Showing papers by "Vienna University of Technology published in 1979"

Manganese deficiency leads to elevated amino acid pools in citric acid accumulating Aspergillus niger

Abstract: Free amino acid pools have been investigated in a citric acid accumulating strain of Aspergillus niger during batch growth under manganese sufficient and deficient conditions by means of an improved chromatographic method. Studies on the mycelial content of several nitrogenous compounds under manganese sufficient and deficient conditions showed that manganese deficiency resulted in lower amino acid pool sizes during trophophase and considerable accumulation during idiophase, and in a reduction of the protein and nucleic acid contents. Addition of cycloheximide to mycelia grown with sufficient manganese also caused an elevation of free amino acid pool sizes, thus indicating that impairment of protein synthesis by manganese deficiency is responsible for the observed rise in amino acid concentration. Furthermore it was observed that the manganese deficient mycelia excreted high amounts of all amino acids suggesting that manganese deficiency may also affect membrane permeability.

Measurement of coherent neutron scattering lengths of gases

Abstract: With the neutron interferometer, measurements of the coherent neutron scattering lengths by various gases have been performed. We get the following numbers for the bound coherent scattering lengths for atoms (in fm):bc(H) =−3.64(3),bc(D)=6.55(8),bc(He−3)=5.74(7),bc(He)=3.26(3),bc(N)=9.30(8),bc(O)=5.83(5),bc(Ne) =4.63(4),bc(Ar)=2.07(2),bc(Kr)=7.52(6),bc(Xe)=4.69(4). In some cases greater accuracy is achieved in comparison with recommended values from the literature. The absolute values for hydrogen and deuterium measured with gaseous samples, are about 2% smaller than the values measured with liquids and other reference values.

29Si-NMR-Untersuchungen an einigen Cyclosilanderivaten

Abstract: 29Si-NMR spectras of some new cyclosilane derivatives were measured. First aspects of the dependence of chemical shift on ring size and kind of substituents are given.

Die Kristallstruktur der Verbindung Li3Zn0,5GeO4

Abstract: The crystal structure of the compound Li3Zn0.5GeO4 has been determined and refined by means of three-dimensionalFourier syntheses and least squares. Li3Zn0.5GeO4 crystallizes orthorhombic with space groupD2h16-Pmnb (No. 62) and the lattice parametersa=6.29,b=10.74 andc=5.17 A. The crystal structure consists of isolated [GeO4] tetrahedra, which are linked together by [(Li,Zn)O4] tetrahedra analogous to Li3PO4(h). An additional eight-fold position is partly occupied by two lithium atoms. The occupancy of this position may vary according to the observed range of composition, which lies between Li3.8Zn0.1GeO4 and Li2.6Zn0.7GeO4.

An improved method for characterization of citrate production by conidia ofAspergillus niger

Abstract: A modification of a method is presented, which enables the characterization of a given conidial material ofAspergillus niger with respect to its capacity to produce citric acid in submerged culture. The procedure can be applied to selection experiments as well as to counteract degeneration during strain maintenance.

Analysis of mixed-mode isochromatic crack-tip fringe patterns

Abstract: Westergaard stress function representations of the stress field around the tip of a stationary crack subjected to mixed-mode loading are employed to develop a general relationship between the isochromatic fringe orderN, its position parametersr and θ and the general stress field expressed in terms of several parameters, the stress intensitiesK 1,K 2, a far field stress parameter α, and higher order term parametersβ 1 andβ 2. These parameters are varied and isochromatic crack tip fringe patterns are constructed for a set of classified combinations. Since the size, shape, orientation, and other particular features of the fringe patterns depend strongly on the combination of parameters chosen they can be used to classify crack tip fringe patterns. The introduction of fringe loop diagrams not only facilitates the classification procedure and enables a classification without plotting fringe patterns, but it also permits qualitative and quantitative evaluation of the isochromatic patterns. Isochromatics which classify fourtyeight different states of stress are investigated and the majority of them have been illustrated.

Algorithm 537: Characteristic Values of Mathieu's Differential Equation [S22]

Abstract: for solutions y ( x ) of periodicity ~r or 2~r. In this case b is a function of S and belongs to a countably infinite set of values for every S [2]. The knowledge of b is a prerequisite for calculating ordinary and modified Mathieu functions. The program has been tested for real S-parameters between zero and 1000, and for a number of characteristic values of up to 24, depending on the value of S. (For negative S, simple equations exist which relate the corresponding b to those for positive S [2, p. xvii]). The calculated b are correct to at least 9 decimal places. Within the calculated finite subset of b, the characteristic values are arranged with increasing magnitude, the first value being the smallest of the infinite set. The algorithm uses a l ibrary subroutine to find the eigenvalues of a real symmetr ic tridiagonal matrix. Four types of solutions y (x) can be distinguished: An odd and an even solution with period 2qr, and an odd and an even solution with period ~r. The corresponding characteristic values b are called bo2r+l, be2r+l, bo2r+2,1 and be2r. ( r = O, 1, 2 , . . . ; within each of the four sets, the smallest index is used for the smallest value of b.)

