Magnetic Flux Increase and Resistance of Circular Indium Rods at the Superconducting Transition

The so-called paramagnetic effect in superconductors has been investigated in indium. The current minimum I_0 required for the occurrence of the magnetic flux increase has been represented by the same functions of the temperature T and the external magnetic field maximum H_0, beyond which we cannot observe the quasi-paramagnetism at that temperature, as in the case of tin i.e. I_0=ξγd(T_c-T) and H_0=ξ(T_c-T)-I_g/γd. Here I_g, ξ and T_c are characteristic constants of the superconductor and have values 0.6 amp, 94.4 Oe/deg and 3.422°K respectively for the case of indium : γ is 0.27 amp/mm Oe. The external magnetic field maximum H_0 and the specimen diameter d are measured in Oe and in mm respectively. It has been shown also that these formulas are understood in a good approximation as those for the intersection of the plane I=I_g+γdH with the transition surface in the (I-H-T) space, and that the resultant magnetic field H_t (the external magnetic field H plus the magnetic field H_1 due to the current) at the specimen surface for the maximum of quasi-paramagnetism at constant magnetic field and temperature is, however, less than H_c. In parallel with the measurement of the magnetic flux, plotted as a function of the current at constant temperature and external magnetic field, a measurement of the resistance of the same specimen has been performed. The result of the resistance measurement is in good accordance with an expression derived in a modified form from the theory proposed by H. Meissner. The results obtained in the present investigation are not in a complete agreement with H. Meissner\u27s theory. A possible explanation for this discrepancy is briefly touched

The Electrical Resistivity of Cu-Ni Alloys and Matthiessen\u27s Rule

The electrical resistivity of copper-nickel alloys has been measured at the temperature-range from ordinary to liquid nitrogen temperature and the validity of Matthiessen\u27s rule concerning the alloys having the compositions approaching copper has been examined. The results obtained are as follows. (1) Both resistivity vs. composition curves obtained at 23℃ and -183℃ are approximately parabolic. (2) It has been ascertained that Matthiessen\u27s rule does not hold in the case of Cu-Ni alloys adjacent to copper, i. e. dp/dt is not constant with the change of nickel-concentration but changes linearly with it. (3) A plausible explanation based upon the conduction theory of electricity in metals has been given for the deviation from Matthiessen\u27s rule

Magnetic Flux Increase in Non-Circular Tin Rods at the Superconducting Transition

In the previous reports, it has been shown that the current minimum I_0 required for the occurrence of magnetic flux increase is represented in the (I-H-T) space by the simultaneous equations I_0 = ξγd(T_c-T) and H_0=ξ(T_c-T)-I_g/γd. Here I_g, T_c and ξ are the characteristic constants of the superconductor measured in amp, °K and Oe/deg respectively. d is the diameter of the specimen in mm and γ seems to have a nearly constant value of 0.25 measured in amp/mm Oe, irrespective of the superconductor. It has been shown also that the formula I_0 = I_g+γdH proposed for the minimum current requirement up to that time can be derived from the above simultaneous equations after eliminating T and that these simultaneous equations are understood in a good approximation as those for the intersection of the plane I= I_g+γdH with the transition surface in the (I-H-T) space. In the present paper the experimental results on the magnetic flux increase in non-circular tin rods at the superconducting transition are reported. Under the expectation that the mysterious constant I_g should be the same in non-circular cylindrical specimens, if the paramagnetic effect should be observed in them and the current minimum should be required also for the appearance of the paramagnetic effect in them, as in the circular cylindrical specimens, measurements were done with cylindrical tin specimens of non-circular cross-sections of several types. In the specimens in which we expected the magnetic flux increase according to the proposed idea of the paramagnetic effect, we observed the magnetic flux increase and obtained the formula I_0=I_g+βH_0 for the current minimum required for the occurrence of the paramagnetic effect. Although β differs from specimen to specimen according to the shape of the specimen cross-section, the magic constant I_g proves to be the same as in the case of circular rod, irrespective of the shape of the specimen cross-section, i.e. I_g is 1.2 amp for tin

