Influence of confinement by smooth and rough walls on particle dynamics in dense hard-sphere suspensions

We used video microscopy and particle tracking to study the dynamics of confined hard-sphere suspensions. Our fluids consisted of 1.1-μm-diameter silica spheres suspended at volume fractions of 0.33–0.42 in water-dimethyl sulfoxide. Suspensions were confined in a quasiparallel geometry between two glass surfaces: a millimeter-sized rough sphere and a smooth flat wall. First, as the separation distance (H) is decreased from 18 to 1 particle diameter, a transition takes place from a subdiffusive behavior (as in bulk) at large H, to completely caged particle dynamics at small H. These changes are accompanied by a strong decrease in the amplitude of the mean-square displacement (MSD) in the horizontal plane parallel to the confining surfaces. In contrast, the global volume fraction essentially remains constant when H is decreased. Second, measuring the MSD as a function of distance from the confining walls, we found that the MSD is not spatially uniform but smaller close to the walls. This effect is the strongest near the smooth wall where layering takes place. Although confinement also induces local variations in volume fraction, the spatial variations in MSD can be attributed only partially to this effect. The changes in MSD are predominantly a direct effect of the confining surfaces. Hence, both the wall roughness and the separation distance (H) influence the dynamics in confined geometries

A radical approach to radical innovation

Innovation pays. Amazon, Apple, Facebook, Google – nearly every one of today’s most successful companies has a talent for developing radical new ideas. But how best to encourage radical initiative taking from employees, and does their previous success or failure at it play a role

Cryptosporidium infections in children in Durban Seasonal variation, age distribution and disease status

One hundred and eleven of 1229 children (9%) aged < 10 years admitted to King Edward VIII Hospital, Durban, with gastro-enteritis over a period of 1 year were found to harbour Cryptosporidium. Of these, 96 (89,7%) were < 2 years of age. Cryptosporidium was the only potential pathogen identified in 80 of these patients (6,50/0). The prevalence in paediatric patients without gastro-enteritis was 2,4% (3/124). During the study period Cryptosporidium infections were significantly more prevalent during the high rainfall season (P = 0,03)

A comparative assessment of commonly employed staining procedures for the diagnosis of ' cryptosporidiosis

Following an increase in the number of reports of Cryptosporidium infections and the problems encountered in detecting these organisms in faecal smears, a comparative assessment of a modification of the Sheather's flotation technique and other commonly employed staining procedures proved the modified Sheather's technique to be most useful in identifying Cryptosporidium oocysts in diarrhoeal stools. This technique not only detected the parasite in the highest number of stools but also proved to be cost-effective and the least timeconsuming. Other staining techniques assessed were the modified Ziehl-Neelsen, safranin-methylene blue and auramine- phenol fluorescence. Both the modified Ziehl-Neelsen and the auramine-phenol fluorescence procedures produced nonspecific staining, while the safranin-methylene blue method was found to be the least sensitive technique

Great successes and great failures: The impact of project leader status on project performance and performance extremeness

Research supporting the Matthew Effect demonstrates that high-status actors experience performance benefits due to increased recognition of their work and greater opportunities and resources, but recent research also indicates that high-status actors face a greater risk of negative performance evaluations. In this paper, we seek to contribute to the status literature by reconciling these findings and ask: To what extent does status influence heterogeneity in performance evaluations? We explore how project leader status affects the performance of innovation projects in the video game industry. We hypothesize that there is an inverted U-shaped relationship between project leader status and project performance, and a positive relationship between project leader status and performance extremeness (i.e., performance variation). In order to test our hypotheses, we analyzed the performance of video game projects and computed the status of project leaders by applying a project affiliation social network analysis. We find that an intermediate level of status—neither too much nor too little—is positively associated with average project performance. We also reveal more extreme performance effects for high-status leaders: While some achieve superior project performance, others experience significant project failures. We therefore provide important theoretical and practical insights regarding how status affects the implementation of innovations. We also discuss the implications of these findings for the literature on middle-status conformity

Shear viscosity of an ordering latex suspension

The shear viscosity of a latex which is ordered at rest is studied as a function of the shear rate and volume fraction. At low shear rates and for moderate to high volume fractions, the flow curves show dynamic yield behavior which disappears below a volume fraction of 8%. At high shear rates, the onset to the high shear rate plateau of the viscosity can be observed. A new model for the shear viscosity for lattices at high volume fractions is described. This model is based upon theories for the shear viscosity of dilute lattices of Blachford et al. [J. Phys. Chem. 73, 1062 (1969)] and Russel [J. Fluid Mech. 85, 673 (1978)]. In terms of this model, the ordered latex is broken down under shear flow into ordered domains suspended in a disordered fluid. The larger the shear rate, the smaller the volume fraction of ordered domains. The experimental results can be described reasonably well with the model discussed here

Irrational Resistance or Irrational Support? Performance Effects of Project Leader Status

In this study, we explore the effects of project leader status in new product development projects. We predict and find that that project leader status increases project performance up to a certain point after which it decreases performance. Further, status increases the variability of project performance, that is, it leads to more extreme performance in both directions

Talk, talk, talk: Exploring idea conversations and the micro-level foundations of knowledge sharing for innovation

In this study we explore the drivers and consequences of micro-level instances of knowledge sharing for innovation. We do so by focusing on the temporally bounded conversations that colleagues have about new ideas and we study specifically how the strength of ties between these colleagues influences the duration and breadth of knowledge sharing in the idea-related conversations they have over time. A 14-month on-site field study in a multinational company, in which we mapped 496 dyadic relationships regarding 17 new product ideas, shows that knowledge sharing can be explained by the ties between people being either strong or weak, rather than intermediate. We also discover that characteristics of the idea itself shape how tie strength influences the duration and breadth of knowledge sharing in idea conversations. Finally, we provide initial evidence to show how important conversations are for the success of an idea. Our study sheds light on micro-level instances of knowledge sharing for innovation and provides important insights into how managers can foster an environment in which weak and strong ties can be utilised optimally for sharing knowledge about ideas