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The continental margin is a key source of iron to the HNLC North Pacific Ocean (open access)

The continental margin is a key source of iron to the HNLC North Pacific Ocean

Here we show that labile particulate iron and manganese concentrations in the upper 500m of the Western Subarctic Pacific, an iron-limited High Nutrient Low Chlorophyll (HNLC) region, have prominent subsurface maxima between 100-200 m, reaching 3 nM and 600 pM, respectively. The subsurface concentration maxima in particulate Fe are characterized by a more reduced oxidation state, suggesting a source from primary volcagenic minerals such as from the Kuril/Kamchatka margin. The systematics of these profiles suggest a consistently strong lateral advection of labile Mn and Fe from redox-mobilized labile sources at the continental shelf supplemented by a more variable source of Fe from the upper continental slope. This subsurface supply of iron from the continental margin is shallow enough to be accessible to the surface through winter upwelling and vertical mixing, and is likely a key source of bioavailable Fe to the HNLC North Pacific.
Date: January 15, 2008
Creator: Lam, P. J. & Bishop, J. K. B
Object Type: Article
System: The UNT Digital Library
ACRF Instrumentation Status: New, Current, and Future - September 2008 (open access)

ACRF Instrumentation Status: New, Current, and Future - September 2008

The purpose of this report is to provide a concise but comprehensive overview of Atmospheric Radiation Measurement Climate Research Facility instrumentation status. The report is divided into the following five sections: (1) new instrumentation in the process of being acquired and deployed, (2) field campaigns, (3) existing instrumentation and progress on improvements or upgrades, (4) proposed future instrumentation, and (5) Small Business Innovation Research instrument development.
Date: October 15, 2008
Creator: Voyles, J. W.
Object Type: Report
System: The UNT Digital Library
Chemical Methods for the Production of Proteins (open access)

Chemical Methods for the Production of Proteins

The goal of this research program was to develop improved methods for chemical peptide and protein synthesis, and to apply these methods to the total synthesis of small proteins (<80 amino acids) & integral membrane proteins.
Date: September 15, 2008
Creator: Kent, Stephen B. H.
Object Type: Report
System: The UNT Digital Library
Electrokinetic Power Generation from Liquid Water Microjets (open access)

Electrokinetic Power Generation from Liquid Water Microjets

Although electrokinetic effects are not new, only recently have they been investigated for possible use in energy conversion devices. We have recently reported the electrokinetic generation of molecular hydrogen from rapidly flowing liquid water microjets [Duffin et al. JPCC 2007, 111, 12031]. Here, we describe the use of liquid water microjets for direct conversion of electrokinetic energy to electrical power. Previous studies of electrokinetic power production have reported low efficiencies ({approx}3%), limited by back conduction of ions at the surface and in the bulk liquid. Liquid microjets eliminate energy dissipation due to back conduction and, measuring only at the jet target, yield conversion efficiencies exceeding 10%.
Date: February 15, 2008
Creator: Duffin, Andrew M. & Saykally, Richard J.
Object Type: Article
System: The UNT Digital Library
Measurement of the Decay B- to D*0 e- anti-nu_e (open access)

Measurement of the Decay B- to D*0 e- anti-nu_e

Using 226 million B{bar B} events recorded on the {Upsilon}(4S) resonance with the BABAR detector at the SLAC e{sup +}e{sup -} PEP-II storage rings, they reconstruct B{sup -} {yields} D*{sup 0}e{sup -}{bar {nu}}{sub e} decays using the decay chain D*{sup 0} {yields} D{sup 0}{pi}{sup 0} and D{sup 0} {yields} K{sup -} {pi}{sup +}. From the dependence of their differential rate on the w, the dot product of the four-velocities of B{sup -} and D*{sup 0}, and using the form factor description by Caprini et al. with the parameters F(1) and {rho}{sub 1{sub 1}}{sup 2}, they obtain the results {rho}{sub A{sub 1}}{sup 2} = 1.16 {+-} 0.06 {+-} 0.08, F(1) {center_dot} |V{sub cb}| = (35.9 {+-} 0.6 {+-} 1.4) {center_dot} 10{sup -3}, and {beta}(B{sup -} {yields} D*{sup 0} e{sup -}{bar {nu}}{sub e}) = (5.56 {+-} 0.08 {+-} 0.41)%.
Date: January 15, 2008
Creator: Aubert, B.
Object Type: Article
System: The UNT Digital Library
LUsim: A Framework for Simulation-Based Performance Modelingand Prediction of Parallel Sparse LU Factorization (open access)

