ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

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Evaluation of the biodegradability of copolyesters containing aromatic compounds by investigations of model oligomers (1996)

Witt, U. ; Müller, R.-J. ; Deckwer, W.-D.

Springer

Journal of polymers and the environment 4 (1996), S. 9-20

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ISSN: 1572-8900

Keywords: Copolyesters ; biodegradability ; aliphatic diol ; adipic acid ; terephthalic acid ; aromatic oligomers

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract Model oligo esters of terephthalic acid with 1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol have been investigated with regard to their biodegradability in different biological environments. Well-characterized oligomers with weight-average molar masses of from 600 to 2600 g/mol exhibit biodegradation in aqueous systems, soil, and compost at 60°C. SEC investigations showed a fast biological degradation of the oligomer fraction consisting of 1 or 2 repeating units, independent of the diol component used for polycondensation, while polyester oligomers with degrees of polymerization higher than 2 were stable against microbial attack at room temperature in a time frame of 2 months. At 60°C in a compost environment chemical hydrolysis also degrades chains longer than two repeating units, resulting in enhanced degradability of the oligomers. Metabolization of the monomers and the dimers as well by the microorganisms could be confirmed by comparing SEC measurements and carbon balances in a “Sturm test” experiment. Based on these results degradation characteristics of potential oligomer intermediates resulting from a primary chain scission from copolyesters consisting of aromatic and aliphatic dicarbonic acids can be predicted depending on their composition. These results will have an evident influence on the evaluation of the biodegradability of commercially interesting copolyesters and lead to new ways of tailor-made designing of new biodegradable materials as well.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02083878

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2

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Proton-Induced Deuteron Breakup at E lab P = 65 MeV in Quasi-Free Scattering Configurations (1996)

Allet, M. ; Bodek, K. ; Hajdas, W. ; [et al.]

Springer

Few body systems 20 (1996), S. 27-40

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ISSN: 1432-5411

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract. The proton-deuteron breakup cross sections and analyzing powers A y for three kinematically complete configurations in a quasi-free-scattering geometry have been measured at E lab P = 65 MeV. The data are compared with predictions of rigorous Faddeev calculations using the Argonne AV14, Bonn-B, Nijmegen-78, and Paris potentials. A satisfactory agreement between theory and experimental data, both for cross sections and analyzing powers, has been found.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s006010050029

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3

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Growth rate-dependent expression of phenol-assimilation pathways in Alcaligenes eutrophus JMP 134–the influence of formate as an auxiliary energy source on phenol conversion characteristics (1996)

Müller, R. H. ; Babel, W.

Springer

Applied microbiology and biotechnology 46 (1996), S. 156-162

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ISSN: 1432-0614

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Abstract Alcaligenes eutrophus JMP 134 was continuously (carbon-source-limited) grown on phenol to determine the maximum growth rates (μmax) as a function of the phenol assimilation pathways expressed. During growth on phenol as the sole source of carbon and energy, an almost exclusive expression of the ortho cleavage pathway (catechol 1,2-dioxygenase) was observed at initially low growth rates. This allowed a μmax of 0.28 h-1. The induction of the meta cleavage pathway (catechol 2,3-dioxygenase), which appeared at around 0.25 h-1, resulted in a further increase in the growth rate to 0.40 h-1 after the enzyme activities of this pathway had been correspondingly expressed. Hence, two maximum growth rates, one for the ortho and one for the meta cleavage pathway, exist for the growth of A. eutrophus JMP 134 on phenol. Growth on phenol was stimulated by formate, which served as an auxiliary energy source in this strain. The simultaneous utilization of phenol and formate at a molar ratio of 1:5.2 resulted in an increase of the yield coefficient from about 0.75 g dry mass/g phenol to 1.25 g/g. Furthermore, formate exerted a pronounced effect on the growth rate. At a molar ratio of phenol to formate of 1:4.2, the growth rate was increased to 0.42 h-1, despite the exclusive induction of the ortho cleavage pathway. The meta cleavage pathway was expressed during growth on this substrate mixture at about 0.4 h-1. However, this did not enable a significant increase of the growth rate beyond 0.4 h-1. This is attributed to an exhaustion of the capacity for formate oxidation at this rate. The results are discussed with respect to energy production capabilities when phenol is assimilated as an energy-deficient heterotrophic substrate.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002530050798

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4

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Isolation and characterization of a thermophilic bacillus strain, that degrades phenol and cresols as sole carbon source at 70 °C (1996)

Mutzel, A. ; Reinscheid, U. M. ; Antranikian, G. ; [et al.]

