Showing papers by "Vienna University of Technology published in 1992"
TL;DR: As a first step to exploit the potential of Trichoderma reesei to produce hemicellulases, two endo-β-1,4-xylanases are purified and cloned and the enzyme encoded by xyn2 appears to more closely resemble several other bacterial and fungal xylanases than does that of xyn1.
Abstract: As a first step to exploit the potential of Trichoderma reesei to produce hemicellulases, we have purified two endo-β-1,4-xylanases (1,4-β-D-xylan xylanohydrolase, EC 3.2.1.8) and cloned their genes. The enzymes were isolated from culture filtrates of T. reesei C 30 grown on xylan as a carbon source, using two steps of cation exchange chromatography. They exhibited molecular weights of 19 (XYN I) and 21 (XYN II) kD, and isoelectric points of 5.2 and 9.0, respectively. These enzymes differed in their pH optimum for activity and affinity for xylan, and accounted for more than 90% of the total xylanolytic activity of the fungus. The purified enzymes were subjected to N-terminal sequence analysis, and after cleavage with trypsin and endoproteinase Glu-C the resulting peptides were sequenced. Oligonucleotides based on these sequences were used to clone gene fragments via PCR, and these were used as probes to isolate full-length copies of xyn1 and xyn2 from a lambda gene bank of T. reesei. The products of xyn1 and xyn2 share considerable homology, but the enzyme encoded by xyn2 appears to more closely resemble several other bacterial and fungal xylanases than does that of xyn1.
222 citations
TL;DR: In this article, an electrochemical glucose sensor was integrated with a pH sensor on a flexible polyimide substrate for in vivo applications for short-term monitoring of glucose and pH in intensive care units and operating theatres, especially for neurosurgical applications.
201 citations
TL;DR: The physical and chemical behaviour of the fog multiphase system was studied experimentally following the temporal evolution of the relevant chemical species in the different phases (gas, droplet, interstitial aerosol) and the evolution of micrometeorological and microphysical conditions, from the pre-fog situation through the whole fog evolution, to the post-fogging period.
Abstract: An outline is presented here of the Po Valley Fog Experiment 1989, carried out within the EUROTRAC-GCE project. This experiment is a joint effort by several European research groups from 5 countries. The physical and chemical behaviour of the fog multiphase system was studied experimentally following the temporal evolution of the relevant chemical species in the different phases (gas, droplet, interstitial aerosol) and the evolution of micrometeorological and microphysical conditions, from the pre-fog situation through the whole fog evolution, to the post-fog period. Some general results, useful for describing the general features of the fog system, are presented here, while specific scientific questions on the different processes taking place within the system itself will be addressed in other companion papers of this same issue. DOI: 10.1034/j.1600-0889.1992.t01-4-00002.x
134 citations
TL;DR: The phenol-degrading strain Pseudomonas putida EKII was isolated from a soil enrichment culture and utilized phenol up to 10.6 mM (1.0 g·1 -1) as the sole source of carbon and energy, and cresols, chlorophenols, 3,4-dimethylphenol, and 4-chloro-m-cresol were metabolized as sole substrates by phenol
Abstract: The phenol-degrading strain Pseudomonas putida EKII was isolated from a soil enrichment culture and utilized phenol up to 10.6 mM (1.0 g·1 -1) as the sole source of carbon and energy. Furthermore, cresols, chlorophenols, 3,4-dimethylphenol, and 4-chloro-m-cresol were metabolized as sole substrates by phenol-grown resting cells of strain EKII. Under conditions of cell growth, degradation of these xenobiotics was achieved only in co-metabolism with phenol. Phenol hydroxylase activity was detectable in whole cells but not in cell-free extracts. The specificity of the hydroxylating enzyme was found during transformation of cresols and chlorophenols: ortho- and meta-substituted phenols were degraded via 3-substituted catechols, while degradation of para-substituted phenols proceeded via 4-substituted catechols. In cell-free extracts of phenol-grown cells a high level of catechol 2,3-dioxygenase as well as smaller amounts of 2-hydroxymuconic semialdehyde hydrolyase and catechol 1,2-dioxygenase were detected. The ring-cleaving enzymes were characterized after partial purification by DEAE-cellulose chromatography.
