Resource Type

Light-Front Holography and Gauge/Gravity Duality: The Light Meson and Baryon Spectra (open access)

Light-Front Holography and Gauge/Gravity Duality: The Light Meson and Baryon Spectra

Starting from the bound state Hamiltonian equation of motion in QCD, we derive relativistic light-front wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. These equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-J modes in anti-de Sitter (AdS) space. Its eigenvalues give the hadronic spectrum, and its eigenmodes represent the probability amplitudes of the hadronic constituents at a given scale. An effective classical gravity description in a positive-sign dilaton background exp(+{kappa}{sup 2}z{sup 2}) is given for the phenomenologically successful soft-wall model which naturally encodes the internal structure of hadrons and their orbital angular momentum. Applications to the light meson and baryon spectrum are presented.
Date: December 9, 2009
Creator: de Teramond, Guy F.; U., /Costa Rica & Brodsky, Stanley J.
System: The UNT Digital Library
Light-Front Holography and Non-Perturbative QCD (open access)

Light-Front Holography and Non-Perturbative QCD

The combination of Anti-de Sitter space (AdS) methods with light-front holography leads to a semi-classical first approximation to the spectrum and wavefunctions of meson and baryon light-quark bound states. Starting from the bound-state Hamiltonian equation of motion in QCD, we derive relativistic light-front wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. These equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-J modes in anti-de Sitter (AdS) space. Its eigenvalues give the hadronic spectrum, and its eigenmodes represent the probability distribution of the hadronic constituents at a given scale. Applications to the light meson and baryon spectra are presented. The predicted meson spectrum has a string-theory Regge form M{sup 2} = 4{kappa}{sup 2}(n + L + S = 2); i.e., the square of the eigenmass is linear in both L and n, where n counts the number of nodes of the wavefunction in the radial variable {zeta}. The space-like pion form factor is also well reproduced. One thus obtains a remarkable connection between the description of hadronic modes in AdS space and …
Date: December 9, 2009
Creator: Brodsky, Stanley J. & de Teramond, Guy F.
System: The UNT Digital Library
Measurements of Charmless B Decays Related to alpha at BaBar (open access)

Measurements of Charmless B Decays Related to alpha at BaBar

We report recent measurements of the CKM angle {alpha} using data collected by the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory. In addition to improved constraints on {alpha} from the decays B{sup {+-}} {yields} {rho}{sup {+-}}{rho}{sup 0}, we also present preliminary results of neutral and charged B meson decays to K{sub 1}(1270){pi} and K{sub 1}(1400){pi} and its impact on the estimate for the CKM angle {alpha} based on time-dependent analysis of CP-violating asymmetries in B{sup 0} {yields} a{sub 1}(1260){sup {+-}} {pi}{sup {-+}}. Moreover we report the first observation of the decay B {yields} a{sub 1}(1260){sup {+-}}a{sub 1}(1260){sup {-+}}; this mode can be used, in principle, to provide an independent measurement of {alpha}.
Date: December 9, 2009
Creator: Lombardo, Vincenzo & /INFN, Milan
System: The UNT Digital Library
Measurements of Time-Dependent CP Asymmetries in b\to s Penguin Dominated Hadronic B Decays at BaBar (open access)

Measurements of Time-Dependent CP Asymmetries in b\to s Penguin Dominated Hadronic B Decays at BaBar

We report measurements of Time-Dependent CP asymmetries in several b {yields} s penguin dominated hadronic B decays, where New Physics contributions may appear. We find no significant discrepancies with respect to the Standard Model expectations.
Date: December 9, 2009
Creator: Biassoni, Pietro
System: The UNT Digital Library
Multi-Device Knob Utility for LCLS (open access)

