Showing papers by "University of Göttingen published in 1970"

A Statistical Theory of Solid Solution Hardening

Abstract: The critical shear stress τc to move a dislocation through a random array of obstacles in the glide plane is calculated using a statistical theory. The result is an expression for τc in terms of the obstacle concentration, the line tension of the dislocation, and of the interaction force between the dislocation and a single obstacle. Fleischer's solution of the same problem is not reproduced by the statistical theory. Quantitatively the two results are not very different, but our new result is supported by some recent experimental evidence. Furthermore the theory provides a definite prescription how to combine the concentrations and interaction forces of obstacles of different kinds in the expression for τc.

Die monodromie der isolierten singularitäten von hyperflächen

Abstract: J. Milnor recently introduced the local Picard-Lefschetz-monodromy of an isolated singularity of a hypersurface. This is an important tool in the investigation of the topology of singularities. The monodromy is an action on a certain cohomology group and is defined in topological terms. In this paper we find an algebraic description of the monodromy. We construct by algebraic methods a regular singular ordinary linear differential operator, such that the monodromy of this singular operator coincides with the Picard-Lefschetz monodromy. As an application we prove that the eigenvalues of the monodromy are roots of unity. Our treatment is close in spirit to Grothendiecks theory of the Gauβ-Manin-connection.

The isolation of mutants not accumulating poly-beta-hydroxybutyric acid.

Abstract: Five mutant strains of Hydrogenomonas H 16 which synthesize poly-β-hydroxybutyric acid either slowly or not at all have been isolated following nitrite and NMG treatment of wild type cells. When grown on a nitrogen deficient agar medium, the colonies of PHB-free cells can be recognized by their diminished retention of the dye sudanblack B. Enrichment procedures for such mutants have been devised employing the 32P-phosphate inactivation technique and sucrose gradient centrifugation. The mutants have been characterized with respect to their growth properties, respiratory control and other properties.

Clostridium formicoaceticum nov. spec. Isolation, description and distinction from C. aceticum and C. thermoaceticum

Abstract: A new species—Clostridium formicoaceticum—is described. It ferments fructose and several hexonic and hexuronic acids to acetate and formate. During active growth acetate is the main product of the fermentation. Considerable quantities of formate appear among the fermentation products in the stationary growth phase.

Neuere Ergebnisse der Carbanionchemie

Abstract: Die Wittig-Umlagerung α-alkalimetallierter Ather gehort zur Klasse der 1,2-Verschiebungen zu einem Atom mit freiem Elektronenpaar. Die Alkyl-Verschiebung vollzieht sich unter Racemisierung (und partieller Retention) am wandernden Kohlenstoffatom. Die experimentellen Befunde legen einen uber ein Radikalpaar verlaufenden Spaltungs-Rekombinations-Mechanismus nahe, wie er auch fur die Ylid-Umlagerungen anzunehmen ist. Bei der Allyl-Wanderung verschiebt sich die Doppelbindung im wandernden Rest (Allyl-Inversion). Das ist zwanglos mit einem einstufigen SNi′-Mechanismus erklarbar, dessen Ubergangszustand symmetrie-erlaubt ist. Beim im Butinylrest metallierten Benzyl-2-butinylather dominiert die (der Sommelet-Umlagerung entsprechende) ortho-Isomerisation. — α-Metallierte Alkylisocyanide konnen mit Carbonylverbindungen zu Olefinen und Metallcyanat reagieren (Carbonyl-Olefinierung). Eine Sonderstellung nehmen α-metallierte Isocyanessigsaureester ein; sie ergeben mit Aldehyden und Ketonen β-substitutierte α-Formylamino-acrylsaureester (Formylamino-alkoxycarbonyl-Methylenierung), welche vielfaltig abzuwandeln sind. Als Zwischenstufen der Carbonyl-Olefinierung lassen sich β-Hydroxy-alkylisocyanide oder 2-Oxazoline abfangen. Mit Acylierungsmitteln reagieren α-metallierte Isocyanide zu β-Keto-alkylisocyaniden, die zu Oxazolen cyclisieren.

