1,121 research outputs found

    Issues of partial credit in mathematical assessment by computer

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    The CALM Project for Computer Aided Learning in Mathematics has operated at Heriot‐Watt University since 1985. From the beginning CALM has featured assessment in its programs (Beevers, Cherry, Foster and McGuire, 1991), and enabled both students and teachers to view progress in formative assessment The computer can play a role in at least four types of assessment: diagnostic, self‐test, continuous and grading assessment. The TLTP project Mathwise employs the computer in three of these roles. In 1994 CALM reported on an educational experiment in which the computer was used for the first time to grade, in part, the learning of a large class of service mathematics students (Beevers, McGuire, Stirling and Wild ,1995), using the Mathwise assessment template. At that time the main issues identified were those of ‘partial credit’ and communication between the student and the computer. These educational points were addressed in the next phase of the CALM Project in which the commercial testing program Interactive PastPapers was developed. The main aim of this paper is to describe how Interactive Past Papers has been able to incorporate some approaches to partial credit which has helped to alleviate student worries on these issues. Background information on other features in Interactive Past Papers is also included to provide context for the discussion

    Isolation of Glyoxysomes from Pumpkin Cotyledons

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    Peroxisomes are singleâ membraneâ bound organelles found in virtually all eukaryotes. In plants, there are several classes of peroxisomes. Glyoxysomes are found in germinating seedlings and contain enzymes specific for the glyoxylate cycle, including isocitrate lyase and malate synthase. After seedlings become photosynthetic, leaf peroxisomes participate in reactions of the photorespiration pathway and contain characteristic enzymes such as glycolate oxidase and hydroxypyruvate reductase. As leaves begin to senesce, leaf peroxisomes are transformed back into glyoxysomes. Root peroxisomes in the nodules of legumes, for example, sequester enzymes such as allantoinase and uricase, which contribute to nitrogen metabolism in these tissues. Thus, peroxisomes participate in many metabolic pathways and contain specific enzyme complements, depending on the tissue source. All peroxisomes contain catalase to degrade hydrogen peroxide and enzymes to accomplish βâ oxidation of fatty acids. Glyoxysomes can be isolated from pumpkin cotyledons by standard differential centrifugation and density separation, as described in this article.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143713/1/cpcb0319.pd

    DCD – a novel plant specific domain in proteins involved in development and programmed cell death

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    BACKGROUND: Recognition of microbial pathogens by plants triggers the hypersensitive reaction, a common form of programmed cell death in plants. These dying cells generate signals that activate the plant immune system and alarm the neighboring cells as well as the whole plant to activate defense responses to limit the spread of the pathogen. The molecular mechanisms behind the hypersensitive reaction are largely unknown except for the recognition process of pathogens. We delineate the NRP-gene in soybean, which is specifically induced during this programmed cell death and contains a novel protein domain, which is commonly found in different plant proteins. RESULTS: The sequence analysis of the protein, encoded by the NRP-gene from soybean, led to the identification of a novel domain, which we named DCD, because it is found in plant proteins involved in development and cell death. The domain is shared by several proteins in the Arabidopsis and the rice genomes, which otherwise show a different protein architecture. Biological studies indicate a role of these proteins in phytohormone response, embryo development and programmed cell by pathogens or ozone. CONCLUSION: It is tempting to speculate, that the DCD domain mediates signaling in plant development and programmed cell death and could thus be used to identify interacting proteins to gain further molecular insights into these processes

    Effects of flow alteration on Apple-ring Acacia (Faidherbia albida) stands, Middle Zambezi floodplains, Zimbabwe

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    The impounding of the Zambezi River by Kariba dam has regulated the river discharge of the Middle Zambezi river. This has been implicated in the failure of regeneration of Faidherbia albida in the downstream flood plain. This study aimed (1) to assess the effect of the altered flow regime of the river on the establishment and growth of F. albida on the Middle Zambezi floodplain and islands and (2) to test the potential of dendrochronology in detecting the age and long-term growth rates of F. albida in response to flow regime. Results indicated an uneven age distribution of F. albida stands on relatively ‘new islands’, dominated by young trees, while the floodplain and the ‘old island’ exhibited an even-aged stand but with a lack of regeneration, and a dying-off of older trees. The lack of F. albida establishment on the floodplain was linked to the decreased occurrence of flooding events, associated with a decrease in alluvial deposits, soil moisture and groundwater recharge. These effects may be enhanced by impact from browsers on regeneration of trees. Tree-ring analyses revealed the presence of distinct annual growth rings in F. albida and the applicability of dendrochronology for estimating F. albida population dynamics. The trees on the ‘new islands’ are younger and grow faster than those on the floodplain. Lack of competition and possible favourable moisture conditions suggest beneficial conditions for establishment and growth of the trees on the islands

    Specificity and overlap of attention and memory biases in depression

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    Attentional and memory biases are viewed as crucial cognitive processes underlying symptoms of depression. However, it is still unclear whether these two biases are uniquely related to depression or whether they show substantial overlap. We investigated the degree of specificity and overlap of attentional and memory biases for depressotypic stimuli in relation to depression and anxiety by means of meta-analytic commonality analysis. By including four published studies, we considered a pool of 463 healthy and subclinically depressed individuals, different experimental paradigms, and different psychological measures. Memory bias is reliably and strongly related to depression and, specifically, to symptoms of negative mood, worthlessness, feelings of failure, and pessimism. Memory bias for negative information was minimally related to anxiety. Moreover, neither attentional bias nor the overlap between attentional and memory biases were significantly related to depression. Limitations include cross-sectional nature of the study. Our study showed that, across different paradigms and psychological measures, memory bias (and not attentional bias) represents a primary mechanism in depression
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