The impact of social influence on adolescent intention to smoke: Combining types and referents of influence

Objectives Theory and research suggest that the intention to smoke is the main determinant of smoking initiation and emphasizes the role of cognitive and social factors on the prediction of the intention to smoke. However, extended models such as the I‐Change and results from published studies reveal inconsistencies regarding the impact of social influence on the intention to smoke. Possible explanations for this may be the definition and measurement of the constructs that have been used. Design and methods The current study was designed with two main goals: (i) to test a measurement model for social influence, combining different types of social influence (subjective norms, perceived behaviour, and direct pressure) with various referents of influence (parents, siblings, peers, and teachers); (ii) to investigate the impact of social influence on adolescent intention to smoke, controlling for smoking behaviour. LISREL was used to test these models. The sample includes 3,064 Portuguese adolescents, with a mean age of 13.5 years, at the beginning of the seventh school grade. Results The hypothesized measurement model of social influence was supported by results and explained 29% of the variance of the intention to smoke. A more extended model, including attitude and self‐efficacy, explained 55% of the variance of the intention to smoke. Perceived behaviour of peers, parental norms, and perceived behaviour of parents were the social influence factors with impact on adolescent intention to smoke. Conclusions Results suggest that different referents exert their influence through distinct types of social influence and recommend further work on the definition and measurement of social influence.     

Quitting Smoking: Applying an Extended Version of the Theory of PlannedBehavior to Predict Intention and Behavior1

This study examined the ability of the theory of planned behavior (TPB)to predict students' intentions to quit smoking and the subsequent behavior6 months later. In addition, the impact of past behavior, moral norms, self‐identity, group identity, and positive/negative anticipated affect was examined. The intention‐behavior relationship was examined by dividing the sample in four subgroups: inclined actors/abstainers and disinclined actors/abstainers. Analyses were based on data from a prospective sample of 698 smokers. Attitude, subjective norms, and perceived behavioral control accounted for 36% (adjusted R²) of the variance in intentions. Moral norms, positive anticipated affect, group identity, and past behavior added 9% (adjusted R²) to the explained variance in intention, beyond the effect accounted for by the TPB components. Subsequent behavior was predicted by intentions (adjusted R²= .12). Past behavior, moral norms, self‐identity, and the Past Behavior x Intention and Moral Norm x Negative Affect interactions explained an additional 9% (adjusted R²) of the variance in behavior. Inclined abstainers constituted the main source of the discrepancy between intention and behavior.     

Theory of planned behaviour and ecstasy use: An analysis of moderator‐interactions

Objective: This study tested potential moderator interactions between components of the Theory of Planned Behaviour (TPB) in relation to ecstasy use, extending previous research. It was expected that attitudes, subjective norms and perceived behavioural control (PBC) would moderate each other in predicting intended use of this drug. Method: A cross‐sectional survey was administered to 200 young adults. Results: In hierarchical multiple regression analysis, past behaviour and attitude independently predicted intention; previous use of ecstasy and more positive attitudes towards ecstasy use were associated with stronger intentions to use this drug in the future. Moreover, there was a significant interaction between attitude and PBC (R²_change = 0.05). Slope analysis revealed that PBC better predicted intention given more positive attitudes towards ecstasy use. Conclusions: This moderator function may help explain predictive inconsistencies reported in the literature. Implications for the TPB are considered.     

Cationic Monomer‐Isomerization Polymerization of Oxetanes Having an Ester Substituent,to Give Poly(orthoester) or Polyether

This study shows the cationic monomer‐isomerization polymerization of 3‐R¹‐oxetanes ( 1 ) having a 3‐ester substituent (—CH₂OCOR²) through two ring‐opening routes (R¹ = CH₃, Ph; R² = Pr, Ph). The polymerization of 1 with Lewis acids usually gave poly(orthoester) ( 3 ) or polyether ( 4 ), together with bicyclic orthoester ( 2 ) as the isomerization product. The isomerization took place prior to polymerization, because of the preferable nucleophilic attack of the intermolecular carbonyl oxygen. Subsequently, 2 polymerized in either a single‐ or double‐ring‐opening manner depending on temperature. The single‐ring‐opening polymerization of 2 below room temperature was an equilibrium polymerization through bicyclic oxonium ends leading to 3 , and the thermodynamic parameters were estimated according to Dainton's equation. Thus, Corey's orthoester synthesis from ester‐substituted oxetanes is regarded as a phenomenon in the equilibrium polymerization only around the ceiling temperature (T_c). Above T_c, 2 brought about the double‐ring‐opening polymerization through monocyclic diaoxacarbenium ends to afford 4 . Relatively bulky R¹ and R² such as the Ph group exerted a large steric effect on both polymerization routes. As a special case arising from this effect, the CF₃SO₃H‐catalyzed reaction of 1 c (R¹, R² = Ph) resulted in an unusual cyclodimerization accompanied by the elimination of benzoic acid, owing to the susceptibility of the neophyl skeleton to cation transfer.     

