Trace element analysis by accelerator mass spectrometry

An Accelerator Mass Spectrometry (AMS) facility has been assembled at the University of North Texas (UNT) in collaboration with Texas Instruments, Inc. The UNT AMS facility is used primarily for the high sensitivity determination of trace elements of stable isotopes in materials. Particle accelerators, in conjunction with magnetic (momentum/charge) and electrostatic (energy/charge) spectrometers and particle energy detectors, may be used to measure rare isotopes at concentrations as low as one part in 10¹² or 10¹⁰ atoms/cm³.     

Determination of cell asymmetry in temperature-modulated DSC

The quality of measurement of heat capacity by differential scanning calorimetry (DSC) is based on the symmetry of the twin calorimeters. This symmetry is of particular importance for the temperature-modulated DSC (TMDSC) since positive and negative deviations from symmetry cannot be distinguished in the most popular analysis methods. Three different DSC instruments capable of modulation have been calibrated for asymmetry using standard non-modulated measurements and a simple method is described that avoids potentially large errors when using the reversing heat capacity as the measured quantity. It consists of overcompensating the temperature-dependent asymmetry by increasing the mass of the sample pan.On leave from Toray Industries, Inc., Otsu, Shiga 520, JapanOn leave from Toray Research Center, Inc., Otsu, Shiga 520, JapanThis work was supported by the Division of Materials Research, National Science Foundation, Polymers Program, Grant # DMR 90-00520 and the Division of Materials Sciences, Office of Basic Energy Sciences, U. S. Department of Energy at Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. for the U. S. Department of Energy, under contract number DE-AC0S-96OR22464. Support for instrumentation came from TA Instruments, Inc. and Mettler-Toledo, Research support was also given by ICI Painls, and Toray Industries, Inc.     

Separation of samarium and neodymium: a prerequisite for getting signals from nuclear synthesis

(146)Sm (T(1/2) = 10(8) y) is a long-lived radionuclide which has been produced in significant amounts during burning in a supernova (SN). Detection of this SN produced long-lived radionuclide on Earth may be helpful for getting information on nuclear synthesis at the time of our solar system's formation. Only accelerator mass spectrometry (AMS) can determine such minute traces of (146)Sm still expected in the Earth's crust. However, the villain of (146)Sm measurement through AMS is its naturally occurring stable isobar (146)Nd which is a million times more abundant than the trace amount of (146)Sm. Therefore an efficient method for the separation of samarium and neodymium is required to measure (146)Sm through AMS. A simple liquid-liquid extraction (LLX) based method for separation of samarium and neodymium has been developed using radiometric simulation. Di-(2-ethylhexyl)phosphoric acid (HDEHP) has been used as the organic reagent. A very high separation factor ( approximately 10(6)) can be achieved when a solution containing samarium and neodymium is reduced by hydroxylamine hydrochloride followed by extraction with 0.1% HDEHP diluted in cyclohexane from 0.025 M HCl solution.     

Polyfluorinated hydrazones in organic synthesis

Oxidation ofN,N-unsubstituted 1,1,1,5,5,5-hexafluoro-4-trifIuoromethylpentane-2,3-dione bishydrazone with sulfuryl chloride or bromine in CCl₄ gives 1-amino-5-trifluoromethyl-4-(1,1,1,3,3,3-hexafluoroisopropyl)-1,2,3-triazole in high yield. Its structure has been confirmed by X-ray structural analysis.For Part 1 see Ref. 1.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No.12, pp. 2465–2467, December, 1995.The work was supported by the Russian Foundation for Basic Research (Project Nos. 94-03-08548 and 94-03-08338) and the International Science Foundation (Grants NDL 000 and NDL 300).     

Variational derivation and extensions of distributed approximating functionals

Summary Extensions of the "Distributed Approximating Functional (DAF) approach to approximating functions and their derivatives are given. The method, although inherently approximate, can be made arbitrarily accurate, numerically stable, and computationally efficient by appropriate choice of parameters. It also provides approximate representations of quantum operators which are analytic and which can be accurate. Differences between the DAFs and more standard basis set approaches are discussed in order to clarify the properties of the DAFs. Some illustrative examples are given.Supported in part under National Science Foundation Grant CHE92-01967.The Ames Laboratory is operated for the Department of Energy by Iowa State University under Contract No 2-7405-ENG82.Supported under National Science Foundation Grants CHE-8907429 and CHE-9403416.Supported under R.A. Welch Foundation Grant E-0608.Supported under National Science Foundation Grants CHE-8907429 and CHE-9403416.     

