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141.
142.
The branching structure of inflorescences of the cultivated strawberry ( Fragaria × ananassa Duch.) is very variable. This paper demonstrates that some aspects of this variability are well described by a simple stochastic model of branching that has two adjustable parameters. The model is shown to provide a good fit to data from a set of almost 700 inflorescences of the cultivar Elsanta, collected over two successive years. For one parameter the maximum likelihood estimator is a moment estimator which is fully efficient even if the detailed branching structure of the inflorescences is not recorded. This parameter provides a convenient summary of branching vigour. The maximum likelihood estimator of the second parameter must be determined iteratively and can be quite inefficient unless the full branching structure is recorded. The model demonstrates that branching structure is affected by the order in which inflorescences emerge on the plant.  相似文献   
143.
Weighted Approximations to Continuous Time Martingales with Applications   总被引:1,自引:0,他引:1  
A weighted approximation to a sequence of continuous time martingales by a time transformed Wiener process is established. The basic tool of proof is the Skorohod imbedding for martingale difference sequences. As an application of the main result a useful weighted approximation to the randomly weighted uniform empirical process is derived. A number of other applications are also discussed.  相似文献   
144.
How does the structure of the world economy determine the gains from participation therein? In order to answer this question, we conduct a state of the art network analysis of international trade to map the structure of the international division of labor (IDL). We regress cross-national variation in economic growth on positional variation and mobility of countries within the IDL from 1965 to 2000. We find that the highest rates of economic growth occurred to countries in the middle of the IDL over the course of globalization. Second, we find that upper tier positions in the IDL are converging with each other, but diverging from the lower tier. This suggests that the mechanism underlying the rapid economic growth in intermediate positions was their uniquely high rates of upward mobility, in turn a function of their middling position. Taken together, these findings suggest that a country’s long-term economic development is conditioned by its position in the IDL.  相似文献   
145.
临床试验是指以人为对象的前瞻性研究,预先将受试者或受试人群分配至接受一种或多种医疗干预,以评价医疗干预对健康结局的影响。其中"医疗干预"包括但不仅限于药物,也包括细胞及其他生物制品、外科治疗、放射治疗、医疗器械、行为疗法、治疗过程的改变和预防保健等[1-2]。  相似文献   
146.
Although a number of studies have uncovered evidence of age differences in religious involvement across the life course, there has been a lack of long-term longitudinal data to test the extent to which these differences are due to changes within individuals over time. This study tracks trajectories of change in religious service attendance using data collected longitudinally over the course of up to 34 years, between 1971 and 2005, and in ages ranging from 15 to 102. Piecewise growth curve modeling was used to examine changes in the patterns of age-related change in three distinct developmental periods: the transition from adolescence to young adulthood, middle adulthood, and older adulthood. Attendance showed an average pattern of quadratic decline in adolescence, stability in middle adulthood, and a quadratic pattern of more rapid increase followed by decrease over the course of older adulthood. These results suggest that developmental factors play a role in changing patterns of religious participation across the adult life course, and may account for some of the apparent differences between age groups.  相似文献   
147.
Utilizing the stress process and life course perspectives, we investigated the influence of non-spousal social support on the associations between marital quality, physical disability, and loneliness among married older adults. Using data from the National Social Life, Health, and Aging Project (NSHAP), we found that the association between physical disability and loneliness was partially accounted for by the fact that physical disability was associated with less supportive nonmarital relationships. While physically-disabled older adults in higher-quality marriages were buffered from loneliness, supportive non-martial relationships did not offset elevated loneliness among those in low-quality marriages. These associations were largely similar for men and women. Thus, although both marital and nonmarital relationships are important for loneliness, when confronted with a stressor such as disablement it is the marital relationship alone that matters.  相似文献   
148.
This paper presents a problem structuring methodology to assess real option decisions in the face of unpredictability. Based on principles of robustness analysis and scenario planning, we demonstrate how decision-aiding can facilitate participation in projects setting and achieve effective decision making through the use of real options reasoning. We argue that robustness heuristics developed in earlier studies can be practical proxies for real options performance, hence indicators of efficient flexible planning. The developed framework also highlights how to integrate real options solutions in firms’ strategic plans and operating actions. The use of the methodology in a location decision application is provided for illustration.  相似文献   
149.
This article responds to calls in the management and leadership literature to articulate a role for wisdom. While many talk about the role of wisdom, few people have attempted to articulate what it consists of. We suggest five principles that define wise leadership. We then position wisdom in a complex world, both within the transformational, authentic and spiritual leadership literature and the knowledge based view of organizations, and suggest how leaders should be evaluated. Finally, we suggest the need for future research directions and practical application.  相似文献   
150.
Affective reactions to the departure of work group leaders are proposed as an important determinant of members' trust-related judgments regarding new leaders. A field test of veterinary hospital employees evaluating new leaders revealed that the affective reaction to the departure of the prior group leader predicted trust when there was no history between the individuals. When there was history between the two individuals, the group member's evaluation of the new leader's ability on their prior job was a significant predictor of trust over and above their affective reaction to the succession. The relationships between affective reactions to succession and trust formation were replicated in a longitudinal simulation of trust formation in student groups. The implications of these findings for the study of trust in organizations and leadership succession processes in work groups are discussed.  相似文献   
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