Biogeography, Substrate Preference, and Feeding Types of North Adriatic Intertidal Collembola

Abstract. A survey of North Adriatic intertidal Collembola is given, including the first records of Friesea acuminata, Archisotoma interstitialis, Entomobrya dollfusi , and Pseudosinella hauseri. Granulometric and biococnological analyses of culittoral loose sediments allowed determination of the animals' substrate preference. The limitation to cuhaline habitats is tested by comparison with mixohaline shores nearby. Life-form typology is applied to elucidate the largely unknown relations of intertidal Collembola to the sediment surface or superficial strata. The different modes of nutrition are distinguished by mouthparts and by gut content analyses.     

Different Behavior of Iron(III) and Aluminum(III) Salts To Coagulate Silica Particle Suspension

The different coagulation‐flocculation behavior of iron(III) and aluminum(III) to coagulate silica particle suspension with four coagulants — FeCl₃, Fe₂(SO₄)₃, AlCl₃, and in our laboratory produced polyaluminum chloride PACl‐2.0 — was investigated through studying particle property changes and coagulation efficiency, for example, variations in zeta potential of particles, particle number, average particle diameter, particle size distribution, and residual turbidity of the supernatant water. Influences of flocculation intensity and pH value on the coagulation‐flocculation process were also studied. The results suggest that, under the test conditions, among these four coagulants FeCl₃ possesses an obviously stronger ability to form larger flocs and to remove turbidity, on the other hand, PACl‐2.0 obviously showed a better charge neutralization ability.     

Intragranular deformation mechanisms in calcite deformed by high-pressure torsion at room temperature

Mineralogy and Petrology - Polycrystalline calcite was deformed to high strain at room-temperature and confining pressures of 1–4 GPa using high-pressure torsion. The high confining...     

Zur Evolution des eukaryotischen Phytoplankton im Riphäikum — Neue Erkenntnisse aus der Belt Serie von Nordamerika

Zusammenfassung Aus dem Proterozoikum der Zeitspanne 1400–1000 M.J. war bisher noch kein Vorkommen von eukaryotischem Phytoplankton bekannt. Unsere neuen Funde aus der Belt-Serie von Idaho und Montana gehören in dieses Intervall und füllen damit eine Kenntnislücke. Die identifizierten Mikrobiota passen gut ins bisher bekannte Bild der früh-riphäischen Algenwelt. Charakteristisch für die Vertreter ist eine einfache Morphologie, ein kleines Formenangebot, eine geringe Individuen-Zahl und ein seltenes Vorkommen, das überdies auf bestimmte Lebensräume der Schelfe beschränkt ist. Offenbar war das eukaryotische Phytoplankton zu dieser Zeit noch im langen Anfangsstadium einer Entwicklung, die dem Fossilbefund zufolge bereits vor mehr als 2000 M.J. begonnen haben mu\. Aber erst vor ca. 850 Millionen Jahren setzte eine stärkere Entwicklung zu neuen Formen ein, die dann schrittweise die urtümliche Cyanobakterien-Welt ablösten.

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On the evolution of the eukaryotic phytoplankton in the Riphean — New evidence from the Beltian Serie of North America

No occurrences of eukaryotic phytoplankton were hitherto known during the time span from 1400–1000 M.Y. of the Proterozoic. Our findings from the Beltian Series of Idaho and Montana belong to this interval and thus fill a gap in our knowledge. The identified microbiota agree well with those from the early Riphean. They are characterized by simple morphologies, a limited variety of forms, a low number of individuals and a rare occurrence restricted to a few environments. The findings suggest, that the eukaryotic plankton of that time was still in its long initial stage of evolution which, according to present evidence, must have begun prior to 2000 M.Y. It was only later than 850 million years ago, that the diversification proceeded more rapidly. The new developments gradually replaced the ancient world of cyanobacteria.

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Résumé La présence de phytoplancton eucaryotique n'était pas connue jusqu'à présent pendant la période allant de 1400 à 1000 Ma, au ProtérozoÏque. Nos nouvelles découvertes dans le domaine de la Série Belt de l'Idaho et du Montana se rapportent à ce laps de temps et comblent ainsi une lacune de nos connaissances. Les microbiota identifiés correspondent bien à l'image que l'on se fait des algues du pré-Riphéen connues jusqu'à présent. Ses représentants se caractérisent par une morphologie simple, une variété de formes limitée, un nombre réduit d'individus et une occurence rare, réduite à un petit nombre de milieux. Visiblement, le phytoplancton eucaryotique était encore à cette époque dans la longue phase initiale de son développement qui, d'après les fossiles trouvés, doit avoir commencé il y a plus de 2000 Ma. Ce n'est qu'à moins de 850 Ma que des formes nouvelles se sont diversifiées de faÇon importante et ont remplacé graduellement le monde des cyanobactéries d'origine.

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Weathering and weathering rates of natural stone

Physical and chemical weathering were studied as separate processes in the past. Recent research, however, shows that most processes are physicochemical in nature. The rates at which calcite and silica weather by dissolution are dependent on the regional and local climatic environment. The weathering of silicate rocks leaves discolored margins and rinds, a function of the rocks' permeability and of the climatic parameters. Salt action, the greatest disruptive factor, is complex and not yet fully understood in all its phases, but some of the causes of disruption are crystallization pressure, hydration pressure, and hygroscopic attraction of excess moisture. The decay of marble is complex, an interaction between disolution, crack-corrosion, and expansion-contraction cycies triggered by the release of residual stresses. Thin spalls of granites commonly found near the street level of buildings are generally caused by a combination of stress relief and salt action. To study and determine weathering rates of a variety of commercial stones, the National Bureau of Standards erected a Stone Exposure Test Wall in 1948. Of the many types of stone represented, only a few fossiliferous limestones permit a valid measurement of surface reduction in a polluted urban environment.