Statistical inference for DNA sequences of promoters: a non-stationary qualitative model

ABSTRACT

Gene promoters have variable repartition of AGCT nucleotides according to some probabilistic behaviours essentially depending on their position in a string. The paper aims to provide a model for this configuration. With this model we derive non-uniform confidence bounds for those probability distributions in the strings. A uniform bound deriving from previous works in Wu and Zhao [Inference of trends in time series. J R Stat Soc B. 2007;69:391–410] is more demanding for the model. A data-based study allows to clarify our suggestions and open the way for applications in molecular biology.     

Telecommunications Network Design—Comparison of Alternative Approaches

The design and development of the network infrastructure to support mission‐critical applications has become a critical and‐complex activity. This study explores the use of genetic algorithms (GA) for network design in the context of degree‐constrained minimal spanning tree (DCMST) problem; compares for small networks the performance of GA with a mathematical model that provides optimal solutions; and for larger networks, compares GA's performance with two heuristic methods—edge exchange and primal algorithm. Two performance measures, solution quality and computation time, are used for evaluation. The algorithms are evaluated on a wide variety of network sizes with both static and dynamic degree constraints on the network nodes. The results indicate that GA provides optimal solutions for small networks. For larger networks it provides better solution quality compared to edge exchange and primal method, but is worse than the two methods in computation time.     

MML Markov classification of sequential data

General purpose un-supervised classification programs have typically assumed independence between observations in the data they analyse. In this paper we report on an extension to the MML classifier Snob which enables the program to take advantage of some of the extra information implicit in ordered datasets (such as time-series). Specifically the data is modelled as if it were generated from a first order Markov process with as many states as there are classes of observation. The state of such a process at any point in the sequence determines the class from which the corresponding observation is generated. Such a model is commonly referred to as a Hidden Markov Model. The MML calculation for the expected length of a near optimal two-part message stating a specific model of this type and a dataset given this model is presented. Such an estimate enables us to fairly compare models which differ in the number of classes they specify which in turn can guide a robust un-supervised search of the model space. The new program, tSnob, is tested against both synthetic data and a large real world dataset and is found to make unbiased estimates of model parameters and to conduct an effective search of the extended model space.     

Modelling safety climate in the prediction of levels of safety activity

This study examined the architecture of the relationships between components of organizational safety climate, including employee attitudes to safety issues and perceptions of the work environment, and related this to self-reported levels of safety activity. Data were collected from a large multinational manufacturing organization by questionnaire. A total of 915 valid questionnaires were returned and formed the basis for structural equation modelling and subsequent analyses. These data showed that a common structure, or architecture, of attitudes to safety issues and perceptions of the work environment could be constructed that explained levels of safety activity. The strength of employees' attitudes with regard to safety management played a pivotal role in this model through both direct and indirect paths. This is consistent with earlier findings on the importance of management commitment in organizations with well developed safety cultures. An examination of the differences between plants/sites showed that employees differed in their attitudes to safety issues, such as the management of safety and communication, and in their perceptions of workplace hazards. It is intended that this model be further utilized within the organization under study as a basis for monitoring safety performance and planned improvements in safety.     

大同御河兴云桥的历史及建筑形制

御河是大同市内最主要的一条河流，它由北而南从城东门外流过。作为东出必经之路，御河桥上建置桥梁有着悠久的历史。目前，根据考古出土文物及参考文献可以得知，御河上建桥有确切记载始于金代，它是一座五拱石桥，元代重修时命名“兴云桥”。金代御河桥经元明二代历时四百余年，万历八年拓故基重建为十九孔石拱桥，‘仍名兴云桥，清嘉庆年间倾圯。     

Environmental taxation and the double dividend hypothesis in CGE modelling literature: A critical review

Computable general equilibrium (CGE) modelling is a flexible and open way to model the economic systems that allow practitioners to assess the impacts of different policies or external shocks over an economic system. There is some empirical literature dedicated to test the double dividend hypothesis of an environmental tax reform using CGE models. This hypothesis claims that is possible to obtain an improvement of both environmental and economic conditions by imposing an environmental tax and recycling revenues obtained to reduce other pre-existing taxes. This research provides a comprehensive review of this literature including a statistical and a meta-regression analysis. 69 different simulations from 40 studies have been analyzed. 55% of simulations have achieved a double dividend, concluding that although the environmental dividend is almost always achieved, the economic dividend still remains an ambiguous question that needs further research.