Showing papers by "Martin Luther University of Halle-Wittenberg published in 1975"

Investigation of the deformation mechanism of MgO crystals affected by concentrated load

Abstract: The mechanism of deformation under the indentation of MgO crystals has been studied by transmission and scanning electron microscopy. The dislocation structure and Burgers vectors of rosette dislocations are determined. The nature and geometry of cathodoluminescence around indentation have been also investigated. The luminescence radiation is shown to be caused by interstitial point defects built up under indentation. [Russian text ignoreed].

Synthese niedrigschmelzender kristallin‐flüssiger Heterocyclen. I. 5‐n‐Alkyl‐2‐(4‐n‐alkoxy‐phenyl)‐pyrimidine

Abstract: Die Synthese der 5-n-Alkyl-2-(4-n-alkoxy-phenyl)-pyrimidine 6 nach zwei Varianten wird beschrieben. Die kristallin-flussigen Eigenschaften dieser Verbindungen werden diskutiert.

Nichtparabolizität des valenzbandes von Bi2Te3 gefolgert aus transporteigenschaften

Abstract: Messungen der galvanomagnetischen und thermoelektrischen Effekte an p-Bi2Te3 werden im Rahmen eines nichtparabolischen Einvalenzbandomodells mit Vieltalstruktur interpretiert. Fur dieses Modell werden die Ausdrucke fur die galvanomagnetischen Koeffizienten und die Thermokraft angegeben. Fur akustische Gitterstreuung werden die Streufaktoren der Hall- und Magnetowiderstandskoeffizienten theoretisch berechnet. Zur Ermittlung des reduzierten Ferminiveaus und der Breite der verbotenen Zone wird ein grafisches Losungsverfahren angegeben. Der anomale Anstieg des Hallkoeffizienten bei steigender Ladungstragerkonzentration wird durch den Einflus des „nichtparabolischen” Streufaktors erklart. Entsprechend dem Erwartungswert fur akustische Gitterstreuung ergibt sich der Temperaturgang der „isotropen” Beweglichkeit proportional T−3/2 im Gegensatz zu den bisherigen Interpretationen mit parabolischem Band. Measurements of galvanomagnetic and thermoelectric effects of p-Bi2Te3 are interpreted by a non-parabolic one-valence-band model with many-valley structure. For this model the formulas of galvanomagnetic coefficients and thermopower are given. For acoustical mode scattering the scattering-factors of the Hall and magnetoresistivity coefficients are theoretically calculated. For the determination of the reduced Fermi level and the magnitude of energy gap a graphic solution-method is given. The anomalous increase of Hall coefficients at increasing carrier concentration is interpreted by the influence of „non-parabolic” scattering factors. According to the expected value for acoustical mode scattering the dependence of „isotropic” mobility is obtained proportional T−3/2 in contrast to previous interpretations in terms of a parabolic band.

Studies of the distribution of proteins bound to CNBr-activated Sepharose 6B at the electron-microscopic level.

Abstract: Proteins were covalently attached to Sepharose by the CNBr method. Their distribution across the carrier beads was studied at the electron microscopic level. The approach has been to ferritinstain and to section the gel beads. Ferritin was either coupled directly to the polysaccharide backbone of the carrier or conjugated with pure rabbit anti-aminopeptidase in order to visualize covalently bound leucine aminopeptidase by the immunferritin technique. The results corroborate earlier fluorescence microscopic findings of a uniform protein distribution, provided that a number of conditions are fulfilled.

The dielectric behaviour of the nematic 5-n-hexyl-2-[4-n-alkyloxyphenyl]-pyrimidines

Abstract: The dielectric constant and the dielectric loss of the 5-n-hexyl-2-[4-n-hexyloxyphenyl]-pyrimidine and the 5-n-hexyl-2-[4-n-nonyloxyphenyl]-pyrimidine were measured in the nematic and the isotropic region in a frequency range from 0.1 to 10 MHz. The dielectric anisotropy of both substances is found to be positive at frequencies below and negative at frequencies above the relaxation region. The temperature dependence of the isotropy frequency (Δϵ′ 0) and the activation energies for the alignment of the dipoles in the electric field are calculated from the temperature dependence of the relaxation times. Es wurden die Dielektrizitatskonstante und der dielektrische Verlust vom 5-n-Hexyl-2-[4-n-hexyloxyphenyl]-pyrimidin und vom 5-n-Hexyl-2-[4-n-nonyloxyphenyl]-pyrimidin im nematischen und isotropen Gebiet im Frequenzbereich von 0,1 bis 10 MHz gemessen. Die dielektrische Anisotropie beider Substanzen ist positiv bei Frequenzen unterhalb und negativ bei Frequenzen oberhalb des Relaxationsgebietes. Die Temperaturabhangigkeit der Isotropiefrequenz (Δϵ′ = 0) und die Aktivierungsenergien fur die Ausrichtung der Dipole im elektrischen Feld wurden aus der Temperaturabhangigkeit der Relaxationszeiten berechnet.

