Problems in the application of structural equation modeling: Comment on Randhawa, Beamer, and Lundberg (1993).

Critique methodological aspects of B. S. Randhawa's et al (see record 1993-23567-001) structural equation modeling (SEM) of relations between self-efficacy, attitudes, and achievement in mathematics. Major findings of their study were that self-efficacy mediated the effects of attitudes on achievement and that self-efficacy and attitudes were more strongly related to achievement for boys than for girls. The authors' reanalysis of their data does not substantiate these conclusions. Rather, it identifies inappropriate applications of SEM and the consequent misinterpretations of results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Influence of C60 Powders On Cultured Human Leukocytes

In order to check its possible acute toxicity, C₆₀ was incorporated into living human phagocytes. It was observed that C₆₀ has no influence on the survival of human leukocytes.     

Regulation of NMDA receptor phosphorylation by alternative splicing of the C-terminal domain

The NMDA (N-methyl D-aspartate) receptors in the brain play a critical role in synaptic plasticity, synaptogenesis and excitotoxicity. Molecular cloning has demonstrated that NMDA receptors consist of several homologous subunits (NMDAR1, 2A-2D). A variety of studies have suggested that protein phosphorylation of NMDA receptors may regulate their function and play a role in many forms of synaptic plasticity such as long-term potentiation. We have examined the phosphorylation of the NMDA receptor subunit NMDAR1 (NR1) by protein kinase C (PKC) in cells transiently expressing recombinant NR1 and in primary cultures of cortical neurons. PKC phosphorylation occurs on several distinct sites on the NR1 subunit. Most of these sites are contained within a single alternatively spliced exon in the C-terminal domain, which has previously been proposed to be on the extracellular side of the membrane. These results demonstrate that alternative splicing of the NR1 messenger RNA regulates its phosphorylation by PKC, and that mRNA splicing is a novel mechanism for regulating the sensitivity of glutamate receptors to protein phosphorylation. These results also provide evidence that the C-terminal domain of the NR1 protein is located intracellularly, suggesting that the proposed transmembrane topology model for glutamate receptors may be incorrect.     

A study of the thermal degradation of polystyrene by thermal volatilization analysis

A TVA study of several anionic polystyrene samples, having number average molecular weights in the range of 4.6 × 10³ to 2 × 10⁶, reveals a hitherto unobserved molecular weight dependence of the overall apparent Arrhenius preexponential factor as determined by the method of Roche.² The latter effect is discussed in terms of a model in which the zip length and chainscission rate constants are both functions of molecular weight. It is suggested that the functional dependence of the kinetic parameters on molecular weight is a reflection of their hydrodynamic coupling to the viscosity of the molten polymer.     

Reliability of B-mode ultrasonic measurements of subcutaneous adipose tissue and intra-abdominal depth: comparisons with skinfold thicknesses

Adipose tissue deposits, particularly intra-abdominal adipose tissue, are associated with health risks such as diabetes mellitus and cardiovascular disease. Anthropometric techniques currently in use can measure subcutaneous adipose tissue (SAT) with skinfold calipers, but are limited to certain sites and cannot measure intra-abdominal adipose tissue (IAAT). Radiography, computerized tomography (CT) and magnetic resonance imaging (MRI) have been used, but they are expensive and some involve exposure to radiation. This study, which investigated the utility of B-mode ultrasound for measuring adipose tissue, found that ultrasonic measurements of SAT were as reliable as skinfold caliper measurements. Intra-observer and inter-observer coefficients of reliability for five of six ultrasonic measurements of SAT ranged from 91-98%, in comparison with coefficients of reliability ranging from 93-98% for three skinfold measurements. Coefficients of reliability for ultrasonic measurements of SAT at the paraspinal site were below 90%. Ultrasonic measurements of intra-abdominal depth (IAD), an index of IAAT, yielded an inter-observer coefficient of reliability of 64%. Ultrasound is recommended for measurement of subcutaneous adipose tissue but not for measurement of IAD.     

