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51.
In this study, the three-dimensional structure of the wild-type human telomerase RNA pseudoknot was predicted via molecular modeling. The wild-type pseudoknot structure is then compared to the recent NMR solution structure of the telomerase pseudoknot, which does not contain the U177 bulge. The removal of the bulge from the pseudoknot structure results in higher stability and significant reduction of activity of telomerase. We show that the effect of the bulge on the structure results in a significant transformation of the pseudoknot junction region where the starting base pairs are disrupted and unique triple base pairs are formed. We found that the formation of the junction region is greatly influenced by interactions of the U177 bulge with loop residues and rotation of residue A174. Moreover, this is the first study to our knowledge where a structure as complex as the pseudoknot has been solved by purely theoretical methods. 相似文献
52.
Donald Bruce 《Computers and the Humanities》1993,27(5-6):357-364
Humanities computing (HC) has failed to integrate into its practices many of the key theoretical elements of contemporary text and discourse theory. This has in turn contributed to the marginalization of HC in research and teaching. Outdated theoretical models must be abandoned in order to develop a critical discourse based on the insights of HC. HC projects remain far too attached to micro-analyses and have not developed the theoretical and methodological tools necessary to undertake systemic macro-analyses on the level of discourse. Given that texts are a mixture of determinate and dynamic systems, recent developments in chaos theory may be of help in modelling the interrelationship of these elements at discourse level.Donald Bruce is Associate Professor of Romance Languages at the University of Alberta. His research interests include literary theory, XIXth century French literature, science and literature, and translation. He recently edited an issue ofRecherches Sémiotiques/Semiotic Inquiry on Literature and Ideology and is presently working on a project entitled,The Socio-semiotic Nexus: Jules Vallès and the Discourse of the Commune. 相似文献
53.
Bruce E. Litow 《Theory of Computing Systems》1985,18(1):11-18
It is shown that a bounded language accepted by a nondeterministic Turing machine in spaceS(n o(logn) can be accepted by a deterministic Turing machine in space MAX {(s(nn))2, logn}. This can be interpreted as extending Savitch's algorithm below logspace. Results of Alt can be used to show that in the general case the indicated space bound cannot be improved. The result can also be interpreted as a sharpening in the special case of bounded languages of the results of Monien and Sudborough. 相似文献
54.
Just how insoluble are monoterpenes? 总被引:16,自引:0,他引:16
Jeffrey D. Weidenhamer Francisco A. Macias Nikolaus H. Fischer G. Bruce Williamson 《Journal of chemical ecology》1993,19(8):1799-1807
Prior generalizations about the ecological roles of monoterpenes may be misleading if based on the presumed insolubility of monoterpenes in water. We determined the aqueous solubility of 31 biologically active monoterpenes by gas chromatography. While hydrocarbons were of low solubility (< 35 ppm), oxygenated monoterpenes exhibited solubilities one or two orders of magnitude higher, with ranges of 155–6990 ppm for ketones and of 183–1360 ppm for alcohols. Many monoterpenes are phytotoxic in concentrations under 100 ppm, well below the saturated aqueous concentrations of oxygenated monoterpenes. Therefore, even dilute, unsaturated solutions of monoterpenes, occurring naturally in plant tissues and soil solutions, may act as potent biological inhibitors. 相似文献
55.
