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661.
Logical foundations of multilevel databases 总被引:2,自引:0,他引:2
In this paper, we propose a formal model for multilevel databases. This model aims at being a generic model, that is it can be interpreted for any kind of database (relational, object-oriented …). Our model has three layers. The first layer corresponds to a model for a non-protected database. The second layer corresponds to a model for a multilevel database. In this second layer, we propose a list of theorems that must be respected in order to build a secure multilevel database. We also propose a new solution to manage cover stories without using the ambiguous technique of polyinstantiation. The third layer corresponds to a model for a MultiView database, that is, a database that provides at each security level a consistent view of the multilevel database. Finally, as an illustration, we interpret our 3-layer model in the case of an object-oriented database. 相似文献
662.
Serteyn Laurent Lourme Olivier Iannello Lisa Baiwir Dominique Mazzucchelli Gabriel Ongena Marc Francis Frederic 《Journal of chemical ecology》2021,47(8-9):747-754
Journal of Chemical Ecology - Plant Growth-Promoting Rhizobacteria (PGPR) induce systemic resistance (SR) in plants, decreasing the development of phytopathogens. The FZB42 strain of Bacillus... 相似文献
663.
Assessing granular media filtration for the removal of chemical contaminants from wastewater 总被引:1,自引:0,他引:1
Ho L Grasset C Hoefel D Dixon MB Leusch FD Newcombe G Saint CP Brookes JD 《Water research》2011,45(11):3461-3472
Granular media filtration was evaluated for the removal of a suite of chemical contaminants that can be found in wastewater. Laboratory- and pilot-scale sand and granular activated carbon (GAC) filters were trialled for their ability to remove atrazine, estrone (E1), 17α-ethynylestradiol (EE2), N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMOR) and N-nitrosodiethylamine (NDEA). In general, sand filtration was ineffective in removing the contaminants from a tertiary treated wastewater, with the exception of E1 and EE2, where efficient removals were observed after approximately 150 d. Batch degradation experiments confirmed that the removal of E1 was through biological activity, with a pseudo-first-order degradation rate constant of 7.4 × 10−3 h−1. GAC filtration was initially able to effectively remove all contaminants; although removals decreased over time due to competition with other organics present in the water. The only exception was atrazine where removal remained consistently high throughout the experiment. Previously unreported differences were observed in the adsorption of the three nitrosamines, with the ease of removal following the trend, NDEA > NMOR > NDMA, consistent with their hydrophobic character. In most instances the removals from the pilot-scale filters were generally in agreement with the laboratory-scale filter, suggesting that there is potential in using laboratory-scale filters as monitoring tools to evaluate the performance of pilot- and possibly full-scale sand and GAC filters at wastewater treatment plants. 相似文献
664.
Matjaz Valant Taras Kolodiazhnyi Iztok Arčon Frederic Aguesse Anna‐Karin Axelsson Neil M. Alford 《Advanced functional materials》2012,22(10):2114-2122
An analysis of Mn substitution in SrTiO3 is performed in order to understand the origin of reported spin coupling in lightly Mn‐doped SrTiO3. The spin glass state magnetoelectrically coupled to the dipolar glass state has previously been reported for SrTiO3 substituted with only 2% of Mn on the B‐site. An analysis of the substitution mechanism for A‐ and B‐site doping shows a strong influence of processing conditions, such as processing temperature, oxygen partial pressure, and off‐stoichiometry. The required conditions for a site‐selective substitution are defined, which yield a single‐phase and almost defect‐free perovskite. Magnetic measurements show no magnetic anomalies resulting from spin coupling and only a simple paramagnetic behavior. Magnetic anomalies are observed only for the samples in which Mn is misplaced within the cation sublattice of the SrTiO3 perovskite. This occurs due to improper material processing, which causes initially unpredicted changes in the valence state of the Mn and results in the formation of structural defects and irregularities associated with segregation and nucleation of the magnetic species. Previously reported spin coupling in Mn‐doped SrTiO3 is not an intrinsic phenomenon and cannot be treated as a spin glass. 相似文献
665.
Alexander W. Jones Marie‐Laure Louillat‐Habermeyer Frederic W. Patureau 《Advanced Synthesis \u0026amp; Catalysis》2015,357(5):945-949
What does it take to force a rigid and strained dehydrogenative ring closure, for example, in phenylcarbazoles? Since the works of Buchwald and Fagnou, palladium‐catalysed ring‐closing dehydrogenative reactions are legion, but will not operate when the strain at the reductive elimination stage becomes too large. We propose here a “muscled up” super‐oxidative palldium‐catalysed C H activation method for the ring closure of strained phenylcarbazoles.