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Seasonal changes in the production of primary nutrients (soluble carbohydrates) and secondary metabolites (terpenes, monomeric phenolics, and tannins) in the current needle tissue of Douglas fir were investigated. All four classes of compounds showed significant seasonal changes in concentration during foliage development. Most terpenes increased significantly in concentration from June 11 to August 3, and then showed declining concentrations to September 20. The most dramatic and significant seasonal increases occurred in-pinene, camphene, and bornyl acetate concentrations. The monomeric phenolics chlorogenic acid, taxifolin glucoside, quercetin galactoside, and those unknown phenolics showed an overall trend of declining in concentration from June 11 through September 20. However, considerable variation between sampling dates in the concentration of these phenolics was noted. Tannin concentration decreased significantly from June 11 to July 9, and then increased in concentration to the September 20 sampling date. Fructose, galactose, glucose, and sucrose tended to decrease from June 11 to September 20. However, significant variation between sampling dates was evident in these compounds as well. Galactose was the major compound in the soluble carbohydrate fraction, amounting to almost 80% of the total concentration throughout the growing season. These data suggest that if phenolics and tannins function as defenses, they would only affect second- and possibly third-instar budworm larvae during the time that these instars mine the buds. Camphene,-pinene, and bornyl acetate increased in concentration throughout the growing season and may be effective deterrents to the budworm. Both bornyl acetate and camphene have been shown in field and laboratory studies to increase larval mortality and adversely affect budworm larval growth. Carbohydrates generally act as nutrients that enhance herbivore growth. However, in a previous study, galactose was found to cause reduced budworm larval growth and increased larval mortality. 相似文献
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This study compared responses to two versions of an end-of-course evaluation instrument completed by graduate students: the traditional printed form completed using pencil and paper, and a microcomputer-based form that presented equivalent items and accepted student responses. A finding of no significant difference in favorableness of composite ratings between the two versions prompted the researcher to perform item-by-item analyses of the two instruments. These analyses revealed that ratings of the individual items on one instrument were highly correlated with the ratings of their matched corresponding items on the other instrument. The paper-and-pencil and computerized evaluation instruments were found to be of almost identically high reliability. Possible limitations of the findings and areas for future research are discussed. 相似文献
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Reports an abrupt downturn in the market for psychologists as shown in a series of spring placement services studies. The number of positions advertised in the base-line year of 1969 was over twice the number advertised in 1971. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Bill Roach Cathy wei Karman Cates 《景观设计》2008,(5):26-37
自20世纪中期第个郊区购物中心兴起之后.北美的商业景观设计也开始逐渐走向成熟。当时的创新理念是打造一个可控制的、无机动车和犯罪行为、室外环境良好的安全购物形式。规模较小的零售点通常会设置在大型购物中心的两端,以吸引购物者。 相似文献
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RP Lemke N Idiong S Al-Saedi K Kwiatkowski DB Cates H Rigatto 《Canadian Metallurgical Quarterly》1998,157(2):470-474
The timing and magnitude of airway narrowing in central apneas is unknown. We have developed a method of apnea classification that relies on the transmission of cardiac airflow oscillation to indicate airway patency. Using a theoretical model, we showed that the amplitude of the cardiac airflow oscillation is proportional to airway diameter for small lumens. While in the majority of central apneas the amplitude of the cardiac airflow oscillation remains nearly constant, in a subset of events the waveform decreases with time, suggesting airway narrowing. We hypothesized that this is not a random occurrence but reflects a critical period of airway instability during central apnea. To test this hypothesis we studied 41 preterm infants. Of 4,456 central apneas, 585 had a decrease in the amplitude of the cardiac oscillation. The amplitude of the cardiac airflow oscillation during an apnea was recorded to provide a dynamic measure of changes in airway diameter with time. To allow for comparisons between patients the amplitude of each cardiac airflow oscillation was expressed as a proportion of the maximum amplitude observed in each infant. We then compared the amplitude at multiple successive 0.5 s intervals with the amplitude of the cardiac airflow oscillation observed at the apnea outset using ANOVA. We found a significant decrease in cardiac airflow oscillation after only 1 s irrespective of the apnea duration (3 to 16 s). We conclude that airway narrowing during central apnea is not a random occurrence but appears shortly after the onset of the apnea. We speculate that the phenomenon is secondary to passive airway relaxation. 相似文献
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The effects of progesterone and RU486, a synthetic anti-progesterone, on ovarian 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity, a key enzyme of progesterone production, were studied during ovulation in immature 22-day-old rats primed with pregnant mares' serum gonadotrophin (PMSG) and human chorionic gonadotrophin (hCG). Ovarian 3 beta-HSD activities had increased significantly 4 h after hCG injection. These increases were inhibited at 4 and 6 h after hCG when 20 mg RU486 kg-1 was administered 2 h before hCG. However, RU486 had no influence on the activity of 3 beta-HSD when administered at the same time as hCG injection. A histochemical study revealed that 3 beta-HSD activities in the granulosa cell layer, but not in the theca cell layer, were inhibited when RU486 was given 2 h before hCG. Serum progesterone concentrations, but not oestradiol concentrations, were significantly suppressed by RU486 treatment 4 and 6 h after hCG. The effect of progesterone on ovarian 3 beta-HSD activity was tested by administering graded doses of progesterone exogenously to rats 2 h before hCG injection. Ovarian 3 beta-HSD activity was increased in a dose-dependent manner, and more than 20 mg progesterone kg-1 significantly stimulated the activity. Although 10 mg progesterone kg-1 did not stimulate ovarian 3 beta-HSD activities, the RU486-inhibited activities were recovered by the concomitant administration of 10 mg progesterone kg-1 with RU486. These results indicate that ovarian 3 beta-HSD activity depends on progesterone concentrations, and suggest an autocrine regulation of progesterone production during ovulation in immature rat ovaries stimulated with PMSG and hCG. 相似文献
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Examined placement listings at 6 regional conventions, the American Psychological Association (APA) Regional Placement Bulletin, and the monthly APA Employment Bulletin (February through June, 1969). Overall, there were 1,931 unduplicated positions and 1,753 unduplicated applicants. Colleges and universities were the most frequent employment setting. Employers generally were successful in locating applicants with the desired educational requirements. For PhDs, there was a surplus of applicants for clinical/counseling positions, while there was a surplus in industrial psychology for those with less than a PhD. Salaries associated with different settings and educational backgrounds are presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献