First- and Second-order Asymptotics for the Tail Distortion Risk Measure of Extreme Risks

The tail distortion risk measure at level p was first introduced in Zhu and Li (2012 Zhu, L., Li, H. (2012). Tail distortion risk and its asymptotic analysis. Insur. Math. Econ. 51(1):115–121.[Crossref], [Web of Science ®] , [Google Scholar]), where the parameter p ∈ (0, 1) indicates the confidence level. They established first-order asymptotics for this risk measure, as p↑1, for the Fréchet case. In this article, we extend their work by establishing both first-order and second-order asymptotics for the Fréchet, Weibull, and Gumbel cases. Numerical studies are also carried out to examine the accuracy of both asymptotics.     

Maximum likelihood estimation,from doubly censored samples,of the mean of a normal distribution with known coeffucient of variation

Let x be a random variable having the normal distribution with mean μ and variance c²μ², where c is a known constant. The maximum likelihood estimation of μ when the lowest r₁ and the highest r₂ sample values censored have been given the asymptotic variance of the maximum likelihood estimator is obtained.     

Asymptotically minimax non–parametric function estimation with positivity constraints I

The spatially inhomogeneous smoothness of the non-parametric density or regression-function to be estimated by non-parametric methods is often modelled by Besov- and Triebel-type smoothness constraints. For such problems, Donoho and Johnstone [D.L. Donoho and I.M. Johnstone, Minimax estimation via wavelet shrinkage. Ann. Stat. 26 (1998), pp. 879–921.], Delyon and Juditsky [B. Delyon and A. Juditsky, On minimax wavelet estimators, Appl. Comput. Harmon. Anal. 3 (1996), pp. 215–228.] studied minimax rates of convergence for wavelet estimators with thresholding, while Lepski et al. [O.V. Lepski, E. Mammen, and V.G. Spokoiny, Optimal spatial adaptation to inhomogeneous smoothness: an approach based on kernel estimators with variable bandwidth selectors, Ann. Stat. 25 (1997), pp. 929–947.] proposed a variable bandwidth selection for kernel estimators that achieved optimal rates over Besov classes. However, a second challenge in many real applications of non-parametric curve estimation is that the function must be positive. Here, we show how to construct estimators under positivity constraints that satisfy these constraints and also achieve minimax rates over the appropriate smoothness class.     

Indications for,and timing of,planned caesarean section: A systematic analysis of clinical guidelines

BackgroundThere has been a worldwide rise in planned caesarean sections over recent decades, with significant variations in practice between hospitals and countries. Guidelines are known to influence clinical decision-making and, potentially, unwarranted clinical variation. The aim of this study was to review guidelines for recommendations in relation to the timing and indications for planned caesarean section as well as recommendations around the process of decision-making.MethodA systematic search of national and international English-language guidelines published between 2008 and 2018 was undertaken. Guidelines were reviewed, assessed in terms of quality and extracted independently by two reviewers.FindingsIn total, 49 guidelines of varying quality were included. There was consistency between the guidelines in potential indications for caesarean section, although guidelines vary in terms of the level of detail. There was substantial variation in timing of birth, for example recommended timing of caesarean section for women with uncomplicated placenta praevia is between 36 and 39 weeks depending on the guideline. Only 11 guidelines provided detailed guidance on shared decision-making. In general, national-level guidelines from Australia, and overseas, received higher quality ratings than regional guidelines.ConclusionThe majority of guidelines, regardless of their quality, provide very limited information to guide shared decision-making or the timing of planned caesarean section, two of the most vital aspects of guidance. National guidelines were generally of better quality than regional ones, suggesting these should be used as a template where possible and emphasis placed on improving national guidelines and minimising intra-country, regional, variability of guidelines.     

Search for optimal designs in a three stagenested random model

In this paper we define a class of unbalanced designs, denoted by C_k,s,t, for estimating the components of variance in a k-stage nested random effects linear model. This class contains many of the designs proposed in the literature for nested components of variance models. We focus on the three-state model and discuss the determination of locally optimal designs within this class using a systematic computer search. For large sample sizes we show that approximate optimal designs may be obtained using a limit argument combined with numerical optimization. A comparison of our designs with previously published designs suggests that, in many cases, our designs result in substantial gains in efficiency.     

