On the Changes of Electrical Properties in Cold-Worked Metal

The increase in electrical resistance of metals due to cold-work was discussed taking into account the perturbing potential due to the edge dislocation caused by the said mechanical treatment. The method of calculating the electric conductivity was based on Peterson and Nordheim\u27s assumption for the perturbing potential. An estimation of thermoelectric power due to cold-work was made from the same point of view. A criticism was given for the theories by Koehler and Machenzie-Sondheimer. The results obtained showed somewhat smaller value than the results of the above-mentioned authors

Formation of Superlattice in Face-Centered Cudic Lattice with a Special Reference to the Copper-Platinum System

Based on the notion that, for the formation of certain types of superlattices in face-centered cubic alloys, the second neighbor interaction becomes appreciable, the formation of superlattice in copper-platinum system was studied, and the ordering energy in such a formation was obtained from the viewpoint of electron theory. The results could interpret both quantitatively and qualitatively various results of many experiments concerning this binary system

Low Temperature Transformation of Fe-Pd and Fe-Pt Invar Alloys

Low temperature structures of Fe-Pd and Fe-Pt alloys in the Invar region have been determined by means of low temperature X-ray diffraction experiment. The phase diagrams are obtained. A new fct phase is found in the ordered and disordered Fe-Pt and the disordered Fe-Pd systems. An effect of the degree of order for Fe_3Pt to the structural transformations are examined. The lattice instability of Fe-based fcc Invar alloys are discussed from the low temperature structures with the lattice softening effect and the lattice distortion anomaly

Coupling of Rotation and Catalysis in F1-ATPase Revealed by Single-Molecule Imaging and Manipulation

SummaryF1-ATPase is a rotary molecular motor that proceeds in 120° steps, each driven by ATP hydrolysis. How the chemical reactions that occur in three catalytic sites are coupled to mechanical rotation is the central question. Here, we show by high-speed imaging of rotation in single molecules of F1 that phosphate release drives the last 40° of the 120° step, and that the 40° rotation accompanies reduction of the affinity for phosphate. We also show, by single-molecule imaging of a fluorescent ATP analog Cy3-ATP while F1 is forced to rotate slowly, that release of Cy3-ADP occurs at ∼240° after it is bound as Cy3-ATP at 0°. This and other results suggest that the affinity for ADP also decreases with rotation, and thus ADP release contributes part of energy for rotation. Together with previous results, the coupling scheme is now basically complete

Diffusion of Iron Group Elements in Silver

The diffusion coefficients of nickel and cobalt into silver has been measured as a function of temperature by the tracer and lathe sectioning techniques. The results obtained were expressed as follows : D=(21.9)・exp(-54, 800/RT)cm^2/sec for nickel D=(104)・exp(-59, 900/RT)cm^2sec for cobalt. Taking into consideration the result by Mullen for the diffusion of iron into silver, the activation energy of diffusion of the first transition elements increases slowly from Cu to Ni and after showing a sharp maximum at cobalt, decreases suddenly at iron. Such behavior is different in the case of copper, in which a flat maximum is found at nickel. Also the frequency factor shown in the above expression is fairly large when compared with copper. It is pointed out here that the solid solubility limits of the first transition metals in silver are extremely small when compared with copper, which has some influence on the result of measurement of the activation energy as well as the frequency factor in the case of silver

Neither Helix in the Coiled Coil Region of the Axle of F1-ATPase Plays a Significant Role in Torque Production

F1-ATPase is an ATP-driven rotary molecular motor in which the central γ-subunit rotates inside the cylinder made of α3β3 subunits. The amino and carboxy termini of the γ-subunit form the axle, an α-helical coiled coil that deeply penetrates the stator cylinder. We previously truncated the axle step by step, starting with the longer carboxy terminus and then cutting both termini at the same levels, resulting in a slower yet considerably powerful rotation. Here we examine the role of each helix by truncating only the carboxy terminus by 25–40 amino-acid residues. Longer truncation impaired the stability of the motor complex severely: 40 deletions failed to yield rotating the complex. Up to 36 deletions, however, the mutants produced an apparent torque at nearly half of the wild-type torque, independent of truncation length. Time-averaged rotary speeds were low because of load-dependent stumbling at 120° intervals, even with saturating ATP. Comparison with our previous work indicates that half the normal torque is produced at the orifice of the stator. The very tip of the carboxy terminus adds the other half, whereas neither helix in the middle of the axle contributes much to torque generation and the rapid progress of catalysis. None of the residues of the entire axle played a specific decisive role in rotation

