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ENSO Simulation in Coupled Ocean-Atmosphere Models: Are the Current Models Better? (open access)

ENSO Simulation in Coupled Ocean-Atmosphere Models: Are the Current Models Better?

Maintaining a multi-model database over a generation or more of model development provides an important framework for assessing model improvement. Using control integrations, we compare the simulation of the El Nino/Southern Oscillation (ENSO), and its extratropical impact, in models developed for the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report with models developed in the late 1990's (the so-called Coupled Model Intercomparison Project-2 [CMIP2] models). The IPCC models tend to be more realistic in representing the frequency with which ENSO occurs, and they are better at locating enhanced temperature variability over the eastern Pacific Ocean. When compared with reanalyses, the IPCC models have larger pattern correlations of tropical surface air temperature than do the CMIP2 models during the boreal winter peak phase of El Nino. However, for sea-level pressure and precipitation rate anomalies, a clear separation in performance between the two vintages of models is not as apparent. The strongest improvement occurs for the modeling groups whose CMIP2 model tended to have the lowest pattern correlations with observations. This has been checked by subsampling the multi-century IPCC simulations in a manner to be consistent with the single 80-year time segment available from CMIP2. Our results suggest that multi-century …
Date: April 29, 2005
Creator: AchutaRao, K. & Sperber, K. R.
System: The UNT Digital Library
Incident Energy Dependence of pt Correlations at RHIC (open access)

Incident Energy Dependence of pt Correlations at RHIC

We present results for two-particle transverse momentum correlations, ({Delta}p{sub t,i}{Delta}p{sub t,j}), as a function of event centrality for Au+Au collisions at {radical}s{sub NN} = 20, 62, 130, and 200 GeV at the Relativistic Heavy Ion Collider. We observe correlations decreasing with centrality that are similar at all four incident energies. The correlations multiplied by the multiplicity density increase with incident energy and the centrality dependence may show evidence of processes such as thermalization, jet production, or the saturation of transverse flow. The square root of the correlations divided by the event-wise average transverse momentum per event shows little or no beam energy dependence and generally agrees with previous measurements at the Super Proton Synchrotron.
Date: April 29, 2005
Creator: Adams, J.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D.; Arkhipkin, D. et al.
System: The UNT Digital Library
Cathodic Arcs: Fractal Voltage and Cohesive Energy Rule (open access)

Cathodic Arcs: Fractal Voltage and Cohesive Energy Rule

This report talks about Cathodic Arcs: Fractal Voltage and Cohesive Energy Rule
Date: January 29, 2005
Creator: Anders, Andre; Oks, Efim M. & Gera, Yu. Yushkov
System: The UNT Digital Library
MICRON-SCALE DEEP HOLE DRILLING FOR BERYLLIUM CAPSULE FILL APPLICATIONS (open access)

MICRON-SCALE DEEP HOLE DRILLING FOR BERYLLIUM CAPSULE FILL APPLICATIONS

A laser processing system has been developed to drill high aspect ratio holes through the impermeable beryllium capsules envisioned for ignition shots on NIF. The drilling system was designed to produce holes with an entrance and exit diameter of approximately 5 {micro}m through the full 175 {micro}m thickness of the capsule. To meet these requirements, a frequency doubled femtosecond-class Ti:Sapphire laser is directed through a high numerical aperture lens to provide the spot geometry needed to drill the hole. The laser pulse is confined by the metallic walls of the hole, thereby maintaining the diameter of the channel well beyond the Rayleigh range of the optical system. Presented is the current state of this work-in-progress, including descriptions of the device and the technique used to produce the holes. The various means of characterizing the laser-drilled channels are also discussed.
Date: November 29, 2005
Creator: Armstrong, J P; Rubenchik, A M; Gunther, J & Stuart, B C
System: The UNT Digital Library
Modified borohydrides for reversible hydrogen storage (open access)