LUsim: A Framework for Simulation-Based Performance Modelingand Prediction of Parallel Sparse LU Factorization

Sparse parallel factorization is among the most complicated and irregular algorithms to analyze and optimize. Performance depends both on system characteristics such as the floating point rate, the memory hierarchy, and the interconnect performance, as well as input matrix characteristics such as such as the number and location of nonzeros. We present LUsim, a simulation framework for modeling the performance of sparse LU factorization. Our framework uses micro-benchmarks to calibrate the parameters of machine characteristics and additional tools to facilitate real-time performance modeling. We are using LUsim to analyze an existing parallel sparse LU factorization code, and to explore a latency tolerant variant. We developed and validated a model of the factorization in SuperLU_DIST, then we modeled and implemented a new variant of slud, replacing a blocking collective communication phase with a non-blocking asynchronous point-to-point one. Our strategy realized a mean improvement of 11percent over a suite of test matrices.
Date: April 15, 2008
Creator: Univ. of California, San Diego
Object Type: Article
System: The UNT Digital Library
Gravity monitoring of CO2 movement during sequestration: Model studies (open access)

Gravity monitoring of CO2 movement during sequestration: Model studies

We examine the relative merits of gravity measurements as a monitoring tool for geological CO{sub 2} sequestration in three different modeling scenarios. The first is a combined CO{sub 2} enhanced oil recovery (EOR) and sequestration in a producing oil field, the second is sequestration in a brine formation, and the third is for a coalbed methane formation. EOR/sequestration petroleum reservoirs have relatively thin injection intervals with multiple fluid components (oil, hydrocarbon gas, brine, and CO{sub 2}), whereas brine formations usually have much thicker injection intervals and only two components (brine and CO{sub 2}). Coal formations undergoing methane extraction tend to be thin (3-10 m), but shallow compared to either EOR or brine formations. The injection of CO{sub 2} into the oil reservoir produced a bulk density decrease in the reservoir. The spatial pattern of the change in the vertical component of gravity (G{sub z}) is directly correlated with the net change in reservoir density. Furthermore, time-lapse changes in the borehole G{sub z} clearly identified the vertical section of the reservoir where fluid saturations are changing. The CO{sub 2}-brine front, on the order of 1 km within a 20 m thick brine formation at 1900 m depth, with 30% CO{sub 2} …
Date: July 15, 2008
Creator: Gasperikova, E. & Hoversten, G.M.
Object Type: Article
System: The UNT Digital Library
Optimal Knot Selection for Least-squares Fitting of Noisy Data with Spline Functions (open access)

Optimal Knot Selection for Least-squares Fitting of Noisy Data with Spline Functions

An automatic data-smoothing algorithm for data from digital oscilloscopes is described. The algorithm adjusts the bandwidth of the filtering as a function of time to provide minimum mean squared error at each time. It produces an estimate of the root-mean-square error as a function of time and does so without any statistical assumptions about the unknown signal. The algorithm is based on least-squares fitting to the data of cubic spline functions.
Date: May 15, 2008
Creator: Blair, Jerome
Object Type: Article
System: The UNT Digital Library
Two-photon Photoemission of Organic Semiconductor Molecules on Ag(111) (open access)

Two-photon Photoemission of Organic Semiconductor Molecules on Ag(111)

