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1.
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
2.
Yang L Crans DC Miller SM la Cour A Anderson OP Kaszynski PM Godzala ME Austin LD Willsky GR 《Inorganic chemistry》2002,41(19):4859-4871
The synthesis and characterization of Co(II) and Co(III) 2,6-pyridinedicarboxylate (dipic(2-)) complexes are reported. Solid-state X-ray characterizations were performed on [Co(H(2)dipic)(dipic)].3H(2)O and [Co(dipic)(mu-dipic)Co(H(2)O)(5)].2H(2)O. Two coordination modes not previously observed in dipicolinate transition metal complexes were observed in these complexes; one involves metal coordination to the short C-O (C=O) bond, and the other involves metal coordination to a protonated oxygen atom. Solution studies, including paramagnetic NMR and UV-vis spectroscopy, were done showing the high stability and low lability of the Co(III) complex, whereas the Co(II) complexes exhibited ligand exchange in the presence of excess ligand. The [Co(dipic)(2)](2-) complex has pH dependent lability and in this regard is most similar to the [VO(2)dipic](-) complex. The [Co(dipic)(2)](2-) was found to be effective in reducing the hyperlipidemia of diabetes using oral administration in drinking water in rats with STZ-induced diabetes. Oral administration of VOSO(4) was used as a positive control for metal efficacy against diabetes. In addition to providing a framework to evaluate structure-function relationships of various transition metal complexes in alleviating the symptoms of diabetes, this work describes novel aspects of structural and solution cobalt chemistry. 相似文献
3.
4.
Sjoerd E. Crans 《K-Theory》2003,28(1):39-105
Let
be n-dimensional teisi, i.e., higher-dimensional Gray-categorical structures. The following questions can be asked. Does a left q-transfor
, i.e., a functor 2
q
, induce a right q-transfor
, i.e., a functor
More generally, does a functor
induce a functor
For k-arrows c and
whose (k – 1)-sources and targets agree, does a q-transfor
induce a q-transfor
, for appropriate k-arrows
For k-arrows c and
whose (k – 1)-sources and targets agree, does a q-transfor
induce a (q + k + 1)-transfor
, for appropriate k-arrows
I give answers to these questions in the cases where n-dimensional teisi and their tensor product have been defined, i.e., for n 3, and for n up to 5 in some cases that do not need all data and axioms of n-dimensional teisi.I apply the above to compositions in teisi, in particular to braidings and syllepses. One of the results is that a braiding on a monoidal 2-category induces a pseudo-natural transformation
, where
is the reverse of ? –, which is almost, but not quite, equal to – ?. However, in higher dimensions need not be reversible, so a braiding on a higher-dimensional tas can not be seen as a transfor A B B A. 相似文献
5.
In subnormal glow discharge under d.c. excitation at different pressure in a varying transverse magnetic field (0 to 30 G)
some measurements have been carried out for various initial average tube currents. The voltage across the discharge increases
and average tube current and residual current decreases in the magnetic field. With the help of Beckman’s expression [4] for
the axial field and the electron density distribution in a transverse magnetic field the observed variation of current and
voltage can be satisfactorily explained. The variation of axial electric field with transverse magnetic field can be represented
to a fair degree of accuracy by the derived equation. The behaviour of residual current with magnetic field has been observed
in these oscillations. 相似文献
6.
W. Crans 《Flow, Turbulence and Combustion》1969,21(1):322-340
An expression for the yield stress of anisotropic materials is applied to the anisotropic strength of hard rolled copper foils whose crystallographic texture is known. We assume that this crystallographic texture is the only cause of the anisotropic plastic behaviour of the material. The model used for the yield stress is also used to deduce:
- Stress-strain relations for isotropic polycrystalline materials;
- A formula for the fully plastic strain tensor, applied to anisotropic hard rolled copper foils.
7.
