Equivariant thinning over a free group

We construct entropy increasing monotone factors in the context of a Bernoulli shift over the free group of rank at least two

Competitive Interactions among Symbiotic Fungi of the Southern Pine Beetle

The southern pine beetle, a damaging pest of conifers, is intimately linked to three symbiotic fungi. Two fungi, Ceratocystiopsis ranaculosus and Entomocorticium sp. A, are transported within specialized structures (mycangia) in the beetle exoskeleton and are mutualists of the beetle. A third fungus, Ophiostoma minus, is transported externally on the beetle exoskeleton (phoretically) and is an antagonist of the beetle. This study examined competitive interactions among these three fungi. The results of de Wit replacement series and primary and secondary resource capture assays with these fungi provide strong evidence for differential competition between the phoretic and mycangial fungi. O. minus was the most able to capture both uncolonized and colonized resources. Entomocorticium sp. A and C. ranaculosus, although equal to one another in compet- itive abilities, differed in their ability to compete with O. minus. Entomocorticium sp. A was able to maintain space free of O. minus to a much greater degree than was C. ranaculosus. The outcome of such competitive interactions may have significant impacts on the biology of this ecologically and economically important beetle

Properties of nanostructured diamond-silicon carbide composites sintered by high pressure infiltration technique

A high-pressure silicon infiltration technique was applied to sinter diamond–SiC composites with different diamond crystal sizes. Composite samples were sintered at pressure 8 GPa and temperature 2170 K. The structure of composites was studied by evaluating x-ray diffraction peak profiles using Fourier coefficients of ab initio theoretical size and strain profiles. The composite samples have pronounced nanocrystalline structure: the volume-weighted mean crystallite size is 41–106 nm for the diamond phase and 17–37 nm for the SiC phase. The decrease of diamond crystal size leads to increased dislocation density in the diamond phase, lowers average crystallite sizes in both phases, decreases composite hardness, and improves fracture toughness

Data report: depths of Site U1553 off-splice data adjusted to the Site U1553 splice, IODP Expedition 378

A near-complete sedimentary sequence was spliced together for the upper part of International Ocean Discovery Program (IODP) Holes U1553A, U1553B, and U1553E. Poor core recovery precluded a complete splice for the deeper section cored in Holes U1553C and U1553D. The history of Deep Sea Drilling Project Site 277, which was cored nearby, suggests that the Site U1553 splice will be heavily sampled and that eventually samples will be taken from intervals of core that are not included in the splice (i.e., off-splice). Although the depths of all cores have been shifted to a common scale during the splicing process by aligning significant features shared by cores from the different holes, core disturbance and natural variability often lead to misalignment between features in the splice and the same features in off-splice data. To remedy this problem for future sampling, data from off-splice intervals are squeezed or stretched to match spliced intervals using a set of tie points between the splice and off-splice data. The difference in depths can be significant when considering sedimentation rates and orbital periods of precession, obliquity, and eccentricity and sometimes even change the phase relationship compared to the splice. Results are presented as tables of tie points between each hole and the splice that can be used to interpolate the proper splice depth of off-splice samples

Data report: splice adjustment for Site U1553

Postcruise examination of the data splice for International Ocean Discovery Program Expedition 378 Site U1553, in light of new X-ray fluorescence data, revealed three cores from Hole U1553E that were misaligned. These cores have been shifted to fill in some gaps in the original splice

Physical Properties of a Set of Sandstones, III: the Effects Of Fine Grained Pore Filling Material on Compressional Wave Velocity

We have used aspect ratio modeling to explain the measured compressional wave velocities of twenty different dry sandstone samples with varying clay contents at a single confining pressure of 0.5 kbar. Velocities of the sandstones range between 3.1 km/sec and 5.7 km/sec. Measured porosities are between 6% and 33%, clay contents between 2% and 30%. Pores were described using three simple type classifications. The pore type distributions of the samples were quantified by point counting polished impregnated thin sections using a scanning electron microscope. A representative aspect-ratio was assigned to each of the three categories of pore type. Velocities were modeled using these aspect ratios weighted by the observed distribution of the porosity types. Agreement between theoretical and measured velocities is generally within 10%. The modeling suggests that the effects of clays in sandstone pores is to reduce the sample porosity without reducing the non-framework (void + clay) volume. Thus, for a given porosity, clay rich samples contain greater non-framework volume, which in turn lowers velocity. The model derived from the dry measurements can be used to successfully approximate empirical relationships for saturated samples of velocity-porosity-clay content taken from the literature.Schlumberger-Doll Research CenterSchlumberger Foundation. Post-Doctoral Fellowshi

Late Miocene to Holocene high-resolution eastern equatorial Pacific carbonate records: stratigraphy linked by dissolution and paleoproductivity

Coherent variation in CaCO3 burial is a feature of the Cenozoic eastern equatorial Pacific. Nevertheless, there has been a long-standing ambiguity in whether changes in CaCO3 dissolution or changes in equatorial primary production might cause the variability. Since productivity and dissolution leave distinctive regional signals, a regional synthesis of data using updated age models and high-resolution stratigraphic correlation is an important constraint to distinguish between dissolution and production as factors that cause low CaCO3. Furthermore, the new chronostratigraphy is an important foundation for future paleoceanographic studies. The ability to distinguish between primary production and dissolution is also important to establish a regional carbonate compensation depth (CCD). We report late Miocene to Holocene time series of XRF-derived (X-ray fluorescence) bulk sediment composition and mass accumulation rates (MARs) from eastern equatorial Pacific Integrated Ocean Drilling Program (IODP) sites U1335, U1337, and U1338 and Ocean Drilling Program (ODP) site 849, and we also report bulk-density-derived CaCO3 MARs at ODP sites 848, 850, and 851. We use physical properties, XRF bulk chemical scans, and images along with available chronostratigraphy to intercorrelate records in depth space. We then apply a new equatorial Pacific age model to create correlated age records for the last 8 Myr with resolutions of 1–2 kyr. Large magnitude changes in CaCO3 and bio-SiO2 (biogenic opal) MARs occurred within that time period but clay deposition has remained relatively constant, indicating that changes in Fe deposition from dust is only a secondary feedback to equatorial productivity. Because clay deposition is relatively constant, ratios of CaCO3 % or biogenic SiO2 % to clay emulate changes in biogenic MAR. We define five major Pliocene–Pleistocene low CaCO3 % (PPLC) intervals since 5.3 Ma. Two were caused primarily by high bio-SiO2 burial that diluted CaCO3 (PPLC-2, 1685–2135 ka, and PPLC-5, 4465–4737 ka), while three were caused by enhanced dissolution of CaCO3 (PPLC-1, 51–402 ka, PPLC-3, 2248–2684 ka, and PPLC-4, 2915–4093 ka). Regional patterns of CaCO3 % minima can distinguish between low CaCO3 caused by high diatom bio-SiO2 dilution versus lows caused by high CaCO3 dissolution. CaCO3 dissolution can be confirmed through scanning XRF measurements of Ba. High diatom production causes lowest CaCO3 % within the equatorial high productivity zone, while higher dissolution causes lowest CaCO3 percent at higher latitudes where CaCO3 production is lower. The two diatom production intervals, PPLC-2 and PPLC-5, have different geographic footprints from each other because of regional changes in eastern Pacific nutrient storage after the closure of the Central American Seaway. Because of the regional variability in carbonate production and sedimentation, the carbonate compensation depth (CCD) approach is only useful to examine large changes in CaCO3 dissolution