Showing papers by "Braunschweig University of Technology published in 1989"

Erste Schritte auf dem Weg zur edelmetallkatalysierten Nitrat‐ und Nitrit‐Entfernung aus Trinkwasser

Abstract: Performances de la reduction des nitrates et degradation des nitrites des eaux potables catalysees par le palladium

Kinematic Analysis of Symmetrical Flight Manoeuvres of Odonata

Abstract: By analysis of slow-motion films of dragonflies and damselflies in free flight, released in front of a backdrop or startled during flight, the following flight parameters have been quantified for symmetrical manoeuvres: wingbeat frequency, relative durations of up- and downstroke, phase relationships of the beats of fore- and hindwings, stroke amplitude, mean stroke velocity, flight velocity, nondimensional flight velocity, advance ratio, acceleration, angle of attack and stroke plane. The wingbeat frequencies are higher in the smaller species and in those with relatively large wing loading. As a rule, Zygoptera have a wingbeat frequency only half that of Anisoptera. The stroke amplitude is almost always much larger in Zygoptera than in Anisoptera, which have a greater range of variation in this respect. Stroke velocity is higher in Anisoptera than in Zygoptera; it is also higher in the more elaborate flight manoeuvres than in others. The calculated stroke velocities resemble those actually measured. Anisoptera fly more rapidly than Zygoptera. With respect to the nondimensional flight velocities, it is notable that although the values for Anisoptera are higher than those for Zygoptera, they are exceeded by the Calopterygidae; the latter can fold their wings back during rapid forward flight and shoot away, as in the ‘ballistic’ flight of small songbirds. However, the advance ratio is higher in Anisoptera than in Calopterygidae. Anisoptera also perform better than Zygoptera with respect to acceleration. Three categories of phase relationships between the beats of the fore- and hindwings are established: counterstroking, phase-shifted stroking and parallel stroking. Counterstroking produces uniform flight, whereas the flight produced by phase-shifted and, in particular, parallel stroking is irregular. The angles of attack of the wings are shown to be associated with particular flight manoeuvres, as are the stroke planes. Flight manoeuvres are discussed without drawing detailed aerodynamic conclusions. The flight of Anisoptera is compared with that of Zygoptera.

Assessment of earthworm burrowing efficiency in compacted soil with a combination of morphological and soil physical measurements

Abstract: Column experiments were carried out to quantify the effect of earthworms on compacted soil. The earthworms (Lumbricus terrestris) were able to burrow into soil which was artificially compacted to a pore volume as low as 40%; they may also penetrate an artificial “plough pan” deep in the soil. The effect of the burrowing activity of Lumbricus terrestris was quantified by measuring hydraulic conductivities and infiltration rates through the whole soil column (19 cm wide, 40 cm long). Morphological parameters, mainly the vertically projected burrow depth, were correlated with the saturated hydraulic conductivity. The amount of casts deposited by Lumbricus terrestris on the soil surface increased with the degree of soil compaction. The bulk density of casts was always less than that of the original soil.

Antimicrobial Effects of Biosurfactants

Abstract: Some biosurfactants possess antimicrobial properties. Gram-positive bacteria were more sensitive against the detergents than gram-negative bacteria, which were weakly or not inhibited. Especially sophoro- and rhamnolipids prevented the growth of Gram-positive bacteria; the conidia germination of the fungus Glomerella cingulata was influenced by sophoro-, rhamno-, trehalose- and cellobiose-lipids, resp. In the case of the Gram- negative bacterium Pseudomonas aeruginosa not inhibited by those surfactants, our studies indicated that the glycolipids are hydrolyzed by enzymatic reactions. Antimikrobielle Wirkung von Biotensiden Einige Biotenside besitzen antimikrobielle Eigenschaften. Gram-positive Bakterien waren starker sensitiv gegenuber diesen Detergentien als Gram-negative Bakterien, die nur schwach oder gar nicht inhibiert wurden. Insbesondere verhinderten Sophoro- und Rhamnolipide das Wachstum von Gram-positiven Bakterien; die Konidien-Keimung des Pilzes Glomerella cingulata wurde beeinflust durch Sophoro-, Rhamno-, Trehalose- und Cellobiose-Lipide. Am Beispiel des Gram-negativen Bakteriums Pseudomonas aeruginosa, welches durch diese Tenside nicht inhibiert worden war, konnte gezeigt werden, das uber enzymatische Reaktionen die Glykolipide hydrolysiert werden.

