Prey capture tactics of spiders: An analysis based on a simulation model for spider's growth

Summary The prey capture tactics of spiders was analyzed, considering the energy gained by the capture of prey and that required for it. For the purpose of it, a growth model of spiders was constructed, expressing the flow rate of prey biomass to the spider's body by differential equations. Solving these equations under the differing values of three parameters, growth curves of spiders was obtained. These three parameters are the amount of prey biomass supplied daily to spiders,x ₀, the rate of prey capture of spiders, α, and a coefficient of the respiration rate required for the capture of prey,k. When the value ofk increased, spiders could grow only at high value ofx ₀. These results suggest that habitats with small prey biomass are preferred by spiders adopting a sit-and-wait tactics for prey capture, which requires small values ofk. Wolf spiders are one of these spiders showing that tactics. On the other hand, web-builders which require large amount of energy for spinning webs (namely, take large value ofk), are able to grow only in the habitats with large prey biomass. Each species of spiders are considered to locate in a certain point between both extremes of these tactics for the capture of prey.     

The feeding from edge towards inner part in soybean plot in rufous turtle dove,Streptopellia orientalis (Latham) and the estimation of passing rate of the flock

Summary Rufous turtle dove,Streptopelia orientalis, coming to the soybean field entered it from the outer part to eat soybean cotyledons. As a result, the injured plants extended from the outer to inner parts in the field. A model expressing these behaviours was constructed here, by assuming that the amount of food birds can eat in one block determines whether they stay there or move into neighbour block. As the food decrease due to exploitation of them by birds, birds enter into farther parts with the passage of time. The rate of feeding in all visiting birds (an ₀ wherea is the rate of feeding per individual andn ₀ the number of birds visiting) and the rate of staying at a block,b, was estimated from the field experimental results, using the above model. The value ofan ₀ fluctuated greatly, depending upon the season in which soybean seeds sowed. The value ofb also fluctuated inversely with that ofan ₀, suggesting the the staying rate decreases with an increase in the number of doves coming, probably because of interference among individuals.     

日本的东洋史研究

日本的东洋史研究,中国史占绝对多数。回顾东洋史研究,是按王朝和地域确定研究范围;文学的两大中心东京帝国大学和京都帝国大学有着不同的治学风格;对中国各时代的研究都有代表性的学者涌现。最近证实个别问题的研究较多,题目多种;人们关注新发掘的资料;中日历史学界考察、交流情况越来越多。日本除了在大学增设东洋史专业教育外,还拥有专门的研究机构,刊载东洋史的学术刊物陆续涌现。     

Wages of regular and irregular workers, the price of education, and income inequality

In this paper, we develop a model characterized by skill-biased technological change and increasing costs of education to investigate income inequality. Irregular workers cannot escape poverty by commencing investment in education because wage inequality between regular and irregular workers widens and the price of education increases with the average level of education. Moreover, if the productivity of elementary education is low relative to that of higher education, middle-income individuals are eventually unable to pursue higher education because the threshold for education expenditure rises with the price of education. Thus, income inequality may widen, even among regular workers.     

Determinants of contraceptive choice among Japanese women: ten years after the pill approval

The Japanese government approved the use of oral contraception (OC) in 1999, but OC users remain a small minority in Japan. Using the results of an online survey conducted in 2010, I examine the factors determining Japanese women’s choice of contraceptive method by estimating multinomial choice models. The estimation results indicate that OC use is positively associated with age, willingness to pay for contraceptive effectiveness, frequency of intercourse and experience with abortion or emergency contraception. These findings suggest that OC use increases as women learn from experience and that the low and declining frequency of intercourse in Japan offers one explanation for the slow diffusion of OC. Additionally, the findings indicate that OC use is more prevalent among women with a higher risk of unintended pregnancies. Subjective probabilities regarding each contraceptive method’s contraceptive effectiveness, disruption of romantic moods, partner disapproval, side benefits and minor, non-life-threatening side effects are important determinants of contraceptive choice. The perceived risk levels of OC side effects are significantly higher than the population-based probabilities, implying that increased medical knowledge might increase OC use.     

Estimation of firm-specific technological bias, technical change and total factor productivity growth: a dual approach

This paper deals with modeling firm-specific technical change (TC), and technological biases (inputs and scale) in estimating total factor productivity (TFP) growth. Several dual parametric econometric models are used for this purpose. We examine robustness of TFP growth and TC among competing models. These models include the traditional time trend (TT) model and the general index (GI) model. The TT and the GI models are generalized to accommodate firm-specific TC and technological bias (in inputs and output). Both nested and non-nested tests are used to select the appropriate models. Firm-level panel data from the Japanese chemical industry during 1968- 1987 is used as an application.     

The ingestion in wolf spiders II. The expression of degree of hunger and amount of ingestion in relation to spider's hunger

Summary To express the degree of hunger during both of feeding and unfeeding periods of spiders, equations for the amount of ingestion and food disappearance from the gut were presented using three components: capacity of gut, rate of ingestion and rate of food disappearance. The degree of hunger was expressed by the rate of unfilled capacity of gut to the capacity of gut based on these equations. The rates of ingestion and food disappearance were estimated from the results of experiment with a wolf spider,Pardosa laura. The equations obtained well applied to the experimental result. By changing values of these rates, it was revealed that the ratio of rates of ingestion to food disappearance determine the amount of ingestion.     

Strategic management in major Japanese hightech companies

Since the early 1980s, there has been remarkable progress in advanced technology in Japan and in leading Western countries. What is the present situation in technological development in major Japanese industries and what are the implications for strategic management? The author describes how Japanese industries have harnessed new technologies and suggests a number of concepts which underly these trends. Given the imperatives of advanced technology, he emphasizes the importance of positioning the technology development strategy in the context of strategic management paying particular attention to developing an open organizational culture through a flexible corporate planning system.