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Jan Fransaer

Bio: Jan Fransaer is an academic researcher from Katholieke Universiteit Leuven. The author has contributed to research in topics: Ionic liquid & Particle. The author has an hindex of 47, co-authored 275 publications receiving 8657 citations. Previous affiliations of Jan Fransaer include University of California, Irvine & Stanford University.


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TL;DR: A review of recent advances in the study of the regulatory pathways that lead to swarming behavior of different model bacteria and the understanding of the transition between motile and sessile lifestyles of bacteria is provided.
Abstract: Swarming is the fastest known bacterial mode of surface translocation and enables the rapid colonization of a nutrient-rich environment and host tissues. This complex multicellular behavior requires the integration of chemical and physical signals, which leads to the physiological and morphological differentiation of the bacteria into swarmer cells. Here, we provide a review of recent advances in the study of the regulatory pathways that lead to swarming behavior of different model bacteria. It has now become clear that many of these pathways also affect the formation of biofilms, surface-attached bacterial colonies. Decision-making between rapidly colonizing a surface and biofilm formation is central to bacterial survival among competitors. In the second part of this article, we review recent developments in the understanding of the transition between motile and sessile lifestyles of bacteria.

432 citations

Journal ArticleDOI
TL;DR: In this article, the effect of aspect ratio of particles on the stability of both water-in-oil and oil-inwater emulsions is investigated experimentally, and the results demonstrate that interfaces with controlled surface rheology, as obtained by using shape induced capillary forces and packing effects, can be used for the rational design of Pickering emulsion and other types of high interface materials.
Abstract: Pickering–Ramsden emulsions and other forms of particle stabilized soft materials have received quite some attention recently because of the relative ease of formulation and the possibility to create novel materials. There is, however, a clear need for approaches that are versatile and efficient. In the present work the effect of aspect ratio of particles on the stability of both water-in-oil and oil-in-water emulsions is investigated experimentally. Two types of non-spherical particles are used. Hydrophobic prolate ellipsoids with aspect ratios ranging from 1 to 9 are obtained by stretching polystyrene latex particles. Hydrophilic spindle type hematite particles have been synthesized with aspect ratios ranging from 1 to 6. A strong dependence of emulsion stability on the aspect ratio of the particles is observed. Optical as well as cryogenic scanning electron microscopy are used to visualize the droplet morphology and particulate structure and reveal fairly densely packed monolayers of ellipsoids, consistent with the mechanism of limited coalescence. Yet stable emulsions are only obtained for particles with a sufficient aspect ratio. Surface rheology on planar monolayers demonstrates the pronounced effect of aspect ratio on the surface moduli. The magnitude of the interfacial viscoelastic properties is shown to strongly depend on the aspect ratio at a given surface coverage. This is most probably due to an increased effective coverage and the occurrence of strong attractive shape induced capillary interactions. The dependence of the surface rheological properties on the aspect ratio of the particles rationalizes the observed emulsion stability as the surface rheological properties play a role in the coalescence process. The results demonstrate that interfaces with controlled surface rheology, as obtained by using shape induced capillary forces and packing effects, can be used for the rational design of Pickering emulsions and other types of high interface materials.

386 citations

Journal ArticleDOI
TL;DR: In this article, the growth of metal-organic frameworks (MOFs) enables the self-completing growth of densely packed crystallite layers in a patterned fashion, a concept that is illustrated by monitoring water adsorption.
Abstract: Electrochemical film growth of metal-organic frameworks (MOFs) enables the self-completing growth of densely packed crystallite layers in a patterned fashion. Coatings produced in this manner might prove useful in the integration of MOF materials with devices such as sensors, a concept that is illustrated by monitoring water adsorption.