Differential roles of prostaglandin E-type receptors in activation of hypoxia-inducible factor 1 by prostaglandin E1 in vascular-derived cells under non-hypoxic conditions

Prostaglandin E1 (PGE1), known pharmaceutically as alprostadil, has vasodilatory properties and is used widely in various clinical settings. In addition to acute vasodilatory properties, PGE1 may exert beneficial effects by altering protein expression of vascular cells. PGE1 is reported to be a potent stimulator of angiogenesis via upregulation of VEGF expression, which is under the control of the transcription factor hypoxia-inducible factor 1 (HIF-1). However, the molecular mechanisms behind the phenomenon are largely unknown. In the present study, we investigated the mechanism by which PGE1 induces HIF-1 activation and VEGF gene expression in human aortic smooth muscle cells (HASMCs) and human umbilical vein endothelial cells (HUVECs), both vascular-derived cells. HUVECs and HASMCs were treated with PGE1 at clinically relevant concentrations under 20% O2 conditions and HIF-1 protein expression was investigated. Expression of HIF- 1α protein and the HIF-1-downstream genes were low under 20% O2 conditions and increased in response to PGE1 treatment in both HUVECs and HASMCs in a dose- and time-dependent manner under 20% O2 conditions as comparable to exposure to 1% O2 conditions. Studies using EP-receptor-specific agonists and antagonists revealed that EP1 and EP3 are critical to PGE1-induced HIF-1 activation. In vitro vascular permeability assays using HUVECs indicated that PGE1 increased vascular permeability in HUVECs. Thus, we demonstrate that PGE1 induces HIF- 1α protein expression and HIF-1 activation under non-hypoxic conditions and also provide evidence that the activity of multiple signal transduction pathways downstream of EP1 and EP3 receptors is required for HIF-1 activation

On the Magnetic Anisotropy of a Pyrrhotite Crystal

Measurement of the magnetic anisotropy energy of a single crystal of natural pyrrhotite in c-plane was made by means of the torque method at room temperature up to a magnetic field of 20000 Oe and at low temperature in a constant field. It was found that the easy axis lay along [210] direction above -80℃ which, however, changed to [100] direction below that temperature. The torque curves in c-plane were composed of two- and six-fold symmetric parts. It was also found that in the range of strong magnetic fields the six-fold symmetric part at room temperature decreased with the inverse square of the applied field ; such a field dependence is explained assuming a triad structure for the single crystal of pyrrhotite. A remark is also given on the origin of the two-fold symmetric torque

Temperature Dependence of the Rotation and Hydrolysis Activities of F1-ATPase

F1-ATPase, a water-soluble portion of the enzyme ATP synthase, is a rotary molecular motor driven by ATP hydrolysis. To learn how the kinetics of rotation are regulated, we have investigated the rotational characteristics of a thermophilic F1-ATPase over the temperature range 4–50°C by attaching a polystyrene bead (or bead duplex) to the rotor subunit and observing its rotation under a microscope. The apparent rate of ATP binding estimated at low ATP concentrations increased from 1.2 × 106 M−1 s−1 at 4°C to 4.3 × 107 M−1 s−1 at 40°C, whereas the torque estimated at 2 mM ATP remained around 40 pN·nm over 4–50°C. The rotation was stepwise at 4°C, even at the saturating ATP concentration of 2 mM, indicating the presence of a hitherto unresolved rate-limiting reaction that occurs at ATP-waiting angles. We also measured the ATP hydrolysis activity in bulk solution at 4–65°C. F1-ATPase tends to be inactivated by binding ADP tightly. Both the inactivation and reactivation rates were found to rise sharply with temperature, and above 30°C, equilibrium between the active and inactive forms was reached within 2 s, the majority being inactive. Rapid inactivation at high temperatures is consistent with the physiological role of this enzyme, ATP synthesis, in the thermophile