432 research outputs found
A Safety Index for Traffic with Linear Spacings
The authors have tried to improve the traffic dynamic theory of Prof. Pipes and have found the fundamental equation of traffic dynamics for a case in which the velocity of the following vehicle is determined not only by the space between following and lead cars but also by the velocity of the lead car. The safety of the following car with respect to rear end collision when the lead car is in sinusoidal motion is quantified by introducing a safety index. At the same time, the authors describe the stability of the indicial response of the following car, and the stability of the propagation of a sinusoidal disturbance down a line of cars
Valence and Na content dependences of superconductivity in NaxCoO2.yH2O
Various samples of sodium cobalt oxyhydrate with relatively large amounts of
Na ions were synthesized by a modified soft-chemical process in which a
NaOH aqueous solution was added in the final step of the procedure. From these
samples, a superconducting phase diagram was determined for a section of a
cobalt valence of +3.48, which was compared with a previously obtained
one of +3.40. The superconductivity was significantly affected by the
isovalent exchanger of Na and HO, rather than by variation of
Co valence, suggesting the presence of multiple kinds of Fermi surface.
Furthermore, the high-field magnetic susceptibility measurements for one sample
up to 30 T indicated an upper critical field much higher than the Pauli limit
supporting the validity of the spin-triplet pairing mechanism.Comment: 4 figures and 1 tabl
Superconducting phase diagram of NaxCoO2.yH2O
We synthesized Nax(H3O)zCoO2yH2O samples with various Na/H3O ratios but with
the constant Co valence of s = +3.40, and measured their magnetic properties to
draw phase diagrams of the system. The superconductivity is very sensitive to
the Na/H3O ratio. With varying x under fixed s of +3.40, magnetically ordered
phase appears in the intermediate range of x sandwiched by two separated
superconducting phases, suggesting that the superconductivity is induced by
moderately strong magnetic interactions. In the vicinity of the magnetic phase,
transition from the superconducting state to the magnetically ordered state was
induced by applying high magnetic field. This transition is of the second
order, at least, above 1.8 K. The upper-critical field is expected to be much
higher than the Pauli limit for a phase located far away from the magnetic
phase regarding the Na/H3O ratio.Comment: proceedings of ISS200
Tightly binding valence electron in aluminum observed through X-ray charge density study
Accurate and high reciprocal resolution experimental structure factors of aluminum were determined from a synchrotron powder X-ray diffraction data measured at 30 K with sin θ/λ < 2.31 Å−1. The structure factors have small deviations from independent atom model in sin θ/λ < 0.83 Å−1. Theoretical structure factors were prepared using density functional theoretical calculations by full potential linearized augmented plane wave method. The deviation between experimental and theoretical data was also observed at around sin θ/λ ≈ 0.4 Å−1. The charge density was determined by an extended Hansen-Coppens multipole modeling using experimental and theoretical structure factors. Charge density maxima at tetrahedral site were observed in both experimental and theoretical deformation density. The charge-density difference peaks indicating directional bonding formation were observed in the difference density between experiment and theory. The present study reveals tight binding like character of valence electron of aluminum. The fact will provide a crucial information for development of high-performance aluminum alloy
The Function of β2-glycoprotein I in Angiogenesis and Its in Vivo Distribution in Tumor Xenografts
Intact β2-glycoprotein I (iβ2GPI) is a glycoprotein that regulates coagulation and fibrinolysis. Nicked β2GPI (nβ2GPI) possesses an angiogenic property at a relatively low concentration, and an antiangiogenic property at a high concentration. Here we investigated the functions of βi 2GPI and nβ2GPI in vascular endothelial growth factor (VEGF)-A-induced endothelial cell proliferation and tube formation. We used noninvasive PET imaging to analyze the in vivo distribution of intravenously injected β2GPI variants in tumor lesions in mice. iβ2GPI was incubated with plasmin to obtain nβ2GPI, and its N-terminal sequence was analyzed. nβ2GPI had at least one other cleavage site upstream of the β2GPIʼs domain V, whereas the former plasmin-cleavage site locates between K317 and T318. Both of intact and nicked β2GPI significantly inhibited the VEGF-A-induced cell proliferation and the tube formation of human umbilical vein endothelial cells (HUVECs). PET imaging visualized considerably distributed intensities of all tested β2GPI variants in tumor lesions of pancreatic tumor cell-xenografts. These results indicate that β2GPI may be physiologically and pathophysiologically important in the regulation of not only coagulation and fibrinolysis, but also angiogenesis
Aspherical and covalent bonding character of d electrons of molybdenum from synchrotron x-ray diffraction
The occupancies and spatial distribution of electrons for 4d-orbitals in pure molybdenum have been experimentally determined by a charge density study from synchrotron radiation x-ray powder diffraction. There are valence charge density maxima in interatomic positions indicating bond formation. The electron deficiencies of Γ12 orbitals were visualized in the observed static deformation density. An electron deficiency of ~0.5 was observed from the orbital population analysis through multipole refinement. The occupancies and spatial distribution have also been calculated by a density functional theoretical calculation using WIEN2k packages for comparison. The observed features agree well with the theoretical study. In addition, the observed charge density has more covalent bonding character than the theoretical one. The present study confirms that a state-of-the-art x-ray charge density study can reveal the spatial structure of d-electrons in 4d-system
How Did the Dollar Peg Fail in Asia?
In this paper we have constructed a theoretical model in which Asian firms maximize their profit, competing with Japanese and US firms in their markets. The duopoly model is used to determine export prices and volumes in response to the exchange rate fluctuations vis-…-vis the Japanese yen and the US dollar. Then, the optimal basket weight to minimize the fluctuation of the growth rate of trade balance is derived. These are the novel features of our model. The export price equation and export volume equation are estimated for several Asian countries for the sample period of 1981 to 1996. Results are generally reasonable. The optimal currency weights for the yen and the US dollars are derived and compared with actual weights that had been adopted before the currency crisis of 1997. For all the countries in the sample, it is shown that the optimal weight of the yen is significantly higher than the actual weight.
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