Similarity of the concentration field of gas-phase turbulent jets

This work is an experimental investigation of the turbulent concentration field formed when the nozzle gas from a round, momentum-driven, free turbulent jet mixes with gas entrained from a quiescent reservoir. The measurements, which were made with a non-intrusive laser-Rayleigh scattering diagnostic at Reynolds numbers of 5000, 16000, and 40000, cover the axial range from 20 to 90 jet exit diameters and resolve the full range of temporal and spatial concentration scales. Reynolds-number-independent and Reynolds-number-dependent similarities are investigated. The mean and r.m.s. values of the concentration are found to be consistent with jet similarity laws. Concentration fluctuation power spectra are found to be self-similar along rays emanating from the virtual origin of the jet. The probability density function for the concentration is also found to be self-similar along rays. Near the centreline of the jet, the scaled probability density function of jet fluid concentration is found to be nearly independent of the Reynolds number

Estimating the Multilevel Rasch Model: With the lme4 Package

Traditional Rasch estimation of the item and student parameters via marginal maximum likelihood, joint maximum likelihood or conditional maximum likelihood, assume individuals in clustered settings are uncorrelated and items within a test that share a grouping structure are also uncorrelated. These assumptions are often violated, particularly in educational testing situations, in which students are grouped into classrooms and many test items share a common grouping structure, such as a content strand or a reading passage. Consequently, one possible approach is to explicitly recognize the clustered nature of the data and directly incorporate random effects to account for the various dependencies. This article demonstrates how the multilevel Rasch model can be estimated using the functions in R for mixed-effects models with crossed or partially crossed random effects. We demonstrate how to model the following hierarchical data structures: a) individuals clustered in similar settings (e.g., classrooms, schools), b) items nested within a particular group (such as a content strand or a reading passage), and c) how to estimate a teacher x content strand interaction.

On Mixing and Structure of the Concentration Field of Turbulent Jets

This work is an investigation of the mixing of the nozzle fluid of a round turbulent jet with the entrained reservoir fluid, using laser-Rayleigh scattering methods. Our measurements, at a Reynolds number of 5000, cover the axial range from 20 to 80 jet exit diameters and resolve the full range of temporal & spatial concentration scales. The measured mean & rms values of the concentration, and the mean scalar dissipation rate, when estimated from the time derivative of concentration, are consistent with jet similarity laws. Concentration fluctuation power spectra are found to be self-similar along rays emanating from the jet virtual origin. The probability density functions for the concentration, the time derivative of concentration, and the square of the time derivative of concentration, are compiled and are also self-similar along rays

Comparative analysis of Dp427-deficient mdx tissues shows that the milder dystrophic phenotype of extraocular and toe muscle fibres is associated with a persistent expression of beta-dystroglycan

The cell biological hypothesis of Duchenne muscular dystrophy assumes that deficiency in the membrane cytoskeletal element dystrophin triggers a loss in surface glycoproteins, such as beta-dystroglycan, thereby rendering the sarcolemmal membrane more susceptible to micro-rupturing. Secondary changes in ion homeostasis, such as increased cytosolic Ca2+ levels and impaired luminal Ca2+ buffering, eventually lead to Ca2+-induced myonecrosis. However, individual muscle groups exhibit a graded pathological response during the natural time course of x-linked muscular dystrophy. The absence of the dystrophin isofom Dp427 does not necessarily result in a severe dystrophic phenotype in all muscle groups. In the dystrophic mdx animal model, extraocular and toe muscles are not as severely affected as limb muscles. Here, we show that the relative expression and sarcolemmal localization of the central trans-sarcolemmal linker of the dystrophin-glycoprotein complex, beta-dystroglycan, is preserved in mdx extraocular and toe fibres by means of two-dimensional immunoblotting and immunofluorescence microscopy. Thus, with respect to improving myology diagnostics, the relative expression levels of beta-dystroglycan appear to represent reliable markers for the severity of secondary changes in dystrophin-deficient fibres. Immunoblotting and enzyme assays revealed that mdx toe muscle fibres exhibit an increased expression and activity of the sarcoplasmic reticulum Ca2+-ATPase. Chemical crosslinking studies demonstrated impaired calsequestrin oligomerization in mdx gastrocnemius muscle indicating that abnormal calsequestrin clustering is involved in reduced Ca2+ buffering of the dystrophic sarcoplasmic reticulum. Previous studies have mostly attributed the sparing of certain mdx fibres to the special protective properties of small-diameter fibres. Our study suggests that the rescue of dystrophin-associated glycoproteins, and possibly the increased removal of cytosolic Ca2+ ions, might also play an important role in protecting muscle cells from necrotic changes

Estimating the Multilevel Rasch Model: With the lme4 Package

Traditional Rasch estimation of the item and student parameters via marginal maximum likelihood, joint maximum likelihood or conditional maximum likelihood, assume individuals in clustered settings are uncorrelated and items within a test that share a grouping structure are also uncorrelated. These assumptions are often violated, particularly in educational testing situations, in which students are grouped into classrooms and many test items share a common grouping structure, such as a content strand or a reading passage. Consequently, one possible approach is to explicitly recognize the clustered nature of the data and directly incorporate random effects to account for the various dependencies. This article demonstrates how the multilevel Rasch model can be estimated using the functions in R for mixed-effects models with crossed or partially crossed random effects. We demonstrate how to model the following hierarchical data structures: a) individuals clustered in similar settings (e.g., classrooms, schools), b) items nested within a particular group (such as a content strand or a reading passage), and c) how to estimate a teacher × content strand interaction

A language for the sociological description of pedagogic texts with particular reference to the Secondary School Mathematics Scheme SMP 11-16.

