748 research outputs found

    Augmenting ERISA with Market Discipline: Transforming Pension Plan Interests into Securities

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    Part I of this Note provides general background information about pension plans and details the problems that ERISA creates because of its dependence on trust law. Part II canvasses recent problems in pension plan governance that courts and pension plan members have faced in takeover defense and social investment contexts, demonstrating that ERISA\u27s use of trust law cannot respond adequately to these problems. Parts I and II draw on an analysis of ERISA presented by Professors Fischel and Langbein but argue that their proposals for changing ERISA inadequately address the problems they identify. Part III argues that the economic realities of the pension plan transaction support the conclusion that an interest in a pension plan is a security. Part IV describes the advantages that will flow from applying the securities laws to all pension plan interests and from using a market in pension plan interests as a monitoring tool. Part IV argues that the advantages of such an approach to pension interests would outweigh its costs

    The Effect of Particle Size and Concentration on Low-Frequency Terahertz Scattering in Granular Compacts

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    Fundamental knowledge of scattering in granular compacts is essential to ensure accuracy of spectroscopic measurements and determine material characteristics such as size and shape of scattering objects. Terahertz time-domain spectroscopy (THz-TDS) was employed to investigate the effect of particle size and concentration on scattering in specially fabricated compacts consisting of borosilicate microspheres in a polytetrafluoroethylene (PTFE) matrix. As expected, increasing particle size leads to an increase in overall scattering contribution. At low concentrations, the scattering contribution increases linearly with concentration. Scattering increases linearly at low concentrations, saturates at higher concentrations with a maximum level depending on particle size, and that the onset of saturation is independent of particle size. The effective refractive index becomes sublinear at high particle concentrations and exceeds the linear model at maximum density, which can cause errors in calculations based on it, such as porosity. The observed phenomena are attributed to the change in the fraction of photons propagating ballistically versus being scattered. At low concentrations, photons travel predominately ballistically through the PTFE matrix. At high concentrations, the photons again propagate ballistically through adjacent glass microspheres. In the intermediate regime, photons are predominately scattered

    SeisCORK meeting report

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    SeisCORK meeting, November 15 and 16, 2004, Stress/Mohr Engineering, Houston, Texas 77041-1205The purpose of this meeting was to explore design options to simultaneously acquire borehole seismic data and hydro-geological data (pressure, temperature, fluid sampling and microbiological sampling) on a single CORK system. The scientific focus was to add a seismic component to the Juan de Fuca Hydrogeology program. By permanently installing a sensor string in the borehole our goal was to enable: l) time-lapse VSP's and offset VSP's with sufficient data quality to study amplitude versus offset, shear wave anisotropy, and lateral heterogeneity; 2) monitoring of micro- and nano- earthquake activity around the site for correlation with pressure transients. Because of the difficulty in ensuring adequate coupling through multiple casing strings we concluded that it was impractical to install the vertical seismic array with 10m spacing (50-60 nodes) that would be necessary for VSP's and time-lapse VSP's. We did describe a scenario for a vertical seismic array with approximately 100m spacing (5-6 nodes) that could be used for offset-VSP's and seismic monitoring. This uses some unique technology and involves two seismic strings: one in the annulus between the 4- 1/2" and 10-3/4" casings and one in the middle of the 4-1/2" casing.Funding was provided by the National Science Foundation under Grant No. OCE-0450318

    Microbial communities at the borehole observatory on the Costa Rica Rift flank (Ocean Drilling Program Hole 896A)

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    The microbiology of subsurface, hydrothermally influenced basaltic crust flanking mid-ocean ridges has remained understudied, due to the difficulty in accessing the subsurface environment. The instrumented boreholes resulting from scientific ocean drilling offer access to samples of the formation fluids circulating through oceanic crust. We analyzed the phylogenetic diversity of bacterial communities of fluid and microbial mat samples collected in situ from the observatory at Ocean Drilling Program Hole 896A, drilled into ~6.5 million-year-old basaltic crust on the flank of the Costa Rica Rift in the equatorial Pacific Ocean. Bacterial 16S rRNA gene sequences recovered from borehole fluid and from a microbial mat coating the outer surface of the fluid port revealed both unique and shared phylotypes. The dominant bacterial clones from both samples were related to the autotrophic, sulfur-oxidizing genus Thiomicrospira. Both samples yielded diverse gamma- and alphaproteobacterial phylotypes, as well as members of the Bacteroidetes, Planctomycetes, and Verrucomicrobia. Analysis of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) genes (cbbL and cbbM) from the sampling port mat and from the borehole fluid demonstrated autotrophic carbon assimilation potential for in situ microbial communities; most cbbL genes were related to those of the sulfur-oxidizing genera Thioalkalivibrio and Thiomicrospira, and cbbM genes were affiliated with uncultured phylotypes from hydrothermal vent plumes and marine sediments. Several 16S rRNA gene phylotypes from the 896A observatory grouped with phylotypes recovered from seawater-exposed basalts and sulfide deposits at inactive hydrothermal vents, but there is little overlap with hydrothermally influenced basaltic boreholes 1026B and U1301A on the Juan de Fuca Ridge flank, suggesting that site-specific characteristics of Hole 896A (i.e., seawater mixing into borehole fluids) affect the microbial community composition

    Polymer pellet fabrication for accurate THz-TDS measurements

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    We investigate fabrication of compacts using polytetrafluoroethylene (PTFE) and polyethylene (PE), and the effect of compaction conditions on their terahertz transmission properties. The conditions used to fabricate compressed powder samples for terahertz time-domain spectroscopy (THz-TDS) can impact the accuracy of the measurements and hence the interpretation of results. This study investigated the effect of compaction conditions on the accuracy of the THz-TDS analysis. Two polymers that are commonly used as matrix materials in terahertz spectroscopy studies were explored using a compaction simulator and a hydraulic press for sample preparation. THz-TDS was used to determine the refractive index and loss coefficient to compare the powder compacts (pellets) to the values of solid material. Sample porosity, axial relaxation and tensile strength were measured to assess the material’s suitability for terahertz spectroscopy. It was found that PTFE is the preferable material for creating THz-TDS samples due to its low porosity and high tensile strength. PE was found to show significant porosity at all compaction pressures making it an unsuitable material for the accurate determination of optical parameters from THz-TDS spectroscopy measurements. The larger particle sizes of PE resulted in compacts that exhibited significantly lower tensile strength than those made from PTFE making handling and storage difficult

    Non-destructive estimation of particle size in powder compacts

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    To develop a model to non-destructively estimate particle size changes in powder compacts using terahertz time-domain spectroscopy (THz-TDS)

    Analysis of THz scattering of compacted granular materials using THz-TDS

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    Scattering of terahertz radiation in compacts is of great interest due to its potential to non-destructively assess various structural elements such as particle size and defects in compacts. In this study, we isolate the scattering contributions to the loss coefficient of borosilicate glass microspheres suspended in a polytetrafluoroethylene (PTFE) compact measured by terahertz time-domain spectroscopy. The particle size and concentration of microspheres in the compacts were varied to resolve their effect on terahertz scattering

    Observation of spurious spectral features in mixed-powder compressed pellets measured by terahertz time-domain spectroscopy

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    Spurious loss features were observed in mixed-powder compressed pellets measured in transmission using terahertz time-domain spectroscopy. Loss features were identified in two types of pellets: PTFE-glass microspheres and PTFE-lactose. The features were found to be dependent on grain size and concentration. An explanation is proposed, based on varying optical thickness of the sample material
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