Mineralogy of deepwater Gulf of Mexico salt formations and implications for constitutive behavior

A majority of the wells for the most significant announced developments in the deepwater Gulf of Mexico will penetrate salt formations thousands of feet thick. Assuring the integrity of these wells over the field lifetime is a major drilling engineering challenge. The effect of salt on long-term well integrity is tied to the constitutive behavior of the salt, and more specifically, to its creep rate. The constitutive behavior of salt has been well studied in two previous geotechnical engineering applications. A sophisticated constitutive model for salt that considers transient and steady state creep was developed under the Waste Isolation Pilot Plant, a licensed repository for transuranic waste. Further studies of salt creep were performed for the Strategic Petroleum Reserve (SPR), a series of leached storage caverns located in salt domes along the U.S. Gulf Coast. However, only a single set of laboratory creep data exists for salt from a deepwater Gulf of Mexico diapir. To constrain the constitutive response of deepwater Gulf of Mexico salt diapirs, the mineralogic composition of salt diapirs from several regions, including Ship Shoal, Ewing Bank, Mississippi Canyon, Garden Banks, Green Canyon, and Walker Ridge, was determined by quantitative X-ray diffraction analyses of drill cuttings. Water depths for the wells ranged from 718 ft to 7590 ft, and salt sections up to nearly 11,000 ft thick were penetrated. The database provides insight into the large-scale geographic variations in salt mineralogy, as well as insight into variations along vertical (or near-vertical) transects through massive salt bodies in the deepwater Gulf of Mexico. To enable comparison with on-shore domal salts with known constitutive response, mineralogic analyses were also conducted on salt cores recovered from various on-shore SPR sites. We show that that the range in composition of the salt diapirs in the deepwater Gulf of Mexico is essentially identical to the observed range in composition of the salt domes located along the U.S. Gulf Coast (to which the deepwater salt diapirs are geologically related). In light of the observed constitutive response of the sole deepwater salt diapir tested to date, we conclude that the expected constitutive response of deepwater Gulf of Mexico salt diapirs is likely to be bracketed by the observed range in constitutive response of the well-characterized Gulf Coast domal salts. We demonstrate with an example how this knowledge can be directly applied in well casing design analyses.     

Quantum-mechanical effects on the threshold voltage of undoped double-gate MOSFETs

Quantum-mechanical (QM), or carrier energy-quantization, effects on the subthreshold characteristics, including the threshold voltage (V/sub t/), of generic undoped double-gate (DG) CMOS devices with ultrathin (Si) bodies (UTBs) are physically modeled. The analytic model, with dependences on the UTB thickness (t/sub Si/), the transverse electric field, and the UTB surface orientation, shows how V/sub t/ is increased, and reveals that 1) the subthreshold carrier population in higher-energy subbands is significant, 2) the QM effects in DG devices with {110}-Si surfaces, common in FinFETs, are comparable to those for {100}-Si surfaces for t/sub Si/>/spl sim/4 nm, 3) the QM effects can increase the gate swing, and (iv) the QM effects, especially for t/sub Si/相似文献   

Exploring the Concept of In Vivo Guided Tissue Engineering by a Single-Stage Surgical Procedure in a Rodent Model

In severe malformations with a lack of native tissues, treatment options are limited. We aimed at expanding tissue in vivo using the body as a bioreactor and developing a sustainable single-staged procedure for autologous tissue reconstruction in malformation surgery. Autologous micro-epithelium from skin was integrated with plastically compressed collagen and a degradable knitted fabric mesh. Sixty-three scaffolds were implanted in nine rats for histological and mechanical analyses, up to 4 weeks after transplantation. Tissue integration, cell expansion, proliferation, inflammation, strength, and elasticity were evaluated over time in vivo and validated in vitro in a bladder wound healing model. After 5 days in vivo, we observed keratinocyte proliferation on top of the transplant, remodeling of the collagen, and neovascularization within the transplant. At 4 weeks, all transplants were fully integrated with the surrounding tissue. Tensile strength and elasticity were retained during the whole study period. In the in vitro models, a multilayered epithelium covered the defect after 4 weeks. Autologous micro-epithelial transplants allowed for cell expansion and reorganization in vivo without conventional pre-operative in vitro cell propagation. The method was easy to perform and did not require handling outside the operating theater.     