Multi-Device Knob Utility for LCLS

At the SLAC National Accelerator Laboratory (SLAC) the Controls Department (CD) has developed a new Multi-Device Knob Utility (MKB) based on the Experimental Physics and Industrial Control System (EPICS) toolkit for controlling one or more Process Variables (PVs) in unison, or simultaneously, from a physical knob located in the control room, or from various software tools such as the EPICS Extensible Display Manager (EDM) or a Swing slider in Java. A group of devices are hooked up to a knob, and then the value written to the devices is a simple function of the value of the knob. This is used, most commonly, to create a bump in the electron beam for the Linac Coherent Light Source (LCLS). Control system variables typically controlled are magnetic fields, phases, and timing offsets. This paper describes the technologies used to implement this utility.
Date: December 9, 2009
Creator: Zelazny, Michael; Chevtsov, Sergei; Chu, Chungming Paul; Fairley, Diane; Krejcik, Patrick; Rogind, Deborah et al.
System: The UNT Digital Library
Next-to-Leading Order Predictions for W + 3-Jet Distributions at Hadron Colliders (open access)

Next-to-Leading Order Predictions for W + 3-Jet Distributions at Hadron Colliders

We present next-to-leading order QCD predictions for a variety of distributions in W + 3-jet production at both the Tevatron and the Large Hadron Collider. We include all subprocesses and incorporate the decay of the W boson into leptons. Our results are in excellent agreement with existing Tevatron data and provide the first quantitatively precise next-to-leading order predictions for the LHC. We include all terms in an expansion in the number of colors, confirming that the specific leading-color approximation used in our previous study is accurate to within three percent. The dependence of the cross section on renormalization and factorization scales is reduced significantly with respect to a leading-order calculation. We study different dynamical scale choices, and find that the total transverse energy is significantly better than choices used in previous phenomenological studies. We compute the one-loop matrix elements using on-shell methods, as numerically implemented in the BlackHat code. The remaining parts of the calculation, including generation of the real-emission contributions and integration over phase space, are handled by the SHERPA package.
Date: December 9, 2009
Creator: Berger, C.F.; /MIT, LNS; Bern, Z.; /UCLA; Dixon, L.J.; /SLAC et al.
System: The UNT Digital Library
NLO QCD Predictions for W+3 jets (open access)

NLO QCD Predictions for W+3 jets

In this contribution we present results from the NLO computation of the production of a W boson in association with three jets in hadronic collisions. The results are obtained by combining two programs: BlackHat for the virtual one-loop matrix elements and Sherpa for the real-emission contributions. We present results for the Tevatron and the LHC, and address the issue of the choice of a common factorization and renormalization scale for this process.
Date: December 9, 2009
Creator: Maitre, Daniel; U., /Durham; Berger, Carola F.; /MIT; Bern, Zvi; Febres Cordero, Fernando et al.
System: The UNT Digital Library
Orbit Display's Use of the Physics Application Framework (open access)

Orbit Display's Use of the Physics Application Framework

At the SLAC National Accelerator Laboratory (SLAC) the Controls Department (CD) is developing a physics application framework based on the Java(tm) programming language developed by Sun Microsystems. This paper will discuss the first application developed using this approach: a new Orbit Display. The software is being developed by several individuals in reusable Java packages. It relies on the Experimental Physics and Industrial Control System (EPICS) toolkit for data collection and XAL - A Java based Hierarchy for Application Programming for model parameters. The Orbit Display tracks and displays electron paths through the Linac Coherent Light Source (LCLS) in both a graphical, beam line plot, and tabular format. It contains many features that may be unique to SLAC and is meant to be used both in the control room and by individuals in their offices or at home. Unique features include BSA Beam Synchronous Acquisition (BSA), Orbit Fitting, and Buffered Acquisition.
Date: December 9, 2009
Creator: Zelazny, Michael; Chevtsov, Sergei; Chu, Chungming Paul; Fairley, Diane; Krejcik, Patrick; Natampalli, Partha et al.
System: The UNT Digital Library
Recent Progress in the Development of Diesel Surrogate Fuels (open access)

