Showing papers by "Martin Luther University of Halle-Wittenberg published in 1981"

Isolation of dominant suppressor mutations for position-effect variegation in Drosophila melanogaster.

Abstract: Dominant suppressor mutations for position-effect variegation have been isolated by using a strongly variegated line carrying the wm4 chromosome (wm4h) and the dominant enhancer mutant En(var)c101. The use of an effective genetic test system made it possible to isolate more than 100 strongly dominant suppressor mutations for position-effect variegation. This suggests that the phenomenon of position-effect variegation is characterised by a complex genetic basis. The significance of the isolated mutants to genetic dissection of structural and regulatory functions of the eukaryotic chromosome is discussed.

Variations of chloroplast DNAs in the genus Pelargonium and their biparental inheritance.

Abstract: The comparison of EcoRI patterns of chloroplast DNAs (ctDNAs) from five species of the genus Pelargonium and from 16 cultivars and varieties of Pelargonium zonale hort. demonstrates a remarkable inter- and intraspecific ctDNA (plastome) variation. The plastome of the P. zonale varieties could be differentiated into groups I, II and III. Reasons for this variation seem to be: occurrence of numerous spontaneous plastome mutations, intense hybridisation by gardeners and breeders, and biparental plastid inheritance.Crosses of P. zonale varieties with different ctDNA types lead to the direct evidence on the molecular level of biparental plastid inheritance and plastid sorting-out in F1-hybrids.

New thermotropic cubic mesophases

Abstract: 1,2-Bis-[4-n-alkyloxybenzoyl]-hydrazines with the general formula possess smectic C phases and at lower temperatures additional optically isotropic phases. According to X-ray investigations these isotropic phases show cubic symmetry. The lattice units consist of aggregations with micellar dimensions. The substances were characterized by microscopic, dilatometric and calorimetric investigations. The new cubic mesophases do not exhibit complete miscibility with the “smectic D” phases. 1,2-Bis-[4-n-alkyloxybenzoyl]-hydrazine mit der allgemeinen Formel Weisen smektische C-Phasen und bei tieferen Temperaturen zusatzlich optisch isotrope Phasen auf. Entsprechen den Rontgen-Untersuchungen zeigen diese isotropen Phasen kubische Symmetrie. Die Gittereinheiten bestehen aus Aggregaten micellarer Dimension. Die Substanzen wurden charakterisiert durch mikroskopische, dilatometrische und kalorimetrische Untersuchungen. Die neuen kubischen Mesophasen sind mit den „smektischen D”-Phasen nicht vollstandig mischbar.

Computing turning points of curves implicitly defined by nonlinear equations depending on a parameter

Abstract: Let the space curveL be defined implicitly by the (n, n+1) nonlinear systemH(u)=0. A new direct Newton-like method for computing turning points ofL is described that requires per step only the evaluation of one Jacobian and 5 function values ofH. Moreover, a linear system of dimensionn+1 with 4 different right hand sides has to be solved per step. Under suitable conditions the method is shown to converge locally withQ-order two if a certain discretization stepsize is appropriately chosen. Two numerical examples confirm the theoretical results.

Induced phase transitions in ferroelectrics with diffuse phase transition

Abstract: Dielectric, thermal, electrocaloric, elastic, optical, and electromechanical properties of three ferroelectrics with diffuse phase transition (PLZT 8/65/35 ceramics, lead magnesium niobate and strontium barium niobate single crystals) are investigated in dependence on temperature and electric field strength. It is shown that a polar phase can be induced by an electric field within the nonpolar phase and vice versa, depending on whether the temperature is above or below Tt < TC. Analogies to stress-induced martensic transformations are emphasized. Dielektrische, thermische, elektrokalorische, elastische, optische und elektromechanische Eigenschaften von drei Ferroelektrika mit diffuser Phasenumwandlung (PLZT 8/65/35-Keramik, Bleimagnesiumniobat- und Strontiumbariumniobat-Einkristalle) werden in Abhangigkeit von der Temperatur und der elektrischen Feldstarke untersucht. Es wird gezeigt, das sich eine polare Phase durch ein elektrisches Feld innerhalb der unpolaren induzieren last und umgekehrt eine unpolare in einer polaren, je nachdem ob die Temperatur ober-oder unterhalb Tt < TC liegt. Auf Analogien zu spannungsinduzierten martensitischen Transformationen wird hinge wiesen.