Geometrical influence of ABn monomer structure on the thermal properties of linear-hyperbranched ether-ketone copolymers prepared via an AB+ABn route

A series of poly(ether ketone) copolymers were prepared by nucleophilic aromatic polymerization reactions of 4-fluoro-4′-hydroxybenzophenone, 2, in the presence of varying percentages of AB_n monomers based on a triarylphosphine oxide platform, 1a (2F), 1b (4F), and 1c (6F), where A=OH and B=F. As expected, the crystallinity of the samples decreased with an increasing AB_n content. However, the tetrahedral geometry of the phosphine oxide-based AB_n monomers proved to be much more efficient at lowering the melt temperature of the copolymers than was the corresponding ketone-based AB_n monomer, 3,5-bis(4-fluorophenylbenzoyl)phenol, 4, that possesses a structure more similar to that of 2. Polymerization of 2 in the presence of as little as 5 mol% of bis-(3,4,5-trifluorophenyl)-(4-hydroxyphenyl)phosphine oxide, 1c (6F), afforded a completely amorphous polymer with a glass transition temperature of 168 °C that was soluble in hot NMP and DMSO. The copolymers also exhibited excellent thermoxidative stability with a number of samples displaying 5% weight loss temperatures, in air, well in excess of 500 °C.     

Short-channel effects in SOI MOSFETs

Short-channel effects in thin-film silicon-on-insulator (SOI) MOSFETs are shown to be unique because of dependences on film thickness and body and back-gate (substrate) biases. These dependences enable control of threshold-voltage reduction, channel-charge enhancement due to a drain bias, carrier velocity saturation, channel-length modulation and its effect on output conductance, as well as device degradation due to hot carriers in short-channel SOI MOSFETs. A short-channel effect exclusive to SOI MOSFETs, back-surface charge modulation, is described. Because of the short-channel effects, the use of SOI MOSFETs in VLSI circuits provides the designer with additional flexibility as compared to bulk-MOSFET design. Various design tradeoffs are discussed     

Benchtop Energetics: Hyperthermal Species Detection

We propose a novel scheme for monitoring the transition between deflagration and “detonation‐like” behavior of small‐scale explosive samples‐in‐vacuum subjected to short duration shock stimuli. Our approach relies on measuring the chemical identities and velocity distributions of the gaseous species produced by such samples; e.g. the relatively low velocity expansion‐quenched reaction intermediates produced by deflagration versus the hyperthermal thermodynamically stable molecules generated by the termination of a detonation wave at an explosive‐vacuum interface. We demonstrate our ability to detect such species by time‐of‐flight mass spectrometry (TOFMS) using fast Al atoms produced by laser ablation of aluminum metal. Extensive SIMION simulations of ion trajectories in our mass spectrometer lead to a semi‐quantitative model connecting the system operating parameters and the velocity‐dependent neutral species detection efficiency. We present a method for correcting our data for these detection biases, and for transforming them into neutral species velocity and kinetic energy distributions. We also present preliminary TOFMS data of hyperthermal organic molecular species produced by direct laser ablation/ignition of thin‐film nitrocellulose samples.     

Implementation of nonlocal model for impact-ionization current inbipolar circuit simulation and application to SiGe HBT designoptimization

A nonlocal characterization of impact-ionization current is implemented in a compact but physical bipolar transistor model for predictive circuit simulation. The charge-based model, which is applicable to SiGe-base HBT's as well as Si BJT's, provides at each bias point, including ones in quasisaturation, the electric field distribution E(x) in the epi-collector, and a simplified form of the energy-balance equation enables characterization of carrier temperature T_e(x) from E(x). Numerical spatial integration of the T_e -dependent ionization rate yields the impact-ionization current as post-processing in the model routine. The nonlocal model is verified by applications to two advanced bipolar (HBT and BJT) technologies in which the device breakdown voltages, which are underestimated by the local-field model, are predicted. The utility of the nonlocal model in assessing design tradeoffs involving impact ionization (i.e., device breakdown versus circuit performance) is demonstrated by simulations based on the two mentioned technologies     

Subthreshold kinks in fully depleted SOI MOSFET's

Measured current-voltage characteristics of scaled, floating-body, fully depleted (FD) SOI MOSFET's that show subthreshold kinks controlled by the back-gate (substrate) bias are presented. The underlying physical mechanism is described, and is distinguished from the well known kink effect in partially depleted devices. The physical insight attained qualifies the meaning of FD/SOI and implies new design issues for low-voltage FD/SOI CMOS     

Chemical and biological evaluation of protein quality of locally produced and processed full-fat soya bean flour from three Tanzanian villages

Samples of locally produced and processed full-fat soya bean flour from three Ujamaa villages in Tanzania were tested for protein quality and trypsin inhibitory activity. Differences were found in true digestibility (t.d.), biological value (b.v.) and net protein utilisation (n.p.u.) of the three flours as tested in balance experiments with rats under standardised conditions. A possible explanation for the differences is suggested on the basis of variations in amino acid content and trypsin inhibitory activity. The possible reasons for the variation in inhibitory activity are discussed.