Springer

Applied microbiology and biotechnology 46 (1996), S. 593-596

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ISSN: 1432-0614

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Abstract A phenol-degrading thermophilic bacterium, designated Bacillus sp. A2, was isolated from a water and mud sample from a hot spring in Iceland. The aerobic isolate grew optimally on phenol at 65 °C. At 70 °C, 85% of the optimal growth rate was still observed. No growth was observed at 40 °C and 75 °C. Bacillus sp. A2 is a gram-positive spore-forming rod. According to 16S rDNA analysis Bacillus sp. A2 is closely related to Bacillus stearothermophilus, Bacillus kaustophilus and Bacillus thermoleovorans. Bacillus sp. A2 degraded phenol completely in concentrations up to 5 mM. In addition, all three isomers of cresol were utilized as sole carbon and energy sources. The degradation of phenols proceeds via the meta-cleavage pathway and the enzymes involved in its degradation are constitutively expressed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002530050866

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5

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A Microtomographic System for the Nondestructive Evaluation of Bone Architecture (1996)

Rüegsegger, P. ; Koller, B. ; Müller, R.

Springer

Calcified tissue international 58 (1996), S. 24-29

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ISSN: 1432-0827

Keywords: Key words: Microtomography — Computed tomography — Bone structure — Bone strength — Osteoporosis.

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine , Physics

Notes: Abstract. Microtomography (micro-computed-tomography, μ-CT) is a method to image and quantify trabecular bone. It has the capability to address the role of trabecular architecture on the mechanical properties of bone and to study trabecular bone remodeling. The system described in this work is based on a compact fan-beam type tomograph that can work in spiral scanning or multislice mode. An X-ray tube with a microfocus is used as a source, a CCD-array as a detector. Samples with diameters from a few millimeters to a maximum of 14 mm can be measured, typically, bone biopsies with a diameter of 8 mm and a length of approximately 10 mm are measured. Spatial resolution is 28 μm. Usually the volume of interest contains 4 × 4 × 4 mm3 and is represented in 14 × 14 × 14 μm3 voxels. 3D stereological indices are extracted according to the standard definitions used in histomorphometry. Triangular surface representation is effected with an extended marching cube algorithm and forms a convenient basis for finite element analysis. Microtomographic measurements may be employed to ``calibrate'' lower-dose, lower-resolution images in vivo as well as to nondestructively assess unprocessed surgical bone biopsy specimens. These specimens remain intact for mechanical or histological testing.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002239900006

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6

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Visualization and measurement of helicopter rotor flow with swept back tip shapes at hover flight using the “flow visualization gun” time line technique (1996)

Müller, R. H. G. ; Mba, M. Nsi ; Aymard, E. ; [et al.]

Springer

Experiments in fluids 21 (1996), S. 161-169

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ISSN: 1432-1114

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract The Flow Visualization Gun (FVG), a novel time line visualization technique, has been used to investigate the flow field of a helicopter rotor with swept back tip shape in hover flight condition. After introducing the FVG-technique, the paper presents some visualization photographs of the rotor blade tip vortices and the rotor downwash. Using orthogonal sets of flow photographs and digital image analysis, the 3-dimensional time line displacement within the flow and the tip vortex structure are determined. The data of 16 time line experiments are interpolated in space and time to obtain velocity data on an evenly spaced 3-dimensional grid. Vorticity contour plots of the flow field show the complex arrangement of the tip vortices of the blade itself and of the preceding blade and some additional vorticity in the direct wake which may form a secondary vortex. Understanding and control of this vorticity distribution is important for the design of new efficient tip shapes. While the FVG technique has been used so far for qualitative investigation of complex flow patterns at local velocities of up to 20 m/s, a good comparison to laser velocimetry data validates the technique as an interesting tool for both qualitative and quantitative investigation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00191687

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7

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Einfluß des ZrO2-Zusatzes auf mechanische Eigenschaften und den ungeschmierten Gleitverschleiß von TiB2-ZrO2-Mischkeramiken (1996)

Schneider, J. ; Zum Gahr, K.-H. ; Müller, R. ; [et al.]

