Showing papers by "Vienna University of Technology published in 1977"

Influence of manganese on enzyme synthesis and citric acid accumulation inAspergillus niger

Abstract: A comparison of citric acid fermentations in manganese-deficient and manganese-containing media showed that manganese strongly influences idiophase metabolism In the presence of manganese, cell growth increases, sugar consumption is diminished and acidogenesis decreases drastically An investigation of the key enzymes of glycolysis, the pentosephosphate pathway, TCA-cycle, nitrogen metabolism, and gluconeogenesis indicated that manganese deficiency was accompanied by a repression of anabolic and TCA-cycle-enzymes with the exception of citrate synthase The activity of this enzyme and the enzymes of glycolysis paralleled the sugar consumption rate In the presence of manganese, no repression of enzyme synthesis was observed Activities of 2-oxoglutarate dehydrogenase and isocitrate lyase could not be detected in either case The results support the hypothesis that manganese deficiency mainly affects the operation of biosynthetic reactions inAspergillus niger, thus leading to an overflow of citric acid as an end product of glycolysis

Iterated defect correction for the efficient solution of stiff systems of ordinary differential equations

Abstract: Iterated Defect Correction (IDeC)-methods based on the implicit Euler scheme are shown to have a fixed point. This fixed point coincides with the solution of certain implicit multi-stage Runge-Kutta methods (equivalent to polynomial collocation). Sufficient conditions for the convergence of the iterates to the fixed point are given for linear problems. These results indicate that for a large variety of general non-linear stiff problems, fixed-point-convergence can be expected, and moreover they indicate that the rate of convergence to the fixed point is very high for very stiff problems. Thus the proposed methods combine the high orders and the high accuracy of multistage-methods with the low computational effort of single-stage methods.

On the theory of the evaluation of joint orientation measurements

Abstract: On the Theory of the Evaluation of Joint Orientation Measurements The current procedure for the evaluation of sets of joint-orientation measurements in terms of regional stresses is critically reviewed. It is shown that the counting circles on a sphere for constructing density diagrams are not circles on an equal-area (Lambert) projection of such a sphere; the correct curves are presented. It is shown that the search for modal maxima in the density diagrams corresponds to a nonparametric statistic for which it is difficult to give confidence limits. General considerations about the statistics of experiments yield the result that 12–15 joint measurements in an outcrop are sufficient to define 3 maxima, if such maxima exist at all. In order to give confidence limits, it is best to introduce a parametric model for the distribution of joint orientations. For a single cluster of orientations the probability density function is chosen as proportional to exp (k2 cos2θ) whereθ is the polar deviation angle from the “mean” direction; since the basic joint-orientations havethree fundamental directions, three probability density functions of the above type have to be superposed. These are determined by giving 11 parameters which can be determined by a function-minimization procedure from a given set of measurements. This procedure is best carried out on a computer. In this fashion, confidence limits for the preferred joint directions can be obtained. For the determination of the stresses, only two preferred sets of joints are required reducing the necessary number of parameters to 7. According to the usual theory of the statistics of trials, it is seen that 21 measurements are required to determine them. Thus, using a parametric statistic, it is seen that 21 measurements of joint orientations in an outcrop should suffice to determine the stress field that produced them. If the sharpness of the distributions is assumed as a priori known, this reduces again to the 15 or 20 measurements required for a non-parametric evaluation.

NMR-spectroscopic studies on solvent electrophilic properties, Part II: Binary aqueous-non aqueous solvent systems

Abstract: Acceptor numbers have been determined for binary mixtures of water with acetonitrile (AN), dioxane, acetone (AC), pyridine (PY), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), hexamethylphosphoramide (HMPA), methanol, ethanol andi-propyl alcohol. The electrophilic properties of binary aqueous-non aqueous solvent mixtures are determined both by selective solvation and specific solvent-solvent interactions. The variation of the acceptor number as a function of solvent composition is interpreted in terms of the previously determined nucleophilic and electrophilic properties of the pure components and their specific solvent structure.

Propagation of modes in curved hollow metallic waveguides for the infrared.

