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Bulk superconducting samples of type Tl0.5Pb0.5Sr1.6Ba0.4CaCu2−x
Ru
x
O7−δ, (Tl, Pb)/Sr-1212, with 0.0 ≤ x ≤ 0.525 were prepared by the conventional one-step solid-state reaction technique. The prepared samples were investigated
using X-ray powder diffraction, electrical resistivity and electron paramagnetic resonance (EPR) measurements. Enhancement
of the phase formation, superconducting transition temperature T
c and hole carriers concentration P was observed up to x = 0.075. For x > 0.075, a reverse trend was observed. EPR spectra were measured at different temperatures (120–290 K) for all prepared samples.
The number of spins N participating in the resonance and the paramagnetic susceptibility χ were calculated as a function of both Ru-content and
temperature. N and χ increased as the Ru-content increased. A linear relationship between logN and 1/T was established, from which the activation energy E
a was calculated as a function of the Ru-content. The temperature dependence of χ was fitted according to Curie–Weiss type
of magnetic behavior. Curie constant C, Curie temperature θ, the effective magnetic moment μ and the electronic specific heat γ were estimated as a function of the Ru-content. 相似文献
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M. E. Keillor L. E. Erikson C. E. Aalseth A. R. Day E. S. Fuller B. D. Glasgow E. W. Hoppe T. W. Hossbach L. K. Mizouni A. W. Myers C. T. Overman A. Seifert T. J. Stavenger 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(2):683-687
The Pacific Northwest National Laboratory (PNNL) is currently developing a custom software suite capable of automating many of the tasks required to accurately analyze coincident signals within gamma spectrometer arrays. During the course of this work, significant crosstalk was identified in the energy determination for spectra collected with a new low-background intrinsic germanium (HPGe) array at PNNL. The HPGe array is designed for high detection efficiency, ultra-low-background performance, and sensitive γ–γ coincidence detection. The first half of the array, a single cryostat containing seven HPGe crystals, was recently installed into a new shallow underground laboratory facility. This update will present a brief review of the germanium array, describe the observed crosstalk, and present a straight-forward empirical correction that significantly reduces the impact of this crosstalk on the spectroscopic performance of the system. 相似文献
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ABSTRACTBayfol (PC-PBT blend ?lm) is a class of polymeric solid-state nuclear track detector which has a lot of applications in several radiation detection ?elds. It is a bisphenol-A polycarbonate PC blended with polybutylene terephthalate PBT. Bayfol/Palladium (PC-PBT/Pd) nanocomposite films have been deposited using the molding technique. It is worth mentioning that this report is almost the first one dealing with the topic of the changes of physical properties of Bayfol/Pd nanocomposite due to laser exposure. Samples from PC-PBT/Pd (5?wt%) nanocomposite were exposed to IR-pulsed laser of 5-W power, capable of producing 2000 pulses per second with pulse duration of 200?ns at 904?nm. The laser fluences were in the range 2–25?J/cm2. The resultant modi?cations in the exposed nanocomposite samples have been studied as a function of fluence using different characterization techniques such as X-ray diffraction (XRD), UV spectroscopy and color difference studies. The results indicate the proper dispersion of Pd nanoparticles in the PC-PBT matrix that causes a strong intermolecular interaction between Pd and PC-PBT, resulted in an increase in refractive index and the amorphous phase. Also, it is found that the laser exposure reduces the optical energy gap that could be attributed to the increase in structural disorder of the exposed PC-PBT/Pd nanocomposites due to crosslinking. Further, the color intensity ΔE, which is the color difference between the exposed samples and the non-exposed one, was increased with increasing the laser fluence, convoyed by a significant increase in the green and yellow color components. 相似文献
