Observation of higher order parametric X-ray spectra in mosaic graphite and single silicon crystals

We have observed up to 8 orders (n) in the spectra of parametric x-radiation (PXR), in the range 5-40 keV, produced by the interaction of a 90 MeV electron beam with mosaic graphite and single silicon crystals. The measured yields and intensity ratios I(n>/_2)/I(n=1), in graphite are not in agreement with the theory of PXR for mosaic crystals. In comparison, the ratios of intensities in silicon are close to the predictions of PXR theory for perfect crystals. The bandwidths of spectral lines measured in both silicon and graphite are in good agreement with theoretical predictions.This work was partially supported by a DOE SBIR Contract (No. DE-FG03-91ER81099), DNA and the Naval Postgraduate SchoolApproved for public release; distribution is unlimited

Critical analysis of the current approaches to modelling educational effectiveness:The importance of establishing a dynamic model

Researchers in the area of educational effectiveness should attempt to develop a new theoretical framework. A critical analysis of the current models of educational effectiveness research is provided and reveals that a dynamic model of effectiveness must: (a) be multilevel in nature, (b) be based on the assumption that the relation of some effectiveness factors with achievement may be curvilinear, (c) illustrate the dimensions upon which the measurement of each effectiveness factor should be based, and (d) define relations among the effectiveness factors. In principle, each factor that refers to the classroom, school, and system, can be measured by taking into account five dimensions: frequency, focus, stage, quality, and differentiation. Examples of measuring effectiveness factors operating at different levels using these 5 dimensions are given. More attention in describing in detail factors associated with teacher behaviour in the classroom is given, since this is seen as the starting point for the development and the testing of the dynamic model. Finally, suggestions for the next steps in the development of other parts of the model are provided