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  1. This volume is an addition to Wiley's Environmental Science and Technology series. It will be useful to environmental scientists, chemists, and others involved in the study of pollutants. As defined by the author, black carbons are impure forms of the element produced by incomplete combustion of fossil fuels or biomass. They are highly variable in makeup and are widely distributed over the globe. As the pace of the fossil fuel consumption and forest burning to clear cropland increases, black carbons will become more pervasive. The text is based on literature from a wide range of scientific fields. Topics explored includemore » chemical and physical properties, formation, distribution, degradation, anthropogenic sources, transport, and reactions in the environment. A broad spectrum of information is presented in a well-organized manner.« less
  2. As a prerequisite to high accuracy measurements involving the bulk configuration of /sup 6/LiD we must have a good grasp of the details of the RTNS-I neutron source energy spectrum. Experiments to this end involving neutron yield vs deuteron energy, ratios of foil activation of selected elements, and pulse height distributions of a Si surface barrier detector are described. With this knowledge, the /sup 4/He-production cross sections for /sup 6/Li and /sup 7/Li are found experimentally to be 0.512b and 0.336b, respectively, at anti E/sub N/ = 15.0 MeV in free-field geometry. 14 references.
  3. A series of calibration experiments has been done to characterize an NE-213 liquid scintillator detector of photons ranging up to approx.7 MeV. Calibrated sources of /sup 24/Na, /sup 22/Na, /sup 60/Co, and /sup 137/Cs were used to infer the conversion factors as a function of electron energy, and detector efficiencies. In the latter effort, comparisons were made of the measured electron recoil spectra with their calculated counterpart. The code SANDYL was used and its results were modified slightly by folding in a normal distribution to account for the anticipated broadening due to variations in the location of light pulses withinmore » the scintillator. The calculated spectra were 0 to 10% above the experimental data. Higher energy gamma rays were generated by a Pu-Be source, which generated the 4.439-MeV line from /sup 12/C*, and the /sup 16/O(n,n')/sup 16/O* reaction, which generated among others the 6.130, 6.919, and 7.117 lines. We observed a marked nonlinearity of light pulse amplitude with electron energy at higher energies. Linearity was confirmed at and below 2.75 MeV, with an estimated threshold at 15 keV. The nonlinearity at higher energy will complicate the analysis.« less
  4. New measurements of the neutron and gamma-ray emission spectra from materials of interest to thermonuclear reactors with a 14 MeV neutron source were done during 1986 and 1987. These measurements characterized by better resolution than those reported in the Summary published in 1982, were performed using the pulsed sphere and time-of-flight techniques. The detector used in these measurements was a NE-213 cylinder, 5.08 cm in diameter by 5.08 cm thick. The new measurements include the following materials: Be, C, N, H/sub 2/O, C/sub 2/F/sub 4/ (teflon), Al, Si, Ti, Fe, Cu, Ta, W, Au, Pb, /sup 232/Th, and /sup 238/U.more » For all these materials, both the neutron and gamma emission spectra were measured. A complete tabulation of all the measurements done under the Pulse Sphere Program is presented. 37 refs., 1 tab.« less
  5. The calibration (in rad/nC) of an air-filled tissue-equivalent ionization chamber for neutrons of l5-MeV average energy was determined by measuring absolute fluences and calculating the kerma per unit fluence. The neutron calibration determined from the ..gamma..-ray calibration and application of the Bragg--Gray relation was found to be 4% higher than that based on the fluence measurement. Additional data were taken to obtain calibration factors with tissue-equivalent gas; the same difference betwen the two methods was observed.
