. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 174 R K. AND C. A. BL'TMAN Concentration Fields Around Spherical Cells Puie diffusion Pf = 0 Svnmuuus, 01 Pe= 1 Inotational she >=u Pf= 1 -10 0- -50- T 1 I I T 1 I I I l^ -50 50 100 -100 -50 00 50 100 -100 -50 00 50 20-. Concentration Figure 6. Concentration distributions of a hypothetical chemical signal molecule uniformly released from the surfaces of microscopic point sources (purple circles) in three different How regimes: stagnant water (pure diffusion, no advective transport
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 174 R K. AND C. A. BL'TMAN Concentration Fields Around Spherical Cells Puie diffusion Pf = 0 Svnmuuus, 01 Pe= 1 Inotational she >=u Pf= 1 -10 0- -50- T 1 I I T 1 I I I l^ -50 50 100 -100 -50 00 50 100 -100 -50 00 50 20-. Concentration Figure 6. Concentration distributions of a hypothetical chemical signal molecule uniformly released from the surfaces of microscopic point sources (purple circles) in three different How regimes: stagnant water (pure diffusion, no advective transport); uniform flow (, cell swimming or sinking in stagnant water; the cell is MIII\ ing from right to left so flow is from left to right); and laminar shear Mow luniaxial eMensional flow), where the third dimension can be visuali/.ed by rotation about the v-axis. The Peclet number (Pel is a measure of ad\ecti\e to molecular diffusion (where Pe = LU/D,,,; L = characteristic length scale, U = iharacleristic velocity scale, and Dnl = coefficient of molecular diffusion). The upper panel illustrates the concentration field at distances up to 10 cell radii from the center of the cell. The lower panel is a "blow-up" of the concentration field near the cell surface, up to a distance of two radii from the center of the cell. In the absence of fluid motion a diffusive boundary layer extends to about nine cell radii from the cell surface. Uniform and shear flows distort the boundary layer and steepen the concentration gradient in certain regions. Because transport via diffusion is dominant in the thinnest regions ol the boundary layer, cells m uniform 01 shear flow will experience enhanced rates of chemical signal release umipaicd to nonmolile cells in stagnant water. This illustration was provided as a courtesy by L. Karp-Boss. and methods used in calculating concentration distributions appealed in Karp-Boss et at. (1996). rates of cell division and populati
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
