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

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

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

Energy cost associated with moving platforms.

Background: Previous research suggests motion induced fatigue contributes to significant performance degradation and is likely related to a higher incidence of accidents and injuries. However, the exact effect of continuous multidirectional platform perturbations on energy cost (EC) with experienced personnel on boats and other seafaring vessels remains unknown. Objective: The objective of this experiment was to measure the metabolic ECs associated with maintaining postural stability in a motion-rich environment. Methods: Twenty volunteer participants, who were free of any musculoskeletal or balance disorders, performed three tasks while immersed in a moving environment that varied motion profiles similar to those experienced by workers on a mid-size commercial fishing vessel (static platform (baseline), low and high motions (HMs)). Cardiorespiratory parameters were collected using an indirect calorimetric system that continuously measured breath-by-breath samples. Heart rate was recoded using a wireless heart monitor. Results: Results indicate a systematic increase in metabolic costs associated with increased platform motions. The increases were most pronounced during the standing and lifting activities and were 50% greater during the HM condition when compared to no motion. Increased heart rates were also observed. Discussion: Platform motions have a significant impact on metabolic costs that are both task and magnitude of motion dependent. Practitioners must take into consideration the influence of motion-rich environments upon the systematic accumulation of operator fatigue

Compounded laxative formulations for substituting phenolphthalein with sennosides A & B in solid dosage forms

Purpose: Following the discovery of the carcinogenicity of phenolphthalein and the subsequent ban of this compound in several countries this study was undertaken to develop compounded formulations of laxative products containing the stimulant laxatives sennosides A and B. Methods: DSC and HPLC analysis was used to determine the compatibility of sennosides with commonly used excipients before compounding capsules, tablets and effervescent tablets containing sennosides A & B. The physical and chemical stability and release properties of these dosage forms were determined for 12 weeks at increased temperature and relative humidity. Results: Sennosides A & B were compatible with a wide variety of powdered excipients. However, these were incompatible with propyl paraben, sodium carbonate, stearic acid, citric acid, PEG, and sugar derivatives such as lactose, glucose and sorbitol when granulated with water. Not withstanding these interactions, it was possible to compound simple capsule, tablet and even an effervescent tablet formulations containing sennosides A & B that complied with pharmacopeial specifications. However, all these formulations were sensitive to moisture because when stored at increased temperature and relative humidity, disintegration times increased and dissolution rates decreased. Conclusion: Based on compatibility and stability studies simple, stable and elegant solid dosage forms containing sennosides A & B were compounded that can be used to replace phenolphthalein in a variety of solid dosage forms. Keywords: Compounding; Sennosides A & B; Phenolphthalein replacement; Drug-Excipient Compatibility > Tropical Journal of Pharmaceutical Research Vol. 3 (1) 2004: pp. 265-27

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

Geometrical Optics Formalism to Model Contrast in Dark-Field X-ray Microscopy

Dark-field X-ray microscopy is a new full-field imaging technique that nondestructively maps the structure and local strain inside deeply embedded crystalline elements in three dimensions. Placing an objective lens in the diffracted beam generates a magnified projection image of a local volume. We provide a general formalism based on geometrical optics for the diffraction imaging, valid for any crystallographic space group. This allows simulation of diffraction images based on micro-mechanical models. We present example simulations with the formalism, demonstrating how it may be used to design new experiments or interpret existing ones. In particular, we show how modifications to the experimental design may tailor the reciprocal-space resolution function to map specific components of the deformation gradient tensor. The formalism supports multi-length scale experiments, as it enables DFXM to be interfaced with 3DXRD. The formalism is demonstrated by comparison to experimental images of the strain field around a straight dislocation

Ensuring the Involvement of Children in the Evaluation of New Tuberculosis Treatment Regimens

William Burman and colleagues review the barriers to involving children in studies of new tuberculosis treatments and recommend strategies for overcoming these barriers

Functional foods with added plant sterols for treatment of hypercholesterolaemia and prevention of ischaemic heart disease

Background. A spread with added plant sterols, Pro-activ, is marketed in South Africa as an adjunct to low-fat diets for lowering of total and low-density lipoprotein (LDL) cholesterol concentrations and to decrease risk of ischaemic heart disease (IHD). Objectives. The need for this functional food in South Africa, its efficacy, safety and target market, are evaluated in this review. Results. The high, and probably increasing incidence of hypercholesterolaemia and cardiovascular disease in South Africa motivates the need for appropriate functional foods. There is convincing evidence in the literature that an average daily intake of about 2 g plant sterols in about 20 g of spread significantly lowers total and LDL cholesterol concentrations by approximately 10 - 15%, without influencing high-density lipoprotein (HDL) cholesterol and triglyceride concentrations. There is some concern about the effects on absorption of lipid-soluble vitamins and pro-vitamins, but safety tests lasting for up to 3 years found no serious adverse effects. Conclusions. The target market for this spread should be nonpregnant, non-lactating adults with hypercholesterolaemia and/or increased risk of IHD. If it is considered for use in hypercholesterolaemic children, fat-soluble vitamin status should be monitored. It is recommended that post-marketing surveillance should be established to determine long-term effects and safety