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The objective of this experimental investigation is to use the ASTM C1138 (underwater) test method to investigate the influence of the quantity and type of coarse aggregates on the hydrodynamic abrasion resistance of concrete. Thereafter, relationships between the abrasion resistance of concrete with its principal mechanical properties are comparatively examined. It is found that the use of natural coarse aggregates to replace fine aggregates by up to 25% does not significantly affect concrete abrasion performance, but the use of recycled tire rubber aggregates with aspect ratios of ∼4 to replace 25% of natural coarse aggregates increases the abrasion resistance by up to 64% depending on the test duration. Further, concretes produced with natural rounded coarse aggregates of 10 mm significantly outperformed those with angular 20 mm maximum particle size at all test durations by up to 57%. Finally, for the concrete mixtures tested, results indicate that tensile splitting strength is a superior parameter to compressive strength for predicting the concrete abrasion resistance in the ASTM C1138 test and the relations developed for the concretes tested predicted percentage abrasion loss within the margin of ±0.5%. [ABSTRACT FROM AUTHOR]

• Waste glass presents a major challenge to environmental sustainability. • Use as concrete aggregate for hydraulic structures increases its applications. • Hydraulic structures are susceptible to abrasion damage. • This paper investigates the abrasion resistance of glass-aggregate concretes. • Recycled glass can be effectively used to partially replace natural coarse aggregates. This experimental study is aimed at evaluating the hydrodynamic abrasion resistance of concrete produced with recycled waste glass as coarse aggregates. The underwater (ASTM C1138) method is used to test concretes containing 0%, 12.5%, 25%, 50% and 100% glass aggregates as replacement for natural coarse aggregates. To benchmark performance, the abrasion resistance of glass-aggregate concretes is compared with that of a high-strength concrete mixture typically used in coastal defences where abrasion resistance is critical. Further comparison is made with a general application concrete mixture containing crushed limestone coarse aggregates. At 95% confidence, results of the Kruskal-Wallis test show that the use of recycled waste glass as coarse aggregates in concrete at contents of up to 25% does not significantly affect its abrasion resistance. When compared with the typical high-strength mixture with proven field performance, the results of the Kruskal-Wallis test at 95% confidence indicated that abrasion resistance at glass aggregate replacement levels of up to 25% was not significantly different. Concrete produced with 100% recycled waste glass coarse aggregates had comparable abrasion resistance with that produced with 100% crushed limestone coarse aggregates. Additionally, there was a stronger and significant dependence of the abrasion resistance of glass-aggregate concretes on tensile splitting strength in comparison to both compressive strength and modulus of elasticity. [ABSTRACT FROM AUTHOR]

We investigated the hypothesis that host immunosuppression due to advancing human immunodeficiency virus (H IV) disease favors the direct development of infective larvae of Strongyloides stercoralis, which may facilitate hyperinfection and, hence, disseminated strongyloidiasis. To do this, we sought correlations between the immune status of the subjects and the development of S. stercoralis infections. Among 35 adults, there were significant negative rank correlations between CD4+ cell counts and the proportions of free-living male and female worms. Thus, in individuals with preserved immune function, direct development of S. stercoralis is favored, whereas, in individuals with lesser immune function, indirect development is relatively more common. These results may explain the notable absence of disseminated strongyloidiasis in advanced HIV disease. Because disseminated infection requires the direct development of infective larvae in the gut, the observed favoring of indirect development in individuals immunosuppressed by advancing HIV disease is not consistent with the promotion of disseminated infection. [ABSTRACT FROM AUTHOR]

SummaryBackground: An association between HIV-1 and malaria is expected in theory, but has not been convincingly shown in practice. We studied the effects of HIV-1 infection and advancing immunosuppression on falciparum parasitaemia and clinical malaria.Methods: HIV-1-positive and HIV-1-negative adults selected from a population-based cohort in rural Uganda were invited to attend a clinic every 3 months (routine visits) and whenever they were sick (interim visits). At each visit, information was collected on recent fever, body temperature, and malaria parasites. Participants were assigned a clinical stage at each routine visit and had regular CD4-cell measurements.Findings: 484 participants made 7220 routine clinic visits between 1990 and 1998. Parasitaemia was more common at visits by HIV-1-positive individuals (328 of 2788 [11.8%] vs 231 of 3688 [6.3%], p<0.0001). At HIV-1-positive visits, lower CD4-cell counts were associated with higher parasite densities, compared with HIV-1-negative visits (p=0.0076). Clinical malaria was significantly more common at HIV-1-positive visits (55 of 2788 [2.0%] vs 26 of 3688 [0.7%], p=0.0003) and the odds of having clinical malaria increased with falling CD4-cell count (p=0.0002) and advancing clinical stage (p=0.0024). Participants made 3377 interim visits. The risk of clinical malaria was significantly higher at visits by HIV-1-positive individuals than HIV-1-negative individuals (4.0% vs 1.9%, p=0.009). The risk of clinical malaria tended to increase with falling CD4-cell counts (p=0.052).Interpretation: HIV-1 infection is associated with an increased frequency of clinical malaria and parasitaemia. This association tends to become more pronounced with advancing immunosuppression, and could have important public-health implications for sub-Saharan Africa. [ABSTRACT FROM AUTHOR]