6,543 research outputs found
Active Matter Alters the Growth Dynamics of Coffee Rings
How particles are deposited at the edge of evaporating droplets, i.e. the
{\em coffee ring} effect, plays a crucial role in phenomena as diverse as
thin-film deposition, self-assembly, and biofilm formation. Recently,
microorganisms have been shown to passively exploit and alter these deposition
dynamics to increase their survival chances under harshening conditions. Here,
we show that, as the droplet evaporation rate slows down, bacterial mobility
starts playing a major role in determining the growth dynamics of the edge of
drying droplets. Such motility-induced dynamics can influence several
biophysical phenomena, from the formation of biofilms to the spreading of
pathogens in humid environments and on surfaces subject to periodic drying.
Analogous dynamics in other active matter systems can be exploited for
technological applications in printing, coating, and self-assembly, where the
standard coffee-ring effect is often a nuisance.Comment: 7 pages, 5 figure
Surface free energy and microarray deposition technology
Microarray techniques use a combinatorial approach to assess complex biochemical interactions. The fundamental goal is simultaneous, large-scale experimentation analogous to the automation achieved in the semiconductor industry. However, microarray deposition inherently involves liquids contacting solid substrates. Liquid droplet shapes are determined by surface and interfacial tension forces, and flows during drying. This article looks at how surface free energy and wetting considerations may influence the accuracy and reliability of spotted microarray experiments
Motivations for an organisation within a developing country to report social responsibility information : evidence from Bangladesh
Purpose â The aim of the paper is to describe and explain, using a combination of interviews and content analysis, the social and environmental reporting practices of a major garment export organisation within a developing country. Design/methodology/approach â Senior executives from a major organisation in Bangladesh are interviewed to determine the pressures being exerted on them in terms of their social and environmental performance. The perceptions of pressures are then used to explain â via content analysis â changing social and environmental disclosure practices. Findings â The results show that particular stakeholder groups have, since the early 1990s, placed pressure on the Bangladeshi clothing industry in terms of its social performance. This pressure, which is also directly related to the expectations of the global community, in turn drives the industry's social policies and related disclosure practices. Research limitations/implications â The findings show that, within the context of a developing country, unless we consider the managers' perceptions about the social and environmental expectations being imposed upon them by powerful stakeholder groups then we will be unable to understand organisational disclosure practices. Originality/value â This paper is the first known paper to interview managers from a large organisation in a developing country about changing stakeholder expectations and then link these changing expectations to annual report disclosures across an extended period of analysis
Origins of the Human Genome Project
Dr. Cook-Deegan recounts some of the scientific and political history leading to controversy about the proper mix of private and public roles in pursuing genome research and bringing its fruits to bear, e.g., in preventing and curing disease
The effect of the thermal conductivity of the substrate on droplet evaporation
The evaporation of liquid droplets is of fundamental importance to industry, with a vast number of applications including ink-jet printing, spray cooling and DNA mapping, and has been the subject of considerable theoretical and experimental research in recent years. Significant recent papers include those by Deegan [1], Deegan et al. [2], Hu and Larson [3], Poulard et al. [4], Sultan et al. [5], and Shahidzadeh-Bonn et al. [6]
Characteristic Angles in the Wetting of an Angular Region: Deposit Growth
As was shown in an earlier paper [1], solids dispersed in a drying drop
migrate to the (pinned) contact line. This migration is caused by outward flows
driven by the loss of the solvent due to evaporation and by geometrical
constraint that the drop maintains an equilibrium surface shape with a fixed
boundary. Here, in continuation of our earlier paper [2], we theoretically
investigate the evaporation rate, the flow field and the rate of growth of the
deposit patterns in a drop over an angular sector on a plane substrate.
Asymptotic power laws near the vertex (as distance to the vertex goes to zero)
are obtained. A hydrodynamic model of fluid flow near the singularity of the
vertex is developed and the velocity field is obtained. The rate of the deposit
growth near the contact line is found in two time regimes. The deposited mass
falls off as a weak power Gamma of distance close to the vertex and as a
stronger power Beta of distance further from the vertex. The power Gamma
depends only slightly on the opening angle Alpha and stays between roughly -1/3
and 0. The power Beta varies from -1 to 0 as the opening angle increases from 0
to 180 degrees. At a given distance from the vertex, the deposited mass grows
faster and faster with time, with the greatest increase in the growth rate
occurring at the early stages of the drying process.Comment: v1: 36 pages, 21 figures, LaTeX; submitted to Physical Review E; v2:
minor additions to Abstract and Introductio
Revisiting elections in Africa.
Any analysis of elections in Africa over recent periods has to be placed within the wider debate about democracy and its application in Africa. Democracy, of course, can be a âlearned tradeâ over time, yet certain critical factors affect electoral efficacy and political reform. (See Box 1) Over 200 elections have taken place in Africa between 1989 and 2009, in certain countries, for the first time. The dynamics of those early elections were important as democracy needed to develop at a local level, particularly in authoritarian or transitional states in which the general population often had very little interaction with national political processes or leaders. Results were mixed, while South Africa moved forward from the apartheid years, Zimbabwe, for example, has flouted electoral principles. It is clear that elections themselves arouse contention and conflict within states. In the early 2000s Cote dâIvoire experienced civil strife following divisive elections; in 2007/2008 Kenya experienced upheaval in the wake of contested elections
The supervision needs of senior clinical psychologists
Section A
This review critically evaluates the published literature regarding what sustains clinical psychologists in their careers over time. A systematic literature search of three online databases (PsychInfo, Assia and Web of Science) and a manual search of relevant reference lists resulted in 10 papers addressing this aim. Eight studies utilised a cross sectional design, two studies used a mixed methods design combining qualitative and quantitative methods. Themes were generated from the findings in these papers and collated. Clinical and research implications were also discussed.
Section B
A Delphi survey investigated what experts consider best practice for the supervision of senior clinical psychologists. Three rounds of online survey were used to gather opinions and assess the level of consensus that existed for the group. The findings of the study are presented and the clinical and research implications are considered
Vibration-induced climbing of drops
We report an experimental study of liquid drops moving against gravity, when
placed on a vertically vibrating inclined plate, which is partially wetted by
the drop. The frequency of vibrations ranges from 30 to 200 Hz, and, above a
threshold in vibration acceleration, drops experience an upward motion. We
attribute this surprising motion to the deformations of the drop, as a
consequence of an up or down symmetry breaking induced by the presence of the
substrate. We relate the direction of motion to contact angle measurements.
This phenomenon can be used to move a drop along an arbitrary path in a plane,
without special surface treatments or localized forcing.Comment: 4 pages, 7 figure
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