George E. Miller

Comparative increases of lead and barium with age in human tooth enamel, rib and ulna

Lead and Ba in postmortem tooth enamel, rib and ulna of six contemporary people (67-96 years; ave. 80) were shown to exhibit similar accumulations with age in the three different types of osseous tissue: Pb/Ca (wt) = 3.0, 5.2, and 3.9 x 10(-5) in rib, ulna, and tooth enamel; and Ba/Ca (wt) = 2.4, 2.4, and 1.8 x 10(-5) in rib, ulna, and tooth enamel, respectively. Mean concentrations of Pb were 11, 19, and 14 micrograms g-1 in rib (ash), ulna (ash), and enamel (dry), respectively. Means for Ba were 8.7, 8.9, and 6.4 micrograms g-1 in rib (ash), ulna (ash), and enamel (dry), respectively. Comparison of Ba in ulna of our 80-year-old subjects with Ba determined by other investigators in bones of younger contemporary populations indicated that Ba accumulates with age at about half the rate of Pb accumulation in bone. Concentrations of Ba in rib, ulna and enamel were positively correlated and similar within an individual, but varied among subjects in proportion to variations in absorptive uptake in portal blood. Barium may diffuse from a blood-dentine source into enamel, where it replaces Ca and accumulates with age. Because of extreme Pb pollution of our 80-year-old subjects and its variation of intake with age, the correlation of Pb in tooth enamel with Pb in bone was more scattered than for Ba. It is shown by means of stable Pb isotopic tracers that: (i) among the three types of osseous tissue, the residence time of Pb is longest in enamel, where it apparently accumulates with age by diffusion with little loss through exchange; and (ii) the residence time of Pb is longer in compact ulna than in trabecular rib, as it accompanies Ca in its osteoblastic transfer from blood to bone and then in its osteoclastic transfer back to blood from bone.

Material balance in coal. 2. Oxygen determination and stoichiometry of 33 coals

Abstract Chemical coal analysis can be supplemented by the determination of oxygen in high- and low-temperature ash, in coal as received, and in dried coal at 105 °C. The rapid method utilizes fast-neutron activation. The reaction 16 O(np) 16 N and counting of the 6.1 and 7.1 MeV gamma radiation of 7.3 s half-life are used. A specially designed dual transfer and simultaneous counting system gives very accurate results. Oxygen in 33 coals ranging from lignite to low-volatile bituminous coal has been determined and results are compared with ‘oxygen by difference’. Considerable discrepancies are observed. Better stoichiometric results are obtained if oxygen in coal ash, in wet coal and the dried coal is determined. This permits the estimation of the true material balances in fuels using data of the ultimate and the proximate coal analysis. The oxygen determination provides the coal chemist with an accurate basis and can be used to rank coal. The summation of the percent of carbon, nitrogen, hydrogen, sulphur and oxygen becomes more meaningful, some errors can be detected, and the state of completeness of coal analysis can be evaluated. Total sulphur can be estimated and oxidation effects during drying can be detected. These affect the moisture determination. It appears that after more data have been collected the interpretation of solid fuel analyses may be facilitated and will be made stoichiometrically more meaningful; the ranks of different coals and other properties such as O C plots will become better defined. This approach may help the coal industry in general to quantize further the energy generating processes. It may be possible to simplify the present time-consuming methods of coal analysis. A brief overview of coal analysis methods in relation to direct determination of oxygen is given ‡ .

Oxygen in coal ash: a simplified approach to the analysis of ash and mineral matter in coal

