排序方式: 共有19条查询结果,搜索用时 31 毫秒
1.
2.
3.
R Bonfiglio RC King TV Olah K Merkle 《Rapid communications in mass spectrometry : RCM》1999,13(12):1175-1185
A post-column infusion system was developed in order to analyze suppression of electrospray ionization (ESI) tandem mass spectrometry response in the presence of endogenous plasma interferences. By enabling direct detection of these interfering components, this experimental system was used to analyze the ability of several common extraction procedures to remove endogenous plasma components that cause changes in the ESI response of model drug substances. Methyl-t-butyl ether (MTBE) liquid-liquid, Oasis and Empore solid-phase, and acetonitrile (ACN) protein precipitation sample preparation methods were tested using the post-column infusion system. In all cases, ACN protein precipitation samples showed the greatest amount of ESI response suppression while liquid-liquid extracts demonstrated the least. In addition, the three test compounds, phenacetin, caffeine, and a representative Merck compound, demonstrated that ESI response suppression is compound dependent. Suppression was greatest with caffeine, the most polar analyte, and the smallest for the Merck compound, the least polar analyte. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
4.
Samit Mandal J Gerl H Geissel K Hauschild M Hellström Z Janas I Kojouharov Y Kopatch RC Lemmon P Mayet Z Podolyak PH Regan H Schaffner C Schlegel J Simpson HJ Wollersheim 《Pramana》2001,57(1):161-164
Feasibility of gamma-ray spectroscopy at relativistic energies with exotic heavy-ions and new generation of germanium detectors
(segmented Clover) is discussed. An experiment with such detector array and radioactive is discussed. 相似文献
5.
We report measurements of non-linear charge transport in epitaxial (La1−x
Pr
x
)0.7Ca0.3MnO3 thin films fabricated on (100) oriented SrTiO3 single crystals by pulsed laser deposition. The end members of this series, namely Pr0.7Ca0.3MnO3 and La0.7Ca0.3MnO3 are canonical charge-ordered (CO) and ferromagnetic manganites, respectively. The onset of the CO state in Pr0.7Ca0.3MnO3 is manifested by a pronounced insulating behavior below ∼ 200 K. The CO state remains stable even when a large (∼ 2×105 V/cm) electric field is applied across the thin film samples. However, on substitution of Pr with La, a crossover from the
highly resistive CO state to a state of metallic character is observed at relatively low electric fields. The current-voltage
characteristics of the samples at low temperatures show hysteretic and history dependent effects. The electric field driven
charge transport in the system is modelled on the basis of an inhomogeneous medium consisting of ferromagnetic metallic clusters
dispersed in a CO background. 相似文献
6.
MA Freitas SR Dillon RC Dougherty AG Marshall 《Rapid communications in mass spectrometry : RCM》1999,13(15):1622-1625
The self-chemical ionization of diethylzinc is examined by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and semiempirical molecular orbital calculations. Electron impact of diethylzinc neutral produces the radical cation, C(4)H(15)Zn(+) (m/z x 122), which reacts further with the neutral (C(2)H(5))(2)Zn to give the following product ions: Zn(+) (m/z x 64), C(2)H(5)Zn(+) (m/z x 93), C(4)H(9)Zn(+) (m/z x 121), C(4)H(11)Zn(2)(+) (m/z x 187), and C(6)H(15)Zn(2)(+) (m/z x 215). To determine the structure and pathways for production of these ions, monoisotopic (12)C(4)H(15)(64)Zn(+), (64)Zn(+) and (12)C(2)H(5)(64)Zn(+) were individually isolated and reacted with the neutral background. We also performed semiempirical molecular orbital calculations (ZINDO/1). The molecular orbital calculations and experimental data are consistent in predicting that the ethyl group on the diethylzinc cation carries the positive charge. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
7.
Aluminum-based icosahedral quasicrystals display a wide variety of magnetic behaviors, which result from the presence of chromium, manganese, or iron. The formation of localized Fe magnetic moments in these materials is discussed in the context of the intrinsic disorder present in these structures as well as structural disorder caused by processing conditions. 相似文献
8.
9.
10.
P. Lázpita J. M. Barandiarán J. Gutiérrez M. Richard S. M. Allen R. C. O'Handley 《The European physical journal. Special topics》2008,158(1):149-154
Structural and magnetic transition temperatures of
ferromagnetic shape memory alloys present a strong dependence on
slight departures from the stoichiometry, as does the mobility of
twin boundaries responsible for the large magnetic field induced
strains. In this work we study four non stoichiometric Ni-Mn-Ga
polycrystalline alloys with compositions of 43–52 at.% nickel,
excess manganese and deficient in gallium, and a single crystal of
composition Ni52Mn26Ga22. Those compounds are of
technical interest due to the observed large room temperature
magnetic field induced strains. Calorimetric and magnetic
measurements determined the martensitic transition and Curie
temperatures of the alloys (AS = 331 K and
TCurie = 366 K for 52 at.% nickel alloy).
Nickel defective alloys present a martensitic transition region
broader than excess nickel ones. Neutron powder diffraction analysis
confirmed orthorhombic martensitic structures for nickel defective
alloys, and tetragonal for excess nickel ones. In the 52 atomic %
nickel alloys case the crystallographic structure of the martensitic
phase was also obtained on a single crystal with the same
composition, trained to get a single variant in agreement with
determined in the powder sample. 相似文献