Triplet energy transfer sensitized fluorescence in 3,9-dibromoperylene

Abstract: Sensitized fluorescence of 3,9-dibromoperylene (DBP) was obtained from triplet energy transfer with ketones as donors. The maximum efficiency of this process (TETSF) in acetonitrile measured with time-correlated single-photon counting was QTS = 0.33 ± 0.08. Because of the high quantum yield of fluorescence (QF = 0.75 ± 0.10) for analytical applications of TETSF DBP is superior to the acceptor molecules investigated earlier. Particular attention was paid to a detailed elucidation of the energy transfer processes involved in TETSF. The analysis of the excess energy dependence provided evidence for the participation of a higher excited triplet state (Tn) of DBP.

Post‐harvest pod storage: A method for pulp preconditioning to impair strong nib acidification during cocoa fermentation in Malaysia

Abstract: In Malaysia, pulp preconditioning by post-harvest storage of cocoa pods leads to the reduction of nib acidification during subsequent fermentation, reduction of the acid note and an increase in cocoa flavour in the resulting raw cocoa Data from several shallow-box fermentations, with material from unstored and stored pods, are compared and interpreted, obtained in the years 1984 to 1987 in a cooperational investigation of the Malaysian Agricultural Research and Development Institute (MARDI), Malaysia, and the Botanical Institute, Technical University of Braunschweig (TUBS), FRG Prior to and during fermentation, pulp volume and pulp sugars; pH value, acetic acid and lactic acid content in the pulp and nibs; and oxygen concentration and temperature in the mass were determined Some flavour assessments from selected samples are given The great reduction in pulp volume per seed rather than the decrease of pulp sugars per seed during pod storage was found to be of the most importance Pulp-volume reduction enhances mass aeration and increases the ratio of respiration to ethanol fermentation and its subsequent oxidation to acetic acid As a consequence, the acidification of the seeds during the formative stages of flavour precursors (after the death of the seeds) is strongly reduced With effectively dry stored pods (pulp volume per gram of seed ≤0·6 ml) the anaerobic phase during the initial stages of fermentation which is common with unstored pods is suppressed Under these conditions the nib pH value does not fall below 5·0 and no drastic acid (and flavour) degradation at the end of fermentation is necessary to reduce the acidity in the seeds

Aerobic stepwise hydrocarbon degradation and formation of biosurfactants by an original soil population in a stirred reactor

Abstract: Using a model system containing 10% soil and a 1.35% hydrocarbon mixture of tetradecane, pentadecane, hexadecene, pristane (2,6,10,14-tetramethylpentadecane), trimethylcyclohexane, phenyldecane and naphthalene suspended in a mineral salts medium, the hydrocarbon degradation rate by a soil population was 25.7 g model oil per kg soil dry weight per day under non-limited conditions within two degradation phases. During the first degradation phase only the most water-soluble naphthalene was degraded, while the other components could only be metabolized when the interfacial tension was lowered by the production of surfactants at the beginning of the second degradation phase. This second degradation phase ended when 89% of the hydrocarbons were metabolized.

Some of the swi genes of Schizosaccharomyces pombe also have a function in the repair of radiation damage.