Angle- and time-resolved two-photon photoemission (2PPE) was used to study systems of organic semiconductors on Ag(111). The 2PPE studies focused on electronic behavior specific to interfaces and ultrathin films. Electron time dynamics and band dispersions were characterized for ultrathin films of a prototypical n-type planar aromatic hydrocarbon, PTCDA, and representatives from a family of p-type oligothiophenes.In PTCDA, electronic behavior was correlated with film morphology and growth modes. Within a fewmonolayers of the interface, image potential states and a LUMO+1 state were detected. The degree to which the LUMO+1 state exhibited a band mass less than a free electron mass depended on the crystallinity of the layer. Similarly, image potential states were measured to have free electron-like effective masses on ordered surfaces, and the effective masses increased with disorder within the thin film. Electron lifetimes were correlated with film growth modes, such that the lifetimes of electrons excited into systems created by layer-by-layer, amorphous film growth increased by orders of magnitude by only a few monolayers from the surface. Conversely, the decay dynamics of electrons in Stranski-Krastanov systems were limited by interaction with the exposed wetting layer, which limited the barrier to decay back into the metal.Oligothiophenes including monothiophene, quaterthiophene, and …
Date: May 15, 2008
Creator: Yang, Aram & Yang, Aram
Object Type: Thesis or Dissertation
System: The UNT Digital Library
SUBSIDENCE STUDY FOR NONCRUSHABLE CONTAINERS IN SLIT TRENCHES AT THE SAVANNAH RIVER SITE (open access)

SUBSIDENCE STUDY FOR NONCRUSHABLE CONTAINERS IN SLIT TRENCHES AT THE SAVANNAH RIVER SITE

This study addresses the issue of waste and cover subsidence caused by corrosion of the non-crushable waste containers defined as containers with significant void space that will not be stabilized by dynamic compaction of the Earea Slit Trenches at the Savannah River Site. Concentrations at the hypothetical 100-m well were evaluated for 1,000 years and compared with the base case value for compliance. To generalize the results, a hypothetical, no-decay radionuclide characterized by a Kd (5 ml/g) that would be most problematic was selected. Although the non-crushable containers will not be stabilized by dynamic compaction, these containers will gradually corrode, eventually collapse after placement of the final closure cap and cause the cap to subside resulting in an increase of the infiltration rates. The vadose zone model estimated the contaminant fluxes that were input to the aquifer model for prediction of concentrations at the 100-m well. To study the potential effect of trench subsidence on the well concentrations within the 1000-year time window, two high-impact cases were considered. In the first case, trenches subsided right after dynamic compaction (i.e., at 125 years). In the second case, trenches subsided at 419 years to make the peak concentrations from both the subsided …
Date: January 15, 2008
Creator: Hang, T; Leonard Collard, L & Mark Phifer, M
Object Type: Article
System: The UNT Digital Library
The effect of temperature on the speciation of U(VI) in sulfate solutions (open access)

The effect of temperature on the speciation of U(VI) in sulfate solutions

Sulfate, one of the inorganic constituents that could be present in the nuclear waste repository, forms complexes with U(VI) and affects its migration in the environment. Results show that the complexation of U(VI) with sulfate is enhanced by the increase in temperature. The effect of temperature on the complexation and speciation of U(VI) in sulfate solutions is discussed.
Date: September 15, 2008
Creator: Rao, Linfeng & Tian, Guoxin
Object Type: Book
System: The UNT Digital Library
Japan&#39;s Residential Energy Demand Outlook to 2030 Considering Energy Efficiency Standards&quot;Top-Runner Approach&quot; (open access)

Japan&#39;s Residential Energy Demand Outlook to 2030 Considering Energy Efficiency Standards&quot;Top-Runner Approach&quot;

As one of the measures to achieve the reduction in greenhouse gas emissions agreed to in the&quot;Kyoto Protocol,&quot; an institutional scheme for determining energy efficiency standards for energy-consuming appliances, called the&quot;Top-Runner Approach,&quot; was developed by the Japanese government. Its goal is to strengthen the legal underpinnings of various energy conservation measures. Particularly in Japan&#39;s residential sector, where energy demand has grown vigorously so far, this efficiency standard is expected to play a key role in mitigating both energy demand growth and the associated CO2 emissions. This paper presents an outlook of Japan&#39;s residential energy demand, developed by a stochastic econometric model for the purpose of analyzing the impacts of the Japan&#39;s energy efficiency standards, as well as the future stochastic behavior of income growth, demography, energy prices, and climate on the future energy demand growth to 2030. In this analysis, we attempt to explicitly take into consideration more than 30 kinds of electricity uses, heating, cooling and hot water appliances in order to comprehensively capture the progress of energy efficiency in residential energy end-use equipment. Since electricity demand, is projected to exhibit astonishing growth in Japan&#39;s residential sector due to universal increasing ownership of electric and other appliances, it is …
Date: May 15, 2008
Creator: Lacommare, Kristina S H; Komiyama, Ryoichi & Marnay, Chris
Object Type: Article
System: The UNT Digital Library
Analysis of Non-Enzymatically Glycated Peptides: Neutral-Loss Triggered MS3 Versus Multi-Stage Activation Tandem Mass Spectrometry (open access)

