Subdynamic asymptotic behavior of microfluidic valves

Decreasing the Reynolds number of microfluidic no-moving-part flow control valves considerably below the usual operating range leads to a distinct “subdynamic” regime of viscosity- dominated flow, usually entered through a clearly defined transition. In this regime, the dynamic effects on which the operation of large-scale no-moving-part fluidic valves is based, cease to be useful, but fluid may be driven through the valve (and any connected load) by an applied pressure difference, maintained by an external pressure regulator. Reynolds number ceases to characterize the valve operation, but the driving pressure effect is usefully characterized by a newly introduced dimensionless number and it is this parameter which determines the valve behavior. This summary paper presents information about the subdynamic regime using data (otherwise difficult to access) obtained for several recently developed flow control valves. The purely subdynamic regime is an extreme. Most present-day microfluidic valves are operated at higher Re, but the paper shows that the laws governing subdynamic flows provide relations useful as an asymptotic reference

Droplet migration: quantitative comparisons with experiment

An important practical feature of simulating droplet migration computationally, using the lubrication approach coupled to a disjoining pressure term, is the need to specify the thickness, H, of a thin energetically stable wetting layer, or precursor lm, over the entire substrate. The necessity that H be small in order to improve the accuracy of predicted droplet migration speeds, allied to the need for mesh resolution of the same order as H near wetting lines, increases the computational demands signicantly. To date no systematic investigation of these requirements on the quantitative agreement between prediction and experimental observation has been reported. Accordingly, this paper combines highly ecient Multigrid methods for solving the associated lubrication equations with a parallel computing framework, to explore the eect of H and mesh resolution. The solutions generated are compared with recent experimentally determined migration speeds for droplet ows down an inclined plane

Logarithmic roughening in a growth process with edge evaporation

Roughening transitions are often characterized by unusual scaling properties. As an example we investigate the roughening transition in a solid-on-solid growth process with edge evaporation [Phys. Rev. Lett. 76, 2746 (1996)], where the interface is known to roughen logarithmically with time. Performing high-precision simulations we find appropriate scaling forms for various quantities. Moreover we present a simple approximation explaining why the interface roughens logarithmically.Comment: revtex, 6 pages, 7 eps figure

Professional-cultural humanitarian values and psychology-pedagogical support of their development in medical students

The article presents the data of the experimental model of the psychology-pedagogical conditions providing the effectiveness of the professional-cultural humanitarian values' development in future doctors within the course of foreign languag

Risk management for drinking water safety in low and middle income countries: cultural influences on water safety plan (WSP) implementation in urban water utilities

We investigated cultural influences on the implementation of water safety plans (WSPs) using case studies from WSP pilots in India, Uganda and Jamaica. A comprehensive thematic analysis of semi-structured interviews (n = 150 utility customers, n = 32 WSP ‘implementers’ and n = 9 WSP ‘promoters’), field observations and related documents revealed 12 cultural themes, offered as ‘enabling’, ‘limiting’, or ‘neutral’, that influence WSP implementation in urban water utilities to varying extents. Aspects such as a ‘deliver first, safety later’ mind set; supply system knowledge management and storage practices; and non-compliance are deemed influential. Emergent themes of cultural influence (ET1 to ET12) are discussed by reference to the risk management, development studies and institutional culture literatures; by reference to their positive, negative or neutral influence on WSP implementation. The results have implications for the utility endorsement of WSPs, for the impact of organisational cultures on WSP implementation; for the scale-up of pilot studies; and they support repeated calls from practitioner communities for cultural attentiveness during WSP design. Findings on organisational cultures mirror those from utilities in higher income nations implementing WSPs – leadership, advocacy among promoters and customers (not just implementers) and purposeful knowledge management are critical to WSP success

Chinese economic reform: approach, vision and constraints

This paper examines the major aspects of economic changes in China in relation to the government's long range goals for economic reform. Various reform experiments introduced in 1978-79 and leading to the reforms of 1984-85 are examined, together with the major elements of the Chinese blueprint for the economic system. A survey is made of the constraints on policy realization in agriculture, industry and the foreign sector