Abstract: In Schizosaccharomyces pombe the frequency of mating-type (MT) switching is reduced by mutations in the swi genes. The ten hitherto known swi genes can be subdivided into three classes: Ia, Ib and II. Strains having swi5 (class Ib), swi9 (class II) and swi10 (class II) mutations do not only show reduced MT switching, but also exhibit an increased sensitivity to UV- and gamma-rays. For that reason, 19 previously described rad genes were tested for their effect on MT switching. We found that swi9, "rad10", "rad16" and "rad20" are allelic with each other indicating that the former allocation of these rad mutations to three different genes must have been erroneous. Among the remaining 16 rad genes examined, rad22 seems to be a new class II swi gene. The double mutants swi5 swi9 and swi5 swi10, but not swi9 swi10, are much more sensitive to radiation than the respective single mutants. Thus a cumulative increase in sensitivity occurs only if the mutants belong to different classes; previously the same correlation was found with regard to cumulative effects in MT switching.

Chemical and physical changes in the pulp during ripening and post-harvest storage of cocoa pods

Abstract: Changes in the pulp during ripening and post-harvest storage of cocoa pods were determined during numerous harvests in Malaysia (1984 to 1987) and Ghana (1985 to 1986), in order to gain a basis for understanding the influence of ripening and storage on acid formation during subsequent fermentation. Changes in the pulp during ripening of fully grown pods were the same but less pronounced than those during dry storage of harvested pods: the percentage of water in the pulp was not changed significantly, but the amount of water and of dry matter per seed was strongly reduced (by 40–50%) due to water evaporation and respiration of sugars. Sucrose was inverted completely. The result of these changes was an equally strong reduction of the pulp volume per seed and increase of the pulp surface to pulp volume ratio. The reduction of acid formation during fermentation with beans from stored pods is ascribed predominantly to these changes rather than to the reduction in the amount of sugars, and is explained not only by the facilitated mass aeration but, above all, by the significant increase in respiration at the pulp surface over ethanol fermentation in the pulp when the pulp volume is reduced prior to fermentation. Ghanaian pods at similar stages of ripeness revealed more advanced stages of the pulp compared with Malaysian pods and consequently less significant change during storage. Water evaporation and respiration during pod storage were significantly higher in the pulp than in the husk.

Laser performance of perylenebis (dicarboximide) dyes with long secondary alkyl chains

Abstract: The laser performance and related photophysical properties of two very soluble perylene dyes with long chain secondary alkyl groups were investigated in cyclohexane solution. With a dye laser as pump source a tuning range of 555–580 nm was obtained at an optimum concentration of 3×10−4 M. The quantum efficiencies (η=0.29 and 0.21) were better than 1/2 that of rhodamine 6G. No photodegradation was observed over an excitation period of several hours.

Orientation, motion, and other properties of flux transfer event structures on September 4, 1984

Abstract: Three flux transfer events (FTEs), observed by the AMPTE/IRM spacecraft in the southern hemisphere magnetosheath are studied by use of variance analysis of measured magnetic fields, B, and convection electric fields, Ec = −v × B, with the objective of determining the orientation and motion of the flux tube or magnetopause bulge causing the FTE signature These FTEs preceded a series of magnetopause crossings during which the high plasma flow speeds, characteristic of quasi-steady reconnection, were present The main results are as follows: (1) For each FTE, a moving so-called deHoffmann-Teller (HT) frame of reference can be found, in which the local plasma velocities are nearly antiparallel to the local B vectors and have magnitudes in the range 70%–90% of the local nominal Alfven speed (assuming all measured ions to be protons) The velocities of motion, vHT, of the HT frames for all three events, and for two subsequent magnetopause crossings, are sufficiently similar so that a single HT frame orders the data in this manner for one full hour (2) In the first FTE, the spacecraft appears to have sampled fields and flow around a moving tube or elongated magnetopause bulge The tube orientation and motion (given by the component of vHT perpendicular to the tube axis) could be determined along with impact parameter (l ≃ 14a), tube diameter (2a ≃ 8000 km), and, with reasonable assumptions, tube length (L>20,000 km) The tube was found to move southward past the spacecraft, consistent with the observed negative-positive signature in the component of B along the magnetopause normal The ambient magnetosheath plasma moved in the opposite direction (3) For the second and third FTEs, which were close encounters (l/a<1), the tube orientation and therefore its motion could not be reliably determined (4) On the whole, the observations are consistent with ongoing magnetopause reconnection with a time-modulated reconnection rate that leads to repeated ejection of bulges in the magnetopause from the reconnection site