Analysis of Non-Enzymatically Glycated Peptides: Neutral-Loss Triggered MS3 Versus Multi-Stage Activation Tandem Mass Spectrometry

Non-enzymatic glycation of tissue proteins has important implications in the development of complications of diabetes mellitus. While electron transfer dissociation (ETD) has been shown to outperform collision-induced dissociation (CID) in sequencing glycated peptides by tandem mass spectrometry, ETD instrumentation is not yet available in all laboratories. In this study, we evaluated different advanced CID techniques (i.e., neutral-loss triggered MS3 and multi-stage activation) during LC-MSn analyses of Amadori-modified peptides enriched from human serum glycated in vitro. During neutral-loss triggered MS3 experiments, MS3 scans triggered by neutral-losses of 3 H2O or 3 H2O + HCHO produced similar results in terms of glycated peptide identifications. However, neutral losses of 3 H2O resulted in significantly more glycated peptide identifications during multi-stage activation experiments. Overall, the multi-stage activation approach produced more glycated peptide identifications, while the neutral-loss triggered MS3 approach resulted in much higher specificity. Both techniques offer a viable alternative to ETD for identifying glycated peptides when that method is unavailable.
Date: October 15, 2008
Creator: Zhang, Qibin; Petyuk, Vladislav A.; Schepmoes, Athena A.; Orton, Daniel J.; Monroe, Matthew E.; Yang, Feng et al.
Object Type: Article
System: The UNT Digital Library
Modeling of Carbon Migration During JET Injection Experiments (open access)

Modeling of Carbon Migration During JET Injection Experiments

JET has performed two dedicated carbon migration experiments on the final run day of separate campaigns (2001 and 2004) using {sup 13}CH{sub 4} methane injected into repeated discharges. The EDGE2D/NIMBUS code modelled the carbon migration in both experiments. This paper describes this modelling and identifies a number of important migration pathways: (1) deposition and erosion near the injection location, (2) migration through the main chamber SOL, (3) migration through the private flux region aided by E x B drifts, and (4) neutral migration originating near the strike points. In H-Mode, type I ELMs are calculated to influence the migration by enhancing erosion during the ELM peak and increasing the long-range migration immediately following the ELM. The erosion/re-deposition cycle along the outer target leads to a multistep migration of {sup 13}C towards the separatrix which is called &#x27;walking&#x27;. This walking created carbon neutrals at the outer strike point and led to {sup 13}C deposition in the private flux region. Although several migration pathways have been identified, quantitative analyses are hindered by experimental uncertainty in divertor leakage, and the lack of measurements at locations such as gaps and shadowed regions.
Date: October 15, 2008
Creator: Strachan, J. D.; Likonen, J.; Coad, P.; Rubel, M.; Widdowson, A.; Airila, M. et al.
Object Type: Report
System: The UNT Digital Library
Final work plan: supplemental upward vapor intrusion investigation at the former CCC/USDA grain storage facility in Hanover, Kansas. (open access)

Final work plan: supplemental upward vapor intrusion investigation at the former CCC/USDA grain storage facility in Hanover, Kansas.