Quantitative XPS analysis without reference samples

Abstract: For approximately ten years there has existed a theoretically based concept of fundamental parameters for XRFA (quantitative X-ray fluorescence analysis). From a comparison of the differences specific for XRFA and XPS it can be learned that this concept is also applicable to XPS and allows quantitative analysis without reference samples. Additionally, the influence of an overlayer on analytical XPS results is discussed. The theoretical considerations are confirmed by a series of measurements performed on binary and ternary alloys of Ag/Au/Cu and the results are compared with those of earlier measurements with reference samples. An averaged absolute accuracy of approximately ±2 wt% has been found for both methods, but the advantage of an absolute method needs no further comment.

Frequency-dependent dielectric behavior of amorphous silicon thin films

Abstract: The admittance $Y=G+j\ensuremath{\omega}C$ of amorphous silicon films, produced by electron-beam evaporation, has been measured at frequencies between dc and ${10}^{7}$ Hz, and at temperatures between 150 and 400 K. At low frequencies the conductance $G$ was nearly independent of frequency, an exponential function of temperature, and influenced by contacts. At medium frequencies $G$ increased almost proportionally to ${\ensuremath{\omega}}^{s}$, with $s\ensuremath{\simeq}0.9$. In this region $G$ was found to be contact independent and superlinearly dependent on temperature. In the high-frequency region a saturation behavior of $G$ was observed. The capacitance $C$ decreased monotonically from low to high frequencies. These measured properties have been attributed to a hopping between sites, randomly distributed in space and energy, and over the barriers separating the sites. The barrier height has been correlated to the intersite separation by assuming Coulomb-like potential wells. This model accounts both for the ${\ensuremath{\omega}}^{s}$ behavior and for the saturation of $G$. However, to obtain good agreement between theory and experiment it was necessary to envisage a minimum relaxation time ${\ensuremath{\tau}}_{o}$ not much smaller than ${10}^{\ensuremath{-}6}$ sec. In contrast, ${\ensuremath{\tau}}_{o}$ has in previous work been interpreted to be of the order of an atomic vibrational period (\ensuremath{\sim} ${10}^{\ensuremath{-}12}$ sec).

Propagating Energy Modes in the Classical Heisenberg Chain: "Magnons" and "Second Magnons"

Abstract: The ferromagnetically coupled classical Heisenberg chain in an applied magnetic field has been studied by computer simulation. The results indicate the presence of a second collective mode, in addition to the damped spin-wave-like modes which have previously been observed in the absence of a magnetic field. For intermediate wavelengths, the mode manifests itself by well-defined oscillations in the energy-density correlation function, and by a second peak in the spectrum of the longitudinal spin-density correlation functions.

ber die Mischbarkeit von UN mit LaN, CeN, PrN, NdN, SmN, GdN, DyN, und ErN

Abstract: X-Ray studies of the mixed nitride phases indicate complete miscibility in all cases. Lattice parameters generally showed negative deviations from the additivity rule.

Thermodynamische Untersuchungen am System Kobalt‐Nickel. Massenspektrometrische Aktivitätsmessungen in der flüssigen und festen Phase und Berechnung des Schmelzdiagramms

