An Approach to Dealing with the Difficulties Undergraduate Chemistry Students Experience with Stoichiometry

Chemistry for first year students has been identified by Tshwane University of Technology as one of the subjects with a low pass rate. It is apparent that students often memorize formulae and definitions, without understanding the underlying concepts required to work with abstract units of measure. We have found that the majority of students at this university are unable to balance reaction equations satisfactorily. They are also unable to predict the reaction yield, or identify limiting reagents. It is imperative that these and other related problems are overcome before any meaningful change to the high failure rate at first year level will be realized. All conventional forms of lecture presentation failed to make any significant impact on the success rate. Structured worksheets were developed and used, together with tactile models, to address the problems and the initial findings showed a marked improvement. It was discovered that the students’ problems originated from their inability to understand the meaning of subscripts and coefficients in chemical equations. The worksheets and the impact they have made on the students’ understanding of stoichiometry are shared in this paper.Keywords: Stoichiometry, limiting reagent, worksheets, tactile model

A new model for the simplification of particle counting data

This paper proposes a three-parameter mathematical model to describe the particle size distribution in a water sample. The proposed model offers some conceptual advantages over two other models reported on previously, and also provides a better fit to the particle counting data obtained from 321 water samples taken over three years at a large South African drinking water supplier. Using the data from raw water samples taken from a moderately turbid, large surface impoundment, as well as samples from the same water after treatment, typical ranges of the model parameters are presented for both raw and treated water. Once calibrated, the model allows the calculation and comparison of total particle number and volumes over any randomly selected size interval of interest

Levelling the playing field: an investigation into the translation of academic literacy tests

It is widely accepted that low levels of proficiency in the languages of learning and teaching (in this article, academic language proficiency refers to academic literacy and the terms will be used interchangeably), affect through-put rates negatively. This unsettling trend is confirmed by local and international literature, and can possibly be attributed to the language curriculum in secondary education that does not prepare students adequately for the higher-order language-thinking skills they need for study at university. By this we refer to Bloom’s taxonomy, especially the three higher-order skills of analysing, synthesising and evaluating, and the way language is used for these purposes. In order to address this problem, and as part of language-planning initiatives, some faculties at Stellenbosch University introduced the integration of academic literacy courses into the first-year curriculum. These courses are fully creditbearing and a system of continuous assessment was adopted. Semester tests form part of this assessment process, and led to the investigation done for this paper. Since both Afrikaans- and English-speaking students register for the same academic literacy module it is imperative that outcomes and assessments should be on the same level. However, the aggregate on the Afrikaans semester tests have continuously been lower than on the English test. The aggregate for the Afrikaans tests was, furthermore, on par with the weighted average for all other first-year courses, which was not always the case with the English tests. After an initial investigation, it was concluded that the Englishspeaking students were not necessarily academically stronger than their Afrikaans counterparts, but it seemed likely that the problem lay with the tests themselves. A first notion was that academic and spoken English are closer than academic and spoken Afrikaans. It was also possible that the level of difficulty of the English test was substantially lower than that of the Afrikaans test. It should, however, be noted that both the Afrikaans and English tests produced excellent reliability coefficients (alpha above 0.88) and most items discriminated adequately. A possible solution to the benchmarking problem was to translate the Afrikaans test into English. The translation framework, adopted for this study, was Nord’s functionalist model. This paper will elaborate on the translation procedure, and the variance in students’ performance on the translated version compared to previous administrations. Preliminary conclusions on bias in translated tests and the success and feasibility of such procedures are drawn.Daar word allerweë aanvaar dat lae vaardigheidsvlakke in die tale van onderrig en leer (in hierdie artikel verwys akademiese taalvaardigheid na akademiese geletterdheid en die twee terme word afwisselend met mekaar gebruik) deurvloeikoerse benadeel. Hierdie onrusbarende tendens word deur plaaslike én internasionale literatuur bevestig, en kan moontlik daaraan toegeskryf word dat die taalkurrikulum in hoërskoolonderrig nie daarin slaag om studente genoegsaam vir die hoërorde-taaldenkvaardighede van universiteitstudie toe te rus nie. Met hoërorde-taaldenkvaardighede word verwys na Bloom se taksonomie, en spesifiek die drie hoërorde-vaardighede van analise, sintese en evaluering, en die wyse waarop taal vir hierdie doel aangewend word. Om hierdie probleem te hanteer, en as deel van taalbeplanningsinisiatiewe, het sommige fakulteite aan die Universiteit Stellenbosch kursusse in Akademiese Geletterdheid by die eerstejaarskurrikulum begin integreer. Hierdie kursusse is ten volle kredietdraend en volg ‘n stelsel van voortgesette assessering. Semestertoetse maak deel uit van hierdie assesseringsproses en het tot die ondersoek vir hierdie navorsingstuk aanleiding gegee. Aangesien sowel Afrikaans- as Engelssprekende studente vir dieselfde module in Akademiese Geletterdheid registreer, is dit noodsaaklik dat uitkomste en assessering op gelyke vlak lê. Tog was die totale punt vir die Afrikaanse semestertoets deurgaans laer as dié vir die Engelse toets. Voorts was die totale punt vir die Afrikaanse toets in lyn met die geweegde gemiddelde vir alle ander eerstejaarskursusse, wat weer nie altyd die geval met die Engelse toets was nie. Ná ‘n aanvanklike ondersoek is afgelei dat die Engelssprekende studente nie noodwendig akademies sterker as hul Afrikaanse eweknieë is nie, maar dat die probleem waarskynlik by die toetse self lê. ‘n Eerste moontlikheid was dat akademiese en gesproke Engels nader aan mekaar is as akademiese en gesproke Afrikaans. Tweedens kon die moeilikheidsgraad van die Engelse toets ook aansienlik laer wees as dié van die Afrikaanse toets. Dit is egter belangrik om daarop te let dat die Afrikaanse én Engelse toetse albei uitstekende betroubaarheidskoëffisiënte (alfa bo 0.88) sowel as merendeels goeie diskrimineringskoëffisiënte opgelewer het. ‘n Moontlike oplossing vir die probleem van rigpuntstelling was om die Afrikaanse toets in Engels te vertaal. Die vertaalraamwerk wat vir hierdie studie aanvaar is, was Nord se funksionalistiese model. Hierdie navorsingstuk wei uit oor die vertaalprosedure sowel as die wisseling in studenteprestasie in die vertaalde toets in vergelyking met vorige toetse. Voorlopige gevolgtrekkings word ook gemaak oor sydigheid in vertaalde toetse, en die sukses en uitvoerbaarheid van sodanige prosedures.Keywords: academic literacy test; functionalist translation approach; back-translation; adaptation of testsThe article is in English

