New insights into the biomechanics of Legg-Calvé-Perthes’ disease: The role of epiphyseal skeletal immaturity in vascular obstruction

ObjectivesLegg–Calvé–Perthes’ disease (LCP) is an idiopathic osteonecrosis of the femoral head that is most common in children between four and eight years old. The factors that lead to the onset of LCP are still unclear; however, it is believed that interruption of the blood supply to the developing epiphysis is an important factor in the development of the condition.MethodsFinite element analysis modelling of the blood supply to the juvenile epiphysis was investigated to understand under which circumstances the blood vessels supplying the femoral epiphysis could become obstructed. The identification of these conditions is likely to be important in understanding the biomechanics of LCP.ResultsThe results support the hypothesis that vascular obstruction to the epiphysis may arise when there is delayed ossification and when articular cartilage has reduced stiffness under compression.ConclusionThe findings support the theory of vascular occlusion as being important in the pathophysiology of Perthes disease

The Relative Contributions Of Parental And Sibling Substance Use To Adolescent Tobacco, Alcohol, And Other Drug Use

While research demonstrates that parental tobacco and alcohol use increases the likelihood of children's substance use, it is unclear whether or not sibling use has a greater, weaker, or similar effect. Based upon self-reported information from Australian adolescents, their siblings and parents, this investigation examines the association between siblings' tobacco and alcohol use. The relationship is consistent, moderately strong, and remains significant when controlling for a number of family-related factors, indicating that the shared environment cannot fully explain the extent of similarity in siblings' behaviors. In addition, sibling substance use has a greater effect on adolescent substance use than does smoking or drinking by parents. These findings indicate the need to include siblings and information regarding sibling relationships in prevention and intervention programs

Impurity segregation in graphene nanoribbons

The electronic properties of low-dimensional materials can be engineered by doping, but in the case of graphene nanoribbons (GNR) the proximity of two symmetry-breaking edges introduces an additional dependence on the location of an impurity across the width of the ribbon. This introduces energetically favorable locations for impurities, leading to a degree of spatial segregation in the impurity concentration. We develop a simple model to calculate the change in energy of a GNR system with an arbitrary impurity as that impurity is moved across the ribbon and validate its findings by comparison with ab initio calculations. Although our results agree with previous works predicting the dominance of edge disorder in GNR, we argue that the distribution of adsorbed impurities across a ribbon may be controllable by external factors, namely an applied electric field. We propose that this control over impurity segregation may allow manipulation and fine-tuning of the magnetic and transport properties of GNRs.Comment: 5 pages, 4 figures, submitte

Sibling Influences on Adolescent Delinquent Behaviour: An Australian Longitudinal Study

This article examines sibling influences on adolescent delinquency at age 14, using data from an Australian longitudinal study of 374 same- and mixed-sex sibling pairs. Based on maternal and self-reports, a moderately strong association between siblings' delinquency is found. The relationship remains significant controlling for childhood aggression and family environment factors measured during childhood (age 5) and adolescence (age 14), using both standardized instruments and new scales. This effect varies according to the sex composition of the sibling pair and is stronger for males and those whose parents have been arrested. The need for increased attention to sibling influences by researchers and prevention practitioners is discussed

Petrology of Chondrule Rims in Yamato-791498 and Asuka-881828, the Least-Altered CR Chondrites in the Japanese NIPR Collection

CR chondrites are a group of car-bonaceous chondrites with well-preserved records of formation of their components in the solar nebula. The CR chondrites have undergone a wide range of aqueous alteration from nearly anhydrous (CR2.8 or CR3.0) to extensive recrystallization of primary minerals, including replacement of coarse-grained silicates in chondrules (CR2.0). At the same time, CRs have experienced only minor thermal metamorphism except for rare CR6 samples. Identifying minimally altered CR chondrites is a priority because they preserve (1) relatively pristine records of the solar nebula and (2) minerals and textures at the beginning stages of aqueous alteration. Here we report the petrologic characteristics of Y-791498 and A-881828 as the least aqueously altered CR chondrites in the Japanese NIPR meteorite collection. Previous studies have shown that fine-grained rims on chondrules are indicators of incipient alteration of primitive CR chondrites, there-fore we focus on rims around chondrules in the two meteorites

Gender differences in the effects of exposure to intimate partner violence on adolescent violence and drug use