Modulated differential scanning calorimetry in the glass transition region

Temperature-modulated calorimetry (TMC) allows the experimental evaluation of the kinetic parameters of the glass transition from quasi-isothermal experiments. In this paper, model calculations based on experimental data are presented for the total and reversing apparent heat capacities on heating and cooling through the glass transition region as a function of heating rate and modulation frequency for the modulated differential scanning calorimeter (MDSC). Amorphous poly(ethylene terephthalate) (PET) is used as the example polymer and a simple first-order kinetics is fitted to the data. The total heat flow carries the hysteresis information (enthalpy relaxation, thermal history) and indications of changes in modulation frequency due to the glass transition. The reversing heat flow permits the assessment of the first and higher harmonics of the apparent heat capacities. The computations are carried out by numerical integrations with up to 5000 steps. Comparisons of the calculations with experiments are possible. As one moves further from equilibrium, i.e. the liquid state, cooperative kinetics must be used to match model and experiment.On leave from Toray Industries, Inc., Otsu, Shiga 520, Japan.This work was supported by the Division of Materials Research, National Science Foundation, Polymers Program, Grant # DMR 90-00520 and the Division of Materials Sciences, Office of Basic Energy Sciences, U. S. Department of Energy at Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. for the U. S. Department of Energy, under contract number DE-AC05-96OR22464. Support for instrumentation came from TA Instruments, Inc. Research support was also given by ICI Paints, and Toray Industries, Inc.     

Nuclear analysis applications in cooperative texas forensic investigation program

For the past two years, a cooperative nuclear forensic investigation program has been in operation in the Nuclear Reactor Laboratory at the University of Texas at Austin. An essential partner in this program has been the Crime Laboratories of the Texas Department of Public Safety, Under this program, both routine analyses of typical physical evidence samples and comprehensive survey analyses of classes of materials with forensic importance have been carried out. Both radioisotope-excited nondispersive X-ray fluorescence and multielement instrumental neutron activation analyses have been used, the first technique for screening incoming samples and performing macro-constituent analyses and the second for performing quantitative trace element analyses. Close coordination of routine analyses with the Crime Laboratories has provided supportive and complementary analyses of physical trace evidence samples for the preparation of investigative results. Carefully selected survey projects, such as the trace element characterization of safe platers and shotgun pellets described in this paper, have contributed to the development of background data available for forensic analysis in other laboratories.     

Single run heat capacity measurements

An outline for the data analysis of single-run heat capacity measurments by dual sample DSC is presented with the following features: 1. Heat flow correction by subtracting the contribution due to the sample pan, including correction for mismatched pan masses. 2. Heat flow and temperature correction with a nonlinear temperature calibration, temperature lag correction, and heating rate correction. 3. Calculation of the cell constants for both cell positions and evaluation of the asymmetry factor between cell positions A and B. 4. Heat capacity calibration and calculation with slope and asymmetry correction. 5. Calculation of heat capacity for multiple runs. 6. Data curve fitting for heat capacity.This work was supported by the Division of Materials Research, National Science Foundation, Polymers Program, Grant # DMR 8818412 and the Division of Materials Sciences, Office of Basic Energy Sciences, U.S. Department of Energy, under Contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc. Thanks are given to TA Instruments, Inc. (New Castle, DE) for providing the commercial heat capacity software and helping with the acquisition of the calorimeter.     

Trace elements in the atmosphere determined by nuclear activation analysis and their interpretation

Concentrations of 30 elements in the atmospheric particulate material were determined by three defferent nuclear activation techniques, namely; photon, thermal neutron and 14 MeV neutron activation analysis. Trace element concentrations observed were interpreted in terms of Enrichment Factor, EF, of each element with respect to crustal abundance and coal in order to find any possible correlation between the existance of highly enriched elements in the atmosphere and pollution source materials. It was also found that enrichment factors of elements are inversly proportional with the size of particulate material. Supported in part by Funds For Overseas Research Grants and Education (FORGE) and Scientific and Technical Research Council (TBTAK) of Turkey.     

The use of multi-element concentration datasets obtained by INAA in the identification of sources of environmental pollutants

Trace element concentration patterns can be used for the identification of objects or materials. Early applications were related to the elucidation of identity or origin of objects. Recently, a number of applications have been reported of the use of trace element concentration patterns to recognize and identify components of mixtures of materials, mainly of environmental interest. In the present paper two examples are discussed of application of Target Transformation Factor Analysis to trace element concentration patterns, to identify sources of heavy metal air pollution. The materials studied are air particulate matter and epiphytic lichens used as biological accumulator.     