134 citations
TL;DR: A critical appraisal of the methods used to assess cellulase multiplicity is presented and the recent elucidation of the three-dimensional domain structure of cellulases, their active center, and the role of both in the hydrolysis of cellulose are dealt with.
Abstract: The filamentous fungus Trichoderma reesei is the predominant industrial producer of cellulolytic enzymes by secreting an enzyme system capable of degrading crystalline cellulose, which consists of several cellobiohydrolases, endoglucanases and β-glucosidases. All of these enzymes occur in multiple forms. A critical appraisal of the methods used to assess cellulase multiplicity is presented. By the aid of gene technology, advanced protein analytics and immunology, “true” isoenzymes and proteolytic fragments of all of these enzymes could be identified, and their structure and properties are described. Also, the recent elucidation of the three-dimensional domain structure of cellulases, their active center, and the role of both in the hydrolysis of cellulose are dealt with. Particular emphasis is presented on the differences in the enzymatic reaction mechanisms of cellobiohydrolase I and II, and their synergism.
112 citations
TL;DR: It is implied that local PCA algorithms should always incorporate hierarchical rather than more competitive, symmetric decorrelation, for reasons of superior performance of the algorithms.
112 citations
TL;DR: In this paper, a recent classification of non-degenerate quasihomogeneous polynomials was used to construct all Landau-Ginzburg potentials for N = 2 superconformal field theories with c=9 and calculate the corresponding Hodge numbers.
99 citations
TL;DR: Electric-field-gradient calculations for TiO in the rutile structure using the standard full-potential linearized-augmented-plane-wave method have shown that the contribution of the Ti 3p semicore states is comparable to that of the valence electrons in contrast to other systems studied so far, where the latter dominate.
Abstract: Electric-field-gradient (EFG) calculations for ${\mathrm{TiO}}_{2}$ in the rutile structure using the standard full-potential linearized-augmented-plane-wave (LAPW) method have shown that the contribution of the Ti 3p semicore states is comparable to that of the valence electrons in contrast to other systems studied so far, where the latter dominate This makes the treatment of the 3p and 4p states of Ti an important issue Two-energy-window calculations with different Ti p energy linearization parameters or different sphere radii yield drastically different calculated EFG's The results of standard LAPW calculations are in poor agreement with experiment An extension of the LAPW basis with local orbitals, however, yields EFG results close to experiment and removes the sensitivity to sphere radii and energy parameters The large contribution from the semicore states remains and thus must be considered to be real
98 citations
TL;DR: Using the results of recent theoretical research, practical guidelines for the optimization of femtosecond solid-state oscillators are presented and reproducible sub-40-fs pulse generation in a synchronously pumped Ti:sapphire laser is demonstrated.
Abstract: Using the results of recent theoretical research, we present practical guidelines for the optimization of femtosecond solid-state oscillators and demonstrate reproducible sub-40-fs pulse generation in a synchronously pumped Ti:sapphire laser.
98 citations
TL;DR: In this paper, a 9.4 km2 basin in the Austrian Alps was examined during spring and summer 1989 using digital mono-plotting from oblique aerophotographs.
Abstract: Snow cover patterns in a 9.4 km2 basin in the Austrian Alps are examined during spring and summer 1989. Digital mono-plotting from oblique aerophotographs is used for mapping. on the basis of a square grid with 25 m spacing, snow cover as mapped during nine surveys is analysed as a function of elevation and slope. During winter conditions the snow cover is found to be much better related to these terrain features than during the late ablation period.