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Transglutaminases (TGases) catalyze the intermolecular cross-linking of certain proteins and tissue TGases (TG2) are involved in diverse biological processes. Unregulated, high TGase activities have been implicated in several physiological disorders, but few reversible inhibitors of TG2 have been reported. Herein, we report the synthesis of a series of novel trans-cinammoyl derivatives, discovered to be potent inhibitors of guinea pig liver transglutaminase. The most effective inhibitors evaluated can be sorted into two subclasses: substituted cinnamoyl benzotriazolyl amides and the 3-(substituted cinnamoyl)pyridines, referred to more commonly as azachalcones. Kinetic evaluation of both of these subclasses revealed that they display reversible inhibition and are competitive with acyl donor TGase substrates at IC50 values as low as 18 microM. An analysis of structure-activity relationships within these series of inhibitors permitted the identification of potentially important binding interactions. Further testing of some of the most potent inhibitors demonstrated their selectivity for TG2 and their potential for further development. 相似文献
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Craig Aalseth Erica Andreotti Dirk Arnold Joan-Albert Sanchez Cabeza Detlev Degering Andrea Giuliani Raquel Gonzales de Orduña Rodolfo Gurriaran Mikael Hult Martin Keillor Matthias Laubenstein Gilbert le Petit Romul Mircea Margineanu Murray Matthews Harry Miley Iolanda Osvath Monica Pellicciari Wolfango Plastino Hardy Simgen Marc Weber Robert Werzi 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):731-735
Aerosol samples collected on filter media were analyzed using HPGe detectors employing varying background-reduction techniques in order to experimentally evaluate the opportunity to apply ultra-low background measurement methods to samples collected, for instance, by the Comprehensive Test Ban Treaty International Monitoring System (IMS). In this way, realistic estimates of the impact of low-background methodology on the sensitivity obtained in systems such as the IMS were assessed. The current detectability requirement of stations in the IMS is 30 μBq/m3 of air for 140Ba, which would imply ~106 fissions per daily sample. Importantly, this is for a fresh aerosol filter. One week of decay reduces the intrinsic background from radon daughters in the sample allowing much higher sensitivity measurement of relevant isotopes, including 131I. An experiment was conducted in which decayed filter samples were measured at a variety of underground locations using Ultra-Low Background (ULB) gamma spectroscopy technology. The impacts of the decay and ULB are discussed. 相似文献
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Martin E. Keillor Craig E. Aalseth Anthony R. Day James E. Fast Eric W. Hoppe Brian J. Hyronimus Todd W. Hossbach Harry S. Miley Allen Seifert Glen A. Warren 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):703-708
Physics experiments, environmental surveillance, and treaty verification techniques continue to require increased sensitivity
for detecting and quantifying radionuclides of interest. This can be done by detecting a greater fraction of gamma emissions
from a sample (higher detection efficiency) and reducing instrument backgrounds. A current effort for increased sensitivity
in high resolution gamma spectroscopy will produce an intrinsic germanium (HPGe) array designed for high detection efficiency,
ultra-low-background performance, and useful coincidence efficiencies. The system design is optimized to accommodate filter
paper samples, e.g. samples collected by the Radionuclide Aerosol Sampler/Analyzer (RASA). The system will provide high sensitivity
for weak collections on atmospheric filter samples, as well as offering the potential to gather additional information from
more active filters using gamma cascade coincidence detection. The current effort is constructing an ultra-low-background
HPGe crystal array consisting of two vacuum cryostats, each housing a hexagonal array of 7 crystals on the order of 70% relative
efficiency per crystal. Traditional methods for constructing ultra-low-background detectors are used, including use of materials
known to be low in radioactive contaminants, use of ultra pure reagents, clean room assembly, etc. The cryostat will be constructed
mainly from copper electroformed into near-final geometry at PNNL. Details of the detector design, simulation of efficiency
and coincidence performance, HPGe crystal testing, and progress on cryostat construction are presented. 相似文献
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Keillor JW 《Chemistry & biology》2005,12(4):410-412
Khosla and coworkers report the synthesis of peptidic dihydroisoxazole derivatives, the in vitro evaluation of these novel compounds as inhibitors of recombinant human tissue transglutaminase (TG2), and their oral bioavailability and efficacy for the synergistic treatment of glioblastoma tumors. 相似文献