A Theoretical Study of the Young\u27s Moduli of Binary Solid Solutions

Formerly the present author worked out an elementary theory which could explain qualitatively the relation between the Young\u27s modulus and the degree of order regarding β-brass. By an analogous reasoning, we examined in this paper the relation between the Young\u27s modulus and the composition of binary solid solutions. Denoting the force constants in regard to the interaction-energy between A atoms, that between B atoms and that between atoms A and B, by ξAA, ξBB and ξAB respectively, we obtained the following results. (1) In case that ξAB is equal to the mean value of ξAA and ξBB, a linear relation between the Young\u27s modulus and the composition is obtained. (2) In case that ξAB is not equal to the mean value, a non-linear relation is obtained. (3) The theoretical curves obtained with appropriate values of ratios of the force constants agree well with the experimental ones. (4) Using the value of ξAA obtained from the measured values of the lattice constant and the compressibility, we are able to estimate the magnitude of the Young\u27s modulus of molybdenum in polycrystalline form which agrees within about ten per cent with the measured value

On the Vibrational Spectrum and the Vibrational Specific Heat of a Binary Superlattice Alloy

The change in the vibrational modes of a binary superlattice alloy due to the change in its own degree of order has previously been discussed. It was then expected that the vibrational specific heat of the superlattice alloy would change in response to the change in its own degree of order. Using the result obtained formerly, we have applied, in the present paper. Houston\u27s approximate method of finding the frequency distribution function N(ν) to the calculation of the vibrational specific heat of β-brass in the state of any specified degree of order. It is shown that the vibrational specific heat of the disordered alloy is generally larger than that of the ordered one at oridnary temperatures. If two kinds of atoms which are the components of alloy are nearly equal in mass, the vibrational specific heat of the ordered alloy becomes larger than that of the disordered one at low temperatures

The Measurement of the Young\u27s Modulus of Metals and Alloys by an Interferometric Method. III : The Influence of Heat-Treatment on the Young\u27s Moduli of Fe-Al Alloys, and the Young\u27s Moduli of Ni-Al, Al-Cu Alloys and German Silver in the Annealed State

The measurement described in the earlier papers of this series has been extended to the study of the influence of heat-treatment on the Young\u27s moduli of Fe-Al alloys having the composition up to 14.75 per cent aluminium. It becomes clear that the Young\u27s modulus of ordered Fe_3Al (13.8 per cent aluminium) is smaller than that of disordered one. This result is contrary to the cases of Cu_3Au and Ni_3Mn. Moreover, measurement has been done on the static Young\u27s moduli of Ni-Al alloys (up to 5.17 per cent aluminium), several specimens of Al-Cu alloys and german silver. The Young\u27s modulus vs. composition curve of Ni-Al alloys seems to be akin to the curve peculiar to Ni-alloys, such as Ni-Cu and Ni-Mn systems

Paramagnetism of Tin Observed at the Superconducting Transition

Measurements have been made of the paramagnetism of tin cylinders in the presence of an external magnetic field and with an externally supplied current at the superconducting transition. It has been ascertained that the paramagnetic effect is not such an apparent one as once supposed, but an intrinsic one without hysteresis. The current minimum I_0, required for the appearance of a paramagnetic effect is represented in the (I-H-T) space by the simultaneous equations I_0=ξd(T_c-T) and H_0=ξT_c-T)-I_g/γd. Here I_g, γ, T_c and ξare characteristic constants of the superconductor and have values 1.2 amp, 0.23, 3.73°K and 1.1×10^2 oersted/deg respectively for the case of tin. H_0 and d are the external magnetic field in cersted and the specimen diameter in mm respectively. It is shown that the formula, I_0 = I_g + γdH obtained by earlier investigators for the minimum current requirement is the one for the orthogonal projection on the. (I-H) plane of the critical line in the (I-H-T) space. The paramagnetic region is shown schematically in the (I-H-T) space. Finally some remarks concerning the theory of the paramagnetic effect are given

