340 research outputs found
Parental Monitoring and Youth's Binge Behaviors: The Role of Sensation Seeking and Life Satisfaction
Framed within an ecological perspective of the onset of adolescent problem behaviors, the current study explored the joint role of parent-adolescents’ relationships and youth's individual factors in binge eating and drinking. Firstly, in line with pieces of research highlighting the beneficial impact of effective parenting on youth development, the present paper sought to enhance the knowledge about the positive influence of parental monitoring on youth's binge drinking and eating. Moreover, since literature evidenced that the explanatory mechanisms of the association between parental monitoring and binge behaviors are not fully explored, the study focused on the potential intervening role of sensation seeking and life satisfaction as mediators. The study design was cross-sectional and self-report questionnaires were administered among a population of 944 high school students (M = 16.35, SD = 1.31) living in Palermo (Italy). Path analysis showed that parental monitoring was directly and negatively related to both binge eating and binge drinking. Moreover, sensation seeking negatively mediated the relationships between parental monitoring and both binge behaviors, whereas life satisfaction only mediated between parental monitoring and binge eating. The current study provided data useful to understand the complex interrelations between intrapersonal (life satisfaction and personality trait, i.e. sensation seeking) and contextual factors (parent–child relationships) that may discourage or cause eating and alcohol use disorders among youth. Finally, implications for parents and practitioners working with youngsters were discussed
Evaluation of Cable Harness Post-Installation Testing
The Cable Harness Post-Installation Testing Report was written in response to an action issued by the Ares Project Control Board (PCB). The action for the Ares I Avionics & Software Chief Engineer and the Avionics Integration and Vehicle Systems Test Work Breakdown Structure (WBS) Manager in the Vehicle Integration Office was to develop a set of guidelines for electrical cable harnesses. Research showed that post-installation tests have been done since the Apollo era. For Ares I-X, the requirement for post-installation testing was removed to make it consistent with the avionics processes used on the Atlas V expendable launch vehicle. Further research for the report involved surveying government and private sector launch vehicle developers, military and commercial aircraft, spacecraft developers, and harness vendors. Responses indicated crewed launch vehicles and military aircraft perform post-installation tests. Key findings in the report were as follows: Test requirements identify damage, human-rated vehicles should be tested despite the identification of statistically few failures, data does not support the claim that post-installation testing damages the harness insulation system, and proper planning can reduce overhead associated with testing. The primary recommendation of the report is for the Ares projects to retain the practice of post-fabrication and post-installation cable harness testing
Investigation of single particle devolatilization in fluidized bed reactors by X-ray imaging techniques
A non-intrusive X-ray imaging technique has been used to investigate the behaviour of solid feedstock particles in a lab-scale fluidized bed reactor operated at temperatures up to 650 °C. Beech wood and polypropylene particles of different sizes have been chosen to represent the main constituents of typical thermochemical processes feedstock. The experiments were conducted under either oxidizing or inert conditions. The presence of oxygen showed a strong effect on the overall devolatilization time, which was found to be in the range of 30-112 seconds and 40-174 seconds for beech wood and polypropylene, respectively. Surprisingly, the oxidizing nature of the fluidizing medium appears to have no influence on the volatiles release within the bed in form of the so-called endogenous bubbles. These volatiles bubbles are responsible for a lift force acting on the feedstock particle itself, which ultimately encourages the segregation towards the bed surface. A one-dimensional physical model has been developed to predict particle axial location over time, taking into account both dynamic and thermal conversion behaviour of a single feedstock particle. A revised version of the model has been proposed due to new knowledge of endogenous bubbles size provided by a novel X-ray imaging approach. Results showed very accurate predictions of the 1D model for biomass particles, which segregate towards the bed surface according to the multiple bubble segregation pattern. However, the model fails in describing plastics behaviour, possibly due to different mechanisms of reactions. The observations reported in this work show the importance of investigation at single particle level and may serve to promote new methods to gain a better understanding of plastics thermal decomposition in fluidized beds, whose mechanism is still uncertain
A Naturally Heteroplasmic Clam Provides Clues about the Effects of Genetic Bottleneck on Paternal mtDNA
Mitochondrial DNA (mtDNA) is present in multiple copies within an organism. Since these copies are not identical, a single individual carries a heterogeneous population of mtDNAs, a condition known as heteroplasmy. Several factors play a role in the dynamics of the within-organism mtDNA population: among them, genetic bottlenecks, selection, and strictly maternal inheritance are known to shape the levels of heteroplasmy across mtDNAs. In Metazoa, the only evolutionarily stable exception to the strictly maternal inheritance of mitochondria is the doubly uniparental inheritance (DUI), reported in 100+ bivalve species. In DUI species, there are two highly divergent mtDNA lineages, one inherited through oocyte mitochondria (F-type) and the other through sperm mitochondria (M-type). Having both parents contributing to the mtDNA pool of the progeny makes DUI a unique system to study the dynamics of mtDNA populations. Since, in bivalves, the spermatozoon has few mitochondria (4-5), M-type mtDNA faces a tight bottleneck during embryo segregation, one of the narrowest mitochondrial bottlenecks investigated so far. Here, we analyzed the F- and M-type mtDNA variability within individuals of the DUI species Ruditapes philippinarum and investigated for the first time the effects of such a narrow bottleneck affecting mtDNA populations. As a potential consequence of this narrow bottleneck, the M-type mtDNA shows a large variability in different tissues, a condition so pronounced that it leads to genotypes from different tissues of the same individual not to cluster together. We believe that such results may help understanding the effect of low population size on mtDNA bottleneck
NASA Perspective and Modeling of Thermal Runaway Propagation Mitigation in Aerospace Batteries
