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Henry P. McKean 《纯数学与应用数学通讯》2003,56(5):638-680
3.
Heavy ion irradiation in the electronic stopping power region induces macroscopic dimensional change in metallic glasses and introduces magnetic anisotropy in some magnetic materials. The present work is on the irradiation study of ferromagnetic metallic glasses, where both dimensional change and modification of magnetic anisotropy are expected. Magnetic anisotropy was measured using Mössbauer spectroscopy of virgin and irradiated Fe40Ni40B20 and Fe40Ni38Mo4B18 metallic glass ribbons. 90 MeV 127I beam was used for the irradiations. Irradiation doses were 5×1013 and 7.5×1013 ions/cm2. The relative intensity ratios D 23 of the second and third lines of the Mössbauer spectra were measured to determine the magnetic anisotropy. The virgin samples of both the materials display in-plane magnetic anisotropy, i.e., the spins are oriented parallel to the ribbon plane. Irradiation is found to cause reduction in magnetic anisotropy. Near-complete randomization of magnetic moments is observed at high irradiation doses. Correlation is found between the residual stresses introduced by ion irradiation and the change in magnetic anisotropy. 相似文献
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Cross-correlation was implemented for flow-injection analysis by using two parallel flow lines, each with amperometric detectors, and driven by peristaltic pumps. One flow line was used to generate the reference signal for an analog correlator circuit and the other to generate the analyte signal. Cross-correlation was performed by multiplying these signals together at a time delay of zero, followed by low pass filtering. Using dopamine as a test system, improvements in signal-to-noise ratios of about two orders of magnitude were found for the correlation signal over the direct measurement of the electrode current. 相似文献
6.
Stephen Cradock Donald C. McKean Moray W. MacKenzie 《Journal of Molecular Structure》1981,74(2):265-276
We have obtained microwave spectra of fully and partially deuterated germyl halides GeD3X and GeHD2X (X = F, Cl, Br, I) and analysed the infrared spectra in the GeH stretching region of the asymmetric species. The resulting Ao and Bo values have been combined with existing data on GeH3X to give improved structures for the germyl halides. The values of the HGeX angles obtained show a correlation with GeH stretching frequencies, as in methyl compounds, but there appears to be no such correlation between stretching frequencies and GeH bond lengths. 相似文献
7.
Letf(Q) be odd and positive near +∞. Then the non-linear wave equation ?2 Q/?t 2??2 Q/?x 2?f(Q)=0, considered on the circle 0≤x<L, can be written in Hamiltonian formQ ⊙ =?H/?P, P ⊙ =??H/?Q with $$P = Q^\cdot and H = \tfrac{1}{2}\mathop \smallint \limits_0^L (Q')^2 + \mathop \smallint \limits_0^L F(Q) + \tfrac{1}{2}\mathop \smallint \limits_0^L P^2 ;$$ the corresponding flow preserves the (suitably interpreted) “petit ensemble”e ?H d ∞ Qd ∞ P; and forL↓∞,Q settles down to the stationary diffusion with infinitesimal operator 1/2 ?2/?Q 2+m(Q)?/?Q,m being the logarithmic derivative of the ground state of ?d 2/dQ 2 ‖F(Q). This diffusion is the “Brownian motion with restoring drift”; see McKean-Vaninsky [1993(1)]. For reasons suggested by the paper of Lebowitz-Rose-Speer [1988] on NLS, it is interesting to study the “micro-canonical ensemble” obtained by restricting to the sphere $\int\limits_0^L {Q^2 } = N$ and makingL↓∞ with fixedD=N/L. Now, forF(Q)/Q 2→∞, the same type of diffusion appears, but with drift arising from the modified potentialF(Q)+cQ 2,c being chosen so that the mean ofQ 2 is the assigned numberD. The proof employs Döblin's method of “loops” [1937] and steepest descent. The same is true forF(Q)=m 2 Q 2, only now the proof is elementary. The outcome is also the same ifF(Q)/Q 2→0, providedD is smaller than the petit canonical mean ofQ 2; forD larger than this mean, the matter is more subtle and the outcome is unknown. 相似文献
8.
Infrared spectra have been obtained in gas and crystalline phases for CH3NO2, CD3NO2, and CHD2NO2. A few Raman liquid measurements have also been made. The crystal spectra show the methyl group to be locked in conformation I, with isolated CH stretching frequencies 3065 (ν∥CH) and 3000 (ν⊥CH), respectively. In the gas phase, the bands due to νaCH3 and νaCD3 are split, the splitting being compatible with isolated frequencies of 3065 (ν∥CH) and 3006 (ν⊥CH) cm?1, respectively. These indicate a variation of 0.006 Å in bond length during internal rotation. The gas phase infrared band at 3028.7 cm?1 and the Raman liquid band at 3024 cm?1 in the spectra of CHD2NO2 represent averages of the frequencies during internal rotation. All calculations are performed with a potential function involving variations both in diagonal bond stretching, and in off-diagonal stretching interaction constants, proportional to cos2π, where π is the internal rotation angle.In the Appendix, vibrational assignments below 1600 cm?1 are examined. Product rule considerations and intensity changes upon deuteration lead to a conflict with the infrared gas phase band contour over the assignment of the rCD3 mode at 884 cm?1. This and other features in the gas phase spectra may arise from the internal rotation. 相似文献
9.
Iain J. W. McKean Joanna C. Sadler Anibal Cuetos Amina Frese Luke D. Humphreys Gideon Grogan Paul A. Hoskisson Glenn A. Burley 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):17747-17752
A tandem enzymatic strategy to enhance the scope of C‐alkylation of small molecules via the in situ formation of S‐adenosyl methionine (SAM) cofactor analogues is described. A solvent‐exposed channel present in the SAM‐forming enzyme SalL tolerates 5′‐chloro‐5′‐deoxyadenosine (ClDA) analogues modified at the 2‐position of the adenine nucleobase. Coupling SalL‐catalyzed cofactor production with C‐(m)ethyl transfer to coumarin substrates catalyzed by the methyltransferase (MTase) NovO forms C‐(m)ethylated coumarins in superior yield and greater substrate scope relative to that obtained using cofactors lacking nucleobase modifications. Establishing the molecular determinants that influence C‐alkylation provides the basis to develop a late‐stage enzymatic platform for the preparation of high value small molecules. 相似文献
10.
The recurrences of initial states for nonlinear wave equations of the form
with odd f are studied. The main result refines and generalizes the investigations of Friedlander and is related to the Poincaré
theorem for finite dimensional Hamiltonian systems. Bibliography: 7 titles.
Published inZapiski Nauchnykh Seminarov POMI, Vol. 235, 1900, pp. 287–294. 相似文献