Dayside and nightside merging rates usually differ; first one dominates and then the other to maintain long‐term flux balance. The polar cap, defined as the area in the ionosphere penetrated by open field lines, expands when closed field lines open during dayside merging and contracts when open field lines close during tail merging. The patterns of convection, electric field and current for polar cap inflation and deflation differ from those of steady state convection. This report models the flow and electrical parameters of polar cap inflation and deflation. We treat the idealized case of uniform conductivity, a planar ionosphere, and “pure Bz” merging (i.e., no By effect, although we note how the approach used here is readily modified to account for the By effect). For this idealized case, the potential associated with polar cap inflation and deflation is seen to be described by the same equations that govern the two‐dimensional hydrodynamic flow into and out of an expanding and contracting cylinder with a gap in its side. The gap corresponds to the breach in the polar cap boundary through which magnetic flux passes as a result of merging. The calculated potential pattern displays the usual two cell convection configuration, but the foci of the two cells are the edges of the flux gaps. Thus the cells are displaced sunward during dayside merging and tailward during tail merging.

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We modify the Jovian ionosphere‐magnetosphere coupling model presented by Hill (1979) to include rotational slippage of the neutral atmosphere at ionospheric heights, relative to a frame of reference corotating rigidly with Jupiter. In the modified model, as altitude increases, the drift velocities of neutrals and ions relative to the corotating frame increase from zero at the bottom of the ionosphere to their respective maximum values at the top, and the corotation lag of the magnetosphere is enhanced for a given rate of mass loading of the magnetosphere. The height variations of the drift velocities of neutrals and ions in the ionosphere and the enhancement factor for the corotation lag of the magnetosphere are related to the atmospheric eddy diffusion coefficient at ionospheric heights. On the basis of ionospheric properties deduced from measurements of Pioneer 11, Voyager 1, and Voyager 2, we derive height profiles of ion and neutral drift speed for various possible values of the eddy diffusion coefficient. If we accept the ion injection rate from Io (1029 ions/s) and the ion transport rate through the Jovian magnetosphere (3×1028 ions/s), corresponding to the observed values of the corotation lag of the Io torus (δωI = 0.04ωJ) and the critical distance for magnetospheric corotation (Lo = 20), respectively, the effective ionospheric conductance is reduced by a factor of the order of 10, resulting in an enhanced corotation lag, for a given rate of mass loading, by the same factor compared to earlier models. The eddy diffusion coefficient in the high‐latitude ionosphere is inferred to be ∼1013 nn−1/2 m1/2/s, or about a factor of 20 larger than the value inferred from Voyager measurements at near‐equatorial latitudes.

To study the organization of fertilization enzymes in the sperm acrosome, we isolated and characterized two physicochemically distinct acrosomal fractions of guinea-pig spermatozoa. A soluble fraction contained the 25,000-Mr acrosomal autoantigen, AA1, and most of the acrosomal hyaluronidase and dipeptidyl peptidase II activity. A particulate fraction, designated acrosomal matrix (AM), consisted of membraneless crescent-shaped structures, and contained most of the acrosomal proacrosin. The AM also contained a 28,000-Mr putative proacrosin-binding protein, and a very-high-Mr component which, on reduction, was dissociated into 48,000-Mr and 67,000-Mr subunits. Autoproteolytic dissolution of the AM correlated with proteolysis by acrosin of the 28,000-Mr and 48,000-Mr AM molecules. Components of both the AM and the soluble fraction were localized by immuno-electron microscopy to the electron-dense region of the guinea-pig sperm acrosome. We conclude that acrosomal molecules are segregated into soluble and matrix compartments. This segregation is a function of disulphide bonding and non-covalent interactions among the relatively few components of the AM. Association of acrosin with the AM may be the mechanism by which this enzyme's release from the spermatozoon during the acrosome reaction is delayed relative to the release of other acrosomal molecules.

Supersaturatable cosolvent (S-cosolvent) and supersaturatable self-emulsifying drug delivery systems (S-SEDDS) are designed to incorporate water soluble cellulosic polymers such as hydroxypropyl methylcellulose (HPMC), which may inhibit or retard drug precipitation in vivo. A poorly soluble drug, PNU-91325, was used as a model drug in this study to illustrate this formulation approach. The comparative in vitro studies indicated that the presence of a small amount HPMC in the formulation was critical to achieve a stabilized supersaturated state of PNU-91325 upon mixing with water. An in vivo study was conducted in dogs for assessment of the oral bioavailability of four formulations of PNU-91325. A five-fold higher bioavailability (approximately 60%) was observed from a S-cosolvent formulation containing propylene glycol (PG)+20 mg/g HPMC as compared to that (approximately 12%) of a neat polyethylene glycol (PEG) 400 formulation. The low bioavailability of the PEG 400 formulation is attributed to the uncontrolled precipitation of PNU-91325 upon dosing, a commonly observed phenomenon with the cosolvent approach. A S-SEDDS formulation composed of 30% w/w Cremophor (surfactant), 9% PEG 400, 5% DMA, 18% Pluronic L44, 20% HPMC, and other minor components showed an oral bioavailability of approximately 76%, comparable to that of a neat tween formulation (bioavailability: approximately 68%). The significant improvement of the oral bioavailability of the supersaturatable S-cosolvent and S-SEDDS formulations is attributed to a high free drug concentration in vivo as a result of the generation and stabilization of the supersaturated state due to the incorporation of polymeric precipitation inhibitor.