Stress fracture of the sternum: an unusual injury?

Stress fracture of the sternum is a rare condition which presents as acute anterior chest pain after repetitive upper-body exercise. Two case reports are presented and it is postulated that this is an often underdiagnosed condition which should be considered in the differential diagnosis of acute chest pain in the athlete. Awareness of the injury together with meticulous clinical examination supported by good quality radiographs or isotope bone scan may lead to an increase in the diagnosis of this injury.     

Temperature-dependent bending loss characteristics of W-type photonic crystal fibres: design and analysis

The temperature-dependent bending loss characteristics of two solid-core W-typephotonic crystal fibres have been reported by employing full-vectorial finite element method. The bending loss characteristics of W-type-I photonic crystal fibrestructure have been found better than that of the W-type-II photonic crystal fibre structure. The proposed photonic crystal fibrestructures show significant nonlinearity and hence can be used in telecommunication and nonlinear applications such as visible to near-infrared supercontinuum generation. Macro-bend insensitive nature of the proposed photonic crystal fibres makes them suitable candidates for fibre-to-the-home applications.     

Electron microscopy of shock deformation in alumina

Shock recovered samples of a coarse grain (10 μm), high density (>99.9% theoretical) alumina from asymmetric impact tests conducted at 6.5 GPa (e.g. 3.2 times its Hugoniot Elastic Limit) in a single stage gas gun and characterized by X-ray diffractometry, scanning and field emission scanning electron microscopy, and transmission electron microscopy showed prolific presence of reduced crystallite size, higher average microstrain, grain localized micro/nano-scale deformations, micro-cleavages, grain-boundary microcracks, micro-wing crack formation, extensive shear induced deformations and fractures localized at grains, grain boundaries and triple grain junctions, grain localized entanglement of dislocations and their pile up impeded at grain boundaries. A new qualitative model based on micro-shear and micro-twist induced deformation and fracture in single and/or multiple planes in suitably oriented grain and/or grain assembly was developed to explain the experimentally observed damage evolution process.     

Measuring leader perceptions of school readiness for reforms: use of an iterative model combining classical and Rasch methods

This study examines validity of data generated by the School Readiness for Reforms: Leader Questionnaire (SRR-LQ) using an iterative procedure that combines classical and Rasch rating scale analysis. Following content-validation and pilot-testing, principal axis factor extraction and promax rotation of factors yielded a five factor structure consistent with the content-validated subscales of the original instrument. Factors were identified based on inspection of pattern and structure coefficients. The rotated factor pattern, inter-factor correlations, convergent validity coefficients, and Cronbach's alpha reliability estimates supported the hypothesized construct properties. To further examine unidimensionality and efficacy of the rating scale structures, item-level data from each factor-defined subscale were subjected to analysis with the Rasch rating scale model. Data-to-model fit statistics and separation reliability for items and persons met acceptable criteria. Rating scale results suggested consistency of expected and observed step difficulties in rating categories, and correspondence of step calibrations with increases in the underlying variables. The combined approach yielded more comprehensive diagnostic information on the quality of the five SRR-LQ subscales; further research is continuing.     

Reading achievement gaps, correlates, and moderators of early reading achievement: Evidence from the Early Childhood Longitudinal Study (ECLS) kindergarten to first grade sample.

This study estimated reading achievement gaps in different ethnic, gender, and socioeconomic groups of 1st graders in the U.S. compared with specific reference groups and identified statistically significant correlates and moderators of early reading achievement. A subset of 2,296 students nested in 184 schools from the Early Childhood Longitudinal Study (ECLS) kindergarten to 1st-grade cohort were analyzed with hierarchical linear models. With child-level background differences controlled, significant 1st-grade reading differentials were found in African American children (-0.51 SD units below Whites), boys (-0.31 SD units below girls), and children from high-poverty households (-0.61 to -1.0 SD units below well-to-do children). In all 3 comparisons, the size of the reading gaps increased from kindergarten entry to 1st grade. Reading level at kindergarten entry was a significant child-level correlate, related to poverty status. At the school level, class size and elementary teacher certification rate were significant reading correlates in 1st grade. Cross-level interactions indicated reading achievement in African American children was moderated by the schools students attended, with attendance rates and reading time at home explaining the variance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The catalyzed reaction of graphite with water vapor

The effects of Li, Na and K carbonates in catalyzing the reaction between graphite and water vapor have been studied in the temperature range 700–1100°C, using simultaneous thermogravimetry-differential thermal analysis. The catalyzed reaction, which is rapidly accelerated at temperatures in the vicinity of the melting point of the alkali metal carbonate, occurs most readily in the presence of the lithium salt. Thermodynamic analysis of the possible reactions suggests that the catalytic mechanism involves an oxidation-reduction cycle with the intermediate formation of the hydroxide of the alkali metal.     

The measurement of paste content in hardened concrete using automatic image analyzing technique

This paper describes a technique for the measurement of paste contents of mortars and concretes. The technique involves etching the polished surfaces of samples with a saturated solution of salicylic acid in 80:20 methyl alcohol: water mixture which does not affect limestone aggregates. The contrast difference between the exposed aggregates and the etched areas is then enhanced by painting the aggregates black and filling the etched areas with a white powder. An automatic image analyzer can then measure either the blackened aggregates or the whitened etched areas.