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- ItemSolutions of the relativistic two-body problem. II. Quantum mechanics(CSIRO, 1972-04) Cook, JLThis paper discusses the formulation of a quantum mechanical equivalent of the relative time classical theory proposed in Part I. The relativistic wavefunction is derived and a covariant addition theorem is put forward which allows a covariant scattering theory to be established. The free particle eigenfunctions that are given are found not to be plane waves. A covariant partial wave analysis is also given. A means is described of converting wavefunctions that yield probability densities in 4-space to ones that yield the 3-space equivalents. Bound states are considered and covariant analogues of the Coulomb potential, harmonic oscillator potential, inverse cube law of force, square well potential, and two-body fermion interactions are discussed. © CSIRO 1972
- ItemRecovery of byproduct uranium from the manufacture of phosphatic fertilizers(Australian Atomic Energy Commission, 1977-01-01) Ring, RJ
- ItemImmobilization of sodium in perovskite(John Wiley & Sons, Inc, 1991-04) Vance, ER; Thorogood, GJPerovskite, a candidate phase for the immobilization of Na bearing nuclear waste, shows excellent Na leach resistance in deionized water, when hot-pressed to 97% theoretical density at 1200°C. Surface reactions in two brines appeared to be minimal. © 1991 The American Ceramic Society
- ItemThermal expansion coefficients of zirconolite (CaZrTi2O7) and perovskite (CaTiO3) from x-ray powder diffraction analysis(Elsevier, 1992-08-02) Ball, CJ; Thorogood, GJ; Vance, ERThe thermal expansion coefficients of zirconolite, both ordered and disordered, and perovskite, were measured by X-ray powder diffraction analysis in the temperature range 25–1200°C. The principal results are: (1) The mean thermal expansion coefficients (K−1) of ordered zirconolite are:αa = (11.35±0.25) × 10−6;αb = (8.72± 0.22) × 10−6;αc = (10.0 ±0.5) × 10−6. (2) The mean thermal expansion coefficients (K−1) of disordered zirconolite areα∥ = (9.89±0.15) × 10−6 in the (001) plane and α⊥ = (9.37±0.14) × 10−6 normal to (001). (3) The mean thermal expansion coefficients (K−1) of perovskite are:αa = (7.86±0.30) × 10−6;αb = (13.46±0.17) × 10−6;α c = (16.55±0.26) × 10−6. © 1992 Published by Elsevier B.V.
- ItemHigh-temperature study of CaZrTi2O7(Elsevier, 1992-08-02) Vance, ER; Cassidy, DJ; Ball, CJ; Thorogood, GJPreviously reported anomalous thermal expansion effects in the 1200–1500°C range for hot-pressed CaZrTi2O7 were shown to be due to irreversible bloating effects, from occluded gases. X-ray diffraction and differential thermal analysis of ordered CaZrTi2O7 did not reveal evidence of a solid-state transformation at temperatures up to 1450°C. © 1992 Elsevier
- ItemMeasurements of 59Ni in meteorites by accelerator mass spectrometry(Elsevier, 1993-10-01) Paul, M; Fifield, LK; Fink, D; Albrecht, A; Allan, GL; Herzog, GF; Tuniz, CIsotopic abundances of the radionuclide 59Ni (T12 = 76000 yr) were measured by accelerator mass spectrometry with the 14UD Pelletron tandem accelerator at the Australian National University and a detection system solely based on a multianode ionization chamber. The sensitivity limit in the measurement of 59Ni isotopic abundances is 5 × 10−13, as determined by residual interferences from isobaric 59Co and isotopic 58Ni ions. Cosmogenic 59Ni abundances 59NiNi = (8–20) × 10−12 were measured in four samples prepared from the metal phase of two meteorites (mesosiderites). The ratio of the 59Ni abundances to those measured for 41Ca in the silicate phase of the same samples, is in fair agreement with the ratio of the production rates via thermal-neutron capture on 58Ni and 40Ca. © 1993 Published by Elsevier B.V.
- ItemReport on workshop on production rates of terrestrial produced in-situ cosmogenic radionuclides(Elsevier, 1994-06-03) Reedy, RC; Tuniz, C; Fink, DProduction rates of cosmogenic nuclides made in-situ in terrestrial samples and how they are applied to the interpretation of measured radionuclide concentrations were discussed at a one-day Workshop held 2 October 1993 in Sydney, Australia. The status of terrestrial in-situ studies using the long-lived radionuclides 14C, 10Be, 26Al, 36Cl, and 41Ca and of various models were presented. The uncertainties in and magnitudes of various factors that go into data interpretation were discussed; no single factor was found to dominate the final uncertainty.© 1994 Elsevier B.V.
