Rapid fitting of particle cascade development data from X-ray film densitometry measurements

A semiautomatic method of fitting transition curves to X-ray film optical density measurements of electromagnetic particle cascades is described. Several hundred singly and multiple interacting cosmic ray events from the JACEE 8 balloon flights were analyzed using this procedure. In addition to greatly increased speed compared to the previous manual method, the semiautomatic method offers increased accuracy through maximum likelihood fitting

Mechanisms of fragmentation of Al-W granular composites under dynamic loading

Numerical simulations of Aluminum (Al) and Tungsten (W) granular composite rings under various dynamic loading conditions caused by explosive loading were examined. Three competing mechanisms of fragmentation were observed: a continuum level mechanism generating large macrocracks described by the Grady-Kipp fragmentation mechanism, a mesoscale mechanism generating voids and microcracks near the initially unbonded Al/W interfaces due to tensile strains, and a mesoscale jetting due to the development of large velocity gradients between the W particles and adjacent Al. These mesoscale mechanisms can be used to tailor the size of the fragments by selecting an appropriate initial mesostructure for a given loading condition.Comment: 10 pages, 3 figures, submitted to AP

Observations of cosmic ray induced phosphenes

Phosphene observations by astronauts on flights near and far from earth atmosphere are discussed. It was concluded that phosphenes could be observed by the naked eye. Further investigation is proposed to determine realistic human tolerance levels for extended missions and to evaluate the need to provide special spacecraft shielding

Three dimensional viscous analysis of a hypersonic inlet

The flow fields in supersonic/hypersonic inlets are currently being studied at NASA Lewis Research Center using 2- and 3-D full Navier-Stokes and Parabolized Navier-Stokes solvers. These tools have been used to analyze the flow through the McDonnell Douglas Option 2 inlet which has been tested at Calspan in support of the National Aerospace Plane Program. Comparisons between the computational and experimental results are presented. These comparisons lead to better overall understanding of the complex flows present in this class of inlets. The aspects of the flow field emphasized in this work are the 3-D effects, the transition from laminar to turbulent flow, and the strong nonuniformities generated within the inlet

The Conformal Anomaly in General Rank 1 Symmetric Spaces and Associated Operator Product

We compute the one-loop effective action and the conformal anomaly associated with the product $\bigotimes_p{\cal L}_p$ of the Laplace type operators ${\cal L}_p, p=1,2$, acting in irreducible rank 1 symmetric spaces of non-compact type. The explicit form of the zeta functions and the conformal anomaly of the stress-energy momentum tensor is derived.Comment: 10 pages, LaTe

Fluorides, orthodontics and demineralization: a systematic review

Objectives: To evaluate the effectiveness of fluoride in preventing white spot lesion (WSL) demineralization during orthodontic treatment and compare all modes of fluoride delivery. Data sources: The search strategy for the review was carried out according to the standard Cochrane systematic review methodology. The following databases were searched for RCTs or CCTs: Cochrane Clinical Trials Register, Cochrane Oral Health Group Specialized Trials Register, MEDLINE and EMBASE. Inclusion and exclusion criteria were applied when considering studies to be included. Authors of trials were contacted for further data. Data selection: The primary outcome of the review was the presence or absence of WSL by patient at the end of treatment. Secondary outcomes included any quantitative assessment of enamel mineral loss or lesion depth. Data extraction: Six reviewers independently, in duplicate, extracted data, including an assessment of the methodological quality of each trial. Data synthesis: Fifteen trials provided data for this review, although none fulfilled all the methodological quality assessment criteria. One study found that a daily NaF mouthrinse reduced the severity of demineralization surrounding an orthodontic appliance (lesion depth difference –70.0 µm; 95% CI –118.2 to –21.8 µm). One study found that use of a glass ionomer cement (GIC) for bracket bonding reduced the prevalence of WSL (Peto OR 0.35; 95% CI 0.15–0.84) compared with a composite resin. None of the studies fulfilled all of the methodological quality assessment criteria. Conclusions: There is some evidence that the use of a daily NaF mouthrinse or a GIC for bonding brackets might reduce the occurrence and severity of WSL during orthodontic treatment. More high quality, clinical research is required into the different modes of delivering fluoride to the orthodontic patient