Synthesis and liquid crystalline properties of 4,4'-disubstituted biphenyls

Abstract: HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. SYNTHESIS AND LIQUID CRYSTALLINE PROPERTIES OF 4,4’-DISUBSTITUTED BIPHENYLS D. Demus, L. Richter, C.-E. Rürup, H. Sackmann, H. Schubert

[The mutagenicity of desmethyltrichlorphone in dominant lethal test on mice (author's transl)].

Abstract: Nach ip-Applikation einer einmaligen Dosis von 405 mg/kg Desmethyl-Trichlorphon (Natriumsalz) sowie von 54 mg/kg taglich uber 3 Wochen an AB-Mause war die mutagene Wirkung im Dominanten-Letal-Test mindestens ebenso gros wie nach Applikation von Trichlorphon in gleicher Dosierung Diesem Befund zufolge scheint die genotoxische Wirkung des Trichlorphons nicht ausschlieslich im Zusammenhang mit seinen alkylierenden Eigenschaften zu stehen

Schlieren textures in smectic liquid crystals

Abstract: The details of well developed schlieren textures have been observed at smectic C and B modifications. In these textures whole numbered point singularities occur and inversion walls with strong similarities to nematic schlieren textures. It is shown that the occurrence of smectic schlieren textures is due to suppositions derived theoretically by Nehring and Saupe. These suppositions are: tilted structure and plane layers with the layers parallel to the supporting glass slides. In smectic B inversion walls occur which allow to conclude on variable tilt angles of the structure.

The equilibrium concentration of aggregates of cation vacancies and divalent impurities in NaCl‐type lattices (Point‐Charge Approximation)

Abstract: A method is derived for the calculation of the free energy of a crystal with aggregates of divalent cation impurities and cation vacancies. The free energy is explicitly given for the case of isolated impurities and vacancies, dipoles, dimers, and trimers. The equilibrium condition for the free energy yields a simple formula for the equilibrium concentration of all aggregates. If the association energy for all aggregates is known an algebraic equation of sixth order has to be solved. As an example the concentrations in the case of the validity of the point charge approximation of the association energies are computed. Es wird eine Methode zur Berechnung der freien Energie eines Kristalls, der Aggregate aus zweiwertigen Kationen-Verunreinigungen und Kationen-Leerstellen enthalt, abgeleitet. Die freie Energie wird explizit fur den Fall angegeben, das isolierte Verunreinigungen und Leerstellen sowie Dipole, Dimere und Trimere vorliegen. Die Gleichgewichtsbedingung fur die freie Energie ergibt eine einfache Formel fur die Gleichgewichtskonzentration aller Aggregate. Wenn die Assoziationsenergie aller Aggregate bekannt ist, mus eine algebraische Gleichung sechster Ordnung gelost werden. Als Beispiel wurden die Konzentrationen fur den Fall berechnet, das die Punktladungsnaherung fur die Assoziationsenergien anwendbar ist.

Neoplastic involvement of the CNS in generalized lymphomas.

Abstract: In 49 autopsies on patients with generalized malignant lymphomas a thorough histological examination of the CNS was performed. Isolated neoplastic foci were found in the CNS in 10 cases. It is believ. d. that most of the tumour infiltrations in the CNS as a result of neoplastic transformation of local mesenchymal cells and are not blood-borne metastases.

A model for the assessment of left ventricular compliance: effect of hypertrophy and infarction

Abstract: Non-linear elastic theory was applied to the problem of diastolic filling of the left ventricle, which was treated as a thick-walled sphere. The mathematical model was used to predict pressure–volume relationships for ventricles with various initial dimensions and myocardial elasticity constants. A reasonable agreement was obtained with data reported in the literature. The results may provide a basis for the use of empirical compliance indices.

