The new proton radioactivities 165,166,167 Ir and 171 Au have been observed. The Ir isotopes were produced via the 92 Mo( 78 Kr,pxn) 165,166,167 Ir reactions at 357 and 384 MeV. 171 Au was produced via the 96 Ru( 78 Kr,p2n) 171 Au reaction at 389 MeV. The proton emitters were each identified by position, time, and energy correlations between the implantation of a residual nucleus into a double-sided silicon strip detector, the observation of a decay proton, and the subsequent observation of a decay alpha particle from the daughter nucleus ͑ 164,165,166 Os and 170 Pt, respectively͒. Both 166 Ir and 167 Ir have proton-emitting ground and isomeric states, which also decay by alpha emission. The proton-decay rates have been reproduced by calculations using the WKB barrier penetration approximation and a low-seniority shell-model calculation of the spectroscopic factors. The alpha decays of the four nuclei are followed by chains of alpha decays, allowing the determination of single-particle orbital orderings. Mass information has also been obtained from the alpha-decay chains because a connection to a known mass can be obtained for one of the nuclei. Ground-state mass excesses are reported for 151 Tm, 154 Yb, 155 Lu, 158 Hf, 159 Ta, 162 W, 163 Re, 166 Os, 167 Ir, and 170 Pt. The mass excess for 171m Au is also given. Proton separation energies are also deduced for the odd-Z alpha daughter nuclei of the Ir proton emitters.
Fourier transform infrared (FTIR) spectroscopy is a powerful tool for the identification and characterization of pollen and spores. However, interpretation and multivariate analysis of infrared microscopy spectra of single pollen grains are hampered by Mie-type scattering. In this paper, we introduce a novel sampling setup for infrared microspectroscopy of pollens preventing strong Mie-type scattering. Pollen samples were embedded in a soft paraffin layer between two sheets of polyethylene foils without any further sample pretreatment. Single-grain infrared spectra of 13 different pollen samples, belonging to 11 species, were obtained and analyzed by the new approach and classified by sparse partial least-squares regression (PLSR). For the classification, chemical and physical information were separated by extended multiplicative signal correction and used together to build a classification model. A training set of 260 spectra and an independent test set of 130 spectra were used. Robust sparse classification models allowing the biochemical interpretation of the classification were obtained by the sparse PLSR, because only a subset of variables was retained for the analysis. With accuracy values of 95% and 98%, for the independent test set and full cross-validation respectively, the method is outperforming the previously published studies on development of an automated pollen analysis. Since the method is compatible with standard air-samplers, it can be employed with minimal modification in regular aerobiology studies. When compared with optical microscopy, which is the benchmark method in pollen analysis, the infrared microspectroscopy method offers better taxonomic resolution, as well as faster, more economical, and bias-free measurement.
In this paper, we first provide an overview of the Mie type scattering at absorbing materials and existing correction methods, followed by a new method to obtain the pure absorbance spectra of biological systems with spherical symmetry. This method is a further development of the recently described iterative algorithm of van Dijk et al. The method is tested on FTIR synchrotron spectra of polymethyl methacrylate (PMMA) microspheres and pollen grains with approximately spherical shape. The imaginary part of the refractive index was successfully recovered for both systems. Good agreement was obtained between the pure absorbance spectra obtained by this method and the measured spectra.
We have developed a methodology for calibrating 68 Ge radioactivity content in a commercially available calibration source for activity calibrators in a way that is traceable to the national standard. Additionally, the source was cross-calibrated for equivalent 18 F content by direct comparison with the national standard for 18 F in the same geometry. Methods: Sources containing standardized 68 GeCl 4 or 18 F-FDG solutions were prepared at the National Institute of Standards and Technology (NIST) with mock syringe blanks used in the construction of a commercially available epoxy-based 68 Ge calibration source. These sources and several NIST-constructed epoxy-based 68 Ge mock syringes were then used as artifact standards to determine calibration factors for NIST-maintained activity calibrators and secondary standard ionization chambers to enable calibration of the actual commercial sources. A direct comparison between the solution-based 68 Ge sources and the 18 F-FDG sources allowed for an empiric determination of the relative response for these radionuclides in several commercial activity calibrators. Potential measurement effects due to differences between the solution composition and the epoxy and theoretic 68 Ge-to-18 F response ratios were studied by Monte Carlo simulation. Results: The calibration factors developed in this study enabled NIST to calibrate epoxy-based mock syringe sources with a relative combined standard uncertainty of 0.52%. The direct comparisons of the 68 Ge and 18 F standards in the various ionization chambers allowed the activity to be expressed in terms of equivalent 18 F activity with a relative combined standard uncertainty of about 0.9%. Conclusion: The ability for NIST to calibrate these epoxybased mock syringes enabled, for the first time to our knowledge, the direct traceability to the national 68 Ge standard to be established for this type of source. Through a direct comparison with the NIST 18 F standard, the determination of the relative response ratios in activity calibrators enabled the equivalent 18 F activity to be determined in a way that was also traceable to the national 18 F activity standard. The ability to obtain quantitative data from PET studies has led to an increase in its use in drug discovery. The comparability of results of biodistribution studies across a population of patients in multiple clinical sites using imaging data acquired with different scanners and analyzed with different algorithms requires the data to be linked to a common standard to reliably draw conclusions about differences in patient response. Moreover, the ability to discern small changes in tumor metabolism during a course of treatment can be realized only if there is a way to ensure that the calibrations of all the associated measurement instrumentation (e.g., activity calibrators, commonly known as dose calibrators, and PET scanners) are constant over time.The National Institute of Standards and Technology (NIST) is the national metrology institute of the United States and is responsib...
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