The Potential Contribution of Mass Treatment to the Control of Plasmodium falciparum Malaria

Mass treatment as a means to reducing P. falciparum malaria transmission was used during the first global malaria eradication campaign and is increasingly being considered for current control programmes. We used a previously developed mathematical transmission model to explore both the short and long-term impact of possible mass treatment strategies in different scenarios of endemic transmission. Mass treatment is predicted to provide a longer-term benefit in areas with lower malaria transmission, with reduced transmission levels for at least 2 years after mass treatment is ended in a scenario where the baseline slide-prevalence is 5%, compared to less than one year in a scenario with baseline slide-prevalence at 50%. However, repeated annual mass treatment at 80% coverage could achieve around 25% reduction in infectious bites in moderate-to-high transmission settings if sustained. Using vector control could reduce transmission to levels at which mass treatment has a longer-term impact. In a limited number of settings (which have isolated transmission in small populations of 1000–10,000 with low-to-medium levels of baseline transmission) we find that five closely spaced rounds of mass treatment combined with vector control could make at least temporary elimination a feasible goal. We also estimate the effects of using gametocytocidal treatments such as primaquine and of restricting treatment to parasite-positive individuals. In conclusion, mass treatment needs to be repeated or combined with other interventions for long-term impact in many endemic settings. The benefits of mass treatment need to be carefully weighed against the risks of increasing drug selection pressure

The role of impulsivity in the aetiology of drug dependence: reward sensitivity versus automaticity

Journal ArticleResearch Support, Non-U.S. Gov'tCopyright © The Author(s) 2011.RATIONALE: Impulsivity has long been known as a risk factor for drug dependence, but the mechanisms underpinning this association are unclear. Impulsivity may confer hypersensitivity to drug reinforcement which establishes higher rates of instrumental drug-seeking and drug-taking behaviour, or may confer a propensity for automatic (non-intentional) control over drug-seeking/taking and thus intransigence to clinical intervention. METHOD: The current study sought to distinguish these two accounts by measuring Barratt Impulsivity and craving to smoke in 100 smokers prior to their completion of an instrumental concurrent choice task for tobacco (to measure the rate of drug-seeking) and an ad libitum smoking test (to measure the rate of drug-taking-number of puffs consumed). RESULTS: The results showed that impulsivity was not associated with higher rates of drug-seeking/taking, but individual differences in smoking uptake and craving were. Rather, nonplanning impulsivity moderated (decreased) the relationship between craving and drug-taking, but not drug-seeking. CONCLUSIONS: These data suggest that whereas the uptake of drug use is mediated by hypervaluation of the drug as an instrumental goal, the orthogonal trait nonplanning impulsivity confers a propensity for automatic control over well-practiced drug-taking behaviour.MR

Bargaining Over Labor: Do Patients Have Any Power?

We provide a new method of identifying the level of relative bargaining power in bilateral negotiations using exogenous variation in the degree of conflict between parties. Using daily births data, we study negotiations over birth timing. In doing so, we exploit the fact that fewer children are born on the inauspicious dates of February 29 and April 1; most likely, we argue, reflecting parental preferences. When these inauspicious dates abut a weekend, this creates a potential conflict between avoiding the inauspicious date (the parents' likely preference), and avoiding the weekend (the doctor's likely preference). Using daily births data, we estimate how often this conflict is resolved in favor of the physician. We show how this provides an estimate of how bargaining power is distributed between patients and physicians

Verbal and physiological manifestations of smoking urges produced through imagery: The role of affect and smoking abstinence

This study investigated the impact of affect and abstinence on urges/cravings to smoke produced in an imagery paradigm. One hundred cigarette smokers were asked to vividly imagine imagery scripts that described positive affect and explicit smoking urges, positive affect alone, negative affect and explicit smoking urges, negative affect alone, neutral affect and explicit smoking urges, and neutral affect alone. Each subject participated in two sessions, scheduled six or twenty-four hours apart, and one-half of the subjects were asked to refrain from smoking over their intersession interval. The results indicated that the imagery manipulation clearly produced content-specific effects in physiological responses and verbal reports of smoking urges. Imagery scripts that contained explicit descriptions of urges elicited significantly stronger urge/craving reports than scripts devoid of urge content. Among scripts without explicit urge descriptors, negative affect scripts produced significantly stronger urge/craving reports than either the positive affect scripts or the neutral affect scripts. Among scripts with explicit urge descriptors, the inclusion of positive or negative affect content resulted in higher levels of urge/craving report than that produced by neutral affect scripts combined with urge descriptors. This suggests that affect contributed to urge elicitation even when the imagery scripts contained explicit urge material. Scripts that elicited the strongest verbal reports of urges/cravings also produced significantly higher levels of heart rate responding than did the scripts that were less effective at eliciting verbal reports of urges. Abstinence did not appear to have an impact on physiological responding, but abstinent subjects reported significantly stronger urges/cravings to all of the imagery scripts than did the subjects who continued to smoke over the intersession interval. The implications of these results for contemporary models of drug urges are discussed

Learning by Accident? Reductions in the Risk of Unplanned Outages in U.S. Nuclear Power Plants after Three Mile Island.

This study uses a Cox proportional hazards model to analyze changes in the risk of unplanned outages in U.S. nuclear power plants after the Three Mile Island (TMI) accident. The unplanned outage hazard is related to safety by the fact that most such outages begin with unplanned reactor scrams. These place extreme stresses on plant equipment, increasing the risk of serious accident. The estimates indicate that the Nuclear Regulatory Commission (NRC)-led efforts to improve nuclear plant safety after TMI were followed by substantial reductions in the risk of unplanned outages

Nash bargaining model of HMO premiums

This paper estimates a model of commercial HMO premiums based on Nash's axiomatic approach to bargaining between HMOs and employers. The bargaining models incorporate variables that measure the 'power' of the parties to affect the division of potential gains from a contract. It is found that an increase in the number of competing HMOs increases the employer's bargaining power and leads to lower premiums, especially for for-profit HMOs. It is also found that employers' bargaining power over non-profit HMOs is positively related to the ratio of the HMO's administrative expenses/total expenses.