Modified borohydrides for reversible hydrogen storage

In attempt to develop lithium borohydrides as the reversible hydrogen storage materials with the high capacity, the feasibility to reduce dehydrogenation temperature of the lithium borohydride and moderate rehydrogenation condition has been explored. The commercial available lithium borohydride has been modified by ball milling with metal oxides and metal chlorides as the additives. The modified lithium borohydrides release 9 wt% hydrogen starting from 473K. The dehydrided modified lithium borohydrides absorb 7-9 wt% hydrogen at 873K and 7 MPa. The additive modification reduces dehydriding temperature from 673K to 473K and moderates rehydrogenation conditions to 923K and 15 MPa. XRD and SEM analysis discovered the formation of the intermediate compound TiB{sub 2} that may plays the key role in change the reaction path resulting the lower dehydriding temperature and reversibility. The reversible hydrogen storage capacity of the oxide modified lithium borohydrides decreases gradually during hydriding-dehydriding cycling due to the lost of the boron during dehydrogenation. But, it can be prevented by selecting the suitable additive, forming intermediate boron compounds and changing the reaction path. The additives reduce dehydriding temperature and improve the reversibility, it also reduces the hydrogen storage capacity. The best compromise can be reached by optimization of the additive loading …
Date: August 29, 2005
Creator: Au, Ming
System: The UNT Digital Library
Branching Fraction for B+ -> pi0 l+ nu, Measured in Upsilon (4S) -> BBbar Events Tagged by B- -> D0 l- nubar (X) Decays (open access)

Branching Fraction for B+ -> pi0 l+ nu, Measured in Upsilon (4S) -> BBbar Events Tagged by B- -> D0 l- nubar (X) Decays

We report a preliminary branching fraction of (1.80 {+-} 0.37{sub stat.} {+-} 0.23{sub syst.}) x 10{sup -4} for the charmless exclusive semileptonic B{sup +} {yields} {pi}{sup 0}{ell}{sup +}{nu} decay, where {ell} can be either a muon or an electron. This result is based on data corresponding to an integrated luminosity of 81 fb{sup -1} collected at the {Upsilon}(4S) resonance with the BABAR detector. The analysis uses B{bar B} events that are tagged by a B meson reconstructed in the semileptonic B{sup -} {yields} D{sup 0}{ell}{sup -}{bar {nu}}(X) decays, where X can be either a {gamma} or a {pi}{sup 0} from a D* decay.
Date: June 29, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
System: The UNT Digital Library
Branching Fraction for B0 -> pi- l+ nu and Determination of |Vub| in Upsilon(4S) -> B0 B0bar Events Tagged by B0bar -> D(*)+ l- nubar (open access)

Branching Fraction for B0 -> pi- l+ nu and Determination of |Vub| in Upsilon(4S) -> B0 B0bar Events Tagged by B0bar -> D(*)+ l- nubar

We report preliminary results from a study of the charmless exclusive semileptonic decay B{sup 0} {yields} {pi}{sup -}{ell}{sup +}{nu} based on the data collected at the {Upsilon}(4S) resonance using the BABAR detector at SLAC. The analysis uses events in which the signal B meson recoils against a B meson that has been reconstructed in a semileptonic decay {bar B}{sup 0} {yields} D{sup (*)+}{ell}{sup -}{bar {nu}}. We extract the total branching fraction {Beta}(B{sup 0} {yields} {pi}{sup -}{ell}{sup +}{nu}) = (1.03 {+-} 0.25{sub stat.} {+-} 0.13{sub syst.}) x 10{sup -4} and the partial branching fractions in three bins of q{sup 2}, the invariant mass squared of the lepton-neutrino system. From the partial branching fractions and theoretical predictions for the form factors, we determine the magnitude of the CKM matrix element |V{sub ub}|. We find |V{sub ub}| = (3.3 {+-} 0.4{sub stat.} {+-} 0.2{sub syst.} {sub -0.4}{sup +0.8}FF) x 10{sup -3}, where the last error is due to normalization of the form factor.
Date: June 29, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
System: The UNT Digital Library
Measurement of Double Charmonium Production in$e^+e^-$ Annihilations at $\sqrt{s}=10.6$ GeV (open access)