Protection motivation theory and the prediction of physical activity among adults with type 1 or type 2 diabetes in a large population sample

Objectives. To investigate the utility of the protection motivation theory (PMT) for explaining physical activity (PA) in an adult population with type 1 diabetes (T1D) and type 2 diabetes (T2D). Design. Cross‐sectional and 6‐month longitudinal analysis using PMT. Methods. Two thousand three hundred and eleven individuals with T1D (N =697) and T2D (N =1,614) completed self‐report PMT constructs of vulnerability, severity, response efficacy, self‐efficacy, and intention, and PA behaviour at baseline and 6‐month follow‐up. Multi‐group structural equation modelling was conducted to: (1) test the fit of the PMT structure; (2) determine the similarities and differences in the PMT structure between the two types of diabetes; and (3) examine the explained variance and compare the strength of association of the PMT constructs in predicting PA intention and behaviour. Results. The findings provide evidence for the utility of the PMT in both diabetes samples (χ²/df =1.27?4.08, RMSEA=.02–.05). Self‐efficacy was a stronger predictor of intention (β=0.64–0.68) than response efficacy (β=0.14–0.16) in individuals with T1D or T2D. Severity was significantly related to intention (β=0.06) in T2D individuals only, whereas vulnerability was not significantly related to intention or PA behaviour. Self‐efficacy (β's=0.20–0.28) and intention (β's=0.12–0.30) were significantly associated with PA behaviour. Conclusions. Promotion of PA behaviour should primarily target self‐efficacy to form intentions and to change behaviour. In addition, for individuals with T2D, severity information should be incorporated into PA intervention materials in this population.     

Reasons for binge drinking among undergraduate students: An application of behavioural reasoning theory

Objectives. This study sought to apply behavioural reasoning theory (BRT) to the prediction of undergraduate students’ binge drinking intentions and behaviour. The reasons students use to justify and defend binge drinking may provide important information on motivations underlying such behaviour. Methods. Undergraduate students (N= 265) completed questionnaires assessing their reasons for and against binge drinking, attitude, subjective norm, perceived behavioural control, intention, and past behaviour. Frequency of binge drinking was assessed at 1‐week follow‐up (N= 172). Results. A series of path analyses were conducted to assess the direct and indirect effects of the BRT variables on binge drinking intentions and behaviour. The variables under consideration accounted for 80% of the variance in binge drinking intentions (with past behaviour, reasons for binge drinking, and attitude having significant direct effects on intention), and 34% of the variance in binge drinking at 1‐week follow‐up (with past behaviour, perceived behavioural control, and intention having significant direct effects on future behaviour). Additional regression analyses revealed that respondents who strongly endorsed being sociable and having fun as reasons for binge drinking were more likely to intend to engage in binge drinking over the subsequent week. Conclusions. The results provide support for BRT as a framework for understanding undergraduate students’ binge drinking intentions and behaviour, and suggest that interventions need to focus on the social reasons for engaging in binge drinking in undergraduate students.     

Blood oxygenation level-dependent (BOLD) total and extravascular signal changes and ΔR2* in human visual cortex at 1.5, 3.0 and 7.0 T

The characterisation of the extravascular (EV) contribution to the blood oxygenation level‐dependent (BOLD) effect is important for understanding the spatial specificity of BOLD contrast and for modelling approaches that aim to extract quantitative metabolic parameters from the BOLD signal. Using bipolar crusher gradients, total (b = 0 s/mm²) and predominantly EV (b = 100 s/mm²) gradient echo BOLD ΔR₂* and signal changes (ΔS/S) in response to visual stimulation (flashing checkerboard; f = 8 Hz) were investigated sequentially (within < 3 h) at 1.5, 3.0 and 7.0 T in the same subgroup of healthy volunteers (n = 7) and at identical spatial resolutions (3.5 × 3.5 × 3.5 mm³). Total ΔR₂* (z‐score analysis) values were ?0.61 ± 0.10 s^?1 (1.5 T), ?0.74 ± 0.05 s^?1 (3.0 T) and ?1.37 ± 0.12 s^?1 (7.0 T), whereas EV ΔR₂* values were ?0.28 ± 0.07 s^?1 (1.5 T), ?0.52 ± 0.07 s^?1 (3.0 T) and ?1.25 ± 0.11 s^?1 (7.0 T). Although EV ΔR₂* increased linearly with field, as expected, it was found that EV ΔS/S increased less than linearly with field in a manner that varied with TE choice. Furthermore, unlike ΔR₂*, total and EV ΔS/S did not converge at 7.0 T. These trends were similar whether a z‐score analysis or occipital lobe‐based region‐of‐interest approach was used for voxel selection. These findings suggest that calibrated BOLD approaches may benefit from an EV ΔR₂* measurement as opposed to a ΔS/S measurement at a single TE. Copyright © 2010 John Wiley & Sons, Ltd.     