The thesis is concerned with the production of a language for the systematic\ud sociological description of pedagogic texts and with the application of this mechanism\ud to two series of textbooks within the secondary school mathematics scheme, SMP\ud 11-16. One series is targeted at the upper end of the 'ability' range, the other is\ud intended for low ability' pupils.\ud The thesis opens with a discussion of two prominent positions within\ud mathematics education, concluding that they both 'mythologise' mathematical\ud knowledge by abstracting it from the social bases of its elaboration. A search of the\ud literature on the analysis of textbooks reveals that the majority of sociologicallyoriented\ud work entails either ideological analysis or the analysis of the representation\ud of one or more particular categories, most frequently gender and/or race. None of this\ud research combines a theoretically coherent position with a set of derived principles for\ud the detailed analysis of text.\ud Chapter 3 presents a general methodological position in relation to three themes.\ud These are, the distinction between the abstract and the concrete, the construction of\ud subjectivity, and the contextualising and recontextualising of practices. The principal\ud resources in this discussion are the works of Basil Bernstein, Pierre Bourdieu,\ud Umberto Eco, Michel Foucault, and Valerie Walkerdine. Out of a critical discussion\ud of this work, ten Theoretical Propositions are derived. These propositions form the\ud general methodological basis of the 'language of description' which is derived from\ud them in Chapter 4.\ud The following five Chapters comprise an introductory description and a detailed\ud analysis of the two series of textbooks. The analysis is predominantly qualitative in\ud nature, but also incorporates a quantitative component. The latter focuses, in\ud particular, on the modes of signification (icon, index, symbol) that are incorporated in\ud the textbooks. The principal findings that emerge from the analysis describe the ways\ud in which the texts select and construct apprenticed and alienated ideal readers. The differentiation between the apprenticed and alienated ideal readers is, primarily,\ud constructed in terms of social class.\ud The concluding Chapter includes an overview of the thesis and a discussion of the\ud limitations of and possibilities arising from the language of description and its\ud application. The concluding Section works more freely with the language and with\ud the findings of the analysis in developing a theoretical speculation in respect of a\ud possible conception of the relationship between sociological research and educational\ud practice

Goodwill Impairment: A New Window For Earnings Management?

The Financial Accounting Standards Board promulgated standard No. 142 in an attempt to improve the understandability of accounting information.  This new rule eliminated the practice of automatically amortizing goodwill.  No. 142 requires public companies to test goodwill for possible impairment at least annually.  An unintended consequence of this new standard is the opportunity for companies to use it in earnings management.  To test the possibility that the rule is being used for this purpose, a sample of companies was chosen, all of which had amounts of goodwill on their balance sheet during the 2003-2005 interval.  The results reveal that the number of companies experiencing losses or low rates of return on total assets who actually impaired goodwill was statistically insignificant during the period under consideration.  Thus, the results strongly suggest that companies are using No. 142 in an attempt to manage the volatility of earnings. &nbsp

Brain dystrophin-glycoprotein complex: Persistent expression of beta-dystroglycan, impaired oligomerization of Dp71 and up-regulation of utrophins in animal models of muscular dystrophy

BACKGROUND: Aside from muscle, brain is also a major expression site for dystrophin, the protein whose abnormal expression is responsible for Duchenne muscular dystrophy. Cognitive impairments are frequently associated with this genetic disease, we therefore studied the fate of brain and skeletal muscle dystrophins and dystroglycans in dystrophic animal models. RESULTS: All dystrophin-associated glycoproteins investigated were reduced in dystrophic muscle fibres. In Dp427-deficient mdx brain and Dp71-deficient mdx-3cv brain, the expression of α-dystroglycan and laminin was reduced, utrophin isoforms were up-regulated and β-dystroglycan was not affected. Immunofluorescence localization of β-dystroglycan in comparison with glial, endothelial and neuronal cell markers revealed co-localization of von Willebrand factor with β-dystroglycan. Its expression at the endothelial-glial interface was preserved in dystrophin isoform-deficient brain from mdx and mdx-3cv mice. In addition, chemical crosslinking revealed that the Dp71 isoform exists in mdx brain predominantly as a monomer. CONCLUSIONS: This suggests an association of β-dystroglycan with membranes at the vascular-glial interface in the forebrain. In contrast to dystrophic skeletal muscle fibres, dystrophin deficiency does not trigger a reduction of all dystroglycans in the brain, and utrophins may partially compensate for the lack of brain dystrophins. Abnormal oligomerization of the dystrophin isoform Dp71 might be involved in the pathophysiological mechanisms underlying abnormal brain functions