Diffusion Fundamentals (E-Journal)
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Hot Brownian motion and photophoretic self-propulsion
Get PDFWe describe the motion of heated particles in a simple liquid, for which we can theoretically derive generalized fluctuation-dissipation relations that hold far from equilibrium, as we demonstrate both experimentally and via molecular-dynamics simulations. Due to persistent laser-light absorption, these particles excite a radially symmetric or asymmetric (Janus particles) temperature profile in the solvent, which affects their random (Brownian) and systematic (self-phoretic) motion. In case of a radially symmetric temperature profile, we show that the particles perform “hot Brownian motion” (HBM), with different effective temperatures pertaining to their various degrees of freedom. We moreover predict and experimentally observe a peculiar dependence of their diffusivity on the particle size. In case of an asymmetric temperature profile, we find a superimposed self-phoretic directed motion. To adjust the importance of this “active” motion relative to the random hot Brownian motion, the shape of the particle is modified by binding DNA molecules and DNA origami to Janus beads. The persistence of the directed transport can thereby greatly be enhanced
Study of the self-diffusion coefficient in the water-methanol binary mixture from the hydrogen bonding viewpoint using DOSY NMR
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Diffusive spread of substance through brain extracellular space in in vitro model of sleep and awake brain states
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Diffusion-controlled kinetics of metallic colloid formation in irradiated Al2O3, MgO and NaCl crystals
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Miniature mobile NMR sensors for material testing and moisture-monitoring
Get PDFMiniaturization plays an essential role in modern life of the 21st century. It is encountered, e.g., in communication, personalized and portable computers and in medicine. Miniaturization also affects NMR, one of the most versatile analytical tools, leading to dedicated sensors and portable devices which lead to new applications of NMR in different disciplines. The miniaturization of two portable stray-field NMR sensor types, the NMR-MOUSE® and an inside-out sensor are reported in this work. The sensors are critically evaluated and compared to other standard probes. Applications in material testing and civil engineering are evaluated
Dynamic correlations between inhomogeneous magnetic fields, internal gradients, diffusion and transverse relaxation, as a probe for pore geometry and heterogeneity
Get PDFIn this study we have applied 2D NMR experiments where the spatial inhomogeneous magnetic field (Bi) inside a porous sample is correlated to respectively internal gradient (G0), diffusion coefficient (D), and transverse relaxation time (T2) of a confined liquid. Experiments were performed on samples having different pore system geometry and heterogeneity, leading to different types of confinement of the liquid. The results show that the correlation between G0 and Bi is more sensitive to the type of confinement, and thus also of the pore geometry and heterogeneity, compared to the corresponding correlations involving D and T2