Manipulation of cortical gray matter oxygenation by hyperoxic respiratory challenge: field dependence of R(2) * and MR signal response

The aim of this study was to quantitatively assess the field strength dependence of the transverse relaxation rate (R₂*) change in cortical gray matter induced by hyperoxia and hyperoxic hypercapnia versus normoxia in an intra‐individual comparison of young healthy volunteers. Medical air (21% O₂), pure oxygen and carbogen (95% O₂, 5% CO₂) were alternatively administered in a block‐design temporal pattern to induce normoxia, hyperoxia and hyperoxic hypercapnia, respectively. Local R₂* values were determined from three‐dimensional, multiple, radiofrequency‐spoiled, fast field echo data acquired at 1.5, 3 and 7 T. Image quality was good at all field strengths. Under normoxia, the mean gray matter R₂* values were 13.3 ± 2.7 s^–1 (1.5 T), 16.9 ± 0.9 s^–1 (3 T) and 29.0 ± 2.6 s^–1 (7 T). Both hyperoxic gases induced relaxation rate decreases ΔR₂*, whose magnitudes increased quadratically with the field strength [carbogen: –0.69 ± 0.20 s^–1 (1.5 T), –1.49 ± 0.49 s^–1 (3 T), –5.64 ± 0.67 s^–1 (7 T); oxygen: –0.39 ± 0.20 s^–1 (1.5 T), –0.78 ± 0.48 s^–1 (3 T), –3.86 ± 1.00 s^–1 (7 T)]. Carbogen produced larger R₂* changes than oxygen at all field strengths. The relative change ΔR₂*/R₂* also increased with the field strength with a power between 1 and 2 for both carbogen and oxygen. The statistical significance of the R₂* response improved with increasing B₀ and was higher for carbogen than for oxygen. For a sequence with pure T₂* weighting of the signal response to respiratory challenge, the results suggested a maximum carbogen‐induced signal difference of 19.3% of the baseline signal at 7 T and TE = 38 ms, but a maximum oxygen‐induced signal difference of only 3.0% at 1.5 T and TE = 76 ms. For 3 T, maximum signal changes of 4.7% (oxygen) and 8.9% (carbogen) were computed. In conclusion, the R₂* response to hyperoxic respiratory challenge was stronger for carbogen than for oxygen, and increased quadratically with the static magnetic field strength for both challenges, which highlights the importance of high field strengths for future studies aimed at probing oxygen physiology in clinical settings. Copyright © 2012 John Wiley & Sons, Ltd.     

Bi‐component T2* analysis of bound and pore bone water fractions fails at high field strengths

Osteoporosis involves the degradation of the bone's trabecular architecture, cortical thinning and enlargement of cortical pores. Increased cortical porosity is a major cause of the decreased strength of osteoporotic bone. The majority of cortical pores, however, are below the resolution limit of MRI. Recent work has shown that porosity can be evaluated by MRI‐based quantification of bone water. Bi‐exponential T₂* fitting and adiabatic inversion preparation are the two most common methods purported to distinguish bound and pore water in order to quantify matrix density and porosity. To assess the viability of T₂* bi‐component analysis as a method for the quantification of bound and pore water fractions, we applied this method to human cortical bone at 1.5, 3, 7 and 9.4 T, and validated the resulting pool fractions against micro‐computed tomography‐derived porosity and gravimetrically determined bone densities. We also investigated alternative methods: two‐dimensional T₁–T₂* bi‐component fitting by incorporation of saturation recovery, one‐ and two‐dimensional fitting of Carr–Purcell–Meiboom–Gill (CPMG) echo amplitudes, and deuterium inversion recovery. The short‐T₂* pool fraction was moderately correlated with porosity (R² = 0.70) and matrix density (R² = 0.63) at 1.5 T, but the strengths of these associations were found to diminish rapidly as the field strength increased, falling below R² = 0.5 at 3 T. The addition of the T₁ dimension to bi‐component analysis only slightly improved the strengths of these correlations. T₂*‐based bi‐component analysis should therefore be used with caution. The performance of deuterium inversion recovery at 9.4 T was also poor (R² = 0.50 vs porosity and R² = 0.46 vs matrix density). The CPMG‐derived short‐T₂ fraction at 9.4 T, however, was highly correlated with porosity (R² = 0.87) and matrix density (R² = 0.88), confirming the utility of this method for independent validation of bone water pools. Copyright © 2015 John Wiley & Sons, Ltd.     

