Studies on lanthanoid sulphites: V. thermal decomposition of cerium and neodymium sulphites

The preparation and thermal behaviour of Ce₂(SO₃)₃· 3H₂O, Nd₂(SO₃)₃·6H₂O and Nd₂(SO₃)₃ have been studied. Cerium sulphite undergoes first dehydration which is followed by decomposition to CeO₂ in the temperature range 500 – 850 °C. The decomposition involves two intermediate phases both in air and nitrogen. According to the TG curves the phases in air are Ce₂(SO₃)₂SO₄ and Ce₂SO₃(SO₄)₂. In nitrogen, Ce₂O₂SO₄ was identified and this provides a synthetic route to cerium oxysulphate.Neodymium sulphite decomposes to Nd₂O₂SO₄ when heated in air or in nitrogen up to 950°C. The intermediate levels observed do not correspond to single phases, and the reaction mechanism depends strongly on the experimental conditions.     

The relationship between students' mathematical thinking types and representation preferences in definite integral problems

ABSTRACT

Given that curriculum materials serve as cultural artefacts, this study addresses the need for more research on curriculum materials in different contexts. Most studies concerning curriculum materials have been conducted in US and, therefore little is known about the nature of materials in other cultural-educational contexts. The aim of this paper is to identify the underlying cultural norms of potentially constructed classrooms, by analysing recurrent activities in the most commonly used Finnish teacher guides at primary-school level. We identified three norms embedded in them: (1) creating opportunities for learning through a variety of activities and communication; (2) keeping the class gathered around a specific mathematical topic; and (3) concurrent active involvement of teachers and students. The results add to knowledge about both teacher guides and the Finnish educational context. Moreover, it adds to the growing body of methodologies, as our analytical approach is novel in the context of textual analysis.     

Torsional interaction in 2-haloethanols: infrared data,ab initio results and treatment of a two-dimensional model

The splittings of the hydroxyl torsional absorption bands observed in the gas phase IR spectra of 2-haloethanols, XCH₂-CH₂-OH are reported for X = Cl, Br, I. The satellite absorptions, assigned to excited states of the skeletal torsion, appear on the low-frequency side of the fundamental, possibly because of weakening of the internal hydrogen bond. The torsional potential surface is investigated by calculations using a two-dimensional model based on the known experimental data for the compound with X = Cl, and by ab initio calculations for the haloethanols with X = F and X = Cl. Models based on the assumption of pure torsion and simple dipole-dipole or central force interaction terms failed to reproduce the observed data for 2-chloroethanol, but good agreement was obtained after local modification of the potential surface interpolated from the ab initio calculations. The results may help devise the phenomenological theory of potential energy needed for quantitative study of the internal hydrogen bond.     

Teaching linear equations: Case studies from Finland,Flanders and Hungary

In this paper we compare how three teachers, one from each of Finland, Flanders and Hungary, introduce linear equations to grade 8 students. Five successive lessons were videotaped and analysed qualitatively to determine how teachers, each of whom was defined against local criteria as effective, addressed various literature-derived equations-related problems. The analyses showed all four sequences passing through four phases that we have called definition, activation, exposition and consolidation. However, within each phase were similarities and differences. For example, all three constructed their exposition around algebraic equations and, in so doing, addressed concerns relating to students’ procedural perspectives on the equals sign. All three teachers invoked the balance as an embodiment for teaching solution strategies to algebraic equations, confident that the failure of intuitive strategies necessitated a didactical intervention. Major differences lay in the extent to which the balance was sustained and teachers’ variable use of realistic word problems.     

Negation and partial axiomatizations of dependence and independence logic revisited

In this paper, we axiomatize the negatable consequences in dependence and independence logic by extending the systems of natural deduction of the logics given in [22] and [11]. We prove a characterization theorem for negatable formulas in independence logic and negatable sentences in dependence logic, and identify an interesting class of formulas that are negatable in independence logic. Dependence and independence atoms, first-order formulas belong to this class. We also demonstrate our extended system of independence logic by giving explicit derivations for Armstrong's Axioms and the Geiger-Paz-Pearl axioms of dependence and independence atoms.     

Molecular mobility of spin-labelled terephthaloyl chloride and 1,10-decanediol copolymer in solution

Intramolecular mobility of spin-labelled terephthaloyl chloride and 1,10-decanediol copolymer in solution was investigated using a polymer in which the label was rigidly attached to the main chain methylene groups. Correlation times and effective segmental dimensions were measured, as were the frequency and amplitude of the high-frequency torsional vibrations of the main chain monomer units. The amplitude of high-frequency torsional vibrations was shown to increase with increasing temperature.     

Occupational Exposure to Pesticides in Finland

Abstract

The annual use of pesticides in Finland counted as ingredients has been around 2000 tons from the seventies. Herbicides, which are mostly used in agriculture, are almost 80% of the total use of pesticides. Amount of workers occupationally exposed to pesticides is about 170000. Farmers are the largest group among exposed persons. Their number is around 50000 but their exposure periods last only for few days every summer. In greenhouses, around 20000, and in forestry, nearly 1500 workers are exposed to pesticides with more regular and longer lasting exposure than that of farmers. In the Finnish Register of Occupational Diseases, 79 cases caused by pesticides were reported during the years 1972-1991. Most of the cases were from greenhouses, agriculture and forestry. Typical symptoms in reports were toxic eczema or acute symptoms. Occupational exposure of workers to pesticides in Finland has been mainly studied by the Kuopio Regional Institute of Occupational Health since 1978. Exposure levels have been evaluated by occupational hygienic measurements and biological monitoring. Field studies done in agriculture, forestry and greenhouses revealed that exposure of the workers in most cases is at low level. Skin contamination is the main factor of exposure. Therefore, the use of personal protective clothing is essential for minimising exposure. Situations, where risk for exposure is high, are the dilution of formulation before spraying, preparation of equipment on fields, and contamination of skin when the work is started immediately after applications on fields and in greenhouses.     

Vibrational spectroscopic investigations of snse8-n molecules

The fundamental vibrations of 13 cyclic S_nSe_8-n (n = 7—2) molecules have been calculated using a modified Urey—Bradley force field with 9–14 independent force constants whose values have been adapted from those of Se₈ and S₈. Calculated wavenumbers are compared to those obtained by Raman spectroscopy for sulfur—selenium phases prepared by recrystallizing quenched molten mixtures of the elements as previously described. Agreement between the observed spectra and calculated wavenumbers is closest by assuming the existence of selenium—selenium bonds and the absence of isolated selenium atoms in S_nSe_8-n molecules. It is assumed that sulfur—selenium phases are mixed crystals with the following components in varying concentrations: 1,2-S₆Se₂, 1,2,3-S₅Se₃, 1,2,3,4-S₄Se₄, 1,2,5,6-S₄Se₄, 1,2,3-S₃Se₅ and 1,2-S₂Se₆. The presence of S₈ and Se₈ in some of the phases is indicated by the Raman spectra.