The Commodity Credit Corporation (CCC), an agency of the U.S. Department of Agriculture (USDA), operated a grain storage facility at the northeastern edge of the city of Hanover, Kansas, from 1950 until the early 1970s. During this time, commercial grain fumigants containing carbon tetrachloride were in common use by the grain storage industry to preserve grain in their facilities. In February 1998, trace to low levels of carbon tetrachloride (below the maximum contaminant level [MCL] of 5.0 {micro}g/L) were detected in two private wells near the former grain storage facility at Hanover, as part of a statewide USDA private well sampling program that was implemented by the Kansas Department of Health and Environment (KDHE) near former CCC/USDA facilities. In 2007, the CCC/USDA conducted near-surface soil sampling at 61 locations and also sampled indoor air at nine residences on or adjacent to its former Hanover facility to address the residents concerns regarding vapor intrusion. Low levels of carbon tetrachloride were detected at four of the nine homes. The results were submitted to the KDHE in October 2007 (Argonne 2007). On the basis of the results, the KDHE requested sub-slab sampling and/or indoor air sampling (KDHE 2007). This Work Plan describes, in …
Date: December 15, 2008
Creator: LaFreniere, L. M.
Object Type: Report
System: The UNT Digital Library
Specific interactions between arbuscular mycorrhizal fungi and plant growth-promoting bacteria--as revealed by different combinations (open access)

Specific interactions between arbuscular mycorrhizal fungi and plant growth-promoting bacteria--as revealed by different combinations

The interactions between two plant growth promoting rhizobacteria (PGPR), Pseudomonas fluorescens SBW25 and Paenibacillus brasilensis PB177, two arbuscular mycorrhizal (AM) fungi (Glomus mosseae and G. intraradices) and one pathogenic fungus (Microdochium nivale) were investigated on winter wheat (Triticum aestivum cultivar Tarso) in a greenhouse trial. PB177, but not SBW25, had strong inhibitory effects on M. nivale in dual culture plate assays. The results from the greenhouse experiment show very specific interactions; e.g. the two AM fungi react differently when interacting with the same bacteria on plants. G. intraradices (single inoculation or together with SBW25) increased plant dry weight on M. nivale infested plants, suggesting that the pathogenic fungus is counteracted by G. intraradices, but PB177 inhibited this positive effect. This is an example of two completely different reactions between the same AM fungus and two species of bacteria, previously known to enhance plant growth and inhibit pathogens. When searching for plant growth promoting microorganisms it is therefore important to test for the most suitable combination of plant, bacteria and fungi in order to get satisfactory plant growth benefits.
Date: May 15, 2008
Creator: Jaderlund, Lotta; Arthurson, Veronica; Granhall, Ulf & Jansson, Janet K.
Object Type: Article
System: The UNT Digital Library
UXO detection and identification based on intrinsic target polarizabilities: A case history (open access)

UXO detection and identification based on intrinsic target polarizabilities: A case history

Electromagnetic induction data parameterized in time dependent object intrinsic polarizabilities allow discrimination of unexploded ordnance (UXO) from false targets (scrap metal). Data from a cart-mounted system designed for discrimination of UXO with 20 mm to 155 mm diameters are used. Discrimination of UXO from irregular scrap metal is based on the principal dipole polarizabilities of a target. A near-intact UXO displays a single major polarizability coincident with the long axis of the object and two equal smaller transverse polarizabilities, whereas metal scraps have distinct polarizability signatures that rarely mimic those of elongated symmetric bodies. Based on a training data set of known targets, object identification was made by estimating the probability that an object is a single UXO. Our test survey took place on a military base where both 4.2-inch mortar shells and scrap metal were present. The results show that we detected and discriminated correctly all 4.2-inch mortars, and in that process we added 7%, and 17%, respectively, of dry holes (digging scrap) to the total number of excavations in two different survey modes. We also demonstrated a mode of operation that might be more cost effective than the current practice.
Date: July 15, 2008
Creator: Gasperikova, E.; Smith, J.T.; Morrison, H.F.; Becker, A. & Kappler, K.
Object Type: Article
System: The UNT Digital Library
Poroelastic modeling of fracture-seismic wave interaction (open access)

