65 research outputs found
Influence of curing conditions on alkali-activated mortars intended for concrete repair
No full textRepair mortars are costly materials with high level of Portland cement and various additives which questions their eco-efficiency. In this respect, cement free material solutions such as alkali-activated mortars based on ground granulated blast furnace slag (BFS) are gaining interest for structural repair. The aim of this research is to study blast furnace slag as a precursor for producing ambient cured alkali-activated repair mortars. To achieve this purpose, a total of four mixtures were prepared using four different molar ratios of the silicate solution. The fresh and hardened properties of the produced mortars including flow retention, dry density, compressive and flexural strength are studied comparing ambient-cured and sealedcured specimens. Furthermore, the tensile bond strength between the repair mortars and a grit blasted concrete substrate was verified (after 7 days sealed + 21 days ambient curing). The results demonstrate, for the tested configurations, the feasibility of the alkali-activated repair mortar, including a good adherence. Given the limited scope of the tests, more work is needed to confirm the observations further
Foods contributing to vitamin B-6, folate, and vitamin B-12 intakes and biomarkers status in European adolescents: The HELENA study
No full textPURPOSE: To examine the association between food groups consumption and vitamin B6, folate and B12 intakes and biomarkers in adolescents. METHODS: In total 2189 individuals participating in the cross-sectional Healthy Lifestyle in Europe by Nutrition in Adolescence study met the eligibility criteria for analysis of dietary intakes (46 % males) and 632 for biomarker analysis (47 % males). Food intakes were assessed by two non-consecutive 24-h recalls. Biomarkers were measured by chromatography and immunoassay. Food groups which best discriminated participants in the extreme tertiles of the distribution of vitamins were identified by discriminant analyses. Food groups with standardised canonical coefficients higher or equal to 0.3 were selected as valid discriminators of vitamins intake and biomarkers extreme tertiles. Linear mixed model elucidated the association between food groups and vitamins intakes and biomarkers. RESULTS: Vitamin B6 intakes and biomarkers were best discriminated by meat (males and females), margarine and mixed origin lipids only in males and breakfast cereals (females). Breakfast cereals (males), and fruits, margarine and mixed origin lipids, vegetables excluding potatoes, breakfast cereals, and soups/bouillon (females) determined the most folate intakes and biomarkers. Considering vitamin B12 intakes and biomarkers, meat, and white and butter milk (males and females), snacks (males), and dairy products (females) best discriminated individual in the extremes of the distribution. Fewer associations were obtained with mixed model for biomarkers than for vitamins intakes with food groups. CONCLUSIONS: Whereas B-vitamin intakes were associated with their food sources, biomarkers did with overall food consumption. Low-nutrient-density foods may compromise adolescents' vitamin status.sponsorship: HELENA study received funding from the European Union's Sixth RTD Framework Programme (Contract FOODCT-2005-007034). Additional support from the Spanish Ministry of Education (AGL2007-29784-E/ALI), Axis-Shield Diagnostics Ltd (Oslo, Norway), Abbot Cientifica S.A. (Spain). The first author was financially supported by EURRECA-Network of Excellence-. This analysis was also supported by the Spanish Ministry of Science and Innovation (JCT-2010-07055) with the contribution of the European Regional Development Fund (FEDER). The authors would like to acknowledge all the adolescents who made possible the HELENA study with their participation. Many thanks to Petra Pickert, Rosa Torres and Ulrike Albers for their contribution to laboratory work. (European Union|FOODCT-2005-007034, Spanish Ministry of Education|AGL2007-29784-E/ALI, Axis-Shield Diagnostics Ltd (Oslo, Norway), Abbot Cientifica S.A. (Spain), EURRECA-Network of Excellence-, Spanish Ministry of Science and Innovation|JCT-2010-07055)status: Publishe
The dynamics of theologies: A transdisciplinary description
No full textIn this article, the author asks why the South African public, especially Afrikaans communities, is largely unaware of the knowledge generated in the field of science and religion. The author describes theologies as complex systems that interact with their environment. To illuminate the environment, the author turns to the theatre system and illustrates how the theatre system can illuminate the modelling choices of theologians
Private security companies and private military companies: a comparative and economical analysis
No full textThis book constructs theoretical models of how States can cope with the increased interest in private security, provides a functional breakdown of “police services” as we understand the term now, and examines the entry barriers several Western jurisdictions have imposed on the companies that are willing to provide these different police functions on a private basis. Lastly, a new input is given to a fairly unexplored market segment: a combination of a security contract with an insurance contract. In a separate chapter, the book touches upon the concept of private military companies. One specific subset of these can be closely linked to the private security industry. When contracted by State agencies, challenges are encountered that also exist with other public-private contracts, but in a more exasperated way. The author proposes some methods, using existing instruments, to minimise costs, maximise benefits, and increase accountability to the benefit of both the State and the company
FRP systems for structural rehabilitation: growth or maturity ?
