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101.
Interoperation and information sharing among databases independently developed and maintained by different organizations is today a pressing need, if not a practice. Governmental, military, financial, medical, and private institutions are more and more required to become part of a distributed infrastructure and selectively share their data with other organizations. This sharing process inevitably opens the local system to new vulnerabilities and enlarges the space of possible threats to the data and resources it maintains. As a complicating factor, in general, data sources are heterogeneous both in the data models they adopt and in the security models by which protection requirements are stated. We present a modeling and architectural solution to the problem of providing interoperation while preserving autonomy and security of the local sources based on the use of wrappers and a mediator. A wrapper associated with each source provides a uniform data interface and a mapping between the source's security lattice and other lattices. The mediator processes global access requests by interfacing applications and data sources. The combination of wrappers and mediator thus provides a uniform data model interface and allows the mapping between restrictions stated by the different security policies. We describe the practical application of these ideas to the problem of trusted interoperation of health care databases, targeted to enforcing security in distributed applications referring to independent heterogeneous sources protected by mandatory policy restrictions. We describe the architecture and operation of the system developed, and describe the tasks of the different components. 相似文献
102.
DW Dawson OV Volpert SF Pearce AJ Schneider RL Silverstein J Henkin NP Bouck 《Canadian Metallurgical Quarterly》1999,55(2):332-338
Mal II, a 19-residue peptide derived from the second type 1 properdin-like repeat of the antiangiogenic protein thrombospondin-1 (TSP-1), was inactive in angiogenesis assays. Yet the substitution of any one of three L-amino acids by their D-enantiomers conferred on this peptide a potent antiangiogenic activity approaching that of the intact 450-kDa TSP-1. Substituted peptides inhibited the migration of capillary endothelial cells with an ED50 of 8.5 nM for the D-Ile-15 substitution, 10 nM for the D-Ser-4 substitution, and 0.75 nM for the D-Ser-5 substitution. A peptide with D-Ile at position 15 could be shortened to its last seven amino acids with little loss in activity. Like whole TSP-1, the Mal II D-Ile derivative inhibited a broad range of angiogenic inducers, was selective for endothelial cells, and required CD36 receptor binding for activity. A variety of end modifications further improved peptide potency. An ethylamide-capped heptapeptide was also active systemically in that when injected i.p. it rendered mice unable to mount a corneal angiogenic response, suggesting the potential usefulness of such peptides as antiangiogenic therapeutics. 相似文献
103.
Compacted graphite iron-A material solution for modern diesel engine cylinder blocks and heads 总被引:1,自引:0,他引:1
The demands for improved fuel economy,performance and emissions continue to pose challenges for engine designers and the materials they choose. This is particularly true for modern diesel engines,where the primary path to achieving improved engine performance and emissions is to increase the Peak Firing Pressure in the combustion chamber. The resulting increase in thermal and mechanical loading has required a change from conventional grey cast iron to Compacted Graphite Iron (CGI) in order to satisfy durability requirements without increasing the size or the weight of the engines. With at least 75% higher tensile strength,45% higher stiffness and approximately double the fatigue strength of conventional grey cast iron,CGI satisfies durability requirements and also provides the dimensional stability required to meet emissions legislation throughout the life of the engine.Currently,there are no CGI diesel engines running on the roads in North America. This is set to change considerably as new commercial vehicle and pick-up SUV diesel engines are launched with CGI cylinder blocks in 2008 and 2009. These initial programs will provide over 2 million CGI diesel engines when ramped to mature volume,potentially accounting for 10%-15% of the North American passenger vehicle fleet within the next four years. 相似文献
104.
Seven straight Salix viminalis genotypes with different levels of rust (Melampsora epitea) susceptibility were grown as mono-plots as well as being incorporated into a range of mixtures. Two 3-year harvests (2003 and 2006) were taken. Disease progress was followed on each of the individual genotypes throughout each growing season 2001–2006. In 2003 there were small but significant yield increases from the mixtures compared to the yield of individual components grown as mono-plots. These differences were not evident at the second harvest in 2006. No consistent effect of mixtures on reducing rust on the most susceptible genotype, Salix viminalis ‘77082’ were observed. In some years, e.g. 2003, at certain times during the growing season, significant reductions were observed on Salix viminalis ‘77082’ in certain 3-way mixtures compared to mono-plots. These, however, were not repeated consistently in subsequent years. It was concluded that the current commercial practice in many parts of Europe of planting mixtures as a disease control strategy will only be effective if there is sufficient genetic diversity between the Salix genotypes incorporated into the mixture. 相似文献
105.
