Molecular diffusion in brain extracellular space (ECS) is primarily controlled by interactions with the geometry and the interstitial matrix. Both factors increase λ, the tortuosity, a measure of hindrance to diffusion where λ2 = D/D∗ with D the free diffusion coefficient and D∗ the effective diffusion coefficient in brain [1]. Geometry lengthens diffusion paths or creates holdup in local voids...

The transport mechanisms of substances in natural water bodies are considered. Dissolved substances can be regarded as passive in that they do not affect the velocity field of the water bodies. The particles of substances can be regarded as either passive or active. Transport of substances is caused by convection, and/or molecular and turbulent diffusion. The buoyancy forces thus have some infl...

1. Review the concept of heat and the processes of diffusion and osmosis. Learn the factors that affect the rate of diffusion. 2. Observe Brownian motion and relate this observation to the concept of heat energy. 3. Measure the speed of diffusion of dyes in a gel, and the speed of diffusion of gases in air. Relate the speed of diffusion to molecular mass and medium. 4. Investigate the process o...

We evaluate various molecular tagging velocimetry (MTV) techniques for application in turbulent flows of gases where the smallest length scales must be resolved. We argue that tracer diffusion dictates the use of large complex molecules and discuss a few candidate molecules. The accuracy of MTV is determined by the profile of written lines which widen due to molecular dynamics, including both d...

We probe the ionic conduction and the molecular dynamics in a pure and lithium-salt doped dinitrile molecular plastic crystal. While the diffusion of the Li(+) ions is decoupled from the molecular reorientational dynamics, in the undoped plastic crystal the temperature dependence of the mobility of dinitrile ions and thus of the conductivity is virtually identical to that of on-site molecular r...

Diffusion processes of intermediate radicals created by the photoinduced hydrogen abstraction reactions of ketones, quinones, and N-hetero aromatic molecules in ethanol and 2-propanol are studied at various temperatures by using the transient grating ~TG! method. The temperature dependences of the translational diffusion coefficients ~D’s! of both the radicals and the parent molecules can be ex...

Pulsed field gradient (PFG) NMR has been used to probe self-diffusion of molecular and ionic species in aqueous mixtures of choline chloride (ChCl) based deep eutectic solvents (DESs), in order to elucidate the effect of water on motion and inter-molecular interactions between the different species in the mixtures, namely the Ch(+) cation and hydrogen bond donor (HBD). The results reveal an int...