Showing papers by "University of Oldenburg published in 1979"

Photolithotropic and chemoorganotrophic activity of bacteria and algae as related to beachrock formation and degradation (gulf of Aqaba, Sinai)

Abstract: Beachrock formation and degradation along the shores of the Gulf of Aqaba (Sinai) were studied in the field and at the laboratory. Different types of beachrock were found, including laminated rocks. Rates of photosynthesis and respiration were studied under high‐and low‐tide conditions. Epilithic, chasmolithic, and endolithic bacteria, cyanobacteria, and algae were studied quantitatively. Bacterial contribution to carbonate precipitation and cementation was estimated in thin sections and by laboratory experiments. Precipitation of aragonite and monohydrocalcite was observed at salinities between 28‰ and 45‰. Concentrations of dissolved organic matter (DOM) and particulate organic matter (POM) were high at initial stages of beachrock formation and extremely low in final rock. Anaerobic and later aerobic decay processes initiate carbonate precipitation. A model is suggested that places beachrock as an intermediate between cyanobacterial influenced subtidal and su‐pratidal rocks. Formation, cementation, and ...

Algorithm 39 Clusterwise linear regression

Abstract: The combinatorial problem of clusterwise discrete linear approximation is defined as finding a given number of clusters of observations such that the overall sum of error sum of squares within those clusters becomes a minimum. The FORTRAN implementation of a heuristic solution method and a numerical example are given.

Calcification in a coccoid cyanobacterium associated with the formation of desert stromatolites

Abstract: In the Borrego Desert (California) and in the Sinai Desert (Israel) laminated, microbially mediated carbonate crusts have been found and analysed biologically and mineralogically, and further studied with scanning electron microscope methods combined with energy dispersive X-ray analyses. All morphological and biological features of the extant crusts justify the term ‘desert stromatolite’, a term applied to stromatolites from desert regions which form under permanent exposure to the atmosphere. These stromatolites are never covered by standing water, and running water (heavy rainfall) covers them for only a few hours during the year. Carbonate deposition is achieved principally by the cyanobacterium Pleurocapsa sp. which exhibits characteristic yet different stages of calcification. Calcification occurs in the sheaths of single cells (including baeocytes) as well as in mature colonies. The specificity for calcification in Pleurocapsa sp. is discussed.

Chapter 2.2 Calcification by Bacteria and Algae

Abstract: Publisher Summary This chapter deals with the biological factors promoting calcification and provides an account of environments favoring biogenic or inorganic carbonate deposition. By far, the most important biological controls on calcification are those that influence the equilibrium between the inorganic carboxy species. This may result from the consumption of CO2 in photosynthesis, chemosynthesis, and heterotrophic CO2 fixation; the release of CO2 during respiration and fermentation; and from the production of bases and acids because of varied metabolic activities. In general, carbonate precipitation by bacteria can be regarded as environmentally-influenced precipitation not involving calcifying matrix systems or cellular organization. Precipitation may be because of an increase in environmental pH or a shift in the carbonate bicarbonate equilibrium system, as the result of photosynthetic CO2 incorporation. Calcification in and by algae is on the borderline between both environmental calcification and calcification controlled by the cellular apparatus, respectively. All algae are capable of precipitating CaCO3 in the environment as a result of photosynthetic CO2 incorporation but certain organisms play a more specific role in calcification. The chapter discusses models of calcification relating physiological control on interspace chemistry to assimilatory and respiratory mechanisms.

O 2 and H 2 S coexistence in stromatolites

Abstract: The coexistence of O2 and H2S in recent microbial mats is demonstrated. Oxygen and H2S are not only coexisting in considerable concentrations within recent stromatolites but high concentrations of the respective gases occur in alternating laminae. This “sandwich structure” is produced by alternating populations of oxygenic and anoxygenic photosynthetic bacteria and cyanobaeteria. The finding of such conditions may explain the alternation of oxidized and reduced iron minerals in Precambrian stromatolites and possibly also in the banded iron formations (BIFs).