The sulfur isotope composition of basaltic rocks

Abstract: The sulfur isotope composition of tholeiitic basalts, olivine alkali basalts and alkalirich undersaturated basalts were investigated. A method of preparation was devised Tholeiitic and olivine alkali basalts show a predominance of sulfide-sulfur. Alkali-rich undersaturated basalts show sulfide- and sulfate-sulfur. The oxidation potential of the magma is reflected in the proportions of sulfide- and sulfate-sulfur. Differences in the conditions of oxidation are also the cause of the sulfur isotope fractionation observed. The mean in the isotope composition of the sulfur in the olivine alkali basalts (with the exception of two samples which show extreme deviation) is δ 34S= +1.3 per mil. The values for the olivine alkali basalts are concentrated around this mean in a remarkable way, showing only small deviation for the individual samples. When the tholeiitic basalts deviate from this mean, it is only with a relative enrichment in the 32S isotope. With a pronounced variation of the individual values, the mean for the sulfide-sulfur is δ 34S=−0.3 per mil. The few sulfate values of both types of basalt are without significance for the discussion of their origin. However, this does not apply to the alkali-rich undersaturated basalts. Due to the higher water content, this basaltic magma had a higher oxygen partial pressure which favoured the formation of SO2 and SO 4 2− besides H2S while pressure was released during the ascent of the magma. The sulfur isotope fractionation connected with this oxidation led to a total enrichment of 34S in the rock, (δ 34S for total sulfur: +3.1 per mil) with particular favouring the sulfate (δ 34S=+4.2 per mil). It is accepted that the sulfur of all three types of basalts derives directly from the mantle. The olivine alkali basalts show the least deviation from the mantle value, which, in the place of origin of the basalts from the region investigated, would probably have been δ 34S=+1.3(±0.5) per mil. From this it may be concluded that the olivine alkali basalts — the most frequent type of basalt in this region — had their origin in the partial melting of the mantle without further differentiation. From the sulfur isotope data we concluded that the primary isotope composition of the continental tholeiitic basalts probably corresponds to that of the olivine-alkali basalts, and to that of the mantle. However, due to degasing in the layers near to the surface, some samples lost 34S, which may be related to the formation of SO2 during the release of pressure. There is no positive indication of a differentiation in shallow depths (<15 km — in the sense of Green and Ringwood, 1967). The reason for the obvious isotopic fractionation of the alkali-rich undersaturated basalts may be seen in their higher primary water content. This is a pronounced indication of the origin of this type of magma. Bultitude and Green (1968) proved by experiment, that the formation of alkali-rich undersaturated basaltic magma is possible in the mantle in the presence of water. Only a small amount of water is available for the formation of magma in the mantle. With a water content higher than normal for basalts, only small amounts of magma can be formed, but at lower temperatures this would allow the melting of a larger fraction of mantle material. By reaction with the wall rock, these magmas could be enriched in those components of mantle minerals which have the lowest melting point. This may help to explain their geochemical characteristics.

Developmental testing of pre-term and small-for-date infants.

Abstract: Twenty-five full-term, newborn infants and 22 small-for-date infants born at term had comparable nerve conduction velocities and were considered to be of equal neurological maturity. Twenty-six pre-term infants equal in weight to the small-for-date infants had significantly slower nerve conduction velocities and were considered on this basis more immature at birth than the term and small-for-date infants. All of these infants were given Gesell developmental tests at approximately 40 weeks of age by an examiner with no knowledge of their neonatal condition. The objective was to determine to what degree performance later in infancy is dependent on neurological maturity at birth. The full-term infants and the small-for-date infants performed at their age level with average developmental quotients of 99 and 96, respectively. The pre-term infants performed at less than their age from birth with an average D.Q. of 88; but, when their age was corrected for weeks of prematurity, the average D.Q. was 99. These findings substantiate the concept that performance on the Gesell schedules is dependent on time from conception rather than time from birth. Preterm infants should have their age determined from their expected date of birth for purposes of calculating a developmental quotient.

Zero-mass infinite spin representations of the Poincaré group and quantum field theory

Abstract: It is shown that a local quantized field with a manifestly covariant transformation law under the Poincare group cannot have nonvanishing matrix elements between the vacuum and an irreducible subspace of zero mass and infinite spin.

Independence of local algebras in Quantum Field Theory

Abstract: It is shown that localC*-algebras\(\mathfrak{A}\)(O1) and\(\mathfrak{A}\)(O2) associated with spacelike separated regionsO1 andO2 in the Minkowski space are independent. The proof is accomplished by a theorem concerning the structure of theC*-algebra generated by\(\mathfrak{A}\)(O1) and\(\mathfrak{A}\)(O2).

Rubromycine, III. Die Konstitution von α‐Rubromycin, β‐Rubromycin, γ‐Rubromycin und γ‐iso‐Rubromycin

Abstract: Alkalihydroxid isomerisiert die Antibiotica β-Rubromycin und γ-Rubromycin durch intramolekulare β-Eliminierung zu α-Rubromycin bzw. γ-iso-Rubromycin und spaltet diese unter energischen Bedingungen in 5a, 15a, 16a und 18a. Damit wird aus der γ-iso-Rubromycin-Teilformel 4 die Konstitutionsformel 25a und aus 3 die α-Rubromycin-Formel 24; in beiden Verbindungen ist ein Naphtho[2.3-b]furanochinon-(4.9)-Chromophor in 2-Stellung uber eine Athylengruppe mit C-6′ eines 7.8-Dihydroxy-3-methoxycarbonyl-isocumarin-Restes verbunden. Aus 24, 25a sowie dem Umlagerungsschema 1–4 ergibt sich 22 fur β-Rubromycin und 23a fur γ-Rubromycin; in den antibiotisch wirksamen Rubromycinen verbindet ein Spiroketal-System den Naphthochinon-Chromophor mit dem Isocumarin-Rest. Rubromycins, III. The Constitution of α-Rubromycin, β-Rubromycin, γ-Rubromycin, and γ-iso-Rubromycin Alkalihydroxide isomerizes the antibiotics β-rubromycin and γ-rubromycin by way of intramolecular β-elimination to α-rubromycin and γ-iso-rubromycin, respectively, and cleaves these under forcing conditions to 5a, 15a, 16a and 18a. Thereby the partial γ-iso-rubromycin structure 4 leads to the total structure 25a, similarly, 3 leads to 24. In both compounds an ethylene group connects a naphtho[2,3-b]furanoquinone-(4,9) chromophore at C-2 with that of a 7,8-dihydroxy-3-methoxycarbonylisocoumarin at C-6′. Compounds 24 and 25a as well as the rearrangement scheme 1–4 give rise to β-rubromycin (22) and γ-rubromycin (23a); in antibiotically active rubromycins a spiroketal system connects the naphthoquinone chromophore with that of the isocoumarin residue.

