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We investigate the relationship between structure and robustness in the metabolic networks of Escherichia coli, Methanosarcina barkeri, Staphylococcus aureus, and Saccharomyces cerevisiae, using a cascading failure model based on a topological flux balance criterion. We find that, compared to appropriate null models, the metabolic networks are exceptionally(More)
We consider the impact of the effective gravitational acceleration g{eff} on gravity-driven granular shear flow utilizing a tumbler of radius R rotating at angular velocity omega when g{eff} is varied up to 25 times the gravitational level on Earth in a large centrifuge. The Froude number Fr=omega{2}R/g{eff} is shown to be the proper scaling to characterize(More)
We investigate the effect of nanoscale variations in the surface roughness of individual particles on macroscale granular flow characteristics. Experiments were conducted in circular rotating tumblers with smooth and rough 2 and 3 mm steel particles. The smooth beads had a rms surface roughness of approximately 30 to 60 nm; rough beads had a surface(More)
Granular surface flows are common in industrial practice and natural systems, however, theoretical description of such flows is at present incomplete. Two prototype systems involving surface flow are compared: heap formation by pouring at a point and rotating cylinders. Continuum models for analysis of these flows are reviewed, and experimental results for(More)
In this paper we briefly review the main issues associated with mixing at the microscale and introduce the papers comprising the Theme Issue. 1. Introduction Microfluidics is the term that is used to describe flow in devices having dimensions ranging from millimetres to micrometres and capable of handling volumes of fluid in the range of nano-to microlitres(More)
The simplest mixing problem corresponds to the mixing of a fluid with itself; this case provides a foundation on which the subject rests. The objective here is to study mixing independently of the mechanisms used to create the motion and review elements of theory focusing mostly on mathematical foundations and minimal models. The flows under consideration(More)
ago (Australia) and even 4 million years ago (Hawaii)—the sorts of time scales studied by Quaternary paleoecologists. They take advantage of a technique called " space-for-time " substitution, which allows them to study modern vegetation and soils on surfaces of different but known ages, and hence to infer what changes in ecology and soils took place over(More)
Through a combined computational–experimental study of flow in a slowly rotating quasi-two-dimensional container, we show several new aspects related to the kinematics of granular mixing. In the Lagrangian frame, for small numbers of revolutions, the mixing pattern is captured by a model termed " streamline jumping. " This minimal model, arising at the(More)
Segregation patterns formed by time-periodic flow of polydisperse granular material (varying in particle size) in quasi-two-dimensional (quasi-2D) tumblers capture the symmetries of Poincaré sections, stroboscopic maps of the underlying flow, derived from a continuum model which contains no information about particle properties. We study this phenomenon(More)
The role of mentorship in protégé performance is a matter of importance to academic, business and governmental organizations. Although the benefits of mentorship for protégés, mentors and their organizations are apparent, the extent to which protégés mimic their mentors' career choices and acquire their mentorship skills is unclear. The importance of a(More)