Pore water chemistry diffusion

HCOs, Cr, F, and N03 The initial pore water chemistry is based on a sample that was ultracentrifuged from the proposed repository host rock (Tptpmn). Minerals considered include silica phases (a-cristobalite, quartz, tridymite, amorphous silica, and opal-CT), calcite, feldspars, smectites, illite, kaolinite, sepiolite, zeolites, fluorite, hematite, and gypsum. Treatment of CO includes gas-water equilibration, diffusion, and advection. 

The redissolution or burial of organic matter in sediments is a decision that is made jointly by the physics of diffusion, chemistry of organic matter oxidation, and the biology which mediates the chemical reactions. The concentration profile of a solute in sediment pore water is governed by the diffusion equation, which can be written most simply as... 

Capillaries in the Brain (the Blood-Brain Barrier). Capillaries in the brain are less permeable than capillaries in other tissues. This limited permeability, which is frequently called the blood-brain barrier, is essential for brain function. Reduced permeation provides a buffer that maintains a constant brain extracellular environment, even at times when blood chemistry is changing. The basis for this lower permeability is the relative paucity of pores in the brain endothelium. Therefore, molecules that move from blood to brain must diffuse through the endothelial cell membranes. As expected from this observation, the permeability of brain capillaries depends on the size and lipid solubility of the solute. In general, molecules that are larger than several hundred in molecular weight do not permeate into the brain. Empirical relationships between cerebrovascular permeability and the oil / water partition coefficient have been developed [26] (see Figure 5.27) ... 

We analyzed the distribution and orientation of the water molecules near the Ti02 surfaces the bound water molecules at the surfaces reduce the dif-fiisivity of water in the Ti02 shts because bound waters form HB network with other water molecules. It suggests a large majority of water molecules would be held in the hydrophUic nanopores. Surface chemistry is critical to the diffusion of water in nanoscale pores in this case, it is more efficient to change surfiice chemistry, rather than to tune the size of nanopores (Alexiadis and Kassinos, 2008 Wei et al, 2011a). 

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