Simulations and Generalized Model of the Effect of Filler Size Dispersity on Electrical Percolation in Rod Networks

We present a three-dimensional simulation of electrical conductivity in isotropic, polydisperse rod networks from which we determine the percolation threshold (ϕc). Existing analytical models that account for size dispersity are formulated in the slender-rod limit and are less accurate for predicting ϕc in composites with rods of modest L/D. Using empirical approximations from our simulation data, we generalized the excluded volume percolation model to account for both finite L/D and size dispersity, providing a solution for ϕc of polydisperse rod networks that is quantitatively accurate across the entire L/D range

Application of Geometric Probability Techniques to the Evaluation of Interaction Energies Arising from a General Radial Potential

A formalism is developed for using geometric probability techniques to evaluate interaction energies arising from a general radial potential V(r12), where r12 = ∣r2−r1∣. The integrals that arise in calculating these energies can be separated into a radial piece that depends on r12 and a nonradial piece that describes the geometry of the system, including the density distribution. We show that all geometric information can be encoded into a “radial density function” G(r12;ρ1,ρ2), which depends on r12 and the densities ρ1and ρ2 of two interacting regions. G(r12;ρ1,ρ2) is calculated explicitly for several geometries and is then used to evaluate interaction energies for several cases of interest. Our results find application in elementary particle, nuclear, and atomic physic

Proximity Driven Enhanced Magnetic Order at Ferromagnetic Insulator / Magnetic Topological Insulator Interface

Magnetic exchange driven proximity effect at a magnetic insulator / topological insulator (MI/TI) interface provides a rich playground for novel phenomena as well as a way to realize low energy dissipation quantum devices. Here we report a dramatic enhancement of proximity exchange coupling in the MI / magnetic-TI EuS / Sb$_{2-x}$V$_x$Te$_3$ hybrid heterostructure, where V doping is used to drive the TI (Sb$_{2}$Te$_3$) magnetic. We observe an artificial antiferromagnetic-like structure near the MI/TI interface, which may account for the enhanced proximity coupling. The interplay between the proximity effect and doping provides insights into controllable engineering of magnetic order using a hybrid heterostructure.Comment: 5 pages, 4 figure

Parental Messages about Substance Use in Early Adolescence: Extending a Model of Drug-Talk Styles

This study extends a typology of parent-offspring drug talk styles to early adolescents and investigates associations with adolescent substance use. Data come from a self-report survey associated with a school-based, 7th grade drug prevention curriculum. Mixed-methods were used to collect data across four measurement occasions spanning 30 months. Findings highlight frequencies of various drug-talk styles over time (i.e., situated direct, ongoing direct, situated indirect, ongoing indirect, never talked), messages adolescents hear from parents, and comparisons of alcohol, cigarette, and marijuana use by drug talk style. This study advances understanding of parent-adolescent communication about substances and holds practical implications for drug prevention efforts

Teacher Narratives and Student Engagement Testing Narrative Engagement Theory in Drug Prevention Education

Testing narrative engagement theory, this study examines student engagement and teachers’ spontaneous narratives told in a narrative-based drug prevention curriculum. The study describes the extent to which teachers share their own narratives in a narrative-based curriculum, identifies dominant narrative elements, forms and functions, and assesses the relationships among teacher narratives, overall lesson narrative quality, and student engagement. One-hundred videotaped lessons of the keepin’ it REAL drug prevention curriculum were coded and the results supported the claim that increased narrative quality of a prevention lesson would be associated with increased student engagement. The quality of narrativity, however, varied widely. Implications of these results for narrative-based prevention interventions and narrative pedagogy are discussed

Describing Teacher–Student Interactions: A Qualitative Assessment of Teacher Implementation of the 7th Grade keepin’ it REAL Substance Use Intervention

