Determining the Tsallis parameter via maximum entropy.

The nonextensive entropic measure proposed by Tsallis [C. Tsallis, J. Stat. Phys. 52, 479 (1988)] introduces a parameter, q, which is not defined but rather must be determined. The value of q is typically determined from a piece of data and then fixed over the range of interest. On the other hand, from a phenomenological viewpoint, there are instances in which q cannot be treated as a constant. We present two distinct approaches for determining q depending on the form of the equations of constraint for the particular system. In the first case the equations of constraint for the operator Ô can be written as Tr(F(q)Ô)=C, where C may be an explicit function of the distribution function F. We show that in this case one can solve an equivalent maxent problem which yields q as a function of the corresponding Lagrange multiplier. As an illustration the exact solution of the static generalized Fokker-Planck equation (GFPE) is obtained from maxent with the Tsallis enropy. As in the case where C is a constant, if q is treated as a variable within the maxent framework the entropic measure is maximized trivially for all values of q. Therefore q must be determined from existing data. In the second case an additional equation of constraint exists which cannot be brought into the above form. In this case the additional equation of constraint may be used to determine the fixed value of q.

In situ diffusion experiment in granite: phase I.

A program of in situ experiments, supported by laboratory studies, was initiated to study diffusion in sparsely fractured rock (SFR), with a goal of developing an understanding of diffusion processes within intact crystalline rock. Phase I of the in situ diffusion experiment was started in 1996, with the purpose of developing a methodology for estimating diffusion parameter values. Four in situ diffusion experiments, using a conservative iodide tracer, were performed in highly stressed SFR at a depth of 450 m in the Underground Research Laboratory (URL). The experiments, performed over a 2 year period, yielded rock permeability estimates of 2 x 10(-21) m(2) and effective diffusion coefficients varying from 2.1 x 10(-14) to 1.9 x 10(-13) m(2)/s, which were estimated using the MOTIF code. The in situ diffusion profiles reveal a characteristic "dog leg" pattern, with iodide concentrations decreasing rapidly within a centimeter of the open borehole wall. It is hypothesized that this is an artifact of local stress redistribution and creation of a zone of increased constrictivity close to the borehole wall. A comparison of estimated in situ and laboratory diffusivities and permeabilities provides evidence that the physical properties of rock samples removed from high-stress regimes change. As a result of the lessons learnt during Phase I, a Phase II in situ program has been initiated to improve our general understanding of diffusion in SFR.

The impact of T-ACASI interviewing on reported drug use among men who have sex with men.

Measurements of drug use and other illicit or stigmatized behaviors are subject to nontrivial underreporting biases. During in-person surveys, respondents are more likely to report such behaviors when interviewed using techniques that maximize interviewee privacy, e.g., use of paper SAQs and audio-CASI rather than questioning by human interviewers. Until recently, respondents in telephone surveys could not be offered similar privacy. A new technology, telephone audio computer-assisted self-interviewing (T-ACASI) overcomes this limitation of telephone surveys by allowing respondents to respond to a computer. A randomized experimental test of T-ACASI was embedded in the Urban Men's Health Study (UMHS). UMHS surveyed a probability sample of 2,881 men from four United States cities and who reported having sex with men. Respondents interviewed using T-ACASI reported a higher prevalence of drug use and drug-related behaviors than respondents interviewed by human interviewers. However, survey respondents were more likely to break off an interview when the interview was conducted by a T-ACASI computer rather than by a human interviewer.

Correlates of sexually transmitted bacterial infections among U.S. women in 1995.

CONTEXT: Sexually transmitted diseases (STDs) of bacterial origin such as gonorrhea and chlamydial infection can lead to pelvic inflammatory disease (PID) and infertility. Identifying behaviors and characteristics associated with infection may assist in preventing these often asymptomatic diseases and their sequelae. METHODS: Data from 9,882 sexually active women who participated in the 1995 National Survey of Family Growth describe the characteristics of women who report a history of infection with a bacterial STD or of treatment for PID. Multivariate analysis is used to determine which demographic characteristics and sexual and health-related behaviors affect the likelihood of infection or the occurrence of complications. RESULTS: Overall, 6% of sexually active women reported a history of a bacterial STD, and 8% reported a history of PID. Women who first had sexual intercourse before age 15 were nearly four times as likely to report a bacterial STD, and more than twice as likely to report PID, as were women who first had sex after age 18. Having more than five lifetime sexual partners also was associated with both having an STD and having PID. PID was more common among women reporting a history of a bacterial STD (23%) than among women who reported no such history (7%). In multivariate analyses, age, race, age at first intercourse and lifetime number of sexual partners had a significant effect on the risk of a bacterial STD. Education, age, a history of IUD use, douching and a history of a bacterial STD had a significant impact on the risk of PID, but early onset of intercourse did not, and lifetime number of partners had only a marginal effect. CONCLUSIONS: The pattern of characteristics and behaviors that place women at risk of infection with bacterial STDs is not uniform among groups of women. Further, the level of self-reported PID would suggest higher rates of gonorrhea and chlamydial infection than reported.