Parameter estimators of random intersection graphs with thinned communities

This paper studies a statistical network model generated by a large number of randomly sized overlapping communities, where any pair of nodes sharing a community is linked with probability $q$ via the community. In the special case with $q=1$ the model reduces to a random intersection graph which is known to generate high levels of transitivity also in the sparse context. The parameter $q$ adds a degree of freedom and leads to a parsimonious and analytically tractable network model with tunable density, transitivity, and degree fluctuations. We prove that the parameters of this model can be consistently estimated in the large and sparse limiting regime using moment estimators based on partially observed densities of links, 2-stars, and triangles.Comment: 15 page

Measurement of the Parallax of PSR B0950+08 Using the VLBA

A new technique has been developed to remove the ionosphere's distorting effects from low frequency VLBI data. By fitting dispersive and non-dispersive components to the phases of multi-frequency data, the ionosphere can be effectively removed from the data without the use of {\em a priori} calibration information. This technique, along with the new gating capability of the VLBA correlator, was used to perform accurate astrometry on pulsar B0950+08, resulting in a much improved measurement of this pulsar's proper motion ($\mu_{\alpha} = -1.6 \pm 0.4$ mas/yr, $\mu_{\delta} = 29.5 \pm 0.5$ mas/yr) and parallax ($\pi = 3.6 \pm 0.3$ mas). This puts the pulsar at a distance of $280 \pm 25$ parsecs, about twice as far as previous estimates, but in good agreement with models of the electron density in the local bubble.Comment: 5 pages, Latex with AASTEX. Accepted for publication in Ap

Parenting Strategies Used by Parents of Children with ASD: Differential Links with Child Problem Behaviour

Here, we explored the structure of the ‘Parenting Strategies Questionnaire’, a new scale designed to measure parenting strategies for problem behaviour in ASD. We then examined links between child behaviour and parenting in a sample of 222 predominantly-UK parents of ASD children exhibiting behaviour found difficult or challenging. Analysis revealed three parenting subscales: Accommodation, Reinforcement Approaches and Reducing Uncertainty. Both Accommodation and Reducing Uncertainty were linked to child problem behaviour. Child factors explained up to 29% of the variance in Accommodation, with Socially Inflexible Non-compliance the strongest predictor, and up to 24% of the variance in Reducing Uncertainty, with Intolerance of Uncertainty the strongest predictor. Child factors were not related to Reinforcement Approaches. Longitudinal studies investigating these relationships are needed. Autism Spectrum Disorders (ASD) are neurodevelopmental impairments characterised by difficulties with communication, socialisation, and rigid and repetitive behaviours (Americal Psychiatric Association 2013). Problem behaviour (also referred to as ‘behaviour that challenges’ or, in the past, ‘challenging behaviour’) often occurs in children with ASD, and is more severe in ASD than in other clinical populations (e.g., Brereton et al. 2006; Estes et al. 2009). Forms of problem behaviour include oppositionality, failures to comply, destructiveness and explosiveness (e.g., Gadow et al. 2004). These behaviours are thought to reflect a dysregulated emotional state, resulting in outbursts and prolonged emotional reactions (Mazefsky et al. 2018a, b). Problem behaviour may reflect attempts by the child to reduce anxiety or distress by escaping aversive activities, or reactivity reflecting frustration when things are not on their terms (Brewer et al. 2014; Larson 2006). Demands to comply have been identified as a key trigger of reactivity in ASD (Chowdhury et al. 2016). Some individuals appear more reactive to routine demands (e.g., to wash or get dressed), and others to demands in socially challenging or novel situations (e.g., when visiting friends) (Chowdhury et al. 2016). The former ‘demand-specific’ profile resembles accounts of extreme/‘pathological’ demand avoidance (‘PDA’), which describe avoidance of and reactivity to routine demands in children with ASD (Newson et al. 2003). Some accounts of PDA explicitly attribute these behaviours to elevated anxiety and distress in the context of demands (Newson et al. 2003). In contrast, the latter ‘socially inflexible’ profile, may particularly reflect intolerance of uncertainty: the tendency to “react negatively on an emotional, cognitive, and behavioural level to uncertain situations and events” (Buhr and Dugas 2009, p. 216), which characterizes some children with ASD (Boulter et al. 2014; Larson 2006)