States

Thermally Induced Reorganization in LCP Fibers: Molecular Origin of Mechanical Strength (open access)

Thermally Induced Reorganization in LCP Fibers: Molecular Origin of Mechanical Strength

The ordering of liquid crystalline polymer fiber during heat treatment is of great interest for many commercial reasons. This is because, by convention, fiber property can be greatly improved by heat-treatment at below the melting temperature and often such processing conditions are also very complex. There are many variations of such treatments, in terms of temperature, exposure time and whether the fibers are under tension or not. The state-of-the-art technology will be to optimize the desired property without significantly enhancing the undesired properties. The types of heat treatment are highly correlated to the understanding of the mechanism of improving the properties at the molecular level and the microstructures. Using WAXS and synchrotron SAXS techniques, the structure and morphology of our commercial LCP (liquid crystalline polymer), a co-polymer of CO (Vectran) and its variant polymer fiber COTHBP are being examined. Both fibers have the typical liquid crystalline polymer structure, ie, highly ordered across the fiber axis and aperiodic sequencing along the fiber axis. Physical testing has revealed a three fold increase in strength in both fibers, however, the modulus is observed to increase significantly in COTBP and not so much CO. This paper reports on the changes and the differences on …
Date: July 16, 2007
Creator: Saw, C. K.; Collins, G.; Menczel, J. & Jaffe, M.
Object Type: Article
System: The UNT Digital Library
Case Study: Northeast Asian Energy Cooperation Council (NAECC) - facilitation of a regional energy project (open access)

Case Study: Northeast Asian Energy Cooperation Council (NAECC) - facilitation of a regional energy project

A case study describing the functions of the Northeast Asian Energy Cooperation Council (NAECC).
Date: November 16, 2007
Creator: Kreyling, Sean J.
Object Type: Report
System: The UNT Digital Library
HANFORD DOUBLE SHELL TANK (DST) THERMAL & SEISMIC PROJECT INCREASED LIQUID LEVEL ANALYSIS FOR 241-AP TANK FARMS (open access)

HANFORD DOUBLE SHELL TANK (DST) THERMAL & SEISMIC PROJECT INCREASED LIQUID LEVEL ANALYSIS FOR 241-AP TANK FARMS

The overall scope of the project is to complete an up-to-date comprehensive analysis of record of the SDT System at Hanford. The "Double-Shell Tank (DST) Integrity Project - DST Thermal and Seismic Project" is in support of Tri-Party Agreement Milestone M-48-14.
Date: February 16, 2007
Creator: Mackey, T. C.; Deibler, J. E.; Johnson, K. I.; Pilli, S. P.; Karri, N. K.; Rinker, M. W. et al.
Object Type: Report
System: The UNT Digital Library
Miniaturized Mid-Infrared Sensor Technologies (open access)

Miniaturized Mid-Infrared Sensor Technologies

Fundamental vibrational and rotational modes associated with most inorganic and organic molecules are spectroscopically accessible within the mid-infrared (MIR; 3-20 {micro}m) regime of the electromagnetic spectrum. The interaction between MIR photons and organic molecules provides particularly sharp transitions, which - despite the wide variety of organic molecules - provide unique MIR absorption spectra reflecting the molecularly characteristic arrangement of chemical bonds within the probed molecules via the frequency position of the associated vibrational and rotational transitions. Given the inherent molecular selectivity and achievable sensitivity, MIR spectroscopy provides an ideal platform for optical sensing applications. Despite this potential, early MIR sensing applications were limited to localized applications due to the size of the involved instrumentation, and limited availability of appropriately compact MIR optical components including light sources, detectors, waveguides, and spectrometers. During the last decades, engineering advances in photonics and optical engineering have facilitated the translation of benchtop-style MIR spectroscopy into miniaturized optical sensing schemes providing a footprint compatible with portable instrumentation requirements for field deployable analytical tools. In this trend article, we will discuss recent advances and future strategies for miniaturizing MIR sensor technology. The Beer-Lambert law implies that achievable limit of detection (LOD) for any optical sensor system improves …
Date: August 16, 2007
Creator: Kim, S.; Young, C. & Mizaikoff, B.
Object Type: Article
System: The UNT Digital Library
NERSC Cyber Security Challenges That Require DOE Development andSupport (open access)