Abgabe von flüchtigen organischen Säuren aus Holzspänen und Holzspanplatten

Abstract: Die Abgabe von fluchtigen Holzsauren aus Buchen-, Kiefern-, Fichten-und Eichenspanen wirde bei 100% rel. Luftfeuchte und bei Temperaturen von 40°C und 103°C mit Hilfe der WKI-Flaschenmethode und der Ionenchromatographie quantitativ bestimmt. Es wurde keine direkte Beziechung zwischen der, Abgabe von fluchtigen Sauren und dem Acetylgruppengehalt der untersuchten Holzer festgestellt. Holzspanplatten geben im allgemeinen eine hohere Menge an fluchtigen Sauren ab als die Spane, aus denen sie, hergestellt sind. Hierbei spielt auch der Bindemitteltyp eine besondere Rolle. Bei PF-Spanplatten ist die Abgabe an Essigsaure besonders gros im Vergleich zu UF-Spanplatten. Im letzteren Plattentyp ist der Formaldehydgehalt des eingesetzten Harzes von Bedeutung. Je groser das Molverhaltnis U: Fist, desto geringer ist die Saureabgabe aus den Spanplatten. Den Ergebnissen ist weiterhin zu entnehmen, das auch Rindenplatten Ameisen- und Essigsaure abgeben.

Penta- and disaccharide lipid formation by Nocardia corynebacteroides grown on n-alkanes

Abstract: Nocardia corynebacteroides SM1 synthesized di- and pentasaccharide lipids when grown on n-alkanes, especially under nitrogen limitation. Optimum conditions for their formation were pH 6.4–6.8, NaNO3 as nitrogen source and yeast extract supplementation of the nutrient. A study of the time course of whole glycolipid production was carried out in a 20-l bioreactor. After extraction of the culture broth with organic solvents three main components could be isolated. Both 1H and 13C nuclear magnetic resonance spectroscopic and elemental analysis studies led to the identification of one novel pentasaccharide lipid and two trehalose corynomycolates. The oligosaccharide lipid showed significant surface and interfacial active properties.

Algebraic Implementation of Objects over Objects

Abstract: This paper gives semantic foundations of (correct) implementation as a relationship between an "abstract" object and a community of "base" objects. In our aproach, an object is an "observed process". Objects and object morphisms constitute a category OB in which colimits reflect object aggregation and interaction between objects. Our concept of implementation allows for composition, i.e. by composing any number of (correct) implementation steps, a (correct) entire implementation is obtained. We study two specific kinds of implementation, extension and encapsulation, in more detail and investigate their close relationship to object morphisms. Our main technical result is a normal form theorem saying that any regular implementation, i.e. one composed of any number of extensions and encapsulations, in any order, can be done in just two steps: first an extension, and then an encapsulation.