Abstract Oxygen was determined accurately in eight U.S. Bureau of Mines coal ash samples A, B, D, F, G, I, and J, NBS coal fly ash 1633 reference material, and two low-temperature ashes (LTA) from lllinois State Geological Survey. The method uses fast-neutron activation (FNA) analysis employing a dual counting and irradiation system which is essentially free from interferences. The stoichiometric balance based on analyses of the ashes performed by the USBM is calculated and summations given in oxide and element percent. Excellent agreement is found with the chemical data obtained by classical silicate analysis methods. Accurate oxygen determination for coal ash and LT-ash (or mineral matter) is important for calculation of data in the ultimate analysis of coal as such. Knowledge is required for recalculation of the data on a dry and dry-ash-free basis. The routinely used ‘oxygen by difference’ values are inadequate for accurate work. In order to determine the organic oxygen in coal one also has to correct for oxygen in mineral matter and oxygen in the water removed as moisture. The Parr formula and other methods of empirical estimation are inadequate and may be replaced in some cases by the oxygen determination. The complete data provide a quantitative basis for stoichiometric interpretation of coal analyses. It was found that the eight coal-ash samples analysed contained 45.5 ± 3% oxygen. Since these ashes represent a large variety of U.S. coals, this figure can be used as an estimate for recalculation and evaluation of the proximate and ultimate coal analyses. It is better, however, to use values actually determined in ash by the rapid fast-neutron activation method. This permits a better estimation of the sum of cations plus sulphates in the ash.

Mapping students’ thinking patterns by the use of the Knowledge Space Theory

The quantitative Knowledge Space Theory is applied here for the first time to specific science concepts in order to evaluate its feasibility as a general assessment method for science learning. In particular, the knowledge states of students in the 4th through 12th grades are suggested for three science concepts before and after classroom teaching/learning experiences. The theory belongs to the vast category of latent trait models based upon the Rasch model, but differs in all its most important characteristics by having the power to extract the cognitive organization of the material. Student responses to the pre‐tests and the post‐tests were analyzed for the pressure concept, the density concept and the conservation of matter, and tentative critical learning pathways for each concept are suggested which describe the most probable sequences of learning steps. In all three cases the quantitative results show a change in the students’ logic structure after the classroom experience. Knowledge Space Theory sh...

A Study of Oxidation of Dental Amalgams with Age

A quantitative test for corrosion due to oxidation has been accomplished. The oxygen concentration of dental amalgams was measured by fast neutron activation which provides a means of detecting oxygen in as small a quantity as 10 to 20 micrograms. An increase in oxygen content with age of spherical blend amalgam implants was observed, confirming the importance of oxidation processes in in vivo corrosion.

Neutron activation analysis (NAA) in the service of other analyses: Determination of calcium

The calcium concentration in bone samples which contain 0 to 37% calcium is readily measured rapidly by neutron activation analysis. Sample and data processing can be minimal and conditions can be adjusted according to sample type and precision desired. Such determinations have contributed important reference data in support of biomedical and archaeometric studies. Repeatability of measurements can be better than 3% relative overall, and better than 5% even for irregularly shaped samples (based on one standard deviation).

Oxygen stoichiometry of common reagents by fast-neutron activation☆

Abstract Oxygen is determined by fast-neutron activation with high accuracy in reagent grade compounds: H 2 O (distilled), Li 2 CO 3 , BeO, (COOH) 2 · 2H 2 O, Na 2 CO 3 , NaHCO 3 , Na 2 C 2 O 4 , C 6 H 5 (COOH), (NH 4 ) 2 C 2 O 4 · H 2 O, MgO, Al 2 O 3 , SiO 2 , Fe(SO 4 ) · 7H 2 O, Fe(NH 4 ) 2 (SO 4 ) 2 · 6H 2 O, BaCl 2 · 2H 2 O, K 2 CO 3 , KMnO 4 , K 2 Cr 2 O 7 , CaCO 3 , TiO 2 , V 2 O 5 , Cr 2 O 3 , MnO 2 , Fe 2 O 3 , CuO, NiO, Co 2 O 3 , ZnO, GeO 2 , As 2 O 5 , RbHCO 3 , SrCO 3 , Y 2 O 3 , ZrO 2 , Nb 2 O 5 , Na 2 MoO 4 · 2H 2 O, CdCO 3 , SnO, Sb 2 O 3 , CsHCO 3 , La 2 O 3 , PrO 1.818 ∗3 , Ta 2 O 5 , WO 2 , WO 3 , HgO (yellow), HgO (red), Tl 2 O 3 , Pb 3 O 4 , PbO, and Bi 2 O 3 . Standard deviation in the range of 0.1–0.3% is achieved. Data are plotted vs. theoretical oxygen percentages and a linear curve is obtained for compounds ranging from hydrogen to bismuth and for oxygen concentrations from 7.17% (PbO) to 88.81% (H 2 O). This work demonstrates the high precision and accuracy of the method and suggests numerous applications not previously considered.