NERSC Cyber Security Challenges That Require DOE Development andSupport

Traditional security approaches do not adequately addressall the requirements of open, scientific computing facilities. Many ofthe methods used for more restricted environments, including almost allcorporate/commercial systems, do not meet the needs of today's science.Use of only the available "state of the practice" commercial methods willhave adverse impact on the ability of DOE to accomplish its sciencegoals, and impacts the productivity of the DOE Science community. Inparticular, NERSC and other high performance computing (HPC) centers havespecial security challenges that are unlikely to be met unless DOE fundsdevelopment and support of reliable and effective tools designed to meetthe cyber security needs of High Performance Science. The securitychallenges facing NERSC can be collected into three basic problem sets:network performance and dynamics, application complexity and diversity,and a complex user community that can have transient affiliations withactual institutions. To address these problems, NERSC proposes thefollowing four general solutions: auditing user and system activityacross sites; firewall port configuration in real time;cross-site/virtual organization identity management and access control;and detecting security issues in application middleware. Solutions arealsoproposed for three general long term issues: data volume,application complexity, and information integration.
Date: January 16, 2007
Creator: Draney, Brent; Campbell, Scott & Walter, Howard
Object Type: Report
System: The UNT Digital Library
MULTISCALE MODELING OF POLYMER NANOCOMPOSITES (open access)

MULTISCALE MODELING OF POLYMER NANOCOMPOSITES

Polymer Nanocomposites are an important class of nanomaterials with potential applications including but not limited to structural and cushion materials, electromagnetic and heat shields, conducting plastics, sensors, and catalysts for various chemical and bio processes. Success in most such applications hinges on molecular-level control of structure and assembly, and a deep understanding of how the overall morphology of various components and the interfaces between them affect the composite properties at the macroscale. The length and time-scales associated with such assemblies are prohibitively large for a full atomistic modeling. Instead we adopt a multiscale methodology in which atomic-level interactions between different components of a composite are incorporated into a coarse-grained simulation of the mesoscale morphology, which is then represented on a numerical grid and the macroscopic properties computed using a finite-elements method.
Date: July 16, 2007
Creator: Maiti, A
Object Type: Article
System: The UNT Digital Library
Dynamics of Adipocyte Turnover in Humans (open access)

Dynamics of Adipocyte Turnover in Humans

Obesity is increasing in an epidemic fashion in most countries and constitutes a public health problem by enhancing the risk for cardiovascular disease and metabolic disorders such as type 2 diabetes. Owing to the increase in obesity, life expectancy may start to decrease in developed countries for the first time in recent history. The factors determining fat mass in adult humans are not fully understood, but increased lipid storage in already developed fat cells is thought to be most important. We show that adipocyte number is a major determinant for the fat mass in adults. However, the number of fat cells stays constant in adulthood in lean and obese and even under extreme conditions, indicating that the number of adipocytes is set during childhood and adolescence. To establish the dynamics within the stable population of adipocytes in adults, we have measured adipocyte turnover by analyzing the integration of {sup 14}C derived from nuclear bomb tests in genomic DNA. Approximately 10% of fat cells are renewed annually at all adult ages and levels of body mass index. Neither adipocyte death nor generation rate is altered in obesity, suggesting a tight regulation of fat cell number that is independent of metabolic profile …
Date: July 16, 2007
Creator: Spalding, K; Arner, E; Westermark, P; Bernard, S; Buchholz, B; Bergmann, O et al.
Object Type: Article
System: The UNT Digital Library
Relative Biological Effectiveness of HZE Fe Ions for Induction of Micro-Nuclei at Low Doses (open access)

Relative Biological Effectiveness of HZE Fe Ions for Induction of Micro-Nuclei at Low Doses