Recent Progress in the Development of Diesel Surrogate Fuels

There has been much recent progress in the area of surrogate fuels for diesel. In the last few years, experiments and modeling have been performed on higher molecular weight components of relevance to diesel fuel such as n-hexadecane (n-cetane) and 2,2,4,4,6,8,8-heptamethylnonane (iso-cetane). Chemical kinetic models have been developed for all the n-alkanes up to 16 carbon atoms. Also, there has been much experimental and modeling work on lower molecular weight surrogate components such as n-decane and n-dodecane that are most relevant to jet fuel surrogates, but are also relevant to diesel surrogates where simulation of the full boiling point range is desired. For two-ring compounds, experimental work on decalin and tetralin recently has been published. For multi-component surrogate fuel mixtures, recent work on modeling of these mixtures and comparisons to real diesel fuel is reviewed. Detailed chemical kinetic models for surrogate fuels are very large in size. Significant progress also has been made in improving the mechanism reduction tools that are needed to make these large models practicable in multi-dimensional reacting flow simulations of diesel combustion. Nevertheless, major research gaps remain. In the case of iso-alkanes, there are experiments and modeling work on only one of relevance to diesel: iso-cetane. …
Date: December 9, 2009
Creator: Pitz, W J & Mueller, C J
System: The UNT Digital Library
Search for a Low-mass Higgs Boson in Y(3S)--> gamma A^0, A^0--> tau^ tau^- at BABAR (open access)

Search for a Low-mass Higgs Boson in Y(3S)--> gamma A^0, A^0--> tau^ tau^- at BABAR

We search for a light Higgs boson A{sup 0} in the radiative decay Y(3S) {yields} {gamma}A{sup 0}, A{sup 0} {yields} T{sup +}T{sup -}, T{sup +} {yields} e{sup +}{nu}{sub e}{nu}{sub T}, or T{sup +} {yields} {mu}{sup +} {nu}{sub {mu}T}. The data sample contains 122 x 10{sup 6} Y(3S) events recorded with the BABAR detector. We find no evidence for a narrow structure in the studied T{sup +}T{sup -} invariant mass region of 4.03 < m{sub T{sup +}T{sup -}} < 10.10 GeV/c{sup 2}. We exclude at the 90% confidence level (C.L.) a low-mass Higgs boson decaying to T{sup +}T{sup -} with a product branching fraction B(Y(3S) {yields} {gamma}A{sup 0}) x B(A{sup 0} {yields} T{sup +}T{sup -}) > (1.5-16) x 10{sup -5} across the mT{sup +}T{sup -} range. We also set a 90% C.L. upper limit on the T{sup +}T{sup -} decay of the {eta}{sub b} at B({eta}{sub b} {yields} T{sup +}T{sup -}) < 8%.
Date: December 9, 2009
Creator: Gabareen Mokhtar, Arafat
System: The UNT Digital Library
SLIM, Short-pulse Technology for High Gradient Induction Accelerators (open access)

SLIM, Short-pulse Technology for High Gradient Induction Accelerators

The conclusions of this paper are: (1) The gradient of the SLIM-based technology is believed to be achievable in the same range as it is for the gradient of a modern rf-linac technology ({approx}100 MeV per meter). (2) The SLIM concept is based on the nsec TEM pulse mode operation with no laser or rf systems. (3) Main components of SLIM are not stressed while the energy is pumped into the induction system. Components can accept the hard environment conditions such as a radiation dose, mismatch, hard electromagnetic nose level, etc. Only for several nanoseconds the switch is OFF and produces a stress in the induction system. At that time, the delivery of energy to the beam takes place. (4) The energy in the induction system initially is storied in the magnetic field when the switch is ON. That fact makes another benefit: a low voltage power supplies can be used. The reliability of a lower voltage power supply is higher and they are cheaper. (5) The coreless SLIM concept offers to work in the MHz range of repetition rate. The induction system has the high electric efficiency (much higher than the DWA). (6) The array of lined up and …
Date: December 9, 2009
Creator: Krasnykh, A.; Kardo-Sysoev, A. & Arntz, F.
System: The UNT Digital Library
THE DOE OFFICE OF ENVIRONMENTAL MANAGEMENT INTERNATIONAL COOPERATIVE PROGRAM: OVERVIEW OF TECHNICAL TASKS AND RESULTS (open access)