Poroelastic modeling of fracture-seismic wave interaction

Rock containing a compliant, fluid-filled fracture can be viewed as one case of heterogeneous poroelastic media. When this fracture is subjected to seismic waves, a strong contrast in the elastic stiffness between the fracture itself and the background can result in enhanced grain-scale local fluid flow. Because this flow--relaxing the pressure building up within the fracture--can increase the dynamic compliance of the fracture and change energy dissipation (attenuation), the scattering of seismic waves can be enhanced. Previously, for a flat, infinite fracture, we derived poroelastic seismic boundary conditions that describe the relationship between a finite jump in the stress and displacement across a fracture, expressed as a function of the stress and displacement at the boundaries. In this paper, we use these boundary conditions to determine frequency-dependent seismic wave transmission and reflection coefficients. Fluid-filled fractures with a range of mechanical and hydraulic properties are examined. From parametric studies, we found that the hydraulic permeability of a fracture fully saturated with water has little impact on seismic wave scattering. In contrast, the seismic response of a partially water-saturated fracture and a heterogeneous fracture filled with compliant liquid (e.g., supercritical CO{sub 2}) depended on the fracture permeability.
Date: August 15, 2008
Creator: Nakagawa, Seiji
Object Type: Article
System: The UNT Digital Library
Characterization of Surplus Plutonium for Disposition Options (open access)

Characterization of Surplus Plutonium for Disposition Options

The United States (U.S.) has identified 61.5 metric tons (MT) of plutonium that is permanently excess to use in nuclear weapons programs, including 47.2 MT of weapons-grade plutonium. Except for materials that remain in use for programs outside of national defense, including programs for nuclear-energy development, the surplus inventories will be stored safely by the Department of Energy (DOE) and then transferred to facilities that will prepare the plutonium for permanent disposition. Some items will be disposed as transuranic waste, low-level waste, or spent fuel. The remaining surplus plutonium will be managed through: (1) the Mixed Oxide (MOX) Fuel Fabrication Facility (FFF), to be constructed at the Savannah River Site (SRS), where the plutonium will be converted to fuel that will be irradiated in civilian power reactors and later disposed to a high-level waste (HLW) repository as spent fuel; (2) the SRS H-Area facilities, by dissolving and transfer to HLW systems, also for disposal to the repository; or (3) alternative immobilization techniques that would provide durable and secure disposal. From the beginning of the U.S. program for surplus plutonium disposition, DOE has sponsored research to characterize the surplus materials and to judge their suitability for planned disposition options. Because many …
Date: July 15, 2008
Creator: Allender, Jeffrey S.; Moore, Edwin N. & Davies, Scott H.
Object Type: Article
System: The UNT Digital Library
Attenuated Vector Tomography -- An Approach to Image Flow Vector Fields with Doppler Ultrasonic Imaging (open access)

Attenuated Vector Tomography -- An Approach to Image Flow Vector Fields with Doppler Ultrasonic Imaging

The measurement of flow obtained using continuous wave Doppler ultrasound is formulated as a directional projection of a flow vector field. When a continuous ultrasound wave bounces against a flowing particle, a signal is backscattered. This signal obtains a Doppler frequency shift proportional to the speed of the particle along the ultrasound beam. This occurs for each particle along the beam, giving rise to a Doppler velocity spectrum. The first moment of the spectrum provides the directional projection of the flow along theultrasound beam. Signals reflected from points further away from the detector will have lower amplitude than signals reflected from points closer to the detector. The effect is very much akin to that modeled by the attenuated Radon transform in emission computed tomography.A least-squares method was adopted to reconstruct a 2D vector field from directional projection measurements. Attenuated projections of only the longitudinal projections of the vector field were simulated. The components of the vector field were reconstructed using the gradient algorithm to minimize a least-squares criterion. This result was compared with the reconstruction of longitudinal projections of the vector field without attenuation. Ifattenuation is known, the algorithm was able to accurately reconstruct both components of the full vector …
Date: May 15, 2008
Creator: Huang, Qiu; Peng, Qiyu; Huang, Bin; Cheryauka, Arvi & Gullberg, Grant T.
Object Type: Report
System: The UNT Digital Library
Correlations and Fluctuations: Status and Perspectives (open access)

Correlations and Fluctuations: Status and Perspectives

We will provide an overview of the physics which can be addressed by studying fluctuations and correlations in heavy ion collisions. Observables, which have been discussed in the literature will be briefly reviewed and put in context with experiment and information from Lattice QCD. Special attention will be given to the QCD critical point and the first order co-existence region.
Date: April 15, 2008
Creator: Koch, Volker & Koch, Volker
Object Type: Article
System: The UNT Digital Library
Test of the consistency of various linearized semiclassical initial value time correlation functions in application to inelastic neutron scattering from liquid para-hydrogen (open access)

