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Half-life of 14O (open access)

Half-life of 14O

We have measured the half-life of 14O, a superallowed (0+\rightarrow 0+) \beta decay isotope. The 14O was produced by the12C(3He,n)14O reaction using a carbon aerogel target. A low-energy ionbeam of 14O was mass separated and implanted in a thin beryllium foil.The beta particles were counted with plastic scintillator detectors. Wefind \tau 1/2 = 70.696 +- 0.037\sigma. This result is 2.0\sigma higherthan an average value from six earlier experiments, but agrees moreclosely with the most recent previous measurment.
Date: January 11, 2006
Creator: Burke, Jason T.; Vetter, Paul A.; Freedman, Stuart J.; Fujikawa,Brian K. & Winter, Wesley T.
System: The UNT Digital Library
Real-Time Quadrupole Mass Spectrometer Analysis of Gas in Borehole Fluid Samples Acquired Using the U-Tube Sampling Methodology (open access)

Real-Time Quadrupole Mass Spectrometer Analysis of Gas in Borehole Fluid Samples Acquired Using the U-Tube Sampling Methodology

Sampling of fluids in deep boreholes is challenging becauseof the necessity to minimize external contamination and maintain sampleintegrity during recovery. The U-tube sampling methodology was developedto collect large volume, multiphase samples at in situ pressures. As apermanent or semi-permanent installation, the U-tube can be used forrapidly acquiring multiple samples or it may be installed for long-termmonitoring applications. The U-tube was first deployed in Liberty County,TX to monitor crosswell CO2 injection as part of the Frio CO2sequestration experiment. Analysis of gases (dissolved or separate phase)was performed in the field using a quadrupole mass spectrometer, whichserved as the basis for determining the arrival of the CO2 plume. Thepresence of oxygen and argon in elevated concentrations, along withreduced methane concentration, indicate sample alteration caused by theintroduction of surface fluids during borehole completion. Despiteproducing the well to eliminate non-native fluids, measurementsdemonstrate that contamination persists until the immiscible CO2injection swept formation fluid into the observationwellbore.
Date: January 11, 2006
Creator: Freifeld, Barry M. & Trautz, Robert C.
System: The UNT Digital Library
Evidence of gating in hundred nanometer diameter pores: an experimental and theoretical study (open access)

Evidence of gating in hundred nanometer diameter pores: an experimental and theoretical study

We report on the observation of an unexpected gating mechanism at the 100 nm scale on track-etched polycarbonate membranes. Transport measurements of methyl viologen performed by absorption spectroscopy under various pH conditions demonstrated that perfect gating was achieved for 100 nm diameter pores at pH 2, while the positively charged molecular ions moved through the membrane according to diffusion laws at pH 5. An oppositely charged molecular ion, naphthalene disulfonate, in the same membrane, showed the opposite trend: diffusion of the negative ion at pH 2 and perfect gating at pH 5. The influence of parameters such as ionic strength and membrane surface coating were also investigated. A theoretical study of the system shows that at this larger length scale the magnitude of the electric field in the vicinity of the pores is too small to account for the experimental observations, rather, it is the surface trapping of the mobile ion (Cl{sup -} or Na{sup +}) which gives rise to the gating phenomena. This surprising effect might have potential applications for high-throughput separation of large molecules and bio-organisms.
Date: January 11, 2006
Creator: Letant, S. E.; Schaldach, C. M.; Johnson, M. R.; Sawvel, A.; Bourcier, W. L. & Wilson, W. D.
System: The UNT Digital Library
Lightning Protection Certification for High Explosives Facilities at Lawrence Livermore National Laboratory (open access)

Lightning Protection Certification for High Explosives Facilities at Lawrence Livermore National Laboratory

