Estimation of Benchmark Dose of Lifetime Cadmium Intake for Adverse Renal Effects Using Hybrid Approach in Inhabitants of an Environmentally Exposed River Basin in Japan

The aim of this study is to estimate the reference level of lifetime cadmium intake (LCd) as the benchmark doses (BMDs) and their 95% lower confidence limits (BMDLs) for various renal effects by applying a hybrid approach. The participants comprised 3,013 (1,362 men and 1,651 women) and 278 (129 men and 149 women) inhabitants of the Cd‐polluted and nonpolluted areas, respectively, in the environmentally exposed Kakehashi River basin. Glucose, protein, aminonitrogen, metallothionein, and β₂‐microglobulin in urine were measured as indicators of renal dysfunction. The BMD and BMDL that corresponded to an additional risk of 5% were calculated with background risk at zero exposure set at 5%. The obtained BMDLs of LCd were 3.7 g (glucose), 3.2 g (protein), 3.7 g (aminonitrogen), 1.7 g (metallothionein), and 1.8 g (β₂‐microglobulin) in men and 2.9 g (glucose), 2.5 g (protein), 2.0 g (aminonitrogen), 1.6 g (metallothionein), and 1.3 g (β₂‐microglobulin) in women. The lowest BMDL was 1.7 g (metallothionein) and 1.3 g (β₂‐microglobulin) in men and women, respectively. The lowest BMDL of LCd (1.3 g) was somewhat lower than the representative threshold LCd (2.0 g) calculated in the previous studies. The obtained BMDLs may contribute to further discussion on the health risk assessment of cadmium exposure.     

Cumulants of random sum distributions

Consider a random variable S being the sum of a number N of independent and identically distributed random variables X_j (j = 1, 2, ...) where the number N is itself a non-negative integer-valued random variable independent of the X_j An explicit expression of the r-th cumulant of S is given in terms of the cumulants of N and X_j, Asymptotic properties of the distribution of S are also discussed.     

利用智能主体分析"时尚"的涌现

时尚作为一种社会现象,是由个别人物的倡导和示范,先在少数人中流行,然后迅速蔓延到社会.多数人出于新奇与从众心理而仿效.对于它的研究有助于人们把握这种社会现象的产生与蔓延过程,深入认识和控制它的发展.由于它的复杂多样性,当前还缺乏对它的定量分析与研究.论文利用基于智能主体的仿真方法,分析了时尚的涌现过程.文中建立了两种模型,用于确定公众能否接受某种时尚的临界值.一种模型基于公众能获取全部信息,另一种则基于个人只能获取邻近信息.     

Recurrence formula on the joint distribution of sample skewness and kurtosis under normality

Abstract

Two recurrence relations with respect to sample size are given concerning the joint distribution of skewness and kurtosis of random observations from a normal population: one between the probability density functions and the other between the product moments. As a consequence, the latter yields a recurrence formula for the moments of sample kurtosis. The exact moments of Jarque-Bera statistic is also given.     

日本对外经济政策的演变(上)——从日美产业结构调整磋商到东亚共同体构想的提出

20世纪90年代,日本对外经济政策经历了两个方面的模式转变:第一,在贸易摩擦的应对和处理方面,摆脱了以往重视双边磋商和达成妥协的作法,转向通过多边框架以法律途径解决争端的轨道;第二,在贸易与投资自由化的促进方面,从多边主义转向了区域主义和双边主义。本文主要探讨导致这一模式转变的原因、模式转变过程中的促进势力和抵制势力以及抵制势力被克服的政策形成过程、两个模式之间的矛盾与冲突以及模式转变的稳定性等问题,在此基础上分析和展望日本今后的对外经济政策走向。     

Optimal training plans on physical performance considering supercompensation

Abstract

A quantitative evaluation of athletic training is one of the most important issues in the sports science, and its optimization problem between fitness and fatigue has to be considered. Although fitness is the gain of athletic training and athletes can acquire extensive fitness by hard training, they cannot continue such training for a long time because of fatigue. After the hard training which exceeds the physical capacity of athletes, a delayed onset muscle soreness (DOMS) appears and they cannot continue the same training hereafter. Because DOMS impedes the progress of training, it must be avoided when the training plan is made. By continuing training for a long period, the performance capacity of athlete body has enhanced and they can endure hard and long training with which it could not tolerate before, and such performance capacity enhancement is called supercompensation. In a planning athletic training, its optimization problem between fitness and fatigue should be discussed considering, both DOMS and supercompensation by forming probabilistic models of fitness and fatigue, optimal training plans which maximize the total fitness during training periods and minimize the occurrence of DOMS are discussed analytically and numerically.     

