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排序方式: 共有74条查询结果,搜索用时 15 毫秒
1.
Yeast viability during fermentation and sur lie ageing of a defined medium and subsequent growth of Oenococcus oeni 总被引:3,自引:0,他引:3
ROBERT J. PATYNOWSKI VLADIMIR JIRANEK REW J. MARKIDES 《Australian Journal of Grape and Wine Research》2002,8(1):62-69
Interactions between the yeast strain used for primary oenological fermentation and the bacterium used to conduct subsequent malolactic fermentation were studied under model winemaking conditions. A commercial Saccharomyces cerevisiae wine yeast (strains, EC 1118, AWRI 835 and CY-3079) was grown in a defined medium whose composition approximated grape juice. Fermentations by all strains reached dryness, and retained a cell viability of greater than 90% upon completion of fermentation. Highest total viable cell number and percentage of viable cells were recorded for EC 1118. A sur lie ageing of the fermented medium over a 12 week period revealed a bi-phasic decay of culture viability for all strains. Thus 99% of cells had died within 2 weeks post-fermentation. Viabilities were then stable for the subsequent 4–6 week period before a second decline phase ensued and ended in either a minimal ( ca 100 CFU/mL, EC 1118) or no viable cells being detected at 12 weeks of ageing. The growth response of an Oenococcus oeni inoculum to yeast culture supernatants, previously aged for up to 12 weeks in the presence or absence of yeast lees, was evaluated in a bio-assay. In this way, yeast strains could be designated as being either inhibitory, neutral or stimulatory to the growth of O. oeni (strain Lc5p). Inhibition by supernatants of strain EC 1118 was evident, but found to be reduced by ageing the supernatant (with or without lees). Conversely, longer ageing on yeast lees increased the magnitude of the stimulatory response in O. oeni (strain Lc5p) to the supernatant from the wine yeast (strain CY-3079). 相似文献
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The grain-boundary diffusion product, D'δ , of 51 Cr in MgO and Cr-doped MgO as a function of grain-boundary orientation and point-defect concentration was determined at T =1200° to 1450°C. A large degree of anisotropy was found in the grain-boundary diffusion behavior in MgO. The ratio of D'δ|| parallel to D'δ‖ perpendicular to the growth direction, D'|| /D'‖ , is 102 for a 5° (100) tilt boundary, decreased to ∼2 in boundaries with tilt angles > 10°. The decrease in D'|| /D'‖ is due to a large increase in D'‖ with increasing tilt angle. The results indicate that grain-boundary diffusion in MgO is connected to the orientation of dislocations and the mechanism is one of dislocation pipe diffusion. The grain-boundary diffusion product D'δ increases with increasing Cr concentration in MgO and is ∼4 times larger for MgO containing 0.56 at. % Cr than for the undoped MgO. For all bicrystals studied, the activation energies are within 180 ± 20 kJ/mol which is 60% of the activation energy for 51 Cr diffusion in undoped MgO. 相似文献
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The phase relations in the systems MgO-Y2 O3 -ZrO2 and CaO-MgO-ZrO2 were established at 1220° and 1420°C. The system MgO-Y2 O3 -ZrO2 possesses a much-larger cubic ZrO2 solid solution phase field than the system CaO-MgO-ZrO2 at both temperatures. The ordered δ phase (Zr3 Y4 O12 ) was found to be stable in the system ZrO2 -Y2 O3 at 1220°C. Two ordered phases φ1 (CaZr4 O9 ) and φ2 (Ca6 Zr19 O44 ) were stable at 1220°C in the system ZrO2 -CaO. At 1420°C no ordered phase appears in either system, in agreement with the previously determined temperature limits of the stability for the δ, φ1 , and φ2 phases. The existence of the compound Mg3 Yz O6 could not be confirmed. 相似文献
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Thermal Drying of Sewage Sludge 总被引:1,自引:0,他引:1
Over the next decade the UK will experience significant, imposed changes in the quantity of sewage sludge produced and in the means available for its disposal. Existing practices are being reappraised and new technologies are being explored to cope with a predicted 40% increase in the quantity for disposal. Thermal drying of sludge undoubtedly has a role to play in coping with this demand.
The two principal process types, i.e. direct and indirect heat application, are appraised in depth and a comparison is drawn. A case study is identified to examine the energy demands of the process, including the potential for heat recovery and for resource reuse. The environmental impact of a typical process is also examined. 相似文献
The two principal process types, i.e. direct and indirect heat application, are appraised in depth and a comparison is drawn. A case study is identified to examine the energy demands of the process, including the potential for heat recovery and for resource reuse. The environmental impact of a typical process is also examined. 相似文献
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VLADIMIR D. KRSTIC PATRICK S. NICHOLSON GARY R. PURDY 《Journal of the American Ceramic Society》1981,64(8):451-455
Precipitation was studied for LiF single crystals containing up to 4 wt% MgF2 . Replica electron microscopy observations, combined with hardness and lattice parameter measurements, showed that, irrespective of the level of MgF2 , precipitation consistently occurs during quenching. Rapidly cooled crystals with lower MgF2 concentrations (<1 wt%) develop large cruciform particles of a metastable phase with approximate composition MgF2 -6LiF. Lower cooling rates or higher MgF2 contents caused transformation of these metastable particles to rod-shaped stable MgF2 phase. This occurs via nucleation on the metastable crosses. The large misfit between the LiF matrix and the MgF2 phase causes development of an incoherent interface and an associated disturbance of a propagating crack was observed near each MgF2 particle. 相似文献