- ItemFirst 26Al analyses at the ANTARES AMS Centre: uptake via oral ingestion of 26Al in rats(Elsevier, 1994-06-03) Fink, D; Walton, J; Hotchkis, MAC; Jacobsen, GE; Lawson, EM; Smith, AM; Tuniz, C; Wilcox, DAs the debate on the role played by aluminium in Alzheimer's disease remains a controversial one, the mechanism and degree of uptake of aluminium into brain tissue is not well understood nor quantified. We report here results from the initial phase of our study of aluminium uptake and retention in tissues of rats following oral administration of a tracer dose of 26Al. An account of our biomedical findings in old rats will be described elsewhere. For a young rat population, we find 26Al retention in the liver to be 7 times that in the brain. A description of our experience in performing aluminium measurements of biological tissues is described and interpretation of the findings are given. © 1994 Elsevier B.V.
- ItemThe ANTARES AMS Centre at the Lucas Heights Research Laboratories(Elsevier, 1994-06-03) Tuniz, C; Fink, D; Hotchkis, MAC; Jacobsen, GE; Lawson, EM; Smith, AM; Bird, JR; Boldeman, JWThe ANTARES AMS facility at the Lucas Heights Research Laboratories is operational and AMS measurements of 14C and 26Al are performed routinely. Measurement programs for a variety of other long-lived cosmogenic radioisotopes are being implemented on specialised beamlines. The overall aim of the facility is to establish an AMS centre for advanced studies in global change and Quaternary science. Other projects in biomedicine and nuclear safeguards monitoring are also being developed. © 1994 Elsevier B.V.
- ItemEquipment and methodology for high precision, high throughput 14C AMS analyses at ANTARES(Elsevier, 1994-06-03) Smith, AM; Fink, D; Hotchkis, MAC; Jacobsen, GE; Lawson, EM; Shying, ME; Tuniz, C; Watt, GC; Fallon, J; Ellis, PJThe original Rutgers FN tandem accelerator has been modified for high-precision high-throughput AMS analyses at the ANTARES AMS Center. The status of this work and future plans are discussed, with emphasis on 14C. Isotopic ratios are measured at ANTARES by sequentially injecting stable isotopes and the radioisotope, and the systems developed for this purpose are described. Progress with a new injection platform and high intensity, multi-sample ion source is also given. © 1994 Elsevier B.V.
- Item14C analyses at the ANTARES AMS Centre: dating the log coffins of northwest Thailand(Elsevier, 1994-06-03) Hotchkis, MAC; Fink, D; Jacobsen, GE; Lawson, EM; Shying, ME; Smith, AM; Tuniz, C; Barbetti, M; Grave, P; Quan, HM; Head, JRecent results of 14C analyses at the ANTARES AMS Centre are presented. Test measurements of 14C blanks demonstrate an ultimate sensitivity of the order of 10−15 (14C/12C ratio). Measurements of unknowns have been made with a precision in the range 1–1.5% using a “slow cycling” mode of operation where the injection magnet field is changed to inject 14C and 13C alternately. Results are presented for a series of log coffins from cave burials in NW Thailand. © 1994 Elsevier B.V.
- ItemTissue disposition of 26aluminum in rats measured by accelerator mass spectrometry(Canadian Society for Clinical Investigation, 1994-10) Walker, VR; Sutton, RA; Meirav, O; Sossi, V; Johnson, R; Klein, J; Fink, D; Middleton, RJA trace quantity of 26aluminum (26Al) was administered intravenously to 1 normal and 1 uremic rat. After a 3-week period, the animals were sacrificed and samples of bone, muscle, kidney, liver, heart, and brain were analyzed for their 26Al content. In the normal and uremic rats, most of the tissue 26Al was found in bone amounting to 0.9% and 2.0%, respectively, of administered dose/g dry weight of tissue. Much smaller amounts of isotope were found in the other tissues in both animals. In the normal rat, the descending order of 26Al content in other tissues was: kidney, 0.2% > liver, 0.06% > heart, 0.03%, > brain and muscle, 0.02%. In the uremic rat, the same order of tissue 26Al content was found with kidney, 0.37% > liver, 0.06% > heart, 0.02% > brain and muscle, 0.01% per g dry weight of tissue. When expressed per g wet weight of tissue in the 2 animals, a similar order of tissue 26Al content was found. In comparing the amount of 26Al in the bone of the 2 rats, the uremic animal was found to have more than twice that found in the bone of the normal rat when expressed either per g dry or wet weight of bone. However, 26Al content of other tissues was similar in the 2 animals. This suggests that uremic bone may have a greater affinity for aluminum than normal bone, but kidney, liver, brain, heart, and muscle appear to behave similarly in uremic and normal rats in regard to incorporation of a single trace dose of isotope in the 3-week time frame of the present study.
