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     

Goodness of fit for the inverse Gaussian distribution

For testing the fit of the inverse Gaussian distribution with unknown parameters, the empirical distribution-function statistic A² is studied. Two procedures are followed in constructing the test statistic; they yield the same asymptotic distribution. In the first procedure the parameters in the distribution function are directly estimated, and in the second the distribution function is estimated by its Rao-Blackwell distribution estimator. A table is given for the asymptotic critical points of A². These are shown to depend only on the ratio of the unknown parameters. An analysis is provided of the effect of estimating the ratio to enter the table for A². This analysis enables the proposal of the complete operating procedure, which is sustained by a Monte Carlo study.     

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.     

The historical decline of fertility in Eastern Europe

I test the hypothesis that the growth of autonomy was the factor responsible for the decline of marital fertility in eight Eastern European countries. By growth of autonomy I mean increased control over one's political, personal, religious, economic and reproductive life. This increased control was manifested in revolutions, democratic political reforms, nationalist movements and declining marital fertility. The political reforms were the result of the growth of autonomy but they also accelerated the dissemination of these new ideas among the populace contributing to further growth of autonomy. My hypothesis is generally supported by the historical data.     

Screening for patients with alcohol problems: severity of patients identified by the CAGE.

Primary care physicians are well situated to identify patients with substance abuse problems and motivate them to seek appropriate assistance, but active programs are the exception. A study in a community setting was undertaken to assess the CAGE (the first letters of key words in a series of four questions about drinking: cut down; annoyed; guilty; and eye-opener), instrument in the routine screening for alcohol problems in both new and established patients. The screening process identified subjects for a pilot evaluation of a motivational interview designed to encourage problem-solving behavior. This article focuses on the screening results and the use of the CAGE instrument. During June and July of 1990, 687 patients of two primary care physicians belonging to a large group practice were asked to complete a health questionnaire that included the CAGE. Those who responded affirmatively to at least two of the four CAGE questions were requested to participate in follow-up assessment of problems associated with alcohol and health. The type and severity of alcohol problems experienced by patients who scored positive on the CAGE are described. Prevalence of a positive score on the CAGE was 8.6 percent with males, smokers, and blue collar and unemployed persons being more likely to score positive. The positive predictive value was .68. Primarily, persons with moderate alcohol problems were identified. Results show that the CAGE instrument is a useful screening device for identifying those with mild to moderate substance abuse problems, increasing the opportunity for intervention prior to serious medical complications. The instrument is easily administered, and has demonstrated relatively high levels of sensitivity and specificity. When combined with assessment and motivational interviews, the CAGE shows promise in the secondary prevention of substance abuse and related health problems.     

Negotiating Role Definitions and the Working Consensus in Self-Work*

Definitions of social roles and the maintenance of a working consensus are two kinds of background expectations which are important for actors’accomplishment of self-work. Interactionists have traditionally assumed that these background expectations are unambiguously available to social actors as they negotiate situated meanings of selves and situations. Using data from dyadic role-play conversations, this study examines instances where interactants reference these expectations as ambiguous or problematic. The findings show that the situated meanings of role definitions and the working consensus are continually subject to potential negotiation. The implications of these findings for future research and theory on self-work in social interaction are discussed.