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YbCu5−x
Al
x
provides the possibility to tune ground state properties by a change of the valence due to the Cu/Al substitution, by pressure
as well as by the application of a magnetic field. Near to the critical concentration x
cr≈1.5 non-Fermi-liquid properties (NFL) are obvious, obeying hyperscaling. If magnetic order sets in for x>1.5, the application of moderate magnetic fields quenches order and again NFL features become evident. Hyperscaling in this
case indicates strongly interacting spin fluctuations. 相似文献
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Lowe RH Karschner EL Schwilke EW Barnes AJ Huestis MA 《Journal of chromatography. A》2007,1163(1-2):318-327
A two-dimensional (2D) gas chromatography/electron impact-mass spectrometry (GC/EI-MS) method for simultaneous quantification of Delta(9)-tetrahydrocannabinol (THC), 11-hydroxy-Delta(9)-tetrahydrocannabinol (11-OH-THC), and 11-nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid (THCCOOH) in human plasma was developed and validated. The method employs 2D capillary GC and cryofocusing for enhanced resolution and sensitivity. THC, 11-OH-THC, and THCCOOH were extracted by precipitation with acetonitrile followed by solid-phase extraction. GC separation of trimethylsilyl derivatives of analytes was accomplished with two capillary columns in series coupled via a pneumatic Deans switch system. Detection and quantification were accomplished with a bench-top single quadrupole mass spectrometer operated in electron impact-selected ion monitoring mode. Limits of quantification (LOQ) were 0.125, 0.25 and 0.125 ng/mL for THC, 11-OH-THC, and THCCOOH, respectively. Accuracy ranged from 86.0 to 113.0% for all analytes. Intra- and inter-assay precision, as percent relative standard deviation, was less than 14.1% for THC, 11-OH-THC, and THCCOOH. The method was successfully applied to quantification of THC and its 11-OH-THC and THCCOOH metabolites in plasma specimens following controlled administration of THC. 相似文献
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Milman G Barnes AJ Schwope DM Schwilke EW Goodwin RS Kelly DL Gorelick DA Huestis MA 《Analytical and bioanalytical chemistry》2011,401(2):599-607
Oral fluid (OF) is an increasingly accepted matrix for drug testing programs, but questions remain about its usefulness for
monitoring cannabinoids. Expectorated OF specimens (n = 360) were obtained from 10 adult daily cannabis smokers before, during, and after 37 20-mg oral Δ9-tetrahydrocannabinol (THC) doses over 9 days to characterize cannabinoid disposition in this matrix. Specimens were extracted
and analyzed by gas chromatography–mass spectrometry with electron-impact ionization for THC, 11-hydroxy-THC, cannabidiol,
and cannabinol, and negative chemical ionization for 11-nor-9-carboxy-THC (THCCOOH). Linear ranges for THC, 11-hydroxy-THC,
and cannabidiol were 0.25–50 ng/mL; cannabinol 1–50 ng/mL; and THCCOOH 5–500 pg/mL. THCCOOH was the most prevalent analyte
in 344 specimens (96.9%), with concentrations up to 1,390.3 pg/mL. 11-hydroxy-THC, cannabidiol, and cannabinol were detected
in 1, 1, and 3 specimens, respectively. THC was detected in only 13.8% of specimens. The highest THC concentrations were obtained
at admission (median 1.4 ng/mL, range 0.3–113.6) from previously self-administered smoked cannabis. A total of 2.5 and 3.7%
of specimens were THC-positive at the recommended Substance Abuse and Mental Health Services Administration (2 ng/mL) and
Driving Under the Influence of Drugs, Alcohol and Medicines (DRUID) (1 ng/mL) confirmation cutoffs, respectively. THC is currently
the only analyte for monitoring cannabis exposure in OF; however, these data indicate chronic therapeutic oral THC administration
and illicit oral THC use are unlikely to be identified with current guidelines. Measurement of THCCOOH may improve the detection
and interpretation of OF cannabinoid tests and minimize the possibility of OF contamination from passive inhalation of cannabis
smoke. 相似文献
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