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51.
Butler M Mañez PA Cabrera GM 《Journal of the American Society for Mass Spectrometry》2011,22(3):545-556
Differentiation between two isomers of hydroxypyridine N-oxide according to the metal cation adducts generated by electrospray ionization (ESI) was investigated for different metal
cations, namely Mg (II), Al (III), Ca (II), Sc (III), Fe (III), Co (II), Ni (II), Cu (II), Zn (II), Ga (III), besides the
diatomic cation VO(IV). Protonated molecules of the isomeric hydroxypyridine N-oxides as well as the singly/doubly charged adducts formed from neutral or deprotonated ligands and a doubly/triply charged
cation were produced in the gas phase using ESI, recording mass spectra with different metal ions for each isomer. While complex
formation was successful for 2-hydroxypyridine N-oxide with trivalent ions, in the case of 3-hydroxypyridine N-oxide, only peaks related to the protonated molecule were present. On the other hand, divalent cations formed specific species
for each isomer, giving characteristic spectra in every case. Hence, differentiation was possible irrespective of the metal
cation utilized. In addition, quantum chemical calculations at the B3LYP/6-31 + G(d,p) level of theory were performed in order
to gain insight into the different complexation of calcium(II) with the isomers of hydroxypyridine N-oxide. The relative stability in the gas phase of the neutral complexes of calcium made up of two ligands, as well as the
singly charged and doubly charged complexes, was investigated. The results of these calculations improved the understanding
of the differences observed in the mass spectra obtained for each isomer. 相似文献
52.
Tsunashima R Long DL Endo T Noro S Akutagawa T Nakamura T Cabrera RQ McMillan PF Kögerler P Cronin L 《Physical chemistry chemical physics : PCCP》2011,13(16):7295-7297
The Dawson-type polyanion [α-Mo(18)O(54)(SO(3))(2)](4-), with two SO(3)(2-) templates embedded inside a polyoxomolybdate(vi) cage, exhibits thermochromism over an exceptionally wide temperature range (~500 K). The temperature dependence of the cluster structure, established from X-ray crystallography, IR and Raman spectroscopy and DFT calculations, is related to a decreasing HOMO-LUMO gap in the near UV with increasing temperature. We postulate this is due to geometrical changes that affect both the occupied and unoccupied frontier molecular orbitals of this cluster anion. 相似文献
53.
54.
S. M. Cotes A. F. Cabrera L. C. Damonte R. C. Mercader J. Desimoni 《Physica B: Condensed Matter》2002,320(1-4):274-277
BCC, FCC and HCP phases in Fe–13.7 wt% Mn alloys were studied by Mössbauer spectroscopy and X-ray diffraction, after ball milling. The relative amounts of the HCP and FCC phases increase with milling times up to 9 h and decline afterwards. Preliminary AC susceptibility measurements show that the blocking temperatures change for different milling times. 相似文献
55.
L. C. Cabrera L. B. Barichello 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2006,57(2):285-312
An analytical version of the discrete-ordinates method is used to derive solutions for a class of problems defined in terms
of the S-model kinetic equations. In addition to a general derivation, which is common to all the problems, specific analytical
and computational aspects for each one of the problems are presented. In particular, numerical results for velocity profile,
heat-flow profile and flow rates are obtained with high accuracy for the plane channel problems. In the case of half-space
problems, the thermal and viscous-slip coefficients are also listed.
Received: September 20, 2004; revised: March 31, 2005 相似文献
56.
A single, symmetrical resonance line, at g = 2.0099 has been detected in single crystals of NH4MnCl3. The temperature dependence of the intensity and width of the line has been measured. The Neel temperature has been determined as 105°K, where an abrupt change in intensity and width of the line takes place. 相似文献
57.
58.
We measure polarization-resolved instantaneous patterns in a large-aspect ratio quasi-isotropic Nd:YAG laser. High correlation between the instantaneous orthogonal polarization patterns recorded at the earlier stages of the laser pulse has been found due to the strong cross saturation between both polarization modes. 相似文献
59.
Michael DG Adamson P Alexopoulos T Allison WW Alner GJ Anderson K Andreopoulos C Andrews M Andrews R Arms KE Armstrong R Arroyo C Auty DJ Avvakumov S Ayres DS Baller B Barish B Barker MA Barnes PD Barr G Barrett WL Beall E Becker BR Belias A Bergfeld T Bernstein RH Bhattacharya D Bishai M Blake A Bocean V Bock B Bock GJ Boehm J Boehnlein DJ Bogert D Border PM Bower C Boyd S Buckley-Geer E Bungau C Byon-Wagner A Cabrera A Chapman JD Chase TR Cherdack D Chernichenko SK Childress S Choudhary BC 《Physical review letters》2006,97(19):191801
This Letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rates and energy spectra of charged current nu(mu) interactions are compared in two detectors located along the beam axis at distances of 1 and 735 km. With 1.27 x 10(20) 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336+/-14 events. The data are consistent with nu(mu) disappearance via oscillations with |Delta(m)2/32|=2.74 +0.44/-0.26 x10(-3)eV(2) and sin(2)(2theta(23))>0.87 (68% C.L.). 相似文献
60.
Reina M González-Coloma A Domínguez-Díaz D Cabrera R Giménez Mariño C Rodríguez ML Villarroel L 《Natural product research》2006,20(1):13-19
A new bioactive eremophilanolide, 1alpha-tigloyloxy-8betaH,10betaH-eremophil-7(11)-en-8alpha,12-olide, was isolated from Senecio poepigii and its structure was elucidated by spectral analysis. 1alpha-Angeloyloxy-8beta-methoxy-10betaH-eremophil-7(11)-en-8alpha,12-olide was also isolated. Antifungal and insect antifeedant properties were evaluated. 相似文献