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排序方式: 共有175条查询结果,搜索用时 31 毫秒
1.
RJ Linnola RP Happonen OH Andersson E Vedel AU Yli-Urpo U Krause L Laatikainen 《Canadian Metallurgical Quarterly》1996,63(4):471-478
The current problem with keratoprosthesis is the ingrowth of corneal or conjunctival epithelium into the anterior chamber. This may lead to infections and extrusion of the prosthesis as well as to the development of retroprosthetic membrane and secondary glaucoma. Glass-ceramic coated and uncoated titanium has been tested as material for the keratoprosthesis to prevent epithelial ingrowth. Twenty-two Supra-Descemet's membrane keratoprostheses were inserted in the eyes of 22 rabbits for 1, 2, 4, 8, or 12 months. The prosthesis had an optic part made of polymethylmetacrylate (PMMA). The support for the optic part and the flange of the prosthesis were made of titanium. Eleven of the prostheses were coated with glass-ceramic. The histological sections of the enucleated eyes were prepared through the central part of the cornea and the prosthesis using a cutting-grinding method. The histological analysis was made on both halves of the implants separately giving two analysis areas in each eye. All 11 titanium prostheses were retained for the time period planned. Two glass-ceramic coated prostheses were lost at 2 and 4 weeks, respectively. This was caused by difficulties at surgery due to a thick coating. These eyes were excluded from the histological analysis. No significant ingrowth of epithelium was seen in 15/18 (83%) and in 16/22 (73%) of the analysed areas of the glass-ceramic coated and titanium prostheses, respectively. Titanium appears to be a suitable material for the keratoprosthesis. The ingrowth of the epithelium may be hindered further by coating the titanium with bioactive glass-ceramic. 相似文献
2.
Isolation and preliminary characterization of Pichia pinus mutants insensitive to glucose repression
A new method for the isolation of glucose repression-insensitive mutants in the methylotrophic yeast Pichia pinus was developed. The method is based on screening of small suspension samples derived from 2-deoxyglucose-resistant colonies for alcohol oxidase activity. Alcohol oxidase activity was evaluated by determination of formaldehyde excreted by cells. Mutants with glucose non-repressible alcohol oxidase and catalase synthesis were obtained. All mutants grew poorly on D -xylose compared to the wild type, whereas growth on L -arabinose was similar to the wild type. Changes in the glucose transport system were suggested to be responsible for altered growth characteristics and defective glucose repression. 相似文献
3.
Tiina Komulainen Mauri Sourander Sirkka-Liisa Jms-Jounela 《Computers & Chemical Engineering》2004,28(12):2611-2619
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Tiina Reponen Anne Hyv rinen Juhani Ruuskanen Taisto Raunemaa Aino Nevalainen 《Journal of aerosol science》1994,25(8):1595-1603
Concentrations and types of airborne fungal spores and their aerodynamic sizes were studied in nine buildings with mould problems and in matched reference buildings in order to characterize the exposure in buildings with mould problems. Samples were taken with Andersen six-stage impactors in the autumn and winter. In winter, total concentrations of fungal spores in buildings with mould problems were twice those in reference buildings, even though all concentrations were quite small. In the autumn, the differences were less obvious due to the masking effect of outdoor air fungi. Also, the compositions of fungal genera differed in buildings with mould problems from that in reference buildings. The difference was most significant in the size range 2.1-4.7 μm. The size distribution of fungal spores in dwellings with mould problems skewed towards larger particles than in reference dwellings. The observed differences in size distribution indicate differences in airborne behaviour of fungal spores and, consequently, in respiratory exposure. 相似文献
6.
Tiina Komulainen Francis J. Doyle III Ari Rantala Sirkka-Liisa Jämsä-Jounela 《Journal of Process Control》2009,19(1):2-15
A two level control strategy that stabilizes and optimizes the production of an industrial copper solvent extraction process is presented. The stabilizing layer consists of a multi-input–multi-output controller or two single-input–single-output controllers with additional four feedforward compensators that regulate the flow rates in the copper solvent extraction process. The optimization layer consists of an optimizer that maximizes the production of the copper solvent extraction process and gives setpoints to the controllers at the stabilizing level. The mechanistic plant models, verified with industrial data, are linearized by identifying first and higher order transfer function models from simulated PRBS data. On the basis of the linear models, the interactions of the controlled variables, and the pairing of the controlled and manipulated variables are studied and the optimizer and the controllers designed. The control strategy employing two PI-control loops or a model predictive controller and additionally four feedforward control loops is successfully tested against simulated disturbances and setpoint changes. The control strategy is also compared to the data collected from the industrial plant under manual control. With this two level control strategy the production of the copper solvent extraction process is increased by 3–5% and the process variation is decreased by 70–90% compared to the manual operation of the case industrial plant. The results gained in simulation environment are successful and encouraging for further testing in an industrial plant. 相似文献
7.
The aim of this study was to examine the response of the autonomic nervous system in younger (mean age 31 yrs, n=14) and older (mean age 54 yrs, n=14) healthy female teachers during work periods of perceived high and low stress. In the younger participants, heart rate, cortisol excretion rate and psychosomatic symptoms were significantly higher during the high work stress period. The older participants experienced no decrease in their heart rate and cortisol excretion during the low stress period and they exhibited no significant decrease in blood pressure after the work in the evening during both periods. It may be concluded that the recovery from the stress in the older teachers was insufficient particularly in view of their elevated diastolic blood pressure during the low work stress period. Ergonomic and individually tailored measures in terms of work time control, specific relaxation techniques, and a part-time retirement may improve the stress management of older teachers. 相似文献
8.
Salmivalli Christina; Ojanen Tiina; Haanp?? Jemina; Peets K?tlin 《Canadian Metallurgical Quarterly》2005,41(2):363
This study examined the links among 5th and 6th graders' (279 girls and 310 boys) self- and peer perceptions, social goals, and social behavior. Social goals mediated the effects of self- and peer perceptions on 3 types of behavior: proactive aggression, prosocial behavior, and withdrawal. In addition to their main effects (self-perception predicting variance in agentic goals, peer perception being related to communal goals), self- and peer perception interacted in influencing social goals; for instance, the effects of a positive view of oneself were different in the contexts of a positive versus a negative perception of peers. It is suggested that in order to predict children's social behavior more accurately, researchers should investigate children's dual perceptions of themselves and of their peers--that is, their peer-relational schemas--instead of assessing self-perception and peer perception in isolation from each other. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.