Markov chain Monte Carlo methods for high dimensional inversion in remote sensing

Summary.  We discuss the inversion of the gas profiles (ozone, NO₃, NO₂, aerosols and neutral density) in the upper atmosphere from the spectral occultation measurements. The data are produced by the 'Global ozone monitoring of occultation of stars' instrument on board the Envisat satellite that was launched in March 2002. The instrument measures the attenuation of light spectra at various horizontal paths from about 100 km down to 10–20 km. The new feature is that these data allow the inversion of the gas concentration height profiles. A short introduction is given to the present operational data management procedure with examples of the first real data inversion. Several solution options for a more comprehensive statistical inversion are presented. A direct inversion leads to a non-linear model with hundreds of parameters to be estimated. The problem is solved with an adaptive single-step Markov chain Monte Carlo algorithm. Another approach is to divide the problem into several non-linear smaller dimensional problems, to run parallel adaptive Markov chain Monte Carlo chains for them and to solve the gas profiles in repetitive linear steps. The effect of grid size is discussed, and we present how the prior regularization takes the grid size into account in a way that effectively leads to a grid-independent inversion.     

领导权理论与后现代思潮

英国著名教授E·拉克劳以其拓展马克思主义的革命理论而闻名,并成为西方“后马克思主义”的著名代表人物之一。在其代表作《领导权与社会主义策略》(“Hegemony”一词,曾有“文化霸权”等译法;但本文译者认为,在拉克劳的著作中,他主要是在“国家、革命、阶级和革命的领导者”等意义上来谈论这一范畴的,所以在这里把“hegemony”译为“领导权”)一书中,拉克劳把马克思主义的领导权理论与后结构主义等当代“时髦”理论相结合的尝试引人注目,但也备受争议。为此,他在另一本著作《我们时代革命的新反思》一书中,系统地回答了《领导权与社会主义策略》一书中的有关问题。这些问题涉及其领导权理论与社会主义革命在当今社会现实中所面临的理论困境,包括革命的主体、阶级的构成、阶级斗争、对立和认同等等。此外,领导权理论还涉及其与现代西方哲学思潮的内在逻辑联系,如胡塞尔的现象学、维特根斯坦的后分析哲学、德里达的解构主义以及其他的后现代主义理论等。针对这些理论和现实问题,拉克劳一一进行了认真的回答和阐述。英国《新左派评论》编委会的部分成员罗宾(Robin Blackburn)、彼德(Peter Dews)和安娜(Anna-Marie Smith)于1988年5月策划专访拉克劳。以下访谈是从拉克劳《我们时代革命的新反思》一书中选译     

UNDERSTANDING THE DECISION TO PARTICIPATE IN A SURVEY

The lack of full participation in sample surveys threatens theinferential value of the survey method. We review a set of conceptualdevelopments and experimental findings that appear to be informativeabout causes of survey participation; offer an integration ofthat work with findings from the more traditional statisticaland survey methodological literature on nonresponse; and, giventhe theoretical structure, deduce potentially promising pathsof research toward the understanding of survey participation.     

Campus attitudes toward alcohol and drugs in a deep southern university.

In our zeal to deal with alcohol and drug abuse, we may have a distorted picture of what the majority of college students actually think about alcohol and drug use. Students in this study done at a public university located in the Deep South report being generally intolerant of substance abuse.     

Fast retraction of evidence in a probabilistic expert system

We present and justify a propagation algorithm to facilitate the simultaneous calculation, for every node in a probabilistic exper system of the distribution of the associated random quantity, conditional on all the evidence obtained about the remaining nodes.     

MEASURING LEVELS OF PARTY IDENTIFICATION DOES QUESTION ORDER MATTER?

This article examines whether asking the vote question beforeparty identification alters the strength of partisanship andits relationship to vote choice. It employs the 1992 BritishElection Survey, which included a random split half-sample experiment,and the 1992–93 American Election Study Panel, where thequestion order for party identification and the vote were changed.The results show that altering the question ordering had verylittle effect in Britain and no significant effect in the UnitedStates. These results are consistent with the notion that partyidentification is one of the more enduring and stable componentsof mass political behavior in both presidential and parliamentarysystems.     

Differences in preferred level of arousal in two sub-groups of problem gamblers: A preliminary report

Twelve problem poker machine players and thirteen horse race gamblers (20 males and 5 females; age range 28–69) completed a series of questionnaires which assessed levels of anxiety, their preferred state of arousal and their motivations to gamble. As predicted, problem poker machine gamblers were found to be more anxious and reported avoiding arousal more frequently than the horse race gamblers. Alternately, problem horse race gamblers were found to prefer heightened levels of arousal and appeared to gamble to achieve these optimal levels of arousal. However, there was no difference between the groups on proneness to boredom. The present results provide evidence which is consistent with the Reversal theory and its application to the field of problem gambling.