Abstract: Field configurations and attenuation constants of TE-modes in curved parallel-plate metallic waveguides are calculated numerically It is assumed that the distance between the plates is much larger than the free-space wavelength and that the radius of curvature is much larger than the distance between the plates For curvatures not too small the attenuation constant is shown to be inversely proportional to the radius of curvature, but independent of the plate distance The discrepancy between theory and experimental observations existing so far is hereby resolved

The study of dipoles in Cu—Al alloys using weak-beam electron microscopy

Abstract: In f.o.c. metals and alloys, dipoles are the predominant dislocation structure during the early stages of plastic deformation. Single crystals of Cu-Al alloys, having low stacking fault energies, have been deformed in tension to the end of stage I of the work-hardening curve. The weak-beam method of electron microscopy has then been used to study the equilibrium configurations of dissociated dipoles having different character and glide-plane separation. By analysing the micrographs, the Burgers vectors of all four partial dislocations can be indexed, the various equilibrium positions identified, and the arrangement of the partial dislocations determined in full. The experimental results are compared with the calculated equilibrium configurations derived by Morton and Forwood (1974, private communication) using linear anisotropic elasticity theory. Various types of equilibrium positions predicted by the theory are observed experimentally and quantitative agreement is good. Deviations from the stre...

Increase of the first natural frequency and buckling load of plates by optimal fields of initial stresses

Abstract: Departing from the common way of optimization of vibrating structures by an optimal mass distribution this paper deals with the problem of maximizing the fundamental frequency of structures by optimizing fields of initial stresses without varying the given appropriate shape of the structure. Thin elastic circular and rectangular plates are considered, which may be loaded by external inplane forces, and optimal initial membrane stress fields are calculated, which produce values of the first natural frequency of the free bending vibrations as high as possible. As a constraint, the strain energy caused by the field of initial stresses in the resting, externally unloaded plate is given. The computation leads to a max-min-problem solved numerically with the help of gradient methods. The optimal fields of initial stresses of the buckling plates are calculated as extreme cases in the same manner.

Characterization of Energy Bands in Terms of Relativistic Local Solid State Models Applications to VC, NbC and UC

Abstract: Relativistic Wigner delay times for resonant states and related quantities are used to characterize the electronic structure of VC, NbC and UC. For comparison the relativistic energy band structure for VC and NbC is calculated.—It is found, that simple relativistic local solid state models are capable to describe the electronic structure of solid compounds containing heavy atoms qualitatively correctly. Relativistische Wignersche Verzogerungszeiten fur Resonanzzustande und davon abgeleitete Grosen werden verwendet, um die elektronische Struktur von VC, NbC und UC zu charakterisieren. Zum Vergleich ist die relativistische Bandstruktur fur VC und NbC berechnet.—Es zeigt sich, das mit Hilfe einfacher, relativistischer, lokaler Festkorpermodelle die elektronische Struktur von Festkorpern mit schweren Atomen qualitativ richtig wiedergegeben werden kann.

Dosimetric studies in the radiological examination of the hips in young infants with a special fenestration method of gonad protection.

Abstract: A special lead shield of 1,5 mm Pb, with a fenestration was used for gonad protection during X-Ray of the hips for detection of dysplasia. The window allows the delineation of all parts of the skeleton required to make a correct diagnosis and check the standardized position of the pelvis, while all other parts, especially the gonads are safely shielded. The scattered radiation for the testes was further reduced by a trough-shaped lead shield behind the scrotum. The effectiveness of this gonad protection was measured by direct dosimetric studies on the infant with LiF and CaF2: Dy dosimeters at different adjustments of the X-ray generator and with medium and ultra high speed screen-film combinations

Die Bildungswärmen von MnSi1,73, MnSi, Mn5Si3 und Mn3Si

Abstract: By means of vapor pressure measurements using theTorker method (Torsion-Knudsen Effusion Recoil) as well as theKnudsen tanspiration technique in connection with a mass spectrometer, the heats of formation of the following compounds were found to be −6.5±0.7 kcal/g atom (Mn0.366Si0.634), −7.8±0.6 kcal/g atom (Mn0.50Si0.50), −7.3±0.6 kcal/g atom (Mn0.625Si0.375), and −6.6±0.6 kcal/g atom (Mn0.75Si0.25).

