Highly polarized very cold neutrons through a permanent magnet quadrupole

We obtained highly polarized very cold neutrons through a quadrupole magnet with a large aperture. When neutrons go through a quadrupole magnet, parallel-spin neutrons are attracted to the magnet axis and anti-parallel-spin neutrons are repelled off the axis. Therefore, the neutrons through a sufficiently long quadrupole magnet have completely parallel-spin. At the downstream of the quadrupole magnet, we placed another quadrupole magnet to divide neutrons into two regions depending on their spin directions. We obtained the neutron polarization from the integrated count of the two regions and found it was 99.88±0.09 (stat.)±0.05 (syst.)%.     

Effects of microcrystallites on swelling behavior in chemically crosslinked poly(vinyl alcohol) gels

We report the swelling ratio and network structure of a poly(vinyl alcohol) (PVA) gel chemically crosslinked by glutaraldehyde with different degrees of crosslinks. Microcrystallites were formed in a chemical PVA gel during a drying process and were confirmed by X‐Ray diffraction (XRD) measurements and Fourier transform infrared (FTIR) spectroscopy. The formation of microcrystallites in the dried gels was suppressed by increasing the degrees of chemical crosslinks. When the dried samples were immersed in pure water at 25 °C, the swelling ratio depended on the degree of chemical crosslinks resulting from the destruction of physical crosslinks by microcrystallites. On the other hand, when the dried samples were immersed in a poor solvent of a mixture of dimethyl sulfoxide and water at 8 °C, the gels did not swell and stayed in the collapsed state. Starting from the collapsed state, the equilibrium swelling ratios were measured while the temperature was increased to 90 °C and then decreased to 8 °C. As a result, irreversible swelling behaviors were observed for all gels with different degrees of crosslinks, which were attributed to the destruction of microcrystallites. The swelling behavior is discussed in terms of the formation and destruction of additional physical crosslinks in the chemical PVA gels. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Direct observations of vortices in a high-Tc superconductor (La1-xSrx)2CuO4 by scanning SQUID microscopy

In order to investigate the behavior of vortices in high-T_c superconductors under low magnetic fields, we have performed scanning SQUID microscopy (SSM) on the ab-surfaces of (La_1-xSr_x)₂CuO₄ (LSCO) single crystals at low temperatures. The observed magnetic images clearly demonstrated vortices in units of K₀ (=hc/2e) below T_c. Vortices trapped inside the overdoped LSCO tended to be arranged in a one-dimensional manner, while those in optimally doped crystals were randomly distributed. From the variable-temperature SSM measurements, it was directly visualized that the normal state with regular magnetic-field distribution gradually changed into the inhomogeneous Meissner state, and finally vortices evolved, with decreasing temperature.     

Binary Optimal Odd Formally Self-Dual Codes

In this paper, we study binary optimal odd formallyself-dual codes. All optimal odd formally self-dual codes areclassified for length up to 16. The highest minimum weight ofany odd formally self-dual codes of length up to 24 is determined. We also show that there is a unique linearcode for parameters [16, 8, 5] and [22, 11, 7], up to equivalence.     

Synthesis and structure of 1‐phospholyl‐ and di(1‐phospholyl)acetylenes and the corresponding sulfides

The acetylenes possessing one and two 1‐phospholyl groups were synthesized by reaction of the alkynyl Grignard reagents with the 1‐chlorophosphole and converted to the corresponding phosphole sulfides. Reaction of the 1‐phenylethynylphosphole sulfide with CpCo(CO)₂ resulted in η⁴‐complexation on the phosphole moiety. The structures of the di(1‐phospholyl)acetylene disulfide and the [η⁴‐(1‐phenylethynylphosphole sulfide)]cobalt(I) complex were characterized by X‐ray crystallography. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:344–349, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20230     

Influence of relaxation phenomena in dynamic magnetization processes on magnetic power losses of non-oriented electrical steel sheets

We have reported that the magnetic power losses per magnetizing cycle change with the magnetization pausing time in a constant rate of magnetization change and some relaxation phenomena exist in the magnetization pausing period. We discuss the influence of the relaxation phenomena on the dynamic magnetic power losses and suggest that the relaxation phenomena seems to be causes of the frequency dependence of the magnetic losses and of the variation of losses that cannot be expressed only by magnetization speed dependence of losses.     

Micro-hole processing of polyimide film by ultra-short laser pulses and its applications

Micro machining of a polyimide film with ultra-short pulsed laser was demonstrated. A through-hole with a diameter of less than 10 μm could be produced by optimizing the pulse duration, repetition rate, and number of shots. Thermal damage around the through-hole can be made negligibly small when the pulse duration was shorter than 140 fs. We also found that the minimum shot number needed for the creation of a through-hole becomes smaller as the repetition rate of laser shot increases. On the basis of the optimum irradiation condition, we demonstrated laser cutting of a polyimide film without thermal damage and copper filling in through-holes with diameters of 9 μm by a plating process.