Small-chirp 40-Gbps electroabsorption modulator with novel tensile-strained asymmetric quantum-well absorption layer

A small-chirp 40-Gbps electroabsorption modulator (EAM) with a novel tensile-strained asymmetric quantum-well (QW) absorption layer has been demonstrated for the first time. The strain and the band line-up of the asymmetric QW structure were designed in order to obtain a small-chirp operation, a clear eye opening, and a high extinction ratio simultaneously. The chirp measured as /spl alpha/-parameter was reduced without any penalty of extinction ratio and eye opening. The measured /spl alpha/-parameter was smaller than 1.5 at any bias voltage from 0 to -2 V. The measured 3-dB bandwidth of a 75-/spl mu/m-long EAM exceeded 50 GHz at -1 V bias voltage. Under a 40-Gbps modulation, a clear eye opening was obtained, and the eye diagram showed no violation of the standard STM256/OC768 mask. The measured dynamic extinction ratio was over 11 dB.     

Method of noninvasive and continuous hemolysis/thrombogenesis measurement by laser photometry during artificial heart development

The purpose of this research is to propose and develop a method to measure hemolysis and thrombogenesis non invasively and continuously to aid in development of an artificial heart. Generally, the optical absorption rate of hemoglobin is influenced by oxygen saturation except at the isosbestic point, which is not influenced by oxygen saturation. The authors, therefore, used an 805 nm laser diode, an optical spectrum analyzer to obtain greater accuracy. An experimental blood circuit system was constructed using a Bio-Pump, Tygon tubing, a soft shell reservoir, and an optical measurement system. Experimental settings for monitoring hemolysis were as follows; blood volume 200 ml, blood flow 6 L/min, and afterload 200 mmHg. Blood was sampled six times (0, 30, 60, 120, 180, and 240 min), and hemolysis in each sampled was measured using a colorimetric method. Comparing continuous laser measurement data with the sample data, an adequate correlation is obtained, proving that the dynamic trend of hemolysis could be continuously measured. Furthermore, to analyze the process of thrombogenesis, simple experiments were performed using blood neutralized by protamine. As a result, the authors could see the process of thrombogenesis as it occurred and could confirm that this method is able to dynamically detect hemolysis and thrombogenesis.     

Electrical properties of α-zirconium phosphate and its alkali salts in a humid atmosphere

Humidity dependence of impedance was examined by using the complex impedance analysis for fine crystalline zirconium bis(monohydrogen phosphate) monohydrate and its alkali salts. The value of C ₀ in C _p()=C ₀(j/ ₀)^– was hardly dependent on the relative humidity and monovalent cation species. The resistive component and its activation energy decreased with increase in the relative humidity and the former was expressed as R=R ^* exp (–E/kT ^*) exp (E/kT) The pre-exponential factor R ^*, was hardly influenced by the humidity and decreased when the acidic protons were replaced with monovalent alkali cations. The activation energy of conduction was strongly affected by the degree of orientation and particle size of crystal with layered structure in a whole humidity region and increased by replacing the protons by alkali cations.     

Effects of firing temperature on morphology and crystal structure of zirconiumbis(monohydrogen phosphate) and its alkali salts

In zirconiumbis(monohydrogen phosphate)monohydrate, the stability of water of crystallization and of the crystal form was strongly influenced by its crystal size. The water of crystallization of a smaller crystal was completely released on heating to 200° C while a part of this water was held at 300° C in a larger crystal with a diameter of several micrometres. While a smaller crystal was decomposed by heating to 900° C and cubic zirconium pyrophosphate was formed, for a larger crystal,-layered zirconium pyrophosphate was formed instead of cubic zirconium pyrophosphate and a layered structure was held. For the Na₂-, K₂- and Rb₂-forms, good layer structure was retained even by heating to 1000° C. For the Li₂-form, the layer structure was decomposed on heating at or above 900° C. The thermal stability of the layered structure increased with increasing crystal size and ionic radii of the alkali cation.     

