A Composite Likelihood-based Approach for Change-point Detection in Spatio-temporal Process

This paper develops a unified, accurate and computationally efficient method for change-point inference in non-stationary spatio-temporal processes. By modeling a non-stationary spatio-temporal process as a piecewise stationary spatio-temporal process, we consider simultaneous estimation of the number and locations of change-points, and model parameters in each segment. A composite likelihood-based criterion is developed for change-point and parameters estimation. Asymptotic theories including consistency and distribution of the estimators are derived under mild conditions. In contrast to classical results in fixed dimensional time series that the asymptotic error of change-point estimator is $O_{p}(1)$, exact recovery of true change-points is guaranteed in the spatio-temporal setting. More surprisingly, the consistency of change-point estimation can be achieved without any penalty term in the criterion function. A computational efficient pruned dynamic programming algorithm is developed for the challenging criterion optimization problem. Simulation studies and an application to U.S. precipitation data are provided to demonstrate the effectiveness and practicality of the proposed method

A novice-expert comparison in information search

In the age of Google, it is commonly believed that university students, especially those at postgraduate level, should have attained enough information searching skills to support their studies. However, recent researches have found that the information literacy level of quite a few postgraduate students is, in fact, far from satisfactory. One possible way for information search specialists to help students effectively search information is to use a novice-expert comparison to examine the differences between novices and experts in information search. The aim of this study is to uncover some of the major differences in the search query statements and information search strategies between eight doctoral students (novice searchers) and an expert information literacy professional. Preliminary findings show that conspicuous differences do exist in the complexity of the formulation of query statements, choice of keywords, use of operators between the novice and the expert searchers.postprin

Doctoral students' development in information literacy

This paper aims to investigate how doctoral level students developed their information literacy in the beginning years of their doctoral research by focusing on the sources, databases and search engines they found relevant, the difficulties they encountered when engaging in information search with different databases, and the affordances offered by the databases which they found useful. This study adopts a one-year longitudinal approach which involved students‟ interactions with a search expert who showed them how to conduct searches more effectively. A combination of quantitative and qualitative data collection methods, such as surveys, interviews, think-aloud protocol, and direct observation were used. The goal is to identify students‟ initial searching abilities and their performance after receiving guidance from an expert. Vygotsky’s social learning theory is used as the theoretical lens. Social learning theory argues that interactions with the more capable ones in the environment stimulate developmental processes and foster cognitive growth. For example, teachers and learners can work together on a difficult task with the teachers providing scaffolding to students. As such, students can complete tasks that they could not have completed on their own. The relationship between the teacher and the learner is essential in student learning as acquiring knowledge and skills from an experienced other is an important method for developing competence in a task. Social learning theory could also be applied into the information seeking situation where a master-apprentice relationship could be a possible solution to improve doctoral students‟ information literacy skills, where scaffolding support by information search experts could probably help them to improve their search techniques.postprin

Evolutionary dynamics on any population structure

Evolution occurs in populations of reproducing individuals. The structure of a biological population affects which traits evolve. Understanding evolutionary game dynamics in structured populations is difficult. Precise results have been absent for a long time, but have recently emerged for special structures where all individuals have the same number of neighbors. But the problem of determining which trait is favored by selection in the natural case where the number of neighbors can vary, has remained open. For arbitrary selection intensity, the problem is in a computational complexity class which suggests there is no efficient algorithm. Whether there exists a simple solution for weak selection was unanswered. Here we provide, surprisingly, a general formula for weak selection that applies to any graph or social network. Our method uses coalescent theory and relies on calculating the meeting times of random walks. We can now evaluate large numbers of diverse and heterogeneous population structures for their propensity to favor cooperation. We can also study how small changes in population structure---graph surgery---affect evolutionary outcomes. We find that cooperation flourishes most in societies that are based on strong pairwise ties.Comment: 68 pages, 10 figure

Facing Challenges in a New Age : A Multicultural and New Generation Identity for Japan, through Kaneshiro Takeshi and Kubozuka Yōsuke

Globalization, Localization, and Japanese Studies in the Asia-Pacific Region : Past, Present, Future, Chinese University of Hong Kong,　2005年9月30日-10月4

Short-chain fatty acids in breast milk and their relationship with the infant gut microbiota

IntroductionThe short-chain fatty acids (SCFAs) contained in breast milk play a key role in infant growth, affecting metabolism and enhancing intestinal immunity by regulating inflammation.MethodsIn order to examine the associations between the microbiota and SCFA levels in breast milk, and explore the roles of SCFAs in regulating the infant gut microbiota, we enrolled 50 paired mothers and infants and collected both breast milk and infant fecal samples. Breast milk SCFA contents were determined by UPLC-MS, and whole genome shotgun sequencing was applied to determine the microbial composition of breast milk and infant feces. The SCFA levels in breast milk were grouped into tertiles as high, medium, or low, and the differences of intestinal microbiota and KEGG pathways were compared among groups.ResultsThe results demonstrated that breast milk butyric acid (C4) is significantly associated with Clostridium leptum richness in breastmilk. Additionally, the specific Bifidobacterium may have an interactive symbiosis with the main species of C4-producing bacteria in human milk. Women with a low breast milk C4 tertile are associated with a high abundance of Salmonella and Salmonella enterica in their infants' feces. KEGG pathway analysis further showed that the content of C4 in breast milk is significantly correlated with the infants' metabolic pathways of lysine and arginine biosynthesis.DiscussionThis study suggests that interactive symbiosis of the microbiota exists in breast milk. Certain breast milk microbes could be beneficial by producing C4 and further influence the abundance of certain gut microbes in infants, playing an important role in early immune and metabolic development

Characterization of the RNA-binding properties of the triple-gene-block protein 2 of Bamboo mosaic virus

The triple-gene-block protein 2 (TGBp2) of Bamboo mosaic virus (BaMV) is a transmembrane protein which was proposed to be involved in viral RNA binding during virus transport. Here, we report on the RNA-binding properties of TGBp2. Using tyrosine fluorescence spectroscopy and UV-crosslinking assays, the TGBp2 solubilized with Triton X-100 was found to interact with viral RNA in a non-specific manner. These results raise the possibility that TGBp2 facilitates intracellular delivery of viral RNA through non-specific protein-RNA interaction