Monitoring the health status and impact of treatment on Americans: the Medicare Beneficiary Health Status Registry.

OBJECTIVE: A major new survey program, the Medicare Beneficiary Health Status Registry (MBHSR), has been proposed to improve the monitoring of the health status of Medicare beneficiaries. The MBHSR would collect data by mail with telephone follow up of nonrespondents to permit economical assessment of a total Registry of approximately 200,000 Medicare beneficiaries, approximately 54,000 of whom would be surveyed in any given year. (Surveys would be conducted of samples of new enrollees who would be reinterviewed every five years.) METHOD: To assess the feasibility of that approach, a field test was conducted with a probability sample (n = 1,922) that comprised approximately equal numbers of new Medicare enrollees (aged, 65) and current beneficiaries (age range, 76-80). The field test was designed to assess the quality of the data that this design would produce. FINDINGS: Results indicate that the proposed design of the MBHSR could achieve response rates of approximately 80% among both age cohorts using a survey instrument that took 30 minutes to complete. Internal reliability of Activities of Daily Living, Instrumental Activities of Daily Living, Mobility, Mental Health Index, General Health, and Prostate Symptomatology scales ranged from 0.77 to 0.93. When measurements were repeated approximately 30 days after the initial survey, moderate to high levels of cross temporal correlation (range, 0.64-0.96) were found for most indexes, with the exception of prostate symptomatology. In addition, an earlier comparison of survey responses in the MBHSR field test to Medicare payment records indicated that the MBHSR field test obtained highly accurate reports of most of the major surgeries that were recorded in Medicare claims files. CONCLUSION: The design proposed for the MBHSR is feasible. If implemented, it should produce acceptably high rates of response and data quality.

Effects of interview mode on bias in survey measurements of drug use: do respondent characteristics make a difference?

Three recent empirical studies have provided strong evidence that self-administered questionnaires (SAQs), compared with interviewer questioning, substantially improve the reporting of drug use in population surveys. Specifically, SAQs appear to diminish underreporting bias. Two of these studies previously reported that this effect of interview mode varied significantly across gender, race/ethnicity, and age. Data from a randomized experiment embedded in the 1990 National Household Survey of Drug Abuse (NHSDA) field test were reanalyzed to test for those interaction effects. To better replicate prior studies, the NHSDA field test sample was restricted to people ages 18 to 45 (N = 1,877). The results of our statistical analyses generally replicated the finding of a main effect of SAQs on the reporting of drug use. However, only weak evidence was found to support the hypothesis that the advantage of SAQs varies substantially by the gender, race/ethnicity, or age of the respondent.

CD40-tumor necrosis factor receptor-associated factor (TRAF) interactions: regulation of CD40 signaling through multiple TRAF binding sites and TRAF hetero-oligomerization.

CD40 is a TNF receptor superfamily member that provides activation signals in antigen-presenting cells such as B cells, macrophages, and dendritic cells. Multimerization of CD40 by its ligand initiates signaling by recruiting TNF receptor-associated factors (TRAFs) to the CD40 cytoplasmic domain. Recombinant human TRAF proteins overexpressed in insect cells were biochemically characterized and used to finely map TRAF binding regions in the human CD40 cytoplasmic domain. TRAF1, TRAF2, TRAF3, and TRAF6, but not TRAF4 or TRAF5, bound directly to the CD40 cytoplasmic domain. CD40 interactions with TRAF2 and TRAF3 were stronger than the interactions with TRAF1 and TRAF6. Full-length TRAF3 and TRAF5 formed hetero-oligomers, presumably through their predicted isoleucine zippers. TRAF3-TRAF5 hetero-oligomers interacted with CD40, indicating that TRAF5 can be indirectly recruited to the CD40 cytoplasmic domain. Overlapping peptides synthesized on cellulose membranes were used to map each TRAF interaction region. TRAF1, TRAF2, and TRAF3 interacted with the same region. The recognition site for TRAF6 was a nonoverlapping membrane proximal region. Using peptides with progressive deletions, a minimal TRAF1, TRAF2, and TRAF3 binding region was mapped to the PVQET sequence in the CD40 cytoplasmic domain. The minimal region for TRAF6 binding was the sequence QEPQEINF. These studies demonstrate that the CD40 cytoplasmic domain contains two nonoverlapping TRAF binding regions and suggest that TRAF1, TRAF2, and TRAF3 could bind competitively to one site. Relative affinities and competition of individual and hetero-oligomeric TRAF proteins for CD40 binding sites may contribute to receptor specificity and cell-type selectivity in CD40-dependent signaling.

