油气田边远地区天然气资源的综合利用研究

油气田边远地区天然气资源包括油田放空天然气(主要是油田伴生气)和低产气井天然气,它们均因气量小,就地无用户和远离输气管网等原因长期未得到开发利用,不仅极大地浪费了资源,而且严重地污染了油田地区的大气。综述了国内外可用于油气田边远地区天然气资源开发利用的净化技术和综合利用技术,认为利用这部分天然气资源应依据气质、气量和市场需求选用合理的净化技术及利用技术,最后对吐哈油田边远地区天然气资源的综合利用进行了研究。     

Lassoing the Determinants of Retirement

This article uses Danish register data to explain the retirement decision of workers in 1990 and 1998. Many variables might be conjectured to influence this decision such as demographic, socioeconomic, financial, and health related variables as well as all the same factors for the spouse in case the individual is married. In total, we have access to 399 individual specific variables that all could potentially impact the retirement decision. We use variants of the least absolute shrinkage and selection operator (Lasso) and the adaptive Lasso applied to logistic regression in order to uncover determinants of the retirement decision. To the best of our knowledge, this is the first application of these estimators in microeconometrics to a problem of this type and scale. Furthermore, we investigate whether the factors influencing the retirement decision are stable over time, gender, and marital status. It is found that this is the case for core variables such as age, income, wealth, and general health. We also point out the most important differences between these groups and explain why these might be present.     

Power analysis for clustered non-continuous responses in multicenter trials

Power analysis for multi-center randomized control trials is quite difficult to perform for non-continuous responses when site differences are modeled by random effects using the generalized linear mixed-effects model (GLMM). First, it is not possible to construct power functions analytically, because of the extreme complexity of the sampling distribution of parameter estimates. Second, Monte Carlo (MC) simulation, a popular option for estimating power for complex models, does not work within the current context because of a lack of methods and software packages that would provide reliable estimates for fitting such GLMMs. For example, even statistical packages from software giants like SAS do not provide reliable estimates at the time of writing. Another major limitation of MC simulation is the lengthy running time, especially for complex models such as GLMM, especially when estimating power for multiple scenarios of interest. We present a new approach to address such limitations. The proposed approach defines a marginal model to approximate the GLMM and estimates power without relying on MC simulation. The approach is illustrated with both real and simulated data, with the simulation study demonstrating good performance of the method.     

Association of sexual abstinence in adolescence with mental health in adulthood

We examined whether adolescent sexual abstinence predicts better adult mental health. 1,917 adolescents, recruited from middle schools at age 13, were surveyed at ages 13, 18, 23, and 29. In bivariate analyses, adolescent sexual abstinence was associated with better mental health at age 29 for females, but not males; three adolescent factors, educational prospects, family bonding, and unconventionality were investigated as explanatory variables of this relationship. The abstinence-mental health relationship was nonsignificant when educational prospects was included in multivariate models, and marginally significant when family bonding and unconventionality were included; all three explanatory factors accounted for significant proportions of the variance in adult mental health. Girls who are uninvolved in school, have weak family backgrounds, and exhibit unconventionality may have poor adult mental health, whether or not they abstain from sex in adolescence. Interventions that strengthen adolescents' connections to families and schools may reduce risk for long-term mental health problems.     

Effects of a single-lesson tobacco prevention curriculum on knowledge, skill identification and smoking intention

One in five students report experimenting with tobacco before the age of 13 and most prevention efforts take place in the school setting. This study measures the effect of a single-lesson tobacco prevention curriculum, conducted by a health education center, focusing on knowledge of tobacco, ability to identify refusal techniques, and intent not to smoke. Data were collected, via electronic keypads, from students visiting a non-school, health education center in Michigan (n = 704 intervention and 85 comparison). Contingency table Chi-squared tests and t-tests demonstrated that a single lesson can improve general knowledge and ability to identify appropriate refusal techniques. Improvement in intent not to smoke was not significant because both groups had very high intent prior to implementation. Similar to results from other programs, multivariate logistic regression of gender, general knowledge, and skill identification revealed that only the skill variable was associated with intent not to smoke at pretest. Recommendations are given for further research and for designing more effective curricula or programs.     

