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61.
Experimental results on the nuclear spin-lattice and nuclear spin-spin relaxation times in the ferromagnetic EuB6 at temperatures below 4·2 K are presented using the external magnetic field,H
ext, in the range of 0 ⩽H
ext ⩽ 10 kG. Nuclear spin-spin relaxation time computed on the basis of the Suhl-Nakamura process turns out to be 3·2μs, which compares well with the experimental value 11·1μs obtained with the 10 kG magnetic field at 1·7 K. It is found that in the ferromagnetic EuB6,T
1 is approximately 5 × 103 times larger thanT
2 at 1·7 K with the 10 kG magnetic field. Thus the effect ofT
1 onT
2 can be neglected. From the experimental value ofT
2, the value of the homogeneous line broadening is found to be 14 kHz. The corresponding value obtained from the cw method
is 175 kHz. This evidently shows the presence of the inhomogeneous line broadening in the cw NMR. 相似文献
62.
K. Kayser W. Collin P. Filss S. Guldbakke G. Nolte H. Reich J. O. Trier W. Witschel 《Zeitschrift für Physik A Hadrons and Nuclei》1970,239(5):447-460
In order to obtain data on the photon absorption process between the giant resonance and the meson threshold the cross sections of the reactions12C(γ,n)11C,12C(γ, 2n)10C,39K(γ,n)38Kg, and40Ca(γ,np)38Kg have been determined by the analysis of yield curves at the 140 MeV electron synchrotron of the PTB. Though the (γ,n) cross sections grow small with increasing photon energy they are different from zero up to energies of 60 MeV and above. The cross section of the reaction12C(γ, 2n) is extremely small; its highest value amounts to 0.15% of the highest value of the12C(γ,n) reaction. The measured40Ca(γ,np) cross section is of the order predicted by the naive quasi-deuteron model. The integrated cross sections of the above reactions up to 140MeV are 85±7,0.90±0.10, 139±16, and 76±7MeVmb respectively. 相似文献
63.
64.
Homochiral 3-hydroxy-4-substituted β-lactams serve as precursors to the corresponding -hydroxy-β-amino acids—key components of many biologically and therapeutically important compounds. We have developed a short synthetic sequence for these targets using a biocatalytic reduction to install the desired chirality. By employing 3-oxo-4-phenyl-β-lactam as a probe, 19 individual yeast reductases were screened for their efficiency and enantioselectivity with respect to this substrate. Four highly selective candidates all belonging to the aldose reductase (AKR) superfamily were identified. Two are Re-face selective and two are Si-face selective. The modelled three-dimensional structures of these enzymes provide a rationale for this behaviour and suggest strategies for their further improvement. 相似文献
65.
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68.
The specific heat of a resole-type phenolic polymer has been determined. A secondary transition is noted at 125° C. The thermodynamic Gruneisen parameter is 1.3 and the lattice Gruneisen parameter is 6.3. Interchain specific heat is about 21% of the total. 相似文献
69.
Brian D. Kayser 《The Journal of mathematical sociology》2013,37(2):295-306
An initial test of the discrete‐time Markov model in the study of educational aspirations throughout high school was carried out. The design of the study permitted testing for sex differences and order effects The results indicate a good fit between the data and the model across several cohorts of students. Order effects were apparent, but sex differences in the transition probabilities were not found. Future change in aspirations appears least likely for students with a history of stable college plans, while it is most likely for those who start with non‐college aspirations and change to college plans. 相似文献
70.
Y. Kayser D. Banaś W. Cao J.‐Cl. Dousse J. Hoszowska P. Jagodziński M. Kavčič A. Kubala‐Kukuś S. Nowak M. Pajek J. Szlachetko 《X射线光谱测定》2012,41(2):98-104
We report on the surface‐sensitive grazing emission X‐ray fluorescence technique combined with synchrotron radiation excitation and high‐resolution detection to realize depth‐profile measurements of Al‐implanted Si wafers. The principles of grazing emission measurements as well as the benefits offered by synchrotron sources and wavelength‐dispersive detection setups are presented. It is shown that the depth distribution of implanted ions can be extracted from the dependence of the X‐ray fluorescence intensity on the grazing emission angle with nanometer‐scale precision provided that an analytical function describing the shape of the depth distribution is assumed beforehand. If no a priori assumption is made, except a bell shaped form for the dopant distribution, the profile derived from the measured angular distribution is found to reproduce quite satisfactorily the depth distribution of the implanted ions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献