On trading wavelengths with fibers: a cost-performance based study

We consider the effect of multiple fibers on wavelength division multiplexing networks without wavelength conversion. We study networks with dynamic wavelength routing and develop accurate analytical models to compare various possible options using single- and multiple-fiber networks. We use results of an analytical model and simulation-based studies to evaluate the blocking performance and cost of multifiber networks. The number of fibers required providing high performance in multifiber networks and their costs are compared. A case is made for using multiple fibers in each link with fewer wavelengths instead of using a single fiber with many wavelengths. In particular, we show that a network with four fibers per link and with four wavelengths on each fiber without any wavelength conversion on any node yields similar same performance as the networks with one fiber per link and 16 wavelengths per fiber on each link and with full wavelength conversion capability on all nodes. In addition, the multifiber network may also offer the cost advantage depending on the relative cost of components. We develop a parametric cost model to show that multiple fibers in each link are an attractive option. Finally, such multifiber networks also has fault tolerance, with respect to a single fiber failure, already built into the system.     

Pool boiling on a superhydrophilic surface

Titanium Dioxide, TiO₂, is a photocatalyst with a unique characteristic. A surface coated with TiO₂ exhibits an extremely high affinity for water when exposed to UV light and the contact angle decreases nearly to zero. Inversely, the contact angle increases when the surface is shielded from UV. This superhydrophilic nature gives a self-cleaning effect to the coated surface and has already been applied to some construction materials, car coatings and so on. We applied this property to the enhancement of boiling heat transfer. An experiment involving the pool boiling of pure water has been performed to make clear the effect of high wettability on heat transfer characteristics. The heat transfer surface is a vertical copper cylinder of 17 mm in diameter and the measurement has been done at saturated temperature and in a steady state. Both TiO₂-coated and non-coated surfaces were used for comparison. In the case of the TiO₂-coated surface, it is exposed to UV light for a few hours before experiment and it is found that the maximum heat flux (CHF) is about two times larger than that of the uncoated surface. The temperature at minimum heat flux (MHF) for the superhydrophilic surface is higher by 100 K than that for the normal one. The superhydrophilic surface can be an ideal heat transfer surface. Copyright © 2002 John Wiley & Sons, Ltd.     

Effect of surfactants on phenol removal by the method of polymerization and precipitation catalysed by Coprinus cinereus peroxidase

The removal of phenol by peroxidase‐catalysed polymerization was examined using Coprinus cinereus peroxidase in the presence of surfactants. The non‐ionic surfactants with poly(oxyethene) residues, Triton X‐100, Triton X‐405 and Tween 20, enhanced the phenol removal efficiency at a level similar to high relative molecular mass poly(ethylene glycol) (relative molecular mass 3000). Although the improvement in the removal efficiency was less than that of Triton X‐100, Span 20, sodium lauryl sulfate (SDS) and lauryl trimethylammonium bromide (DTAB) also enhanced the removal efficiency. The requirement of the enzyme for almost 100% removal of 100 mg dm^?3 phenol decreased to one‐fourth by the addition of 30 mg dm^?3 Triton X‐100. Triton X‐100, Triton X‐405, Tween 20 and DTAB could reactivate the enzyme precipitated with the phenol polymer, leading to the restarting of the phenol removal reaction. Copyright © 2003 Society of Chemical Industry     

Persistent caching: an implementation technique for complex objectswith object identity

Many recent complex object database systems support the concepts of object identity and object identifier. Following an object identifier to access the referenced object is called navigation operation and is an essential operation in dealing with complex objects. Navigation operation is a difficult operation to implement efficiently since every navigation operation inherently causes one disk access operation. A scheme to notably accelerate the navigation operation among a sea of complex objects, by increasing the effective number of objects in one disk page is proposed. The main concept of the presented technique is threefold. The first idea is to store a cached value within a complex object that is referencing another complex object. The second is that when the referenced object is to be updated the update propagation is delayed until the time when the cached value is referenced. The third is to utilize a hashed table on main memory to efficiently validate the consistency between the cached values and the original values     