Effects of catalase, peroxidase, superoxide dismutase and 10 scavengers of oxygen radicals in carrageenin edema and in adjuvant arthritis of rats.

Abstract: Catalase, peroxidase and superoxide dismutase were found to inhibit significantly carrageenin edema and the primary phase of adjuvant arthritis in rats after i.v. injection. Heat-inactivated enzymes were as effective as the native enzymes. None of 10 scavengers of oxygen radicals inhibited the adjuvant arthritis at any time. Accordingly, no evidence for a participation of oxygen radicals in the secondary arthritis phase could be found, whereas a role of oxygen radicals in the primary arthritis phase and in carrageenin edema cannot be ruled out.

Kristallin‐flüssige Heterocycloalkane. I. Synthese und Eigenschaften substituierter 1,3‐Dioxane

Abstract: Liquid-crystalline Heterocycloalkanes. I. Synthesis and Properties of Substituted 1,3-Dioxanes The synthesis of 2,5-disubstituted 1,3-dioxanes is described, their melting and clearing points and their physical properties (dielectric anisotropy, viscosity, transition enthalpies, optical birefringence) are investigated. The cyano substituted 1,3-dioxans 5 and 7 are valuable materials for application in displays.

Traumatized Anterior Teeth in Iraqi and Sudanese Children-A Comparative Study

Abstract: This epidemiological study describes the prevalence of trauma to the anterior teeth of 6090 Iraqi and 3507 Sudanese primary school children. 7.7% of Iraqi and 5.1% of Sudanese presented incisal trauma. The male to female ratio was 1.3:1 in Iraqis and 2.6 :1 in Sudanese.The frequency of trauma to Iraqi females below age nine yr was higher than the males, but the condition was reversed with age. In Sudanese children the frequency was higher in males in all age groups.In general, males suffered a higher rate of trauma in both countries, but the Iraqi children had a significantly higher rate of trauma than the Sudanese in both sexes.

EDA Complexes in Liquid Crystalline Mixed Phases

Abstract: The diagrams of state of 11 binary systems are presented which form EDA Complexes in the liquid dcrystalline state. The influence of the molecular length and the complex stability on the formation of enhanced smectic A phases have been studied.

Synthesis of ribosomal RNA in ribosome-deficient plastids of the mutant "albostrians" of Hordeum vulgare L.

Abstract: The nuclear gene-induced plastome mutant “albostrians” of Hordeum vulgare L. is characterized by a plastid ribosome-deficiency. This ribosome deficiency could be caused by the lack of or a defect in chloroplast RNA polymerase. However in our investigations we found an activity of chloroplast RNA polymerase in wild-type and mutant leaves of “albostrians” barley by (1) electron microscopic autoradio-graphy after in vivo labelling of RNA, (2) determination of RNA polymerase activity in isolated plastids, and (3) characterization of the newly synthesized RNA by electrophoresis in polyacrylamide gels. The genes of 23S and 16S rRNA are transcribed in mutant plastids and the RNAs are processed. From these results we conclude that the enzymes involved in transcription and processing of chloroplast rRNA are synthesized on cytoplasmic ribosomes and that the plastid ribosome deficiency in albostrians barley is probably not caused by a defective chloroplast DNA dependent RNA polymerase or by a mutation in the genes of 23S and 16S chloroplast rRNA.