Africa’s neglected area of human resources for health research – the way forward

Building the skills for doing, managing and delivering healthresearch is essential for every country’s development. Yet humanresources for health research (HRHR) are seldom considered inAfrica and elsewhere. Africa’s health research capacity has grownconsiderably, with potential to increase this growth. However, asystemic way of defining, co-ordinating and growing the HRHRneeded to support health systems development is missing.Reviewing the status of HRHR in Africa, we assert that it consistsof unco-ordinated, small-scale activities, primarily driven fromoutside Africa. We present examples of ongoing HRHR capacitybuilding initiatives in Africa. There is no overarching framework, strategy or body for African countries to optimise research support and capacity in HRHR. A simple model is presented to help countries plan and strategisefor a comprehensive approach to research capacity strengthening.Everyone engaged with global, regional and national researchfor health enterprises must proactively address human resourceplanning for health research in Africa. Unless this is made explicitin global and national agendas, Africa will remain only an interestedspectator in the decisions, prioritisation, funding allocations,conduct and interpretation, and in the institutional, economic andsocial benefits of health research, rather than owning and drivingits own health research agendas

Decoherence-assisted transport in quantum networks

It is shown that energy transfer in a homogeneous fully connected quantum network is assisted by a decohering interaction with environmental spins. Analytic expressions for the transfer probabilities are obtained for the zero temperature case, and the effect is shown to persist at physiological temperatures. This model of decoherence-assisted energy transfer is applied to the Fenna-Matthews-Olson complex

