Search results for "Diffusion"

Tip-induced mobilization upon cooling of Ni monolayers on Re(0001)

2021

Usually, cooling a metal sample down to cryogenic temperatures leads to immobilization of the surface atoms. In this study, we demonstrate a movement of Ni adatoms at $4.6\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ on Ni films grown on a Re(0001) single crystal, while the surface is rigid at room temperature. The mobility is observed from 2 to 20 atomic-layer-thick films. Measurements at intermediate temperatures reveal an increasing mobility with decreasing temperature. The observed velocity of advancing steps is consistent with a model considering a sudden release of material, eventually triggered by the tip, followed by free diffusion. According to the model, an increasing length scale for t…

Anomalous tracer diffusion in film forming colloidal dispersions

2000

Film forming colloidal dispersions can be conceived as a material composed of interpenetrating hydrophobic (polymer) and hydrophilic (partially broken interfaces) phases where the transport properties of one phase are influenced by the geometric confinement effect imposed by the other. We studied the transport properties of film forming colloidal dispersions by introducing hydrophobic dye molecules into the colloidal particles and determining their motion with forced Rayleigh Scattering as a function of length scale (grating distance A) and water content. At water contents between 18 and 3 weight percent we find signatures of anomalous tracer diffusion, namely stretched exponential decay cu…

Two-Length-Scale Structure in Some Computer-Generated Aggregates Grown by Diffusion-Limited Aggregation

1994

AbstractThe properties of some aggregates “grown” on a computer by diffusion-limited aggregation have been investigated. Calculations showed that the intensity of the small-angle x-ray and neutron scattering from the aggregates was proportional to q−D for qL ≫ 1, where D > 0, L is a length that characterizes the large-scale structure of the aggregate, q = 4πλ−1 sin(θ/2), γ is the wavelength, and θ is the scattering angle. The magnitude of the exponent D was appreciably smaller than the fractal dimensions that many simulations have shown to be typical of the mass fractal aggregates grown by diffusion-limited aggregation. The calculations suggest that the aggregates have structure on two d…

Halogenido ligand exchange synthesis, spectroscopic properties and thermal behaviour of the inorganic–organic hydrogen-bonded network solid [4,4′-H2b…

2014

Abstract Dark-red single crystals of 4,4′-bipyridinium triaquahydrogen(1+) hexabromidorhodate(III) [4,4′-H2bipy][H7O3][RhBr6] (1) have been synthesized by a diffusion-controlled ligand exchange process from rhodium(III) chloride trihydrate and 4,4′-bipyridine dissolved in hydrochloric and hydrobromic acid, respectively. 1 could be considered as an inorganic–organic hydrogen-bonded network solid built up from the inorganic isolated hexabromidorhodate [RhBr6]3− octahedra, organic 4,4′-bipyridinium(2+) [4,4′-H2bipy]2+ and triaquahydrogen(1+) [H7O3]+ cations with nearly symmetrical O⋯O distances. The oppositely charged components in the structure of 1 are bound together by an intricate system o…

Some diffusion equations with finite propagation speed

2007

We summarize some of our recent results on diffusion equations with finite speed of propagation. These equations have been introduced to correct the infinite speed of propagation predicted by the classical linear diffusion theory. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Diffusion, drift, and the irrelevance of media influence

2014

In situ synthesis of lipopeptides as versatile receptors for the specific binding of nanoparticles and liposomes to solid-supported membranes.

2008

A detailed study of the in situ coupling of small peptides such as CGGH6 (H6) and CGWK8 (K8) to maleimide functionalized phospholipid bilayers is presented. Individually addressable microstructured membranes are employed to unequivocally probe the conjugation. The in situ coupling of peptides via a terminal cysteine moiety to maleimide functionalized phospholipids is shown to be a convenient and versatile way to selectively fabricate peptide-modified phospholipid bilayers serving as specific receptor platforms for functionalized vesicles and nanoparticles. Specific binding of functional vesicles to the peptide-modified bilayers is achieved by either histidine complexation with Ni-NTA-DOGS c…

Innovation activity of SMEs in different locations

2013

Todtling and Trippl (2005) argue that innovation activity is a key element in regional economic development (see also Ronde and Hussler, 2005; Audretsch and Lehmann, 2005; Cooke, 2005). However, we know little about the formation, development and diffusion of innovations in different milieux. The aim of this study is to clarify the factors – in particular, the regional factors – that affect the innovation activity of small and medium-sized enterprises (SMEs). Our analyses of the innovation activity of Finnish SMEs revealed that innovation activity is very brisk in towns and relatively brisk in rural areas, although the difference between the two was not statistically significant. A logistic…

O2Transport in Skeletal Muscle: Development of Concepts and Current State

1994

When comparing oxygen consumption rates(V O2) of various organs — as shown in Fig. 1 —skeletal muscle is exceptional in two respects: Its consumption rate attains the second largest absolute value of all organs and may vary between rest (0.2 mlO 2.100g-1’• min -1 ) and maximum performance (16 m1O 2.100g-1 • min -1 for electrical stimulation) by a factor of 80, thus covering a range that is by far larger than in any other tissue. In order to understand muscle O 2 transport one has to identify transport mechanisms and evaluate their importance towards bringing about the observed high O 2 fluxes and allowing for their enormous variability.

Guar gum/borax hydrogel: Rheological, low field NMR and release characterizations

2013

Guar gum (GG) and Guar gum/borax (GGb) hydrogels are studied by means of rheology, Low Field Nuclear Magnetic Resonance (LF NMR) and model drug release tests. These three approaches are used to estimate the mesh size (ζ) of the polymeric network. A comparison with similar Scleroglucan systems is carried out. In the case of GGb, the rheological and Low Field NMR estimations of ζ lead to comparable results, while the drug release approach seems to underestimate ζ. Such discrepancy is attributed to the viscous effect of some polymeric chains that, although bound to the network to one end, can freely fluctuate among meshes. The viscous drag exerted by these chains slows down drug…