Advice to the Nymphs of New S—m

Fielding, Henry; Miller, Henry Knight

doi:10.1093/oseo/instance.00058138

Cited by 28 publications

(47 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These effects can be expected to vary with particle shape and swimming type, and indeed our observations are almost the opposite of what happens in (neutral) squirmers [22], where HIs act to suppress rather than enhance the formation of density inhomogeneities.…”

Section: Dynamics In the Semi-dilute Regimementioning

confidence: 43%

“…The intrinsic difference in the models can cause strong variations in the nature of near-field HIs as well as in the interparticle torques at close approach, both of which will alter cooperative behaviors at finite density. We will draw attention to these differences occasionally in what follows, in relation to recent simulations of squirmers [22].…”

Section: Methodsmentioning

confidence: 96%

See 1 more Smart Citation

Activity-induced clustering in model dumbbell swimmers: The role of hydrodynamic interactions

2014

View full text Add to dashboard Cite

Using a fluid-particle dynamics approach, we numerically study the effects of hydrodynamic interactions on the collective dynamics of active suspensions within a simple model for bacterial motility: each microorganism is modeled as a stroke-averaged dumbbell swimmer with prescribed dipolar force pairs. Using both simulations and qualitative arguments, we show that, when the separation between swimmers is comparable to their size, the swimmers' motions are strongly affected by activity-induced hydrodynamic forces. To further understand these effects, we investigate semi-dilute suspensions of swimmers in the presence of thermal fluctuations. A direct comparison between simulations with and without hydrodynamic interactions shows these to enhance the dynamic clustering at a relatively small volume fraction; with our chosen model the key ingredient for this clustering behavior is hydrodynamic trapping of one swimmer by another, induced by the active forces. Furthermore, the density dependence of the motility (of both the translational and rotational motions) exhibits distinctly different behaviors with and without hydrodynamic interactions; we argue that this is linked to the clustering tendency. Our study illustrates the fact that hydrodynamic interactions not only affect kinetic pathways in active suspensions, but also cause major changes in their steady state properties.

show abstract

Section: Dynamics In the Semi-dilute Regimementioning

confidence: 43%

Section: Methodsmentioning

confidence: 96%

Activity-induced clustering in model dumbbell swimmers: The role of hydrodynamic interactions

2014

View full text Add to dashboard Cite

show abstract

“…This would, however, require more time and resources for training, planning, implementing the research and analysing data, as has been seen in some other pupil research projects (e.g. Bland and Atweh 2007;Fielding and Bragg 2003). While engagement in inclusive research brings a number of benefits, it nevertheless involves the investment of a great deal of time, organization and reflection if the process and the outcomes are to be valuable to the pupils, the school and the wider (research) community.…”

Section: Conclusion and Recommendationsmentioning

confidence: 99%

Aspirations and assumptions: a researcher's account of pupil involvement in school-based research

Mearns

Coyle

Graaff

2014

International Journal of Research & Method in Education

View full text Add to dashboard Cite

This paper describes a research project conducted in collaboration with 10 'pupil co-researchers' (PCRs) and their classes in a secondary school in the Netherlands. The main research tools employed were online and face-to-face group discussions, in which PCRs contributed as consultants, co-designers and assistants. The research proved a learning experience for both the adults and the young people involved and led to the collection of insightful qualitative data. Working collaboratively with pupils, however, presented a number of challenges. Ethical issues such as consent, inclusion and the pressure placed on pupils, and logistical challenges such as the availability of time and resources, were particularly prominent. Perhaps the most valuable challenge, however, was the opportunity that this research presented to the adult researcher to reflect upon the role played by her own assumptions when working with young people.Keywords: students as researchers; inclusive research; bilingual education Introduction Inclusive research with young people in schools has its ups and its downs, its advocates and its critics. This contribution gives a personal account of one example of inclusive research, which involved working together with pupils in the design and implementation of online and face-to-face discussions with their classmates. We subsequently used the qualitative data we obtained through these means to inform the design of a motivation questionnaire, which I administered to pupils at five different schools in a later, non-participatory phase of my doctoral research. The methods and processes of the collaborative phase of this research are described in some detail, as are some of the challenges encountered and the resulting considerations for future work of this kind.We have chosen to write this account in the first person in order to reflect the personal nature of collaborative research. This project afforded an opportunity not only for data collection and for pupil learning, but also for researcher growth. The challenges involved in attempting to share the control over this research with a group of young people, and in balancing assumptions with their input, led to the investment of a significant amount of energy and personal reflection. We believe that this story is therefore better told from a subjective and possibly a more 'human' perspective. This paper is written largely with the singular 'I', not to belittle the contribution and considerable

