Abstract. Seeking a global empirical relationship between compressional wave velocity and porosity for siliciclastic sediments, we have brought together an extensive suite of both new and published log-and core-based data. We undertook a detailed statistical analysis of Ocean Drilling Program data from Amazon Fan to examine variables affecting compressional velocity in shallow, unconsolidated sediments. We identify three dominant variables (porosity, shale fraction, and consolidation history) and present two empirically determined boundary curves (one for normally consolidated sediments and a second for highly consolidated environments (e.g., accretionary prisms)). These two empirical relationships predict the compressional velocity of siliciclastic sedimentary rocks with water-filled pores as a function of porosity and clay content for the full range of observed porosities. Velocities of siliciclastic sedimentary rocks decrease rapidly with both increasing porosity and increasing clay content. At fractional porosities higher than about 0.4, fluid dominates the elastic properties, and velocity exhibits a subtle dependence on porosity. Remarkably, the Amazon Fan data show that clay content has no direct influence on velocity at high porosities. Both clay content and sorting do indirectly affect velocity, through their control of porosity. Burial affects velocity not only by compaction-related porosity decrease but also by pressure-induced increase of intergrain coupling. Because of the sensitivity of velocity to consolidation history, particularly at intermediate fractional porosities of about 0.30-0.40, no single velocity-porosity relationship can apply to all high-porosity sediments. The two proposed relationships fit the majority of published and new data. They are applicable, however, only for normally pressured, in situ conditions and water-filled pores.

Introduction The objective of this study is to assess the efficacy of local tacrolimus (FK506) delivery to improve outcomes in the setting of nerve transection injury. Methods FK506 embedded poly(lactide‐co‐caprolactone) films capable of extended, localized release of FK506 were developed. FK506 rate of release testing and bioactivity assay was performed. Mouse sciatic nerve transection and direct repair model was used to evaluate the effect extended, local delivery of FK506 had on nerve regeneration outcomes. Results Linear release of FK506 was observed for 30 days and released FK506 matched control levels of neurite extension in the dorsal root ganglion assay. Groups treated with local FK506 had greater gastrocnemius muscle weight, foot electromyogram, and number of axons distal of the repair site than non‐FK506 groups. Discussion Results of this study indicate that extended, localized delivery of FK506 to nerve injuries can improve nerve regeneration outcomes in a mouse sciatic nerve transection and repair.

Abstract. Ocean Drilling Program Leg 171A collected logging while drilling (LWD) data to investigate the porosity and velocity structure of Barbados accretionary complex. Porosity and velocity measurements were needed for interpretation of prism dynamics. However, the LWD tool string did not measure velocity, and previous velocity data from Barbados prism are scarce and generally of low quality. Furthermore, most density-based porosities are subject to errors associated with variations in smectite content. To determine porosities more accurately, we use smectite-corrected, density-based porosities to calibrate a porosity-formation factor (FF) transform, then calculate porosities from resistivity logs. We used cation exchange capacity (CEC) measurements and LWD logs to evaluate the possibility that resistivity is affected by clay conduction. The CEC data warn of potential clay conduction, especially in smectite-rich zones, but LWD data indicate that clay conduction is minor in these high-porosity sediments. Instead, tortuosity is the secondary control of FF, after porosity. By comparing resistivity-based porosities to velocities from vertical seismic profiles, we determine a porosity-velocity transform applicable to Barbados. We then use this transform to calculate velocity logs from resistivity-based porosity logs.

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Abstract. The electrical resistivity of siliciclastic rocks is a function both of pore-fluid resistivity and of formation factor (FF), an intrinsic rock property. For low-porosity rocks, FF depends on clay conduction and porosity. In contrast, we find that FF of high-porosity sediments (fractional porosities of 0.3-0.6) from Amazon Fan is controlled primarily by porosity and pore geometry; clay conduction is a minor effect. Porosity vs. formation factor (FF) plots for Amazon Fan well logs demonstrate two distinct trends which are dependent on the amount of shale present. Muds, with more than about 0.4 shale fxaction, follow a trend that increases to much higher FF as porosity decreases, compared to sands and slightly muddy sands. This separation is of opposite sign to the separation between low-porosity sandstones and shales attributable to clay conduction. We conclude that in high-porosity muds, presence of clays reduces formation conductivity by increasing the tortuosity of pores.

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