The interaction of aging and 10 years of racing on ultraendurance running performance

The aim of this study was to examine the interaction between aging and 10 years of racing in endurance runners. Race-time data from 194 runners who had completed 10 consecutive 56-km ultramarathons were obtained. The runners were either 20.5 +/- 0.7, 30.0 +/- 1.0, 39.9 +/- 0.9, or 49.4 +/- 1.0 years old at their first race. Each runner's race speed was determined for each race over the 10 years. Data were analyzed using repeated-measures ANOVA, one-way ANOVA, and independent t tests and showed that performance improved and declined at greater rates for younger runners; younger runners had a greater capacity for improvement than older runners; approximately 4 years were required to reach peak racing speed, regardless of age; it was not possible to compete at peak speed for more than a few years; and the combined effects of 10 years of aging and racing neither improve nor worsen net performance. In conclusion, these data suggest that although these runners showed similar patterns of change in race speed over a 10-year period, the extent of change in performance was greater in younger than in older runners.     

Pitfalls in portfolio planning

This paper presents an analysis and comparison of the Boston Consulting Group, McKinsey & Co., and Arthur D. Little portfolio models and a discussion of the theoretical and operational problems with the general portfolio construct. The models seem to share the goal of optimizing the firm's financial performance and the same fundamental assumptions. The strategies suggested by each model will not always be the same because of differences in the structure of the three models. Also strategic analysis of each unit is necessary to avoid the pitfalls caused by the theoretical and operational problems with the portfolio construct.     

Infrence for non-negative autoregressive schemes

The object of this paper is the statistical analysis of Several Closely related models arising in water quality analysis. In particular, concern is with the autoregressive scheme X_r = ρX_r?1 + Y_r where 0 < ρ < 1 and Y's are i.i.d, and non-negative. The estimation and testing problem is considered for three parametric models - Gaussian, uniform and exponential - as well as for the nonparametric case where it is assumed that the Y's have a positive continuous distribution.     

An augmented data scoring algorithm for maximum likelihood

The expectation-maximization (EM) method facilitates computation of max¬imum likelihood (ML) and maximum penalized likelihood (MPL) solutions. The procedure requires specification of unobservabie complete data which augment the measured or incomplete data. This specification defines a conditional expectation of the complete data log-likelihood function which is computed in the E-stcp. The EM algorithm is most effective when maximizing the iunction Q{0) denned in the F-stnp is easier than maximizing the likelihood function.

The Monte Carlo EM (MCEM) algorithm of Wei & Tanner (1990) was introduced for problems where computation of Q is difficult or intractable. However Monte Carlo can he computationally expensive, e.g. in signal processing applications involving large numbers of parameters. We provide another approach: a modification of thc standard EM algorithm avoiding computation of conditional expectations.     

A Note on Overdifferencing and the Equivalence of Seasonal Time Series Models With Monthly Means and Models With (0, 1, 1)12 Seasonal Parts When ⊖ = 1

Two general models for monthly seasonal time series are considered, one in which seasonality is modeled with monthly means and another in which seasonality is modeled with a (0, 1, 1)₁₂ ARIMA structure. The models are shown to be equivalent if the seasonal moving average parameter (?) is 1 and if the same assumptions about the 12 initial observations are made for both models. The role of the assumptions about the initial observations is analyzed, and it is argued that for practical purposes the two models can be regarded as equivalent when ? = 1. It is observed that the result extends easily to more general models involving overdifferencing.     

《周易》与北宋治国理政思想——以《宋朝诸臣奏议》为中心的考察

北宋士大夫为复兴三代之治,重建王道政治秩序,主张以经术治天下,重视经学的经世功能。在探索王道的过程中,士大夫以《周易》为经世之大法而推崇备至,并注重运用《周易》义理指导现实的政治实践。他们通过在奏议中引用《周易》经义议论时政,为朝廷提出合乎圣人之道的治国之策以实现儒家通经致用的理想。在北宋奏议中,士大夫不仅以《周易》经义培育皇帝的政治道德,而且还从《周易》中厘定出内政治理原则施用于今,从修己、治人两方面充分展现了易学的经世指向。他们以《周易》经义作为评判现实政治得失的标准,批评并制止不合经义的政治行为,规正政治发展方向,从而使《周易》对北宋治国理政思想产生了深远影响。     

Measuring community mobilization in the Seattle Minority Youth Health Project.

This article assesses the validity and reliability of the approach used to measure community mobilization in the Seattle Minority Youth Health Project (MY Health), a neighborhood-based program to prevent drug use, violence, teen pregnancy, and sexually transmitted diseases (STDs). Two constructs were measured: neighborhood cooperation in solving problems, and sense of pride and identification with the neighborhood. The convergent validity of the measurement approach was assessed by comparing several independent measures of community mobilization generated from surveys of key neighborhood leaders, youth, and parents. For the neighborhood cooperation construct, correlations were uniformly positive across measures from different surveys and statistically significant about a quarter of the time. The correlations for the neighborhood pride construct were weaker and generally not statistically significant. Interrater reliability was low for all of the surveys, possibly reflecting varying ideas about what community mobilization meant among survey respondents.