267 research outputs found

    The temporal variation of teleseismic P-residuals for stations in southern California

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    Teleseismic P residuals have been monitored as a function of time at 13 stations in southern California during the 5-year period 1972 to 1976. These residuals, when normalized to minimize common path and source effects, and corrected for the marked azimuthal dependence of residuals in southern California, show no significant variation. This indicates that no detectable velocity changes have occurred during this time in the vicinity of the stations monitored. It is estimated that a velocity change of ∼9 per cent occurring over a path length of 10 km and lasting for at least 6 months should be resolvable. Either such changes have not taken place in the region monitored, or any velocity anomalies are confined to a small depth range in the crust, and are poorly sampled by teleseismic waves

    Regional variations in upper mantle compressional velocities beneath southern California 1. Post-shock temperatures: Their experimental determination, calculation, and implications, 2.

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    The compressional velocity within the upper mantle beneath Southern California is investigated through observations of the dependence of teleseismic P-delays at all stations of the array on the distance and azimuth to the event. The variation of residuals with azimuth was found to be as large as 1.3 sec at a single station; the delays were stable as a function of time, and no evidence was found for temporal velocity variations related to seismic activity in the area. These delays were used in the construction of models for the upper mantle P-velocity structure to depths of 150 km, both by ray tracing and inversion techniques. The models exhibit considerable lateral heterogeneity including a region of low velocity beneath the Imperial Valley, and regions of increased velocity beneath the Sierra Nevada and much of the Transverse Ranges. The development is described of a technique for the experimental determination of post-shock temperatures, and its application to several metals and silicates shocked to pressures in the range 5 to 30 GPa. The technique utilizes an infra-red radiation detector to determine the brightness temperature of the free surface of the sample after the shock wave has passed through it

    Measuring of child development and learning

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    Background paper prepared for the 2016 Global Education Monitoring ReportThe proposed education goal for the post-2015 sustainable development agenda includes a target focused on ensuring children begin formal schooling developmentally on track and “ready for primary school.” What does it mean for a child at school entry to be developmentally on track, and how should it be measured? This paper reviews issues and approaches to measurement of young children’s development in light of the education target on early childhood development. Basic principles of child development with implications for measurement are described, along with issues in accurately capturing the complex nature of early development with feasible, cost-effective measures. Analyses of some of the most commonly-used regional and global measures of young children’s development are described, with emphasis on identifying the policy relevance, feasibility, and methodologies that influence their potential usefulness for measuring national, regional or global progress towards proposed global education goals. Finally, directions for measuring early childhood development and learning in the proposed agenda are outlined

    Post-shock temperatures in minerals

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    An experimental technique has been developed for the measurement of post-shock temperatures in a wide variety of materials, including those of geophysical interest such as silicates. The technique uses an infrared radiation detector to determine the brightness temperature of samples shocked to pressures in the range 5 to ∼ 30 GPa; in these experiments measurements have been made in two wavelength ranges (4.5 to 5.75 μm; 7 to 14 μm). Reproducible results, with the temperatures in the two wavelength bands generally in excellent agreement, have been obtained for aluminium-2024 (10.5 to 33 GPa; 125 to 260°C), stainless steel-304 (11.5 to 50 GPa; 80 to 350°C), crystalline quartz (5.0 to 21.5 GPa; 80 to 250°C), forsterite (7.5 to 28.0 GPa; ∼ 30 to 160°C) and Bamble bronzite (6.0 to 26.0 GPa; ∼ 30 to 225°C). These results are generally much higher at low pressures (where they may even be in excess of the calculated shock temperatures) than the values calculated assuming a hydrodynamic rheology and isentropic release parallel to the Hugoniot but tend towards them at higher pressures. In aluminium-2024, the theoretical post-shock temperatures, assuming a fluid-like rheology, are 35 to 218°C, for the pressure range 10.5 to 33 GPa. However, the results are in considerably better agreement with values calculated assuming elasto-plastic behaviour (80 to 270°C) which probably also causes the high measured temperatures for stainless steel. In forsterite the measured values ranged from 65°C at 9.6 GPa (there was no detectable rise at 7.5 GPa) to 156° at 28.0 GPa, whereas the ‘hydrodynamic values’ were 30 to 120°C. Values obtained for quartz were in excellent agreement with those calculated by Mashimo et al. using release adiabat data. It is concluded that release adiabat data should be used, wherever available, for calculations of residual temperature, and that adequate descriptions of the shock and release processes in minerals need to be more complex than generally assumed

    Father Involvement in Early Head Start Research Programs

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    This study examined fathers\u27 participation in Early Head Start programs using quantitative and qualitative data from 326 Early Head Start fathers when children were 36 months of age. About half (49%) of the fathers were involved in at least one program activity. A quarter (26%) of the fathers participated at a higher level, in two or more types of program activities. Fathers participated in parent education programs (17%), group socializations (15%), father-only activities (6%), policy councils and program committees (9%), home visits (32% ever, 17% monthly), and in dropping children off at the Early Head Start center (24% ever, 12% nine times or more). In multivariate analyses, at least one level of involvement was predicted by maternal engagement in the program and maturity of the father involvement program. Higher level involvement in the program was predicted by the father being African American/Black or Hispanic, maternal engagement in the program, and maturity of the father involvement program. Bivariate analyses showed that fathers in predominantly homebased programs who participated in frequent home visits were more often married, non-English speaking, and in families where both mothers and fathers had lower than typical levels of education. Fathers in predominantly center-based programs who frequently dropped off the Early Head Start child at the center were more often men of color, fathers of girls, and partnered with an employed mother or a mother rated as engaged in the Early Head Start program. Qualitative analyses underscore the potential for father program participation in mature programs and among policy-relevant groups

    Shock and Release Temperatures in Molybdenum

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    Shock and release temperatures in Mo were calculated, taking account of heating from plastic flow predicted using the Steinberg-Guinan model. Plastic flow was calculated self-consistently with the shock jump conditions: this is necessary for a rigorous estimate of the locus of shock states accessible. The temperatures obtained were significantly higher than predicted assuming ideal hydrodynamic loading. The temperatures were compared with surface emission spectrometry measurements for Mo shocked to around 60GPa and then released into vacuum or into a LiF window. Shock loading was induced by the impact of a planar projectile, accelerated by high explosive or in a gas gun. Surface velocimetry showed an elastic wave at the start of release from the shocked state; the amplitude of the elastic wave matched the prediction to around 10%, indicating that the predicted flow stress in the shocked state was reasonable. The measured temperatures were consistent with the simulations, indicating that the fraction of plastic work converted to heat was in the range 70-100% for these loading conditions

    Families' social backgrounds matter : socio-economic factors, home learning and young children's language, literacy and social outcomes

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    Parental support with children's learning is considered to be one pathway through which socio-economic factors influence child competencies. Utilising a national longitudinal sample from the Millennium Cohort Study, this study examined the relationship between home learning and parents' socio-economic status and their impact on young children's language/literacy and socio-emotional competence. The findings consistently showed that, irrespective of socio-economic status, parents engaged with various learning activities (except reading) roughly equally. The socio-economic factors examined in this study, i.e., family income and maternal educational qualifications, were found to have a stronger effect on children's language/literacy than on social-emotional competence. Socio-economic disadvantage, lack of maternal educational qualifications in particular, remained powerful in influencing competencies in children aged three and at the start of primary school. For children in the first decade of this century in England, these findings have equity implications, especially as the socio-economic gap in our society widens
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