Non-Newtonian Couette-Poiseuille flow of a dilute gas

The steady state of a dilute gas enclosed between two infinite parallel plates in relative motion and under the action of a uniform body force parallel to the plates is considered. The Bhatnagar-Gross-Krook model kinetic equation is analytically solved for this Couette-Poiseuille flow to first order in the force and for arbitrary values of the Knudsen number associated with the shear rate. This allows us to investigate the influence of the external force on the non-Newtonian properties of the Couette flow. Moreover, the Couette-Poiseuille flow is analyzed when the shear-rate Knudsen number and the scaled force are of the same order and terms up to second order are retained. In this way, the transition from the bimodal temperature profile characteristic of the pure force-driven Poiseuille flow to the parabolic profile characteristic of the pure Couette flow through several intermediate stages in the Couette-Poiseuille flow are described. A critical comparison with the Navier-Stokes solution of the problem is carried out.Comment: 24 pages, 5 figures; v2: discussion on boundary conditions added; 10 additional references. Published in a special issue of the journal "Kinetic and Related Models" dedicated to the memory of Carlo Cercignan

Adolescents' Responses to Pictorial Warnings on Their Parents' Cigarette Packs

PURPOSE: Pictorial cigarette pack warnings are a promising policy solution to increase smoking cessation among adults. However, little is known regarding adolescents' responses to pictorial warnings, particularly in real-world settings. METHODS: Participants were 112 adolescent children, ages 13–17, whose parents received either text-only warnings on the side of their cigarette packs or pictorial warnings on the top half of the front and back of their cigarette packs for 4 weeks as part of a trial. We measured adolescents' recall and recognition of these warnings, negative emotional reactions to the warnings, perceived effectiveness of the warnings, social interactions about the warnings, and smoking risk beliefs. RESULTS: Adolescents accurately recalled pictorial warnings more often than text-only warnings (82% vs. 19%, p < .001). Recognition of warnings was also higher for pictorial than text-only warnings (82% vs. 34%, p < .001). Pictorial warnings drew greater attention (p < .001), elicited greater negative emotional reactions (p < .05), and sparked more social interactions (p < .01) than text-only warnings. CONCLUSIONS: Pictorial warnings on cigarette packs may have important effects on adolescent children of smokers. Future research should further investigate the impact of such messages on adolescents' susceptibility to smoking initiation and interest in quitting smoking, particularly as the United States and other countries work to implement pictorial warning regulations

Non-Smoking Male Adolescents' Reactions to Cigarette Warnings

BACKGROUND: The U.S. Food and Drug Administration (FDA) is working to introduce new graphic warning labels for cigarette packages, the first change in cigarette warnings in more than 25 years. We sought to examine whether warnings discouraged participants from wanting to smoke and altered perceived likelihood of harms among adolescent males and whether these warning effects varied by age. METHODS: A national sample of 386 non-smoking American males ages 11–17 participated in an online experiment during fall 2010. We randomly assigned participants to view warnings using a 2×2 between-subjects design. The warnings described a harm of smoking (addiction or lung cancer) using text only or text plus an image used on European cigarette package warnings. Analyses tested whether age moderated the warnings' impact on risk perceptions and smoking motivations. RESULTS: The warnings discouraged most adolescents from wanting to smoke, but lung cancer warnings discouraged them more than addiction warnings did (60% vs. 34% were “very much” discouraged, p<.001). Including an image had no effect on discouragement. The warnings affected several beliefs about the harms from smoking, and age moderated these effects. Adolescents said addiction was easier to imagine and more likely to happen to them than lung cancer. They also believed that their true likelihood of experiencing any harm was lower than what an expert would say. CONCLUSIONS: Our findings suggest that warnings focusing on lung cancer, rather than addiction, are more likely to discourage wanting to smoke among adolescent males and enhance their ability to imagine the harmful consequences of smoking. Including images on warnings had little effect on non-smoking male adolescents' discouragement or beliefs, though additional research on the effects of pictorial warnings for this at-risk population is needed as the FDA moves forward with developing new graphic labels

Pictorial cigarette pack warnings: a meta-analysis of experimental studies

OBJECTIVE: To inform international research and policy, we conducted a meta-analysis of the experimental literature on pictorial cigarette pack warnings. DATA SOURCES: We systematically searched 7 computerised databases in April 2013 using several search terms. We also searched reference lists of relevant articles. STUDY SELECTION: We included studies that used an experimental protocol to test cigarette pack warnings and reported data on both pictorial and text-only conditions. 37 studies with data on 48 independent samples (N=33 613) met criteria. DATA EXTRACTION AND SYNTHESIS: Two independent coders coded all study characteristics. Effect sizes were computed from data extracted from study reports and were combined using random effects meta-analytic procedures. RESULTS: Pictorial warnings were more effective than text-only warnings for 12 of 17 effectiveness outcomes (all p<0.05). Relative to text-only warnings, pictorial warnings (1) attracted and held attention better; (2) garnered stronger cognitive and emotional reactions; (3) elicited more negative pack attitudes and negative smoking attitudes and (4) more effectively increased intentions to not start smoking and to quit smoking. Participants also perceived pictorial warnings as being more effective than text-only warnings across all 8 perceived effectiveness outcomes. CONCLUSIONS: The evidence from this international body of literature supports pictorial cigarette pack warnings as more effective than text-only warnings. Gaps in the literature include a lack of assessment of smoking behaviour and a dearth of theory-based research on how warnings exert their effects