Restricted mean survival time as a summary measure of time‐to‐event outcome

Many clinical research studies evaluate a time‐to‐event outcome, illustrate survival functions, and conventionally report estimated hazard ratios to express the magnitude of the treatment effect when comparing between groups. However, it may not be straightforward to interpret the hazard ratio clinically and statistically when the proportional hazards assumption is invalid. In some recent papers published in clinical journals, the use of restricted mean survival time (RMST) or τ ‐year mean survival time is discussed as one of the alternative summary measures for the time‐to‐event outcome. The RMST is defined as the expected value of time to event limited to a specific time point corresponding to the area under the survival curve up to the specific time point. This article summarizes the necessary information to conduct statistical analysis using the RMST, including the definition and statistical properties of the RMST, adjusted analysis methods, sample size calculation, information fraction for the RMST difference, and clinical and statistical meaning and interpretation. Additionally, we discuss how to set the specific time point to define the RMST from two main points of view. We also provide developed SAS codes to determine the sample size required to detect an expected RMST difference with appropriate power and reconstruct individual survival data to estimate an RMST reference value from a reported survival curve.     

Replacement policies for age and working numbers with random life cycle

It has been modeled for several replacement policies in literatures that the whole life cycle or operating interval of an operating unit should be finite rather than infinite as is done with the traditional method. However, it is more natural to consider the case in which the finite life cycle is a fluctuated parameter that could be used to estimate replacement times, which will be taken up in this article. For this, we first formulate a general model in which the unit is replaced at random age U, random time Y for the first working number, random life cycle S, or at failure X, whichever occurs first. The following models included in the general model, such that replacement done at age T when variable U is a degenerate distribution, and replacement done at working numbers N summed by number N of variable Y, are optimized. We obtain the total expected cost until replacement and the expected replacement cost rate for each model. Optimal age T, working number N, and a pair of (T, N) are discussed analytically and computed numerically.     

Cross-sectional analysis between prostate volumes and serum sex hormones in Japanese men attending a urological clinic

Aim: To evaluate epidemiologically the association between measured prostate volume and sex hormones.

Methods: Between December 2012 and September 2014, 226 patients attending the urological clinic were assessed for the relationship between prostate volume (PV) and, serum sex hormones, physical size, personal habits, etc. Prostate volume was measured by using transabdominal ultrasonography. Statistically, the Pearson correlation coefficients test was used.

Results: Total cases, the cases of PV?≤?25?ml, and the cases of PV?>?25?ml were evaluated respectively. Total cases and the cases of PV?>?25?ml showed a positive significant correlation with testosterone (T), but the cases of PV?≤?25?ml showed no such correlation. The cases of PV?>?25?ml had a positive significant correlation with estradiol (E2), but total cases and cases of PV?≤?25?ml did not. Dehydroepiandrosterone sulfate (DHEAS) showed no correlation with any case of PV, however it decreased significantly with age and had a correlation with alopecia. The E2/T ratio had no correlation with any case of PV, but on the other hand, the T/DHEAS and E2/DHEAS ratios had significant positive correlation with PV?>?25?ml.

Conclusions: Serum T and E2 had significant positive correlation with measured PV especially in larger prostates. This result seems to correspond with the conventional theory that T and E2 have an etiological effect on benign prostatic hyperplasia. DHEAS did not show direct correlation with PV, however it appeared to suppress the role of T and E2 on benign prostatic hyperplasia growth. DHEAS might be a key to understanding the etiology of benign prostatic hyperplasia with aging.