Dose-response curves for induction of micro-nuclei (MN) was measured in Chinese hamster V79 and xrs6 (Ku80-) cells and in human mammary epithelial MCF10A cells in the dose range of 0.05-1 Gy. The Chinese Hamster cells were exposed to 1 GeV/u Fe ions, 600 MeV/u Fe ions, and 300 MeV/u Fe ions (LETs of 151, 176 and 235 keV/{micro}m respectively) as well as with 320 kVp X-rays as reference. Second-order polynomials were fitted to the induction curves and the initial slopes (the alpha values) were used to calculate RBE. For the repair proficient V79 cells the RBE at these low doses increased with LET. The values obtained were 3.1 (LET=151 keV/{micro}m), 4.3 (LET = 176 keV/{micro}m) and 5.7 (LET = 235 keV/{micro}m), while the RBE was close to 1 for the repair deficient xrs6 cells regardless of LET. For the MCF10A cells the RBE was determined for 1 GeV/u Fe ions and found to be 5.4, slightly higher than for V79 cells. To test the effect of shielding, the 1 GeV/u Fe ion beam was intercepted by various thickness of high-density polyethylene plastic absorbers, which resulted in energy loss and fragmentation. It was found that the MN yield for V79 cells …
Date: January 16, 2007
Creator: Groesser, Torsten; Chun, Eugene & Rydberg, Bjorn
Object Type: Article
System: The UNT Digital Library
Multidimensional Conservation Laws and Low Regularity Solutions (open access)

Multidimensional Conservation Laws and Low Regularity Solutions

This is the concluding report for the project, a continuation of research by Keyfitz and co-workers on multidimensional conservation laws, and applications of nonhyperbolic conservation laws in the two-fluid model for multiphase flow. The multidimensional research project was started with Suncica Canic, at the University of Houston and with Eun Heui Kim, now at California State University Long Beach. Two postdoctoral researchers, Katarina Jegdic and Allen Tesdall, also worked on this research. Jegdic's research was supported (for a total of one year) by this grant. Work on nonhyperbolic models for two-phase flows is being pursued jointly with Michael Sever, Hebrew University. Background for the project is contained in earlier reports. Note that in 2006, the project received a one-year no-cost extension that will end in September, 2007. A new proposal, for continuation of the research and for new projects, will be submitted in the Fall of 2007, with funding requested to begin in the summer of 2008. The reason for the 'funding gap' is Keyfitz's four-year stint as Director of the Fields Institute in Toronto, Canada. The research has continued, but has been supported by Canadian grant funds, as seems appropriate during this period.
Date: June 16, 2007
Creator: Keyfitz, Barbara Lee
Object Type: Report
System: The UNT Digital Library
CFD Analysis for the Applicability of the Natural Convection Shutdown Heat Removal Test Facility (NSTF) for the Simulation of the Vhtr Rccs. Topical Report. (open access)

CFD Analysis for the Applicability of the Natural Convection Shutdown Heat Removal Test Facility (NSTF) for the Simulation of the Vhtr Rccs. Topical Report.

The Very High Temperature gas cooled reactor (VHTR) is one of the GEN IV reactor concepts that have been proposed for thermochemical hydrogen production and other process-heat applications like coal gasification. The USDOE has selected the VHTR for further research and development, aiming to demonstrate emissions-free electricity and hydrogen production at a future time. One of the major safety advantages of the VHTR is the potential for passive decay heat removal by natural circulation of air in a Reactor Cavity Cooling System (RCCS). The air-side of the RCCS is very similar to the Reactor Vessel Auxiliary Cooling System (RVACS) that has been proposed for the PRISM reactor design. The design and safety analysis of the RVACS have been based on extensive analytical and experimental work performed at ANL. The Natural Convective Shutdown Heat Removal Test Facility (NSTF) at ANL that simulates at full scale the air-side of the RVACS was built to provide experimental support for the design and analysis of the PRISM RVACS system. The objective of this work is to demonstrate that the NSTF facility can be used to generate RCCS experimental data: to validate CFD and systems codes for the analysis of the RCCS; and to support …
Date: May 16, 2007
Creator: Tzanos, C. P.
Object Type: Report
System: The UNT Digital Library
Long-Term Modeling of Solar Energy: Analysis of Concentrating Solar Power (CSP) and PV Technologies (open access)

