Modular knowledge systems accelerate human migration in asymmetric random environments

Migration is a key mechanism for expansion of communities. In spatially heterogeneous environments, rapidly gaining knowledge about the local environment is key to the evolutionary success of a migrating population. For historical human migration, environmental heterogeneity was naturally asymmetric in the north-south (NS) and east-west (EW) directions. We here consider the human migration process in the Americas, modeled as random, asymmetric, modularly correlated environments. Knowledge about the environments determines the fitness of each individual. We present a phase diagram for asymmetry of migration as a function of carrying capacity and fitness threshold. We find that the speed of migration is proportional to the inverse complement of the spatial environmental gradient, and in particular we find that north-south migration rates are lower than east-west migration rates when the environmental gradient is higher in the north-south direction. Communication of knowledge between individuals can help to spread beneficial knowledge within the population. The speed of migration increases when communication transmits pieces of knowledge that contribute in a modular way to the fitness of individuals. The results for the dependence of migration rate on asymmetry and modularity are consistent with existing archaeological observations. The results for asymmetry of genetic divergence are consistent with patterns of human gene flow.Comment: 13 pages, 6 figures, 1 table in Proc. Roy. Soc. Interface 201

On utilization of elliptical rings in assessing cracking tendency of concrete

A new experimental method by utilizing elliptical rings to replace circular rings recommended by ASTM and AASHTO was explored for assessing cracking potential of concrete and other cement-based materials under restrained condition. A series of thin and thick elliptical concrete rings were tested alongside circular ones until cracking. Cracking age, position, and propagation were carefully examined. It is found that thin elliptical rings with appropriate geometry can initiate cracks quicker than circular ones, which is desirable for accelerating the ring test. However, thick elliptical rings seem not to exhibit a desirable geometry effect of accelerating ring test compared with circular ones. There were multiple visible cracks that occurred in an elliptical ring and some cracks were initiated but did not propagate through the ring wall. In comparison, there was only one crack in the circular rings. Finally, the features of multiple cracks in restrained elliptical rings were examined and their impact on interpreting elliptical ring test results was elaborated. © 2014 4th International Conference on the Durability of Concrete Structures

A fracture mechanics-based method for prediction of cracking of circular and elliptical concrete rings under restrained shrinkage

A new experimental method, utilizing elliptical ring specimens, is developed for assessing the likelihood of cracking and cracking age of concrete subject to restrained shrinkage. To investigate the mechanism of this new ring test, a fracture mechanics-based numerical approach is proposed to predict crack initiation in restrained concrete rings by using the R-curve method. It has been found that numerical results accord well with experimental results in terms of cracking ages for both circular and elliptical concrete rings, indicating that the proposed fracture mechanics-based numerical approach is reliable for analyzing cracking in concrete ring specimens subject to restrained condition.UK Engineering and Physical Sciences Research Council under the grant of EP/I031952/1, and the National Natural Science Foundation of China under the grant of NSFC 51121005/5110902

A statistical framework for the design of microarray experiments and effective detection of differential gene expression

Four reasons why you might wish to read this paper: 1. We have devised a new statistical T test to determine differentially expressed genes (DEG) in the context of microarray experiments. This statistical test adds a new member to the traditional T-test family. 2. An exact formula for calculating the detection power of this T test is presented, which can also be fairly easily modified to cover the traditional T tests. 3. We have presented an accurate yet computationally very simple method to estimate the fraction of non-DEGs in a set of genes being tested. This method is superior to an existing one which is computationally much involved. 4. We approach the multiple testing problem from a fresh angle, and discuss its relation to the classical Bonferroni procedure and to the FDR (false discovery rate) approach. This is most useful in the analysis of microarray data, where typically several thousands of genes are being tested simultaneously.Comment: 9 pages, 1 table; to appear in Bioinformatic

High throughput powder diffraction: II Applications of clustering methods and multivariate data analysis

In high throughput crystallography is possible to accumulate over 1000 powder diffraction patterns on a series of related compounds, often polymorphs. We present a method that can analyse such data, automatically sort the patterns into related clusters or classes, characterise each cluster and identify any unusual samples containing, for example, unknown or unexpected polymorphs. Mixtures may be analysed quantitatively if a database of pure phases is available. A key component of the method is a set of visualisation tools based on dendrograms, cluster analysis, pie charts, principal component based score plots and metric multidimensional scaling. Applications are presented to pharmaceutical data, and inorganic compounds. The procedures have been incorporated into the PolySNAP commercial computer software

Strange matrix elements of the nucleon

Results for the disconnected contributions to matrix elements of the vector current and scalar density have been obtained for the nucleon from the Wilson action at beta=6 using a stochastic estimator technique and 2000 quenched configurations. Various methods for analysis are employed and chiral extrapolations are discussed.Comment: Lattice2002(matrixel), 3 pages, 3 figure