Zusammenhang zwischen freien standard-transferenthalpien von ionen und empirischen lösungsmittelparametern

Abstract: Standard free energies of transfer from the reference solvent acetonitrile to various protic and aprotic solvents have been calculated based on the assumption of negligible diffusion potentials in certain galvanic cells. The standard free energies of transfer of Cl−, Br−, and I− are linearly related to the acceptor numbers of unstructured solvents. Similarly, linear relationships were found to exist between the donor numbers of unstructured solvents and the standard free energies of transfer of K+ and in part Ag+. Deviations from linearity occuring in protic solvents like water, methanol, ethanol or trifluoroethanol are interpreted in terms of changes in solvent structure.

Volumssuszeptibilitätsmessungen mit kernmagnetischer Resonanzspektroskopie

Abstract: By means of NMR-spectroscopy the volume susceptibilities of various solvents have been determined.

Current-kink noise of n-channel enhancement e.s.f.i.-m.o.s. s.o.s. transistors

Abstract: An experimental study of the low-frequency-noise properties of n-channel epitaxial silicon films on insulator m.o.s. s.o.s. transistors has been performed. The measurements show an excessive noise contribution at drain voltages corresponding to the current-kink effect for temperatures ranging from 4.2 to 300 K.

Einfluß des Lösungsmittels auf das Redoxverhalten von Tetrakis(triphenylphosphin)-platin(0), Tetrakis(triphenylphosphin)-palladium(0) und Tetrakis(triphenylphosphin)-nickel(0)

Abstract: The redox behaviour of tetrakis(triphenylphosphine)-platinum(0) [Pt(TPP)4], tetrakis(triphenylphosphine)-palladium(0) [Pd(TPP)4] and tetrakis(triphenylphosphine)-nickel(0) [Ni(TPP)4] has been studied in N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile (AN), propanediol carbonate (PDC), N,N-dimethylthioformamide (DMTF) N-methylpyrrolidine-2-thione (NMTP) and nitromethane (NM). The platinum complex was found to undergo irreversible two electron oxidations with partial or complete loss of the ligands in all solvents but nitromethane. The palladium complex was also oxidized to the divalent form in the solvents studied except inPDC andNM where the complex was found to be polarographically inactive; Ni(TTP)4 was reversibly or almost reversibly oxidized to a movovalent form inDMF, AN andDMTF followed by an irreversible oxidation to a divalent complex. Direct oxidation to the divalent form occurred inDMSO, no oxidation was observable inNMTP andPDC, decomposition took place in nitromethane. The half-wave potentials were recorded versus bisbiphenylchromium iodide (BBCr)I as an internal standard. The influence of the solvents on the redox behaviour and the dissociation of ligands is discussed.

Solvent effects on metal carbonyls and related compounds

Abstract: The observed solvent effects on the CO and NO frequencies in metal carbonyls and related compounds are shown to be influenced by the solvent acceptor properties, as expressed by the acceptor number.

Verbesserung des kontrastes von magnetischen domänen in SmCo5 im rasterelektronenmikroskopischen sekundärelektronenbild

Abstract: IMPROVEMENT OF MAGNETIC DOMAIN CONTRAST OF SmCo5 IN THE SE-MODE OF A SCANNING ELECTRON MICROSCOPE By means of a diaphragm in front of the detector, the SE-contrast of magnetic domains observed in a SEM has been improved and a resolution of 0.17 G. cm obtained. Investigations on SmCo5 show that the contrast can be improved by increasing the acceleration voltage and tilting the specimen. ZUSAMMENFASSUNG Durch eine zusatzliche Blende vor dem Detektor wurde der SE-Kontrast magnetischer Domanen in REM verbessert und eine Empfindlichkeit von 0, 17 G . cm erreicht. Untersuchungen an SmCo5 ergaben, das sich der Kontrast der Domanen mit zunehmender Beschleunigungsspannung verbessert.

Theoretical interpretation of the valence X-ray photoelectron spectrum of TiC

Abstract: The valence X-ray photoelectron spectrum of TiC is interpreted in terms of the density of states and in terms of a simple model for transition matrix elements. The conceptual difficulties arising with both the initial and the final state are discussed.