Superconductivity of Dilute Primary Solid Solutions of In-Mg and In-Pb

By measuring magnetic moments and electrical resistances of pure indium and indium alloys containing 0.28 to 13.7 atomic per cent of magnesium and 0.06 to 0.73 atomic per cent of lead at liquid helium temperatures, the variation of the superconducting critical temperature, T_c, with the concentration of solute metals was studied. T_c decreases initially with the increasing concentration of solute in so far as a small amount of solute metals is concerned. When the amount becomes large, the alloying effect of magnesium differs from that of lead, i.e., in the former case T_c continues to decrease steadily, while in the latter it shows a gradual increase after passing through a minimum. These results qualitatively agree with the theoretical consideration of Anderson and of Nakamura. The threshold magnetic field at 0°K and the coefficient of electronic specific heat in the normal state were estimated from the data obtained

加温後のtsAF8細胞の細胞周期

Thermotolerance in tsAF8 cells develops during incubation at 34℃ after heating at 45℃, while it is suppressed by the following incubation at a non-permissive temperature of 39.7℃ after the same heating. The incubation temperature after heating may affect the cell cycle and consequently thermotolerance. In the present study, a relationship between the thermotolerance and the cell cycle of tsAF8 was investigated. The cell cycle fractions and DNA synthesis were measured by flow cytometry using double staining with propidium iodide and bromodeoxyuridine. When the tsAF8 cells were heated at 45℃ for 20 min, and thereafter incubated at 34℃, bromodeoxyuridine uptake in the S phase cells (DNA synthesis) was recovered to 65.1% 6 h after the heating, and the cells showed gradual accumulation in the G(2)/M phase. When the cells were incubated at 39.7℃ after heating at 45℃ for 20 min, then showed inhibition of thermotolerance development, the DNA synthesis was recovered to 15.1% temporarily 6 h after the heating, but it became 0% after 12 h, and the cells did not remarkably accumulate in any phases of the cell cycle. This inhibition of DNA synthesis at 39.7℃ was considered to be the result of cell survival decreasing by a step-down heating. However, the relationship between the thermotolerance and the cell cycle was not found out in tsAF8 cells, because the cells did not accumulate in any phases of the cell cycle under the inhibitory condition of thermotolerance.tsAF8細胞は45℃の加温後34℃で培養すると温熱耐性が速やかに発現するが,加温後,制限温度である39.7℃で培養すると温熱耐性の発現が抑制される｡加温後の培養温度が細胞周期に影響し,その結果として温熱耐性発現に影響を与えている可能性があることから,今回,Propidium Iodide(PI)とbromodeoxyuridine(BrdU)でtsAF8細胞を二重染色し,フローサイトメトリーによって温熱耐性と細胞周期の関係の有無について調べた｡tsAF8細胞を45℃20分の加温後34℃で培養すると,6時間後にはG(1)期の細胞が減少し,12時間後にはG(2)/M期への蓄積が見られた｡しかし,加温後39.7℃で培養した場合には細胞周期の進行がほとんど見られなかった｡BrdU の取込みは,加温せずに39.7℃で培養した場合には活発に行われ,また,45℃20分加温後34℃で培養した場合には,6時間後にはBrdUの取り込みは65.1%まで回復した｡しかし,温熱耐性発現の抑制が観察される45℃20分加温後39.7℃で培養した場合には,BrdUの取込み量は6時間後に一時的に15.1%に回復するが,12時間後には取込み量はゼロとなった｡BrdUの取り込みが阻害されたのはstep-down heatingの現象による細胞生存率の減少が原因だと考えられたが,温熱耐性発現の抑制が観察される条件下では細胞周期の特定の時期への集積がなかったことから,温熱耐性と細胞周期との関係はtsAF8細胞においては見い出されなかった