South African physical sciences teachers’ use of formulae and proportion when answering reaction-based stoichiometry calculation questions

Stoichiometry calculation competence tends to be particularly poor in the developing world, even among teachers. Various methods, including the unit factor method, have the potential to be effective in developing such competence. To evaluate the likelihood of such a generic proportion method, which downplays traditional formula usage, succeeding in a particular context, it is necessary first to understand teachers’ existing competence with proportion and the extent to which their calculation success relies on the explicit provision of and substitution into formulae in their written solutions. This quantitative survey study of 171 South African Physical Sciences teachers’ use of formulae and proportion found that most teachers failed to recognise the need to use proportion for some of the four reaction-based stoichiometry calculation questions used. Provision of and substitution into a formula in the written solution was found to be valuable in helping participants who underutilised proportion to obtain process marks, but to be largely irrelevant to obtaining the correct answer. The findings suggest that professional development interventions in similar contexts should focus on proportion within stoichiometry, particularly on recognition of its relevance to reaction-based questions. While a generic proportion method is well suited to this purpose, questions are raised concerning the likelihood that teachers would accept such a method in a context where process marks favour traditional formats of formula provision and substitution and where process mark attainment is highly valued. The findings also point to the need for teacher education to address competencies other than proportion.

Experiment: Conceptual Basis

Texts and teaching of Experimental Statistics emphasize the statistical analysis of experiments and superficially consider the conceptual basis of experimental research. Definitions of basic concepts are imprecise, incoherent and ambiguous. This is the case, for example, with the concepts of experimental material, experimental factor, experimental unit and experimental error. In particular, the lack of distinction between experimental factor and unit factor and between the two classes of experimental factor: treatment factor and intrinsic factor leads to flaws in the plan and analysis of experiments that originate biased inferences. This approach gives rise to ignorance and misunderstanding of these concepts, underestimation of the importance of the planning of the experiment and, consequently, the inefficiency of many research. This paper reviews and reformulates important concepts with the purpose of contributing a rational basis for experimental research and, in particular, for Experimental Statistics. These revised concepts provides a basis for the formulation of an experiment structure that provides appropriate inferences for the achievement of the objectives of the experiment.

Effects of Trade Reform on Health and Tourism Sectors of the Reforming Country

Health trade and related tourism have become prevalent in recent times, particularly in countries where quality medical services are provided at a relatively low cost. Therefore, using a competitive general equilibrium trade model, this article theoretically attempts to find possible complementarity between the health sector and the tourism sector in a small open developing economy. While exploring the results, this article also finds the effect of trade reform on factor prices, per unit factor requirement and output of different sectors of the economy. Capital owners are seen to lose with trade reform, while labours and doctors gain. Eventually, both health and tourism sectors are found to be complementary in nature. However, expansion of these sectors is conditional on factor intensity assumption. Following this, we briefly touch upon the possible effects of deglobalisation in such an economy. We find that capitalists gain, whereas both doctors and labours suffer loss. Complementarity between health and tourism sectors persists, and the size of different sectors is again found to depend on factor intensity.

analysis of the multivariate-repeated-measures-experiment evaluating the influence of gibberellic acid on cherry fruit quality

A repeated-measures experiment design including two between-unit factors and one within-unit factor was performed in order to examine the influence of gibberellic acid on cherry fruit quality. One of the two between-unit factors had two levels represented by two cherry cultivars ('Van', 'Sunburst') and the other consisted of two treatments: spraying with gibberellic acid and spraying with pure water as a control. An experimental unit was a cherry branch on which 20 cherries were sampled randomly and marked. The three variables which describe ripeness of cherries were measured over 6 time points at three or four day intervals during maturation. After picking the cherries, measurements of fruit firmness were made on 3 different sides of each marked cherry. The univariate and multivariate repeated measures ANOVA was used for the analysis of two sets of data.