Growth condition of iodine-doped n+-CdTe layers in metal-organic vapor phase epitaxy

Iodine doping of CdTe layers grown on (100) GaAs by metal-organic vapor phase epitaxy (MOVPE) was studied using diethyltelluride (DETe) and diisopropyltelluride (DiPTe) as tellurium precursors and ethyliodine (EI) as a dopant. Electron densities of doped layers increased gradually with decreasing the growth temperature from 425°C to 325°C. Doped layers grown with DETe had higher electron densities than those grown with DiPTe. When the hot-wall temperature was increased from 200°C to 250°C at the growth temperature of 325°C, doped layers grown with DETe showed an increase of the electron density from 3.7×10¹⁶ cm⁻³ to 2.6×10¹⁸ cm⁻³. On the other hand, such an increase of the electron density was not observed for layers grown with DiPTe. The mechanisms for different doping properties for DETe and DiPTe were studied on the basis of the growth characteristics for these precursors. Higher thermal stability of DETe than that of DiPTe was considered to cause the difference of doping properties. With increasing the hot-wall temperature from 200°C to 250°C, the effective ratio of Cd to Te species on the growth surface became larger for layers grown with DETe than those grown with DiPTe. This was considered to decrease the compensation of doped iodine and to increase the electron density of layers grown with DETe. The effective ratio of Cd to Te species on the growth surface also increased with decreasing growth temperature. This was considered to increase the electron density with decreasing growth temperature.     

Gain-shifted TDFA employing high concentration doping techniquewith high internal power conversion efficiency of 70%

The amplification characteristics of a high Tm³⁺ concentration gain-shifted Tm-doped fluoride fibre amplifier (GS-TDFA) have been determined with a high input signal power. This GS-TDFA achieved the highest reported internal power conversion efficiency of 70% with a double pass configuration     

Planar AlGaAs/GaAs heterojunction bipolar transistors fabricatedusing selective W-CVD

The authors describe a planar process for the AlGaAs/GaAs HBTs in which collector vias are buried selectively, even to the base layers, with chemical vapor deposited tungsten (CVD-W) films. By using WF₆ /SiH₄ chemistry, W could be deposited on Pt films, which were overlapped 50 nm thick on the AuGe-based collector electrodes, without depositing W on the surrounding SiO₂ layers. Current gains of planar HBTs with 3.5-μm×3.5-μm emitters were up to 150, for a collector current density of about 2.5×10⁴ A/cm²     

Thieno[2,3-d]pyrimidine-3-acetic acids. A new class of nonpeptide endothelin receptor antagonists

On the basis of structural information for the cyclic hexapeptide endothelin (ET) receptor antagonist, TAK-044, a series of thieno[2,3-d]pyrimidine-2,4-dione derivatives bearing a carboxyl group and aromatic rings that were important for receptor binding were designed, synthesized, and evaluated for ET receptor binding affinities and inhibitory activities against ET-induced vasoconstriction. Optimization of each substituent in the thieno[2,3-d]pyrimidine ring led to the discovery of a novel and potent nonpeptide ET receptor antagonist, 6-(4-methoxymethoxyphenyl)-5-methylsulfonylaminomethyl-1-(2- methylthiobenzyl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]p yrimidine-3- acetic acid (32 g), which binded to human ETA and ETB receptor subtypes with affinities (IC50) of 7.6 and 100 nM, respectively. Compound 32 g effectively antagonized ET-induced vasoconstriction and the inhibitory effect mediated by the ETB receptor was more potent than that of bosentan, while the inhibitory effect mediated by the ETA receptor was slightly less potent than that of bosentan.     

Plasma lens experiment at the final focus test beam

The proposed plasma lens experiment at the Final focus Test Beam (FFTB) facility of the Stanford Linear Accelerator Center has been approved by the adminstration. The experiment would allow the examination of plasma focusing devices for particle beams in the parameter regime of interest to future high-energy colliders. It is expected to lead to compact plasma lens designs capable of focusing the beam to unprecedented small spot sizes.