A Quantitative Assessment of Atmospherically generated Foam Cements: Insights, Impacts, and Implications of Wellbore Integrity and Stability.

The primary function of well cement is to provide casing support and zonal isolation for the life of a well (Thiercelin et al., 1998; Singamshetty, 2004; Iverson et al., 2008). Failure to achieve one or both of these conditions can lead to a migration of fluids up the wellbore and result in both economic and ecological disasters, as exemplified by the Deepwater Horizon oil spill on April 20, 2010. To avoid these kinds of failures, the cement must have sufficient strength to secure the casing in the hole and withstand the stresses of drilling, perforating, enhanced oil recovery, and hydraulic fracturing and also be able to keep the annulus sealed against the formation. This thesis analyzes and presents in detail some of the mechanical and physical properties of atmospherically generated foamed cements typically used in deep offshore wells in the Gulf of Mexico. Both static and dynamic measurements were taken across a range of foam qualities and include permeability, porosity, compressive strength, Young’s modulus (E), and Poisson’s ratio (ν). Investigating the properties of a range of foam qualities and cement recipes provides better understanding of the effect that different amounts of entrained air can have on cement performance and reliability. To better represent the behavior of cements in the wellbore, we subjected cements to pressure cycling and the measurements were analyzed over the range of these pressures. Our results show how these foamed cements behave and will prove to be a good baseline for future testing on cements generated under in-situ conditions

Field-effect transistor noise at low temperatures

Low temperature noise measurements on junction field-effect transistors tend to substantiate a theory of low frequency field-effect transistor noise based on the presence of generation centers in the gate-channel depletion region. Measurements of device noise voltage versus temperature reveal pronounced maxima and minima over the temperature range of 300° K to 77° K. Analysis of the maxima can yield information on time constants, capture cross-sections and energy levels of generation centers in the depletion region. The pertinent theories of junction FET noise are reviewed with regard to temperature-dependent phenomena. Contributions due to thermal noise, shot noise, induced gate noise, surface leakage and generation centers are considered. Techniques for measuring the temperature dependence of FET noise are discussed, and a practical approach is described. Measurements are made in a typical circuit configuration in order that the results may be directly related to device applications. Measured data on the temperature dependence of noise in the 300° K to 77°K range is presented for 14 n- and p-channel FET's. Salient features of the data are analyzed and correlated with theoretical predictions

Reduction of Taxonomic Bias in Diatom Species Data

Inconsistency in taxonomic identification and analyst bias impede the effective use of diatom data in regional and national stream and lake surveys. In this study, we evaluated the effect of existing protocols and a revised protocol on the precision of diatom species counts. The revised protocol adjusts four elements of sample preparation, taxon identification and enumeration, and quality control (QC). We used six independent data sets to assess the effect of the adjustments on analytical outcomes. The first data set was produced by three laboratories with a total of five analysts following established protocols (Charles et al., Protocols for the analysis of algal samples collected as part of the U.S. Geological Survey National Water-Quality Assessment, 2002) or their slight variations. The remaining data sets were produced by one to three laboratories with a total of two to three analysts following a revised protocol. The revised protocol included the following modifications: (1) development of coordinated precount voucher floras based on morphological operational taxonomic units, (2) random assignment of samples to analysts, (3) postcount identification and documentation of taxa (as opposed to an approach in which analysts assign names while they enumerate), and (4) increased use of QC samples. The revised protocol reduced taxonomic bias, as measured by reduction in analyst signal, and improved similarity among QC samples. Reduced taxonomic bias improves the performance of biological assessments, facilitates transparency across studies, and refines estimates of diatom species distributions

Holocene Earthquakes and Right-lateral Slip on the Left-lateral Darrington-Devils Mountain Fault Zone, Northern Puget Sound, Washington

