Shape of a liquid front upon dewetting

We examine the profile of a liquid front of a film that is dewetting a solid substrate. Since volume is conserved, the material that once covered the substrate is accumulated in a rim close to the three phase contact line. Theoretically, such a profile of a Newtonian liquid resembles an exponentially decaying harmonic oscillation that relaxes into the prepared film thickness. For the first time, we were able to observe this behavior experimentally. A non-Newtonian liquid - a polymer melt - however, behaves differently. Here, viscoelastic properties come into play. We will demonstrate that by analyzing the shape of the rim profile. On a nm scale, we gain access to the rheology of a non-Newtonian liquid.Comment: 4 pages, 4 figure

Amplification of Fluctuations in Unstable Systems with Disorder

We study the early-stage kinetics of thermodynamically unstable systems with quenched disorder. We show analytically that the growth of initial fluctuations is amplified by the presence of disorder. This is confirmed by numerical simulations of morphological phase separation (MPS) in thin liquid films and spinodal decomposition (SD) in binary mixtures. We also discuss the experimental implications of our results.Comment: 15 pages, 4 figure

Resonance properties and microstructure of ultracompliant metallic nanoelectromechanical systems resonators synthesized from Al-32 at. % Mo amorphous-nanocrystalline metallic composites

This study details the resonance properties of 20 nm thick nanoelectromechanical system scale cantilevers fabricated from a metallic Al-32 at. %Mo nanocomposite. The advantage of the Al-32 at. %Mo alloy is that its strength and near-atomic surface smoothness enable fabrication of single-anchored metallic cantilevers with extreme length-to-thickness ratios, as high as 400:1. This yields uniquely compliant structures with exquisite force sensitivity. For example, an 8 ??m long, 20 nm thick Al-32 at. %Mo device has a spring constant of K280 ??Nm. We show through transmission electron microscope analysis and continuum modeling that the relevant damping mechanisms are related to the device microstructure.open3

Green infrastructure in relation to informal urban settlements

Green infrastructure plays a critical role in environmentally sustainable urbanization in developing countries. Based on a review of academic outputs, this paper explores green infrastructure in the context of informal urban settlements. It identifies three ways informal settlements are connected to green spaces and natural ecosystems functioning as urban green infrastructure and then shows examples of benefits derived (ecosystem services) by the urban poor from these connections. Undesirable aspects and negative outcomes, regarded as ecosystem disservices, from the connection to natural ecosystems are also pointed out. The potentials of enhancing ecosystem services in terms of improving quality of life and the environment in informal settlements came to the fore. This work contributes to the growing body of knowledge on urban green infrastructure from the perspective of informal settlements in developing countries

The Agenda and Relevance of Recent Research in Microfinance

This paper studies recent research efforts in the field of microfinance. Two questions guide the study: What is the agenda of recent research efforts? And, for who is the research relevant? As for the agenda the “yin and yang” of microfinance; impact and sustainability, continue to influence most research efforts. The study illustrates that microfinance attracts mainly the interest of development researchers and journals. Accordingly the researchers seem mainly to interact with the donors’ and practitioners’ communities. The research produced seems to be relevant for them and less so for the governmental and banking communities. The paper concludes proposing the design of a new research agenda, this time in cooperation with the banking community

The effect of interface movement and viscosity variation on the stability of a diffusive interface between aqueous and gaseous CO2

Carbon dioxide injected in an aquifer rises quickly to the top of the reservoir and forms a gas cap from where it diffuses into the underlying water layer. Transfer of the CO2 to the aqueous phase below is enhanced due to the high density of the carbon dioxide containing aqueous phase. This paper investigates the behavior of the diffusive interface in an enclosed space in which initially the upper part is filled with pure carbon dioxide and the lower part with liquid. Our analysis differs from a conventional analysis as we take the movement of the diffusive interface due to mass transfer and the composition dependent viscosity in the aqueous phase into account. The same formalism can also be used to describe the situation when an oil layer is underlying the gas cap. Therefore we prefer to call the lower phase the liquid phase. In this paper we include these two effects into the stability analysis of a diffusive interface between CO2 and a liquid in the gravity field. We identify the relevant bifurcation parameter as q = ?Ra, where ? is the width of the interface. This implies the (well known) scaling of the critical time ?Ra?2 and wavelength ?Ra?1(The critical time tc and critical wavelength kc are defined as follows: ?(k) ? 0??t ? tc; equality only holds for t = tc and k = kc). Inclusion of the interface upward movement leads to earlier destabilization of the system. Increasing viscosity for increasing CO2 concentration stabilizes the system. The theoretical results are compared to bulk flow visual experiments using the Schlieren technique to follow finger development in aquifer sequestration of CO2. In the appendix, we include a detailed derivation of the dispersion relation ?(k) in the Hele-Shaw case [C. T. Tan and G. M. Homsy, Phys. Fluids 29, 3549–3556 (1986)]10.1063/1.865832 which is nowhere explicitly given.Delft Institute of Applied MathematicsElectrical Engineering, Mathematics and Computer Scienc

Synthesis and characterization of Au-Ta nanocomposites for nanomechanical cantilever devices

A gold-tantalum nanocomposite material synthesized using a co-sputtering technique and designed specifically for nanomechanical systems applications is reported. X-ray diffraction, atomic force microscopy, scanning electron microscopy, nanoindentation and four-point probe contact measurements were performed to characterize the bulk and surface characteristics of the films. The films exhibited an increased reduced modulus and hardness as well as a significant grain size reduction while retaining the face-centered cubic (FCC) structure of pure gold with a very strong texture. In addition, the mechanical characterization of a number of 800 nm wide, 50 nm thick Au-5 at.% Ta cantilevers was performed using optical interferometry. Such devices exhibited resonant frequencies ranging from 371 kHz to 10.9 MHz, with resonant qualities as high as Q = 640.close4