THE DOE OFFICE OF ENVIRONMENTAL MANAGEMENT INTERNATIONAL COOPERATIVE PROGRAM: OVERVIEW OF TECHNICAL TASKS AND RESULTS

The DOE Office of Environmental Management (DOE-EM) Office of Engineering and Technology is responsible for implementing EM's International Cooperative Program. Over the past 15 years, collaborative work has been conducted through this program with researchers in Russia, Ukraine, France, United Kingdom and Republic of Korea. Currently, work is being conducted with researchers in Russia and Ukraine. Efforts aimed at evaluating and advancing technologies to support U.S. high-level waste (HLW) vitrification initiatives are being conducted in collaboration with Russian researchers. Work at Khlopin Radium Institute (KRI) is targeted at improving the throughput of current vitrification processes by increasing melting rate. These efforts are specifically targeted at challenging waste types identified at the Savannah River Site (SRS) and Hanford Site. The objectives of current efforts at SIA Radon are to gain insight into vitrification process limits for the cold crucible induction melter (CCIM) technology. Previous demonstration testing has shown that the CCIM offers the potential for dramatic increases in waste loading and waste throughput. However, little information is known regarding operational limits that could affect long-term, efficient CCIM operations. Collaborative work with the Russian Electrotechnical University (ETU) 'LETI' is aimed at advancing CCIM process monitoring, process control and design. The goal is …
Date: December 8, 2009
Creator: Marra, J.; Fox, K.; Farfan, E. & Jannik, T.
System: The UNT Digital Library
Generation of transgenic wheat (Triticum aestivum L.) accumulating heterologous endo-xylanase or ferulic acid esterase in the endosperm (open access)

Generation of transgenic wheat (Triticum aestivum L.) accumulating heterologous endo-xylanase or ferulic acid esterase in the endosperm

Endo-xylanase (from Bacillus subtilis) or ferulic acid esterase (from Aspergillus niger) were expressed in wheat under the control of the endosperm specific 1DX5 glutenin promoter. Constructs both with and without the endoplasmic reticulum retention signal KDEL were used. Transgenic plants were recovered in all four cases but no qualitative differences could be observed whether KDEL was added or not. Endo-xylanase activity in transgenic grains was increased between two and three fold relative to wild type. The grains were shriveled and had a 25-33% decrease in mass. Extensive analysis of the cell walls showed a 10-15% increase in arabinose to xylose ratio, a 50% increase in the proportion of water extractable arabinoxylan, and a shift in the MW of the water extractable arabinoxylan from being mainly larger than 85 kD to being between 2 kD and 85 kD. Ferulic acid esterase expressing grains were also shriveled and the seed weight was decreased by 20-50%. No ferulic acid esterase activity could be detected in wild type grains whereas ferulic acid esterase activity was detected in transgenic lines. The grain cell walls had 15-40% increase in water unextractable arabinoxylan and a decrease in monomeric ferulic acid between 13 and 34%. In all the …
Date: December 8, 2009
Creator: Harholt, Jesper; Bach, Inga C; Lind-Bouquin, Solveig; Nunan, Kylie J.; Madrid, Susan M.; Brinch-Pedersen, Henrik et al.
System: The UNT Digital Library
THE RETRIEVAL KNOWLEDGE CENTER EVALUATION OF LOW TANK LEVEL MIXING TECHNOLOGIES FOR DOE HIGH LEVEL WASTE TANK RETRIEVAL 10516 (open access)

THE RETRIEVAL KNOWLEDGE CENTER EVALUATION OF LOW TANK LEVEL MIXING TECHNOLOGIES FOR DOE HIGH LEVEL WASTE TANK RETRIEVAL 10516

The Department of Energy (DOE) Complex has over two-hundred underground storage tanks containing over 80-million gallons of legacy waste from the production of nuclear weapons. The majority of the waste is located at four major sites across the nation and is planned for treatment over a period of almost forty years. The DOE Office of Technology Innovation & Development within the Office of Environmental Management (DOE-EM) sponsors technology research and development programs to support processing advancements and technology maturation designed to improve the costs and schedule for disposal of the waste and closure of the tanks. Within the waste processing focus area are numerous technical initiatives which included the development of a suite of waste removal technologies to address the need for proven equipment and techniques to remove high level radioactive wastes from the waste tanks that are now over fifty years old. In an effort to enhance the efficiency of waste retrieval operations, the DOE-EM Office of Technology Innovation & Development funded an effort to improve communications and information sharing between the DOE's major waste tank locations as it relates to retrieval. The task, dubbed the Retrieval Knowledge Center (RKC) was co-lead by the Savannah River National Laboratory (SRNL) …
Date: December 8, 2009
Creator: Fellinger, A.
System: The UNT Digital Library
Thermo-Mechanical Response of a TRISO Fuel Particle in a Fusion/Fission Engine for Incineration of Weapons Grade Plutonium (open access)