Effects of fatty acid concentration and positional specificity on maize triglyceride structure

The effects of fatty acid concentration and positional specificity on maize triglyceride structure were evaluated from the stereospecific analyses of triglycerides from 12 genotypes. The fatty acids at each position were influenced by the fatty acid concentration in the total triglyceride except for the saturates in the 2 position. The fatty acid concentration had the greatest effect on the fatty acid composition of position 3. The existence of positional specificity was evident from the nonrandom distribution of the fatty acids among the three positions of the triglycerides. The concentration and positional specificity effects could be separated in selected genotypes and their crosses. This indicated different genetic controls for each effect.     

A three-point flexure test configuration for improved sensitivity to metal/ adhesive interfacial phenomena

A three-point flexure test was used to evaluate the effects of chemical surface treatments on the performance of adhesively-bonded structures of Ti6A14V. A single adherend/adhesive structure rather than a double adherend sandwich configuration is shown to be sensitive to pre-bonding adherend surface treatments. Data is presented which relates mechanical properties with chemically treated adherend surfaces. Photoelastic isochromatic fringes were recorded simultaneously with the flexure test as a means to monitor stress distribution, failure initiation, and crack propagation.     

(Science) Fiction,Ecophysical Apparatus and Skizoid Machines: Animism,Vitalism and Machinism as a Way to Rearticulate the Need to Confront the Unknown in a Contradictory Manner

François Roche of R&Sie(n) ruminates on the contradictory nature of the present: a time that is ‘vibrating’ while ultimately ‘lacking momentum’. Reclaiming ‘the scenarios and substances that condition architecture’, he rejects the large-scale flights of fancy of international signature architects and argues for the reactivation of ‘a throbbing, complex and unfinished “localism”’. In so doing, he advocates a machinism that enables fictionalisation and speculation. Copyright © 2010 John Wiley & Sons, Ltd.     

Generation adequacy and transmission interconnection in regional electricity markets

The power system capacity adequacy has public good features that cannot be entirely solved by electricity markets. Regulatory intervention is then necessary and established methods have been used to assess adequacy and help regulators to fix this market failure. In regional electricity markets, transmission interconnections play an important role in contributing to adequacy. However, the adequacy problem and related policy are typically considered at a national level. This paper presents a simple model to study how the interconnection capacity interacts with generation adequacy. First results indicate that increasing interconnection capacity between systems improves adequacy up to a certain level; further increases do not procure additional adequacy improvements. Furthermore, besides adequacy improvement, increasing transmission capacity under asymmetric adequacy criteria or national system characteristics could create several concerns about externalities. These results imply that regional coordination of national adequacy policies is essential to internalise adequacy of cross-border effects.     

Dietary cation-anion difference and the health and production of pasture-fed dairy cows 2. Nonlactating periparturient cows

Anecdotal observations of reduced hypocalcemia due to small reductions in the precalving dietary cation-anion difference (DCAD) are widely reported in Australia and New Zealand. Diets offered to nonlactating, periparturient dairy cows in pasture-based dairy systems in southeastern Australia can vary in their cation-anion difference from 0 to +76 mEq/100 g. The effects of such a range in the DCAD on the health and production of cows, on a pasture-based diet, were examined in an indoor feeding experiment. Four groups of four cows were offered pasture-hay and freshly cut pasture, a periparturient diet typical of that associated with the grazing system in Australia and New Zealand. Varying levels of salt supplementation were used to alter the dietary cation-anion difference, which ranged from -12 to +69 mEq/100 g. Blood and urine pH and mineral concentrations and urine hydroxyproline were measured. The addition of anions to the diet, to produce a negative DCAD, resulted in a nonrespiratory systemic acidosis. With decreasing DCAD, the pH of blood and urine and the strong ion difference of urine decreased curvilinearly, blood bicarbonate decreased linearly and the urinary ratio of Ca to creatinine increased curvilinearly. Although systemic pH was not reduced at a DCAD of +16 mEq/100 g, urine Ca-to-creatinine ratio had begun to rise, probably indicating increased calcium absorption. The absorption and renal excretion of Mg increased with decreasing DCAD. No differences were observed in urine hydroxyproline concentrations and no significant differences in milk production were measured.