Syllable-final /s/ as an index of language,gender, and ethnicity in a contact variety of Mexican Spanish

This study of syllable-final /s/ reduction in a 55-speaker corpus of Spanish in Juchitán, México, a contact variety, uses both language contact and social processes to explain its results. Contact with the indigenous Isthmus Zapotec language leads to decreased rates of syllable-final /s/ retention, creating a locally salient n+1-order index between “Zapotecness” and /s/ reduction that influences the indexical field for syllable-final /s/ reduction. Zapotec identity is associated with tradition and femininity. Therefore, in this new indexical field, syllable-final /s/ reduction comes to directly index Zapotec language dominance and indirectly index both femininity and tradition. This leads feminine and elderly speakers to reduce /s/ more frequently than “less feminine” and young speakers, even though the opposite pattern is usually found in other varieties. The results show, therefore, that language contact can influence the indexical field typically linked to socially meaningful variation and thereby cause unexpected patterns of variation to emerge.     

蔡元培翻译观的认识论诠释

本文从哲学认识论的角度对蔡元培在《国文学讲义.叙言》中隐含的“译即易”的译学观点进行了诠释。认为翻译过程就是译者主体对于文本客体的认识活动,在这一认识过程中,译者主体的认知结构、价值观念、情感等都对翻译起着重要的作用,从而产生不同的认识结果即不同的译本。但译者主体作用的发挥最终还是要受到文本这个客体和原文本作者这另一主体的制约。文本内容,即原作者的思想仍旧是无法改变的。     

Remove unwanted variation retrieves unknown experimental designs

Remove unwanted variation (RUV) is an estimation and normalization system in which the underlying correlation structure of a multivariate dataset is estimated from negative control measurements, typically gene expression values, which are assumed to stay constant across experimental conditions. In this paper we derive the weight matrix which is estimated and incorporated into the generalized least squares estimates of RUV-inverse, and show that this weight matrix estimates the average covariance matrix across negative control measurements. RUV-inverse can thus be viewed as an estimation method adjusting for an unknown experimental design. We show that for a balanced incomplete block design (BIBD), RUV-inverse recovers intra- and interblock estimates of the relevant parameters and combines them as a weighted sum just like the best linear unbiased estimator (BLUE), except that the weights are globally estimated from the negative control measurements instead of being individually optimized to each measurement as in the classical, single measurement BIBD BLUE.     

Asymptotically optimal Berry-Esseen-type bounds for distributions with an absolutely continuous part

Recursive and closed form upper bounds are offered for the Kolmogorov and the total variation distance between the standard normal distribution and the distribution of a standardized sum of n independent and identically distributed random variables. The method employed is a modification of the method of compositions along with Zolotarev's ideal metric. The approximation error in the CLT obtained vanishes at a rate O(n^−k/2+1), provided that the common distribution of the summands possesses an absolutely continuous part, and shares the same k−1 (k?3) first moments with the standard normal distribution. Moreover, for the first time, these new uniform Berry-Esseen-type bounds are asymptotically optimal, that is, the ratio of the true distance to the respective bound converges to unity for a large class of distributions of the summands. Thus, apart from the correct rate, the proposed error estimates incorporate an optimal asymptotic constant (factor). Finally, three illustrative examples are presented along with numerical comparisons revealing that the new bounds are sharp enough even to be used in practical statistical applications.     

写实主义理论在日本近代的发展与变异

坪内逍遥提出的写实主义理论对日本近代文学的影响,一方面表现在催生了以二叶亭四迷为代表的现实主义文学的诞生,一方面为长谷川天溪等代表的自然主义理论提供了某些方法论的基础,从而引起人们对写实主义与自然主义在概念理解上的分歧。写实主义理论之所以会有这样的发展与变异,是因为日本近代的写实主义与左拉的自然主义都与实证主义哲学有着或明或暗的关系。