Measurement of Double Charmonium Production in$e^+e^-$ Annihilations at $\sqrt{s}=10.6$ GeV

The authors study e{sup +}e{sup -} {yields} J/{psi} c{bar c} by measuring the invariant mass distribution recoiling against fully reconstructed J/{psi} decays, using 124.4 fb{sup -1} of data collected with a center-of-mass energy of 10.6 GeV with the BABAR detector. They observe signals for {eta}{sub c}(1S), {chi}{sub c0}, and {eta}{sub c}(2S) in the recoil mass distribution, thus confirming previous measurements. The authors measure {sigma}(e{sup +}e{sup -} {yields} J/{psi} + c{bar c}){Beta}(c{bar c} {yields} > 2 charged) to be 17.6 {+-} 2.8(stat){sub -2.1}{sup +1.5}(syst) fb, 10.3 {+-} 2.5(stat){sub -1.8}{sup +1.4}(syst) fb, and 16.4 {+-} 3.7(stat){sub -3.0}{sup +2.4}(syst) fb with c{bar c} = {eta}{sub c}(1S), {chi}{sub c0}, and {eta}{sub c}(2S), respectively.
Date: June 29, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
System: The UNT Digital Library
Measurement of the B+- --> rho+- pi0 Branching Fraction and Direct CP Asymmetry (open access)

Measurement of the B+- --> rho+- pi0 Branching Fraction and Direct CP Asymmetry

An improved measurement of the process B{sup {+-}} {yields} {rho}{sup {+-}}{pi}{sup 0} is presented. The data sample of 211 fb{sup -1} comprises 232 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. The yield and CP asymmetry are calculated using an extended maximum likelihood fitting method. The branching fraction and asymmetry are found to be {Beta}(B{sup {+-}} {yields} {rho}{sup {+-}}{pi}{sup 0}) = [10.0 {+-} 1.4 (Stat.) {+-} 0.9 (Syst.)] x 10{sup -6} and {Alpha}{sub CP}(B{sup {+-}} {yields} {rho}{sup {+-}}{pi}{sup 0}) = -0.01 {+-} 0.13 (Stat.) {+-} 0.02 (Syst.), superseding previous measurements. The statistical significance of the signal is calculated to be 8.7{sigma}.
Date: June 29, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
System: The UNT Digital Library
Search for Lepton-Flavor and Lepton-Number Violation in the Decay tau to lhh' (open access)

Search for Lepton-Flavor and Lepton-Number Violation in the Decay tau to lhh'

A search for lepton-flavor and lepton-number violation in the decay of the tau lepton into one charged lepton and two charged hadrons is performed using 221.4 fb{sup -1} of data collected at an e{sup +}e{sup -} center-of-mass energy of 10.58 GeV with the BABAR detector at the PEP-II storage ring. In all 14 decay modes considered, the observed data are compatible with background expectations, and upper limits are set in the range {Beta}({tau} {yields} {ell}hh') < (0.7-4.8) x 10{sup -7} at 90% confidence level.
Date: June 29, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
System: The UNT Digital Library
Graph-based Methods for Orbit Classification (open access)

Graph-based Methods for Orbit Classification

An important step in the quest for low-cost fusion power is the ability to perform and analyze experiments in prototype fusion reactors. One of the tasks in the analysis of experimental data is the classification of orbits in Poincare plots. These plots are generated by the particles in a fusion reactor as they move within the toroidal device. In this paper, we describe the use of graph-based methods to extract features from orbits. These features are then used to classify the orbits into several categories. Our results show that existing machine learning algorithms are successful in classifying orbits with few points, a situation which can arise in data from experiments.
Date: September 29, 2005
Creator: Bagherjeiran, A. & Kamath, C.
System: The UNT Digital Library
Russian Military and Security Forces: A Postulated Reaction to a Nuclear Detonation (open access)