show abstract

“…In general, persistent occurrence of shear-bands has been linked to nonmontonic constitutive laws leading to flow instabilities [6,10] (e.g. in micelles [11]).…”

mentioning

confidence: 99%

Impact of Attractive Interactions on the Rheology of Dense Athermal Particles

2014

View full text Add to dashboard Cite

Using numerical simulations, the rheological response of an athermal assembly of soft particles with tunable attractive interactions is studied in the vicinity of jamming. At small attractions, a fragile solid develops and a finite yield stress is measured. Moreover, the measured flow curves have unstable regimes, which lead to persistent shearbanding. These features are rationalized by establishing a link between the rheology and the inter-particle connectivity, which also provides a minimal model to describe the flow curves.PACS numbers: 83.10. Rs,83.60.Wc,66.20.Cy In nature, soft disordered solids occur in different forms (eg. gels, emulsions, colloids, foams, grains etc) across a wide range of packing fractions φ, which is made possible by the tuning of particle interactions. The flow properties of these soft materials have been harnessed for various applications, e.g. in the food or the chemical industry. Thus, understanding the role of particle interactions and the corresponding mechanisms which lead to observed rheological behaviour is an important recurrent theme.For non-Brownian suspensions of frictionless repulsive spheres, it is observed that ramping up the packing fraction results in the occurrence of jamming at φ = φ J [1, 2]. The rheological signature of the onset of jamming is the development of a finite yield stress at φ J [3]. For Brownian suspensions of such particles, it has been shown that a yield stress exists at φ < φ J , due to the presence of thermal vibrations [4]. A similar systematic investigation of how the jamming paradigm is changing upon the introduction of attractive particle interactions is still missing. It is known that at smaller φ, such systems do exhibit finite yield stress [5,9,19,24]; but, a quantitative bridge with the jamming scenario needs to be developed.Such studies are also needed since shear-banding, the phenomenon of spatially inhomogeneous flows observed in many soft yield-stress fluids [6, 7], has often been attributed to attractive interactions [8,9]. In general, persistent occurrence of shear-bands has been linked to nonmontonic constitutive laws leading to flow instabilities [6, 10] (e.g. in micelles [11]). It is not known how interparticle attractions could result in such instabilities.Conceptually, one can imagine the steady flowing state to be a regime where there is a continuous competition between the rupturing induced by shear and processes that try to restore local structure. Theoretical models suggest that non-monotonic flow curves can occur due to long-lived local fluidizations when the post-rupture restructuring takes a very long time [12][13][14]. However, experiments and numerical simulations have shown that for φ > φ J , no such instabilities occur in the flow curve for either repulsive or attractive systems [15][16][17][18]. The question now arises whether for φ < φ J , a short-ranged attraction which introduces a new lengthscale for structure formation leads to longer restoration timescales and if this is indeed the origin of a shear banding ...

show abstract

Advice to the Nymphs of New S—m

Cited by 28 publications

References 0 publications

Activity-induced clustering in model dumbbell swimmers: The role of hydrodynamic interactions

Activity-induced clustering in model dumbbell swimmers: The role of hydrodynamic interactions

Aspirations and assumptions: a researcher's account of pupil involvement in school-based research

Impact of Attractive Interactions on the Rheology of Dense Athermal Particles

Contact Info

Product

Resources

About