Interaction of organic compounds with calcium carbonate—III. Amino acid composition of sorbed layers

Nitrogenous organic compounds in sorbed surface layers and in calcified organic matter associated with calcium carbonate sediment particles consist of 40–50% amino acids, 2% amino sugars and 25% ammonia. In grain size classes > 20 μm these compounds are mainly contained in the calcified protein of carbonate secreting organisms but with smaller grain sizes—and consequently increased specific surface area—they are contained in sorbed layers at the mineral surface. The composition of the sorbed layer is characterized by a predominance of neutral amino acids, a relative enrichment of basic and weakly polar amino acids, and a deficiency of acidic amino acids in comparison with the proteinaceous matter of calcifying organisms. The respective abundances for sorbed and calcified matter are: 505 and 380 Res./ of neutral amino acids, 262 and 450 Res./1000 of acidic amino acids, 92 and 51 Res./l000 of basic amino acids, and 141 and 129 Res./1000 of weakly polar amino acids.The composition of the sorbed layer appears to be the result of sorption of proteinaceous matter from solution since it reflects the free and peptide-bound amino acid composition of seawater. The characteristic amino acid assemblage could also be the result of preferential decomposition of protein and subsequent enrichment of neutral and basic amino acids; however, sorption from solution appears more likely since the total amount of amino acids sorbed to calcium carbonate (0.58 mg m ^?2) corresponds closely to the amount of protein known to cover one m² of aqueous substrate in monolayer arrangement. Sorption from solution is further supported by the low arginine/ornithine ratios in both the sorbed layer and the natural dissolved organic matter. This process might lead to a characteristic amino acid spectrum in fine grained calcareous sediments that reflects the composition of the dissolved organic matter in seawater rather than that of the carbonate secreting proteinaceous matter.     

Dependence of the Love numbers upon the inner structure of the Earth and comparison of theoretical models with results of measurements

Summary The question this paper is examining is the following: to what extent are the Love numbers dependent on certain characteristics of the inner structure of the Earth? It has been proven — on the basis of calculations carried out by the author-that these quantities are only in a small degree dependent on the density values measured on the surface of the Earth and on the selection of the density function in the mantle of the Earth. On the other hand the value of Love numbersh, k andl is considerably influenced by the assumptions made about the core of the Earth, namely by the position of the boundary between the core and the mantle and by the magnitude of the rigidity coefficient presumed in the core in the vicinity of the core-mantle boundary.The results of the calculations are compared with those mean values of Love numbers obtained from the data of stations operating at different places of the Earth. By reason of this it can be assumed that the core of the Earth has, in the vicinity of the core-mantle boundary, a coefficient of effective rigidity of the order of 10¹⁰ dyn/cm², if the core-mantle boundary is placed at the relative Earth radius of 0.545 from the centre of the Earth.     

40Ar/39Ar dating of the long range dikes,Newfoundland

Stepwise outgassing experiments were performed on eleven whole rock samples from a sequence of diabase dikes from the Great Northern Peninsula. Gas released at high temperatures (> ? 925–950°C) was consistently characterized by anomalously high apparent ages. These are attributed to the release of excess radiogenic argon, gas which probably resides in the mineral augite. At temperatures below ? 700°C, a wide range in apparent age was observed. On the other hand, the medium temperature region (? 700–950°C) is characterized by a relatively small range in apparent age. Data points corresponding to this region are rather well correlated in an isochron-type diagram; the slope of the best-fitting straight line corresponds to an aget = 605 ± 10m.y. We suggest that the outgassing of unaltered plagioclase is dominating the age spectra in this temperature interval. Consequently, we take 605 ± 10 m.y. as the time of emplacement of the Long Range dike swarm. This event may have marked the opening of a proto-Atlantic Ocean. The Acadian Orogeny (perhaps the ocean-closing event ? 380 m.y. ago) appears to be recorded in the low-medium temperature regions in the cases of two rather extensively altered samples.     

Festigkeit, verformbarkeit und gefügeregelung von anhydrit — experimentelle stauchverformung unter manteldrucken bis 5 kbar bei temperaturen bis 300°C

The dependence of strength, ductility, and preferred orientation of polycrystalline anhydrite upon confining pressure (up to 5 kbar), temperature (up to 300° C), and strain (up to 30%) has been evaluated by compression tests.Strength and ductility increase at room temperature with increasing mantle pressure. Up to 1 kbar mantle pressure anhydrite is brittle and failure occurs by tension and shear fractures. Homogeneous flow between 1 and 3 kbar mantle pressure is mostly due to intercrystalline slip which is sensitive to pressure. Beyond the elastic limit the stress—strain curves are nearly horizontal. No preferred orientation develops. Between 3 and 4 kbar mantle pressure the intracrystalline mechanisms become noticeable. The stress—strain curves show weak strain hardening. The (210)-planes reveal a weak preferred orientation perpendicular to the axis of compression.With increasing temperature the strength decreases at low strains (< 5%). Intracrystalline mechanisms become more dominant, because the critical resolved shear stresses are lower with increasing temperature. At high strains (> 15%) both strength and ductility increase at higher temperatures. At even higher strains, strain hardening ceases once again and the stress—strain curves become nearly horizontal. From that point on preferred orientation is no longer increased. The stress—strain curves differ with the orientation of the specimen axis to the original fabric.

