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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. 相似文献
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The resistance of some NiCr alloys to Na2SO4-induced hot corrosion at 900°C has been found to be strongly affected by surface treatments such as grit-blasting and mechanical indentation. These cold-work procedures, when followed by recrystallization anneal, produced a large number of new grain boundaries in the deformed region. When deformed-and-annealed specimens of NiCr, Ni15 Cr and IN 738 were placed directly in contact with molten Na2SO4, the grain boundaries facilitated sulphur penetration and enhanced metal wastage. The deleterious effects of mechanical treatments could, in the case of Ni15 Cr, be offset by suitable thermal treatments such as pre-oxidation prior to Na2SO4 exposure. 相似文献
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Chatterji M 《Journal of applied measurement》2002,3(4):455-485
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. 相似文献
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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) 相似文献
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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. 相似文献
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Halldor Gudmundsson S. Chatterji A.Damgaard Jensen Niels Thaulow Preben Christensen 《Cement and Concrete Research》1979,9(5):607-612
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. 相似文献
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Gupta Surbhi; Pandit Shashi Bhushan; Srinivasan Narayanaswamy; Chatterji Dipankar 《Protein engineering, design & selection : PEDS》2002,15(6):503-511
Mycobacterium tuberculosis is a globally successful pathogen,infecting more than one third of total world's population. Thesebacteria have the remarkable ability to persist in the hostfor long periods of time unrecognized by the immune system andthen to re-emerge later in life causing the disease. The physiologyof such persistent or dormant bacilli is not very well characterized.Some evidence suggests that the dormant bacilli survive in anutrient-deprived state that is similar to the stationary phaseof the bacteria with respect to gene expression and physiology.Under this assumption we have studied the survival of Mycobacteriumsmegmatis in carbon starvation conditions as a model for mycobacterialpersistence. M.smegmatis, being a fast-growing strain, servesas a good model to study starvation responses. Using the two-dimensionalelectrophoresis-based proteomics approach, we identified a proteinwhich was found to be expressed preferentially under starvationconditions. This protein is homologous to a family of proteinscalled Dps (DNA binding Protein from Starved cells) that areknown to protect DNA under various kinds of environmental stressesand its existence has, so far, not been reported in mycobacteria.Upon expression and purification of this protein, we observedthat it has non-specific DNA-binding ability. Formation of acage-like dodecamer structure is a characteristic feature ofDps. Using comparative modelling we were able to show that Dpsfrom M.smegmatis could form a dodecamer structure similar tothe crystal structure of Dps from Escherichia coli. 相似文献