Cyclopenase, ein Lipoproteid der Protoplasmamembran von Konidiosporen des Pilzes Penicillium cyclopium WESTLING

Abstract: Cyclopenase, an enzyme which transforms cyclopenin and cyclopenol to viridicatin and viridicatol respectively under elimination of CO2 and methylamine is a constituent of the inner side of the protoplasma membrane of the conidiospores of Penicillium cyclopium. This is shown by the following facts. The cell wall-protoplasma membrane fraction of homogenates contains nearly all the enzyme activity. By surface active agents the membrane-bound enzyme may be solubilized as a protein-phospholipid complex. Cyclopenase in vivo is separated from its substrates, which at least partly are deposited in the cell wall of the conidia. By treating the solubilized enzyme-phospholipid complex with n-butanol it is separated into the lipid part and the enzyme protein maintaining a considerable part of its activity. The reaction of cyclopenase in the membrane bound and in the solubilized forms with and without the phospholipid part follows the MICHAELIS-MENTEN kinetics. Changes of the pH-optima and Km-values indicate an alteration of the catalytic properties of the enzyme during solubilization whereas no differences in this respect were found between the soluble phospholipid complex and the phospholipid-free enzyme.

Beiträge zur Taxonomie und Evolution der Gattung Calendula L. III. Revision der marokkanischen perennierenden Sippen unter Berücksichtigung einiger marokkanischer Annueller Mit 6 Tafeln und 4 Abbildungen

Abstract: Die marokkanischen perennierenden Calendula-Sippen wurden einer taxonomischen Revision unterzogen. Zur Definition dieser Taxa werden die fruher ausfuhrlich beschriebenen Merkmale herangezogen (Ohle 1974). Nach der Darstellung von Schlusseln zur Abtrennung der marokkanischen diploiden Taxa der Calendula-maroccana-Gruppe von den polyploiden perennierenden Sippen der Gattung und einem Schlussel der Calendula-maroccana-Sippen folgen Einzelbeschreibungen und Diskussionen von vier perennierenden und einer annuellen Sippe, deren Areale mehr oder weniger eng an die Gebirge Marokkos gebunden sind. Morphologische Vergleiche zweier erstmalig beschriebener Arten (Calendula meuselii Ohle und Calendula eckerleinii Ohle) mit den perennierenden Taxa um Calendula incana Willd. und Calendula suffruticosa Vahl ergeben Schlusfolgerungen zur Evolution und Ausbreitung der perennierenden Taxa, die auch durch cytologische und chorologische Fakten unterstutzt werden. The maroccan-perennial Calendula-taxa have been revised taxonomically. The delimination of the taxa is based upon the earlier described characters (Ohle 1974). Keys for distinguishing the maroccan diploid taxa from the polyploid perennial taxa of the genus and a key of the Calendula-maroccana-taxa are followed by descriptions and discussions of one annual and four perennial taxa, which living around the central-maroccan mountains. Morphological comparisons between two firstly described species (Calendula meuselii Ohle and Calendula eckerleinii Ohle) with the perennial taxa of the relationships of Calendula incana Willd. s. lat. and Calendula suffruticosa Vahl s. lat. allow conclusions refering to the evolution and distribution of the perennial taxa, which could be supported by cytological and chorological facts.

Aspekte der Koordinationschemie des 3-bindigen Phosphors

Abstract: After introductory considerations of the various uses of coordination complexes containing tervalent phosphorus ligands and a discussion of the metalphosphorus bond, the complex-forming behaviour of the derivatives of various structures in the reaction with metal salts is considered. As to be proved by spectroscopic and magnetic data, the transition metal complexes of various structures, which depend on the substituents at the phosphorus atoms, are obtainable. The reactions of the primary and the secondary phosphines and of phosphine with carbonyls result in a series of substituted products, the constitution of which resembles that of the tertiary or polytertiary phosphines respectively. Even the highly reactive alkali phosphides react with carbonyls in accordance with a substitution scheme. An interaction with the carbon oxide fixed in the complex, which yields carbene complexes, may only be realized by lithium dimethyl. In the reaction of V(CO)6 and Fe(CO)5 with ligands containing the P—H function an emission of hydrogen occurs as well as a separation of carbon monoxide. Finally this process results in the formation of the phosphides of the transition metals. Complexes with the phosphido–carbonylic, cyclopentadienylic and nitrosylic groups are obtainable by the use of tetraorganobiphosphines. Besides formation of the μ-phosphido bridges, polynuclear complexes containing carbonyls or P2 or P as bridging ligands may be gained respectively. In the reaction of alkali phosphides with various transition metal salts the corresponding metal phosphides are obtained. Cyclic compounds of this kind are accessible from MRP—(PR)n—PRM. Similar to the behaviour of the polytertiary phosphines an analogous complex formation with metal salts is to be observed in the case of diprimary and disecondary phosphines respectively. The existence of phosphido–phosphine complexes was stated in several cases. Phosphorus-nitrogen ligands act towards transition-metal ions both as monodentate and as multidentate ligands as well. This is due to the different donor properties of P and N respectively. The formation of chelate complexes in the proper sense is to be observed with mercaptoalkyl or o-mercaptophenyl-phosphine respectively. If SH groups are present in the molecules the substituted phosphine inner complexes are favoured. Structural data of all important complex compounds discussed in this connection are given. Finally the special importance of the phosphine transition metal complexes is exemplified by the transition metal hydrides and the complex bonding of carbon oxides, oxygen, sulphur dioxide and elementary phosphorus respectively.