Roles of aluminium and chromium in sulfidation and oxidation of sputter-deposited Al- and Cr-refractory metal alloys

Our recent results of the sulfidation and oxidation behavior of sputter-deposited Al- and Cr-refractory metal alloys at high temperatures are reviewed, and the roles of the aluminum and chromium in sulfidation and oxidation of these alloys are discussed in this paper. Niobium, molybdenum and tantalum are highly resistant to sulfide corrosion. Their sulfidation resistance is further enhanced by alloying with aluminum. Although Cr-refractory metal alloys also reveal high sulfidation resistance, their sulfidation rates do not become lower than those of the corresponding refractory metals. The sulfide scales formed on the Al-refractory metal and Cr-refractory metal alloys consist of two layers, comprising an outer Al₂S₃ or Cr₂S₃ layer and an inner refractory metal disulfide layer. The inner layer has a columnar structure, and the growth direction of the refractory metal disulfides is perpendicular to 0 0 1 direction. Intercalation of Al³⁺ ions into NbS₂ and a decrease in the sulfur activity at the outer layer/inner layer interface by the presence of the Al₂S₃ layer are probably responsible for the improvement of the sulfidation resistance by the addition of aluminum. The oxidation resistance of niobium and tantalum is improved more effectively by the addition of chromium rather than aluminum. Although preferential oxidation of chromium does not occur, an outer protective Cr₂O₃ layer in the oxide scales is formed on Cr-rich Cr-Nb and Cr-Ta alloys due to outward diffusion of Cr³⁺ ions. In contrast, continuous alumina layer cannot be formed on the Al-Nb and Al-Ta alloys, and the alloys reveal a pest phenomenon at 1073 K, and at higher temperatures rapid oxidation occurs. Concerning the oxidation of molybdenum, the addition of aluminum, which has higher activity for oxidation than chromium, is more effective in improving the oxidation resistance of molybdenum than chromium addition, since preferential oxidation of aluminum suppresses the formation of volatile molybdenum oxide.     

Wood photography using light irradiation and heat treatment

To apply the coloring method using light irradiation and thermal treatment to print photographs on wood, the effect of the transmittance of negative films was investigated. ΔE* decreased with light irradiation when specimens covered with films with transmittances exceeding 20% were irradiated for 100 h. It was thought that this phenomenon was due to the decrease in Δb*. The color of light‐irradiated wood changed remarkably with thermal treatment; however, the change in the color of exposed specimens covered with films with transmittances exceeding roughly 20% became constant. Clear photographs could be printed on wood using negative films with transmittances less than approximately 20%. Furthermore, the difference between the maximum and minimum values of ΔE* after thermal treatment was about 22. Humans can distinguish four to seven colors that can be created by this method. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 312–316, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20027     

A surface silylated single-layer resist based on limited gas permeation

A simple alternative was studied for the tri-layer resist system. One single thick layer of resist polymer was surface silylated to obtain a bilevel structure that functioned similarly to the bilayer resist composed of the Si-containing top imaging and the bottom planalizing layers. A resist or matrix polymer layer containing phenolic – OH groups was silylated by exposing it to hexamethyldisilazane vapor, and Si atoms were effectively incorporated in the surface sublayer by limited gas permeation and reaction with the – OH groups. Oxygen RIE durability of the silylated poly(vinyl phenol) or the positive-working commercial EB resist, RE-5000P, was > 10 times as high as that of PVP or RE-5000P before silylation. The surface silylated single-layer (SSS) resist derived from RE-5000P was flood-exposed through a mesh mask to 11.7°C/cm² of 4 KeV electrons, developed with tetramethylammonium hydroxide in aqueous methanol, and plasma-developed in an O₂ RIE chamber to form a positive-tone relief image.     

Synthesis of Nanowire TiO2 Thin Films by Hydrothermal Treatment and their Photoelectrochemical Properties

Nanowire TiO₂ thin films were successfully prepared on Ti metal substrates by hydrothermal treatment of calcined Ti foils in 10 M NaOH. The nanowire TiO₂ thin films exhibited much larger surface area and higher photoelectrochemical performance than the TiO₂ thin films prepared on Ti metal substrates by the calcination of Ti foil. These nanowire films were shown to act as an efficient photoanodes for the photoelectrochemical water splitting reaction.     

A memory‐in‐pixel reflective‐type LCD using newly designed system and pixel structure

A 7.03‐in. extended graphics array reflective LCD prototype has been developed by using memory‐in‐pixel (MIP) technologies with a newly designed system and pixel structure. The MIP system comprising a MIP backplane and a display driver has been optimized to reduce power consumption. The MIP backplane has specific circuits that allow accessing row drivers randomly, and the display driver manages which row should be accessed. Thus, the system is capable of showing a mixture of still and moving images, resulting in low power consumption. A dithering block embedded in the display driver enables to select an appropriate dithering algorithm according to the types of images and the position on the screen. In addition, the novel pixel structure, “three divided patterns”, has been designed to improve image quality and to provide visibility in dark environments. The latter is based on a novel approach; interpixel area is used for an aperture to transmit light from the backlight, and the fringe field from adjacent pixel electrodes is used to control LC directions. The feature of the pixel structure is also effective for obtaining equivalent gamma between reflective and transmissive images.