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61.
F. Fernandéz Barquín J. C. Gómez Sal P. Gorria J. S. Garitaonandia J. M. Barandiarán 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,35(1):3-12
Melt-spun amorphous alloys of Fe91Zr9, Fe91Zr7B2, Fe90Zr7B3 and Fe88Zr8B4 have been characterized by AC susceptibility at frequencies between 30 Hz and 10 KHz. The measurements reflect the existence of reentrant spin glass transitions below 40 K for all cases. The transition shift per frequency decade is large compared to the observed in conventional spin-glass alloys. The shift value increases with the boron content and becomes closer to values in fine-particle systems. We find that the relaxation in Fe91Zr9 follows a critical slowing down at the reentrant transition, with exponents
and
. The non-linear susceptibility displays a peak at the transition in this alloy, but wider than in canonical spin glasses. A Vogel-Fulcher (VF) activation process can explain the frequency variation in all the Fe-Zr-B alloys. The reduction of the ideal glass temperature in the VF approach, found in the higher Boron content alloys, is an indication of a superparamagnetic-like behavior. The behavior shown by these alloys is intermediate between a collective freezing and superparamagnetic-like relaxation. We propose that this is arising due to a heterogeneous spin structure. The inclusion of a reduced amount of B, affects the magnetic spin structure.Received: 13 May 2003, Published online: 22 September 2003PACS:
75.50.Lk Spin glasses and other random magnets - 75.50.Kj Amorphous and quasicrystalline magnetic materials - 75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)J.S. Garitaonandia: Present address: Dept. Física Aplicada, F. Ciencias, Universidad del País Vasco, Bilbao 48080, Spain 相似文献
62.
63.
Jonathan Leblanc Mathilde Mercier Christian Fonteix Fernand Pla 《Macromolecular Symposia》2007,259(1):85-93
Summary: This work deals with the development of the dispersed phase morphology in immiscible blends of poly(ethylene glycol)/polyamide 66 (PEG/PA) with an extremely low viscosity ratio. The blends were obtained, under different operating conditions, by melt blending in an internal mixer. The objective was to examine the influence of the main processing parameters on the particles size of the minor phase (PEG). A model was elaborated to describe the dependence of the particle size on interfacial tension, PEG concentration, shear rate and viscosity ratio between the two blend components. 相似文献
64.
Analytical and Bioanalytical Chemistry - 相似文献
65.
Heitz MC Durand G Spiegelman F Meier C Mitrić R Bonacić-Koutecký V 《The Journal of chemical physics》2004,121(20):9906-9916
Short-time, excited-state dynamics of the lowest isomer of the Na(3)F cluster is studied theoretically in order to interpret the features of recent time-resolved pump-probe ionization experiments [J. M. L'Hermite, V. Blanchet, A. Le Padellec, B. Lamory, and P. Labastie, Eur. Phys. J. D 28, 361 (2004)]. In the present paper, we propose an identification of the vibrational motion responsible for the oscillations in the ion signal, on the basis of quantum mechanical wave packet propagations and classical trajectory calculations. The good agreement between experiment and theory allows for a clear interpretation of the detected dynamics. 相似文献
66.
Atamestane (SH 489) was synthesized from 17β-Acetoxy-1α-methyl-5α-androstan-3-one. Thus dibromination followed by dehydrobromination of the A-ring gave dienone (5) in good yield, which was hydrolyzed and oxidized to give the title compound in 60% overall yield. 相似文献
67.