96 citations
TL;DR: Calculations of the electronic structure for higher-order rational approximations to quasi-crystals with up to 12380 atoms in the unit cell, based on a tight-binding linear-muffin-orbital technique show highly degenerate free-electron states found close to the Fermi level.
Abstract: We present calculations of the electronic structure for higher-order rational approximations to quasicrystals up to 12 380 atoms in the unit cell, based on a tight-binding linear-muffin-tin-orbital technique. The dispersion relations of the electronic states of quasicrystals are related to those of quasiperiodic free-electron model. Highly degenerate free-electron states are found close to the Fermi level. Their wave vectors define the analog of a Brillouin zone; the ``Brillouin-zone''--Fermi-sphere interaction leads to the formation of a pseudogap at the Fermi level.
TL;DR: A cautious point estimate of R0 congruent to 11 is suggested, and its significance for leishmaniasis control is commented briefly on.
Abstract: Assessment of the resilience of canine leishmaniasis to control or, more ambitiously, the effort needed to eradicate infection, requires an estimate of the basic case reproduction number (R0). This paper applies the theoretical results of Hasibeder, Dye & Carpenter (1992) to data from a cross-sectional survey on the Maltese island of Gozo in which dogs of known age, sex and occupation (pet, guard etc) were subjected to three different serological tests for the presence of specific antibody (IFAT, DAT and ELISA). Difficulties in interpreting these test results, and hence of determining the proportion of dogs infected, present the main obstacle to estimating R0: estimates are critically dependent on the choice of threshold separating seropositives from seronegatives. The data do, however, allow a robust comparative analysis of risk which shows that the force of infection experienced by working dogs is about three times higher than that of pet dogs, a degree of non-homogeneous contact which actually has little effect on estimates of R0. We suggest a cautious point estimate of R0 ≃ 11, and comment briefly on its significance for leishmaniasis control.
TL;DR: In this article, the electronic and magnetic structure of the antiperovskite-structure transition-metal nitrides was calculated employing the augmented-spherical-wave method, and the binding character was found to be mainly covalent for the nitrogen-iron bonds and metallic between the iron and nickel atoms.
Abstract: The electronic and magnetic structure of the antiperovskite-structure transition-metal nitrides ${\mathrm{NiFe}}_{3}$N and ${\mathrm{PdFe}}_{3}$N are calculated employing the augmented-spherical-wave method. From these calculations the binding character is found to be mainly covalent for the nitrogen-iron bonds and metallic between the iron and nickel atoms, as stated in the earlier literature. The magnetic structure exhibits itinerant moments for the iron atoms and more localized moments at the Ni (Pd) atoms. Effects of external pressure are studied by varying the lattice constant. Such calculations yield the pressure dependence of the magnetic moments and the hyperfine fields. The total energy is computed as a function of magnetic moment and volume, yielding total-energy surfaces, that provide the basis for a spin-fluctuation model at finite temperatures. The possibility of an Invar-like behavior is found.
TL;DR: In this article, the exact solution for this depth distribution function has been found in the transport approximation, employing transport theory, and the results are in good agreement with data found in literature and emphasize that strong deviations from exponential behavior occur.
Abstract: The probability that an Auger electron, generated at a certain depth in a semi-infinite target, escapes from the surface under a certain emission angle is described by the so-called depth distribution function. The exact solution for this depth distribution function has been found in the transport approximation, employing transport theory. The results are in good agreement with data found in the literature and emphasize that strong deviations from exponential behavior occur. These deviations are most pronounced for oblique emission. To assess the validity of the transport approximation two kinds of Monte Carlo calculations have been performed. In one case the realistic Mott cross section for elastic scattering has been used while in the other the corresponding momentum transfer cross section was used. The latter procedure exactly fits the transport approximation. A very good agreement between the two approaches has been obtained. This indicates that the transport approximation is an effective tool in transport problems provided the angular distribution of the particle flux density varies slowly with the angle.