Russian Military and Security Forces: A Postulated Reaction to a Nuclear Detonation

In this paper, we will examine how Russia's military and security forces might react to the detonation of a 10-kiloton nuclear weapon placed next to the walls surrounding the Kremlin. At the time of this 'big bang,' Putin is situated outside Moscow and survives the explosion. No one claims responsibility for the detonation. No other information is known. Numerous variables will determine how events ultimately unfold and how the military and security forces will respond. Prior to examining these variables in greater detail, it is imperative to elucidate first what we mean by Russia's military and security forces.
Date: April 29, 2005
Creator: Ball, D
System: The UNT Digital Library
Proceedings of the Workshop on Accelerator Driven High Energy Density Physics (open access)

Proceedings of the Workshop on Accelerator Driven High Energy Density Physics

None
Date: April 29, 2005
Creator: Barnard, J J
System: The UNT Digital Library
Hands-on lessons in ergonomics for youth (open access)

Hands-on lessons in ergonomics for youth

Ergonomics risk factors apply to everybody. Numerous adults have experienced disabling injuries related to use of computers and other forms of technology. Now children are using technology even more than adults. Increasingly ergonomics risk factors are being recognized as present in the world of children. Outreach to schools and the surrounding community by employers may help protect the future work force. A growing body of researchers believe that children can benefit from the early introduction of ergonomics awareness and preventative measures. While individual representatives of the educational system may embrace the concept of introducing ergonomics into the classroom, a number of barriers can prevent implementation of integrated programs. Some of the barriers to introducing ergonomics in schools have been absence of a tie to educational standards, the existing demands on teaching hours, and the absence of easily executable lesson plans. Ergonomics is rarely included in teacher training and professional ergonomics expertise is needed for the development of a class-based program. As part of Strategic Vision plan for 2025, a National Laboratory identified community outreach and the future workforces as key areas for initiatives. A series of hands-on interactive modules have been developed by professional ergonomics specialists. They are being tested …
Date: September 29, 2005
Creator: Bennett, C; Alexandre, M & Jacobs, K
System: The UNT Digital Library
High Order Finite Volume Nonlinear Schemes for the Boltzmann Transport Equation (open access)

High Order Finite Volume Nonlinear Schemes for the Boltzmann Transport Equation

The authors apply the nonlinear WENO (Weighted Essentially Nonoscillatory) scheme to the spatial discretization of the Boltzmann Transport Equation modeling linear particle transport. The method is a finite volume scheme which ensures not only conservation, but also provides for a more natural handling of boundary conditions, material properties and source terms, as well as an easier parallel implementation and post processing. It is nonlinear in the sense that the stencil depends on the solution at each time step or iteration level. By biasing the gradient calculation towards the stencil with smaller derivatives, the scheme eliminates the Gibb's phenomenon with oscillations of size O(1) and reduces them to O(h{sup r}), where h is the mesh size and r is the order of accuracy. The current implementation is three-dimensional, generalized for unequally spaced meshes, fully parallelized, and up to fifth order accurate (WENO5) in space. For unsteady problems, the resulting nonlinear spatial discretization yields a set of ODE's in time, which in turn is solved via high order implicit time-stepping with error control. For the steady-state case, they need to solve the non-linear system, typically by Newton-Krylov iterations. There are several numerical examples presented to demonstrate the accuracy, non-oscillatory nature and efficiency …
Date: March 29, 2005
Creator: Bihari, B L & Brown, P N
System: The UNT Digital Library
ELECTROKINETIC WAVE PHENOMENA IN FLUID-SATURATED GRANULAR MEDIA (open access)