NASA has traditionally sought to reduce the likelihood of a single cell thermal runaway (TR) in their aerospace batteries to an absolute minimum by employing rigorous screening program of the cells. There was generally a belief that TR propagation resulting in catastrophic failure of the battery was a forgone conclusion for densely packed aerospace lithium-ion batteries. As it turns out, this may not be the case. An increasing number of purportedly TR propagation-resistant batteries are appearing among NASA partners in the commercial sector and the Department of Defense. In the recent update of the battery safety standard (JSC 20793) to address this paradigm shift, the NASA community included requirements for assessing TR severity and identifying simple, low-cost severity reduction measures. Unfortunately, there are no best-practice guidelines for this work in the Agency, so the first project team attempting to meet these requirements would have an undue burden placed upon them. A NASA engineering Safety Center (NESC) team set out to perform pathfinding activities for meeting those requirements. This presentation will provide contextual background to this effort, as well as initial results in attempting to model and simulate TR heat transfer and propagation within battery designs
Axial segregation behaviour of a reacting biomass particle in fluidized bed reactors: experimental results and model validation
Axial segregation behaviour of a single biomass particle in a lab-scale bubbling fluidized bed has been investigated from both experimental and modelling perspectives. Experiments were conducted using beech wood particles of different sizes, ranging from 8 to 12 mm under either oxidizing or inert conditions. The fluidized bed reactor was operated at temperatures and fluidization velocity ratios, U/Umf, in the range of 500–650 °C and 1–2, respectively. A one-dimensional model has been developed to predict the axial location of the particle over time, taking into account both dynamic and thermal conversion mechanisms. X-ray imaging techniques allowed to identify endogenous bubbles released during devolatilization and carry out direct measurements of their size. This information was used to propose an expression for the lift force acting on the fuel particle. The model showed very accurate predictions and the segregation behaviour of the fuel particle appeared to be independent of the nature of the fluidizing medium
Confocal light sheet microscopy: micron-scale neuroanatomy of the entire mouse brain.
Elucidating the neural pathways that underlie brain function is one of the greatest challenges in neuroscience. Light sheet based microscopy is a cutting edge method to map cerebral circuitry through optical sectioning of cleared mouse brains. However, the image contrast provided by this method is not sufficient to resolve and reconstruct the entire neuronal network. Here we combined the advantages of light sheet illumination and confocal slit detection to increase the image contrast in real time, with a frame rate of 10 Hz. In fact, in confocal light sheet microscopy (CLSM), the out-of-focus and scattered light is filtered out before detection, without multiple acquisitions or any post-processing of the acquired data. The background rejection capabilities of CLSM were validated in cleared mouse brains by comparison with a structured illumination approach. We show that CLSM allows reconstructing macroscopic brain volumes with sub-cellular resolution. We obtained a comprehensive map of Purkinje cells in the cerebellum of L7-GFP transgenic mice. Further, we were able to trace neuronal projections across brain of thy1-GFP-M transgenic mice. The whole-brain high-resolution fluorescence imaging assured by CLSM may represent a powerful tool to navigate the brain through neuronal pathways. Although this work is focused on brain imaging, the macro-scale high-resolution tomographies affordable with CLSM are ideally suited to explore, at micron-scale resolution, the anatomy of different specimens like murine organs, embryos or flies. (C) 2012 Optical Society of Americ
Maternal Parenting Stress and Preschoolers’ Social-Emotional Competence and Behavioural Difficulties: A Variable- and Person-Centred Approach
Background: The present study examined the relations between maternal parenting stress and preschoolers’ psychosocial adjustment, using both a variable-centred and a person-centred approach. Methods: The study had three main purposes: (a) evaluating the associations of maternal parenting stress with children’s social-emotional competence and behavioural difficulties, as perceived by their mothers; (b) inquiring the existence of different children’s clusters based on their level of social-emotional competence and behavioural difficulties; (c) exploring differences in maternal parenting stress linked to cluster membership. Participants were 91 Italian mothers, aged from 22 to 47 years old (M = 35.14, SD = 5.80), having a preschool child from 3 to 6 years old (M = 4.6, SD = 0.80).
Results: Overall, results showed that maternal parenting stress was negatively associated with children’s social-emotional competence, and positively associated with their behavioural difficulties. A cluster analysis allowed identifying four children’s profiles characterized by different levels of social-emotional competence and behavioural difficulties: Maladjusted, Troubled, Adjusted and Controversial.
Conclusions: Results also evidenced differences among clusters in maternal parenting stress. Ultimately, this study suggests that interventions may consider reducing maternal parenting stress to promote children’s psychosocial adjustment
Social Anxiety and Bullying Victimization in Children and Early Adolescents: The Role of Developmental Period and Immigrant Status
Research reveals that social anxiety may be predictive of bullying victimization, but it is not clear whether this relation stands for different groups of youth. The present study examines this association by employing a longitudinal design over 1 year and including the moderating role of developmental period (childhood vs. early adolescence) and students’ immigrant status (native vs. non-native). T1 sample included 506 children (46.44% girls, mean age M = 8.55 years, SD = 0.55) and 310 early adolescents (50% girls, mean age = 12.54 years, SD = 0.59) recruited in schools in Northern Italy. Due to missing cases and drop-outs from T1 to T2, the final sample comprised 443 and 203 students from primary and middle school, respectively. Social anxiety and peer victimization were assessed through self-reported questionnaires. Results indicated that victimization at T2 was predicted by a 3-way interaction between T1 social anxiety, immigrant status, and developmental period. In particular, socially anxious early adolescents with an immigrant background were the most victimized. The results are discussed in terms of group dynamics and intergroup processes. The findings highlight the importance of personal variables in the cumulation of risks: social anxiety is more predictive of bullying victimization for immigrant early adolescents than for children or native early adolescents
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