Objective This study investigated the long-term effects of exposure to intimate partner violence in the home on adolescent violence and drug use and gender differences in these relationships. Although the general relationship between exposure to IPV and negative outcomes for youth has been demonstrated in past research, gender differences in the effects of IPV on adolescents have been rarely assessed using longitudinal data. Methods Longitudinal data was obtained from 1,315 adolescents and their primary caregivers participating in the Project on Human Development in Chicago Neighborhoods (PHDCN). The sample was 51% female and ethnically diverse (45% Hispanic, 37% African-American, and 14% Caucasian). Two waves of data were assessed to examine the effects of exposure to IPV, reported by caregivers when their children were aged 12 and 15, on violence and drug use, reported by adolescents 3 years later. Multivariate statistical models were employed to control for a range of child, parent, family, and neighborhood risk factors. Results Exposure to IPV did not significantly predict subsequent violence among males or females in multivariate analyses. IPV exposure was significantly related to the frequency of drug use for females but did not predict drug use among males. This gender difference was not statistically significant, however, which suggests more similarities than differences in the relationship between exposure to IPV and subsequent violence and drug use. Conclusions This study supports prior research indicating that exposure to IPV can negatively impact adolescent development, but it suggests that these effects may be more likely to influence some outcomes (e.g., drug use) than others (e.g., interpersonal violence). The findings also emphasize the need for additional research examining the overall impact of IPV on adolescent problem behaviors and gender differences in these relationships, including longitudinal studies and investigations that control for a range of other important predictors. A better understanding of these relationships can help inform intervention efforts aimed at ensuring that adolescents living in violent households receive timely and appropriate services to help prevent the occurrence of future problem behaviors

The Effects of Neighborhood Context on Youth Violence and Delinquency: Does Gender Matter?

This study examined the effects of neighborhood structural and social characteristics on offending among girls and boys aged 8–17 residing in 80 Chicago neighborhoods. The results demonstrated gender differences in contextual effects, although not in ways predicted by social disorganization theory. Collective efficacy and concentrated disadvantage were not significantly associated with self-reported offending among males. Among females, collective efficacy was related to higher rates of general delinquency and violence, while disadvantage reduced the likelihood of self-reported violence. These outcomes suggest that neighborhoods may impact individual offending in complex ways and highlight the importance of considering gender when researching contextual effects on youth offending

The Cycle of Violence in Context: Exploring the Moderating Roles of Neighborhood Disadvantage and Cultural Norms

Although the cycle of violence theory has received empirical support (Widom, 1989a, 1989b), in reality, not all victims of child physical abuse become involved in violence. Therefore, little is known regarding factors that may moderate the relationship between abuse and subsequent violence, particularly contextual circumstances. The current investigation used longitudinal data from 1,372 youth living in 79 neighborhoods who participated in the Project on Human Development in Chicago Neighborhoods (PHDCN), and it employed a multivariate, multilevel Rasch model to explore the degree to which neighborhood disadvantage and cultural norms attenuate or strengthen the abuse–violence relationship. The results indicate that the effect of child physical abuse on violence was weaker in more disadvantaged communities. Neighborhood cultural norms regarding tolerance for youth delinquency and fighting among family and friends did not moderate the child abuse–violence relationship, but each had a direct effect on violence, such that residence in neighborhoods more tolerant of delinquency and fighting increased the propensity for violence. These results suggest that the cycle of violence may be contextualized by neighborhood structural and cultural conditions

Exposure to Intimate Partner Violence: Does the Gender of the Perpetrator Matter for Adolescent Mental Health Outcomes?

Youth who are exposed to intimate partner violence (IPV) between their parents may be at increased risk for a multitude of behavioral and emotional problems, including mental health problems such as depression, anxiety, posttraumatic stress disorder (PTSD), and internalizing symptoms (Fergusson & Horwood, 1998; Finkelhor, Ormond, & Turner, 2009; Graham-Bermann, DeVoe, Mattis, Lynch, & Thomas, 2006; Zinzow et al., 2009). Research also suggests that males and females may react differently to being exposed to parental violence, although most of the findings in this area are mixed with regard to mental health outcomes. For instance, some evidence suggests that male witnesses are more likely to develop externalizing behaviors and females are more likely to suffer from internalizing disorders (Clements, Oxtoby, & Ogle, 2008; Kennedy, Bybee, Sullivan, & Greeson, 2010; Moylan et al., 2010; Yates, Dodds, Sroufe, & Egeland, 2003), whereas other studies have found that girls exposed to IPV are more likely than boys to demonstrate externalizing problems such as anger (Sigfusdottir, Farkas, & Silver, 2004). Yet others have found no gender differences in these outcomes (Fergusson & Horwood, 1998; Kitzmann, Gaylord, Holt, & Kenny, 2003; Sternberg, Baradaran, Abbott, Lamb, & Guterman, 2006)

Penny for Your Thoughts? The Protective Effect of Youths’ Attitudes Against Drug Use in High-Risk Communities

Individual-level attitudes about drugs are strong predictors of substance use among adolescents, and aggregate-level community norms regarding deviancy and drug use may influence youth attitudes as well as their drug use. This study examined the direct effects of neighborhood norms about deviance, disadvantage, immigrant concentration, and residential stability on youths’ attitudes about drug harmfulness as well as their variety of past month substance use. The moderating effect of community norms on the relationship between youth attitudes and drug use was also examined. Results suggest that community norms favorable to deviance and drug use reduced youth’s attitudes that drugs were harmful. Further, youth’s perceptions of drug harmfulness significantly reduced their substance use in the past month. Neighborhood concentrated immigration also significantly reduced substance use. Finally, living in areas where norms were favorable to deviance enhanced the protective effect of youths’ perceptions. Implications for research and substance use prevention strategies are discussed