Zenilman's anomaly reconsidered: fallible reports, ceteris paribus, and other hypotheses.

BACKGROUND AND OBJECTIVES: In the January-February, 1995 issue of Sexually Transmitted Diseases, Zenilman and colleagues reported a null association between incident sexually transmitted diseases (STDs) and self-reported condom use. That anomalous finding generated a flurry of letters to the editor, some of which were quite heated. This article reconsiders the Zenilman team's results. STUDY DESIGN: New statistical analyses were conducted to test two hypotheses that sought to account for the null association: (1) deviation from study protocol, and (2) differential risks of acquiring an incident STD among segments of the study population that varied by reported level of condom use. RESULTS: No support was found for hypotheses concerning deviation from study protocol and differential risk of acquiring an incident STD by level of condom use. Indeed, for respondents who reported multiple sexual partners, the analyses found increased rates of infection among those who reported more consistent condom use. CONCLUSIONS: Two of the most promising hypotheses for explaining Zenilman's anomalous findings are unsupported by reanalysis of the available empirical evidence. It is still possible that respondents who reported that they used condoms consistently differed from self-reported nonusers or inconsistent users in some way that altered their risk of acquiring an STD and thus obscured the protective effects of properly used condoms. Nonetheless, as Zenilman and others suggest, fallibility in self-reports of condom use remains the primary suspect as the cause of these anomalous results. Such fallibility may be particularly pronounced when self-reported behavioral data are collected in contexts that include strong educational campaigns or other norm-setting interventions.

Monitoring trends in drug use: strategies for the 21st century.

Since the 1970s the United States and other nations have conducted regular statistical monitoring of the prevalence and patterns of drug use in their populations. Given the importance of such surveys for policymaking, their quality is a critical issue, and the biases that may affect their measurements become a major concern. An increasing volume of empirical evidence shows that the mode of administration of a survey can strongly influence the validity of respondents' reports. Compared with interviewer-administered questionnaires, self-administered forms appear to elicit more complete reporting of drug use, but the challenges they pose to the literacy skills of respondents may result in measurement biases. In addition, processes of social change may confound true shifts in drug use with changes in the willingness of respondents to report such use. The authors propose several strategies to improve monitoring of trends in drug use. Those approaches include 1) more frequent use of a survey technology--audio computer-assisted self-interviewing--that ensures full privacy for all survey respondents but does not require literacy; 2) increased use of time-series of indicators of drug use consequences built from blinded surveys of medical records; and 3) population-based surveys that collect biological specimens (e.g., hair samples). Data from the latter two sources are not subject to the same constellation of biases that afflict self-reports of drug use. Time-series of those data can be integrated with self-reports to provide a better understanding of changes over time in the prevalence and patterns of drug use.

Quality of treatment data. Reliability over time of self-reports given by clients in treatment for substance abuse.

This study examines the reliability over a 2-month period of self-reports of drug use, sexual behaviors, and use of treatment services provided by 2,968 clients participating in a large, multisite, prospective study of drug treatment in the United States-the Drug Abuse Treatment Outcome Study (DATOS). Analyses focus on responses to 62 pairs of logically related questions that were asked at two points in time: (1) 1 month after entry into treatment, and (2) 3 months after entry into treatment. Subjects' responses to questions asked at these two time points are assessed for logical consistency. Prior analyses of self-reports provided by DATOS clients at one point in time (entry into treatment) found surprisingly high levels of within-interview consistency in their reporting of alcohol use (Turner & Hubbard, 1995) and cocaine use (Adair, Craddock, Miller, & Turner, 1995). The crosstemporal tests of consistency reported in this article eliminate several potential sources of artifactual consistency that may have affected prior analyses, (e.g., consistency imposed by an interviewer or constructed by a respondent during the course of a single interview). Contrary to expectations, crosstemporal comparisons reveal high levels of logical consistency in clients' responses. The mean percent of substantively inconsistent responses ranges from 0.7% for questions asking about frequency of drug use to 4.4% for questions asking about sexual behaviors.