Thermo-Mechanical Response of a TRISO Fuel Particle in a Fusion/Fission Engine for Incineration of Weapons Grade Plutonium

The Laser Inertial Fusion-based (LIFE) engine is an advanced energy concept under development at Lawrence Livermore National Laboratory (LLNL). LIFE engine could be used to drive a subcritical fission blanket with fertile or fissile fuel. Current LIFE engine designs envisages fuel in pebble bed form with TRISO (tristructural isotropic) particles embedded in a graphite matrix, and pebbles flowing in molten salt Flibe (2LiF+BeF{sub 2}) coolant at T {approx} 700C. Weapons-grade plutonium (WGPu) fuel is an attractive option for LIFE engine involving the achievement of high fractional burnups in a short lifetime frame. However, WGPu LIFE engine operating conditions of high neutron fast fluence, high radiation damage, and high Helium and Hydrogen production pose severe challenges for typical TRISO particles. The thermo-mechanical fuel performance code HUPPCO (High burn-Up fuel Pebble Performance COde) currently under development accounts for spatial and time dependence of the material elastic properties, temperature, and irradiation swelling and creep mechanisms. In this work, some aspects of the thermo-mechanical response of TRISO particles used for incineration of weapons grade fuel in LIFE engine are analyzed. Preliminary results show the importance of developing reliable high-fidelity models of the performance of these new fuel designs and the need of new experimental …
Date: December 8, 2009
Creator: Caro, M.; DeMange, P.; Marian, J. & Caro, A.
System: The UNT Digital Library
Direct Observation of Room-Temperature Polar Ordering in Colloidal GeTe Nanocrystals (open access)

Direct Observation of Room-Temperature Polar Ordering in Colloidal GeTe Nanocrystals

Ferroelectrics and other materials that exhibit spontaneous polar ordering have demonstrated immense promise for applications ranging from non-volatile memories to microelectromechanical systems. However, experimental evidence of polar ordering and effective synthetic strategies for accessing these materials are lacking for low-dimensional nanomaterials. Here, we demonstrate the synthesis of size-controlled nanocrystals of the polar material germanium telluride (GeTe) using colloidal chemistry and provide the first direct evidence of room-temperature polar ordering in nanocrystals less than 5 nm in size using aberration-corrected transmission electron microscopy. Synchrotron x-ray diffraction and Raman studies demonstrate a sizeable polar distortion and a reversible size-dependent polar phase transition in these nanocrystals. The stability of polar ordering in solution-processible nanomaterials suggests an economical avenue to Tbit/in2-density non-volatile memory devices and other applications.
Date: December 7, 2009
Creator: Polking, Mark J.; Zheng, Haimei; Urban, Jeffrey J.; Milliron, Delia J.; Chan, Emory; Caldwell, Marissa A. et al.
System: The UNT Digital Library
OPERATIONAL CHALLENGES IN MIXING AND TRANSFER OF HIGH YIELD STRESS SLUDGE WASTE (open access)