ELECTROKINETIC WAVE PHENOMENA IN FLUID-SATURATED GRANULAR MEDIA

Electrokinetic (EK) phenomena in sediments arise from relative fluid motion in the pore space, which perturbs the electrostatic equilibrium of the double layer at the grain surface. We have developed EK techniques in the laboratory to monitor acoustic wave propagation in electrolyte-saturated, unconsolidated sediments. Our experimental results indicate that as an acoustic wave travels through electrolyte-saturated sand, it can generate electric potentials greater than 1 mV. A careful study of these potentials was performed using medium-grain sand and loose glass microspheres for a range of pore fluid salinities and ultrasonic frequencies. Experimental results are also shown to compare well with numerical and analytical modeling based on the coupled electrokinetic-Biot theory developed by Pride (1994).
Date: March 29, 2005
Creator: Block, G
System: The UNT Digital Library
Resolving the tips of the tree of life: How much mitochondrialdata doe we need? (open access)

Resolving the tips of the tree of life: How much mitochondrialdata doe we need?

Mitochondrial (mt) DNA sequences are used extensively to reconstruct evolutionary relationships among recently diverged animals,and have constituted the most widely used markers for species- and generic-level relationships for the last decade or more. However, most studies to date have employed relatively small portions of the mt-genome. In contrast, complete mt-genomes primarily have been used to investigate deep divergences, including several studies of the amount of mt sequence necessary to recover ancient relationships. We sequenced and analyzed 24 complete mt-genomes from a group of salamander species exhibiting divergences typical of those in many species-level studies. We present the first comprehensive investigation of the amount of mt sequence data necessary to consistently recover the mt-genome tree at this level, using parsimony and Bayesian methods. Both methods of phylogenetic analysis revealed extremely similar results. A surprising number of well supported, yet conflicting, relationships were found in trees based on fragments less than {approx}2000 nucleotides (nt), typical of the vast majority of the thousands of mt-based studies published to date. Large amounts of data (11,500+ nt) were necessary to consistently recover the whole mt-genome tree. Some relationships consistently were recovered with fragments of all sizes, but many nodes required the majority of the mt-genome …
Date: April 29, 2005
Creator: Bonett, Ronald M.; Macey, J. Robert; Boore, Jeffrey L. & Chippindale, Paul T.
System: The UNT Digital Library
Stability Studies of Transition-Metal Linkage Isomers Using Quantum Mechanical Methods, Groups 11 and 12 Transition Metals (open access)

Stability Studies of Transition-Metal Linkage Isomers Using Quantum Mechanical Methods, Groups 11 and 12 Transition Metals

Article discussing the stability studies of transition-metal linkage isomers using quantum mechanical methods and groups 11 and 12 transition metals.
Date: April 29, 2005
Creator: Buda, Corneliu; Kazi, Abul B.; Dinescu, Adriana & Cundari, Thomas R., 1964-
System: The UNT Digital Library
Current Status of Deep Geological Repository Development (open access)

Current Status of Deep Geological Repository Development

This talk provided an overview of the current status of deep-geological-repository development worldwide. Its principal observation is that a broad consensus exists internationally that deep-geological disposal is the only long-term solution for disposition of highly radioactive nuclear waste. Also, it is now clear that the institutional and political aspects are as important as the technical aspects in achieving overall progress. Different nations have taken different approaches to overall management of their highly radioactive wastes. Some have begun active programs to develop a deep repository for permanent disposal: the most active such programs are in the United States, Sweden, and Finland. Other countries (including France and Russia) are still deciding on whether to proceed quickly to develop such a repository, while still others (including the UK, China, Japan) have affirmatively decided to delay repository development for a long time, typically for a generation of two. In recent years, a major conclusion has been reached around the world that there is very high confidence that deep repositories can be built, operated, and closed safely and can meet whatever safety requirements are imposed by the regulatory agencies. This confidence, which has emerged in the last few years, is based on extensive work around …
Date: August 29, 2005
Creator: Budnitz, R. J.
System: The UNT Digital Library
Deducing the 237U(n,f) cross-section using the Surrogate Ratio Method (open access)