Test of the consistency of various linearized semiclassical initial value time correlation functions in application to inelastic neutron scattering from liquid para-hydrogen

The linearized approximation to the semiclassical initial value representation (LSC-IVR) is used to calculate time correlation functions relevant to the incoherent dynamic structure factor for inelastic neutron scattering from liquid para-hydrogen at 14 K. Various time correlations functions were used which, if evaluated exactly, would give identical results, but they do not because the LSC-IVR is approximate. Some of the correlation functions involve only linear operators, and others involve non-linear operators. The consistency of the results obtained with the various time correlation functions thus provides a useful test of the accuracy of the LSC-IVR approximation and its ability to treat correlation functions involving both linear and nonlinear operators in realistic anharmonic systems. The good agreement of the results obtained from different correlation functions, their excellent behavior in the spectral moment tests based on the exact moment constraints, and their semi-quantitative agreement with the inelastic neutron scattering experimental data all suggest that the LSC-IVR is indeed a good short-time approximation for quantum mechanical correlation functions.
Date: March 15, 2008
Creator: Miller, William; Liu, Jian & Miller, William H.
Object Type: Article
System: The UNT Digital Library
Temperature dependence of the interface moments in Co2MnSi thin films (open access)

Temperature dependence of the interface moments in Co2MnSi thin films

X-ray magnetic circular dichroism (XMCD) is utilized to explore the temperature dependence of the interface moments in Co{sub 2}MnSi (CMS) thin films capped with aluminium. By increasing the thickness of the capping layer we demonstrate enhanced interface sensitivity of the measurements and the existence of a thin Mn oxide layer at the CMS/Al interface even when a thick capping layer is used. We show that for well ordered L2{sub 1} CMS films there is no significant variation in either the Co or Mn interface moments as a function of temperature. However, a dramatic reduction in the interface moments at low temperature is observed in a disordered CMS film that is likely to be caused by increased Mn-Mn antiferromagnetic coupling. It is suggested that for ordered L2{sub 1} CMS films the temperature dependence of the tunneling magnetoresistance is not related to changes in the interface moments. However, the existence of residual Mn oxide at the CMS/barrier interface could be a contributing factor.
Date: March 15, 2008
Creator: Arenholz, Elke; Telling, N.; Keatley, P.; Shelford, L.; Arenholz, E.; van der Laan, G. et al.
Object Type: Article
System: The UNT Digital Library
Measurements of Branching Fractions for B+ -> rho+ gamma, B0 -> rho0 gamma, and B0 -> omega gamma (open access)

Measurements of Branching Fractions for B+ -> rho+ gamma, B0 -> rho0 gamma, and B0 -> omega gamma

The authors present branching fraction measurements for the radiative decays B{sup +} {yields} {rho}{sup +}{gamma}, B{sup 0} {yields} {rho}{sup 0}{gamma}, and B{sup 0} {yields} {omega}{gamma}. The analysis is based on a data sample of 465 million B{bar B} events collected with the BABAR detector at the PEP-II asymmetric-energy B Factory located at the Stanford Linear Accelerator Center (SLAC). They find {Beta}(B{sup +} {yields} {rho}{sup +}{gamma}) = (1.20{sub -0.37}{sup +0.42} {+-} 0.20) x 10{sup -6}, {Beta}(B{sup 0} {yields} {rho}{sup 0}{gamma}) = (0.97{sub -0.22}{sup +0.24} {+-} 0.06) x 10{sup -6}, and a 90% C.L. upper limit {Beta}(B{sup 0} {yields} {omega}{gamma}) &lt; 0.9 x 10{sup -6}, where the first error is statistical and the second is systematic. They also measure the isospin-violating quantity {Lambda}(B{sup +} {yields} {rho}{sup +}{gamma})/2{Lambda}(B{sup 0} {yields} {rho}{sup 0}{gamma}) - 1 = -0.43{sub -0.22}{sup +0.25} {+-} 0.10.
Date: August 15, 2008
Creator: Aubert, B.
Object Type: Article
System: The UNT Digital Library