Die Kristallstruktur von Zirkoniumtetrachlorid

Abstract: ZrCl4 kristallisiert monoklin in der Raumgruppe P2/c mit a = 6,361, b = 7,407, c = 6,256 A, β = 109,30°, Z = 2. Die Rontgenstrukturanalyse ergab einen neuen Strukturtyp, in dem ZrCl6-Oktaeder uber zwei gemeinsame Kanten zu gewinkelten Ketten [ZrCl4/2Cl2] verknupft sind. Die Cl-Atome bilden eine verzerrte kubisch-dichteste Packung. Die jeweils zwei endstandigen Cl-Atome pro Oktaeder befinden sich in cis-Stellung zueinander. Die Struktur hat enge Beziehungen zu denen des TcCl4, PtJ4 und MoOCl3. Die ZrCl-Bindungsabstande betragen 2,655 (Brucke), 2,498 (Brucke) und 2,307 A ZrBr4, HfCl4 und HfBr4 sind mit ZrCl4 isotyp.

Stereochemistry of Enzymic Citrate Synthesis and Cleavage

Abstract: By enzymic reactions using and generating asymmetrically labelled acetic acids, it is shown that R and S citrate synthases, citrate lyase and ATP citrate lyase all produce inversion of configuration at the methyl group when citrate is synthesized, or at the methylene group where citrate is cleaved

Differences in the development of the obese-hyperglycemic syndrome in obob and NZO mice.

Abstract: Marked differences were shown in the development of the obese-hyperglycemic syndrome in NZO andobob mice. — In NZO mice glucose tolerance decreases continuously with increasing age and body weight. — Inobob mice three phases in the development of the obese-hyperglycemic syndrome are differentiated. In the first, dynamic phase glucose tolerance decreases and insulin secretion increases as does body weight. The intermediary or transitional phase, when the animals weigh about 55 g, is characterised by rapidly changing glucose patterns, i. e. an extremely poor glucose tolerance and extremely high serum insulin level is followed by improving glucose tolerance and decreasing insulin levels. In the third, static phase blood sugar values and serum insulin levels have nearly returned to those of the lean littermates. Body weight slowly decreases. The changes in glucose tolerance and serum insulin are parallelled by changes in islet cell morphology. The gluconeogenic capacity is increased during the dynamic and transitional phases, it declines during the static phase.

Untersuchungen an spilitischen Gesteinen der variskischen Geosynkline in Nordwestdeutschland

Abstract: 21 samples of spilitic rocks of Devonian to Carboniferous age from NW-Germany have been analyzed for major elements, a large group of minor elements and the modal mineral composition Their major element and mineral composition is comparable to Recent spilites from oceanic ridges Major emphasis has been given to the absolute and relative abundance of the lanthanides and yttrium Their pattern, which is most probably not altered during processes of spilitization is that of tholeiitic basalts occuring on the continents and in oceanic islands

Electron Microscopic Observations in Subacute Sclerosing Panencephalitis Brain Cell Cultures: Their Correlation with Cytochemical and Immunocytological Findings

Abstract: Three cell cultures established from brain tissue obtained by biopsy of patients with subacute sclerosing panencephalitis (SSPE) were studied with the electron microscope in an attempt to correlate ultrastructural changes with those found by cytochemistry and immunocytology. These cells contained a large number of nucleocapsids resembling those of a paramyxovirus concentrated in the nuclear inclusions, but also seen free in the nucleus and occasionally in the cytoplasmic inclusions. Nuclear bodies associated with the nucleocapsids and granular filaments occupied a vast area of the cytoplasm. The nuclear inclusions containing nucleocapsids corresponded to the eosinophilic and fluorescent nuclear inclusions. The areas occupied by granular filaments corresponded to the diffuse cytoplasmic fluorescence. The ultrastructural changes were similar to those seen in the original brain biopsies. In addition papova-like virions were noted in brain cell cultures derived from a biopsy but not in the brain tissue itself. Their relationship to SSPE remains undetermined.