Misspecified prediction for time series

Let {X_t} be a stationary process with spectral density g(λ).It is often that the true structure g(λ) is not completely specified. This paper discusses the problem of misspecified prediction when a conjectured spectral density f_θ(λ), θ∈Θ, is fitted to g(λ). Then, constructing the best linear predictor based on f_θ(λ), we can evaluate the prediction error M(θ). Since θ is unknown we estimate it by a quasi‐MLE . The second‐order asymptotic approximation of is given. This result is extended to the case when X_t contains some trend, i.e. a time series regression model. These results are very general. Furthermore we evaluate the second‐order asymptotic approximation of for a time series regression model having a long‐memory residual process with the true spectral density g(λ). Since the general formulae of the approximated prediction error are complicated, we provide some numerical examples. Then we illuminate unexpected effects from the misspecification of spectra. Copyright © 2001 John Wiley & Sons, Ltd.     

西部大开发带给图书馆事业的机遇和挑战

在西部大开发中,面对机遇和挑战,图书馆应充分发挥自身优势,有效地利用信息资源,服务于西部地区经济发展,实现图书馆社会价值,为加快西部大开发做出贡献.     

Genome-wide association analysis identifies 20 loci that influence adult height

Adult height is a model polygenic trait, but there has been limited success in identifying the genes underlying its normal variation. To identify genetic variants influencing adult human height, we used genome-wide association data from 13,665 individuals and genotyped 39 variants in an additional 16,482 samples. We identified 20 variants associated with adult height (P < 5 x 10(-7), with 10 reaching P < 1 x 10(-10)). Combined, the 20 SNPs explain approximately 3% of height variation, with a approximately 5 cm difference between the 6.2% of people with 17 or fewer 'tall' alleles compared to the 5.5% with 27 or more 'tall' alleles. The loci we identified implicate genes in Hedgehog signaling (IHH, HHIP, PTCH1), extracellular matrix (EFEMP1, ADAMTSL3, ACAN) and cancer (CDK6, HMGA2, DLEU7) pathways, and provide new insights into human growth and developmental processes. Finally, our results provide insights into the genetic architecture of a classic quantitative trait.     

Thirty new loci for age at menarche identified by a meta-analysis of genome-wide association studies

To identify loci for age at menarche, we performed a meta-analysis of 32 genome-wide association studies in 87,802 women of European descent, with replication in up to 14,731 women. In addition to the known loci at LIN28B (P = 5.4 × 10???) and 9q31.2 (P = 2.2 × 10?33), we identified 30 new menarche loci (all P < 5 × 10??) and found suggestive evidence for a further 10 loci (P < 1.9 × 10??). The new loci included four previously associated with body mass index (in or near FTO, SEC16B, TRA2B and TMEM18), three in or near other genes implicated in energy homeostasis (BSX, CRTC1 and MCHR2) and three in or near genes implicated in hormonal regulation (INHBA, PCSK2 and RXRG). Ingenuity and gene-set enrichment pathway analyses identified coenzyme A and fatty acid biosynthesis as biological processes related to menarche timing.     

Engineering microbes for targeted strikes against human pathogens

Lack of pathogen specificity in antimicrobial therapy causes non-discriminant microbial cell killing that disrupts the microflora present. As a result, potentially helpful microbial cells are killed along with the pathogen, altering the biodiversity and dynamic interactions within the population. Moreover, the unwarranted exposure of antibiotics to microbes increases the likelihood of developing resistance and perpetuates the emergence of multidrug resistance. Synthetic biology offers an alternative solution where specificity can be conferred to reduce the non-specific, non-targeted activity of currently available antibiotics, and instead provides targeted therapy against specific pathogens and minimising collateral damage to the host’s inherent microbiota. With a greater understanding of the microbiome and the available genetic engineering tools for microbial cells, it is possible to devise antimicrobial strategies for novel antimicrobial therapy that are able to precisely and selectively remove infectious pathogens. Herein, we review the strategies developed by unlocking some of the natural mechanisms used by the microbes and how these may be utilised in targeted antimicrobial therapy, with the promise of reducing the current global bane of multidrug antimicrobial resistance.     