1,6‐Anhydrofuranosen, IX. Selektive Monotosylierung der 1,6‐Anhydro‐α‐D‐galactofuranose. Synthese und Bestimmung der Molekülstruktur der 1,6 :3,5‐Dianhydro—α‐D‐gulofuranose

Abstract: Umsetzung von 1,6-Anhydro-α-D-galactofuranose (1a) mit 17 mol ρ-Toluolsulfonylchlorid liefert ein Gemisch aller denkbaren Tosylate, in dem das 3-0-Derivat 1fmit uber 40% isolierter Ausbeute uberwiegt Dieses last sich zur 1,6:3,5-Dianhydro-α-D-gulofuranose (2a) mit 2,5,7-Trioxatricyclo[421038] nonan-Gerust cyclisieren, deren Struktur wie die der 1,6-Anhydro-α-L-gulofuranose (3a) durch Rontgenstrukturanalyse bestimmt und diskutiert wird 1,6-Anhydrofuranoses, IX Selective Monotosylation of 1,6-Anhydro-α-D-galactofuranose Synthesis and Structure Determination of 1,6: 3,5–Dianhydro-α-D-gulofuranose Reaction of 1,6-anhydro-α-D-galactofuranose (1a) with 17 mol ρ-toluenesulfonyl chloride gives a mixture of all possible tosylates, the 3-0-derivative 1f with than 40% isolated yield predominating Cyclization of 1f yields 1,6:3,5-dianhydro-α-D-gulofuranose (2a) with 2,5,7-trioxatricyclo[421038]nonane skeleton the structure of it being determined by X-ray crystallography and discussed in comparison to the equally determind structure of 1,6-anhydro-α-L-gulofuranose (3a)

NP -Complete operations research problems and approximation algorithms

Abstract: For a large number of discrete optimization problems like the traveling salesman problem, the quadratic assignment problem, the general flow-shop problem, the knapsack problem etc. all known algorithms have the discouraging property that their (worst-case) running times on a computer grow exponentially with the size of the problem. All efforts to find polynomial bounded algorithms for these problems have failed. Recent results in complexity theory show that these problems belong to the classes ofNP-complete orNP-hard problems. It is a common belief that for problems belonging to these classes no polynomial bounded algorithms exist. Heuristics or approximation algorithms should be applied to these problems.

2,5‐Dioxabicyclo[2.2.2]octan‐Derivate: Methyl‐2,6‐anhydro‐D‐hexopyranoside mit talo‐ und altro‐Konfiguration

Abstract: Umsetzung des Methyl-2,6-anhydro-β-D-talo-hexopyranosids 1 b mit α-Acetoxyisobuttersaurechlorid in Acetonitril in Gegenwart von NaI liefert ein Gemisch der trans-Iodhydrinacetate 2 und 4 im Verhaltnis 8:1. Katalytische Hydrierung von 2 fuhrt zum Desoxyzucker 6. Reaktion von 1 b mit dem Mattocks-Moffatt-Reagenz in Abwesenheit von NaI liefert die trans-Chlorhydrinacetate, die jedoch nicht isoliert, sondern sofort mit Natriummethylat und Natronlauge behandelt wurden. Das komplexe Reaktionsgemisch enthielt 7 Komponenten, die alle isoliert und identifiziert wurden. Neben den Methyl-2,6:3,4-dianhydro-D-talopyranosiden 10a und b waren dies die trans-Diole 11 a und b sowie 15 mit ido- bzw. manno-Konfiguration, ferner deren Monomethylether 13b und 17, wobei das Methyl-2,6-anhydro- β-D-idopyranosid 11 b mit ca. 39% Ausbeute das Hauptprodukt darstellte. Die 1H-NMR-Spektren lassen auf eine 2S0(D)-Pyranosering-Konformation bei den β-Anomeren und auf die alternative 5S1(D)-Konformation in der α-Reihe schliesen. Eine Verbindung, der irrtumlicherweise die Konstitution einer 2,6-Anhydro-idopyranose zuerkannt worden war, konnte durch Synthese als 3,6-Anhydro-idofuranose-Derivat 21 identifiziert werden. 2,5-Dioxabicyclo[2.2.2]octane Derivatives: Methyl 2,6-Anhydro-D-hexopyranosides with ido- and manno-Configuration Reaction of methyl 2,6-anhydro- β-D-talo-hexopyranoside 1 b with α-acetoxyisobutyryl chloride sodium iodide in acetonitrile yields a 8:1 mixture of the trans iodohydrin acetates 2 and 4. Hydrogenation of 2 gives the deoxysugar 6. Treatment of lb with the Mattocks-Moffatt reagent in absence of sodium iodide yields the trans chlorohydrin acetates, which were treated without isolation with sodium methoxide in methanol and sodium hydroxide in water. From the resulting complex reaction mixture 7 compounds could be separated, which were identified as methyl 2,6:3,4-dianhydro-D-talopyranosides 10a and b, trans diols 11 a and b and 15 with ido- and manno-configuration and monomethylethers 13 b and 17, methyl 2,6-anhydro-β-D-idopyranoside 11 b being the main product (39% yield). 1H NMR spectra present evidence for a 2S0(D) conformation of the pyranose ring in the β-anomers and the alternative 5S1(D) conformation in the α-series. A compound, which was erroneously assumed to be a 2,6-anhydro-idopyranose, was identified by synthesis as a 3,6-anhydro-idofuranose derivative 21.