Oxygen stoichiometry in the geochemical standards of the U.S. Geological Survey: A blind study

Abstract A blind study of total O content in nine USGS standard rocks G-2, AGV-1, GSP-1, DTS-1, BCR-1, SCo-1, MAG-1, RGM-1 and QLO-1, Reagent Grade oxalic acid and Specpure SiO 2 was performed using the activation method by 14.3-Me V neutrons and a dedicated dual sample transfer and counting system. Over a composition range varying from 43 to 76% O absolute deviation from stoichiometric O varied from 0.07 to 0.88%. A simple computer program was used to calculate the stoichiometric O from chemical analyses of the rocks and to show summations including the FNAA oxygen. Accurate O data permit the evaluation of overall accuracy of rock analysis and help to detect dificiencies, errors, and incomplete work by enabling the chemist to calculate the analysis unambiguously.

Neutron activation analysis of core and drill cutting samples from geothermal well drilling

Samples of sandstones and shales were analysed by instrumental neutron activation analysis for a total of 30 elements. Three irradiation and five counting periods wer employed. Solutions and National Bureau of Standards Reference Materials wer used for comparison. The samples were obtained from drill cuttings (with a few core samples) from drillings in the Salton Sea geothermal field of California. These determinations form part of a major study to elemental variation as a function of mineral variation as depth and temperature in the well vary. The overall goal is to examine mineral alteration and/or element migration under typical geothermal conditions. The techniques involve typical compromises between maximizing precision for individual element determinations and the amount of time and effort that can be expended, as it is desired to examine large numbers of samples. With the limitations imposed by the reactor flux ailable at the U. C. Irvine TRIGA reactor, the detectors available, and time factors, most precisions are acceptable for geological comparison purposes. Some additional measurements wer made by delayed-neutron counting methods to compare with uranium determinations made by conventional instrumental neutron activation analysis methods.

High Linear Energy Transfer Degradation Studies Simulating Alpha Radiolysis of TRU Solvent Extraction Processes

Treatment of used nuclear fuel through solvent extraction separation processes is hindered by radiolytic damage from radioactive isotopes present in used fuel. The nature of the damage caused by the radiation may depend on the radiation type, whether it be low linear energy transfer (LET) such as gamma radiation or high LET such as alpha radiation. Used nuclear fuel contains beta/gamma emitting isotopes but also a significant amount of transuranics which are generally alpha emitters. Studying the respective effects on matter of both of these types of radiation will allow for accurate prediction and modeling of process performance losses with respect to dose. Current studies show that alpha radiation has milder effects than that of gamma. This is important to know because it will mean that solvent extraction solutions exposed to alpha radiation may last longer than expected and need less repair and replacement. These models are important for creating robust, predictable, and economical processes that have strong potential for mainstream adoption on the commercial level. The effects of gamma radiation on solvent extraction ligands have been more extensively studied than the effects of alpha radiation. This is due to the inherent difficulty in producing a sufficient and confluent dose of alpha particles within a sample without leaving the sample contaminated with long lived radioactive isotopes. Helium ion beam and radioactive isotope sources have been studied in the literature. We have developed a method for studying the effects of high LET radiation in situ via 10B activation and the high LET particles that result from the 10B(n,α)7Li reaction which follows. Our model for dose involves solving a partial differential equation representing absorption by 10B of an isentropic field of neutrons penetrating a sample. This method has been applied to organic solutions of TBP and CMPO, two ligands common in TRU solvent extraction treatment processes. Rates of degradation of TBP and CMPO and their respective degradation products in the presence of high LET radiation are presented and discussed. These results are also compared to gamma studies performed in our lab and other gamma and alpha studies found in the literature. The possible application of this method to a variety of other solvent extraction ligands to study the effects of high LET radiation is also considered.Copyright