OPERATIONAL CHALLENGES IN MIXING AND TRANSFER OF HIGH YIELD STRESS SLUDGE WASTE

The ability to mobilize and transport non-Newtonian waste is essential to advance the closure of highly radioactive storage tanks. Recent waste removal operations from Tank 12H at the Savannah River Site (SRS) encountered sludge mixtures with a yield stress too high to pump. The waste removal equipment for Tank 12H was designed to mobilize and transport a diluted slurry mixture through an underground 550m long (1800 ft) 0.075m diameter (3 inch) pipeline. The transfer pump was positioned in a well casing submerged in the sludge slurry. The design allowed for mobilized sludge to enter the pump suction while keeping out larger tank debris. Data from a similar tank with known rheological properties were used to size the equipment. However, after installation and startup, field data from Tank 12H confirmed the yield stress of the slurry to exceed 40 Pa, whereas the system is designed for 10 Pa. A revision to the removal strategy was required, which involved metered dilution, blending, and mixing to ensure effective and safe transfer performance. The strategy resulted in the removal of over 255,000 kgs of insoluble solids with four discrete transfer evolutions for a total transfer volume of 2400 m{sup 3} (634,000 gallons) of sludge …
Date: December 7, 2009
Creator: Caldwell, T. & Bhatt, P.
System: The UNT Digital Library
Thin Silicon MEMS Contact-Stress Sensor (open access)

Thin Silicon MEMS Contact-Stress Sensor

This work offers the first, thin, MEMS contact-stress (CS) sensor capable of accurate in situ measruement of time-varying, contact-stress between two solid interfaces (e.g. in vivo cartilage contact-stress and body armor dynamic loading). This CS sensor is a silicon-based device with a load sensitive diaphragm. The diaphragm is doped to create piezoresistors arranged in a full Wheatstone bridge. The sensor is similar in performance to established silicon pressure sensors, but it is reliably produced to a thickness of 65 {micro}m. Unlike commercial devices or other research efforts, this CS sensor, including packaging, is extremely thin (< 150 {micro}m fully packaged) so that it can be unobtrusively placed between contacting structures. It is built from elastic, well-characterized materials, providing accurate and high-speed (50+ kHz) measurements over a potential embedded lifetime of decades. This work explored sensor designs for an interface load range of 0-2 MPa; however, the CS sensor has a flexible design architecture to measure a wide variety of interface load ranges.
Date: December 7, 2009
Creator: Kotovsky, J; Tooker, A & Horsley, D A
System: The UNT Digital Library
Medial thalamic 18-FDG uptake following inescapable shock correlates with subsequent learned helpless behavior (open access)

Medial thalamic 18-FDG uptake following inescapable shock correlates with subsequent learned helpless behavior

The learned helplessness paradigm has been repeatedly shown to correlate with neurobiological aspects of depression in humans. In this model, rodents are exposed inescapable foot-shock in order to reveal susceptibility to escape deficit, defined as 'learned helplessness' (LH). Few methods are available to probe the neurobiological aspects underlying the differences in susceptibility in the living animal, thus far being limited to studies examining regional neurochemical changes with microdialysis. With the widespread implementation of small animal neuroimaging methods, including positron emission tomography (PET), it is now possible to explore the living brain on a systems level to define regional changes that may correlate with vulnerability to stress. In this study, 12 wild type Sprague-Dawley rats were exposed to 40 minutes of inescapable foot-shock followed by metabolic imaging using 2-deoxy-2[{sup 18}F]fluoro-D-glucose (18-FDG) 1 hour later. The escape test was performed on these rats 48 hours later (to accommodate radiotracer decay), where they were given the opportunity to press a lever to shut off the shock. A region of interest (ROI) analysis was used to investigate potential correlations (Pearson Regression Coefficients) between regional 18-FDG uptake following inescapable shock and subsequent learned helpless behavior (time to finish the test; number of successful lever presses …
Date: December 6, 2009
Creator: Mirrione, M. M.; Schulz, D.; Dewey, S. L. & Henn, F. A.
System: The UNT Digital Library
Durable Glass for Thousands of Years (open access)

