Automatically Controlled 2-Vessel Pressure-Cooker Test-Equipment

A highly accelerated humidity test for plastic encapsulated IC reliability short-term evaluation has been studied. 2-Vessel pressure cooker test (PCT) equipment capable of controlling relative humidity and temperature independently, and of keeping specimens free from water droplet condensation, has been designed. This equipment consists of a test chamber and a vapor chamber. Humidity conditions are set by controlling the temperature difference between the test chamber and the vapor chamber. Humidity levels are controlled with the direct pressure adjustment. The whole test chamber is heated in an oven, thereby obtaining temperature stability and uniformity. Using this equipment, humidity tests were carried out on plastic molded ICs. As a result, good test reproducibility and excellent correlation in test results between PCT and conventional humidity test such as 85°C/85%RH, were obtained. As a consequence, it was found possible, in a short time, to evaluate plastic molded IC reliability quantitatively in humidity ambients using this 2-vessel PCT equipment. This equipment can be used for quality assurance testing of plastic-encapsulated ICs in a short time.     

A scenario-driven conceptual design information model and its formation

This study describes a scenario-driven conceptual design information model and its formation from the viewpoint of the designers cognition, which is a fundamental part of practical design support tools. Four design meetings were observed in a company, at intervals of several weeks, in order to derive the model. The model consists of information elements generated through the cognitive design problem-solving process, which is a basic design process defined in this study. The study describes the relationship among these information elements, which illustrate the design information model and its formation. The model described in this study is based on scenarios, which promote the evolution of product design. Examples of designers discourse in the design meetings are presented to validate the model.     

The evaporation and carburization behavior of coated systems of niobium on molybdenum and niobium on titanium

The evaporation, carburization and diffusion behavior of Nb-coated Mo and of Nb-coated Ti were investigated in order to estimate the surface characteristics of the coated systems. Nb layers were formed on Mo by both chemical and physical vapor deposition and on Ti by just physical vapor deposition. From the diffusion behavior, interdiffusion coefficients were obtained at 1860°C, 1980°C and 2080°C for the chemically vapor-deposited Nb/Mo system. From evaporation experiments it was found that simultaneous evaporation of Nb and Mo occured at about 2300°C for thick films of Nb on Mo. For thin films of Nb on Mo, the evaporation of both Nb and Mo was confirmed at 1900°C by ion microprobe analysis of the condensate. For Nb/Ti, rapid diffusion of Nb into Ti and evaporation of Ti similar to the case of Nb-Ti alloys were observed. From the carburization study, it was found that an Nb coating appreciably retards the carburization of Ti and Mo.     

Trace gas measurement with an integrated porous tube collector/long-path absorbance detector

Porous membrane tubes filled with an absorbing solution that change colors upon selective reactions with specific gases provide high sensitivity inexpensive gas sensors. These can be routinely used for ambient monitoring in a fully automated manner. We consider both stopped and continuous flow operations and show the superiority of the stopped flow mode theoretically and experimentally. Light throughput through various membrane tubes is presented, and superior performance of such tubes over Teflon AF is shown. Sensors for NO2 and for O3 were based on Griess-Saltzman and indigotrisulfonate chemistries, respectively. A computer-controlled two-LED absorbance measurement system (one wavelength monitors the signal, the other references the system) that also governs automated reagent refilling was implemented. Sub-parts-per-billion-volume detection limits are attainable within a few minutes for both gases. Comparative data with a commercial UV-photometry-based ozone monitor showed excellent agreement with the response pattern of the present instrument. Low cost, ready applicability to the measurement of different gases by merely changing the light source and chemistry, and high sensitivity makes this instrument attractive for both pedagogic and practical purposes.     

Cautionary observations on preparing and interpreting brain images using molecular biology-based staining techniques

Though molecular biology-based visualization techniques such as antibody staining, in situ hybridization, and induction of reporter gene expression have become routine procedures for analyzing the structures of the brain, precautions to prevent misinterpretation have not always been taken when preparing and interpreting images. For example, sigmoidal development of the chemical processes in staining might exaggerate the specificity of a label. Or, adjustment of exposure for bright fluorescent signals might result in overlooking weak signals. Furthermore, documentation of a staining pattern is affected easily by recognized organized features in the image while other parts interpreted as "disorganized" may be ignored or discounted. Also, a higher intensity of a label per cell can often be confused with a higher percentage of labeled cells among a population. The quality, and hence interpretability, of the three-dimensional reconstruction with confocal microscopy can be affected by the attenuation of fluorescence during the scan, the refraction between the immersion and mounting media, and the choice of the reconstruction algorithm. Additionally, visualization of neurons with the induced expression of reporter genes can suffer because of the low specificity and low ubiquity of the expression drivers. The morphology and even the number of labeled cells can differ considerably depending on the reporters and antibodies used for detection. These aspects might affect the reliability of the experiments that involves induced expression of effector genes to perturb cellular functions. Examples of these potential pitfalls are discussed here using staining of Drosophila brain.     

An improved procedure of electron microscopic in situ hybridization for detecting adenovirus DNA

Electron microscopic in situ hybridization (EM-ISH) is a useful method in determining the localization of a specific nucleic acid at the ultrastructural level. Since the EM-ISH protocol includes many steps, no standard protocol for EM-ISH is available yet. In this study, we optimized quantitatively the critical conditions with respect to embedding resin, nucleic acid labeling and hybridization reaction time, by using adenovirus-infected cells as the indicator cells. The optimal detection of an adenovirus-specific nucleic acid was obtained by overnight hybridization reaction on sections embedded in Lowicryl K4M resin. Random-primed-labeled probes improved the reactivity. At least 60% of virus particles in paracrystalline arrays was found to contain viral DNA. These arrays in adenovirus-infected cells are useful in evaluating quantitatively the efficiency of protocols of EM-ISH.     

ε-Entropy and Fractal Dimension of a State for a Gaussian Measure

Kolmogorov introduced the concept of -entropy to analyze information in classical continuous systems. The fractal dimension of a geometric set was introduced by Mandelbrot as a new criterion to analyze the geometric complexity of the set. The -entropy and the fractal dimension of a state in a general quantum system were introduced by one of the present authors (MO) in order to characterize chaotic properties of general states.In this paper, we show that -entropy of a state includes Kolmogorov's -entropy, and that the fractal dimension of a state describes fractal structure of Gaussian measures.     

Metamorphic Heterostructure InP/GaAsSb/InP HBTs on GaAs Substrates by MOCVD

Good-quality metamorphic InP buffer layers have been successfully grown on GaAs substrates by metal-organic chemical vapor deposition. Characterization by atomic force microscope, transmission electron microscopy, high-resolution X-ray diffraction, and Hall measurements indicated that the layers are of high crystalline quality, good mobility, and excellent surface morphology. On this buffer, we demonstrated the first metamorphic InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) with good material quality and device performance. Metamorphic DHBTs showed direct-current and radio-frequency characteristics that are comparable to those grown on lattice-matched InP substrates.