Deducing the 237U(n,f) cross-section using the Surrogate Ratio Method

The authors have deduced the cross section for {sup 237}U(n,f) over an equivalent neutron energy range from 0 to 20 MeV using the Surrogate Ratio method. A 55 MeV {sup 4}He beam from the 88 Inch Cyclotron at Lawrence Berkeley National Laboratory was used to induce fission in the following reactions: {sup 238}U({alpha},{alpha}{prime}f) and {sup 236}U({alpha},{alpha}{prime}f). The {sup 238}U reaction was a surrogate for {sup 237}U(n,f) and the {sup 236}U reaction was used as a surrogate for {sup 235}U(n,f). Scattered alpha particles were detected in a fully depleted segmented silicon telescope array (STARS) over an angle range of 35{sup o} to 60{sup o} with respect to the beam axis. The fission fragments were detected in a third independent silicon detector located at backward angles between 106{sup o} and 131{sup o}.
Date: December 29, 2005
Creator: Burke, J. T.; Bernstein, L. A.; Escher, J.; Ahle, L.; Church, J. A.; Dietrich, F. S. et al.
System: The UNT Digital Library
The BaBar Level 1 Drift-Chamber Trigger Upgrade With 3D Tracking (open access)

The BaBar Level 1 Drift-Chamber Trigger Upgrade With 3D Tracking

At BABAR, the Level 1 Drift Chamber trigger is being upgraded to reduce increasing background rates while the PEP-II luminosity keeps improving. This upgrade uses the drift time information and stereo wires in the drift chamber to perform a 3D track reconstruction that effectively rejects background events spread out along the beam line.
Date: November 29, 2005
Creator: Chai, X. D.
System: The UNT Digital Library
Spin Orbit Effects and Superconductivity in Oxide Materials (open access)

Spin Orbit Effects and Superconductivity in Oxide Materials

In a variety of materials superconductivity is associated with the existence of a quantum critical point (QCP). In the case of the hole doped cuprates there is evidence which suggests that the important quantum degrees of freedom near the superconducting critical point are localized charge and spin density fluctuations. We argue that if these degrees of freedom are strongly coupled by spin-orbit interactions, a new type of quantum criticality arises with monopole-like quasi-particles as the important quantum degrees of freedom,. In layered material this type of quantum criticality can be modeled using a 2-dimensional non-linear Schrodinger equation with an SU(N) gauge field. We exhibit a pairing wave function for quasi-particles that has topological order and anisotropic properties. The superconducting transition would in some respects resemble a KT transition.
Date: September 29, 2005
Creator: Chapline, G F
System: The UNT Digital Library
Charm Physics at BaBar (open access)

Charm Physics at BaBar

Large production of the c{bar c} pairs and high integrated luminosity make the PEPII B Factory an excellent place for studying the charm hadrons. In this paper, we present a few most recent results from BaBar collaboration in charm sector.
Date: June 29, 2005
Creator: Chen, Chunhui
System: The UNT Digital Library
Changing Perspectives on Nonproliferation and Nuclear Fuel Cycles (open access)

Changing Perspectives on Nonproliferation and Nuclear Fuel Cycles

The concepts of international control over technologies and materials in the proliferation sensitive parts of the nuclear fuel cycle, specifically those related to enrichment and reprocessing, have been the subject of many studies and initiatives over the years. For examples: the International Fissionable Material Storage proposal in President Eisenhower's Speech on Atoms for Peace, and in the Charter of the International Atomic Energy Agency (IAEA) when the organization was formed in 1957; the regional nuclear fuel cycle center centers proposed by INFCE in the 80's; and most recently and notably, proposals by Dr. ElBaradei, the Director General of IAEA to limit production and processing of nuclear weapons usable materials to facilities under multinational control; and by U.S. President George W. Bush, to limit enrichment and reprocessing to States that have already full scale, functioning plants. There are other recent proposals on this subject as well. In this paper, the similarities and differences, as well as the effectiveness and challenges in proliferation prevention of these proposals and concepts will be discussed. The intent is to articulate a ''new nuclear regime'' and to develop concrete steps to implement such regime for future nuclear energy and deployment.
Date: March 29, 2005
Creator: Choi, J & Isaacs, T H
System: The UNT Digital Library