Thickening process of polyethylene single crystals at an early stage of annealing

By the use of a position sensitive proportional counter, changes in small and wide angle X-ray scattering during annealing of polyethylene single crystal mats were measured from the start in successive spans of very short measuring time. At high temperatures, the long period relating to stacking of lamellae rapidly increased at an early stage, passed through a plateau, and thereafter again increased gradually. With a decrease in annealing temperature, the amount of its first rapid increase was reduced and the plateau changed into an ascending slope. At much lower annealing temperatures, the long period increased following the logt law after an induction time. The integral breadth of a peak corresponding to the long period first increased rapidly, simultaneously with the rapid increase in the long period, and thereafter decreased. Wide angle X-ray measurement showed that the integrated intensity of 110 reflection first decreased and then increased during annealing at high temperatures. This fall and rise process was more marked, when the annealing temperature is higher and the initial thickness of lamellae is smaller. From these observations, it was inferred that in the thickening process, stacking order of lamellae at first decreased because of rapid reorganization due to partial melting or melt-recrystallization and subsequently increased through increasing evenness of lamellar thickness.     

Frequency tunable beat note from a dual-polarization emitting external cavity diode laser

A method is presented to generate tunable millimetre waves by photomixing one TE mode and one TM mode of a dual-polarization external cavity diode laser emitting in the 1.55 μm wavelength domain. Beat notes in the frequency range 0.2 to 60GHz have been measured where the upper frequency is limited by the detector system bandwidth only. The frequency and amplitude stability are investigated. Typical beat intensity fluctuations are within 0.5 dB. The frequency stability is around 5MHz. The relative intensity noise of a TE and a TM mode was measured and a correlation found around multiples of the cavity roundtrip frequency and in the low frequency regime. Theoretical calculations show qualitative agreement with the measurement results. This revised version was published online in November 2006 with corrections to the Cover Date.     

Subject index for volume 107

The far-infrared laser magnetic resonance spectrum of AsH in the ground X³Σ^? state has been observed using five optically pumped laser lines as sources. The AsH radical was produced by the reaction of metallic arsenic with microwave discharge products of a H₂ and O₂ mixture. From an analysis of the observed spectrum, the following rotational and fine structure constants were obtained: B₀ = 215 877.54 (23), D₀ = 9.834 (11), λ = 1 763 488 (56), and γ = ?8 114.5 (60), all in MHz with 3σ in parentheses. The hyperfine coupling constants were also determined for the two nuclei as follows: α_As = ?11.5 (14), β_As = ?159.4 (13), eQq_As = ?97.6 (72), α_H=?49.80 (66), and β_H=4.15 (60), again in MHz with 3σ in parentheses.     

General description of mechanical anisotropy of semicrystalline polymers in relation to orientation of structural units composed of crystalline and noncrystalline materials

A mathematical representation of the transformation of an orientation function between two sets of Cartesian coordinates is discussed in terms of a series expansion of the distribution function in generalized spherical harmonics. A general procedure for calculating the mechanical anisotropy of a single-phase system (a polycrystalline material) from the orientation of its structural units and the intrinsic mechanical anisotropy of the structural unit is discussed in relation to the transformation of the orientation distribution function, i.e., mutual conversion of the coefficients in the expansion of the distribution function between the two sets of Cartesian coordinates. The procedure is extended to a two-phase systems (semicrystalline polymers) containing structural units composed of crystalline and noncrystalline materials in three different geometrical arrangements.     

The geometrical structure of the parameter space of the two-dimensional normal distribution

The differential geometrical consideration of the parameter space, especially as a Riemannian geometry, was initiated by C.R. Rao in 1945. This approach appears to be important for the problem of estimation and test of hypotheses as well as for applications to physical problems. It has been shown that the parameter spaces of univariate normal distribution, univariate exponential distribution and multinomial distribution are Riemannian spaces of constant curvature. In the present paper the discussion is confined to the parameter space of the two-dimensional normal distribution. It has been shown that in general the parameter space is not necessarily of a constant curvature and that, if the correlation coefficient vanishes, the parameter space becomes an Einstein space. In addition, some invariant quantities, as sectional curvature, mean curvature and scalar curvature, have been calculated.     

Canonical height functions for affine plane automorphisms

Let be a polynomial automorphism of dynamical degree δ≥2 over a number field K. We construct height functions defined on that transform well relative to f, which we call canonical height functions for f. These functions satisfy the Northcott finiteness property, and a -valued point on is f-periodic if and only if its height is zero. As an application, we give an estimate on the number of points with bounded height in an infinite f-orbit.     

Einstein-de Haas effect in dipolar Bose-Einstein condensates

The general properties of the order parameter for a dipolar spinor Bose-Einstein condensate are discussed based on symmetries of interactions. An initially spin-polarized dipolar condensate is shown to dynamically generate a nonsingular vortex via spin-orbit interactions--a phenomenon reminiscent of the Einstein-de Haas effect in ferromagnets.     

Buffer-gas pressure broadening for the (3 0(0) 1)III <-- (0 0 0) band of CO2 measured with continuous-wave cavity ring-down spectroscopy

Buffer-gas pressure broadening for the (3 0(0) 1)(III)<--(0 0 0) band of CO(2) in the 1600 nm region was investigated with continuous wave cavity ring-down spectroscopy within the temperature range 263-326 K. The measured absorption profiles were analyzed with Voigt functions. Pressure broadening coefficient, gamma(gas), and the temperature dependent parameter (broadening exponent), n, were determined for a variety of buffer gases: N(2), O(2), He, Ne, Ar, Kr and Xe. gamma(air) values estimated subsequently are 0.096(2) for R(0), 0.085(5) for P(8), 0.075(2) for P(16), 0.070(4) for P(26), and 0.069(2) for P(38) in units of cm(-1) atm(-1), where numbers in parentheses are one standard deviation in units of the last digits quoted. n(air) values are 0.77(4) for R(0), and 0.73(11) for P(8).     

Use of laser drilling in the manufacture of organic inverter circuits

Inverter circuits have been made by connecting two high-quality pentacene field-effect transistors. A uniform and pinhole-free 900 nm thick polyimide gate-insulating layer was formed on a flexible polyimide film with gold gate electrodes and partially removed by using a CO₂ laser drilling machine to make via holes and contact holes. Subsequent evaporation of the gold layer results in good electrical connection with a gold gate layer underneath the gate-insulating layer. By optimization of the settings of the CO₂ laser drilling machine, contact resistance can be reduced to as low as 3 Ω for 180 μm square electrodes. No degradation of the transport properties of the organic transistors was observed after the laser-drilling process. This study demonstrates the feasibility of using the laser drilling process for implementation of organic transistors in integrated circuits on flexible polymer films.