Presented here is an innovation in lighting safety certification, and a description of its implementation for high explosives processing and storage facilities at Lawrence Livermore National Laboratory. Lightning rods have proven useful in the protection of wooden structures; however, modern structures made of rebar, concrete, and the like, require fresh thinking. Our process involves a rigorous and unique approach to lightning safety for modern buildings, where the internal voltages and currents are quantified and the risk assessed. To follow are the main technical aspects of lightning protection for modern structures and these methods comply with the requirements of the National Fire Protection Association, the National Electrical Code, and the Department of Energy [1][2]. At the date of this release, we have certified over 70 HE processing and storage cells at our Site 300 facility.
Date: January 11, 2006
Creator: Clancy, T. J.; Brown, C. G.; Ong, M. M. & Clark, G. A.
System: The UNT Digital Library
BaBar: sin(2beta+gamma) (open access)

BaBar: sin(2beta+gamma)

The time-dependent CP asymmetries in fully reconstructed B{sup 0} {yields} D{sup (*){+-}}{pi}{sup {-+}}/{rho}{sup {-+}} decays (new preliminary result), and in partially reconstructed B{sup 0} {yields} D{sup (*){+-}}{pi}{sup {-+}} decays, are measured with the BABAR detector at the PEP-II asymmetric B factory at SLAC, using 232 million {Upsilon}(4S) {yields} B{bar B} decays. We combine the above results and, using other measurements and theoretical assumptions, they interpret them in terms of the angles of the unitarity triangle describing the Cabibbo-Kobayashi-Maskawa matrix. They find |sin(2{beta} + {gamma})| > 0.64(0.42) at 68%(90%) confidence level using a frequentistic approach and |2{beta}+ {gamma}| = (90 {+-} 43){sup o} using a Bayesian approach.
Date: January 11, 2006
Creator: Voena, Cecilia
System: The UNT Digital Library
AGN Feedback And Evolution of Radio Sources: Discovery of An X-Ray Cluster Associated With Z=1 Quasar (open access)

AGN Feedback And Evolution of Radio Sources: Discovery of An X-Ray Cluster Associated With Z=1 Quasar

We report the first significant detection of an X-ray cluster associated with a powerful (L{sub bol} {approx} 10{sup 47} erg sec{sup -1}) radio-loud quasar at high redshift (z=1.06). Diffuse X-ray emission is detected out to {approx} 120 kpc from the CSS quasar 3C 186. A strong Fe-line emission at the z{sub rest} = 1.06 confirms its thermal nature. We find that the CSS radio source is highly overpressured with respect to the thermal cluster medium by 2-3 orders of magnitude. This provides direct observational evidence that the radio source is not thermally confined as posited in the ''frustrated'' scenario for CSS sources. Instead, the radio source may be young and at an early stage of its evolution. This source provides the first detection of the AGN in outburst in the center of a cooling flow cluster. Powerful radio sources are thought to be triggered by the cooling flows. The evidence for the AGN activity and intermittent outbursts comes from the X-ray morphology of low redshift clusters, which usually do not harbour quasars. 3C186 is a young active radio source which can supply the energy into the cluster and potentially prevent its cooling. We discuss energetics related to the quasar activity …
Date: January 11, 2006
Creator: Siemiginowska, Aneta; Cheung, C. C.; LaMassa, S.; Burke, D.; Aldcroft, T. L.; Bechtold, J. et al.
System: The UNT Digital Library
Discrete Symmetries on the Light Front and a General Relation connecting Nucleon Electric Dipole and Anomalous Magnetic Moments (open access)

Discrete Symmetries on the Light Front and a General Relation connecting Nucleon Electric Dipole and Anomalous Magnetic Moments

