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161.
Burnett TJ Lombardi K Rodewald JM Brunelle SL MacDougall J Coleman MR 《Journal of AOAC International》2012,95(4):959-991
The single-laboratory validation (SLV) of an LC-MS/MS method for determination and confirmation of two ionophores, narasin and monensin, in animal tissues is described. The data demonstrated linearity of matrix-matched calibration curves using a weighted (1/x) regression and selectivity of the method for narasin and monensin in the presence of lasalocid, salinomycin, maduramycin, nicarbazin, and sulfadiazine. Recoveries varied from 86.2 to 103.5% for narasin and 89.1 to 105.1% for monensin. Intertrial repeatability precision [relative standard deviation of repeatability (RSDr)] varied from 3.9 to 13.8% for narasin and 3.3 to 16.3% for monensin in fortified tissue. Precision of the method was verified in incurred tissues. The LOQ of the method was validated and ranged from 0.45 ng/g in milk, to 4.0 ng/g in chicken fat, but was 0.75 ng/g for most tissues. Two confirmatory ions for each analyte were examined across all matrixes, resulting in estimated false-negative rates of 0.00% (95% confidence interval of 0.00-0.68%) for monensin ions (540 samples) compared to the U.S. and European Union (EU) acceptance criteria. The confirmatory ions for narasin demonstrated 0.00% false-negative rates (95% confidence interval of 0.00-0.58%) when compared to either the U.S. or EU criteria in 630 samples. The method was robust when small changes in method parameters were made and stability of fortified tissues, extracts, and calibration solutions were estimated. The data satisfy the requirements of the AOAC Stakeholder Panel on Veterinary Drug Residue for SLV studies, and the method was adopted Official Methods of Analysis First Action 2011.24 by the AOAC Expert Review Panel on Veterinary Drug Residues. 相似文献
162.
J. L. Burnett I. W. Croudace P. E. Warwick 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(1):25-28
Rapid determination of 222Rn and 220Rn progeny (214Pb, 212Pb, 214Bi, 212Bi) is achievable using manganese dioxide (MnO2) precipitation with analysis by γ-spectrometry. This is of interest to environmental monitoring programmes that utilise gross activity methods to screen for anthropogenic radionuclides. The contribution from these naturally occurring radionuclides (NOR) varies, and is difficult to experimentally measure due to short half-lives (t ½ = 19.9 m–10.64 h) and low environmental activity (<0.1 Bq L?1). The extraction efficiency of the technique is above 90%, and above 80% for other nuclides (232Th, 238U, 235U, 228Ac, 226Ra, 224Ra, 210Pb, 54Mn). Short-lived NOR have been measured at two surface water locations, and indicates elevated 214Bi activity of 4.0 ± 1.1 Bq L?1. 相似文献
163.
Jenny Wooldridge Steph Ryding Simon Brown Tim L. Burnett Markys G. Cain Robert Cernik Ricardo Hino Mark Stewart Paul Thompson 《Journal of synchrotron radiation》2012,19(5):710-716
The characteristics of a new ferroelectric measurement system at the European Synchrotron Radiation Facility are presented. The electric‐field‐induced phase transitions of Pb(Mg1/3Nb2/3)O3–xPbTiO3 are determined viain situ measurements of electric polarization within the synchrotron diffraction beamline. Real‐time data collection methods on single‐crystal samples are employed as a function of frequency to determine the microstructural origin of piezoelectric effects within these materials, probing the dynamic ferroelectric response. 相似文献
164.
G. Leslie Burnett John C. Rohanna Steve Rosenberg Alfred K. Schultz Javier Read de Alaniz 《Journal of polymer science. Part A, Polymer chemistry》2016,54(13):1955-1960
We present the development of a method for the determination of methylene bridge crosslinking in 13C‐labeled chloromethylated polystyrene‐divinylbenzene resins. Our system uses a new room temperature reduction of the chloromethyl groups that circumvents the possible challenges associated with additional crosslinking. We demonstrate how the reduction of the chloromethyl groups allowed for the determination of methylene bridging, derived from the methylenebis(ethenylbenzene) crosslinker, based on the integration of the methylene signal in the 13C NMR spectra. Utilizing this method, the total crosslinking within the chloromethylated resin generated at 35 °C was determined to be upward of 10 wt %, which increased from 6 wt % in the unfunctionalized resin. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1955–1960 相似文献
165.