Durable Glass for Thousands of Years

The durability of natural glasses on geological time scales and ancient glasses for thousands of years is well documented. The necessity to predict the durability of high level nuclear waste (HLW) glasses on extended time scales has led to various thermodynamic and kinetic approaches. Advances in the measurement of medium range order (MRO) in glasses has led to the understanding that the molecular structure of a glass, and thus the glass composition, controls the glass durability by establishing the distribution of ion exchange sites, hydrolysis sites, and the access of water to those sites. During the early stages of glass dissolution, a 'gel' layer resembling a membrane forms through which ions exchange between the glass and the leachant. The hydrated gel layer exhibits acid/base properties which are manifested as the pH dependence of the thickness and nature of the gel layer. The gel layer ages into clay or zeolite minerals by Ostwald ripening. Zeolite mineral assemblages (higher pH and Al{sup 3+} rich glasses) may cause the dissolution rate to increase which is undesirable for long-term performance of glass in the environment. Thermodynamic and structural approaches to the prediction of glass durability are compared versus Ostwald ripening.
Date: December 4, 2009
Creator: Jantzen, Carol M.; Brown, Kevin G. & Pickett, J. B.
System: The UNT Digital Library
An Experimental and Kinetic Modeling Study of Methyl Decanoate Combustion (open access)

An Experimental and Kinetic Modeling Study of Methyl Decanoate Combustion

Biodiesel is a mixture of long chain fatty acid methyl esters derived from fats and oils. This research study presents opposed-flow diffusion flame data for one large fatty acid methyl ester, methyl decanoate, and uses the experiments to validate an improved skeletal mechanism consisting of 648 species and 2998 reactions. The results indicate that methyl decanoate is consumed via abstraction of hydrogen atoms to produce fuel radicals, which lead to the production of alkenes. The ester moiety in methyl decanoate leads to the formation of low molecular weight oxygenated compounds such as carbon monoxide, formaldehyde, and ketene.
Date: December 4, 2009
Creator: Sarathy, S M; Thomson, M J; Pitz, W J & Lu, T
System: The UNT Digital Library
Metal Angle Correction in the Cylinder Test (open access)

Metal Angle Correction in the Cylinder Test

None
Date: December 4, 2009
Creator: Souers, P. C.; Garza, R.; Hornig, H.; Lauderbach, L.; Owens, C. & Vitello, P.
System: The UNT Digital Library
NANOSTRUCTURED METAL OXIDES FOR ANODES OF LI-ION RECHARGEABLE BATTERIES (open access)

NANOSTRUCTURED METAL OXIDES FOR ANODES OF LI-ION RECHARGEABLE BATTERIES

The aligned nanorods of Co{sub 3}O{sub 4} and nanoporous hollow spheres (NHS) of SnO{sub 2} and Mn{sub 2}O{sub 3} were investigated as the anodes for Li-ion rechargeable batteries. The Co{sub 3}O{sub 4} nanorods demonstrated 1433 mAh/g reversible capacity. The NHS of SnO{sub 2} and Mn{sub 2}O{sub 3} delivered 400 mAh/g and 250 mAh/g capacities respectively in multiple galvonastatic discharge-charge cycles. It was found that high capacity of NHS of metal oxides is sustainable attributed to their unique structure that maintains material integrity during cycling. The nanostructured metal oxides exhibit great potential as the new anode materials for Li-ion rechargeable batteries with high energy density, low cost and inherent safety.
Date: December 4, 2009
Creator: Au, M.
System: The UNT Digital Library
Nuclear quantum effects in the structure and lineshapes of the N2 NEXAFS spectrum (open access)

Nuclear quantum effects in the structure and lineshapes of the N2 NEXAFS spectrum

We study the relative ability of several models of the X-ray absorption spectrum to capture the Franck-Condon structure apparent from an experiment on gaseous nitrogen. In doing so, we adopt the Born-Oppenheimer approximation and a constrained density functional theory method for computing the energies of the X-ray-excited molecule. Starting from an otherwise classical model for the spectrum, we systematically introduce more realistic physics, first by substituting the quantum mechanical nuclear radial density in the bond separation R for the classical radial density, then by adding the effect of zero-point energy and other level shifts, and finally by including explicit rovibrational quantization of both the ground and excited states. The quantization is determined exactly, using a discrete variable representation. We show that the NEXAFS spectrum can be predicted semiquantiatively within this framework. We also address the possibility of non-trivial temperature dependence in the spectrum. Finally, we show that it is possible to improve the predicted spectrum by using constrained DFT in combination with more accurate potentials.
Date: December 4, 2009
Creator: Fatehi, Shervin; Schwartz, Craig P.; Saykally, Richard J. & Prendergast, David
System: The UNT Digital Library