Response Order Effects in Dichotomous Categorical Questions Presented Orally: The Impact of Question and Respondent Attributes

Using data from 548 experiments in telephone surveys conductedby the Gallup Organization, we explored how attributes of questionsand respondents moderate response order effects in dichotomouscategorical questions. These effects were predominantly recencyeffects and occurred most in questions that were more difficultto comprehend (especially among respondents with the least education),with response choices that were more difficult to comprehend(because they were complete sentences instead of words or phrasesand because they were not mutually exclusive), and that wereasked after many prior questions. Recency effects were alsomore common in questions that explicitly or implicitly encouragedrespondents to wait until they had heard all the answer choicesbefore formulating a judgment than in questions that inducedrespondents to begin formulating a judgment before all the answerchoices had been read (especially among the least educated respondents).A study of interviewer behavior revealed patterns of pausingbetween and within sentences that help to explain why some typesof questions are especially prone to recency effects and othersare not.     

Effects of at-work exercises on computer operators

At-work exercises are commonly recommended for computer operators. This randomized control trial assessed adherence, pain and satisfaction after 4 weeks of at-work exercise. Subjects (n=72) were randomized into 3 groups: resistance exercise, stretching, and control. Outcomes included a satisfaction survey, a visual analogue pain scale (VAS), a pain drawing, and the Neck Disability Index (NDI). The VAS, the drawing, and NDI were analyzed together as a composite variate referred to as Pain Impact. Exercise frequency was similar across the 3 groups (median=1.5 times per day). No differences were found between groups on Pain Impact p=0.714) or individual pain variables. Most satisfaction survey item scores did not differ between groups. However, a significant difference between groups on the survey item related to discomfort. The resistance and stretching group differed from the control group with regard to their perception that the exercises were helpful in reducing discomfort in the back and neck (p<0.001). We conclude that most subjects found the resistance and the stretching exercises easy to do, performed them 1 to 2 times daily, and said they reduced discomfort. To determine optimal type and frequency of at-work exercises, further study is needed.     

Effectiveness of a Web-based alcohol-misuse and harm-prevention course among high- and low-risk students

OBJECTIVE: In the current study, the authors assessed whether a new online alcohol-misuse prevention course (College Alc) is more effective at reducing alcohol use and related consequences among drinkers and nondrinkers. PARTICIPANTS: The authors compared incoming college freshmen who reported any past 30-day alcohol use before the beginning of the semester with those who did not. METHOD SUMMARY: The authors randomly assigned students who completed a precollege baseline survey to either complete a 3-hour noncredit version of College Alc or serve as members of a control group. The authors conducted a follow-up survey 3 months later. RESULTS: Findings indicated that among freshmen who were regular drinkers before college, College Alc appeared to reduce the frequency of heavy drinking, drunkenness, and negative alcohol-related consequences. Among freshmen who did not report any past-30-day alcohol use before college, College Alc did not appear to have any beneficial effects. CONCLUSIONS: Results suggest that College Alc may be an effective program for students with a history of alcohol use.     

College and university compliance with a required meningococcal vaccination law

OBJECTIVE: Maryland became the first state to pass a vaccination law requiring college and university students living on campus to obtain a meningococcal vaccination or to sign a waiver refusing vaccination because college students are at increased risk for disease. The authors sought to identify how Maryland colleges addressed the law and determine whether schools were in full compliance. PARTICIPANTS: The authors surveyed 32 college/university administrators via a self-administered questionnaire. METHODS: The authors calculated vaccination and waiver rates and assessed compliance with the law overall and with specific law components. RESULTS: Among 28 participating schools, annual vaccination rates and waiver rates among students during 2000-2004 ranged from 66%-76% and 12%-17%, respectively. Two (7%) schools were compliant with all components of the law. CONCLUSIONS: Mandatory vaccination laws do not ensure compliance at the college and university level. Mandatory reporting, increased education, and collaboration between colleges and universities and public health agencies are needed.