Valle BC Morris KF Fletcher KA Fernand V Sword DM Eldridge S Larive CK Warner IM 《Langmuir : the ACS journal of surfaces and colloids》2007,23(2):425-435
Chiral separations employing four diastereomers of poly sodium N-undecanoyl leucylvalinate (p-SULV) as chiral selectors are probed by use of MEKC, steady-state fluorescence anisotropy, and NMR. By employing diastereomers and thus altering the stereochemistry of a single amino acid in a systematic way, one may control the enantiorecognition ability of the chiral selector. As a result, one can gain a better understanding of the mechanisms of chiral recognition for the two classes of neutral or anionic chiral analytes studied. Evaluation of the chiral interactions leading to chiral separations confirmed our earlier observation of a strong relationship between the selectivity (alpha) observed using a chromatographic separation technique (MEKC) and that determined from the spectroscopic parameter, beta. A linear alpha versus beta relationship was observed for the molecular micelle p-(L)-SULV with all eight analytes included in this study. However, as we earlier predicted, different groups of analytes had different slopes, i.e., values of m, suggesting different chiral separation mechanisms. Evaluation of the data allowed a grouping of the analytes according to the primary site of chiral interaction with the leucine or valine moiety of molecular micelle chiral headgroup. 相似文献
68.
Fernand Ranwez 《Fresenius' Journal of Analytical Chemistry》1893,32(1):495-497
Ohne Zusammenfassung 相似文献
69.
Esaïe Tchetan Sergio Ortiz Pascal Abiodoun Olounlad Kristelle Hughes Patrick Laurent Erick Virgile Bertrand Azando Sylvie Mawule Hounzangbe-Adote Fernand Ahokanou Gbaguidi Joëlle Quetin-Leclercq 《Molecules (Basel, Switzerland)》2023,28(1)
Terminalia leiocarpa is a medicinal plant widely used in ethnoveterinary medicine to treat digestive parasitosis whose extracts were shown to be active against gastrointestinal nematodes of domestic ruminants. The objective of our study was to identify compounds responsible for this activity. Column fractionation was performed, and the activity of the fractions was assessed in vitro on Haemonchus contortus and Caenorhabditis elegans as well as their cytotoxicity on WI38 fibroblasts. Two fractions were the most active on both nematode models and less cytotoxic. LC-MS/MS analysis and manual dereplication coupled to molecular networking allowed identification of the main compounds: ellagic acid and derivatives, gallic acid, astragalin, rutin, quinic acid, and fructose. Other potentially identified compounds such as shikimic acid, 2,3-(S)-hexahydroxydiphenoyl-D-glucose or an isomer, quercetin-3-O-(6-O-galloyl)-β-D-galactopyranoside or an isomer, and a trihydroxylated triterpenoid bearing a sugar as rosamultin are reported in this plant for the first time. Evaluation of the anthelmintic activity of the available major compounds showed that ellagic and gallic acids were the most effective in inhibiting the viability of C. elegans. Their quantification in fractions 8 and 9 indicated the presence of about 8.6 and 7.1 µg/mg ellagic acid and about 9.6 and 2.0 µg/mg gallic acid respectively. These concentrations are not sufficient to justify the activity observed. Ellagic acid derivatives and other compounds that were found to be positively correlated with the anthelmintic activity of the fractions may have additive or synergistic effects when combined, but other unidentified compounds could also be implicated in the observed activity. 相似文献
70.
M.-C. Heitz G. Durand F. Spiegelman C. Meier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):181-184
The excited state dynamics of the
Na2F cluster initiated by a femtosecond
laser pulse is studied considering a thermally excited initial
sample. Within a pump-probe set-up, the time-dependent
photoelectron spectrum is calculated, which is shown to be a
sensitive tool to study intramolecular motion of the cluster.
Temperature effects are taken into account through thermal
averaging over the time-dependent spectra obtained from
different initial vibrational states of the cluster. The nuclear
motion upon laser excitation is described by full-dimensional
quantum wavepacket propagation using explicit, realistic pump
and probe pulses. The characteristic features of the
time-resolved photoelectron spectra of the
Na2F cluster, identified as due to
periodic bending motion of the cluster as well as to the
excitation of the stretching mode, are found to be robust
against increasing vibrational temperature of the cluster beam.
This finding is important for possible future experiments. 相似文献