We consider the electric dipole form factor, F{sub 3}(q{sup 2}), as well as the Dirac and Pauli form factors, F{sub 1}(q{sup 2}) and F{sub 2}(q{sup 2}), of the nucleon in the light-front formalism. We derive an exact formula for F{sub 3}(q{sup 2}) to complement those known for F{sub 1}(q{sup 2}) and F{sub 2}(q{sup 2}). We derive the light-front representation of the discrete symmetry transformations and show that time-reversal- and parity-odd effects are captured by phases in the light-front wave functions. We thus determine that the contributions to F{sub 2}(q{sup 2}) and F{sub 3}(q{sup 2}), Fock-state by Fock-state, are related, independent of the fundamental mechanism through which CP violation is generated. Our relation is not specific to the nucleon, but, rather, is true of spin-1/2 systems in general, be they lepton or baryon. The empirical values of the anomalous magnetic moments, in concert with empirical bounds on the associated electric dipole moments, can better constrain theories of CP violation. In particular, we find that the neutron and proton electric dipole moments echo the isospin structure of the anomalous magnetic moments, {kappa}{sup n} {approx} -{kappa}{sup p}.
Date: January 11, 2006
Creator: Brodsky, Stanley J.; Gardner, Susan & Hwang, Dae Sung
System: The UNT Digital Library
Near-Infrared, Kilosecond Variability of the Wisps And Jet in the Crab Pulsar Wind Nebula (open access)

Near-Infrared, Kilosecond Variability of the Wisps And Jet in the Crab Pulsar Wind Nebula

We present a time-lapse sequence of 20 near-infrared (J- and K'-band) snapshots of the central 20'' x 20'' of the Crab pulsar wind nebula, taken at sub-arcsecond resolution with the Hokupa'a/QUIRC adaptive optics camera on the Gemini North Telescope, and sampled at intervals of 10 minutes and 24 hours. It is observed that the equatorial wisps and polar knots in the termination shock of the pulsar wind appear to fluctuate in brightness on kilosecond time-scales. Maximum flux variations of {+-}24 {+-} 4 and {+-}14 {+-} 4 per cent relative to the mean (in 1.2 ks) are measured for the wisps and knots respectively, with greatest statistical significance in J band where the nebula background is less prominent. The J and K' flux densities imply different near-infrared spectra for the nonthermal continuum emission from the wisps and outermost polar knot (''sprite''), giving F{sub {nu}} {proportional_to} {nu}{sup -0.56{+-}0.12} and F{sub {nu}} {proportional_to} {nu}{sup -0.21{+-}0.13} respectively. The data are compared with existing optical and UV photometry and applied to constrain theories of the variability of the wisps (relativistic ion-cyclotron instability) and knots (relativistic fire hose instability).
Date: January 11, 2006
Creator: Melatos, Andrew.; Scheltus, D.; Whiting, M.T.; Eikenberry, S. S.; Romani, R. W.; Rigaut, F. et al.
System: The UNT Digital Library
Structure in the Radio Counterpart to the 2004 Dec 27 Giant Flare From SGR1806-20 (open access)

Structure in the Radio Counterpart to the 2004 Dec 27 Giant Flare From SGR1806-20

The formation of an expanding, moving, and fading radio source. We report observations of this radio source with the Multi-Element Radio-Linked Interferometer Network (MERLIN) and the Very Long Baseline Array (VLBA). The observations confirm the elongation and expansion already reported based on observations at lower angular resolutions, but suggest that at early epochs the structure is not consistent with the very simplest models such as a smooth flux distribution. In particular there appears to be significant structure on small angular scales, with {approx}10% of the radio flux arising on angular scales <= 100 milliarcsec. This structure may correspond to localized sites of particle acceleration during the early phases of expansion and interaction with the ambient medium.
Date: January 11, 2006
Creator: Fender, Rob P.; Muxlow, T.W.B.; Garrett, M.A.; Kouveliotou, C.; Gaensler, B.M.; Garrington, S.T. et al.
System: The UNT Digital Library
Sensitivity Analysis and Disposal Strategy for I-129 Wastes with Different Retardations (open access)

Sensitivity Analysis and Disposal Strategy for I-129 Wastes with Different Retardations

None
Date: January 11, 2006
Creator: Collard, Leonard B. & Ades, M. J.
System: The UNT Digital Library