Polar rectification of stereo images implemented on a GPU

Polar rectification of stereo image pairs is reviewed and the implementation on a graphics processing unit (GPU) discussed. The rectification process requires the fundamental matrix as the only parameter and its performance will be tested using images with varying SNR. The computational time for the process as implemented will also be discussed

Vegetation and microbial determinants of soil carbon isotopic composition

Typically, soil δ¹³C and δ¹⁵N values tend to increase with depth across a wide range of ecosystems. Changes in δ¹³C with depth have been attributed to vegetation changes (i.e. C₃/C₄ shifts), but the similarity in δ¹³C and δ¹⁵N profiles suggest that microbial decomposition may play an important role. The determinants of soil δ¹³C and δ¹⁵N, however, are complex and microbial decomposition and vegetation shifts are not the only mechanisms that drive the fractionation of the isotopes with depth. We explored the utility of using δ¹³C as a proxy for vegetation change by considering alternative mechanisms for the changes in soil δ¹³C with depth. These alternate mechanisms may weaken the interpretation of soil δ¹³C as an indicator of vegetation change if the measured δ¹³C changes are small. We hypothesized that: (1) if soil-related processes such as mineralization and dark CO₂-fixation by microbes and roots contribute significantly to the δ¹³C signature of bulk soil at depth, one cannot simply determine whether the δ¹³C value of the soil at depth is indicative of a past vegetation assemblies (i.e. C₃/C₄ transitions); (2) changes in soil δ¹³C and δ¹⁵N values are linked through common microbially mediated decomposition-related processes; (3) anaplerotic CO₂ fixation by microbes and roots may contribute significantly to soil δ¹³C values, while N₂-fixation may contribute to soil δ¹⁵N values with depth. Microbial processing of SOM during decomposition leads to ¹³C-enrichement of SOM with depth and has been modelled using a Rayleigh distillation process. Anaplerotic fixation of soil CO₂ is, however, known to occur in microbes and roots and we suggest that this has a role in determining soil SOM δ¹³C values through cumulative incorporation of bulk atmosphere CO₂ into SOM. These processes vary greatly between soils and environments. The correspondence between soil δ¹³C and δ¹⁵N was assessed by compiling data from soil depth profiles from widely distributed sites and conducting an analysis of global δ¹³C and δ¹⁵N variations in surface soils in order to determine relationships between soil isotopes and with climate and soil properties. Strong positive correlations between δ¹³C and δ¹⁵N values through soil profiles were found at a number of sites and were found to be independent of vegetation type. Globally, soil δ¹³C and δ¹⁵N values were also found to be significantly positively correlated across a wide range of climates and biomes. The global correspondences between δ¹³C and δ¹⁵N values may suggest a mechanistic link between δ¹³C and δ¹⁵N through the process of SOM decomposition and microbial processing. Anaplerotic CO₂ fixation by soil microbes and roots was assessed using soils from 10 sites across South Africa differing in soil properties and incubated in the dark for 3 d under continuous exposure to ¹³CO₂- and ¹⁵N₂-enriched atmospheres with varying soil moisture (10, 50 and 100% of field capacity) and temperature (4, 25, 40°C). There was no evidence of significant N₂ fixation in any treatment. Significant soil anaplerotic CO₂ fixation, however, occurred in all soils. Highest rates of anaplerotic CO₂ fixation occurred in soils at 50% field capacity and 25°C, suggesting a link with microbial biotic activity. Soils with low C and N concentrations and low C:N ratios exhibited the highest rates of CO₂ fixation in soils, indicating a link between anaplerotic CO₂ fixation rates and soil nutrient status. The higher rates of CO₂ fixation in soils with low nutrients may indicate that soil microbes rely increasingly on anaplerotic fixation as SOM-N declines, forcing greater reliance on de novo amino acid synthesis, and thus anaplerotic CO₂ fixation. The ubiquitous occurrence of anaplerotic ¹³CO₂ fixation in these soils indicates that anaplerotic fixation is likely important in contributing to determining soil δ¹³C values. Diffusion of low δ¹³C bulk atmospheric CO₂ (ca. -10‰) into the soil atmosphere (<< -10‰) will drive soil CO₂ δ¹³C towards ca. -10‰, and constant anaplerotic CO₂ fixation will result in SOM δ¹³C also tending towards 10‰ in more highly processed SOM deeper in the soil. The consequences of decomposition and the linked anaplerotic activity for soil δ¹³C values may be erroneously interpreted as evidence for C₄ vegetation being invaded by C₃ vegetation, potentially leading to incorrect conservation decisions. We argue that δ¹³C should only be used as a proxy for vegetation change where decomposition rates and anaplerotic CO₂ fixation are low and/or their effect on soil δ¹³C values can be accounted for

Agreement between NRS-2002 and MUST nutrition risk scores – a retrospective study