Thorough examination of the current literature as well as publicly available databases allowed us to qualify aromatic fluorine as a unique modulator of biological properties of organic compounds. In some rare cases, introduction of fluorine increased biological activity 100,000 times and even higher. We have also identified several examples where aromatic fluorine substantially reduced biological activity. Selected individual cases of extreme modulation are presented and discussed in the paper. 相似文献
166.
Dean P Burnett AD Tych K Khanna SP Lachab M Cunningham JE Linfield EH Davies AG 《The Journal of chemical physics》2011,134(13):134304
We report terahertz (THz) diffuse reflectance measurements of bulk powdered samples at a frequency of 2.83 THz using a narrowband quantum cascade laser. Samples studied comprise polydisperse powders with absorption coefficients extending over two orders of magnitude from ~3 cm(-1) to >200 cm(-1). Diffuse reflectance measurements are used to obtain the effective absorption coefficient of these samples from the backscattering cross-section, predicted under the quasi-crystalline approximation (QCA) in the T-matrix formulation and in conjunction with the Percus-Yevick pair distribution function. Results are compared with effective absorption coefficients obtained from THz time-domain spectroscopy measurements on pressed pellet samples, and show good agreement over the range of effective absorption coefficients studied. We observe that the backscattering cross-section predicted under the QCA is strongly dependent on both the real and imaginary components of the complex permittivity of the sample, and we show that reliable determination of the absorption coefficient from diffuse reflectance measurements therefore requires knowledge of the sample's refractive index. This work demonstrates the applicability of diffuse reflectance measurements, using a THz frequency quantum cascade laser, to the high-resolution spectroscopic analysis of bulk powdered samples at THz frequencies. 相似文献
167.
168.
S.M. Burnett A.M. Baxter S. Hinds F. Pribac R.H. Spear W.J. Vermeer 《Nuclear Physics A》1985,432(2):514-524
Reduced transition probabilities, B(E2) and B(E3), have been measured for low-lying 2+ and 3? states in 132, 134, 136, 138Ba using Coulomb excitation by 40 MeV 12C ions. The B(E2) values are in general consistent with previous measurements and the B(E3;0+ → 31?) values are 0.176 ± 0.022, 0.148 ± 0.018, 0.155 ± 0.018 and 0.133 ± 0.013 e2 · b3 for 132, 134, 136, 138Ba respectively. These B(E3) values correspond to about 24 to 17 W.u. and such enhancements suggest that these 3? states have an essentially collective character which may be attributed to octupole vibrations. 相似文献
169.
M. Dayon V. Rappoport V. Smirnitsky R. Ammar V. Ammosov A. Bakich V. Baranov Yu. Batusov S. Bunyatov T. Burnett D. Coppage R. Davis O. Egorov V. Gapienko P. Goritchev J. Gress M. Ivanova A. Jurak V. Klukhin E. Kolganova V. Koreshev S. Krzywdzinski O. Kuznetsov N. Kwak J. Lord V. Lyukov A. Olszewski L. Peak P. Pitukhin E. Pozharova R. Riemer R. Rosenbladt H. Rubin V. Shamanov V. Sirotenko W. Smart R. Stump H. Tchernev L. Voyvodic B. Wilczynska H. Wilczynski R. Wilkes W. Wolter B. Wosiek 《Zeitschrift fur Physik C Particles and Fields》1992,56(3):391-393
Backward emitted protons with momentump>0.3 GeV/c in interactions of neutrino in the energy range 10–200 GeV with photoemulsion nuclei were investigated. Energy spectrum slope parameter of backward protons was measured to beT 0=48.9±7.9 MeV. TheA-dependence power index of relative mean yield of backward protons was found to bea=0.68±0.12. A drop in the mean yield of backward protons at the four momentum squared over ~15 (GeV/c)2 (the neutrino energy over ~50 GeV) was observed. 相似文献
170.
J. L. Burnett M. G. Cantaloub M. F. Mayer H. S. Miley 《Journal of Radioanalytical and Nuclear Chemistry》2017,312(1):81-86
A high-sensitivity multidimensional gamma-spectrometer is being developed within the shallow underground laboratory at Pacific Northwest National Laboratory (PNNL, USA). The system consists of two broad energy germanium detectors, inside a low-background shield, fitted with a cosmic veto system. The detector has advanced functionality, including operation in single or combined detector mode, with reductions in the cosmic background of 49.6% and Compton suppression of 6.5%. For selected radionuclides this provides increased peak identification, reductions in uncertainty of 27.6% and MDA improvements of 52.7%. The design uses commercially off-the-shelf components to provide a powerful solution for low-level nuclear measurements. 相似文献