Conditioning film and environmental effects on the adherence of Candida spp. to silicone and poly(vinylchloride) biomaterials.

The reported incidence of colonization of oropharyngeal medical devices with Candida spp. has increased in recent years, although few studies that have systematically examined the adherence of yeast cells to such biomaterials, the primary step in the process of colonization. This study, therefore, examined the effects of oropharyngeal atmospheric conditions (5% v/v carbon dioxide) and the presence of a salivary conditioning film on both the surface properties and adherence of Candida albicans, Candida krusei and Candida tropicalis to PVC and silicone. Furthermore, the effects of the salivary conditioning film on the surface properties of these biomaterials are reported. Growth of the three Candida spp. in an atmosphere containing 5% v/v CO2 significantly increased their cell surface hydrophobicity and reduced the zeta potential of C. albicans and C. krusei yet increased the zeta potential of C. tropicalis (p < 0.05). Furthermore, growth in 5% v/v CO2 decreased the adherence of C. tropicalis and C. albicans to both PVC and silicone, however, increased adherence of C. krusei (p < 0.05). Pre-treatment of the microorganisms with pooled human saliva significantly decreased their cell surface hydrophobicity and increased their adherence to either biomaterial in comparison to yeast cells that had been pre-treated with PBS (p < 0.05). Saliva treatment of the microorganisms had no consistent effect on microbial zeta potential. Interestingly, adherence of the three, saliva-treated Candida spp. to saliva-treated silicone and PVC was significantly lower than whenever the microorganisms and biomaterials had been treated with PBS (p < 0.05). Treatment of silicone and PVC with saliva significantly altered the surface properties, notably reducing both the advancing and receding contact angles and, additionally, the microrugosity. These effects may contribute to the decreased adherence of saliva-treated microorganisms to these biomaterials. In conclusion, this study has demonstrated the effects of physiological conditions within the oral cavity on the adherence of selected Candida spp. to biomaterials employed as oropharyngeal medical devices. In particular, this study has ominously shown that these materials act as substrates for yeast colonization, highlighting the need for advancements in biomaterial design. Furthermore, it is important that physiological conditions should be employed whenever biocompatibility of oropharyngeal biomaterials is under investigation. © 2001 Kluwer Academic Publishers.

Polymer conditioning of alum sludge and discrepancies between estimates of the optimum dosage

The paper outlines the effects of polymer conditioning on alum sludge properties, such as floc size, density, fractal dimension (DF) and rheological properties. Experimental results demonstrate that polymer conditioning of alum sludge leads to: larger floc size with a plateau reached in higher doses; higher densities associated with higher doses; increased degree of compactness; and an initial decrease followed by an increase of supernatant viscosity with continued increase in polymer dose. The secondary focus of this paper dwells on a comparison of the estimates of optimum dose using different criteria that emanate from established dewatering tests such as CST, SRF, liquid phase viscosity and modified SRF as well as a simple settlement test in terms of CML30. Alum sludge was derived from a water works treating coloured, low-turbidity raw waters.

The Macroeconomic Factors Conditioning the Impact of Identity on Attitudes towards the EU

Factors relating to identity and to economics have been shown to be important predictors of attitudes towards the European Union (EU). In this article, we show that the impact of identity is conditional on economic context. First, living in a member state that receives relatively high levels of EU funding acts as a 'buffer', diluting the impact of an exclusive national identity on Euroscepticism. Second, living in a relatively wealthy member state, with its associated attractiveness for economic migrants, increases the salience of economic xenophobia as a driver of sceptical attitudes. These results highlight the importance of seeing theories of attitude formation (such as economic and identity theories) not as competitors but rather as complementary, with the predictive strength of one theoretical approach (identity) being a function of system-level variation in factors relating to the other theoretical approach (macro-level economic conditions).

Authoritarianism, threat, and prejudice: An analysis of mediation and moderation

Right-wing authoritarianism is a central construct in individual differences approaches to prejudice. Its power to predict prejudice is often attributed to perceived threat. However, the exact moderating and mediating processes involved are little understood. In two studies (Ns=53, 84), exposure to threatening versus nonthreatening information about an ethnic out-group had reliable indirect effects on prejudice in authoritarians, but not in nonauthoritarians, largely because authoritarians were more likely to perceive actual threat when they interpreted the information received to represent a threatening argument. Additionally, in Study 2, authoritarians reacted more strongly with negative emotions when they perceived actual threat.