Long-Term Modeling of Solar Energy: Analysis of Concentrating Solar Power (CSP) and PV Technologies

This report presents an overview of research conducted on solar energy technologies and their implementation in the ObjECTS framework. The topics covered include financing assumptions and selected issues related to the integration of concentrating thermal solar power (CSP) and photovoltaics PV technologies into the electric grid. A review of methodologies for calculating the levelized energy cost of capital-intensive technologies is presented, along with sensitivity tests illustrating how the cost of a solar plant would vary depending on financing assumptions. An analysis of the integration of a hybrid concentrating thermal solar power (CSP) system into the electric system is conducted. Finally a failure statistics analysis for PV plants illustrates the central role of solar irradiance uncertainty in determining PV grid integration characteristics.
Date: August 16, 2007
Creator: Zhang, Yabei & Smith, Steven J.
Object Type: Report
System: The UNT Digital Library
Estimates of Optimal Backward Perturbations for Linear LeastSquares Problems (open access)

Estimates of Optimal Backward Perturbations for Linear LeastSquares Problems

Numerical tests are used to validate a practical estimatefor the optimal backward errors of linear least squares problems. Thissolves a thirty-year-old problem suggested by Stewart andWilkinson.
Date: July 16, 2007
Creator: Grcar, Joseph F.; Saunders, M.A. & Su, Zheng
Object Type: Article
System: The UNT Digital Library
HOM and LOM Coupler Optimizations for the ILC Crab Cavity (open access)

HOM and LOM Coupler Optimizations for the ILC Crab Cavity

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Date: July 16, 2007
Creator: Xiao, L.; Ko, K.; Li, Z.; Ng, C.; Schussman, G.; Seryi, A. et al.
Object Type: Article
System: The UNT Digital Library
On the non-invariance of space and time scale ranges under Lorentztransformation, and its implications for the study of relativisticinteractions (open access)

On the non-invariance of space and time scale ranges under Lorentztransformation, and its implications for the study of relativisticinteractions

We present an analysis which shows that the ranges of space and time scales spanned by a system are not invariant under the Lorentz transformation. This implies the existence of a frame of reference which minimizes an aggregate measure of the range of space and time scales. Such a frame is derived for example cases: free electron laser, laser-plasma accelerator, and particle beam interacting with electron clouds. Implications for experimental, theoretical and numerical studies are discussed. The most immediate relevance is the reduction by orders of magnitude in computer simulation run times for such systems.
Date: January 16, 2007
Creator: Vay, J. L.
Object Type: Article
System: The UNT Digital Library
Effect of Titanium Substitution on the Compatiblity of Electrodeswith Pyrrolidinium-Based Ionic Liquid Electrolytes (open access)

Effect of Titanium Substitution on the Compatiblity of Electrodeswith Pyrrolidinium-Based Ionic Liquid Electrolytes

The quest for the development of rechargeable lithium-metal batteries has attracted vigorous worldwide research efforts because this system offers the highest theoretical specific energy [1]. For this to be achieved, the repetitive deposition and stripping of lithium must be close to fully reversible. Thus, alternative electrolytes have been investigated, such as the room-temperature ionic liquid (RTILs). Lithium can be cycled with a high degree of reversibility with efficiencies exceeding 99% using systems based on N-methyl N-alkyl pyrrolidinium (P{sub 1X}{sup +}) combined with the TFSI anion [2]. More recent efforts have been directed towards systems based on P{sub 1X}{sup +} cations with the FSI anion and appear to be even more promising [3,4]. In this work, we discuss to what extent RTILs based on P{sub 1X}{sup +} cations with TFSI or FSI anions can be used as electrolytes for rechargeable Li batteries. In particular, their physical and chemical properties are thoroughly discussed so as to explain the difference observed in their electrochemical behavior. Although these two systems seem to be stable against lithium, their compatibilities with cathode materials require full assessment as well. Thus, various manganese oxide cathodes are investigated in this study. Strategies to minimize cathode dissolution are also debated, …
Date: May 16, 2007
Creator: Saint, Juliette A.; Shin, Joon-Ho; Best, Adam; Hollenkamp,Anthony; Kerr, John & Doeff, Marca M.
Object Type: Article
System: The UNT Digital Library
Lepton Flavour Violation And Baryon Number Non-Conservation in tau to Lambda + h (open access)