Assessing consistency of responses to questions on cocaine use.

This study examines consistency of self-reported responses to items within the questionnaire of a multi-site, prospective study of drug abuse treatment in the United States (DATOS). The analyses use data from 2842 interviewer-administered intake interviews. Questions that were logically related are paired and responses compared. The questions cover three topics: (1) age at which different types of cocaine was used, (2) reports on most recent use and (3) frequency of cocaine use during period of "heaviest" use. Responses are coded as consistent, inconsistent, or as survey administration error. The latter is related to interviewer errors such as erroneous skip pattern, out-of-range responses, "don't know" responses, missing data, or illegible responses. Contrary to expectations inconsistent responses were relatively rare in this study, with fewer than 5% (0.5-4.6%) of respondents reporting inconsistent answers for pairs of logically related questions. A careful review of responses also found few survey administration errors (0.2-1.3%).

Negative pressure pulmonary edema.

Pulmonary Edema associated with negative airway pressure caused by upper airway obstruction is a most serious complications in anaesthetic practice (Tami et al, 1986). Laryngospasm associated with intubation and general anaesthesia is the most common cause of upper airway obstruction leading to negative pressure pulmonary edema (NPPE) in the anaesthetic adult (Tami et al, 1986). Other risk factors for the development of upper airway obstruction are identified, and individuals at risk should be observed closely while they remain at risk during the post anaesthetic period. NPPE appears to be related to markedly negative intrathoracic pressure due to forced inspiration against a closed upper airway resulting in transudation of fluid from pulmonary capillaries to the interstitium. The following is a presentation of a case of a healthy young male who developed NPPE secondary to airway obstruction caused by biting down on the endotracheal tube while awakening from general anaesthesia.

Response to heavy nitrogen applications in fertilizer experiments in British forests.

Increasing concern over the level of nitrogen inputs to forests in polluted rain has led to a number of suggestions of possible adverse consequences under the general heading of nitrogen saturation. A saturated ecosystem may be one (a) in which the trees show no growth response to the addition of further nitrogen, (b) in which addition of further nitrogen leads to growth disturbances or reduction, or (c) in which elevated nitrogen inputs lead to increased losses of nitrate in streamwater. Experience gained from forest fertilizer experiments is used to examine each of these suggestions. A definition involving a lack of growth response (a) is shown to be based on a lack of understanding of the continuing changing patterns of nitrogen demand and mineralization in even-aged forests. Similarly, using growth disturbances (b) is unsatisfactory because, it is suggested, these are either secondary deficiencies that appear once growth accelerates with added nitrogen or are a consequence of changing growth with increasing size. A definition based on increased loss of nitrate is, by analogy with the situation for sulphate, at least superficially attractive. However, the fact that nitrate retention is predominantly biological, rather than chemical, makes for difficulties and the limited evidence available suggests that many exceptions and variations may exist. Whilst experience with forest fertilizers might not be entirely apposite, for example foliar uptake from polluted rain may be a factor, it is urged that at least any hypothesis put forward should be compatible with information gained from fertilizer trials.

Carbon x nutrient interactions-the limitations to productivity.

The interaction of nutrient cycles with the production, accumulation and death of organic matter is considered, in particular the relation to changes with stand age. It is shown that, because of efficient recycling within the tree and through the litter, the demands made by forests on the soil nutrient capital fall markedly after canopy closure. Because this effect is primarily a result of the ability of the tree to conserve and reuse nutrients in the foliage, the significance of the evergreen habit is examined. Although there are many reports of a net photosynthetic contribution from foliage older than one year, the relationships examined suggest that whereas there is virtually no correlation between growth rate and total foliage carried, there is quite a good relationship with weight of current-year foliage irrespective of whether trees are deciduous or the age at which evergreen foliage is shed. It is suggested that the evergreen habit would be a nutritional disadvantage prior to canopy closure but thereafter a considerable advantage.