Valence Band Structure of (Bi1-xSbx)2Te3 Single Crystals

Abstract: For the first time the anisotropy of reflectivity of polarized infrared light of p-(Bi1–xSbx)2Te3 single crystals (0.5 ≦ x ≦ 1) is given in the wave number range of 300 to 4000 cm−1. In addition to the excitation of free carriers in the reflection spectra of the mixed crystals also interband excitations are observed. For the mixed crystals the optical results are consistently described in terms of a six-valley band model and scattering on acoustical phonons together with the data for the dc conductivity, the Hall coefficients, and the thermopower. The main axis masses mii, the ellipsoid tilt angle θ, the effective density of states mass m, the cyclotron mass and the susceptibility masses are given in dependence on composition, also the Fermi level EF, the carrier density p, the mobility u⊥c, the high frequency dielectric constant ϵ′∞, and the relaxation time τ. The interband influence is interpreted by a simple band model and the energy gap Eg calculated. Die Anisotropie des Reflexionsvermogens von polarisiertem infrarotem Licht im Wellenzahlbereich von 300 bis 4000 cm−1 von p-(Bi1–xSbx)2Te3-Einkristallen (0,5 ≦ x ≦ 1) wird erstmals mitgeteilt. Dabei werden in den Reflexionsspektren der Mischkristalle neben der Anregung der freien Trager auch Interbandanregungen beobachtet. Die optischen Resultate werden zusammen mit den experimentellen Ergebnissen fur die dc-Leitfahigkeit, die Hallkoeffizienten und die Thermokraft durch ein Sechs-Tal-Bandmodell und Streuung an akustischen Phononen fur die Mischkristalle konsistent beschrieben. Die Hauptachsenmassen mii, der Ellipsoid-Neigungswinkel θ, die effektive Zustands-dichtemasse m, die Zyklotronmasse und die Suszeptibilitatsmassen werden in Abhangigkeit von der Kristallzusammensetzung angegeben; ebenso die Fermienergie EF, die Tragerkonzentration p, die Beweglichkeit uτc die Hochfrequenz-Dielektrizitatskonstante ϵ′∞ und die Relaxationszeit τ. Der Interbandeinflus wird mittels eines einfachen Bandermodells ausgewertet und die Energielucke Eg berechnet.

Crystal and Molecular Structure of the Nematogenic Compound 4′-Cyanophenyl-4-n-Pentoxybenzoate

Abstract: The title compound with the formula C5H11O-C6H4-COO-C6H4-CN (CPPOB) crystallizes in the orthorhombic space group Pnam with a = 16.465 A, b = 13.577 A, c = 7. 621 A and four molecules per unit cell. The structure has been solved by direct methods and refined to a final R value of 0.050. The CPPOB molecules have exact Cs symmetry as a consequence of their location on crystallographic mirror symmetry planes, the benzene ring to which the cyano group is attatched has a perpendicular orientation to the other ring in the plane. The molecules adopt a nearly optimal stretched form, neighbouring molecules make an angle of 35.2°. The results are discussed in relation to the mesomorphic behaviour of CPPOB.

Synthesis and Properties of New Liquid Crystalline Materials

Abstract: In the last years several reviews on liquid crystalline substances were published. These reviews concern different topics, however, mainly aspects of practical use of liquid crystals. Now we try to give a survey on the activities of the Halle Liquid Crystal Group in the last years with respect to synthesis and physicochemical investigation of new materials for liquid crystal displays.

Liquid Crystalline Phases in the Homologous Series of Terephthalylidene-BIS-[4-n-Alkylanilines]

Abstract: The liquid crystalline polymorphism in the homologous series of terphthalylidene-bis-4-n-alkylanilines was investigated by miscibility experiments. The variants of polymorphism found in the members with carbon atoms n = 3 to n = 10 in the alkyl chains can be derived from a variant HGFICA Nthrough the absence of one or several phases. Beside the known phases H, G, F, C, A, and N, the new phase type 1 was found. The results are discussed in connection with investigations on structure.

Distribution of Cardenolides in Digitalis lanata

Abstract: By means of a digoxin-RIA it has been shown that all organs and tissues of Digitalis lanata contain cardenolides.

Malignant fibrous histiocytoma of bone. Light microscopic and electron microscopic examination of four cases.

Abstract: Malignant fibrous histiocytoma (MFH) of bone is a well-defined tumor by light microscopy but no agreement has been achieved concerning its histogenesis. We present the light and electron microscopic findings of four cases of MFH of bone. In case 1 multiple bone tumors were observed and in case 4 the tumor developed after irradiation. It was our aim to document the cytological variability and to arrange the findings in a histogenetic concept of primary intraosseous MFH. We observed some undifferentiated cells but mainly histiocyte- and fibroblast-like cells including intermediate forms, and several types of giant cells. We should emphasize the fact that there were also some large cells with a light microscopic resemblance to rhabdomyoblasts and with electron microscopic characteristics of myoblastic differentiation. From the ultrastructural point of view, therefore, MFHs seem to derive from a primitive mesenchymal stem cell rather than from the ordinary histiocyte. It is suggested that osteosarcoma and MFH of bone may have a common progenitor cell but it is important to make a clear clinico-pathological distinction between the tumors because of differing biological behavior.