TL;DR: In this paper, a hybridized nearly free-electron tight-binding approach to interatomic forces in disordered transition-metal alloys is presented, where the s-Electron contribution to the pair and volume forces is calculated in a pseudopotential perturbation expansion; the d-electRON contribution, within a tight binding-bond approach is calculated analytically on a Bethe-lattice reference system.
Abstract: A hybridized nearly-free-electron tight-binding-approach to interatomic forces in disordered transition-metal alloys is presented. The s-electron contribution to the pair and volume forces is calculated in a pseudopotential perturbation expansion; the d-electron contribution, within a tight-binding-bond approach. The bond order is calculated analytically on a Bethe-lattice reference system. It is shown that the bond order depends strongly on the form of the d band in the alloy. As the electronic density of states changes from a common band to a split-band form, the pair forces in the alloy change from a set of additive pair potentials to nonadditive potentials with a strong preference for the formation of pairs of unlike atoms and short bond distances in the AB pairs. This is illustrated for a series of Ni-M alloys (with transition metal : M=Y, Zr,. . ., or Pd) as a function of alloy composition.
TL;DR: It is shown that the Weyl correspondence allows a simple and effective design of linear time-frequency filters and the proposed method of linear filtering turns out to have both superior performance and reduced cost compared to the nonlinear signal synthesis method.
TL;DR: In this article, a recent classification of non-degenerate quasihomogeneous polynomials was used to construct all Landau-Ginzburg potentials for N = 2 superconformal field theories with c=9 and calculate the corresponding Hodge numbers.
Abstract: We use a recent classification of non-degenerate quasihomogeneous polynomials to construct all Landau-Ginzburg (LG) potentials for N=2 superconformal field theories with c=9 and calculate the corresponding Hodge numbers. Surprisingly, the resulting spectra are less symmetric than the existing incomplete results. It turns out that models belonging to the large class for which an explicit construction of a mirror model as an orbifold is known show remarkable mirror symmetry. On the other hand, half of the remaining 15\% of all models have no mirror partners. This lack of mirror symmetry may point beyond the class of LG-orbifolds.
TL;DR: A mathematical model for canine leishmaniasis is described and formulae which can be used to estimate the basic reproduction number, R0, are presented, in which the essence of heterogeneous transmission can be captured merely by measuring relative rather than absolute contact rates.
Abstract: The paper describes a mathematical model for canine leishmaniasis and presents formulae which can be used to estimate the basic reproduction number, R0. The primary concern has been to devise methods of estimation which make best use of those data most easily obtained by fieldwork, e.g. surveys of prevalence in dog (by age) and sandfly populations. A range of formulae are offered which are more or less demanding of data, and which consequently give more or less precise estimates of R0. They include methods for assessing the influence on R0 of heterogeneous biting rates of sandflies on dogs, in which the essence of heterogeneous transmission can be captured merely by measuring relative rather than absolute contact rates.
TL;DR: The influence of dispersive pulse-broadening effects on femtosecond pulse formation in solid-state lasers has been investigated and empirical formulas derived from computer simulations permits the estimation of the magnitude of performance-limiting effects in practical solid- state systems.
Abstract: The influence of dispersive pulse-broadening effects on femtosecond pulse formation in solid-state lasers has been investigated. Empirical formulas are derived from computer simulations, which permits the estimation of the magnitude of performance-limiting effects in practical solid-state systems.
TL;DR: In this article, the effect of HMSA formation was found to increase HCHO solubility in fog water up to 100 times, and 95% on average of HCHO is present as HMSA in fog-water samples with pH > 4.5.
