Adolescent health-risk behavior : a study of 15,650 images

Despite recognition in the literature that adolescence represents a relatively high-risk developmental period for health-risk behaviors, only limited attention has been given to the subjective meanings adolescents assign to such behaviors. One potentially fruitful avenue to explore in understanding the adolescent perspective on health-risk behaviors is the use of word association techniques. Word association techniques are an efficient way of determining the content and representational systems of human minds without requiring their expression in the full discursive structure of human language. A free-association technique was used to provide insight into the meanings adolescents give to a variety of behaviors. Using this technique, 411 high-school students (age range 14-20 years) provided up to five associations for each of nine behaviors. Six of these behaviors (drinking beer, drinking liquor, smoking cigarettes, smoking marijuana, using cocaine, and having sexual intercourse) were conceptualized as health-risk behaviors. The remaining three behaviors (exercising, using a seatbelt when riding in a car, and using a condom) were conceptualized as health-protective behaviors. Based upon a five-point scale (from 1=very negative to 5=very positive), respondents also indicated whether their associations meant something negative or something positive to them. In addition to exploring the subjective meanings adolescents assigned to a variety of behaviors, the study examined whether assigned meanings differed by degree of participation in the behaviors, by gender, and by age. Results indicated that images associated with adolescent health-risk and health-protective behaviors were linked to the anticipation of specific outcomes. The specific goals of adolescent health-risk behaviors that emerged from this study included: social facilitation, having fun, physiological arousal, relaxation and tension reduction, sexual facilitation, and positive affective change. Given that health-risk behaviors were found to be associated with specific outcomes for adolescents, the present study supported a possible shift in prevention and intervention programs from a problem-focused approach to an approach that offers less destructive alternatives for meeting adolescent needs

Regional in vivo transit time measurements of aortic pulse wave velocity in mice with high-field CMR at 17.6 Tesla

<p>Abstract</p> <p>Background</p> <p>Transgenic mouse models are increasingly used to study the pathophysiology of human cardiovascular diseases. The aortic pulse wave velocity (PWV) is an indirect measure for vascular stiffness and a marker for cardiovascular risk.</p> <p>Results</p> <p>This study presents a cardiovascular magnetic resonance (CMR) transit time (TT) method that allows the determination of the PWV in the descending murine aorta by analyzing blood flow waveforms. Systolic flow pulses were recorded with a temporal resolution of 1 ms applying phase velocity encoding. In a first step, the CMR method was validated by pressure waveform measurements on a pulsatile elastic vessel phantom. In a second step, the CMR method was applied to measure PWVs in a group of five eight-month-old apolipoprotein E deficient (ApoE^(-/-)) mice and an age matched group of four C57Bl/6J mice. The ApoE^(-/-)group had a higher mean PWV (PWV = 3.0 ± 0.6 m/s) than the C57Bl/6J group (PWV = 2.4 ± 0.4 m/s). The difference was statistically significant (p = 0.014).</p> <p>Conclusions</p> <p>The findings of this study demonstrate that high field CMR is applicable to non-invasively determine and distinguish PWVs in the arterial system of healthy and diseased groups of mice.</p

Assessing Causality in the Relationship Between Adolescents’ Risky Sexual Online Behavior and Their Perceptions of this Behavior

The main aim of this study was to investigate the causal nature of the relationship between adolescents’ risky sexual behavior on the internet and their perceptions of this behavior. Engagement in the following online behaviors was assessed: searching online for someone to talk about sex, searching online for someone to have sex, sending intimate photos or videos to someone online, and sending one’s telephone number and address to someone exclusively known online. The relationship between these behaviors and adolescents’ perceptions of peer involvement, personal invulnerability, and risks and benefits was investigated. A two-wave longitudinal study among a representative sample of 1,445 Dutch adolescents aged 12–17 was conducted (49% females). Autoregressive cross-lagged structural equation models revealed that perceived peer involvement, perceived vulnerability, and perceived risks were all significant predictors of risky sexual online behavior 6 months later. No reverse causal paths were found. When the relationships between perceptions and risky sexual online behavior were modeled simultaneously, only perceived peer involvement was a determinant of risky sexual online behavior. Findings highlight the importance of addressing peer involvement in future interventions to reduce adolescents’ risky sexual online behavior

A Functional Genomics Approach to Establish the Complement of Carbohydrate Transporters in Streptococcus pneumoniae

The aerotolerant anaerobe Streptococcus pneumoniae is part of the normal nasopharyngeal microbiota of humans and one of the most important invasive pathogens. A genomic survey allowed establishing the occurrence of twenty-one phosphotransferase systems, seven carbohydrate uptake ABC transporters, one sodium∶solute symporter and a permease, underlining an exceptionally high capacity for uptake of carbohydrate substrates. Despite high genomic variability, combined phenotypic and genomic analysis of twenty sequenced strains did assign the substrate specificity only to two uptake systems. Systematic analysis of mutants for most carbohydrate transporters enabled us to assign a phenotype and substrate specificity to twenty-three transport systems. For five putative transporters for galactose, pentoses, ribonucleosides and sulphated glycans activity was inferred, but not experimentally confirmed and only one transport system remains with an unknown substrate and lack of any functional annotation. Using a metabolic approach, 80% of the thirty-two fermentable carbon substrates were assigned to the corresponding transporter. The complexity and robustness of sugar uptake is underlined by the finding that many transporters have multiple substrates, and many sugars are transported by more than one system. The present work permits to draw a functional map of the complete arsenal of carbohydrate utilisation proteins of pneumococci, allows re-annotation of genomic data and might serve as a reference for related species. These data provide tools for specific investigation of the roles of the different carbon substrates on pneumococcal physiology in the host during carriage and invasive infection

Interactive ray tracing of free-form surfaces

Even though the speed of software ray tracing has recently been increased to interactive performance even on standard PCs, these systems usually only supported triangles as geometric primitives. Directly handling free-form surfaces such as spline or subdivision surfaces instead of first tessellating them offers many advantages such as higher precision results, reduced memory requirements, and faster preprocessing due to less primitives. However, existing algorithms for ray tracing free-form surfaces are much too slow for interactive use. In this paper we present a simple and generic approach for ray tracing free-form surfaces together with specific implementations for cubic B\'ezier and Loop subdivision surfaces. We show that our approach allows to increase the performance by more than an order of magnitude, requires only constant memory, and is largely independent on the total number of free-form primitives in a scene. Examples demonstrate that even scene with over one hundred thousand free-form surfaces can be rendered interactively on a single processor at video resolution