- ItemRetention of actinides in natural pyrochlores and zirconolites(De Gruyter, 1994-12-01) Lumpkin, GR; Hart, KP; McGlinn, PJ; Payne, TENatural pyrochlore and zirconolite undergo a crystalline-aperiodic transformation caused by alpha-decay of 232Th and 238U at dose levels between 2X1014 and 3X1017 α/mg. The principal effects of the transformation are volume expansion and micro-fracturing, providing potential pathways for fluids. Geochemical alteration of the minerals may occur under hydrothermal conditions or in low temperature, near surface environments, but Th and U usually remain immobile and can be retained for time scales up to 10 9 years. However, the Th-U isotope systematics of a zirconolite-bearing vein and dolomite host rock may provide evidence for disequilibrium between 230Th, 234U and 238U. © 1994 R. Oldenbourg Verlag, München
- ItemUptake of trace amounts of aluminium into the brain from drinking water(Elsevier, 1995-01) Walton, J; Tuniz, C; Fink, D; Jacobsen, GE; Wilcox, DThroughout the world, alum (aluminum sulfate) is used in municipal water treatment plants to clarify water. Alum treatment usually removes aluminosilicate particles from drinking water but can substantially increase its soluble aluminum content (Zhang et al., 1994; Tran et al., 1993; Kopp, 1970). Soluble aluminum is the more bioavailable and potentially toxic form. We gavaged simulated tap water, containing a low level of radioactive soluble aluminum (26Al), into the stomachs of rats. Measurements with accelerator mass spectrometry showed that trace amounts of 26Al from this single exposure directly entered their brain tissue. Uptake of a comparable level of aluminum into the human brain, from alum-treated drinking water over a prolonged period of time, may contribute to long-term health consequences for some people.
- ItemNeutron-capture 36Cl, 41Ca, 36Ar, and 150Sm in large chondrites: evidence for high fluences of thermalized neutrons(Wiley, 1995-05-25) Bogard, DD; Nyquist, LE; Bansal, BM; Garrison, DH; Wiesmann, H; Herzog, GF; Albrecht, A; Vogt, S; Klein, JWe have measured significant concentrations of 36Cl, 41Ca, 36Ar from decay of 36Cl, and 150Sm produced from the capture of thermalized neutrons in the large Chico L6 chondrite. Activities of 36Cl and 41Ca, corrected for a high-energy spallogenic component and a terrestrial age of ∼50 ka, give average neutron-capture production rates of 208 atoms/min/g-Cl and 1525 atoms/min/kg-Ca, which correspond to thermal neutron (n) fluxes of 6.2 n/cm2/s and 4.3 n/cm2/s, respectively. If sustained for the ∼65 Ma single-stage, cosmic ray exposure age of Chico, these values correspond to thermal neutron fluences of ∼1.3×1016 and 0.8 × 1016 n/cm2 for 36Cl and 41Ca, respectively. Stepwise temperature extraction of Ar in Chico impact melt shows 36Ar/38Ar ratios as large as ∼9. The correlation of high 36Ar/38Ar with high Cl/Ca phases in neutron-irradiated Chico indicates that the excess 36Ar above that expected from spallation is due to decay of neutron-produced 36Cl. Excess 36Ar in Chico requires a thermal neutron fluence of 0.9–1.7×1016 n/cm2. Decreases in 149Sm/152Sm due to neutron-capture by 149Sm correlate with increases in 150Sm/152Sm for three samples of Chico, and one of the Torino H-chondrite. The 0.08% decrease in 149Sm/152Sm shown by Chico corresponds to a neutron fluence of 1.23×1016 n/cm2. This fluence derived from Sm considers capture of epithermal neutrons and effects of chemical composition on the neutron energy distribution. Excess 36Ar identified in the Arapahoe, Bruderheim, and Torino chondrites and the Shallowater aubrite suggest exposure to neutron fluences of ∼0.2–0.6×1016 n/cm2. Depletion of 149Sm in Torino and the LEW86010 angrite suggest neutron fluences of 0.8×1016 n/cm2 and 0.25×1016 n/cm2, respectively. Neutron fluences of ∼1016 n/cm2 in Chico are almost as large as those previously observed for some lunar soils. Consideration of exposure ages suggests that the neutron flux in Chico may have been greater than that in many lunar soils. Neutron-capture effects, although seldom reported, may be common for large meteorites and could affect calculation of exposure ages based on cosmogenic Ar. Combining measurements of radioactive and stable species produced from neutron-capture has the potential for identifying large meteorites with complex exposure histories. © 2021 American Geophysical Union
- ItemGrowth of high purity liquid phase epitaxial GaAs in a silica growth system(Elsevier, 1995-12-01) Butcher, KSA; Mo, L; Alexiev, D; Tansley, TLLiquid phase epitaxial gallium arsenide layers, greater than 200 μm thickness and with a low net carrier concentration (NA,D ≈ 1013 cm−3) have been grown in a silicia growth system with silica crucibles. Analysis of electrical and chemical defects was carried out using capacitance-voltage (C---V) measurements, deep level transient spectroscopy (DLTS) and secondary ion mass spectroscopy (SIMS). Details of the growth procedure are given and it is shown that silicon incorporation in the growth layer is not suppressed by the addition of ppm levels of oxygen to the main hydrogen flow. © 1995, Elsevier Ltd.