No full textThe use of fibre reinforced polymer (FRP) based advanced composite systems for the repair and strengthening of structures has evolved from an emerging technology to an established engineering technique. Structural rehabilitation with externally bonded FRP reinforcement has a track record of over 15 years of widespread commercial applications world-wide and this has been reflected in growing availability of standards and codes. Moreover, it has been 26 years since the first on-site application of bonded FRP strips. Hence, one could state that the technology life cycle reached maturity and that it is time to rest on our tremendous achievements as a research community? Reflecting on this statement, the author believes and demonstrates the opposite, and proposes some challenges and focal points for academia and industry on the use of FRP systems for the construction sector and more specific looking into FRP systems for structural rehabilitation
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
Assessment of shrinkage and bond behaviour of high performance cement-based composites as a repair mortar
No full textThere is a need to develop innovative repair materials which can overcome the challenges of cement-based repair mortars being relatively prone to shrinkage effects. In practice, free shrinkage of repair mortar is often considered as an indicator for potential cracking and delamination of applied repair mortars due to restrained shrinkage effects. As it is hard to measure restrained shrinkage directly, a restraint factor (R) can be used to correlate both. This study investigates the shrinkage characteristics of strain-hardening cementitious composites (SHCC), making use of polyvinyl-alcohol (PVA), high-density poly-ethylene (HDPE), or short glass fibres, for the repair and strengthening of existing concrete structures. Along with drying shrinkage and autogenous shrinkage, restrained shrinkage has been characterized with respect to the concrete substrate. Furthermore, pull-off tests were performed to assess the bond properties of these repair mortars. The results show around 65% higher autogenous shrinkage in high strength SHCC mixes while there was a decrease in drying shrinkage compared to the reference mix. In contradiction to what was initially expected, an increase in fibre content from 1.5 to 2.0 vol% resulted in a significant increase in autogenous shrinkage, especially in the high strength SHCC mixes. The restraint factor for all repair mortars was determined and was found to be in the range of 0.82–0.94. The pull-off tests showed an overall excellent bond behaviour of all studied mortars
Engineering model for SFRC shear strength based on MC2010 MCFT approach
No full textRecent developments and ongoing research in the field of steel fibre reinforced concrete (SFRC) have led to its implementation into national and international design codes and guidelines. Since fibres are promising as an alternative for (minimum) shear reinforcement, special attention is given towards new shear design provisions for FRC elements. Although these design models are available and validated with respect to research results, the application of fibres as shear reinforcement for both reinforced and prestressed concrete beams is rather limited in daily practice, due to lack of experience in the engineering community with respect to these design guidelines, as well as limited insight in their accuracy.
In perspective to a PhD study of the second author, the most important shear design models available for SFRC (RILEM, Model Code, Plasticity Model) are verified in terms of accuracy of the models against a shear test database containing 99 SFRC elements (69 reinforced concrete and 30 prestressed concrete). Based on the obtained insights, a simplified engineering model is proposed for further evaluation by the research community. This model, which predicts the shear capacity of SFRC beams without stirrups, can be regarded as a closed form version of the modified compression field theory (MCFT) approach presented in fib Model Code 2010
Presentations of masculinity in a selection of male-authored post-apartheid novels
No full textThesis (MA (English Literature))--University of Stellenbosch, 2005.In this thesis I examine the presentations of masculinity in several novels published in the post-apartheid period in South Africa, that is, the period after 1994. The novels under discussion are all male-authored texts and include novels by J M Coetzee (1999), André Brink (2000), Phaswane Mpe (2001), K Sello Duiker (2001), Zakes Mda (2002) and Damon Galgut (2003).
In the introduction theoretical issues regarding masculinity are discussed on the basis of Morrell (2001) and a broad framework for the thesis is outlined. Subsequently the presentation of masculinity is analysed in each of the respective novels under discussion.
Issues such as a definition of masculinity (or rather, masculinities), the interaction between men as friends, as colleagues; as well as issues such as heterosexuality and homosexuality are discussed. What perspectives does the author provide on masculinity? How do the male characters experience the new South Africa? What is the nature of their interaction with the female characters in the novels? Another aspect dealt with is the repression of homosexual desire for another man and the way in which it is suppressed beneath a macho façade.
In the conclusion the different perspectives are compared and similarities and differences are briefly pointed out. In the end, an important question that comes to mind is: Do these men present a different type of masculinity emerging in the period after liberation, or do they merely (as depicted by their authors) perpetuate the patriarchal masculinities associated with the period before 1994?Master
Early life seizures and olfactory communication in rats
No full textObjective
Early life seizures (ELS) are commonly associated with autism spectrum disorder (ASD); however, the exact role of ELS in the pathology is unknown. Prior studies have demonstrated social deficits, a core feature of ASD, following ELS; consequently, alterations in sensory modalities may contribute to the overall social deficits. Considering the speculated contribution of sensory deficit to social communication, we examined the developmental consequences of early postnatal kainic acid (KA)-induced seizures on olfactory preference and neural markers in the olfactory bulb in both male and female Sprague Dawley rats.
Methods
KA-induced seizures or saline was administered. Rats were then exposed to a series of biologically relevant scents including male scent, female scent, nest scent, and phenylethylamine during the juvenile period and again during adulthood. Alterations in sensory modalities were expected to be expressed via abnormal preference for certain scents and/or production of abnormal ultrasonic vocalizations in response to scents. The olfactory bulbs were also assessed for the biologically relevant markers glial fibrillary acidic protein (GFAP) and calcium/calmodulin-dependent protein kinase II (CAMKII).
Results
Our findings resulted in no significant differences in olfactory preference following ELS for juveniles or adults compared to controls. Similarly, there were no differences in GFAP expression or the ratio of phosphorylated CAMKII to CAMKII in either olfactory bulb. Interestingly, despite a lack of treatment differences, different scents were shown to elicit different responses in juvenile rats, yet these differences subsided in adulthood.
Significance
Overall, the results of this study suggest that olfaction does not contribute to socialization deficit following ELS within the KA model.National Institutes of Healt
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