Fractality of self-grown nanostructured tungsten by He plasma irradiation

Fractal property of the helium irradiated nanostructured tungsten was investigated from the scanning electron microscope (SEM) micrographs, gas adsorption isotherms, and transmission electron microscope (TEM) micrographs. From the SEM micrographs, fractal dimension and the parameter _dmin$d_{\min }$, which characterizes the SEM texture image, were deduced, and the fractal dimension was compared with the one obtained from the gas adsorption isotherms. It was revealed that the fractal dimension obtained from the top view SEM micrographs was significantly lower than that from the adsorption isotherms. From the cross sectional SEM micrographs, two power law relations were identified in two different scales, and the fractal dimension from the adsorption was in between the two fractal dimensions. From the TEM micrographs, it was found that the porosity distribution also has fractal relation with height of the nanostructures when the nanostructures were sufficiently grown.     

Loss estimation of electrostatically trapped ND3 molecules

Losses of electrostatically trapped molecules are caused by the Majorana transition or the inelastic collisions between trapped molecules. The loss rate of electrostatically trapped ND₃ molecules in the (J=1,K=1,M=1, A) state was estimated: ND₃ molecules in this state have actually been trapped. When trapping cold molecules, using ¹⁵ND₃ molecules (fermion) with a minimum electric field higher than 10 kV/cm yields high stability.     

Influence of the neighboring transition on polarization gradient cooling

g =4→F_e ^′=5 transition. As the detuning becomes larger, the equilibrium temperature becomes lower. When the detuning is larger than 150 MHz, the influence of the F_g=4→F_e ^′=4 transition also becomes significant. We show our numerical analysis of polarization gradient cooling, taking into account actual sublevels of the ground state and two excited states. We conclude that it is preferable to use a detuning of greater than 180 MHz, to get both a high deceleration and low equilibrium temperature. Received: 25 September 1996/Revised version: 10 January 1997     

Synthesis and Enzymatic Degradation of Nylon 66 Copolymers with Poly(Ethyleneglycol)s

Abstract

Nylon 66 (N66) copolymers were prepared by melt polycondensation of adipic acid and hexamethylenediamine with 5–80 mol% poly(ethylene glycol) (PEG), where the molecular weight (MW) of PEG was 200–1000. The reduced specific viscosity of the copolymers was increased by the copolymerization. The crystallinity and melting temperature (T _m) of N66 components decreased with increasing PEG content, but T _m depression of copolymers at the same mole content decreased with increasing MW of PEG, suggesting that the copolymer structures are not of the random type but of the block type at the higher MW of PEG. The water absorption increased with increasing PEG content, and its increase was much higher at the higher MW of PEG. The enzymatic degradation was estimated by the weight loss of copolymer films in the buffer solution with and without a lipase at 37°C. The weight loss was enhanced appreciably by the presence of a lipase, and increased abruptly at higher PEG content, which was correlated to water absorption and the concentration of ester linkages. The enzymatic degradation of these N66 copolymers was much higher than that of previously reported PET copolymers with PEG. The abrupt increase of weight loss by alkali hydrolysis was fairly comparable to that of water absorption.     

Enhancement of the fluorescence intensity of DNA intercalators using nano-imprinted 2-dimensional photonic crystal

We have fabricated polymer-based 2-dimensional photonic crystals that play a key role in enhancing the fluorescence of DNA intercalators. Highly ordered 2-dimensional photonic crystals possessing triangle-shaped and nm-sized hole arrays were fabricated on a 100 μm thick polymer film using nano-imprint lithography. Samples of double-stranded DNAs (sizes: 4361 and 48502 bp; concentration: 1 pM to 10 nM) were adsorbed on the surface of the 2-dimensional photonic crystal by electrostatic interactions and then treated with intercalators. It is found that the fluorescence intensity of the intercalator is enhanced by a factor of up to 10 compared to the enhancement in the absence of the 2-dimensional photonic crystal. Fluorescence intensity increases with increasing length and concentration of the DNAs. If the 2-dimensional photonic crystal is used as a Bragg reflection mirror, the enhancement of fluorescence intensity can be easily observed using a conventional spectrofluorometer. These results suggest that the printed photonic crystal offers a great potential for highly sensitive intercalator-based fluorescent detection of DNAs.

Improved search for nu(mu) --> nu(e) oscillation in a long-baseline accelerator experiment

We performed an improved search for nu(mu) --> nu(e) oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of 9.2 x 10(19) protons on target. No evidence for a nu(e) appearance signal was found, and we set bounds on the nu(mu) --> nu(e) oscillation parameters. At Deltam(2)=2.8 x 10(-3) eV(2), the best-fit value of the K2Knu(mu) disappearance analysis, we set an upper limit of sin(2)2theta(mue) < 0.13 at a 90% confidence level.     

Double‐probe measurement in recombining plasma using NAGDIS‐II

We have studied the validity of the double‐probe method in recombining plasmas. Electron temperature (T_e) measured with a double probe was quantitatively evaluated by taking into account the influences of plasma potential fluctuation, plasma resistivity, and electron density fluctuation on the current–voltage characteristics. Differential potential fluctuation and plasma resistivity between two electrodes have a minor effect on T_e especially when the inter‐distance is small (typically 1 mm). Scattering of measured T_e due to the density fluctuation was sufficiently suppressed by making the data acquisition time long (typically 4 s) and taking the average. There is a good agreement between T_e measured with the optimized double‐probe method and that with laser Thomson scattering diagnostics.     

Indications of neutrino oscillation in a 250 km long-baseline experiment

The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.