Ultra-soft 100 nm Thick Zero Poisson’s Ratio Film with 60% Reversible Compressibility

About a 100 nm thick multilayer film of nanoparticle monolayers and polymer layers is shown to behave like cellular-foam with a modulus below 100 KPa. The 1.25 cm radius film adhered to a rigid surface can be compressed reversibly to 60% strain. The more than four orders of magnitude lower modulus compared to its constituents is explained by considering local bending in the (nano)cellular structure, similar to cork and wings of beetles. As the rigidity of the polymer backbone is increased in just four monolayers the modulus of the composite increases by over 70%. Electro-optical map of the strain distribution over the area of compression and increase in modulus with thickness indicates the films have zero Poisson’s ratio

Spatially resolved optical measurements of electric terahertz signals on passive devices

Background: Low-fluoride dentifrices have been suggested as alternatives to reduce dental fluorosis risk, but there is no consensus regarding their clinical effectiveness, which has been suggested to be increased when their pH is acidic. Aims: This single-blind randomized clinical trial evaluated the caries increment during the use of a low-fluoride acidic liquid dentifrice. Methods: Four-year-old schoolchildren (n = 1,402) living in a fluoridated area (0.6-0.8 ppm F) were randomly allocated to 4 groups differing according to the type of dentifrice used over a 20-month period. Group 1 (n = 345): liquid dentifrice, 1,100 ppm F, pH 4.5. Group 2 (n = 343): liquid dentifrice, 1,100 ppm F, pH 7.0. Group 3 (n = 354): liquid dentifrice, 550 ppm F, pH 4.5. Group 4 (n = 360): toothpaste, 1,100 ppm F, pH 7.0. At baseline and after 20 months, clinical examinations were conducted (dmfs index) and caries increment was calculated. Data were analysed by GLM procedure using classrooms (cluster) as unit of analysis (p < 0.05). Results: The mean +/- SD (95% CI) net increments found were as follows. Group 1: 2.06 +/- 2.38 (1.8-2.3); group 2: 2.08 +/- 2.87 (1.7-2.4); group 3: 2.05 +/- 2.79 (1.7-2.4), and group 4: 2.08 +/- 2.34 (1.8-2.4). No significant differences were detected among the groups. Conclusion: In a population with high caries risk living in a fluoridated area, as the selected sample, and according to the present protocol, the low-fluoride acidic liquid dentifrice seems to lead to similar caries progression rates as conventional 1,100 ppm F toothpaste. Copyright (C) 2010 S. Karger AG, Base

Relational trust in international cooperation: The case of North–South trade negotiations

The positive impact of trust on the willingness to cooperate has been widely recognised within social sciences. Trust, however, has not been adequately incorporated into the dominant paradigms on explaining international cooperation in international relations. This paper argues that in situations of uncertainty, trusting or mistrusting a cooperation partner influences the negotiating behaviour of state actors. Trusting behaviour is understood to be based on a non-rational mode of reasoning, which shapes negotiating behaviour beyond the cognitive calculation of risks in a given situation. Whether or not the other actor is considered as trustworthy depends to a large extent on the conception of the identity relationship between the cooperation partners. This is suggestive of a constructivist understanding of trust as a relational, identity-based concept that is difficult to capture using a measurable, calculative notion of trust employed in a game-theoretical, strictly rationalist framework. The article presents two conceptual lenses: benevolence-based trust and identification-based trust. The empirical analysis covers evidence from two of the six regions that were negotiating an economic partnership agreement with the european union: west africa and the caribbean region