Wave-packet dynamics of Bloch electrons—Role of Berry phase

Motivated by a recent proposal on the possibility of observing a monopole in the band structure, and by an increasing interest in the role of Berry phase in spintronics, we reconsidered the problem of adiabatic motion of a wave packet of Bloch functions, under a perturbation varying slowly and incommensurately to the lattice structure. We showed, using only the fundamental principles of quantum mechanics, that the effective wave-packet dynamics of Bloch electrons is conveniently described by a set of equations of motion (EOM) in which a non-Abelian Berry phase associated with the internal degree of freedom appears.     

Correlation of57Fe hyperfine interactions with Fe-Fe distance in Laves phase compounds RFe2 (R=rare earth)

The⁵⁷Fe Mössbauer isomer shifts and magnetic hyperfine fields in Laves phase compounds RFe₂ (R=Pr, Nd and Sm) are studied with particular reference to the effect of the Fe–Fe interatomic distance on the hyperfine interactions. It is shown that the charge density at the Fe nuclei scales linearly with fractional volume change up to 20%. The⁵⁷Fe hyperfine field corrected for the influence of rare-earth moment shows a systematic variation with the distance, which can be understood in terms of the Bethe-Slater curve arguments. The similarity of the atomic volume dependence of the⁵⁷Fe hyperfine interactions in Lves phase compounds to those in iron with close-packed structure is emphasized.This paper is based on a paper presented at the 5th Int. Conf. on hyperfine interactions, Berlin, July 21–25, 1980.     

Solution behavior of styrene–ethylene oxide block copolymers

Hydrophobic–hydrophilic water-soluble block copolymers were prepared by “living” anionic polymerization. They consist of a polystyrene block and a polyethylene oxide block. From data on solution viscosity and high-resolution NMR in water, the molecular dimensions of the two-blocks copolymers are found similar to that of polyethylene glycols of the same molecular weight in the same solvent. These block copolymers exhibit microphase separation.     

Synthesis and electrochemical properties of novel dimeric fullerenes incorporated in a 2,3-diazabicyclo[2.2.2]oct-2-ene framework

Novel dimeric fullerenes incorporated in a 2,3-diazabicyclo[2.2.2]oct-2-ene framework, with and without direct inter-fullerene-cage bonds, were synthesized and fully characterized spectroscopically; the electronic communication between the two fullerene cages was clarified by differential pulse voltammetry.     

On a unit group generated by special values of Siegel modular functions

There has been important progress in constructing units and -units associated to curves of genus 2 or 3. These approaches are based mainly on the consideration of properties of Jacobian varieties associated to hyperelliptic curves of genus 2 or 3. In this paper, we construct a unit group of the ray class field of modulo 6 with full rank by special values of Siegel modular functions and circular units. We note that . Our construction of units is number theoretic, and closely based on Shimura's work describing explicitly the Galois actions on the special values of theta functions.

     

Effect of debris fragments on direct initiation of spherical detonation waves in stoichiometric oxygen/hydrogen mixtures

Paper reports a result of experiments of spherical shock waves generated by explosions of micro-explosives weighing from 1 to 10 mg ignited by the irradiation of Q-switched laser beam and direct initiation to a spherical detonation wave in stoichiometric oxygen/hydrogen mixtures at 10–200 kPa. We visualized the interaction of debris particles ejected micro-explosives’ surface with shock waves by using double exposure holographic interferometry and high-speed video recording. Upon explosion, minute inert debris launched supersonically from micro-charge surface precursory to shock waves initiated spherical detonation waves. To examine this effect we attached 0.5–2.0 μm diameter SiO₂ particles densely on micro-explosive surfaces and observed that the supersonic particles, significantly promoted the direct initiation of spherical detonation waves. The domain and boundary of detonation wave initiations were experimentally obtained at various initial pressures and the amount of micro-charges.     

Silver nanosintering: a lead-free alternative to soldering

We propose a lead-free silver paste as a replacement for a high-temperature lead-rich solder used for electronics. The pastes tested here contain a small amount of solvent, but primarily consist of silver powder and alkoxide-passivated silver nanoparticles that undergo nanosintering when heated. The pastes were used to connect silicon diode chips to copper bases at 350°C in nitrogen ambient without external pressure. The resulting diode packages had electrical and thermal properties about equal to those with lead-solder joints. The mechanical strengths also were comparable to the lead joint. These properties make this nanosilver paste the first viable lead-free alternative to a lead solder.     

Explicit formulae for sums of products of Bernoulli polynomials,including poly-Bernoulli polynomials

We study sums of products of Bernoulli polynomials, including poly-Bernoulli polynomials. As a main result, for any positive integer $m$ , explicit expressions of sums of $m$ products are given. This result extends that of the first author, as well as the famous Euler formula about sums of two products of Bernoulli numbers.     

Three-dimensional melting of ice around a liquid-carrying tube

Three-dimensional melting of ice around a liquid-carrying tube placed in an adiabatic rectangular cavity is investigated mainly by means of a numerical analysis. Natural convection in the melt layer enhances melting by about 1.2 times compared with the approximate solution of a conduction mode derived from London and Seban and Hausen. The morphology of the melt layer changes in axial direction. Melting is not sensitive to the cavity height and the tube length, but is very responsive to the liquid inlet temperature.