate) decreased the fast transient outward current to 58 ± 3% of the control and did not produce a slowly activating current. When potassium was replaced by caesium in the pipette solution, depolarization to 0 mV resulted in an inward calcium current which was abolished by nifedipine. Intracellular alkalinization increased this current to 126 ± 11% of the control whereas acidification had the opposite effect, decreasing it to 55 ± 10%. Furthermore, current-clamp experiments showed that intracellular alkalinization inhibited the amplitude of the action potential, therefore decreasing excitability of the cell. From our results, we suggest that the predominant effects of intracellular pH on force production in the guinea-pig ureter are mediated via the modulation of outward potassium currents (thereby reducing excitability of the tissue) rather than the effects on the inward calcium current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050547
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  • 4
    Electronic Resource
    Electronic Resource
    Changes of pH affect calcium currents but not outward potassium currents in rat myometrial cells (1995)
    Springer
    Pflügers Archiv 431 (1995), S. 135-137 
    Details
    ISSN: 1432-2013
    Keywords: pH ; uterus ; calcium current ; potassium current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Spontaneous contraction of uterine smooth muscle is enhanced by alkalinization and depressed by acidification. We have investigated the ionic currents responsible for this in single myometrial cells. Intracellular acidification (20 mM butyrate) at constant external pH depressed the magnitude of the calcium current to 58±6% of control, but had little effect on outward currents. Similar but slower effects were also observed when the extracellular pH was lowered to 6.9 (56±9% of control). Correspondingly, when the intracellular or extracelluar pH was elevated (20 mM NH4Cl or pH 7.9 respectively) the calcium current magnitude increased (165±15 % in NH4Cl; 136±2 % at pH 7.9) and there was, again, no effect on the outward currents. These observations are consistent with the effects of pH on spontaneous contractile activity being due to an effect on the membrane calcium current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374388
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  • 5
    Electronic Resource
    Electronic Resource
    The link between physics and chemistry in track modelling (1999)
    Springer
    Radiation and environmental biophysics 38 (1999), S. 221-228 
    Details
    ISSN: 1432-2099
    Keywords: Key words Track structure ; Radiation tracks ; Stochastic simulations ; Molecular dynamics ; Spin effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract  The physical structure of a radiation track provides the initial conditions for the modelling of radiation chemistry. These initial conditions are not perfectly understood, because there are important gaps between what is provided by a typical track structure model and what is required to start the chemical model. This paper addresses the links between the physics and chemistry of tracks, with the intention of identifying those problems that need to be solved in order to obtain an accurate picture of the initial conditions for the purposes of modelling chemistry. These problems include the reasons for the increased yield of ionisation relative to homolytic bond breaking in comparison with the gas phase. A second area of great importance is the physical behaviour of low-energy electrons in condensed matter (including thermolisation and solvation). Many of these processes are not well understood, but they can have profound effects on the transient chemistry in the track. Several phenomena are discussed, including the short distance between adjacent energy loss events, the molecular nature of the underlying medium, dissociative attachment resonances and the ability of low-energy electrons to excite optically forbidden molecular states. Each of these phenomena has the potential to modify the transient chemistry substantially and must therefore be properly characterised before the physical model of the track can be considered to be complete.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004110050162
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