Lepton Flavour Violation And Baryon Number Non-Conservation in tau to Lambda + h

We have searched for the violation of baryon number B and lepton number L in the (B - L)-conserving modes {tau}{sup -} {yields} {bar {Lambda}}{pi}{sup -} and {tau}{sup -} {yields} {bar {Lambda}}K{sup -} as well as the (B - L)-violating modes {tau}{sup -} {yields} {Lambda}{pi}{sup -} and {tau}{sup -} {yields} {Lambda}K{sup -} using 237 fb{sup -1} of data collected with the BaBar detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage rings. We do not observe any signal and we determine preliminary upper limits on the branching fractions {Beta}({tau}{sup -} {yields} {bar {Lambda}}{pi}{sup -}) < 5.9 x 10{sup -8}, {Beta}({tau}{sup -}{yields} {Lambda}{pi}{sup -}) < 5.8 x 10{sup -6}, {Beta}({tau}{sup -} {yields} {bar {Lambda}}K{sup -}) < 7.2 x 10{sup -8}, and {Beta}({tau}{sup -} {yields} {Lambda}K{sup -}) < 15 x 10{sup -8} at 90% confidence level.
Date: November 16, 2007
Creator: Lafferty, G.D.
Object Type: Article
System: The UNT Digital Library
Kaolinite dissolution and precipitation kinetics at 22oC and pH4 (open access)

Kaolinite dissolution and precipitation kinetics at 22oC and pH4

Dissolution and precipitation rates of low defect Georgia kaolinite (KGa-1b) as a function of Gibbs free energy of reaction (or reaction affinity) were measured at 22 C and pH 4 in continuously stirred flow through reactors. Steady state dissolution experiments showed slightly incongruent dissolution, with a Si/Al ratio of about 1.12 that is attributed to the re-adsorption of Al on to the kaolinite surface. No inhibition of the kaolinite dissolution rate was apparent when dissolved aluminum was varied from 0 and 60 {micro}M. The relationship between dissolution rates and the reaction affinity can be described well by a Transition State Theory (TST) rate formulation with a Temkin coefficient of 2 R{sub diss} (mol/m{sup 2}s) = 1.15 x 10{sup -13} [1-exp(-{Delta}G/2RT)]. Stopping of flow in a close to equilibrium dissolution experiment yielded at solubility constant for kaolinite at 22 C of 10{sup 7.57}. Experiments on the precipitation kinetics of kaolinite showed a more complex behavior. One conducted using kaolinite seed that had previously undergone extensive dissolution under far from equilibrium conditions for 5 months showed a quasi-steady state precipitation rate for 105 hours that was compatible with the TST expression above. After this initial period, however, precipitation rates decreased by an …
Date: July 16, 2007
Creator: Yang, Li & Steefel, Carl I.
Object Type: Article
System: The UNT Digital Library
Science & Technology Review November 2007 (open access)

Science & Technology Review November 2007

This month's issue has the following articles: (1) Simulating the Electromagnetic World--Commentary by Steven R. Patterson; (2) A Code to Model Electromagnetic Phenomena--EMSolve, a Livermore supercomputer code that simulates electromagnetic fields, is helping advance a wide range of research efforts; (3) Characterizing Virulent Pathogens--Livermore researchers are developing multiplexed assays for rapid detection of pathogens; (4) Imaging at the Atomic Level--A powerful new electron microscope at the Laboratory is resolving materials at the atomic level for the first time; (5) Scientists without Borders--Livermore scientists lend their expertise on peaceful nuclear applications to their counterparts in other countries; and (6) Probing Deep into the Nucleus--Edward Teller's contributions to the fast-growing fields of nuclear and particle physics were part of a physics golden age.
Date: October 16, 2007
Creator: Chinn, D J
Object Type: Report
System: The UNT Digital Library
Commissioning Results of the LCLS Injector (open access)