Galvanomagnetische und thermoelektrische Transportuntersuchungen an Sb2Te3

Abstract: Es werden erstmalig alle zwolf galvanomagnetischen Schwachfeldtransportkoeffizienten sowie die beiden Seebeck-Koeffizienten von Sb2Te3 im Temperaturbereich von 100 bis 360 K angegeben. Ferner wird die Anderung einiger dieser Effekte bei Pb-Dotierung beobachtet. Ausgehend von qualitativen Unterschieden im Transportverhalten von Sb2Te3 und der Analogiesubstanz Bi2Te3 werden Modelle zur konsistenten Beschreibung der Transporteigenschaften von Sb2Te3 diskutiert. For the first time the temperature dependences are presented of all of the twelve galvanomagnetic low field transport coefficients and the two Seebeck coefficients of Sb2Te3 in the temperature range from 100 to 360 K. Furthermore the change of some of these effects by Pb doping is observed. Starting from qualitative differences in the transport behaviour of Sb2Te3 and the analogous substance Bi2Te3 some models for a consistent description of transport properties of Sb2Te3 are discussed.

X‐ray and X‐ray photoelectron spectra of vanadium oxides

Abstract: X-ray (XS) and X-ray photoelectron (XPS) spectra are reported for vanadium oxides. Because of the multivalent character of vanadium in the oxide system high quality measurements can be used for chemical shift investigation. Both inner level and valence band spectroscopy give information on the electronic structure and their systematic change with increasing oxidation state. The experimental results are discussed favourable in terms of molecular orbital theory (MO-theory). The complete set of XS and XPS data reported here for V-oxides allows the identification of unknown vanadium oxidation states too. Es wird uber Rontgen- und Rontgenphotoelektronenspektren der Vanadiumoxide berichtet. Auf Grund des multivalenten Charakters von Vanadium im Oxidsystem eignen sich exakte Messungen vorteilhaft zum Studium der chemischen Verschiebung. Sowohl die Spektroskopie der Rumpfniveaus als auch der Valenzbander liefert Informationen uber die Elektronenstruktur und ihre systematische Anderung mit Erhohung des Oxydationszustandes. Die experimentellen Ergebnisse konnen vorteilhaft im Bild der Molekulorbital-theorie diskutiert werden. Die hier aufgefuhrten XS- und XPS-Daten erlauben auch die Identifizierung unbekannter Vanadiumoxydationsstufen.

Calculation of the Compton Profile of Beryllium

Abstract: Starting from a pseudopotential calculation for h.c.p. beryllium the Compton profiles are calculated for the directions 〈101〉, 〈102〉, 〈111〉, and 〈112〉. The profiles for 〈001〉, 〈100〉, and 〈110〉 are improved by detailed considerations on the orthogonalization corrections. A strong anisotropy is found for I〈001〉 — I〈102〉 and I〈001〉 — I〈112〉, respectively. The contribution from the correlation tail in the momentum distribution is estimated. It must be included, if the calculated profiles are compared with high resolution measurements. Ausgehend von einer Pseudopotentialrechnung fur h.d.p.-Beryllium werden die Comptonprofile fur die Richtungen 〈101〉, 〈102〉, 〈111〉 und 〈112〉 berechnet. Die Ergebnisse fur 〈001〉, 〈100〉 und 〈110〉 werden durch weitgehende Einbeziehung der Orthogonalitatskorrekturen verbessert. Es wird eine bemerkenswert grose Anisotropie fur I〈001〉 — I〈102〉 bzw. I〈001〉 — I〈112〉 gefunden. Der Beitrag des Korrelationsschwanzes in der Impulsverteilung wird abgeschatzt. Beim Vergleich mit Messungen hoher Auflosung mus die Korrelation berucksichtigt werden.

Chemical Structure and Reentrant Behavior

Abstract: Several homologous series of chemically related compounds were synthesized. The influence of the terminal polar group and of the length of the conjugated system on the reentrant phenomenon was studied.

A positron study of age-hardenable Al-Zn-Mg alloys

Abstract: Age-hardenable Al-Zn-Mg alloys have been studied by positron lifetime, Doppler broadening and angular correlation measurements. Zinc-rich Guinier-Preston zones in the Al-Zn alloy are observed to trap positrons. In the quenched alloys containing magnesium, positrons are localized at stable vacancy-type defects, which are evidently bound to Mg atoms. Some indications of positron trapping by incoherent precipitate-matrix interfaces are also shown.