Zusammenfassung

In Stauchversuchen an polykristallinem Anhydrit wurde die Abhängigkeit der Festigkeit, der Verformbarkeit und der Gefügeregelung vom Manteldruck (bis 5 kbar), von der Temperatur (bis 300°C) und vom Verformungsgrad (bis 30%) untersucht.Festigkeit und Verformbarkeit nehmen bei Raumtemperatur mit steigenden Mantel-drucken zu. Bis etwa l kbar Manteldruck verhält sich der Anhydrit spröde und es treten Trenn und Verschiebungsbrüche auf. Die gleichmässige Fliessverformung bei Manteldrucken über 1 kbar erfolgt durch überwiegend interkristalline, manteldruckempfindliche Verformungsmechanismen. Die Spannungs—Verformungskurven verlaufen nach Überschreiten der elastischen Verformung nahezu horizontal. Eine Regelung tritt nicht ein. Ab 3 kbar bis 4 kbar Manteldruck beginnen sich intrakristalline Mechanismen bemerkbar zu machen. Die Spannungs—Verformungskurven weisen eine schwache Verfestigung auf. Durch die eintretende schwache Regelung stellt sich eine (210)-Ebene bevorzugt senkrecht zur Stauchachse ein.Mit steigender Temperatur bei sonst gleichen Bedingungen nimmt die Festigkeit bei geringen Verformungsgraden (< 5%) ab. Die Verformung erfolgt überwiegend durch intrakristalline Mechanismen, deren kritische Schubspannungen mit zunehmender Temperatur geringer werden. Die Spannungs—Verformungskurven steigen nach Überschreiten des elastischen Bereichs stärker an als zuvor. Es tritt mit zunehmender Temperatur eine stärkere Verfestigung und eine intensivere Einregelung von (210) senkrecht zur Stauchachse ein. Im Bereich hoher Verformungsgrade (> 15%) liegen die Festigkeiten bei höheren Temperaturen höher als bei niedrigen Temperaturen. Bei sehr hohen Verformungsgraden wird die Verfestigung so gross, dass interkristalline Mechanismen die intrakristallinen wieder ablösen. Die Spannungs—Verformungskurven werden wieder flacher und die Zunahme in der Regelung hört auf.Je nach der Orientierung der Stauchachse zum Ausgangsgefüge verlaufen die Spannungs—Verformungskurven unterschiedlich.Die Abhängigkeit der Verformungsmechanismen vom Manteldruck, Verformungsgrad und der Temperatur wird in einem dreidimensionalen Modell vorgestellt.     

Some steineresque comments,and monodian asides on geography in Europe

The question of whether geography is an art or a science is discussed within the context of comments made by Steiner about the current state of literary criticism. Several problems of geographic development parallel this situation. Problems of translation go beyond the common meaning of the word, and include questions of teaching and public communication. Mapping is seen as a fundamental act of human enquiry. The lack of even elementary mathematical training has severe consequences, because new perspectives are difficult to achieve. These are illustrated by the work of Wilson, with analogies drawn from Monod.     

Cryptotephra from the 74 ka BP Toba super-eruption in the Billa Surgam caves,southern India

The ～74 ka BP Youngest Toba Tuff (YTT), from the largest known Quaternary volcanic eruption, has been found for the first time as a non-visible (crypto-) tephra layer within the Billa Surgam caves, southern India. The occurrence of the YTT layer in Charnel House Cave provides the first calendrical age estimate for this much debated Pleistocene faunal sequence and demonstrates the first successful application of cryptotephrochronology within a cave sequence. The YTT layer lies ～50 cm below a major sedimentological change, which is related to global cooling around the MIS 5 to MIS 4 transition. Using this isochronous event layer the Billa Surgam Cave record can be directly correlated with other archaeological sites in peninsular India and palaeoenvironmental archives across southern Asia.     

Minor ions in the solar wind

Ions heavier than ⁴He are treated as “minors” in the solar wind. This is justified for many applications since minor ions have no significant influence on the dynamics of the interplanetary plasma. However, minor ions carry information on many aspects of the formation, on the acceleration and on the transfer of solar plasma from the corona into the interplanetary space. This review concentrates on various aspects of minor ions as diagnostic tracers. The elemental abundance patterns of the solar wind are shaped in the chromosphere and in the lower transition region by processes, which are not fully understood at this moment. Despite this lack of detailed understanding, observed abundance patterns have been classified and are now commonly used to characterize the sources, and to trace back solar-wind flows to their origins in the solar atmosphere. Furthermore, the solar wind is the most important source of information for solar isotopic abundances and for solar abundances of volatile elements. In order to fully exploit this information, a comprehensive understanding of elemental and isotopic fractionation processes is required. We provide observational clues to distinguish different processes at work.