Transmission distance of in-line amplifier systems withgroup-velocity-dispersion compensation

Group-velocity dispersion (GVD) compensation in in-line amplifier systems is evaluated from the viewpoint of improving the transmission distance. The nonlinear Schrodinger equation, which simulates signal propagation in optical fibers, is numerically evaluated to clarify the optimum configuration for GVD compensation. It is shown that the optimum amount of GVD compensation is about 100% of the GVD experienced by the transmitted signal. The optimum compensation interval is found to be a function of the bit rate, signal power, and dispersion parameter. For dispersion parameter values ranging from about -0.1 ps/nm/km to -10 ps/nm/km, and an amplifier noise figure of about 6 dB, the optimum compensation configuration can eliminate the GVD from in-line amplifier systems, thus improving transmission distances to those limited by self-phase modulation and higher-order GVD     

Molecular basis of a hereditary type I protein S deficiency caused by a substitution of Cys for Arg474

The molecular basis for a hereditary type I protein S (PS) deficiency was investigated. DNA sequence analysis in the proband showed a novel missense mutation substituting Cys (TGT) for Arg474 (CGT) that is a highly conserved amino acid residue among the related proteins. This missense mutation cosegregated with the type I PS deficiency in this family. Transient expression studies showed that the secretion of the recombinant Cys-mutant PS was markedly decreased compared with that of the recombinant wild-type PS, reproducing the observed phenotype of type I deficiency. Stable expression and pulse-chase experiments demonstrated an intracellular degradation and an impaired secretion of the recombinant Cys-mutant PS. Furthermore, the substitution of Arg474 by Ala or Glu, but not by Lys, markedly reduced the secretion of the recombinant PS mutants in transient expression studies, suggesting that a positively charged basic amino acid might be needed at residue 474 and might play a key role in the protein structure and conformation of the sex hormone binding globulin-homology domain of the PS molecule. We postulate that the loss of the highly conserved Arg474 might be responsible for the type I PS deficiency inherited in this family.     

Prolonged exposure to intravesical foreign body induces a giant calculus with attendant renal dysfunction

A 31-year-old man came to our hospital complaining of severe voiding pain. He had inserted a fishing line made of nylon into his urethra at the age of eighteen, which was unable to be taken out and had been left there for 13 years. Preoperative ultrasonogram showed severe bilateral hydronephrosis and the serum BUN and creatinine level were as high as 45.2 mg/dl and 4.8 mg/dl, respectively. A huge bladder stone was demonstrated in X-ray film, the patient was admitted and vesicolithotomy was performed. The size of the stone was 10.5 x 7.5 x 7.5 cm and the weight was 360 grams. The fishing line was found inside the stone and the length was over 3 meters. The serum BUN and creatinine level after the operation were still high as 28.4 mg/dl and 4.1 mg/dl, respectively, and they did not improve even after six months following.     

Annealing behavior of Ar ion irradiated Bi2Sr2Can-1CunO4+2n superlattice and intergrowth films

Artificially layered Bi₂Sr₂Ca_n–1Cu_nO_4+n films were synthesized by sequential sputter deposition of BiO, SrCu_0.5O_1.5 and CaCuO₂ layers. Annealing behavior of these films which were irradiated by Ar ions was studied. Defect assisted improvement of their crystalline perfection is expected which might results in the improvement of the superconducting properties of these films. An artificial film, such as an intergrowth of 2223 and 2234 phases, and superstructure films of (2245)₁(2201)₁ and (2234)₁(2212)₁, were irradiated by Ar ions (150 keV, 2–10×10¹² ions/cm₂) and annealed at 730 °C. An improvement of superconducting transition temperatures were observed.     

Relative zinc-binding capacity of metallothionein: studies in renal cytosols from zinc-injected rats

Each rat was injected intraperitoneally once with 0.9% NaCl or zinc (10, 20, 40, or 60 mg zinc/kg b.w.). The zinc content in kidney reached a maximum level of approx. 50 microgram/g kidney, corresponding to a dose (40 mg zinc/kg b.w.). The distribution profiles of the renal cytosols of zinc-injected rats on a Sephadex G-75 column showed that most of the increased zinc was attributable to metallothionein. There was a linear relationship between the zinc contents in cytosol and metallothionein. Our results demonstrated that there was a limit of zinc accumulation in kidneys of zinc-injected rats and that 57% of the increased zinc in renal cytosols was bound to metallothionein. Our results suggest that the role of metallothionein in zinc accumulation in the kidney is similar to that of zinc accumulation in liver.     

Fibre transmission distance determined by eye opening degradation due to selfphase modulation and group-velocity dispersion

Numerical analysis of IM signal propagation in an optical fibre is carried out taking selfphase modulation and group-velocity dispersion into account. The transmission distance yielding a prescribed eye opening penalty, in the normal dispersion region, is shown to be inversely proportional to the square root of the signal power.<>     

Interaction of two close quantized vortices in superfluid4He

The three-dimensional dynamics of two interacting quantized vortex filaments is studied. The equations of motion and the method of numerical calculation follow Schwarz. Whether two approaching filaments reconnect or not depends on their arrangement before approach. When a ring moves toward a line from a distance, only within a critical initial distance they can reconnect. The critical distance is minimized when their circulations are parallel at the closest place, while it increases as their circulations begin to deviate from being parallel. Hence the reconnection probability can be less than unity.     

An over 2200-km coherent transmission experiment at 2.5 Gb/s usingerbium-doped-fiber in-line amplifiers

A 2223 km transmission distance was achieved with a 2.5-Gb/s heterodyne detection system that used erbium-doped-fiber in-line amplifiers and dispersion-shifted single-mode fibers. Twenty-five amplifiers, placed at approximately 80-km intervals, offered a total gain of more than 440 dB. Receiver sensitivity was -42.0 dBm, with only a 4.2-dB penalty from the initial sensitivity achieved by the back-to-back configuration     

High-reliability GaAs-AlGaAs HBTs by MBE with Be base doping andInGaAs emitter contacts

The authors have developed a modified MBE growth process to produce high-gain n-p-n GaAs-AlGaAs heterojunction bipolar transistors (HBTs) with a mean time to failure (MTTF) of 1.5×10⁸ h at 125°C. Beryllium incorporation and diffusion are controlled through a combination of reduced substrate temperature and increased As/Ga flux ratio during MBE growth, resulting in extremely stable HBT profiles. The authors also demonstrate graded InGaAs surface layers with nonalloyed refractory metal contacts that significantly improve ohmic reliability compared to alloyed AuGe contacts. The ability to produce robust HBTs by MBE is critically important to this technology