Browning in processed yams: peroxidase or polyphenol oxidase?

Polyphenol oxidase and peroxidase were purified from white yam (Dioscorea rotundata) using DEAE‐cellulose ionexchange chromatography. Thermoinactivation curves for polyphenol oxidase showed monophasic kinetics, while those for peroxidase were biphasic. Urea partially stabilised peroxidase against irreversible thermoinactivation, but did not do so in the case of polyphenol oxidase. Only peroxidase was capable of regenerating activity after thermoinactivation. The results showed that thermoinactivation of peroxidase was mainly due to conformational changes, while that of polyphenol oxidase was probably due to covalent damage. Peroxidase reactivation might play an important role in the browning of processed yam. © 2002 Society of Chemical Industry     

Tree automata for code selection

We deal with the generation of code selectors in compiler backends. The fundamental concepts are systematically derived from the theory of regular tree grammars and finite tree automata. We use this general approach to construct algorithms that generalize and improve existing methods.Funded by the ESPRIT Project #5399 (COMPARE)Funded by DFG SFB #124 VLSI-Design and Parallelism     

Behavior of Bragg gratings, written in germanosilicate fibers,against γ-ray exposure at low dose rate

Bragg gratings have been written within four germanosilicate fibers either by a pulsed or by a continuous-wave exposure of each fiber to a coherent UV two-beam interference pattern. These gratings have been exposed under steady state conditions to γ-ray doses as high as 10 ⁴ Grays. The dose rates ranged between 10 Gy/h and 1.3×10² Gy/h. The transmission spectra of the fibers have been recorded during and after the ⁶⁰Co irradiation, near the grating Bragg wavelengths. Whereas the induced loss reached 600 dB/km near 1.3 μm, no significant change in the spectral characteristics of the gratings could be detected within the experimental accuracy, enabling their future use in a nuclear environment     

PHOTOINITIATED POLYMERIZATION OF ACRYLAMIDE AND METHACRYLAMIDE

A dilatometric technique was used to obtain kinetic data for UV-photoinitiated polymerization of acrylamide and methacrylamide. In this study, benzoinmethylether was the initiator. Two mixed-solvent systems, 30% acetic acid in water (for both monomers) and 40% methanol in water (for acrylamide only) were examined. In all three systems the rate of polymerization varies with the monomer concentration to the 1.4 to 1.5 power and to the initiator concentration to the 0.4 to 0.8 power. Energies of activation are very low, less than 1.5 kcal/mol. Molecular weights estimated from viscosity measurements support the idea that chain transfer to monomer is important in the case of methacrylamide.     

A model-based control system for a distillation column

A control concept which includes an adaptive multivariable control algorithm and an observer model has been put into practice in the operation of a distillation column which separates water from a solvent. The model yields predictions of solvent concentration in the waste water which forms the top product. Early detection of disturbances permits an adjustment of the process in time. This has resulted in an exceptionally smooth operation of the column, with a drastic reduction in solvent concentration fluctuations, observed with conventional control technology. Since the only measurements required are pressure, temperature and the rate of flow, this control system is largely free from disturbances. In addition to considerably reducing the burden on operating personnel, use of this control system has lowered the costs of waste water treatment, solvent losses, analysis expenditure and energy consumption.     

Steady state creep in two Ni-Al alloys

Creep of two Ni-AI alloys containing 4.8 and 7.0 wt pct Al was studied in the temperature range 873 to 1073 K and stress range 30 to 400 MPa. The former alloy represents the solid solution of aluminum in nickel, the latter a solid solution strengthened by NI3AI particles. As to its creep behavior the solid solution alloy belongs to the Class n of solid solu-tions,i.e. the creep controlling mechanism is the same as in pure nickel. From the analy-sis of an effective stress dependence of steady state creep rate it follows that the mo-tion of jogged screw dislocations can be considered as the most probable creep control-ling mechanism. The apparent activation energy of creep in the two phase alloy increases with tempera-ture. This effect is caused by changes in the volume fraction of second phase particles and by the onset of climb around particles at high temperatures. At lower temperatures particles are cut by dislocation pairs.     

Vergleichende Untersuchung der anatomischen und physikalischen Eigenschaften des Holzes vonPopulus Simonii undPopulus robusta

Zusammenfassung Vergleichend-anatomische Untersuchungen des Holzes vonPopulus Simonii undPopulus robusta ergaben, da? die besten Unterscheidungsmerkmale für diese beiden Pappelarten Unterschiede in den Markstrahlh?hen und im Reichtum an Strangparenchym sind. Auf Grund der vergleichend-physikalischen Untersuchung wird das Holz vonP. robusta als “ziemlich schwer”, das Holz vonP. Simonii als “mittelschwer” befunden. BeiP. Simonii besteht au?erdem eine Beziehung zwischen Rohwichte und Raumschwindung. Die Schwindung im Splint der Balsampappel ist wesentlich geringer als diejenige beiP. robusta.

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Comparative study on the anatomical and physical properties of wood ofPopulus Simonii andPopulus robusta

Summary Comparative anatomical studies on the wood of Populus Simonii and Populus robusta proved that their differences in ray height and richness in parenchyma are the most reliable characteristics for the distinction of these two poplar species. According to the results of comparative physical investigations the wood of P. robusta is designated as “rather heavy”, the wood of P. Simonii is found to be of “medium weight”. In the case of P. Simonii there is also a relationship between density and volume shrinkage. The shrinkage in the sapwood of balsam-poplar is considerably less than that of P. robusta.