Commissioning Results of the LCLS Injector

The Linac Coherent Light Source (LCLS) is a SASE xray Free-Electron Laser (FEL) project presently under construction at SLAC. The injector section, from drive-laser and RF photocathode gun through first bunch compressor chicane, was installed in fall 2006. Initial system commissioning with an electron beam has recently been completed. The second phase of construction, including second bunch compressor and full linac, is planned for 2008. In this paper, we report experimental results and experience gained during the first phase of machine commissioning. This includes the cathode, drive laser, RF photocathode gun, linac booster section, S-band and X-band RF systems, first bunch compressor, and the various beam diagnostics.
Date: November 16, 2007
Creator: Dowell, D. H.; Akre, R.; Ding, Y.; Emma, P.; Frisch, J.; Gilevich, S. et al.
Object Type: Article
System: The UNT Digital Library
Heights integrated model as instrument for simulation of hydHeights Integrated Model as Instrument for Simulation of Hydrodynamic, Radiation Transport, and Heat Conduction Phenomena of Laser-Produced Plasma in EUV Applications. (open access)

Heights integrated model as instrument for simulation of hydHeights Integrated Model as Instrument for Simulation of Hydrodynamic, Radiation Transport, and Heat Conduction Phenomena of Laser-Produced Plasma in EUV Applications.

The HEIGHTS integrated model has been developed as an instrument for simulation and optimization of laser-produced plasma (LPP) sources relevant to extreme ultraviolet (EUV) lithography. The model combines three general parts: hydrodynamics, radiation transport, and heat conduction. The first part employs a total variation diminishing scheme in the Lax-Friedrich formulation (TVD-LF); the second part, a Monte Carlo model; and the third part, implicit schemes with sparse matrix technology. All model parts consider physical processes in three-dimensional geometry. The influence of a generated magnetic field on laser plasma behavior was estimated, and it was found that this effect could be neglected for laser intensities relevant to EUV (up to {approx}10{sup 12} W/cm{sup 2}). All applied schemes were tested on analytical problems separately. Benchmark modeling of the full EUV source problem with a planar tin target showed good correspondence with experimental and theoretical data. Preliminary results are presented for tin droplet- and planar-target LPP devices. The influence of three-dimensional effects on EUV properties of source is discussed.
Date: January 16, 2007
Creator: Sizyuk, V.; Hassanein, A.; Morozov, V.; Sizyuk, T. & Science, Mathematics and Computer
Object Type: Report
System: The UNT Digital Library
ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS (open access)

ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS

Comprehensive test ban monitoring in terms of location and discrimination has progressed significantly in recent years. However, the characterization of sources and the estimation of low yields remains a particular challenge. As the recent Korean shot demonstrated, we can probably expect to have a small set of teleseismic, far-regional and high-frequency regional data to analyze in estimating the yield of an event. Since stacking helps to bring signals out of the noise, it becomes useful to conduct comparable analyses on neighboring events, earthquakes in this case. If these auxiliary events have accurate moments and source descriptions, we have a means of directly comparing effective source strengths. Although we will rely on modeling codes, 1D, 2D, and 3D, we will also apply a broadband calibration procedure to use longer periods (P>5s) waveform data to calibrate short-period (P between .5 to 2 Hz) and high-frequency (P between 2 to 10 Hz) as path specify station corrections from well-known regional sources. We have expanded our basic Cut-and-Paste (CAP) methodology to include not only timing shifts but also amplitude (f) corrections at recording sites. The name of this method was derived from source inversions that allow timing shifts between 'waveform segments' (or cutting the …
Date: July 16, 2007
Creator: Helmberger, D; Tromp, J & Rodgers, A
Object Type: Article
System: The UNT Digital Library
Autocatalytic water dissociation on Cu(110) at near ambient conditions (open access)