Young adults' social drinking as explained by an augmented theory of planned behaviour: The roles of prototypes,willingness, and gender

Objective. This study focused on young adults' alcohol consumption in social contexts. A dual‐process model (including reasoned action and social reaction) was applied by combining the theory of planned behaviour (TPB) and the prototype/willingness model. A key question was whether willingness and actor and abstainer prototype variables would augment the TPB by increasing explained variance. Design. Participants completed questionnaires prior to spending an evening socializing over the weekend (Time 1). Behavioural data were obtained by telephone interviews a few days after the social drinking occasion (Time 2). Method. N =300 people (mean age 25 years) took part in the study. The outcome measure of pure alcohol in grams was calculated based on participants' reports about their consumed drinks. Multigroup path analyses were conducted because of sex differences on behavioural and psychological variables. Results. The TPB explained 35% of the variance in men's and 41% in women's alcohol consumption. Augmentation with prototype perception and willingness contributed significantly to the prediction of intention (ΔR²=.07) and alcohol consumption for men (ΔR²=.14). A significant interaction implied that willingness led to heavy drinking particularly among those men who made negative evaluations of the abstainer prototype. Conclusion. Women's alcohol consumption is explained by TPB variables via a more controlled reasoned‐action path only, whereas additional processes (e.g., pursuing the actor image intentionally, rejecting the abstainer image more intuitively) are important for men. The moderating role of gender is discussed in light of traditional gender roles and recent trends in alcohol consumption.     

The development of health protective behaviors among college students

This study uses structural equation modeling and a panel design to explain participation in health protective behavior (HPB) among college students. The direct, indirect, and total effects of gender, social influences (parental and peer behavior), social attachments (activity involvement, social support, and romantic involvement), social triggers (personal health, acute illnesses, and personal or family health crisis), health value, and effort to improve health behavior on HPB are examined. A path model with a high goodness of fit and an R² of. 418 shows that gender, health value, and effort to change health behaviors are the most powerful predictors of HPB participation, while parents and peers influence HPB indirectly through influence on health value and effort to change. Neither the social attachment nor social trigger items influenced HPB in this sample. Implications of these findings are discussed.     

Low numbers of CD8+ T lymphocytes in hereditary haemochromatosis are explained by a decrease of the most mature CD8+ effector memory T cells

Low CD8⁺ T lymphocyte numbers have long been described in hereditary haemochromatosis (HH). Recently, two conserved haplotypes localized near the microsatellite D6S105 at the major histocompatibility complex (MHC) class I region were described predicting the clinical expression of HH and the CD8⁺ T lymphocyte numbers. The A‐A‐T haplotype was associated with a severe clinical expression of HH and low CD8⁺ T lymphocyte numbers, while the G‐G‐G haplotype was associated with a milder clinical expression of HH and high CD8⁺ T lymphocyte numbers. As CD8⁺ T lymphocytes are a very heterogeneous population, in this study we analysed the CD8⁺ subpopulations of naive, central memory (T_CM) and effector memory (T_EM), and further subsets of CD8⁺ T_EM cells in 47 HH patients and 68 controls. In addition, association studies were conducted between the conserved haplotypes and the CD8⁺ T cell subpopulations in HH. Variations of the numbers of naive and central memory cells with age were similar between HH patients and controls. For T_EM cells and the T_EM CD27^‐CD28^‐ subset no effect of age was observed in HH [R² = 0·001, not significant (n.s.) and R² = 0·01, n.s., respectively] contrasting with the increasing of these subpopulations with age in controls (R² = 0·09, P = 0·017 and R² = 0·22, P = 0·0005, respectively). Interestingly, patients homozygous for the A‐A‐T haplotype have lower numbers of CD8⁺ T_EM cells due especially to lower numbers of T_EM CD27^‐CD28^‐ (0·206 ± 0·119 and 0·066 ± 0·067 × 10⁶ cells/ml, respectively) than patients carrying the G‐G‐G haplotype (0·358 ± 0·195 and 0·246 ± 0·202 × 10⁶ cells/ml, respectively). This may suggest an inability of HH patients to differentiate the CD8⁺ T cells into the most mature phenotype.     

