Search results for "Geology"

Organic matter dynamics and aggregation in soils under rain forest and pastures of increasing age in the eastern Amazon Basin

1997

Abstract In the eastern Amazon basin, four neighbouring clayey Oxisols with similar particle-size distributions were selected, one under rain forest and three under pasture for 7, 12 and 17 years, respectively. These soils were sampled at depth intervals of 0.1 m down to 1 m. Although no clear effect of pasture establishment on aggregate stability was assessed, significant negative effects of cattle trampling on porosity and water retention and of vegetation change on clay water-dispersion were observed in the organic-rich horizons (0–0.40 m layers). Indirect evidence of a great change of the nature of organic materials was also suggested, particularly with (i) an increase in both negative …

Nano‐Powdered Calcium Carbonate Reference Materials: Significant Progress for Microanalysis?

2019

Strukturuntersuchung von polyestern durch direkten abbau im massenspektrometer, 1. Polyester der terephthalsäure

1976

Die Abbaureaktionen von Poly(athylenterephthalat) (1a), Poly(tetradeuteroathylenterephthalat) (1b), Poly(trimethylenterephthalat) (1c) und Poly(tetramethylenterephthalat) (1d) im Massenspektrometer wurden untersucht. Hierzu wurden die Polymeren direkt in der Ionenquelle des Massenspektrometers pyrolysiert und die entstehenden thermischen Bruchstucke durch Elektronenstos ionisiert und fragmentiert. Die thermisch- und elektronenstosinduzierten Abbaureaktionen lassen sich nebeneinander nachweisen. Die untersuchten polymeren Terephthalate 1a–d folgen in beiden Abbauschritten den gleichen Mechanismen und konnen anhand ihrer Pyrolyse-Massenspektren unterschieden werden. The degradation reactions …

Reply to the discussion by E. Soman

1985

Recycling of heterogeneous plastics wastes. II—The role of modifier agents

1993

Abstract Recycling of mixed plastics waste, mainly composed of PEs, PET and PVC has been carried out by blending with recycled polyethylene. Although the extrusion of these blends has been carried out at high temperatures, the degradation of the PVC was modest due to the short residence times. The mechanical properties of these secondary materials, up to about 30% of mixed plastics waste, are very similar to those of the recycled polyethylene, except for the elongation to break. By adding some modifier agents, the elongation at break and especially the impact strength can be further improved.

1976

The thermal degradation of poly(oxycarbonylpentamethylene), (poly-e-caprolactone), (3), was investigated at 220°C and 80 mm Hg under nitrogen. 3 was found to be thermally much more stable than poly(oxycarbonylethylene), (poly-β-propiolactone), (1), although it decomposed faster than poly(oxycarbonyl-1,1-dimethylethylene), (polypivalolactone), (2). The reaction was of the first order with a rate constant of k=6,2.10−4 min−1 and proceeded via a “zipper mechanism” to yield monomeric e-caprolactone. Der thermische Abbau von Poly(oxycarbonylpentamethylen), (Poly-e-caprolacton), (3), wurde bei 220°C im Stickstoffstrom bei 80 mm Hg untersucht. Dabei wurde gefunden, das 3 thermisch wesentlich stabi…

New Porphyrin/Fe-Loaded TiO2 Composites as Heterogeneous Photo-Fenton Catalysts for the Efficient Degradation of 4-Nitrophenol

2013

A new class of porphyrin(Pp)/Fe co-loaded TiO2 composites opportunely prepared by impregnation of [5,10,15,20-tetra(4-tert-butylphenyl)] porphyrin (H2Pp) or Cu(II)[5,10,15,20-tetra(4-tert-butylphenyl)] porphyrin (CuPp) onto Fe-loaded TiO2 particles showed high activities by carrying out the degradation of 4-nitrophenol (4-NP) as probe reaction in aqueous suspension under heterogeneous photo-Fenton-like reactions by using UV-visible light. The combination of porphyrin-Fe-TiO2 in the presence of H2O2 showed to be more efficient than the simple bare TiO2 or Fe-TiO2.

Formation and significance of black pebbles from the ota limestone (Upper Jurassic, Portugal)

1987

Black pebbles are a characteristic facies element of the Upper Jurassic Ota carbonate bank (Portugal). They occur both scattered or concentrated in two horizons, the upper of which is very widespread and may serve as a lithostratigraphic correlation level.

δ18O values of coexisting brachiopods and fish: Temperature differences and estimates of paleo–water depths

1998

To estimate vertical thermal gradients and paleo–water depths to marine platforms we present a new method based on the difference between δ 18 O values of contemporaneous brachiopod carbonate and fish phosphate. Present-day marine fauna of well-known ecology from the surface to the sea floor record isotopic temperatures that agree with measured temperatures. We predict distributions of isotopic data that result from sampling strategy, basin morphology, and fauna ecology and discuss limitations. Application of the method to the Jurassic Paris-London basin gives vertical thermal variations of up to 14 °C associated with depths varying from a few meters to 170 ± 30 m. The estimated depths are …

Cryogenic cave carbonate – a new tool for estimation of the Last Glacial permafrost depth of the Central Europe

2012

Abstract. Cryogenic cave carbonate (CCC) represents a specific type of speleothems, whose precipitation is triggered by freezing of mineralized karst water. Coarse-crystalline CCC, which formed during slow freezing of water in cave pools, is known in 20 Central European caves located in Germany, the Czech Republic, Slovakia and Poland. All these caves are situated in an area, which was glacier-free during the Weichselian. Whereas the formation of usual types of speleothems in caves of this region usually ceased during glacials, CCC precipitation was restricted to glacial periods. Since CCC represents a novel, useful paleoclimate proxy, data from Weichselian CCC occurrences in caves in Centr…