- ItemExposure history of the Torino meteorite(Wiley, 1996-03) Wieler, R; Graf, T; Signer, P; Vogt, S; Herzog, GF; Tuniz, C; Fink, D; Fifield, LK; Klein, J; Middleton, R; Jull, AJT; Pellas, P; Masarik, J; Dreibus, GWe determined He, Ne, Ar, 10Be, 26Al, 36Cl, and 14C concentrations, as well as cosmic-ray track densities and halogen concentrations in different specimens of the H6 chondrite Torino, in order to constrain its exposure history to cosmic radiation. The Torino meteoroid had a radius of ∼20 cm and travelled in interplanetary space for 2.5–10 Ma. Earlier, Torino was part of a larger body. The smallest possible precursor had a radius of 55 cm and a journey through space longer than ∼65 Ma. If the first-stage exposure took place in a body with a radius of >3 m or in the parent asteroid, then it lasted nearly 300 Ma. The example of Torino shows that it is easy to underestimate first-stage exposure ages when constructing two-stage histories. © 1999-2021 John Wiley & Sons, Inc.
- ItemEffect of crucible materials on impurities in LPE-GaAs(Elsevier, 1996-03-01) Mo, L; Butcher, KSA; Alexiev, DLPE-GaAs grown in carbon, boron nitride and alumina crucibles has been examined using standard characterisation techniques including capacitance-voltage (C-V) measurements and deep level transient spectroscopy (DLTS). The epitaxial layers have net carrier concentration ranging from 5 × 1014 to 8 × 1015 carriers per cm3. DLTS data has shown that all epitaxial layers have deep level traps. © 1996, Elsevier Ltd.
- ItemElemental composition of reactively sputtered indium nitride thin films(The Japan Society of Applied Physics, 1996-04-15) Sunil, K; Mo, L; Motlan; Tansley, TLIndium nitride (InN) thin films have been grown on a variety of substrates using low-temperature radio frequency reactive sputtering of indium metal in pure nitrogen plasma. Quantitative compositional analyses of the films, carried out using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS), suggest that large amounts of oxygen are present in them. The high concentration of oxygen in our films is attributed to the voided microstructure as revealed by cross-sectional scanning electron microscopy. The XPS studies also suggest that the oxygen incorporated into the films is bonded to nitrogen. © 1996, The Japan Society of Applied Physics
- ItemComplex exposure histories for meteorites with “short” exposure ages(Wiley, 1997-05) Herzog, GF; Vogt, S; Albrecht, A; Xue, S; Fink, D; Klein, J; Middleton, R; Weber, H; Schultz, LWe report measurements of 26Al and 10Be activities in nine ordinary chondrites and of the light noble gas concentrations and 36Cl and 41Ca activities in subsets of those meteorites. All but Murray have low 21Ne concentrations (<1.0 × 10−8cm3STP/g) and have previously been used to estimate 21Ne production rates. Ladder Creek, Murchison, Sena, and Timochin have inventories of cosmogenic radionuclides that are compatible with a single stage of irradiation and give 21Ne production rates that are consistent with the standard L-chondrite value of 0.33 × 10−8cm3STP/g/Ma. In contrast, Cullison, Guenie, Shaw, and Tsarev experienced complex irradiation histories. They and several other meteorites with low nominal exposure ages also have lower 3He/21Ne ratios than expected based on their 22Ne/21Ne ratios. A general association between low 21Ne contents and 3He losses suggests that meteorites with short lifetimes often occupy orbits with small perihelia. However, meteorites with low 21Ne contents, one-stage exposure histories, and losses of cosmogenic 3He are rare. Possible explanations for the scarcity are (1) statistical, (2) that it is harder for more deeply buried protometeoroids to lose gas in a liberating collision, and (3) that it is harder to insert more deeply buried protometeoroids directly into orbits with small perihelia. © 1999-2021 John Wiley & Sons, Inc.