Abstract: Concurrent gas and fog water measurements of formic, acetic and pyruvic acids and formaldehyde carried out during the Po Valley Fog Experiment 1989 are presented. The reaction between HCHO and S(IV) in fog water solution to form HMSA was studied. The effect of HMSA formation was found to increase HCHO solubility in fog water up to 100 times. 95% on average of HCHO is present as HMSA in fog water samples with pH > 4.5. At lower pH values, HMSA formation is limited by the availability of S(IV) in solution. A common feature of HCOOH, CH 3 COOH and HCHO gas/liquid distribution is represented by the large departures from theoretical predictions when fog water pH is in the region where a large fraction of these compounds is partitioned into the liquid phase. A limitation in mass transport across the air/droplet interface is a likely explanation for this behaviour. DOI: 10.1034/j.1600-0889.1992.t01-3-00007.x
TL;DR: In this paper, it was shown that non-einsteinian gravity in d = 2 resembles a gauge theory with noncompact group and with nonpolynomial self-interactions.
TL;DR: Results of a molecular-dynamics study on liquid cesium, just above the melting point, are presented, where analysis of the transverse current correlation function shows that the corresponding decay mechanism is built up by two relaxation processes (a fast binary one and a slow collective one); starting from \ensuremath{\sim}1 A$ the latter one is completely extinguished.
Abstract: We present results of a molecular-dynamics study on liquid cesium, just above the melting point; i.e., we have performed a computer experiment on exactly the same system that was studied recently in a very accurate neutron-scattering experiment by Bodensteiner et al. In this simulation the interaction of the cesium atoms is based on an Ashcroft empty-core pseudopotential; the total simulation length extends over 100 000 time steps, i.e., 8\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}10}$ s real time. Both static and dynamic structure factors are in very good agreement with experimental results: as in the experiment, we also get\char22{}within very good accuracy\char22{}a positive dispersion relation. However, concerning propagating sound modes beyond the main peak in S(q) (q\ensuremath{\ge}${\mathit{q}}_{\mathit{p}}$\ensuremath{\sim}1.4 \AA{}) we cannot find sufficient evidence for their existence. Analysis of the transverse current correlation function shows that the corresponding decay mechanism is built up by two relaxation processes (a fast binary one and a slow collective one); starting from \ensuremath{\sim}1 A${\mathrm{\r{}}}^{\mathrm{\ensuremath{-}}1}$ the latter one is completely extinguished. The correlation functions are fitted to hydrodynamic and memory-function models that contain generalized thermodynamic and elastic quantities as parameters. In several cases\char22{}if statistics allows\char22{}the true physical values can be recovered; then agreement with experimental values is quite satisfactory (differences of 10\char21{}15 % are observed).
TL;DR: In this article, the authors investigated the hydrogenation of crotonaldehyde over a series of Pt/Ni catalysts and found that the selectivity of the carbonyl group was attributed to the presence of polar surfaces (negatively charged Pt and positively charged Ni).
TL;DR: In this article, a comparison of one-and two-stage spring-suspended systems with magnetic eddy-current damping is made, and it is shown that the two stages suffer from poor isolation at high frequencies, which can be improved by additional elastomer elements.
TL;DR: Using light-cone variables, it is shown that R2 gravity with dynamical torsion in two dimensions is one of the rare field theories whose complete classical solution in closed form can be obtained and fulfils an invariant relation between the cosmological constant, the curvature scalar, and the scalar formed by the torsional tensor.
Abstract: Using light-cone variables, we show that R2 gravity with dynamical torsion in two dimensions is one of the rare field theories whose complete classical solution in closed form can be obtained. It fulfils an invariant relation between the cosmological constant, the curvature scalar, and the scalar formed by the torsion tensor. We conjecture that this relation, interpreted as a local conservation law, is closely connected to the integrability of the theory. The solutions may possess a rich spectrum of singularities in curvature and torsion. Special cases, including one with nonvanishing torsion, can be used to elucidate some physical properties of the solution where by "physical" we imply the validity of concepts from general relativity such as measurements of distances and times and of extremal trajectories of a scalar test particle.
15 Jul 1992
TL;DR: By generalizing the notion of a semantic tree, the completeness of resolution and of some effective refinements are demonstrated and translation calculi that convert formulae of many valued logics to clause syntax are presented.
