A new phlorotannin from the brown alga Ecklonia stolonifera

A new phlorotannin, named eckstolonol (1), was isolated from the EtOAc soluble fraction of the methanolic extract of the brown alga, Ecklonia stolonifera OKAMURA, along with three known phlorotannins, eckol (2), phlorofucofuroeckol A (3), and dieckol (4). The structure of eckstolonol was identified as 5,8,13,14-tetraoxa-pentaphene-1,3,6,9,11-pentaol on the basis of spectroscopic evidence. The new compound was found to be a radical scavenger on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical.     

A note on treating a second order cone program as a special case of a semidefinite program

It is well known that a vector is in a second order cone if and only if its arrow matrix is positive semidefinite. But much less well-known is about the relation between a second order cone program (SOCP) and its corresponding semidefinite program (SDP). The correspondence between the dual problem of SOCP and SDP is quite direct and the correspondence between the primal problems is much more complicated. Given a SDP primal optimal solution which is not necessarily arrow-shaped, we can construct a SOCP primal optimal solution. The mapping from the primal optimal solution of SDP to the primal optimal solution of SOCP can be shown to be unique. Conversely, given a SOCP primal optimal solution, we can construct a SDP primal optimal solution which is not an arrow matrix. Indeed, in general no primal optimal solutions of the SOCP-related SDP can be an arrow matrix.Mathematics Subject Classification (2000): 20E28, 20G40, 20C20     

Estimation of probability characteristics by generalized Bernstein polynomials

Approximations based on Bernstein polynomials are used for smoothing a sample quantile function and estimating the underlying distribution and its characteristics. Generalized Bernstein-type polynomials are introduced to reduce the bias of estimation under various types of distributions including finite distributions. The asymptotic behavior of the expectations of these estimators is studied. Bibliography: 10 titles.Published in Zapiski Nauchnykh Seminarov POMI, Vol. 294, 2002, pp. 127–138.     

Performance evaluation of N × 40 Gbps CS-RZ and DCS-RZ modulated signals transmitted over single mode fiber based on non-ideal LiNbO<Subscript>3</Subscript> Mach-Zehnder modulators

We investigate the transmission performance of N × 40 Gbps carrier-suppressed return-to-zero (CS-RZ) and duobinary CS-RZ (DCS-RZ) modulated wavelength division multiplexed (WDM) signals over the standard single-mode fiber (SSMF) based on non-ideal Mach-Zehnder (MZ) modulators through numerical simulations. In addition to that, the impact on receiver margin related to the residual chirp due to an asymmetry ratio of modulators as well as the effect of the applied chirp of modulators has been studied. As the asymmetry ratio of modulators is increased, dispersion penalties are increased asymmetrically at around the zero dispersion wavelength for the CS-RZ format. The DCS-RZ modulation format has a symmetric behavior due to different characteristics of the residual chirp of modulators. The receiver margin for the DCS-RZ modulation format is larger than the CS-RZ modulation format above the asymmetry ratio of 0.82 of modulators (extinction ratio of 20 dB) with the optimal Δλ_DCF. By controlling the negative/positive applied chirp of the first/second modulator, dispersion penalties can be reduced for both the CS-RZ and DCS-RZ formats. In the DCS-RZ format compared to the CS-RZ format, the effect of the applied chirp of the first modulator is more dominant than that of the second modulator. The simulation results show that the receiver margin is limited by the asymmetry ratio of modulators as well as a deviated wavelength from the zero dispersion wavelength of dispersion compensating fibers (DCF) in order to be fully post-compensated. Dispersion penalties can be reduced with appropriate chirp parameters of two non-ideal modulators.     

Observation of ferromagnetic ordering in Mn‐doped 8‐hydroxy‐quinoline aluminum

The ferromagnetic property of Mn‐doped 8‐hydroxy‐quinoline aluminum (Alq₃), synthesized by thermal co‐evaporation of pure Mn metals and Alq₃ powders, was investigated. The weak ferromagnetic property was observed in 5%‐doped Alq₃, with saturation magnetization of around 0.05μ_B/Mn. The doped Mn chemically interacted with O atoms, producing a new gap state at 0.34 eV above the highest occupied molecular orbital and reducing the effective electron concentration. This led to the decrease of the electron affinity and increase of the optical bandgap, resulting in the reduction of the hole‐injection barrier in comparison with the electron‐injection barrier to the Alq₃ layer. From these, the origin of the observed ferromagnetism is suggested. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A simple synthesis of 5-fluorouracil by a novel ring transformation reaction

A very simple method for the preparation of 5-fluorouracil ( 1 ) from 1,3-dimethyl-5-azauracil ( 2 ) by a novel ring transformation reaction is reported.     

On the bounds for the Kℓ3 form factors

A complete solution is given to a mathematical problem encountered in the search for bounds on the K_?3 scalar form factor. Besides standard analyticity assumptions, the information used is, firstly, the Mathur-Okubo inequality derived from a chiral model, secondly the experimental low-energy $\text{I =}\text{1}\text{2}$, S-wave, Kπ phase shift. Upper and lower bounds are computed, compared with previous bounds, and found to be in agreement with recent experimental data.     

Dependence on plasma density of the conductivity of an electron-hole plasma in germanium at 2 K

High densities of electron-hole plasma have been optically injected into Ge at T ∼ 2K, and the plasma density inferred from measurements of the plasma absorption at 3.39μ. The behavior of the conductivity with increasing density and at different electric fields can be understood from a model of a plasma condensation into high density drops, with the plasma density in the drops ? 6 × 10¹⁶ c⁻³.     

Comparison of compensation ratios determined by photoluminescence and electrical methods in epitaxial GaAs

Compensation ratios in high purity epitaxial GaAs layers are determined by Nam et al.'s photoluminescence method at a well-defined finite excitation intensity. This excitation intensity is obtained from the excitation-dependence of the peak energy of the neutral donor-acceptor transition. The values of compensation ratio determined in this way are in excellent agreement with those obtained by the conventional electrical method.