Melting of indium by temperature-modulated differential scanning calorimetry

The melting and crystallization of a sharply melting standard has been explored for the calibration of temperature-modulated differential scanning calorimetry, TMDSC. Modulated temperature and heat flow have been followed during melting and crystallization of indium. It is observed that indium does not supercool as long as crystal nuclei remain in the sample when analyzing quasi-isothermally with a small modulation amplitude. For standard differential scanning calorimetry, DSC, the melting and crystallization temperatures of indium are sufficiently different not to permit its use for calibration on cooling, unless special analysis modes are applied. For TMDSC with an underlying heating rate of 0.2 K min^–1 and a modulation amplitude of 0.5–1.5 K at periods of 30–90 s, the extrapolated onsets of melting and freezing were within 0.1 K of the known melting temperature of indium. Further work is needed to separate the effects originating from loss of steady state between sample and sensor on the one hand and from supercooling on the other.On leave from Toray Research Center, Inc., Otsu, Shiga 520, Japan.This work was supported by the Division of Materials Research, National Science Foundation, Polymers Program, Grant # DMR 90-00520 and the Division of Materials Sciences, Office of Basic Energy Sciences, U.S. Department of Energy at Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. for the U.S. Department of Energy, under contract number DEACOS-960R22464. Support for instrumentation came from TA Instruments, Inc. and Mettler-Toledo Inc. Research support was also given by ICI Paints.     

Crown-ether styryl dyes

Styryl dyes (4a,b) containing a 15-crown-5 fragment and isomeric 2- and 4-quinolinium residues with anN-sulfopropyl substituent undergo [2+2]-autophotocycloaddition to give cyclobutane derivatives (9a,b) in acetonitrile only in the presence of Mg(ClO₄)₂ or Ca(ClO₄)₂. The stereospecificity of both pathways of photocycloaddition and its efficiency are explained by the preorganization of the supramolecular dimers derived from thetrans-isomers of the dyes when they are bound into complexes with Mg and Ca cations.For Part 14, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2225–2230, November, 1995.The work was carried out with financial support from the Russian Foundation for Basic Research (Project code 94-03-08531) and the International Science Foundation (Grants ISF, M8Q000 and N38000).     

Crown-containing styryl dyes

New crown ether styryl dyes containing various heterocyclic moieties and substituents were synthesized. Thecis andtrans isomers of crown ether styryl dyes and their complexes with metal cations were characterized by their absorption and fluorescence spectra. Based on an analysis of the spectral parameters and the shifts of the absorption and fluorescence maxima upon photoisomerization and complexation, the effects of the nature and structure of the heterocyclic moiety on the photochromism of styryl ionophores were revealed.For Part 12, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 129–135, January, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grants No. 94-03-08-531 and 93-03-04-089) and the International Science Foundation (Grant M8QOO).     

New version of redox-troponization — oxidative expansion of apara-semiquinoid ring in the reaction of 4-methyl-4-bromomethyl-2,5-cyclohexadien-1-one with tetrakis(triphenylphosphine)palladium

4-Methyl-4-bromomethyl-2,5-cyclohexadien-1-one reacts with Pd(PPh₃)₄ in benzene to give 4-methyl-2,4,6-cycloheptatrien-1-one. The reaction occurs as intramolecular carbometallation of the enone fragment of the starting dienone followed by rearrangement—dehydrometallation or involves a sequence of steps,viz., homolytic abstraction of the halogen atom, cyclization, recyclization, and dehydrogenation.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1836–1837, September, 1995.This work was carried out with financial support from the Russian Foundation for Basic Research (Project No. 95-03-09784) and the International Science Foundation (Grants MHW 000 and MHW 300).     

Synthesis of an AIE-active fluorogen and its application in cell imaging

A fluorogen named 1-decyl-1-methyl-2,5-bis{4-[(N,N-diethylamino)methyl]phenyl}-3,4-diphenylsilole (3) was synthesized. It emitted weakly as isolated molecule but strongly as supramolecular aggregate, showing a characteristic behavior of aggregation-induced emission (AIE). The molecules of 3 formed highly emissive nanoparticles in aqueous media, which quickly and selectively marked cytoplasm of HeLa cells and posed no toxicity to the living cells. The fluorogen is thus a promising candidate material for cell imaging as a sensitive, selective and cytocompatible biosensor. Supported by the Research Grants Council of Hong Kong (Grant Nos. 603008, 601608 and 602707), the National Natural Science Foundation of China (Grant No. 20634020) and the CAO GuangBiao Foundation of Zhejiang University.     