Chapter 2.1 The Carbon Cycle

Abstract: Publisher Summary This chapter discusses carbon cycle. Within its global biogeochemical cycle, the element carbon occurs in the form of various chemical compounds that are continuously being transformed and moved within two major, mutually interconnected cycles: (1) the inorganic carbon, or carbonate cycle in which carbon passes through a series of chemical equilibria; and (2) the organic carbon cycle in which carbon passes through the processes of biosynthesis and mineralization of organic matter. The cycling of the element carbon depends primarily on its chemical properties. Like nitrogen and sulfur, but unlike phosphorus, silica, and iron, carbon forms volatile, soluble, and insoluble compounds and can thus circulate through the atmosphere, hydrosphere, and lithosphere. Because carbon is the basic element of life, its circulation through the biosphere is of particular importance. From the global viewpoint, two interlocking carbon cycles have been recognized: the exogenic cycle (including the carbonate and the organic carbon cycles) with carbon cycled by the atmosphere, hydrosphere and biosphere, and the endogenic cycle, with carbon cycled by the crust of the earth, the lithosphere and, in part, by the external mantle.

[Detection of acetamide in the thermal degradation products of chitin (author's transl)].

Abstract: Beim thermischen Abbau von Chitin, das auch Bestandteil einiger Nahrungsmittel ist, wird als fluchtige organische Hauptkomponente Acetamid gefunden (9% des Trockengewichtes), was moglicherweise von physiologischer Bedeutung ist. Thermoanalysen zeigen, das die Zersetzung bereits bei 200 °C beginnt.

1,6-Anhydrofuranosen, X. Eine einfache Synthese für 1,6-Anhydro-3-desoxy-α-D-xylo-hexofuranose

Abstract: 1,6-Anhydrofuranoses, X. A Simple Synthesis for 1,6-Anhydro-3-deoxy-α-D-xylo-hexofuranose Treatment of 1,6-anhydro-2,3,5-tri-O-tosyl-α-D-galactofuranose (1) with KOH in dioxane/water gives by way of cis-elimination 1,6-anhydro-3deoxy-5-O-tosyl-α-D-threo-hexofuranos-2-ulose (2) in good yield, which tends to dimerize easily in an aldol type reaction to 3. NaBH4 reduces 2 stereoselectively to 4a Removal of the tosyl group giving the title compound 4c is accomplished by sodium amalgam.

Klassenweise Diskrete Approximation

Abstract: The combinatorial problem of clusterwise discrete approximation is defined as finding a given number of Clusters of observations such that the overall sum of sums of squared deviations within the Clusters becomes a minimum. A heuristic Solution method is proposed, its implementation for linear models is discussed, a numerical example is given, and possible generalizations are indicated.

Entscheidung über gemeindliche Aufgaben: Kommunale Selbstverwaltung oder Demokratie in überschaubaren Einheiten

Abstract: Die Frage „Wie wird uber Angelegenheiten einer Gemeinde entschieden?“ bildet den Kern einer politikwissenschaftlichen Gemeindeforschung. Rein juristisch ware diese Frage durch einen Blick in die Gemeindeordnung des betreffenden Bundeslandes rasch zu beantworten. Ein Vergleich der Gemeindeordnungen fordert eine erstaunliche Vielfalt zutage, die sich weitgehend aufvier Gemeindeverfassungstypen zuruckfuhren last.380 In diesen Typen mischen sich Verarbeitung landesspezifischer Selbstverwaltungstraditionen (insbesondere Suddeutsche Ratsverfassung in Bayern und Baden-Wurttemberg 381 , Burgermeisterverfassung in Rheinland-Pfalz, Saarland, Hessen und Schleswig-Holstein, Magistratsverfassung in Hessen und Schleswig-Holstein)382 mit deutschen Umsetzungen von Demokratisierungsabsichten der westlichen Besatzungsmachte (insbesondere Norddeutsche Ratsverfassung in Niedersachsen und Nordrhein-Westfalen 383).