H. M. Williams E. A. Dawson P. A. Barnes G. M. B. Parkes L. A. Pears C. J. Hindmarsh 《Journal of Porous Materials》2009,16(5):557-564
Key factors in achieving effective adsorption are the size of the pores relative to those of the adsorbate molecules and often
the presence of small metal particles which can confer catalytic activity. While microporous carbons are excellent adsorbents
for small molecules they are not as effective for larger species. A new low temperature approach to activation using an oxygen
gas pulsing technique to achieve a carbon with controllable meso/micropore structure is described which also minimises metal
sintering. The porosity of the samples was analysed by nitrogen adsorption at 77 K. Microporous metal-doped ASC carbon showed
significant increases in the level of mesoporosity, its mesopore volume increasing from 0.06 to 0.24 cm3 g−1. However, undoped BPL carbon treated under the same conditions remained unchanged. The catalytic effect of the metals in
the ASC carbon is thought to account for the observed mesopore development. At the temperatures used, a continuous oxidative
activation yielded no pore widening in either carbon, suggesting that the gas pulsing method is far more effective in increasing
mesopore sizes. 相似文献
106.
A New Longitudinal End Effect Factor for Linear Induction Motors 总被引:4,自引:0,他引:4
The longitudinal end effect in a linear induction motor (LIM) is analysed assuming two travelling magnetic flux density waves in the airgap: the wave travelling with synchronous velocity and the wave representing end effect [1]. A simple equation for the end effect factor which modifies the airgap EMF is obtained, and a simple equivalent circuit incorporating the end effect factor is established. Analysis is compared with measurements from two largescale single-sided LIM's. The equation for the end effect factor is sufficiently accurate to be used for design studies of LIMs. Since end effects are negligible at low speeds, the end effect factor has application for medium and high-speed LIMs. 相似文献
107.
J.L. Paterson J. Dorrian S.A. Ferguson S.M. Jay N. Lamond P.J. Murphy S.S. Campbell D. Dawson 《Applied ergonomics》2011,42(2):196-201
A number of studies have described mood change during sleep loss in the laboratory, however, an understanding of fluctuations in structural aspects of mood under such conditions is lacking. Sixty-two healthy young adults completed one of three possible conditions: one (n = 20) or two (n = 23) nights of sleep loss or the control condition which consisted of one (n = 9) or two (n = 10) nights of 9 h time in bed. The Mood Scale II was completed every two waking hours and data were analysed in terms of the frequency and intensity of mood reports. Overall, sleep loss conditions were associated with significantly less frequent happiness and activation and more frequent fatigue reports (p < 0.001). Intensity was also significantly reduced for activation and happiness, and increased for depression, anger and fatigue (p < 0.05). Interestingly, there were no significant differences in anger following two nights in the laboratory with or without sleep. Further, two nights in the lab with normal sleep was associated with significant increases in depression intensity (p < 0.05). Findings support the hypothesis of a mood regulatory function of sleep and highlight the relative independence of frequency and intensity and of positive and negative mood dimensions. Findings also suggest that the laboratory environment, in the absence of sleep loss, may have a significant negative impact on mood. 相似文献
108.
K. J. Bai C. W. Dawson J. W. Kim J. V. Wehausen 《Journal of Engineering Mathematics》1999,35(1-2):119-134
A possible first step in determining the flow about a steadily advancing ship is to consider the ship plus its mirror image in the undisturbed free surface. If the ship has a bulbous bow, the question may be asked whether a stagnation point can be expected not only at the intersection of the stem and the undisturbed surface, but also at some point on the stem near the bulb. In analogous two-dimensional situations the latter could not happen. That it can happen in three dimensions is shown here by the example of two dipoles situated perpendicularly to an oncoming flow. Both two- and three dimensional versions are considered. The conditions under which these stagnation points can occur in three dimensions are determined and the reason why this does not happen in two dimensions is explained. 相似文献
109.
T L Dawson 《Coloration Technology》2001,117(4):185-192
The mechanism by which the coloured image is formed by digital ink jet printing is very different from that of conventional screen printing methods and success depends on the use of sophisticated software and hardware. Some commercially available systems are listed in this paper and the basic principles of the standardisation of scanners, monitors and jet printers given. Ink jet printing machines at present available for textiles are reviewed and their limitations with regard to dye selection, shade gamuts and reproducibilty are quantified. Repeatability and shade reproducibility tests of digitally printed textiles are reported showing that improvements are required in the transformation of pattern data to the printed output. 相似文献
110.
Levine Brian; Dawson Deirdre; Boutet Isabelle; Schwartz Michael L.; Stuss Donald T. 《Canadian Metallurgical Quarterly》2000,14(4):491
Standard neuropsychological tests administered in a constrained and artificial laboratory environment are often insensitive to the real-life deficits faced by patients with traumatic brain injury (TBI). The Revised Strategy Application Test (R-SAT) creates an unstructured environment in the laboratory in which environmental cues and internal habits oppose the most efficient strategy, thus mimicking the real-life situations that are problematic for patients with TBI. In this study, R-SAT performance was related both to severity of TBI (i.e., depth of coma) sustained 2–3 years earlier and to quality of life outcome as assessed by the Sickness Impact Profile. This relationship held after accounting for variance attributable to TBI-related slowing and inattention. These findings support the validity of the R-SAT and suggest that behavioral correlates of quality of life outcome in TBI can be assessed in the laboratory with unstructured tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献