From FeNi-Invar to FeNiMn reentrant spin-glasses

Abstract: Thirty years of Mossbauer spectroscopy correspond roughly to twenty-five years of FeNi-invar research using this method. The first systematic study of hyperfine fields in FeNi alloys, in both bcc and fcc phases, appeared in 1963, the first spectra were published probably in 1964. A very important fact is that fcc iron is an antiferromagnet; however, this iron phase is unstable at low temperature. In 1963, the possibility of performing low-temperature Mossbauer spectroscopy experiments on fcc iron precipitates in copper was shown. We shall demonstrate that the low temperature57Fe Mossbauer spectra reveal a spatially inhomogeneous magnetic structure in FeNi-invar alloys. This structure corresponds to magnetic invar anomalies. From the viewpoint of basic research in magnetism, it was opportune to enhance these anomalies. One possible way to do this was the alloying of manganese into the invar matrix. In this contribution, we limited our examples to the study of the classical Fe0.65Ni0.35 and the new (Fe0.65Ni0.35)1−x .Mn x alloys, and refer to the literature with respect to other transition metal systems with similar properties. We will show the goal of Mossbauer spectrometry investigating the spin structure in disordered alloy systems via the vector nature of the hyperfine fields. Additionally, the combination of Mossbauer spectrometry with global techniques, i.e. DC magnetization and AC susceptibility allowed us to study the changes in magnetic properties of our disordered 3d transition metal alloys from a nearly collinear ferromagnet (pure FeNi-invar) over the reentrant spin-glasses and “pure” concentrated spinglasses towards the antiferromagnetic behaviour by varying the manganese concentration in small steps.

A Strongly Polynomial Algorithm for Minimum Cost Submodular Flow Problems

Abstract: The only known strongly polynomial algorithm for solving minimum cost submodular flow problems is due to Frank and Tardos Frank, A., E. Tardos. 1985. An application of the simultaneous approximation in combinatorial optimization. Report No. 85375, Institut fur Okonometrie und Operations Research, Bonn, May. and is based on the simultaneous approximation algorithm of Lenstra, Lenstra, and Lovasz Lenstra, A. K., H. W. Lenstra, L. Lovasz. 1982. Factoring polynomials with rational coefficients. Math. Ann.261 515--534.. We propose a purely combinatorial strongly polynomial algorithm. It consists in solving a sequence of at most m + nn-1 minimum cost submodular flow problems with cost coefficients bounded by n2, where n is the number of the vertices and m is the number of the arcs in the underlying graph. The current cost coefficients are calculated by means of tree projection and scaling.

Poly(vinylsaccharide)s, 5. Synthesis and characterization of poly(vinylsaccharide)s of the amide type with disaccharides in the side chain

Abstract: The synthesis of well-defined monovinylsaccharide monomers containing disaccharide units is described. Four different monomers, N-disaccharide-substituted acryl- and methacrylamides, were prepared and polymerized to the corresponding polymers by free-radical polymerization in aqueous solution using different initiator systems. The influence of the structural differences of the disaccharide units on the solution properties was studied by viscosity and light scattering measurements. A comparison with known poly(vinylsaccharide)s with monosaccharides in the side chain is made.

A Procedure for Facilitating an Expert’s Judgements on a Set of Rules

Abstract: A knowledge structure that is known to be a formal basis for a system assessing students’ knowledge is constructed from an expert’s judgements. Such judgements refer to a body of questions from a specified field, and represent the information concerning which of these questions may be asked, and which can be considered redundant, depending on the answers given by a student during the assessment procedure. The expert’s judgements therefore select rules of the form: “if a student has answered all questions of this subset of questions incorrectly, then do not ask this specific question.”

Investigations on the vorticity sheets of a close-coupled delta-canard configuration

Abstract: Comprehensive aerodynamic investigations have been carried out on a close-coupled, A = 231 delta-canard configuration at low speed Results of three-component, surface-pressure, and flowfield measurements, as well as oil-flow patterns, are presented for the canard-off and canard-on configurations The main interference effects take place above the wing; the formation of the wing vortices is delayed considerably to positions downstream of the apex The canard vortices pass the wing leading edge relatively high, and they are moved downward and inward above the wing During this process, a fusion between the canard's vorticity sheet and the suction-side boundary layer of the wing takes place in the inner portion of the wing The canard vortex system is maintained up to stations downstream of the wing trailing edge