IR-Spektroskopische Charakterisierung der BlutvertrÄglichkeit von Polyurethan-Silicon-Copolymeren

Abstract: In der vorliegenden Arbeit wird zunAchst die Anwendbarkeit der IR-ATR-Spektrometrie (GerAt: Perkin-Elmer, Mod. 180) zur relativ-quantitativen Analyse des HauptkomponentenverhAltnisses von Polyurethan-Silicon-Copolymeren untersucht. Nach Optimierung der Analysenparameter (Kristallmaterial, Probengro\e, Probenlage, Anpre\druck, Auswertemethode) wurde eine reprAsentative Analysenreproduzierbarkeit von v=0,64% ermittelt. Anschlie\end an die Modelluntersuchungen an Standardproben (Teile von handelsublichen intraaortalen Ballonpumpen) wurden Messungen der Zusammensetzung von verschiedenen MembranoberflAchen durchgefuhrt. Je nach Herstellungsmethode der Copolymerisate wurden signifikant unterschiedliche OberflAchenzusammensetzungen festgestellt. Durch Korrelation der Analysenresultate und klinischen Beobachtungen bzw. Literaturwerten wurde ein „relativer BlutvertrAglichkeitsindex“ abgeleitet, welcher ein Ma\ fur das VerhAltnis Polyurethan/Silicon an der ProbenoberflAche (Informationstiefe ≦ 3 Μm) relativ zu einer Standardzusammensetzung ist. Blutkompatible OberflAchen haben Indices ≧ 80%, OberflAchen mit Indices ≦ 65% neigen zur ThrombogenitAt. Auf diese Weise konnten zur Implantation ungeeignete Proben erkannt und Resultate neuer Herstellungsverfahren fur Membranen in kunstlichen Herzen auf ihre BlutkompatibilitAt uberpruft werden.

Flux pinning by precipitates

Abstract: Measurements of pinning forces in two model system superconductors containing either incoherent normal-conducting or coherent superconducting precipitates are reported. An analysis of the bulk pinning forces shows that in both cases the statistical summation of basic interaction forces is appropriate. Furthermore, from the magnitude and the temperature dependence of these basic interaction forces we conclude that in both systems the core pinning interaction, i.e. the gain of condensation energy upon moving the flux line core onto the precipitate, is responsible for pinning.

Massenspektrometrische Bestimmung der thermodynamischen Aktivitäten in flüssigen Nickel-Germanium-Legierungen

Abstract: Die Knudsen-Effusions-Methode in Verbindung mit einem Massenspektrometer wird zur Ermittlung der thermodynamischen Aktivitaten, der freien Zusatzenthalpien ΔGE und der Mischungswarmen ΔHE des Systems Ni — Ge im Temperaturbereich von 1640 K bis 1920 K herangezogen. Zur Auswertung der massenspektrometrischen Messungen wird ein analytisches Verfahren benutzt, das von dem Naherungsansatz fur die thermodynamischen Zusatzfunktionen von Redlich und Kister ausgeht. — Die erhaltenen thermodynamischen Aktivitaten weisen negative Abweichungen vom idealen Verhalten auf. Die freien Zusatzenthalpien ΔGE und die Mischungswarmen ΔHE sind im gesamten Konzentrationsbereich negativ. Bei 1870 K betragt das Minimum von ΔGE — 19,8 kJ · mol−1 (43 At.% Ge) und das Minimum der Mischungswarme — 29,6 kJ · mol−1 (42,5 At.% Ge). 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 system Nickel-Germanium in the temperature range 1640 K to 1920 K. For the evaluation of the mass spectrometric measurements an analytical procedure is used, which is based on the Redlich-Kister approximation for the thermodynamic excess functions. — The calculated thermodynamic activities show negative deviations from the ideal behaviour. The excess Gibbs free energies ΔGE and the heats of mixing ΔHE are negative over the whole concentration range. At the temperature of 1870 K the minimum value of ΔGE is — 19.8 kJ · mol−1 (43 At.% Ge) and the minimum value of ΔHE is — 29.6 kJ · mol−1 (42.5 At.% Ge).

Neue Erkenntnisse über den Abbau der Stärke mit Hypochlorit 6. Enzymatischer Abbau von oxydierter Stärke

Abstract: New Knowledge on Degradation of Starch by Hypochlorite. Part 6. Enzymatic Degradation of Oxidized Starch. For the detection of structural changes in hypochlorite-oxidized potato starch starches of variously high degrees of oxidation were enzymatically degraded by amyloglucosidase and a mixture of α- and β-amylase. As a function of the number of functional groups, and, therefore, of the degree of oxidation an increased number of non-degradable glucose units (GU's) was traced in the starch molecule. According to the results, not only the GU with a functional group but also the two neighbouring GU's were not affected by enzymatic degradation.