47 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
Effect of a serotonin blocking agent on renal hemodynamics in the normal rat
No full textEffect of a serotonin blocking agent on renal hemodynamics in the normal rat. These studies were designed to explore the effects of ketanserin (K), a serotonergic S2-receptor blocker on glomerular filtration rate (GFR), renal plasma flow (RPF) and autoregulation of renal blood flow (RBF) in the normal, anesthetized rat. Two doses of ketanserin were used: a high dose that, in addition to its serotonin blocking effect, possessed alpha 1-adrenergic blocking capacities; and a low dose that acted only as a serotonin S2 blocking agent. The effects of the high dose were compared to the effects of phenotolamine. Both the high dose of K and phentolamine resulted in a similar fall of systemic blood pressure from 117 ± 4 to 78 ± 3 and from 121 ± 4.5 to 76 ± 5mm Hg, respectively (P < 0.01). Despite this fall, GFR and RPF remained unchanged from 2.36 ± 0.16 ± to 2.26 ± 0.12 ml/min, and from 5.33 ± 0.41 to 5.76 ± 0.5ml/min with K, while both parameters significantly decreased with phentolamine. A remarkable preservation of the autoregulation of RBF until a renal perfusion pressure (RPP) of 70 to 75mm Hg was noted with K, but not with phentolamine or Ringer infusion. With the low dose of K, a significant rise in GFR and PAH clearance was noted, from 2.12 ± 0.17 to 2.59 ± 0.18 and from 4.81 ± 0.35 to 5.66 ± 0.48 ml/min, respectively (P < 0.05). A similar preservation of autoregulation of RBF was observed. Our studies suggest that in the pressure ranges below normal autoregulation of RBF in the rat, serotonin blockade is associated with maintenance of both GFR and RBF
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