Theaflavins in black tea Comparison of the flavognost and HPLC analysis — preliminary in results

Abstract: The flavognost method and an isocratic reversed-phase HPLC method were compared in determining the theaflavins of black tea. A diode-array-detector was used. The flavognost method is a rapid procedure producing good reproducible results. Using the HPLC method, which is much more time consuming due to the necessity of a pre-separation by gel chromatography, one can determine four different theaflavins (theaflavin, theaflavin-3-gallate, theaflavin 3′-gallate and theaflavin 3,3′-digallate) and their relative amounts. The difference between the results from these two methods normally increases with increasing theaflavin content. In most cases, the values of the flavognost method were considerably higher. Relative amounts of theaflavins are different in teas from different origins, especially those of theaflavin and theaflavin 3,3′-digallate.

Studies on Benzophenanthridine Alkaloid Production in Elicited Cell Cultures of Papaver somniferum L.

Abstract: Benzophenanthridine alkaloids occur widely in members of the Papaveraceae (poppy family) and have been detected in cell cultures of several species (Furuya et al. 1972, Ikuta et al. 1979, Berlin et al. 1983, Krane et al. 1984). Aspects of production in elicited cultures of Eschscholtzia californica (Schumacher et al. 1987) and Papaver bracteatum (Cline and Coscia 1988) have recently been described. In this regard, our laboratory has demonstrated that a cell line (PBI# 2009) of Papaver somniferum L. initiated approximately 10 years ago (Tarn et al. 1980) synthesizes and accumulates sanguinarine, a quaternary benzophenanthridine alkaloid, when treated with any of a number of elicitor preparations (Eilert et al. 1985). A portion of the sanguinarine is released into the culture medium. This cell line normally accumulates trace quantities, at best, of benzophenanthridines in unelicited suspension culture.

Enzymatic resolution of rac-1,1-dimethyl-1-sila-cyclohexan-2-ol by ester hydrolysis or transesterification using a crude lipase preparation of Candida cylindracea

Abstract: rac-2-Acetoxy-1,1-dimethyl-1-sila-cyclohexane (rac-2) was synthesized by esterification of rac-1,1-dimethyl-1-sila-cyclohexan-2-ol (rac-1) with acetic anhydride. Enantioselective hydrolysis of rac-2 in aqueous solution, catalysed by a crude lipase preparation of Candida cylindracea (EC 3.1.1.3), led to the formation of (S)-1 (95% ee). Enantioselective transesterification of rac-1 with triacetin in isooctane, catalysed by the same enzyme preparation, yielded (S)-2 (95% ee), which was separated by chromatography from non-reacted (R)-1 (96% ee). Recrystallization led to an improvement of the enantiomeric purity of (R)-1 and (S)-1 up to >98% ee. Thus the enantiomers of rac-1 were prepared (100 mg scale) with high enantiomeric purities by the use of two different types of enzyme-catalysed reaction.

Resolution of D,L-menthol by interesterification with triacetin using the free and immobilized lipase of Candida cylindracea*

Abstract: Interesterification in isooctane with triacetin as an acyl donor was found to be a new and effective method of racemic resolution of d,l-menthol, when using the free and immobilized lipase of Candida cylindracea. No water was produced by this highly stereoselective type of reaction in contrast to ester synthesis with acetic acid as an acyl donor. Even with diacetin no possible back reaction occurred and the enzyme was easily separated from the reaction solution as opposed to ester hydrolysis in aqueous systems. Inhibition of interesterification was caused by increasing concentrations of the acyl donor triacetin by more than 10 mmol·l-1 on the one hand, and especially by diacetin on the other hand. The reaction product menthyl acetate had no influence. By adding water the interesterification activity of the lipase was reduced significantly. An alteration of the acyl donor triacetin to longerchained triglycerides caused changes in higher specific activities but poor enantioselectivities of the products, as in the case of ester synthesis starting from longer-chained organic acids.