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81.
An endo-N-acetyl-beta-D-glucosaminidase activity towards an asialo-N-acetyl-lactosaminic-type glycoasparagine substrate was demonstrated in rat liver. This activity was optimal at pH 7.0 and was predominantly present in the soluble (cytosolic) fraction. 相似文献
82.
News media coverage of smoking and health is associated with changes in population rates of smoking cessation but not initiation 总被引:4,自引:0,他引:4 下载免费PDF全文
OBJECTIVE: To determine whether changes in news media coverage of smoking and health issues are associated with changes in smoking behaviour in the USA. DESIGN AND MAIN OUTCOME MEASURES: Issue importance in the US news media is assessed by the number of articles published annually in major magazines indexed in The Reader's Guide to Periodical Literature. Annual incidence rates for cessation and initiation in the USA were computed from the large, representative National Health Interview Surveys (1965-1992). Patterns in cessation incidence were considered for ages 20-34 years and 35-50 years. Initiation incidence was examined for adolescents (14-17 years) and young adults (18-21 years) of both sexes. RESULTS: From 1950 to the early 1980s, the annual incidence of cessation in the USA mirrored the pattern of news media coverage of smoking and health, particularly for middle aged smokers. Cessation rates in younger adults increased considerably when second hand smoke concerns started to increase in the US population. Incidence of initiation in young adults did not start to decline until the beginning of the public health campaign against smoking in the 1960s. Among adolescents, incidence rates did not start to decline until the 1970s, after the broadcast ban on cigarette advertising. CONCLUSIONS: The level of coverage of smoking and health in the news media may play an important role in determining the rate of population smoking cessation, but not initiation. In countries where cessation has lagged, advocates should work to increase the newsworthiness of smoking and health issues. 相似文献
83.
In video-based particle-image velocimetry (PIV) systems for fluid mechanics research, it is sometimes desirable to image seed particles to be smaller than a camera pixel. However, imaging to this size can lead to marginal image contrast such that significant numbers of erroneous velocity vectors can be computed, even for simple flow fields. A variety of image-enhancement techniques suitable for a low-cost PIV system that uses video cameras are examined and tested on three representative flows. Techniques such as linear contrast enhancement and histogram hyperbolization are shown to have good potential for improving the image contrast and hence the accuracy of the data-reduction process with only a 15% increase in the computational time. Some other schemes that were examined appear to be of little practical value in PIV applications. An automated shifting algorithm based on mass conservation is shown to be useful for displacing the second interrogation region in the direction of flow, which minimizes the number of uncorrelated particle images that contribute noise to the data-reduction process. 相似文献
84.
Paul J. Yanhua Hong Spencer P.S. Pierce I. Shore K.A. 《Photonics Technology Letters, IEEE》2007,19(21):1708-1710
It is demonstrated that accurate distance measurement may be effected using a commercially available distributed feedback (DFB) semiconductor laser subject to frequency-shifted optical feedback. A simple experimental arrangement is employed wherein a chirped frequency comb is generated in an external cavity DFB laser using an intracavity acoustic-optic modulator. The frequency comb generates a beat frequency which is proportional to the path difference of a target and reference arm. An estimate of the accuracy and resolution of the measurement is given. 相似文献
85.
A new model for the static polarisability tensor elements of small particles is proposed and investigated. The static polarisability tensor for nearly agglomerated and agglomerated homogeneous dielectric spheres is investigated using a numerical procedure. Excellent agreement is obtained with a recent theoretical formulation for the slightly separated case.<> 相似文献
86.
J. Hensman R. Mills S.G. Pierce K. Worden M. Eaton 《Mechanical Systems and Signal Processing》2010,24(1):211-223
A standard technique in the field of non-destructive evaluation is to use acoustic emissions to characterise and locate the damage events that generate them. The location problem is typically posed in terms of the times of flight of the waves and results in an optimisation problem, which can at times be ill-posed. A method is proposed here for learning the relationship between time of flight differences and damage location using data generated by artificially stimulated acoustic emission (AE)—a classic problem of regression. A structure designed to represent a complicated aerospace component was interrogated using a laser to thermoelastically generate AE at multiple points across the structure's surface. Piezoelectric transducers were mounted on the surface of the structure, and the resulting waveforms were recorded. A Gaussian process (GP) with RBF kernels was chosen for regression. Since during AE monitoring not all events can be guaranteed to be detected by all sensors, a GP was trained on data for all possible combinations (subsets) of sensors. The inputs to the GPs were the differences in time of flight between sensors in the set, and the targets were the locations of the source of ultrasonic stimulation. Subsequent (test) data points were located by every possible GP, given the active sensors. It is shown that maps learned on a given structure can generalise effectively to nominally identical structures. 相似文献
87.
