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81.
We have examined the 3'-terminal sequence of the "small" structural ribosomal RNA ("13S") of hamster cell mitochondria, using a procedure involving [3H]isoniazide labeling of samples subjected to sequential periodate oxidation and beta-elimination. The terminus was found to be PyUAUUAOH, which is similar, but not identical, to the corresponding terminus of eukaryotic cytoplasmic 18S rRNA. 相似文献
82.
Igor Goldfarb Vladimir Gol’dshtein J. Barry. Greenberg Ann Zinoviev 《Journal of Engineering Mathematics》2006,56(2):129-142
Recent experimental evidence has uncovered the peculiar behavior of certain gel droplets which, under appropriate ambient
thermal conditions, evaporate and burn in an oscillatory fashion. In this work a preliminary foray is made into the theoretical
analysis of the nature of the evolution of a hot gas mixture containing organic gel fuel droplets with oscillatory evaporation
within the context of thermal-explosion theory. The problem is modeled as a system of highly nonlinear singularly perturbed
ordinary differential equations. Non-dimensionalization of the equations enables identification of the parameters that play
a major role in determining the dynamical regimes of the system of equations. The method of integral manifolds is exploited
for the analysis and it is found, that for certain parametric regions, the system exhibits new dynamical behavior that is
quite different from that found for conventional liquid droplets. 相似文献
83.
John J. A. Barry Marta M. C. G. Silva Sarah H. Cartmell Robert E. Guldberg Colin A. Scotchford Steven M. Howdle 《Journal of Materials Science》2006,41(13):4197-4204
Porous scaffold structures are used in tissue engineering to provide structural guidance for regenerating tissues. The use
of carbon dioxide (CO2) to create such scaffolds has received some attention in the past but many researchers believe that although CO2 processing of polymers can lead to porous scaffolds there is limited interconnectivity between the pores. In this study,
highly porous (greater than 85%) and well interconnected scaffolds were obtained in which the size, distribution and number
of pores could be controlled. This control was achieved by altering the rate of venting from polymer discs saturated with
CO2 under modest temperature and pressure. The polymer used is a blend of poly (ethyl methacrylate) and tetrahydrofurfuryl methacrylate
(PEMA/THFMA). This polymer system has shown promise for potential applications in cartilage repair. 相似文献
84.
Joseph Stephen; Linley P. Alex; Andrews Leanne; Harris George; Howle Barry; Woodward Clare; Shevlin Mark 《Canadian Metallurgical Quarterly》2005,17(1):70
The Changes in Outlook Questionnaire (CiOQ; S. Joseph, R. Williams, & W. Yule, 1993) is a 26-item self-report measure that was designed to assess positive and negative changes in the aftermath of adversity. This article had 3 aims: 1st, to investigate the factor structure of the CiOQ; 2nd, to test for internal consistency reliability and convergent and discriminant validity; and, 3rd, to investigate the association between positive and negative changes in outlook, posttraumatic stress, and psychological distress. Three studies are reported. Study 1 provides evidence that positive and negative changes are statistically separable and that the 2-factor model is a better fit than the 1-factor model. Studies 2 and 3 provide evidence for internal consistency reliability, convergent and discriminant validity of the CiOQ, and its associations with posttraumatic stress and psychological distress. In conclusion, the CiOQ has much promise for research on responses to stressful and traumatic events. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
Identifying and tracking changing interests 总被引:4,自引:0,他引:4
87.
This paper investigates the benefits that the partial least squares (PLS) modelling approach offers engineers involved in the operation of fed-batch fermentation processes. It is shown that models developed using PLS can be used to provide accurate inference of quality variables that are difficult to measure on-line, such as biomass concentration. It is further shown that this model can be used to provide fault detection and isolation capabilities and that it can be integrated within a standard model predictive control framework to regulate the growth of biomass within the fermenter. This model predictive controller is shown to provide its own monitoring capabilities that can be used to identify faults within the process and also within the controller itself. Finally it is demonstrated that the performance of the controller can be maintained in the presence of fault conditions within the process. 相似文献
88.
Jincheng Wang Yujing Liu Chirag Dhirajlal Rabadia Shun-Xing Liang Timothy Barry Sercombe Lai-Chang Zhang 《材料科学技术学报》2021,61(2):221-233
Although using elemental powder mixtures may provide broad alloy selection at low cost for selective laser melting(SLM), there is still a concern on the resultant microstructural and chemical homogeneity of the produced parts. Hence, this work investigates the microstructure and mechanical properties of a SLM-produced Ti-35 Nb composite(in wt%) using elemental powder. The microstructural characteristics including ? phase, undissolved Nb particles and chemical homogeneity were detailed investigated.Nanoindentation revealed the presence of relatively soft undissolved Nb particles and weak interface bonding around Nb-rich regions in as-SLMed samples. Solid-solution treatment can not only improve chemical homogeneity but also enhance bonding through grain boundary strengthening, resulting in43 % increase in tensile elongation for the heat-treated Ti-35 Nb compared to the as-SLMed counterpart. The analyses of tensile fractures and shear bands further confirmed the correlation between the different phases and the ductility of Ti-35 Nb. In particular, the weak bonding between undissolved Nb and the matrix in the as-SLMed sample reduces its ductility while the ? grains in solid-solution treated Ti-Nb alloy can induce a relatively stable plastic flow therefore better ductility. This work sheds insight into the understanding of homogenization of microstructure and phases of SLM-produced alloys from an elemental powder mixture. 相似文献
89.
Engineering metal-impurity nanodefects for low-cost solar cells 总被引:1,自引:0,他引:1
Buonassisi T Istratov AA Marcus MA Lai B Cai Z Heald SM Weber ER 《Nature materials》2005,4(9):676-679
As the demand for high-quality solar-cell feedstock exceeds supply and drives prices upwards, cheaper but dirtier alternative feedstock materials are being developed. Successful use of these alternative feedstocks requires that one rigorously control the deleterious effects of the more abundant metallic impurities. In this study, we demonstrate how metal nanodefect engineering can be used to reduce the electrical activity of metallic impurities, resulting in dramatic enhancements of performance even in heavily contaminated solar-cell material. Highly sensitive synchrotron-based measurements directly confirm that the spatial and size distributions of metal nanodefects regulate the minority-carrier diffusion length, a key parameter for determining the actual performance of solar-cell devices. By engineering the distributions of metal-impurity nanodefects in a controlled fashion, the minority-carrier diffusion length can be increased by up to a factor of four, indicating that the use of lower-quality feedstocks with proper controls may be a viable alternative to producing cost-effective solar cells. 相似文献
90.
Traditionally, collaborative recommender systems have been based on a single-shot model of recommendation where a single set
of recommendations is generated based on a user’s (past) stored preferences. However, content-based recommender system research
has begun to look towards more conversational models of recommendation, where the user is actively engaged in directing search
at recommendation time. Such interactions can range from high-level dialogues with the user, possibly in natural language,
to more simple interactions where the user is, for example, asked to indicate a preference for one of k suggested items. Importantly, the feedback attained from these interactions can help to differentiate between the user’s
long-term stored preferences, and her current (short-term) requirements, which may be quite different. We argue that such
interactions can also be beneficial to collaborative recommendation and provide experimental evidence to support this claim. 相似文献