Autocatalytic water dissociation on Cu(110) at near ambient conditions

Autocatalytic dissociation of water on the Cu(110) metal surface is demonstrated based on X-ray photoelectron spectroscopy studies carried out in-situ under near ambient conditions of water vapor pressure (1 Torr) and temperature (275-520 K). The autocatalytic reaction is explained as the result of the strong hydrogen-bond in the H{sub 2}O-OH complex of the dissociated final state, which lowers the water dissociation barrier according to the Broensted-Evans-Polanyi relations. A simple chemical bonding picture is presented which predicts autocatalytic water dissociation to be a general phenomenon on metal surfaces.
Date: May 16, 2007
Creator: Mulleregan, Alice; Andersson, Klas; Ketteler, Guido; Bluhm, Hendrik; Yamamoto, Susumu; Ogasawara, Hirohito et al.
Object Type: Article
System: The UNT Digital Library
Strings on AdS2 and the high-energy limit of noncritical M-theory (open access)

Strings on AdS2 and the high-energy limit of noncritical M-theory

Abstract. Noncritical M-theory in 2+1 dimensions has been defined as a double-scaling limit of a nonrelativistic Fermi liquid on a flat two-dimensional plane. Here we study this noncritical M-theory in the limit of high energies, analogous to the alpha' --> infinity limit of string theory. In the related case of two-dimensional Type 0A strings, it has been argued that the conformal alpha' --> infinity limit leads to AdS_2 with a propagating fermion whose mass is set by the value of the RR flux. Here we provide evidence that in the high-energy limit, the natural ground state of noncritical M-theory similarly describes the AdS_2 x S1 spacetime, with a massless propagating fermion. We argue that the spacetime effective theory in this background is captured by a topological higher-spin extension of conformal Chern-Simons gravity in 2+1 dimensions, consistently coupled to a massless Dirac field. Intriguingly, the two-dimensional plane populated by the original nonrelativistic fermions is essentially the twistor space associated with the symmetry group of the AdS_2 x S1 spacetime; thus, at least in the high-energy limit, noncritical M-theory can be nonperturbatively described as a"Fermi liquid on twistor space.''
Date: April 16, 2007
Creator: Horava, Petr; Horava, Petr & Keeler, Cynthia A.
Object Type: Article
System: The UNT Digital Library
Evaluation of the Gas Production Potential of Marine HydrateDeposits in the Ulleung Basin of the Korean East Sea (open access)

Evaluation of the Gas Production Potential of Marine HydrateDeposits in the Ulleung Basin of the Korean East Sea

Although significant hydrate deposits are known to exist in the Ulleung Basin of the Korean East Sea, their survey and evaluation as a possible energy resource has not yet been completed. However, it is possible to develop preliminary estimates of their production potential based on the limited data that are currently available. These include the elevation and thickness of the Hydrate-Bearing Layer (HBL), the water depth, and the water temperature at the sea floor. Based on this information, we developed estimates of the local geothermal gradient that bracket its true value. Reasonable estimates of the initial pressure distribution in the HBL can be obtained because it follows closely the hydrostatic. Other critical information needs include the hydrate saturation, and the intrinsic permeabilities of the system formations. These are treated as variables, and sensitivity analysis provides an estimate of their effect on production. Based on the geology of similar deposits, it is unlikely that Ulleung Basin accumulations belong to Class 1 (involving a HBL underlain by a mobile gas zone). If Class 4 (disperse, low saturation accumulations) deposits are involved, they are not likely to have production potential. The most likely scenarios include Class 2 (HBL underlain by a zone of …
Date: November 16, 2007
Creator: Moridis, George J.; Reagan, Matthew T.; Kim, Se-Joon; Seol,Yongkoo & Zhang, Keni
Object Type: Article
System: The UNT Digital Library