Epoxy nanocomposites containing magnetite-carbon nanofibers aligned using a weak magnetic field

Abstract Novel magnetite-carbon nanofiber hybrids (denoted by Fe3O4@CNFs) have been developed by coating carbon nanofibers (CNFs) with magnetite nanoparticles in order to align CNFs in epoxy using a relatively weak magnetic field. Experimental results have shown that a weak magnetic field (∼mT) can align these newly-developed nanofiber hybrids to form a chain-like structure in the epoxy resin. Upon curing, the epoxy nanocomposites containing the aligned Fe3O4@CNFs show (i) greatly improved electrical conductivity in the alignment direction and (ii) significantly higher fracture toughness when the Fe3O4@CNFs are aligned normal to the crack surface, compared to the nanocomposites containing randomly-oriented Fe3O4@CNFs. The mechanisms underpinning the significant improvements in the fracture toughness have been identified, including interfacial debonding, pull-out, crack bridging and rupture of the Fe3O4@CNFs, and plastic void growth in the polymer matrix.

On the weak monotonicity of Gini means and other mixture functions

Weak monotonicity was recently proposed as a relaxation of the monotonicity condition for averaging aggregation, and weakly monotone functions were shown to have desirable properties when averaging data corrupted with outliers or noise. We extended the study of weakly monotone averages by analyzing their ϕ-transforms, and we established weak monotonicity of several classes of averaging functions, in particular Gini means and mixture operators. Mixture operators with Gaussian weighting functions were shown to be weakly monotone for a broad range of their parameters. This study assists in identifying averaging functions suitable for data analysis and image processing tasks in the presence of outliers.

Firm compliance with social insurance obligations where there is a weak surveillance and enforcement mechanism: empirical evidence from Shanghai

This article examines why firms in Shanghai comply or over-comply with social insurance obligations in a regulatory environment where the expected punishment for non-compliance is low. Our first finding is that firms found to be in non-compliance in the first audit in 2001 were moved into a separate violation category and the probability of being reaudited in 2002 was significantly higher if the firm was in that category. Our second main result is that, across the board, firms which were reaudited continued to underpay in 2002 but the extent of underpayment was significantly reduced. © 2007 The Authors. Journal compilation © 2007 Blackwell Publishing Ltd.

Social network perspectives reveal strength of academic developers as weak ties

Social network perspectives acknowledge the influence of disciplinary cultures on academics’ teaching beliefs and practices with implications for academic developers. The contribution of academic developers in 18 scholarship of teaching and learning (SoTL) projects situated in the sciences are explored by drawing on data from a two-year national project in Australia within a case study research design. The application of a social network lens illuminated the contribution of eight academic developers as weak ties who infused SoTL knowledge within teams. Two heuristic cases of academic developers who also linked across networks are presented. Implications of social network perspective are discussed.

Weak monotonicity of Lehmer and Gini means

We analyze directional monotonicity of several mixture functions in the direction (1,1...,1), called weak monotonicity. Our particular focus is on power weighting functions and the special cases of Lehmer and Gini means. We establish limits on the number of arguments of these means for which they are weakly monotone. These bounds significantly improve the earlier results and hence increase the range of applicability of Gini and Lehmer means. We also discuss the case of affine weighting functions and find the smallest constant which ensures weak monotonicity of such mixture functions.

Weak negative associations between avian influenza virus infection and movement behaviour in a key host species, the mallard Anas platyrhynchos

Animal movements may contribute to the spread of pathogens. In the case of avian influenza virus, [migratory] birds have been suggested to play a role in the spread of some highly pathogenic strains (e.g. H5N1, H5N8), as well as their low pathogenic precursors which circulate naturally in wild birds. For a better understanding of the emergence and spread of both highly pathogenic (HPAIV) and low pathogenic avian influenza virus (LPAIV), the potential effects of LPAIVs on bird movement need to be evaluated. In a key host species, the mallard Anas platyrhynchos, we tested whether LPAIV infection status affected daily local (< 100 m) and regional (> 100 m) movements by comparing movement behaviour 1) within individuals (captured and sampled at two time points) and 2) between individuals (captured and sampled at one time point). We fitted free-living adult males with GPS loggers throughout the autumn LPAIV infection peak, and sampled them for LPAIV infection at logger deployment and at logger removal on recapture. Within individuals, we found no association between LPAIV infection and daily local and regional movements. Among individuals, daily regional movements of LPAIV infected mallards in the last days of tracking were lower than those of non-infected birds. Moreover, these regional movements of LPAIV infected birds were additionally reduced by poor weather conditions (i.e. increased wind and/or precipitation and lower temperatures). Local movements of LPAIV infected birds in the first days of tracking were higher when temperature decreased. Our study thus demonstrates that bird-assisted dispersal rate of LPAIV may be lower on a regional scale than expected on the basis of the movement behaviour of non-infected birds. Our study underlines the importance of understanding the impact of pathogen infection on host movement in order to assess its potential role in the emergence and spread of infectious diseases.

The weak natural law thesis and the common good

The weak natural law thesis asserts that any instance of law is either a rational standard for conduct or defective. At first glance, the thesis seems compatible with the proposition that the validity of a law within a legal system depends upon its sources rather than its merits. Mark C. Murphy has nonetheless argued that the weak natural law thesis can challenge this core commitment of legal positivism via an appeal to law’s function and defectiveness conditions. My contention in the current paper is that in order to make good on the challenge, the defender of the weak natural law thesis should appeal explicitly to the common good, understood as the principal normative reason in the political domain. In section I I outline the main implications of the weak natural law thesis and clarify a common misunderstanding regarding its explanatory role. Section II then argues for the indispensability of the common good to the natural law jurisprudential thesis on the grounds that it has an essential role to play in a natural law account of law’s defectiveness conditions and the presumptive moral obligatoriness of legal norms. Finally, in section III I examine the compatibility of a strengthened version of the weak natural law thesis with legal positivism in light of the centrality of the common good to the natural law jurisprudential position.