Community involvement and victimization at school: an analysis through family,personal and social adjustment

The present study analyzes the impact of adolescents' community involvement on victimization by peers at school through various indicators of family, personal and social adjustment (openness of communication with mother and father, life satisfaction, social self‐esteem, and loneliness). Participating in the project were 565 adolescents aged 11 to 18 (51% male) drawn from secondary schools in Spain. Statistical analyses were conducted using bivariate correlations, the t test and structural equation modeling. Results indicated an indirect and protective influence of community involvement, openness of communication with parents and life satisfaction on victimization by peers. There was also a direct protective effect of social self‐esteem and a direct risk effect of loneliness on victimization at school. Findings are discussed in light of the consideration that community involvement is a key factor in the promotion of other protective factors related to adolescent victimization at school. © 2009 Wiley Periodicals, Inc.     

Changes in the MR relaxation rate R(2)* induced by respiratory challenges at 3.0 T: a comparison of two quantification methods

The consistent determination of changes in the transverse relaxation rate R₂* (ΔR₂*) is essential for the mapping of the effect of hyperoxic and hypercapnic respiratory challenges, which enables the noninvasive assessment of blood oxygenation changes and vasoreactivity by MRI. The purpose of this study was to compare the performance of two different methods of ΔR₂* quantification from dynamic multigradient‐echo data: (A) subtraction of R₂* values calculated from monoexponential decay functions; and (B) computation of ΔR₂* echo‐wise from signal intensity ratios. A group of healthy volunteers (n = 12) was investigated at 3.0 T, and the brain tissue response to carbogen and CO₂–air inhalation was registered using a dynamic multigradient‐echo sequence with high temporal and spatial resolution. Results of the ΔR₂* quantification obtained by the two methods were compared with respect to the quality of the voxel‐wise ΔR₂* response, the number of responding voxels and the behaviour of the ‘global’ response of all voxels with significant R₂* changes. For the two ΔR₂* quantification methods, we found no differences in the temporal variation of the voxel‐wise ΔR₂* responses or in the detection sensitivity. The maximum change in the ‘global’ response was slightly smaller when ΔR₂* was derived from signal intensity ratios. In conclusion, this first methodological comparison shows that both ΔR₂* quantifications, from monoexponential approximation as well as from signal intensity ratios, are applicable for the monitoring of R₂* changes during respiratory challenges. Copyright © 2010 John Wiley & Sons, Ltd.     

Evaluation of renal oxygenation change under the influence of carbogen breathing using a dynamic R2, R2′ and R2* quantification approach

The purpose of this study is to demonstrate the feasibility of dynamic renal R₂/R₂′/R₂* measurements based on a method, denoted psMASE‐ME, in which a periodic 180° pulse‐shifting multi‐echo asymmetric spin echo (psMASE) sequence, combined with a moving estimation (ME) strategy, is adopted. Following approval by the institutional animal care and use committee, a block design of respiratory challenge with interleaved air and carbogen (97% O₂, 3% CO₂) breathing was employed in nine rabbits. Parametrical R₂/R₂′/R₂* maps were computed and average R₂/R₂′/R₂* values were measured in regions of interest in the renal medulla and cortex. Bland–Altman plots showed good agreement between the proposed method and reference standards of multi‐echo spin echo and multi‐echo gradient echo sequences. Renal R₂, R₂′ and R₂* decreased significantly from 16.2 ± 4.4 s^?1, 9.8 ± 5.2 s^?1 and 25.9 ± 5.0 s^?1 to 14.9 ± 4.4 s^?1 (p < 0.05), 8.5 ± 4.1 s^?1 (p < 0.05) and 23.4 ± 4.8 s^?1 (p < 0.05) in the cortex when switching the gas mixture from room air to carbogen. In the renal medulla, R₂, R₂′ and R₂* also decreased significantly from 12.9 ± 4.7 s^?1, 15.1 ± 5.8 s^?1 and 27.9 ± 5.3 s^?1 to 11.8 ± 4.5 s^?1 (p < 0.05), 14.2 ± 4.2 s^?1 (p < 0.05) and 25.8 ± 5.1 s^?1 (p < 0.05). No statistically significant differences in relative R₂, R₂′ and R₂* changes were observed between the cortex and medulla (p = 0.72 for R₂, p = 0.39 for R₂′ and p = 0.61 for R₂*). The psMASE‐ME method for dynamic renal R₂/R₂′/R₂* measurements, together with the respiratory challenge, has potential use in the evaluation of renal oxygenation in many renal diseases