Abstract: To achieve efficient proof procedures for quantificational logics with finitely many truth values we extend the classical resolution principle By generalizing the notion of a semantic tree we demonstrate the completeness of resolution and of some effective refinements We also present translation calculi that convert formulae of many valued logics to clause syntax As an application we investigate some well known examples of many-valued logics
TL;DR: In this paper, the authors describe the formation, evolution, and dissipation of fog in terms of the total acidity of a unit volume of air containing gas species, interstitial aerosol particles and fog droplets.
Abstract: Concentration and phase distribution of sulfur and nitrogen species during a particular fog episode in the Po Valley are experimentally described in this paper. Chemical measurements were carried out simultaneously at different heights within the fog layer, up to 50 m. Microphysical and meteorological parameters necessary for the description of the fog multiphase system were also concurrently measured as a function of height. The fog cycle (formation, evolution, dissipation) is described in terms of the total acidity of a unit volume of air containing gas species, interstitial aerosol particles and fog droplets. The fog system was not closed and input of acidic and basic components was observed during fog evolution. The driving force which determines the acidity of the fog multiphase atmospheric system was found to be the presence of NH 3 and its partitioning among the different phases. A strong decrease of fog water pH (from 5.6 down to 2.8) was observed during fog evolution and was attributed to a HNO 3 input to the system. These acidic and basic inputs are described in terms of a titration/back-titration process of the fog system. The SO 2 oxidation process in fog water was found to be of minor importance in determining the SO 4 = concentration within the fog system, due to both low SO 2 concentration and limited oxidant availability during the experiment. DOI: 10.1034/j.1600-0889.1992.t01-4-00005.x
TL;DR: In this article, a flexural theory of elastic sandwich beams is derived which renders quite precise results within a wide range of ratios of dimensions, mass densities, and elastic constants of the core and faces.
Abstract: A flexural theory of elastic sandwich beams is derived which renders quite precise results within a wide range of ratios of dimensions, mass densities, and elastic constants of the core and faces. The assumptions of the Timoshenko theory of shear-deformable beams are applied to each of the homogeneous, linear elastic, transversely isotropic layers individually. Core and faces are perfectly bonded. The principle of virtual work is applied to derive the equations of motion of a symmetrically designed three-layer beam and its boundary conditions. By definition of an effective cross-sectional rotation the complex problem is reduced to a problem of a homogeneous beam with effective stiffnesses and with corresponding boundary conditions. Thus, methods of classical mechanics become directly applicable to the higher-order problem. Excellent agreement of the results of illustrative examples is observed when compared to solutions of other higher-order laminate theories as well as to exact solutions of the theory of elasticity.
TL;DR: Evidence of different ortho-cleavage enzymes in Pseudomonas acidovorans CA28 involved in aniline and 3-chloroaniline metabolism, respectively, is indicated.
Abstract: During degradation of aniline and 3-chloroaniline, respectively, by Pseudomonas acidovorans CA28, selective induction of two catechol 1,2-dioxygenases (C12O) was observed. C12O I activity was the sole ring-cleaving enzyme detectable in cell-free extracts after growth on aniline, while C12O II was exclusively found after growth on 3-chloroaniline. Both enzymes were clearly differentiated by their elution behaviour on DEAE-cellulose and their substrate specificities. For C12O I high activity was demonstrable only with unsubstituted catechol, while C12O II showed preference for and high affinity towards chlorinated catechols. Therefore, evidence of different ortho-cleavage enzymes in Pseudomonas acidovorans CA28 involved in aniline and 3-chloroaniline metabolism, respectively, is indicated.
TL;DR: In this article, the surface composition of Pt 10 Ni 90 (100), Pt 25 Ni 75 (111), and Pt 50 Ni 50 (110) single crystal alloys has been determined by ion scattering spectroscopy (ISS) and ultraviolet photoelectron spectroscopic (UPS).