Elementary School Children's Ability to Distinguish Hypothetical Beliefs From Statements of Preference.

The authors examined students' understanding of hypotheses as beliefs that can be empirically verified. Thirty second graders and 30 sixth graders considered cases of disagreement about foods and colors that reflected either alternative hypotheses or different preferences. Their task was to decide whether the validity of each expressed belief could be determined and to justify their decision. Younger students considered both hypotheses and preferences as empirically verifiable, whereas older students were better able to recognize in some cases that preferences are legitimately variable. This lack of distinction may reflect limited metaconceptual ability or a deterministic epistemological view, both of which might interfere with the understanding of the hypothesis-testing process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The evaluation in the Ames test of the mutagenicity of tetrahydro-beta-carboline-3-carboxylic acids from smoked foods.

This paper reports the evaluation of five tetrahydro-beta-carboline carboxylic acids, formed from the interaction of woodsmoke carbonyls and tryptophan, for mutagenicity in the Ames test. Three of the compounds tested have been detected recently in smoked foods at levels in the micrograms/kg or mg/kg range. None of the compounds induced mutagenicity in TA 97, TA 98 or TA 100 strains of Salmonella typhimurium either with or without prior activation. However, tetrahydro-beta-carboline-3-carboxylic acid, and to a lesser extent 1-methyl-tetrahydro-beta-carboline-3-carboxylic acid were toxic to the strains of Salmonella typhimurium used. The inability of these beta-carbolines to induce mutation contrasts markedly with the mutagenicity of some beta-carbolines found in grilled meat products.     

Effect of dopants on the performance of CuO–CeO2 catalysts in methanol steam reforming

Steam reforming of methanol was carried out over a series of doped CuO–CeO₂ catalysts prepared via the urea–nitrate combustion method. XRD analysis showed that at least part of the dopant cations enter the ceria lattice. The addition of various metal oxide dopants in the catalyst composition affected in a different way the catalytic performance towards H₂ production. Small amounts of oxides of Sm and Zn improved the performance of CuO–CeO₂, while further addition of these oxides caused a decrease in catalyst activity. XPS analysis of Zn- and Sm-doped catalysts showed that increase of dopant loading leads to surface segregation of the dopant and decrease of copper oxide dispersion. The addition of oxides of La, Zr, Mg, Gd, Y or Ca lowered or had no effect on catalytic activity, but led to less CO in the reaction products. Noble-metal modified catalysts had slightly higher activity, but the CO selectivity was also significantly higher.     

Alcohol reforming on cobalt-based catalysts prepared from organic salt precursors

Co–MnO catalysts have been prepared by pyrolytic decomposition of the corresponding fumarate or gluconate salts and examined in the reactions of methanol and ethanol reforming. The synthesis parameters were the type of organic salt, the Co:Mn ratio and the temperature of decomposition. The decomposition pathway depends on the type of carboxylate, with the fumarate group being more stable than the gluconate. In-situ XRD measurements of salt decomposition showed that the reducing atmosphere prevailing during thermal treatment, as well as the presence of solid carbon, facilitates reduction of cobalt oxides towards metallic cobalt at temperatures above ∼500 °C. Thus, the reduced form of the catalyst, consisting mainly of metallic cobalt and MnO dispersed in a carbonaceous matrix can be prepared in a single step. It was found that reforming of both methanol and ethanol proceeds under comparable reaction conditions and hydrogen yield is maximized at temperatures of 400–450 °C. The activity of catalysts prepared under an inert atmosphere was considerably higher than the one of catalysts prepared through oxidative pre-treatment.     

Mathematical analysis of lead field expansions

The solution to the bioelectromagnetic inverse problem is discussed in terms of a generalized lead field expansion, extended to weights depending polynomially on the current strength. The expansion coefficients are obtained from the resulting system of equations which relate the lead field expansion to the data. The framework supports a family of algorithms which include the class of minimum norm solutions and those of weighted minimum norm, including FOCUSS (suitably modified to conform to requirements of rotational invariance). The weighted-minimum-norm family is discussed in some detail, making explicit the dependence (or independence) of the weighting scheme on the modulus of the unknown current density vector. For all but the linear case, and with a single power in the weight, a highly nonlinear system of equations results. These are analyzed and their solution reduced to tractable problems for a finite number of degrees of freedom. In the simplest magnetic field tomography (MFT) case, this is shown to possess expected properties for localized distributed sources. A sensitivity analysis supports this conclusion.     

Histamine release from rat mast cells induced by the metabolic activation of drugs of abuse into free radicals

Techniques such as positron-emission tomography, single-photon-emission computed tomography, functional magnetic-resonance imaging and magnetoencephalography permit the observation of biological processes in the brain in a noninvasive manner. They have yielded new insights into the biological interrelations of sensory, motor and cognitive functions, as well as into brain diseases. Combined use of these techniques may provide more information than just the sum of its constituents, and this may narrow the gap between the biological data provided by these techniques and the mental models described by clinicians, mathematicians, psychologists and philosophers.     

Speed and power factor controller for AC adjustable speed drives

The speed and power factor of an adjustable speed slip power recovery drive are controlled in order to optimize the operation. This is accomplished by means of a variable-voltage-variable-frequencies power converter. The function of the digital controller of the power converter is to provide the online speed and power factor regulation. The hardware and software are described. This scheme has an accurate voltage output with very low harmonic content, a good resolution for the phase angle regulation and the frequency control with the possibility of range extension