Authors:K. Ngai, S. Capaccioli, M. Shahin Thayyil, and N. Shinyashiki
In several current important problems in different areas of soft matter physics, controversy persists in interpreting the
molecular dynamics observed by various spectroscopies including dielectric relaxation, light scattering, nuclear magnetic
resonance, and neutron scattering. Outstanding examples include: (1) relaxation of water in aqueous mixtures, in molecular
sieves and silica-gel nanopores, and in hydration shell of proteins; and (2) dynamics of each component in binary miscible
polymer blends, in mixtures of an amorphous polymer with a small molecular glassformer, and in binary mixtures of two small
molecular glassformers. We show the applications of calorimetry to these problems have enhanced our understanding of the dynamics
and eliminated the controversies.
Digital signal processors are now available commercially for incorporation into high resolution gamma-ray spectroscopy systems. In this work, we have compared throughput, peak resolution and peak stability found in two Canberra 2060 Digital Spectrum Processors with a conventional analog processing setup in our laboratory. We have made the comparisons for five separate high purity germanium detectors which provide a range in detector size and construction. In addition, the range of input count rates chosen for study reflect those likely to be encountered in NAA. Our initial results indicate the performance to be detector specific and highly dependent on DSP setup parameters.
Authors:A. Kuno, G. Zheng, M. Matsuo, B. Takano, J. Shi, and Q. Wang
57Fe Mössbauer spectroscopy has been applied to the ultramafic rocks collected from the Jinchuan nickel deposit in China to elucidate their mineralization process. Their Mössbauer spectra consisted of two sextets ascribable to magnetite, two doublets ascribable to Fe2+ and Fe3+ in chromite, and one doublet ascribable to olivine. The closest sample to the ore body did not contain chromite and contained a doublet ascribable to pyrite and a sextet ascribable to pyrrhotite. The valence and site distribution of iron species suggested low oxygen fugacity for the formation of the Jinchuan nickel deposit.
Authors:S. Cebulak, A. Matuszewska, and A. Langier-Kuźniarowa
The paper presents the applicability of oxyreactive thermal analysis (OTA) for the investigation of different kinds of resins
both natural (recent and fossil) and synthetic. For comparative reasons and a more precise interpretation, along with OTA
infrared spectroscopy was used as a method commonly applied for the investigation of fossil resins. The results obtained prove
that the OTA method may be very useful for diversification of different kinds of resins. The parameter most valuable for the
preliminary characteristics of resins and the evaluation of their transformation was found to be the mass loss recorded on
TG curves in three definite temperature ranges.
Gamma-rays emitted from the surfaces of atmosphere-free extraterrestrial bodies such as asteroids, planets, or moons, can be measured to determine their chemical surface composition. Gamma-rays are emitted from naturally radioactive elements and, in their majority, are induced by the interaction of the energetic galactic cosmic particle radiation. Neutrons of the secondary hadron cascade contribute considerably to the gamma-ray line surface fluxes via nonelastic scattering and neutron-capture reactions. In principle, planetary gamma-ray spectroscopy resembles laboratory applications of prompt activation techniques. However, the evaluation of an orbital gamma-ray spectrum of other bodies than the Moon is difficult, as comparisons to so-called ground truth values, which functioned as standards, are not possible. Future planetary exploration missions will require the evaluation of recorded gamma-ray spectra without such standards. Therefore, in an attempt to overcome some of these difficulties, prompt gamma-ray spectra of planetary constituents were measured in a set of laboratory experiments with neutron-generator and cyclotron produced neutrons of energies up to 78 MeV. The significance of neutron-capture and nonelastic scattering gamma-ray lines for the characterization of major elements were established, and the application of the results to planetary gamma-ray spectroscopy of asteroids is discussed.
Authors:R. Keyser, W. Hensley, T. Twomey, and D. Upp
The necessity to monitor international commercial transportation for illicit nuclear materials resulted in the installation
of many nuclear radiation detection systems in Portal Monitors. To overcome the difficulty of innocent alarms due to a large
content of natural radioactivity or medical nuclides, Department of Homeland Security (DHS) supported the writing of the ANSI
N42.38 standard (Performance Criteria for Spectroscopy-Based Portal Monitors used for Homeland Security) to define the performance
of a portal monitor with nuclide identification capabilities, called a Spectroscopy Portal Monitor. To accomplish the necessary
performance, several different HPGe detector configurations were modeled using MCNP for the horizontal field of view (FOV)
and vertical linearity of response over the detection zone of 5 meters by 4.5 meters for 661 keV as representative of the
expected nuclides of interest. The configuration with the best result was built and tested. The results for the FOV as a function
of energy and the linearity show good agreement with the model and performance exceeding the requirements of N42.38.
The transition of cubic indium hydroxide to cubic indium oxide has been studied by thermogravimetric analysis complimented
with hot-stage Raman spectroscopy. Thermal analysis shows the transition of In(OH)3 to In2O3 occurs at 219 °C. The structure and morphology of In(OH)3 synthesised using a soft chemical route at low temperatures was confirmed by X-ray diffraction and scanning electron microscopy.
A topotactical relationship exists between the micro/nano-cubes of In(OH)3 and In2O3. The Raman spectrum of In(OH)3 is characterised by an intense sharp band at 309 cm−1 attributed to ν1 In–O symmetric stretching mode, bands at 1137 and 1155 cm−1 attributed to In-OH δ deformation modes, bands at 3083, 3215, 3123 and 3262 cm−1 assigned to the OH stretching vibrations. Upon thermal treatment of In(OH)3, new Raman bands are observed at 125, 295, 488 and 615 cm−1 attributed to In2O3. Changes in the structure of In(OH)3 with thermal treatment is readily followed by hot-stage Raman spectroscopy.
The thermal denaturation of β-lactoglobulin in the presence of urea and alkylurea solutions were measured. In the presence
of a high concentration of urea this protein shows not only heat but also cold denaturation. For studying the effect of temperature
two methods were used, differential scanning calorimetry (DSC) and UV-spectroscopy. DSC provides direct model-independent
determination of the transition enthalpy in comparison with UV-spectroscopy, which gives only apparent or van't Hoff enthalpy
of transition. The UV-melting curves were analyzed on the basis of a two-state approximation. The apparent standard enthalpies
of thermal denaturation, ΔHapp.o
, were compared with calorimetric ones.
Sensitivity data for low energy photon spectroscopy used in photon activation analysis are compiled and compared with those
for classical gamma-spectroscopy. All elements of the periodic table with a few exceptions were irradiated with 30 MeV-bremsstrahlung
of a linear electron accelerator. Low energy photon spectra were taken with a LEP-detector as well as with a coaxial Ge(Li)-detector.
Resulting data were processed by computer. The results show that in some cases low energy photon spectroscopy used in photon
activation analysis provides higher sensitivity than can be achieved by classical gamma-spectroscopy.
Compton suppression gamma-spectroscopy provides an efficient method for measuring the concentration of226Ra,228Ra, and210Pb in ocean sediments. The background reduction realized from the suppressed mode of operation provides an “active shield”
to allow for the low-level counting required for these measurements. We have used the method to study the possible accumulation
of radium from produced waters in sediments from Gulf of Mexico sites of varied distances from drill platforms. In addition,210Pb levels were determined to evaluate the use of our spectrometer for this purpose. Baseline undisturbed concentrations have
been obtained from the study of subsurface core material which predates drilling activities. Correlations of radium isotope
concentrations with iron and barium provide information concerning the possible relationships between radium levels and drilling
activity (excess barium) and natural variations in sediment texture (iron).