The oxygenase component of toluene dioxygenase from Pseudomonas putida F1 is an iron-sulfur protein (ISPTOL) consisting of alpha (TodC1) and beta (TodC2) subunits. Purified TodC1 gave absorbance and electron paramagnetic resonance spectra identical to those given by purified ISPTOL. TodC1 was reduced by NADH and catalytic amounts of ReductaseTOL and FerredoxinTOL. Reduced TodC1 did not oxidize toluene, and catalysis was strictly dependent on the presence of purified TodC2. 相似文献
88.
Two Pheromones of Coniferophagous Bark Beetles Found in the Bark of Nonhost Angiosperms 总被引:4,自引:0,他引:4
Dezene P. W. Huber Regine Gries John H. Borden Harold D. Pierce Jr. 《Journal of chemical ecology》1999,25(4):805-816
Volatiles from fresh bark of black cottonwood, Populus trichocarpa; trembling aspen, P. tremuloides; paper birch, Betula papyrifera; bigleaf maple, Acer macrophyllum; red alder, Alnus rubra; and Sitka alder, Alnus viridis, were collected on Porapak Q and subjected to coupled gas chromatographic–electroantennographic detection analyses by utilizing the antennae of several scolytid beetles (Dendroctonus pseudotsugae, D. rufipennis, D. ponderosae, Ips pini, and Dryocoetes confusus). Among the antennally active volatiles identified by coupled gas chromatographic-mass spectroscopic analysis were frontalin, 1,5-dimethyl-6,8-dioxabicyclo[3.2.1]-octane, in the two Alnus species and conophthorin, (E)-7-methyl-1,6-diox-aspiro[4.5]decane, in the other four species. Field trapping experiments demonstrated that conophthorin had a significant disruptant effect on the response to a pheromone-host kairomone blend by both Dendroctonus pseudotsugae and D. ponderosae. Our results, and the recent identification of other scolytid pheromones in various tree species, pose major questions regarding the evolution and ecological roles of these semiochemicals, including the possibility of Batesian mimicry by the beetles. They also suggest a need for comparative studies on the biosynthetic pathways for these compounds. 相似文献
89.
PP Lee D Zeng AE McCaulay YF Chen C Geiler DT Umetsu NJ Chao 《Canadian Metallurgical Quarterly》1997,90(4):1611-1617
The precise role of the endogenous immune system in modulating cancer development remains unclear. Tumor cells are generally thought to be nonimmunogenic because they are of 'self' origin. However, tumor-reactive lymphocytes can be isolated from patients with many types of cancer. It is unclear what role these lymphocytes play and why they fail to protect the host. Using a murine B-cell leukemia/lymphoma (BCL1) model, we showed the development of a vigorous antitumor T-cell response in the tumor-susceptible host. Specific T-cell responses against BCL1 developed as early as day 4. However, the nature of this nonprotective response is different from the protective response produced in a major histocompatibility complex-matched tumor-resistant host. Susceptible hosts developed a T helper 2 (Th2)-dominant response, whereas resistant hosts developed a Th1-dominant response to BCL1. Cytolytic activity against BCL1 developed in both resistant and susceptible hosts, but in the susceptible host, this response was weaker and delayed compared with that in the resistant host. Thus, tumor susceptibility does not necessarily mean the absence of an antitumor immune response. Rather, the nature of the antitumor immune response is critical in determining clinical outcome. 相似文献
90.
DT Jones 《Canadian Metallurgical Quarterly》1997,7(3):377-387
If protein structure prediction methods are to make any impact on the impending onerous task of analyzing the large numbers of unknown protein sequences generated by the ongoing genome-sequencing projects, it is vital that they make the difficult transition from computational 'gedankenexperiments' to practical software tools. This has already happened in the field of comparative modelling and is currently happening in the threading field. Unfortunately, there is little evidence of this transition happening in the field of ab initio tertiary-structure prediction. 相似文献