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191.
192.
Sung‐Hee Cho Jeongae Lee Man Ho Choi Won‐Yong Lee Bong Chul Chung 《Biomedical chromatography : BMC》2009,23(4):426-433
Capillary electrophoresis–electrospray tandem mass spectrometry (CE‐ESI/MS/MS) is a simple and highly sensitive method for quantifying seven urinary androgen glucuronides. The urine samples were diluted and filtered through a membrane filter, and the filtrate was injected into a CE‐MS/MS system without further sample preparation steps such as extraction and derivatization. The calibration ranges were 0.01–5 µg/mL for glucuronides of androsterone and 11β‐OHAn‐3G, and 5–500 ng/mL for glucuronides of 11‐ketoAn, DHEA, testosterone, epitestosterone and DHT. The linearity of the method was 0.992–0.998, and the limits‐of‐detection at a signal‐to‐noise ratio of 3 were 5–10 ng/mL. The coefficients of variation were in the range of 4.0–9.0% for intra‐day assay and 4.1–9.8% for inter‐day assay. The proposed method may be applicable to metabolic profiling in both quantitative and qualitative analysis. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
193.
Il Yoon Ki-Min Park Jineun Kim Bong Gon Kim Shim Sung Lee 《Analytical sciences》2003,19(10):1461-1462
The structure of an S2O mixed-donor macrocycle incorporating para-substituted xylyl subunit was characterized by a single crystal X-ray analysis. The crystal structure shows an exo-dentate orientation of sulfur and oxygen donor atoms due to the fully stretched aliphatic ring conformation. Thus all of torsional angles between donor atoms are arranged anti and S...S distance in a ring is 6.764(1)A, which is larger than those values of ortho- and meta-type analogs. The observed high rigidity of the ring conformation may induce the extraordinary behaviors in chelation. 相似文献
194.
Yang WJ Kim DY Jeong MY Kim HM Lee YK Fang X Jeon SJ Cho BR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(14):4191-4198
A series of 2,6- and 2,7-bis(styryl)anthracene derivatives with the donors at the styryl group and acceptors at the 9,10-positions have been synthesized, and their two-photon cross sections (Phidelta(max)) were determined. These compounds exhibit a peak two-photon absorptivity (delta(max)) in the range of 700-2500 GM at 780-1030 nm. Values of lambda(max) and Stokes shifts increase as the acceptor is changed to a stronger one. There is also a parallel increase in lambda(2)max and delta(max) with the same variation of the chromophore structure. Both lambda (2)(max)and Phidelta(max) have been optimized by introducing donor-substituted styryl groups at the 2,6-positions and p-cyanophenyl groups at the 9,10-positions, respectively. The effect of a pi center on the two-photon absorption properties has been assessed by comparing the existing data for a variety of D-pi-D derivatives. 相似文献
195.
Ciprian?FoiasEmail author Il?Bong?Jung Eungil?Ko Carl?Pearcy 《Israel Journal of Mathematics》2005,145(1):83-91
We consider the question of which operators on Hilbert space admit a moment sequence, and show, in particular, that ifT is any operator inL(itH) that can be written asT=N+K, whereN is normal andK is compact, andM⊂itH is any invariant subspace forT, then the restrictionT/itM admits such a sequence. 相似文献
196.
In this note we give an example of an ∞-hyponormal operator T whose Aluthge transform
is not (1+ɛ)-hyponormal for any ɛ > 0 and show that the sequence
of interated Aluthge transforms of T need not converge in the weak operator topology, which solve two problems in [6]. 相似文献
197.
Gaffney KJ Lindenberg AM Larsson J Sokolowski-Tinten K Blome C Synnergren O Sheppard J Caleman C MacPhee AG Weinstein D Lowney DP Allison T Matthews T Falcone RW Cavalieri AL Fritz DM Lee SH Bucksbaum PH Reis DA Rudati J Macrander AT Fuoss PH Kao CC Siddons DP Pahl R Moffat K Als-Nielsen J Duesterer S Ischebeck R Schlarb H Schulte-Schrepping H Schneider J von der Linde D Hignette O Sette F Chapman HN Lee RW Hansen TN Wark JS Bergh M Huldt G van der Spoel D Timneanu N Hajdu J Akre RA Bong E 《Physical review letters》2005,95(12):125701
The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid. 相似文献
198.
N. J. Fine and L. Gillman (1962) showed the existence of a remote point in βR using the Continuum Hypothesis(CH). In this paper we show that the existence of a remote point is independent from the CH for a class of spaces which includes metric spaces. 相似文献
199.
Elimination reactions of 2-X-4-NO2C6H3CH2C(O)OC6H3-2-Y-4-NO2 [X = H (1), NO2 (2)] promoted by R2NH/R2NH2+ in 70 mol % MeCN(aq) have been studied kinetically. The base-promoted eliminations from 1 proceeded by the E2 mechanism when Y = Cl, CF3, and NO2. The mechanism changed to the competing E2 and E1cb mechanisms by the poorer leaving groups (Y = H, OMe) and to the E1cb extreme by the strongly electron-withdrawing beta-aryl group (2, X = NO2). The values of beta = 0.14 and beta(lg) = 0.10-0.21 calculated for elimination from 1 (Y = NO2) indicate a reactant-like transition state with small extents of proton transfer and C(alpha)-OAr bond cleavage. The extent of proton transfer increased with a poorer leaving group, and the degree of leaving group bond cleavage increased with a weaker base. Also, the changes in the k(1) and k(-1)/k(2) values with the reactant structure variation are consistent with the E1cb mechanism. From these results, a plausible pathway of the change of the mechanism from E2 to the E1cb extreme is proposed. 相似文献
200.
Open-configuration magnetic resonance imaging (MRI) systems are becoming increasingly desirable for musculoskeletal imaging and image-guided radiotherapy because of their non-claustrophobic configuration. However, geometric image distortion in large fields-of-view (FOV) due to field inhomogeneity and gradient nonlinearity hinders the practical applications of open-type MRI. We demonstrated the use of geometric distortion correction for increasing FOV in open MRI. Geometric distortion was modeled and corrected as a global polynomial function. The appropriate polynomial order was identified as the minimum difference between the coordinates of control points in the distorted MR image space and those predicted by polynomial modeling. The sixth order polynomial function was found to give the optimal value for geometric distortion correction. The area of maximum distortion was < 1 pixel with an FOV of 285 mm. The correction performance error was increased at most 1.2% and 2.9% for FOVs of 340 mm and ~ 400 mm compared with the FOV of 285 mm. In particular, unresolved distortion was generated by local deformation near the gradient coil center. 相似文献