No Abstrac

Realiteite van kantoorparkontwikkelings

The purpose of the study was to high­light the characteristic features of office parks. The importance of loca­tion and accessibility in orderly plan­ning in public interest, the new Deve­lopment Facilitation Act, Act 67 of 1995 (DFA), as well as, site size and establishment conditions were empha­sized. A literature study was done, interviews were conducted, with ques­tionnaires in large cities in South Africa, as office parks have not yet been established in the smaller cities.&nbsp;The conclusion was reached that the typical peripheral location can possi­bly still move further from the city (with reservations), even to more rural areas to avoid traffic congestion and&nbsp;ensure more pleasant residential areas. In the more rural areas a smaller site can still convey the office park con­cept, even with higher coverage and floor space ratio (FSR). Finally possi­ble guidelines for urban planners and developers were suggested.*This article is written in Afrikaans

A comparison between Daphnia pulex and Hydra vulgaris as possible test organisms for agricultural run-off and acid mine drainage toxicity assessments

Bioassays, consisting of a diverse selection of organisms, aid in assessing the ecotoxicological status of aquatic ecosystems. Daphnia pulex and Hydra vulgaris are commonly used test organisms belonging to different trophic levels. The current study focused on comparing the sensitivity of H. vulgaris to D. pulex when exposed to geometric dilutions of two different water sources, the first (Site 1) from a source containing agricultural run-off and the second (Site 2), acid mine drainage. These sources were selected based on the contribution that the agricultural and mining sectors make to water pollution in South Africa. The bioassay method followed in this study was a modified version of the method described by the USEPA and additional peer-reviewed methods. The mortalities as well as morphological changes (H. vulgaris) were analysed using Microsoft Excel. The LC50-values were statistically determined using the EPA Probit Analysis Model and the Spearman-Karber analysis methods. Prior to being used, analysis of the physico-chemical properties, nutrients and metals of both water samples was performed. These results showed a relationship to the results obtained from the D. pulex and H. vulgaris bioassays, as Site 1 (lower concentration of contaminants) was less hazardous to both test organisms than Site 2 (higher concentration of contaminants). Both organisms can be used for ecotoxicity testing, with D. pulex being a more sensitive indicator of toxicity with regards to water sampled from the acid mine drainage site. Due to the sensitivities of sub-lethal endpoints observed over time, H. vulgaris may be used for chronic toxicity testing and D. pulex for acute toxicity testing.Keywords: Hydra, Daphnia, toxicity, ecotoxicity, definitive toxicity tes

Rick Warren, purpose driven en die 40 dae doelgerigte lewe veldtog

More than 532 churches/congregations in South-Africa have already purchased “The purpose driven campaign kit” and completed the 40 days campaign or are planning to do so. The name Rick Warren is synonymous with “Purpose driven” and the popularity of his work as well as his influence in this country, justifie a study of this nature. This study wants to determine the effect of Rick Warren's 40 days of purpose in the circuit of Klerksdorp of the Nederduitsch Hervormde Kerk van Afrika. Warren provides five purposes for a believer in the church in his book, A purpose driven life, which according to him is the church's purpose of existence. The hypothesis of this study is that the 40 days of purpose is an excellent project for congregations to discover their purpose of existence, while it also strengthens the process of building the local congregation. Eight congregations participated in the research project. HTS Theological Studies Vol. 63 (2) 2007: pp. 751-77

ANA as part of a comprehensive reading literacy school assessment system

Making decisions about teaching and learning is as core a component to teaching as providing the teaching itself. Effective use of assessment data to plan, judge, and modify teaching is a fundamental competency for good teaching. According to the Department of Basic Education (2013b), the purpose of the ANA is to determine learner performance with regard to the skills and knowledge that they have acquired as a result of teaching and learning experiences in school. In addition, it provides important evidence to inform planning and development at national, provincial, district and school level. The purpose of this article is to report on the results of an exploratory action research study that indicate that the Annual National Assessment is overstepping its boundaries in terms of supporting the development of a systematic, dynamic and effective reading literacy assessment system to address the early literacy skills of foundation phase learners. ANA was not designed or standardised to be a screening, diagnostic, and progress monitoring assessment.Keywords: Annual National Assessments, data-based decision making, progress monitoring assessment, basic early literacy skill

Biomimetic reactions relevant to the study of abasic sites in DNA

Abasic (Ap) sites represent the most common form of DNA damage in mammalian cells. With steady state levels of 10,000 sites existing in each cell, there is a dire need to study these noxious biological electrophiles. While much work has been done to study these lesions using small biomolecules, such as oligonucleotides, there is still much to be learned regarding the fundamental organic chemistry. This thesis attempts to use the tools of basic organic chemistry to understand the complex reactions, structure, and equilibria of the abasic site

The oldest fossil piesmatid bug in the Lowermost Eocene amber of the Paris Basin (Heteroptera: Lygaeoidea : Piesmatidae)

The oldest fossil Piesmatidae, Eopiesma trimerum n. gen., n. sp. is described from the Lowermost Eocene amber of Paris Basin (France). It is considered as the sister group of all other Piesmatidae. This family probable diversified during the Lower Cenozoic