A generating function for the yield criterion of isotropic and anisotropic polycrystalline materials
W. Crans 《Applied Scientific Research》1966,16(1):256-272
Summary A yield criterion for elastic pure-plastic polycrystalline materials is generated under simplified conditions by assuming that for yielding a certain fraction Q
c of the total number of slip planes in the material has to be active. This fraction Q
c is called the critical active quantity. We suppose Q
c to be independent of the state of stress. The yield criterion is mathematically expressed as an integral, which is a function of Q
c. This criterion can also be used for anisotropic materials.For isotropic materials the ratio (r) of the yield stress in torsion to that in tension is calculated as a function of Q
c. We find 0.5r0.61.The value r=0.5 (Tresca's criterion) is obtained for Q
c=0 and Q
c=1. The value r=0.577 (von Mises criterion) is obtained for Q
c=0.34 and Q
c=0.79. The difference between two criteria with the same r is the magnitude of the yield stress. We think the value Q
c=0.79 corresponds to the experiments for f.c.c. materials, since a rough estimation gives Q
c>0.75 for yielding.The independence of Q
c on the state of stress brings on that r>0.5 is more probable. This is caused by the slower increase to Q
c in torsion compared with the case of tension.From the theory follows that in the general case (Q
c0) the middle principal stress has influence on yielding.In this paper we don't determine Q
c, but adapt its value to the experimental results. However, a rough estimation of Q
c is given for isotropic materials. 相似文献
8.
Todea AM Szakács J Konar S Bögge H Crans DC Glaser T Rousselière H Thouvenot R Gouzerh P Müller A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(24):6635-6642
The present study refers to a variety of reduced metal-oxide core-shell hybrids, which are unique with regard to their electronic structure, their geometry, and their formation. They contain spherical {Mo72Fe30} Keplerate-type shells encapsulating Keggin-type polyoxomolybdates based on very weak interactions. Studies on the encapsulation of molybdosilicate as well as on the earlier reported molybdophosphate, coupled with the use of several physical methods for the characterization led to unprecedented results (see title). Upon standing in air at room temperature, acidified aqueous solutions obtained by dissolving sodium molybdate, iron(II) chloride, acetic acid, and molybdosilicic acid led to the precipitation of monoclinic greenish crystals (1). A rhombohedral variant (2) has also been observed. Upon drying at room temperature, compound 3 with a layer structure was obtained from 1 in a solid-state reaction based on cross-linking of the shells. The compounds 1, 2, and 3 have been characterized by a combination of methods including single-crystal X-ray crystallography, magnetic studies, as well as IR, M?ssbauer, (resonance) Raman, and electronic absorption spectroscopy. In connection with detailed studies of the guest-free two-electron-reduced {Mo72Fe30}-type Keplerate (4) and of the previously reported molybdophosphate-based hybrids (including 31P NMR spectroscopy results), it is unambiguously proved that 1, 2, and 3 contain non-reduced Keggin ion cores and reduced {Mo72Fe30}-type shells. The results are discussed in terms of redox considerations (the shell as well as the core can be reduced) including those related to the reduction of "molybdates" by FeII being of interdisciplinary including catalytic interest (the MoVI/MoV and FeIII/FeII couples have very close redox potentials!), while also referring to the special formation of the hybrids based on chemical Darwinism. 相似文献
9.
10.
Chelation of vanadium(V) by difluoromethylene bisphosphonate, a structural analogue of pyrophosphate
Crans DC Holder AA Saha TK Prakash GK Yousufuddin M Kultyshev R Ismail R Goodman MF Borden J Florian J 《Inorganic chemistry》2007,46(16):6723-6732
The structural and functional analogy between difluoromethylene bisphosphonate (CF2PP) and pyrophosphate (PPi) is investigated in a reaction with V(V) in the form of vanadate. The reaction of CF2PP with vanadate was investigated using 1.00 M KCl as supporting electrolyte over the ranges 3 < or = [CF2PP] < or = 60 mM and 2.06 < or = pH < or = 11.80. 51V, 19F, and 31P NMR spectroscopic studies showed that a 1:1 species was formed with an H+-dependent formation constant of 110 M-1 at pH 7.22. Results of solution experiments and ab initio calculations are consistent with CF2PP coordinating V(V) in a bidentate manner, as previously reported for PPi. Below pH 4, a minor complex forms, which is consistent with a 1:2 stoichiometry. This complex was also observed with pyrophosphate. The X-ray crystal structure of the monoprotonated difluoromethylene bisphosphonate anion (H[CF2PP]3-)-toludine complex is presented. The H[CF2PP]3- anion crystallized in the triclinic space group P with a = 12.7629(7) A, b = 13.3992(7) A, c = 17.1002(9) A, and V = 2584.4(2) A3, and Z = 2. Sheets of the layers of anions are connected through a network of H-bonds and separated by a layer of toludine cations. The structural features are investigated, and the CF2PP anion was found to be longer and wider than the corresponding PPi. Given the larger size of this anion compared to PPi, the chelation affinity upon CF2 substitution was found to be 4-5-fold reduced at neutral pH. 相似文献