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L. Seetha Lakshmi V Sridharan DV Natarajan V Sankara Sastry T S Radhakrishnan 《Pramana》2002,58(5-6):1019-1026
Mn site is substituted with closed shell ions (Al, Ga, Ti, Zr and a certain combination of Zr and Al) and also with Fe and
Ru ions carrying the magnetic moment (S=5/2 and 2 respectively) at a fixed concentration of 5 at %. Substitution did not change either the crystal symmetry or the
oxygen stoichiometry. All substituents were found to suppress both the metal-insulator and ferromagnetic transition temperatures
(T
p(ρ) and T
C, respectively) to varied extents. Two main contributions identified for the suppression are the lattice disorder arising
due to difference in the ionic radii between the substituent (r
M) and the Mn3+ ion (r
Mn
3+) and in the case of the substituents carrying a magnetic moment, the type of magnetic coupling between the substituent and
that of the neighboring Mn ion. 相似文献
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Zagorevski D 《European journal of mass spectrometry (Chichester, England)》2005,11(3):267-275
Neutralization-reionization mass spectrometry is applied for the generation of low-valence iron derivatives. Neutralization of Rfe(+) (R=H, F, Cl, Br, I, CN, OH, NH(2), acac, C(6)H(5)) ions resulted in the corresponding neutrals having lifetimes of at least 5 micros. Atom connectivities in RFe ions and neutrals were elucidated by a variety of tandem mass spectrometry techniques. The present study provides the first experimental evidence of the intrinsic stability of neutral IFe, NCFe, acacFe and C(6)H(5)Fe. 相似文献
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Zagorevski DV Loughmiller-Newman JA 《Rapid communications in mass spectrometry : RCM》2012,26(4):403-411
Several ancient Mayan vessels from the Kislak Collection of the US Library of Congress were examined for the presence of alkaloids. One of them, a codex-style flask, bears a text that appears to read yo-'OTOT-ti 'u-MAY, spelling y-otoot 'u-may 'the home of its/his/her tobacco'. Samples extracted from this Late Classic period (600 to 900?AD) container were analyzed by gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) methods. Nicotine was identified as the major component of the extracts. LC/MS analyses also yielded signals due to nicotine mono-oxides. The identities of the compounds were determined by comparison of the chromatographic and/or mass spectral characteristics with those from standards and literature data. High-resolution high mass accuracy tandem mass spectrometry (MS/MS) spectra of protonated nicotine and nicotine mono-oxides were measured to verify and to correct previous product ion assignments. These analyses provided positive evidence for nicotine from a Mayan vessel, indicating it as a likely holder of tobacco leafs. The result of this investigation is the first physical evidence of tobacco from a Mayan container, and only the second example where the vessel content recorded in a Mayan hieroglyphic text has been confirmed directly by chromatography/mass spectrometry trace analysis. 相似文献
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Richard DV. Espiritu Alberto V. AmorsoloJr. 《Journal of Thermal Analysis and Calorimetry》2012,107(2):483-487
Cu–Zn–Sn shape memory alloy strips with composition range of 13.70–46.30 mass% Sn were fabricated by electrodepositing Sn
on a shim brass surface and then subsequently annealed at a constant temperature of 400 °C for 120 min under flowing nitrogen.
Subjecting the Sn-plated strips to differential scanning calorimetry (DSC) analysis revealed that the austenitic start (A
s) temperature was essentially constant at 225 °C while the martensite start (M
s) temperature was consistently within the 221.5–222 °C interval. Austenite to martensite phase transformation showed two distinct
peaks on the DSC thermogram which can be attributed to the non-homogeneity of the bulk Cu–Zn–Sn ternary alloy. The latent
heats of cooling and heating were found to increase with the mass% Sn plated on the shim brass. Effect of annealing temperature
was also investigated wherein strips with an essentially constant composition of 26 mass% Sn were annealed at a temperature
range of 350–420 °C for 120 min under flowing nitrogen. Varying the annealing temperature has no significant effect on the
transformation temperatures of the ternary alloy. 相似文献
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Mellisa Ly Zhenyu Wang Tatiana N. Laremore Fuming Zhang Weihong Zhong Dennis Pu Dmitri V. Zagorevski Jonathan S. Dordick Robert J. Linhardt 《Analytical and bioanalytical chemistry》2011,399(2):737-745
Heparosan is the key precursor for the preparation of bioengineered heparin, a potential replacement for porcine intestinal heparin, an important anticoagulant drug. The molecular weight (MW) distribution of heparosan produced by the fermentation of E. coli K5 was investigated. Large-slab isocratic and mini-slab gradient polyacrylamide gel electrophoresis (PAGE) were used to analyze the MW and polydispersity of heparosan. A preparative method that allowed fractionation by continuous-elution PAGE was used to obtain heparosan MW standards. The MWs of the heparosan standards were determined by electrospray ionization Fourier-transform mass spectrometry (ESI-FT-MS). A ladder of the standards was then used to determine the MW properties of polydisperse heparosan samples. Unbleached and bleached heparosan produced by fermentation of E. coli K5 had similar number-averaged MWs (MN), weight-averaged MWs (MW), and MW ranges of 3,000 to 150,000?Da. 相似文献
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Dmitri V. Zagorevski Jennifer A. Loughmiller‐Newman 《Rapid communications in mass spectrometry : RCM》2012,26(4):403-411
Several ancient Mayan vessels from the Kislak Collection of the US Library of Congress were examined for the presence of alkaloids. One of them, a codex‐style flask, bears a text that appears to read yo‐'OTOT‐ti 'u‐MAY, spelling y‐otoot 'u‐may 'the home of its/his/her tobacco'. Samples extracted from this Late Classic period (600 to 900 AD) container were analyzed by gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) methods. Nicotine was identified as the major component of the extracts. LC/MS analyses also yielded signals due to nicotine mono‐oxides. The identities of the compounds were determined by comparison of the chromatographic and/or mass spectral characteristics with those from standards and literature data. High‐resolution high mass accuracy tandem mass spectrometry (MS/MS) spectra of protonated nicotine and nicotine mono‐oxides were measured to verify and to correct previous product ion assignments. These analyses provided positive evidence for nicotine from a Mayan vessel, indicating it as a likely holder of tobacco leafs. The result of this investigation is the first physical evidence of tobacco from a Mayan container, and only the second example where the vessel content recorded in a Mayan hieroglyphic text has been confirmed directly by chromatography/mass spectrometry trace analysis. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Experimental observations of time-delay-induced amplitude death in two coupled nonlinear electronic circuits that are individually capable of exhibiting limit-cycle oscillations are described. The existence of multiply connected death islands in the parameter space of coupling strength and time delay for coupled identical oscillators is established. The existence of such regions was predicted earlier on theoretical grounds [Phys. Rev. Lett. 80, 5109 (1998); Physica (Amsterdam) 129D, 15 (1999)]. The experiments also reveal the occurrence of multiple frequency states, frequency suppression of oscillations with increased time delay, and the onset of both in-phase and antiphase collective oscillations. 相似文献
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Experiments with reaction fronts (detonation waves and solidflames) reveal that, near the combustion limit, the fronts movein a spinning regime when localized zones of intensive reactiontravel along spiral trajectories. In the paper, the spinningwave is interpreted as an autosoliton and described phenomenologicallyby a nonlinear partial differential equation. The equation isstudied numerically, and the presence of the stable spinningand autosoliton solutions is shown. 相似文献
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