The effect of perceptual skill of RFT scores : a cross-cultural study

The increasing need to select individuals for tasks suited to their personality make-up, has added to the challenge psychology faces of developing tests which can be applied to subjects from different cultures and environments. Many attempts at such designs litter the history of industrial and cross- cultural personality research. Among those to have survived years of reassessment, is the cognitive style approach developed by Herman Witkin. Intro., p. 1

A new 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) precursor isolated from Riesling grape products: Partial structure elucidation and possible reaction mechanism

A heteroside, which produces 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) by acid hydrolysis, was isolated from Riesling grapes by retention on Amberlite XAD-2 resin, followed by preparative TLC and HPLC techniques. It was partially identified by NMR spectroscopic procedures. The presence of a megastigm-4-en-9-one structure with an enol-ether function in the C4 position and a OH/OR function in the C6 position was ascertained. The sugar part should be constituted of two or three glucose moieties with the same NMR characteristics. The linkage of these moieties to the megastigmane structure in the C4 position and possibly also in the C6 position remains to be determined. The isolated conjugated form produced only a TDN-d4 isomer when reacted at 50 degrees C in D2O at different acid pH values. A possible reaction mechanism was proposed, considering the kinetics of TDN-d(4) formation during the hydrolysis of the raw glycosidic fraction from two differently aged Riesling wines at pH 2, and comparing it with the kinetics of TDN formation as well. The latter may correspond to the mechanism proposed by WINTERHALTER (1991). Thus, the presence of at least two different TDN precursors in grape products at different concentrations was proved

Critical Values for Yen’s Q3: Identification of Local Dependence in the Rasch model using Residual Correlations

The assumption of local independence is central to all IRT models. Violations can lead to inflated estimates of reliability and problems with construct validity. For the most widely used fit statistic Q3 there are currently no well-documented suggestions of the critical values which should be used to indicate local dependence, and for this reason a variety of arbitrary rules of thumb are used. In this study, we used an empirical data example and Monte Carlo simulation to investigate the different factors that can influence the null distribution of residual correlations, with the objective of proposing guidelines that researchers and practitioners can follow when making decisions about local dependence during scale development and validation. We propose that a parametric bootstrapping procedure should be implemented in each separate situation in order to obtain the critical value of local dependence applicable to the data set, and provide example critical values for a number of data structure situations. The results show that for the Q3 fit statistic no single critical value is appropriate for all situations, as the percentiles in the empirical null distribution are influenced by the number of items, the sample size, and the number of response categories. Furthermore, our results show that local dependence should be considered relative to the average observed residual correlation, rather than to a uniform value, as this results in more stable percentiles for the null distribution of an adjusted fit statistic

Spectral and stratigraphic mapping of hydrated sulfate and phyllosilicate-bearing deposits in northern Sinus Meridiani, Mars

We present detailed stratigraphic and spectral analyses that focus on a region in northern Sinus Meridiani located between 1°N to 5°N latitude and 3°W to 1°E longitude. Several stratigraphically distinct units are defined and mapped using morphologic expression, spectral properties, and superposition relationships. Previously unreported exposures of hydrated sulfates and Fe/Mg smectites are identified using MRO CRISM and MEX OMEGA near‐infrared (1.0 to 2.5 µm) spectral reflectance observations. Layered deposits with monohydrated and polyhydrated sulfate spectral signatures that occur in association with a northeast‐southwest trending valley are reexamined using highresolution CRISM, HiRISE, and CTX images. Layers that are spectrally dominated by monohydrated and polyhydrated sulfates are intercalated. The observed compositional layering implies that multiple wetting events, brine recharge, or fluctuations in evaporation rate occurred. We infer that these hydrated sulfate‐bearing layers were unconformably deposited following the extensive erosion of preexisting layered sedimentary rocks and may postdate the formation of the sulfate‐ and hematite‐bearing unit analyzed by the MER Opportunity rover. Therefore, at least two episodes of deposition separated by an unconformity occurred. Fe/Mg phyllosilicates are detected in units that predate the sulfateand hematite‐bearing unit. The presence of Fe/Mg smectite in older units indicates that the relatively low pH formation conditions inferred for the younger sulfate‐ and hematitebearing unit are not representative of the aqueous geochemical environment that prevailed during the formation and alteration of earlier materials. Sedimentary deposits indicative of a complex aqueous history that evolved over time are preserved in Sinus Meridiani, Mars