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81.
Model‐based phase I dose‐finding designs rely on a single model throughout the study for estimating the maximum tolerated dose (MTD). Thus, one major concern is about the choice of the most suitable model to be used. This is important because the dose allocation process and the MTD estimation depend on whether or not the model is reliable, or whether or not it gives a better fit to toxicity data. The aim of our work was to propose a method that would remove the need for a model choice prior to the trial onset and then allow it sequentially at each patient's inclusion. In this paper, we described model checking approach based on the posterior predictive check and model comparison approach based on the deviance information criterion, in order to identify a more reliable or better model during the course of a trial and to support clinical decision making. Further, we presented two model switching designs for a phase I cancer trial that were based on the aforementioned approaches, and performed a comparison between designs with or without model switching, through a simulation study. The results showed that the proposed designs had the advantage of decreasing certain risks, such as those of poor dose allocation and failure to find the MTD, which could occur if the model is misspecified. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
82.
Takashi Sekita 《Long Range Planning》1990,23(6):17-22
Yamato Transport Corporation recently entered the parcels business and has been very successful, taking the largest share of the market, in competition with the Japanese Post Office. By the use of a computerized information system, the company provides a rapid high quality service. Yamoto offers a pick up and delivery service. It uses retail stores for receiving the parcels and every driver has a small ‘point of sale’ terminal. The company has built its transportation network systematically, one step at a time. 相似文献
83.
84.
Sadao Tomizawa Takashi Seo Hideharu Yamamoto 《Journal of applied statistics》1998,25(3):387-398
For square contingency tables that have nominal categories, Tomizawa considered two kinds of measure to represent the degree of departure from symmetry. This paper proposes a generalization of those measures. The proposed measure is expressed by using the average of the power divergence of Cressie and Read, or the average of the diversity index of Patil and Taillie. Special cases of the proposed measure include Tomizawa's measures. The proposed measure would be useful for comparing the degree of departure from symmetry in several tables. 相似文献
85.
86.
Yukibumi Kaneko Keisuke Nakata Takashi Saitoh Nils Chr Stenseth Ottar N. Bj?rnstad 《Researches on Population Ecology》1998,40(1):21-37
The biology of the gray-sided voleClethrionomys rufocanus in Hokkaido, concerning taxonomy, morphology, phylogeny, distribution, and natural history, is reviewed. Applied issues in
forest management (damage, control and census) are also mentioned. AlthoughClethrionomys rufocanus of Hokkaido was originally identified as a distinct species,Evotomys (=nowClethrionomys) bedfordiae Thomas, 1905, current literature generally refers to the gray-sided vole of Hokkaido asClethrionomys rufocanus or asC. rufocanus bedfordiae (vernacular name, the Bedford’s red-backed vole). The gray-sided vole is the most common small mammal in Hokkaido. It inhabits
open areas as well as forests, and mainly feeds on green plants. The gray-sided vole has a high reproductive potential; litter
size: 4–7; gestation period: 18–19 days; maturation age: 30–60 days old. Although spring-born individuals usually attain sexual
maturity in their summer/fall of birth, their maturation is sometimes suppressed under high densities. The breeding season
is generally from April to October, but with some regional variation.Clethrionomys rufocanus has a rather specialized diet (folivorous), particularly during winter when it feeds on bamboo grass. Many predators specialize
on the grey-sided vole in Hokkaido; even the red fox, which is a typical generalist predator, selectively feeds on this vole.
Damage by voles’ eating bark used to be sever on forest plantations in Hokkaido. Censuses of small rodents have been carried
out for management purpose since 1954. 相似文献
87.
How does the development of collaborative research networks vary? This paper investigates how research networks have developed in the same technological fields in North America, Europe, and Asia. Exploring inter-organizational co-authored papers published in the Applied Physics Letters from 1975 to 1994, we first map the collaborative research networks and demonstrate that research networks were more developed in scale and scope in North America than in Europe and Asia in semiconductor laser technology. U.S. organizations played a nodal role in networking throughout this time period. Addressing how research networks were more developed in the U.S. than in Japan in particular, this paper concludes that engineer mobility, academic–industry relationships, and entrepreneurial startups were the key factors for the development of collaborative networks during the periods studied. 相似文献
88.
Current challenges for the study of population ecology of microtine rodents are reviewed. Comparisons with other taxonomic
groups (other mammals, birds and insects) are given throughout. A major challenge is to link patterns and processes (i.e.
mechanisms) better than is the case today. Other major challenges include the furthering of our understanding of the interaction
between deterministic and stochastic processes, and as part thereof, the interaction between density-dependent and density-independent
processes. The applicability of comparative studies on populations exhibiting different temporal dynamical patterns is, in
this connection, emphasized. Understanding spatiotemporal dynamical patterns is another major challenge, not the least from
a methodological point of view. Long-term and large-scale ecological data on population dynamics (in space and time) are critical
for this purpose. Looking for consistency between hypothesized mechanisms and observed patterns is emphasized as a good platform
for further empirical and theoretical work. The intellectual feedback process between different approaches to the study of
microtine population ecology (observational studies, experimental manipulative studies, statistical modeling and mathematical
modeling) are discussed. We recommend a pluralistic approach (involving both observational and experimental as well as theoretical
studies) to the study of small rodent ecology. 相似文献
89.
Ottar N. Bj?rnstad Nils Chr Stenseth Takashi Saitoh Ole Chr Lingj?rde 《Researches on Population Ecology》1998,40(1):77-84
We study the regional transitions in dynamics of the gray-sided vole,Clethrionomys rufocanus, within Hokkaido, Japan. The data-set consists of 225 time series of varying length (most from 23 to 31 years long) collected
between 1962 and 1992 by the Forestry Agency of the Japanese Government. To see clearly how the periodic behavior changes
geographically, we estimate the spectral density functions of the growth rates of all populations using a log-spline method.
We subsequently apply functional data analysis to the estimated densities. The functional data analysis is, in this context,
analogous to a principal component analysis applied to curves. We plot the results of the analysis on the map of Hokkaido,
to reveal a clear transition from relatively stable populations in the southwest and west to populations undergoing 3–4 year
cycles in the northeast and east. The degree of seasonality in the vegetation and the rodent demography appear to be strongest
in the cyclic area. We briefly speculate that the destabilization of the rodent dynamics is linked to increased seasonalforcing
on the trophic interactions in which the gray-sided voles are involved. 相似文献
90.
The clinical efficacy of a new treatment may often be better evaluated by two or more co-primary endpoints. Recently, in pharmaceutical drug development, there has been increasing discussion regarding establishing statistically significant favorable results on more than one endpoint in comparisons between treatments, which is referred to as a problem of multiple co-primary endpoints. Several methods have been proposed for calculating the sample size required to design a trial with multiple co-primary correlated endpoints. However, because these methods require users to have considerable mathematical sophistication and knowledge of programming techniques, their application and spread may be restricted in practice. To improve the convenience of these methods, in this paper, we provide a useful formula with accompanying numerical tables for sample size calculations to design clinical trials with two treatments, where the efficacy of a new treatment is demonstrated on continuous co-primary endpoints. In addition, we provide some examples to illustrate the sample size calculations made using the formula. Using the formula and the tables, which can be read according to the patterns of correlations and effect size ratios expected in multiple co-primary endpoints, makes it convenient to evaluate the required sample size promptly. 相似文献