Asymptotic models and inference for extremes of spatio-temporal data

Recently there has been a lot of effort to model extremes of spatially dependent data. These efforts seem to be divided into two distinct groups: the study of max-stable processes, together with the development of statistical models within this framework; the use of more pragmatic, flexible models using Bayesian hierarchical models (BHM) and simulation based inference techniques. Each modeling strategy has its strong and weak points. While max-stable models capture the local behavior of spatial extremes correctly, hierarchical models based on the conditional independence assumption, lack the asymptotic arguments the max-stable models enjoy. On the other hand, they are very flexible in allowing the introduction of physical plausibility into the model. When the objective of the data analysis is to estimate return levels or kriging of extreme values in space, capturing the correct dependence structure between the extremes is crucial and max-stable processes are better suited for these purposes. However when the primary interest is to explain the sources of variation in extreme events Bayesian hierarchical modeling is a very flexible tool due to the ease with which random effects are incorporated in the model. In this paper we model a data set on Portuguese wildfires to show the flexibility of BHM in incorporating spatial dependencies acting at different resolutions

The effects of mining on a community in rural Syria : a case Study of mining in the region of ArRuhayba, Syria

This thesis addresses the effects of mining activities on the livelihoods of rural people and their environment in ArRuhayba, close to Syria’s capital Damascus. A public and political debate about such potential effects has not existed yet in Syria, probably because of the ongoing civil war in the country, which leaves a research gap to be filled. Hence, this study explores the effects mining activities have on the livelihoods of local people, who live in the proximity of the mining area, their environment and their lifeworld at large. This is conducted through using different methods to generate data, such as various forms of interviews and participant observation of the mining sites. The study finds that while mining activities have negative effects on the environment and the lifeworld of local people, the effects on the livelihood system of local people varies between negative effects and positive effects, that are influenced by multiple factors, such as the geographical location; the participation of the local people in carrying out the activities of mining; and the nature of activity. In addition, the study finds that the market economy approach influences the actors in the field who underestimates protecting the environment and considering sustainability. This facilitates the acceleration of mining activities and their expansion over a large geographical area in the absence of relevant regulatory rules and the absence of the participation of local people in the decision-making process. The findings of this study support the findings of many previous studies that address the same phenomenon. Consequently, the study fills a research gap in the field of rural development and natural resource management by addressing another context with different conditions

Absolute and convective instabilities of parallel propagating circularly polarized Alfven waves: Beat instability

Ruderman and Simpson [Phys. Plasmas 11, 4178 (2004)] studied the absolute and convective decay instabilities of parallel propagating circularly polarized Alfven waves in plasmas where the sound speed c(S) is smaller than the Alfven speed upsilon(A). We extend their analysis for the beat instability which occurs in plasmas with c(S)>upsilon(A). We assume that the dimensionless amplitude of the circularly polarized Alfven wave (pump wave), a, is small. Applying Briggs' method we study the problem analytically using expansions in power series with respect to a. It is shown that the pump wave is absolutely unstable in a reference frame moving with the velocity U with respect to the rest plasma if U-lU-r, the instability is convective. The signaling problem is studied in a reference frame where the pump wave is convectively unstable. It is shown that the spatially amplifying waves exist only when the signaling frequency is in two narrow symmetric frequency bands with the widths of the order of a(3). These results enable us to extend for the case when c(S)>upsilon(A) the conclusions, previously made for the case when c(S)<upsilon(A), that circularly polarized Alfven waves propagating in the solar wind are convectively unstable in a reference frame of any spacecraft moving with the velocity not exceeding a few tens of km/s in the solar reference frame. The characteristic scale of spatial amplification for these waves exceeds 1 a.u

Stomach cancer incidence in Southern Portugal 1998-2006:a spatio-temporal analysis

Understanding geographical differences in health, particularly in small areas, became a major concern of epidemiologists. Geographical association studies and, more recently, several spatial disease mapping studies have emerged due to the development of new spatial statistical tools. Among other diseases, these methods are being applied to analyze cancer data. However, in this kind of studies, it is of utmost importance to also investigate the influence of temporal variability and that is why spatio-temporal studies became so popular. The aim of this study is to investigate spatial and temporal trends for the incidence of this type of cancer. This retrospective population-based study is based on data on all stomach cancers registered by the Southern Portuguese Cancer Registry (ROR Sul) between 1998 and 2006. Because several studies have underlined the important role of socioeconomic status in cancer risk, information on this variable has also been taken into account. Bayesian hierarchical models were applied to model stomach incidence at a county level and resulting relative risks were used to build risk maps for cancer incidence. Age-Period-Cohort models were also applied.N/