Factors Associated with E-cigarette Use: Analysis of the Population Assessment of Tobacco and Health (PATH) Study

INTRODUCTION: Smoking is the leading cause of preventable death in the United States and has been shown to be harmful to human health. Among alternative tobacco products, e-cigarettes have been widely regarded as the safest substitute to the traditional cigarette. However, debate remains about their safety and possible ill effects. AIM: The purpose of this study was to assess characteristics associated with e-cigarette use (everyday/some days/no use) and examine factors related to former smokers replacing a traditional smoking habit with e-cigarette use (yes/no). METHODS: A secondary data analysis was conducted with the Public Use Files (PUFs) for the Population Assessment of Tobacco and Health (PATH) Study, a nationally representative, longitudinal cohort study of tobacco use. Bivariate and multivariable unweighted and weighted generalized linear models were developed for value and comparative purposes, as well as multilevel models to account for within geographical region clustering. Ordinal logistic regression was used to analyze the ordinal e-cigarette use outcome, and logistic regression with the e-cigarette smoking status of former smokers outcome. RESULTS: Covariates associated with e-cigarette use included having rules that allowed smoking non-combustible tobacco inside the home (everyday vs no use: OR = 0.33, CI = 0.27-0.41; somedays vs no use: OR = 0.58, CI = 0.53-0.64), older than 35 years old (everyday vs no use: OR = 0.63, CI = 0.52-0.75; somedays vs no use: OR = 0.86, CI = 0.76-0.96), and positive or neutral self-opinion on tobacco (everyday vs no use: OR = 0.88, CI = 0.73-1.05; somedays vs no use: OR = 1.38, CI = 1.22-1.55). Factors related to e-cigarette use in former smokers included rules allowing non-combustible tobacco products inside the home (Weighted: OR = 0.19, CI = 0.15-0.24; Unweighted: OR = 0.15, CI = 0.12-0.19; Mixed: OR = 0.19, CI = 0.15-0.24), aged 18-35 years (Weighted: OR = 1.45, CI = 1.16-1.80; Unweighted: OR = 2.91, CI = 2.27-3.72; Mixed: OR = 1.45, CI = 1.16-1.80), and not having any health insurance (Weighted: OR = 0.57, CI = 0.44-0.75; Unweighted: OR = 0.47, CI = 0.34-0.64; Mixed: OR = 0.57, CI = 0.44-0.75). DISCUSSION: Family tolerance of smoking and one’s self-opinion on tobacco were factors found to be strongly associated with e-cigarette use. The prevalence of e-cigarette use among young adults raises concerns and necessitates a multi-disciplinary approach to monitor and intervene. Further study is needed to better understand e-cigarette smoking consumption behavior and effects

Numerical Study on the Route of Flame-Induced Thermoacoustic Instability in a Rijke Burner

The self-excited thermoacoustic instability in a two-dimensional Rijke-type burner with a center-stabilized premixed methane–air flame is numerically studied. The simulation considers the reacting flow, flame dynamics, and radiation model to investigate the important physical processes. A finite volume-based approach is used to simulate reacting flows under both laminar and turbulent flow conditions. Chemical reaction modeling is conducted via the finite-rate/eddy dissipation model with one-step reaction mechanisms, and the radiation heat flux and turbulent flow characteristics are determined by using the P-1 model and the standard k-ε model, respectively. The steady-state reacting flow is first simulated for model verification. Then, the dynamic pressure, velocity, and reaction heat evolutions are determined to show the onset and growth rate of self-excited instability in the burner. Using the fast Fourier transform (FFT) method, the frequency of the limit cycle oscillation is obtained, which agrees well with the theoretical prediction. The dynamic pressure and velocity along the tube axis provide the acoustic oscillation mode and amplitude, also agreeing well with the prediction. Finally, the unsteady flow field at different times in a limit cycle shows that flame-induced vortices occur inside the combustor, and the temperature distribution indicates that the back-and-forth velocity changes in the tube vary the distance between the flame and honeycomb in turn, forming a forward feedback loop in the tube. The results reveal the route of flame-induced thermoacoustic instability in the Rijke-type burner and indicate periodical vortex formation and breakdown in the Rijke burner, which should be considered turbulent flow under thermoacoustic instability

Co-up-regulation of three P450 genes in response to permethrin exposure in permethrin resistant house flies, Musca domestica

BACKGROUND: Insects may use various biochemical pathways to enable them to tolerate the lethal action of insecticides. For example, increased cytochrome P450 detoxification is known to play an important role in many insect species. Both constitutively increased expression (overexpression) and induction of P450s are thought to be responsible for increased levels of detoxification of insecticides. However, unlike constitutively overexpressed P450 genes, whose expression association with insecticide resistance has been extensively studied, the induction of P450s is less well characterized in insecticide resistance. The current study focuses on the characterization of individual P450 genes that are induced in response to permethrin treatment in permethrin resistant house flies. RESULTS: The expression of 3 P450 genes, CYP4D4v2, CYP4G2, and CYP6A38, was co-up-regulated by permethrin treatment in permethrin resistant ALHF house flies in a time and dose-dependent manner. Comparison of the deduced protein sequences of these three P450s from resistant ALHF and susceptible aabys and CS house flies revealed identical protein sequences. Genetic linkage analysis located CYP4D4v2 and CYP6A38 on autosome 5, corresponding to the linkage of P450-mediated resistance in ALHF, whereas CYP4G2 was located on autosome 3, where the major insecticide resistance factor(s) for ALHF had been mapped but no P450 genes reported prior to this study. CONCLUSION: Our study provides the first direct evidence that multiple P450 genes are co-up-regulated in permethrin resistant house flies through the induction mechanism, which increases overall expression levels of P450 genes in resistant house flies. Taken together with the significant induction of CYP4D4v2, CYP4G2, and CYP6A38 expression by permethrin only in permethrin resistant house flies and the correlation of the linkage of the genes with resistance and/or P450-mediated resistance in resistant ALHF house flies, this study sheds new light on the functional importance of P450 genes in response to insecticide treatment, detoxification of insecticides, the adaptation of insects to their environment, and the evolution of insecticide resistance

Experimental Study on Early-Age Crack of Mass Concrete under the Controlled Temperature History

Thermal deformation under restrained conditions often leads to early-age cracking and durability problems in mass concrete structures. It is crucial to monitor accurately the evolution of temperature and thermal stresses. In this paper, experimental studies using temperature stress testing machine (TSTM) are carried out to monitor the generated thermal cracking in mass concrete. Firstly, components and working principle of TSTM were introduced. Cracking temperatures and stress reserves are selected as the main cracking evaluation indicators of TSTM. Furthermore, effects of temperature controlling measures on concrete cracking were quantitatively studied, which consider the concrete placing temperature (before cooling) and cooling rates (after cooling). Moreover, the influence of reinforcement on early-age cracking has been quantitatively analyzed using the TSTM. The experimental results indicate that the crack probability of reinforced concrete (RC) is overestimated. Theoretical calculations proved that the internal stress can transfer from concrete to reinforcement due to creep effect. Finally, the experimental results indicate that the reinforcement can improve the crack resistance of concrete by nearly 30% in the TSTM tests, and the ultimate tensile strain of RC is approximately 105% higher than that of plain concrete with the same mix proportions

Signature functions of knots

The signature function of a knot is an integer-valued step function on the unit circle in the complex plane. Necessary and sufficient conditions for a function to be the signature function of a knot are presented.Comment: 4 page