The quasi-elastic neutron scattering (QENS) technique was first used to derive self-diffusivities of hydrocarbons in zeolites, but transport diffusivities of deuterated molecules and of molecules which do not contain hydrogen atoms can now be measured. The technique allows to probe diffusion over length scales ranging from an Å to hundreds of Å. The mechanism of diffusion can thus be followed f...

Development of spatial patterns in multicellular organisms depends on gradients in the concentration of signaling molecules that control gene expression. In the Drosophila embryo, Bicoid (Bcd) morphogen controls cell fate along 70% of the anteroposterior axis but is translated from mRNA localized at the anterior pole. Gradients of Bcd and other morphogens are thought to arise through diffusion,...

Spin-valve, weak localization/antilocalization, and scanned probe microscopy measurements are used to investigate the influence of sulfur-based surface treatments and electrically insulating barrier layers on spin injection into, and spin transport within, the two-dimensional electron layer at the surface of p-type InAs at 4.2 K. An electrically insulating barrier layer is found to be required ...

The apparent diffusion coefficient (ADC) measured using magnetic resonance imaging methods provides information on microstructural properties of biological tissues, and thus has found applications as a useful biomarker for assessing changes such as those that occur in ischemic stroke and cancer. Conventional pulsed gradient spin echo methods are in widespread use and provide information on, for...

We present force-clamp data on the collapse of ubiquitin polyproteins in response to a quench in the force. These nonequilibrium trajectories are analyzed using a general method based on a diffusive assumption of the end-to-end length to reconstruct a downhill free energy profile at 5pN and an energy plateau at 10pN with a slow diffusion coefficient on the order of 100nms. The shape of the free...

Thermal diffusion has been studied for over 150 years. Despite of the long history and the increasing importance of the phenomenon, the physics of thermal diffusion remains poorly understood. In this paper Ludwig’s thermal diffusion is explained using Einstein’s random walk. The only new structure added is the spatial heterogeneity of the random walk to reflect the temperature gradient of therm...

In this paper, a theory on the determination of the diffusion coefficient of the excess minority carriers of a silicon solar cell is presented. The expression of the diffusion coefficient, related to the modulation frequency, the irradiation energy and the damage coefficient is studied and then performed by using the impedance spectroscopy method and Bode and Nyquist diagrams. Based on the diff...

The effect of the mechanical deformation of metal-organic frameworks on guest diffusion was investigated by employing molecular dynamics simulations. Two basic deformation modes, uniaxial tensile and shear deformation, were considered. The computed shear modulus of the zeolitic imidazolate framework-8 (ZIF-8) model system was much lower than the Young's modulus, which is in agreement with the e...

We have extended the utility of NMR as a technique to probe porous media structure over length scales of ;100–2000 mm by using the spin 1/2 noble gas Xe imbibed into the system’s pore space. Such length scales are much greater than can be probed with NMR diffusion studies of water-saturated porous media. We utilized Pulsed Gradient Spin Echo NMR measurements of the time-dependent diffusion coef...