Neues mathematisches Verfahren zur Charakterisierung unbekannter organischer Vielstoffgemische durch die Adsorptionsanalyse

The adsorption analysis, a process-technology-oriented analytical method, characterizes complex organic multicomponent mixtures with respect to their different adsorbability by a sorbent such as activated carbon. The analytical method is based on the determination of adsorption isotherms and their mathematical interpretation. So far, this interpretation has required the use of a large computer or a time-consuming computing program, in general. With the BASIC computing program “MAVIAS 10”, on the basis of the IAS theory a mathematical approach has been found which provides sufficient accuracy, demands low expenditure of time and makes the use of a small computer possible.     

Orogen-struktur und Metallverteilung Im östlichen Zagros (Südost-Iran)

Zusammenfassung Zwischen dem zentral-iranischen Hochplateau im NE und dem arabischen Block in SW entstanden im Verlauf mehrerer Faltungsphasen vom mittleren Mesozoikum bis ins jüngste Tertiär eine Reihe von Struktur-Zonen, die wir als IranidenOrogen (i. w. S.) zusammenfassen. Im östlichen Zagros-Gebirge (Kerman-Gebiet) zeichnet sich jede dieser Zonen durch typische, mehr oder weniger komplexe Metallkonzentrationen aus.     

Infrared and submillimetre studies of Vega-excess stars

We report new infrared and submillimetre observations of a sample of 24 candidate Vega-excess stars, and derive CO masses, dust masses, gas to dust ratios and the strengths of various emission lines. Most of these stars have dustier discs than the class archetypes (Vega, Fomalhaut, β Pic, etc.), yet, like the archetypes, all the stars observed in CO show the gas content of their discs to be depleted compared with molecular cloud values. We discuss how the extra dust content might imply that these stars are less evolved than the archetypes, and use other infrared and submillimetre characteristics to support this contention.     

Sustainable environmental and resource management futures for Sub-Saharan Africa

Reports

MEDACTA '93 Modern Educational Technologies     

Metals in sediments and fish from Sea Lots and Point Lisas Harbors, Trinidad and Tobago

Concentrations of heavy metals were determined in nearshore marine sediments and fish tissue from Sea Lots area on the west coast, at Caroni Lagoon National Park, and in the Point Lisas harbor, Trinidad. The most dominant metals found in sediments were Al, Fe and Zn with mean concentrations highest at Sea Lots (Al-39420 μg/g; Fe-45640 μg/g; Zn-245 μg/g), when compared to sediments from Point Lisas (Al-11936 μg/g; Fe-30171 μg/g; Zn-69 μg/g) and Caroni (Al-0400 μg/g; Fe-19000 μg/g; Zn-32 μg/g), High concentration of Cu, Al, Fe and Zn were also detected in fish tissue from Point Lisas and Caroni. Metal concentrations in fish tissue showed significant correlation with sediment metals concentration, which suggests that tissue levels are influenced by sediment concentration. Of the metals, only Zn, Hg and Cu had a bioaccumulation factor (BAF) greater than one, which suggests a high bioaccumulation potential for these metals.     

Lattice strain measurements on sandstones under load using neutron diffraction

Neutron diffraction methods (both time-of-flight- and angle-dispersive diffraction) are applied to intracrystalline strain measurements on geological samples undergoing uniaxial increasing compressional load. The experiments were carried out on Cretaceous sandstones from the Elbezone (East Germany), consisting of >95% quartz which are bedded but without crystallographic preferred orientation of quartz. From the stress–strain relation the Young’s modulus for our quartz sample was determined to be (72.2±2.9) GPa using results of the neutron time-of-flight method. The influence of different kinds of bedding in sandstones (laminated and convolute bedding) could be determined. We observed differences of factor 2 (convolute bedding) and 3 (laminated bedding) for the elastic stiffness, determined with angle dispersive neutron diffraction (crystallographic strain) and with strain gauges (mechanical strain). The data indicate which geological conditions may influence the stress–strain behaviour of geological materials. The influence of bedding on the stress–strain behaviour of a laminated bedded sandstone was indicated by direct residual stress measurements using neutron time-of-flight diffraction. The measurements were carried out six days after unloading the sample. Residual strain was measured for three positions from the centre to the periphery and within two radial directions of the cylinder. We observed that residual strain changes from extension to compression in a different manner for two perpendicular directions of the bedding plane.     