385 citations

Journal ArticleDOI
03 Feb 2009-Langmuir
TL;DR: The mechanical properties of these monolayers, as measured by surface shear rheology, showed that the monolayer of ellipsoids exhibit a substantial surface modulus even at low surface coverage and can be used to create more elastic monol layers compared to aggregate networks of spheres of the same size and surface properties.
Abstract: Colloidal particles confined at liquid interfaces have important applications, for example in the stabilization of emulsions and foams. Also the self-assembly of particles at interfaces offers potential for novel applications and structured particle films. As the colloidal interactions of colloidal particles at interfaces differ from those in bulk, colloidal microstructures can be achieved at an interface which cannot be produced in bulk. In the present work the particle shape, surface charge, and wetting properties are varied, and the resulting self-assembly of particles at a fluid interface is studied. Model monodisperse micrometer-sized ellipsoidal particles were prepared by a mechanical stretching method. These particles were chosen to be well-suited for investigation by optical microscopy. When deposited at an interface between two fluids, shape-induced capillary interactions compete with the electrostatic repulsion. Changing the surface charge and the position at the interface can be used to manipulate the experimentally observed self-assembly process. The initial microstructure of charged ellipsoids at a decane-water interface consists of individual ellipsoids coexisting with linear chains of ellipsoids, connected at their tips. The aggregation behavior in these monolayers was investigated by optical microscopy combined with quantitative image analysis and a dominant tip-tip aggregation was observed. Microstructural information was quantified by calculating the pair-distribution and orientation-distribution functions, as a function of time. Compared to particles at an oil-water interface, particles of the same surface chemistry and charge at an air-water interface seem to have weaker electrostatic interactions, and they also have a different equilibrium position at the interface. The latter leads to differences in the capillary forces. The subsequent change in the balance between electrostatic and capillary forces gave rise to very dense networks having as a typical building block ellipsoids connected at their tips in triangular or flower-like configuration. These networks were very stable and did not evolve in time. The resulting monolayers responded elastically and buckled under compression. Furthermore, the mechanical properties of these monolayers, as measured by surface shear rheology, showed that the monolayer of ellipsoids exhibit a substantial surface modulus even at low surface coverage and can be used to create more elastic monolayers compared to aggregate networks of spheres of the same size and surface properties.

304 citations

Journal ArticleDOI
TL;DR: In this article, Ni-SiC composite coatings containing 4−5 vol.% submicron SiC particles were evaluated in uni-and bi-directional sliding tests against corundum balls.
Abstract: SiC particles of three different sizes, namely 5, 0.7 and 0.3 μm, were codeposited with nickel from Watts’ solutions. It was found that for a given number density of particles in the plating solution, the number density of particles in the coating increases with decreasing particle size. The friction and wear behavior of these composite coatings was evaluated in uni- and bi-directional sliding tests against corundum balls. The best sliding wear resistance was obtained with Ni–SiC composite coatings containing 4–5 vol.% submicron SiC particles.

296 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
10 Mar 1970

8,159 citations

Journal ArticleDOI
TL;DR: The potential to computationally predict, with good accuracy, affinities of guests for host frameworks points to the prospect of routinely predesigning frameworks to deliver desired properties.
Abstract: 1. INTRODUCTION Among the classes of highly porous materials, metalÀorganic frameworks (MOFs) are unparalleled in their degree of tunability and structural diversity as well as their range of chemical and physical properties. MOFs are extended crystalline structures wherein metal cations or clusters of cations (\" nodes \") are connected by multitopic organic \" strut \" or \" linker \" ions or molecules. The variety of metal ions, organic linkers, and structural motifs affords an essentially infinite number of possible combinations. 1 Furthermore, the possibility for postsynthetic modification adds an additional dimension to the synthetic variability. 2 Coupled with the growing library of experimentally determined structures, the potential to computationally predict, with good accuracy, affinities of guests for host frameworks points to the prospect of routinely predesigning frameworks to deliver desired properties. 3,4 MOFs are often compared to zeolites for their large internal surface areas, extensive porosity, and high degree of crystallinity. Correspondingly, MOFs and zeolites have been utilized for many of the same applications

5,925 citations