Phase noise cancellation in a carrier recovered optical heterodynereceiver

The performance and application of an optical heterodyne receiver which uses a carrier recovery demodulator are described. Phase sensitive demodulators used in coherent optical transmission are compared, and the suppression of both phase noise and frequency instability of light sources by a carrier recovery (CR-) demodulator is described. A carrier recovered PSK (CR-PSK) demodulator and a phase noise canceling circuit (PNC) for a coherent SCM receiver are introduced as examples of CR-demodulators. The relationship between laser diode spectral linewidths and the delay time difference between the two paths in the CR-PSK demodulator necessary to keep the system performance within a certain power penalty is then derived. In a preliminary experiment using 560-Mb/s CR-PSK transmission, a receiver sensitivity of -51.6 dBm was obtained, and a laser phase noise suppression of about ¹/₂ that of DPSK was confirmed. The results suggest the possibility of constructing a heterodyne receiver which has no AFC-loop. Applications of a CR-demodulator to an optical frequency division multiplexing (OFDM) system and to a multivalue modulation scheme are discussed     

A way to stabilize linear systems with delayed state

A simple method is proposed for stabilizing linear systems with delayed state, using linear feedback. The method requires checking the negativity of a matrix containing two free parameters, and solving a matrix Lyapunov equation with these parameters. A known stabilizability criterion and a simple stability theorem for the open-loop system are obtained as special cases of the main result.     

Oral low-dose etoposide therapy for refractory multiple myeloma with extramedullary involvement

A 65-year-old man was hospitalized with IgG kappa-type multiple myeloma (MM) and enormous subcutaneous plasmacytomas. Two different combination chemotherapy regimens (MMCP and AVPP) and alpha-interferon therapy were ineffectual. Oral administration of etoposide at 50 mg/day was subsequently started, the tumors completely disappeared after 5 months. The blood level of monoclonal protein became undetectable after 8 months of continuous treatment. The side effect noted was loss of hair. The course in this patient suggests that long-term daily low-dose administration of etoposide should be attempted in patients with refractory MM and extramedullary plasmacytoma.     

Theoretical study of NO decomposition on Cu-ZSM-5 catalyst models

The decomposition mechanism of NO on Cu-ZSM-5 catalyst models was investigated using ab initio molecular orbital calculations with Huzinaga's MIDI-P basis set [see S. Huzinaga, Gaussian Basic Sets for Molecular Calculations, Elsevier, Amsterdam, 1984]. Two reaction routes were assumed for each model and the geometry of all molecules was optimized.     

Yeast sequencing reports. Molecular cloning and sequencing of the hcs gene,which encodes 3-hydroxy-3-methylglutaryl coenzyme a synthase of Schizosaccharomyces pombe

We have cloned and sequenced the hcs gene, which is thought to encode a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase consisting of 447 amino acids, from the fission yeast Schizosaccharomyces pombe. The predicted amino acid sequence of the hcs product of S. pombe has homology with the HMG-CoA synthase of rat (47·8%), chicken (49·2%), hamster (47·1%) and human cells (46·9%). One of the hcs genes was replaced with a marker gene in the diploid cell. No viable hcs-disrupted haploid was isolated after tetrad dissection, suggesting that the hcs gene is essential for growth. However the hcs-defective mutant could be grown on a medium containing 5 mg/ml mevalonate. These results strongly support that the hcs gene encodes HMG-CoA synthase and S. pombe contains a single copy of the hcs gene. The sequence of the hcs gene has been entered into the public data libraries under Accession Number U32187.     

Effect of Mn on Aging of (Pb0.63Ba0.37)(Zr0.7Ti0.3)O3 Dielectric Ceramics

An aging model for relaxors is suggested on the basis of the transformation of a supercooled cubic lattice into a tetragonal lattice. Manganese ions distort the crystal lattice, and the distortion affects the phase transformation rate. As a result, the aging rate may be expected to change. The lattice constant of (Pb_0.63Ba_0.37)(Zr_0.7Ti_0.3)O₃+χ MnO mol% dielectric ceramics was used as a measure of the degree of the distortion. As the lattice constant decreased up to 0.5 MnO mol%, the aging rate increased, justifying the proposed model.     

On the discrete Riccati equation

Several bounds have been reported recently for the trace of the solution to the discrete algebraic matrix Riccati equation. This note adds an alternative one to them.     

Luminescence emission of isotactic polypropylene

In order to elucidate the origin of luminescent species in unstabilized commercial isotactic polypropylene (IPP), effects of hexane extraction and exposure of the extracted IPP film to the atmosphere on both fluorescence and phosphorescence emissions were examined. Fluorescence emission from the unextracted IPP film disappeared by the extraction, and only a very weak phosphorescence emission was found. During the exposure of the extracted IPP film to the atmosphere, both fluorescence and phosphorescence emissions appeared again. The intensity of the spectra increased with the exposure time and finally almost reached that from the unextracted IPP film. The results indicated that main fluorescent species in IPP are foreign impurities originating from an ambient atmosphere, and that contribution of a very minor amount of phosphorescence species such as carbonyl groups incorporated with the polymer was scarce.