Abstract: Sowohl fur die flussige als auch fur die feste Phase des Systems Co-Ni wurde zur Ermittlung der freien Zusatzenthalpien ΔGE, der Mischungswarmen ΔHE und der thermodynamischen Aktivitaten ai die Knudsen-Effusionsmethode in Verbindung met einem Massenspektrometer herangezogen. Die Auswertung der massenspektrometrischen Messungen erfolgt nach einem analytischen Verfahren, das von dem Naherungsansatz fur die thermodynamischen Zusatzfunktionen von Redlich und Kister ausgeht. Die erhaltenen thermodynamischen Aktivitaten weisen sowohl fur die flussige als auch fur die feste Phase geringfugig negative Abweichungen vom Raoultschen Gesetz auf. Sowohl fur die flussige als auch fur die feste Phase sind im gesamten Konzentrationsbereich die Mischungswarmen positiv und die freien Zusatzenthalpien negativ. Fur flussige Legierungen bei 1800 K betragt das Maximum von ΔHE = 425 J · mol−1 (54 At% Ni) und das Minimum von ΔGE = -630J · mol−1 (49 At% Ni). Fur feste Legierungen bei 1600 K betragt das Maximum von ΔHE = 660 J · mol−1 (55 At% Ni) und das Minimum von ΔGE = -550 J · mol−1 (47, 25 At% Ni). Unter Verwendung der in der vorliegenden Arbeit ermittelten Werte fur die thermodynamischen Zusatzfunktionen und unter Heranziehung von Literaturdaten fur die Schmelz- und Molwarmen wurde das Schmelzdiagramm von Co-Ni nach einer allgemein anwendbaren Methode zur Berechnung der Gleichgewichtskonzentrationen koexistierender Phasen ermittelt. Die Methode beruht auf dem verallgemeinerten Newtonschen Verfahren zur numerischen Losung von Gleichungen. The Knudsen-Effusion method in combination with a mass spectrometer is used for the determination of the thermodynamic activities, the excess Gibbs free energies ΔGE and the heats of mixing ΔHE of the liquid and solid alloys of cobalt and nickel in the temperature range 1480 K to 1875 K. The evaluation of the mass spectrometric measurements is accomplished by an analytical procedure, which is based on the Redlich-Kister equation for the thermodynamic excess functions. The thermodynamic activities for the liquid as well as for the solid phase show slightly negative deviations from Raoult's Law. For both phases the heats of mixing ΔHE are positive and the excess Gibbs free energies ΔGE are negative over the whole concentration range. For the liquid alloys the maximum value of ΔHE is 425 J · mol−1 (54 at% Ni) and the minimum value of ΔGE is - 630 J · mol−1 (49 at % Ni) at 1800 K. For the solid alloys the maximum value of ΔHE is 660 J · mol−1 (55 at% Ni) and the minimum value of ΔGE is - 550 J · mol−1 (47.25 at% Ni) at 1600 K. Based on results of this study and on literature data

Determination of stress intensity factors by the dynamic method of caustics for optically isotropic materials

Abstract: The method of caustics is an optical method for experimental determination of stress intensity factors at crack tips. The paper generalizes the method of caustics to dynamic situations and the dynamic stress intensity factor at the tip of a running crack in an optically isotropic material is determined. Higher order terms of the Westergaard type stress functions are included and their effect on the shape and extension of the highly constrained zone surrounding a crack tip is discussed. Analytical equations for the caustic are presented. For the singular solution it is found that dynamic K-values associated with larger shadow spots are lower than their static counterparts. Higher order terms induce a generalized evaluation formula for the stress intensity factor where powers of the order n + 5/2 (n = 0, ...) of the caustic diameter are present. The effect of superposition of dynamic and higher order term corrections on the K-value is discussed. The dynamic correction implies that the K(c)-characteristic (c ... crack velocity) is to be modified towards lower values of K. This correction is negligible for small and moderate crack velocities justifying the use of static equations for practical purposes. The K-values for crack branching, however, turn out to be smaller than assumed hitherto, a fact which is of particular interest in connection with SEN-type fracture test specimens.

Orientationsstruktur der Talanlagen in der Schweiz

Abstract: . The orientation of the Valleys in Switzerland shows a remarkable symmetry. It is the aim of this paper to represent this symmetry in numerical terms and to seek a physical cause thereof. For this purpose, the valley directions have been «rectified» (i. e. straightened) by considering them as edges in a graph. In this fashion, the distribution of orientations can be represented numerically and, in consequence, can be analyzed statistically. It is shown that the preferred orientations are ENE and SSE, which is the same as the preferred orientations of the strikes of the rock-joints in the region. Inasmuch as the joints are thought to be caused by the neotectonic stress field, the coincidence of the orientations of joints and river valleys is a strong indication that the latter are determined by the same neotectonic stress field as well. Data from fault plane solutions of earthquakes support this contention.

Probenahme von atembaren und lungengängigen Staubinimissionen zur „Integrierten Staubanalyse“

Abstract: Eine korngrosenfraktionierende Probenahme von Staub zur nachfolgenden chemischen Analyse ist in einem weiten Korngrosenbereich mit Niederdruck-Kaskadenimpaktoren moglich.

Implementation of defect correction methods for stiff differential equations

Abstract: There is a large gap between the theoretical results about iterated defect corrections (IDeC) and practical implementations of IDeC methods for stiff systems. This paper tries to close this gap by providing general principles which are essential for the construction of efficient IDeC codes. Numerical results gathered with one particular IDeC based experimental code furnish evidence of the inherent power of the defect correction concept in the context of stiff systems of ordinary differential equations.