Sources of seismic hazard in the Puget Sound region of northwestern Washington include deep earthquakes associated with the Cascadia subduction zone, and shallow earthquakes associated with some of the numerous crustal (upper-plate) faults that crisscross the region. Our paleoseismic investigations on one of the more prominent crustal faults, the Darrington–Devils Mountain fault zone, included trenching of fault scarps developed on latest Pleistocene glacial sediments and analysis of cores from an adjacent wetland near Lake Creek, 14 km southeast of Mount Vernon, Washington. Trench excavations revealed evidence of a single earthquake, radiocarbon dated to ca. 2 ka, but extensive burrowing and root mixing of sediments within 50–100 cm of the ground surface may have destroyed evidence of other earthquakes. Cores in a small wetland adjacent to our trench site provided stratigraphic evidence (formation of a laterally extensive, prograding wedge of hillslope colluvium) of an earthquake ca. 2 ka, which we interpret to be the same earthquake documented in the trenches. A similar colluvial wedge lower in the wetland section provides possible evidence for a second earthquake dated to ca. 8 ka. Three-dimensional trenching techniques revealed evidence for 2.2 ± 1.1 m of right-lateral offset of a glacial outwash channel margin, and 45–70 cm of north-side-up vertical separation across the fault zone. These offsets indicate a net slip vector of 2.3 ± 1.1 m, plunging 14° west on a 286°-striking, 90°-dipping fault plane. The dominant right-lateral sense of slip is supported by the presence of numerous Riedel R shears preserved in two of our trenches, and probable right-lateral offset of a distinctive bedrock fault zone in a third trench. Holocene north-side-up, right-lateral oblique slip is opposite the south-side-up, left-lateral oblique sense of slip inferred from geologic mapping of Eocene and older rocks along the fault zone. The cause of this slip reversal is unknown but may be related to clockwise rotation of the Darrington–Devils Mountain fault zone into a position more favorable to right-lateral slip in the modern N-S compressional stress field

ProSight PTM 2.0: improved protein identification and characterization for top down mass spectrometry

ProSight PTM 2.0 (http://prosightptm2.scs.uiuc.edu) is the next generation of the ProSight PTM web-based system for the identification and characterization of proteins using top down tandem mass spectrometry. It introduces an entirely new data-driven interface, integrated Sequence Gazer for protein characterization, support for fixed modifications, terminal modifications and improved support for multiple precursor ions (multiplexing). Furthermore, it supports data import and export for local analysis and collaboration

An aging Interventions Testing Program: study design and interim report

The National Institute on Aging's Interventions Testing Program (ITP) has developed a plan to evaluate agents that are considered plausible candidates for delaying rates of aging. Key features include: (i) use of genetically heterogeneous mice (a standardized four-way cross), (ii) replication at three test sites (the Jackson Laboratory, TJL; University of Michigan, UM; and University of Texas, UT), (iii) sufficient statistical power to detect 10 changes in lifespan, (iv) tests for age-dependent changes in T cell subsets and physical activity, and (v) an annual solicitation for collaborators who wish to suggest new interventions for evaluation. Mice in the first cohort were exposed to one of four agents: aspirin, nitroflurbiprofen (NFP), 4-OH- -phenyl-N-tert-butyl nitrone (4-OH-PBN), or nordihydroguiaretic acid (NDGA). An interim analysis was conducted using survival data available on the date at which at least 50 of the male control mice had died at each test site. Survival of control males was significantly higher, at the interim time-point, at UM than at UT or TJL; all three sites had similar survival of control females. Males in the NDGA group had significantly improved survival ( P 0.0004), with significant effects noted at TJL ( P < 0.01) and UT ( P < 0.04). None of the other agents altered survival, although there was a suggestion ( P 0.07) of a beneficial effect of aspirin in males. More data will be needed to determine if any of these compounds can extend maximal lifespan, but the current data show that NDGA reduces early life mortality risks in genetically heterogeneous mice at multiple test sites.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74625/1/j.1474-9726.2007.00311.x.pd