Far from equilibrium enstatite dissolution rates in alkaline solutions at earth surface conditions

Far from equilibrium enstatite dissolution rates both open to atmospheric CO₂ and CO₂ purged were measured as a function of solution pH from 8 to 13 in batch reactors at room temperature. Congruent dissolution was observed after an initial period of incongruent dissolution with preferential Si release from the enstatite. Steady-state dissolution rates in open to atmospheric CO₂ conditions decrease with increase in solution pH from 8 to 12 similar to the behavior reported by other investigators. Judging from the pH 13 dissolution rate, rates increase with pH above pH 12. This is thought to occur because of the increase in overall negative surface charges on enstatite as Mg surface sites become negative above pH 12.4, the pH of zero surface charge of MgO.Steady-state dissolution rates of enstatite increase above pH 10 when CO₂ was purged by performing the experiments in a N₂ atmosphere. This suggests inhibition of dissolution rates above pH 10 when experiments were open to the atmosphere. The dissolved carbonate in these solutions becomes dominantly CO₃²⁻ above pH 10.33. It is argued that CO₃²⁻ forms a >Mg₂-CO₃ complex at positively charged Mg surface sites on enstatite, resulting in stabilization of the surface Si-O bonds. Therefore, removal of solution carbonate results in an increase in dissolution rates of enstatite above pH 10. The log rate of CO₂-purged enstatite dissolution in moles per cm² per s as a function of increasing pH above pH 10 is equal to 0.35. This is consistent with the model of silicate mineral dissolution in the absence of surface carbonation in alkaline solutions proposed earlier in the literature.     

Towards sectoral and standardised vulnerability assessments: the example of heatwave impacts on human health

The relevance of climate change is especially apparent through the impacts it has on natural and societal systems. A standardised methodology to assess these impacts in order to produce comparable results is still lacking. We propose a semi-quantitative approach to calculate vulnerability to climate change, with the ability to capture complex mechanisms in human-environmental systems. The key mechanisms are delineated and translated into a deterministic graph (impact chain). A fuzzy logic algorithm is then applied to address uncertainty regarding the definition of clear threshold values. We exemplify our approach by analysing the direct impacts of climate change on human health in North Rhine-Westphalia, Germany, where the urban heat island potential, the percentage of elderly population as well as the occurrence of heat waves determine impact intensity. Increases in heatwaves and elderly population will aggravate the impacts. While the influence of climatic changes is apparent on larger spatial scales, societal factors determine the small scale distribution of impacts within our regional case study. In addition to identifying climate change impact hot spots, the structured approach of the impact chain and the methodology of aggregation enable to infer from the results back to the main constituents of vulnerability. Thus, it can provide a basis for decision-makers to set priorities for specific adaptation measures within the complex field of climate change impacts.     

Inter-annual variability in isotope and elemental ratios recorded in otoliths of an anadromous fish

Isotope ratios and elemental concentrations in otoliths are often used as natural tags to reconstruct migratory movements and connectivity patterns in marine and anadromous fishes. Although differences in otolith geochemistry have been documented among geographically separated populations, inter-annual variation within locations is less frequently examined. We compared otolith isotope (δ¹⁸O and ⁸⁷Sr:⁸⁶Sr) and elemental ratios (Sr:Ca and Ba:Ca) from several annual cohorts of juvenile American shad (Alosa sapidissima) in three rivers. These four geochemical signatures distinguished among river-specific populations of this species at both large and small geographic scales, with δ¹⁸O and ⁸⁷Sr:⁸⁶Sr generating the majority of multivariate variation. We found significant variation among years for all variables in two to three rivers. However, the magnitude of variability differed among ratios, with δ¹⁸O ratios showing substantial inter-annual shifts while ⁸⁷Sr:⁸⁶Sr ratios were relatively stable across years. Sr:Ca and Ba:Ca ratios also varied among years. These results imply that investigators using environmentally labile signatures must quantify geochemical signatures for each cohort of interest in order to confidently identify origins of migrants.