Weinheim : Wiley-Blackwell

Materialwissenschaft und Werkstofftechnik 27 (1996), S. 359-366

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ISSN: 0933-5137

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Description / Table of Contents: Effect of ZrO2 addition on mechanical and tribological properties of TiB2-ZrO2-compositesTiB2-ZrO2-composites were produced by hot-pressing in argon. The mechanical and tribological properties of the composites were investigated in relation to the amount and the type of the ZrO2 added. Addition of ZrO2 reduced the sintering temperature of the TiB2-ZrO2-composites and led to growth inhibition of the TiB2 phase. ZrO2 also increased the bending strength and fracture toughness of the composites. Tribological tests were carried out using laboratory tribometers under unlubricated oscillating sliding contact against Al2O3-, Si3N4- and SiC-counterbodies. Abrasive wear of the ceramics against 80 mesh SiC grits was studied by using an abrasive wheel test. During sliding contact the composites showed high wear resistance but caused extensive wear of the counterbodies and high friction coefficients compaired to self-mated monolithic Al2O3- and ZrO2-ceramics. Volumetric wear loss of the TiB2-ZrO2-composites due to abasive SiC grits was by a factor up to 30 lower than that of a commercial monolithic Al2O3. Wear resistance of the composites increased with decreasing amount of ZrO2 and was higher for the composites with addition of partially stabilized tetragonal ZrO2 than for those with addition of monoclinic ZrO2.

Notes: TiB2-ZrO2-Mischkeramiken wurden durch Heißpressen hergestellt und mechanische sowie tribologische Eigenschaften in Abhängigkeit vom Volumenanteil und der Modifikation des zugegebenen ZrO2 bestimmt. Durch die Zugabe von ZrO2 konnte die zum Erreichen hoher Enddichten notwendige Preßtemperatur auf 1500°C gesenkt und das Kornwachstum des TiB2 verhindert werden. Die Mischkeramiken wiesen gegenüber reiner TiB2-Keramik, bei einer reduzierten Härte, höhere Festigkeiten und Bruchzähigkeiten auf. Die tribologischen Untersuchungen wurden unter ungeschmierter, reversierender Gleitbeanspruchung in Paarung mit Al2O3-, Si3N4- und SiC-Gegenkörpern sowie unter Furchungsbeanspruchung durch SiC-Abrasivpartikel durchgeführt. Im Gleitkontakt zeigten die Mischkeramiken einen hohen Verschleißwiderstand, führten jedoch zu einem starken Verschleiß der keramischen Gegenkörper und hohen Reibungszahlen verglichen mit selbstgepaarten, monolithischen Al2O3- und ZrO2-Keramiken. Unter Furchungsbeanspruchung durch SiC-Abrasivpartikel lag der Verschleißwiderstand der TiB2-ZrO2-Keramiken um einen Faktor biszu 30 höher als der monolithischer Al2O3-Keramik. Der Verschleißwiderstand der TiB2-ZrO2-Kermiken nahm mit abnehmendem ZrO2-Anteil zu und erreichte bei den mit teilstabilisiertem, tetragonalem ZrO2 höhere Werte als bei den mit unstabilisiertem, monoklinen ZrO2 hergestellten Mischkeramiken.

Additional Material: 10 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/mawe.19960270713

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8

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Degradation of chloro- and methyl-substituted benzoic acids by a genetically modified microorganism (1996)

Müller, R. ; Deckwer, W.-D. ; Hecht, V.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 51 (1996), S. 528-537

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ISSN: 0006-3592

Keywords: chlorobenzoic acid ; methylbenzoic acid ; genetically modified strain ; Pseudomonas sp. B13 FR1 SN45P ; batch cultivation ; chemostat ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Degradation of 3-chlorobenzoic acid (3CB), 4-chlorobenzoic acid (4CB), and 4-methylbenzoic acid (4MB) as single substrates (carbon sources) and as a substrate mixture were studied in batch and continuous culture using the genetically modified microorganism Pseudomonas sp. B13 FR1 SN45P. The strain was able to mineralize the single compounds as well as the substrate mixture completely. Conversion of the three compounds in the substrate mixture proceeded simultaneously. Maximum specific substrate conversion rates were calculated to be 0.9 g g-1 h-1 for 3 CB and 4CB and 1.1 g g-1 h-1 for 4MB. Mass balances indicated the transient accumulation of pathway intermediates during batch cultivations. Hence, the rate limiting step in the degradative pathway is not the initial microbial attack of the original substrate or its transport through the cell membrane. Degradation rates on 3CB were comparable to those of the parent strain Pseudomonas sp. B13. The stability of the degradation pathways of strain Pseudomonas sp. B13 FR1 SN45P could be demonstrated in a continuous cultivation over 3.5 months (734 generation times) on 3CB, 4MB, and 4CB, which were used as single carbon sources one after the other.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

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