The Additional Magnetic Anisotropy Induced by Magnetic Anneal in Ferromagnetic Face-Centered Cubic Solid Solutions : Part I. Dependence of the Induced Magnetic Anisotropy on the Temperature and Duration of Magnetic Anneal, on the Measuring Temperature, and on the Alloy Composition in Face-Centered Cubic Nickel-Cobalt Alloys

We have studied systematically the character of the induced magnetic anisotropy in face-centered cubic Ni-Co alloys, using a torque magnetometer designed specially for high-temperature measurements. Specimens used are polycrystalline disks of 10.57, 20.78, 30.84, 40.67, 50.17, and 60.20 %Co-Ni alloys and (110) disk single crystal of 12 %Co-Ni alloy. The results and conclusions obtained are as follows : -The magnetic anisotropy energy, E_u, induced by magnetic anneal is uniaxial. Generally, as the duration of magnetic anneal increases, E_u increases nearly exponentially and, as the temperature of magnetic anneal becomes higher, the rate of development of E_u increases but its saturation value decreases. The development of E_u can not be described in terms of single relaxation time and the associated relaxation times become longer as the duration of magnetic anneal increases. The dependence of E_u\u27 on the temperature, Θ, of magnetic anneal and on the measuring temperature, T, can be expressed well by an expression E_u=const. ×{ (I_Θ/I_0)^2/Θ} (I_T/I_0)^2 where I_Θ, I_T, and I_0 are the values of saturation magnetization at Θ(°K), T(°K), and 0°K, respectively, which was derived by Taniguchi and Yamamoto from the so-called directional order theory. The comparison of the measured data on the alloy composition dependence of E_u as corrected for the composition dependence of the Curie temperature with Neel\u27s theoretical formula indicates that the ordering energy of Ni-Co alloys is negative and hence the alloys may be of the precipitation type. In connection with this study, the temperature dependence of the cubic magnetocrystalline anisotropy constants, K_1 and K_2, was measured with 12 %Co-Ni alloy and pure nickel, and it has been found that, as the temperature rises, K_1 of 12 %Co-Ni alloy changes from positive to negative at about 150℃, while K_1 of nickel takes small positive values above 200℃ and that K_2 of 12% Co-Ni alloy is always positive, while K_2 of nickel changes from positive to negative at about 100℃

Ferromagnetic Domain Structure as Affected by the Uniaxial Anisotropy Induced in a 40 Percent Co-Ni Single Crystal

We have found that the domain structure in the annealed state of a 40 percent cobalt-nickel single crystal is very fine and complicated as compared with those of ordinary ferromagnetic crystals but it becomes simpler and larger after quenching from above the Curie temperature. This can be explained as follows : Since the domain structure may in general be fine and complicated at temperatures just below the Curie temperature, domain walls must displace to establish a more stable domain configuration as the temperature lowers. But, this process is suppressed appreciably at relatively low temperatures, because, in solid solution, the ferromagnetic uniaxial anisotropy is induced, in compliance with the domain distribution, by the anisotropic distribution of atoms at high temperatures and the domain wall displacement can take place only by being accompanied by the redistribution of atoms which can not occur at low temperatures. While, in quenching, the specimen crystal is cooled down so rapid that the uniaxial anisotropy and hence the anisotropic distribution of atoms can not be induced, and thus the quenched specimen crystal behaves just as ordinary ferromagnetic crystals. It is shown that these findings together with the results of considerations reported previously lead us to the conclusion that the perminvar-type magnetic properties are due to the stabilization of domain walls by the induced uniaxial anisotropy in f. c. c. solid solutions with cubic anisotropy constants of any sign and b. c. c. solid solutions with negative cubic anisotropy constants

内視鏡下リンパ系マッピングによる胃癌リンパ節転移診断の精度 : 胃癌センチネルリンパ節の同定

取得学位：博士(医学)，学位授与番号：医博甲第1447号，学位授与年月日：平成12年12月31日,学位授与年：200

P301S Mutant Human Tau Transgenic Mice Manifest Early Symptoms of Human Tauopathies with Dementia and Altered Sensorimotor Gating

Tauopathies are neurodegenerative disorders characterized by the accumulation of abnormal tau protein leading to cognitive and/or motor dysfunction. To understand the relationship between tau pathology and behavioral impairments, we comprehensively assessed behavioral abnormalities in a mouse tauopathy model expressing the human P301S mutant tau protein in the early stage of disease to detect its initial neurological manifestations. Behavioral abnormalities, shown by open field test, elevated plus-maze test, hot plate test, Y-maze test, Barnes maze test, Morris water maze test, and/or contextual fear conditioning test, recapitulated the neurological deficits of human tauopathies with dementia. Furthermore, we discovered that prepulse inhibition (PPI), a marker of sensorimotor gating, was enhanced in these animals concomitantly with initial neuropathological changes in associated brain regions. This finding provides evidence that our tauopathy mouse model displays neurofunctional abnormalities in prodromal stages of disease, since enhancement of PPI is characteristic of amnestic mild cognitive impairment, a transitional stage between normal aging and dementia such as Alzheimer's disease (AD), in contrast with attenuated PPI in AD patients. Therefore, assessment of sensorimotor gating could be used to detect the earliest manifestations of tauopathies exemplified by prodromal AD, in which abnormal tau protein may play critical roles in the onset of neuronal dysfunctions

Pressure effect on micellar formation of sodium dodecyl sulfate in saturated aqueous solution of naphthalene

Micellar formation of sodium dodecyl sulfate (SDS) in the presence of naphthalene has been measured by the electrical conductivity method up to about 3 kbars. The critical micelle concentration (cmc)-pressure plots show the maximum at about 1.3 kbars, contrary to the increasing cmc with pressure up to 5.5 kbars by Rodriguez and Offen

Biopolymer solutions and model systems under high pressure (The co-operative researches on the fundamental studies of the liquid phase reactions at high pressures)

The evidences are presented that the effects of pressure on proteins are inverted, in the range 2, 000～3, 000atm. This curious inversion can be illustrated according to the following conclusion derived from the studies of the model systems: pressures below about 3, 000 atm favor the formation of hydrogen bonds and the disruption of hydrophobic bonds, and above this pressure these trends are inverse in aqueous solutions. All of these inversion phenomena in the range 1, 000～3, 000 atm will reflect the change of water structure under high pressure. Deoxyribonucleic acids (DNA) can not be denatured by compression up to 10, 000 atm in contrast with proteins. The facts are discusssed from the view of the differences in conformations between DNA and proteins