Isotopic hydrogen exchange in reactions catalysed by cysteine lyase and serine sulphhydrase.

Abstract: Serine sulphhydrase from chicken liver and cysteine lyase from chicken-embryo yolk sae catalyse the exchange of α-H atoms of the amino acid substrate with 3H2O. The degree of labelling of the unreacted substrate approaches a maximum of one atom per mol of amino acid. In the absence of replacing agent there is practically no H-exchange in the substrate. The α-H of the accumulating β-substitution product is completely replaced by the labelled hydrogen of the solvent water, irrespective of the duration of incubation. The amount of labelled α-hydrogen incorporated into excess (unreacted) amino acids substrate within 3.5-h incubation is somewhat less than the amount incorporated into the product of the complete enzymic β-replacement reaction. Within the sensitivity limits of detection, the enzymes do not induce any isotopic exchange either of β-H atoms in the amino substrate or of 18O-labelled β-HO groups, in the case of l-serine. Neither serine sulphhydrase nor cysteine lyase will catalyse α-hydrogen exchange in close structural analogues of their substrates, e.g. l-alanine, d-serine, threonine, 3-phosphoserine. A special case is the interaction of cysteine lyase with the competitive inhibitor, l-serine (whose inhibitor constant, Ki, is equal to the Michaelis constant, Km, of l-cysteine): the lyase catalyses, only in presence of a cosubstrate thiol, α-H exchange in l-serine at approximately the same rate as in l-cysteine. The present data concerning isotopic α-H exchange in substrate amino acids, and evidence published earlier, suggest that the catalytic mechanism of replacement-specific β-lyases may significantly differ from that of the eliminating or ambivalent (mixed-function) lyases. Formation of α,β-unsaturated pyridoxylidene aldimines as real reaction intermediates is unlikely in the case of lyases specifically catalysing β-replacement reactions; these may proceed by some alternative mechanism of the type suggested in this paper.

Untersuchungen zum Kossel-Effekt nichtzentrosymmetrischer Kristalle

Abstract: Werden die Atome eines Kristallgitters durch fein fokussierte Rontgen- oder Elektronenstrahlen zur Emission ihrer Eigenstrahlung angeregt, so interferiert diese Strahlung an den Netzebenenscharen des umgebenden Raumgitters, sofern die Interferenzbedingung λ < 2 d η1 η2 η3 erfullt ist (λ = Wellenlange der Eigenstrahlung, d η1 η2 η3 = Abstand der Netzebenen mit den Millerschen Indizes η1,η2,η3). Registriert man diese Strahlung auf einem Film, so findet man auf dem durch Bremsstrahlung und nichtgebeugter Eigenstrahlung geschwarzten Film neben hellen und dunklen Linien auch Linien mit helldunkler Feinstruktur. Diese Linien werden nach ihrem Entdecker auch Kossel-Linien genannt. Sie sind die Schnittlinien des Films mit den Kreiskegeln, die jeweils senkrecht auf den reflektierenden Netzebenen stehen und einen halben Offnungswinkel von 90°θ B besitzen (θ B = Braggscher Winkel). In Abb. 1 ist die Geometrie der Kossel-Kegel dargestellt.

Motor nerve conduction velocity after carbon monoxide or m-dinitrobenzene poisoning following elimination of the poisons.

Abstract: 24 hrs after acute carbon monoxide or m-dinitrobenzene poisoning (about 60% CO-Hb or Met-Hb) the sciatic motor conduction velocity of rats is significantly reduced by 33% and 16%, respectively. Whereas 48 hrs after methemoglobinemia the nerve conduction is normal, a retardation is detectable even 4 weeks following carboxyhemoglobinemia. Also, 4 weeks after single carbon monoxide intoxication producing a mean CO-Hb content of 19%, the motor conduction velocity is significantly decreased. This effect may be useful for detection of carbon monoxide intoxication after elimination of the poison. The results show that there are carbon monoxide effects independent of blockade of hemoglobin.