An analytic model for Throughput Optimal Distributed Coordination Function (TO-DCF).

TO-DCF, a new backoff scheme for 802.11, has the potential to significantly increase throughput in dense wireless LANs while also opportunistically favouring nodes with heavier traffic loads and/or better channel conditions. In this paper we present an analytical model to investigate the behaviour and performance of the TO-DCF protocol with regards to operating parameters such as the number of nodes, the contention window size and the backoff countdown probabilities. We then compare numerical results from an implementation of our model with simulations. Our model shows a high level of accuracy, even when the model assumptions are relaxed, and provides guidance for network operators to correctly configure the weight functions for nodes running TO-DCF given the network's operating conditions.

Efficacy of the nicotine inhaler in smoking reduction: A double-blind, randomized trial.

Many smokers are not ready to quit but are interested in changing their smoking behavior, particularly if such a change is associated with a reduction in health risk. The present study evaluated the efficacy of the nicotine inhaler in reducing smoking. Exploratory studies assessed whether reduction in smoking was associated with reduction in markers of disease risk. A total of 429 healthy smokers (smoking at least 20 cigarettes/day) were randomly assigned to either nicotine-containing or placebo inhalers, which subjects were allowed to use ad libitum for up to 1 year. The nicotine inhaler was significantly superior to placebo in achieving reduction in daily cigarette consumption by at least 50% after 4 months, compared with baseline (18% vs. 8%, p = .004). Active treatment promoted smoking cessation: 8% of subjects in the nicotine group and 1% in the placebo group were abstinent at month 15. Throughout the study, smoking reduction, per se, independent of treatment group, was associated with a statistically significant decrease in exhaled carbon monoxide and serum cotinine and thiocyanate. Smoking reduction also improved established risk markers for cardiovascular disease over 4 months. The incidence of adverse events did not differ significantly between the active and placebo groups. The most common treatment-related adverse events were throat irritation and cough. In conclusion, the nicotine inhaler can help smokers who are unable or unwilling to quit to reduce daily cigarette consumption, which may be a health benefit on its own and may further promote quitting.

Smoking reduction treatment with 4-mg nicotine gum: a double-blind, randomized, placebo-controlled study.

BACKGROUND: Smoking reduction may provide a harm-reduction alternative treatment for smokers who are not ready to quit smoking. This study evaluated the efficacy of nicotine gum in helping smokers reduce or quit smoking. METHODS: This randomized, double-blind, placebo-controlled trial involved 364 smokers who were not ready to quit but were willing to reduce their smoking intensity. Participants received either 4-mg nicotine gum (n = 184) or placebo gum (n = 180) as desired for up to 12 months. The primary outcome was sustained smoking reduction, which was defined as a decrease in daily cigarette consumption of at least 50% compared with baseline. Secondary measures included point-prevalence abstinence, intention to quit, and cardiovascular risk markers. RESULTS: At 4 months, the sustained smoking reduction rate in the nicotine gum group was twice that of the placebo group (15.8% versus 6.7%, P = .008). Point-prevalence abstinence was 6.6% for the nicotine gum group and 2.2% for the placebo group (P = .07). At 13 months, there was a significant difference in the smoking reduction rate for the nicotine (8.2%) and placebo (2.8%) groups (P = .036). At month 13, the abstinence rates were 12% and 4.5% for the nicotine and placebo groups, respectively (P = .012). Concomitant use of nicotine gum and cigarette smoking was well tolerated. Carbon monoxide levels decreased significantly (P = .01). CONCLUSION: Nicotine gum may be an efficacious harm-reduction alternative for smokers who are not ready to quit and may promote smoking cessation, the ultimate goal in the treatment of tobacco dependence.

Smoking reduction promotes smoking cessation: results from a double blind, randomized, placebo-controlled trial of nicotine gum with 2-year follow-up.

AIM: To test the effect of nicotine gum and placebo in smokers not motivated or not able to quit smoking with regard to smoking reduction and smoking cessation. DESIGN: This randomized study evaluated nicotine gum versus placebo for up to 1 year in 411 healthy smokers highly motivated to reduce cigarette use. Smoking reduction was defined as self-reported daily smoking less than 50% of baseline and any decrease (1 p.p.m. or more) in carbon monoxide. SETTING: Pulmonary department, Copenhagen, Denmark. FINDINGS: The overall success rate for sustained smoking reduction was significantly higher at all time-points for active versus placebo gum (6.3% versus 0.5% after 24 months). Nicotine gum achieved significantly higher point prevalence cessation rates than placebo at 12 and 24 months [11.2% versus 3.9% (odds ratio = 3.1; 95% CI, 1.4-7.2 and 9.3% versus 3.4% (odds ratio = 2.9; 95% CI, 1.2-7.1), respectively]. There was a linear relationship between decrease in number of daily cigarettes and decrease in plasma cotinine, exhaled carbon monoxide and plasma thiocyanate, with significantly greater reduction in the nicotine gum group after 4 and 12 months (maximum treatment duration) but not after 24 months. The decrease in toxin intake was smaller than the decline in daily cigarette consumption, suggesting that compensatory smoking occurred. CONCLUSIONS: Nicotine gum promoted cessation in this population of smokers unwilling to quit. Among reducers, the toxin intake correlated with reduced cigarette consumption although some compensatory smoking occurred.

Impact of messages on concomitant use of nicotine replacement therapy and cigarettes: a randomized trial on the Internet.

AIMS: To assess the impact of messages recommending the concomitant use of nicotine replacement therapy (NRT) and cigarettes on smokers' intention to quit smoking. DESIGN: Randomized trial. SETTING: Internet. PARTICIPANTS: A total of 2027 people who answered an e-mail sent to 9074 current and former smokers recruited on a smoking cessation website. INTERVENTION: Participants were divided randomly into four groups, each of which received a unique message (in French) by e-mail. The 'control' message said that nicotine replacement therapy (NRT) attenuates withdrawal symptoms in smokers who want to quit. The 'temporary abstinence' message added that NRT can also be used by current smokers to manage smoke-free situations. The 'reduction' message indicated that NRT can be used by current smokers who do not want to quit but want to smoke fewer cigarettes. The 'side-effects' message discouraged concomitant use of NRT and cigarettes. MEASUREMENTS: Perceived impact of these messages on motivation to quit smoking. FINDINGS: The e-mail was answered by 2027 people (25% of 8124 valid addresses). Smokers who received the 'reduction' message were slightly more likely than controls to report that this message increased their motivation to quit (66% versus 60%, P = 0.02). In contrast, smokers who received the 'side-effects' message were less likely than controls to report that this message increased their motivation (45% versus 60%, P < 0.001). The 'temporary abstinence' message had no detectable impact on motivation to quit. CONCLUSIONS: Among smokers recruited via a smoking cessation website, messages encouraging concomitant use of NRT and cigarettes may have either no effect or a positive effect on motivation to quit smoking.