Polynomially bounded multisequences and analytic continuation

Given a polynomially bounded multisequence {fm}, where m = (m1, …, mk) ∈ ℤk, we will consider 2k power series in exp(iz1), …, exp(izk), each representing a holomorphic function within its domain of convergence. We will consider this same multisequence as a linear functional on a class of functions defined on the k-dimensional torus by a Fourier series, , with the proper convergence criteria. We shall discuss the relationships that exist between the linear functional properties of the multisequence and the analytic continuation of the holomorphic functions. With this approach we show that a necessary and sufficient condition that the multisequence be given by a polynomial is that each of the power series represents, up to a unit factor, the same function that is entire in the variables

A Unit Factor Method for Solving Proportion Problems

Here is an alternative for enabling your students to solve proportions.

Heterogeneity of Factor IX in Therapeutic Concentrates

In vivo and in vitro experience shows that factor IX concentrates are partially activated. A rabbit antibody to human factor IX was used to investigate the factor IX antigenic content and electrophoretic mobility of commercial products as well as experimental “activated products”.“Rocket” Immunoelectrophoresis of all concentrates showed a 1.5–3 fold increased antigenic content/unit factor IX clotting activity when compared to plasma. Two dimensional crossed Immunoelectrophoresis of standard factor IX preparation produced a single sharp peak whether electrophoresed in Ca or EDTA containing buffer. “Activated” preparations produced a dome shaped precipitin arc. The addition of plasma to factor IX concentrates yielded a marked shoulder only when the electrophoresis was done in EDTA. This effect could not be reproduced by the addition of antithrombin III (AT-III). The addition of plasma to the activated IX (IXa) revealed an even more pronounced heterogeneity whether in Ca or EDTA. The addition of AT-III produced a second precipitin peak when activated IX was electrophoresed in the presence of Ca++.These results indicate that at least three forms of factor IX exist in factor IX preparations. The absence of detectable AT-III reacting material in the regular IX preparations is a priori evidence of the absence of major amounts of IXa, whereas the presence of AT-III reacting material in the “activated” complex is evidence of biologically active material.

INHERITANCE OF COLOR IN THE EGGPLANT

(1) Inheritance studies on the color in the eggplants have been made by various investigators but the first one to attempt an analysis was Halsted (5) who reported a 3:1 ratio of green to white color of flesh and a similar ratio of purple to colorless skin; also a 9:3:3:1 ratio of purple, green, pink, and white fruit. Several workers have pointed out the dominance of purple color over white in fruits. Bayla (1) apparently regarded F1 generations of reciprocal crosses as dissimilar. (2) The methods employed in the various crosses are given. (3) Seedlings in some of the crosses could be classified according to their color during the very early stages. Plants of the Green variety remain green throughout the entire life cycle, those of Fajardo and White Pompadour are green during the first two or three weeks only and then turn light purple; while those of Camuy, Black Beauty and University are purple from the very beginning. (4) Intense purple color of Camuy is inherited in a 3:1 ratio to Green. The same ratio exists between the green of Green and the purple of University and Black Beauty. The University purple is inherited in the same ratio in respect to Fajardo green purple striped. For all these a unit factor Pr pr is assumed. (5) Green color of fruit in the crosses studied is always associated with green plant color; and purple, red and pink with purple color of plant. White corolla is always associated with green color of plant; striped anthers with a recessive factor for fruit or plant color. (6) Red, purple and pink color of fruit is dominant over green and inherited in a 3:1 ratio. Likewise green purple striped is dominant over white purple striped and is inherited in a 3:1 ratio. Purple was proved to be also dominant over white purple striped. Green purple striped acts as a recessive in respect to pink or purple, but as a dominant in respect to white purple striped. (7) Violet or purple corolla is dominant over white corolla. They stand in a 3:1 ratio in the F2 generation. (8) Striping of anthers is dominant over non-striping and is inherited in a 3:1 ratio. (9) A unit factor appears to exist for each of the characters; color of plant, color of fruit, color of corolla and striping of anthers. The following allelomorphic pairs of factors are assumed: plant color Pr pr, fruit color Cc, corolla color C1c1, and striped character of anthers St st. A. single factor might be assumed as affecting all the characters here involved. (10) There may be complete linkage between these characters White corolla and non-striped anthers always stand for green fruit, and green plant (all recessive characters). On the other hand striped anthers always go with bright colored fruit and with purple plants. (11) The composition of a green plant with white corolla, green fruit and non-striped anthers may be represented as prpr cc C1 c1 stst, or as prpr, cc, etc.