A three-parameter fault-detection software reliability model with the uncertainty of operating environments

As requirements for system quality have increased, the need for high system reliability is also increasing. Software systems are extremely important, in terms of enhanced reliability and stability, for providing high quality services to customers. However, because of the complexity of software systems, software development can be time-consuming and expensive. Many statistical models have been developed in the past years to estimate software reliability. In this paper, we propose a new three-parameter fault-detection software reliability model with the uncertainty of operating environments. The explicit mean value function solution for the proposed model is presented. Examples are presented to illustrate the goodness-of-fit of the proposed model and several existing non-homogeneous Poisson process (NHPP) models based on three sets of failure data collected from software applications. The results show that the proposed model fits significantly better than other existing NHPP models based on three criteria such as mean squared error (MSE), predictive ratio risk (PRR), and predictive power (PP).     

风中声速与时间相对性计算公式

本文根据无风声速的现有知识 ,通过数学推导 ,得到了风中声速公式和时间相对性公式     

SPIN90 dephosphorylation is required for cofilin-mediated actin depolymerization in NMDA-stimulated hippocampal neurons

Actin plays a fundamental role in the regulation of spine morphology (both shrinkage and enlargement) upon synaptic activation. In particular, actin depolymerization is crucial for the spine shrinkage in NMDAR-mediated synaptic depression. Here, we define the role of SPIN90 phosphorylation/dephosphorylation in regulating actin depolymerization via modulation of cofilin activity. When neurons were treated with NMDA, SPIN90 was dephosphorylated by STEP61 (striatal-enriched protein tyrosine phosphatase) and translocated from the spines to the dendritic shafts. In addition, phosphorylated SPIN90 bound cofilin and then inhibited cofilin activity, suggesting that SPIN90 dephosphorylation is a prerequisite step for releasing cofilin so that cofilin can adequately sever actin filaments into monomeric form. We found that SPIN90 YE, a phosphomimetic mutant, remained in the spines after NMDAR activation where it bound cofilin, thereby effectively preventing actin depolymerization. This led to inhibition of the activity-dependent redistribution of cortactin and drebrin A, as well as of the morphological changes in the spines that underlie synaptic plasticity. These findings indicate that NMDA-induced SPIN90 dephosphorylation and translocation initiates cofilin-mediated actin dynamics and spine shrinkage within dendritic spines, thereby modulating synaptic activity.     

业余少儿体操训练三角形管理模式的实验研究

运用实验方法，提出并验证了三角形管理模式在业余少儿体操训练中的积极作用。实验表明，在业余少儿体操训练过程中运用三角形模式进行管理，可以有效提高训练效果，有利于运动员再次选材，促进少儿健康地发展。     

Molecular basis of xeroderma pigmentosum group C DNA recognition by engineered meganucleases

Xeroderma pigmentosum is a monogenic disease characterized by hypersensitivity to ultraviolet light. The cells of xeroderma pigmentosum patients are defective in nucleotide excision repair, limiting their capacity to eliminate ultraviolet-induced DNA damage, and resulting in a strong predisposition to develop skin cancers. The use of rare cutting DNA endonucleases-such as homing endonucleases, also known as meganucleases-constitutes one possible strategy for repairing DNA lesions. Homing endonucleases have emerged as highly specific molecular scalpels that recognize and cleave DNA sites, promoting efficient homologous gene targeting through double-strand-break-induced homologous recombination. Here we describe two engineered heterodimeric derivatives of the homing endonuclease I-CreI, produced by a semi-rational approach. These two molecules-Amel3-Amel4 and Ini3-Ini4-cleave DNA from the human XPC gene (xeroderma pigmentosum group C), in vitro and in vivo. Crystal structures of the I-CreI variants complexed with intact and cleaved XPC target DNA suggest that the mechanism of DNA recognition and cleavage by the engineered homing endonucleases is similar to that of the wild-type I-CreI. Furthermore, these derivatives induced high levels of specific gene targeting in mammalian cells while displaying no obvious genotoxicity. Thus, homing endonucleases can be designed to recognize and cleave the DNA sequences of specific genes, opening up new possibilities for genome engineering and gene therapy in xeroderma pigmentosum patients whose illness can be treated ex vivo.