On the limitations of comparing mean square forecast errors

Linear models are invariant under non-singular, scale-preserving linear transformations, whereas mean square forecast errors (MSFEs) are not. Different rankings may result across models or methods from choosing alternative yet isomorphic representations of a process. One approach can dominate others for comparisons in levels, yet lose to another for differences, to a second for cointegrating vectors and to a third for combinations of variables. The potential for switches in ranking is related to criticisms of the inadequacy of MSFE against encompassing criteria, which are invariant under linear transforms and entail MSFE dominance. An invariant evaluation criterion which avoids misleading outcomes is examined in a Monte Carlo study of forecasting methods.     

Clustering the rows and columns of a contingency table

A number of ways of investigating heterogeneity in a two-way contingency table are reviewed. In particular, we consider chi-square decompositions of the Pearson chi-square statistic with respect to the nodes of a hierarchical clustering of the rows and/or the columns of the table. A cut-off point which indicates significant clustering may be defined on the binary trees associated with the respective row and column cluster analyses. This approach provides a simple graphical procedure which is useful in interpreting a significant chi-square statistic of a contingency table.The author gratefully acknowledges the constructive comments of the referees and the editor.     

Microstructure and functional morphology of the Early Cambrian problematical fossil Rhombocorniculum

Rhombocorniculum cancellatum from the Lower Cambrian of southern Shaanxi Province (South China) is represented by the dextral and sinistral tooth-like sclerites (both in nearly equal numbers), indicating that the body plan of the organism with these sclerites probably was bilaterian. The main feature of the microstructure of the sclerites is the presence of longitudinally arranged, mutually contiguous hollow tubules, the shared walls consisting of microcrystalline apatite. In transverse cross sections, the sclerite wall mainly exhibits a spongy structure, with pore size decreasing adapically. Functional morphological analysis indicates that the sclerites serve as a defensive rather than a grasping function.     

Cadmium is a mutagen that acts by inhibiting mismatch repair

Most errors that arise during DNA replication can be corrected by DNA polymerase proofreading or by post-replication mismatch repair (MMR). Inactivation of both mutation-avoidance systems results in extremely high mutability that can lead to error catastrophe. High mutability and the likelihood of cancer can be caused by mutations and epigenetic changes that reduce MMR. Hypermutability can also be caused by external factors that directly inhibit MMR. Identifying such factors has important implications for understanding the role of the environment in genome stability. We found that chronic exposure of yeast to environmentally relevant concentrations of cadmium, a known human carcinogen, can result in extreme hypermutability. The mutation specificity along with responses in proofreading-deficient and MMR-deficient mutants indicate that cadmium reduces the capacity for MMR of small misalignments and base-base mismatches. In extracts of human cells, cadmium inhibited at least one step leading to mismatch removal. Together, our data show that a high level of genetic instability can result from environmental impediment of a mutation-avoidance system.     

Complex reorganization and predominant non-homologous repair following chromosomal breakage in karyotypically balanced germline rearrangements and transgenic integration

We defined the genetic landscape of balanced chromosomal rearrangements at nucleotide resolution by sequencing 141 breakpoints from cytogenetically interpreted translocations and inversions. We confirm that the recently described phenomenon of 'chromothripsis' (massive chromosomal shattering and reorganization) is not unique to cancer cells but also occurs in the germline, where it can resolve to a relatively balanced state with frequent inversions. We detected a high incidence of complex rearrangements (19.2%) and substantially less reliance on microhomology (31%) than previously observed in benign copy-number variants (CNVs). We compared these results to experimentally generated DNA breakage-repair by sequencing seven transgenic animals, revealing extensive rearrangement of the transgene and host genome with similar complexity to human germline alterations. Inversion was the most common rearrangement, suggesting that a combined mechanism involving template switching and non-homologous repair mediates the formation of balanced complex rearrangements that are viable, stably replicated and transmitted unaltered to subsequent generations.     

基于多源浮动车数据融合的道路交通运行评估

针对当前出租车浮动车数据覆盖范围和数据质量不足的问题,在现有数据特征分析的基础上引入百度手机导航和公交车浮动车导航数据,面向道路运行评估和拥堵管理提出了基于出行时间的交通运行指数算法和一种基于出租车、百度、公交车多源浮动车数据融合的道路交通运行评估方法,构建了多源数据融合规则和融合算法.以深圳为例进行了融合效果分析,结果表明所提出的多源数据融合方法效果显著,很大程度上提高了融合结果精度、数据覆盖率、数据可靠性和数据样本量,最后提出了主要应用方向和初步应用效果,能够为国内外城市开展交通运行评估工作提供借鉴.     

断层相互作用产生同震库仑应力改变分布图像

讨论了同震库仑应力改变的基本含义,以及基于静应力位错理论求解同震库仑应力改变的边界元方法,对与发震断层相互平行和相互垂直两种典型构造模式下,断层相互作用产生的同震库仑应力改变进行了数值模拟研究,分别获取了相应条件下的同震库仑应力改变空间分布图像.结果表明:不同构造模式的断层相互作用,其产生的同震库仑应力改变分布图像存在较大差异,在分析和评价断层相互作用产生的同震库仑应力改变,及其对活动断层地震危险性的影响时,应该充分考虑待评价断层与发震断层之间的空间几何关系、断层的性质和产状等特定的构造条件.     

Constant darkness is a circadian metabolic signal in mammals

Environmental light is the 'zeitgeber' (time-giver) of circadian behaviour. Constant darkness is considered a 'free-running' circadian state. Mammals encounter constant darkness during hibernation. Ablation of the master clock synchronizer, the suprachiasmatic nucleus, abolishes torpor, a hibernation-like state, implicating the circadian clock in this phenomenon. Here we report a mechanism by which constant darkness regulates the gene expression of fat catabolic enzymes in mice. Genes for murine procolipase (mClps) and pancreatic lipase-related protein 2 (mPlrp2) are activated in a circadian manner in peripheral organs during 12 h dark:12 h dark (DD) but not light-dark (LD) cycles. This mechanism is deregulated in circadian-deficient mPer1-/-/mPer2m/m mice. We identified circadian-regulated 5'-AMP, which is elevated in the blood of DD mice, as a key mediator of this response. Synthetic 5'-AMP induced torpor and mClps expression in LD animals. Torpor induced by metabolic stress was associated with elevated 5'-AMP levels in DD mice. Levels of glucose and non-esterified fatty acid in the blood are reversed in DD and LD mice. Induction of mClps expression by 5'-AMP in LD mice was reciprocally linked to blood glucose levels. Our findings uncover a circadian metabolic rhythm in mammals.