Analysis of Iodine-129 in Environmental Materials: Quality Assurance and Applications

The long-lived radionuclide ¹²⁹I (T _1/2 = 15.7 My) occurs in the nature in very low concentrations. Since the middle of our century the environmental levels of ¹²⁹I have been dramatically changed as a consequence of civil and military use of nuclear fission. Its investigation in environmental materials is of interest for environmental surveillance, retrospective dosimetry and for the use as a natural and man-made fracers of environmental processes. We are comparing two analytical methods which presently are capable of determining ¹²⁹I in environmental materials, namely radiochemical neutron activation analysis (RNAA) and accelerator mass spectrometry (AMS). Emphasis is laid upon the quality control and detection capabilities for the analysis of ¹²⁹I in environmental materials. Some applications are discussed.     

Scanning force microscopy visualization of adsorption from liquids

Adsorption of residual impurities from liquid media on various substrates was studied by scanning force microscopy. A new express method for controlling the purity of liquids was suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2168-2173, November. 1995.The authors are sincerely grateful to T. Eriksson (Royal Institute of Technology, Stockholm, Sweden) for providing the samples of two-component films. The work of one of the authors (I. V. Yaminsky) was partially supported by the International Science Foundation (Grants N1C000 and N1C300).     

拉曼光谱在核领域研究中的应用

从核材料腐蚀就地实时监测、反应过程中核素形态表征、核环境化学极低核素浓度的分析、燃料后处理强放射性料液远距离测量等4个方面,综述了拉曼光谱在核领域中化合物分析研究中的应用现状,并指出拉曼光谱将成为未来放射性核素化合物分析表征的重要方法之一.     

Multiple melting peak analysis with gel-spun ultra-high molar mass polyethylene

The multiple melting peaks observed on differential scanning calorimetry (DSC) of ultrahigh molar-mass polyethylene fibers (UHMMPE) are analyzed as a function of sample mass. Using modern DSC capable of recognizing single fibers of microgram size, it is shown that the multiple peaks are in part or completely due to sample packing. Loosely packed fibers fill the entire volume of the pan with rather large thermal resistance to heat flow. On melting, the fibers contract and flow to collect ultimately at the bottom of the pan. This process seems to be able to cause an artifact of multistage melting dependent on the properties of the fibers. A method is proposed to greatly reduce, or even eliminate, errors of this type. The crucial elements of the analysis of melting behavior and melting temperature are decreasing the sample size and packing the individual fibers in a proper geometry, or to introduce inert media to enhance heat transport.This work was supported by the Division of Materials Research, National Science Foundation, Polymers Program, Grant # DMR 90-00520 and the Division of Materials Sciences, Office of Basic Energy Sciences, US Department of Energy at Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. for the US Department of Energy, under contract number DE-ACOS-96OR22464. Support for instrumentation came from TA Instruments, Inc. and Mettler-Toledo, research support was also given by ICI Paints.     

Learning about calorimetry

Calorimetry deals with the energetics of atoms, molecules, and phases and can be used to gather experimental details about one of the two roots of our knowledge about matter. The other root is structural science. Both are understood from the microscopic to the macroscopic scale, but the effort to learn about calorimetry has lagged behind structural science. Although equilibrium thermodynamics is well known, one has learned in the past little about metastable and unstable states. Similarly, Dalton made early progress to describe phases as aggregates of molecules. The existence of macromolecules that consist of as many atoms as are needed to establish a phase have led, however, to confusion between colloids (collections of microphases) and macromolecules which may participate in several micro- or nanophases. This fact that macromolecules can be as large or larger than phases was first established by Staudinger as late as 1920. Both fields, calorimetry and macromolecular science, found many solutions for the understanding of metastable and unstable states. The learning of modern solutions to the problems of materials characterization by calorimetry is the topic of this paper.This work was financially supported by the Div. of Materials Res., NSF, Polymers Program, Grant # DMR 90-00520 and Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. for the U. S. Department of Energy, under contract number DE-AC05-96OR22464. Support for instrumentation came from TA Instruments, Inc. Research support was also given by ICI Paints, and Toray Industries, Inc.