  6. Subsequent to the analysis of the June 1986 series of experiments at RTNS-1, we thought it sensible to repeat some of the experiments with greater care given to the high energy portions of the effluent gamma ray spectra. In addition, some new materials were recommended for study, such as silicon. And since among our earlier experiments we observed data which was not highly reproducible, repeated runs would provide a quantitative assessment of the precision of the experiments. Accordingly, we followed the procedure outlined in UCID-20884. First, we calibrated the NE-213 detector with standard gamma ray sources and checked for linearitymore » of pulse height with energy deposited by electrons. We then conducted experiments at RTNS-1, using spherical configurations of C, Si, Al, H/sub 2/O, N/sub 2/,Ti, Fe, and C/sub 2/F/sub 4/. The H/sub 2/O was contained in a modified glass flask, while the liquid nitrogen was held in a double-walled steel dewar. 25 refs., 17 figs., 9 tabs.« less
  7. We have performed a number of experiments at LLNL recently to investigate the leakage of gamma rays from spheres of selected materials pulsed centrally with 14-MeV neutrons. Such spectral information may be carefully compared to calculational results to validate the transport models, particularly the nuclear cross section data base. In the present case, the TART code and SANDYL codes are used to explicitly calculate the observable, the recoil electron spectrum. The materials studied were H/sub 2/O, /sup 6/LiD, Be, C, /sup 14/N, CF/sub 2/, Al, Si, Ti, Fe, Cu, Ta, W, Au, Pb, Th, and /sup 238/U. Generally, agreement wasmore » good between experiment and calculation. However, for some, the calculations significantly underestimated or overestimated experiment. For oxygen (i.e., H/sub 2/O), the ENDL cross section set led to a sizeable calculational overestimate. Re-examination led to a large improvement. For tungsten, the calculated output was approx.30% below experiment. A re-evaluation led to closer agreement. 16 refs., 10 figs., 1 tab.« less
  8. The sequence and structure of human testis-specific L-lactate dehydrogenase (LDHC/sub 4/, LDHX; (L)-lactate:NAD/sup +/ oxidoreductase, EC has been derived from analysis of a complementary DNA (cDNA) clone comprising the complete protein coding region of the enzyme. From the deduced amino acid sequence, human LDHC/sub 4/ is as different from rodent LDHC/sub 4/ (73% homology) as it is from human LDHA/sub 4/ (76% homology) and porcine LDHB/sub 4/ (68% homology). Subunit homologies are consistent with the conclusion that the LDHC gene arose by at least two independent duplication events. Furthermore, the lower degree of homology between mouse and human LDHC/submore » 4/ and the appearance of this isozyme late in evolution suggests a higher rate of mutation in the mammalian LDHC genes than in the LDHA and -B genes. Comparison of exposed amino acid residues of discrete anti-genic determinants of mouse and human LDHC/sub 4/ reveals significant differences. Knowledge of the human LDHC/sub 4/ sequence will help design human-specific peptides useful in the development of a contraceptive vaccine.« less
  9. A series of measurements were previously performed at LLNL on many materials from Be to U-238 to study the gamma ray leakage spectra resulting form the interactions of 14 MeV neutrons with these materials. Sizable discrepancies were found in these experiments between measured and calculated gamma ray induced recoil electron spectra, while the agreement among the respective measured and calculated neutron spectra was quite good. The present report discusses the same type of measurements and calculations for 0 to 16 and serves to illustrate the above discrepancies. A water filled glass vessel was the target used to study the transportmore » of 14 MeV neutrons through 0 to 16 and the respective emission of secondary neutrons and gamma rays. The design and execution of the experiment and the re-evaluations of the nuclear cross section data base for 0 to 16 in the ENDL library (that resulted in a considerable improvement in the agreement with the measured electron recoil spectra) are presented. 11 refs., 8 figs., 2 tabs.« less
  10. A series of experiments has been conducted that involve gamma-ray production from the irradiation of materials with 14-MeV neutrons to further test the Monte Carlo transport code TART and its nuclear data base. Gamma rays emitted from spherical assemblies pulsed at their centers with 14-MeV neutrons were detected at a distant point (8.51-m flight path) with an NE213 detector. The neutron- and gamma-emission spectra were measured simultaneously using pulse-shape discrimination. The 14-MeV neutron source was the T(d,n)/sup 4/He reaction with the 400-keV deuteron beam from the Lawrence Livermore National Lab. (LLNL) insulated core transformer accelerator. The materials and their thicknessesmore » (in grams per square centimetre) include carbon (17.7), H/sub 2/O (13.4 H/sub 2/O + 1.1 + Pyrex), aluminum (22.4), iron (31.3), copper (32.9), tantalum (51.5), tungsten (49.0), gold (120.0), thorium (61.6), and /sup 238/U (55.7). It is concluded that the integral measurements of gamma-ray leakage spectra provide a sensitive test of the quality of the nuclear cross sections in the 14-MeV neutron energy range and complement the findings of neutron time-of-flight intercomparisons.« less

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