Goodyear Rodney K.; Abadie Philip D.; Walsh W. Bruce 《Canadian Metallurgical Quarterly》1983,30(2):283
Examined the graduate school origins of authors of Journal of Counseling Psychology (JCP) articles in Volumes 15–28 to extend a previous analysis of Volumes 1–24 by the 3rd author et al (1969). Comparisons of the 2 14-yr periods reveal that some universities retained the same or similar ranks across both periods, some declined in importance as sources of authors, and others emerged as major sources of JCP authors. (6 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
William A. Aiello F. T. Leighton Bruce M. Maggs Mark Newman 《Theory of Computing Systems》1991,24(1):253-271
In this paper we describe anO(logN)-bit-step randomized algorithm for bit-serial message routing on a hypercube. The result is asymptotically optimal, and improves upon the best previously known algorithms by a logarithmic factor. The result also solves the problem of on-line circuit switching in anO(1)-dilated hypercube (i.e., the problem of establishing edge-disjoint paths between the nodes of the dilated hypercube for any one-to-one mapping).Our algorithm is adaptive and we show that this is necessary to achieve the logarithmic speedup. We generalize the Borodin-Hopcroft lower bound on oblivious routing by proving that any randomized oblivious algorithm on a polylogarithmic degree network requires at least (log2
N/log logN) bit steps with high probability for almost all permutations.This research was supported by the Defense Advanced Research Projects Agency under Contracts N00014-87-K-825 and N00014-89-J-1988, the Air Force under Contract AFOSR-89-0271, and the Army under Contract DAAL-03-86-K-0171. This work was completed while the third and fourth authors were at the Laboratory for Computer Science, Massachusetts Institute of Technology. 相似文献
57.
58.
Patricia R. Pfeiffer Angela R. Bielefeldt Tissa Illangasekare Bruce Henry 《Canadian Metallurgical Quarterly》2005,131(10):1447-1452
Laboratory experiments were conducted to investigate the abiotic interactions of soybean oil (SoyOil) and chlorinated ethene (CE) nonaqueous phase liquids (NAPLs). The mixed NAPL density and interfacial tension behaved ideally, as predicted by the volume ratio. The mixed NAPL viscosity increased exponentially from that of the pure CE to that of pure SoyOil as the volume fraction increased. The measured contact angle was highly variable and was unpredictable as a function of the volume composition of the mixed NAPL. The physical property effects indicate that the mobilization of residual CE NAPLs because of SoyOil injection is unlikely. Equilibrium dissolution of CEs from the NAPL mixtures behaved linearly as a function of the mole fraction. Dissolved SoyOil in simulated groundwater enhanced the dissolution of trichloroethene (TCE) during flow tests, increasing the effluent TCE concentration from 141?to?202?mg/L. The ready intermingling of the CE dense nonaqueous phase liquids (DNAPLs) and SoyOil indicate that such interactions may be significant at sites where vegetable oil is injected into DNAPL source areas to enhance in situ anaerobic bioremediation. 相似文献
59.
Sachs-Ericsson Natalie; Blazer Dan; Plant E. Ashby; Arnow Bruce 《Canadian Metallurgical Quarterly》2005,24(1):32
In a population sample (N = 5,877; ages 15 to 54), the authors found childhood sexual and physical abuse to be associated with the 1-year prevalence of serious health problems for both men and women. The authors also found that participants' psychiatric disorders partially mediated the effects of physical and sexual abuse on adult health. However, childhood abuse continued to independently influence health status after the authors controlled for psychiatric disorders. Contrary to expectations, individuals who experienced a combination of sexual and physical abuse did not have a higher frequency of health problems than those who experienced either type of abuse alone. Implications for these findings are discussed, including possible mechanisms that may account for the association between childhood abuse and adult health problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
60.
David J. Fair Rakesh Venkatesh Bruce Boghosian Douglas M. Matson 《Microgravity science and technology》2005,16(1-4):55-58
Certain commercial steel alloys exhibit a two-step phase transformation process during solidification when substantial undercooling of the liquid allows access to the metastable phase. This two-step transformation leads to a desirable microstructure under certain conditions. Electrostatic Levitation (ESL) and Electromagnetic Levitation (EML) are two methods of containerless processing used to study how nucleation and growth kinetics influence the transformation delay between phases. Because the two facilities show substantially different delay results, the test environment differences have been analyzed to determine the root cause of this deviation. In particular, the difference in sample size between ESL and EML is examined and modeling shows that this difference is not the controlling factor in determining transformation delay behavior. 相似文献