Variations in the delivery of school-based substance use prevention curricula affect students\u27 acquisition of the lesson content and program outcomes. Although adaptation is sometimes viewed as a lack of fidelity, it is unclear what types of variations actually occur in the classroom. This observational study investigated teacher and student behaviors during implementation of a middle school-based drug prevention curriculum in 25 schools across two Midwestern states. Trained observers coded videos of 276 lessons, reflecting a total of 31 predominantly Caucasian teachers (10 males and 21 females) in 73 different classes. Employing qualitative coding procedures, the study provides a working typology of implementation patterns based on varying levels of teacher control and student participation. These patterns are fairly consistent across lessons and across classes of students, suggesting a teacher-driven delivery model where teachers create a set of constraints within which students vary their engagement. Findings provide a descriptive basis grounded in observation of classroom implementation that can be used to test models of implementation fidelity and quality as well as impact training and other dissemination research

Loss of Tsc2 in radial glia models the brain pathology of tuberous sclerosis complex in the mouse

Tuberous sclerosis complex (TSC) is an autosomal dominant, tumor predisposition disorder characterized by significant neurodevelopmental brain lesions, such as tubers and subependymal nodules. The neuropathology of TSC is often associated with seizures and intellectual disability. To learn about the developmental perturbations that lead to these brain lesions, we created a mouse model that selectively deletes the Tsc2 gene from radial glial progenitor cells in the developing cerebral cortex and hippocampus. These Tsc2 mutant mice were severely runted, developed post-natal megalencephaly and died between 3 and 4 weeks of age. Analysis of brain pathology demonstrated cortical and hippocampal lamination defects, hippocampal heterotopias, enlarged dysplastic neurons and glia, abnormal myelination and an astrocytosis. These histologic abnormalities were accompanied by activation of the mTORC1 pathway as assessed by increased phosphorylated S6 in brain lysates and tissue sections. Developmental analysis demonstrated that loss of Tsc2 increased the subventricular Tbr2-positive basal cell progenitor pool at the expense of early born Tbr1-positive post-mitotic neurons. These results establish the novel concept that loss of function of Tsc2 in radial glial progenitors is one initiating event in the development of TSC brain lesions as well as underscore the importance of Tsc2 in the regulation of neural progenitor pools. Given the similarities between the mouse and the human TSC lesions, this model will be useful in further understanding TSC brain pathophysiology, testing potential therapies and identifying other genetic pathways that are altered in TSC

Ultrasonography for chairside evaluation of periodontal structures: A pilot study

BackgroundThe crestal bone level and soft tissue dimension are essential for periodontal diagnosis and phenotype determination; yet, existing measurement methods have limitations. The aim of this clinical study was to evaluate the correlation and accuracy of ultrasound in measuring periodontal dimensions, compared to direct clinical and cone- beam computed tomography (CBCT) methods.MethodsA 24- MHz ultrasound probe prototype, specifically designed for intraoral use, was employed. Periodontal soft tissue dimensions and crestal bone levels were measured at 40 teeth and 20 single missing tooth gaps from 20 patients scheduled to receive a dental implant surgery. The ultrasound images were interpreted by two calibrated examiners. Inter- rater agreement was calculated by using inter- rater correlation coefficient (ICC). Ultrasound readings were compared with direct clinical and CBCT readings by using ICC and Bland- Altman analysis.ResultsThe following six parameters were measured: 1) interdental papilla height (tooth), 2) mid- facial soft tissue height (tooth), 3) mucosal thickness (tooth), 4) soft tissue height (edentulous ridge), 5) mucosal thickness (edentulous ridge), and 6) crestal bone level (tooth). Intra- examiner calibrations were exercised to achieve an agreement of at least 0.8. ICC between the two readers ranged from 0.482 to 0.881. ICC between ultrasound and direct readings ranged from 0.667 to 0.957. The mean difference in mucosal thickness (tooth) between the ultrasound and direct readings was - 0.015 mm (95% CI: - 0.655 to 0.624 mm) without statistical significance. ICC between ultrasound and CBCT ranged from 0.654 to 0.849 among the measured parameters. The mean differences between ultrasound and CBCT range from - 0.213 to 0.455 mm, without statistical significance.ConclusionUltrasonic imaging can be valuable for accurate and real- time periodontal diagnosis without concerns about ionizing radiation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156207/2/jper10483_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156207/1/jper10483.pd